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UBC Theses and Dissertations

The effect of space at constant densities on growth in a cichlid Aequidens pulcher Gill Minchin, J. Daniel deC. E. 1972

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THE EFFECT OF SPACE AT CONSTANT DENSITIES ON GROWTH I N A CICHLID Aecruidens p u l c h e r G i l l •by J . DANIEL deC. E. MINCHIN B.A., T r i n i t y C o l l e g e , D u b l i n U n i v e r s i t y , I r e l a n d , 1969 A THESIS SUBMITTED I N PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n t h e Department o f Z o o l o g y We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d The U n i v e r s i t y o f B r i t i s h C o l u m b i a J u n e , 1972 In present ing th i s thes is in pa r t i a l ' fu l f i lmen-t o f the requi rements fo r an advanced degree at the Un ive rs i t y of B r i t i s h Columbia, I agree that the L ib ra ry sha l l make it f r ee l y ava i l ab le for reference and study. I f u r the r agree that permission for extensive copying o f th i s thes i s fo r s cho l a r l y purposes may be granted by the Head of my Department or by h is representa t i ves . It is understood that copying or pub l i c a t i on of t h i s thes is fo r f i nanc i a l gain sha l l not be allowed without my wr i t ten permiss ion. Department The Un ive rs i t y of B r i t i s h Columbia Vancouver 8 , Canada ABSTRACT The e f f e c t o f space a t c o n s t a n t d e n s i t i e s on g r o w t h i n a c i c h l i d A e q u i d e n s p u l c h e r G i l l . J . D a n i e l deC. E. M i n c h i n . The e f f e c t o f impoundment s i z e on f i s h has been i n v e s t i g a t e d . I n v e s t i g a t o r s have r e p o r t e d t h a t g r e a t e s t growth has t a k e n p l a c e i n l a r g e i n some i n s t a n c e s and i n s m a l l impoundments i n o t h e r s . The e f f e c t o f v a r y i n g space on t h e c i c h l i d A equidens p u l c h e r G i l l , was examined i n f o u r t a n k s o f e q u a l volume. Each t a n k was d i v i d e d i n t o two r e p l i c a t e s i n t h e compartment r a t i o s 9:3:1 and each c o n t a i n e d 90:30:10 f i s h r e s p e c t i v e l y . A h i g h e r d e n s i t y t a n k had t w i c e t h e f i s h number i n a l l compartments and had l o w e s t growth due t o e i t h e r r e d u c e d oxygen a v a i l a b i l i t y , i n c r e a s e d b i o m a s s , i n c r e a s e i n a c t i v i t y o r s t r e s s due t o s m a l l n e a r e s t n e i g h b o u r d i s t a n c e s . F i s h i n a t a n k w i t h m i r r o r s on a l l compartment w a l l s had a r e d u c e d g r o w t h p o s s i b l y due t o v i s u a l s t r e s s compared t o a c o n t r o l l a c k i n g m i r r o r s . A f u r t h e r t a n k had t w i c e t h e s u r f a c e a r e a o f t h e c o n t r o l , a g r e a t e r d i s t a n c e between n e a r e s t n e i g h b o u r s and g r e a t e s t f i s h g r o w t h . Growth was s i g n i f i c a n t l y g r e a t e r , a t t h e 95 p e r c e n t c o n f i d e n c e l i m i t , i n a l l s m a l l compartments of t a n k s and a c t i v i t y was s i g n i f i c a n t l y g r e a t e r i n l a r g e compartments. I n an i d e n t i c a l t r e a t m e n t d e s i g n t o t h a t o f t h e c o n t r o l f i s h were shown t o l o s e w e i g h t w h i l e b e i n g s t a r v e d . The f i s h i n t h e l a r g e r compartments were more a c t i v e and l o s t most w e i g h t . A s t r o n g s u g g e s t i o n t h a t t h e l o w e r growth r a t e i n l a r g e compartments was due t o g r e a t e r a c t i v i t y , p o s s i b l y - 1 1 -t h i s was r e l a t e d t o t h e t o t a l a v a i l a b l e swimming space p e r f i s h . F i s h a g g r e s s i o n was g r e a t e s t i n s m a l l compartments and d e c r e a s e d over t i m e , p o s s i b l y as a r e s u l t o f c o n d i t i o n i n g . - i i i -TABLE OF CONTENTS PAGE INTRODUCTION 1 METHODS AND DESIGN 1 RESULTS 5 R e s u l t s o f growth 5 F i s h m o r t a l i t y 5 GROWTH BETWEEN COMPARTMENT SIZES 16 Energy g a i n due t o 16 A l g a e 16 Faeces 17 Energy l o s s and 18 E f f e c t o f a c t i v i t y 21 E f f e c t o f f i s h s i z e 21 E f f e c t o f a g g r e s s i o n 25 GROWTH BETWEEN TREATMENTS 25 E f f e c t o f a c t i v i t y 25 E f f e c t o f a g g r e s s i o n 26 E f f e c t o f n e a r e s t n e i g h b o u r d i s t a n c e 26 Gross e n e r g e t i c s 27 DISCUSSION 33 Growth i n compartments 33 Growth i n t r e a t m e n t s 38 P o t e n t i a l a p p l i c a t i o n 43 CONCLUSIONS 47 LITERATURE CITED 49 APPENDIX 52 - i v -LIST OF TABLES TABLE PAGE 1 A n a l y s i s o f f i s h growth on day 119. 6 2 A n a l y s i s o f f i s h growth,on day 190. 7 3 M o r t a l i t y o f f i s h (numbers d y i n g ) i n compart- 15 ments and t r e a t m e n t s . 4 Mean numbers o f a g g r e s s i v e e n c o u n t e r s f o r f i s h 20 on day 86,and 118. 5 A c t i v i t y i n s t a r v a t i o n t r e a t m e n t . 22 6 A n a l y s i s o f f i s h a c t i v i t y on day 118. 23 7 A n a l y s i s o f v a r i a n c e f o r l e n g t h and w e i g h t 24 o f s t a r v e d f i s h on day 1 and day 45. 8 N e a r e s t n e i g h b o u r d i s t a n c e s f o r l a r g e 28 compartments o f t r e a t m e n t s on day 122. 9 , Gross e n e r g e t i c s f o r t r e a t m e n t s and compart- 32 ments e x p r e s s e d i n grams per k i l o g r a m p e r day. 10 L e n g t h f r e q u e n c i e s o f f i s h w i t h i n compart- 36 ments f o r t r e a t m e n t s e x p r e s s e d as a p e r c e n t -age o f t o t a l number o f f i s h f o r each compart-ment s i z e . 11 L e n g t h f r e q u e n c i e s o f f i s h w i t h i n compartments 37 f o r t r e a t m e n t s e x p r e s s e d as a p e r c e n t a g e o f t o t a l number o f f i s h f o r each compartment s i z e . 12 Means o f f i s h g r o w t h . 53 - V -LIST OF FIGURES FIGURE PAGE 1 V a r i a t i o n o f pH and t e m p e r a t u r e i n 3 t r e a t m e n t s . 2 Growth i n compartments and r e p l i c a t e s i n 8 t h e c o n t r o l t r e a t m e n t . 3 Growth i n compartments and r e p l i c a t e s i n 9 t h e s h a l l o w t r e a t m e n t . 4 Growth i n compartments and r e p l i c a t e s i n 10 the m i r r o r t r e a t m e n t . 5 Growth i n compartments and r e p l i c a t e s i n 11 t h e d e n s i t y t r e a t m e n t . 6 Growth dn l a r g e compartments i n a l l t r e a t m e n t s . 12 7 Growth i n medium s i z e d compartments i n a l l 13 t r e a t m e n t s . 8 Growth o f s m a l l compartments f o r a l l 14 t r e a t m e n t s . 9 A c t i v i t y o f Aequidens p u l c h e r over 24 h o u r s . 19 10 An e s t i m a t i o n o f energy c o s t . 30 11 Model o f Aequidens p u l c h e r growth i n compart- 45 ments. 12 P l a n o f m i r r o r and c o n t r o l t r e a t m e n t s . 55 13 P l a n o f s h a l l o w and d e n s i t y t r e a t m e n t s . 56 - v i -ACKNOWLEDGEMENTS I thank D r s . Dean F i s h e r , N e i l G i l b e r t and C a r l W a l t e r s f o r t h e i r c o n s t r u c t i v e c r i t i c i s m . I a p p r e c i a t e t h e h e l p g i v e n t o me by Dr. Norman J . W i l i m o v s k y and R o b i n A l l e n f o r a s s i s t a n c e i n a n a l y s i n g t h e d a t a . I would a l s o l i k e t o thank my a d v i s o r f o r h i s g u i d a n c e and f o r s u g g e s t i n g t h e problem, as w e l l as h i s c o n f i d e n c e i n me. F i n a l l y , I am g r a t e f u l t o t h o s e f i s h and my w i f e t h a t l i v e d w i t h me t h r o u g h t h e s t u d y . - 1 -INTRODUCTION The e f f e c t o f l i v i n g space on growth a t c o n s t a n t d e n s i t y has n o t been i n v e s t i g a t e d f u l l y i n p i s c i c u l t u r e . S h o u l d a v a i l a b l e space i n f l u e n c e f i s h g rowth a g r e a t e r growth r a t e may be o b t a i n e d w i t h i n a c e r t a i n impoundment s i z e . Y o s h i h a r a (1952) and l a t e r Kamamoto e t a l . (1957) have s t u d i e d t h e e f f e c t o f growth o f C y p r i n u s c a r p i o (Linneaus) i n ponds o f t h e r a t i o o f 9:3:1 by volume and found growth t o be g r e a t e r i n s m a l l e r compartments. Chen and Prowse (1964) found growth o f T i l a p i a riiossambica ( P e t e r s ) t o be g r e a t e r i n l a r g e r compartments. M a z l a n (M.S.) i n v e s t i g a t e d t h e growth o f L e b i s t e s r e t i c u l a t u s ( P e t e r s ) and found growth g r e a t e s t w i t h i n s m a l l e r compartments. T h i s d i s p a r i t y has o n l y been s p e c u l a t e d upon. The p r e s e n t s t u d y i n v e s t i g a t e s t h e v a r y i n g growth a t c o n s t a n t d e n s i t y w i t h i n d i f f e r e n t compartment s i z e s under d i f f e r e n t t r e a t m e n t s f o r Aequidens p u l c h e r . G i l l , and a t t e m p t s t o i s o l a t e t h o s e f a c t o r s r e s p o n s i b l e . The n u l l h y p o t h e s i s formed i s t h a t no d i f f e r e n c e i n growth between compartments o r t r e a t m e n t s e x i s t . S h o u l d growth be g r e a t e r w i t h i n one compartment s i z e i t i s assumed t h a t b e h a v i o u r a l and p h y s i o l o g i c a l changes i n v o l v i n g e i t h e r e nergy g a i n o r energy l o s s a r e r e s p o n s i b l e . METHODS AND DESIGN The b a s i c e x p e r i m e n t a l d e s i g n was t o measure f i s h g rowth f o r a s e r i e s o f d i f f e r e n t c o n t a i n e r s i z e s and t r e a t m e n t s . These were: - 2 -1) A c o n t r o l . 2) One w i t h t w i c e t h e s u r f a c e a r e a and h a l f t h e depth t o t h a t o f t h e c o n t r o l , termed " s h a l l o w " . 3) One w i t h m i r r o r e d w a l l s u sed t o v i s u a l l y i n c r e a s e space and f i s h numbers w i t h o u t a l t e r i n g t h e d e n s i t y , termed " m i r r o r " . 4) One w h i c h had an i n i t i a l d e n s i t y and f i s h number t w i c e t h a t o f t h e c o n t r o l , termed " d e n s i t y " . A l l t r e a t m e n t s were r e p l i c a t e d . Each r e p l i c a t e c o n s i s t e d o f t h r e e compartment s i z e s w i t h volume r a t i o s - o f 9:3:1 (5433: 1811:603 c u b i c i n c h e s , r e s p e c t i v e l y ) . The numbers o f f i s h s t o c k e d i n each r e p l i c a t e were 90:30:10 and i n t h e d e n s i t y t r e a t m e n t 180:60:20. Temperatures were k e p t w i t h i n i2.5°C o f 25°C f o r a l l t r e a t m e n t s , pH ranged from 5.9 - 7.0. D i s s o l v e d oxygen c o n c e n t r a t i o n s were d e t e r m i n e d , u s i n g t h e W i n k l e r method, t o be 2.2 - 4.1 m i l l i g r a m s o f oxygen p e r l i t r e ( F i g u r e 1 ) . C i r c u l a t i o n was m a i n t a i n e d a t a c o n s t a n t r a t e o f two l i t r e s p e r m i n u t e . The w a t e r was a e r a t e d by a i r s t o n e s p l a c e d i n i n t e r c o m p a r t m e n t a l p o c k e t s . The t r e a t m e n t s r e c e i v e d a p h o t o p e r i o d o f f o u r t e e n h o u r s o f f l u o r e s c e n t l i g h t p e r day. The t a n k s were w e l l c l e a n e d and r i n s e d e v e r y two weeks and r e f i l l e d w i t h f r e s h w a t e r a t 25°C and a pH o f 7.0. The d e n s i t y t a n k was c l e a n e d e v e r y week. T h i s p r o c e d u r e m i n i m i z e d t h e e f f e c t o f waste s u b s t a n c e s on f i s h g r o w t h . Waste m a t e r i a l from t a n k s c o n t a i n i n g t a d p o l e s has been de m o n s t r a t e d t o reduce t h e i r growth r a t e (Rose, 1952, 1959) . CONTROL 27-1 ^-O. 25 23 4 1 MG/0 2/L. 4 0 MG(0 2/L. -O O •O-o o — -80 -70 •60 SHALLOW. 40 MG|0 2 | L . 4 0 MG|0 2 | L . 27-i 25-23 - - - - - 7 ° - o - ^ - - ° \ : ^ - N * ^ MIRROR. 3-9 MG| 0 2 | L . _ 0 = . o - e -O^- —-^O O 9 3 95 MG/0 2|L. 27-2S-\ O — O O — © -23 A o o o-o • ' •o—«-o- -o—o -—e o-o -8 0 - 7 0 L6 0 "8 0 - 7 0 -6 0 I DENSITY. 27 25-23 O O. 2-3MG/0 2/L. O—O-OO^ ,OOx Ch-O o-22 MG|0 2 /L . ^O — 0 ^ r ^ O - = • O O O- - C -80 -70 -60 -• PH. -O - C° r — i 1 1 1 ' 1 r—] 1 1 ' 1 r—| . 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 i 1 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 DAY NUMBER. Figure 1. V a r i a t i o n of pH and temperature i n treatments. _ 4 -A s l i m e c o l l e c t e d from t h e s i d e s o f t a n k s was shown by West (1960) t o i n h i b i t g r o w t h . F a e c a l m a t e r i a l can c o n t a i n as much as 5.8 p e r c e n t o f n i t r o g e n (Kawamoto, 1961) w h i c h may have r e s u l t e d i n a l o w e r growth r a t e i n C v p r i n u s c a r p i o . A c c o r d i n g t o Brockway (1950) and Kawamoto (1958) a n i t r o g e n o u s s u b s t a n c e can o c c u r i n t a n k s w h i c h e f f e c t s w a t e r q u a l i t y and r e duces f i s h g r o w t h . I n n o r t h e r n South A m e r i c a i n t h e d r y season t h e c i c h l i d A equidens p u l c h e r becomes crowded i n s m a l l ponds (Bred e r 1 9 3 4 ) . The h i g h t e m p e r a t u r e s o f t h i s r e g i o n would i n d i c a t e t h a t t h i s f i s h was p r o b a b l y t o l e r a n t t o low c o n c e n t r a t i o n s o f d i s s o l v e d oxygen. The f i s h has a h i g h g rowth r a t e and does not e x h i b i t any s t r o n g s e x u a l dimorphism. I t s s m a l l s i z e and t o l e r a n c e t o h a n d l i n g make i t a good e x p e r i m e n t a l a n i m a l . F i f t e e n hundred immature f i s h were randomly d i v i d e d so t h a t t h e means and ranges o f l e n g t h f r e q u e n c y were t h e same f o r a l l t r e a t m e n t s and compartments. The f i s h were f e d b r i n e s h r i m p and T e t r a m i n f i s h f o o d . Food i n e x c e s s was d e l i v e r e d f o r a h a l f hour p e r i o d , a f t e r t h r s t i m e t h e r e m a i n i n g f o o d and f a e c e s were removed. Food was d i s t r i b u t e d randomly t o p r e v e n t dominant f i s h from d e f e n d i n g a r e a s where i t was i n t r o d u c e d (Magnuson, 1962) . One l a r g e t a n k and two s m a l l e r t a n k s were c o n s t r u c t e d . The l a r g e t a n k c o n t a i n e d t h e m i r r o r e d and c o n t r o l t r e a t m e n t s ( F i g u r e 12) . A l l t r e a t m e n t s i n t a n k s c o n t a i n e d t h e same w a t e r volume. One s m a l l t a n k had t h e same number o f f i s h and t w i c e t h e s u r f a c e a r e a , t h e o t h e r had t w i c e t h e d e n s i t y - 5 -t o t h a t o f t h e c o n t r o l ( F i g u r e 1 3 ) . White p l e x i g l a s s p a r t i t i o n s d i v i d e t r e a t m e n t s i n t o compartment s i z e s o f t h e r a t i o o f 9:3:1 by volume. The compartment s i z e s a r e r e p l i c a t e d i n each t r e a t m e n t . The j o i n t s o f t h e p a r t i t i o n s and o f t h e t a n k s were f i l l e d w i t h a non t o x i c s e a l a n t . The t a n k s were s u p p o r t e d on frames because o f co n v e n i e n c e o f a c c e s s ( F i g u r e s 14, 15 and 1 6 ) . RESULTS Growth a n a l y s i s F i s h were measured i n s t a n d a r d l e n g t h over a p e r i o d o f 180 d a y s . S i x measurements were made d u r i n g t h i s t i m e . Growth was s i g n i f i c a n t l y g r e a t e r a t t h e 95 p e r c e n t c o n f i d e n c e l i m i t i n s m a l l compartments compared t o l a r g e compartments (T a b l e s 1, 2) . Growth i n medium s i z e d compartments was a l s o g r e a t e r i n comparison w i t h l a r g e compartments ( F i g u r e s 2, 3, 4, and 5 ) . The d i f f e r e n c e o f growth between t r e a t m e n t s was s i g n i f i c a n t ( F i g u r e s 6, 7, and 8 ) . F i s h l e n g t h was s m a l l e s t i n t h e d e n s i t y t r e a t m e n t and g r e a t e s t i n t h e s h a l l o w t r e a t m e n t . The m i r r o r e d t r e a t m e n t had a l o w e r growth t o t h e c o n t r o l . No s i g n i f i c a n t d i f f e r e n c e between r e p l i c a t e s e x i s t e d . M o r t a l i t y There was a 39 p e r c e n t m o r t a l i t y o f f i s h w i t h i n m i r r o r and d e n s i t y t r e a t m e n t s . T h i s was h i g h e r t h a n t h e 15 p e r c e n t o b s e r v e d i n c o n t r o l t r e a t m e n t s . The s h a l l o w t r e a t m e n t had• a low m o r t a l i t y o f 2 p e r c e n t (Table 3 ) . There was a g r e a t e r ANALYSIS OF FISH GROWTH - Day 11.9 ANALYSIS OF VARIANCE - for all compartments in all treatments SOURCE :DF'- SUM SQ. MEAN SQ. F PROB. Size 2 7. 1565 3. 5782 24. 03 -0. 0 Treatment 3 8. 7909 2. 9303 19. 68 -0. 0 Replicate 1 0. 25676 0. 25676 1. 72 0. 1859 SizeXTreat- 6 'J ''ment 0.47456 0. "07909 •: 0. 53 0. 7866 Error 1216 181. 04 0. 14888 Total 1228 . 197. 7.2 MEANS Size Large Medium Small X 3. 4467 3. 5088 3. 7298 N 850 / 283 96 Treatment Control Shallow Mirror Density X 3. 5129 3. 6203 3. 4826 3. 3960 N 248 258 233 490 Replicate s X N Left 3. 4998 526 Right 3. 4706 703 Size X Treatment T reatment Control Shallow M irror Density 4 J (-H Large X 3. 4660 3. 5943 3. 4278 3. 3681 fi <U a N 173 179 157 341 C u Medium X 3. 5627 3. 6520 3. 5191 3. 4027 Corripa Small N X 55 3. 7810 59 3. 7595 56 3. 8100 113 3. 6403 Corripa N 20 20 20 36 GRAND MEAN 3.4831 ."Table 1. Analysis of fish growth. - 7 -ANALYSIS OF FISH GROWTH - Day 190 ( L a s t t i m e p e r i o d ) ANALYSIS OF VARIANCE - F o r a l l compartments i n a l l t r e a t m e n t s SOURCE S i z e Treatment R e p l i c a t e S i z e X Treatment DF SUM SQ. MEAN SQ. E r r o r T o t a l 2 3 1 6 1141 1153 15 .700 35.241 0.04880 1.5496 237.84 290.38 7.8501 11.747 0.04880 0.25827 0.20845 37.66 56.35 0.23 1.24 PROB. -0.0 -0.0 0.6341 0.2828 MEANS S i z e X N Treatments X N R e p l i c a t e s X N S i z e X Treatment -P 1 •P u s L a r g e X N Medium X N S m a l l X N GRAND MEAN La r g e 3.7090 799 C o n t r o l 3 .8852 250 L e f t 3.7749 592 C o n t r o l 3.8140 174 3.9109 56 4.4330 20 3.7686 Medium 3.8199 258 S h a l l o w 3.9978 258 R i g h t 3.7619 562 S m a l l 4.1230 97 M i r r o r 3.7676 222 Treatment S h a l l o w 3.9553 178 4.0398 60 4.2495 20 M i r r o r 3.7142 151 3.7918 51 4.1095 20 D e n s i t y 3.5600 424 D e n s i t y 3.4965 296 3.6347 91 3.8943 37 T a b l e 2. A n a l y s i s o f f i s h growth. F i g u r e 2. Growth i n compartments and r e p l i c a t e s i n t h e c o n t r o l t r e a t m e n t . T a b l e t o Figu: Time p e r i o d s measured 1 2 3 4 5 2. Large (L) S.D. X 0.216 2.68 0.272 3.02 0.317 3.25 0.377 3.47 0.436 3.81 COMPARTMENTS Medium (M) S.D. X 0.241 2.67 0.312 3.03 0.387 3.31 0.368 3.56 0.489 3.91 S m a l l (S) S .D. X 0.265 2.70 0.354 3.08 0.451 3.45 0.575 3.78 0.682 4.43 STANDARD LENGTH (CM) (Figure 3. Growth i n compartments and r e p l i c a t e s i n s h a l l o w t r e a t m e n t T a b l e t o F i g u r e 3. Time p e r i o d s measured Large (L) S .D. X COMPARTMENTS Medium (M) S .D. X S m a l l (S) S.D. X 1 0.218 2.42 0.233 2.40 0.222 •2.41 2 0 .268 2.68 0.290 2.68 0.302 2.71 3 0.302 3.10 0.338 3.13 0.374 3.20 4 0.338 3.59 0.368 3.65 0.437 3.76 5 0.428 3.95 0.489 4.04 0.515 4.25 F i g u r e 4. Growth i n compartments and r e p l i c a t e s i n m i r r o r t r e a t m e n t . T a b l e t o F i g u r e 4. Time Large p e r i o d s measured S.D. 1 0.231 2 0.279 3 0.314 4 0.382 5 0.435 COMPARTMENTS (L) Medium (M) S m a l l (S) X S.D. X V S.D. x 2.71 0.240 2.77 07,264 2.82 2.97 0.298 3.08 0.308 3 .22 3.19 0.340 3.28 0.297 3 .51 3.42 0.435 3.52 0.307 3.81 3.71 0.435 3.79 0.421 4.11 c \ F i g u r e 5. Growth i n compartments and r e p l i c a t e s i n d e n s i t y t r e a t m e n t . vTable t o F i g u r e 5. COMPARTMENTS Time Large (L) Medium (M) S m a l l (S) p e r i o d _ _ _ measured S.D. X S.D. X S.D. X 1 0.218 *2.65 0.249 -2.65 0.268 2.71 2 0.216 2.93 0.330 2.95 0.368 3.10 3 0.315 3.17 0.392 3.18 0.451 3.38 4 0.360 3.37 0.437 3.40 0.476 3.60 5 0.441 3.50 0.482 3.63 0.540 3.89 Figure 5 . NUMBER OF OAVS. F i g u r e 6. Growth i n l a r g e compartments i n a l l t r e a t m e n t s . T a b l e t o F i g u r e 6, Txme p e r i o d measured S.D. C o n t r o l (C) X TREATMENTS S h a l l o w (S) M i r r o r (M) S.D. X S.D. X D e n s i t y (D) S.D. X 1 0.216 2.68 0.218 2.42 0.231 2.71 0.218 2.65 2 0.272 3.02 0.268 2.68 0.279 2.97 0.261 2.93 3 0.317 3.25 0.302 3.10 0.314 3.19 0.315 3.17 4 0.377 3.47 0.338 3.59 0.382 3.43 0.360 3.37 5 0.436 3.81 0.428 3 .96 0.435 3.71 0.441 3.50 h-1 i F i g u r e 7. Growth i n medium s i z e d compartments i n a l l t r e a t m e n t s . vTable t o F i g u r e 7. •Time p e r i o d measured S.D C o n t r o l (C) X TREATMENTS S h a l l o w (S) s M i r r o r (M) S.D. X S.D. X D e n s i t y (D) S .D. X 1 0.241 <2.67 i0.233 -2.40 D.240 '2.77 0.249 2.71 i 2 0.312 3.03 0.290 2.68 0.298 3.08 0.330 3.10 H co 3 0.387 3.31 0.338 3.13 0.340 3.28 0.392 3.38 1 4 0.489 3.56 0.368 3.65 0.353 3.52 0.437 3.40 5 0.529 3391 0.489 4.04 0.435 3.79 0.482 3.89 Figure 7. 90 N U M B E R O F D A Y S . Control Small Medium Density F i g u r e 8. Growth o f s m a l l compartments f o r a l l t r e a t m e n t s . T a b l e t o F i g u r e 8. Time p e r i o d measured S.D. C o n t r o l (C) X TREATMENTS S h a l l o w (S) M i r r o r (M) S.D. X S.D. X D e n s i t y (D) S.D. X 1 0.265 2.70 0.222 2.41 0.264 2.82 0.268 2.71 2 0.354 3.08 0.302 2.71 0.308 3.22 0.368 3.10 3 0.451 3.45 0.374 3.20 0.297 3.51 0.451 3.38 4 0.575 3.78 0.437 3.76 0.307 3.81 0.476 3.64 5 0.682 4.43 0.515 4.25 0.421 4.11 0.540 3.89 I Figure 8 34-il-J O -II-IS-Shallow Control Medium Density - 15 -Day 1-24 Day 25-49 Day 50-97 Day 98-187 T o t a l C o n t r o l (N=260) S m a l l Medium L a r g e T o t a l 3 1 2 5 2 4 11 3 1 0 8 6 5 19 19 10 11 40 S h a l l o w (N=260) S m a l l M edium L a r g e T o t a l 0 1 0 0 0 0 0 0 1 4 0 0 4 1 1 0 M i r r o r (N=260) S m a l l Medium L a r g e T o t a l 2 4 4 10 3 6 20 29 2 5 11 18 4 12 32 48 11 27 65 103 D e n s i t y (N=520) S m a l l M edium L a r g e 14 1 14 */7 9 15 2 17 13 9 29 72 32 56 114 T o t a l 29 31 32 110 202 T a b l e 3 . M o r t a l i t y o f f i s h (numbers d y i n g ) i n c o m p a r t m e n t s a n d t r e a t m e n t s . - 16 -m o r t a l i t y i n s m a l l compartment s i z e s . The r e a s o n f o r t h i s w i l l be t r e a t e d l a t e r . GROWTH BETWEEN COMPARTMENT SIZES A growth d i f f e r e n c e between compartments was demonstrated and a f o l l o w i n g s t u d y was d e s i g n e d t o i n v e s t i g a t e how such d i f f e r e n c e s c o u l d o c c u r . D i f f e r e n c e s o f growth between compartment s i z e s may have been due t o d i f f e r e n c e s o f energy g a i n o r energy l o s s . ENERGY GAIN I t was p o s t u l a t e d t h a t t h e way i n w h i c h a d d i t i o n a l n u t r i e n t e n ergy c o u l d be o b t a i n e d i n s m a l l compartments i n t h e s e e x p e r i m e n t s was by a s s i m i l a t i o n o f a l g a e o r f a e c e s . A l g a e The f l o o r and s i d e s o f t h e compartments were f r e q u e n t l y seen t o be n i p p e d by f i s h , t h i s o c c u r r e d p a r t i c u l a r l y w i t h i n s m a l l compartments. The a l g a e p r e s e n t on t h e s e s u r f a c e s may have been e a t e n . The s u r f a c e a r e a t o volume r a t i o w i t h i n s m a l l compartments i s g r e a t e r t h a n w i t h i n l a r g e r compartments; f o r t h i s r e a s o n each f i s h w i t h i n s m a l l s i z e d compartments has p o t e n t i a l l y g r e a t e r q u a n t i t i e s o f a l g a e t o e a t . S m a l l amounts o f s l i m e and a l g a e were found on t h e w a l l s o f t h e tanks." T h i s i s s i m i l a r t o t h e m a t e r i a l d e s c r i b e d by West .(I960) . Onl y s m a l l amounts o f m a t e r i a l were p r e s e n t on t h e f r e q u e n t l y c l e a n e d t a n k w a l l s , such m a t e r i a l w ould be d i f f i c u l t t o a s s i m i l a t e and f o r t h i s r e a s o n a l g a e i s not c o n s i d e r e d t o be i m p o r t a n t i n a f f e c t i n g f i s h g r o w t h . - 17 -Faeces Some a n i m a l s a r e coprophagous. F a e c a l m a t e r i a l may c o n t r i b u t e t o a d d i t i o n a l g r o w t h . A l t h o u g h r e m a i n i n g f a e c e s were removed from t h e t a n k a f t e r f e e d i n g , f a e c a l m a t e r i a l d i d r e m a i n w i t h i n t h e t a n k s . The f o l l o w i n g e x p e r i m e n t was d e s i g n e d t o t e s t whether t h e f a e c e s might c o n t r i b u t e a d d i t i o n a l e n e r g y f o r g r o w t h . T h i r t y f i s h , from t h r e e compartment s i z e s , were i s o l a t e d and s t a r v e d f o r f i v e d a y s . F a e c a l m a t e r i a l s t a i n e d w i t h methylene b l u e was i n t r o d u c e d i n t o t h e t a n k compartments. The f r e s h f a e c e s were o b t a i n e d , from a d i f f e r e n t compartment i n t h e same t a n k , from p r e v i o u s l y f e d f i s h o f t h e same s p e c i e s . The s t a i n e d f a e c e s were a l l o w e d t o remai n i n t h e t a n k s f o r h a l f an h o u r , a f t e r w h i c h f i v e f i s h from each compartment s i z e were examined. No methylene b l u e s t a i n e d m a t e r i a l was found i n t h e g u t o f t h e s e f i s h . The f i v e f i s h t h a t remained i n each compartment were f e d , b r i n e s h r i m p i n e x c e s s s t a i n e d w i t h methylene b l u e , f o r a h a l f hour p e r i o d . The gut o f t h e f i s h was t h e n examined; i t c o n t a i n e d s t a i n e d m a t e r i a l . I c o n c l u d e t h a t t h e s e f i s h a r e u n l i k e l y t o o b t a i n a d d i t i o n a l energy by e a t i n g f a e c e s under t h e e x p e r i m e n t a l c o n d i t i o n s . I n a d d i t i o n i t i s u n l i k e l y t h a t t h e s e f i s h a s s i m i l a t e enough a l g a l m a t e r i a l t o cause a d i f f e r e n c e i n growth between compartments. D i f f e r e n c e s o f growth r a t e between compartments a r e not due t o d i f f e r e n t r a t e s o f ? a s s i m i l a t i n g energy b u t from d i f f e r e n c e s i n energy l o s s . - 18 -The g r e a t e r growth r a t e w i t h i n s m a l l compartments may be due t o an i n c r e a s e i n energy l o s s w i t h i n l a r g e compartments. The h y p o t h e s i s t h a t growth d i f f e r e n c e s between compartments were due t o energy l o s s was t h e n t e s t e d . ENERGY LOSS A d i f f e r e n t i a l l o s s o f energy may be due t o d i f f e r e n c e s i n f i s h b e h a v i o u r between compartments. The v a r i a b l e o f b e h a v i o u r t h a t was measured was a c t i v i t y . A c t i v i t y was d e f i n e d as t h e movement of t h e f i s h body t h r o u g h t h e w a t e r mass by means o f i t s own power, and was e x p r e s s e d as a p e r c e n t a g e o f t i m e a c t i v e o v er a f i v e minute p e r i o d . The number o f chases and f l e e s o f each i n d i v i d u a l f i s h t h a t was t r a c k e d o v er th e f i v e minute p e r i o d was a l s o r e c o r d e d as a measure o f a g g r e s s i o n . The f i s h were o b s e r v e d from b e h i n d a s c r e e n w i t h s m a l l background i l l u m i n a t i o n t o p r e v e n t th e r e c o r d e r from d i s t u r b i n g them. The f i s h were o b s e r v e d b e f o r e t h e y were f e d . They e x h i b i t e d a d i u r n a l b e h a v i o u r p a t t e r n and a c t i v i t y v a r i e d ( F i g u r e 9 ) . P r e l i m i n a r y s t u d i e s o f b e h a v i o u r , on day 86, i n d i c a t e d t h a t a g g r e s s i o n was g r e a t e s t i n s m a l l compartments and a c t i v i t y was g r e a t e s t i n l a r g e compartments (Table 4 ) . The r e s u l t s o f a more complete s t u d y , on day 118, showed no s i g n i f i c a n t d i f f e r e n c e a t t h e f i v e p e r c e n t l e v e l , f o r t h e numbers o f chases and f l e e s between compartments; b u t d i f f e r e n c e s i n a c t i v i t y were s i g n i f i c a n t ' . . The e f f e c t o f t h i s a c t i v i t y on growth was i n v e s t i g a t e d . - 19 -100 • < 50-0. O 1 16 LIGHT. —r~ 20 — i 24 4 DARK. — l 12 -+DARK. TIME OF MEASUREMENT (HRS.) Figure 9. A c t i v i t y of Aequidens pulcher over 24 hours. - 20 -TREATMENTS F l e e s C o n t r o l Chases N L a r g e 4 3.6 5 Medium 3.8 8.4 5 S m a l l 5.4 6.2 5 Day 86 F l e e s S h a l l o w Chases N F l e e s M i r r o r Chases N 2.8 0.2 5 8.6 5.2 5 F l e e s D e n s i t y Chases N 0.8 7.2 5 Day 118 F l e e s 0.6 0 0.3 C o n t r o l Chases 1.0 0.2 0 N 10 10 10 F l e e s 1.0 0.2 0.5 S h a l l o w Chases 0.3 0.8 0.1 N F l e e s 0.3 0.9 0.8 M i r r o r Chases 0.2 0.3 0.2 N 10 10 10 F l e e s 1.9 0.8 1.4 S h a l l o w Chases 0.9 1.0 0.3 N 10 10 10 T a b l e 4. Mean numbers of a g g r e s s i v e e n c o u n t e r s f o r f i s h on day 86 and 118. - 21 -The e f f e c t o f a c t i v i t y on growth I have shown t h a t a c t i v i t y v a r i e s between compartment s i z e s ; t h e f o l l o w i n g e x p e r i m e n t was d e s i g n e d t o t e s t i t s e f f e c t on growth by s t u d y i n g a c t i v i t y and t h e w e i g h t l o s s o f s t a r v e d f i s h i n compartments. F i s h (the s o u r c e o f w h i c h was t h e m i r r o r e d and d e n s i t y t r e a t m e n t s ) were s e l e c t e d such t h a t t h e means o f s t a n d a r d l e n g t h s i n a l l s i x e x p e r i m e n t a l compartments were s i m i l a r . The t r e a t m e n t was s e t up as i n t h e b a s i c growth s t u d y o f t h e c o n t r o l , e x c e p t t h e f i s h were s t a r v e d f o r 45 d a y s . D u r i n g s t a r v a t i o n f i s h a c t i v i t y and a g g r e s s i o n were measured, u s i n g t h e same methods u s e d above. The amount of a c t i v i t y was s i g n i f i c a n t l y g r e a t e r i n l a r g e compartments t h a n i n s m a l l compartments (Table 5 ) . No d i f f e r e n c e between r e p l i c a t e s o c c u r r e d . The a c t i v i t y means were s i m i l a r t o t h e i r c o u n t e r p a r t measured i n t h e c o n t r o l t r e a t m e n t i n t h e growth s t u d y (Table 6 ) . There was a s i g n i f i c a n t d i f f e r e n c e o f l o s s i n w e i g h t and l e n g t h a t t h e f i v e p e r c e n t p r o b a b i l i t y l e v e l between t h e two time p e r i o d s (Table 7 ) . The l o s s o f o r i g i n a l w e i g h t was 16.7, 15.4 and 12.0 p e r c e n t f o r l a r g e , medium and s m a l l compartments r e s p e c t i v e l y . The l o s s i n l e n g t h o f t h e f i s h may be due t o r e a b s o r p t i o n o f c e n t r a l d i s c s . The f i s h were weighed and measured a f t e r 45 d a y s . An a n a l y s i s o f v a r i a n c e t e s t o f l e n g t h and w e i g h t demonstrated t h a t no s i g n i f i c a n t d i f f e r e n c e o c c u r r e d between r e p l i c a t e s . E f f e c t o f f i s h s i z e No c o r r e l a t i o n s were found between f i s h s i z e , compartment s i z e , t h e number o f chases and f l e e s , and t h e amount o f a c t i v i t y - 22 -ANALYSIS OF VARIANCE - f o r a c t i v i t y o f s t a r v e d f i s h SOURCE DF SUM SQ. MEAN SQ. F PROB. S i z e 2 8042.2 4021.1 74.93 -0.0 1 15.696 15.696 0.29 0.5994 E r r o r 26 1395.3 53.665 T o t a l 29 9453.2 MEANS S i z e X N R e p l i c a t e X N La r g e 66.2300 10 44.6733 15 Medium 38.2700 10 43.2267 15 S m a l l 27.3500 MEANS AND S.E. OF PERCENTAGE ACTI.VITY R e p l i c a t e 1 La r g e X S.D. N Medium X S.D. N S m a l l X S.D. N 67.7399 8.1071 5 39.400 9.3989 5 26.8800 5.0247 5 R e p l i c a t e 2 L a r g e Medium S m a l l X S.D. N X S.D. N X S.D. N 67.7200 9.1610 5 37.1400 7.7569 5 27.8200 4.4623 5 GRAND MEAN 43.9500 T a b l e 5. A c t i v i t y i n s t a r v a t i o n t r e a t m e n t . - 23 -ANALYSIS OF VARIANCE - of activity for all treatments and compartments SOURCE Size Treatment Replicate Error Total DF 2 3 1 113 119 SUM SQ. 36124. 3641. 3 17. 480 12970. 52753. MEAN SQ. 18062. 1213. 8 17.480 114. 78 157. 36 10. 57 0. 15 PROB. -0. 0 0. 0000 0. 6980 MEANS Size X N Treatment Replicate X N X N GRAND MEAN Large 71. 7975 40 Control 43. 3400 30 Left 48. 1367 60 48. 5183 Medium 43.5950 40 Shallow 50. 3967 30 Right 48. 9000 60 Small 30. 1625 40 Mirror 43.6267 30 Density 56.7100 30 MEANS AND S. E. Compartments Replicate 1 Control Shallow Mirror Density Replicate Control Shallow Mirror Density-Large X SE N 64.3799 8.5111 5 71.4600 4.4666 5 69. 0199 4. 3355 5 82. 0199 7. 0443 5 65. 2200 12. 2824 5 67. 2400 16. 9660 5 66. 2000 17. 6121 5 88. 8399 3. 3276 5 Medium X 35.5200 46.0000 42.7400 SE 6. 7747 6. 5910 8. 7059 50. 9800 12. 7106 41.6000 8.9911 49. 5400 8. 3539 26. 9200 12. 7551 55. 4600 10. 1450 N 5 5 5 5 Small X 25. 5400 32. 4600 33.0400 24.4800 SE 6. 4225 6. 5508 11. 1697 12. 9471 N 5 5 5 5 27.7800 5.4473 5 35. 6800 11. 2879 5 23. 8400 14. 0279 5 38.4800 8.6918 5 Table 6. Ana lys i s of f i s h a c t i v i t y on day 118. - 24 -ANALYSIS OF VARIANCE - of starved fish length at Day 1 and Day 45 SOURCE Size R e p l i c a t e Time Er r o r Total DF 2 1 1 SUM SQ. 0. 19847 0. 01719 0.79555 502 31.418 508 32.415 MEAN SQ. 0. 09924 0. 01719 0. 79555 0. 62585D-01 1. 59 0. 27 12. 71 PROB. 0. 2039 0. 6070 0. 0005 MEANS - LENGTH Size X N Replicate Time X N X N SizexTime Day 1 Day 45 X N X N Large 3.6801 357 3. 6858 257 Day 1 3. 7307 257 Large 3.7210 177 3. 6398 180 Medium 3. 72 85 111 3. 6975 252 Day 2 3. 6517 252 Medium 3. 7636 58 3.6900 53 Small 3.6922 41 Small 3. 7223 22 3. 6574 19 GRAND MEAN 3. 6916 ANALYSIS OF VARIANCE - of starved fish weight at Day 1 and Day 45 SOURCE Size R e p l i c a t e Time E r r o r Total DF 2 1 1 SUM SQ. 1. 9283 0. 03215 19. 903 502 87.280 508 108.98 MEAN SQ. 0. 96416 0. 03215 19. 903 0. 17386 5. 55 0. 18 114. 47 PROB. 0. 0043 0. 6707 -0. 0 MEANS - WEIGHT Size X N Replicate Tit X N X N SizexTitr.e Day 1 X N Day 45 X N Large 2. 2272 357 . 2709 257 Day 1 2. 4588 257 Large 2. 4299 177 2. 0278 180 Medium 2. 3781 111 2. 2550 252 Day 2 2. 0633 .252 Medium 2.5679 58 2. 1704 53 Small 2.2629 41 Small 2.4032 22 2. 1005 19 GRAND MEAN 2. 2630 T a b l e 7. A n a l y s i s o f v a r i a n c e f o r l e n g t h and w e i g h t o f s t a r v e d f i s h on day 1 and day 45. - 25 -w i t h i n and between t r e a t m e n t s . E f f e c t o f a g g r e s s i o n The e f f e c t o f a g g r e s s i o n on growth i s not c o m p l e t e l y known. I n i t i a l b e h a v i o u r r e s u l t s , on day 86, i n d i c a t e d t h a t a g g r e s s i o n was h i g h , t h e more complete s t u d y on day 118 i n d i c a t e d t h a t a g g r e s s i o n was low (Table 4 ) . O b s e r v a t i o n s o f mouth f i g h t i n g and o t h e r a g g r e s s i v e a c t i v i t i e s were r e c o r d e d w i t h i n s m a l l compartments d u r i n g t h e f i r s t t h i r t y d a y s . On one o c c a s i o n mouth f i g h t i n g was o b s e r v e d i n a medium s i z e d compartment. A t r e n d o f d e c r e a s i n g a g g r e s s i o n i n s m a l l compartments w i t h t i m e t o o k p l a c e , perhaps t h r o u g h c o n d i t i o n i n g . GROWTH BETWEEN TREATMENTS A growth d i f f e r e n c e between t r e a t m e n t s has been demonstrated and no one f a c t o r appeared t o be t o t a l l y r e s p o n s i b l e . The e f f e c t s o f a c t i v i t y , a g g r e s s i o n and n e a r e s t n e i g h b o u r d i s t a n c e were examined. E f f e c t o f a c t i v i t y Mean f i s h a c t i v i t y was compared between t r e a t m e n t s . The a c t i v i t y mean o f 57 p e r c e n t o f t h e d e n s i t y t r e a t m e n t was shown t o be s i g n i f i c a n t l y d i f f e r e n t a t a f i v e p e r c e n t p r o b a b i -l i t y l e v e l from t h e c o n t r o l t r e a t m e n t o f 43 p e r c e n t (Table 6 ) . The d i s s o l v e d oxygen c o n c e n t r a t i o n i n t h e d e n s i t y t r e a t -ment was 2.20 m i l l i g r a m s o f oxygen p e r l i t r e , a l l o t h e r t r e a t -ments had a range o f 3.95 - 4.10 m i l l i g r a m s o f oxygen p e r l i t r e , ( F i g u r e 1 ) . The lo w e r oxygen a v a i l a b i l i t y was l i k e l y t o be due t o biomass i n c r e a s e and h i g h e r a c t i v i t y ; each may have - 26 -red u c e d growth. The measured mean a c t i v i t y o f t h e m i r r o r (44 p e r c e n t ) and c o n t r o l (43 p e r c e n t ) t r e a t m e n t s were s i m i l a r , b u t growth i n t h e m i r r o r t r e a t m e n t was l e s s ( F i g u r e s 6, 7 and 8 ) . I n t h e s h a l l o w t r e a t m e n t t h e mean a c t i v i t y was 50 p e r c e n t and t h e growth was a l s o h i g h e r . E f f e c t o f a g g r e s s i o n There i s a s u g g e s t i o n from i n i t i a l b e h a v i o u r measure-ments on day 84 t h a t a g g r e s s i o n was g r e a t e r i n s m a l l e r compart-ment s i z e s o f t h e c o n t r o l t r e a t m e n t t h a n i n t h e s h a l l o w t r e a t -ment (Table 4 ) . A g g r e s s i o n i n s m a l l c o n t r o l compartments was low and no d a t a f o r t h e s h a l l o w l a r g e compartments were c o l l e c t e d a t t h e t i m e b u t from g e n e r a l o b s e r v a t i o n appeared t o be l o w e r . I f t h i s i s t r u e t h e n a g g r e s s i o n was h i g h e r i n c o n t r o l t r e a t m e n t s t h a n i n s h a l l o w t r e a t m e n t s a t t h a t t i m e . A l a t e r s t u d y showed no d i f f e r e n c e between t r e a t m e n t s . The p o s s i b l e i n f l u e n c e o f c o n d i t i o n i n g i s d i s c u s s e d l a t e r . E f f e c t o f n e a r e s t n e i g h b o u r d i s t a n c e Growth d i f f e r e n c e s between t r e a t m e n t s e x i s t e d ( F i g u r e s 6, 7 and 8 ) . One v a r i a b l e between c o n t r o l and s h a l l o w t r e a t -ments were d i f f e r e n c e s i n compartmental shape, w h i c h may e f f e c t g rowth. I t was p o s t u l a t e d t h a t t h e g r e a t e r s u r f a c e a r e a o f t h e s h a l l o w t r e a t m e n t would i n c r e a s e n e a r e s t n e i g h b o u r d i s t a n c e and reduce i n t e r a c t i o n . T h i s l e a d t o s p e c u l a t i o n t h a t n e a r e s t n e i g h b o u r d i s t a n c e might e f f e c t growth, perhaps t h r o u g h a g g r e s s i o n . Photographs o f f i s h were used t o determine t h e d i s t a n c e o f n e a r e s t n e i g h b o u r s . - 27 -The mean n e a r e s t n e i g h b o u r d i s t a n c e i n the s h a l l o w t a n k was g r e a t e r t h a n t h e c o n t r o l ; i n t h e d e n s i t y t a n k i t was l o w e s t . The apparent n e a r e s t n e i g h b o u r d i s t a n c e s (the d i s t a n c e s between a f i s h and i t s n e a r e s t n e i g h b o u r o r m i r r o r image w h i c h e v e r was c l o s e s t ) i n t h e m i r r o r e d t r e a t m e n t were s m a l l e r t h a n t h e r e a l d i s t a n c e s between f i s h (Table 8 ) . Method u s e d t o d e t e r m i n e n e a r e s t n e i g h b o u r d i s t a n c e A shadow was produced b y a l i g h t s o u r c e a t a known p o s i t i o n . The d i s t a n c e between a f i s h image and i t s shadow was used t o c a l c u l a t e t h e f i s h p o s i t i o n i n t h r e e c o - o r d i n a t e s , from w h i c h n e a r e s t n e i g h b o u r d i s t a n c e s may be c a l c u l a t e d . The method used i s s i m i l a r t o t h a t d i v i s e d by C u l l e n e t a l . U964) . GROSS ENERGETICS A c t i v i t y may a f f e c t f i s h growth (Table 7) and account or p a r t l y a c c o u n t f o r t h e growth d i f f e r e n c e between and w i t h i n t r e a t m e n t s . The t o t a l l o s s i n w e i g h t between t h e l a r g e , medium, and s m a l l t r e a t m e n t s i n grams p e r k i l o g r a m p e r day w h i l e under s t a r v a t i o n was L a r g e Medium S m a l l D i f f e r e n c e L o ss i n Gms/Kg p e r day 8.94 8.83 6.73 2.21 G a i n i n Gms/Kg per day 8.89 10.00 18.27 9.38 % A c t i v i t y / 5 M i n u t e s 66% 38% 27% 39% I n t h e c o n t r o l w e i g h t g a i n was c a l c u l a t e d from f e d f i s h . I have assumed t h a t energy r e q u i r e m e n t s are t h e same f o r s t a r v e d and f e d f i s h , b u t Beamish (1964) has shown t h a t energy r e q u i r e m e n t s a r e o f t e n l e s s when s t a r v e d . - 28 -D i s t a n c e i n C e n t i m e t e r s C o n t r o l S h a l l o w M i r r o r Dens. 0-1 1-2 4 2 ( I D * 6 2-3 4 1 5 (8) 16 3-4 11 2 20 (9) 23 4-5 15 4 19 (9) 6 5-6 8 10 5 (4) 3 6-7 18 8 4 (1) 7-8 6 12 3 (3) 8-9 5 12 2 9-10 2 5 1 10-11 1 1 1 11-12 1 3 12-13 .1 N 67 59 53 (45) 54 X 6.01 7 .47 5 . 53 (3 .58) 3 Ta b l e 8. N e a r e s t n e i g h b o u r d i s t a n c e s f o r l a r g e compartments o f treatments""on day 122. Apparent n e a r e s t n e i g h b o u r d i s t a n c e o f f i s h i n m i r r o r e d compartments matched w i t h i t s m i r r o r image o r i t s n e a r e s t n e i g h b o u r w h i c h e v e r was c l o s e r . Measured on day 86. - 29 -Spoor (1946) demonstrated a c o r r e l a t i o n o f a c t i v i t y and oxygen consumption above t h e b a s i c m e t a b o l i c r a t e ; c o n s e q u e n t l y I have assumed t h a t t h e b a s a l m e t a b o l i c r a t e i s c o n s t a n t w i t h i n a l l t r e a t m e n t s and compartment s i z e s . The 39 p e r c e n t d i f f e r e n c e i n a c t i v i t y o f 66 p e r c e n t and 27 p e r c e n t i s e q u i v a l e n t t o 2.21 grams per k i l o g r a m p e r day. I f one assumes t h a t a c t i v e m e t a b o l i s m i s d i r e c t l y p r o p o r t i o n a l t o a c t i v i t y , t h e n each one p e r c e n t o f a c t i v i t y i s assumed t o be e q u i v a l e n t t o 0.059 grams per k i l o g r a m p e r day. T h i s i s o b t a i n e d b y d i v i d i n g 2.21 b y 39. The energy c a l c u l a t e d , t h a t i s u s ed i n l a r g e compartments i s 66 t i m e s 0.059 w h i c h i s 3.73 and i n s m a l l compartments i s 1.53 grams p e r k i l o g r a m p e r day. I d e f i n e d maintenance c o s t as t h e amount o f energy o t h e r t h a n a c t i v i t y u s ed i n c a t a b o l i s m ( F i g u r e 1 0 ) . Maintenance was found by s u b t r a c t i o n from Loss i n growth ( C a t a b o l i s m ) = Maintenance + A c t i v i t y , t o be: 5.20 gms/kg p e r day 6.68 gms/kg p e r day 5.20 gms/kg p e r day i n l a r g e , medium, and s m a l l compartments r e s p e c t i v e l y . F i s h n ot under s t a r v a t i o n have f u r t h e r energy e x p e n d i t u r e f o r : D i g e s t i o n , A s s i m i l a t i o n on f o o d , I n c r e a s e i n a c t i v i t y d u r i n g and a f t e r f e e d i n g , and A g g r e s s i o n a f t e r f e e d i n g . % ACTIVITY. Figure 10. An estimation of energy cost. - 31 -S t a r v e d f i s h had t h e same mean measured a c t i v i t y f o r compartments as t h e c o n t r o l t r e a t m e n t , 66 p e r c e n t ( l a r g e ) , 37 p e r c e n t (medium) and 27 p e r c e n t ( s m a l l ) . The t o t a l energy e x p e n d i t u r e i n gms/kg per day i s p r e s e n t e d i n T a b l e 9. I t was assumed t h a t maintenance was c o n s t a n t i n a l l t r e a t m e n t s because w a t e r t e m p e r a t u r e and q u a l i t y were t h e same, and e s t i m a t e s o f maintenance o f t h e c o n t r o l were used t o c a l c u l a t e t o t a l energy r e q u i r e m e n t s o f f i s h i n compartments and t r e a t m e n t s (Table 9 ) . The v a l u e f o r t o t a l energy c o s t i n medium compartments i s h i g h e r t h a n e x p e c t e d ( F i g u r e 1 0 ) . A l l e s t i m a t e s o f a c t i v i t y energy c o s t f o r t r e a t m e n t s were e x t r a p o l a t e d from d i f f e r e n c e s between l a r g e and s m a l l compart-ment v a l u e s . The h i g h v a l u e o f t h e medium compartments may have been due t o : 1) V a r i a n c e between compartmental s i z e s r e g a r d i n g a d d i t i o n a l e nergy expenses, 2) F i s h a c t i v i t y i n l a r g e r compartment s i z e s demanding more energy. There was a g r e a t e r swimming space i n l a r g e r compart-ments, s h a r p t u r n i n g would be e x p e c t e d t o have been reduced, b u t h i g h e r v e l o c i t i e s may have been m a i n t a i n e d . B r e t t (1968) has c l e a r l y demonstrated t h a t i n Onchorhynchus an i n c r e a s e i n swimming speed caused h i g h e r energy e x p e n d i t u r e . 3) I n a d e q u a t e l y measured a c t i v i t y . Growth Maintenance Activity-Additional Expenses Total - 32 -CONTROL Large 8.89 5. ZO 3. 73 17.82 + Medium 10.00 6.68 2.15 + 18 . 8 3 + Small 18. 27 5. 20 1.53 +_ 25.00+ Growth Maintenance Activity Additional Expenses Total SHALLOW Large 10.49 5. 20 3.89 + 19.591 + Medium 12.35 6.68 2. 70 + 21. 74 + Small 14. 57 5*20 1 .93 + 21. 69 + Growth Maintenance Activity Additional Expenses Total MIRROR Large 6. 79 5. 20 3.82 + 15.81 + Medium 9.01 6.68 1 .97 + 17.67 + Small 9. 75 5.20 1 .61 + 16.56 + Growth Maintenance Activity Additional Expenses Total DENSITY Large 2.96 5.20 4.84 + Medium 6.05 6.68 3.01 + 13.00 + 15. 75 + Small 7. 28 5. 20 1 . 78 + 14.27 + Ta b l e 9. Gross e n e r g e t i c s f o r t r e a t m e n t s and compartments • . v e x p r e s s e d in'grams p e r ^ k i i o g r a m per day,. - 33 -DISCUSSION Many factors e f f e c t f i s h growth and differences i n growth have been attributed to temperature, pH, density or oxygen a v a i l a b i l i t y . Subtle factors causing change i n growth have not been examined f u l l y and may be more s i g n i f i c a n t than o r i g i n a l l y suspected, for example the influence of pond space on f i s h growth. The e f f e c t of space on growth was studied i n compartments and treatments. GROWTH IN COMPARTMENTS The growth rate of A. pulcher at constant density i n small compartments i s s i g n i f i c a n t l y greater at the 95 percent confidence l i m i t than i n larger compartments (Table 2). This difference may be due to the higher a c t i v i t y i n larger compartments. A c t i v i t y was the only variable that could be iso l a t e d i n terms of energy l o s t from the t o t a l energy budget. Differences i n the t o t a l energy estimates are greater between treatments than between compartments, with the except-ion of the small control compartment. In t h i s study, a c t i v i t y included aggression. Brett and Sutherland (1964) demonstrated that aggressive behaviour i n Lepomis gibbosus (Linnaeus) demanded as muchnas h a l f the t o t a l energy of the most active periods recorded. The e f f e c t of aggression on growth consequently can not be eliminated. No c o r r e l a t i o n of aggression with compartment size was found i n my preliminary and f i n a l behaviour measurements. The volumes and surface areas of compartments have a ration:of 9:3:1. Differences i n growth could be attributed to r e l a t i v e - 34 -d i f f e r e n c e s i n compartmental shape. The c o n t r o l compartments have a g r e a t e r d epth t o s u r f a c e a r e a r a t i o and have l o w e r growth t h a n t h e s h a l l o w compartments, i f t h i s t r e n d o c c u r r e d i n a l l t r e a t m e n t s t h e n growth i n s m a l l e r compartments where t h e depth t o s u r f a c e a r e a r a t i o n - i s g r e a t e r would be e x p e c t e d t o be l e s s , b u t i t i s n o t . Chen and Prowse (1964) s u g g e s t e d t h a t t h e c i c h l i d T i l a p i a mossambica i n l a r g e compartments grew l a r g e r because f i s h i n s m a l l compartments u s e d up more energy t h r o u g h a g g r e s s i o n . T h e i r r e s u l t s d i f f e r from t h o s e i n t h i s s t u d y . T h i s may be due t o t h e i r use o f l a r g e r o u t d o o r ponds, w h i c h were n o t c o n s i s t e n t i n d e p t h and were s u b j e c t t o e n v i r o n m e n t a l change. T h e i r f i s h were grown t o m a t u r i t y and t h o s e f i s h t h a t d i e d were n ot r e p l a c e d , so a d i f f e r e n t i a l m o r t a l i t y may have o c c u r r e d w i t h i n t h e d i f f e r e n t pond s i z e s . The ponds c o u l d a l s o have had d i f f e r e n t l e v e l s of p l a n t p r o d u c t i v i t y w i t h i n them. GENERAL ACTIVITY AND ITS CAUSE The d i f f e r e n c e o f mean a c t i v i t y between s t a r v e d and c o n t r o l t r e a t m e n t s , b e f o r e f e e d i n g , was n o t s i g n i f i c a n t . F i s h a c t i v i t y was s i g n i f i c a n t l y g r e a t e r i n l a r g e compartments ( F i g u r e 6) . Three p o s s i b i l i t i e s e x i s t f o r g r e a t e r f i s h a c t i v i t y i n l a r g e r compartments: 1) Swimming space. The l a r g e r compartment o f each t r e a t m e n t p r e s e n t s a g r e a t e r t o t a l volume f o r each i n d i v i d u a l f i s h t o swim i n t h a n a s m a l l compartment a t t h e same s t o c k i n g d e n s i t y ; as a r e s u l t a c t i v i t y i n t h e l a r g e r i s g r e a t e r . - 35 -2) S o c i a l h i e r a r c h y . F i s h may r e c o g n i z e each o t h e r i n d i v i d u a l l y , p a r t i c u l a r l y when numbers a r e s m a l l . When f i s h numbers i n c r e a s e , r e c o g n i t i o n d e c r e a s e s . S m a l l numbers o f f i s h e s t a b l i s h a h i e r a r c h y where t h e dominant f i s h e s a r e f r e q u e n t l y t h e l a r g e s t . Dominant f i s h u s u a l l y h o l d t e r r i t o r -i e s , and r e s t r i c t t h e a v a i l a b l e w a t e r space p e r i n d i v i d u a l f i s h . These dominance systems p r o b a b l y d i s s o c i a t e w i t h an i n c r e a s e i n f i s h number. 3) T e r r i t o r i a l i t y . F i s h may e s t a b l i s h t e r r i t o r i e s , f o r w h i c h r e f e r e n c e p o i n t s are n e c e s s a r y . Compartments had f o u r c o r n e r s w h i c h were o f t e n defended by f i s h . I n s m a l l compartments f i s h dominated t h e bottom. F i s h w i t h o u t t e r r i t o r i e s wander more t h a n t h o s e w i t h t e r r i t o r i e s . A c t i v e f i s h would t h e n be found i n compartments where fewer t e r r i t o r i e s e x i s t e d . A l l t h r e e e f f e c t s may be i n v o l v e d , b u t t h e most i m p o r t a n t s i n g l e f a c t o r i s p r o b a b l y a v a i l a b l e swimming space. E v i d e n c e f o r t h e o t h e r two t h e o r i e s e x i s t . The range o f s t a n d a r d l e n g t h i n s m a l l compartments was as g r e a t and o f t e n g r e a t e r t h a n l a r g e compartments (Tables 10 and 1 1 ) . T h i s i n d i c a t e s t h a t a h i e r a r c h y i s p r o b a b l y p r e s e n t i n t h e s m a l l compartments. Dominance o f f i s h has been o b s e r v e d . A g g r e s s i v e f i s h d u r i n g t h e growth e x p e r i m e n t dominated t h e f l o o r o f s m a l l compartments, w h i l e s m a l l s u b s e r v i e n t i n d i v i d u a l s o c c u p i e d t h e h i g h e r r e g i o n s o f t h e w a t e r column and r e g u l a r l y a v o i d e d o t h e r f i s h t h a t chased them. The second and t h i r d l a r g e s t f i s h , were u s u a l l y a c c e p t e d near t h e bottom t h r o u g h - 36 -Treatments Length in m i l l i m e t e r s L a r g e C o n t r o l Medium S m a l l L a r g e Shallow Medium Smal 27-28 0.6 28-29 0 1.8 29-30 1.1 1.8 0.6 30-31 2.3 1.8 0.6 31-32 2.9 5.4 5.0 0 3.6 32-33 5.2 •5.4 0 1.7 0 33-34 10.9 3.6 5.0 2.3 0 34-35 12.6 10.7 5.0 6.7 10. 7 35-36 9.8 5.4 0 7.9 7.1 40.0 36-37 9.2 8.9 0 11.2 1.8 0.0 37-38 5.2 12.5 10.0 8.4 14.3 0 38-39 5. 7 3.6 0 10.1 7.1 15.0 39-40 7.5 3.6 10.0 7.9 7.1 5.0 40-41 5.7 8.9 5.0 7.9 7.1 0 41-42 2.9 5.4 0 10.1 10. 7 5.0 42-43 5.2 1.8 0 5.1 5.4 5.0 43-44 4.0 1.8 5.0 8.4 ,1.8 10.0 44-45 2.3 5.4 10.0 2.8 7.1 5.0 45-46 2.9 3.6 5.0 1.1 3.6 0 46-47 0.6 U 8 5.0 2.3 1.8 0 47-48 1.1 1.8 5.0 2. 3 0 5.0 48-49 0.6 3.6 0 2.3 3.6 0 49-50 0.6 0 5.0 0 1.8 5.0 50-51 0 10.0 0.6 1.8 0 51-52 1.8 5.0 0 0 0 52-53 5.0 0 3.6 5.0 53-54 5.0 1.7 T a b l e 10. Length frequencies of f i s h within compartments for treatments expressed as a percentage of total number of f i s h f o r each compartment s i z e . Length in millimeters 27- 28 28- 29 29- 30 30- 31 31- 32 32- 33 33- 34 34- 35 35- 36 36- 37 37- 38 38- 39 39- 40 40- 41 41- 42 42- 43 43- 44 44- 45 45- 46 46- 47 47- 48 48- 49 49- 50 50- 51 - 37 -TREATMENTS MIRROR Large Medium Small 1. 3 0.6 5.8 3.9 3.8 1.9 7. 7 5.9 6.4 9.8 5.0 9.6 3.9 0 7.1 0 5.0 5.8 3.9 10.0 6.4 0 10.0 9.6 5.9 10.0 9.0 7.8 0 4.5 3.9 5.0 1.9 5.9 5.0 4. 5 5.9 5.0 5.8 3.9 10.0 2.6 1.9 10.0 3.2 1.9 20.0 0.6 3.9 5.0 0 0 0 1.9 0.6 DENSITY Large Medium Small 1.0 2.2 2.4 2. 2 4. 7 4.4 11.1 4.4 2.7 8.4 5.5 5.4 10.1 9.9 8.1 7.1 3.3 5.4 11.1 ,7. 7 2. 7 7.8 7. 7 8.1 8.1 10.1 10.8 5.4 5.5 8.1 6.1 4. 4 2.7 3.7 5.5 5.4 1.3 6.6 2.7 4.4 7. 7 2.7 1. 3 4.4 5.4 1.0 2.2 10.8 0.7 0 8.1 0.3 1.1 2.7 2.0 2.2 2.7 0.3 1.1 0 0.3 0 0 0 0 1.1 5.4 Table 11. Length frequencies of fish within compartments for treatments expressed as a percentage of total number of fish for each compartment size. - 38 -"appeasement" a c t i v i t y . Kodama (1963) i n h i s s t u d i e s on growth and b e h a v i o u r on t h e s a l m o n o i d f i s h P l e c o g l o s s u s  a l t i v e l i s , Temminck e t S c h l e g e l , found t h a t t e r r i t o r i a l i t y was p o s i t i v e l y c o r r e l a t e d w i t h f i s h g r o w t h . T h i s s i t u a t i o n appears t o o c c u r i n t h e s m a l l compartments i n my s t u d y . Kodama u s e d s m a l l samples o f s i x f i s h each, and under t h e s e c o n d i t i o n s f i s h r e c o g n i t i o n may have enhanced t h e growth d i f f e r e n c e s t h r o u g h t h e s o c i a l mechanism. He o b s e r v e d t h a t t h e s m a l l e s t f i s h were f r e q u e n t l y t h e t a r g e t o f o t h e r f i s h . I n my l a r g e compartments f i s h t e r r i t o r i e s were l e s s e s t a b l i s h e d and a s o c i a l h i e r a r c h y was l e s s a p p arent t h a n i n s m a l l compart-ments. Kodama (1963) has shown t h a t growth i s r e l a t e d t o dominance, t h e most dominant f i s h b e i n g t h e l a r g e s t . The l e n g t h f r e q u e n c i e s o f Aequidens pulcher ( T a b l e s 10 and 11) i n d i c a t e t h a t t h e same r e l a t i v e numbers o f l a r g e f i s h o c c u r i r r e s p e c t i v e o f t h e compartment s i z e . The i d e a t h a t a s o c i a l h i e r a r c h y i s p r e s e n t i n compartments i s enhanced by t h e s m a l l e r l e n g t h f r e q u e n c y range found i n m i r r o r e d compartments (Table 1 1 ) , where t h e s o c i a l h i e r a r c h y i s not as s t r o n g , presumably due t o t h e m i r r o r s w h i c h r e s t r i c t t h e f i s h e s a b i l i t y t o e s t a b l i s h t e r r i t o r i a l r e f e r e n c e p o i n t s . GROWTH IN TREATMENTS D i f f e r e n c e s between t r e a t m e n t s e x i s t , b u t no s i n g l e f a c t o r appears t o be r e s p o n s i b l e f o r t h e d i f f e r e n c e s . The f o l l o w i n g t h r e e h y p o t h e s e s a r e p r e s e n t e d t o e x p l a i n t h e r e s u l t s between t r e a t m e n t s : 1) That a c t i v i t y i s r e s p o n s i b l e f o r growth d i f f e r e n c e s , - 39 -2) That s t r e s s i s r e s p o n s i b l e f o r r e d u c i n g growth, and 3) That a s m a l l e r n e a r e s t n e i g h b o u r d i s t a n c e causes growth t o be r e d u c e d . 1) A c t i v i t y There i s a d i f f e r e n c e i n a c t i v i t y between t r e a t m e n t s , p a r t i c u l a r l y between l a r g e compartments o f t h e c o n t r o l w i t h 66 p e r c e n t and d e n s i t y t r e a t m e n t w i t h 86 p e r c e n t a c t i v i t y . I n t h e d e n s i t y t r e a t m e n t , t h e i n c r e a s e d a c t i v i t y may be i n r e s p o n s e t o t h e r e d u c e d oxygen a v a i l a b i l i t y . The d e c r e a s e i n oxygen i s due t o an i n c r e a s e i n biomass, b u t whether t h e a c t i v i t y i n c r e a s e i s due t o t h e l o w e r a v a i l a b i l i t y of t h e oxygen, t h e s m a l l e r n e a r e s t n e i g h b o u r d i s t a n c e o r t h e i n c r e a s e i n biomass i s not known. M c F a r l a n d and Moss (1967) have s u g g e s t e d t h a t i n a f i s h s c h o o l , M u g i l , p r e s e n t i n a r e g i o n where c o n c e n t r a t i o n s o f d i s s o l v e d oxygen a r e low, t e n d t o move t o a r e g i o n where the c o n c e n t r a t i o n i s h i g h e r . The a c t i v i t y o f m u l l e t i n c r e a s e s and t h e i r b e h a v i o u r changes w i t h l o w e r d i s s o l v e d oxygen a v a i l a b i l i t y and f i s h d e n s i t y . The b e h a v i o u r i n t h e d e n s i t y t r e a t m e n t i s s i m i l a r t o t h a t d e s c r i b e d i n t h e h i g h d e n s i t y r e g i o n o f a m u l l e t s c h o o l . Whitmore e_t a l . (1960) demonstrated a v o i d a n c e of h i g h c a r b o n d i o x i d e l e v e l s i n c e r t a i n s a l m o n i d s and c e n t r a r c h i d s . Jones (1952) showed t h a t G a s t e r o s t e u s , P hoxinus and Salmo i n c r e a s e d a c t i v i t y when f i s h e n t e r e d an a r e a o f low d i s s o l v e d oxygen c o n c e n t r a t i o n . T h i s a c t i v i t y r e s p o n s e t o low oxygen l e v e l s i s r a p i d . H i g h a c t i v i t y i n d e n s i t y t a n k s c o u l d be r e l a t e d t o low d i s s o l v e d oxygen - 40 -concentration. The s e l e c t i v e advantage of t h i s mechanism would be s i m i l a r to the reaction of the crustacean P o r c e l l i o  scaber to humidity (Gunn 1937). A higher a c t i v i t y of 50 percent occurred i n the shallow tank. This increase i n a c t i v i t y may have been due to an increase i n the available horizontal swimming area by a l t e r a t i o n of the tank shape. The e f f e c t of nearest neighbour distance might also be responsible. 2) Stress No difference i n a c t i v i t y or aggression between mirrored and control treatments existed. The growth rate i n the mirror treatment was lower than i n the control, and no other e f f e c t s were observed between treatments that were studied. The only variable was the presence of mirrors on the walls of the compartments which may have caused a growth i n h i b i t i n g e f f e c t , perhaps from stress caused by a small apparent nearest neighbour distance (Table 8). B i l t o n and Robins (1970, 1971) studied the growth of Oncorhynchus nerka (Walbaum) 1972, and found the rate of growth i n a mirrored tank was lower than i n a control without mirrors. They speculated that lower growth i n the mirrored tank was possibly due to increased a c t i v i t y , which has not been demostrated for A. pulcher. The length frequency range i n mirrored compartments i s less than the control, p a r t i c u l a r l y for small compartments (Tables 10 and 11). This may be because of three reasons: 1) The apparent number of f i s h present i n small compartments i s greater than the f i s h can recognize. This could tend to dissolve the s o c i a l hierarchy i n that compartment. - 41 -2) The e s t a b l i s h i n g o f a r e f e r e n c e p o i n t f o r t e r r i t o r i a l f u n c t i o n s may be e f f e c t e d , because t h e m i r r o r produces a p p a r e n t i n f i n i t e s p a c e . 3) The image o f each f i s h p r e s e n t s a f i s h e q u a l i n s o c i a l s t a t u s , w h i c h may cause added s t r e s s . I t i s n o t c e r t a i n i f any o f t h e s e e x p l a n a t i o n s were i n o p e r a t i o n . I f one o f t h e s e f a c t o r s was i n v o l v e d , t h e mechr anism t h r o u g h w h i c h i t a c t s may be s u p p r e s s i o n o f a g g r e s s i o n , c a u s i n g s t r e s s . The l o w e r growth' r a t e i n m i r r o r e d compartments i s n o t a d i r e c t r e s u l t o f f i s h b e h a v i o u r b u t i s p r o b a b l y due t o some e n d o c r i n a l d i s t u r b a n c e caused by v i s u a l s t r e s s . B i l t o n and Robins (1970, 1971) su g g e s t t h a t r e d u c e d growth i n 0. n e r k a may be due t o imposed s t r e s s w i t h i n t h e m i r r o r e d compartments. The o n l y documented i n f o r m a t i o n o f s t r e s s on a n i m a l growth i s i n mammals. S e l y e (1956) s t a t e s t h a t s t r e s s may a f f e c t t h e r a t e o f growth i n i n d i v i d u a l s . " I f c h i l d r e n a r e exposed t o h i g h l e v e l s o f s t r e s s , t h e s t r e s s i t s e l f can a f f e c t t h e growth o f t h e body as a whole." D a v i d and C h r i s t i a n (1957) and Gorbman (1959) have shown t h a t i n mammals a d r e n a l w e i g h t and s o m a t i c growth were r e l a t e d t o s o c i a l r a n k , i n d i c a t i n g t h a t hormonal a c t i v i t y had a n e g a t i v e feedback e f f e c t on growth. Hormones t h a t might be r e s p o n s i b l e f o r t h i s a r e ACTH ( A d r e n o c o r t i c o t r o p h i c hormone) from the a n t e r i o r l o b e o f t h e hypothalamus and COL ( C o r t i s o l ) o f t h e a d r e n a l g l a n d . T u r n e r ' s (1955) d e f i n i t i o n o f s t r e s s i s - 42 -"a h a r m f u l c o n d i t i o n r e s u l t i n g from t h e i n a b i l i t y o f t h e org a n i s m t o m a i n t a i n an adequate i n t e r n a l e q u i l i b r i u m . " T h i s d e f i n i t i o n i s g e n e r a l b u t adequate t o d e s c r i b e s t r e s s s h o u l d i t o c c u r w i t h i n m i r r o r e d compartments. Because s t r e s s has no p r e c i s e b i o l o g i c a l i n t e r p r e t a t i o n , i t i s n o t always p o s s i b l e t o de t e r m i n e when an a n i m a l i s under s t r e s s . I t i s q u i t e p o s s i b l e t h a t s t r e s s e f f e c t s have been i n t e r p r e t e d as b e i n g due t o some o t h e r cause. 3) I n d i v i d u a l d i s t a n c e The n e a r e s t n e i g h b o u r d i s t a n c e and growth i s g r e a t e r and a c t i v i t y i s h i g h e r i n t h e s h a l l o w t r e a t m e n t compared t o th e c o n t r o l . I t i s d i f f i c u l t t o see how growth can be g r e a t e r when a c t i v i t y i s h i g h e r u n l e s s some s t r e s s e f f e c t r e l a t e d t o t h e n e a r e s t n e i g h b o u r d i s t a n c e i s i n v o l v e d i n t h e c o n t r o l t r e a t m e n t . I p o s t u l a t e t h a t n e a r e s t n e i g h b o u r d i s t a n c e and a g g r e s s i o n were r e l a t e d a f t e r e x a m i n i n g t h e r e s u l t s o f f i s h b e h a v i o u r on day 86. A l a t e r d e t a i l e d s t u d y on day 118 showed no r e l a t i o n s h i p t o e x i s t . I t i s p o s s i b l e t h a t i f a g g r e s s i o n caused by a s m a l l e r n e a r e s t n e i g h b o u r d i s t a n c e was i n v o l v e d i n t h e c o n t r o l t r e a t m e n t and t h a t a g g r e s s i o n was h i g h e r a t t h a t t i m e , t h e c o n d i t i o n i n g o f t h e f i s h may have caused a g g r e s s i o n t o d e c r e a s e w i t h t i m e . G r a d u a l change i n a g g r e s s i o n may be r e s p o n s i b l e f o r t h e t r e n d i n t h e growth c u r v e found w i t h i n s m a l l c o n t r o l compartments. F i s h were seen t o mouth f i g h t and d i s p l a y d u r i n g t h e f i r s t month o f t h e growth s t u d y w i t h i n c o n t r o l and s h a l l o w compartments; t h i s was not o b s e r v e d a t l a t e r d a t e s . The a p p a r e n t n e a r e s t - 43 -n e i g h b o u r d i s t a n c e (3.58 cms) may have i n f l u e n c e d t h e growth r a t e w i t h i n m i r r o r e d compartments t o be reduced (Table 8 ) . P o t e n t i a l a p p l i c a t i o n o f t h i s work I t i s not p o s s i b l e t o s t a t e whether f i s h i n i n c r e a s i n g l y s m a l l e r compartments w i l l i n c r e a s e t h e i r growth r a t e o r whether f i s h i n l a r g e r compartments w i l l have l o w e r growth r a t e s . An i n c r e a s e towards l a r g e r compartment s i z e s c o u l d however r e s u l t i n d e c r e a s i n g l y l o w e r growth r a t e s t i l l a p o i n t o f a c t i v i t y s a t u r a t i o n i s r e a c h e d . T h i s i s a p o i n t where th e growth o f f i s h a t c o n s t a n t d e n s i t y would not be reduced by f u r t h e r compartmental e n l a r g e m e n t . The g r e a t e s t change i n growth r a t e t a k e s p l a c e a t t h e medium t o s m a l l compartmental l e v e l , and t h i s i s where f u r t h e r i n v e s t i g a t i o n i s needed. A s t u d y o f s m a l l e r compartment s i z e s may a l s o be b e n e f i c i a l . I t i s n o t known i f l a r g e r f i s h i n p r o p o r t i o n a l l y l a r g e r t a n k s would g i v e t h e same t r e n d o f growth r e s u l t s o r n o t . Buss e t a l . (1971) have demonstrated t h a t 7.7 pounds o f Salmo g a i r d n e r i R i c h a r d s o n , can be r e a r e d i n 6.2 pounds o f w a t e r . T h i s m i g h t come c l o s e t o r e p r e s e n t i n g t h e s m a l l e s t compartment s i z e i n r e l a t i o n t o t h e s i z e o f t h e f i s h t h a t c o u l d be u s e d . I t would be d i f f i c u l t f o r t h e f i s h t o undergo a c t i v e and a g g r e s s i v e movements under such c o n f i n e d c o n d i t i o n s . A model u s i n g growth i n grams p e r k i l o g r a m p e r day a g a i n s t compartment s i z e and d e n s i t y can be c o n s t r u c t e d from t h e i n f o r m a t i o n g a t h e r e d i n t h i s s t u d y . An a d d i t i o n a l d i m e n s i o n t h a t i s used i s n e a r e s t n e i g h b o u r d i s t a n c e a t a s p e c i f i c d e n s i t y , o r some f a c t o r w h i c h i s p o s i t i v e l y c o r r e l a t e d w i t h i t . - 44 -T h i s model ( F i g u r e 11) i n d i c a t e s t h a t r e d u c t i o n i n volume a t c o n s t a n t d e n s i t y i n c r e a s e s growth and t h a t i n c r e a s e i n d e n s i t y r e duces growth; presumably a d e c r e a s e i n d e n s i t y w i l l promote g r o w t h . There i s an i n c r e a s e o f n e a r e s t n e i g h b o u r d i s t a n c e w i t h an i n c r e a s e o f growth r a t e . I n m i r r o r e d compartments th e a p p a rent n e a r e s t n e i g h b o u r d i s t a n c e i s s m a l l and so i s th e growth r a t e , i t i s p r o b a b l e t h a t t h e reduced growth i s due t o s t r e s s caused by t h e s m a l l a p p a r e n t n e a r e s t n e i g h b o u r d i s t a n c e . The f i s h Aecpaidens p u l c h e r i s not u s e d i n a q u a c u l t u r e , b u t many c i c h l i d s a r e c u l t i v a t e d . S h o u l d t h e same p r i n c i p l e s a p p l y t o o t h e r f i s h as t h e y do f o r A. p u l c h e r t h e n i t can be e x p e c t e d t h a t f i s h r e a r e d i n s m a l l e r compartments w i l l have g r e a t e r growth because t h e compartment s i z e w i l l c u r b t h e i r a c t i v i t y . The energy used f o r a c t i v i t y i s u t i l i z e d f o r f u r t h e r i n g g r o w t h . T i l t o n and K e l l e y (1971) i n d i c a t e d t h a t growth i n l e t a l u m s p u n c t a t u s (Raf i n e s q u e ) was g r e a t e r w i t h i n cages t h a n w i t h i n l a r g e ponds where t h e d e n s i t y w a s ' l e s s . I n a n i m a l husbandry i t i s found t o be more f e a s i b l e t o l i m i t t h e a c t i v i t y o f p o u l t r y b y u s i n g c a g e s . The same g e n e r a l p r i n c i p l e s may a p p l y t o f i s h c u l t u r e management. F i s h w i t h i n cages would u s u a l l y r e q u i r e s upplementary f e e d i n g and as a r e s u l t i t may n o t be an advantage once economics have been c o n s i d e r e d . Cages f l o a t e d i n moving w a t e r u s u a l l y have an advantage because of good w a t e r q u a l i t y . F i s h i n c u l t u r e a re u s u a l l y s t o c k e d a t h i g h d e n s i t i e s , N e a r e s t n e i g h b o u r d i s t a n c e i n c e n t i m e t e r s a t c o n s t a n t and s p e c i f i c d e n s i t y U n i t s o f volume F i g u r e 11. Model o f f i e r u i d e n s p u l c h e r growth i n compartments. - 46 -h i g h e r t h a n t h o s e o b t a i n e d under n a t u r a l c o n d i t i o n s . A n i m a l p o p u l a t i o n s have p r o t e c t i v e d e v i c e s t h a t a c t under h i g h density-c o n d i t i o n s so as t o e n s u r e t h e s u r v i v a l o f t h e s p e c i e s ( C h r i s t i a n 1 9 6 4 ). These m o d i f i c a t i o n s e nsure t h a t t h e s p e c i e s does not e l i m i n a t e i t s e l f t h r o u g h a n n i h i l a t i n g i t s f o o d s o u r c e , by r e d u c t i o n o f f e c u n d i t y , i n c r e a s e d m o r t a l i t y , and d i s e a s e . Such an i n c r e a s e i n m o r t a l i t y can be seen i n t h e d e n s i t y and m i r r o r e d t r e a t m e n t s (Table 3 ) . T h i s causes a p roblem i n f i s h c u l t u r e , and s e l e c t i o n o f d e n s i t y t o l e r a n t f a s t g r o w i n g f i s h may be t h e answer. - 47 -CONCLUSIONS 1) The growth i n s m a l l compartments was c o n s i s t e n t l y and s i g n i f i c a n t l y g r e a t e r t h a n i n l a r g e compartments i n a l l t r e a t m e n t s . 2) There was adequate e v i d e n c e t o suggest t h a t a c t i v i t y was r e s p o n s i b l e o r p a r t l y r e s p o n s i b l e f o r t h e d i f f e r e n c e i n g r o w t h . 3 ) I t was p o s t u l a t e d t h a t t h e cause f o r i n c r e a s e d a c t i v i t y i n l a r g e r compartments was due t o g r e a t e r a b s o l u t e a v a i l a b l e swimming space. The s o c i a l h i e r a r c h y and numbers o f t e r r i t o r i e s may have a f f e c t e d t h e f r e e space a v a i l a b l e t o each f i s h . I n s m a l l compartments f i s h were c o n f i n e d t o c e r t a i n r e g i o n s by o t h e r f i s h and t h e i r a c t i v i t y was r e s t r i c t e d . 4) Growth was c o n s i s t e n t l y l o w e r i n t h e d e n s i t y t r e a t m e n t . I n c r e a s e o f biomass caused r e d u c t i o n o f d i s s o l v e d oxygen and i n c r e a s e o f f i s h a c t i v i t y i n t u r n c a u s i n g a l o w e r growth r a t e and h i g h e r m o r t a l i t y r a t e . The lo w e r d i s s o l v -ed oxygen a v a i l a b i l i t y may have been r e s p o n s i b l e f o r i n c r e a s e i n a c t i v i t y . 5) M i r r o r e d compartments had l o w e r growth r a t e s t h a n c o n t r o l compartments even though a c t i v i t y f o r b o t h t r e a t m e n t s was s i m i l a r . I t was p o s t u l a t e d t h a t t h e l o w e r growth r a t e was due t o v i s u a l s t r e s s c a u s i n g an e n d o c r i n a l d i s t u r b a n c e c u r b i n g t h e growth r a t e . T h i s s t r e s s c o u l d a l s o be due t o a s m a l l a p parent n e a r e s t n e i g h b o u r d i s t a n c e . - 48 -6) The a c t i v i t y , growth and n e a r e s t n e i g h b o u r d i s t a n c e were g r e a t e s t i n t h e s h a l l o w t r e a t m e n t . The g r e a t e r a c t i v i t y and growth o f t h i s t r e a t m e n t i n d i c a t e s t h a t a f u r t h e r f a c t o r , perhaps s t r e s s o r a g g r e s s i o n e f f e c t e d by n e a r e s t n e i g h b o u r d i s t a n c e , caused t h e growth o f t h e c o n t r o l t o be l o w e r t h a n t h a t o f t h e s h a l l o w t r e a t m e n t . 7) No c o r r e l a t i o n o f f i s h s i z e w i t h a c t i v i t y o r a g g r e s s i o n was found t o e x i s t . D i s p l a y and f i g h t i n g were o b s e r v e d i n s m a l l compartments a t t h e b e g i n n i n g o f t h e growth s t u d y . An e a r l y measure o f a g g r e s s i o n s u g g e s t e d t h a t i t was h i g h e s t w i t h i n s m a l l e s t compartments. A l a t e r s t u d y i n d i c a t e d t h a t no d i f f e r e n c e i n a g g r e s s i o n e x i s t e d between l a r g e o r s m a l l compartments i n any t r e a t m e n t . I t i s s p e c u l a t e d t h a t a g g r e s s i o n d e c r e a s e d over t h e p e r i o d o f t i m e p o s s i b l y as a r e s u l t o f c o n d i t i o n i n g . 8) I t i s not known i f a growth i n c r e a s e i n s m a l l e r compart-ments would a p p l y i t o o t h e r f i s h o r n o t b u t h i g h growth r a t e s o f some c u l t u r e d f i s h i n cages may be due t o r e d u c e d a c t i v i t y by r e d u c t i o n o f t o t a l a v a i l a b l e swimming s p a c e . - 49 -LITERATURE CITED B i l t o n , H. T. and G. L. R o b i n s . 1970. P o s s i b l e e f f e c t s o f r e f l e c t e d images o f young sockeye (Oncorhynchus n e r k a ) on t h e i r g r o w t h . M a n u s c r i p t r e p o r t S e r i e s No. 1116. B i o l . S t a . F i s h e r i e s R e s e a r c h B o a r d . Nanaimo. Canada. B i l t o n , H. T. and G. L. R o b i n s . 1971. F u r t h e r e v i d e n c e o f t h e e f f e c t s o f m i r r o r e d a q u a r i a on t h e g r o w t h o f young sockeye (Oncorhynchus n e r k a ) . M a n u s c r i p t r e p o r t S e r i e s No. 1146. B i o l . S t a . F i s h e r i e s R e s e a r c h B o a r d . Nanaimo. Canada. B r e d e r , C. M. 1934. An e x p e r i m e n t a l s t u d y o f t h e r e p r o d u c t i v e h a b i t s and l i f e h i s t o r y o f t h e f i s h A e q u i dens  l a t r i f r o n s ( S t e i n d a c h n e r ) . Z o o l o g i c a 18: 1-42. B r e t t , J . R. 1970. F i s h — t h e e n ergy c o s t o f l i v i n g . I n W. J . M c N e i l (ed.) M a r i n e a q u i c u l t u r e . Oregon S t a t e U n i v e r s i t y P r e s s . pp 37-52. B r e t t , J . R. and D. B. S u t h e r l a n d . 1965. R e s p i r a t o r y m e t a b o l i s m o f pumpkinseed (Lepomis g i b b o s u s ) i n r e l a t i o n t o swimming speed. J . F i s h . Res. Bd. Canada 22: 405-409. Brockway, D. R. 1950. M e t a b o l i c p r o d u c t s and t h e i r e f f e c t s . P r o g r e s s i v e F i s h C u l t u r a l i s t 12: 127-129. B u s s , K., D. G r a f f and E. R. M i l l e r . 1970. T r o u t c u l t u r e i n v e r t i c a l u n i t s . P r o g r e s s i v e F i s h C u l t u r a l i s t 32: 187-191. Chen, F. Y. and G. A. Prowse. 1964. The e f f e c t o f l i v i n g space on t h e growth r a t e o f f i s h . I c h t h y o l o g i c a 3 ( 1 - 2 ) : 11 - 20. C h r i s t i a n , J . J . 1964. E n d o c r i n e s , b e h a v i o u r and p o p u l a t i o n . S c i e n c e 146: 1550-1560. C u l l e n , J . M., H. A. B a l d w i n and E. Shaw. 1965. Methods f o r m e a s u r i n g t h e t h r e e d i m e n s i o n a l s t r u c t u r e o f f i s h s c h o o l s . Anim. Behav. 13: 534-543. D a v i s , D. E. and J . J . C h r i s t i a n . 1957. R e l a t i o n o f a d r e n a l w e i g h t t o s o c i a l r a n k i n m i c e . J . P r o c . Soc. E x p t l . B i o l . Med. 94: p. 724. Gorbman, A. 1959. E d i t o r . P r o c e e d i n g s o f C o l u m b i a U n i v e r s i t y Symposium o f C o m p a r a t i v e E n d o c r i n o l o g y . W i l e y . New Y o r k . 31 pp. Gunn, D. 1937. The h u m i d i t y r e a c t i o n s o f t h e woodlouse P o r c e l l i o s c a b e r . J . Exp. B i o l . 14: 178-186. - 5:o -J o n e s , J . R. R e a c t i o n s o f f i s h t o w a t e r o f low oxygen c o n c e n t r a -t i o n . J . o f Exp. B i o l . 29: 403-415. Kawamoto, N.Y. 1958. F r e s h w a t e r f i s h c u l t u r e from t h e p h y s i o l o g i c a l p o i n t o f v i e w . I n f l u e n c e s o f ammonia n i t r o g e n e x c r e t e d by f i s h e s on t h e i r growth i n t h e c u l t u r e ponds. Rep. F a c . F i s h . R e f . U n i v . M i e . Japan. 3: 104-121. Kawamoto, N.Y. 1961. The i n f l u e n c e o f e x c r e t a r y s u b s t a n c e s on growth o f f i s h . P r o g . F i s h . C u l t . 23: 70^75. Kodama, Y. 1963. Growth r e l a t e d t o b e h a v i o u r o f Ayu P l e c o g l o s s u s a l t i v e l i s r e a r e d under low d e n s i t y . Res. P o p u l . E c o l . J a pan. 5: 65-73. M c F a r l a n d , W. N. and S. A. Moss. 1967. I n t e r n a l b e h a v i o u r i n f i s h s c h o o l s . S c i e n c e 156: 260-262. Magnuson, J . J . 1962. An a n a l y s i s o f a g g r e s s i v e b e h a v i o u r , growth and c o m p e t i t i o n f o r f o o d and space i n medaka O r y z i a s l a t i p e s ( P i s c e s , C y p r i n o d o n t i d a e ) . Can. J . o f Z o o l . 40: 313-363. M a z l a n , M. M. S. The e f f e c t o f space on growth under c o n s t a n t d e n s i t y i n t h e guppy ( L e b i s t e s r e t i c u l a t u s ) B.Sc. T h e s i s . U n i v . o f B r i t i s h C o l u m b i a . 1970. 72 pp. Rose, S. M. 1952. A feedback mechanism o f growth c o n t r o l i n t a d p o l e s . E c o l o g y 41: 188-199. Rose, S. M. 1959. F a i l u r e o f s u r v i v a l o f s l o w l y g r o w i n g members of a p o p u l a t i o n . S c i e n c e 129: 1026. Spoor, W. A. 1946. A q u a n t i t a t i v e s t u d y o f t h e r e l a t i o n s h i p between a c t i v i t y and oxygen consumption o f g o l d f i s h , and i t s a p p l i c a t i o n t o t h e measurement of r e s p i r a t o r y m e t a b o l i s m i n f i s h e s . B i o l . B u l l . 91: 312-315. S e l y e , H. 1956. The s t r e s s o f l i f e . McGraw H i l l . New Y o r k . 324 pp. T i l t o n , J . E. and J . E. K e l l y . 1971. E x p e r i m e n t a l cage c u l t u r e o f c h a n n e l c a t f i s h i n h e a t e d d i s c h a r g e w a t e r . I n C o n f e r e n c e on M a r i n e A q u i c u l t u r e . Oregon S t a t e U n i v e r s i t y M a r i n e S e r v i c e C e n t e r , p. 73-85. T u r n e r , C. D. 1955. G e n e r a l E n d o c r i n o l o g y . W. B. Saunders Co. New Y o r k . 511 pp. Whitmore, C. M., C. E. Warren and P. D o u d o r o f f . 1960. A v o i d a n c e r e a c t i o n s o f s a l m o n o i d and c e n t r a r c h i d f i s h e s t o low oxygen c o n c e n t r a t i o n s . T r a n s . Am. F i s h . Soc. 89: 17-26. - 51 -West, L. B. 1960. The n a t u r e o f growth i n h i b i t o r y m a t e r i a l from crowded Rana p i p i e n s t a d p o l e s . P h y s i o l . Z o o l . 33: 232-239. Y o s h i h a r a , T. 1952. E f f e c t o f p o p u l a t i o n d e n s i t y and pond a r e a on t h e growth o f f i s h . J . o f t h e Tokyo U n i v e r s -i t y o f F i s h e r i e s 39: 47-61. - 52 -APPENDIX - 53 -DAY 0 Replicate 1 L a r g e M e d i u m Small X SE N X SE N X SE N Control 2. 4180 0. 1831 90 2. 4013 0. 2074 30 2. 3960 0. 2134 10 Shallow 2. 4247 0. 1886 90 2. 3941 0. 2026 29 2. 4060 0. 2058 10 M i r r o r 2. 4208 0. 1884 91 2. 4053 0. 1954 30 2. 4130 0. 2036 10 Density 2. 4463 0. 3176 178 2. 4150 0. 2029 62 2. 4090 0. 2180 20 Replicate 2 Control 2. 4128 0. 1883 90 2. 4077 0. 2094 31 2. 3960 0. 2112 10 Shallow 2. 4173 0. 1788 88 2. 4063 0. 1915 30 2. 4090 0. 1969 10 M i r r o r 2. 4122 0. 1836 90 2. 4060 0. 2018 30 2. 3950 0. 2270 10 Density 2. 4125 0. 1890 181 2. 4415 0. 1981 58 2. 4090 0. 2178 20 D A Y 24 Replicate 1 Control 2. 6933 0. 2110 91 2. 7333 0. 2499 30 2. 7200 0. 2350 10 Shallow 2. 6744 0. 2148 92 2. 6683 0. 2223 30 2. 6880 0. 2312 10 M i r r o r 2. 7672 0. 2434 90 2. 7683 0. 2389 30 2. 8280 0. 2559 10 Density 2. 6165 0. 2150 170 2. 6505 0. 2632 59 2. 7189 0. 2529 18 Replicate 2 Control 2. 6770 0. 2213 89 2. 6068 0. 23 11 31 2. 6830 0. 2941 10 Shallow 2. 7016 0. 2208 89 2. 6903 0. 2438 30 2. 7320 0. 2128 10 M i r r o r 2. 6894 0. 2188 89 2. 7700 + 0. 2382 30 2. 8180 0. 2724 10 Density 2. 6424 0. 2208 179 2. 6635 0. 2348 57 2. 7075 0. 2839 20 D A Y 51 Replicate 1 Control 3. 0425 0. 2715 90 3. 0707 0. 3159 30 3. 1110 0. 3649 10 Shallow 3. 1108 0. 2673 91 3. 1013 0. 2850 30 3. 1660 0. 2900 10 M i r r o r 2. 9723 0. 2784 91 3. 0607 0. 2987 30 3. 2150. 0. 2878 10 Density 2. 9216 0. 2574 171 2. 9368 0. 3373 56 3. 1094 0. 3464 17 Replicate 2 Control 2. 9956 0. 2724 89 2. 9728 0. 3090 29 3. 0240 0. 3437 10 Shallow 3. 1032 0. 2696 88 3. 1560 0. 2956 30 3. 2410 0. 3146 10 M i r r o r 2. 9777 0. 2808 89 3. 1037 0. 2978 30 3. 2190 0. 3275 10 Density 2. 9388 0. 2637 178 2. 9651 0. 3220 59 3. 0960 0. 3895 20 D A Y 78 Replicate 1 Control 3. 2620 0. 3118 84 3. 3711 0. 3828 27 3. 4670 0. 4380 10 Shallow 3. 3350 0. 3131 90 3. 3693 0. 3355 29 3. 4430 0. 3630 10 M i r r o r 3. 2117 0. 3175 80 3. 2855 0. 3496 29 3. 5060 0. 2901 10 Density 3. 2114 0. 3178 167 3. 1758 0. 4020 57 3. 4283 0. 4503 18 Replicate 2 Control 3. 2434 0. 3225 89 3. 2561 0. 3902 28 3. 4440 0. 4642 10 Shallow 3. 3132 0. 2899 88 3. 4257 0. 3403 30 3. 5310 0. 3852 10 M i r r o r 3. 1828 0. 3095 77 3. 2859 0. 3304 27 3. 5190 0. 3036 10 Density 3. 1430 0. 3119 174 3. 1691 0. 3827 58 3. 3335 0. 4513 20 Table 12. Means of fisiv growth. - 54 -DAY 109 Replicate 1 L a r g e M e d i u m S m a l l X SE N X ' SE N X SE N Control 3. 4821 0. 3695 84. . 3. 6137 0. 4907 27 3. 7950 0. 5203 10 Shallow 3. 5753 0. 3403 91 3. 6100 0. 3752 29 3. 7100 0. 4039 . 10 M i r r o r 0. 0 0. 3821 76 3. 5279 0. 4035 ,29 3. 8180 0. 2991 10 Density- 3. 3894 0. 3644 166 3. 3900 0. 4386 55 3. 7427 0. 4625 15 Replicate 2 Control 3. 4508 0. 3865 89 3. 5136 0. 4873 28 3. 7670 0. 6295 10 Shallow 3. 6138 0. 3360 88 : 3. 6927 0. 3599 30 3. 8090 0. 4707 10 M i r r o r 3. 4278 0. 3821 81 3. 5096 0. 3026 27. . 3. 8020 0. 3156 10 Density 3. 3477 0. 3572 175 3. 4146 0. 4359 58 3. 5671 0. 4885 21 D A Y 190 Replicate 1 Control 3. 8231 0. 4379 85 3. 9452 0. 4917 27 4. 3421 0. 6565 14 Shallow 3. 9770 0. 4553 80 4. 0560 0. 5143 30 4. 2570 0. 5037 + 16 M i r r o r 3. 7732 0. 4502 78 3. 7432 0. 4203 25 4. 0654 0. 4722 11 Density 3. 4880 0. 4337 164 3. 6986 0. 5049 43 3. 8510 0. 5566 19 Replicate 2 Control 3. 8052 0. 4353 89 3. 8790 0. 5664 29 4. 4440 0.7081 10 Shallow 3. 9330 0. 3998 88 4. 0237 0. 4642 30 4. 2420 0. 5261 10 M i r r o r 3. 6511 0. 4207 73 3. 8385 0. 4501 26 4. 1633 0. 3688 9 Density 3. 5069 0. 4480 132 3. 5775 0. 4590 48 3. 9400 0. 5229 18 Table 12. Means of f i s h growth. DETAIL AT 'x'. DETAIL AT Y. Figure 13. SIDE ELEVATION. Plan of shallow and density treatments. 

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