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A further investigation of the homing behaviour of the intertidal cottid, Oligocottus maculosus Girard Craik, Gwenneth Jean Steele 1978

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A FURTHER INVESTIGATION OF THE HOMING BEHAVIOUR OF THE INTERTIDAL COTTID, OLIGOGOTTUS MAGOLOSUS GIRARD B.Sc.(Hons.)i A u s t r a l i a n N a t i o n a l U n i v e r s i t y , 1973 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE FACULTY OF GRADUATE STUDIES (Department' of Zoology) He accept t h i s t h e s i s as conforming t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA March, 1978 ((^SGwenneth Jean S t e e l e C r a i k , 1978) BY GWENNETH JEAN STEELE CRAIK THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n In presenting th i s thesis in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i l ab le for reference and study. I fur ther agree that permission for extensive copying of th is thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of th is thes is fo r f i nanc ia l gain sha l l not be allowed without my writ ten permission. Department of Z o o l o g y  The Univers i ty of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date 22 inarch, 1978 ABSTRACT The purposes o f t h i s study were to f i n d the causes o f the v a r i a b i l i t y p r e v i o u s l y observed i n the homing behaviour of °J:i20£ottus maqulosus G i r a r d and t o attempt to c l a r i f y the mechanisms by which the f i s h homes; i n p a r t i c u l a r whether o l f a c t i o n i s the major sensory mechanism i n v o l v e d . The study was conducted a t 12 s i t e s on t h e southwest coast of Vancouver I s l a n d , B r i t i s h Columbia. V a r i a b i l i t y i n homing behaviour and morphological c h a r a c t e r s between f i s h i n d i f f e r e n t t i d e p o o l and i n l e t areas, as w e l l as age, y e a r - c l a s s and length d i f f e r e n c e s i n homing behaviour i n one t i d e p o o l area were examined. C o n s i d e r a t i o n of the sensory mechanisms i n v o l v e d i n homing behaviour i n c l u d e d : i n t e r a c t i o n s between r e s i d e n t and i n t r o d u c e d f i s h , the nature of movement between the t r a n s p l a n t and home poo l s , d e t e c t i o n of chetaosensory c l u e s , the use of the p a i r e d f i n s t o d e t e c t touch and/or chemosensory c l u e s and i n g r e a t e s t d e t a i l , the r o l e s of v i s i o n and o l f a c t i o n i n homing behaviour. P r i o r t o i n v e s t i g a t i n g age and y e a r - c l a s s d i f f e r e n c e s , a method of age determination using o t o l i t h s was developed and compared with r e s u l t s from v e r t e b r a e and length-freguency a n a l y s i s . At any one time t h e r e are three major age groups i n the p o p u l a t i o n with decreasing numbers o f age 3 and 4 f i s h . Age-length r e l a t i o n s h i p s d i f f e r e d between areas. D i f f e r e n c e s were found i n homing behaviour between a r e a s , which c o u l d be r e l a t e d t o wave a c t i o n (turbulence) and i i i the t o p o g r a p h i c a l i r r e g u l a r i t y (roughness) of the t e r r a i n . Sfith decreasing turbulence and i n c r e a s i n g r e g u l a r i t y of the t e r r a i n , f i d e l i t y i s shown to an i n c r e a s i n g number of pools or a wider area and, i n t i d e p o o l areas, i n c r e a s i n g percentages of f i s h show homing behaviour. However, the f i s h which do home i n t u r b u l e n t rough areas show highest percentages r e t u r n i n g t o the home po o l . In i n l e t s , l i t t l e homing behaviour i s expressed. With de c r e a s i n g t u r b u l e n c e and i n c r e a s i n g r e g u l a r i t y of the t e r r a i n , d e c r e a s i n g numbers of f i s h remain i n the t r a n s p l a n t area., These f i n d i n g s can be r e l a t e d t o the reduced high t i d e a c t i v i t y of 0. maculosus i n t u r b u l e n t areas shown by Green (1971b,c). No c o n s i s t e n t d i f f e r e n c e s , which could be r e l a t e d t o exposure or homing behaviour, were found i n the m e r i s t i c and morphometric c h a r a c t e r s of 0. maculosus i n d i f f e r e n t a r e a s . I n v e s t i g a t i o n of c i r r i on 0. maculosus i n d i f f e r e n t areas showed t h a t t h e r e i s a v a r i a b l e i n c r e a s e i n the number of c i r r i , on a l l p a r t s o f the body, with l e n g t h and age. There are d i f f e r e n c e s i n these r e l a t i o n s h i p s between areas but they do not seem t o be r e l a t e d d i r e c t l y t o exposure. Y e a r - c l a s s d i f f e r e n c e s i n c i r r i numbers are not apparent. The f u n c t i o n of the c i r r i c o uld not be determined. Age r e l a t e d d i f f e r e n c e s i n homing behaviour are apparent, although y e a r - c l a s s d i f f e r e n c e s are not. Examination of the age d i f f e r e n c e s i n homing behaviour by s m a l l e r s i z e -c l a s s e s than one year age groups showed that there i s an improvement i n the percentage s u c c e s s f u l l y homing with l e n g t h up to about 5 cm. Homing i s best expressed i n f i s h between 5 and 7 cm (age 2) and a f t e r t h i s s i z e t h e r e i s a decrease i n the percentage s u c c e s s f u l l y homing. The percentage of homing f i s h r e t u r n i n g to the home pool appears to be about equal f o r a l l s i z e c l a s s e s . There i s a d e c l i n e i n t h e percentage remaining i n the t r a n s p l a n t area with l e n g t h except i n the l a r g e s t s i z e c l a s s e s of f i s h . r. J u v e n i l e f i s h (about 2.3 to 2.7 cm) which have moved i n t o lower t i d e p o o l s from the high t i d e p o o l s i n which they s e t t l e , show e x t e n s i v e movement between t i d e p o o l s and appear t o begin showing evidence of home range f i d e l i t y and homing behaviour a t about 3 cm. I t i s suggested t h a t during t h i s p e r i o d o f e x t e n s i v e movement, the area i s i n some way " l e a r n e d " and "memorized". I n v e s t i g a t i o n of the sensory mechanisms i n v o l v e d i n homing behaviour d i d not produce any evidence to show t h a t pool d e n s i t y or "space", b e h a v i o u r a l i n t e r a c t i o n s , touch o r t a s t e c l u e s detected by the p a i r e d f i n s or t a s t e r e c e p t o r s l o c a t e d elsewhere on the body are i n v o l v e d i n homing.,, Some evidence was found t o suggest t h a t movement between the t r a n s p l a n t and home pool i s d i r e c t e d . V i s i o n and o l f a c t i o n appear t o be i n v o l v e d i n homing, a combination o f b l i n d n e s s and anosmia being the most e f f e c t i v e i n red u c i n g homing success t o low l e v e l s . Both senses are e s s e n t i a l to the s u c c e s s f u l homing o f j u v e n i l e f i s h but v i s i o n and subsequently o l f a c t i o n become unnecassary i n o l d e r f i s h . I t i s suggested t h a t a d u l t f i s h are unable t o home u n l e s s V one of these senses i s a v a i l a b l e . Because of the d i f f i c u l t i e s of a p p r e c i a t i n g how e i t h e r o l f a c t i o n or v i s i o n can be used over any d i s t a n c e i n the t u r b u l e n t i n t e r t i d a l , i t i s suggested t h a t o l f a c t o r y and v i s u a l , and perhaps other c l u e s from p a r t i c u l a r pools are used to home and t h a t the f i s h moves from " p o o l " to " p o o l " to home. However, n e i t h e r conspicuous v i s u a l landmarks nor o l f a c t o r y c l u e s emanating from the home pool were shown t o be recognized by 0. maculosus. The data from t h i s and a r e l a t e d study (Khoo, 1971) suggest t h a t the r e l a t i v e importance of sensory mechanisms may d i f f e r both i n the development of homing behaviour and between areas. v i TABLE OF CONTENTS ABSTRACT ............... ..... .........................,.. ,. l i TABLE OF CONTENTS v i LIST OF FIGORES xi LIST OF TABLES x i i i ACKNOWLEDGEMENTS ................ ........... , . xvi I. GENERAL INTRODUCTION .................................. 1 II. DESCRIPTIONS OF STUDY SITES AND CAPTURE BETHODS ......5 I.Major study s i t e .....................................5 F i r s t Beach . ..... ..... 5 2.Other study s i t e s 10 Exposed study s i t e s ................................. 10 Moderately exposed study s i t e s 11 Sheltered study s i t e s ............................... 12 3. Enclosure 14 4. Capture methods ...................................... 18 I I I . AGE DETERMINATION IN O. HACOLOSUS ................... 19 1. Methods .................... 19 Age determination using o t o l i t h s ..............19 Age determination using vertebrae ................... 21 Analysis of length freguency data ................... 22 Age-length relationships ............................24 F i r s t Beach .........................................2<4 Other areas ..........25 2. Results ..............................................26 Otoliths ... . . . . 26 Vertebrae ........................................... 28 v i i G r a p h i c a l a n a l y s i s of length-frequency data .........32 Age-length r e l a t i o n s h i p s 43 F i r s t Beach 43 Other areas 47 3.D i s c u s s i o n .....................................53 IV. VARIABILITY IN HOMING BEHA VIGOR 57 1. Tagging and r e c a p t u r e methods ........................57 Tagging methods ............57 Reacapture methods 59 2. Homing i n d i f f e r e n t l o c a t i o n s ......60 F i r s t Beach .........................................60 Home range and area f i d e l i t y ........................60 Methods .............., . 61 Re s u l t s ........................................ ..... 62 Homing behaviour .................................... 66 Methods ............................................. 66 Re s u l t s 68 I n l e t s 71 Home range and area f i d e l i t y ........................ 71 Methods ............... 72 R e s u l t s .............................................72 Homing behaviour along i n l e t s 74 Methods .................... 75 Results ....................... .. .................... 76 Homing behaviour a c r o s s i n l e t s ...................... 78 Methods ... .79 Re s u l t s ............................................. 80 v i i i 3.Homing with r e s p e c t t o exposure ...................... 80 Met hoas 83 Res u l t s 85 4.Measurement o f wave a c t i o n and t o p o g r a p h i c a l r e g u l a r i t y ...........90 Methods 92 Re s u l t s ............................................. 95 5. D i s c u s s i o n ........................................... 99 V. MORPHOLOGICAL DIFFERENCES BETWEEN FISH IN DIFFERENT LOCATIONS .............................................. 106 L P o r t Renfrew, F i r s t Beach, G r a p p l e r I n l e t ............ 106 Methods 106 Res u l t s 108 2. The r e l a t i o n s h i p o f c i r r i to exposure 110 Methods 110 Re s u l t s ......................113 3. Experimental manipulation o f c i r r i number ............ 128 Methods ........ 128 Res u l t s .............................................132 4. H i s t o l o g i c a l examination o f c i r r i 138 Methods 138 Res u l t s 138 5. D i s c u s s i o n ...........................................140 71. OTHER FACTORS AFFECTING VARIABILITY IN HOMING BEHAVIOUR .............................. ..... ........... 144 1. Age ............. 144 i x Methods 144 Res u l t s ............................................. 145 2. Y e a r - c l a s s 148 Methods ........... ....»...........................,.148 R e s u l t s ,... 149 3. Length ............................................... 154 Methods ..................... ............. ........... 154 Re s u l t s ............................................. 157 4. D i s c u s s i o n ........................................... 172 VII. SENSORY MECHANISMS INVOLVED IN HOMING BEHAVIOUR .....177 1.Sensory impairment methods ........................... 177 V i s i o n 177 O l f a c t i o n ............................ ........... 178 Taste ..... ....... 179 F i n Removal ........... .............................. 181 2 . I n t e r a c t i o n s between r e s i d e n t and i n t r o d u c e d f i s h ....182 Methods ..... 183 R e s u l t s 183 3. Nature of movement between r e l e a s e and home pool .....186 Methods ......................... 186 Re s u l t s 187 4. Touch and/or chemosensory c l u e s ...................... 190 Methods 191 R e s u l t s 192 5. R e l a t i v e importance of d i f f e r e n t senses .............. 195 Methods ...................... 195 Results 196 X 6.Simultaneous impairment of vi s i o n and smell .......... 202 Methods ........203 Results ... ........ 204 7. Visual and olfactory tidepool clues .................. 210 Methods 211 Results ..216 8. Discussion ...........................................220 VIII. GENERAL DISCUSSION 237 1. V a r i a b i l i t y in homing behaviour ...................... 237 2.Sensory mechanisms involved i n homing behaviour ......242 IX. SUMMARY ...... .... ......... .....245 X. LITERATURE CITED .....250 XI. . APPENDICES 269 Appendix 1 .............................................269 Descriptions of study s i t e s ......................... 269 Appendix 2 276 Total length (TL) to and from standard length (SL) ..276 Appendix 3 ......................... .... ................ 277 Algae and invertebrates from experimental tank ...... 277 x i LIST OF FIGURES F i g u r e Paqe 1. G e n e r a l l o c a t i o n s o f s t u d y s i t e s 6 2. L o c a t i o n s o f s t u d y s i t e s 7 3. A e r i a l p h c t o q r a p h o f F i r s t Beach 8 4. E n c l o s u r e f r o m o u t s i d e (above) and i n s i d e {below) .... 16 5. O t o l i t h s o f 0. m a c u l o s u s s h o w i n g opaque and h y a l i n e z o n e s ( a l l t a k e n on 30 A u g u s t ) 27 6. L e n g t h - a g e r e q r e s s i o n s f o r F i r s t Beach 0. m a c u l o s u s d e t e r m i n e d by o t o l i t h s ( m a l e s and f e m a l e s s e p a r a t e l y ) . 29 7. V e r t e b r a e o f age 3 0. m a c u l o s u s s h o w i n q opaque and h y a l i n e z o n e s ( t a k e n on 5 December) 31 8. L e n q t h - a q e r e g r e s s i o n s f o r F i r s t B e a c h 0. m a c u l o s u s d e t e r m i n e d by v e r t e b r a e ( m a l e s and f e m a l e s s e p a r a t e l y ) 33 9. L e n q t h - f r e q u e n c y a n a l y s i s o f aqe g r o u p s u s i n q C a s s i e ' s method 35 10. L e n q t h - a g e r e q r e s s i o n s f o r F i r s t B e a c h C. m a c u l o s u s d e t e r m i n e d by o t o l i t h s , v e r t e b r a e and l e n q t h - f r e q u e n c y a n a l y s i s ( m a l e s and f e m a l e s combined) 38 11. L e n g t h - f r e q u e n c y h i s t o g r a m s o v e r t i m e o f F i r s t Beach 0* 12.f2ili2Sil5 42 12. A g e - l e n g t h r e g r e s s i o n s o f F i r s t Beach 0. m a c u l o s u s d e t e r m i n e d by o t o l i t h s ( m a l e s and f e m a l e s s e p a r a t e l y and c o m b i n e d ) 45 13. A g e - l e n g t h r e g r e s s i o n s o f 0. j n a c u l o s u s f r o m e i g h t • a r e a s d e t e r m i n e d by o t o l i t h s ( males and f e m a l e s c ombined) 50 14. Cement b l o c k d e s i g n and cement b l o c k a n c h o r e d i n t i d e p o o l 94 15. G r a p h i c a l a n a l y s i s o f e i g h t m e r i s t i c and m c r p h c m e t r i c c h a r a c t e r s o f 0. m a c u l o s u s a t f o u r a r e a s 109 16. T o t a l c i r r i - l e n g t h r e g r e s s i o n s f o r 0. m a c u l o s u s f r o m f i f t e e n a r e a s ( m a l e s and f e m a l e s c o m b i n e d ) 116 17. T o t a l c i r r i - a g e r e g r e s s i o n s f o r 0. m a c u l o s u s f r o m n i n e x i i a r e a s (males and f e m a l e s combined) 123 18. T o t a l c i r r i - a g e by y e a r - c l a s s r e g r e s s i o n s f o r 0. m a c u l o s u s from two s e l e c t e d a r e a s (rcales and f e m a l e s combined) 126 19. D e s i g n o f e x p e r i m e n t a l t a n k showing calm and e x p o s e d s i d e s and wave making t a n k 130 20. T o t a l c i r r i - l e n q t h r e g r e s s i o n s from 0, m a c u l o s u s i n t r o d u c e d i n t o e x p e r i m e n t a l t a n k and from F i r s t Beach 134 21. T o t a l c i r r i - l e n g t h r e g r e s s i o n s from 0. rcaculosu s i n the c a l m and e x p o s e d s i d e s o f e x p e r i m e n t a l t a n k 136 22. S e c t i o n s of c i r r i from t h e l a t e r a l l i n e and head o f 0. m a c u l o s u s 139 23. Homing p e r f o r m a n c e by age (mean ± 2 s.e.) 146 24. Homing p e r f o r m a n c e by y e a r - c l a s s (mean ± 2 s.e.) 150 25. Homing p e r f o r m a n c e by l e n g t h c l a s s e s (mean ± 2 s.e.) . 163 2f>. C i r c u l a r p l o t s o f d i r e c t i o n o v e r f i r s t 3 d a ys t a k e n by two samples o f f i s h d i s p l a c e d t o c e n t r a l p e e l 188 27. S e c t i o n s o f t i p s o f p e c t o r a l f i n (above) and p e l v i c f i n (below) 194 28. Landmarks i n s t a l l e d i n p o o l s at F i r s t Beach 212 29. Y-shaped c h o i c e tank 214 x i i i L I S T OF TABLES T a b l e Page 1. F i r s t Beach 0. m a c u l o s u s ( o t o l i t h s ) l e n g t h - a g e f u n c t i o n a l r e g r e s s i o n s t a t i s t i c s 30 2. F i r s t B e a ch 0. m a c u l o s u s ( v e r t e b r a e ) l e n q t h - a q e f u n c t i o n a l r e q r e s s i o n s t a t i s t i c s 34 3. wean l e n g t h (cm) f o r e a c h aqe q r o u p d e t e r m i n e d by t h r e e d i f f e r e n t methods 36 4. 0. t n a c u l o s u s ( F i r s t Beach) l e n g t h - a q e r e q r e s s i o n s t a t i s t i c s f r o m t h r e e d i f f e r e n t methods o f aqe d e t e r m i n a t i o n 39 5. C o m p a r i s o n o f aqe d e t e r m i n e d by o t o l i t h s and v e r t e b r a e o f t h e same 0. m a c u l o s u s i n d i v i d u a l s 40 6. G r o w t h o f t a q q e d 0. m a c u l o s u s i n d i v i d u a l s 44 7. F i r s t B e a c h 0. m a c u l o s u s ( o t o l i t h s ) a q e - l e n q t h r e g r e s s i o n s t a t i s t i c s and a n a l y s i s o f c o v a r i a n c e s t a t i s t i c s ( m a l e s v s f e m a l e s ) 46 8. A l l a r e a s 0. m a c u l o s u s ( o t o l i t h s ) a q e - l e n q t h r e g r e s s i o n s t a t i s t i c s ( m a l e s and f e m a l e s s e p a r a t e l y ) . 48 9. A l l a r e a s a n a l y s i s o f c o v a r i a n c e s t a t i s t i c s ( m a l e s vs f e m a l e s ) 49 10. A l l a r e a s 0. maculos_us ( o t o l i t h s ) a q e - l e n q t h r e g r e s s i o n s t a t i s t i c s ( m a l e s and f e m a l e s c o m b i n e d ) ... 52 11. A n a l y s i s o f c o v a r i a n c e s t a t i s t i c s f o r a l l a r e a s ( m a l e s and f e m a l e s c o m b i n e d ) 54 12. F i r s t Beach r e p l a c e m e n t e x p e r i m e n t 63 13. L o n g - t e r m p o o l f i d e l i t y o f i n d i v i d u a l 0. m a c u l o s u s f r o m 30 J u n e r e p l a c e m e n t e x p e r i m e n t 64 14. Homing p e r f o r m a n c e o f u n t r e a t e d o. i a c u l o = u s a t F i r s t Beach 69 15. G r a p p l e r I n l e t r e p l a c e m e n t e x p e r i m e n t 73 16. Homing b e h a v i o u r a l o n g G r a p p l e r I n l e t 77 17. Homing b e h a v i o u r a c r o s s G r a p p l e r I n l e t 81 18. Homing b e h a v i o u r i n a r e a s o f d i f f e r e n t e x p o s u r e 86 x i v 19. A r e a f i d e l i t y i n s i t e s o f d i f f e r e n t e x p o s u r e 89 20. F i n a l s t u d y o f r e l a t i v e e x p o s u r e - w e i g h t s t a t i s t i c s o f cement b l o c k s 96 21. Homing b e h a v i o u r a c c o r d i n g t o t o p o g r a p h i c a l r e g u l a r i t y and t u r b u l e n c e 100 22. 0. m a c u l o s u s (15 a r e a s ) t o t a l c i r r i - l e n g t h f u n c t i o n a l r e h r e s s i o n s t a t i s t i c s ( m a l e s and f e m a l e s s e p a r a t e l y and c o m b i n e d ) 120 23. 0. m a c u l o s u s (9 a r e a s ) t o t a l c i r r i - a g e f u n c t i o n a l r e g r e s s i o n s t a t i s t i c s ( m a l e s and f e m a l e s s e p a r a t e l y and c o m b i n e d ) 125 24. 0. m a c u l o s u s (9 a r e a s ) t o t a l c i r r i - a g e by y e a r - c l a s s f u n c t i o n a l r e g r e s s i o n s t a t i s t i c s (males and f e m a l e s c o m b i n e d ) 127 25. E x p e r i m e n t a l m a n i p u l a t i o n c f c i r r i i n 0. m a c u l c s u s f u n c t i o n a l r e g r e s s i o n s t a t i s t i c s f o r i n i t i a l and f i n a l s a m p l e s and F i r s t B e a c h 135 26. Homing p e r f o r m a n c e by age 147 27. Homing p e r f o r m a n c e by y e a r - c l a s s 151 28. Summary o f e x p e r i m e n t a l i n t r o d u c t i o n s i n t o t i d e p o o l e n c l o s u r e 159 29. Homing p e r f o r m a n c e by l e n g t h c l a s s e s 164 30. A n a l y s i s o f r e p l a c e m e n t e x p e r i m e n t s by l e n g t h 168 31. Homing p e r f o r m a n c e o f j u v e n i l e 0. m a c u l o s u s 169 32. Homing p e r f o r m a n c e o f j u v e n i l e 0. m a c u l o s u s k e p t i n t h e l a b o r a t o r y f o r v a r y i n g p e r i o d s p r i o r t o r e l e a s e .. 171 33. Homing p e r f o r m a n c e a f t e r t r a n s p l a n t p o o l s c l e a r e d o f r e s i d e n t f i s h 184 34. Homing p e r f o r m a n c e a f t e r r e m o v a l o f p a i r e d f i n s 193 35. R e l a t i v e homing p e r f o r m a n c e a f t e r f o u r d i f f e r e n t i m p a i r m e n t t r e a t m e n t s 197 36. Homing p e r f o r m a n c e a f t e r f o u r s i m u l t a n e o u s i m p a i r m e n t t r e a t m e n t s 199 37. R e l a t i v e i m p o r t a n c e o f b l i n d n e s s and a n o s m i a 205 X V 38. Homing p e r f o r m a n c e a f t e r s i m u l t a n e o u s b l i n d n e s s and anosmia 206 39 . R e l a t i v e homing p e r f o r m a n c e f o l l o w i n g b l i n d n e s s and an o s m i a by l e n g t h 208 ao . Homing p e r f o r m a n c e a f t e r p o o l " l a n d m a r k s " e x c h a n g e d .. 217 41. C h o i c e t a n k t e s t s of arm p r e f e r e n c e 219 x v i ACKNOWLEDGEMENTS I wish to thank the members of my committee. Dr. J . D. McPhail, Dr. T. G. Northcote and Dr. G. G. E. Scudder f o r t h e i r advice and c r i t i c i s m s o f t h i s t h e s i s , and I am e s p e c i a l l y g r a t e f u l t o my s u p e r v i s o r , Dr. N. J. Wilimovsky, f o r h i s guidance, advice and a s s i s t a n c e i n the f i e l d d u r i n g the course o f t h i s work. T h i s work was conducted out of the Western Canadian U n i v e r s i t i e s Marine B i o l o g i c a l S t a t i o n at Bamfield, and I thank the s t a f f , p a r t i c u l a r l y Myriam Haylock, f o r t h e i r h e l p and patie n c e . My thanks goes to Emmanuel Chundoma, Dave Peacock, P h i l Rhynas, Kent Ross and Rick S t a n l e y f o r h e l p i n g to b u i l d the encl o s u r e and t o Brodie B r o d e r i c k and Barbara Bunting f o r help with i d e n t i f i c a t i o n s of algae and i n v e r t e b r a t e s and a s s i s t a n c e i n the f i e l d on numerous o c c a s i o n s . I a p p r e c i a t e the help of Barbara Bunting, J u l i e C e l e s t i n o and Myriam Haylock who i d e n t i f i e d the algae and i n v e r t e b r a t e s from an experimental tank. I am g r a t e f u l t o Bruce Lea man f o r h i s t h o u g h t f u l c r i t i c i s m s of t h i s t h e s i s . Daphne Hards prepared the h i s t o l o g i c a l s e c t i o n s and Floy Z i t t i n drew most o f the f i g u r e s . The majority o f t h i s work was conducted while I was on a CSIRO Portgraduate Studentship. 1 I. GENERAL INTRODUCTION Var i o u s aspects of homing behaviour have been s t u d i e d i n about a dozen d i f f e r e n t i n t e r t i d a l f i s h e s (Hubbs, 1921; Gersbacher and Denison, 1930; Beebe, 1931; Aronson, 1951, 1971; Wil l i a m s , 1957; Peppar, 1965; Gibson, 1967; Stephens et a l . , 1970; Green, 1971a,b,c, 1973; Khoo, 1971, 1974). The ma j o r i t y of i n t e r t i d a l f i s h examined i n t h i s r e g a r d appear t o show some evidence o f l i m i t e d home range and i n some s p e c i e s , evidence o f the a b i l i t y to r e t u r n to a s m a l l area when d i s p l a c e d , t h a t i s , homing. For only one i n t e r t i d a l f i s h , Bathyqobius soporator (Cuvier and V a l e n c i e n n e s ) , does t h e r e appear to be r e l a t i v e l y c l e a r evidence of the primary sensory mechanism i n v o l v e d : v i s i o n (Aronson, 1951, 1971) . The i n t e r t i d a l f i s h which has r e c e i v e d the most a t t e n t i o n with r e s p e c t to home range, homing behaviour and sensory mechanisms i n v o l v e d i n homing, i s the t i d e p o o l s c u l p i n , O l i g o c o t t u s maculosus G i r a r d , which ranges from northern C a l i f o r n i a t o t h e Bering Sea, K u r i l I s l a n d s and Okhotsk Sea (Hart, 1973)., Gersbacher and Denison (1930) suggested, on the b a s i s of f i n d i n g tagged O. maculosus i n the same pool over a p e r i o d o f at l e a s t 10 days, t h a t the f i s h showed r e l a t i v e l y r e s t r i c t e d movement. Green (1971b) demonstrated t h a t 0. maculosus showed homing behaviour. Subsequently, Khoo (1971, 1974) undertook a comprehensive examination of v a r i o u s a s p e c t s of the homing behaviour of 0. maculosus a t Port Renfrew.- He found, i n c o n t r a s t to the su g g e s t i o n s of Green, and Gersbacher 2 and Denison, that 0. maculosus in d i v i d u a l s r a r e l y r e s t r i c t e d t h e i r natural movement to one pool, and showed that their home range was usually a small group of pools with a maximum extent of about 30 m. He found that 0. maculosus could home from up to 300m away and that the ef f e c t of increasing distance on homing a b i l i t y was modified by wave action. Adverse weather, rough t e r r a i n and deep subtidal areas decreased homing success and there was a difference i n homing performance between naive and experienced f i s h , although after one displacement there was no improvement i n homing performance of repeatedly displaced f i s h . Sex and size (from 4.5 to 9.0 cm t o t a l length) appeared to have no effect on homing performance. From sensory impairment experiments he concluded that touch or taste clues detected by the paired f i n s were not involved i n homing, but that v i s i o n and o l f a c t i o n were, o l f a c t i o n being more important than visi o n . He concluded that 0. maculosus uses o l f a c t i o n and/or some kind of exploratory search process to home. This study was designed to continue the work of Khoo, investigating the homing behaviour of O. maculosus. The two purposes of t h i s study were: to f i n d the causes of the v a r i a b i l i t y i n homing success observed by Khoo and to examine further the sensory mechanisms involved in homing, to determine whether o l f a c t i o n i s the major mechanism involved and whether other mechanisms are also involved. The v a r i a b i l i t y in the percentage of f i s h successfully homing observed by Khoo led him to suggest that there were 3 homing and non-homing members of the population. To attempt to elucidate the factors that cause v a r i a b i l i t y i n homing performance, several approaches were taken. Homing behaviour i n diffe r e n t areas was examined to determine whether any v a r i a b i l i t y existed between areas and i f i t could be related to a particular factor. In addition, homing behaviour was investigated by age, year class and length to determine whether these factors affect homing performance. In the study of length differences i n homing performance, pa r t i c u l a r emphasis was placed on juvenile f i s h . I t was f e l t that following the development of homing behaviour i n juvenile f i s h might be more productive than examination of homing performance i n adults i n which t h i s behaviour i s r e l a t i v e l y well developed. The investigation of the sensory mechanisms involved i n homing behaviour was c h i e f l y designed to c l a r i f y the role of ol f a c t i o n i n homing, since the mixing processes of the i n t e r t i d a l make i t d i f f i c u l t to understand the existence and u t i l i z a t i o n of d i s t i n c t odour streams, as suggested by Khoo, Additional mechanisms were examined to investigate whether they played any role i n homing behaviour. The role of sensory mechanisms i n the homing behaviour of juvenile f i s h was also investigated. In t h i s study, home range i n tidepool areas i s used i n the way i n which i t was used by Khoo (1971) and Gerking (1959), as the area covered by the f i s h during normal t r a v e l (modified from Hayne, 1949). Thus, the home range i s regarded as an area of l i m i t e d extent, c o v e r i n g the t i d e p o o l s i n which an 0. maculosus i n d i v i d u a l i s found. In n o n - t i d e p o o l areas, home range was regarded as a sm a l l area comparable t o a group o f t i d e p o o l s . In t h i s study, the term homing was a l s o used i n the way i t was used by Khoo (1971), as the r e t u r n to t h e home range when e x p e r i m e n t a l l y d i s p l a c e d . T h i s study i s composed o f f i v e p a r t s . Since the e f f e c t s of age and y e a r - c l a s s on homing were to be i n v e s t i g a t e d , i t was necessary t o develop a v a l i d method of age d e t e r m i n a t i o n . Thus the f i r s t s e c t i o n i s concerned w i t h ageing s t u d i e s . I n v e s t i g a t i o n s of b e h a v i o u r a l d i f f e r e n c e s i n homing and morphological d i f f e r e n c e s between p o p u l a t i o n s i n v a r i o u s areas comprise the f o l l o w i n g two s e c t i o n s . The f o u r t h s e c t i o n i s concerned with the i n v e s t i g a t i o n s o f age, year^-class and l e n g t h d i f f e r e n c e s i n homing behaviour. The f i n a l s e c t i o n c o n s i d e r s the r o l e of v a r i o u s sensory mechanisms i n homing. 5 I I . DESCRIPTIONS OF ST DDI SITES UND CAPTURE METHODS 1.Major study s i t e F i r s t Beach F i r s t Beach i s situated on the east side of Trevor Channel i n Barkley Sound (48°49»N,125°10*W) (Figures 1 and 2, s i t e L ). This s i t e was chosen as the major study area because i t offered a large selection of tidepools at both the north and south ends of the beach and because i t permitted access from both Trevor Channel and the head of Bamfield Inlet (Figure 3). The beach i s moderately exposed since prevailing adverse weather (from the southeast and p a r t i c u l a r l y the north) produce r e l a t i v e l y large waves breaking outside the bay. Further description of t h i s area i s provided in appendix 1. The majority of experimental work conducted at F i r s t Beach was carried out i n two groups of tidepools at eith e r end of the southern rocky shelf. The distance between these two groups of pools i s about 60 metres. There were s i x pools i n each group, but f o r most experiments only about four of the s i x pools i n each group were used to trap f i s h . The choice of pools depended largely on the season and abundance of 0. maculosus. Both groups of pools ranged between about the 1 and 2.5 m t i d e l e v e l . Since the v e r t i c a l d i s t r i b u t i o n of O. ma,culosus i n the F i g u r e 1 G e n e r a l l o c a t i o n o f s t u d y s i t e s 125° 10' F i g u r e 2 L o c a t i o n s of study sites Figu re 3 A e r i a l view of F i r s t Beach 9 i n t e r t i d a l i s r e l a t e d t o the s i z e of the f i s h (Green, 1971a), th e r e was some s i z e s e l e c t i v i t y i n the f i s h used i n experiments. At Port Renfrew, Green found t h a t few f i s h l e s s than 3.5 cm ( t o t a l length) occurred below about the 2 m l e v e l and few f i s h l e s s than 5.0 cm occurred below about the 1.5 m l e v e l . Although l a r g e r f i s h o c c u r r e d i n t i d e p o o l s a t a l l l e v e l s , f i s h l a r g e r than 5.5 cm d i d not normally i n h a b i t t i d e p o o l s l e s s than 10 cm deep. At F i r s t Beach, few pools i n the upper i n t e r t i d a l are deeper than 10 cm, so t h e r e are r e l a t i v e l y few l a r g e 0. maculosus at high l e v e l s . Since settlement of 0. maculosus appears t o occur l a r g e l y i n high shallow t i d e p o o l s , there i s a movement of f i s h down the i n t e r t i d a l as they i n c r e a s e i n s i z e . Thus, at F i r s t Beach, some 0* maculosus between about 2.0 t o 3.0 cm ( t o t a l length) can be found i n t i d e p o o l s a t about the 1.5 t o 2 m t i d e l e v e l i n about mid-June. The number o f f i s h l e s s than 4.0 cm i n c r e a s e s i n pools at and below t h i s l e v e l as the summer progresses. 10 2. Other studY s i t e s Exposed study s i t e s Benson I s l a n d (H8°53» N, 125° 22'») i s s i t u a t e d i n the southwest of the Broken Group i n Barkley Sound. The study s i t e chosen on Benson I s l a n d i s a narrow, steep rocky s h e l f f a c i n g n o r t h e a s t t o east ( F i g u r e 1, s i t e A). While the m a j o r i t y o f oceanic s w e l l s and severe storms come from the s o u t h e a s t , the study s i t e i s r e l a t i v e l y unprotected and thus was s e l e c t e d as an exposed s i t e . Cape Beale i s s i t u a t e d at the mouth of B a r k l e y Sound on the e a s t s i d e of Trevor Channel (48°47»N,125°13*«) (Figure 1, s i t e B). The study s i t e chosen at Cape Beale was a narrow, rocky s h e l f d i r e c t l y i n f r o n t of the l i g h t h o u s e f a c i n g west a c r o s s Barkley Sound. The s i t e was chosen as an exposed s i t e s i n c e even on a calm day l a r g e waves can be seen breaking on the o f f s h o r e r e e f s surrounding Cape Beale, and on the shore i t s e l f . B o t a n i c a l Beach at Port Renfrew, h e r e a f t e r r e f e r r e d t o as Port Renfrew, i s l o c a t e d on the west c o a s t of Vancouver I s l a n d near San Juan I n l e t (48°32*N,124°27*tf) (Figure 1, s i t e D). The beach c o n s i s t s of e x t e n s i v e sandstone and s h a l e s h e l v e s . Although i t i s s i t u a t e d i n the S t r a i t of Juan de Fuca, the beach faces i n a westerly and north w e s t e r l y d i r e c t i o n onto 1 1 t h e P a c i f i c Ocean. Thus i t r e c e i v e s t h e f u l l e f f e c t o f P a c i f i c s w e l l s . For t h i s r e a s o n i t was s e l e c t e d as an exposed s i t e . The beach d e s i g n a t e d as Pachena P o i n t i n t h i s s t u d y i s s i t u a t e d on t h e west c o a s t o f Vancouver I s l a n d about one k i l o m e t r e n o r t h o f t h e Pachena P o i n t l i g h t h o u s e (48°**3»N, 125°07« H) ( F i g u r e 1, s i t e C) . The beach f a c e s southwest d i r e c t l y onto t h e P a c i f i c Ocean and t h u s was s e l e c t e d as an exposed s i t e . The upper i n t e r t i d a l i s composed o f a s t e e p l y s l o p i n g g r a v e l beach, below which l i e s a broad f l a t sandstone s h e l f , i n which most o f the e x p e r i m e n t a l work was conducted. On e i t h e r s i d e o f t h i s s h e l f a r e l o w e r r o c k y s h e l v e s w i t h l a r g e r t i d e p o o l s and s c a t t e r e d b o u l d e r s . K i r b y P o i n t i s s i t u a t e d on the southwest c o r n e r o f Diana I s l a n d i n t h e Deer Group (48°51«N, 125°12»W) ( F i g u r e 1, s i t e M) . Two s t u d y s i t e s were used a t K i r b y P o i n t , both c o n s i s t i n g o f r e l a t i v e l y narrow ro c k y s h e l v e s f a c i n g s o u t h w e s t , and t h u s r e c e i v i n g t h e impact o f o c e a n i c s w e l l s . More d e t a i l e d d e s c r i p t i o n s of t h e s e a r e a s a r e p r o v i d e d i n a ppendix 1. Mo d e r a t e l y exposed s t u d y s i t e s Haines I s l a n d i s s i t u a t e d towards t h e s o u t h e r n end o f t h e Deer Group o f i s l a n d s i n B a r k l e y Sound. The s o u t h e a s t s i d e of H a ines I s l a n d c o n s i s t s o f a l a r g e r o c k y s h e l f which i s 12 exposed at low t i d e (48°49.9»N,125°11.7«W). Since the strongest prevailing winds are generally from the southeast, an area on the shelf facing t h i s d i r e c t i o n was chosen as a moderately exposed study s i t e (Figure 2, s i t e H). Helby Island i s situated i n the Deer Group of islands in Barkley Sound. The s i t e selected f o r study i s a rocky shelf on the southwestern side of the island, facing Ohiat Island and Imperial Eagle Channel (48°51 'N, 125°11»5?) (Figure 2, s i t e E) . Although the beach i s somewhat protected by Ohiat Island, the numerous d r i f t logs and absence of low brush just below the tree l i n e suggest that the beach i s moderately exposed. More detailed descriptions of these s i t e s are provided in Appendix 1. Sheltered study s i t e s Grappler Inlet i s situated on the eastern side of Trevor Channel i n Barkley Sound. Two s i t e s i n the i n l e t were chosen as major study s i t e s . One, on the south side of the i n l e t , i s a small r e l a t i v e l y sheltered bay (48°49.9* N, 125°07.7'W) and the second, an extremely sheltered mudflat, adjacent to the Government Wharf i n Port Desire (48°49.8» N,125°07.6'S) (Figure 2, s i t e s I and J r e s p e c t i v e l y ) . A second s i t e on Haines Island was selected as a sheltered study s i t e (48°50.1»N,125°11.7»W). On the eastern 1 3 s i d e of the i s l a n d i s a l a r g e i r r e g u l a r area of rock exposed at low t i d e . Between the i s l a n d i t s e l f and the rocky s h e l f i s an extremely l a r g e t i d e p o o l , which p a r t i a l l y d r a i n s at low t i d e i n t o Dodger Channel (Figure 2, s i t e G). The pool i s r e l a t i v e l y p r o t e c t e d from s w e l l s from T r e v o r Channel by the rocky outcrops on i t s southern and e a s t e r n s i d e s . One s i t e on the Haines I s l a n d s i d e o f Dodger Channel was s e l e c t e d f o r study (-48°50. 1 »N, 125°11. 8»W) ( F i g u r e 2, s i t e F ) . The s i t e was s e l e c t e d as a s h e l t e r e d s i t e s i n c e i t remains calm during most storms. A bed of Z o s t e r a marina extends along the Haines I s l a n d shore of Dodger Channel and the s i t e chosen was at the eastern end o f the bed. An area of the i n t e r t i d a l between Ranee I s l a n d and the south east s i d e of Bamfield I n l e t (48°49»N, 125°8 * W) was chosen as a s h e l t e r e d study s i t e (Figure 2, s i t e K). At low t i d e t here i s a shallow channel of water surrounding Sance i s l a n d and j o i n i n g up with Bamfield I n l e t . Two s p e c i f i c areas were chosen f o r study. One was a l a r g e t i d e p o o l adjacent to Ranee I s l a n d , which i s i s o l a t e d from the main channel a t low t i d e . The other was an area i n the main channel adjacent to the mainland. More d e t a i l e d d e s c r i p t i o n s of these s i t e s are provided i n Appendix 1. 14 3. Enclosure A large enclosure containing a r t i f i c i a l tidepools and spanning the i n t e r t i d a l from about the 1 m level to about the 3.5 a l e v e l was constructed i n the small bay i n Grappler Inlet (48o49.9»N,125<>07.7*W) {Figure 2, s i t e I ) . The enclosure was designed to serve several purposes in the study of homing behaviour of 0. maculosus. , In homing experiments conducted i n the f i e l d , a large percentage of 0. maculosus indivi d u a l s which do not home are l o s t for study. In a completely enclosed system of tidepools, those f i s h which do not home may be c o l l e c t e d for examination of any differences between homing and non-homing 0. maculosus. The other major reason for the construction of the enclosure was to investigate the pool f i d e l i t y and homing behaviour of juvenile 0. maculosus. Following the development of homing behaviour of tagged juvenile f i s h i n the f i e l d as they moved into lower tidepools would e n t a i l tagging large numbers of small f i s h . The r e l a t i v e l y controlled environment of the enclosure offered the p o s s i b i l i t y of introducing large numbers of juvenile Q_. maculosus and monitoring t h e i r movements and homing behaviour much more readily. The enclosure was constructed on a r e l a t i v e l y steep rocky outcrop i n the otherwise gently sloping bay. The 15 framework of the e n c l o s u r e , 10 m l o n g , 3.5 m wide and 5 m high at the seaward end was made of two f I shaped c o n s t r u c t i o n s of 7.7 cm g a l v a n i z e d pipe embedded i n concrete at e i t h e r end. On top of these supports two l o g s were lashed t o the outer edges of the h o r i z o n t a l pipes. Wooden poles embedded i n c o n c r e t e served as i n t e r m e d i a t e s u p p o r t s along the s i d e s of the e n c l o s u r e . S e v e r a l d i a g o n a l and c r o s s supports were added t o t h e e n c l o s u r e t o i n c r e a s e s t a b i l i t y (Figure 4 ) . To e l i m i n a t e escape of i n t r o d u c e d f i s h the fo u r s i d e s of t h e e n c l o s u r e were covered with an e x t e r i o r l a y e r of 2. 5 cm mesh c h i c k e n wire and an i n t e r i o r l a y e r o f f i b r e g l a s s window s c r e e n i n g . The s m a l l mesh o f the window s c r e e n i n g served to prevent escape of j u v e n i l e f i s h . In the f i r s t summer o f o p e r a t i o n , the c h i c k e n wire and window screening were atta c h e d c o n t i n u o u s l y down the s i d e s and acr o s s the bottom o f the enc l o s u r e . T h i s proved u n s a t i s f a c t o r y because walking on the mesh produced l a r g e numbers of h o l e s . In the second summer, the mesh and c h i c k e n wire on the s i d e s were fastened t o 2.5 cm x 10 cm planks embedded i n c o n c r e t e at the base of the s i d e s . The bottom was l e f t uncovered. Deep (30 cm) and shallow (15 cm) p l a s t i c dishpans (40 cm i n diameter) served as t i d e p o o l s . These were a t t a c h e d with polypropylene l i n e s t i e d t o e y e b o l t s embedded i n the s u b s t r a t e with h y d r a u l i c cement. T h i s arrangement allowed a l t e r a t i o n o f the p o s i t i o n s of p a r t i c u l a r t i d e p o o l s . G r a v e l , pebbles and s m a l l r o c k s with attached Fucus sp. and N x t i l u s e d u l i s were Figure 4 Enclosure from outside (above) and i n s i d e (below) 17 placed i n the t i d e p o o l s . A shallow c o n c r e t e trough was c o n s t r u c t e d a t the seaward end of the e n c l o s u r e to enable the f i s h which d i d not r e t u r n t o a t i d e p o o l at low t i d e but followed the r e c e d i n g water l e v e l t o remain i n water at t i d e l e v e l s lower than t h a t o f the seaward end of the e n c l o s u r e . A l a r g e wooden plank was placed on top of the c r o s s supports about one metre from the top o f the e n c l o s u r e to enable viewing from above at high t i d e . Around the o u t s i d e of the e n c l o s u r e , a s m a l l boom o f l o g s and t i r e s was c o n s t r u c t e d to provide a p a r t i a l b a r r i e r t o boat wake, which had severe e f f e c t s on the s c r e a n i n g . A g r e a t e r problem was the e f f e c t o f waves and s t r o n g winds caused by winter storms. S e v e r a l severe storms were s u f f i c i e n t t o destroy the s c r e e n i n g . Thus, experiments i n the e n c l o s u r e were o n l y f e a s i b l e during the summer months. 18 4.Capture methods Two methods of ca p t u r e were used. The vast m a j o r i t y of 0. f a c u l o s u s used i n homing experiments were caught using wire minnow t r a p s . ft p i e c e of mussel ( u s u a l l y M y t i l u s c a l i f q r n i a n u s ) was atta c h e d t o a hook c e n t r a l l y l o c a t e d i n the t r a p . Traps were placed i n pools f o r about f o u r hours around low t i d e (depending on weather c o n d i t i o n s and t i d e h e i g h t ) . When r e c i p r o c a l t r a n s p l a n t s were being conducted and an i n s u f f i c i e n t number o f 0. maculosus had been captured from one group of p o o l s , s m a l l dipnets were sometimes used to c a t c h the necessary remaining f i s h . Minnow t r a p s c o l l e c t few f i s h l e s s than about 3.5 to 4.0 cm ( t o t a l length) because t h e s i z e of the wire mesh a l l o w s s m a l l e r f i s h t o enter and e x i t anywhere i n the t r a p . Thus, s i n c e the m a j o r i t y of homing experiments were conducted i n pools up t o about the 2.5 m t i d e l e v e l , j u v e n i l e s f o r s p e c i f i c s t u d i e s ( f i s h l e s s than about 3.5 t o 4.0 cm) were c o l l e c t e d with s m a l l d i p n e t s . To c a t c h f i s h f o r c i r r i counts and age dete r m i n a t i o n s t u d i e s a combination of minnow t r a p s and d i p n e t s were used. I n pool p o p u l a t i o n s t u d i e s , pools were b a i l e d by bucket u n t i l very l i t t l e water remained.. F i s h were then captured using s m a l l d i p n e t s and by hand. 19 I I I . AGE DETERMINATION IN 0. BACULOSUS To evaluate the e f f e c t of age and y e a r - c l a s s on homing behaviour and other f a c t o r s , i t was necessary to develop a v a l i d method f o r determining the age o f 0. maculosus i n d i v i d u a l s . I n i t i a l l y , r i n g s on o t o l i t h s were i n t e r p r e t e d and v a l i d a t i o n of t h i s method of ageing was attempted by examining r i n g s on vertebrae and by using the g r a p h i c a l method of s e p a r a t i n g age groups devised by C a s s i e (1954). !• Methods Age determination using o t o l i t h s F o l l o w i n g c o l l e c t i o n , 0. maculosus i n d i v i d u a l s were preserved i n 10% f o r m a l i n . Within 48 hours of c o l l e c t i o n and a f t e r s o a k i n g i n f r e s h water, the f i s h were measured ( t o t a l l e n g t h ) 1 with a d i a l c a l i p e r t o the nearest 0.005 cm, sexed and both l e f t and r i g h t o t o l i t h s removed and s t o r e d i n g l y c e r i n . O t o l i t h s were examined while immersed i n water under r e f l e c t e d l i g h t on a black s u r f a c e , using 30 x m a g n i f i c a t i o n . / *A11 length measurements of 0. maculosus i n t h i s study were made of t o t a l l e n g t h , except i n t h e a n a l y s i s o f m e r i s t i c and morphometric c h a r a c t e r s , where standard l e n g t h was used. For convers i o n s from t o t a l l e n g t h t o standard length and v i c e v e r s a , see Appendix 2. 20 I n i t i a l l y , a l a r g e number of o t o l i t h s were examined t o determine whether t h e r e was evidence o f growth r i n g s . A f t e r i t was e s t a b l i s h e d that a c o n s i s t e n t p a t t e r n of r i n g s e x i s t e d , at l e a s t two readings were made o f one o t o l i t h from each p a i r . E i t h e r o t o l i t h was used, s i n c e t h e r e was no d i f f e r e n c e between l e f t and r i g h t o t o l i t h s i n the number or form of opague and h y a l i n e r i n g s . The numbers of opague and h y a l i n e zones and the consequent age of the f i s h was noted. Disagreements between the f i r s t and second r e a d i n g s were r e s o l v e d by f u r t h e r examination of both o t o l i t h s u n t i l a d e c i s i o n was reached. O t o l i t h s were read without p r i o r r e f e r e n c e t o length or sex. Six c o l l e c t i o n s t o t a l l i n g 365 0. maculosus were made at F i r s t Beach. The c o l l e c t i o n s were taken on 9 February, 1976; 1 June, 1976; 21 J u l y , 1976; 29 September, 1976; 5 December, 1976 and 12 February, 1977. F u n c t i o n a l r e g r e s s i o n s of le n g t h on age were c o n s t r u c t e d t o examine the nature of the growth r e l a t i o n s h i p shown by o t o l i t h s . Regressions were c a l c u l a t e d s e p a r a t e l y f o r males and females. Since e x t e r n a l sex dete r m i n a t i o n i s impossible f o r 0. maculosus j u v e n i l e s l e s s than 3.50 cm ( t o t a l l e n g t h ) , age data f o r t h i s group o f f i s h (22 f i s h ) were i n c l u d e d i n both the male and female r e g r e s s i o n s . The r e g r e s s i o n s were compared to determine whether they were s t a t i s t i c a l l y d i f f e r e n t , and, i f not, the data were combined t o form a s i n g l e r e g r e s s i o n . In the combined r e g r e s s i o n t h e data from j u v e n i l e f i s h were i n c l u d e d only once. 21 Age determination using vertebrae To attempt t o v a l i d a t e the r e s u l t s of age determination u s i n g o t o l i t h s , the vertebrae and o t o l i t h s were e x t r a c t e d from 0. maculosus i n d i v i d u a l s i n two of the c o l l e c t i o n s made at F i r s t Beach. These c o l l e c t i o n s were taken on 5 December, 1976 and 12 February, 1977 and i n v o l v e d 177 f i s h . , Vertebrae were e x t r a c t e d a f t e r measuring and sexing the f i s h and removing the o t o l i t h s . An o b l i q u e forward p o i n t i n g cut was made between the f i r s t and second d o r s a l f i n s and fo r c e p s were used to hold the vertebrae while t w i s t i n g u n t i l the v e r t e b r a l column broke and i t was p o s s i b l e t o e x t r a c t s e v e r a l v e r t e b r a e . The v e r t e b r a e were r i n s e d i n water and placed i n a s o l u t i o n of t r y p s i n and water t o d i g e s t the a t t a c h e d t i s s u e . , A f t e r s e v e r a l days, the ve r t e b r a e were removed from the t r y p s i n s o l u t i o n , r i n s e d i n water and allowed t o dry f o r s e v e r a l days, p r i o r to being s t o r e d i n g l a s s v i a l s . Examination of the vertebrae was made under 30 x m a g n i f i c a t i o n on a black s u r f a c e u s i n g r e f l e c t e d l i g h t . A s i n g l e v e r t e b r a was c u t away from the group and the centrum examined f o r evidence of growth r i n g s . A f t e r examining a l a r g e number of v e r t e b r a e to determine whether there was any c o n s i s t e n c y i n the p a t t e r n s o f r i n g s , a l l the v e r t e b r a e were read and t h e number of opaque and h y a l i n e zones and the age of the f i s h were noted. Two r e a d i n g s were made of a l l v e r t e b r a e 22 and disagreements were r e s o l v e d by f a r t h e r r e f e r e n c e t o the s i n g l e v e r t e b r a e x t r a c t e d and i f necessary, t o other v e r t e b r a e e x t r a c t e d . Readings of v e r t e b r a e were made without p r i o r r e f e r e n c e to l e n g t h and sex. Although o t o l i t h s were a l s o e x t r a c t e d from these f i s h , readings of vertebrae were made without r e f e r e n c e to o t o l i t h r e a d i n g s . F u n c t i o n a l r e g r e s s i o n s of l e n g t h on age were c a l c u l a t e d s e p a r a t e l y f o r males and females t o examine the growth r e l a t i o n s h i p . As i n the case of o t o l i t h s , data from f i s h l e s s than 3.50 cm ( t o t a l length) were i n c l u d e d i n both male and female r e g r e s s i o n s , but onl y once i n the combined r e g r e s s i o n , which was c a l c u l a t e d i f there was no s i g n i f i c a n t d i f f e r e n c e between the separate r e g r e s s i o n s f o r each sex. A comparison of the age of each f i s h determined by o t o l i t h s and ve r t e b r a e was made us i n g the method of Yasuda (1940) to determine the degree of agreement between the two methods. A n a l y s i s of l e n g t h frequency data During the course o f t h e study a c o n s i d e r a b l e number of c o l l e c t i o n s of 0. maculosus were made a t F i r s t Beach f o r v a r i o u s purposes: pool p o p u l a t i o n s t u d i e s , homing behaviour experiments, i n v e s t i g a t i o n o f morphological c h a r a c t e r i s t i c s and ageing s t u d i e s . Except i n the case of f i s h c o l l e c t e d f o r the l a s t two purposes, a l l f i s h were measured with a r u l e r t o the 23 nearest 0.1 cm { t o t a l length) and sexed. F i s h used f o r morphological and ageing s t u d i e s were measured with a d i a l c a l i p e r t o the n e a r e s t 0.005 cm and sexed. For the purposes of t h i s a n a l y s i s , the l e n g t h s were rounded to the nearest 0.1 cm. The l e n g t h data from these c o l l e c t i o n s were combined i n the case of c l o s e l y a s s o c i a t e d c o l l e c t i o n s and were used to c o n s t r u c t length-frequency histograms spanning a p e r i o d from May, 1975 t o February, 1977. The l e n g t h - f r e q u e n c y histogram from the October, 1975 c o l l e c t i o n was s e l e c t e d (because of the r e l a t i v e l y l a r g e sample s i z e ) f o r a n a l y s i s of age groups u s i n g the g r a p h i c a l method developed by C a s s i e (1954). A percent cumulative frequency curve was c o n s t r u c t e d on p r o b a b i l i t y paper, the p o i n t s o f i n f l e c t i o n determined and the v a r i o u s aqe groups e x t r a c t e d . A length-rage f u n c t i o n a l r e g r e s s i o n was then c a l c u l a t e d u s i n g the o r i g i n a l l e n g t h data as c l a s s i f i e d by age from the g r a p h i c a l a n a l y s i s . The r e g r e s s i o n o b t a i n e d was compared with the length-age r e g r e s s i o n s obtained using o t o l i t h s and v e r t e b r a e . A s i g n i f i c a n t d i f f e r e n c e between th e t h r e e r e g r e s s i o n s might suggest t h a t age d e t e r m i n a t i o n u s i n g o t o l i t h s was an i n v a l i d technigue. As a f u r t h e r p o s s i b l e c o r r o b o r a t i o n of age groups i n the p o p u l a t i o n , the length-frequency histograms over time were examined to determine whether the modes of s i z e groups, corresponding to d e r i v e d ages, c o u l d be f o l l o w e d over the months 24 repr e s e n t e d throughout the p o p u l a t i o n . F i n a l l y , data from tagged f i s h measured and sexed when i n i t i a l l y caught f o r b e h a v i o u r a l experiments and subsequently measured at a l a t e r date when re t r a p p e d , were i n v e s t i g a t e d t o determine whether they provided any support f o r the growth r a t e s suggested by the methods o u t l i n e d above. These data were c o l l e c t e d i n t e r m i t t e n t l y over t h e d u r a t i o n of the r e s e a r c h . F i r s t Beach To enable the determination o f age f o r any given l e n g t h of 0. maculosus, p r e d i c t i v e r e g r e s s i o n s of age on l e n g t h were c a l c u l a t e d s e p a r a t e l y from data obtained from o t o l i t h r e a d ings. As i n the case o f t h e length-age r e g r e s s i o n s , data f o r 0. maculosus l e s s than 3.5 cm ( t o t a l length) were used i n both male and female r e g r e s s i o n s s i n c e sex de t e r m i n a t i o n was not p o s s i b l e . The r e g r e s s i o n s were compared t o determine whether they were s i g n i f i c a n t l y d i f f e r e n t , and i f not, they were combined i n t o one age-length r e g r e s s i o n , i n c l u d i n g the data from j u v e n i l e f i s h only once. 25 Other areas C o l l e c t i o n s of 0. maculosus were made at e i g h t other areas on the west c o a s t of Vancouver I s l a n d to determine t h e age-length r e l a t i o n s h i p i n each l o c a t i o n f o r use i n c i r r i a n a l y s i s . C o l l e c t i o n s were made at Port Renfrew, Pachena P o i n t , Benson I s l a n d , Cape B e a l e , Helby I s l a n d , Haines I s l a n d ( l a r g e t i d e p o o l ) , Grappler I n l e t (bay) and Ranee I s l a n d . In each case, f i s h were f i x e d i n 10% f o r m a l i n immediately f o l l o w i n g c o l l e c t i o n . Within HQ hours and a f t e r r i n s i n g with water, the f i s h were measured with a d i a l c a l i p e r t o t h e nearest 0.005 cm ( t o t a l length) sexed and the l e f t and r i g h t o t o l i t h s removed and sto r e d i n g l y c e r i n . The procedures f o l l o w e d i n r e a d i n g the o t o l i t h s were the same as o u t l i n e d f o r o t o l i t h s e x t r a c t e d from 0. maculosus i n d i v i d u a l s from F i r s t Beach. For each area, p r e d i c t i v e age-length r e g r e s s i o n s were c a l c u l a t e d s e p a r a t e l y f o r males and females. I n cases where j u v e n i l e 0. maculosus l e s s than 3.50 cm ( t o t a l length) had been c o l l e c t e d , the age-length data were used i n both male and female r e g r e s s i o n s , and onl y once i n the combined r e g r e s s i o n c a l c u l a t e d i f t h e r e was no s i g n i f i c a n t d i f f e r e n c e between the separate male and female r e g r e s s i o n s . The r e g r e s s i o n s f o r a l l areas ( i n c l u d i n g F i r s t Beach) were compared t o determine whether t h e r e were any d i f f e r e n c e s i n the age-length r e l a t i o n s h i p between l o c a t i o n s . 26 2. R e s u l t s O t o l i t h s From i n s p e c t i o n of o t o l i t h s i t i s e v i d e n t t h a t the f i r s t summer growth zone appears as a broad opaque band of numerous f i n e r almost h e m i s p h e r i c a l r i n g s surrounding the c e n t r a l nucleus (Figure 5). T h i s opaque zone does not u s u a l l y form a complete c i r c l e . The f i r s t winter zone i s {usually) a narrower h y a l i n e band. Opaque growth zones i n the second and subsequent summer are g e n e r a l l y narrower than t h a t of the f i r s t summer and form complete c i r c l e s . These opaque growth zones are c l e a r l y separated by t r a n s l u c e n t h y a l i n e zones (Figure 5). An i n d i r e c t i n d i c a t i o n of the v a l i d i t y of o t o l i t h readings i s the occurrence of a broad opague band and a t h i n h y a l i n e zone i n j u v e n i l e f i s h caught i n l a t e summer., S t e i n (1973) i n v e s t i g a t i n g l a b o r a t o r y reared o. maculosus l a r v a e i n C a l i f o r n i a found t h a t the adoption of a b e n t h i c h a b i t a t occurred s i x t o seven weeks a f t e r hatching and t h a t a f t e r 51 days, one j u v e n i l e was 12.2 mm and metamorphosis was w e l l advanced. Thus j u v e n i l e s c o l l e c t e d i n August can be expected to have been spawned e a r l i e r t h a t year ( a l s o see Atkinson, 1939). The onset of growth i n the second summer as shown by o t o l i t h s may s t a r t as e a r l y as February or as l a t e as Hay, Age 1 Age 2 1.0 mm Age 3 Figure 5 Otol i t h s of O. maculosus showing opaque and hyaline zones ( a l l taken on 30 August) 28 depending on l o c a t i o n and probably seasonal c o n d i t i o n s . I t appears t h a t f i s h showing s m a l l opaque growth zones f o r the f i r s t summer*s growth commence the second summer's growth p r i o r to f i s h showing a wide growth zone f o r the f i r s t summer. , The c e s s a t i o n of y e a r l y growth, as shown by o t o l i t h s , appears t o occur sometime a f t e r J u l y . Again f i s h with r e l a t i v e l y s m a l l growth zones appear to continue growing l o n g e r than f i s h with wide growth zones. For the f u n c t i o n a l r e g r e s s i o n s of length-age f o r males and females s e p a r a t e l y {Figure 6) , l o g t o the base 10 t r a n s f o r m a t i o n s o f the age v a l u e s were made as suggested by the untransformed data. I n s p e c t i o n of the 95% c o n f i d e n c e l i m i t s o f v (slope) of the r e g r e s s i o n s (Table 1) r e s u l t s i n r e j e c t i o n o f the n u l l hypothesis that males grow more r a p i d l y than females. Thus the length-age data f o r males and females were combined t o produce a s i n g l e r e g r e s s i o n . Vertebrae The opaque and h y a l i n e zones are more d i f f i c u l t t o see i n vertebrae than o t o l i t h s . Frequent moving of the v e r t e b r a i s necessary t o permit the l i g h t t o shine through the centrum a t an angle which a l l o w s r e s o l u t i o n of the r i n g s . However the p a t t e r n s of r i n g s are s i m i l a r t o those of o t o l i t h s except t h a t on vertebrae there are f i n e r i d g e s i n the opaque zones (which Chadwick (1976) i n t e r p r e t e d as annual marks) (Figure 7 ) . The 29 E .0. c First Beach O. maculosus female (otoliths) . Y= 4., 4 2 0 + 5.4 ^2 x log X N= 2 28 8. 7. 6. 5. 4. 3. 2. 0.2 Age (years) First Beach O. maculosus male (otoliths) Y= 4. 4 4 6 + 5. 1 3 8 x log X .N= 1 6 0 8. 7. 6. 5. /—\ S 4. o> 3 0) 1. 0.2 1. Age (years) Figure 6 Length-age r e g r e s s i o n s of F i r s t Beach 0. maculosus determined by o t o l i t h s (males and females separately) T a b l e 1 F i r s t Beach O l i g oc o 11 u s m ac u 1 o sg s ( o t o l i t h s ) Length-age f u n c t i o n a l r e g r e s s i o n s t a t i s t i c s l o g x vs y: y = u + v l o g x S t a t i s t i c Males Females 4.420 5.138 5.499 Lower 95% c o n f i d e n c e 4.511 5.021 l i m i t of v Opper 95% c o n f i d e n c e 5.765 5.977 l i m i t of v 159 228 31 Figure 7 Vertebrae of age 3 0. maculosus showing opaque and hyaline zones ( a l l taken on 5 December) 32 position of these ridges does not always correspond with the edges of the opague growth zones which were used in t h i s study. Figure 8 shows the calculated length-age regressions for males and females separately as determined by vertebrae, again, inspection of the 95% confidence l i m i t s of v (slope) of the regressions (Table 2) r e s u l t s i n rejection of the n u l l hypothesis that males grow more rapidly than females. Thus the length-age data for males and females were combined i n a si n g l e regression. Graphical analysis of 1enqth-frequency d§ta Graphical analysis of a length-frequency d i s t r i b u t i o n using the method of Cassie (1954) (Figure 9), provides the mean lenqths f o r each aqe group which can be compared with the mean lengths for each age from o t o l i t h and vertebrae analysis (Table 3). Although the standard deviations for the mean lenqths at each age derived from Cassie*s method are rather large, there i s f a i r l y good agreement i n mean lengths between the three methods. The small sample numbers at the upper end of the length d i s t r i b u t i o n and the absence of any f i s h f o r several length values make inter p r e t a t i o n of the upper end of the percent cumulative frequency curve somewhat d i f f i c u l t . While the i n f l e c t i o n point at 98.5% t h e o r e t i c a l l y marks the upper length of the four year age group, the paucity of data (four f i s h unevenly distributed) for the remaining four lengths 33 F i r s t B e a c h O . m a c u l o s u s f e m a l e ( v e r t e b r a e ) Y= 3 . 5 3 5 " ^ 7. 9 7 8 x l o g X N = 1 1 4 8, 7. 6. I 51 O) 4.. OJ 31 2 1.1 0.2 1. A g e ( y e a r s ) F i r s t B e a c h O . m a c u l o s u s m a l e ( v e r t e b r a e ) Y= 3 . 3 9 4 + 8 . 2 6 9 x l o g X N= 7 3 8. 7. 6. S 5. si cn 4 c OJ 3 2. 1 0.2 1. A g e ( y e a r s ) F i g u r e 8 Length-age r e g r e s s i o n s of F i r s t Beach O. maculosus determined by v e r t e b r a e (males and females s e p a r a t e l y ) Table 2 F i r s t Beach O l i g o c o t t u s m a c u l o s u s ( v e r t e b r a e ) Length-age f u n c t i o n a l r e g r e s s i o n s t a t i s t i c s l o g x vs y: y = u + v l o g x S t a t i s t i c Hales Females u 3.394 3.535 v 8.269 7.978 Lower 95% c o n f i d e n c e 7.047 7.214 l i m i t of v Upper 95% c o n f i d e n c e 9.492 8.743 l i m i t of v N 73 114 100 2 y i r -o -z. LU 8.0 6.0 4.0 2.0 OCTOBER, 1975 N=278 o -o-J l L -1 1 1 1 1 1 I I I I I I I I I 0.1 12 5 10 50 90 CUMULATIVE FREQUENCY (%>) 99.99 F i g u r e 9 Length f r e q u e n c y a n a l y s i s o f age groups u s i n g C a s s i e ' s method LA cn T a b l e 3 Hean l e n g t h s (cm) f o r each age group determined by t h r e e d i f f e r e n t methods Length O t o l i t h s Vertebrae C a s s i e ' s S t a t i s t i c s method x 4.21 4.02 3.9 Age 1 s.d. .73 .38 . 30 N 127 26 89 x 5.01 4.99 5.5 Age 2 s.d. , .96 1.19 2.41 N 194 119 111 x 6.49 6.14 6.4 Age 3 s.d. .60 .84 3.49 N 43 32 67 x 7.30 7.3 Age 4 s.d. .21 N 1 7 x 7.8 Age 4+ s.d. .13 N 4 37 t h e o r e t i c a l l y c l a s s i f i e s them as four plus age group f i s h although they probably belong to the f o u r year age group. In the c a l c u l a t i o n of t h e length-age r e g r e s s i o n u s i n g the i n f o r m a t i o n obtained from C a s s i e ' s method (F i g u r e 10), f i s h of the f o u r plus age group were not c o n s i d e r e d s i n c e a d e f i n i t e age c o u l d not be a s c r i b e d to them. For the purposes o f comparison the r e g r e s s i o n s c a l c u l a t e d f o r males and females (combined) from o t o l i t h and v e r t e b r a e a n a l y s i s a r e a l s o shown i n F i g u r e 10. I n s p e c t i o n of the r e l e v a n t s t a t i s t i c s f o r the t h r e e r e g r e s s i o n s (Table 4) suggests t h a t t h e r e i s good agreement between the growth r e l a t i o n s h i p s d e s c r i b e d by o t o l i t h s and C a s s i e ^ s method, but t h a t growth de s c r i b e d by vertebrae may not f i t i n t o t h i s p a t t e r n . S e v e r a l reasons may account f o r the d i f f e r e n c e between the r e g r e s s i o n s f o r o t o l i t h s and v e r t e b r a e . Although t h e r e i s agreement between the age determined by vertebrae and o t o l i t h s f o r 86% of the f i s h from which both were e x t r a c t e d (Table 5 ) , the Kolmogorov-smirnov t e s t ( S i e g e l , 1956) shows a s i g n i f i c a n t d i f f e r e n c e between the two methods i n age d e t e r m i n a t i o n (p<.05). Examination of each age group i n d i v i d u a l l y r e v e a l s no s i g n i f i c a n t d i f f e r e n c e s between the methods f o r age one or two f i s h (p>.05), but a s i g n i f i c a n t d i f f e r e n c e f o r age t h r e e f i s h (p<.05). Thus, there i s a tendency f o r data d e r i v e d from o t o l i t h s from o l d e r f i s h t o show more r a p i d growth than that d e r i v e d from vertebrae. Vertebrae appear to be a s u c c e s s f u l method o f v a l i d a t i n g age determination using o t o l i t h s , a t l e a s t 38 First Beach O . macu losus otoliths First Beach O. maculosus C a s s i e curve 8 7. 6. 5. 4. 3. 2. Y= 4. 509 + 5.076 x log X N=3 65 Y= 4.340 + 4.892 x | o g X N=274 \ . _ 8. 0.2 7. 6. 5 & 5. P 4. cu _ J 3, 2. A g e (years) 0.2 A g e (years) First B e a c h Q. maculosus vertebrae Y« 3. 570 +• 7.805 x log X N=178 8 7. 6 fc 5 a c 3. 2 1 0.2 4. A g e (years) F i g u r e 10 Length-age r eg re s s ions of F i r s t Beach 0 . maculosus determined by o t o l i t h s , ve r tebrae and l eng th frequency a n a l y s i s (males and females combined) Table 4 O l i g o c o t t u s maculosus ( F i r s t Beach) Length-age r e g r e s s i o n s t a t i s t i c s from three d i f f e r e n t methods of age d e t e r m i n a t i o n l o g x vs y: y = u -f v l o g x S t a t i s t i c O t o l i t h s Vertebrae C a s s i e * s method u 4.509 3.570 4.340 v 5.076 7. 805 4.892 Lower 95% c o n f i d e n c e 4.702 7.162 4.708 l i m i t of v Upper 95% c o n f i d e n c e 5.451 8.447 5.076 l i m i t of v H 365 178 274 Table 5 Comparison o f age determined by o t o l i t h s and vertebrae of the same Oli.ggcottus maculosus i n d i v i dua Is V e r t e b r a l O t o l i t h age age ( d i f f e r e n c e from vertebrae) (years) -1 0 +1 1 0 25 1 2 8 107 4 3 11 21 0 % of 10.7 86.4 2.8 t o t a l +: age determined by o t o l i t h s greater than by v e r t e b r a e 0: age determined by o t o l i t h s egual to t h a t by vertebrae -: age determined by o t o l i t h s l e s s than by v e r t e b r a e 41 for age one and two f i s h . The other possible reason for the difference between the regressions i s that the samples f o r vertebrae analysis contain few juveniles less than 3.50 cm (total length) and few f i s h i n the one year age group, compared with the data for o t o l i t h and length-freguency analysis. „ Taking these factors into consideration, there appears to be good agreement i n age determination between o t o l i t h s and Cassie's method of length-freguency analysis, and good agreement between these methods and vertebrae for at least age one and two f i s h . Further va l i d a t i o n of two major age groups and progressively smaller numbers of three and four year age group f i s h e x i s t i n g i n the population i s provided by analysis of length-frequency histograms over time (Figure 11). The variation in the size of any one length class i s a r e f l e c t i o n of the purpose for which, and the r e l a t i v e height of the pool i n which, the f i s h were caught. Collections for behavioural experiments (in pools up to about the 2.5 m level) tended to produce more larger sized f i s h than pool population c o l l e c t i o n s (in pools around the 2 to 3 m l e v e l ) . Following the modes over the months shown makes i t evident that the young of the year appear i n pools below about 3 m between May and J u l y , that the majority of growth takes place s t a r t i n g sometime between February and May (probably A p r i l or early May) and continues u n t i l about July or August, after which there i s very l i t t l e growth ( p a r t i c u l a r l y i n older fish) u n t i l the following spring. The data suggest that the young of the year appear i n lower 15 15 15 15 1.0 N=75 42 • MAY 25, 26, 29, 1975 N = 135 SEPT 4 5 1975 N = 278 t l J i l OCT. 30, 31, NOV. 11, 1975 n ^  N=76 MAY 12, 1976 JULY 20, 23, 28, 1976 N = 217 Uy AUG. 8,9,10,12, 1976 N=230 I | „ AUG. 25,26, 1976 N=129 P] rn PI m SEPT. 29, 30, -1976 N=92 i j DEC. 5, 1976 m a N=206 M FEB. 12, 1977 h i 3.0 5.0 7.0 9.0 L E N G T H (CM) F i g u r e 11 Length frequency histograms of 0. maculosus t i d e p o o l s a t a mean s i z e o f about 3.0 cm and grow t o a mean s i z e of about 4.0 cm by the end o f one growing season., In t h e i r second year they appear to grow t o about 6.0 cm mean s i z e and i n t h e i r t h i r d year t o about 7.5 cm mean s i z e . While no f i s h have been tagged p r i o r to the summer growth p e r i o d and thus no d i r e c t estimate of growth over the e n t i r e p e r i o d i s a v a i l a b l e , the amount of growth shown by tagged f i s h i s not i n c o n s i s t e n t with o t h e r d e r i v e d v a l u e s , although i t may be somewhat lower (Table 6 ) . , One f i s h which was tagqed i n mid-summer 1976 and r e c a p t u r e d i n mid-summer 1977 showed growth c o n s i s t e n t with t h a t d e s c r i b e d by the length-frequency histograms. I t i s e v i d e n t t h a t very l i t t l e , i f any growth occurs a f t e r September u n t i l the f o l l o w i n g s p r i n q . The data are i n s u f f i c i e n t to conclude t h a t t a q q i n q r e t a r d s qrowth, as has been found f o r other f i s h ( S i c k e r , 1971). Age-length r e l a t i o n s h i p s F i r s t Beach For the r e g r e s s i o n s c a l c u l a t e d f o r males and females (Figure 12 and Table 7) l o g to t h e base 10 t r a n s f o r m a t i o n s were made of both age and l e n g t h data. Both r e g r e s s i o n s are s i g n i f i c a n t (p<.01). On the b a s i s o f the r e s u l t s from a n a l y s i s of c o v a r i a n c e , which showed no s i g n i f i c a n t d i f f e r e n c e s between male and female r e g r e s s i o n s i n v a r i a n c e s , s l o p e s or i n t e r c e p t s T a b l e 6 Growth of tagged Q l i g o c o t t u s maeulosus i n d i v i d u a l s Month f i r s t Month l a s t I n i t i a l F i n a l Growth trapped trapped length l e n g t h (cm) (cm) (cm) May October December August October November J u l y September October October November 4.0 5.7 1.7 5.2 6.1 0.9 5.7 6. 5 0.8 5.7 7.8 2.1 4.7 5. 4 0.7 5.1 5.2 0.1 5.5 5.7 0.2 6.3 6.6 0.3 6.6 6.6 0 3.9 6.2 2.3 5.4 5.6 0.2 6.1 6.2 0.1 6.2 6.3 0.1 6.6 6.8 0.2 6.7 6.8 0.1 6.8 6.8 0 4.6 4. 8 0.2 4.8 4.8 0 6.9 6.9 0 45 50 r FIRST BEACH Q MACULOSUS FEMALE (OTOLITHS) LOG Y = -0.8787 . 1.423 LOG X N = 228 1.0 02 FIRST BEACH Q_ MACULOSUS MALE (OTOLITHS) 5"r LOG Y = -0.7427.1.202LOG X NU159 < u ^ 1.0 UJ 3 Q2 LENGTH (CM) LENGTH (CM) CO cr < UJ .> U J 3 F I R S T B E A C H Q M A C U L O S U S ( O T O L I T H S ) 5 0 r L O G Y = - 0 . 9 1 3 7 • 1 . 4 5 9 L O G X N = 3 6 5 1.0 0.2 L E N G T H (CM) F i g u r e 12 A g e - l e n g t h r e g r e s s i o n s of F i r s t B e a c h O. maculosus .determined by otoliths (males and females s e p a r a t e l y .and combined) Table 7 F i r s t Beach O l i g o c o t t u s maculosus ( o t o l i t h s ) Age-length r e g r e s s i o n s t a t i s t i c s l o g x vs l o g y: y = a + b (x-x) Sex a b x N s.e. F p< of b Females .08 1.42 .67 228 .091 244.0 .01 Hales .05 1.20 .66 159 .12 86.73 .01 Combinea .08 1.46 .68 365 .085 249.7 .01 a n a l y s i s of c o v a r i a n c e Males vs females Source Common v a r i a n c e D i f f e r e n t s l o p e s (b) D i f f e r e n t i n t e r c e p t s (a) 1.33 .024 2.07 .151 .464 .496 til (p>.01) (Table 7 ) , the data were combined i n t o a s i n g l e age-l e n g t h r e g r e s s i o n f o r F i r s t Beach (Figure 12 and T a b l e 7 ) . T h i s r e g r e s s i o n was a l s o s i g n i f i c a n t (p<.01). Other areas The r e g r e s s i o n s t a t i s t i c s c a l c u l a t e d s e p a r a t e l y f o r males and females at each area (Table 8) were a l l s i g n i f i c a n t (p<.01). For Ranee I s l a n d , t h e r e were i n s u f f i c i e n t data t o c a l c u l a t e separate male and female r e g r e s s i o n s , thus a s i n g l e combined r e g r e s s i o n o n l y was c a l c u l a t e d f o r t h i s area. A n a l y s i s of c o v a r i a n c e s t a t i s t i c s comparing male and female r e g r e s s i o n s f o r each area (Table 9) show v a l u e s to two decimal p l a c e s except where the p r o b a b i l i t y was c l o s e t o z e r o , i n which case three decimal p l a c e s are shown. I t i s evident t h a t f o r a l l areas except Grappler I n l e t and Pachena Point t h e r e are no s i g n i f i c a n t d i f f e r e n c e s between male and female r e g r e s s i o n s i n v a r i a n c e s , s l o p e s and i n t e r c e p t s (p>.01). Thus combined r e g r e s s i o n s were c a l c u l a t e d f o r each area (Figure 13 and Table 10). The combined r e g r e s s i o n s are a l l s i g n i f i c a n t (p<.01). In the case of Pachena P o i n t the r e g r e s s i o n s were combined s i n c e the agreement between s l o p e s and i n t e r c e p t s was good. The d i f f e r e n c e between v a r i a n c e s was probably due to t h e preponderance o f age two females r e l a t i v e t o males. In the case of Grappler I n l e t , the r e g r e s s i o n s are e v i d e n t l y s i g n i f i c a n t l y d i f f e r e n t i n v a r i a n c e s and s l o p e s (p<.01). The r e g r e s s i o n f o r males shows good agreement with r e g r e s s i o n s f o r both sexes f o r a l l p l a c e s except Table 8 A l l areas O l i g o c o t t u s maculosus ( o t o l i t h s ) Age-length r e g r e s s i o n s t a t i s t i c s Males and females s e p a r a t e l y l o g x vs l o g y: y =a -f b(x-x) Area s.e. of b P< Cape F .21 1. 18 .63 41 . 10 140.32 .01 Beale M .27 1. 23 .66 23 .15 57.153 .0 1 Benson F -.092 1.31 .55 36 I s l a n d M -. 14 1.20 .52 30 .12 12 5.00 .01 .13 88.802 .01 Port F .18 Renfrew M .18 .796 .67 .772 .66 49 18 .10 .17 68.239 20.4 94 ,01 .01 Pachena F . P o i n t M .32 1.47 .70 46 1. 42 .76 26 .062 556.91 .14 95.790 ,01 ,01 Helby F . 17 I s l a n d M .21 1.43 .65 50 1.56 .68 37 .14 109.83 .01 .19 64.981 .01 Haines F .23 I s l a n d M .18 1. 33 .73 42 1.36 .71 30 .11 146.43 .01 .21 40.338 .01 Grappler F .11 I n l e t M .22 .846 .67 23 .16 28.891 .01 1.37 .74 17 .054 629.33 .01 Table 9 A l l areas a n a l y s i s o f c o v a r i a n c e s t a t i s t i c s Males vs females Area F P F P F P (va) (b) (a) Cape Beale 1. 47 . 14 .092 .76 1.85 . 18 Benson I s l a n d 1. 17 .34 .41 .53 . 119 .73 Port Renfrew 1.08 .40 .15 .90 .602 . 44 Pachena Po i n t 2. 60 .003 . 15 .70 .263 .61 Belby I s l a n d •1.57 .07 .32 .57 .059 .81 Haines I s l a n d 1.02 .49 .012 . 91 2. 22 . 14 Grappler I n l e t 5. 42 .001 10.07 .00 3 3.69 .06 va: v a r i a n c e , b: s l o p e s . a: i n t e r c e p t s / 50 Figure 13 Age-length regressions of 0. maculosus from eight areas determined by o t o l i t h s (males and females combined) 51 HEL8Y I S L A N O Q MACULOSUS (OTOLITHS) LOG Y . - Q 7 6 7 7 . 1.4.47LOG X N * 87 L E N G T H (CM)' ' O f RANCE I S L A N D Q MACUIOSUS M A L E F E M A L E (OTOLITHS) L O G Y • -0.4691 . 0.8721 LOG X N . 39 L E N G T H (CM) HAINES I S L A N D Q MACULQSLS (OTOLITHS) ""l LOG Y • - 0 . 7 7 8 0 • 1.362 L O G X N = 72 02 L E N G T H (CM) GRAPPLER I N L E T Q MACULOSUS (OTOLITHS) L O G Y . - 0 . 6 9 2 6 • 1.216 L O G X N * 4 0 ' L E N G T H (CM) F i g u r e 13 (continued) T a b l e 10 A l l areas O l i g p c o t t u s maculosus ( o t o l i t h s ) Age-length r e g r e s s i o n s t a t i s t i c s Hales and females combined l o g x vs l o g y: y = a + b(x - x) area a b x N s.e. F p< of b Cape Beale .24 1.23 .66 57 .094 169.60 .01 Benson I s l a n d -.057 1.33 .58 44 .11 146.12 .01 Port Renfrew .18 .872 .68 62 .086 106.63 .01 Pachena Point .27 1.46 .72 72 .061 570.60 .01 Helby I s l a n d .19 1.45 .66 87 .11 173.19 .01 Haines I s l a n d .21 1.36 .72 72 .10 201.77 .01 Grappler I n l e t .16 1.22 .70 40 .088 189.96 .01 Ranee I s l a n d .13 .872 .69 39 ,14 40.570 .01 53 Port Renfrew, but the r e g r e s s i o n f o r females does not. The d i f f e r e n c e may be at l e a s t p a r t i a l l y accounted f o r by one f o u r year old male and no corresponding females, which, given the s m a l l sample s i z e , may produce s i g n i f i c a n t d i f f e r e n c e s . In view of the good agreement betwen male and female r e g r e s s i o n s a t a l l other p l a c e s and the absence o f any obvious reason f o r a s i g n i f i c a n t d i f f e r e n c e between male and female age-length r e l a t i o n s h i p s i n G r a p p l e r I n l e t , the r e g r e s s i o n s were combined i n t o a s i n g l e r e g r e s s i o n f o r the area. A n a l y s i s of c o v a r i a n c e s t a t i s t i c s f o r a l l s i t e s (Table 11) show s i g n i f i c a n t d i f f e r e n c e s between the r e g r e s s i o n l i n e s ; the slopes are s i g n i f i c a n t l y d i f f e r e n t (p=,01) and the adjusted group means d i f f e r s i g n i f i c a n t l y (p<.01). I n s p e c t i o n o f the l i n e s and t h e i r r e l e v a n t s t a t i s t i c s suggests t h a t the r e g r e s s i o n s f o r P o r t Renfrew and Ranee I s l a n d are d i f f e r e n t from the other s i t e s . 3 . D i s c u s s i o n The study of age d e t e r m i n a t i o n i n 0. majculosjjs a t F i r s t Beach r e v e a l e d t h r e e major age groups and a f o u r t h s m a l l e r age group. T h i s i s i n c o n t r a s t t o the work of Chadwick (1976) whose study of age d e t e r m i n a t i o n u s i n g vertebrae of 0. maculosus at Port Renfrew and B r u e l s P o i n t , C a l i f o r n i a l e d him to suggest t h a t there were s i x age groups at both l o c a l i t i e s . The s i n g l e c o l l e c t i o n of f i s h he made at Port Renfrew was taken i n l a t e J u l y at which time the young of the year have appeared i n Table 11 A n a l y s i s o f c o v a r i a n c e A l l s i t e s males and females combined Source d. f . Mean Sgua re D i f f e r e n c e between group means sl o p e 1 .055 ,05 and common sl o p e Group means from 7 ,50 t h e i r l i n e Between i n d i v i d u a l 8 .034 .01 l i n e s About i n d i v i d u a l 820 .014 l i n e s P r o b a b i l i t y of common v a r i a n c e 0 Slope of group means 1.35 Common s l o p e of l i n e s 1.62 55 t i d e p o o l s . Chadwick*s length-frequency d i s t r i b u t i o n curve (us i n g a moving average of t h r e e and standard length) shows one prominent mode a t about 2.5 cm and another l e s s prominent one a t about 1.5 cm. These correspond to h i s I and 0 age c l a s s e s , r e s p e c t i v e l y . I f age c l a s s I was r e c r u i t e d t o the p o p u l a t i o n i n the p r e v i o u s year, and t a k i n g growth a f t e r J u l y i n t o account, i t should be p o s s i b l e t o f i n d a s i z e c l a s s of f i s h of l e s s than 2.5 cm (about 3.0 cm t o t a l length) between October and Hay. Reference t o the len g t h - f r e q u e n c y histograms of Figure 11 shows no such s i z e c l a s s at t h a t time and shows t h a t Chadwick's 0 and I y e a r - c l a s s e s belong to the one year age group d e f i n e d here. T h i s a n a l y s i s of the length-frequency histoqrams f o r F i r s t Beach i s supported by Green*s (1967) length-frequency histoqrams f o r 0. maculosus a t B o t a n i c a l Beach, and Atkinson's (1939) lenqth-freguency histoqrams f o r 0. maculosus at Puqet Sound, Washington. Other s t u d i e s of age determination i n marine c o t t i d s are few., Chadwick (1976) conducted age determination s t u d i e s i n C l i n o c o t t u s globicep.s ( G i r a r d ) , and as f o r O. , maculosus concluded that t h e r e are s i x age c l a s s e s . Weiss (1969) examined ageing i n the more e u r y h a l i n e L e p t p c o t t u s arm,atus G i r a r d , a c o t t i d which has been rep o r t e d t o grow to 46 cm (Hart, 1973). He examined f i s h up t o about 25 cm ( t o t a l length) and on the b a s i s of o t o l i t h r e a d ings suggested ten age groups. H c E l d e r r y (1975) examined the age-length r e l a t i o n s h i p of C l i n o c o t t u s a n a l i s (Girard) i n C a l i f o r n i a . On the b a s i s o f o t o l i t h 56 examination he concluded there were seven age c l a s s e s , although few f i s h were more than two years o l d . O'Connell (1953) conducted ageing s t u d i e s , u s i n g o t o l i t h s , i n the cabezon, Scor paenichtljYs mar mora tus (Ayres) , a l a r g e s u b t i d a l c o t t i d , and found t h i r t e e n year o l d females and nine plus males. Length-frequency data from rotenone c o l l e c t i o n s i n k e l p beds i n Barkley Sound suggest t h a t A r t e d i u s h a r r i n g t o n i ( S t a r k s ) , a c o t t i d which i s recorded t o grow to 10 cm {Hart, 1973), comparable t o 0. maculosus, shows two and p o s s i b l y three age groups w i t h i n the p o p u l a t i o n , the approximate mean le n g t h s of which correspond t o those f o r 0. maculosus age groups. Although there are fewer data on which t o base c o n c l u s i o n s , A r t e d i u s l a t e r a l l y ( G i r a r d ) , another e s s e n t i a l l y s u b t i d a l c o t t i d , appears t o show a t l e a s t two age groups (Bruce Leaman, p e r s o n a l communication). 57 IV. VARIABILITY IN HOMING BEHAVIOUR 1.Tagging and r e c a p t u r e methods Tagging methods Tags f o r a d u l t 0. maculosus c o n s i s t e d of three co l o u r e d beads and monofilament l i n e . Nineteen c o l o u r s o f beads were used. A piece of monofilament ( u s u a l l y 4 o r 6 l b t e s t , but h e a v i e r when t h i s was not a v a i l a b l e ) about 20 cm long was threaded with a bead and attached with a double improved c i n c h knot, l e a v i n g one end about 3 cm long and t h e o t h e r about 15 cm long. Another bead was then threaded on the long end of the l i n e . A l a r g e number o f these were made p r i o r to t a g g i n g f i s h , to e x p e d i t e the a c t u a l t a g g i n g process. The long end o f the monofilament was threaded through a f i n e needle and the needle i n s e r t e d through the d o r s a l musculature of the f i s h between the d o r s a l f i n s from the l e f t t o r i g h t s i d e s of the f i s h . Another bead was threaded onto the l i n e and the l i n e threaded once more through the bead. T h i s bead was then manoeuvred down to the r i g h t s i d e of the f i s h so t h a t the beads on both s i d e s s e r e adjacent t o the body. The long end of monofilament was then looped and i t s f r e e end wound through the loop f i v e or s i x times. A d i s s e c t i n g needle was i n s e r t e d i n t h e l o o p and 58 pushed down the l i n e t o the outer s i d e of the bead. Both f r e e ends of monofilament were then p u l l e d , causing the l a s t knot t o t i g h t e n . The f r e e ends of monofilament were than c u t o f f . Once f a m i l i a r i t y with the technigue was gained, a f i s h c o u l d be tagged i n w e l l under one minute. A l l f i s h were tagged with unigue tags so that i n d i v i d u a l r e c o g n i t i o n was p o s s i b l e . Over 2800 f i s h were tagged u s i n g t h i s technique. No a n a e s t h e t i c was used. Tag l o s s , from f i s h g r e a t e r than 2.5 cm, as i n d i c a t e d by recovery of f i s h with l e s i o n s on the d o r s a l musculature was very low (about 256}. Taqqed f i s h were kept i n the l a b o r a t o r y f o r v a r y i n q p e r i o d s from o v e r n i g h t t o almost f i v e months. The only m o r t a l i t y recorded from untreated, tagged f i s h o c c u r r e d a f t e r blockages i n the seawater system. S e v e r a l methods were attempted f o r the tag g i n g of j u v e n i l e s . P i e c e s of v a s e l i n e coated nylon thread about 5 cm l o n g , and l a r g e (8 mm x 3 mm) and s m a l l (3 mm square) p i e c e s of coloured s u r v e y o r s 1 tape were attached through the d o r s a l musculature with nylon thread., However, w i t h i n s e v e r a l days, the taqs e i t h e r came o f f or entangled the f i s h i n a s s o r t e d d e b r i s . F i n a l l y j u v e n i l e f i s h were tagged with two c o l o u r e d beads (one bead each s i d e of the body) and monofilament l i n e (2 l b test) i n the same manner as a d u l t f i s h . T h i s method proved r e l a t i v e l y s a t i s f a c t o r y except f o r f i s h l e s s than about 2.5 cm 59 ( t o t a l length) f o r which no r e a l l y s a t i s f a c t o r y i n d i v i d u a l tag was developed. Reacapture methods In homing behaviour experiments two methods were used to f i n d tagged f i s h a f t e r r e l e a s e . ftt F i r s t Beach about once every two weeks, b a i t e d minnow t r a p s were set i n t i d e p o o l s f o r about f o u r hours around l o s t i d e . Traps were s e t o n l y i n pools used f o r capture and t r a n s p l a n t i n g o f f i s h . In a d d i t i o n , and whenever p o s s i b l e between t r a p p i n g s , pools were i n s p e c t e d thoroughly f o r tagged 0. maculosus. The pools i n which f i s h were captured and t r a n s p l a n t e d and pools between the home and r e l e a s e p ools were examined, although the l a t t e r l e s s t horoughly, except where otherwise s t a t e d . In homing experiments conducted i n other a r e a s , a combination of t r a p p i n g and o b s e r v a t i o n was a l s o used., In Grappler I n l e t , t r a p s were s e t , over two t i d a l c y c l e s (approximately 24 h o u r s ) , at l e a s t once every two weeks and f r e g u e n t l y s e v e r a l times per week f o r the f i r s t month of an experiment. Simultaneously, o b s e r v a t i o n s from the s u r f a c e were a l s o made f o r tagged f i s h , In other p l a c e s , the r e c a p t u r e schedule i s o u t l i n e d i n the d e s c r i p t i o n s of experiments conducted there, 60 2. Homing, i n d i f f e r e n t l o c a t i o n s F i r s t Beach Home range and area f i d e l i t y S ince the m a j o r i t y o f i n v e s t i g a t i o n s i n t o homing behaviour of 0. maculosus have been conducted at P o r t Renfrew, i t was regarded as e s s e n t i a l t o i n v e s t i g a t e pool f i d e l i t y and s i z e of home range of 0. maculosus at F i r s t Beach, p r i o r t o commencing homing s t u d i e s . I n t h i s study, the term home range i s used as i n Khoo (1971) as the area covered by the f i s h d u r i n g normal t r a v e l , Gersbacher and Denison (19 30) and Green (1967) suggested t h a t the m a j o r i t y o f 0. maculosus d i s p l a y r a t h e r s t r i c t f i d e l i t y t o p a r t i c u l a r p o o l s . Khoo's (1971) s t u d i e s however, showed t h a t the m a j o r i t y of f i s h move w i t h i n a group of neighbouring pools., He suggested t h a t the amount of movement between pools may depend on the s i z e of the pools i n v o l v e d . Despite Green's o b s e r v a t i o n s t h a t few f i s h are found more than t h r e e metres from t h e i r home p o o l , Khoo proposed that the maximum extent of the home range was not more than 30.5 metres. Three experiments were conducted s p e c i f i c a l l y to determine whether 0. maculosus e x h i b i t e d pool f i d e l i t y at F i r s t 61 Beach. These experiments were a l s o designed t o g i v e an i n d i c a t i o n of the s i z e o f the home range. A n a l y s i s of data from other experiments on the pool movements a f t e r homing of untre a t e d , tagged 0. maculosus i n d i v i d u a l s was a l s o undertaken to determine the degree o f n a t u r a l movement between t i d e p o o l s . Methods In the f i r s t experiment a t o t a l of 33 0. maculosus were tagged and r e t u r n e d to the t i d e p o o l i n which they were captured. F i s h were c o l l e c t e d from three a d j a c e n t t i d e p o o l s . In the second experiment, a t o t a l o f 76 0. maculosus were tagged and returned to the pool i n which they were captured. F i s h were c o l l e c t e d from two groups of t h r e e and f i v e pools each. I n the t h i r d experiment, a t o t a l of 44 O. maculosus were captured from two groups of two and t h r e e pools each and ret u r n e d t o the pool i n which they were captured. The pool i n which a f i s h was captured was termed the home p o o l . A l l o b s e r v a t i o n s o f tagged f i s h i n any pool over four months, 10 weeks and f i v e weeks, r e s p e c t i v e l y , were recorded and used f o r a n a l y s i s . Percentages o f tagged f i s h found i n the home pool only, i n the home and nearby pools and i n d i s t a n t pools were c a l c u l a t e d . To provide an i n d i c a t i o n of the pool f i d e l i t y o f i n d i v i d u a l 0. maculosus, l o c a t i o n records of i n d i v i d u a l s from the second replacement experiment seen at l e a s t f i v e times over 62 a p e r i o d of at l e a s t 28 days were analyzed. These f i s h were regarded as having r e l a t i v e l y e x t e n s i v e l o c a t i o n r e c o r d s . The p e r i o d over which the f i s h was seen, the number of pools i n which the f i s h was seen and the number of times seen i n each pool were c a l c u l a t e d . R e s u l t s The r e s u l t s o f the three replacement experiments (Table 12) show that i n each experiment, about 30 t o U0% o f the f i s h were subsequently found only i n t h e home p o o l . about the same or s l i q h t l y h iqher percentaqes of f i s h were found i n the home and nearby pools. In each case, a majority of the f i s h r e p l a c e d were found i n the area of the home pool ( e i t h e r the home pool o n l y or the home and nearby p o o l s ) , t h a t i s , the home range. S e v e r a l f i s h were found i n d i s t a n t pools from 30 to 60 m away from the home pool. I t thus appears t h a t i n a d d i t i o n to a s m a l l percentage of f i s h which s t r a y widely, equal p r o p o r t i o n s of 0. maculosus show f i d e l i t y to a p a r t i c u l a r p o o l , as t o a s m a l l qroup o f poo l s . This qroup comprises u s u a l l y about two or t h r e e p o o l s , but o c c a s i o n a l l y up t o f i v e , c o v e r i n q an area with a diameter o f about 10 to 15 m maximum. From the a n a l y s i s of lonq term pool f i d e l i t y from the second replacement experiment (Table 13) i t i s evident that some 0. maculosus show s t r i c t f i d e l i t y over a lonq pe r i o d t o one Tafcls 12 F i r s t Beach r e p l a c e m e n t e x p e r i m e n t s Date r e l e a s e d 28 May 75 2 Number r e l e a s e d 19 Nunber f o u n d i n home 9 p o o l c n l y P e r c e n t f o u n d i n home 17 p o o l c n l y Number foun d i n home 7 and nearby p o o l s P e r c e n t f o u n d i n home 37 and nearby p o o l s Number foun d i n home p o o l 16 and home and nearby p o o l s P e r c e n t f o u n d i n hone p o o l 81 and heme and nearby p o o l s Number found i n d i s t a n t 0 p o o l s P e r c e n t f o u n d i n d i s t a n t 0 F o o l s June 75 T o t a l 30 June 77 9 Aug 77 11 33 76 11 2 11 27 17 14 33 36 39 2 9 10 18 11 27 53 11 1 20 67 35 29 61 . 88 80 2 2 2 2 11 6 3 5 T a b l e 13 Long t e r n p o o l f i d e l i t y o f i n d i v i d u a l Q l i g o c o t t u s m a c u l o s u s from 30 June r e p l a c e m e n t e x p e r i m e n t ( l o n g term: seen a t l e a s t f i v e t i m e s over a t l e a s t 28 days) One p o o l Two p o e l s T h r e e r e e l s F our p o o l s F i v e p o o l s Cays o v e r Number which o f t i m e s o b s e r v e d o b s e r v e d per p o o l Days e v e r Number which o f ti m e s o b s e r v e d o b s e r v e d per p o o l Days o v e r Number which c f t i m e s cb s e r v e d o b s e r v e d per p o o l Days o v e r Number Days o v e r Number which o f t i m e s which o f t i m e s o b s e r v e d o b s e r v e d o b s e r v e d o b s e r v e d per p o o l per p o o l 61 61 75 75 74 61 38 61 52 5fi 34 12 25 20 18 25 11 17 7 12 5 7. 75 in 75 71 75 48 58 58 71) 30 43 17,1 15.3 18,7 9,8 26,1 17,1 17,1 7,2 6,1 6* 8,0 75 75 75 42 60 41 37 19,1,1 5 1,2,1 17,4,2 7,2,1 7.5,2 4,3,3 2,2,1 58 60 60 57 7,4,4,1 15,7,2,2 13,5,4,1 5,2,1,1 70 10,8,7,1,1 75 12,4,3,2,1 * always found i n a d i f f e r e n t p o c l from t h e p o o l o f f i r s t c a p t u r e 65 p o o l . T h i s was a l s o evident from the l o c a t i o n data of some of the f i s h used i n homing experiments: f o r example, one 0. maculosus was seen 17 times a f t e r homing over 179 days, always i n the same pool; another was seen 41 times over 83 days a f t e r homing always i n the home p o o l ; two f i s h which were r e l e a s e d i n 1976 were found eleven and twelve months l a t e r i n t h e i r o r i g i n a l capture pools. There i s no doubt t h a t some 0. maculosus d i s p l a y very s t r i c t f i d e l i t y t o a p a r t i c u l a r p o o l . , Examination of the number of times t h a t i n d i v i d u a l s were observed i n pools of the home range shows t h a t i n a m a j o r i t y of cases, t h e r e i s one pool w i t h i n the group of pools around which the f i s h moves, t o which g r e a t e r f i d e l i t y i s shown. Again, t h i s r e s u l t i s supported by a n a l y s i s of pool l o c a t i o n records from 0. maculosus seen over long p e r i o d s of time a f t e r homing: f o r example, two f i s h were seen i n two p o o l s a t o t a l o f 16 times each over a p e r i o d of 101 days, one f i s h 15 times i n one pool and once i n the other, the other f i s h 11 times i n one pool and f i v e i n the o t h e r ; a f i s h was seen a t o t a l o f 29 times i n f o u r pools over 83 days, the number of times i n each pool being 18, 6, 4 and 1., From 10 homing experiments i n v o l v i n g u n t r e a t e d , tagged f i s h which s u c c e s s f u l l y homed and were subsequently seen at l e a s t f i v e times over a p a r i o d of a t l e a s t 28 days, 37 were found o n l y i n one pool and 56 were found i n more than one pool . o f those 56, 42 (75%) were found i n one pool more than twice as many times as any other pool. Thus i t appears that the m a j o r i t y o f O. maculosus show q r e a t e r f i d e l i t y 66 to one p a r t i c u l a r p o o l than t o other pools i n the home range. T h i s pool i s termed t h e p r e f e r r e d p o o l . Homing behaviour Two experiments were conducted s p e c i f i c a l l y t o determine whether 0. maculosus at F i r s t Beach demonstrate homing behaviour, t h a t i s , r e t u r n t o the home range when e x p e r i m e n t a l l y d i s p l a c e d . The experiments were a l s o designed t o compare the d i f f e r e n c e , i f any, i n homing behaviour between r e c i p r o c a l and n o n - r e c i p r o c a l t r a n s p l a n t s of f i s h . A n a l y s i s of data from other homing experiments i n v o l v i n g u ntreated, tagged 0. maculosus was a l s o undertaken to p r o v i d e a more comprehensive p i c t u r e of homing behaviour at F i r s t Beach. Methods In the f i r s t experiment, a t o t a l of 42 tagged 0. maculosus taken from a group of f i v e pools were t r a n s p l a n t e d t o a pool about 60 m away. A l l o b s e r v a t i o n s of tagged f i s h i n any pool over a f o u r month pe r i o d were recorded and used f o r a n a l y s i s . The second and subsequent experiments i n v e s t i g a t e d the e f f e c t of approximately m a i n t a i n i n g t h e number of 0. maculosus i n the study t i d e p o o l s while t r a n s p l a n t i n g f i s h . In the second experiment 0. maculosus were c o l l e c t e d from two groups of pools 67 about 60 m a p a r t . A t o t a l o f 54 f i s h were tagged, 20 from one pool i n one group and 34 from f o u r pools i n the oth e r group. Releases were made i n t o the pool i n each group from which the most f i s h were taken, so that i n one pool 20 f i s h were removed and 34 i n t r o d u c e d , and i n the other pool 2 2 f i s h were removed and 20 were i n t r o d u c e d . Data c o l l e c t e d over a f o u r month p e r i o d were used i n the a n a l y s i s . The a n a l y s i s of data from other experiments i n v o l v e d examining the homing performance of unt r e a t e d , tagged 0. maculosus used i n seven experiments designed t o examine the sensory b a s i s o f homing, and one t r a n s p l a n t experiment (4 J u l y , 1977). In a l l cases, f i s h were taken from two groups of pools about 60 m apart. R e c i p r o c a l t r a n s p l a n t s were made as f a r as p o s s i b l e , so t h a t the number of f i s h t r a n s p l a n t e d t o each pool was egual to the number o f f i s h removed (and t r a n s p l a n t e d t o pools i n the other group). I n the f i r s t two experiments conducted i n 1977, about 25% of the f i s h r e l e a s e d i n each experiment were l e s s than 4.0 cm ( t o t a l l e n g t h ) , which was not the case f o r the other experiments. Data c o l l e c t e d over a f o u r month p e r i o d were used i n the a n a l y s i s except i n the cases o f the experiments s t a r t i n g on 23 August, 1976, 15 September, 1976, 4 J u l y 1977, 16 J u l y 1977 and 9 August 1977 f o r which data c o l l e c t e d over 3.5, 2.5, 2+, 2 and 1+ months, r e s p e c t i v e l y , were used., F o l l o w i n g the method of Khoo (1971), homing was regarded as s u c c e s s f u l i f a tagged 0, maculosus returned t o i t s 68 home range (either the home pool or nearby pools). The f i r s t pool i n the home range i n which a tagged f i s h was found was regarded as the pool to which the f i s h homed, even i f the f i s h subsequently was located in another pool. A record was kept of f i s h located i n pools other than those of the home range. Calculations were made of the percentage of 0. maculosus homing, the percentage of homers returning to the home pool and the percentages of released f i s h remaining in the transplant area for any period of time. Results Although there i s considerable v a r i a b i l i t y i n the re s u l t s from the ten homing experiments (Table 14) and some of the percentage returns are small, there i s d e f i n i t e evidence to indicate that a majority of 0. maculosus in d i v i d u a l s are able to return to a r e l a t i v e l y small area when displaced. In nine out of the ten experiments the percentaqe of successfully hominq f i s h which returned to the home pool was considerably greater than the percentage returning to the home range. Although many of these f i s h were subsequently found i n other pools i n the home range, the fact that they i n i t i a l l y returned to the home pool demonstrates the a b i l i t y of 2» I§.£Slosus to return to a small area from a considerable distance. It i s in t e r e s t i n g to note that in a l l experiments, T a b l e 14 Honing p e r f o r m a n c e o f u n t r e a t e d O l i g o c p t t u s magulgsus a t F i r s t Beach Date releasee 26 11 4 21 16 23 15 Hay &uq Sept Sept Hay Auq Sept 1975 1976 J u l y 16 J u l y 1977 9 Auq Number r e l e a s e d 42 54 69 33 38 31 20 60 45 32 Number homed P e r c e n t homed 15 30 52 24 36 56 75 73 20 53 15 4ft 14 70 31 52 19 42 20 63 Nuaber fo u n d i n 6 t r a n s p l a n t a r e a P e r c e n t found i n 14 t r a n s p l a n t a r e a 8 17 3 15 25 9 8 2 1 8 26 4 20 27 45 26 58 14 44 Days s p e n t i n t r a n s p l a n t a r e a a. hemers non-homers 1,1, 13,22,1,1, 1, 4 1,1 25,41 1,1,4, 6,6,7, 17,18 1, 1,21, 6,6,7, 3,78 102 42,82 13,22, 42 2,27 2 1,1 2,2, 1,2, 10,26 73,73, 10,11, 83, 46,80, 110 104 1,1,2, 2,4,7 2,2,2, 2,5, 42 3,3, 8,18 1,1,2,2, 1,1,1,2, 1,3,3,3, 2,4,10,10, 2,5,6,6, 8,8,11, 16,17,17, 6,13,14, 11,18,30 18,21,21, 14,14,27, 22,26,26, 27,32,55,55 44,54,57,58 59,59 P e r c e n t o f homers r e t u r n i n q t o home p o o l 73 87 73 6 0 70 60 64 65 42 60 70 c o n s i d e r a b l e numbers (from 9% to 58%) o f f i s h remained i n the t r a n s p l a n t pool area f o r v a r i a b l e periods of time (from 1 to 10 4 days) a f t e r being r e l e a s e d . T h i s i m p l i e s t h a t while the majorit y o f 0. maculosus i n d i v i d u a l s show homing behaviour, t h e r e i s a reasonable number o f f i s h which do not demonstrate t h i s behaviour. Of those f i s h , a c o n s i d e r a b l e percentage (up t o 17% of non-homing f i s h ) remain i n the t r a n s p l a n t area. Comparison of the percentages homed between the non-r e c i p r o c a l t r a n s p l a n t and the r e c i p r o c a l t r a n s p l a n t s shows that i n c r e a s i n g the d e n s i t y or r e d u c i n g the "space" does not appear to be a f a c t o r i n f l u e n c i n g s u c c e s s f u l homing. I t i s p o s s i b l e , however, t h a t the number of non-homing f i s h remaining i n the t r a n s p l a n t area i s i n f l u e n c e d by t h i s f a c t o r . A number of f i s h which s u c c e s s f u l l y homed were l o c a t e d at l e a s t once i n pools between t h e t r a n s p l a n t p o o l and the home range. The majori t y of f i s h were found on the p e r i p h e r y of the home ranges. For example, one f i s h d i s p l a c e d t o a high pool i n the i n t e r t i d a l was found i n a lower pool the day f o l l o w i n g r e l e a s e and was back i n the home range f o r a p e r i o d of 3 t o 33 days a f t e r r e l e a s e . Another f i s h , o r i g i n a l l y captured i n a high t i d e p o o l and t r a n s p l a n t e d was observed a f t e r r e l e a s e , i n a low poo l i n i t s home range a f t e r f i v e days, the next highest pool a f t e r seven days and the higher home pool many times from 17 to 98 days a f t e r r e l e a s e . Not a l l f i s h d i s p l a y e d t h i s apparent type of movement between pools. Some were observed i n pools a t or o u t s i d e the edges of the home ranges i n the m i d - i n t e r t i d a l . 71 A few f i s h were observed i n a s e r i e s of m i d - i n t e r t i d a l pools from the r e l e a s e pool to the home range. S e v e r a l f i s h which were found out of the t r a n s p l a n t and home areas a f t e r r e l e a s e were found i n pools up t o 30 m away from the t r a n s p l a n t area and i n the o p p o s i t e d i r e c t i o n from t h e home pool. I n l e t s Home range and area f i d e l i t y Homing behaviour of O. maculosus has t o date, only been examined i n t i d e p o o l areas (Gersbacher and Denison, 1930; Green, 1967; Khoo, 1971). In s e v e r a l areas of Barkley Sound (Grappler I n l e t , Bance I s l a n d and Dodger Channel) l a r g e , but p a r t i c u l a r l y i n Dodger Channel, seasonal p o p u l a t i o n s of O. maculosus can be found. I f homing i s d e f i n e d as the r e t u r n to a home range when e x p e r i m e n t a l l y d i s p l a c e d , i t i s necessary to e s t a b l i s h whether i n l e t 0. maculosus d i s p l a y f i d e l i t y t o a p a r t i c u l a r area. One experiment was conducted t o determine whether 0. maculosus can be r e g u l a r l y found i n a r e s t r i c t e d area o f an i n l e t , comparable to a group o f t i d e p o o l s . 72 Methods a t o t a l of 58 f i s h from two s i t e s on the south s i d e o f Grappler I n l e t were tagged and r e p l a c e d i n the area i n which they were captured. Of these f i s h , 43 0. maculosus were captured and r e l e a s e d i n t h e s m a l l bay about halfway along the i n l e t and 15 f i s h were captured and r e l e a s e d at the mudflat i n Port D e s i r e . at each s i t e a s e r i e s o f minnow t r a p s was spread i n a l i n e p a r a l l e l with the shore l i n e and c o v e r i n g a l i n e a r d i s t a n c e of about 7 t o 10 ra. Traps were always s e t at low t i d e , however the l e v e l of the i n t e r t i d a l a t which the t r a p s were s e t depended on the h e i g h t o f the t i d e . at higher low t i d e s , the t r a p s were s e t a t a higher water l e v e l but i n t h e same t r a n s e c t p e r p e n d i c u l a r t o t h e shore as the lowest t r a p p i n g s i t e . Trapping was conducted and o b s e r v a t i o n s were made only a t the two s i t e s . Data were c o l l e c t e d over a fo u r month p e r i o d . R e s u l t s The r e l a t i v e l y low percentages of f i s h r e s i g h t e d suggest that i n i n l e t s 0. maculosus i n d i v i d u a l s do not d i s p l a y the same degree of f i d e l i t y t o a s m a l l area comparable t o t h a t shown by 0. maculosus i n d i v i d u a l s found i n t i d e p o o l s (Table 15). One tagged f i s h was l o c a t e d t h r e e times a t the capture s i t e (50, 52 and 64 days a f t e r r e l e a s e ) , but the majority were seen again only once a f t e r r e l e a s e , and w i t h i n the f i r s t month. One tagged T a b l e 15 Grappl e r I n l e t replacement experiment Date r e l e a s e d Number r e p l a c e d Number r e s i g h t e d there Percent r e s i g h t e d t h e r e Bay Mudflat T o t a l 2 October 1975 43 15 58 12 6 18 28 40 31 74 0. Maculosus was observed a number of times at t h e s m a l l bay, a t v a r y i n g t i d e l e v e l s from 0.5 to 3 m. T h i s f i s h was always found about 0.6 m below the water l e v e l , a p p a r e n t l y f o l l o w i n g the t i d e . I t i s p o s s i b l e t h a t the home range of i n l e t 0. maculosus i s l a r g e r than the areas trapped or observed. , I t i s a l s o p o s s i b l e t h a t the e f f i c i e n c y o f t r a p p i n g and ob s e r v a t i o n s i s c o n s i d e r a b l y l e s s i n i n l e t s than i n t i d e p o o l s where much b e t t e r d e f i n e d areas are under c o n s i d e r a t i o n . However the low percentages trapped or seen again over the d u r a t i o n of the experiment appear t o suggest t h a t some i n l e t O' maculosus show some f i d e l i t y t o a p a r t i c u l a r area but t h a t the m a j o r i t y range over a wider area. Even those f i s h which do d i s p l a y a degree of a s s o c i a t i o n with a s m a l l area appear t o do so o n l y f o r a l i m i t e d p e r i o d of time. Horning behaviour along i n l e t s Although t h e degree o f f i d e l i t y t o a p a r t i c u l a r area shown by i n l e t 0. maculosus appears t o be s m a l l , two t r a n s p l a n t experiments were conducted t o determine whether 0. maculosus d i s p l a y s homing behaviour i n i n l e t s , t h a t i s , r e t u r n s t o a small area (as i n t i d e p o o l 0. maculosus) when e x p e r i m e n t a l l y d i s p l a c e d . 75 Methods In the f i r s t experiment a t o t a l of 78 0. ma cu lapsus were c o l l e c t e d from the two s i t e s i n Grappler I n l e t , 42 from the bay and 36 from the mudflat. The f i s h were r e c i p r o c a l l y t r a n s p l a n t e d (although the numbers were not q u i t e e q u a l ) . Trapping was conducted and o b s e r v a t i o n s were made only a t these two s i t e s . Data were c o l l e c t e d over a four month p e r i o d . In the second experiment a t o t a l of 88 p. maculosus were c o l l e c t e d , 64 from the bay and 24 from the mudflat. These f i s h were r e l e a s e d at a s i t e approximately halfway between the capture s i t e s . a t the r e l e a s e p o i n t , 0. maculosus does not appear t o occur i n any numbers, as three days by t r a p p i n g p r i o r to the experiment produced o n l y four 0. maculosus. F o l l o w i n g r e l e a s e , t r a p p i n g was conducted and o b s e r v a t i o n s were made a t a l l t h r e e s i t e s . Data were c o l l e c t e d over a four month p e r i o d . a n a l y s i s o f data i n v o l v e d c a l c u l a t i n g percentages s u c c e s s f u l l y homing and percentages remaining i n the t r a n s p l a n t area. 76 R e s u l t s The low percentages s u c c e s s f u l l y homing (Table 16) suggest t h a t homing behaviour i s not w e l l developed i n 0. maculosus found i n i n l e t s . Even when the d i s t a n c e t o home was c o n s i d e r a b l y reduced the percentages homing were s m a l l . In the f i r s t experiment the percentages remaining i n the t r a n s p l a n t area were sm a l l . In the second experiment no f i s h were found at the t r a n s p l a n t s i t e . Few untagged 0* fiaculosus were trapped at t h i s s i t e . The data from the f i r s t experiment may imply t h a t the s l i g h t l y more exposed area (the bay) i s a more d e s i r a b l e h a b i t a t than the mudflat. The absence of tagged f i s h a t the t r a n s p l a n t s i t e i n the second experiment suggests t h a t while they move away from the t r a n s p l a n t area, the ma j o r i t y d i d not r e t u r n t o the capture s i t e , as shown by the percentage s u c c e s s f u l l y homing., Compared with homing behaviour of 0* maculosus i n t i d e p o o l areas, i t appears t h a t homing behaviour i s not as well developed i n i n l e t f i s h . An attempt was made t o determine whether i n l e t f i s h showed improved homing performance i n a t i d e p o o l s i t u a t i o n . On 17 October, 1975, 71 tagged 0. maculosus from Grappler I n l e t were i n t r o d u c e d t o a group o f t i d e p o o l s a t F i r s t Beach. In t h r e e of the t i d e p o o l s an egu a l number of f i s h was removed as was r e p l a c e d (31 f i s h ) . I t was intended t h a t the movements of the f i s h between t i d e p o o l s be monitored f o r some T a b l e 16 Homing behaviour along G r a p p l e r I n l e t Bay Mud f l a t T o t a l Bay Mudflat T o t a l Date r e l e a s e d 2 October 1975 4 February 1976 Number r e l e a s e d 42 36 78 64 24 88 Number homed Percent homed 5 12 3 8 8 10 2 3 3 5 13 6 Number s t a y i n g i n t r a n s p l a n t area Percent s t a y i n g i n t r a n s p l a n t area 5 14 6 8 Days s t a y i n g i n t r a n s p l a n t area a. homers b. non-homers 1,15 20,22, 54 78 p e r i o d of time and i f f i d e l i t y t o a po o l or group of pools became apparent, t r a n s p l a n t experiments were; to be conducted t o examine homing behaviour. F o l l o w i n g the i n t r o d u c t i o n , severe storms o c c u r r e d r e s u l t i n g i n a n o t i c e a b l e decrease i n both n a t u r a l t i d e p o o l p o p u l a t i o n s of 0. maculosus and tagged 0. maSiJiosus. In the f i r s t two weeks a f t e r r e l e a s e 23 f i s h were l o c a t e d . The m a j o r i t y were found i n the group of pools i n t o which they were intr o d u c e d and adjacent pools. Of those f i s h seen a f t e r r e l e a s e , about egual percentages were introduced i n t o c l e a r e d and uncleared pools. Most showed some tendency t o move from the r e l e a s e pool t o other pools. a f t e r the f i r s t two weeks o n l y one tagged 0. maculosus was l o c a t e d , 54 days a f t e r r e l e a s e i n a pool about 60 m away from the r e l e a s e area. Thus i t was not p o s s i b l e to conduct any t r a n s p l a n t experiments t o examine homing a b i l i t y . Homing behaviour a c r o s s i n l e t s C a r l s o n and Haight (1972) found t h a t the y e l l o w t a i l r o c k f i s h , Se bastes f l a v i d u s (ayres) was u n s u c c e s s f u l i n homing i f t h e area between the displacement and home s i t e s i n c l u d e d deep water. Green (1975) found that the cunner Tautoqolabrus adspersus (Walbaum) was unable to home over deep water. Khoo's (1971) work at Port Renfrew showed t h a t rough t e r r a i n or deep s u b t i d a l areas appeared t o have adverse e f f e c t s on the homing a b i l i t y of 0. maculosus. 79 To determine whether deep water has adverse e f f e c t s on the homing a b i l i t y o f i n l e t f i s h , two experiments were conducted on the homing a b i l i t y of 0. maculosus across G r a p p l e r I n l e t , at the same time as the homing experiments along Grappler I n l e t were conducted. Although the a b i l i t y o f i n l e t 0. maculosus to home i s not as w e l l developed as i n t i d e p o o l f i s h , there a p p a r e n t l y i s a small percentage which are able t o home s u c c e s s f u l l y . Methods A t o t a l of 72 0. maculosus (56 from the bay and 26 from the mudflat i n Grappler I n l e t ) were t r a n s p l a n t e d to a s i t e on the nort h s i d e of Grappler I n l e t d i r e c t l y opposite the s m a l l bay. The d i s t a n c e across the i n l e t i s approximately 80 m and the depth i n the middle of the i n l e t about 12 m at high t i d e . Trapping was conducted and o b s e r v a t i o n s were made a t the r e l e a s e s i t e f o r one month a f t e r r e l e a s e and at the cap t u r e s i t e s f o r f o u r months a f t e r r e l e a s e . ., In the second experiment HU 0. maculosus were t r a n s p l a n t e d from the bay on the south s i d e o f Gr a p p l e r I n l e t to the r e l e a s e s i t e d i r e c t l y o p posite on the north s i d e o f the i n l e t . Trapping and o b s e r v a t i o n s at the r e l e a s e s i t e were conducted f o r one month a f t e r r e l e a s e and at the capture s i t e f o r four months a f t e r r e l e a s e . 80 R e s u l t s Table 17 makes i t abundantly c l e a r t h a t i n l e t O. maculosus are unable t o home over deep water. I t i s i n t e r e s t i n g t o note t h a t although t h e r e are c o n s i d e r a b l e numbers of 0. maculosus at the r e l e a s e s i t e , none of the t r a n s p l a n t e d f i s h was found at t h i s s i t e a f t e r r e l e a s e . Since no f i s h were removed from the t r a n s p l a n t s i t e p r i o r t o r e l e a s i n g f i s h , d e n s i t y dependent e x c l u s i o n cannot be e l i m i n a t e d . 3. Homing with resjaect t o exposure Khoo (1971) found t h a t 0. maculosus at Port Renfrew were r a r e l y r e s t r i c t e d t o one p a r t i c u l a r p o o l . T h i s study has shown t h a t i n the course of t h e i r normal movements a t F i r s t Beach, egual p r o p o r t i o n s of f i s h show f i d e l i t y t o a p a r t i c u l a r pool as t o a group of pools, and t h a t i n the l a t t e r group there i s u s u a l l y one p r e f e r r e d pool. In i n l e t s , 0. maculosus appear to show l i t t l e f i d e l i t y t o a p a r t i c u l a r area, comparable to a group of t i d e p o o l s . With r e s p e c t to homing behaviour, 0, maculosus at both F i r s t Beach and Port Renfrew show moderate to high, but v a r i a b l e percentages homing and 0. maculosus i n Grappler I n l e t show l i t t l e evidence of homing. The work of Green (1967) at P o r t Table 17 Homing behaviour across Grappler I n l e t Bay Mudflat T o t a l Bay Date r e l e a s e d 16 October 1975 4 Feb 76 Number r e l e a s e d 56 26 72 44 Number homed 0 0 0 0 Number s t a y i n g at 0 0 0 0 t r a n s p l a n t s i t e 82 Renfrew showed that the vast majority of transplanted O. laculosus l e f t the transplant pool within a few t i d a l c ycles. In a nomber of experiments Green found that only four f i s h out of over 100 transplanted f i s h remained in the transplant pool for any period of time: one was taken with poison the day following release, two remained three weeks and one about four weeks. The l a t t e r three subsequently homed. Khoo (1971) trapping on a two-weekly basis found that a l l f i s h l e f t the transplant pool at the end of the f i r s t two weeks. At F i r s t Beach a sizeable percentage of f i s h remained in the transplant area f o r considerable periods of time, either prior to homing or to taking up residence i n the area. I t thus appears that there may be differences i n homing behaviour of 0. maculosus in areas of d i f f e r e n t exposures (substrates) . Results from F i r s t Beach and Grappler Inlet and the work of Green and Khoo at Port Renfrew suggest that i n more exposed tidepool areas, 0. maculosus displays l e s s f i d e l i t y to p a r t i c u l a r pools and fewer f i s h remain i n the transplant area. In sheltered i n l e t areas much less area f i d e l i t y i s shown than in any tidepool area, few f i s h home and r e l a t i v e l y few remain i n the transplant area. Thus a series of experiments designed to compare hominq behaviour simultaneously i n exposed and sheltered areas was conducted. 83 Methods Four experiments i n v o l v i n g nine d i f f e r e n t l o c a t i o n s of d i f f e r i n g exposures were conducted t o compare the homing behaviour o f 0. maculosus. Each s i t e was i n i t i a l l y c l a s s i f i e d as exposed, moderately exposed or s h e l t e r e d a c c o r d i n g to l o c a t i o n and ob s e r v a t i o n . In each experiment r e l e a s e s , r e t r a p p i n g and o b s e r v a t i o n s of f i s h were made si m u l t a n e o u s l y i n a l l l o c a t i o n s as f a r as p o s s i b l e . Homing behaviour was compared i n 0. maculosus from Port Renfrew (exposed), F i r s t Beach (moderately exposed), and Grappler I n l e t ( s h e l t e r e d ) . a t o t a l of 286 f i s h were t r a n s p l a n t e d as f o l l o w s : Grappler I n l e t - two groups of 50 f i s h were r e c i p r o c a l l y t r a n s p l a n t e d between the s m a l l bay and the mudflat on the south s i d e of the i n l e t , a d i s t a n c e o f about 120 m; F i r s t Beach - two groups of 49 f i s h were r e c i p r o c a l l y t r a n s p l a n t e d between two groups o f four pools each about 60 m apart; Port Renfrew - two groups o f 44 f i s h were r e c i p r o c a l l y t r a n s p l a n t e d between two groups o f thr e e and f i v e pools each, about 60 m apa r t . Subsequent t r a p p i n g was conducted and ob s e r v a t i o n s were made a t two week i n t e r v a l s as f a r as p o s s i b l e , up t o f o u r months. Homing behaviour was compared i n 0. maculosus from Benson I s l a n d (exposed) and Ranee I s l a n d ( s h e l t e r e d ) . a t o t a l of 103 f i s h were t r a n s p l a n t e d as f o l l o w s : Ranee I s l a n d - two 84 groups of 17 and 34 f i s h each were interchanged between t h e two study s i t e s i n the i n l e t , about 50 m a p a r t ; Benson I s l a n d - two groups of 26 f i s h each were r e c i p r o c a l l y t r a n s p l a n t e d between two groups of t h r e e pools each about 80 ffl a p a r t . Subsequent r e t r a p p i n g and o b s e r v a t i o n s were attempted on a number of oc c a s i o n s f o r almost two months. Homing behaviour of O. maculosus was compared on the south e a s t e r n s i d e of Haines I s l a n d (moderately exposed) and the Haines I s l a n d shore of Dodger Channel (sheltered) . A t o t a l o f 88 f i s h were t r a n s p l a n t e d as f o l l o w s : Dodger Channel - 34 f i s h were t r a n s p l a n t e d from the western to eastern end o f the % p s t e r a bed i n the channel, about 70 m; Haines I s l a n d - two groups of 30 and 24 f i s h each were approximately r e c i p r o c a l l y t r a n s p l a n t e d between two groups of t h r e e p o o l s each, about 50 m a p a r t . Subseguent r e t r a p p i n g and o b s e r v i n g were conducted a number of times u n t i l the experiment was terminated a f t e r s i x weeks. Homing behaviour and area f i d e l i t y were compared i n 0. maculosus from K i r b y P o i n t (exposed). F i r s t Beach (moderately exposed) and the l a r g e t i d e p o o l on Haines I s l a n d ( s h e l t e r e d ) . A t o t a l of 111 f i s h were t r a n s p l a n t e d as f o l l o w s : Haines I s l a n d -a group of 52 f i s h were d i s p l a c e d about 60 m from the l a r g e t i d e p o o l to Dodger Channel, F i r s t Beach - 32 f i s h were approximately r e c i p r o c a l l y t r a n s p l a n t e d between two groups of pools about 60 m a p a r t ; K i r b y P o i n t - one group of 18 f i s h and another of nine f i s h were approximately r e c i p r o c a l l y t r a n s p l a n t e d between two groups of pools at two l o c a t i o n s on the 85 p o i n t . In both cases the f i s h were d i s p l a c e d about 50 m. Percentages homing and remaining a t the t r a n s p l a n t areas were c a l c u l a t e d f o r a l l nine s i t e s . In a d d i t i o n , a t o t a l o f 123 f i s h were r e p l a c e d i n the area i n which they were captured, as f o l l o w s : Haines I s l a n d - 53 f i s h were r e p l a c e d i n t o the l a r g e t i d e p o o l i n t h e area i n which they were captured; F i r s t Beach - 44 f i s h were r e p l a c e d i n t o the t i d e p o o l s i n which they were f i r s t captured; K i r b y P o i n t - 26 f i s h were r e p l a c e d i n t o the pools i n which they were cap t u r e d . Subsequent r e t r a p p i n g was conducted and o b s e r v a t i o n s were made twi c e weekly at a l l s i t e s u n t i l the experiment was terminted a f t e r f i v e weeks. Percentages found i n the home and home and nearby pools and i n d i s t a n t pools were c a l c u l a t e d f o r each s i t e . R e s u l t s The r e s u l t s of the fou r t r a n s p l a n t experiments (Table 18) show that i n s p i t e of the low percentages l o c a t e d a f t e r r e l e a s e i n some areas, i n each case the percentages s u c c e s s f u l l y homing a r e g r e a t e r i n areas of moderate . to g r e a t e r exposure ( t i d e p o o l areas) than i n s h e l t e r e d areas ( i n l e t s ) . However the percentages homing i n d i f f e r e n t t i d e p o o l areas show a g r e a t e r degree of v a r i a b i l i t y than a n t i c i p a t e d , and there appears t o be no r e l a t i o n s h i p between t h i s v a r i a b i l i t y and exposure as determined by l o c a t i o n and o b s e r v a t i o n . The percentages o f 0. maculosus remaining a t the t r a n s p l a n t s i t e s a re v a r i a b l e , but T a b l e 18 Honing b e h a v i o u r i n a r e a s o f d i f f e r e n t e x p o s u r e P.R. F.E. G.I. B.I. P.I. H . I . i D.C. K.P. F.B. H.I.z Date r e l e a s e d 5 Nov 2 Nov 1975 4 June 2 June 1976 21 O c t o b e r 1976 8 Aug 9 Auq 7 Aug 1977 Number r e l e a s e d 88 98 100 52 54 34 27 32 52 Number homed P e r c e n t homed 18 20 35 36 27 50 7 26 19 59 Number s t a y i n g 0 2 i n t r a n s p l a n t a r e a P e r c e n t s t a y i n g 0 2 i n t r a n s p l a n t a r e a 33 63 11 41 13 41 Days s t a y i n g i n t r a n s p l a n t area a. homers b. non-homers 15,26 2 3 , 3 9 , 90 ,94 1x21 , 2 8 x 9 , 53x3 11,11 39 1 , 3 , 3 , 3 , 3 , 3 , 3 , 3 1 , 3 , 3 , 3 , 3 , 3 , 1 0 , 2 2 , 1 1 , 11 , 18 2 2 , 2 3 , 3 6 18 ,18 P e r c e n t o f 42 homers r e t u r n i n g t o home p o o l 74 100 70 100 68 P.P.: E o r t Renfrew, F.B.: F i r s t Beach, G . 1 . : G r a p p l e r I n l e t , B . I . : Benson I s l a n d , R.I.: Ranee I s l a n d , H.I. 1 : H a i n e s I s l a n d (south e a s t s i d e ) , D . C : Dodger C h a n n e l , K.P.: K i r b y P o i n t , H. I. 2 : H a i n e s i s l a n d ( l a r g e t i d e p o o l ) co 87 do not show i n c r e a s i n g numbers of f i s h remaining a t the t r a n s p l a n t s i t e i n l e s s exposed t i d e p o o l areas. Only i n i n l e t s and channels are the p r e d i c t e d f i n d i n g s confirmed. In the f i r s t experiment the s m a l l percentage of f i s h l o c a t e d a f t e r r e l e a s e may be the r e s u l t of a s e r i e s o f extremely severe storms which occurred j u s t subsequent t o t r a n s p l a n t i n g . At both F i r s t Beach and Port Renfrew a r e d u c t i o n i n the number of 0. maculosus was e v i d e n t f o l l o w i n g the storms. Khoo (1971) found an i n v e r s e r e l a t i o n s h i p between homing performance and sea s t a t e c o n d i t i o n s (as measured by percent o b s e r v a t i o n s of s w e l l s g r e a t e r than or equal t o s i x f e e t ) . The second experiment (Benson I s l a n d and Ranee Island) produced very unexpected r e s u l t s . At the time of t r a p p i n g and r e l e a s e t h e r e were numerous 0. maculosus i n the i n l e t around Ranee I s l a n d . F o l l o w i n g r e l e a s e of the tagged f i s h , the p o p u l a t i o n of 0. maculosus i n the area almost completely disappeared t o be r e p l a c e d by l a r g e numbers of L e p t o c o t t u s armatus. A n a l y s i s of stomach c o n t e n t s of 0. maculosus from t h i s area showed a low d i e t d i v e r s i t y when compared with f i s h from F i r s t Beach and Por t Renfrew (Ruth, 1976). The a p p a r e n t l y u n s t a b l e p o p u l a t i o n of 0. maculosus at Ranee I s l a n d may be a r e f l e c t i o n of t h i s . Although t h e t h i r d experiment (Haines I s l a n d and Dodger Channel) was conducted f o r only s i x weeks and a t a time when t h e r e i s a high freguency of storms, the percentage o f 88 O, maculpsus at Haines Island which had successfully homed by the end of t h i s period was considerably greater than the percentage homing i n Dodger Channel. No 0. maculosus were seen or trapped at the western end of the eel grass bed and intensive trapping of t h i s s i t e prior to the experiment produced none. This and the low percentage homing suggest that while the release s i t e was not f e a s i b l e as an alternative habitat f o r the transplanted f i s h , homing behaviour i s not strongly expressed i n 0. maculosus found in i n l e t s . The fourth experiment (Kirby Point, F i r s t Beach, Haines Island) was terminated aft e r f i v e weeks. although this i s a r e l a t i v e l y short period of time, data from F i r s t Beach suggest that the majority of information i s acquired in the f i r s t month followinq release. Since the weather was favourable almost simultaneous twice weekly v i s i t s to each s i t e were possible for the duration of the experiment. In aqreement with the other experiments, the data suggest that homing behaviour (that i s , returning to the area of capture) i s better developed or at least expressed, i n tidepool than i n l e t areas, but f a i l to show that a gradient of a b i l i t y i n homing behaviour e x i s t s which corresponds to a v i s u a l l y determined exposure gradient. From the r e s u l t s of the replacement experiment at Kirby Point, F i r s t Beach and the large tidepool on Haines Island (Table 19) i t i s evident that the percentage of f i s h found i n the home pool only i s much greater at Kirby Point than at F i r s t Beach, where the usual s i t u a t i o n of equal percentaqes in the Table 19 Area f i d e l i t y i n s i t e s o f d i f f e r e n t exposures Area r e l e a s e d Date r e l e a s e d Number r e l e a s e d Number found i n home pool only Percent found i n home pool only Number found i n home and nearby pools Percent found i n home and nearby pools Number found i n home pool and home and nearby pools Percent found i n home pool and home and nearby pools K.P. F.B. H.I. 8 Aug 77 9 Aug 77 7 Aug 77 26 aa 53 23 17 1 88 3 9 2 2 18 8 a 1 25 35 96 80 2 0 5 0 Number found i n d i s t a n t 0 pools Percent found i n d i s t a n t 0 pools K.P.: Ki r b y P o i n t , F. B.: F i r s t Beach, H. I . : Haines I s l a n d 90 home and nearby pools was found. As a n t i c i p a t e d , l i t t l e area f i d e l i t y was shown to the l a r g e t i d e p o o l on Haines I s l a n d . The data suggest t h a t my perception of exposure, based on l o c a t i o n and o b s e r v a t i o n , bears l i t t l e r e l a t i o n s h i p t o the homing behaviour of 0. maculosus. Since wave a c t i o n (turbulence) has been demonstrated as important i n t h e d i s t r i b u t i o n and a c t i v i t y of 0. maculosus (Green, 1971a,b,c), c o n s i d e r a t i o n of t h i s and a r e l a t e d f a c t o r (the roughness of the t e r r a i n , i n terms of the steepness and i r r e g u l a r i t y o f the shore) with r e s p e c t t o the homing behaviour of 0. maculosus, may be more r e l e v a n t than an o v e r a l l s u b j e c t i v e i mpression of exposure. These f a c t o r s are con s i d e r e d i n the next s e c t i o n . 4.Measurement of wave a c t i o n and t o p o g r a p h i c a l r e g u l a r i t y The problem o f measuring the r e l a t i v e exposure i n terms of wave a c t i o n or t u r b u l e n c e i n d i f f e r e n t l o c a l i t i e s has been a t t a c k e d i n a number of ways. B a l l a n t i n e (1961) suggested e i g h t b i o l o g i c a l l y determined exposure c a t e g o r i e s , e s s e n t i a l l y based on the abundance o f common s p e c i e s , ranging from extremely s h e l t e r e d to extremely exposed. While b i o l o g i c a l s c a l e s a re u s e f u l i n a d e s c r i p t i v e sense they are not e a s i l y g e n e r a l i z e d over wider areas. Determinations of exposure or wave a c t i o n based on wind measurements have been used by Moore (1935) and Southward 91 (195 3 ) , u s i n g the percentage of winds over 10 0 days blowing i n t o the exposed a p e r t u r e of a given l o c a l i t y and t h e percentage of winds egual to or g r e a t e r than 10 knots which produced a wash at l e a s t one f o o t over the p r e d i c t e d t i d a l h e i g h t , r e s p e c t i v e l y . The former method does not take account of wind f o r c e or s w e l l s and the l a t t e r does not take i n t o account the s l o p e of the l o c a l i t y . Green (1967) used a submersion-emersion sensor (Druehl and Green, 1970), b o l t e d t o the s u b s t r a t e at a known v e r t i c a l height and attached t o a r e c o r d e r which recorded the times of emergence and submergence of t i d e p o o l s . Comparing the a c t u a l times with p r e d i c t e d times of submergence enabled him to r a t e pools i n t o f o u r c a t e g o r i e s from exposed to s h e l t e r e d . At l e a s t two such sensors are r e g u i r e d t o be p o s i t i o n e d s i m u l t a n e o u s l y . Jones and Demetropoulos (1968) developed a drogue attached to a s p r i n g dynamometer which r e c o r d s the maximum drag produced by waves i n the l o c a l i t y . , No measurement of freguency i s provided. Harger (1970) measured wave impact over one t i d a l period by the movement down a n a i l o f a s t e e l p l a t e held i n p o s i t i o n with a C c l i p . A method f o r measuring s h o r t term exposure was d e s c r i b e d by Huus (1968) i n which P l a s t e r o f P a r i s b a l l s are a t t a c h e d t o s t e e l rods embedded i n the s u b s t r a t e and the weight l o s s o f the b a l l s compared t o weight l o s s f i g u r e s at known water v e l o c i t i e s . While these methods may be u s e f u l i n some s t u d i e s they do not provide a simple means of measuring exposure i n a v a r i e t y of widely spaced areas over a long period of time. In t h i s 92 study a method was r e g u i r e d which measured t h e exposure where t h e f i s h a r e l o c a t e d over a r e l a t i v e l y e x t e n s i v e p e r i o d . Thus the method used was based on t h e weight l o s s o f cement b l o c k s a t t a c h e d t o t h e s u b s t r a t e ( i n p o o l s and on roc k s ) but a b l e t o move i n a hemisphere about the anchor and undergo a b r a s i o n by th e a c t i o n of waves moving t h e b l o c k over t h e s u b s t r a t e . I n i t i a l l y , a p i l o t s t u d y was co n d u c t e d l a s t i n g a p p r o x i m a t e l y two months. However, the weakness o f t h e p i n s used r e s u l t e d i n a h i g h l o s s o f cement b l o c k s i n more exposed a r e a s . S u b s e g u e n t l y , a l o n g e r term s t u d y , l a s t i n g a l m o s t n i n e months was conducted. Only t h e r e s u l t s o f t h e f i n a l s t u d y a r e r e p o r t e d . The r e l a t i v e roughness o f t h e t e r r a i n was e v a l u a t e d by a s u b j e c t i v e e s t i m a t e based on o b s e r v a t i o n s of the s t u d y a r e a s . The s t e e p n e s s o f t h e r o c k y s h e l v e s and t h e degree of i r r e g u l a r i t y o f t h e s e s h e l v e s were used i n t h i s e s t i m a t e . Methods Styrofoam cups were c u t down to make moulds 4.5 cm h i g h . The cups were then g r e a s e d w i t h v a s e l i n e and e y e b o l t s 6.35 cm l o n g were i n s e r t e d i n t h e bottom of the cup so t h a t p a r t of the eye was i n s i d e t h e cup. Con c r e t e was mixed u s i n g P o r t l a n d CSA Type 20 cement i n the f o l l o w i n g p r o p o r t i o n s cement : sand : water - 5 : 1 : 3. T h i s m i x t u r e was poured i n t o t h e cups and a l l o w e d t o s e t . The s t y r o f o a m cups were then 93 peeled o f f l e a v i n g a c o n c r e t e block with an i n s e r t e d e y e b o l t ( F i g u r e 14a). The b l o c k s were weighed to the nearest grant. The b l o c k s were anchored i n t i d e p o o l s and t o the s u b s t r a t e a t nine s i t e s on t h e west coast o f Vancouver I s l a n d : Cape Beale, Port Renfrew, Benson I s l a n d , Pachena P o i n t , F i r s t Beach, Helby I s l a n d , Grappler I n l e t (bay), Ranee I s l a n d and the l a r g e t i d e p o o l on Haines I s l a n d . Ten b l o c k s were anchored at each s i t e using a p i n attached to an e y e b o l t embedded i n h y d r a u l i c cement. To overcome the problem of the weakness of the shower c u r t a i n c l i p s used i n the p i l o t study, h a l i b u t snaps were used as the pin between the cement block and the anchored eyebolt (Figure 14b). In a d d i t i o n to the cement b l o c k s anchored i n the f i e l d , ten blocks each were anchored to b r i c k s i n the calm and "exposed" s i d e s of a tank used i n an experimemt t o determine whether g r e a t e r numbers of c i r r i c o u l d be e x p e r i m e n t a l l y produced on f i s h i n an "exposed" tank as opposed t o a calm tank. T h i s provided a measure of the e f f e c t of constant immersion on the b l o c k s and the r e l a t i v e exposure of the s i d e of the tank r e c e i v i n g waves. A l l the cement blocks were put i n t o p o s i t i o n between 30 August and 12 September, 1976 and were removed between 21 May and 28 Say, 1977., A f t e r removal the b l o c k s were u n i f o r m l y washed and scrubbed with s t e e l wool, and then oven d r i e d at 55°C f o r 48 hours. Keeping the b l o c k s dry, they were again u n i f o r m l y scrubbed with s t e e l wool. T h i s procedure succeeded i n removing the attached animals, such as S p i r o r b i s sp. , The b l o c k s were 5.8 c m - + — 4 . 5 c m — * • F i g u r e 14a Cement b l o c k d e s i g n F i g u r e 14b Cement b l o c k a n c h o r e d i n p o o l 95 weighed to the nearest gram. The Kruksal-Wallis one-way analysis of variance by ranks, corrected f o r t i e s (Siegel, 1956), was used to compare the i n i t i a l weights of the blocks at each s i t e to determine whether there were any s i g n i f i c a n t differences between the samples when they were i n s t a l l e d . Results The Kruksal-Wallis one-way analysis of variance by ranks, corrected f o r t i e s , on the i n i t i a l weights f o r a l l samples (Table 20) showed no s i g n i f i c a n t differences between samples (H=.958, p>.05). Weight loss (mean grams and mean ranks) and the number of cement blocks remaining are also shown in Table 20. Examination of the mean ranks shows several clusters of ranks: Cape Beale and Benson Island; Port Renfrew, Pachena Point and F i r s t Beach; Ranee Island, Helby Island, Grappler I n l e t and the wave tank; Haines Island and the calm tank. Since only a r e l a t i v e exposure rating was reguired and since the individual sample sizes were small, especially f o r several groups, i t appeared that considering the samples i n the groups delineated above was the most useful approach. Dsing the multiple comparisons test based on rank sums, and corrected for t i e s (Hollander and Wolfe, 1973; Dunn, 1964), the four groups of samples were compared with each other. Dunn suggests using a r e l a t i v e l y high s i g n i f i c a n c e l e v e l (such T a b l e 20 F i n a l study o f r e l a t i v e exposure Weight s t a t i s t i c s o f cement blocks I n i t i a l I n i t i a l N Mean wt Mean wt N mean wt mean wt l o s s l o s s (grams) (ranks) (grams) (ranks) Cape Beale 175.9 56.1 10 32.0 80.3 2 Benson I s l a n d 174.6 47.2 10 53.8 75 41 4 P o r t Renfrew 176.2 56.7 10 21.3 59.6 7 Pachena Point 175.6 54.6 10 22.1 57.0 10 F i r s t Beach 176.1 56.4 10 29.0 63.4 7 Helby I s l a n d 176.0 57.0 10 17.0 38.8 6 Ranee I s l a n d 175.9 56.4 10 19.2 49.9 9 Gr a p p l e r I n l e t . 175.6 53.7 10 17.7 39.3 10 Haines I s l a n d 175.7 56.3 10 12.7 17.3 10 Wave Tank 176.0 57.0 10 17.1 38.3 10 Calm Tank 176.4 59.4 10 12.2 14.0 10 97 as 0.20) i n such multiple comparison tests, since taking a more t r a d i t i o n a l l e v e l of 0.05 for example, "makes establishing substantial differences exceedingly d i f f i c u l t " . Hence, comparisons were made using a value of of 0.20. This resulted i n the following ranking of s i t e s i n order of decreasing exposure (with the mean number of cement blocks remaining i n parentheses): Cape Beale, Benson Island (3) Port Eenfrew, Pachena Point, F i r s t Beach (8) Ranee Island, Helby Island, Grappler I n l e t , Wave Tank (8.75) Haines Island, Calm Tank (10). The four groups were a l l s i g n i f i c a n t l y d i f f e r e n t (p<.20) from each other except Cape Beale, Benson Island and Port Renfrew, Pachena Point, F i r s t Beach., However, since the lack of si g n i f i c a n c e i s primarily due to the small number of blocks remaining at these s i t e s and since t h i s i n i t s e l f i s an indication of r e l a t i v e exposure, Cape Beale and Benson Island are rated as more exposed than Port Renfrew, Pachena Point and F i r s t Beach. The ranking of s i t e s according to the r e l a t i v e roughness of the terrain resulted in a somewhat di f f e r e n t order. 98 The s i t e s at Cape Beale, Benson I s l a n d and K i r b y Point are extremely i r r e g u l a r , with r e l a t i v e l y narrow, sometimes s t e e p l y s l o p i n g s h e l v e s and s m a l l surge channels, compared with the wider, l e s s p e r i l o u s shelves a t F i r s t Beach and the southeast s i d e of Haines I s l a n d , and again with the broad, f l a t s h e l v e s a t Port Renfrew and Pachena P o i n t , , In s h e l t e r e d areas, G r a p p l e r I n l e t and Ranee I s l a n d appear to be more t o p o g r a p h i c a l l y i r r e g u l a r than the sand/mud f l a t s of the l a r g e t i d e p o o l on Haines I s l a n d and Dodger Channel. C o n s i d e r a t i o n of the r e s u l t s of the cement block e v a l u a t i o n of wave a c t i o n together with the s u b j e c t i v e estimates of roughness of the t e r r a i n suggests t h a t e v a l u a t i n g the exposure o f an area simply by o b s e r v a t i o n and l o c a t i o n may be somewhat misleading. an area which by l o c a t i o n and o b s e r v a t i o n might be c l a s s e d among the most exposed <for example, Port Renfrew, Pachena Point) may, because o f the r e g u l a r i t y of the t e r r a i n ^ have a s i m i l a r o v e r a l l exposure to a s i t e which by l o c a t i o n appears more s h e l t e r e d but which has a rougher t e r r a i n ( f o r example, F i r s t Beach). In the f o l l o w i n g a n a l y s i s of homing behaviour and exposure, the study s i t e s and the homing behaviour observed t h e r e were c l a s s i f i e d i n i t i a l l y i n t o the groups suggested by the cement block r a t i n g s , and w i t h i n these groups f u r t h e r d i v i d e d by the t o p o g r a p h i c a l i r r e g u l a r i t y e s t i m a t e s to provide an i n d i c a t i o n of the e f f e c t of these two f a c t o r s on homing behaviour. 99 5»Discussion From Table 21 i t i s evident t h a t with d e c r e a s i n g turbulence and i n c r e a s i n g r e g u l a r i t y of the t e r r a i n ^ the area to which f i d e l i t y i s shown i n t i d e p o o l areas, i n c r e a s e s i n s i z e from one pool, to one p r e f e r r e d pool t o a group of pools. In more s h e l t e r e d t o p o g r a p h i c a l l y r e g u l a r i n l e t s , f i d e l i t y i s shown to a p p a r e n t l y l a r g e r areas. When d i s p l a c e d , f i s h i n t u r b u l e n t rough areas d i s p l a y l e s s evidence o f homing than f i s h i n l e s s t u r b u l e n t , rough areas. However, those few f i s h which do home i n t u r b u l e n t rough areas r e t u r n t o t h e home range with g r e a t e r p r e c i s i o n than i n other areas (that i s , g r e a t e r percentages r e t u r n to the i n i t i a l pool o f capture, the home p o o l , than to other pools i n the home r a n g e ) i n i n l e t s few f i s h home. With de c r e a s i n g t u r b u l e n c e and i n c r e a s i n g r e g u l a r i t y of the t e r r a i n , d e creasing numbers of f i s h s t a y i n the t r a n s p l a n t area. These r e s u l t s c o n f i r m and extend Khoo's (1971) f i n d i n g s t h a t poor weather and rough t e r r a i n , i n the form o f steep trenches and a b r u p t l y s l o p i n g shelves a d v e r s e l y a f f e c t homing a b i l i t y . The ki n d o f homing behaviour e x h i b i t e d a p p a r e n t l y depends on the degree o f wave a c t i o n and roughness o f the t e r r a i n . Turbulence has been shown t o play a major r o l e i n the v e r t i c a l d i s t r i b u t i o n , high t i d e d i s t r i b u t i o n and a c t i v i t y o f T a b l e 21 Honing b e h a v i o u r a c c o r d i n g to t o p o g r a p h i c a l r e g u l a r i t y and t u r b u l e n c e TIDEFCOIS INLETS T u r b u l e n c e h i g h moderate low v e r y low T o p c g r a phy h i g h l y i r r e g u l a r i r r e g u l a r r e l a t i v e l y r e g u l a r r e g u l a r e x t r e m e l y r e g u l a r Area f i d e l i t y p a r t i c u l a r p o o l u s u a l l y one p r e f e r r e d p o o l group o f p o o l s l a r g e a r e a ? l a r g e a r e a ? Honing b e h a v i o u r P e r c e n t homing P e r c e n t r e m a i n i n g i n t r a n s p l a n t a r e a P e r c e n t o f homers homing t o home p o o l r e l a t i v e l y low moderate t o h i g h moderate t o h i g h low v e r y low moderate t o h i g h lew t c moderate v e r y low low v e r y low hi g h moderate to h i g h moderate to h i g h H-1 o o 101 0. maculosus (Green, 1971a,b,c). In exposed t r a n s e c t s 0. maculosus t e n d s t o be c o n f i n e d t o higher t i d e p o o l s , whereas i n s h e l t e r e d a r e a s , i t occurs throughout the i n t e r t i d a l . Seasonal changes i n d i s t r i b u t i o n are evident when storm induced d i s r u p t i o n of pools o c c u r s and the r e s i d e n t p o p u l a t i o n i s washed out of the pool or d e p a r t s (Green, 1971a; personal o b s e r v a t i o n ) . In winter months, when t u r b u l e n c e i s g r e a t e s t , a d e c l i n e i n f i s h numbers i s e v i d e n t . T h i s has a l s o been shown f o r another i n t e r t i d a l f i s h , Acanthocottus L=Eno£hrj;sJ b u b a l i s (Euphrasen) (Gibson, 1967). At high t i d e , only 0. maculosus i n s h e l t e r e d areas l e a v e the pool ( i n some s h e l t e r e d areas there i s an almost complete onshore s h i f t i n the d i s t r i b u t i o n of O. maculosus l e s s thsn 5.5 cm); i n exposed areas they seek cover u n t i l the pool i s i s o l a t e d again (Green, 1971b,c). In moderately exposed a r e a s , the only time at which a s i g n i f i c a n t p r o p o r t i o n of f i s h leave the pool i s i n J u l y , August and September, the calmest months of the year (Green, 1971b). Although t h e s e are a l s o t h e h o t t e s t months of the year, and Q. maculosus remain i n or r e t r e a t t o deeper water i n pools at temperatures above 15° C, t i d a l f l o o d i n g i n June has been shown t o reduce the temperature from 200C to 11°C i n the warmest p a r t s of a pool w i t h i n one hour (Green, 1971c). Green found the change duri n g the f a l l from b e i n g a c t i v e t o i n a c t i v e at high t i d e occurred f i r s t i n the 0. maculosus i n h a b i t i n g the more exposed of two otherwise s i m i l a r pools (1971a). Reduced a c t i v i t y d u r i n g t u r b u l e n t 102 peri o d s has a l s o been rep o r t e d i n C l i n o c o t t i s a n a l i s ( W i l l i a m s , 1957} . There appears to be a r e l a t i o n s h i p between the amount of wave a c t i o n and the amount of high t i d e movement of 0. maculosus, from v i r t u a l l y none i n an exposed t i d e p o o l areas t o an onshore s h i f t i n s h e l t e r e d t i d e p o o l areas and p o s s i b l y almost c o n t i n u a l movement i n i n l e t s , as the f i s h f o l l o w the t i d e . Thus i n rough t u r b u l e n t areas, few f i s h l e a v e the p o o l a t high t i d e and hence d i s p l a y s t r i c t pool f i d e l i t y . When t r a n s p l a n t e d , f i d e l i t y i s changed t o the new pool and few f i s h home, although those which do home show grea t e r p r e c i s i o n i n the area t o which they r e t u r n , presumably because they r a r e l y move out of the home pool i n t h e i r n a t u r a l movements. In l e s s t u r b u l e n t , l e s s rough areas, the degree of movement at high t i d e appears t o depend on the r e g u l a r i t y of the t e r r a i n . Where the t e r r a i n i s more r e g u l a r , presumably t u r b u l e n c e between pools i s reduced and movement between pools l e s s hazardous. When f i s h from these areas are d i s p l a c e d , the numbers remaining i n the t r a n s p l a n t area appear to depend on the roughness of the t e r r a i n ; i n more r e g u l a r areas the f i s h leave the t r a n s p l a n t p o o l . I n s h e l t e r e d i n l e t s , where t u r b u l e n c e i s never great and movement i s p o s s i b l e at a l l times, a much g r e a t e r amount of movement appears to take p l a c e , r e s u l t i n g i n l i t t l e area f i d e l i t y and homing success. The absence of d i s t i n c t t o p o g r a p h i c a l i r r e g u l a r i t i e s a l s o appears t o reduce the occurrence o f f i d e l i t y to a s m a l l area comparable t o t h a t of a 10 3 group of t i d e p o o l s . To my knowledge, t h e r e i s only one published study comparing home range f i d e l i t y i n t h e same i n t e r t i d a l s p e c i e s {Blennius johplis (Linnaeus) and Acanthocottus f =Enophrys 1 b u b a l i s ) i n two semi-exposed ( B a l l a n t i n e , 1961) ar e a s . D i f f e r e n c e s were noted i n one s p e c i e s (Blennia§ fih.olis) which were suggested as p o s s i b l y being due to the t o p o g r a p h i c a l d i s s i m i l a r i t y o f t h e two areas; the area where a higher frequency of r e t u r n to t h e home pool a f t e r being absent was observed, i s i r r e g u l a r l y d i v i d e d by v e r t i c a l rock edges producing g u l l i e s , i n c o n t r a s t to the f l a t t e r , u n d i vided rocky shore at the other s i t e (Gibson, 1967). Although t h e r e are few p u b l i s h e d data comparing home range i n the same s p e c i e s i n d i f f e r e n t areas, comparisons can be drawn between the f a i r l y l i m i t e d home ranges r e p o r t e d f o r t i d e p o o l f i s h e s Am phi g on op t er u s f- =ili£E2E§trusJ au r o r a (Jordan and G i l b e r t ) (Hubbs, 1921), c l i n o c o t t u s a n a l i s . G i r e l l a n i g r i c a n s (Ayres) ( W i l l i a m s , 1957), Acanthocottus L= Enophrysl b u b a l i s , B l e n n i u s £holis (Gibson, 1967), Hypsoblennius q i l b e r t i (Jordan) (Stephens e t a l . , 1970), C l i n o c o t t u s q l p b i c e p s (Green, 1973) and small c o r a l r e e f f i s h D a s c y l l u s aruanus (Linnaeus) ( S a l e , 1971), Holacanthus bermudensis Goode (Bardach, 1958) , the somewhat l a r g e r but f a i r l y r e s t r i c t e d home ranges shown by near shore rocky and c o r a l r e e f f i s h Sebastes f l a v i d u s ( C a r l s o n and Haight, 1972), Tautoqolabrus adspersus (Green, 1975), Epinephelus s t r i a t u s •• (Bloch) , E. gutt§tus (Linnaeus) (Bardach, 104 1958) and the apparently comparatively poorly developed area f i d e l i t y shown by freshwater f i s h G a l a x i a s bongbong Macleay (Berra, 1973), Cottus b a i r d i p u n c t u l a t u s ( G i l l ) ( B a i l e y , 1952) , Cottus b a i r d i (Girard) (McCleave, 1964) # L§£2ffiis mega l o t i s (Rafinesque) (Berra and Gunning, 1972) and i n t i d a l c r e e k s and s a l t marshes H e n i d i a menidia (Linnaeus), Fundulns h e t e r o c l i t u s (Linnaeus) (Buttner and B r a t t s t r o m , 1960; L o t r i c h , 1975). Comparison of the r e s u l t s of these s t u d i e s appears t o suggest t h a t f i s h c l o s e l y a s s o c i a t e d with the s u b s t r a t e where the r e are t o p o g r a p h i c a l i r r e g u l a r i t i e s , f o r example, p o o l s , r e e f s , wrecked boats, boulder patches e t c . show evidence o f f a i r l y r e s t r i c t e d area f i d e l i t y . In a d d i t i o n , where t u r b u l e n c e can be c o n s i d e r a b l e and the f i s h i s l i a b l e to be swept out of the area, r e s t r i c t e d area f i d e l i t y appears to be shown. With regard to homing behaviour, there do not appear to be any p u b l i s h e d r e p o r t s of d i f f e r e n c e s i n homing behaviour of the same i n t e r t i d a l s p e c i e s i n d i f f e r e n t areas. D i f f e r e n t s p e c i e s of i n t e r t i d a l f i s h have been shown to d i s p l a y v a r y i n g success i n homing performance, from high percentage r e t u r n s i n C l i n o c o t t u s g l o b i c e p s (Green, 1973) and Bathy gobius s o p o r a t o r (Beebe, 1931), moderate to low r e t u r n s i n Hypsoblennius g i l b e r t i (Stephens e t a l . , 1970), Blennius p. ho i i s , ftcanthocottus L=Eng£hr ;ysJ b u b a l i s , C i l i a t a mustela (Linnaeus) (Gibson, 1967), G i E g l l a n i g r i c a n s ( W i l l i a m s , 1957), to almost complete i n a b i l i t y to home i n C l i n o c o t t u s a n a l i s ( W i l l i a m s , 1957). Hear shore marine f i s h e s show s i m i l a r v a r i a b i l i t y from r e l a t i v e l y high 105 percentage returns in Tautogolabrus adsgersus (Green, 1975), moderate returns i n Sebastes flayidus (Carlson and Haight, 1972), low to moderate returns i n EjDine^helus str^atus and E. guttatus (Bardach, 1958) and i n a b i l i t y to return from a considerable distance i n Holacanthus berjrudensis (Bardach, 1958) . In general, freshwater f i s h and f i s h in t i d a l creeks show much les s success i n homing than marine fi s h e s i n which t h i s has been examined (Lotrich, 1975; McCleave, 1964; Berra, 1973; Gerking, 1959; Gunning, 1959).. While turbulence, topography (and distance displaced) evidently appear to have a general effect on homing success, other factors such as changes i n area f i d e l i t y over the l i f e of the f i s h and existence and s i z e of home range may also be s i g n i f i c a n t . 106 V. MORPHOLOGICAL DIFFERENCES BETWEEN FISH IN DIFFERENT LOCATIONS 1.Port Renfrew, F i r s t Beach, Grappler I n l e t The e a r l y s u g g e s t i o n t h a t there were d i f f e r e n c e s i n homing behaviour of 0. maculosus i n areas o f d i f f e r e n t exposures prompted f u r t h e r i n v e s t i g a t i o n of b e h a v i o u r a l d i f f e r e n c e s . At the same time as the f i r s t b e h a v i o u r a l experiment i n v e s t i g a t i n g homing behaviour i n d i f f e r e n t l o c a t i o n s was conducted, examination o f m e r i s t i c and morphometric c h a r a c t e r s i n these p o p u l a t i o n s was undertaken to determine whether t h e r e were any d i f f e r e n c e s between the p o p u l a t i o n s . . Such d i f f e r e n c e s , i f present, might c o n c e i v a b l y be r e l a t e d t o b e h a v i o u r a l d i f f e r e n c e s . Methods To examine m e r i s t i c and morphometric c h a r a c t e r s , a t o t a l o f 304 0. maculosus were c o l l e c t e d as f o l l o w s : 136 from the bay i n Grappler I n l e t (29 October, 1975), 53 from the mudflat i n Grappler I n l e t (1 November, 1975), 59 from F i r s t Beach (2 November 1975) and 56 from Port Renfrew (5 November, 1975). The f i s h were f i x e d i n 10% f o r m a l i n immediately a f t e r c o l l e c t i o n and l a t e r t r a n s f e r r e d t o 37.5% i s o p r o p y l a l c o h o l , , 107 The f i s h were measured (standard l e n g t h - f o r con v e r s i o n t o t o t a l l e n g t h see appendix 2) and sexed, and s i x c h a r a c t e r s were measured: head l e n g t h , head depth, eye l e n g t h , i n t e r o r b i t a l d i s t a n c e , d i s t a n c e between a n t e r i o r nares and d i s t a n c e between p o s t e r i o r nares. a l l measurements were made with d i a l c a l i p e r s to the n e a r e s t 0.005 cm. Head depth, l e n g t h and eye l e n g t h were expressed and examined as percentages of standard l e n g t h . , I n t e r o r b i t a l d i s t a n c e and d i s t a n c e between a n t e r i o r and p o s t e r i o r nares were expressed and examined as percentages of head l e n g t h . Counts were made of d o r s a l f i n sp i n e s and r a y s and a n a l f i n ra y s . C i r r i were a l s o examined with r e s p e c t t o number, t h e i r nature ( s i n g l e , b i f i d , t r i p l e etc.) and l o c a t i o n ( l a t e r a l l i n e , around eye, head ( o r b i t t o o c c i p i t ) , m a x i l l a r y , preoperculum, operculum and behind the o p e r c u l a r f l a p above the base of the p e c t o r a l f i n ) . a n a l y s i s o f a l l c h a r a c t e r s except c i r r i was made ac c o r d i n g t o the method of Hubbs and Hubbs (1953). The number of c i r r i and the number of l a t e r a l l i n e c i r r i were c a l c u l a t e d and p l o t t e d a g a i n s t l e n g t h to determine i f any r e l a t i o n s h i p was apparent. 108 R e s u l t s From i n s p e c t i o n o f the g r a p h i c a l a n a l y s i s of the e i g h t c h a r a c t e r s examined ( F i g u r e 15), i t i s evident t h a t there are no obvious or c o n s i s t e n t d i f f e r e n c e s i n these c h a r a c t e r s between the f o u r p o p u l a t i o n s examined. The a n a l y s i s o f t o t a l and l a t e r a l l i n e c i r r i number against l e n g t h suggested an e x p o n e n t i a l r e l a t i o n s h i p , with the asymptotic number of c i r r i i n c r e a s i n g i n the order Grappler I n l e t , F i r s t Beach and P o r t Renfrew. T h i s r a i s e d the p o s s i b i l i t y that i f c i r r i c o n t a i n e d sensory r e c e p t o r s , there might be some r e l a t i o n s h i p between exposure, homing performance and the number o f such sensory r e c e p t o r s . I f d i f f e r e n c e s i n homing behaviour c o u l d be r e l a t e d to d i f f e r e n c e s i n the number of sensory r e c e p t o r s , and i f the nature of the sensory r e c e p t o r s could be determined ( f o r example, chemoreceptors), an i n d i c a t i o n of both the mechanism and v a r i a b i l i t y i n i t s p e r c e p t i v e n e s s i n r e l a t i o n to v a r i a b i l i t y i n homing behaviour might be provided. Hence a l a r g e r s c a l e i n v e s t i g a t i o n of the number and d i s t r i b u t i o n of c i r r i i n areas o f d i f f e r e n t exposure was undertaken. To determine e x p e r i m e n t a l l y whether c i r r i number i s a f u n c t i o n of exposure, each of two groups of s m a l l j u v e n i l e 0. maculosus was exposed t o e i t h e r continuous waves or calm water i n the l a b o r a t o r y . Exposure, u s i n g the same method as f o r the study s i t e s , was examined f o r each of the two c o n d i t i o n s . D O R S A L FIN RAYS Botanica l B e a c h F i r s t B e a c h G r a p p l e r inlet (bay) G r a p p l e r Inlet (mudf lat ) Botanical B e a c h F i rst B e a c h G r a p p l e r inlet (bay) G r a p p l e r Inlet (mudflat) Botanical B e a c h L_ First B e a c h i_ G r a p p l e r Inlet (bay) G r a p p l e r Inlet • I X X _ l 14 16 A N A L FIN RAYS 18 X • I L X 9 11 H E A D L E N G T H 13 I L L 1 I (mudf lat ) 22 26 30 H E A D D E P T H Botanical Beach i r~is Fi rst B e a c h I I ^ G r a p p l e r Inlet (bay) i I A i 34 1 I G r a p p l e r Inlet (mudflat) 12 16 20 15 E Y E L E N G T H I i L X X I 22 26 30 34 I N T E R O R B I T A L D ISTANCE I I 4 i i db l _ L~ 10 14 18 DISTANCE B E T W E E N POSTERIOR N A R E S L X = i : 1 _J J I L J 38 38 06 10 . 14 DISTANCE B E T W E E N ANTERIOR N A R E S !8 I C X .18 22 .26 .30 F i g u r e 15 Graphical analysis of eight m e r i s t i c characters at four areas 110 F i n a l l y , h i s t o l o g i c a l examination of the c i r r i was undertaken to determine whether any sensory receptors were apparent. 2.The re l a t i o n s h i p of c i r r i to exposure Since the preliminary investigation of c i r r i on f i s h from three d i f f e r e n t areas suggested that f i s h i n more exposed areas have more c i r r i (although l i t t l e difference was subseguently found i n r e l a t i v e exposure between Port Renfrew and F i r s t Beach) examination of t h i s apparent phenomenon was undertaken. 0. maculosus were collected from six additional s i t e s on the west coast of Vancouver Island and f i v e Alaskan c o l l e c t i o n s were examined. Methods To add to the i n i t i a l c o l l e c t i o n s made at Port Renfrew, F i r s t Beach and both the bay and the mudflat i n Grappler I n l e t , further c o l l e c t i o n s were taken at a l l s i t e s except the mudflat for c i r r i analysis. C o l l e c t i o n s of O* l i c u l o s u s f o r c i r r i analysis were also made at Cape Beale, Benson Island, Pachena Point, Helby Island, Ranee Island and the large tidepool on Haines Island. The s i t e s were chosen as covering a range of exposures, the r e l a t i v e positions of each s i t e in an exposure scale subseguently being determined by the weight loss of the cement blocks i n s t a l l e d at each s i t e , except 111 the mudflat i n Grappler I n l e t . Immediately a f t e r c o l l e c t i o n the f i s h were f i x e d i n 105S f o r m a l i n and l a t e r t r a n s f e r r e d to 37.5% i s o p r o p y l a l c o h o l . The f i s h were measured ( t o t a l length) t o the nearest 0.005 cm, sexed and the c i r r i were counted and recorded a c c o r d i n g t o t h e i r nature and l o c a t i o n . In a d d i t i o n , f i v e Alaskan c o l l e c t i o n s of 0. maculosus from the O.B.C. F i s h Huseum were examined with r e s p e c t t o c i r r i to determine whether the apparent phenomenon i s widespread. The c o l l e c t i o n s examined were from S h e l t e r I s l a n d (BC63-251: 58°26»N,134°52*W), F i s h Egg I s l a n d (BC63-151: 55°28'30"N,133°11•15"W), Saginaw Bay, Kuiu I s l a n d (BC61 - 0 9 9 : 56055'N, 13i*°16'W) , Tee Harbor, Cohen I s l a n d (BC63-87: 58°26 fN,134°46«50"W) and L i t t l e Port Walter, Baranof I s l a n d (BC63-1255; 56°23*N,134°38'30"W)• These areas were l o c a t e d on c h a r t s t o o b t a i n an estimate of t h e i r exposures r e l a t i v e t o each other and i n a g e n e r a l manner to the s i t e s on Vancouver I s l a n d . However, s i n c e no o b j e c t i v e measurement of the exposure o f the Alaskan s i t e s has been made, the exposure r a n k i n g s must be regarded c a u t i o u s l y . The f i s h from these c o l l e c t i o n s were measured ( t o t a l length) t o the n e a r e s t 0.005 cm, sexed and the number of c i r r i recorded a c c o r d i n g to nature and l o c a t i o n . T o t a l c i r r i number was examined with r e s p e c t to l e n g t h f o r each area and then e v a l u a t e d a c c o r d i n g t o exposure. 112 F u n c t i o n a l r e g r e s s i o n s of t o t a l c i r r i number vs l eng th were c o n s t r u c t e d f o r males and females s e p a r a t e l y and combined. In the case of j u v e n i l e s ( l e s s than 3.5 cm t o t a l length) where sex c o u l d not be de te rmined , the data on c i r r i were i n c l u d e d i n both the male and female r e g r e s s i o n s but only once i n the combined r e g r e s s i o n . Using the a g e - l e n g t h r e g r e s s i o n s c a l c u l a t e d f o r n ine o f the areas on the west c o a s t o f Vancouver I s l a n d , except the mudf lat i n G r a p p l e r I n l e t , the ages o f the f i s h from each area were c a l c u l a t e d and t o t a l c i r r i number was examined with r e s p e c t to age i n each of these a reas . Aga in, f u n c t i o n a l r e g r e s s i o n s were c a l c u l a t e d f o r males and females s e p a r a t e l y and combined. J u v e n i l e s were i n c l u d e d i n both the sepa ra te male and female r e g r e s s i o n s but on ly once i n the combined r e g r e s s i o n . Us ing the age o f f i s h from each of the a rea s where t h i s cou ld be c a l c u l a t e d , the y e a r - c l a s s o f each f i s h was r e c o r d e d . For each a r e a , f i s h o f each y e a r - c l a s s were e x t r a c t e d and f u n c t i o n a l r e g r e s s i o n s o f t o t a l c i r r i vs age were c a l c u l a t e d . S ince the sample s i z e s were s m a l l i n some c a s e s , on ly combined r e g r e s s i o n s were c a l c u l a t e d . 113 Results The d i s t r i b u t i o n and nature of c i r r i are highly variable between f i s h . Young f i s h possess few c i r r i ; the smallest 0, maculjosus examined (1.4 cm t o t a l length) had no c i r r i and on f i s h l e s s than 2.0 cm few c i r r i are apparent. There i s an increase in the number of c i r r i and the number of branched c i r r i with increasing length, as observed by Bolin (1944). C i r r i increase i n number on a l l parts of the body although m u l t i f i d c i r r i do not appear to occur at a l l c i r r i locations, even i n larger f i s h . C i r r i appear f i r s t around the eye and on the top of the head prior to being found along the l a t e r a l l i n e s and maxillaries, preoperculars, operculars etc. C i r r i do not appear to be b i l a t e r a l l y symmetrical i n d i s t r i b u t i o n . Uneven d i s t r i b u t i o n appears to be more common than not. Along the l a t e r a l l i n e c i r r i begin to appear i n small f i s h immediately i n front of the anterior pores. In larger f i s h the c i r r i precede the anterior half to two-thirds of the l a t e r a l l i n e pores and are b i f i d and t r i f i d in larger f i s h . Around the mid and upper margin of the eye, small specimens may have one or two c i r r i while large specimens may have up to nine c i r r i , many of them mul t i f i d . On the top of the head the d i s t r i b u t i o n i s highly variable, although the pattern found on the f i s h examined in 114 t h i s study does not appear t o be the same as t h a t d e s c r i b e d by B o l i n (1944, p. 66) : "The g e n e r a l p a t t e r n i n l a r g e a d u l t s i s u s u a l l y formed by a l i n e of three m u l t i f i d c i r r i extending along each f r o n t o — p a r i e t a l r i d g e , and a p a r a l l e l s e r i e s of two or thr e e s i m i l a r c i r r i s l i g h t l y l a t e r a d to the s e , while two t r a n s v e r s e s e r i e s of up to three c i r r i each extend a c r o s s the top o f the head i n t h e o c c i p i t a l r e g i o n . One to th r e e c i r r i o f t e n occur i n the m i d l i n e a n t e r i o r l y . In j u v e n i l e s the c i r r i on top of the head are a l l simple and may be l i m i t e d to as few as f o u r on each s i d e . " The g e n e r a l p a t t e r n found on l a r g e a d u l t s i n t h i s study c o n s i s t e d of two p a r a l l e l t r a n s v e r s e p a i r s of f r e q u e n t l y m u l t i f i d c i r r i behind each eye. P o s t e r i o r to these, two p a r a l l e l rows of up t o f i v e (when t h i s row occurred) and s i x (sometimes m u l t i f i d ) c i r r i r e s p e c t i v e l y were found. O c c a s i o n a l l y one or two c i r r i were found s l i g h t l y behind and to the s i d e of the l a s t o c c i p i t a l row of c i r r i . One or two c i r r i were sometimes found i n the m i d l i n e a n t e r i o r l y . In the s m a l l e s t f i s h examined one or two symmetrical p a r a l l e l p a i r s of unbranched c i r r i were found i n the o c c i p p i t a l r e g i o n . Up t o f o u r c i r r i were o c c a s i o n a l l y found a t the p o s t e r i o r end of the m a x i l l a r i e s ; one t o t h r e e was more common. M a x i l l a r y c i r r i were absent i n s m a l l specimens, along the 115 p r e o p e r c u l a r margin, up to s i x c i r r i were found although two o r t h r e e was more common. Small f i s h showed only one or two, i f any were present. In l a r g e r f i s h , s e v e r a l c i r r i were l o c a t e d j u s t above the base of the p r e o p e r c u l a r s p i n e . At the upper end of the o p e r c u l a r f l a p l a r g e r f i s h showed up to ten c i r r i , while i n s m a l l e r i n d i v i d u a l s one to four was u s u a l and i n the s m a l l e s t specimens none was apparent. These c i r r i are not mentioned by B o l i n (1944), although Hart (1973) mentions them, while o m i t t i n g to mention c i r r i on the m a x i l l a r y , eye, above the p r e o p e r c u l a r spine and p o s t e r i o r t o the o p e r c u l a r f l a p above the base of the p e c t o r a l f i n . In t h i s l a s t l o c a t i o n , two or t h r e e c i r r i commonly oc c u r r e d although up t o f i v e were found i n l a r g e r f i s h . Smaller f i s h showed one, i f any. F u n c t i o n a l r e g r e s s i o n s of t o t a l c i r r i number vs l e n g t h (Figure 16 and Table 22) f o r Vancouver I s l a n d s i t e s are arranged i n order of d e c r e a s i n g exposure as shown by the cement block exposure r a t i n g . The mudflat i n G r a p p l e r I n l e t i s a r b i t r a r i l y c l a s s i f i e d as about the same exposure as the l a r g e t i d e p o o l on Haines I s l a n d . The graphs f o r the Alaskan s i t e s are c l a s s i f i e d i n order of d e c r e a s i n g exposure as determined from c h a r t s . I t i s evident t h a t t h e r e i s c o n s i d e r a b l e v a r i a b i l i t y i n the r e l a t i o n s h i p of t o t a l c i r r i number with l e n g t h , but that i n a l l cases, the number o f c i r r i i n c r e a s e s with l e n g t h . For areas where there are reasonably l a r g e sample s i z e s f o r both sexes and where the l e n g t h d i s t r i b u t i o n s a r e s i m i l a r , t h e r e i s good agreement between the r e g r e s s i o n s f o r males and females. 116 2 0 0 . C a p e B e a l e 150. o o v_ CD 100. -Q E c " r o 5 0 . J—> /—\ 0. L e n g t h (cm) 2QQ B e n s o n I s l and .b 1 5 0 . o _§100. E C o 0. 2. L e n g t h (cm) 10. 200.. F i r s t B e a c h 2 0 0 ^ o r t R e r , f r e w L e n g t h (cm) L e n g t h (cm) F i g u r e 16 T o t a l c i r r i - l e n g t h r eg re s s ions fo r 0. maculosus from f i f t e e n areas (males and females combined) 117 Figure 16 (continued) 1 1 8 figure 16 (continued) 119 2 0 0 S a g i n a w B a y A l a s k a 2 0 0 . S h e l t e r I s l and A l a s k a L e n g t h (cm) . ' L e n 9 t h ( ° m ) 2 0 0 . C o h e n I s l and A l a s k a 5 150. o j§ 100., E 1 c 2 50 . 0. L e n g t h (cm) F i g u r e 16 ( c o n t i n u e d ) T a b l e 22 fiiAsocottus m a c u l o s u s (15 a r e a s ) t o t a l number o f c i r r i - l e n g t h f u n c t i o n a l r e q r e s s i o n s t a t i s t i c s ( m a l e s , f e m a l e s and s e x e s combined) l o g x vs y: y = u • v l o g x N u v Upper 9 5 * c . l . Lower 95X c . l . o f v o f v H a l e s 25 - 1 0 2 . 7 261 . a 306 .9 216. 6 Cape B e a l e Fe males 42 - 1 4 5 . 6 3 35. 3 3 86 . 9 283 . 7 Combined 58 - 130 .1 318. 1 360 . 1 276 . 0 Males 16 - 2 9 . 9 7 157.7 218 .6 96 .75 Benson I s l a n d Females 34 - 1 0 7 . 9 271 .97 3 3 2 . 8 210 .6 Combined 50 - 8 3 . 1 7 234. 2 279. 1 189.2 Males 40 - 6 3 . 1 3 210 .7 24 1. 7 179.7 P o r t Renfrew Fe males 83 - 7 9 . 2 3 230 .2 254.1 206. 3 Combined 1 18 - 7 8 . 6 9 229. 7 2 49 . 9 209 .6 Males 26 - 1 1 2 . 4 262.0 3 25 . 0 198.9 Pachena P o i n t Females 46 - 4 6 . 8 0 178. 1 216 .4 139.9 Co abined 72 - 6 7 . 0 5 205.0 273 . 3 172. 6 Males 37 - 1 0 5 . 7 262 .7 300 .7 224 .7 P i r s t Beach Females 71 - f i 8 . 0 7 234. 2 264 .4 204. 0 Combined 102 - 9 6 . 9 4 248. 2 273 .0 223 . 5 Males • 46 - '80.20 219.8 267.6 172. 1 H e l b y I s l a n d Females 72 - 9 4 . 7 4 244 .0 275 . 9 212. 1 Combined 1 18 - 8 6 . 9 7 231.0 257 .0 205 .0 Males 75 - 9 0 . 7 6 236 .6 285. 2 188. 0 Ranee I s l a n d Females 79 - 142.5 305 .5 356 .2 254. 3 Co mbined 154 - 1 1 8 . 3 274. 2 308. 1 240. 4 Males 98 - 8 9 . 4 5 233 . 9 261 .5 206. 4 G r a p p l e r I n l e t (bay) Females 179 - 1 1 7 . 2 281 .0 3 11 . 5 250. 6 Combined 275 - 1 0 0 . 6 253. 2 273. 3 23 3.2 to o T a b l ^ 22 ( c o n t i n u e d ) Upper 95X c . l . Lower 9555 c . l . o f v o f v H a i n e s I s l a n d Males Females Combined 1C7 79 186 •102. i* -74.60 -83.ec 253. 212. 226. 8 294. 3 243.8 250.6 213.6 181.9 203. 0 G r a p p l e r I n l e t (mud) H a l e s Females Combined 26 28 54 -78.04 -174. 9 -143.5 213. 369. 317. 275. 2 447.7 372.6 152. 0 290. 3 263. 3 F i s h Egg I s l a n d Males Females Combined 20 30 45 -74.83 -80. 10 -76.33 218.2 233. 1 224. 1 267. 1 276.3 258. 1 169. 2 189. 9 190. 1 B a r a n o f Islan-d Mai es Females Combined 21 21 23 -35.31 -41. S7 -38.04 159. 181. 168. 182.0 205.7 188.4 136. 0 156. 8 147.7 Saginaw Bay Males Females Combined 39 24 62 -7C.46 -103. 6 -94.89 210. 266. 248. 0 255.5 333. 1 290.0 164. 199. 206. S h e l t e r I s l a n d Males Females Combined 22 45 54 -46.56 -56. 23 -52.45 174. 196. 187, 211. 224, 213, 137. 4 167. 9 161.9 Cohen I s l a n d Males F e a a l e s Combined 13 26 39 -166. 4 -64.72 -98.31 315. 185. 229. 515.0 261. 9 302.5 115.8 108. 6 156. 2 122 f o r example. P o r t Renfrew, F i r s t Beach and Helby I s l a n d . I n cases i n which the sample s i z e s are s m a l l , where l e n g t h d i s t r i b u t i o n s are d i f f e r e n t , p a r t i c u l a r l y i n the l a r g e r s i z e c l a s s e s , and where one or two l a r g e f i s h i n a sample show a l a r g e number of c i r r i and th e r e a r e no f i s h o f comparable s i z e i n the sample f o r the other sex, the r e g r e s s i o n s are widely d i v e r g e n t , f o r example, Benson I s l a n d , Cape Beale and Pachena P o i n t . No c o n s i s t e n t d i f f e r e n c e s are apparent between sexes and t h e r e i s no evidence of a g r e a t e r number of c i r r i on f i s h from more exposed areas. T h i s i s borne out by the combined r e g r e s s i o n s of t o t a l c i r r i vs l e n g t h f o r each a r e a . There i s v a r i a b i l i t y between areas but i t does not f o l l o w a p a t t e r n c o n s i s t e n t with r e l a t i v e exposure. From the r e g r e s s i o n s of t o t a l c i r r i number vs age (Figure 17 and Tab l e 23), i t i s evident again that t h e r e i s c o n s i d e r a b l e v a r i a b i l i t y , f o r the same reasons t h a t the l e n g t h data show v a r i a b i l i t y . Comparison of the r e g r e s s i o n s does not show any c o n s i s t e n t d i f f e r e n c e s between sexes or areas and the r e g r e s s i o n s f o r the sexes combined f a i l t o show any c o n s i s t e n t d i f f e r e n c e s between areas r e l a t e d to exposure. The r e g r e s s i o n s of t o t a l c i r r i number vs age by year-c l a s s are simply a good i l l u s t r a t i o n of the hopelessness of c o n s t r u c t i n g r e g r e s s i o n s on few p o i n t s (Figure 18 and Table 24). The v a r i a b i l i t y i s such t h a t comparisons are rendered 200. « 150. 1 100. C " T O £ 50. l — Benson Island 2QQ C a p e Beale 0.5 i Age (years) 4. 200. First Beach \_ 150. o u— o \_ 0) X> 100. E 3 C " r o 50 0 o M— o a) E C 0-5 ^Age (years) 200 P a c n e n a Point 150. 100 S 50 ,o 1 A g e (years) 200 P o r t Renfrew 150. 4. o o Q) 100. E 3 C "ro .o 50 0.5 ^-Age (years) 4 200 ^ ' b y Island t 150. o o _g 100. E C S' 50. .o 0.5 1. Age (years) 0.5 1- Age (years) 4 Figure 17 Total c i r r i - a g e regressions for 0. maculosus from nine areas (males and females combined) 124 Rcince Island Age (years) 2QQ Grappler Inlet bay 150. o M— O _g 100. E 3 C J2 50. .o 0.5 1- Age (years) .4. 200. .b 150. o u— Q | 100. E 3 C £ 50. ,o Haines Island 0.5 1. Age (years) Figu re 17 (continued) T a b l e 2 3 O l i g o c o t t u s n a c u l o s u s (9 a r e a s ) t c t a l number o f c i r r i - aqe f u n c t i o n a l r e g r e s s i o n s t a t i s t i e s (males , f e m a l e s and s e x e s combined) l o q x vs y: y = u • v l o g x N u V Upper 95? c.1. Lower 95* c, o f V o f V H a l e s 25 17.44 214.2 251.3 177. 2 Cape B e a l e F e n a l e s 12 9. 18 3 270. 4 312. 1 228.7 Combined 58 8.847 256.9 290.9 223. 0 H a l e s 16 69.02 117. 1 162. 8 71. 40 Benson I s l a n d F e n a l e s 3D 62 . 15 201.5 247.8 155.2 Combined 50 63.44 174. 2 208. 1 140. 3 H a l e s UO 36. 66 238.6 273.6 203. 5 P o r t Renfrew Females 83 30. C8 259.0 286.3 231.7 Combined 1 18 30. 45 258.6 281.5 235.6 Ha l e s 26 29.74 176.2 219.1 133. 2 Pachena P o i n t Females • 46 48. 90 121.8 143. 8 95. 35 Combined 72 43.33 139.8 16 2.1 1 17.5 Ha l e s 37 59.67 170. 8 197.0 144. 6 F i r s t Beach Feu a l e s 71 59. 75 150. 4 170.4 ,130. 4 Combined 102 59.60 159.9 176.5 143. 4 H a l e s 46 36.0 8 152. 1 185.4 118.8 H e l b y I s l a n d Females 72 35.15 166.6 188.6 144. 6 Combined 1 18 35. 82 158.0 175.9 140. 1 H a l e s 75 38. 95 247. 5 299.3 195.7 Ranee I s l a n d Females 79 22.04 352.0 409.7 294.4 Combined 154 29.73 311.0 - 349.6 273. 0 H a l e s 98 43.9 7 190.9 213.8 167.9 G r a p p l e r I n l e t (bay) Females 179 42.89 229.3 254.5 204. 1 Combined 275 41.70 206.8 223.4 190. 2 H a l e s 107 41.80 182.9 212. 3 153. 5 Haines I s l a n d Females 79 41). 00 151.8 174.7 128.9 Combined 186 4 6.61 162.0 179.7 144.-9 126 200. •5 1 5 0 ' g 100. E c 2 50. |2 ' Port Renfrew 1973 0. 0-5 1. Age (years) 4. 200 1 150. o o _§ 100. E 3 C jB 50. ,o Grappler Inlet bay 1973 0.5 1- Age (years) 4. 200. 'E 150. o o o3 100. X! E 3 C ro 50. .o Port Renfrew 1974 0. 0.5 1- Age (years) 4. 200 •5 1 5 0 -.8 100. E 3 C Grappler Inlet bay 1974 ro 50. 0.5 1- Age (years) • 4. 2 0 0 , £ 150. o o _§ 100. E 3 C S 50. .o Port Renfrew '1975 0. 0.5 1 A g e (yeais) 4. 200 150. o _§ 100. E 3 C ~2 50. ,o Grappler Inlet bay 1975 I °-5 1 A g e (years) . 4 -Figu re 18 T o t a l c i r r i - a g e by y e a r - c l a s s r eg re s s ions for 0 ' raaculosus from two s e l e c t e d areas (males and females combined) T a b l e 24 O l i q o c o t t u s n a c u l o s u s (9 a r e a s ) t o t a l nuirber o f c i r r i - aqe by y e a r - c l a s s f u n c t i o n a l r e q r e s s i o n s t . a t i s t i e s ( s e x e s combined) l o q X vs y: y = l) + v l o q X N u v Upper 95* c . l . Lower 95% c. o f v o f v Cape B e a l e 1974 16 -10 1.3 533. 7 788.2 279. 2 1975 41 23.60 183. 2 207.7 158.7 Benson I s l a n d 1974 3 -18.21 359. 5 2710 -1991 1975 37 5 5.91 224. 0 278.6 169. 4 1973 13 -150.4 744. 4 1173 315.3 P o r t Renfrew 1974 48 20. 80 301. 1 344. 4 257. 8 1975 56 34.51 245. 6 277.0 214.1 1973 8 -363.4 882. 3 1742 22. 27 Pachena P o i n t . 1974 19 -59.25 395. 8 576. 5 215. 2 1975. 44 34.79 215. 3 271. 3 159. 2 1974 29 44.28 231. 8 298.7 164.8 F i r s t Beach 1975 60 6 0.23 154.7 181.0 128. 4 1976 12 64.4 3 204. 9 338. 0 71.78 H e l b y I s l a n d 1974 16 -129.7 637. 6 990. 9 284. 3 1975 102 35.26 166. 9 190.7 143. 2 Ranee I s l a n d 1975 154 29.73 311.3 349. 6 273. 0 1973 9 -41.57 417.0 787. 6 46.32 G r a p p l e r I n l e t (bay) 1974 223 39.99 238. 1 26 1. 7 214. 5 1975 43 53. 45 875. 4 1151 599.4 H a i n e s I s l a n d 1974 15 -79 .95 500. 0 708.8 291. 3 1975 170 4 1.67 183. 9 207. 5 160.4 128 i m p o s s i b l e . The a n a l y s i s o f t o t a l c i r r i number by l e n g t h , age and age by y e a r - c l a s s with r e s p e c t t o exposure confirms the i n c r e a s e i n number of c i r r i with l e n g t h and age. I t a l s o i n d i c a t e s t h a t t h e r e i s a great d e a l of v a r i a b i l i t y between p o p u l a t i o n s with r e s p e c t to t o t a l c i r r i number, but that t h i s v a r i a b i l i t y i s not a d i r e c t f u n c t i o n o f exposure, as measured by the cement block e v a l u a t i o n of wave a c t i o n . , 3.Experimental mani.p.uj.ation o f c i r r i number In an attempt to determine e x p e r i m e n t a l l y whether the number of c i r r i i s a f u n c t i o n of exposure ( e s s e n t i a l l y determined by wave a c t i o n ) , egual numbers of j u v e n i l e 0. maculosus were pl a c e d i n t o two separated s i d e s of a l a r g e tank, h a l f of which was s u b j e c t e d to almost continuous waves and the other h a l f of which remained calm, except f o r a c o n s t a n t water i n f l o w . Methods A l a r g e plywood tank, 183 cm x 122 cm x 31 cm was d i v i d e d i n h a l f lengthways and to a height of 3U cm with a piece of 1.9 cm plywood, t o provide "calm" and "exposed" s i d e s of the tank. At one end of the tank on the exposed s i d e a wave tank 129 was erected (Figure 19) . The wave tank, based on one at the Scripps I n s t i t u t e of Oceanography, was constructed of plexiglass and was supported by and pivoted on two threaded rods passing through the top end of 5 cm x 10 cm wooden uprights screwed to the inside corners of the exposed tank. By d r i l l i n g a guincunx of holes through each of two 10 cm x 10 cm x 5 cm blocks of plexiglass attached to each side of the wave tank, i t was possible to a l t e r the pivoting point of the tank and thus manipulate the amplitude and freguency of the waves. The wave tank was f i l l e d with water from an overhead pipe u n t i l the maximum equilibrium l e v e l was exceeded, at which time the sloping edge of the tank would begin to f a l l and the water would be emptied out as a wave. The empty tank would then r i g h t i t s e l f and r e f i l l . The tank was positioned f o r the experiment so that a freguency of one wave every 20 seconds with a volume of approximately 13 cm3 was established. A constant flow of water was maintained into both sides of the tank as f a r as the seawater system permitted. The end of the tank at which the wave tank was positioned was raised 10 cm to f a c i l i t a t e the flow of waves to the outlet end of the tank, the last 0.6 m of which was covered with nitex screening to permit f i s h from being washed out by waves. An i d e n t i c a l piece of nitex was f i t t e d to the calm side of the tank, to maintain uniform conditions. On each side of the tank, "shelter" was provided i n the form of connected styrofoam egg cartons and a sheet of f r u i t box packing stapled F i g u r e 19 Design of experimental tank showing c a l m and exposed sides and wave making tank 131 to the bottom. In a d d i t i o n , ten cement b l o c k s a t t a c h e d to e y e b o l t s anchored i n h y d r a u l i c cement t o 5 b r i c k s were spaced throughout each s i d e of the tank, to determine the r e l a t i v e exposure of each s i d e . J u v e n i l e 0. maculosus were c o l l e c t e d from F i r s t Beach and d i v i d e d i n t o t hree groups. One group was placed i n the exposed s i d e of the tank, one i n the calm s i d e and the t h i r d group was f i x e d and preserved f o r c i r r i counts. , Four i n t r o d u c t i o n s of f i s h were made between 6 J u l y and 19 August 1976 g i v i n g a t o t a l o f 102 f i s h i n each of the t h r e e groups. The j u v e n i l e s preserved at the time of i n t r o d u c t i o n were measured ( t o t a l length) to t h e nearest 0.005 cm and c i r r i were examined t o provide data on i n i t i a l c i r r i nature and d i s t r i b u t i o n f o r the j u v e n i l e f i s h i n the calm and exposed tanks. The f i s h remained i n the tanks u n t i l 16 December 1976, a p e r i o d of approximately f o u r months, during which time they were fed p i e c e s of mussel (mostly M y t i l u s c a l i f o r n i a n u s but o c c a s i o n a l l y Jf. e d u l i s ) , chopped f r o z e n e u p h a u s i i d s and f r e s h amphipods. Fresh food was always used i n preference to f r o z e n f o od. To enable the f i s h i n the exposed s i d e o f the tank to feed without danger of being washed out of the tank, the water i n t o the wave tank was turned o f f f o r s e v e r a l hours each time the f i s h were f e d . When the f i s h were removed from each s i d e o f the tank 132 at the c o n c l u s i o n o f the experiment, they were f i x e d and preserved. Subsequently, they were measured ( t o t a l length) t o the nearest 0 . 0 0 5 cm and c i r r i number and l o c a t i o n examined t o see i f there were any d i f f e r e n c e s between the two groups. F u n c t i o n a l r e g r e s s i o n s of t o t a l c i r r i vs l e n g t h were c a l c u l a t e d f o r the f i s h preserved a t the time of i n t r o d u c t i o n and the f i s h removed from each s i d e of the tank a t the c o n c l u s i o n of the experiment. Loq t o the base 10 t r a n s f o r m a t i o n s of l e n g t h were made as suggested by the untransformed data. Although the f i s h were removed a f t e r approximately fo u r months the tank was maintained f o r a longer p e r i o d . The cement b l o c k s were removed i n May 1977 and t h e c o n s i d e r a b l e f l o r a and fauna which had developed were removed over a p e r i o d of s e v e r a l weeks i n l a t e August and e a r l y September 1977 and i d e n t i f i e d . The tank was i n s i d e from i t s c o n s t r u c t i o n (July) u n t i l January, 1977, a f t e r which time i t was moved o u t s i d e , thus r e c e i v i n g c o n s i d e r a b l y more l i g h t . R e s u l t s Subsequent to t h i s experiment manipulating c i r r i number, the exposure of the exposed s i d e of the experimental tank r e l a t i v e to other areas i n Barkley Sound was shown by the l o s s of weight of the cement b l o c k s to be about e q u i v a l e n t t o that of Grappler i n l e t . Ranee I s l a n d and Helby I s l a n d , 133 s i g n i f i c a n t l y more exposed than the calm side of the tank, but s i g n i f i c a n t l y l e s s exposed than t h e m a j o r i t y of t i d e p o o l areas. I n s p e c t i o n of the l i s t s of algae and i n v e r t e b r a t e s i n each s i d e o f the tank appears t o provide some b i o l o g i c a l i n d i c a t i o n of the degree of wave a c t i o n , s i n c e presumably the chance of se t t l e m e n t i n e i t h e r s i d e of the tank was equal (Appendix 3). The kin d s of s p e c i e s found a l s o shows t h e e f f e c t of r a i s i n g deep water (20 m) i n t o a shallow tank exposed to a great d e a l of l i g h t . Many o f the s p e c i e s found are not common i n the mid t o upper i n t e r t i d a l and are c h a r a c t e r i s t i c a l l y found i n the lower i n t e r t i d a l and s u b t i d a l . Comparison of the d i s t r i b u t i o n s of c i r r i with r e s p e c t to l e n g t h from the sample p r e s e r v e d at t h e time of i n t r o d u c t i o n of j u v e n i l e 0. maculosus i n t o the experimental tank and on f i s h from F i r s t Beach used i n c i r r i a n a l y s i s shows a c o n s i d e r a b l e d i f f e r e n c e ( Figure 20 and Table 25). T h i s i s probably a r e s u l t of the d i f f e r e n t l e n g t h d i s t r i b u t i o n s on which the r e g r e s s i o n s were c o n s t r u c t e d , s i n c e there i s very l i t t l e o v e r l a p i n l e n g t h d i s t r i b u t i o n between the two samples. From the r e g r e s s i o n s o f t o t a l c i r r i vs l e n g t h of f i s h from the calm and exposed s i d e s o f the experimental tank (Figure 21 and Table 25), i t i s evident t h a t i n both s i d e s of the tank th e r e was high m o r t a l i t y (77% and &H% i n the calm and exposed s i d e s r e s p e c t i v e l y ) . The f a c t that so few f i s h s u r v i v e d precludes any d e f i n i t e c o n c l u s i o n s . ^^Experimental tank initial cirri counts 1 3 4 ._ 100. o 75. 0) -a 50. E ' f 25. ro 0. CF) Length (cm) 7. o o 125. 100. 75. First Beach % 50. E = 25. CO o 0. 1. H 1 1 . 7. Length (cm) F i g u r e 20 T o t a l c i r r i - l e n g t h r eg re s s ions from 0. maculosus in t roduced i n t o exper imenta l tank and from F i r s t Beach 135 T a b l e 25 Experimental manipulation of c i r r i i n O l i q o c o t t u s maculosus F u n c t i o n a l r e g r e s s i o n s t a t i s t i c s ( t o t a l c i r r i number - length) f o r i n i t i a l and f i n a l samples and F i r s t Beach l o g x vs y: y = u • vlog x S t a t i s t i c F i r s t I n i t i a l Calm Have Beach c i r r i s i d e s i d e number -95.91 -43.27 -154.9 -99.24 246.7 172.3 333.0 242.9 Lower 95% c o n f i d e n c e 221.1 157.6 278.3 183.2 l i m i t of v Upper 95% conf i d e n c e 271.4 186.9 387.7 302.6 l i m i t of v 101 102 23 16 Figu re 21 T o t a l c i r r i - l e n a t h r eg re s s ions from 0. maculosus i n the calm and exposed s ides of exper imenta l tank 1 3 7 Comparison of these r e g r e s s i o n s with the r e g r e s s i o n o f i n i t i a l c i r r i counts appears to show t h a t p l a c i n g the j u v e n i l e f i s h i n the experimental tank delayed c i r r i f o r m a t i o n , i n both the calm and exposed s i d e s . . The p r e d i c t i o n that 0. maculosus i n the exposed s i d e of the tank would produce g r e a t e r numbers of c i r r i than i n the calm s i d e o f the tank i s not borne out by the r e s u l t s . I n s p e c t i o n o f the 95% confidence l i m i t s of v (slope) r e s u l t s i n r e j e c t i o n of the n u l l h y p othesis. I t i s i n t e r e s t i n g to note that the r e l a t i o n s h i p between t o t a l c i r r i number and l e n g t h shown by f i s h i n the exposed s i d e of the tank bears much c l o s e r resemblance to t h a t shown by f i s h from F i r s t Beach than does the r e l a t i o n s h i p shown by f i s h from the calm s i d e of the tank. Thus while the exposure of the exposed s i d e o f the tank can only be regarded as moderate, and the p a t t e r n of c i r r i f o rmation appears t o have been a l t e r e d somwhat by the experiment, the numbers o f c i r r i found on the s m a l l percentages of s u r v i v i n g f i s h suggest t h a t while wave a c t i o n may have some i n f l u e n c e on the production of c i r r i , t h e r e i s not a d i r e c t r e l a t i o n s h i p between the degree of wave a c t i o n and the number of c i r r i produced. 138 4 . H i s t o l o g i c a l examination of c i r r i To determine whether c i r r i c o n t a i n any sensory r e c e p t o r s such as t a s t e buds, s e c t i o n s of c i r r i were examined. Methods Small p i e c e s o f s k i n bearing c i r r i were taken from the l a t e r a l l i n e s and heads of ten male amd female 0. maculosus (3.9 to 6.3 cm t o t a l length) from F i r s t Beach, s e c t i o n e d and s t a i n e d with eosin-haemotoxylin and examined. F i v e of the f i s h had been kept i n 5 ppm Triton-X-100 f o r seven days i n an attempt t o destroy chemoreceptors, i f any were present. R e s u l t s There i s no evidence from any o f the s e c t i o n s (Figure 22) to suggest the presence of chemoreceptors i n the c i r r i . They seem t o be composed of some s o r t o f e l a s t i c c a r t i l a g e (W.S. M a r s h a l l , p e r s o n a l communication) surrounded by a l a y e r of chromatophores and the basement membrane of the e p i t h e l i u m . Blood v e s s e l s are present i n the c a r t i l a g e . While the e p i t h e l i u m o f the s k i n c o n t a i n s e o s i n o p h i l i c g r a n u l a r c e l l s , l a r g e g o b l e t c e l l s and s m a l l g o b l e t c e l l s the e p i t h e l i u m of the c i r r i appears to c o n t a i n only a few s m a l l , s c a t t e r e d g o b l e t 0.5 mm 0.5 mm Q5 mm d 0.5 mm F i g u r e 22 S e c t i o n s of c i r r i f r o m l a t e r a l l i n e (a, b) and head (c, d) s h o w i n g s m a l l (g) and l a r g e (G) goble t c e l l s , e o s i n o p h i l i c g r a n u l a r c e l l s (e), c h r o m a t o p h o r e s (c) , b l o o d v e s s e l s (b), l a t e r a l l i n e p o r e (p), b a s e m e n t m e m b r a n e of e p i t h e l i u m (B) CD i a o c e l l s , and these seem to occur only towards the base of the c i r r i . Since the e o s i n o p h i l i c granular c e l l s and the g o b l e t c e l l s are mucous s e c r e t i n g c e l l s ( M a r s h a l l , 1977) t h e i r absence i n the c i r r i e p i t h e l i u m suggests t h a t the c i r r i may remain uncovered by a mucous coa t although the r e s t of the s k i n i s covered with mucous. Since there appear t o be no sensory r e c e p t o r s i n the c i r r i , t h e i r f u n c t i o n remains unknown. 5.Discussion The i n v e s t i g a t i o n of morphological d i f f e r e n c e s between f i s h i n areas of d i f f e r e n t exposures produced no evidence t o suggest that there are any m o r p h o l o g i c a l d i f f e r e n c e s between f i s h t h a t can be r e l a t e d t o exposure.. I n p a r t i c u l a r , there appears to be no evidence t h a t there i s a g r e a t e r number of c i r r i on 0. maculosus i n more exposed areas. T h i s appeared t o be confirmed by the f a i l u r e o f the attempt t o manipulate the number of c i r r i , i n t h e d e s i r e d d i r e c t i o n , by wave a c t i o n i n the l a b o r a t o r y . The absence of any d i f f e r e n c e s i n m e r i s t i c and morphometric c h a r a c t e r s between areas was not a l t o g e t h e r s u r p r i s i n g . Even i f the r e l a t i v e placement of sensory r e c e p t o r s i s important with r e s p e c t t o homing, s e l e c t i o n a c t s on the t o t a l i t y of a t t r i b u t e s possessed by an organism and homing i s presumably only one of these a t t r i b u t e s . Any r e l a t i v e 141 differences i n the placement of sensory receptors would be small and may have l i t t l e e f f e c t on the perception of clues. While l a t i t u d i n a l differences i n meristic characters have been demonstrated (Hubbs and Hubbs, 1953; Taning, 1952), the difference involved in the study areas on Vancouver Island i s less than half a degree. The importance of temperature i n determining numbers i n meristic characters has been demonstrated (Taning, 1952), but the temperature differences involved here are probably small. Decreased oxygen pressure and increased carbon dioxide pressure, and i n some cases, s a l i n i t y , have been shown to influence meristic characters (Taning, 1952) . However, since meristic and morphometric characters are large l y determined before hatching, and the larvae are pelagic, differences would not be expected over such a small change i n latitude. Although there were differences in the r e l a t i o n s h i p between c i r r i and length with di f f e r e n t amounts of wave action, the r e l a t i o n s h i p does not take the form of a simple increase i n number of c i r r i with increasing wave action. No record was made of any environmental parameters other than wave action, although one temperature recording i n July showed l i t t l e difference between the sides of the tank (calm side: 9.3-10.2°C, wave side: 9.2-10.2°C). The high mortality observed i n both sides of the tank may, however, obscure any possible r e l a t i o n s h i p which may be v a l i d i n the f i e l d . , 142 There i s an increase in the number of c i r r i with length and age. However, there do not appear to be any obvious differences i n the r e l a t i o n s h i p between number of c i r r i and age by year-classes. The increase i n c i r r i number and branching with length and age has been noted before (Bolin, 1944)., In t h i s respect, c i r r i d i f f e r from the majority of morphological c h a r a c t e r i s t i c s investigated i n f i s h populations where constant proportions or ranges of values are found throughout the length d i s t r i b u t r i o n of the species. This study has provided no evidence f o r (or against) genetic differences i n number of c i r r i , since the members of one year-class may have parents belonging to several year-classes. The function of the c i r r i remains unknown. While the presence of structures similar to taste buds in the tentacles and c i r r i - l i k e structures of other f i s h , for example, Blennius tentacularis (Schulte and H o l l , 1972) and the chemoreceptive s e n s i t i v i t y of c a t f i s h barbels (Hoagland, 1933; Bardach et a l . , 1967) suggested that such a function was l i k e l y for the c i r r i of 0. maculosus. t h i s does not appear to be the case. The presence of s i m i l a r structures on other i n t e r t i d a l and s u b t i d a l c o t t i d s , for example, Oligocottu.s snyderi Greeley, 0. rimensis (Greeley), Clinocottus embryum (Jordan and Starks), C. qlobiceps» D§sycottus setiger Bean, ftsemichthys t a y l p r j G i l b e r t , Artedius l a t e r a l i s , A. harringtoni, A. f e n e s t r a l i s Jordan and G i l b e r t , and agonids, for example, Agonus acipenserinus T i l e s i u s , Asterotheca p.entacanthus (Gilbert) , A. infraspinata (Gilbert) , 143 Bothraggnus swani (Steindachner) (Hart, 1973) makes i t i n t e r e s t i n g t o s p e c u l a t e on t h e i r f u n c t i o n . The most p l a u s i b l e f u n c t i o n seems t o be some k i n d of water movement (or p o s s i b l y pressure) d e t e c t i o n . The c i r r i a r e f l e x i b l e s t r u c t u r e s and on l i v e 0. maculosus stand out from the body, such t h a t the movement of water might cause d e f l e c t i o n s of these appendages. Hoagland ( 1933 ) showed t h a t c a t f i s h ameirus r = I c t a l u r u s 1 nebulosus (Lesueur) b a r b e l s responded t o minimal touch or water c u r r e n t s and B a y l i s s (1914) suggested t h a t the head t e n t a c l e s o f Blenn i u s g a t t p r u ^ i n e Linnaeus were p a r t i c u l a r l y s e n s i t i v e t o touch. However, f u r t h e r i n v e s t i g a t i o n i s r e g u i r e d to determine the true f u n c t i o n of these s t r u c t u r e s . 144 VI. OTHER FACTORS AFFECTING VARIABILITY IN HOSING BEHAVIOUR Si n c e homing a b i l i t y may change over the l i f e of 0. maculosus and i t i s p o s s i b l e that t h e r e may be g e n e t i c d i f f e r e n c e s i n homing a b i l i t y , age, l e n g t h and y e a r - c l a s s d i f f e r e n c e s were examined. P a r t i c u l a r emphasis was placed on j u v e n i l e 0. maculosus, s i n c e examination o f behaviour a t the time they f i r s t begin to show evidence of area f i d e l i t y and homing might be more r e v e a l i n g than examination of the r e l a t i v e l y w e l l developed homing behaviour of l a r g e r f i s h . 1. Age To determine whether the v a r i a b i l i t y i n homing behaviour i s a f u n c t i o n of age the homing performance of untreated f i s h was examined with r e s p e c t t o age and sex. Methods Data on homing behaviour o f untreated O l i g o c o t t u s maculpsns used i n ten homing experiments over 60 m a t F i r s t Beach were used f o r t h i s a n a l y s i s . Using the age-length r e g r e s s i o n c a l c u l a t e d p r e v i o u s l y , the ages o f f i s h were determined from the known lengths and the data c l a s s i f i e d by age and i n i t i a l l y by sex. Since i t was apparent t h a t t h e r e were no d i f f e r e n c e s between sexes, only the combined data were used. 145 Three a n a l y s e s were conducted on homing performance f o r each age group i n each experiment: the percentage s u c c e s s f u l l y homing, the percentage remaining i n the t r a n s p l a n t area and the percentage of s u c c e s s f u l homers r e t u r n i n g t o the home po o l . To f a c i l i t a t e p r e s e n t a t i o n of the data, the mean percentages and standard e r r o r s of the means (Snedecor and Cochran, 1967) were c a l c u l a t e d f o r each a n a l y s i s i n each age group. The mean values are used merely to r e f l e c t what i s apparent from the i n d i v i d u a l l y t a b u l a t e d percentages, but i n a more s t r a i g h t f o r w a r d manner. R e s u l t s While t h e r e i s c o n s i d e r a b l e v a r i a b i l i t y between experiments and w i t h i n age groups (Figure 23 and Table 26) , i t i s e v i d e n t t h a t one year o l d f i s h are r e l a t i v e l y poor homers compared with two year o l d f i s h , and to a l e s s e r e x t e n t , three year o l d f i s h . However, o f those f i s h which do home, a l l age groups appear to show e q u i v a l e n t percentages r e t u r n i n g to the home p o o l , t h a t i s egual p r e c i s i o n . With r e s p e c t t o 0. maculosus remaining i n the t r a n s p l a n t a r e a , i t appears t h a t there i s a d e c l i n e with aqe i n the percentage remaining i n the area to which they were t r a n s p l a n t e d . These r e s u l t s suggest t h a t a t l e a s t some of the v a r i a b i l i t y i n homing performance i s r e l a t e d t o the age of the f i s h under c o n s i d e r a t i o n . , I t i s p o s s i b l e t h a t "learning*' of Mean Percentage Homing irjor by Age c CD 5 0 0 104 287 146 33 Mean Percentage Remaining in the Transplant Area by Age c CD u OJ D_ 1 0 0 r 50 0 104 287 33 Mean Percentage of Homers Returning to Home Pool by Age c U 100r 50 0 18 190 16 Age (Years) F i g u r e 23 H oming p e r f o r m a n c e by age (mean + 2 s . e.) T a b l e 26 Hcming p e r f o r m a n c e b y age Date r e l e a s e d 26 May 1975 11 Aug 4 s e p t 21 Sept .23 Aug 15 Sept 4 J u l y 16 J u l y 5 Aug 9 Auq 1975 1975 1975 1976 1976 1977 1977 1977 1977 P e r c e n t a g e s u c c e s s f u l l y hcming Age 1 Number r e l e a s e d P e r c e n t homed Age 2 Number r e l e a s e d P e r c e n t homed Age 3 Number r e l e a s e d P e r c e n t hcmed 13 8 21 08 8 50 1 100 44 59 9 33 1 100 59 78 9 56 30 77 3 33 13 31 18 61 17 82 21 19 38 68 1 100 15 20 30 53 38 11 30 60 2 100 P e r c e n t a g e r e m a i n i n g i n t r a n s p l a n t a r e a Age 1 P e r c e n t r e m a i n i n g Age 2 P e r c e n t r e m a i n i n g Age 3 P e r c e n t r e m a i n i n g 15 14 13 14 22 0 29 33 31 22 50 18 67 34 67 53 66 47 0 P e r c e n t a g e of homers r e t u r n i n g t o home p o o l Age 1 P e r c e n t hcming t o home p o o l 100 100 100 Age 2 P e r c e n t hcming t o home p o o l 60 88 72 Aqe 3 P e r c e n t homing t o home p o o l 100 67 60 57 100 25 73 64 50 33 69 0 44 100 61 50 148 some kind i s i n v o l v e d i n homing, but d i v i s i o n s of the f i s h t e s t e d simply i n t o age groups are o b v i o u s l y t o o g r o s s to e i t h e r account f o r a great deal of the observed v a r i a b i l i t y or t o e l u c i d a t e the time at which t h i s l e a r n i n g of the area might take p l a c e . 2.Year-class To determine whether the v a r i a b i l i t y i n homing behaviour i s a r e s u l t of g e n e t i c d i f f e r e n c e s and s p e c i f i c a l l y a f u n c t i o n of y e a r - c l a s s , the homing performance o f untreated f i s h was examined with r e s p e c t t o y e a r - c l a s s and sex. Methods Data on homing performance of untreated 0. maculosus used i n ten displacement experiments over 60 m at F i r s t Beach were used i n t h i s a n a l y s i s . Using the ages c a l c u l a t e d from age-le n g t h r e g r e s s i o n s , and the year i n which the experiment was conducted, a y e a r - c l a s s was assigned t o each f i s h . The data on homing behaviour were then analyzed by y e a r - c l a s s , and i n i t i a l l y , by sex. Again, s i n c e t h e r e were no sex d i f f e r e n c e s , the data were combined. The subseguent a n a l y s i s conducted on the data was i d e n t i c a l t o t h a t f o r the examination of homing performance by 149 age, except t h a t i n t h i s case, the analyses were performed by y e a r - c l a s s . R e s u l t s While again there i s c o n s i d e r a b l e v a r i a b i l i t y w i t h i n y e a r - c l a s s e s and between experiments ( F i g u r e 24 and T a b l e 27), i t i s e v i d e n t t h a t the only apparent y e a r - c l a s s d i f f e r e n c e s i n homing performance are a r e f l e c t i o n of the age r e l a t e d d i f f e r e n c e s i n homing performance. Thus f o r example, the 1977 y e a r - c l a s s which c o n s i s t s of only one year o l d f i s h , shows lower percentages homing and g r e a t e r percentages remaining i n the t r a n s p l a n t area than the other y e a r - c l a s s e s . Only two of the y e a r - c l a s s e s examined (1974 and 1975) c o n t a i n f i s h from a l l t h r e e age groups. Thus, i n g e n e r a l , there appear t o be no year-c l a s s d i f f e r e n c e s i n homing performance with r e s p e c t t o the three f a c t o r s examined. Mean Percentage Homing by Year Class lOOi 5 3 1 5 5 113 C <D if 29 50 0' 73 74 75 76 Mean Percentage Remaining in the Transplant' Area by Year Class c Q_ 100r 50 0 29 1 5 5 5 3 I 113 73 74 75 76 vlean Percentage of Homers Returning to Home Pool by Year Class c U 100r 50 0 13 1 0 5 31 6 4 73 74 75 76 Year Class F i g u r e 24 Homing p e r f o r m a n c e by y e a r - c l a s s (mean + 2 s. e.) T a b l e 27 a. Homing p e r f o r m a n c e hy y e a r - c l a s s , ( p e r c e n t a g e s s u c c e s s f u l l y homing) Date r e l e a s e d 26 May 11 Aug 4 Sept 21 Sept 23 Aug 15 Sept 4 J u l y 16 J u l y 5 Aug 9 Auq 1975 1975 1975 1975 1976 1976 1977 1977 1977 1977 Y e a r - c l a s s 1977 Number r e l e a s e d 21 15 38 P e r c e n t homed 19 20 11 ' e a r - c l a s s 1976 F e r c e n t r e l e a s e d 13 2 38 30 30 P e r c e n t hcnted 31 0 68 53 60 Y e a r - c l a s s 1975 Number r e l e a s e d 13 1 1 18 17 1 2 P e r c e n t hcmed 8 100 100 61 82 100 100 Y e a r - c l a s s 1974 Number r e l e a s e d 21 44 59 30 1 P e r c e n t homed 48 59 78 77 0 Y e a r - c l a s s 1973 Number r e l e a s e d 8 9 9 3 P e r c e n t homed 50 33 56 33 T a b l e 27 ( c o n t i n u e d ) b. Hominq p e r f o t u a n c e by y e a r - c l a s s ( p e r c e n t a g e r e m a i n i n g i n t r a n s p l a n t a r e a ) Date r e l e a s e d 26 May 11 Aug 4 Sept 21 Sept 23 Auq • 15 Sept 4 J u l y 16 J u l y 5 Auq 9 Auq 1975 1975 1975 1975 1976 1976 1977 1977 1977 1977 Y e a r - c l a s s 1977 Number r e l e a s e d 21 15 38 P e r c e n t s t a y e d 67 67 66 K e a r - c l a s s 1976 P e r c e n t r e l e a s e d 13 2 38 30 30 P e r c e n t s t a y e d 31 50 34 53 47 Y e a r - c l a s s 1975 Number r e l e a s e d 13 1 1 18 17 1 2 P e r c e n t s t a y e d 15 0 0 22 18 0 0 Y e a r - c l a s s 1974 Number r e l e a s e d 21 44 59 30 1 P e r c e n t s t a y e d 14 14 29 7 0 Y e a r - c l a s s 1973 Number r e l e a s e d 8 9 9 3 P e r c e n t s t a y e d 13 22 0 33 Cn t a b l e 27 ( c o n t i n u e d ) c. Homing p e r f o r m a n c e by y e a r - c l a s s ( p e r c e n t a g e o f homers homing t o home p o o l ) Date r e l e a s e d 26 Hay 1975 11 Aug 1975 4 Sept 1975 2 1 S ept 1975 2 3 Aug 1976 15 Sept 1976 14 J u l y 1977 16 J u l y 1977 5 Auq 1977 9 Auq 1977 Y e a r - c l a s s 1977 Number r e l e a s e d P e r c e n t homing t o home p o o l 21 50 15 33 38 100 Y e a r - c l a s s 1976 P e r c e n t r e l e a s e d P e r c e n t hcming t o home p o o l 13 25 38 69 30 44 30 61 Y e a r - c l a s s 1975 Number r e l e a s e d 13 ' 1 1 P e r c e n t hcming t o home p o o l 100 100 100 18 73 17 64 2 50 Y e a r - c l a s s 1974 Number r e l e a s e d 21 44 59 30 P e r c e n t homing t o home p o o l 60 88 72 £7 Y e a r - c l a s s 1973 Number r e l e a s e d 8 9 9 3 P e r c e n t homing t o home p o o l 100 . 67 60 100 154 3. Length Since t h e r e appears t o be an improvement i n homing performance with age, homing performance was examined i n s m a l l e r s i z e c l a s s e s than are encompassed by one year age groups. T h i s was done to e l u c i d a t e more p r e c i s e l y t h e s i z e (and age) at which j u v e n i l e f i s h commence homing, the s i z e c l a s s e s over which improvement appears t o occur and the s i z e s at which homing i s best expressed. A n a l y s i s of experiments conducted i n the e n c l o s u r e i n G r a p p l e r I n l e t and homing performance by s i z e c l a s s e s a t F i r s t Beach was undertaken. In a d d i t i o n , s e v e r a l experiments at F i r s t Beach i n v e s t i g a t i n g homing i n j u v e n i l e f i s h were conducted. One of these i n v o l v e d removing from the f i e l d j u v e n i l e 0. maculosus which had j u s t moved i n t o lower pools and determining whether on replacement, they showed s i m i l a r homing c a p a b i l i t i e s t o j u v e n i l e s which had been i n the f i e l d f o r t h a t p e r i o d o f time. I n f e r i o r homing a b i l i t y of the removed f i s h might imply t h a t " l e a r n i n g " had begun t o occur a t t h i s time. Methods A number of experiments i n v o l v i n g the i n t r o d u c t i o n of tagged and untagged 0. maculosus i n t o the e n c l o s u r e were conducted. 172 tagged f i s h were i n t r o d u c e d i n seven experiments where attempts were made to examine pool f i d e l i t y and hcming 155 behaviour, c o n c e n t r a t i n g on j u v e n i l e f i s h . About another 100 tagged and untagged 0. maculosus o f a l l s i z e s were i n t r o d u c e d a t v a r y i n g times t o t r y t o e s t a b l i s h pool r e s i d e n t s , which i f untagged but r e c o g n i z a b l e by i n d i v i d u a l markings, c o u l d l a t e r be tagged and experiments conducted on them. The m a j o r i t y of f i s h used i n the e n c l o s u r e were c o l l e c t e d a t F i r s t Beach, although a number o f j u v e n i l e s were c o l l e c t e d i n the bay i n Gr a p p l e r I n l e t . F i s h used i n experiments were measured, sexed where p o s s i b l e , tagged and in t r o d u c e d i n t o v a r i o u s pools i n the e n c l o s u r e . I n a l l but one of the experiments r e p o r t e d , i n t r o d u c t i o n s were made with a view to the f i s h t a k i n g up r e s i d e n c e i n the a v a i l a b l e p o o l s , determining the s i z e at which they d i d t h i s and then d i s p l a c i n g them t o determine at what l e n g t h they homed. Conseguent on t h i s , v a r i o u s i n v e s t i g a t i o n s of homing behaviour were t o be undertaken. One experiment was conducted t o determine i f s u r v i v a l was a f f e c t e d by re s i d e n c e i n the poo l s ; tagged f i s h were put i n a pool and the pool covered with f i b r e g l a s s window s c r e e n i n g . In two experiments j u v e n i l e s were i n t r o d u c e d i n t o the h i g h e s t pool i n the e n c l o s u r e which would not be covered by high t i d e s f o r s e v e r a l days. T h i s was undertaken t o enhance the chances of f i s h r e t u r n i n g to t h a t pool a f t e r s e v e r a l u n i n t e r r u p t e d days of r e s i d e n c e i n i t . Regular monitoring ( u s u a l l y d a i l y and sometimes twice d a i l y at low t i d e s and l e s s f r e q u e n t l y a t high t i d e s ) of pools was conducted to determine the l o c a t i o n o f i n t r o d u c e d f i s h . The 156 trough at the f r o n t of the enclosure was a l s o examined t o determine which f i s h had f o l l o w e d the r e c e d i n g water l i n e without moving i n t o a p o o l . A n a l y s i s of homing performance by l e n g t h c l a s s e s a t F i r s t Beach was a l s o undertaken. The data on homing performance from ten displacement experiments over 60 m at F i r s t Beach were used i n t h i s a n a l y s i s . Emphasis was placed on f i s h l e s s than 4,0 cm ( t o t a l l e n g t h ) . . T h i s s i z e group was d i v i d e d i n t o three c l a s s e s - 2,5 t o 2.9 cm, 3.0 to 3.4 cm and 3.5 to 3.9 cm. Larger s i z e c l a s s e s were examined i n 1.0 cm s i z e i n t e r v a l s . In a d d i t i o n to c a l c u l a t i n g percentages by length c l a s s s u c c e s s f u l l y homing, remaining i n the t r a n s p l a n t area and of homers r e t u r n i n g to the home pool f o r each experiment, t h e mean percentages and standard e r r o r s of the means (Snedecor and Cochran, 1967) were a l s o c a l c u l a t e d f o r each length c l a s s . The r e l a t i o n s h i p between s i z e and pool f i d e l i t y was i n v e s t i g a t e d by a n a l y z i n g the data from the th r e e replacement experiments a t F i r s t Beach by l e n g t h c l a s s e s . Percentages found o n l y i n the home pool, i n the home and nearby pools, i n the home range and i n d i s t a n t pools were c a l c u l a t e d . One of the homing experiments included i n the above a n a l y s i s was s p e c i f i c a l l y conducted t o examine homing performance o f j u v e n i l e f i s h , A t o t a l of 38 O. maculosus j u v e n i l e s ( l e s s than 3.4 cm t o t a l length) were t r a n s p l a n t e d t o pools approximately 60 m away. Data were c o l l e c t e d f o r f i v e weeks. Percentages homing and remaining i n the t r a n s p l a n t area 157 were c a l c u l a t e d . To examine whether " l e a r n i n g " may take p l a c e when j u v e n i l e f i s h have j u s t moved i n t o lower pools, t h r e e c o l l e c t i o n s of j u v e n i l e f i s h were made from study pools a t F i r s t Beach. Pools from which c o l l e c t i o n s were made spanned the v e r t i c a l d i s t r i b u t i o n of study pools at the s i t e . The f i r s t two c o l l e c t i o n s i n v o l v e d 24 and 14 0, maculosus between 2.3 and 2.7 cm ( t o t a l l e n g t h ) . These f i s h were kept i n the l a b o r a t o r y f o r seven and f i v e weeks, r e s p e c t i v e l y , p r i o r t o r e l e a s e . The t h i r d c o l l e c t i o n i n v o l v e d 42 0. maculosus between 2.7 and 3.3 cm ( t o t a l length) which were kept i n the l a b o r a t o r y f o r t h r e e weeks p r i o r t o r e l e a s e . The second c o l l e c t i o n i n i t i a l l y i n v o l v e d over 30 O. maculosus but a number o f these d i e d . The f i s h i n the l a b o r a t o r y were fed almost d a i l y with s m a l l p i e c e s of mussel (i?Jtiia§ £3liJoEfii§Sfis) and chopped mussel was l e f t i n the tanks between f e e d i n g times. F o l l o w i n g t a g g i n g , the f i s h were t r a n s p l a n t e d about 60 m. Data were c o l l e c t e d f o r f o u r weeks. Percentages homing and remaining i n the t r a n s p l a n t areas were c a l c u l a t e d . Results In each o f the seven experiments conducted i n the en c l o s u r e , the movements of the f i s h were monitored u n t i l no tagged f i s h c o u l d be found. I t i s evident that i n a l l cases few f i s h were seen a f t e r i n t r o d u c t i o n f o r any length of time (Table 158 28). It i s apparent that there i s l i t t l e difference i n the re s u l t s whether the f i s h were introduced into high or low tidepools. In experiments 1 and H r e l a t i v e l y high percentages of juvenile f i s h moved from the pool of introduction to the trough at the seaward end of the enclosure prior to disappearing. Only i n two experiments (6 and 7) where f i s h were introduced into the highest tidepool was there any evidence of pool f i d e l i t y . However once the pool was well flooded by higher t i d e s , the f i s h l e f t the pool and enclosure very r a p i d l y . Results not included i n t h i s table from tagged and untagged f i s h introduced and observed i n the enclosure present much the same pattern. Larger f i s h were ra r e l y found aft e r release and i f they were located i t was i n the trough at the front. Only one introduced adult f i s h was found on several successive days i n one pool. & number of untagged juveniles (recognized by i n d i v i d u a l markings) were observed f o r several successive days i n various pools, but never f o r longer than three days. From these r e s u l t s i t i s evident that nothing can be concluded about the length at which juvenile f i s h adopt and home to a tidepool. The results of the analysis of homing experiments at F i r s t Beach (Figure 25 and Table 29) show that while there i s considerable v a r i a b i l i t y within and overlap between size T a b l e 28 Summary of experimental i n t r o d u c t i o n s i n t o t i d e p o o l e n c l o s u r e Experiment 1 Date r e l e a s e d 19 September 1975 Length classes(cm) <3.0 3.0-3.4 3.5-3.9 >4.Q T o t a l Number r e l e a s e d 6 15 13 0 34 Percent found i n 0 7 8 6 r e l e a s e pool Percent found i n 0 13 8 9 other pools Percent moved t o 0 7 8 6 more seaward pools Percent found i n 67 53 69 62 trough 1. F i s h i n t r o d u c e d i n t o a l l t i d e p o o l s 2. No f i s h seen a f t e r 6 days 3. 2 f i s h found i n bay o u t s i d e e n c l o s u r e f o r 13 days Experiment 2 Date r e l e a s e d 7 October 197 5 Length classes(cm) <3. 0 3.0-3.4 3.5-3.9 >4 .0 T o t a l Number r e l e a s e d 10 23 14 0 47 Percent found i n 0 9 0 4 r e l e a s e pool Percent found i n 0 9 0 4 other pools Percent moved t o 0 9 0 4 more seaward pools Percent found i n 0 0 7 2 trough 1. F i s h i n t r o d u c e d i n t o one r e l a t i v e l y high pool 2. No f i s h seen a f t e r 8 days 3. 2 f i s h seen i n bay once a f t e r 8 days Table 28 (continued) Experiment 3 Date r e l e a s e d 2 October 1975 Length classes(cm) <3.0 3.0-3.4 3.5-3.9 >4.0 T o t a l Number r e l e a s e d 8 4 3 0 15 Percent found i n r e l e a s e pool Percent found i n other pools Percent moved t o more seaward pools Percent found i n trough 1. A l l f i s h i n t r o d u c e d as c o n t r o l s i n t o one covered p o o l 2. A l l f i s h s u r v i v e d up to 21 days 3. A f t e r 21 days storm destroyed pool cover and e n c l o s u r e Experiment 4 Date r e l e a s e d 8 J u l y 1976 Length classes(cm) <3.0 3.0 -3.4 3.5-3.9 >4 .0 Tota Number r e l e a s e d 10 4 3 8 25 Percent found i n 40 25 33 0 24 r e l e a s e pool Percent found i n 30 0 0 0 8 other pools Percent moved to 10 0 0 0 4 more seaward pools Percent found i n 70 50 0 0 36 trough 1. F i s h i n t r o d u c e d i n t o highest p o o l 2. No f i s h seen a f t e r 7 days Table 28 (continued) Experiment 5 Date r e l e a s e d 19 J u l y 1976 Length c l a s s e s (cm) <3.0 3.0-3. 4 3.5-3.9 >4.0 T o t a l Number r e l e a s e d 0 2 1 8 11 Percent found i n 0 0 0 0 r e l e a s e p o o l Percent found i n 0 0 25 18 other pools Percent moved to 0 0 25 18 more seaward pools Percent found i n 0 0 25 18 trough 1. F i s h i n t r o d u c e d i n t o second h i g h e s t t i d e p o o l 2. No f i s h seen a f t e r 14 days Experiment 6 Date r e l e a s e d 24 J u l y 1976 Length classes(cm) <3.0 3.0-3.4 3.5-3.9 >4.Q T o t a l Number r e l e a s e d 8 12 0 0 20 Percent found i n 100 75 85 r e l e a s e pool Percent found i n 0 8 5 other pools Percent moved t o 0 8 5 more seaward pools Percent found i n 0 0 0 trough 1. Fi s h i n t r o d u c e d i n t o highest pool 2. No f i s h seen a f t e r 14 days 162 Table 28 {continued) Experiment 7 Date r e l e a s e d 10 August 1976 Length c l a s s e s (cm) <3.0 3.0-3.4 3.5-3.9 >4.0 T o t a l Number r e l e a s e d 6 9 5 0 20 Percent found i n 100 100 100 100 r e l e a s e p o o l Percent found i n 0 0 0 0 other pools Percent moved to 0 0 0 0 more seaward pools Percent found i n 0 0 0 0 trough 1. F i s h i n t r o d u c e d i n t o h i ghest t i d e p o o l 2. No f i s h seen a f t e r 3 days Mean Percentage Homing by Length Class c OJ u $_ OJ Q_ c OJ u l _ OJ Q_ c OJ OJ Q_ 1 0 0 5 0 0 vlean Percentage Remaining 1 0 0 in the Transplant Area by Length Class 5 0 /lean Percentage of Homers q 0 o Returning to Home Pool by Length Class 5 0 h 1 6 3 6 0 108 147 20 21 34 27 J l X l -I 1 1 1 I I I 8 Length (cm) F i g u r e 25 H oming p e r f o r m a n c e by s i z e c l a s s e s (mean + 2 s. e.) T a b l e 29 a. Homing pe r f o r m a n c e by l e n g t h c l a s s e s ( p e r c e n t a q e s u c c e s s f u l l y homing) Date r e l e a s e d 26 May 11 Aug 4 Sept 21 Sept 23 Aug 15 S e p t 4 J u l y 16 J u l y 5 Auq 9 Auq 1975 1975 1975 1975 1976 1976 1976 1977 1977 1977 l e n g t h c l a s s (cm) 2.5 - 2.9 Number r e l e a s e d 1 0 0 0 0 0 5 4 17 0 P e r c e n t homed 0 0 25 0 3.0 - 3.4 Number r e l e a s e d 0 0 0 0 5 0 6 2 2 1 0 P e r c e n t homed 0 0 0 19 3.5 - 3.9 Number r e l e a s e d 5 0 0 0 6 0 5 5 0 0 P e r c e n t homed 0 50 20 40 4.0 - 4.9 Number r e l e a s e d 18 9 16 3 3 2 25 24 0 6 P e r c e n t homed 17 78 93 100 33 0 56 38 33 5.0 - 5.9 Number r e l e a s e d 4 31 26 21 13 7 13 8 0 24 P e r c e n t homed 100 61 69 76 62 86 92 75 67 6.0 - 6.9 Number r e l e a s e d 6 7 18 7 4 10 6 2 0 0 P e r c e n t homed 67 29 89 71 75 80 67 50 7.0 - 7.9 Number r e l e a s e d 4 6 6 1 0 1 0 0 0 2 P e r c e n t homed 50 33 67 0 0 100 8.0 - 8.9 Number r e l e a s e d . 4 1 3 1 0 0 0 0 0 0 P e r c e n t homed 50 100 33 0 T a b l e 29 ( c o n t i n u e d ) b. H o s i n g p e r f o r m a n c e by l e n g t h c l a s s e s ( p e r c e n t a g e r e m a i n i n g i n t r a n s p l a n t area) Date r e l e a s e d 26 day 11 Aug 4 Sept 21 Sept 23 Aug 15 S e p t <J J u l y 16 J u l y 5 Auq 9 Auq 1975 1975 1975 1975 1976 1976 1976 1977 1977 1977 L e n g t h c l a s s (cm) 2.5 - 2.9 Number r e l e a s e d 1 P e r c e n t s t a y e d 0 5 80 4 75 17 71 3.0 - 3.4 Number r e l e a s e d P e r c e n t s t a y e d 5 20 6 67 2 50 21 62 3.5 - 3.9 Number r e l e a s e d 5 P e r c e n t s t a y e d 0 6 33 5 80 5 80 4.0 - 4.9 Number r e l e a s e d 18 9 16 3 3 2 25 P e r c e n t s t a y e d 17 0 31 0 33 50 48 24 63 6 50 5.0 - 5.9 Number r e l e a s e d 4 31 26 21 13 ' 7 P e r c e n t s t a y e d 25 19 35 48 31 14 13 23 8 25 24 46 6.0 - 6.9 Number r e l e a s e d 6 7 18 7-P e r c e n t s t a y e d 17 14 17 0 10 20 6 67 2 50 7.0 - 7.9 Nurater released 4 6 6 1 Percent stayed 0 0 0 0 8.0 - 8.9 Number r e l e a s e d .4 1 3 1 P e r c e n t s t a y e d 25 100 0 100 T a b l e 29 ( c o n t i n u e d ) c . Honing p e c f o r m a r c e by l e n g t h c l a s s e s ( p e r c e n t a g e o f h o i e r s hcming t o home pool) Date r e l e a s e d 26 May 11 Aug 4 Sept 21 Sept 23 Aug 15 S e p t 4 J u l y 16 J u l y 5 Auq 9 Aug 1975 1975 1975 1975 1976 1976 1976 1977 1977 1977 L e n g t h c l a s s (cm) 2.5 - 2.9 Humber r e l e a s e d 1 0 0 0 0 0 5 4 17 0 P e r c e n t homing 100 t o home p o o l 3.0 - 3.4 Number r e l e a s e d 0 0 0 0 5 0 6 2 2 1 0 P e r c e n t homing 100 t o home p o c l 3.5 - 3.9 Number r e l e a s e d 5 0 0 0 6 0 5 5 0 0 P e r c e n t homing 0 100 0 t o home p o o l 4.0 - 4.9 Number r e l e a s e d 18 9. 16 3 3 2 25 24 0 6 P e r c e n t homing 33 71 60 33 100 71 50 50 to home p o o l 5.0 - 5.9 Number r e l e a s e d 4 31 26 21 13 7 13 8 0 24 P e r c e n t homing 75 89 61 63 88 83 58 50 63 t o home p e e l 6.0 - 6.9 Number r e l e a s e d 6 7 18 7 4 10 6 2 0 0 P e r c e n t homing 75 100 88 100 33 50 50 0 t o home p o c l 7.0 - 7.9 Number r e l e a s e d 4 6 6 1 0 1 0 0 0 2 P e r c e n t homing 100 50 50 50 to home p o c l 8.0 - 8.9 Number r e l e a s e d 4 1 3 1 0 0 0 0 0 0 H" Percent homin t o home p o c l P g 100 10C 100 °? CT\ 167 classes, there i s a d e f i n i t e improvement in homing performance with size from about 2.5 to 5.0 cm. Between 5.0 and 7.0 cm homing i s best exhibited. Older f i s h {7.0 to 9.0 cm) appear to show some decline in homing performance. Despite the small sample s i z e s f o r smaller f i s h , i t generally appears to be true that of those f i s h which home, a l l si z e classes show about the same a b i l i t y t o return to a small area from a considerable distance. The mean percentages remaining i n the transplant area by length show a smaller percentages of f i s h remaining i n the transplant areas with increasing si z e , except f o r the large s t size c l a s s found at F i r s t Beach. Again, these data show considerable v a r i a t i o n within and between length classes, but the r e l a t i v e l y greater v a r i a b i l i t y shown i n the 3.5 to 3.9 cm size c l a s s , the siz e at which any sizeable percentage of f i s h are beginning to home, may r e f l e c t the d i f f e r i n g staqes of development of homing a b i l i t y within t h i s length range. , Analysis of the data, by length classes, from replacement experiments (Table 30) suggests that home range f i d e l i t y i s not well developed in juvenile f i s h compared with large f i s h . From Table 31 i t i s evident that the percentaqe of successful juvenile f i s h hominq i s small and that while the majority of f i s h remain i n the transplant area for some period of time, many subsequently move elsewhere. The r e s u l t s appear Table 30 Ana lys i s of replacement experiments by l ength Date re leased 28 May 6 2 June 30 June 9 August 1975 1977 1977 Length c l a s s (cm) 3.0 - 3 . 1 Number re leased Percent found in home fcol only Percent found in home and near pools Percent found in heme ranqe Percent found in d i s t a n t pools 3.5 -3.9 Number re leased 4 Percent found in heme pool only 25 Percent found in home and near pools Percent found in heme ranqe Percent found in d i s t a n t pools 4.0 - a.9 Number re leased 17 Percent found in home pool only 35 Percent found i n home and near pools Percent found in heme ranqe Percent found in d i s t a n t pools 5.0 - 5.9 Number re leased 1 Percent found in heme pcol only 0 Percent found in home and near pools Percent found in heme ranqe Percent found in d i s t a n t pools 6.0 - 6.9 Number re leased 3 Percent found in heme pool only 33 Percent found in home and near pools Percent found i n heme ranqe Percent found in d i s t a n t pools 7.0 - 7.9 Number re leased 1 Percent found in heme pcol only 75 Percent found in heme and near pools Percent found in heme ranqe Percent found in d i s tant pools 24 100 25 59 100 33 3 3 18 34 13 44 28 38 38 1 1 56 59 54 100 100 56 83 97 92 100 1 1 15 25 40 40 25 33 44 50 73 8 4 75 75 100 8.0 - 8.9 Number released Percent found in heme peel only Percent found in home and near pools Percent found in home ranqe Percent found i n d i s t a n t pools 100 100 CTl co T a b l e 31 Homing performance of j u v e n i l e Q l i a o c o t t u s maculosus Length c l a s s (cm) 2.5 - 2.9 3.0 - 3.4 T o t a l Date r e l e a s e d 5 August 1977 Number r e l e a s e d 17 21 38 Number homed 0 4 4 Percent homed 0 19 11 Number s t a y i n g i n 12 13 25 t r a n s p l a n t area Percent s t a y i n g i n 71 62 66 t r a n s p l a n t area Days s t a y i n g i n t r a n s p l a n t area a. homers 1,4,6,6 b. non-homers 1#1,1»1, 1,1,2,2, 1,1,1,2, 6,7,7,12, 5,7,12,16 39 Percent of homers homing t o home pool 100 100 1 7 0 to suggest t h a t homing behaviour i s not p o s s i b l e f o r f i s h l e s s than about 3.0 cm, a t which l e n g t h a s m a l l percentage are beginning to show homing behaviour. Taken i n c o n j u n c t i o n with the a n a l y s i s of pool f i d e l i t y data by length c l a s s e s , the apparent i n a b i l i t y of s m a l l 0. maculosus t o home may be a s s o c i a t e d with the absence of home range f i d e l i t y , t h a t i s , homing behaviour i s not demonstrated u n t i l a home range has been e s t a b l i s h e d . T a b l e 32 shows t h a t 0. maculosus which were between 2.3 amd 2.7 cm when c o l l e c t e d were unable t o home a f t e r being kept i n the l a b o r a t o r y f o r f i v e and seven weeks. P i s h between 2.7 and 3.3 cm when c o l l e c t e d and kept i n the l a b o r a t o r y f o r three weeks showed some evidence o f being a b l e t o home. The number o f f i s h seen a f t e r r e l e a s e given the s m a l l percentage homing was s u r p r i s i n g l y high, i n view of the f a c t t h a t i f homing was not undertaken, presumably the f i s h were moving around between t i d e p o o l s and c o u l d have moved almost anywhere on the beach. Of the f i s h seen a f t e r r e l e a s e more than once i n the t r a n s p l a n t area the m a j o r i t y moved around widely between pools i n the t r a n s p l a n t area r a t h e r than remaining i n the one pool. The amount of movement was comparable t o t h a t o f a d u l t s from high t i d e p o o l s , t h a t i s they showed a wider range of movement than the r e s i d e n t s of the p o o l s i n t o which they were i n t r o d u c e d . Of a l l the f i s h r e l e a s e d o n l y seven ( a l l of which were 2.9 cm or g r e a t e r i n s i z e ) showed any evidence of s t r i c t pool f i d e l i t y . 171 T a b l e 32 Homing performance o f j u v e n i l e Q l i g o c o t t u s maculosus kept i n the l a b o r a t o r y f o r v a r y i n g p e r i o d s o f time p r i o r to r e l e a s e Length c l a s s (cm) when r e l e a s e d 2.5-2.9 3.0-3.4 3.5-3.9 T o t a l Date r e l e a s e d 19 august 1977 Group A Number r e l e a s e d Percent homed Percent stayed i n t r a n s p l a n t area 17 0 47 7 0 71 24 0 54 Group B Number r e l e a s e d Percent homed Percent stayed i n t r a n s p l a n t area 9 0 67 5 0 60 14 0 64 Group C Number r e l e a s e d Percent homed Percent stayed i n t r a n s p l a n t area 12 17 42 29 14 62 2 0 50 43 14 56 Time i n l a b o r a t o r y Group a 7 weeks Group B 5 weeks Group C 3 weeks Size when c o l l e c t e d 2. 3 - 2. 7 cm 2 . 3 - 2. 7 cm 2.7 - 3.3 cm 172 Previous experiments shoved t h a t 0, maculosus are beginning t o show evidence of home range f i d e l i t y between 2.5 and 3.0 cm, and to a g r e a t e r degree between 3.0 and 3.4 cm. Homing behaviour a l s o begins to become ev i d e n t i n these s i z e c l a s s e s o f f i s h (2.5 to 2.9 cm - one f i s h out of 27 (2.9 cm); 3.0 to 3.4 cm - f o u r f i s h out of 34). Since removal of O. maculosus from the f i e l d at t h i s time (Groups A and B) r e s u l t e d i n t h e i r being unable to home when r e p l a c e d , whereas l a r g e r f i s h (Group C) were a b l e t o home when r e p l a c e d , i t appears t h a t ^ l e a r n i n g , , of the i n t e r t i d a l and adoption of a home range begins to occur d u r i n g t h i s p e r i o d of time. 4. D i s c u s s i o n D i f f e r e n c e s i n homing behaviour between y e a r - c l a s s e s are not apparent. Atkinson (1939) suggested, on the b a s i s of t h r e e d i s t i n c t modes i n the diameter f r e q u e n c i e s of ova from a mature female, t h a t 0. maculosus may spawn more than once a year. I f t h i s i s the case, and s i n c e Q. macnlgsus probably spawn over s e v e r a l y e a r s , any g e n e t i c a l l y r e l a t e d d i f f e r e n c e s i n homing behaviour would be d i f f i c u l t t o d i s t i n g u i s h . Age r e l a t e d d i f f e r e n c e s i n homing behaviour are apparent, although the d i v i s i o n i n t o only three age groups i s too g r o s s to provide much i n d i c a t i o n o f the stage at which f i s h 173 are l e a r n i n g t o d i s p l a y s u c c e s s f u l honing behaviour and pool f i d e l i t y . I t i s e v i d e n t t h a t t h e r e i s an i n c r e a s e i n the percentage of s u c c e s s f u l homers between age one and two and some d e c l i n e i n age three f i s h , although o f the f i s h which do home, a l l age groups home with egual p r e c i s i o n . There i s a d e c l i n e i n the number of f i s h remaining i n the t r a n s p l a n t area with age. Examination of homing behaviour by s m a l l e r s i z e c l a s s e s r e v e a l s the r e l a t i o n s h i p between homing behaviour and age i n much g r e a t e r d e t a i l . J u v e n i l e f i s h do not appear t o adopt a home range or s t a r t homing to i t u n t i l they are about 2.8 to 3.0 cm long. Between t h i s s i z e and about 5 cm they show i n c r e a s i n g l y b e t t e r developed home range f i d e l i t y and homing performance. The h i g h e s t percentages s u c c e s s f u l l y homing occur i n f i s h between 5.0 and 7.0 cm. There appears to be some d e c l i n e i n percentages homing with l a r g e r f i s h . A l l s i z e c l a s s e s appear t o home with egual p r e c i s i o n . Percentages remaining i n the t r a n s p l a n t area show a d e c l i n e with l e n g t h , except f o r the l a r g e s t s i z e c l a s s . I t appears t h a t j u v e n i l e f i s h (greater than about 2 cm), having moved i n t o lower pools from the high t i d e p o o l s i n which they s e t t l e , show f a i r l y e x t e n s i v e movement between t i d e p o o l s , p r i o r to adopting a home range and demonstrating homing behaviour. " L e a r n i n g " and "memorizing* 1 the area appear t o begin when the f i s h are about 2.3 to 2.7 cm l o n g . Removal from the f i e l d of O. maculosus which are g r e a t e r than 2.7 cm does not appear to a f f e c t homing performance, r e l a t i v e to f i s h 174 of the same s i z e which have always been i n the f i e l d . I t i s suggested t h a t j u v e n i l e s move e x t e n s i v e l y between pools up t o about 3 cm, and to a l e s s e r e x t e n t , up to about 4 cm. Although the low t i d e d i s t r i b u t i o n of j u v e n i l e 0. maculosus p r o v i d e s evidence of e x t e n s i v e movement between p o o l s . Green's (1971b) work suggests t h a t high t i d e movements may be even more e x t e n s i v e i n some cases. He found that f i s h l e s s than 5.5 cm i n some s h e l t e r e d and moderately s h e l t e r e d areas were the o n l y group to show an almost complete t i d a l s h i f t i n t h e i r v e r t i c a l d i s t r i b u t i o n , moving shorewards with the advancing t i d e and seawards with the f a l l i n g t i d e . I f t h i s i s the case, i n f o r m a t i o n a c q u i s i t i o n , a t l e a s t f o r f i s h i n s h e l t e r e d a r e a s , may continue to occur u n t i l the f i s h are q u i t e l a r g e . , The d e c l i n e i n the percentage s u c c e s s f u l l y homing and i n c r e a s e i n the percentage remaining i n the t r a n s p l a n t area i n the l a r g e s t s i z e c l a s s e s of f i s h may be due to the s m a l l sample s i z e s , impaired "memory", reduced swimming a b i l i t i e s , or some combination of these f a c t o r s . Gerking (1957) found t h a t f a s t e r growing f i s h tend to mature e a r l i e r and a l s o become s e n i l e and d i e e a r l i e r than slower growing f i s h of the same brood. Since P o r t Renfrew 0. maculosus do not appear to show any d e c l i n e i n the percentage of s u c c e s s f u l homers i n the l a r g e s t s i z e c l a s s e s (Green, 1967; Khoo, 1971) and s i n c e the data from t h i s study suggests t h a t they grow more s l o w l y , perhaps the e a r l i e r onset of s e n i l i t y i s a f a c t o r i n t h e d e c l i n e i n homing performance i n 175 the largest f i s h at F i r s t Beach. A reduced rate of growth i n Port Renfrew f i s h r e l a t i v e to F i r s t Beach f i s h may also account for the absence of any difference in homing performance i n the smaller size classes. Since age or time i s presumably more important with respect to learning information than actual length, i t i s probable that by the time 0. maculosus at Port Renfrew are 4 cm long the majority have had s u f f i c i e n t time to acquire the information to home with a b i l i t y comparable to that of larger F i r s t Beach f i s h . Thus examination of homing performance of smaller size classes of f i s h (less than 4 cm) may be necessary to determine the size and age at which Port Renfrew f i s h adopt a home pool and sta r t homing to i t . Another factor which may be of relevance here i s the topography of the two areas, and i t s apparent e f f e c t on pool f i d e l i t y discussed e a r l i e r . Port Renfrew Q. maculosus move more freely between pools than F i r s t Beach 0. lasulosus and may acguire information e a r l i e r since the beach i s less i r r e g u l a r . Investigation of the homing performance of another c o t t i d , Clinocottus globiceps. by s i z e classes showed no differences (Green, 1973). A si m i l a r situation was found to e x i s t i n the homing performance of Tantoqolabrus adspersus (Green, 1975). Gibson (1967) showed that juvenile Blennius fiholis (less than 5 cm) display the same degree of pool f i d e l i t y as adults but that juvenile Acanthocottus r=Enophrys1 bubalis (less than 5 cm) appeared to show less pool f i d e l i t y than adults. Williams (1957) found no s i z e differences (between 36 176 and 100* mm) i n pool f i d e l i t y of C l i n o c o t t u s a n a l i s , although a n a l y s i s of h i s data shows an i n c r e a s e i n the percentage d i s a p p e a r i n g a f t e r t a g g i n g , with s i z e . T h i s was a l s o t r u e f o r G i r e l l a n i g r i c a n s . , Although he d i d not tag any C . , a n a i l s l e s s than 36 mm, f i n c l i p p i n g showed t h a t f i s h as s m a l l as 11 mm were found i n the same pools. although Williams p r o v i d e s some evidence to suggest s h o r t term pool f i d e l i t y occurs i n s m a l l G i r e l l a n i g r i c a n s (23 to 28 mm l o n g ) , long term p o o l f i d e l i t y o f t h i s s i z e group was not e x h i b i t e d . Both these f i s h move t o deeper s u b t i d a l water as they i n c r e a s e i n s i z e , which suggests that pool f i d e l i t y changes over t h e l i f e o f the f i s h . In freshwater f i s h , Larimore (1952) showed that smallmouth bass H i c r o p t e r u s dolomieu Lacepede l a r g e r than 25.4 cm showed hig h e r r a t e s of r e t u r n than s m a l l e r f i s h . , Complementary evidence was p r o v i d e d by Funk (1957) who found t h a t bass up to 3 3 cm were i n c r e a s i n g l y mobile but the number o f mobile i n d i v i d u a l s d e c l i n e d s h a r p l y i n l a r g e r f i s h . Funk a l s o showed d i f f e r e n t degrees of m o b i l i t y according to s i z e i n rock bass, Ajnbloplites r.up_es_tris (Rafinesgue) and channel c a t f i s h l£i§J:.3£i§ fiUSctatus (Rafinesgue) , g r e a t e s t m o b i l i t y being shown by i n t e r m e d i a t e s i z e c l a s s e s i n both s p e c i e s . 177 VII. SENSORY MECHANISMS INVOLVED IN HOMING BEHAVIOUR !• Sensory, impairment methods V i s i o n F i s h were b l i n d e d a c c o r d i n g t o the method used by Khoo (1971). A s l i t was made i n the cornea of the e y e b a l l with a sharp s c a l p e l and the s i d e s o f the e y e b a l l were pressed with f o r c e p s u n t i l the l e n s emerged. The l e n s was then removed. Although perception of l i g h t and dark i s p o s s i b l e s h o r t l y a f t e r lens removal, both the r e t i n a and the o p t i c nerve u l t i m a t e l y degenerate (Rasguin, 1949). When t h i s o p e r a t i o n was performed i n 1976, f i s h were a n a e s t h e t i z e d i n g u i n a l d i n e (1 ml per 4.5 l i t r e s ) . Recovery from the o p e r a t i o n seemed good as i n d i c a t e d by s u r v i v a l i n both the f i e l d and l a b o r a t o r y . As experience was gained i n the technigue, use of a n a e s t h e t i c o n l y i n c r e a s e d h a n d l i n g time; no d i f f e r e n c e i n r e c o v e r y from the o p e r a t i o n was observed between an a e s t h e t i z e d f i s h and those which were not a n a e s t h e t i z e d . In experiments conducted i n 1977 no a n a e s t h e t i c was used. 178 O l f a c t i o n S e v e r a l methods were attempted to make f i s h anosmic. I n i t i a l l y heat c a u t e r i z a t i o n was used (Khoo, 1971). A red hot needle was i n s e r t e d i n t o the a n t e r i o r nares and moved i n t o the p o s i t i o n o f the o l f a c t o r y r o s e t t e . F i s h were a n a e s t h e t i z e d i n g u i n a l d i n e p r i o r to the o p e r a t i o n . Recovery from the o p e r a t i o n appeared t o be s a t i s f a c t o r y , as i n d i c a t e d by s u r v i v a l both i n the f i e l d and l a b o r a t o r y . Examination o f o l f a c t o r y r o s e t t e s of s i x 0. maculosus which had undergone t h i s treatment showed d e s t r u c t i o n of the r o s e t t e . However, s i n c e i t i s i m p o s s i b l e t o examine each f i s h i n t h i s regard p r i o r t o r e l e a s e , i t i s p o s s i b l e t h a t not a l l r e l e a s e d f i s h were f u l l y anosmic a f t e r treatment. To overcome the problem o f the u n c e r t a i n t y o f the t o t a l d e s t r u c t i o n of the o l f a c t o r y r o s e t t e s , s e v e r a l other methods were attempted to make the f i s h anosmic. C u t t i n g o f the o l f a c t o r y nerve was attempted but was u n s u c c e s s f u l . I n j e c t i o n of l a t e x proved i m p o s s i b l e because of the s m a l l s i z e of the nares. Covering the nares with v i n y l a c e t a t e was u n s a t i s f a c t o r y because of the i r r i t a t i n g nature of the fumes and because i t peeled o f f when i t hardened. O r a f i x S p e c i a l P l a s t i c Denture Adhesive ( N o r c l i f f Products) and Lepage*s P l a s t i c Hodel Cement e i t h e r d i s s o l v e d or f a i l e d to adhere. 179 In one experiment the nares were blocked with Kodak Eastman 910 Adhesive which adhered s a t i s f a c t o r i l y f o r about t h r e e days i n the l a b o r a t o r y . A f t e r t h i s time i t peeled o f f . F i n a l l y , a d e n t a l g l u e , Durelon C a r b o x y l a t e Cement (ESPE F a b r i k Pharmazeutische Praparate GMBH) was used t o block the nares. T h i s adhered extremely w e l l i n the l a b o r a t o r y from seven days to two weeks, but again a f t e r t h i s p e r i o d i t peeled o f f . No a n a s e t h e t i c was used when e i t h e r of these treatments was a p p l i e d . Taste The p o s s i b i l i t y t h a t the c i r r i o f 0. maculosus contained t a s t e buds, s i m i l a r to those found i n the t e n t a c l e s o f Blenni u s t e n t a c u l a r i s Brunn (Schulte and Ho.ll, 1972) and t h a t these and other chemosensory r e c e p t o r s might be i n v o l v e d i n homing, r e s u l t e d i n u s i n g the method o f Bardach e t a l , (1965) i n an attempt t o destroy any such t a s t e buds. Detergents reduce s u r f a c e t e n s i o n and a c t as f a t s o l v e n t s thus making a l l membranes of f i s h t h a t come i n t o contact with d e t e r g e n t s s u s c e p t i b l e t o damage. Bardach et a l . (1965) examined the e f f e c t of low c o n c e n t r a t i o n s o f detergents (1 to 5 ppm) on I c t a l u r u s n a t a l i s (Lesueur) and found t h a t observable h i s t o l o g i c a l d i s i n t e g r a t i o n o f t a s t e buds occurred ( a f t e r three t o ten days). B e h a v i o u r a l o b s e r v a t i o n s suggested t h a t damage to 180 the olfactory epithelium and g i l l s may have occurred although h i s t o l o g i c a l examination did not support t h i s . Recovery of the taste buds was not observed even a f t e r four to s i x weeks i n clean water. This technique was used i n i t i a l l y i n attempts to eliminate the sense of taste i n 0. maculosus. Ten O. maculosus individuals were put in low s a l i n i t y water {5 ppt) containing 5 ppm household detergent. The water and detergent were changed daily. However, a l l f i s h died within three days, Whether t h i s was due to the freshwater or to the detergent was unknown. Nakamura (1970) found that O. ..maculosus -• exposed to two ppt s a l i n i t y survived from 88 to 102 hours and at a s a l i n i t y of 7.5 ppt to 192 hours, when the experiment was terminated. This suggests that the complete mortality recorded here was a r e s u l t of the combined e f f e c t of low s a l i n i t y water and detergent. k second attempt to eliminate chemosensory c e l l s was made using octylphenoxypolyethoxyethanol (Triton-X-100), a non-i o n i c detergent which was found to induce involuntary convulsive ef f e c t s on the mollusc, Succinum undatum, s i m i l a r to the e f f e c t induced by saponins from the s t a r f i s h Astgrjas rubens and Marthasterias g l a c i a l i s (Mackie et a l . , 1968). This escape response i s suggested by the authors to be caused by saponins reacting with, or causing damage to, chemosensory c e l l s of nervous o r i g i n i n or near the surface epithelium of the foot muscle. Damage i s caused by the detergent or surface active properties of the saponins, 181 Ten 0. saculosus were put i n seawater containing 5 ppm Triton-X-100. Another ten 0. maculosa s were run as controls i n the same volume of seawater (10 1) only. The water and Triton-X-100 were changed d a i l y . The f i s h were kept under these conditions for seven days, at which time f i v e of the experimental f i s h and a l l the control f i s h were fixed separately i n 10% formalin. The remaining f i v e experimental f i s h were returned to clean seawater to determine the period of recovery of chemosensory c e l l s ( i f they were destroyed). although, subseguent to the homing experiments i n which the e f f e c t of 7 days immersion in Triton-X-100 was examined, no evidence was found to show that the c i r r i of 0. maculosus contain any taste buds, i t i s possible that taste buds may be located elsewhere on the body and may be affected by detergent. l i s Removal Pectoral and pelvic f i n s were removed from 2« maculosus • in d i v i d u a l s by cutting with sharp scissors. Removal of one set of paired f i n s appeared to have no e f f e c t on the s u r v i v a l of f i s h . Moring (1976) reported that 0. maculosus whose pectoral and caudal fi n s were p a r t i a l l y clipped showed "no unusual mortalities or l o s s of movement over an extended period" i n the laboratory, although none was kept in the laboratory for 182 any period of time i n t h i s study, f i e l d o b s e r v a t i o n s o f 0« I§SJ?i2sus which had p e l v i c f i n s removed were made up to seven months a f t e r r e l e a s e , by which time t h e f i n s appeared t o be f u l l y regenerated. F i s h which had had p e c t o r a l f i n s removed were observed up t o f i v e months l a t e r , by which time these f i n s a l s o appeared to be f u l l y r egenerated. Boring (1976) re p o r t e d p a r t i a l f i n r e g e n e r a t i o n i n 0. maculosus and Gibson (1967) rep o r t e d f u l l f i n r e g e n e r a t i o n a f t e r c l i p p i n g i n Blennius p h o l i s and Acanthocottus [=Enophrysj b u b a l i s . Removal of both s e t s o f p a i r e d f i n s (as was undertaken i n one experiment) r e s u l t e d i n an obvious l o s s o f manoeuvreability and c o n t r o l o f movement. 0. maculosus i n d i v i d u a l s t r e a t e d i n t h i s manner tended t o l i e on one s i d e . One 0. maculosus with both s e t s o f p a i r e d f i n s removed was seen i n the f i e l d 81 days a f t e r r e l e a s e . 2 . I n t e r a c t i o n s between r e s i d e n t and i n t r o d u c e d f i s h T h i s experiment was designed to determine whether a be h a v i o u r a l or other i n t e r a c t i o n between the r e s i d e n t and in t r o d u c e d 0. maculosus i n a t i d e p o o l r e s u l t s i n the i n t r o d u c e d f i s h d e p a r t i n g from the t r a n s p l a n t pool and p o s s i b l y r e t u r n i n g to t h e i r home p o o l . 183 Methods A t o t a l o f 36 O l i g o c o t t u s maculosus were c o l l e c t e d from two nearby pools and t r a n s p l a n t e d to two other p o o l s about 100 m away. The t r a n s p l a n t pools were b a i l e d out and the r e s i d e n t f i s h c o l l e c t e d and r e t u r n e d to the lab. The pools were r e f i l l e d by bucketing water i n from other pools p r i o r t o i n t r o d u c i n g the t r a n s p l a n t e d f i s h . From the two t r a n s p l a n t pools 11 and 21 f i s h were removed and 10 and 26 were r e p l a c e d , r e s p e c t i v e l y . Data were c o l l e c t e d f o r two months. Re s u l t s While the percentage of 0. maculosus s u c c e s s f u l l y homing i s r e l a t i v e l y s m a l l i t i s evident that the percentage o f f i s h remaining i n the t r a n s p l a n t pool i s not s i g n i f i c a n t l y l a r g e r than i n many o f the o t h e r homing experiments (Table 33). In a d d i t i o n , a l l of the f i s h observed i n the t r a n s p l a n t pools a f t e r r e l e a s e subseguently homed. The s m a l l percentage of f i s h s u c c e s s f u l l y homing may be p a r t i a l l y a f u n c t i o n of the d i s t a n c e between the home and t r a n s p l a n t pools which was g r e a t e r than i n the other homing experiments. However i t was s t i l l w e l l w i t h i n the range o f 300 m from which d i s t a n c e Khoo (1971) found that 0. maculosus can home. Table 33 Homing performance a f t e r t r a n s p l a n t p o o l s c l e a r e d o f r e s i d e n t f i s h Date r e l e a s e d 12 October 1976 Number r e l e a s e d 36 Number homed 14 Percent homed 39 Number remaining i n t r a n s p l a n t area Percent remaining i n t r a n s p l a n t area Days remaining i n t r a n s p l a n t area a. homers 1,1,1 b. non-homers Percent of homers 86 r e t u r n i n g to home pool 185 T h i s experiment and the data from untreated 0. maculosus i n other homing experiments suggest that while some i n c r e a s e i n the percentage of f i s h remaining i n the t r a n s p l a n t pool f o r some p e r i o d o f time may occur, because o f the removal of some of the t r a n s p l a n t pool r e s i d e n t s , there i s no evidence to suggest t h a t b e h a v i o u r a l i n t e r a c t i o n s between r e s i d e n t and in t r o d u c e d f i s h are r e s p o n s i b l e f o r the ma j o r i t y of f i s h l e a v i n g the t r a n s p l a n t pool and homing. Since b a i l i n g out a t i d e p o o l does not remove a l l t r a c e s of water from the p o o l , i t s t i l l remains a p o s s i b i l i t y t h a t t h e r e i s some pheromonal i n f l u e n c e (from the r e s i d e n t f i s h ) which, although d i l u t e d a f t e r b a i l i n g and r e f i l l i n g the p o o l , i s s t i l l d e t e c t a b l e by the i n t r o d u c e d f i s h and r e s u l t s i n t h e i r departure from the pool. Although t h i s problem might be overcome by d e l a y i n g the i n t r o d u c t i o n o f t r a n s p l a n t e d f i s h f o r s e v e r a l t i d e c y c l e s , t o allow t i d a l f l u s h i n g of the p o o l , i t i s p o s s i b l e t h a t other f i s h may have moved i n t o the pool over t h i s p e r i o d . 186 3. Nature of movement between r e l e a s e and home, J2Qol One experiment was conducted to determine whether homing p. maculosus showed any evidence o f d i r e c t e d movement as r e v e a l e d by t h e i r low t i d e d i s t r i b u t i o n . The l o c a t i o n s , between the r e l e a s e and the home pools, of two groups o f f i s h t r a n s p l a n t e d to a c e n t r a l pool were analyzed with r e s p e c t to angular d i r e c t i o n . Methods A t o t a l o f 66 f i s h from two groups o f pools (29 from one group and 37 from the other group) were t r a n s p l a n t e d t o a pool about midway between the home pool a r e a s (27 and 33 m from the home p o o l s ) . As f a r as the t i d e height p e r m i t t e d , pools i n a l l d i r e c t i o n s between the r e l e a s e and home pools were searched f o r t r a n s p l a n t e d f i s h . When a f i s h was l o c a t e d , the angle of t h a t p o o l r e l a t i v e t o the r e l e a s e pool was recorded. Data from each of the f i r s t t h r e e days f o l l o w i n g r e l e a s e and, because the sample s i z e s were s m a l l , from the f i r s t t h r e e days combined, were p l o t t e d on c i r c l e s , s i m i l a r t o diagrams of vanishing p o i n t s used f o r b i r d s i n o r i e n t a t i o n a n a l y s i s . In the case of the combined data, a l l except one f i s h had been seen only once, o r more than once i n the same pool i n t h e area under c o n s i d e r a t i o n . For the one f i s h seen i n pools i n d i f f e r e n t d i r e c t i o n s from the 187 r e l e a s e pool, the i n i t i a l s i g h t i n g , i n the d i r e c t i o n o p p o s i t e i t s home pool was used, t o avoid b i a s . Two kin d s o f a n a l y s i s were conducted. For each day's re c o r d s and f o r the combined r e c o r d s , s i g n t e s t s were used t o compare the home d i r e c t i o n s (85° and 235°) with the mean d i r e c t i o n s of each of the two samples to determine whether the mean d i r e c t i o n taken by each sample c o u l d be c o n s i d e r e d as the home d i r e c t i o n ( B a t s c h e l e t , 1965). To determine whether the two samples f o r each day and f o r the combined data were s i g n i f i c a n t l y d i f f e r e n t , the Watson nonparametric two sample t e s t , based on a mean sguare d e v i a t i o n was used (Watson, 1961; 1962; B a t s c h e l e t , 1965). R e s u l t s For a l l but one of the samples from each day where t h e r e are s u f f i c i e n t data, i t i s ev i d e n t t h a t the mean d i r e c t i o n s taken by f i s h l o c a t e d between the r e l e a s e and home pools were the home d i r e c t i o n s . However, f o r only the f i r s t day, does the Watson t e s t show a s i g n i f i c a n t d i f f e r e n c e between samples (Figure 26). T h i s may be due t o the sm a l l sample s i z e s . The combined data f o r the f i r s t t h ree days, i n which each f i s h i s c o n s i d e r e d o n l y once, shows t h a t the mean d i r e c t i o n s taken are the home d i r e c t i o n s , and f u r t h e r t h a t the samples are s i g n i f i c a n t l y d i f f e r e n t (Figure 26). Since the samples may be s i g n i f i c a n t l y d i f f e r e n t i n angular d e v i a t i o n or Ts m e a n d i r e c t i o n (Q) h o m e d ; r e c t : o n { 0 )? 0 = 2 3 5 ° - 0 = 8 5 ° « w °° ^ % N=7, n =2 N=7, n =2 Day 1 / \ l l  / \ p = . 4 5 4 > . 0 5 p = . 4 5 4 > . 0 5 homepoo i s (85°) 0=0 0=0 ooooooo J , • • • • • O O homepoois (235°) ov . S a m p l e s s i g n i f i c a n t l y d i f f e r e n t [ m e a n d ; r ' n ] n o ° ° \ • . / Un =.348 p < . 0 5 ( B u r r , 1964) 0 x Day 2 ^ N=12, n =2 N=4 p=.038 <.05 i n s u f f i c i e n t da ta F270- 90'4« S p o o l s (85°) 0 ^ ^ ooo J o.••••*. O homepoois (235°) \ / • S a m p l e s not s i gnif i c a n t l y d i f f e r ent: 0 o ° f 0 ° V . 1 8 0 ° U 1 ? 4 = -0994 P > . 0 5 ( B u r r , 1964) Day3 ' °" ^ \ N = 7 ' V 3 N = 3 p = 1 . 0 ) . 0 5 ' nsuffi c i ent da ta [270° 9 0 ° + homepoois (85°) 0 = 0 homepoois (235°) -\ 4. ^ Q t ab les a v a ' l a b l e f o r U „ =.2019 o° fVV > 7 ^ _ 1 8 0 ° o^  " c T ^ X . N=22, n =8 N=9, n =3 Day 1* Day 2 • Day 3 / ' P = . 2 8 6 > . 0 5 P= .508 ! >.05 0 = 0 0 = 0 j o . « . . . . . . . . . . S a m p l e s s i g n ; f ' c a n t l y d i f f e ren t : homepoois (235°) n 0 \ 1 * j 2 ^ _° - > • l n , c . o ° ° o \ y* U _ _ = .2787 p < . 0 5 S t e p h e n s , 1965) oo(oooo) co ° V ./ 2 2 , 9 F i g u r e 26 C i r c u l a r p lo t s of d i r e c t i o n ove r f i r s t 3 days t a k e n b y two s a m p l e s of f i s h d i s p l a c e d to c e n t r a l p o o l ( s u c c e s s f u l h o m e r s shown under h o m e p o o l s ; those i n p a r e n t h e s e s found b e t w e e n r e l e a s e and h o m e pools) 189 mean d i r e c t i o n ( B a t s c h e l e t , 1965) (although the data suggest mean d i r e c t i o n ) , 150° was added t o t h e angular d i r e c t i o n s o f t h e s m a l l e r sample (so th a t the home d i r e c t i o n s were i d e n t i c a l f o r both samples) and the t e s t s t a t i s t i c was r e c a l c u l a t e d (Watson, 1962). T h i s r e s u l t e d i n U 2 22,9 = .1168, showing no s i g n i f i c a n t d i f f e r e n c e between the samples (p>.05). Thus the d i f f e r e n c e between the samples l i e s i n the mean d i r e c t i o n . I t may be concluded, t h e r e f o r e , t h a t f o r the f i s h seen between the r e l e a s e pool and the home pools w i t h i n the f i r s t t h r e e days f o l l o w i n g r e l e a s e , the mean d i r e c t i o n taken, as revealed by t h e i r presence i n t i d e p o o l s , by the groups from each s i d e of the r e l e a s e pool was the home d i r e c t i o n and t h a t the mean d i r e c t i o n s taken by each sample were s i g n i f i c a n t l y d i f f e r e n t . Of the 31 f i s h seen between the r e l e a s e and home pools, 24 or 77% homed.. In t o t a l , 80% of the f i s h r e l e a s e d homed. While t h i s experiment appears t o provide evidence t o show that homing O. maculosus d i s p l a y d i r e c t e d movement towards the home p o o l , two g u a l i f i c a t i o n s must be made. In the f i r s t t hree days on l y 31 out of the 66 O. M£3l°§Ji§ r e l e a s e d were found between the r e l e a s e and home pools. (Another f i v e f i s h remained i n the r e l e a s e pool and 12 f i s h which were not seen i n the area under c o n s i d e r a t i o n had homed.) Since no f i s h were found i n t r u l y landward p o o l s , t h e f i s h not seen may w e l l have been i n pools lower than those uncovered by the t i d e . Bore i m p o r t a n t l y , while the low t i d e d i s t r i b u t i o n o f f i s h s upports 190 the idea of d i r e c t e d homeward movement, nothing can be concluded about t h e i r behaviour at high t i d e . However, i f some kind of random s e a r c h i s i n v o l v e d i n homing, g r e a t e r numbers of f i s h than were observed might be expected to be found i n pools i n the "wrong" d i r e c t i o n from the home pool. 4.Touch and/gr chemosensory c l u e s A number of f i s h , f o r example, Urophycis chuss (Walbaum) , P r i o n i t u s c a r o l i n u s (Linnaeus), P. evolans (Linnaeus) (Bardach and case, 1965) and I c t a l u r u s sp. (Bardach, et a l . , 1967) have been shown to possess sensory r e c e p t o r s (t a s t e buds) on t h e i r f i n s , b a r b e l s and body s u r f a c e s . Given t h a t the p a i r e d f i n s of 0. maculosus are i n c o n s t a n t c o n t a c t with the sea f l o o r , Khoo (1971) conducted s e v e r a l homing experiments i n v o l v i n g removal of p e c t o r a l or p e l v i c f i n s t o determine whether d e t e c t i o n of sea bottom c l u e s i s used as a method of homing. Since the r e s u l t s he obtained were i n c o n c l u s i v e , s e v e r a l experiments were conducted in t h i s study i n v o l v i n g t h e removal o f p a i r e d f i n s . 191 Methods Three experiments i n v e s t i g a t i n g the homing a b i l i t y o f 0. maculosus without e i t h e r p e c t o r a l or p e l v i c f i n s were conducted. ft t o t a l o f 134 0. maculosus were t r a n s p l a n t e d , 65 with p e l v i c f i n s removed and 69 as u n t r e a t e d c o n t r o l s . (In t h i s and subseguent experiments, u n t r e a t e d 0. maculosus are r e f e r r e d t o as c o n t r o l f i s h , even though they were not sham operated.) In the second experiment a t o t a l o f 66 f i s h were t r a n s p l a n t e d , 33 with both p e c t o r a l f i n s removed and 33 as c o n t r o l s . In the t h i r d experiment a t o t a l of 113 f i s h were t r a n s p l a n t e d , 38 with both p e l v i c f i n s removed, 37 with both p e c t o r a l f i n s removed and 38 as c o n t r o l s . In a l l three experiments r e c i p r o c a l t r a n s p l a n t s were made as f a r as p o s s i b l e between two groups of f o u r p ools each about 60 m apart. Data were c o l l e c t e d f o r f o u r months i n each experiment. fts a f u r t h e r examination of the a b i l i t y of the p a i r e d f i n s to d e t e c t chemosensory (or touch) c l u e s , h i s t o l o g i c a l examination was made of the p e c t o r a l and p e l v i c f i n s of s i x 0* ISLSulosus. S e c t i o n s s t a i n e d with eosin-haemotoxylin were examined to determine whether t h e r e i s any evidence o f sensory r e c e p t o r s . 192 R e s u l t s Compared with u n t r e a t e d 0. maculosus, the removal o f pa i r e d f i n s appears t o have l i t t l e e f f e c t on homing a b i l i t y (Table 34). The percentages o f 0. maculosus remaining i n the t r a n s p l a n t area f o l l o w i n g r e l e a s e are a l l r e l a t i v e l y high, although i t i s not p o s s i b l e t o de t e c t any major d i f f e r e n c e s i n percentages s t a y i n g between c o n t r o l and t r e a t e d f i s h . In a l l thre e cases the percentages of s u c c e s s f u l l y homing f i s h r e t u r n i n g t o the home pool exceeded the percentages r e t u r n i n g to the home range. None of the s e c t i o n s of p e c t o r a l and p e l v i c f i n s examined showed any evidence of sensory r e c e p t o r s (Figure 27). In t h i s connection, i t i s i n t e r e s t i n g to note t h a t , from examination of Scorpaenichthys marmo r a t u s , F r e i h o f e r (1963) suggested the f i b r e s of the ramus l a t e r a l i s a c c e s s o r i u s (the main branches of which c a r r y t a s t e or gus t a t o r y f i b r e s ) a re d i s t r i b u t e d t o t h e p e c t o r a l and p e l v i c f i n s i n c o t t i d s . The t r a n s p l a n t experiments and the h i s t o l o g i c a l s t u d i e s provide no evidence t o suggest t h a t sensory r e c e p t o r s d e t e c t i n g chemosensory or touch c l u e s i n the p a i r e d f i n s are i n v o l v e d i n the homing o f 0. maculosus. 193 T a b l e 34 Homing performance a f t e r removal of p a i r e d f i n s Pect Cont Pelv Cont Pect Pelv Cont Date r e l e a s e d 21 September 4 September 1975 1975 16 May 1976 Number r e l e a s e d 33 33 65 69 38 37 38 Number homed 23 24 Percent homed 70 73 41 63 52 75 21 55 18 49 20 53 Number s t a y i n g 4 i n t r a n s p l a n t area Percent s t a y i n g 12 i n t r a n s p l a n t area 19 29 17 25 10 26 14 21 Days s t a y i n g i n t r a n s p l a n t area a. homers 13 b. non-homers 2,2,2 3,78 1,1,1, 1,1,1, 1,1,2 2,27 1,5,5, 1,1,4, 6,7 6,6,7, 17,18, 1,4, 6,6, 1,1, 1,2, 2,2 6,6,7, 22,43, 1,2, 2,56, 73,73, 12,32, 13,17 27, 56 83, 42,43, 85, 110 49,50 123 Percent of homers r e t u r n i n g to home pool 65 67 88 73 81 61 80 Pect: both p e c t o r a l f i n s removed Pe l v : both p e l v i c f i n s removed Cont: untreated gure 27 Sec t ions of t i p s of p e c t o r a l f i n (above) and p e l v i c f i n (below) 195 5 . R e l a t i v e importance of d i f f e r e n t senses To determine the r e l a t i v e e f f e c t o f d i f f e r e n t sensory impairments on homing a b i l i t y an experiment was conducted i n which homing performance was compared between groups of 0 . maculosus, each group o f which was s u b j e c t e d t o a d i f f e r e n t treatment i n v o l v i n g d e s t r u c t i o n of sensory r e c e p t o r s . T h i s experiment was designed to show whether homing performance was s i g n i f i c a n t l y more a d v e r s e l y a f f e c t e d by any one treatment. To determine whether there i s redundancy i n the sensory systems i n v o l v e d i n homing, the homing performance of a group of 0. maculosus which had undergone a l l f o u r sensory impairment treatments was compared with t h a t of untreated f i s h . Methods In the f i r s t experiment, a t o t a l of 150 0. maculosus were r e c i p r o c a l l y t r a n s p l a n t e d between two groups of f o u r pools each about 60 m apart. F i v e e g u a l s i z e d groups of 0. maculosus were i n v o l v e d having been t r e a t e d as f o l l o w s ; b l i n d e d , made anosmic, one s e t of p a i r e d f i n s removed, immersion i n T r i t o n - X -100 f o r seven days and untreated. Ten b l i n d f i s h and f i v e anosmic f i s h were held i n the l a b o r a t o r y to i n v e s t i g a t e the e f f e c t of treatment on s u r v i v a l . 196 Data were c o l l e c t e d f o r three and a h a l f months. In the experiment examining simultaneous sensory impairment of the same f o u r senses, a t o t a l of 46 0. maculosus were r e c i p r o c a l l y t r a n s p l a n t e d between two groups o f pools about 60 m a p a r t . A group of 20 f i s h were untreated c o n t r o l s and 26 were s u b j e c t e d t o a l l f o u r impairments. F o l l o w i n g treatment, the f i s h were kept i n the l a b o r a t o r y f o r s e v e r a l days b e f o r e r e l e a s e . One m o r t a l i t y occurred i n t h i s p e r i o d . Another ten tr e a t e d f i s h were kept i n the l a b o r a t o r y to i n v e s t i g a t e s u r v i v a l over the same pe r i o d as the experiment. Data were c o l l e c t e d f o r two and a h a l f months. In these and the two subsequent experiments, t e s t s of s i g n i f i c a n c e were conducted u s i n g the two f a c t o r G t e s t of independence (Sokal and R o h l f , 1969). R e s u l t s Given the low percentage of untreated f i s h which s u c c e s s f u l l y homed i t appears t h a t no s i n g l e sensory impairment treatment has any s i g n i f i c a n t e f f e c t on the percentage o f s u c c e s s f u l l y homing 0. maculosus (p>.05) (Table 35). Although the d i f f e r e n c e s are not s i g n i f i c a n t (p>.05), the percentages of s u c c e s s f u l l y homing f i s h r e t u r n i n g to the home pool are lower f o r b l i n d and anosmic groups than f o r any other treatment suggesting that there may be a s l i g h t e f f e c t of these treatments on t h e p r e c i s i o n with which the home pool can be l o c a t e d . The percentages o f 0. maculosus remaining i n the Table 35 Relative homing performance after four d i f f e r e n t impairment treatments Blind Anosmic F i n l e s s * 7 days i n Control Triton-X -100 Date released 23 August 1976 Number released 30 29 3 0 3 0 31 Number homed 21 12 15 22 15 Percent homed 70 41 50 73 48 Number remaining i n transplant ar ea Percent remaining in transplant area 17 10 34 30 20 26 Days staying in transplant area a. homers 1,1,2 1 1,11 1,1,1,1, 2 11,24 b. non-homers 24,31 1,2,2,2, 1,1,2, 1,2,10, 11,49,73, 8,24, 11,46, 74, 104 74, 101 80, 104 Percent of homers 48 42 53 59 60 homing to home pool *: one set of paired f i n s removed 198 transplant area are high p a r t i c u l a r l y in the cases of the anosmic, f i n l e s s and control groups. The f a c t that the control group shows an egually high percentage of f i s h remaining i n the transplant area as the treated groups suggests l i t t l e e f f e c t of the treatments themselves i n t h i s regard. Mortality of treated f i s h held i n the laboratory was low, u n t i l a blockage in the seawater system caused t o t a l mortality a f t e r two and a half months. U n t i l then no anosmic and one blind f i s h died. Mortality i n the f i e l d was unknown, although b l i n d , anosmic and control f i s h were observed in the f i e l d u n t i l the experiment was terminated. From t h i s experiment no single sensory impairment can be shown to have a s i g n i f i c a n t l y more adverse e f f e c t on homing a b i l i t y compared with that of untreated controls. Despite the small numbers of control f i s h used i n the simultaneous impairment experiment, i t i s evident that the homing performance of treated f i s h i s substantially affected by the treatments (Table 36). , The difference in the percentages successfully homing i s s i g n i f i c a n t (p<. 05). Two explanations or a combination of both may account for t h i s . Homing a b i l i t y may have been impaired because al t e r n a t i v e sensory mechanisms were destroyed so that no system was available for homing. , The two f i s h which successfully homed may have employed additional mechanisms or complete destruction of one of the sensory systems may not have been effected. T a b l e 36 Homing performance a f t e r four simultaneous sensory impairment treatments Impaired C o n t r o l Date r e l e a s e d 15 September 1976 Number r e l e a s e d 2 6 2 0 Number homed 2 14 Percent homed 8 70 Number remaining i n 4 4 t r a n s p l a n t area Percent remaining i n t r a n s p l a n t area 15 20 Days s t a y i n g i n t r a n s p l a n t area a. homers 1,1 b. non-homers 10,10, 10,26 23,28 Percent of homers r e t u r n i n g t o home pool 50 64 200 The a l t e r n a t i v e e x p l a n a t i o n may be t h a t t r e a t e d 0. maculosus were unable to s u r v i v e , r e g a r d l e s s o f being a b l e t o home, a f t e r such d r a s t i c treatment. The s i g n i f i c a n t l y h i g h e r percentage (p<.05) of t r e a t e d f i s h which were not l o c a t e d a t any time dur i n g the experiment {77% compared with 20% f o r c o n t r o l s ) suggests that t h a t the ma j o r i t y of f i s h e i t h e r moved out of the are a , were s u b j e c t to heavy p r e d a t i o n o r d i e d . S p e c i f i c predators of p. maculosus are unknown, but p o s s i b l e c a n d i d a t e s i n c l u d e mink, g u l l s , crows, g a r t e r snakes, d i v i n g b i r d s and f i s h . However, the m a j o r i t y of mink observed i n t h i s study were c o l l e c t i n g c r a b s , no g a r t e r snakes were observed i n t i d e p o o l s , crows were seen at the study areas i n the i n t e r t i d a l but never i n a p o o l , and gut content a n a l y s i s of Sebastes spp., hexagrammids and i n s h o r e c o t t i d s suggests t h a t perhaps only A r t e d i u s spp. are the major f i s h p r e d a t o r s of p. magulosus (Bruce Leaman, David Z i t t i n , p e r s o n a l communications; p e r s o n a l o b s e r v a t i o n ) . Gut content a n a l y s i s of d i v i n g b i r d s suggests t h a t p e l a g i c cormorants and pigeon g u i l l e m o t s are probably the only d i v i n g b i r d s l i k e l y to eat p. maculosus and i f they do, i t i s only as i n c i d e n t a l catch (Ian Robertson, p e r s o n a l communication). Although g u l l s are the f i n a l host f o r a p a r a s i t i c trematode { C r y p t o c o t y l e lingua) f o r which O. maculosus can act as an i n t e r m e d i a t e host (Ching, 1978) , o b s e r v a t i o n s of g u l l s i n t i d e p o o l areas suggests t h a t only f i s h i n high t i d e p o o l s may be v u l n e r a b l e and even f o r these f i s h , i t seems u n l i k e l y t h a t p r e d a t i o n o f t h i s k i n d i s very severe. C e r t a i n l y , the f i s h which had undergone f o u r sensory impairment treatments 201 appeared more v u l n e r a b l e to p r e d a t i o n by t h e i r behaviour i n t i d e p o o l s . Known m o r t a l i t y o f t r e a t e d f i s h h eld i n the l a b o r a t o r y was r e l a t i v e l y low (one death and one escape) u n t i l f a i l u r e of the seawater system a f t e r two months. Behaviour of t r e a t e d f i s h i n the l a b was n o t i c e a b l y d i f f e r e n t from t h a t o f untreated f i s h . The former tended t o group i n c o r n e r s of t h e tank and r a r e l y moved about i n comparison with untreated f i s h . T r e a t e d f i s h e x h i b i t e d no i n t e r e s t i n mussel pieces dropped i n t o the tank. T h i s can be c o n t r a s t e d with the r e l a t i v e a c t i v i t y o f untreated 0. maculosus and the almost i n s t a n t response to mussel p i e c e s . When t r e a t e d f i s h were r e l e a s e d i n t o t i d e p o o l s a t F i r s t Beach t h e i r i n i t i a l swimming was h i g h l y e r r a t i c compared with untreated f i s h , showing r o l l i n g and unsteadiness i n t h e i r movements. Untreated f i s h immediately swam away from the r e l e a s e p o i n t t o s h e l t e r underneath or at the s i d e of r o c k s , stones or algae. Treated f i s h merely sat i n the open i n the pool o c c a s i o n a l l y swimming back and forward. I f they swam i n t o a s o l i d o b j e c t they remained b e s i d e or under i t . By comparison the t r e a t e d f i s h moved very l i t t l e and f o r the most p a r t s a t i n the open area of the pool i n t o which they were r e l e a s e d or to which they swam d u r i n g t h e i r e r r a t i c movements. I t appears t h e r e f o r e t h a t while the cumulative e f f e c t of these f o u r sensory impairment treatments may have a c o n s i d e r a b l e e f f e c t on the s u r v i v a l of O. maculosus, homing a b i l i t y i s d e f i n i t e l y i mpaired. The r e s u l t s o f other sensory 2 0 2 impairment homing experiments suggest that i t i s a combination of b l i n d n e s s and anosmia which together prevent homing, s i n c e the homing performance o f f i s h without p a i r e d f i n s or a f t e r seven days immersion i n T r i t o n - X - 1 0 0 appears t o be r e l a t i v e l y u n a f f e c t e d . §.•Simultaneous impairment of v i s i o n and sme l l To e x p l o r e f u r t h e r the suggestion t h a t both v i s i o n and sm e l l a re i n v o l v e d i n homing, two experiments were conducted t o determine the e f f e c t of simultaneous impairment of these senses on homing performance. In one experiment, the r e l a t i v e homing performance o f a group of both b l i n d and anosmic f i s h was compared with that of groups of b l i n d , anosmic and untreated f i s h . In t h i s experiment the e f f e c t of such treatments on j u v e n i l e f i s h was i n v e s t i g a t e d with a view t o determining whether these senses, and i n p a r t i c u l a r , v i s i o n , a re used to a c g u i r e the i n f o r m a t i o n r e g u i r e d to home. I f s i n g l y impaired a d u l t p. maculosus can home, but j u v e n i l e s cannot, i t i s p o s s i b l e that i n s u f f i c i e n t i n f o r m a t i o n or experience i s a v a i l a b l e to them to use a l t e r n a t i v e mechanisms t o home. In the second experiment, a d i f f e r e n t method of making f i s h anosmic was used t o compare the homing performance o f simu l t a n e o u s l y b l i n d and anosmic f i s h with that of untreated 203 controls. Only adult f i s h were used in t h i s experiment. ; Methods A t o t a l of 180 0. maculosus were r e c i p r o c a l l y transplanted between two groups of pools about 6 0 m apart., One group of 45 f i s h were untreated controls, 46 f i s h were blinded, 44 were made anosmic using Kodak Eastman 910 Adhesive and a group of 45 f i s h were made b l i n d and anosmic. In each group, about 25% of the f i s h were les s than 4.0 cm, to investigate the eff e c t of the impairment treatments on juveniles. A group of 10 0. maculosus which were both blind and anosmic were kept i n the laboratory to examine su r v i v a l . Data were collected for two months. In the second experiment, a t o t a l of 72 f i s h were r e c i p r o c a l l y transplanted between two groups of pools approximately 60 m apart. One group of 32 f i s h consisted of untreated controls and the other group of 40 f i s h were made bli n d and anosmic, the l a t t e r by blocking the nares with Durelon dental glue. A group of 10 f i s h which were b l i n d and anosmic were kept i n the laboratory. Data were collected f o r f i v e weeks. 204 R e s u l t s In the f i r s t experiment (Table 37) i n which anosmia was e f f e c t e d by b l o c k i n g the nares with Kodak Eastman adhesive, i t was evident t h a t the adhesive came o f f the nares a f t e r one or two days i n the f i e l d . Thus w h i l e the f i s h were c e r t a i n l y anosmic when r e l e a s e d , i t cannot be s a i d with any c e r t a i n t y how l o n g the c o n d i t i o n p e r s i s t e d a f t e r r e l e a s e . In the second experiment (Table 38) DureIon d e n t a l glue was used.. In the l a b o r a t o r y i t remained i n and around t h e nares f o r a c o n s i d e r a b l y l o n g e r p e r i o d than the Eastman adhesive. However the b l i n d and anosmic f i s h r e l e a s e d i n t o t i d e p o o l s e x h i b i t e d unusual behaviour, swimming r a p i d l y towards the s u r f a c e and back towards the bottom of the po o l "nose d i v i n g " i n t o the g r a v e l and rocks i n the po o l . In t h i s manner s e v e r a l f i s h succeeded i n knocking the c o v e r i n g s o f f the nares. I t was e v i d e n t , s i n c e the Durelon i s pink, t h a t none o f the e x t e r i o r a p p l i c a t i o n s of i t remained on the f i s h l onger than three days. Thus a g a i n , although some of the Durelon may have remained i n s i d e the nares, the p e r i o d of anosmia cannot be s t a t e d with any c e r t a i n t y . The r e s u l t s c e r t a i n l y suggest t h a t simultaneous b l i n d i n g and "anosmia" i m p a i r homing performance compared with t h a t o f un t r e a t e d c o n t r o l s and e i t h e r b l i n d or "anosmic" f i s h . In both experiments the percentage o f s u c c e s s f u l l y homing b l i n d and anosmic f i s h was s i g n i f i c a n t l y lower than the percentages f a b l e 37 R e l a t i v e importance o f b l i n d n e s s and anosmia B l i n d Anosmic B l i n d and C o n t r o l anosmic Date r e l e a s e d 16 J u l y 1977 Number r e l e a s e d 46 44 45 45 Number homed 23 18 9 19 Percent homed 50 41 20 42 Number found i n 28 27 20 26 t r a n s p l a n t area Percent found i n 61 61 44 58 t r a n s p l a n t area Days spent i n t r a n s p l a n t area a. homers 1,1,2,2, 1,1,1,1, 1,2,2,5, 2,2,2,2, 2,6,9, 1,2,5,6, 9,10 5,42 18,35 6,6,14 b. non-homers 1,1,1,1, 1,1,1,1, 1,1,2,5, 1,1,1,2, 2.2.2.5, 2,2,2,5, 9,10,11, 2,5,6,6, 5.6.6.6, 5,10,42, 22,26 ,26 , 6,13,14, 10,10, 45,45,59, 27, 59,59, 14, 14,27, 14,18, 59,59, 59 27,32,55, 32,36,42 55,59,59 Percent of homers homed to home pool 22 39 44 42 Percent of f i s h 91 seen a f t e r r e l e a s e 77 51 87 T a b l e 38 Homing performance a f t e r s i m u l t a n e o u s b l i n d i n g and anosmia Impaired C o n t r o l Date r e l e a s e d 9 August 1977 Number r e l e a s e d 40 32 Number homed Pe r c e n t homed 8 20 20 63 Number r e m a i n i n g i n t r a n s p l a n t a r e a P e r c e n t r e m a i n i n g i n t r a n s p l a n t a r e a 18 45 14 44 Days s t a y i n g i n t r a n s p l a n t a r e a a. homers b. non-homers 3,3,3*3, 9,14,17 1 ,2,2,2, 3,3,8, 18 1,3,3,3, 3,3,3,14, 8,8,11, 14,14,20 11,18,30 Pe r c e n t o f homers r e t u r n i n g t o home p o o l 38 60 Pe r c e n t o f f i s h seen a f t e r r e l e a s e 48 94 207 homing i n the other groups employed i n each experiment (p<.05). However the r e s u l t s must be t r e a t e d with c a u t i o n because o f the u n c e r t a i n t y concerning the anosmic f i s h and because the percentages of f i s h seen a f t e r r e l e a s e are s i g n i f i c a n t l y lower (p<.05) f o r the si m u l t a n e o u s l y b l i n d and anosmic groups (51% and 48%) than f o r any other groups {77% to 94%), su g g e s t i n g t h a t t h i s treatment may have some impact on s u r v i v a l . C o n s i d e r a t i o n o f the time t o home i n the d i f f e r e n t l y impaired groups i n the f i r s t experiment showed l i t t l e d i f f e r e n c e between treatments, although the percentages of homers observed i n the t r a n s p l a n t area do - c o n t r o l : 32%, b l i n d : 39%, anosmic: 61%, b l i n d and anosmic: 67%. In the second experiment, the time taken to home was i n general c o n s i d e r a b l y longer f o r b l i n d and anosmic f i s h than f o r c o n t r o l s ; 60% of the c o n t r o l s which homed did so before any b l i n d and anosmic f i s h homed. Furthermore only 20% of the s u c c e s s f u l l y homing c o n t r o l f i s h were observed i n the t r a n s p l a n t area while 88% o f the b l i n d and anosmic f i s h were. T h i s might suggest t h a t the anosmic f i s h were unable t o home u n t i l the d e n t a l glue was removed from the nares, and the sense of s m e l l was again present. The a n a l y s i s of homing performance by length i n the f i r s t experiment (Table 39) appears t o show that by the time the f i s h are 3,5 cm long some of them have a c g u i r e d s u f f i c i e n t i n f o r m a t i o n to use a l t e r n a t e senses to home; a t l e a s t they do not r e g u i r e v i s i o n . U n t i l t h a t s i z e i s reached however, any impairment appears to be s u f f i c i e n t t o prevent homing. •Table 39 R e l a t i v e homing p e r f o r m a n c e ( p e r c e n t a g e s u c c e s s f u l l y homing) f o l l o w i n g b l i n d n e s s and anosmia by l e n g t h L e n g t h c l a s s (cn) 2. 5-2.9 3.0-3.4 3. 5-3. 9 4.0-4.9 5.0-5.9 6.0-6.9 7.0-7.9 T o t i E a t e r e l e a s e d 16 J u l y 197 7 E l i n d Number r e l e a s e d 3 5 il 25 7 1 1 46 Number homed 0 0 2 13 7 1 0 23 P e r c e n t hcmed 0 0 50 52 100 100 0 50 Anosmic Number r e l e a s e d 5 2 3 21 12 1 0 44 Number homed 0 0 0 12 6 0 18 P e r c e n t hcmed 0 0 0 57 50 0 41 E l i n d and Anosmic Nuirber r e l e a s e d 4 3 3 21 1 1 3 0 45 Number hcmed 0 0 0 3 4 2 9 P e r c e n t hcmed 0 0 0 14 36 67 20 C o n t r o l Number r e l e a s e d 4 2 5 24 8 2 0 45 Number homed 1 0 2 9 6 1 19 P e r c e n t homed 25 0 10 38 75 50 42 T a b l e 39 ( c o n t i n u e d ) R e l a t i v e homing p e r f o r m a n c e ( p e r c e n t a g e r e m a i n i n g i n t r a n s p l a n t a r e a ) f o l l o w i n g b l i n d n e s s and anosmia, by l e n g t h L ength c l a s s (cm) 2.5-2.9 3.0-3.4 3.5-3.9 4.0-4.9 5 . 6-5.9 6.0-6.9 7.0-7.9 T o t a l Date r e l e a s e d 16 J u l y 197 7 B l i n d Number r e l e a s e d 3 5 4 25 7 1 1 46 Number s t a y e d 3 3 3 15 3 0 1 27 P e r c e n t s t a y e d 100 60 75 60 43 0 100 59 Anosmic Nuirber r e l e a s e d 5 2 3 21 12 1 0 44 Number s t a y e d 3 1 1 14 8 0 27 P e r c e n t s t a y e d 60 50 33 67 67 0 61 E l i n d and Anosmic Nuirber r e l e a s e d 4 3 3 21 11 3 0 45 Number s t a y e d 1 0 2 11 7 1 20 P e r c e n t s t a y e d 25 0 67 52 64 33 44 C o n t r o l Nunber r e l e a s e d 4 2 5 24 8 2 0 45 Number s t a y e d 3 1 4 15 5 1 26 P e r c e n t s t a y e d 75 50 80 63 25 50 58 O 1£> 210 Laboratory s u r v i v a l o f both groups o f b l i n d and anosmic f i s h was good up to f o u r weeks, although the f i s h were f a r l e s s a c t i v e than untreated f i s h . U n t i l about seven days a f t e r the Eastman adhesive and the d e n t a l glue had come o f f the nares, the f i s h would not respond to mussel p i e c e s . Even though they would feed d e s u l t o r i l y a f t e r t h i s time, the Durelon t r e a t e d f i s h began to d i e a f t e r f o u r weeks and the Eastman adhesive t r e a t e d f i s h a f t e r s i x weeks. 7. V i s u a l and o l f a c t o r y , t i d e p o o l c l u e s Since both v i s i o n and o l f a c t i o n appear to be i n v o l v e d i n homing, the r o l e o f v i s u a l and o l f a c t o r y c l u e s i n t i d e p o o l r e c o g n i t i o n was i n v e s t i g a t e d . To determine whether homing 0. maculosus r e c o g n i z e pools by "landmarks", two k i n d s of conspicuous a r t i f i c i a l landmarks were i n s t a l l e d i n t i d e p o o l s and then exchanged to determine whether homing O, maculosus i n d i v i d u a l s would home to the pool of capture or t o t h e pool with the f a m i l i a r landmark. To i n v e s t i g a t e the r o l e o f o l f a c t o r y c l u e s emanating from t h e t i d e p o o l a c h o i c e experiment was conducted t o determine whether 0.maculosus i n d i v i d u a l s c o u l d d i s t i n g u i s h water from the t i d e p o o l i n which they were captured from seawater pumped i n t o the Bamfield Marine S t a t i o n from a depth of 20 m. 211 Methods To i n v e s t i g a t e v i s u a l landmarks, two p a i r s o f somewhat s i m i l a r t i d e p o o l s at F i r s t Beach were s e l e c t e d . ; Because of the d i f f i c u l t y of f i n d i n g s i m i l a r t i d e p o o l s low i n the i n t e r t i d a l , the pools s e l e c t e d were high r e l a t i v e l y shallow p o o l s . Two p a i r s of conspicuous landmarks were made and one landmark was anchored with cod l i n e and cement n a i l s i n each p o o l , so t h a t each p a i r o f pools c o n t a i n e d one p a i r of landmarks. The landmarks c o n s i s t e d of f i r e p l a c e b r i c k s p a i n t e d f l o u r e s c e n t orange and i n v e r t e d d i s h pans painted green (Figure 28). A f t e r the landmarks had been i n s t a l l e d f o r nine days, p. maculosus were c o l l e c t e d and tagged. The height of the pools r e s u l t e d i n a l a r g e number of s m a l l p. maculogj|s- ( l e s s than 4.0 cm) being c o l l e c t e d . I t was a n t i c i p a t e d that i f the pool to which the f i s h homed was i n f l u e n c e d by landmarks, j u v e n i l e f i s h would be more r e a d i l y i n f l u e n c e d than a d u l t f i s h . A t o t a l o f 154 f i s h from the f o u r pools were r e l e a s e d i n t o a pool about 65 m away, 11 days a f t e r the landmarks were i n i t i a l l y i n s t a l l e d . P r i o r t o high t i d e , the landmarks from one pool p a i r were exchanged. The landmarks i n the other pool p a i r were l e f t unchanged to provide data on pool f i d e l i t y . Data were c o l l e c t e d f o r almost two months. Percentages homing to each pool were c a l c u l a t e d . To i n v e s t i g a t e o l f a c t o r y c l u e s , ten p. maculosus were 212 213 c o l l e c t e d from F i r s t Beach at v a r y i n g i n t e r v a l s over a p e r i o d of s e v e r a l months. At the time a f i s h was caught, about 4 1 of water from the capture pool was c o l l e c t e d and r e t u r n e d to the l a b . T e s t i n g of each f i s h began wit h i n s e v e r a l hours of r e t u r n i n g t o the l a b . A Y-shaped c h o i c e tank s i m i l a r t o that used by Khoo (1971) was c o n s t r u c t e d of p l e x i g l a s s and painted black to reduce the e f f e c t of e x t e r i o r d i s t u r b a n c e (Figure 29). S t a t i o n seawater was run through the i n l e t s at the ends of the c h o i c e arms. B u r e t t e s were placed so as t o d r i p t e s t ( t i d e p o o l ) or c o n t r o l ( s t a t i o n ) seawater i n t o each arm of the tank at a r a t e of 40 t o 50 ml per minute, s l i g h t l y higher than the r a t e of flow i n Khoo's (1971) experiments. The outer 12.7 cm of the non-c h o i c e arm was a h o l d i n g chamber with a s l i d i n g gate. F i s h were placed i n the holding chamber and allowed to a c c l i m a t e f o r two hours before t e s t i n g . T e s t s were run as a s e r i e s of 20 or 40 t e s t and c o n t r o l t r i a l s i n the f o l l o w i n g seguence; h a l f t e s t t r i a l s , a l l c o n t r o l t r i a l s , h a l f t e s t t r i a l s . A break of at l e a s t ten minutes was allowed between t r i a l s t o permit f l u s h i n g out o f the c h o i c e tank. C o n t r o l t r i a l s c o n s i s t e d of running s t a t i o n seawater through both b u r e t t e s . In t e s t t r i a l s home t i d e p o o l water was run through one b u r e t t e and s t a t i o n water through t h e other. The b u r e t t e through which t i d e p o o l water was run was changed throughout the t e s t t r i a l s f o r a l l f i s h . In each t r i a l the Figure 29 Y shaped choice tank IS) —\ 4s-215 appropriate water was run through the burettes and the gate raised to allow the f i s h to swim out and make a choice. For the f i r s t six f i s h tested each t r i a l was continued u n t i l the f i s h made a choice either r i g h t or l e f t . This proved to be so time consuming that f o r the remaining four f i s h each t r i a l was terminated a f t e r a period of 30 minutes and *no choice' was recorded. On completion of the testing seven of the f i s h were tagged and released about 60 m away from t h e i r home pool to determine whether they were able to home. The proportions of l e f t and ri g h t choices made i n the control t r i a l s were calculated and compared with the respective proportions of correct l e f t and r i g h t choices i n the test t r i a l s . ft correct choice i n a test t r i a l was one i n which the fi s h chose the arm containing home tidepool water. ., In the comparison of control and correct test choices for each arm of the choice tank, a 'negative 1 denoted that the proportion of control choices i n that arm was greater than the proportion of correct test choices in that arm. A 'positive* denoted that the proportion of correct test choices was greater than the number of control choices i n that arm. Even i f a f i s h being tested showed a bias towards a pa r t i c u l a r arm in the control t e s t s , a preference for home tidepool water would be shown as a greater proportion of test choices in that arm. 216 R e s u l t s T a b l e 40 c l e a r l y shows that the exchange of landmarks ( P a i r 1) had no e f f e c t on the homing behaviour of the 0* l§£2l£>sus i n d i v i d u a l s from the f i r s t p a i r of pools. Of the r e l a t i v e l y s m a l l percentages o f f i s h which homed, only two f i s h returned to the a l t e r n a t e pool. Of those f i s h which d i d home, the majority d i s p l a y e d l i t t l e f i d e l i t y t o the pool of c a p t u r e , moving between a wide range o f p o o l s , although i n f r e g u e n t l y moving t o the a l t e r n a t e pool i n t h e p a i r . The data from the " c o n t r o l ' 1 pools ( P a i r 2) support the evidence of t r a n s i e n c e of the 0. maculosus i n d i v i d u a l s from these high t i d e p o o l s . No f i s h homed t o one p o o l i n the p a i r and o n l y a few t o the other pool i n the p a i r . H h i l e most of the tagged f i s h were seen a f t e r r e l e a s e , i t was e v i d e n t t h a t they moved t o pools i n the d i r e c t i o n of the capture pools, and moved about amongst pools i n between the r e l e a s e and capture p o o l s more than the r e s i d e n t f i s h from these pools. I t i s p o s s i b l e t h a t t h i s experiment may have been more s u c c e s s f u l i f conducted i n lower pools, where pool f i d e l i t y i s a p p a r e n t l y c o n s i d e r a b l y g r e a t e r , however, the t o t a l f a i l u r e of the experiment may be due to the b r e v i t y of t h e p e r i o d f o r which the landmarks were i n s t a l l e d . The apparent l a c k of e f f e c t of the landmarks c o u l d a l s o be i n t e r p r e t e d as meaning t h a t a landmark conspicuous t o the human eye i s not so conspicuous to a T a b l e 40 Homing performance a f t e r p o o l "landmarks" exchanged P a i r 1 P a i r 2 I n i t i a l placement I n i t i a l S f i n a l placement Br i c k Pan B r i c k Pan Date r e l e a s e d 20 J u l y 1977 Number r e l e a s e d 42 37 21 54 Number homed to " b r i c k " 19 0 0 0 Percent homed to " b r i c k " 45 0 0 0 Number homed to "pan" 2 16 0 18 Percent homed to "pan" 5 43 0 33 Number s t a y i n g i n t r a n s p l a n t area 18 9 8 33 Percent s t a y i n g i n t r a n s p l a n t area 43 24 3 8 61 Number found i n d i s t a n t pools 2 0 6 1 Percent found i n d i s t a n t p o ols 5 0 2 9 2 218 f i s h i n a t i d e p o o l o r t h a t the po o l i s not s o l e l y r e c o g n i z e d by a conspicuous v i s u a l landmark. In the c h o i c e tank experiments, i f 0. maculosus i n d i v i d u a l s demonstrated a d i s t i n c t p r e f e r e n c e f o r home t i d e p o o l water over s t a t i o n water, a predominance o f plus s i g n s would be expected. T h i s i s not shown (Table 41), The d i s t r i b u t i o n o f plus and minus s i g n s provides no evidence to suggest t h a t 0» maculosus i n d i v i d u a l s d i s t i n g u i s h home pool water from water pumped i n t o the marine s t a t i o n . These r e s u l t s would appear to suggest t h a t o l f a c t o r y c l u e s emanating from home t i d e p o o l water a t low t i d e a re not a s i g n i f i c a n t f a c t o r i n g u i d i n g the f i s h back to t h e i r home t i d e p o o l . T h i s does not n e c e s s a r i l y e l i m i n a t e o l f a c t i o n as a p o s s i b l e homing mechanism, f o r two reasons. I f o l f a c t o r y c l u e s emanate from the t i d e p o o l a t high t i d e (when the f i s h are homing) mixing with other water may a l t e r t h e i r nature. , Re c o g n i t i o n of o l f a c t o r y c l u e s from t i d e p o o l water taken at low t i d e presumably need not be of great s i g n i f i c a n c e to the f i s h . , F u r t h e r , i f the substance or substances producing o l f a c t o r y c l u e s are of a v o l a t i l e nature, the time d e l a y s i n v o l v e d between c o l l e c t i n g the water and t e s t i n g the f i s h might be s u f f i c i e n t t o e l i m i n a t e any chance of the substance being d e t e c t e d . although these r e s u l t s suggest t h a t n e i t h e r conspicuous landmarks nor o l f a c t o r y c l u e s emanating from the t i d e p o o l are very important i n the homing of 0. maculosus, a 219 T a b l e 41 Choice tank t e s t s of arm preference F i s h C o n t r o l Test Sign C o n t r o l T e s t Sign T o t a l c h o i c e s c h o i c e s c h o i c e s c h o i c e s number o f percent percent percent percent t r i a l s L c o r r e c t R c o r r e c t L R 1 60 50 40 50 * 40 2 90 70 - 10 30 • 40 3 80 60 - 20 0 20 4«* 70 100 + 30 60 + 20 5'* 80 40 - 20 100 • 20 6* 90 60 - 10 80 • 20 7* 10 20 • 0 20 • 20 8« 0 20 + 0 40 + 20 9' 30 20 - 60 0 - 20 10» 10 0 - 10 0 - 20 -: percent c o n t r o l c h o i c e s > percent c o r r e c t t e s t c h o i c e s percent c o n t r o l c h o i c e s < percent c o r r e c t t e s t c h o i c e s ': tagged and r e l e a s e d *: homed 2 2 0 s m a l l amount of evidence was o b t a i n e d from the behaviour of one r e c o g n i z a b l e a d u l t 0. maculosus which had taken up r e s i d e n c e i n the enclosure i n Grappler I n l e t , s u g g e s t i n g t h a t i t i s some a t t r i b u t e (s) of the pool i t s e l f t o which the f i s h homes, r a t h e r than the p o s i t i o n of the pool. On the three o c c a s i o n s when the f i s h was moved to pools other than t h e one i n which i t was r e g u l a r l y found i n the e n c l o s u r e , i t had always returned t o the home pool by the f o l l o w i n g low t i d e . When the home pool was exchanged with another p o o l i n the e n c l o s u r e , and the f i s h d i s p l a c e d , i t returned t o the r e l o c a t e d home po o l . F u r t h e r displacement of the f i s h and pools r e s u l t e d i n the f i s h d i s a p p e a r i n g . 8 . D i s c u s s i o n A number of senses and b e h a v i o u r a l responses were examined t o determine how 0. maculosus f i n d s i t s way back t o i t s home range. No evidence was found to show that touch and/or chemosensory c l u e s detected by t h e p a i r e d f i n s are i n v o l v e d i n homing and immersion f o r seven days i n a d e t e r g e n t - l i k e substance which was designed t o destroy chemosensory c e l l s had no e f f e c t on homing a b i l i t y . B e h a v i o u r a l i n t e r a c t i o n s between r e s i d e n t and i n t r o d u c e d f i s h and "space" or d e n s i t y i n the t r a n s p l a n t pool do not appear t o be i m p l i c a t e d i n homing. Evidence t h a t homing i s a d i r e c t e d movement was 221 suggested by the low t i d e d i s t r i b u t i o n of t r a n s p l a n t e d f i s h . Comparison of observed percentages homing with c a l c u l a t e d percentages homing and the r a t i o o f p r e d i c t e d d i s t a n c e to be t r a v e l l e d with the d i r e c t d i s t a n c e , using v a r i o u s search p a t t e r n s d e s c r i b e d by G r i f f i n (1952) supports t h e concept o f d i r e c t e d movement. With simple r a d i a l s c a t t e r i n g along s t r a i g h t l i n e s , a r e c t a n g u l a r s e a r c h p a t t e r n or an expanded r e c t a n g u l a r search p a t t e r n over a d i r e c t d i s t a n c e o f 60 m, the p r e d i c t e d percentages homing a r e l e s s than 30% and there i s a two to thr e e f o l d i n c r e a s e i n the p r e d i c t e d d i s t a n c e t o be t r a v e l l e d . ft s p i r a l e x p l o r a t i o n i n v o l v i n g more than one tu r n r e g u i r e s t r a v e l l i n g about 12 times the d i r e c t d i s t a n c e . Khoo (1974) showed t h a t b l i n d or anosmic f i s h were s i g n i f i c a n t l y l e s s f a i t h f u l t o t h e i r home ranges than c o n t r o l f i s h at Port Renfrew and that the homing success of b l i n d o r anosmic f i s h was s i g n i f i c a n t l y l e s s than f o r c o n t r o l f i s h , anosmic f i s h being s i g n i f i c a n t l y l e s s s u c c e s s f u l than b l i n d f i s h . U n i l a t e r a l l y b l i n d or anosmic f i s h homed as w e l l as c o n t r o l f i s h (Khoo, 1971). These r e s u l t s suggested t o Khoo t h a t while v i s i o n appears to be important i n ma i n t a i n i n g home range, i t i s not as important as o l f a c t i o n i n homing. The r e s u l t s of t h i s study g e n e r a l l y support Khoo's c o n c l u s i o n s although the importance of o l f a c t i o n , by i t s e l f , does not appear to be as great f o r F i r s t Beach f i s h as f o r Port Renfrew f i s h . B i l a t e r a l b l i n d n e s s r e s u l t e d i n higher percentages homing than c o n t r o l f i s h , and had l i t t l e e f f e c t on 222 the percentage remaining i n t h e t r a n s p l a n t area. However, conspicuous v i s u a l landmarks do not appear t o be the pool c h a r a c t e r i s t i c s r e c o g n i z e d by the f i s h . Anosmia r e s u l t e d i n low pecentages homing (41% i n each experiment), but these were s i m i l a r t o the percentages o f c o n t r o l f i s h homing (48% and 42%). The percentages of anosmic f i s h homing i n these experiments were h i g h e r than those g e n e r a l l y observed by Khoo (0 t o 20%). The percentages of f i s h remaining i n the t r a n s p l a n t area and the percentages of homers r e t u r n i n g to the home po o l do not seem t o be a f f e c t e d by anosmia. While the p e r i o d o f anosmia remains d o u b t f u l i n the experiments using a d h e s i v e s , heat cautery, the method used by Khoo, d i d not appear t o produce very d i f f e r e n t r e s u l t s . The amount of water mixing which accompanies high t i d e suggests t h a t o l f a c t i o n may be more important i n r e c o g n i z i n g the home pool (and p o s s i b l y other pools) than i n gu i d i n g the f i s h home be means of an odour stream. Although Khoo found t h a t 0. maculosus kept i n an aguarium f o r t h r e e months showed a p r e f e r e n c e f o r aguarium over g e n e r a l source water, 0. maculosus t e s t e d i n t h i s study showed no p r e f e r e n c e f o r water from t i d e p o o l s i n which they were captured, compared with water pumped i n t o t he Bamfield Marine S t a t i o n . Although t h i s does not n e c e s s a r i l y e l i m i n a t e o l f a c t o r y c l u e s emanating from the t i d e p o o l as a means of g u i d i n g the f i s h home or at l e a s t r e c o g n i z i n g the home p o o l , f o r the reasons d i s c u s s e d e a r l i e r , i t does cast some doubt on the o l f a c t o r y hypothesis. 223 A combination o f b l i n d n e s s and anosmia was shown to be the most e f f e c t i v e method of r e d u c i n g homing success t o about 20% of r e l e a s e d f i s h at F i r s t Beach. A d d i t i o n a l treatment (removal of p a i r e d f i n s and immersion i n detergent f o r seven days) appears to reduce homing success even f u r t h e r , but the la c k of e f f e c t of these treatments i n d i v i d u a l l y suggests t h a t although l a b o r a t o r y s u r v i v a l i s good, s u r v i v a l i n the f i e l d may be r a t h e r d r a s t i c a l l y a f f e c t e d . The d i f f i c u l t i e s i n keeping the nares blocked with adhesives was mentioned e a r l i e r . However, the percentages of si m u l t a n e o u s l y b l i n d and anosmic f i s h found i n the t r a n s p l a n t areas p r i o r to homing (67% and 88% compared with 28% and 20% f o r c o n t r o l s ) suggest t h a t at l e a s t i n the l a t t e r experiment the t r e a t e d f i s h may have been unable to home u n t i l the nares were freed from o b s t r u c t i o n s . In t h i s experiment the percentage o f homers r e t u r n i n g to the home pool was very low r e l a t i v e to c o n t r o l f i s h . Although l a b o r a t o r y s u r v i v a l was s a t i s f a c t o r y f o r almost the e n t i r e d u r a t i o n o f the experiment, the r e l a t i v e l y s m a l l percentages of b l i n d and and anosmic f i s h seen a f t e r r e l e a s e (51% and 48% compared with 87% and 94% r e s p e c t i v e l y ) suggests t h a t e i t h e r s u r v i v a l i n the f i e l d was a f f e c t e d or that s t r a y i n g i s much more l i k e l y i n f i s h t r e a t e d i n t h i s way. Both v i s i o n and o l f a c t i o n appear to be e s s e n t i a l f o r the homing of f i s h l e s s than about 3.5 cm. V i s i o n appears t o become unnecessary before o l f a c t i o n but i t does not appear to be s u f f i c i e n t (without o l f a c t i o n ) t o enable the f i s h t o home u n t i l 224 they are l a r g e r . Homing performance of b l i n d and anosmic f i s h shows an i n c r e a s e i n the percentage s u c c e s s f u l l y homing with l e n g t h . Simultaneous b l i n d n e s s and anosmia seems t o r e s u l t i n s t r a y i n g (or death) i n a g r e a t e r percentage of f i s h l e s s than 3.5 cm than the other treatments. These r e s u l t s suggest t h a t both v i s i o n and o l f a c t i o n are important i n a c q u i r i n g the i n f o r m a t i o n necessary f o r homing and t h a t both are i n v o l v e d to some extent i n homing, although o l f a c t i o n appears t o be of g r e a t e r importance. I f a technique which d e f i n i t e l y p r ecludes t h e p e r c e p t i o n o f o l f a c t o r y c l u e s can be found (e. q. c u t t i n g the o l f a c t o r y nerve) conclusive^ experiments can be conducted. These r e s u l t s i n d i c a t e t h a t t h e r e are at l e a s t two mechanisms a v a i l a b l e f o r homing, the r e l a t i v e importance v a r y i n g between areas. Thus i t appears p o s s i b l e t h a t when Q. maculosus i s unable t o s m e l l , but can see, homing performance i s b e t t e r i n areas of more i r r e g u l a r topography.. T h i s might suggest that o l f a c t i o n i s more important i n t o p o g r a p h i c a l l y r e g u l a r areas. The r e l a t i v e importance and kinds of v i s u a l c l u e s used i n homing and o r i e n t a t i o n behaviour have been shown to d i f f e r i n homing and o r i e n t a t i o n behaviour i n d i f f e r e n t f i s h occupying d i f f e r e n t a r e a s , e.g. ponds, streams, r e e f s e t c . . The p o s s e s s i o n of a t o p o g r a p h i c memory (presumably a t l e a s t p a r t l y v i s u a l l y acquired) has been suggested f o r a number of l i t t o r a l f i s h : B l e n n i u s o c e l l a r i s Linnaeus (Pieron, 1914), Fundulus 225 (Hast, 1915) and perhaps the best documented, Bathygobius s o p o r a t o r (aronson, 1951, 1971). The jumping goby i s b e l i e v e d to a c g u i r e knowledge of the l o c a l topography by swimming over the area at high t i d e , a l l o w i n g i t to o r i e n t i t s jumps c o r r e c t l y a t low t i d e . The importance of s m a l l landmarks i n t h e l e a r n e d o r i e n t a t i o n of Phoxinus phoxinus (Linnaeus) was demonstrated by H a s l e r (1956). V i s i o n (and o l f a c t i o n ) appear to be important i n the homing of r e e f f i s h e s Epinephelus g u t t a t a and E. s t r i a t u s (Bardach, 1958) and C a r l s o n and Haight (1972) suggested t h a t the i n a b i l i t y o f Sebagtes f l a v i d u s to home over deep water might be due to l o s s of v i s u a l c o n t a c t with the bottom. In e s s e n t i a l l y s t i l l water, v i s i o n seems t o be more important than o l f a c t i o n . Hasler and Hisby (195 8) suggested that the green s u n f i s h , Lepomis megalotis used v i s u a l c l u e s t o home and Gunning (1959) r e p o r t e d that when Hasler made the f i s h anosmic, they homed as r e a d i l y as c o n t r o l s . Experiments on v a r i o u s s p e c i e s of f i s h i n the Kiev r e s e r v o i r (bream, Abramis-brama (Linnaeus), A. b a l l e r u s (Linnaeus) and B l j c c a bjorkna (Linnaeus); roach, R u t i l u s r u t i l u s (Linnaeus); p i k e , Esox l u s c i u s Linnaeus; and p e r c h , Perca f l u v i a t i l u s Linnaeus) showed that b l i n d n e s s , anosmia, l a t e r a l l i n e a n a e s t h e s i a , simultaneous b l i n d n e s s and anosmia and simultaneous anosmia and l a t e r a l l i n e a n a esthesia r e s u l t e d i n l i t t l e d i f f e r e n c e i n i n i t i a l azimuth of o r i e n t a t i o n and f i n a l o r i e n t a t i o n determined by t r a c k i n g f l o a t s , between t r e a t e d f i s h and c o n t r o l s (Abrosimova, 1975). 226 Simultaneous b l i n d n e s s and l a t e r a l l i n e anaesthesia r e s u l t e d i n d i f f e r e n t o r i e n t a t i o n from c o n t r o l f i s h , but c o r r e c t o r i e n t a t i o n was e s t a b l i s h e d f a s t e r when eye caps were removed than when the novocaine wore o f f (Abrosimova, 1976). Neither v i s i o n nor o l f a c t i o n , taken s i n g l y , was shown t o be e s s e n t i a l f o r the homing of c u t t h r o a t t r o u t , Salmo c ^ a r k i Richardson i n Yellowstone Lake, although b l i n d f i s h took longer to home than anosmic or c o n t r o l f i s h (McCleave and LaBar, 197 2 ) i The authors b e l i e v e d t h a t as many b l i n d t r o u t reached the home area as other f i s h but were unable t o l o c a t e the t r a p . P e r c e p t i o n of v i s u a l c l u e s other than landmarks has been demonstrated as p o s s i b l e i n a number of f i s h : white bass, B pec us chrysops (Rafinesgue) , pumpkinseeds, Lejgomj.s gibbosus (Linnaeus), b l u e g i l l s , LeBomis machrochirus Rafinesgue, (Hasler S i 1958), p a r r o t f i s h e s , Scarus guacamaja C u v i e r , !>• £2§I§§£ifi!JS Valenciennes (Winn e t a l . , 1964) and mo s q u i t o f i s h , Gambusia a f f i n u s (Baird and G i r a r d ) (Goodyear and Ferguson, 1969) ( o r i e n t a t i o n to the sun) ; salmonids (Groot, 1965) c i c h l i d s (Waterman, 1958-1959, c i t e d i n Waterman, 1972) and halfbeaks (Waterman, 1972) ( o r i e n t a t i o n t o p o l a r i z e d l i g h t ) . However, i t does not seem f e a s i b l e t h a t c e l e s t i a l bodies o r p o l a r i z e d l i g h t are important i n the homing of 0. maculosus. s i n c e they can home from any d i r e c t i o n and circumnavigate o b s t a c l e s , and s i n c e they can home on cloudy days and n i g h t s (Khoo, 1971), the freguency o f which i s high. In any case, other i n f o r m a t i o n i s r e q u i r e d f o r the f i s h to r e c o q n i z e the home 227 pool or range. The r o l e of v i s i o n t h e r e f o r e , would appear to be i n the r e c o g n i t i o n of landmarks. Given the p o s s i b l e t u r b i d i t y and t u r b u l e n c e of the i n t e r t i d a l , i t i s d i f f i c u l t t o a p p r e c i a t e how t h i s sense could be used over any d i s t a n c e . In streams, the r o l e of o l f a c t i o n i n homing seems t o be more important than v i s i o n . Gunning (1959) showed t h i s to be the case f o r homing longear s u n f i s h Lejaomis megalotis megaj-otis (Rafinesgue). That v i s i o n must play a r o l e however, was shown by the f a i l u r e of s i m u l t a n e o u s l y b l i n d and anosmic f i s h to home. The importance of o l f a c t i o n i n the homing of salmonids t o p a r t i c u l a r streams seems to be f a i r l y w e l l e s t a b l i s h e d . In the homing o f Chinook salmon, Oncorhynchus tshawytscha (Walbaum), o l f a c t i o n was shown to be more important than v i s i o n , although simultaneous b l i n d n e s s and anosmia almost completely e l i m i n a t e d homing (Groves et a l . , 1968). The r e t u r n t o a p p r o p r i a t e l y scented streams of coho salmon Oncorhynchus k i s u t c h (Salbaum) and rainbow t r o u t Salmo g a i r d n e r i Richardson. i m p r i n t e d t o an o r g a n i c chemical (morpholine or phenet hy 1 a l c o h o l ) as smolts or f i n g e r l i n g s , and e l e c t r o p h y s i o l o g i c a l s t u d i e s of o l f a c t o r y bulb responses t o morpholine scented water, by homing i m p r i n t e d and c o n t r o l f i s h , appear to confirm the importance of o l f a c t i o n (Cooper et a l . , 1976; Cooper and S c h o l z , 1976; Scholz e t a l . , 1976; Cooper and Hasler, 1976). The involvement of long term memory i n the o l f a c t o r y d i s c r i m i n a t i o n o f home and other stream waters has been demonstrated e l e c t r o p h y s i o l o g i c a l l y (Oshima et a l . , 1969). However Bodznick (1975) has suggested c a u t i o n be 228 exercised in the interpretation of electrophysiological results re l y i n g on the amplitude of olfactory bulb discriminations. The a b i l i t y of f i s h other than salmonids to discriminate between odours has been shown. Bluntnose minnows Hybgrhynchus notatus Kafinesgue were trained to discriminate between the waters of two d i f f e r e n t streams (Hasler, 1966) and between rinses of natural plants (Walker and Hasler, 1949). Previously trained b l i n d f i s h could make these discriminations but anosmic f i s h could not. Angsiilsl. vulgaris (Turton) = £132.1115. anguiiia (Linnaeus) elvers have been shown to be able to discriminate between ebb and flood t i d e water using additions of natural inland water, presumably through o l f a c t i o n . Simply changing the s a l i n i t y did not produce the same response (Creutzberg, 1959). The a b i l i t y to locate the source of an odour in a c i r c u l a r tank divided into compartments was shown by Kleerekoper (1967) to depend on an increased rate of flow i n the odour releasing compartment r e l a t i v e to the other compartments. The importance of o l f a c t i o n in the homing of 0. maculosus has been demonstrated and i t appears necessary to postulate the existence of discrete odour streams i n the turbulent i n t e r t i d a l , or the existence of discrete odours associated with p a r t i c u l a r pools. Since v i s i o n appears to be involved i n the a c g u i s i t i o n of information, a topographic memory may be established which i s associated with the perception of clues from other senses, e.g. the l a t e r a l l i n e , and o l f a c t i o n may be used to a s s i s t i n recognizing the particular pools. When 229 both v i s i o n and o l f a c t i o n are e l i m i n a t e d the f i s h may be unable, u s i n g other senses, t o determine where i t i s , i n r e l a t i o n to the home range, thus being unable to home. The f a c t t h at b l i n d f i s h can home coupled with the d i f f i c u l t y of a p p r e c i a t i n g how the o l f a c t o r y sense can be used over any d i s t a n c e i n the mixed i n t e r t i d a l , suggests the a u x i l l i a r y involvement of another sense (or senses) when only v i s i o n or o l f a c t i o n i s e l i m i n a t e d . Since t h i s study has not e l i m i n a t e d the p o s s i b i l i t y t h a t a d d i t i o n a l mechanisms are involved i n homing, some c o n s i d e r a t i o n of them must be made. The a c o u s t i c o - l a t e r a l i s system seems t o be the most l i k e l y a u x i l l i a r y mechanism ( i f there i s one) i n v o l v e d i n homing. A c o u s t i c energy i s present i n two forms; displacement and pressure. Displacement i s p a r t i c u l a r l y e v i d e n t at c l o s e range to the source and the phenomenon has been termed the " n e a r - f i e l d " e f f e c t and i s c h i e f l y detected by the a r r a y of displacement r e c e p t o r s i n the l a t e r a l l i n e . , P r e s s u r e , on the other hand, i s regarded as a " f a r - f i e l d " e f f e c t and the i n n e r ear-swim bladder complex i s b e l i e v e d to be p r i m a r i l y s e n s i t i v e t o compression waves (Tavolga, 1971a) although the n e a r - f i e l d e f f e c t can s t i m u l a t e the a c o u s t i c a l and v e s t i b u l a r apparatus ( H a r r i s and van B e r g e i j k , 1962). The l a t e r a l l i n e can d e t e c t c u r r e n t s and other near-f i e l d movements of water produced when a f i s h approaches an o b s t a c l e (or v i c e versa) ( D i j k g r a a f , 1962) and p o s s i b l y other 230 hydrographic phenomena produced by t h e locomotion of the f i s h i n the v i c i n i t y of o b s t a c l e s (Tavolga, 1971b). Lowenstein (1957) suggested t h a t the l a t e r a l l i n e c o u l d give a " f a i r l y a c c u r a t e t h r e e - d i m e n s i o n a l r e p r e s e n t a t i o n o f the immediate environment". In a d d i t i o n , the l a t e r a l l i n e appears t o be ab l e t o d e t e c t low frequency v i b r a t i o n s w i t h i n the n e a r - f i e l d ( H a r r i s and van B e r g e i j k , 1962) d e f i n e d as being w i t h i n one s i x t h of a wavelength (van B e r g e i j k , 1962). Low frequency sounds of 50 t o 100 Hz pr o v i d e an e f f e c t i v e n e a r - f i e l d range of about 50 to 3 m, r e s p e c t i v e l y (Tavolga, 1971a). Because the l a t e r a l l i n e i s an a r r a y of displacment r e c e p t o r s the f i s h s h o u l d be ab l e t o get range and bearing i n f o r m a t i o n q u i t e r e a d i l y (Tavolqa, 1971b). L o c a l i z a t i o n of f a r f i e l d sounds by f i s h e s appears t o be more open t o d i s p u t e (Popper and Fay, 1973). , While i t seems h i q h l y improbable t h a t hominq 0* maculosus are responding to f a r f i e l d sound sou r c e s , near f i e l d e f f e c t s may be of qrea t e r importance. Whether i n f o r m a t i o n r e c e i v e d by the l a t e r a l l i n e can do more than prevent the f i s h swimming i n t o o b s t a c l e s and beinq swept out t o sea, that i s , mai n t a i n i n g the general movement of the animal, i s d i f f i c u l t t o assess. I t i s p o s s i b l e t h a t t i d e p o o l s have s p e c i f i c c h a r a c t e r i s t i c water movements which can be detected and d i s c r i m i n a t e d by 0. maculosus. Whether areas between t i d e p o o l s have s p e c i f i c r e c o g n i z a b l e water movement c h a r a c t e r i s t i c s , given weather and sea s t a t e changes seems more d o u b t f u l , although i f at l e a s t general d i r e c t i o n ( p e r p e n d i c u l a r to t i d a l flow) and 2 3 1 g e n e r a l area can be p e r c e i v e d , the use of v i s i o n or o l f a c t i o n t o rec o g n i z e s p e c i f i c pools may be i n v o l v e d . Although t o my knowledge, t h i s has not been i n v e s t i g a t e d , i t has been suggested that t i d e p o o l s may have "sounds" which are pool s p e c i f i c (Norman Wilimovsky, personal communication) or s p e c i f i c harmonics (Bruce Leaman, p e r s o n a l communication). I f t h i s i s the case and i f t h i s i n f o r m a t i o n can be detected and used by 0. maculosus, a f u r t h e r means of r e c o g n i t i o n o f s p e c i f i c p o o ls i s a v a i l a b l e to the f i s h . The p o s s i b i l i t y t h a t O. maculosus may use some kind of crude e c h o - l o c a t i o n t o f i n d i t s way home has not been i n v e s t i g a t e d , but i t seems u n l i k e l y . I t i s not known whether t h i s s p e c i e s i s cap a b l e of sound p r o d u c t i o n although another c o t t i d , gioxocephalus pctodecimspinosus ( B i t e h i l l ) . i s known to produce sounds (Barber and Mowbray, 1956) w However, Tavolga (1971b) found no evidence to suggest that t h e sea c a t f i s h 5Si§ichthys [_=AriusJ f e l i s (Linnaeus) was using i n f o r m a t i o n from r e f l e c t i o n s and r e v e r b e r a t i o n s o f emitted sound t o o r i e n t i t s e l f . However, the ambient l e v e l of shallow water no i s e (wenz, 1962) and the amount of water movement and degree of turbul e n c e i n the i n t e r t i d a l may reduce the e f f e c t i v e n e s s o f any c l u e s p e r c e i v e d by the a c o u s t i c o - l a t e r a l i s system. I n v e s t i g a t i o n s of the r o l e of the l a t e r a l l i n e are d i f f i c u l t to conduct. A major problem seems to be t o f i n d a way of e l i m i n a t i n g the p e r c e p t i v e n e s s of the l a t e r a l l i n e . Heat c a u t e r y of the l a t e r a l l i n e pores and c u t t i n g nerves are 232 d i f f i c u l t on such small f i s h , and t o date, no adhesive has been found which w i l l adhere to the s k i n o f 0. maculosus f o r any perio d of time. The e f f e c t s of a n a e s t h e t i c s , such as novocaine, wear o f f too soon (Abrosimova, 1975, 1976). Even i f a s a t i s f a c t o r y method c o u l d be found to e l i m i n a t e the sensory p e r c e p t i v e n e s s of the l a t e r a l l i n e , and i f t h i s r e s u l t e d i n poor homing performance, i t might be d i f f i c u l t t o conclude t h a t the l a t e r a l l i n e was i n v o l v e d i n homing s i n c e the p e r c e p t i o n of water movements must be r e l a t i v e l y important to a f i s h l i v i n g i n the i n t e r t i d a l zone. E l i m i n a t i n g the a b i l i t y t o p e r c e i v e these movements might r e s u l t i n the f i s h being unable to maintain i t s e l f a t a l l i n such an environment. Since i n t e r t i d a l f i s h l i v e i n an area where pressure changes can be c o n s i d e r a b l e and depth d e t e c t i o n may be of some importance, the p o s s i b i l i t y t h a t these f a c t o r s are i n v o l v e d i n the homing of 0. maculosus cannot be excluded. In a b r i e f examination of response to pressure, s i x f i s h {from 1,2 t o 5.0 cm) from F i r s t Beach were placed i n a p l e x i g l a s s tank i n which the pressure c o u l d be adjusted, by manipulating by-pass v a l v e s connected t o a mercury column and the pressure tank. A f t e r a l l o w i n g the f i s h to a c c l i m a t e f o r s e v e r a l minutes, the pressure was s l o w l y i n c r e a s e d from sea l e v e l t o 1.8 atmospheres. The pressure was then r a p i d l y r a i s e d and lowered p r o v i d i n g pressure f l u c t u a t i o n s of 4 m {simulating l a r g e waves). Both t e s t s were performed under l i g h t and dark c o n d i t i o n s . I n none of the t e s t s was there any o v e r t r e a c t i o n by t h e f i s h t o pressure changes. 233 Tbe majority of f i s h remained in their i n i t i a l positions i n the tank, and although a few f i s h occasionally moved, the movement did not immediately follow pressure changes. 0. maculosus i n the laboratory have been shown to display a t i d a l rhythm of locomotor a c t i v i t y the peak and midpoint of which coincide with high t i d e (Green, 1971c). He suggested that the possible synchronizer of the a c t i v i t y rhythm was hydrostatic pressure, since temperature, turbulence and s a l i n i t y are too dependent on sea and weather conditions to be r e l i a b l e synchronizers. Gibson (1971) found that experimental pressure cycles were capable of entraining a t i d a l a c t i v i t y rhythm i n arhythmic Blennius pholis i n d i v i d u a l s as well as a l t e r i n g the phase of an existing rhythm. Thus while there i s some circumstantial evidence, from Green's work, to suggest that 0. maculosus perceives pressure changes, the nature of the mechanism i s not clear. While detection of pressure changes i s possible i n f i s h with swim bladders, p. maculosus l i k e a l l c o t t i d s , does not possess a swim bladder. However at least two l a r v a l teleosts lacking swim bladders have been shown to respond to pressure changes, Plf^u/r^nectes platessa Linnaeus and Cen tronotus gun n e l l us (Linnaeus), although they do not appear to be as sensitive as larvae possessing swim bladders, for example. Blennius phpjLis (Qasim et a l . , 1966). Pressure responses i n invertebrates lacking g a s - f i l l e d organs are well known (Knight-Jones and Morgan, 1966). Green (1971c) points out that Morris and 234 Kittleman (1967) r e p o r t e d two s p e c i e s of f i s h which have p i e z o e l e c t r i c o t o l i t h s 1 which they suggest may be a mechanism of pressure r e c e p t i o n . F u r t h e r , Shamos and Lavine (1967) suggest that p i e z o e l e c t r i c i t y may be a u n i v e r s a l property of a l l l i v i n g t i s s u e . Although the r o l e of pressure and depth d e t e c t i o n i n homing cannot be eval u a t e d from t h i s study, other c l u e s would be re g u i r e d t o home s i n c e no account i s taken o f d i r e c t i o n and s i n c e pools at the same v e r t i c a l height w i l l be a t the same depth a t high t i d e . , The p o s s i b i l i t y t h a t i n e r t i a l n a v i g a t i o n might be i m p l i c a t e d i n the homing of 0. maculosus seems u n l i k e l y . According t o t h i s h y p o t h e s i s , the animal keeps track of a l l outward movements ( d i r e c t l y r e c o r d i n g a c c e l e r a t i o n , i n t e g r a t i n g a c c e l e r a t i o n with r e s p e c t to time to o b t a i n v e l o c i t y , and i n t e g r a t i n g again with r e s p e c t t o time to o b t a i n d i s t a n c e ) i n order to e i t h e r r e t r a c e p r e c i s e l y the outward journey back home or t o c a l c u l a t e the course back home (Barlow, 1963; Keeton, 1974) . The former p o s s i b i l i t y ( p r e c i s e l y r e t r a c i n g the outward journey) can e a s i l y be r u l e d out f o r 0..maculosus. Animals c o l l e c t e d a t F i r s t Beach (and at the m a j o r i t y of other * 0 t o l i t h s with a mechanical s t r e s s i s generated. c r y s t a l l i n e arrangement (pressure) i s a p p l i e d , an such t h a t when a e l e c t r o m o t i v e f o r c e 235 s i t e s ) were t r a n s p o r t e d to and from the l a b o r a t o r y by f o o t and by boat, t a k i n g e i t h e r of two p o s s i b l e r o u t e s . The f i s h were kept a t l e a s t o v e r n i g h t i n the l a b o r a t o r y and were moved around f o r t a g g i n g and other purposes. The second a l t e r n a t i v e ( c a l c u l a t i n g the course back home) r e g u i r e s t h a t the f i s h "know" or c a l c u l a t e the geo g r a p h i c a l c o o r d i n a t e s o f the home and r e l e a s e s i t e s and "compute" a path, not n e c e s s a r i l y d i r e c t , home. The m a j o r i t y o f i n v e s t i g a t i o n s o f t h i s p o s s i b i l i t y have been conducted with b i r d s and although the a v a i l a b l e evidence i s l a r g e l y n e g a t i v e , the p o s s i b i l i t y cannot be e l i m i n a t e d (Schmidt-Koenig, 1965; Keeton, 1974). However b i r d s c a r r i e d t o the r e l e a s e s i t e s on t u r n t a b l e s , i n l i g h t p r o o f drums, under deep an a e s t h e s i a or with s u r g i c a l l e s i o n s of the v e s t i b u l a r apparatus (the presumed p r i n c i p a l d e t e c t o r s of a c c e l e r a t i o n ) showed no d i f f e r e n c e i n i n i t a l bearings or homing suc c e s s s from c o n t r o l s (Keeton, 1974). Moreover, the t h r e s h o l d a c c e l e r a t i o n t o which v e r t e b r a t e s respond (,5°/sec and 6 cm/sec 2) i s t h r e e t o fou r o r d e r s o f magnitude gre a t e r than that which would be t o l e r a t e d i n a p r e c i s i o n system (Harden Jones, 1968). The p o s s i b i l i t y t h a t f i s h may make use of such a system has not been examined. However, Kleerekoper e t a l . (1969) found t h a t i n the absence o f d i r e c t i o n a l cues, C a r a s s i u s a u r a t us (Linnaeus) maintains a ne a r l y constant r e l a t i o n s h i p between r i g h t and l e f t t u r n s (that i s , cumulative l e f t and r i g h t t u r n s are nea r l y symmetric) over thousands of t u r n s of v a r y i n g 236 magnitude, d i r e c t i o n and seguence. T h i s suggests t h a t once a d i r e c t i o n i s e s t a b l i s h e d continuous compensation of angle of t u r n occurs and the d i r e c t i o n can be maintained f o r some p e r i o d (11 hours). The authors suggest t h a t t h i s a b i l i t y may be important i n long range o r i e n t a t i o n i f the i n i t i a l d i r e c t i o n was e s t a b l i s h e d by other c l u e s . However i n the presence o f t i d e s and c u r r e n t s the p o s i t i o n of the f i s h may be a l t e r e d at a r a t e below the p e r c e p t i o n t h r e s h o l d of angular a c c e l e r a t i o n and the f i s h would soon be swimming on a d i f f e r e n t course., Other c l u e s would be r e g u i r e d t o maintain p o s i t i o n (Tesch, 1975). Since the movement of 0. maculosus appears to be composed of s h o r t hops r a t h e r than long swims, and s i n c e t i d a l flow and c u r r e n t s would be present at times of homing, i n e r t i a l n a v i g a t i o n without the r a t h e r e x t e n s i v e use of other d i r e c t i o n a l c l u e s seems u n l i k e l y . The p o s s i b i l i t y t h a t 0. maculosus uses an e l e c t r i c sensory mechanism i n o r i e n t a t i o n i s u n l i k e l y , s i n c e e l e c t r i c r e c e p t o r s have yet t o be i d e n t i f i e d i n the majority of t e l e o s t s . For the same reason and the s h o r t d i s t a n c e s i n v o l v e d , as w e l l as the absence of any evidence i n favour of the h y p o t h e s i s (McCleave et a l . , 1971), the p o s s i b i l i t y t h a t i n f o r m a t i o n d e r i v e d from the e a r t h ' s magnetic f i e l d i s used i n o r i e n t a t i o n fey Q. maculosus i s u n l i k e l y . In e i t h e r case, other i n f o r m a t i o n i s r e g u i r e d t o r e c o g n i z e the home pool. 237 V I I I . GENERAL DISCUSSION 1* V a r i a b i l i t y , i n homing behaviour T h i s study has shown t h a t homing behaviour o f 0. maculosus d i f f e r s between areas and that t h i s v a r i a b i l i t y can be r e l a t e d t o tu r b u l e n c e and the roughness o f the topography. With decreasing t u r b u l e n c e and r e g u l a r i t y of the t e r r a i n , f i d e l i t y i s shown to an i n c r e a s i n g l y l a r g e area., Homing success i n c r e a s e s and the percentage of f i s h remaining i n the t r a n s p l a n t area decreases with decreasing t u r b u l e n c e and t o p o g r a p h i c a l i r r e g u l a r i t y i n t i d e p o o l a r e a s , but i n i n l e t s , very few f i s h home or remain i n the t r a n s p l a n t area. The f i s h which do home i n t u r b u l e n t rough areas show the highest percentages r e t u r n i n g to the home p o o l , compared with other t i d e p o o l areas. I t does not seem unreasonable t o e x t r a p o l a t e from t h i s f i n d i n g t o suggest t h a t a t l e a s t some of the v a r i a b i l i t y i n homing behaviour observed w i t h i n any one area i s p a r t l y a f u n c t i o n of the t u r b u l e n c e of p a r t i c u l a r pools and the nature of the topography surrounding the pools. In a d d i t i o n to the v a r i a b i l i t y which appears t o be r e l a t e d to turbulence and topography, s i z e or age r e l a t e d v a r i a b i l i t y i n homing appears t o e x i s t , so t h a t homing success i n c r e a s e s with age up to about 2 years and then d e c l i n e s . The percentage o f f i s h remaining i n the t r a n s p l a n t area decreases with age except f o r the o l d e s t f i s h . 238 The v a r i a b i l i t y i n homing behaviour may be a s s o c i a t e d with the s i g n i f i c a n c e of such behaviour. Two major reasons have been put forward f o r the f u n c t i o n of homing i n i n t e r t i d a l f i s h , W i lliams (1957) suggested that homing s e r v e s t o prevent the f i s h from being stranded a t low t i d e i n unfavourable s i t u a t i o n s such as on dry l a n d or i n pools t h a t disappear through subsurface drainage. Green (1971b) and Khoo (1971) suggested t h a t i t may serve as a s t a b i l i z i n g mechanism f o r p o p u l a t i o n d i s t r i b u t i o n and balanced u t i l i z a t i o n of r e s o u r c e s i n the i n t e r t i d a l . Space or the a v a i l a b i l i t y of t i d e p o o l s appears t o be the main resource i n v o l v e d i n the d i s t r i b u t i o n of p. jmaculosus. I f d i s p e r s a l and establishment of home occur e a r l y i n t h e l i f e of the f i s h and i f s t r i c t f i d e l i t y to the adopted home i s maintained throughout a d u l t l i f e , these f a c t o r s added to a homing mechanism would ensure an balanced e x p l o i t a t i o n o f the environment. C o n v e r s e l y , an i n f l e x i b l e homing mechanism would be disadvantageous to the s p e c i e s , s i n c e t u r b u l e n t c o n d i t i o n s may r e s u l t i n complete a n n i h i l a t i o n of the p o p u l a t i o n . However, the 'non-homers* which may provide the a d u l t r e c r u i t s i n t i d e p o o l s may serve a d i s p e r s a l and r e p o p u l a t i o n f u n c t i o n . Both suggested reasons have some v a l i d i t y . However, s e l e c t i o n a g a i n s t the k i n d o f mistake suggested by W i l l i a m s would seem t o be severe. Knowledge of those c h a r a c t e r i s t i c s o f a pool which make i t an ac c e p t a b l e p l a c e a t low t i d e , would seem to be a l l t h a t i s r e g u i r e d , and homing to a p a r t i c u l a r pool f o r 239 t h i s reason would seem t o s u b j e c t the f i s h t o unnecessary r i s k . In i n l e t areas, a r e s t r i c t e d home range and i n f l e x i b l e homing behaviour c o n c e i v a b l y could r e s u l t i n s t r a n d i n g , unless the home range encompassed a v e r t i c a l t r a n s e c t which allowed the f i s h t o move seawards with the f a l l i n g t i d e . S i t h regard to the second reason, i t appears that pool f i d e l i t y and homing behaviour i s very c l o s e l y a s s o c i a t e d with the degree of r i s k i n v o l v e d i n movement around a p a r t i c u l a r area. In rough areas, where movement between pools a t high t i d e may r e s u l t i n p o p u l a t i o n r e d u c t i o n , such movement i s not shown, and displacement to other pools appears to r e s u l t i n adoption of the new pool as the home area. Only where the danger of being l o s t from the p o p u l a t i o n by movement between pools i s reduced, i s there an i n c r e a s i n g amount of movement and homing behaviour. Thus i n each a r e a , the k i n d o f homing behaviour shown can be r e l a t e d to the maintenance o f the l o c a l p o p u l a t i o n , and because i t r e s u l t s i n a balanced d i s t r i b u t i o n of f i s h throughout the i n t e r t i d a l , a l l o w s the even u t i l i z a t i o n of r e s o u r c e s . although the g u e s t i o n o f 'non-homing' f i s h i n t i d e p o o l areas was not d i r e c t l y addressed, i n f o r m a t i o n from t h i s study provides a number of suggestions concerning t h e i r d e r i v a t i o n and f u n c t i o n . , There appear to be s e v e r a l c a t e g o r i e s of non-hcming f i s h : those i n t u r b u l e n t , rough areas which adopt the new pool when d i s p l a c e d , those from s h e l t e r e d ( f r e g u e n t l y high) t i d e p o o l s which appear t o show l i t t l e area f i d e l i t y or homing behaviour but move e x t e n s i v e l y between pools, those f i s h which are never 210 seen again a f t e r displacement, and j u v e n i l e f i s h which move r e l a t i v e l y widely around the i n t e r t i d a l before adopting a home range. Since there appears to be a "space" f a c t o r of some s o r t i n v o l v e d i n the det e r m i n a t i o n of pool numbers of 0. maculosus (John Green, p e r s o n a l communication; p e r s o n a l observation) the r e l a t i v e l y e x t e n s i v e movements of j u v e n i l e f i s h p r i o r t o the adoption of a home range may permit the " b a l a n c i n g " of pool p o p u l a t i o n numbers over r e l a t i v e l y wide areas. Those f i s h which adopt the t r a n s p l a n t pool as the new home pool provide a d i s p e r s a l and r e p o p u l a t i o n mechanism i n t u r b u l e n t rough areas, and those from s h e l t e r e d pools which show e x t e n s i v e movement presumably serve a s i m i l a r f u n c t i o n i n l e s s rough areas. However, the l i m i t e d data from t h i s study suggest t h a t t h i s l a t t e r category of f i s h c o ntinue t o move around widely even when they encounter more exposed pools. I f these f i s h are a c c i d e n t l y d i s p l a c e d o r move to a lower pool and are caught and used i n a homing experiment, they may be the f i s h which do not show homing behaviour, p o s s i b l y moving elsewhere on the beach or being s u b j e c t t o m o r t a l i t y by moving out of a t i d e p o o l d u r i n g t u r b u l e n t c o n d i t i o n s . The f a t e o f f i s h which are never seen again i s unknown; m o r t a l i t y , d i s p e r s a l out of the study area or pred a t i o n appear to be the a l t e r n a t i v e s . In i n l e t s , l i t t l e area f i d e l i t y and homing behaviour are shown. The r e l a t i v e absence o f t u r b u l e n c e and the t o p o g r a p h i c a l r e g u l a r i t y of such areas a l l o w s r e l a t i v e l y 241 u n r e s t r i c t e d l a t e r a l movement and a c o n s i d e r a b l e amount of v e r t i c a l movement. I t i s suggested t h a t these f a c t o r s and the seasonal i n s t a b i l i t y o f i n l e t p o p u l a t i o n s ( b e l i e v e d t o be l a r g e l y a r e s u l t of t h e s e a s o n a l turbulence and i n s t a b i l i t y o f food and s h e l t e r resources) c o n t r i b u t e to the r e l a t i v e absence of home range f i d e l i t y and homing behaviour i n such a r e a s . In a d d i t i o n to the p o s s i b i l i t y o f being stranded a t low t i d e , the f a c t t h at movement i s both p o s s i b l e and and s u b j e c t to l i t t l e r i s k of being swept away f o r a l a r g e part of the year, suggests that the adoption of a s m a l l home range and homing behaviour s e r v e l i t t l e purpose. When food and s h e l t e r r e s o u r c e s disappear at the most t u r b u l e n t times o f year, the maintenance of a home range would s u b j e c t the f i s h t o unnecessary r i s k . T h i s may be the reason f o r the winter d i s p e r s a l of many i n l e t f i s h (presumably to deeper water). Another f a c t o r which may c o n t r i b u t e t o the absence of homing behaviour i n i n l e t s i s that of p r e d a t i o n , which i s b e l i e v e d to be much more important i n i n l e t areas than t i d e p o o l areas. Herons, g u l l s , k i n g f i s h e r s and other b i r d s have f r e q u e n t l y been observed feeding i n such areas and presumably at l e a s t some of the prey i s 0. maculosus. P o s s i b l e f i s h p r e d a t o r s , A r t e d i u s f e n e s t r a l i s and L e p t o c q t t u s armatus, have been caught (sometimes i n g r e a t e r numbers than 0. maculosus) i n a l l the s h e l t e r e d areas s t u d i e d . The adoption of a s m a l l home range and i n f l e x i b l e homing behaviour might w e l l disadvantageous f o r the avoidance of predators. Thus the k i n d s of movement shown by 0. maculosus may 242 be c l o s e l y r e l a t e d to the demands f o r s u r v i v a l imposed by a p a r t i c u l a r area, and i n t h i s way determine a balanced p o p u l a t i o n d i s t r i b u t i o n and resource u t i l i z a t i o n . g.Sensory mechanisms i n v o l v e d i n homing behaviour The mechanism(s) used by 0. maculosus t o home are s t i l l u n c l e a r , Movement from the r e l e a s e t o the home pool appears t o be d i r e c t e d , r a t h e r than i n v o l v i n g some k i n d o f expanded search process, and there i s a suggestion that a t t r i b u t e s of the pool are re c o g n i z e d by the f i s h , r a t h e r than the p o s i t i o n of the pool. O l f a c t i o n and v i s i o n are known t o be in v o l v e d i n homing behaviour, p a r t i c u l a r l y i n i t s a c g u i s i t i o n . However, i n a d u l t s n e i t h e r appears t o be e s s e n t i a l f o r s u c c e s s f u l r e t u r n to the home range. The t u r b u l e n c e of the i n t e r t i d a l suggests t h a t o l f a c t i o n (and p o s s i b l y a l s o v i s i o n ) cannot be used over any d i s t a n c e . , Thus i t seems that t h a t the use of o l f a c t i o n may be r e s t r i c t e d t o r e c o g n i t i o n o f the home pool, and p o s s i b l y other pools a l s o . Presumably v i s i o n i s concerned with the r e c o g n i t i o n of landmarks of some s o r t , although whether t h i s i s c o n f i n e d t o home range r e c o g n i t i o n or i n v o l v e s wider areas i s u n c l e a r . Although t h i s study f a i l e d t o show t h a t e i t h e r v i s u a l home pool landmarks, or o l f a c t o r y c l u e s from the home pool were recognized by the f i s h , nether can be e l i m i n a t e d as p o s s i b l e , f o r the 243 reasons d i s c u s s e d e a r l i e r . A "memory" of the odours and landmarks of p a r t i c u l a r s p o ols and t h e i r r e l a t i v e p o s i t i o n s i n the i n t e r t i d a l may be e s t a b l i s h e d d u r i n g the period of e x t e n s i v e j u v e n i l e movement. S p e c i f i c water movement c h a r a c t e r i s t i c s of pools and areas between pools may a l s o be l e a r n e d . In a d d i t i o n , d e t e c t i o n of when the t r a n s p l a n t p o o l , as opposed to the home po o l , i s f l o o d e d may p r o v i d e an i n d i c a t i o n of the r e l a t i v e height of the t r a n s p l a n t pool i n the i n t e r t i d a l , and the f i s h , u sing d i r e c t i o n a l i n f o r m a t i o n from t i d a l flow c u r r e n t s , may be able t o swim from " p o o l " t o " p o o l " to r e t u r n to the home p o o l . Although no evidence has been found i m p l i c a t i n g other senses, the p o s s i b i l i t y cannot be r u l e d out. The work on homing pigeons has demonstrated t h a t a number of mechanisms are a v a i l a b l e f o r homing, and most importantly^ t h a t d i f f e r e n t mechanisms may be used under d i f f e r e n t c o n d i t i o n s (Keeton, 1974). F u r t h e r , t h e r e may be d i f f e r e n c e s between i n d i v i d u a l animals a t any one time, r e g a r d l e s s o f changes over time o r i n c o n d i t i o n s , i n the mechanisms used i n homing. The v a r i a b i l i t y i n homing behaviour between areas due to t u r b u l e n c e and topography, suggests t h a t the r e l a t i v e importance of d i f f e r e n t senses may be very d i f f e r e n t between areas. C e r t a i n l y , the r e s u l t s of Khoo's (1971) work and t h i s study suggest t h a t o l f a c t i o n i s more important to homing at Port Renfrew than a t F i r s t Beach. Emlen and Keeton (Adler, 1971; Keeton, 1974) have po i n t e d out that cues which may be e s s e n t i a l i n the o n t o g e n e t i c 2HH development of o r i e n t a t i o n and homing behaviour may not be e s s e n t i a l to a d u l t s , and even i f t h e same set of cues i s being used, the r e l a t i v e importance of the cues may d i f f e r f o r j u v e n i l e s and a d u l t s . T h i s study has shown t h a t both v i s i o n and o l f a c t i o n are e s s e n t i a l t o the homing o f j u v e n i l e 0. l a c u l s s u s but v i s i o n and subseguently o l f a c t i o n a p p a r e n t l y become unnecessary, a t l e a s t at F i r s t Beach. T h i s does suggest t h a t these senses may be e s s e n t i a l t o " l e a r n i n g " the a r e a , but once other senses have a c g u i r e d s u f f i c i e n t i n f o r m a t i o n , they can be used g u i t e s u c c e s s f u l l y i n the absence of e i t h e r v i s i o n or o l f a c t i o n . A s s o c i a t e d with t h i s are the d i f f e r e n c e s i n hcming behaviour between areas and the app a r e n t l y d i f f e r e n t s i z e s (ages) a t which f i s h begin t o show homing behaviour i n d i f f e r e n t areas. The r e l a t i v e importance of d i f f e r e n t senses may be very d i f f e r e n t i n t h e o n t o g e n e t i c development of homing behaviour i n areas of d i f f e r i n g t u r b u l e n c e . 2H5 IX. SOMH&BY V a r i a b i l i t y i n homing behaviour i n d i f f e r e n t areas The m a j o r i t y o f 0. maculosus at F i r s t Beach showed evidence of home range f i d e l i t y , with egual p r o p o r t i o n s of f i s h showing f i d e l i t y to one p a r t i c u l a r pool as to a small group o f pools. Of the l a t t e r group, the majority showed g r e a t e r f i d e l i t y t o one of the pools i n the group than the other p o o l s . The m a j o r i t y of 0. maculosus d i s p l a c e d at F i r s t Beach showed evidence of homing behaviour, although v a r i a b i l i t y i n the percentages homing was observed. The m a j o r i t y of homing 0. maculosus returned t o the i n i t i a l pool of capture. V a r i a b l e but sometimes c o n s i d e r a b l e percentages of t r a n s p l a n t e d 0. maculosus remained i n the t r a n s p l a n t area, some f o r ex t e n s i v e p e r i o d s of time. In Grappler I n l e t , p. maculosus d i s p l a y e d l i t t l e evidence of r e s t r i c t e d home range f i d e l i t y or homing behaviour. V a r i a b l e but low percentages o f f i s h remained i n the t r a n s p l a n t area. Homing a c r o s s the deep water of the i n l e t was found to be impos s i b l e . D i f f e r e n c e s i n homing behaviour between 0. maculosus at F i r s t Beach, Grappler I n l e t and Port Renfrew were i n i t i a l l y b e l i e v e d to be r e l a t e d to exposure, as determined by l o c a t i o n and o b s e r v a t i o n . F u r t h e r examination of homing behaviour a t d i f f e r e n t areas showed t h a t d i f f e r e n c e s i n homing behaviour 246 could be related to wave action (turbulence) and the roughness of the terr a i n . With decreasing turbulence and increasing r e g u l a r i t y of the t e r r a i n , f i d e l i t y i s shown to an increasing number of pools or a wider area. In tidepool areas, increasing percentages of f i s h show homing behaviour. The f i s h which do home i n turbulent rough areas show the highest percentages of homing f i s h returning to the home pool. In i n l e t s , l i t t l e homing behaviour i s expressed. With decreasing turbulence and increasing r e g u l a r i t y of the t e r r a i n , decreasing numbers of f i s h remain i n the transplant area. These findings can be related to the reduced high tide a c t i v i t y of p. maculosus i n turbulent areas shown by Green (1971b,c). Age, length and year-class differences in homing behaviour There i s an increase in the percentage of 0. maculosus successfully homing from age 1 to age 2 f i s h . Age 3 f i s h show a decline i n the percentage successfully homing. A l l ages of f i s h show equal percentages of homing f i s h returning to the home pool. There i s a decline in the percentage remaining in the transplant area with age. There do not appear to be any year class differences in homing behaviour. Examination of the age related differences i n hcming behaviour by smaller s i z e classes shows an increase i n the percentage of f i s h successfully homing with length up to about 5 cm. Between 5 and 7 cm, homing i s best expressed and there seems to be some decline i n the percentage successfully homing 247 with the l a r g e s t s i z e c l a s s e s o f f i s h . A l l s i z e c l a s s e s appear to show egual percentages of homing f i s h r e t u r n i n g to the home po o l . There i s a d e c l i n e i n the percentage remaining i n the t r a n s p l a n t area with l e n g t h , except f o r the l a r g e s t s i z e c l a s s e s . J u v e n i l e f i s h {about 2.3 to 2.7 cm) which have j u s t moved down i n t o lower t i d e p o o l s , show e x t e n s i v e movement between pools and i t i s suggested t h a t at t h i s time they begin t o " l e a r n " and "memorize" the area. By t h e time they are about 3 cm long, the f i s h are beginning t o show some evidence of home range f i d e l i t y and homing behaviour. Sensory mechanisms i n v o l v e d i n homing behaviour There i s no evidence t h a t touch or t a s t e r e c e p t o r s i n the paired f i n s and p o s s i b l y t a s t e r e c e p t o r s l o c a t e d elsewhere are i n v o l v e d i n homing. There i s no evidence that d e n s i t y , "space" or b e h a v i o u r a l i n t e r a c t i o n s i n the t r a n s p l a n t pool have any e f f e c t on homing performance. L i m i t e d evidence was found t o suggest t h a t homing i s a d i r e c t e d movement from the r e l e a s e pool to the home pool. Both v i s i o n and o l f a c t i o n are i n v o l v e d i n homing, a combination of b l i n d n e s s and anosmia being the most e f f e c t i v e i n reducing homing success to low l e v e l s . I t i s suggested t h a t the f i s h are unable to home u n t i l one of these senses i s a v a i l a b l e . Both senses are e s s e n t i a l to the s u c c e s s f u l homing of j u v e n i l e f i s h but v i s i o n seems to become unnecessary before o l f a c t i o n . Although i t appears t h a t the homing f i s h r e c o g n i z e some 248 a t t r i b u t e s of the home p o o l , r a t h e r than the p o s i t i o n o f the p o o l , n e i t h e r conspicuous v i s u a l landmarks i n the pools nor o l f a c t o r y c l u e s emanating from home pool water were shown to be recognized by 0. maculosus. I t i s suggested t h a t the r e l a t i v e importance of sensory mechanisms may a l t e r i n both the ontogeny of homing behaviour and between areas. M o r p h o l o g i c a l d i f f e r e n c e s between f i s h i n d i f f e r e n t areas There are no c o n s i s t e n t d i f f e r e n c e s i n m e r i s t i c o r morphometric c h a r a c t e r s between 0* maculosus i n the areas s t u d i e d , which can be r e l a t e d t o exposure or homing behaviour. There i s a v a r i a b l e i n c r e a s e i n t h e number o f c i r r i , on a l l p a r t s of the body with l e n g t h and age, but there are no apparent d i f f e r e n c e s between year c l a s s e s i n the number o f c i r r i . There are d i f f e r e n c e s i n the r e l a t i o n s h i p between c i r r i and l e n g t h and age from 0. maculosus i n d i f f e r e n t areas but thase do not appear to be r e l a t e d to exposure. The f u n c t i o n of the c i r r i i s unknown. They do not possess any sensory r e c e p t o r s d e t e c t a b l e by l i g h t microscopy. , Age determination i n 0. maculosus O t o l i t h s were shown t o be a v a l i d method o f age determination i n 0. maculosus by comparison o f r e s u l t s from v e r t e b r a e and len g t h freguency a n a l y s i s . 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APPENDICES Appendix J D e s c r i p t i o n s of study s i t e s Major study s i t e : F i r s t Beach At the south end of the beach t h e r e i s a rocky s h e l f s i t u a t e d below a s m a l l steep g r a v e l beach. In the lower i n t e r t i d a l Hedophyllum s e s s i l e i s abundant. Moving up the i n t e r t i d a l , Olva spp., and Porph.yra p e r f o r a t a occur, g i v i n g way t o t h e Fucjus zone i n which most of the study pools occur. Higher than the Fucus zone some patches of Ente^omo^pha sp. can be found. In the t i d e p o o l s , P r i o n i t i s sp. i s most abundant. Also o c c u r r i n g are I r i d a e a spp., clumps of P h y l l o s p a d i x s c o u l e r i ( e s p e c i a l l y i n the lower p o o l s ) , Cla^ophora sp., c o r a l l i n e a l g a e , p a r t i c u l a r l y C o r a l l i n a Vancouverensis, and i n t h e higher pools, G i g a r t i n a sp.. In the Fucus zone and lower, extensive beds of M y t i l u s c a l i f o r n i a n u s occur. M. c a l i f o r n i a n u s i s a l s o present i n lower t i d e p o o l s along with some M. e d u l i s . L i t t o r i n e s and Tequla f u n e b r a l i s are extremely numerous i n most study pools. Limpets that are present i n c l u d e Notoacmaea JB§£§21§» N. scutum. 270 C o l l i s e l l a d i g i t a l i s and C. p e l t a . Balanus j l a n d u l a i s extremely common, and some B. c a r i o s u s can be found, ftnthopleura xanthogrammica and A. e l e g a n t i s s i m a are very abundant, p a r t i c u l a r l y i n lower p o o l s . The hermit c r a b s , Pagurus n i r s u t i u s c u l u s and P. granosimanus are common and S§li3JE§£Sus nudus can a l s o be found. Some P i g a s t e r oohraceus, S t r o n g y l o c e n t r o t u s purpuratus and o c c a s i o n a l l y S. dro g b a c h i e n s i s occur i n lower p o o l s . Along the west coast o f Vancouver I s l a n d , about 26 s p e c i e s of f i s h are commonly found i n t i d e p o o l s , o f which about 14 s p e c i e s belong to the f a m i l y C o t t i d a e , the remaining s p e c i e s being composed p r i m a r i l y o f s p e c i e s from the f a m i l i e s S t i c h a e i d a e and P h o l i d a e , with a few r e p r e s e n t a t i v e s from the f a m i l i e s l i p a r i d a e , Gobiesocidae and Hexagrammidae (Green, 1967; Chadwick, 1976; p e r s o n a l o b s e r v a t i o n ) . The most abundant f i s h i n a l l t i d e p o o l areas s t u d i e d was 0. maculosus. The only other f i s h at F i r s t Beach r e g u l a r l y trapped was C l i n o c o t t u s globjeeps but t h i s s p e c i e s was not n e a r l y as numerous. 0. s n y d e r i and Jknoplarchus purpurescens G i l l were captured o c c a s i o n a l l y . , Exposed study s i t e s : Cape Beale, Port Renfrew, Benson I s l a n d , Pachena P o i n t , K i r b y P o i n t In a l l areas the lower i n t e r t i d a l i s c h a r a c t e r i z e d by l a r g e beds of the C a l i f o r n i a mussel, My.tilus c a l i f o r n i a n u s and the goose neck b a r n a c l e , P o l l i c e p e s pplymerns. Hedophyllum s e s s i l e i s abundant at these l e v e l s and P o s t e l s i a pa^maefarmis 271 occurs on exposed rocky outcrops, except a t K i r b y P o i n t . Moving up the i n t e r t i d a l , Fucus sp. (and at Pachena P o i n t , E n d o c l a d i a sp. and Cladophora sp.) surrounds the more seaward study pools, except at Cape Beale and Kirby Point where M y t i l u s c a l i f o r n i a n u s and P o l l i c e p e s £olymerus cover the s h e l v e s . At h i g h e r l e v e l s , the study s i t e s are bare or have a s c a t t e r e d c o v e r i n g of Enteromorpha spp. L i t t o r i n e s are numerous at these l e v e l s a t both Pachena Point and B o t a n i c a l Beach. In the pools themselves, Phy.llospadix s c o u l e r i , Codium f r a g i l e and P r i o n i t i s sp. are common i n a l l a r e a s . At B o t a n i c a l Beach and Pachena P o i n t , the pools are e x t e n s i v e l y covered with c o r a l l i n e s . The pools a t K i r b y P o i n t are c o m p a r a t i v e l y bare except f o r clumps of P o l l i c e p e s polymerus. I n v e r t e b r a t e s t y p i c a l l y found on exposed rocky s h o r e s which were found i n pools i n a l l areas i n c l u d e M. c a l i f o r n i a n n s , S t r o n g y l p c e n t r o t u s purpuratus ( p a r t i c u l a r l y a t Pachena P o i n t ) , S. d r o e b a c h i e n s i s , Anthopleura xanthogrammica. A. e l e q a n t i s s i m a (except a t K i r b y P o i n t ) , Col l i s e l l a pe I t a , Katherina t u n i c a t a and P i s a s t e r ochraceus. At higher l e v e l s i n and around the pools, Balanus g l a n d u l a and B. c a r i o s u s were present. Again, 0. maculosus was the most abundant f i s h s p e c i e s i n the t i d e p o o l s . Other f i s h trapped at the study s i t e s i n c l u d e d C l i n o c o t t u s g l o b i c e p s , C. embrxaj, 0. s n y d e r i and A s e l i c h t h y s rhodorus Jordan and G i l b e r t . 272 Moderately exposed study s i t e s : Helby I s l a n d , Haines I s l a n d (southeast side) Both study s i t e s l i e i n the Fucus zone. Amongst t h e Fu cu s, Cladop_hora sp. , and L e a t h e s i a d i f f o r m i s are present. At Haines I s l a n d , patches of c o r a l l i n e s , ,Halo§accign glandiforme and Diva spp. a l s o occur. The pools i n both areas are l i n e d with g r a v e l and mussel s h e l l s and the predominant algae at both s i t e s i s P r i o n i t i s spp. C o r a l l i n e s , Fucus spp., P h y l l o s g a d i x s c o u l e r i and at Haines I s l a n d , Olya spp. a l s o occur. I n v e r t e b r a t e s t o be found i n pools at both s i t e s i n c l u d e Myti,lus ca l j . f o r n i a n u s . M. e d u l i s , Anthopleura xanthogrammica, A. e l e q a n t i s s i m a , Notoacmaea persona, N. scutum, C o l l i s e l l a d i g i t a l i s , Hemigrapsus nudus, Pagurus spp., Tggula f u n e b r a l i s and Mojealia spp. and i n a few of t h e lower pools a t Haines I s l a n d , S t r o n g y l o c e n t r o t u s purpuratus. At higher l e v e l s i n both areas, Balanus q l a n d u l a . B. c a r i o s u s and l i t t o r i n e s a r e common. F i s h s p e c i e s caught or observed a t these s i t e s were s i m i l a r t o those at F i r s t Beach, except t h a t on two o c c a s i o n s at Helby I s l a n d , Gastergsteus a c u l e a t u s Linnaeus were observed i n s e v e r a l high shallow t i d e p o o l s . S h e l t e r e d study s i t e s : G r a p p l e r I n l e t (bay and m u d f l a t ) , Hance I s l a n d , Dodger Channel, Haines I s l a n d ( l a r g e t i d e p o o l ) The s u b s t r a t e i n the bay i n G r a p p l e r I n l e t c o n s i s t s o f 273 boulders and rocks of v a r i o u s s i z e s over a mixture of crushed s h e l l , g r a v e l and mud. Clumps of U t i l u s e d u l i s , Fucus sp,, P o l x s i p h o n i a c o l l i n s i i , L e a t h e s i a d i f f o r m i s and Enteromorpha sp, are found on the rocks and stones. The area i s somewhat s i m i l a r t o the channel behind Ranee I s l a n d except t h a t the Ranee I s l a n d s i t e i s muddier and the predominant alg a e are Fucus sp., Rhodomela l a r e x and G r a c i l a r i a sp, Balanus g l a n d u l a , B, c a r i g s u s , Pagurus spp., Hemigrapsus sp., and Notoacmaea persona are common i n both areas, Pycnopodia h e l i a n t h o d e s i s common i n Grapp l e r I n l e t but not at Ranee I s l a n d and the r e v e r s e i s true f o r T h a i s l a m e l l g s a and s h e l l s of Tresus capax. Saxidomas giganteus and Cr ass o s t r g a g i g a s . The mudflat i n Port D e s i r e supports a c o n s i d e r a b l e bed of e e l g r a s s . Z o s t e r a marina, covered with S mi t h g r a naiadum. A beached f i s h boat and s e v e r a l waterlogged logs a t the study s i t e have outcroppings of M y t i l u s e d u l i s , Fucus spp. and Balanus g l a n d u l a . The other most obvious i n v e r t e b r a t e s are Hemigrapsus nudus, Pagurus sp., H o p a l i a sp., T h a i s l a m e l l g s a , P i s a s t e r gchraceus, Pycnopodia h e l i a n t h o d e s , Cucumaj;ia m i n i a t a and Tresus capax. The two s i t e s on Haines I s l a n d have s i m i l a r s u b s t r a t e s of sand and mud with s m a l l stones and embedded r o c k s and rocky outcrops. There i s a s m a l l e e l g r a s s bed in the l a r g e t i d e p o o l and i n summer months t h i s and the ex t e n s i v e bed i n Dodger Channel are covered with Smithora naiadum. Fucus sp. and Diva sp. occur on rocky patches at both s i t e s w h i le H a l o s a c c i p n 274 gland i f or me i s common in Dodger Channel and Enteromorpjia sp. i n the large tidepool. Mytilus edulis, Balanus . a l a n J f l i S * B. cariosus and s h e l l s of T res us capax, Sa_xidom as gj,ganteus and Protothaca staminea are found i n both areas, fiotoacmaea scutum. Pagurus spp., Hemigrapsus sp. and Dermasterias imbricata are common i n the tidepool while anjthc»plejjr.a elegant issima i s extremely numerous i n Dodger Channel. The pool at Ranee Island i s somewhat s i m i l a r to the pool on Haines Island with a muddy, sandy substrate and large boulders scattered throughout. Fucus sp., Ulva sp., Mytilus edulis, Balanus giandula, Notpacmaea scutum, N. persona and Mopalia sp. occur i n the rocky areas. £ a a u£us sp. and lemigrapsus sp. are numerous. while 0 . maculosus was the most numerous f i s h at certain times of year i n a l l areas, r e l a t i v e to tidepool areas other f i s h were more abundant in sheltered areas. at the bay in Grappler I n l e t , Artedius f e n e s t r a l i s , Cory_phopterus n i c h o l s i (Bean) and Nautichthys pculofasciatus (Girard) were frequently caught, although they were never as numerous as 0 . maculosus. Gasterpsteus aculeatus and aselichthys rhodorus were also trapped occasionally. at the mudflat i n Grappler I n l e t , G. aculeatus was sometimes numerous, and a. f e n e s t r a l i s , A. xhodorus and Isopsetta isQlepis (Lockington) were occasionally caught. At Ranee Island, Leptocottus armatus were sometimes trapped in greater numbers than 0 . maculosus. G. aculeatus were frequently caught there, and less freguently. 275 Ph2i.i§ l a e t a (Cope) , P. ornata- (Girard) , A. f e n e s t r a l i s and s m a l l P o r i c h t h y s notatus G i r a r d . In the l a r g e t i d e p o o l on Haines I s l a n d and at the e a s t e r n of the Dodger Channel e e l grass bed, L. armatus was commonly trapped along with o c c a s i o n a l C l i n o c o t t u s g l o b i c e g s . At the western end of the e e l grass bed, I § x a a i a S § o s decagramjus ( P a l l a s ) was the only s p e c i e s caught. Note: For d e s c r i p t i o n s and p i c t u r e s o f the i n v e r t e b r a t e s and algae r e f e r r e d t o above, see any g e n e r a l r e f e r e n c e on i n t e r t i d a l b i o l o g y such as: C a r e f o o t , Thomas. 1977. P a c i f i c Seashores. J . J . Douglas L t d . , Vancouver, B. C. 208 pp. K o z l o f f , Eugene N. 1973. Seashore l i f e of Puget Sound, the S t r a i t of Georgia and the San Juan A r c h i p e l a g o . J . J . , Douglas L t d . , Vancouver, B. C. 282 pp. R i c k e t t s , Edward F. and Jack C a l v i n . Revised by J o e l Hedgepeth. 1968. Between P a c i f i c T i d e s . S t a n f o r d U n i v e r s i t y Press, S t a n f o r d , C a l i f o r n i a . , 614 pp. 276 Appendix 2 C o n v e r s i o n s o f t o t a l l e n g t h (TL) t o and from s t a n d a r d l e n g t h (SL) T L to SL: S L = -.08132 + .8343TL (N=58) ' 8.T 0. 2. 4. 6. Total length (cm) S L to T L : T L .1180 + 1 .193SL (N=58) 8.. - <p> 0 ' 2. 4. 6. Standard length (cm) AEE£I!S\iZ 2 A l s a e an£ iHZSE*£b_ra.te.s f_E°JD e x ^ e x i n e n t a l i a n k Exposed s i d e C h l o r o p y b c e a e H l ^ a exp.ansa ( S e t c h e l l ) s e t c h e l l and G a r d n e r I H i e r c r i o r D h a l i n ^ a (L.) C. Aqardh £li'°2sis e l u i p s a (Hudson) C. Aqardh S c o n g o s o r p h a g a x a t i l i s ( R u p r e c h t ) C o l l i n s Phaeophyceae N£E£Ocjystis l u g t k e a n a (Mertens) P o s t e l s and R u p r e c h t H a o r o c v s t i s i n t e g r i f o l i a Bory I 3 £ g 3 i 3 . ™ § S 2 i " s i i (Turner) A r e s c h o u q D££!i:2.iest i a l i g u l a t a v a r . I L g u l a t a ( L i q h t f c o t ) Lamouroux L ^ r c i n a r i a enhengra S e t c h e l l L a n i n a r i a s a c c h a r i n a ( L i n n a e u s ) Laraouroux Jis§2i3 a r b o r ^ a A r e s c h o u q Agarum sp. (Eory) P o s t e l s and R u p r e c h t Rhodophyceae Ant i t hasinion J s i l i n i i G a r d n er P o i E l l I E a £ i n i a t a (C. Aqardh) C. Aqardh f H g d v x a n i a £ ° r t u s a ( P o s t e l s and Rupre c h t ) J . Aqardh C a l l o p h v l l i s f i i B i ( K y l i n ) N o r r i s l E l i i g a c o r d a t a ( T u r n e r ) . B o r y fauch°a l a c i n i a t a J . G. Aqardh *5tiiM2£ions22a g l i n d u l i f e r a ( K y l i n ) H o l l a s t o n P i a t X t h a - ^ n i on E t c t i n a t u s i K y l i n C i r r i p e d i a BalaE-Us c a r i o s u s ( ? a l l a s ) .fialanus I Q ^ t r a t u s a l a s k e n s i s P i l s b r y G a s t r o p o d a S s i l i s e l l a p_Si£a Rathke i j o t g a c r e a E g r s g n a Pathke i i S t o a c n e a s c u t u n (Pathke) £ a l 2 i o s t g 2 a l i o a t u ^ Gould I i i i 2 E i D 3 . s s u l n l a t a r.ouid Iiit2rifi3. e c N n a s s e s ia£Una o a r i n a t a Gould .Lacuna e cJT n a s s e s £ 2 I S 3 l i i £ S nup _ i l l u s (Gould) I l E l l I a r i a l i E l i l a t a ( C a r p e n t e r ) C a i n s i d e C h l o r o p h y c e a e M l i a e x g a n s a ( S e t c h e l l ) S e t c h e l l and G a r d n e r Entergmgr^ha sp. L i n k Rhodophyceae C a l l o 2 h Y . l l i s f i r r a a ( K y l i n ) N o r r i s C i r r i p e d i a B a l a n u s c a r i g s u s ( P a l l a s ) ^ a l a n u s r g s t r a t u s a l a s k e n s i s P i l s b r y G a s t r o p o d a C Q l i i s e l l a a e l t a R a thke Ifotgacmga 2 2 i s g n a R a t h k e liQ^oacnea Scutura (Rathke) £a 1 1 i g s ^ g n a l i g a t u n G o u l d I l i i 2 l i E a s c u t u l a t a G o u l d L i t t Q r i n a °qq masses Lacuna c a r i n a t a G o u l d L3.SUS2 ^IQ i s s s o s " a r g a r i t P s Eiinillug (Gould) l i l ! l l 3 E i 3 l i r u l a t a ( C a r p e n t e r ) £2iatgstgma f o l i a t u m (Gra^lin) V e l u t i n a l a e v i g a t a L i n n a e u s M f l h i s s a c o l u i i b i a n a D a l l ~ J A s c i d i a c e a £°I°Il£ " i l l ^ e E i a n a Herdman B i v a l v i a Chlamvs r u b i d a H i n d s H l ' t i l u s g d u l i s L i n n a e u s H X t i l u s ca l i f o r n i a n u s Conrad H o l o t h u r o i d e a C u c u r a r i a o s a u d o c u r a t a Deichraann C a l e e r e a S c y c h a sp. B r y o z o a Arcph i p o d a C a p r e l l i d a e F o l y c h a e t a N e r e i s p r o c g r a E h l e r s 5 5 i l 2 r b i s sp. P i a t v n S r s i s b i c a n a l i c u l a t a ( B a i r d ) A s c i d i a c e a £°I!2ll2 " i l l u s r i a n a Herdman B i v a l v i a ^ i l l a B Y S r u b i d a H i n d s J5Xi-iIl!§ §3tilis L i n n a e u s i i l t i l l i s c a l l f o r r . i a n u s C o n r a d A n t h o z o a A n t h o 2 i S i ! r a e l e g a n t i s s i m a B r a n d t C a l c a r e a Scygha s p . B r y o z o a Anph i p o d a C a p r e l l i d a e P o l y c h a e t a E a o i t ^ l l a ^ a g i t a t a ( F a b r i c i u s ) S p i r o r b i s sp. PI§£ynereis b i c a n a l i c u l a t a ( B a i r d ) N e r e i s n e o s j a z t h e s Hartman H a r n o t h o o i r a b r i c a t a ( L i n n a e u s ) " O l i q o c h a e t a E n c h y t r a e i d a e I s o o o d a Manna s p . 

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