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A comparison of agonistic behaviour between two populations of juvenile coho salmon (Oncorhynchus kisutch) Rosenau, Marvin Leslie 1984

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C .( A COMPARISON OF AGONISTIC BEHAVIOUR BETWEEN TWO POPULATIONS OF JUVENILE COHO SALMON (ONCORHYNCHUS KISUTCH) by MARVIN LESLIE ROSENAU B.Sc. Univ. of B.C. 1978 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA March 1984 (c^ Marvin L e s l i e Rosenau, 1984 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I further agree that permission for extensive copying of t h i s thesis f o r s c h o l a r l y purposes may be granted by the head of my department or by his or her representatives. I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 ABSTRACT I n t e r p o p u l a t i o n v a r i a b i l i t y i n e l e c t r o p h o r e t i c a l l y d e t e c t a b l e isozyme f r e q u e n c i e s , morphology, m e r i s t i c s and migratory behaviour has been demonstrated i n many s t u d i e s f o r salmonids and these c h a r a c t e r d i f f e r e n c e s are known to o f t e n have an i n h e r i t e d b a s i s . In t h i s study, a g o n i s t i c behaviours were compared in two B r i t i s h Columbia lower mainland p o p u l a t i o n s of j u v e n i l e coho salmon and i n h e r i t e d d i f f e r e n c e s were shown to occur. Using m i r r o r image s t i m u l a t i o n techniques, r e c e n t l y emerged l a b o r a t o r y incubated and reared coho j u v e n i l e s from the study p o p u l a t i o n s were t e s t e d f o r l a t e r a l d i s p l a y d i f f e r e n c e s and the Hope Slough coho were found to have an higher a c t i v i t y l e v e l than the Nathan Creek f i s h i n two brood y e a r s , 1979 and 1980. A d d i t i o n a l l y , coho of the 1980^experimental group were c r o s s f e r t i l i z e d p roducing i n t e r p o p u l a t i o n a l " h y b r i d s " and these f i s h were i n t e r m e d i a t e to the "pure" f i s h i n l a t e r a l d i s p l a y behaviour a c t i v i t y l e v e l s . R e c e ntly emerged w i l d j u v e n i l e coho were, obtained and brought back to the l a b o r a t o r y and t e s t e d with the same m i r r o r image s t i m u l a t i o n t e c h n i q u e s . S i m i l a r i n t e r p o p u l a t i o n a l d i f f e r e n c e s i n behaviour were found to occur. Laboratory r e a r e d f i s h were a l s o compared i n groups i n stream tanks as w e l l as i n p a i r s i n i s o l a t e d a q u a r i a . Hope Slough j u v e n i l e coho were found to be r e l a t i v e l y more a g g r e s s i v e than Nathan Creek f i s h . I t was f e l t that these observed d i f f e r e n c e s have an a d a p t i v e b a s i s i n nature. T h e r e f o r e , some p h y s i c a l and b i o l o g i c a l c h a r a c t e r i s t i c s were measured i n the two study watersheds. P o t e n t i a l d i f f e r e n c e s i n growth c o n d i t i o n s and/or d i f f e r i n g d e n s i t i e s of p r e d a t o r s were • p o s t u l a t e d as having p o t e n t i a l s e l e c t i v e e f f e c t s on the b e h a v i o u r a l r e p e r t o i r e s of the j u v e n i l e coho i n the study p o p u l a t i o n s . i i i TABLE OF CONTENTS ABSTRACT •....„> i i LIST OF TABLES i v LIST OF FIGURES v ACKNOWLEDGEMENTS v i I n t r o d u c t i o n 1 M a t e r i a l s and Methods 4 Sampling S i t e s 4 Nathan Creek 4 Hope Slough 7 Incubation and Rearing 10 Data Recording 11 M i r r o r Image S t i m u l a t i o n 11 M i r r o r Image S t i m u l a t i o n Experiments 12 P i l o t Experiment 12 R e p l i c a t e Experiment 13 Wild F i s h Experiment. ............ 19. Stream Tank Experiment 20 I n t e r p o p u l a t i o n Challenge 23 F i e l d Data 25 Data A n a l y s i s 26 Re s u l t s 27 M i r r o r S t i m u l a t i o n Experiments 27 P i l o t Experiment 27 R e p l i c a t e Experiment 33 Wild F i s h Experiment 40 Stream Tank Experiment 40 A g o n i s t i c A c t i v i t y 40 Stream Tank D i s t r i b u t i o n 53 I n t e r p o p u l a t i o n Challenge 57 F i e l d Data 58 Species Composition 58 J u v e n i l e Coho Growth 61 D i s c u s s i o n 65 L i t e r a t u r e C i t e d 1 72 Appendix 1 79 LIST OF TABLES Table 1. A p h y s i c a l d e s c r i p t i o n of the study streams 9 Table 2. A d e s c r i p t i o n of behaviours recorded i n t h i s study 18 Table 3. Anova comparisons of l a t e r a l d i s p l a y d u r a t i o n s f o r a l l M i r r o r Image S t i m u l a t i o n Experiments 32 Table 4. Summary of G-test comparisons f o r a g o n i s t i c behaviours i n the stream tanks 48 Table 5. Anova comparisons f o r a l l stream tank a g o n i s t i c behaviours 53 Table 6. Anova comparisons f o r f i s h d i s t r i b u t i o n s i n the stream tanks 56 Table 7. Summary of Hope/Nathan i n t e r - f i s h c o n t e s t wins ... 57 V LIST OF FIGURES F i g u r e 1. Map of study area 5 F i g u r e 2. M i r r o r Image S t i m u l a t i o n equipment 14 F i g u r e 3. Photograph of a j u v e n i l e coho 16 F i g u r e 4. Schematic diagram of the stream tank 21 F i g u r e 5. Mean l a t e r a l d i s p l a y d u r a t i o n s f o r the P i l o t Experiment 28 F i g u r e 6. I n c r e a s i n g complexity of l a t e r a l d i s p l a y s over time i n the P i l o t experiment 30 F i g u r e 7. Percentage of the t o t a l o b s e r v a t i o n d u r a t i o n p e r i o d that l a t e r a l d i s p l a y was performed i n a l l M i r r o r Image S t i m u l a t i o n experiments 34 F i g u r e 8. Mean l a t e r a l d i s p l a y d u r a t i o n s f o r the R e p l i c a t e Experiment 36 F i g u r e 9. Percent of t o t a l o b s e r v a t i o n time "Swim Against M i r r o r " behaviour was performed i n the R e p l i c a t e experiment- . ... .............. ..... ........... .... .,. ... .... ....... ... 38-F i g u r e 10. Mean l a t e r a l d i s p l a y d u r a t i o n s f o r the Wild F i s h experiment 41 F i g u r e 11. Summary of mean l a t e r a l d i s p l a y f r e q u e n c i e s i n the Stream Tank experiment 44 F i g u r e 12. Summary of mean o v e r t a g o n i s t i c behaviour f r e q u e n c i e s i n the Stream Tank experiments 46 F i g u r e 13. A comparison of the r e l a t i v e percentages f o r a l l a g o n i s t i c behaviour f r e q u e n c i e s i n the Stream Tank experiment 49 F i g u r e 14. A summary of mean behaviour f r e q u e n c i e s i n the Stream Tank experiment 51 F i g u r e 15. A comparison of space u t i l i z a t i o n by the study f i s h i n the Stream Tank experiment 54 F i g u r e 16. Species composition i n the study streams 59 F i g u r e 17. Change i n l e n g t h of w i l d Nathan and Hope Slough coho 63 v i ACKNOWLEDGMENTS I would l i k e to express a p p r e c i a t i o n to my s u p e r v i s o r , Dr. J.D. McPhail, f o r h i s help, encouragement.,, and. support i,n t h i s study. His p h i l o s o p h i c and s c i e n t i f i c musings were always a p p r e c i a t e d and because of h i s i n f l u e n c e the town of C h i l l i w a c k w i l l never be the same again. A l s o , f o r reviewing t h i s t h e s i s and p r o v i d i n g h e l p f u l comments I would l i k e to thank Drs. J . Meyers and C.C. Lindsey. Thanks must a l s o go to Ms. M. Borland and R.J. D e v l i n f o r t h e i r reviews and c r i t i c i s m . A s p e c i a l word of a p p r e c i a t i o n goes out to Clyde B. Murray. He helped i n the f i e l d work, s e t t i n g up of l a b o r a t o r y equipment and p r o v i d i n g ideas f o r experimentation. During our long hours of d i s c u s s i o n I'm sure that we saved a l l of the stocks of salmon i n B r i t i s h Columbia many times over. Dave Z i t t i n p r o v i d e d i n v a l u a b l e a i d on the computer and helped me overcome my fe a r of these machines. Thanks must a l s o go out to my Mennonite f r i e n d and f e l l o w a n a r c h i s t , Len Dyck, who pr o v i d e d the artwork f o r F i g u r e s 1, 2 and 4. F i n a l l y , I would l i k e to d e d i c a t e t h i s t h e s i s i n memory of my f a t h e r , A.G. Rosenau, who was the prime m o t i v a t i n g f o r c e i n my e d u c a t i o n a l c a r e e r . 1 INTRODUCTION Coho salmon (Oncorhynchus k i sutch) e x h i b i t i n t e r p o p u l a t i o n v a r i a b i l i t y i n d i v e r s e t r a i t s such as body p r o p o r t i o n s and m e r i s t i c s ( H j o r t and Schreck 1982, T a y l o r 1984), time of downstream movement ( B i r c h 1984), and e l e c t r o p h o r e t i c a l l y d e t e c t a b l e a l l e l e f r e q u e n c i e s (Utter e_t §_1. 1970, H j o r t and Schreck 1982, Powell and Wehrhahn 1984). The ecology and behaviour of coho are e q u a l l y v a r i a b l e and j u v e n i l e s use a v a r i e t y of r e a r i n g h a b i t a t s ( l a k e s ; streams, and r i v e r s ) f o r d i f f e r i n g time p e r i o d s (Scott and Crossman 1973). J u v e n i l e coho possess e x t e n s i v e innate a g o n i s t i c b e h a v i o u r a l r e p e r t o i r e s (Hoar 1951) and stream d w e l l i n g coho use many of these behaviours i n defending t e r r i t o r i e s a g a i n s t e i t h e r c o n s p e c i f i c s (Hoar 1951, Chapman 1962) or other s p e c i e s of salmonids (Hartman 1965, Glova 1978). Aggres s i v e behaviour i n stream r e a r i n g j u v e n i l e coho i s so frequent that i t occurs n e a r l y c o n t i n u o u s l y from f r y emergence i n the s p r i n g u n t i l autumn (Chapman 1962). A number of hypotheses attempt to e x p l a i n the high l e v e l of t e r r i t o r i a l behaviour i n stream d w e l l i n g coho. The hypotheses u s u a l l y are not mutually e x c l u s i v e and normally i n v o l v e two b a s i c concepts: 1) that t e r r i t o r i a l i t y i n coho a c t s as a mechanism to d i s p e r s e the p o p u l a t i o n and thus decrease the i n c i d e n c e of d i s e a s e , p a r a s i t i s m and p r e d a t i o n (Chapman 1962), and 2) that t e r r i t o r i a l i t y ensures an adequate supply of food i n an environment where food i s p o t e n t i a l l y a l i m i t i n g resource 2 (Chapman 1962, D i l l 1978b, D i l l et a l . 1981). Since a d u l t coho r e t u r n to t h e i r n a t a l streams to spawn, and thus form demes, and s i n c e d i f f e r e n t p o p u l a t i o n s of j u v e n i l e coho may l i v e in e c o l o g i c a l l y d i f f e r e n t environments (Chapman 1962, Burns 1971, Scott and Crossman 1973), a v a r i e t y of s e l e c t i v e p ressures probably i n f l u e n c e the extent and nature of t e r r i t o r i a l behaviour in d i f f e r e n t environments. C e r t a i n l y , g e n e t i c d i f f e r e n c e s i n behaviour occur between p o p u l a t i o n s i n a number of salmonid s p e c i e s (Bowler 1967, Brannon 1967, R a l e i g h 1967, 1971), and such d i f f e r e n c e s appear to be a d a p t a t i o n s to l o c a l environments. Consequently, i f there are d i f f e r e n c e s i n t e r r i t o r i a l behaviour between coho p o p u l a t i o n s l i v i n g i n d i f f e r e n t environments, the d i f f e r e n c e s may be at l e a s t p a r t i a l l y i n h e r i t e d . For example, Chapman (1962) suggested "...a coho stream r i c h i n d r i f t food should have a n a t i v e race of coho with s m a l l e r t e r r i t o r i a l requirements than would be the case i n a stream with low food a v a i l a b i l i t y . " He a l s o s t a t e d "...the s e l e c t i v e advantages gained by coho through aggression are obvious. Probably there i s a l i m i t maximizing p r o f i t a b l e a g g r e s s i o n at a l e v e l compatible with maximum growth and s u r v i v a l . " The purpose of t h i s t h e s i s i s to determine i f j u v e n i l e coho from d i f f e r e n t p o p u l a t i o n s show d i f f e r e n c e s i n t h e i r a g o n i s t i c d i s p l a y s and i f so to determine i f these d i f f e r e n c e s are i n h e r i t e d . My hypothesis i s that t e r r i t o r i a l behaviour i n j u v e n i l e coho i s a d a p t i v e and thus s e l e c t i o n w i l l produce i n h e r i t e d d i f f e r e n c e s i n t e r r i t o r i a l behaviour between 3 p o p u l a t i o n s from e c o l o g i c a l l y d i f f e r e n t environments. I t should be s t r e s s e d at the outset that environmental f a c t o r s can d i r e c t l y modify the exp r e s s i o n of innate behaviours. In stream r e a r i n g salmonids t e r r i t o r i a l i t y i s not a f i x e d phenomenon and D i l l e_t a l . (1981) have demonstrated that changes i n the environment of j u v e n i l e coho can change t e r r i t o r i a l behaviour. For t h i s reason my comparisons i n v o l v e animals reared i n the l a b o r a t o r y from eggs and t e s t e d under h i g h l y c o n t r o l l e d c o n d i t i o n s . In a d d i t i o n , I a l s o measured some e c o l o g i c a l f a c t o r s i n the n a t u r a l r e a r i n g environments of the study areas and these data were used to make i n f e r e n c e s about the a d a p t i v e ' s i g n i f i c a n c e of the behaviour d i f f e r e n c e s observed between the study coho p o p u l a t i o n s . 4 MATERIALS AND METHODS Samplinq S i t e s The lower and middle F r a s e r River system i n B r i t i s h Columbia supports a l a r g e number of coho runs. My study p o p u l a t i o n s were from two lower mainland F r a s e r t r i b u t a r i e s : Nathan Creek and Hope Slough ( F i g . 1). These streams are e c o l o g i c a l l y d i s s i m i l a r although i n the same gen e r a l c l i m a t i c zone and are separated by l e s s than 80 k i l o m e t e r s . The f o l l o w i n g accounts b r i e f l y d e s c r i b e the p h y s i c a l c o n d i t i o n s i n these two streams. Nathan Creek Nathan Creek i s l o c a t e d on the south shore of the F r a s e r River about 6 k i l o m e t e r s east of F o r t Langley. The t o t a l drainage area i s approximately 35 square k i l o m e t e r s (Hartman and G i l l 1968) and has a maximum e l e v a t i o n of l e s s than 200 meters. The lower three k i l o m e t e r s of stream a r e d i t c h e d and diked but the r e s t i s c r e e k - l i k e with a t y p i c a l small stream morphometry of p o o l s , r i f f l e s and runs. Much of the watershed i s wooded but there are some*farms and c l e a r e d land w i t h i n the drainage b a s i n . The s i d e s of the narrow g u l l y through which the creek flows ( f o r most of i t s length) are covered i n low deciduous brush and c o n i f e r o u s t r e e s . The stream bottom i s composed of boulders, rocks and g r a v e l (Table 1). Coho, at one or other l i f e - h i s t o r y stage use almost the 5 F i g u r e 1. Map of study area. Sample s i t e l o c a t i o n s N and N' (Nathan Creek) H and H' (Hope Slough) 7 e n t i r e stream. Spawning occurs from the upstream end of the d i t c h e d s e c t i o n (pers. obs.) throughout the upper mainstream to the small headwater t r i b u t a r i e s ( M a r s h a l l et a l . 1979). Department of F i s h e r i e s and Oceans spawning surveys i n d i c a t e that a d u l t coho enter Nathan Creek i n l a t e October. There i s a spawning peak i n l a t e November and spawning i s u s u a l l y f i n i s h e d by l a t e December (M a r s h a l l et a l . 1979). J u v e n i l e coho are found in s u i t a b l e r e a r i n g h a b i t a t throughout the e n t i r e stream. Hope Slough The morphometry of Hope Slough i s markedly d i f f e r e n t from that of Nathan Creek. Hope Slough a l s o l i e s on the south side of the F r a s e r R i v e r . I t empties i n t o the main r i v e r approximately 2 k i l o m e t e r s east of C h i l l i w a c k . Hope Slough i s approximately 16 km long and flows i n a we s t e r l y d i r e c t i o n . I t i s a s m a l l , o f t e n slowly moving s i d e channel of the F r a s e r River and i n a d d i t i o n to water from the main r i v e r the slough r e c e i v e s s e v e r a l farmland drainage d i t c h e s as w e l l as two major stream t r i b u t a r i e s : D u n v i l l e and Elk c r e e k s . These t r i b u t a r i e s have drainage areas of 13 and 53 square k i l o m e t e r s ( M a r s h a l l e_t a l . 1980). They are p r i m a r i l y fed from snowmelt water o r i g i n a t i n g at e l e v a t i o n s of g r e a t e r than 1500 meters. A l l of the a v a i l a b l e spawning and r e a r i n g areas i n the Hope Slough system have been d i t c h e d . Thus they are mostly slow moving and of r e l a t i v e l y constant depth: The- lower p o r t i o n s ' of D u n v i l l e and Elk creeks flow through farmland. The streamside 8 v e g e t a t i o n i n t h i s area c o n s i s t s p r i m a r i l y of low l y i n g grasses and brambles. The upper p o r t i o n s of D u n v i l l e and Elk C r e e k s -above b a r r i e r s impassable to f i s h - - f l o w through second growth deciduous and c o n i f e r o u s t r e e s . The stream s u b s t r a t e s i n the Hope Slough system are g e n e r a l l y composed of much f i n e r m a t e r i a l than Nathan Creek (Table 1). A d u l t coho spawn in the small t r i b u t a r y streams. Impassable sediment t r a p s 3.2 k i l o m e t e r s upstream of the slough on D u n v i l l e Creek and 5 k i l o m e t e r s above the slough on Elk Creek r e s t r i c t spawning to the lower p o r t i o n s of these streams. Ad u l t s enter Hope Slough as e a r l y as the beginning of November and spawning peaks i n December; however, the spawning p e r i o d i s p r o t r a c t e d and some f i s h spawn as l a t e as A p r i l . J u v e n i l e coho i n h a b i t these t r i b u t a r i e s and i n the main slough as f a r downstream as the Reeves Road Bridge (8 k i l o m e t e r s above the slough mouth). Table 1. A p h y s i c a l d e s c r i p t i o n of the study streams. Nathan Creek Hope Slough Drainage Area Maximum E l e v a t i o n General Appearance Surrounding Vegetat ion 35 sq km 200 meters c r e e k l i k e deciduous and c o n i f e r o u s t r e e s 117 sq km 1500 meters ditched/channeled c l e a r e d farmland grasses and brambles Spawning Timing October to December November to A p r i l S u bstrate composition s i z e s ( i n m i l l i m e t e r s ) P a r t i c l e S i z e > 50 3.25-50 < 3.25 Nathan Creek 1 1% 70% 29% Hope S l o u g h 2 2% 1% 97% D u n v i l l e Creek 2 2% 28% 70% Elk Creek 2 2% 18% 80% 1. da t a c o u r t e s y of C. B=". Murray 2. from M a r s h a l l et a l . (1980) 10 Incubation and Rear ing On November 7, 1979. coho eggs were obtained from a sing-le Nathan Creek female and f e r t i l i z e d with m i l t from a s i n g l e male. On November 24 eggs were obtained from a Hope Slough female and f e r t i l i z e d with m i l t from a s i n g l e male. The f e r t i l e eggs were immediately brought back to the l a b o r a t o r y and reared at a constant temperature (2° C).. The i n c u b a t i o n system i s d e s c r i b e d by Murray (1980). In November 1980 s i n g l e p a i r s of coho were again obtained from Nathan Creek and Hope Slough. They were brought back to U.B.C. and on the same day a r e c i p r o c a l c r o s s was made in the l a b o r a t o r y . The eggs from both the Nathan Creek and Hope Slough females were d i v i d e d i n t o two batches. A batch from each female was f e r t i l i z e d with Nathan Creek m i l t and the remaining batch from each female was f e r t i l i z e d with Hope Slough m i l t . T h i s procedure r e s u l t e d i n four f e r t i l i z e d egg batches: Nathan Creek female x Nathan Creek male; Nathan Creek female x Hope Slough male; Hope Slough female x Nathan Creek male; Hope Slough female x Hope Slough male. The eggs were incubated at 10° ( + 1.0 degrees). A f t e r h a t c h i n g , salmonid embryos are r e f e r r e d to as a l e v i n s . Coho a l e v i n s remain i n the g r a v e l f o r a v a r i a b l e p e r i o d of time (depending on temperature). When the a l e v i n s become p h o t o p o s i t i v e (Carey and Noakes, 1981) they emerge from the g r a v e l as free-swimming f r y . For some experiments the newly emerged f r y were reared i n i s o l a t i o n in• i n d i v i d u a l a q u a r i a , and in other experiments they were reared i n groups i n stream tanks. 11 The d e t a i l s are given under the separate experiments. Laboratory reared f r y were fed crushed Tetramin. To compare l a b o r a t o r y reared f r y with w i l d f r y , newly emerged f r y were c o l l e c t e d on A p r i l 22, 1981 from both Nathan Creek and the Hope Slough system. The f r y were c o l l e c t e d by pole seine from s i t e N' on Nathan Creek and s i t e H' on Elk Creek ( F i g . 1). Data Recording A l l behaviours were recorded on an e l e c t r o n i c data c o l l e c t i o n system ( O b s e r v a t i o n a l Systems Inc., Micropr o c e s s o r Operated Recording Equipment). For convenience, an acronym (MORE) i s used. Data were entered i n t o the MORE through a keyboard and then t r a n s f e r r e d to a PDP 11 computer. M i r r o r Image S t i m u l a t i o n To compare behaviours between p o p u l a t i o n s i t i s d e s i r a b l e to use a standard s t i m u l u s . Many v e r t e b r a t e s r e a c t to t h e i r own m i r r o r image as i f i t were another i n d i v i d u a l . The technique of e x p e r i m e n t a l l y m a n i p u l a t i n g behaviour using m i r r o r s i s known as M i r r o r Image S t i m u l a t i o n (G a l l u p 1968). Again, f o r convenience an acronym, MIS, i s used f o r t h i s technique. J u v e n i l e coho are known to r e a c t to mirror images in much the same way that they r e a c t to c o n s p e c i f i c s (Dr. L. D i l l , Simon F r a s e r U n i v e r s i t y , pers. comm.). S t r i n g e r and Hoar (1955) found that when us i n g models with salmonids, movement was 12 important i n e l i c i t i n g a g o n i s t i c responses. Undoubtedly an advantage of using m i r r o r images i s that u n l i k e c o n v e n t i o n a l wood or p l a s t i c models mi r r o r images are l i f e l i k e and show n a t u r a l swimming motions. In a d d i t i o n , s i z e i s important in j u v e n i l e coho behaviour f o r determining the outcome of a g o n i s t i c encounters (Chapman 1962). The MIS technique ensures that the opponent i s always the same s i z e as the t e s t f i s h . A l s o s i n c e the m i r r o r image looks and moves i n e x a c t l y the same manner as the t e s t f i s h , i t e x a c t l y r e f l e c t s the m o t i v a t i o n a l s t a t e of the t e s t f i s h . T h e r e f o r e , i f the t e s t f i s h i s motivated to f i g h t , the image i s a l s o "ready". An a d d i t i o n a l advantage to the MIS technique i s that severe damage to the p r o t a g o n i s t i s minimized. M i r r o r Image S t i m u l a t i o n Experiments The purpose of the MIS experiments was to measure the a g o n i s t i c behaviour of j u v e n i l e coho under r i g i d l y c o n t r o l l e d c o n d i t i o n s . The aim was to e l i m i n a t e p o p u l a t i o n d i f f e r e n c e s i n experience and environment. If t h i s can be done, then any remaining p o p u l a t i o n d i f f e r e n c e s i n behaviour can be a t t r i b u t e d to g e n e t i c d i f f e r e n c e s . P i l o t Experiment The f i s h used i n the P i l o t experiment were l a b o r a t o r y reared from the 1979 egg c o l l e c t i o n . The eggs were incubated i n the dark, and on emergence, the f r y were t r a n s f e r r e d immediately 1 3 to i s o l a t e d a q u a r i a . Thus the f r y had no chance to see other f i s h and t h i s procedure probably e l i m i n a t e d a l l s o c i a l l e a r n i n g . The f r y were p l a c e d i n i n d i v i d u a l 35 l i t e r a q u a r i a (Nathan f i s h on J u l y 12 and Hope Slough f i s h on J u l y 29). The aq u a r i a were v i s u a l l y i s o l a t e d from other a q u a r i a by sheets of black p l a s t i c . One sid e of each aquarium was l e f t open f o r o b s e r v a t i o n s ( F i g . 2). Each day a f t e r being t e s t e d , the f i s h were fed a pinch of crushed Tetramin. T h i s amounted to approximately 10% of t h e i r wet weight. L i g h t was pr o v i d e d by f l u o r e s c e n t l i g h t s set on a 16 hour l i g h t and 8 hour, dark schedule. The i n d i v i d u a l aquaria were kept i n a l a r g e water bath that maintained the water temperature at 15° C ( + 1.5 de g r e e s ) . F i s h from both p o p u l a t i o n s were t e s t e d f o r ten c o n s e c u t i v e days; however, the data f o r day one were l o s t due to an equipment m a l f u n c t i o n . Twenty-nine f i s h were used from each p o p u l a t i o n and the t e s t c o n s i s t e d of p l a c i n g a m i r r o r i n f r o n t of the f i s h f o r three minutes ( F i g . 2). The b e h a v i o u r a l r e a c t i o n s of each f i s h to i t s own image were recorded. These behaviours are* summarized' and de s c r i b e d 4 in- Table 2. Because-l a t e r a l d i s p l a y behaviours are d i s t i n c t and t h e r e f o r e easy to re c o r d they were emphasized i n t h i s and the f o l l o w i n g MIS exper iments. R e p l i c a t e Experiment The purpose of t h i s experiment was to r e p l i c a t e the P i l o t experiment and a l s o to document the* behaviour of' r e c i p r o c a l h y b r i d s o b t a i n e d from an i n t e r p o p u l a t i o n c r o s s . The f i s h were 1 4 Figure 2. M i r r o r Image S t i m u l a t i o n equipment. (mirror i s i n s e r t e d to bottom of the aquarium f o r MIS experiments, black p l a s t i c covers three s i d e s of the aquarium to v i s u a l l y i s o l a t e subject from f i s h i n n e i g h b o r i n g aquaria) 15 MIRROR BLACK PLASTIC COVERING 16 / Figure 3. Photograph of a j u v e n i l e coho. Table 2. A d e s c r i p t i o n of behaviours recorded in t h i s study. N u l l - - n o n ~ d e f i n e d behaviour. Swim Against Mirror--any swimming motion with the nose of the f i s h touching the m i r r o r . (MIS experiments only) Heads-Up Wig-Wag--extended d o r s a l and anal f i n s , opening of the mouth, and a s t i f f e n i n g of the body with an accentuated swimming, motion performed p a r a l l e l to the mi r r o r and the the p o s i t i o n of the head higher than h o r i z o n t a l . The wig-wag d i s p l a y s are e s s e n t i a l l y a form of ' l a t e r a l d i s p l a y while swimming' (see North, 1979). H o r i z o n t a l Wig-Wag--as d e s c r i b e d f o r Heads-Up Wig-Wag but with the body i n a h o r i z o n t a l p o s i t i o n . Heads-Down Wig-Wag--as d e s c r i b e d f o r Heads-Up Wig-Wag but with the head lower than h o r i z o n t a l . D o r s a l F i n Erec t i o n - - m a x i m a l l y extended d o r s a l and an a l f i n s . T h i s d i s p l a y i s performed while the f i s h i s mo t i o n l e s s . T h i s d i s p l a y corresponds to the l a t e r a l d i s p l a y of Chapman (1962) and Hartman (1965). Submission D i s p l a y - - a completely depressed d o r s a l f i n . Often the caudal f i n i s f o l d e d when performing t h i s d i splay (Chapman 1962). (MIS experiments only) Charge--the swimming d i r e c t l y at another f i s h with an i n c r e a s e d v e l o c i t y (Keenleyside and Yamamoto 1962, D i l l 1978a). (stream tank experiments only) C h a s e - - i n v o l v e s chase and f l i g h t with one f i s h swimming a f t e r another and pursuing i t past the p o i n t from where the chased f i s h was s t a t i o n e d (Chapman 1965). (stream tank experiments only) Nip--those b i t e s in which there appeared to be d e f i n e c o n t a c t or b i t e s which missed but were d e f i n i t e l y aimed at another f i s h ( t h r e a t n i p s r of f Chapman 1'96-5,)>. (stream tank experiments only) 19 l a b o r a t o r y reared from the 1980 egg c o l l e c t i o n . Again the eggs were incubated i n the dark and the r e s u l t i n g f r y immediately t r a n s f e r r e d to i s o l a t e d a q u a r i a . Since f r y emergence in coho i s a p r o t r a c t e d process, a set of 15 i n d i v i d u a l s from each f e r t i l i z a t i o n was t r a n s f e r r e d from the i n c u b a t o r s to aquaria on February 2, 1981 and another set of 15 from each f e r t i l i z a t i o n was t r a n s f e r r e d on February 3. The i s o l a t e d a q u a r i a were housed in a c o n t r o l l e d environment chamber set at 15° C and with a 16 hour l i g h t and 8 hour dark photoperiod. On February 3 the f i r s t set of 15. f i s h from each p o p u l a t i o n was t e s t e d with the MIS technique. T h e r e a f t e r t h i s group was t e s t e d every other day f o r twenty days. On February 4 the second set of 15 f i s h from each p o p u l a t i o n was t e s t e d i n the same manner as the f i r s t group. Each o b s e r v a t i o n p e r i o d was f o r two minutes and the behaviours recorded were the same as i n the P i l o t experiment. Wild F i sh Exper iment A comparison of a g o n i s t i c behaviours i n w i l d j u v e n i l e s from Nathan Creek and Hope Slough was undertaken f o r two reasons: 1) to determine i f w i l d coho from the study p o p u l a t i o n s show s i m i l a r d i f f e r e n c e s i n behaviour to the l a b o r a t o r y reared f i s h , and 2) to o b t a i n a comparison based on a v a r i e t y of i n d i v i d u a l s of probable d i f f e r e n t parentages, and thus a more r e p r e s e n t i t i v e sample of the g e n e t i c v a r i a b i l i t y i n the two p o p u l a t i o n s . Recently emerged w i l d f r y from the 1 two s t u d y a-reas were-brought i n t o the l a b o r a t o r y on A p r i l 22, 1981. MIS t e s t i n g 20 began on A p r i l 23 and the t e s t procedure was the same as i n pr e v i o u s MIS experiments with two major e x c e p t i o n s : 1) the sample s i z e was doubled (60 f i s h from each p o p u l a t i o n ) , and 2) the experiment was terminated, due to an equipment m a l f u n c t i o n , a f t e r 14 days (7 sample p e r i o d s ) . S i m i l a r s i z e d f i s h were used from both p o p u l a t i o n s (standard lengths--Hope Slough mean=30.03 mm, range-29-32 mm; Nathan Creek mean = 30.12 mm, range=29-32 mm).' S.treanv T.an.k,. Experiment Since j u v e n i l e coho o f t e n l i v e i n f l o w i n g water, a s e r i e s of stream tank o b s e r v a t i o n s were made to determine i f the behaviours recorded in the MIS experiments were s i m i l a r to the behaviours d i s p l a y e d under more n a t u r a l c o n d i t i o n s . The f i s h used i n the stream tank experiments were obtained from the 1980 egg c o l l e c t i o n . Only "pure" ( i . e. non-hybrid) f i s h were used. On February 3, 1981 s i x t y r e c e n t l y emerged Nathan and Hope j u v e n i l e coho were d i v i d e d i n t o s i x groups (three l o t s of ten f i s h from each p o p u l a t i o n ) . Each l o t was then p l a c e d i n an i s o l a t e d s e c t i o n of i d e n t i c a l c i r c u l a t i n g stream tanks. Each stream tank contained two s e c t i o n s ( F i g . 4). The water v e l o c i t y i n each tank was maintained at 5 to 10 cm per second and the water temperature at approximately 15° C. L i g h t was h e l d at a 16 hour l i g h t and 8 hour dark schedule, and each day the f i s h were fed g r e a t e r than 10% of the t o t a l wet f i s h weight of crushed Tetramin-. The f o l l o w i n g behaviours were observed and recorded: gure 4. Schematic diagram of the stream tank. GRAVEL BED PLEXIGLASS WALLS SCREEN .CURRENT M)IRECT/flN (25 cm DEEP) WATER LEVEL EQUALIZATION SCREEN 23 charging, c h a s i n g , n i p p i n g (overt b e h a v i o u r s ) , and l a t e r a l d i s p l a y s (wig-wags and d o r s a l f i n e r e c t i o n ) . These behaviours are d e s c r i b e d i n Table 2. A f t e r the b e h a v i o u r a l o b s e r v a t i o n s on the stream tank f i s h were completed, the f i s h were maintained i n the tanks f o r s e v e r a l weeks. On March 1, 1981, and f o r two days t h e r e a f t e r , the d i s t r i b u t i o n of f i s h in the stream tanks was measured. T h i s was accomplished by a r b i t r a r i l y d i v i d i n g each s e c t i o n of the tanks i n t o h a l v e s : an upstream and a downstream a r e a . The number of f i s h i n the upstream half, of each tank was recorded three times d u r i n g d a i l y 10 minute o b s e r v a t i o n p e r i o d s . A between tank and between p o p u l a t i o n ANOVA comparison was made of these o b s e r v a t i o n s . I n t e r p o p u l a t i o n Challenge A l l the other experiments measured agg r e s s i v e n e s s i n the study j u v e n i l e coho e i t h e r i n i s o l a t i o n or among members of t h e i r own p o p u l a t i o n . In the I n t e r p o p u l a t i o n Challenge t e s t , f i s h of equal s i z e from the two p o p u l a t i o n s were p i t t e d a g a i n s t one another. The o b j e c t was to determine, in a competitive s i t u a t i o n , i f f i s h from one of the p o p u l a t i o n s c o n s i s t e n t l y dominated f i s h of the other p o p u l a t i o n . The f i s h used in t h i s experiment were "pure" Nathan Creek and Hope Slough f r y d e r i v e d from the 1980 egg c o l l e c t i o n . They were incubated at 2° C and on emergence ( J u l y 4, 1981) t r a n s f e r r e d to experimental a q u a r i a i n the c o n t r o l l e d environment chamber. These f i s h were then t e s t e d with the MIS 24 technique to c o n f i r m that they behaved in the same manner as f i s h i n the p r e v i o u s experiments. On J u l y 20 f o r t y f i s h from each p o p u l a t i o n were measured f o r l e n g t h and then marked with a v e n t r a l f i n c l i p . Three days l a t e r they were, p a i r e d with a s i m i l a r s i z e d f i s h ( + 0.5 mm) from the other p o p u l a t i o n and moved as p a i r s i n t o t e s t tanks. The winner of the ensuing a g o n i s t i c encounter was then determined using the f o l l o w i n g three c r i t e r i a : 1) . color--submi ssdve- salmonids, almost., i n v a r i a b l y become dark along the s i d e , whereas dominant f i s h remain l i g h t e r (Newman 1956, Keenleyside and Yamamoto 1962). 2) n i p p i n g - - t h e dominant f i s h w i l l more of t e n n i p submissives than the converse (Newman 1956). 3) p o s i t i o n of d o r s a l f i n - - s u b m i s s i v e coho u s u a l l y drop t h e i r d o r s a l f i n lower than dominant f i s h . Submission a l s o u s u a l l y i n c l u d e s d e p r e s s i o n of the anal f i n and a f o l d i n g of the caudal f i n (Newman 1956). 25 F i e l d D a t a From O c t o b e r 1980 t h r o u g h September 1981 two s e c t i o n s on b o t h t h e Hope S l o u g h s y s t e m and Nathan C r e e k were sampled e v e r y two t o t h r e e weeks. The Hope S l o u g h s i t e s were on t h e s l o u g h p r o p e r a t B i g D i t c h Road ( s i t e H, F i g . 1) as w e l l as a t r i b u t a r y , E l k C r e e k , j u s t below t h e i m p a s s a b l e s e d i m e n t t r a p ( s i t e H ' ). The Nathan C r e e k s i t e s were l o c a t e d j u s t above th e d i t c h e d s e c t i o n a t t h e Jackman Road b r i d g e ( s i t e N, F i g . 1) and a b o u t 3 km u p s t r e a m a t t h e Nathan Road b r i d g e ( s i t e N ' ) . S p e c i e s c o m p o s i t i o n a t e a c h s i t e was d e t e r m i n e d by e l e c t r o s h o c k i n g and s e i n i n g . A S m i t h - R o o t b a c k p a c k e l e c t r o s h o c k e r and p o l e s e i n e s were u s e d t o c o l l e c t f i s h . The c a p t u r e d f i s h were i d e n t i f i e d t o s p e c i e s ( e x c e p t f o r c u t t h r o a t (Salmo c l a r k i ) o r rainbow (Salmo g a i r d n e r i ) t r o u t f r y w h i c h were c a t e g o r i z e d a s Salmo sp. due t o t h e d i f f i c u l t i e s i n f i e l d i d e n t i f i c a t i o n ) . J u v e n i l e c o h o , d e p e n d i n g on t h e s i z e c l a s s , were s e p a r a t e d i n t o y o u n g - o f - t h e - y e a r or s m o l t s . S t a n d a r d l e n g t h s were measured on a l l f i s h . Water t e m p e r a t u r e , water f l o w r a t e , and amount of t i m e t h e s h o c k e r was i n o p e r a t i o n were a l s o r e c o r d e d a t e a c h s i t e . 26 Data A n a l y s i s , The MIS experiments were analysed using, the. MORE., s t a t i s t i c a l package and the U.B.C. General Least Squares A n a l y s i s of Variance Program (GENLIN). The t o t a l d a i l y d u r a t i o n of behaviours for a l l f i s h i n each population were compared over the experimental p e r i o d . The data were transformed (base ten log (x+1)) before the a n a l y s i s of varia n c e . For the R e p l i c a t e experiment Scheffe's Test was used to compare the mean duration of l a t e r a l d i s p l a y i n the two p a r e n t a l populations and t h e i r r e c i p r o c a l h y b r i d s . The stream tank experiments were a l s o recorded with the MORE. In these experiments observations were made for 10 minutes on each group each day. The observations s t a r t e d the day a f t e r f r y emergence and continued for 10 days. The data were analysed a s i m i l a r way as the MIS experiments using an anova t e s t . The frequencies of the recorded behaviours i n the d i f f e r e n t populations i n stream tanks were compared with the G-te s t (Sokal and Rohlf 1981). The i n t e r p o p u l a t i o n challenge t e s t was analyzed using the Chi square t e s t while the f i e l d samples were analysed using regression and covariance a n a l y s i s . The f i e l d sampling length data were f i r s t transformed to n a t u r a l logarithms. In a l l t e s t s the n u l l hypothesis i s that there are no d i f f e r e n c e s between the popul a t i o n s . The l e v e l of s i g n i f i c a n c e i s 5 percent. 27 RESULTS M i r r o r S t i m u l a t i o n Experiments P i l o t Experiment The r e s u l t s of the P i l o t Experiment ( F i g s . 5, 7A) c l e a r l y demonstrate c o n s i s t e n t d i f f e r e n c e s i n the l a t e r a l d i s p l a y r e p e r t o i r e s of Nathan Creek and Hope Slough coho. Comparison, over a l l o b s e r v a t i o n p e r i o d s , of mean l a t e r a l d i s p l a y d u r a t i o n s i n d i c a t e s i g n i f i c a n t d i f f e r e n c e s between p o p u l a t i o n s (Two way anova, p<0.00l, Table 3A). Over the t e s t p e r i o d the amount of l a t e r a l d i s p l a y behaviour i n c r e a s e d i n both p o p u l a t i o n s ( F i g . 5), although at d i f f e r e n t r a t e s . In a d d i t i o n , as the experiment progressed (and the number of days from emergence i n c r e a s e d ) , the complexity of the l a t e r a l d i s p l a y r e p e r t o i r e a l s o i n c r e a s e d . T h i s i s shown by the p r o p o r t i o n a l i n c r e a s e i n wig-wag d i s p l a y s ( F i g . 6). (The wig-wag d i s p l a y s are complex l a t e r a l d i s p l a y s , Table 2). S i m i l a r ontogenetic changes i n the complexity of be h a v i o u r a l d i s p l a y s have been r e p o r t e d p r e v i o u s l y in salmonids. Mason and Chapman (1965) and Cole and Noakes (1980) found that although a g o n i s t i c behaviour i n salmonids i s of t e n i n i t i a t e d soon a f t e r emergence, the complexity of behaviour t y p i c a l l y i n c r e a s e s with age. The P i l o t experiment c l e a r l y i n d i c a t e s t h a t under r i g i d l y c o n t r o l l e d c o n d i t i o n s j u v e n i l e s from the two study p o p u l a t i o n s d i f f e r i n the d u r a t i o n of t h e i r l a t e r a l d i s p l a y behaviour. Hope 28 F i g u r e 5. . Mean l a t e r a l d i s p l a y d u r a t i o n s f o r the P i l o t Exper iment. Nathan Creek (x) Hope Slough (+) (with standard e r r o r s ) n=29 f i s h per group \ 30 F i g u r e 6 . I n c r e a s i n g complexity of l a t e r a l d i s p l a y s over time i n the P i l o t experiment. Wig-wag d i s p l a y s are expressed as a p r o p o r t i o n (%) of t o t a l l a t e r a l d i s p l a y time for the f i r s t f i v e days of the P i l o t experiment. (Nathan Creek (x) and Hope Slough (+) coho) 32 Table 3. Anova comparisons of l a t e r a l d i s p l a y d u r a t i o n s f o r a l l M i r r o r Image S t i m u l a t i o n Experiments. A. P i l o t Experiment Source df Mean Square P o p u l a t i o n 1 29.777 Day 8 3.409 Pop*Day 8 2.038 R e s i d u a l 504 1.150 F - r a t i o P r o b a b i l i t y 25.901 2. 9,59 1 .773 0.00000 # 0. 0,0303 #, 0.08004 B. R e p l i c a t e Experiment Source df Mean Square F - r a t i o P r o b a b i l i t y P o p u l a t i o n 3 22.169 24.776 0.00000 # Day 9 34.831 28.927 0.00000 # Pop*Day 27 1.639 1 .832 0.00600 # Re s i d u a l 1 1 60 0.895 C. Wild F i s h Experiment Source df Mean Square P o p u l a t i o n 1 12.840 Day 6 35.574 Pop*Day 6 1.424 R e s i d u a l 826 1.429 F - r a t i o P r o b a b i l i t y 8.983 24.888 0.997 0.00281 # 0.00000 # 0.42656 # s i g n i f i c a n t 33 Slough f i s h , on average, d i s p l a y f o r longer time d u r a t i o n s than Nathan Creek f i s h . R e p l i c a t e Experiment The r e s u l t s of t h i s experiment are summarized in F i g s . 7 and 8. As i n the P i l o t experiment, Hope Slough f i s h d i s p l a y e d more than Nathan Creek f i s h . I n t e r e s t i n g l y , the r e c i p r o c a l h y b rids are intermediate to the p a r e n t a l p o p u l a t i o n s i n the l e v e l of d i s p l a y ( F i g . 7B). The amount of l a t e r a l d i s p l a y , as compared over time with a two way a n a l y s i s of v a r i a n c e , i s s i g n i f i c a n t l y d i f f e r e n t between the groups (p<0.00l, Table 3B). A comparison of means with S c h e f f e ' s t e s t suggests three homogeneous subsets (Nathan female x Nathan male; Nathan female x Hope male, Hope female x Nathan female;. Hope female x Hope male). The r e c i p r o c a l F1 h y b r i d s ( F i g s . 7B, 8B) are s i m i l a r to each other i n the q u a n t i t y of l a t e r a l d i s p l a y . Thus there i s no evidence f o r e i t h e r a p a t e r n a l or maternal e f f e c t i n the i n h e r i t a n c e of the l e v e l of d i s p l a y . A d d i t i o n a l l y , the "Swim Against M i r r o r " behaviour a l s o was intermediate f o r the h y b r i d s ( F i g . 9 ) . As i n the P i l o t experiment, the l a t e r a l d i s p l a y s i n a l l groups became more complex as time progressed. Since the experimental animals were reared from eggs i n i d e n t i c a l environments, the above r e s u l t s i n d i c a t e that the d i f f e r e n c e s i n l a t e r a l d i s p l a y behaviour between Nathan Creek and Hope Slough f i s h uncovered 1 i n - the- P-i hlot experiment, a5re-' probably i n h e r i t e d . The in t e r m e d i a t e nature of the r e c i p r o c a l 3 4 F i g u r e 7. Percentage of the t o t a l o b s e r v a t i o n d u r a t i o n p e r i o d that l a t e r a l d i s p l a y was performed i n a l l M i r r o r Image S t i m u l a t i o n experiments. A. PILOT EXPERIMENT B. REPLICATE EXPERIMENT C. WILD FISH EXPERIMENT Hope "pure" Hope female x Nathan male Nathan male x Hope female Nathan "pure" PERCENTAGE IN LATERAL DISPLAY o ru i>. m m o ro I 1 1 1——-| 1 h-> CO - o 36 F i g u r e 8. Mean l a t e r a l d i s p l a y d u r a t i o n s f o r the R e p l i c a t e Experiment. 20 days (with standard e r r o r s ) n=30 f i s h per group A--Nathan males and females (x) Hope males and females (+) F1 pure B--Nathan female x Hope male (x) Hope female x Nathan male (+) F1 h y b r i d s 37 •B5ERVATIDN DAY 38 F i g u r e 9. Percent of t o t a l o b s e r v a t i o n time "Swim Against M i r r o r " behaviour was performed i n the R e p l i c a t e experiment. Hope female x Hope male Hope male x Nathan female J J Nathan female x Hope male : Nathan female x Nathan male PERCENT DF TOTAL TIME ui .a 8 6£ 40 F1 h y b r i d s suggest that these behaviours probably are p o l y g e n i c a l l y i n h e r i t e d . WiId F i s h Experiment F i g u r e 10 i n d i c a t e s that w i l d f i s h from Nathan Creek and the Hope Slough a l s o d i f f e r i n t h e i r l e v e l of l a t e r a l d i s p l a y . The d i f f e r e n c e i s i n the same d i r e c t i o n as the l a b o r a t o r y reared animals and i s s t a t i s t i c a l l y s i g n i f i c a n t (p=0.002, Table 3 C ) . The s i m i l a r i t y i n behaviour between w i l d and l a b o r a t o r y reared f i s h suggests that the d e t e c t e d d i f f e r e n c e s between the p o p u l a t i o n s i n the MIS experiments are n e i t h e r l a b o r a t o r y a r t i f a c t s nor abnormal chance e f f e c t s r e s u l t i n g from s i n g l e c r o s s e s . Instead these r e s u l t s imply that the b e h a v i o u r a l d i f f e r e n c e s between these experiments r e f l e c t g e n e t i c d i f f e r e n c e s between the p o p u l a t i o n s . Stream Tank Experiment A g o n i s t i c A c t i v i t y The MIS experiments demonstrated that the two study p o p u l a t i o n s have d i f f e r e n t l e v e l s of a g o n i s t i c behaviour. These experiments, however, were performed with s i n g l e i s o l a t e d f i s h . The stream tank experiments were an attempt to observe and compare these same p o p u l a t i o n s under more n a t u r a l c o n d i t i o n s . A g o n i s t i c a c t i v i t y developed i n the stream tanks i n the same sequence as i n the MIS experiments. I t began at a low 41 F i g u r e 10. Mean l a t e r a l d i s p l a y d u r a t i o n s f o r the Wild F i s h exper iment. (with standard e r r o r s ) n=60 f i s h per group Nathan Creek (x) Hope Slough (+) in • o LJ L d cn a <: a: I D • >-<C _ J a_ •cn H—\ • 15L-l Q l . OBSERVATION DAY 4 3 l e v e l and as the f r y aged i t r a p i d l y i n creased i n i n t e n s i t y and complexity ( F i g s . 11 and 12). The major r e s u l t s of the stream tank experiments, however, once again demonstrate s t r i k i n g d i f f e r e n c e s between the two p o p u l a t i o n s . For example, l a t e r a l d i s p l a y s (wig-wags and d o r s a l f i n e r e c t i o n s ) were s i g n i f i c a n t l y more common i n Hope Slough f i s h than in Nathan Creek f i s h ( F i g . 11, Table 5). In a d d i t i o n , Hope Slough f i s h performed s i g n i f i c a n t l y (p<0.00l) more overt a g o n i s t i c behaviour (chases, n i p s , charges) than Nathan Creek f i s h ( F i g . 12, Table 5). When a.1-1- a g o n i s t i c , a c t i v i t i e s , (cha.rges ,r>». chases., nips-,, and., the v a r i o u s l a t e r a l d i s p l a y s ) are compared, the Hope Slough f i s h performed 1929 a g o n i s t i c a c t s over the ten day o b s e r v a t i o n p e r i o d while Nathan Creek f i s h performed only 920 a g o n i s t i c a c t s . Thus, Nathan Creek coho showed l e s s than 50 percent of the a g g r e s s i v e a c t i v i t y of Hope Slough f i s h (see F i g . 1 4 ) . Many of the i n d i v i d u a l behaviours between p o p u l a t i o n s occur at s i m i l a r r e l a t i v e f r e q u e n c i e s - - e . g . d o r s a l f i n e r e c t i o n s are about 40% while chases are s l i g h t l y l e s s than 20% of the t o t a l frequencies' for' both*Nathan 1 and' Hope.* Slough- f i s h ( F i g . 13). A comparison (G-test) of these behaviors i n d i c a t e s t hat charges, n i p s , and d o r s a l f i n e r e c t i o n s are performed at the same r e l a t i v e f r e q u e n c i e s i n both p o p u l a t i o n s . In c o n t r a s t , chases and wig-wags occur at s l i g h t l y d i f f e r e n t f r e q u e n c i e s in the two p o p u l a t i o n s (Table 4). In g e n e r a l , however, the stream tank behaviours were s i m i l a r to the behaviours observed i n the MIS experiments. Since the stream tanks represent a more n a t u r a l environment f o r 44 F i g u r e 11. Summary of mean l a t e r a l d i s p l a y f r e q u e n c i e s i n the Stream Tank experiment. ( l a t e r a l displays--wig-wags and d o r s a l f i n e r e c t i o n s ) Nathan Creek (x) Hope Slough (+) range bars i n c l u d e d (3 tanks per p o p u l a t i o n , 10 f i s h per tank) 46 F i g u r e 12. Summary of mean overt a g o n i s t i c behaviour f r e q u e n c i e s i n the Stream Tank experiments, (overt behaviours--charges, chases, and ni p s ) Nathan Creek (x) Hope Slough (+) range bars i n c l u d e d (3 tanks per p o p u l a t i o n , 10 f i s h per tank) FREQUENCY DF BEHAVIOURS 4. Summary of G-test comparisons f o r a g o n i s t i c behaviours in the stream tanks. AGONISTIC ACTS Hope Nathan charge 297 1 33 G-stat=0.382 remainder 1 632 784 Chi tab (df=1) = 3 .841 chase 236 76 G-stat=l0.339 * remainder 1693 841 Chi tab (df=1) = 3 .841 n i p 370 182 G-stat=0.175 remainder 1 559 735 Chi tab (df = 1 ) = 3 .841 wig-wag 533 209 G-stat=7.66l * remainder 1 396 708 Chi tab (df=1) = 3 .841 d o r s a l f i n e r e c t 833 383 G-stat=0.507 remainder 1096 534 Chi tab (df=!) = 3 .841 * s i g n i f i c a n t at the p<0.05 l e v e l 49 F i g u r e 13. A comparison of the r e l a t i v e percentages f o r a l l a g o n i s t i c behaviour f r e q u e n c i e s i n the Stream Tank experiment. (each bar re p r e s e n t s the percent use of each behaviour summed f o r a l l groups and a l l days r e s p e c t i v e of p o p u l a t i o n ) Nathan Creek Hope Slough 1- -charges 2- -chases 3- - n i p s 4- -heads up wig-wag 5- - h o r i z o n t a l wig-wag 6- -heads down wig-wag 7 - d o r s a l f i n e r e c t i o n PERCENTAGE OS 51 F i g u r e 14. A summary of mean behaviour f r e q u e n c i e s in the Stream Tank experiment. (each bar r e p r e s e n t s the mean frequency f o r each behaviour over the t o t a l d u r a t i o n of the experiment f o r a l l tanks of f i s h , r e s p e c t i v e of p o p u l a t i o n ) Nathan Creek £;'£v Hope Slough 1- -charges 2- -chases 3- - n i p s 4- -heads up wig-wag 5- - h o r i z o n t a l wig-wag 6- -heads down wig-wag 7- - d o r s a l f i n e r e c t i o n s (with range bars) 52 S3IJN3T l03ciJ ynDIAVK39 53 Table 5. Anova comparisons f o r a l l stream tank a g o n i s t i c behaviours. A. L a t e r a l D i s p l a y Behaviours Source df Mean Square F - r a t i o P r o b a b i l i t y P o p u l a t i o n 1 6.809 18.976 0.00009 # Day 9 9.412 26.230 0.00000 # Pop*Day 9 0.295 0.823 0.59853 Re s i d u a l 40 0.359 B.- Overt A g o n i s t i c A c t i v i t i e s — c h a r . g e s , chases, and nips-Source df Mean Square F - r a t i o P r o b a b i l i t y P o p u l a t i o n 1 9.890 23.849 0.00002 # Day 9 6.365 15.347 0.00000 # Pop*Day 9 0.523 1.261 0.28785 Re s i d u a l 40 0.415 # s i g n i f i c a n t j u v e n i l e coho than the MIS a q u a r i a , these r e s u l t s support the view that the observed d i f f e r e n c e s i n behaviour between the populations' probably e x i s t i n nature. Stream Tank D i s t r i b u t i o n Nathan Creek and Hope Slough f i s h , when allowed time to s e t t l e i n t o the stream tanks, developed markedly d i f f e r e n t s p a c i a l d i s t r i b u t i o n s ( F i g . 15). When f i r s t i n t r o d u c e d to the tanks the f r y aggregated and there was l i t t l e a g g r e s s i o n . A f t e r a month, however, the> leve'ls 1 of aggression' were high ( p a r t i c u l a r l y i n Hope Slough ,fish) and the s p a c i a l d i s t r i b u t i o n s 54 F i g u r e 15. A comparison of space u t i l i z a t i o n by the study f i s h i n the Stream Tank experiment. (mean number of f i s h observed i n f r o n t h a l f of tank f o r the d u r a t i o n the the experiment) Nathan Creek coho Hope Slough coho with standard e r r o r s N U M B E R C F F I S H nj 56 of the two p o p u l a t i o n s were c l e a r l y d i f f e r e n t . Table 6. Anova comparisons f o r f i s h d i s t r i b u t i o n s i n the stream t Source df Mean Square F - r a t i o P r o b a b i l i t y P o p u l a t i o n Day Tank Pop*Day Pop*Tank Day*Tank Pop*Day*Tank 1 2 2 2 2 4 4 253.50 5. 167 2.889 10.056 1 .556 3.806 2.361 258.28 5.264 2.943 10.245 1 .585 3.877 2.406 0.00000 # 0.00987 # 0.06547 0.00030 # 0.2.1894 0.01016 # 0.06747 # s i g n i f i c a n t Nathan Creek f i s h had spread f a i r l y evenly throughout the tanks with the v a r i o u s dominant f i s h s c a t t e r e d from the f r o n t screen to the back of the tank (see F i g . 4 f o r a diagram of the t a n k s ) . Subordinate f i s h were i n t e r s p e r s e d between the dominant f i s h and were o f t e n c l o s e to the wa l l s of the tank. In c o n t r a s t , i n the Hope Slough f i s h one f i s h dominated each tank and the subordinates were c o n f i n e d to an area i n the downstream qu a r t e r of the tank. The dominant f i s h ' p a t r o l l e d ' the upstream t h r e e - q u a r t e r s of the tank and kept i n t r u d e r s out. T h i s arrangement d i d not appear to l e s s e n the q u a n t i t y of a g o n i s t i c a c t i v i t y i n the Hope Slough tanks. The number of f i s h i n the f r o n t h a l f of the tank was taken as a measure of the d i f f e r e n c e s i n d i s t r i b u t i o n . F i g u r e 15 summarizes these o b s e r v a t i o n s . The d i f f e r e n c e s are s i g n i f i c a n t (p<0.000l, Table 6). The d i f f e r e n c e s between the two p o p u l a t i o n s i n t h e i r 57 s p a c i a l d i s t r i b u t i o n s w i t h i n the stream tanks suggests that the high l e v e l of aggression c o n s i s t e n t l y observed i n Hope Slough f i s h may f u n c t i o n i n nature to spread j u v e n i l e s over a wide a r e a . If these o b s e r v a t i o n s are a r e f l e c t i o n of t e r r i t o r y s i z e , Hope Slough coho j u v e n i l e s maintain l a r g e r t e r r i t o r i e s than Nathan Creek coho. I n t e r p o p u l a t i o n Challenge I n d i v i d u a l f i s h of equal s i z e , from each p o p u l a t i o n , were p i t t e d a g a i n s t one another i n a n e u t r a l t e s t tank. The r e s u l t s of these i n t e r p o p u l a t i o n c h a l l e n g e t e s t s are presented i n Table 7. I t i s c l e a r that i n such c o n t e s t s the more a g g r e s s i v e Hope Table 7. Summary of Hope/Nathan i n t e r - f i s h c o n t e s t wins. Winners Hope 31 Nathan 9 n=40 c o n t e s t s df = 1 Chi' tab (0.01 ) = 6.64 Chi c a l c = 8.01 P<0.01 Slough f i s h dominate. T h i s r e s u l t a l s o suggests that the high l e v e l of aggression of the Hope Slough f i s h would r a d i c a l l y a f f e c t the d i s t r i b u t i o n s and c o u l d e v e n t u a l l y a l t e r the ge n e t i c make-up of the p o p u l a t i o n s i f the two p o p u l a t i o n s were"' to come in c o n t a c t i n nature. Probably Nathan Creek f i s h would be 58 d i s p l a c e d i n t o sub-optimal h a b i t a t s with r e s u l t i n g lowered s u r v i v a l r a t e s . F i e l d Data Species Composition The f i s h s p e c i e s composition i n the two study streams was c o n s i d e r a b l y d i f f e r e n t ( F i g s . 16). The f a r t h e s t upstream sample s i t e in Nathan Creek (N', F i g . 1) was occupied only by salmonids. The predominant group of f i s h ( i n terms of numbers) at t h i s s i t e were young of the year coho (65%), followed by t r o u t (Salmo sp., 33%). Nineteen percent of the t r o u t were over 80 mm i n standard l e n g t h . At the lower Nathan Creek sampling s i t e (N, F i g . 1) the s p e c i e s composition was somewhat more d i v e r s e . However, salmonids s t i l l dominated the f i s h fauna although the s p e c i e s numerical dominance r e v e r s e d . Here t r o u t were the dominant s p e c i e s (53%) with 36% over 80 mm i n l e n g t h . Coho young of the year made up 21% of the f i s h taken at t h i s s i t e . U n l i k e the upper s i t e , the lower Nathan Creek area a l s o c o n tained j u v e n i l e chinook salmon (Oncorhynchus tshawytscha). T h i s s p e c i e s , however, occupied the area f o r only a short time p e r i o d . The j u v e n i l e chinook moved i n t o lower Nathan Creek from the F r a s e r River i n e a r l y March but by May, when most of the coho f r y begin appearing, the chinook had l e f t . The Nathan Creek mis c e l l a n e o u s category i n F i g u r e 16 was composed*" p r i m a r i l y of s t i c k l e b a c k s (Gasterosteus a c u l e a t u s ) and some c o t t i d s 59 F i g u r e 16. Species composition i n the study streams. These graphs i n d i c a t e the sum of a l l f i s h sampled r e s p e c t i v e of study stream. S i t e s N & N' as w e l l as H & H' are combined and the t o t a l s are converted i n t o percent f o r comparative purposes (number of f i s h sampled above b a r s ) . 1- -coho young of the year 2- - t r o u t (Salmo s p . ) — s t i p p l i n g , i n d i c a t e s p r o p o r t i o n of f i s h 80+ mm. 3- -coho smolts 4- ~chinook f r y (Oncorhynchus tshawytscha) 5- - c y p r i n i d s 6- -miscellaneous (suckers, Catostomus sp.; s c u l p i n s , Cottus sp.; s t i c k l e b a c k s , G asterosteus a c u l e a t u s ) PERCENT PERCENT oB8«ft.8 8S8 8'8oB8&488S888 i i i i i i i i i i i- i i i i i i i i i i 0 -4 X o 61 (Cottus s p . ) . The f i s h fauna of Hope Slough c o n t r a s t s s h a r p l y with that of Nathan Creek ( F i g . 16). At the Hope Slough upstream sampling s i t e (H', F i g . 1) j u v e n i l e coho were the n u m e r i c a l l y dominant s p e c i e s (88 p e r c e n t ) . Trout, however, were extremely rare (4 p e r c e n t ) . At the downstream s i t e (H, F i g . 1) coho young were again the most common s p e c i e s (71 percent, F i g . 17B) and t r o u t were even r a r e r (1 percent) than at the upstream s i t e . I t appears that j u v e n i l e t r o u t do not commonly use the Hope Slough system f o r r e a r i n g since, only one t r o u t less, than 80 mm was sampled. In a d d i t i o n to salmonids, other f i s h s p e c i e s present at the lower Hope Slough s i t e i n c l u d e d northern squawfish ( P t y c h o c h e i l u s oregonensis) and r e d s i d e s h i n e r s (Richardsonius  b a l t e a t u s ) , as w e l l as suckers (Catostomus s p . ) , s c u l p i n s (Cottus s p . ) , and t h r e e s p i n e s t i c k l e b a c k (Gasterosteus  a c u l e a t u s ) . A l s o , the i n t e n s i t y of sampling was s i m i l a r f o r the two study streams and the Hope Slough appeared to have lower densities--of j u v e n i l e coho-. J u v e n i l e Coho Growth There were obvious s i z e d i f f e r e n c e s i n the young of the year coho captured i n the two study streams. Over the sampling season, j u v e n i l e coho in Nathan Creek (sample s i t e N') were l a r g e r than those in the Hope Slough system (sample s i t e H'). The rate= at which these' f i s h were observed to i n c r e a s e i n size< with time was s i g n i f i c a n t l y d i f f e r e n t i n the two study areas 62 ( p < 0 . 0 0 0 l , F i g . 17). I f these d i f f e r e n c e s r e f l e c t d i f f e r i n g growth r a t e s between coho i n the study streams, Nathan Creek f i s h appear to be growing at a f a s t e r r a t e than the f i s h i n the Hope Slough system, suggesting that t h i s stream may represent a b e t t e r j u v e n i l e coho h a b i t a t . In summary, the f i e l d data i n d i c a t e that t r o u t d e n s i t y i s r a d i c a l l y d i f f e r e n t i n the two systems. At some times of the year j u v e n i l e t r o u t may compete with j u v e n i l e coho f o r both food and space i n Nathan Creek, and' such i n t e r a c t i o n s c o u l d i n f l u e n c e the l e v e l s of aggression i n the two coho p o p u l a t i o n s . Subadult t r o u t (80+ mm) may a l s o i n f l u e n c e coho behaviour s i n c e they are p o t e n t i a l p redators on j u v e n i l e coho and found at high d e n s i t y l e v e l s i n Nathan Creek. A l s o , the d i f f e r e n c e i n growth r a t e s between coho i n Nathan Creek and Hope Slough suggests that there may be d i f f e r e n c e s i n the p r o d u c t i v i t y of the two systems as coho i n Nathan Creek appear to grow f a s t e r than i n Hope Slough under higher d e n s i t i e s of f i s h . 63 F i g u r e 17. Change i n length of w i l d Nathan and Hope Slough coho. ( j u v e n i l e young of the year, 1981) A. Nathan Creek n=354 (x) p r o b a b i l i t y of slope being zero p<0.00l r 2 = 0.86 B. Hope Slough n=236 (+) p r o b a b i l i t y of slope being zero p<0.00l r 2 = 0.60 t e s t of d i f f e r e n t slopes p<0.00l 65 DISCUSSION In recent years phenotypic d i f f e r e n c e s between salmonid p o p u l a t i o n s have been s t u d i e d e x t e n s i v e l y . Because salmonids u s u a l l y home to t h e i r n a t a l streams with a high degree of accuracy they o f t e n form l o c a l l y d i s t i n c t interdemic d i f f e r e n c e s which are p o t e n t i a l l y important to f i s h e r i e s managers. The subject of i n t r a s p e c i f i c d i f f e r e n t i a t i o n i n salmonids has been reviewed r e c e n t l y i n a number of papers (Ricker 1972, K i r p i c h n i k o v 1981, W i t h l e r e_t a l . 1982) i n c l u d i n g a major i n t e r n a t i o n a l . symposium (The Stock Concept. I n t e r n a t i o n a l  Symposium, Can. J . F i s h . Aquat. S c i . , V o l . 38, No. 12). Most i n t e r p o p u l a t i o n v a r i a b i l i t y s t u d i e s i n salmonids are of a b i o c h e m i c a l nature and concentrate on e l e c t r o p h o r e t i c a l l y d e t e c t a b l e d i f f e r e n c e s i n isozymes (e.g. f o r coho, C h i l d e_t a l . , 1976, A l l e n d o r f and U t t e r 1 979, H j o r t and Schreck 1982; see May (1980) f o r a summary of a l l salmonids). However, g e n e t i c d i f f e r e n c e s a l s o appear to occur i n the ecology (Trojnar and Behnke 1974), morphology ( R i d d e l l and Leggett 1981, R i d d e l l et a a l . 1981, H j o r t and 1 Schreck 1982), migratory behaviour (Bramvon 1967, Bams 1976, Northcote and Kelso 1981) and p h y s i o l o g y (Ihssen and T a i t 1974) of salmonids. D e s p i t e much i n t e r e s t i n salmonid g e n e t i c s , s t u d i e s of i n h e r i t e d b e h a v i o u r a l d i f f e r e n c e s are s t i l l r a r e . The i n v e s t i g a t i o n s of Brannon (1967), R a l e i g h (1967, 1971), Bowler (1975) and Northcote and Kelso (1981) are among the few good demonstrations of i n h e r i t e d i n t r a s p e c i f i c b e h a v i o u r a l d i f f e r e n c e s i n salmonids. A l l of these l a t t e r s t u d i e s i n v o l v e migratory behaviour. 66 The only suggestion of i n h e r i t e d d i f f e r e n c e s f o r a g o n i s t i c behaviour i n salmonids i s by Chapman (1962). He observed two c l a s s e s of ag g r e s s i v e behaviour i n j u v e n i l e coho salmon: s l i g h t l y a g g r e s s i v e nomads, and h i g h l y a g g r e s s i v e r e s i d e n t s . Chapman suggested these b e h a v i o u r a l c l a s s e s might have a ge n e t i c b a s i s but he had no experimental evidence to support t h i s i d e a . R i c k e r (1972) a p p r e c i a t e d the p o t e n t i a l d i f f i c u l t y i n demonstrating b e h a v i o u r a l d i f f e r e n c e s between d i f f e r e n t s p e c i e s of salmonids, much l e s s between p o p u l a t i o n s of the same s p e c i e s . He. suggested tha-f to- demonstrate, h e r i t a b l e behavioural-d i f f e r e n c e s between salmonid stocks comparisons must be made under i d e n t i c a l c o n d i t i o n s . To achieve t h i s end my t e s t animals were hatched from eggs incubated together and then reared i n d i v i d u a l l y under standard c o n d i t i o n s . M i r r o r Image S t i m u l a t i o n (MIS) was chosen as the t e s t regime because the c o n d i t i o n s c o u l d be r i g i d l y c o n t r o l l e d . The r e s u l t s of my experiments demonstrate c l e a r d i f f e r e n c e s in the l e v e l of agg r e s s i o n between j u v e n i l e s of the two study coho p o p u l a t i o n s ; Hope- Slough' f i s h ate 1 s t r i k i n g l y more ag g r e s s i v e than Nathan Creek f i s h . Moreover, these d i f f e r e n c e s are c o n s i s t e n t w i t h i n years ( f i s h reared at d i f f e r e n t temperatures) and between years (1980 and 1981) as w e l l as under d i f f e r i n g methodologies (MIS and stream t a n k s ) . T h i s c o n s i s t e n c y p r o v i d e s evidence f o r the argument that the d i f f e r e n t l e v e l s of a g g r e s s i o n are i n h e r i t e d . F u r t h e r evidence f o r an i n h e r i t e d b a s i s of these d i f f e r i n g l e v e l s of aggression come from the h y b r i d i z a t i o n study i n the 67 R e p l i c a t e experiment. Barnard (1983) i n d i c a t e s that one method of determining the genetic b a s i s of a b e h a v i o u r a l c h a r a c t e r i s to compare the behaviour of interdemic h y b r i d s with pure progeny. In r e c i p r o c a l c r o s s e s between Hope Slough and Nathan Creek coho the hybrids were c o n s i s t e n t l y intermediate i n t h e i r l e v e l of a g g r e s s i o n . T h i s intermediacy of h y b r i d s suggests a poly g e n i c system with approximately equal and a d d i t i v e e f f e c t s (Avers 1981, K i r p i c h n i k o v 1981, Barnard 1983). A d d i t i o n a l l y , w i l d caught j u v e n i l e s of the same p o p u l a t i o n s brought i n t o the l a b o r a t o r y and t e s t e d under the same c o n t r o l l e d -c o n d i t i o n s as l a b o r a t o r y reared f i s h gave s i m i l a r r e s u l t s . T h i s suggests that the r e s u l t s are not due to e i t h e r an abnormal l a b o r a t o r y r e a r i n g regime or to chance sampling e f f e c t s . Together, a l l of the above l i n e s of evidence argue s t r o n g l y that the d i f f e r e n c e s i n l e v e l s of agg r e s s i o n between Hope Slough and Nathan Creek coho j u v e n i l e s are i n h e r i t e d . In a d d i t i o n , the v a r i o u s behaviour f r e q u e n c i e s are p r o p o r t i o n a l l y s i m i l a r i n the two p o p u l a t i o n s i n d i c a t i n g that the d i f f e r e n c e i s that of i n t e n s i t y . The f u n c t i o n of v a r i a t i o n i n b e h a v i o u r a l c h a r a c t e r s i s of t e n open f o r debate (Tinbergen 1967), but a behaviour which i s i n h e r i t e d and at a high frequency i n a p o p u l a t i o n i s l i k e l y to be adaptive (Hinde 1975). With salmonids i t i s sometimes easy to c o r r e l a t e v a r i a t i o n i n c h a r a c t e r s with environmental d i f f e r e n c e s between h a b i t a t s (Brannon 1967, Ihssen and T a i t 1974, Bowler 1975, R i d d e l l and Leggett 1981). For en v i r o n m e n t a l l y l a b i l e t r a i t s such as 68 behaviour, however, the reasons f o r d i f f e r e n c e s can o f t e n only be i n f e r r e d rather than demonstrated (Ihssen et a_l. 1982). However, by comparing measurable d i f f e r e n c e s i n the niche parameters encountered i n study p o p u l a t i o n s with t r a i t d i f f e r e n c e s ( c o n t e x t u a l i n f o r m a t i o n , Hinde 1975), i t may be p o s s i b l e to match an adaptive b i o l o g i c a l t r a i t to the s e l e c t i v e a g e n t ( s ) . A p o s s i b l e s e l e c t i v e d i f f e r e n c e between Hope Slough and Nathan Creek i n v o l v e s p o t e n t i a l i n t e r a c t i o n s between coho and other c o e x i s t i n g f i s h . The t r o u t s ( c u t t h r o a t , Salmo c l a r k i and ste e l h e a d , S. g a i r d n e r i ) are known to i n t e r a c t s t r o n g l y with j u v e n i l e coho (Hartman 1965, Glova 1978). In the Hope Slough watershed t r o u t are rare whereas i n Nathan Creek many t r o u t were observed to c o e x i s t with coho. Sympatric coho and young t r o u t o f t e n segregate e c o l o g i c a l l y i n t o p o ols and r i f f l e s , r e s p e c t i v e l y . T h i s s e g r e g a t i o n i s achieved i n part through a g o n i s t i c s o c i a l i n t e r a c t i o n s (Hartman 1965, Glova 1978). These s o c i a l i n t e r a c t i o n s ( a g o n i s t i c behaviours) are s i m i l a r f o r both t r o u t and*- coho, although' t r o u t appear to*-be1 the? subordinate s p e c i e s . I n t u i t i v e l y , s i n c e coho and t r o u t i n t e r a c t a g g r e s s i v e l y , one would expect that the added burden of t r o u t competing f o r space i n Nathan Creek would s e l e c t f o r more aggr e s s i o n i n the Nathan Creek coho genotype. The experimental r e s u l t s are completely at odds with t h i s h y p o t h e s i s . There i s , however, an added f a c t o r . A d u l t and subadult (80+ mm) t r o u t are known to be pr e d a t o r s on j u v e n i l e coho (Sco t t and Crossman 1973) and although t r o u t form 46% of the s p e c i e s 69 composition by numbers i n Nathan Creek, 31% of these f i s h are 80 mm or l o n g e r ; that i s , they are l a r g e enough to be p o t e n t i a l p r e d a t o r s on j u v e n i l e coho. In c o n t r a s t , t r o u t form only 2% of the t o t a l f i s h sample f o r a l l of the Hope Slough study s i t e s ; a q u a n t i t y I c o n s i d e r to be n e g l i g i b l e . H u n t i n g f o r d (1976) prov i d e s evidence with t h r e e - s p i n e s t i c k l e b a c k s (Gasterosteus a c u l e a t u s ) a g g r e s s i v e l e v e l s vary i n the presence of p r e d a t o r s and she suggests reduced a c t i v i t y i s an a n t i p r e d a t o r d e v i c e . Seghers (1974) and B a l l i n (1974) i n d i c a t e that a s i m i l a r phenomenon occurs, w i t h . n a t u r a l guppies ( P o e c i l i a r e t i c u l a t a ) . Consequently, the reduced a g g r e s s i v e a c t i v i t y i n Nathan Creek coho may be due to a s e l e c t i v e p r essure imposed by p r e d a t o r s . T h i s hypothesis assumes that h i g h l y a g g r e s s i v e f i s h w i l l be removed from the p o p u l a t i o n by p r e d a t o r s more f r e q u e n t l y than l e s s a g g r e s s i v e f i s h . A second p o s s i b l e e x p l a n a t i o n f o l l o w s . Coho salmon rear i n f r e s h water for one to two years before smolting (Scott and Crossman 1973) and those f i s h . that are not able to h o l d t e r r i t o r i e s - , a p p a r e n t l y a d i r e c t r e s u l t - of agond-stic a c t i v i t y ' , are d i s p l a c e d downstream i n t o sub-optimal h a b i t a t s (Chapman 1962). U l t i m a t e l y , coho j u v e n i l e s that enter s a l t w a t e r prematurely have an extremely low s u r v i v a l r a t e ( P r i t c h a r d 1936, Mason 1976). T e r r i t o r i e s i n stream d w e l l i n g salmonids are p r i m a r i l y f e e d i n g t e r r i t o r i e s (Chapman 1962, Chapman 1966, Edmundson et a l . 1968, Mason 1976, D i l l 1978a, D i l l et a l . 1981). Because food i s c l o s e l y a s s o c i a t e d with a g o n i s t i c a c t i v i t y i n j u v e n i l e 70 salmonids (Slaney and Northcote 1974, Mason 1976, D i l l et a l . 1981) i t i s easy to envisage strong s e l e c t i v e pressures a s s o c i a t e d with food supply. There i s an i m p l i c i t assumption i n the salmonid l i t e r a t u r e that i t i s advantageous f o r j u v e n i l e s to get as l a r g e as p o s s i b l e as q u i c k l y as p o s s i b l e (Wedemeyer et a l . 1980, D i l l et a l . 1981, B i l t o n et a l . 1982). Smolting i n salmonids appears, at l e a s t i n p a r t , to be a f u n c t i o n of s i z e (Elson 1957, Hoar 1976, Wedemeyer et a l . 1980) and a f i s h that does not reach a t h r e s h o l d s i z e by the a p p r o p r i a t e time of the year may have to spend, a<n ex.tra., year in f.r-es,h. water,, and. thus be. exposed to an e x t r a year of p r e d a t o r s and the winter environment (Bustard and Narver 1975). D i f f e r e n t growth r a t e s i n salmonids are a r e s u l t of a v a r i e t y of f a c t o r s . Growth d i f f e r e n c e s can be due to h e r i t a b l e d i f f e r e n c e s ( R e i s e n b i c h l e r and Mclntyre 1977, Saunders 1981) or to d i f f e r e n c e s i n environmental parameters such as temperature and food abundance w i t h i n r e a r i n g areas ( B r e t t et a_l. 1969, B r e t t 1976). Fitness- (the relative', s u r v i v a l of- a* genotype"- in' a» pop u l a t i o n ) i n j u v e n i l e coho may be a f u n c t i o n of food. D i l l (1978b) i m p l i e s that under s i m i l a r c o n d i t i o n s energy intake (food) i n j u v e n i l e coho i s a f u n c t i o n of t e r r i t o r y s i z e and that a g g r e s s i v e i n d i v i d u a l s h o l d l a r g e r t e r r i t o r i e s than l e s s a g g r e s s i v e i n d i v i d u a l s . Hope Slough f i s h show a much higher a b s o l u t e l e v e l of aggression as demonstrated i n the I n t e r p o p u l a t i o n Challenge t e s t and dominant Hope Slough f i s h garner l a r g e r t e r r i t o r i e s than 71 Nathan Creek f i s h (Stream Tank D i s t r i b u t i o n o b s e r v a t i o n s ) . Consequently the s u r v i v a l r a t e s of these d i f f e r e n t genotypes would vary i n d i f f e r i n g environments. Large t e r r i t o r i e s , however, may be too c o s t l y to defend. Thus, i f the- l e v e l of aggression i s at l e a s t i n pa r t g e n e t i c a l l y c o n t r o l l e d and the growth rate d i f f e r e n c e s in these p o p u l a t i o n s are a r e s u l t of environment, n a t u r a l s e l e c t i o n should operate to ad j u s t to a long term food abundance j u s t as D i l l et a l . (1981) argue that i n d i v i d u a l coho can b e h a v i o u r a l l y change to ad j u s t to a p r e v a i l i n g l o c a l food a v a i l a b i l i t y . In Hope Slough and Nathan Creek there are major d i f f e r e n c e s in coho growth r a t e s . These suggest that Nathan Creek possesses much b e t t e r h a b i t a t f o r coho. Perhaps, i n the more benign h a b i t a t of Nathan Creek, food and s u i t a b l e t e r r i t o r y s i t e s are more abundant than i n Hope Slough and thus s e l e c t i o n f o r aggr e s s i o n i s l e s s i n t e n s e . 72 LITERATURE CITED A l l e n d o r f , F.W. and F.M. U t t e r . 1979. P o p u l a t i o n g e n e t i c s , p. 407-454. In W.S. Hoar, D.S. R a n d a l l , and J.R. B r e t t [eds.] F i s h P h y s i o l o g y . V o l . 8. Academic p r e s s , New York, NY. Avers, C.J. 1980. G e n e t i c s . D. Van Nostrand Company. New York. 659 pp. B a l l i n , P.J. 1973. Geographic v a r i a t i o n i n c o u r t s h i p behaviour of the guppy, P o e c i l i a r e t i c u l a t a . M.Sc. T h e s i s . Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia. Barnard, C.J. 1983. Animal behaviour: ecology and e v o l u t i o n . Croon Helm, London. 339 pp. Bams, R.A. 1976. S u r v i v a l and p r o p e n s i t y f o r homing as a f f e c t e d by presence or absence of l o c a l l y adapted p a t e r n a l genes in two t r a n s p l a n t e d p o p u l a t i o n s of pink salmon (Oncorhynchus gorbuscha). J . F i s h . Res. Bd. Canada 33: 2716-2725. B i l t o n , H.T., D.F. A l d e r d i c e , and J.T. Schnute. 1982. I n f l u e n c e of time and s i z e at r e l e a s e of j u v e n i l e coho salmon (Oncorhynchus k i s u t c h ) on r e t u r n s at m a t u r i t y . Can. J . F i s h . Aquat. S c i . 39:426-447. B i r c h G-.J. V984-. A comparison' of smoTt-ing- i n two p o p u l a t i o n s of coho salmon (Oncorhynchus k i s u t c h ) i n B r i t i s h Columbia. M.Sc. T h e s i s . Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia, ( i n p r e p a r a t i o n ) . Bowler, B. 1975. F a c t o r s i n f l u e n c i n g g e n e t i c c o n t r o l i n lakeward m i g r a t i o n s of c u t t h r o a t t r o u t f r y . Trans. Am. F i s h . Soc. 104:474-482. Brannon, E.L. 1967. Genetic c o n t r o l of migratory behaviour of newly emerged sockeye salmon f r y . I n t . Pac. Salmon F i s h . Comm. Prog. Rep. No. 16:1-31. 73 B r e t t , J.R. 1976. Scope f o r metabolism and growth of sockeye salmon, Oncorhynchus nejrka, and some r e l a t e d e n e r g e t i c s . J . F i s h . Res. Bd. Canada 33:307-313. B r e t t , J.R., J.E. Shelbourn, and C T . Shoop. 1969. Growth r a t e and body composition of f i n g e r l i n g sockeye salmon, Oncorhynchus nerka, i n r e l a t i o n to temperature and r a t i o n s i z e . J . F i s h . Res. Bd. Canada 26:2363-2394. Burns, J.W. 1971. The c a r r y i n g c a p a c i t y f o r j u v e n i l e salmonids i n some northern C a l i f o r n i a streams. C a l i f . F i s h and Game 57:44-57. Bustard, D.R. and D.W. Narver. 1975. Aspects of the winter ecology of j u v e n i l e coho salmon (Oncorhynchus k i s u t c h ) and s.teelhead. trout. (Salmo. qa-i.r.dneri.) . J . Fish.. Res.. Bd.. Canada 32:667-680. Carey, W.E. and D.L.G. Noakes. 1981. Development of photobehavioural responses i n young rainbow t r o u t , Salmo  g a i r d n e r i Richardson. J . F i s h . B i o l . 14:285-296. Chapman, D.W. 1962. Aggressive behavior i n j u v e n i l e coho salmon as a cause of e m i g r a t i o n . J . F i s h . Res. Bd. Canada 19: 1047-1080. Chapman, D.W. 1966. Food and space as r e g u l a t o r s of salmonid p o p u l a t i o n s i n streams. Amer. Nat. 100:345-357. C h i l d , A.R. , A.M. B u r n e l l , and N.P. W i l k i n s . 19'-7-6v The- e x i s t e n c e of two races of A t l a n t i c salmon (Salmo s a l a r L.) i n the B r i t i s h I s l e s . J . F i s h . B i o l . 8:35-43. Cole, K.S. and D.L.G. Noakes. 1980. Development of e a r l y s o c i a l behaviour of rainbow t r o u t , Salmo g a i r d n e r i ( P i s c e s , Salmonidae). B e h a v i o u r a l Processes 5:97-112. D i l l , L.M. 1978a. Aggressive d i s t a n c e i n j u v e n i l e coho salmon (Oncorhynchus k i s u t c h ) . Can. J . Zool. 56:1441-1446. 74 D i l l , L.M. 1978b. An energy-based model of optimal f e e d i n g -t e r r i t o r y s i z e . T h e o r e t i c a l P o p u l a t i o n B i o l o g y . 14:396-429. D i l l , L.M., R.C. Ydenberg, and A.H.G. F r a s e r . 1981. Food abundance and t e r r i t o r y s i z e i n j u v e n i l e coho salmon (Oncorhynchus k i s u t c h ) . Can. J . Zool. 59:1801-1809. Edmundson, E., F.E. E v e r e s t , and D.W. Chapman. 1968. Permanence of s t a t i o n in j u v e n i l e chinook salmon and ste e l h e a d t r o u t . J . F i s h . Res. Bd. Canada 25:1453-1464. E l s o n , P.F. 1957. The importance of s i z e in the change from par r to smolt i n A t l a n t i c salmon. Canad. F i s h C u l t . 21:1-6. G a l l u p , G.G. 1968. Mirror-image s t i m u l a t i o n . P s y c h o l . B u l l . 70: 782-793. Glova, G.J. 1978. P a t t e r n and mechanism of resource p a r t i t i o n i n g between stream p o p u l a t i o n s of j u v e n i l e coho salmon (Oncorhynchus k i s u t c h ) and c o a s t a l c u t t h r o a t t r o u t (Salmo  c l a r k i c l a r k i ) . Ph.D. T h e s i s . Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia. Hartman, G.F. 1965. The r o l e and i n t e r a c t i o n of u n d e r y e a r l i n g coho salmon (Oncorhynchus k i s u t c h ) and st e e l h e a d t r o u t (Salmo g a i r d n e r i ) . J . F i s h . Res. Bd. Canada 22: 1035-1081. Hartman-, G'-.F". and' C".A-. G i l l . 19'G8K D i s t r i b u t i o n s ? of juvenile-s t e e l h e a d and c u t t h r o a t t r o u t (Salmo g a i r d n e r i and S. c l a r k i c l a r k i ) w i t h i n streams i n southwestern B r i t i s h Columbia. J . F i s h . Res. Bd. Canada 25:33-48. Hinde, R.A. 1975. The concept of f u n c t i o n , p. 3-15. I_n G. Baerends, C. Beer, and A. Manning [eds.] F u n c t i o n and e v o l u t i o n i n behaviour: essays i n honour of P r o f e s s o r Niko Tinbergen FRS. Clarendon Press, Oxford. 393 pp. H j o r t , R.C. and C.B. Schreck. 1982. Phenotypic d i f f e r e n c e s among stocks of hatchery and w i l d coho salmon, Oncorhynchus  k i s u t c h , i n Oregon, Washington, and C a l i f o r n i a . F i s h . B u l l . , U.S. 80: 105-1 1 9-. 75 Hoar, W.S. 1951. The behaviour of chum, pink and coho salmon in r e l a t i o n to t h e i r seaward m i g r a t i o n . J . F i s h . Res. Bd. Canada 8:241-263. Hoar, W.S. 1976. Smolt t r a n s f o r m a t i o n : e v o l u t i o n , behaviour, and p h y s i o l o g y . J . F i s h . Res. Bd. Canada 33:1234-1252. Huntingford, F.A. 1976. The r e l a t i o n s h i p between a n t i - p r e d a t o r behaviour and a g g r e s s i o n among c o n s p e c i f i c s i n the t h r e e -spined s t i c k l e b a c k , Gasterosteus a c u l e a t u s . Animal Behaviour 24:245-260. Ihssen, P.E., H.E. Booke, J.M. Casselman, J.M. McGlade, N.R. Payne, and F.M. U t t e r . 1982. Stock i d e n t i f i c a t i o n : m a t e r i a l s and methods. Can. J . F i s h . Aquat. S c i . 38: 1838-1855. Ihssen, P.E. and J.S. T a i t . 1974. Genetic d i f f e r e n c e s i n r e t e n t i o n of swimbladder gas between two p o p u l a t i o n s of lake t r o u t S a l v e l i n u s namaycush. J . F i s h . Bd. Canada 31: 1351-1354. Keenleyside, M.H.A. and F.T. Yamamoto. 1962. T e r r i t o r i a l behaviour of j u v e n i l e A t l a n t i c salmon (Salmo s a l a r L . ) . Behaviour 19:139-169. K i r p i c h n i k o v , V.S. 1981. Genetic bases of f i s h s e l e c t i o n . S p r i n g e r - V e r l a g . B e r l i n . 410 pp. M a r s h a l l , D.E. , R-.F. Brown, M';M. Musgrave-, and D. G. Demontier. 1979. P r e l i m i n a r y catalogue of salmon streams and spawning escapements of s t a t i s t i c a l area 29 (New W e s t m i n i s t e r ) . Canad. Data Rep. of F i s h . & Aquat. S c i . 115:1-73. M a r s h a l l , D.E., C.I. Manzon, and E.W. B r i t t o n . 1980. Catalogue of salmon streams and spawning escapements of C h i l l i w a c k -Hope s u b d i s t r i c t . Canad. Data Rep. of F i s h . & Aquat. S c i . 203:1-167. Mason, J.C. 1976. Response of u n d e r y e a r l i n g coho salmon to supplemental f e e d i n g i n a n a t u r a l stream. J . W i l d l . Manag. 40:775-788. 76 Mason, J.C. and D.W. Chapman. 1965. S i g n i f i c a n c e of e a r l y emergence, environmental r e a r i n g c a p a c i t y , and behav i o u r a l ecology of j u v e n i l e coho salmon i n stream' channels. J . F i s h . R e s v Bd-. Canada. 22:173r~1 9-0**-. May, B.P. 1980. The salmonid genome: e v o l u t i o n a r y r e s t r u c t u r i n g f o l l o w i n g a t e t r a p l o i d event. Ph.D. Th e s i s Pennsylvania State U n i v e r s i t y , P e n n s y l v a n i a . Murray, C B . 1980. Some e f f e c t s of temperature on zygote and a l e v i n s u r v i v a l , r a t e of development and s i z e of hatching and emergence of P a c i f i c salmon and rainbow t r o u t . M.Sc. T h e s i s . Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia. Newman,. M.A. 1956. S o c i a l behav.i.o.r and. inter.sped,fl-a c.ompetition-in two t r o u t s p e c i e s . P h y s i o l . Z o o l . 29:64-81. North, E. 1979. Aggressive behaviour of j u v e n i l e brown t r o u t Salmo t r u t t a L: an a n a l y s i s of the wigwag d i s p l a y . J . F i s h B i o l . 15:571-577. Northcote, T.G. and B.W. Kelso. 1981. D i f f e r e n t i a l response to water c u r r e n t by two homozygous LDH phenotypes of young rainbow t r o u t (Salmo g a i r d n e r i ) . Can. J . F i s h . Aquat. S c i . 38:348-352. Powell, R. and C F . Wehrhahn. 1984. E l e c t r o p h o r e t i c v a r i a t i o n i n the coho salmon of B r i t i s h Columbia, ( i n p r e p a r a t i o n ) . P r i t c h a r d , A.L. 1936. Fa c t s concerning the coho salmon (Oncorhynchus k i s u t c h ) i n the commercial ca t c h e s of B r i t i s h Columbia as determined from t h e i r s c a l e s . Prog. Rep. Pac. Bio. S t a t i o n , Naniamo, B r i t i s h Columbia and Pac. F i s h . Expt. S t a t i o n , P r i n c e Rupert, B r i t i s h Columbia 29: 16-20. R a l e i g h , R.F. 1967. Genetic c o n t r o l i n the lakeward m i g r a t i o n s of sockeye salmon (Oncorhynchus nerka) f r y . J . F i s h . Res. Bd. Canada 24:2613-2622. 77 R a l e i g h , R.F. 1971. Innate c o n t r o l of m i g r a t i o n s of salmon and t r o u t f r y from n a t a l g r a v e l s to r e a r i n g areas. Ecology 52: 291-297. R e i s e n b i c h l e r , R.K. and J.D. M c l n t y r e . 1977. Genetic d i f f e r e n c e s i n growth and s u r v i v a l of j u v e n i l e hatchery and w i l d s t e e l h e a d t r o u t Salmo g a i r d n e r i . J . F i s h . Res. Bd. Canada 34:123-128. R i c k e r , W.E. 1972. H e r e d i t y and environmental f a c t o r s a f f e c t i n g c e r t a i n salmonid p o p u l a t i o n s , p. 19-160. _In R.C. Simon and P.A. L a r k i n [eds.] H.R. MacMillan L e c t u r e s i n F i s h e r i e s , The Stock Concept i n P a c i f i c Salmon, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia. R i d d e l l , B.E. and W.C. Leggett. 1981. Evidence of an a d a p t i v e b a s i s f o r geographic v a r i a t i o n in body morphology and time of downstream m i g r a t i o n of j u v e n i l e A t l a n t i c salmon (Salmo  s a l a r ) . Can. J . F i s h . Aquat. S c i . 38:308-320. R i d d e l l , B.E., W.C. Leggett, and R.L. Saunders. 1981. Evidence of a daptive p o l y g e n i c v a r i a t i o n between two p o p u l a t i o n s of A t l a n t i c salmon (Salmo s a l a r ) n a t i v e to t r i b u t a r i e s of the S.W. Miramichi R i v e r , N.B. Can. J . F i s h . Aquat. S c i . 38: 321-333. Saunders, R.L. 1981. A t l a n t i c salmon (Salmo s a l a r ) stocks and management i m p l i c a t i o n s i n the Canadian A t l a n t i c p r o v i n c e s and New England, USA. Can. J . F i s h . Aquat. S c i . 38:1612-1625. S c o t t , W.B. and E . J . Crossman. 1973. Freshwater F i s h e s of Canada. F i s h . Res. Bd. Canada B u l l . 184:1-966. Seghers, B.H. 1974. An a n a l y s i s of geographic v a r i a t i o n i n the a n t i - p r e d a t o r a d a p t a t i o n s of the guppy, P o e c i l i a  r e t i c u l a t a . Ph.D. T h e s i s . Department of Zoology. U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia. Slaney, P.A. and T.G. Northcote. 1974. E f f e c t s of prey abundance on d e n s i t y and t e r r i t o r i a l behaviour of young rainbow t r o u t (Salmo g a i r d n e r i ) i n l a b o r a t o r y stream channels. J . F i s h . Res-. Bd". Canada- 31 : 120T'-1'-209v 78 Sokal, R.R. and F . J . R o h l f . 1981. Biometry: the p r i n c i p l e s and p r a c t i c e of s t a t i s t i c s i n b i o l o g i c a l r e s e a r c h . 2nd ed. N.H. Freeman. San F r a n s i s c o . 859 pp. S t r i n g e r G.E. and W.S. Hoar. 1955. Aggressive behaviour of u n d e r y e a r l i n g Kamloops t r o u t . Can. J . Z o o l . 33:148-160. T a y l o r , E.B. 1984. Adaptive v a r i a t i o n i n body morphology and i t s r e l a t i o n s h i p to swimming performance in p o p u l a t i o n s of coho salmon (Oncorhynchus k i s u t c h ) i n B r i t i s h Columbia. M.Sc. T h e s i s . Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia, ( i n p r e p a r a t i o n ) . Tinbergen, N. 1967. S o c i a l behaviour i n animals: with s p e c i a l r e f e r e n c e to v e r t e b r a t e s . 2nd ed. Methuen and Co. L t d . London; and John Wil e y and-Sons,. I n c . New-York-. 150 pp... T r o j n a r , J.R. and R.J. Behnke. 1974. Management i m p l i c a t i o n s of e c o l o g i c a l s e g r e g a t i o n between two i n t r o d u c e d p o p u l a t i o n s of c u t t h r o a t t r o u t i n a small Colorado l a k e . Trans. Am. F i s h . Soc. 103:423-430. U t t e r , F.E., W.E. Ames, and H.O. Hodgins. 1970. T r a n s f e r r i n polymorphism in coho salmon (Oncorhynchus k i s u t c h ) . J . F i s h . Res. Bd. Canada 27:2371-2373. Wedemeyer, G.A., R.L. Saunders, and W.C. C l a r k e . 1980. Environmental f a c t o r s a f f e c t i n g s m o l t i f i c a t i o n and e a r l y marine s u r v i v a l of anadromous salmonids. Mar. F i s h . Rev. NOAA. 42:1-14. Wi t h l e r R.E., M.C. Healy, and B.E. R i d d e l l . 1982. Annotated b i b l i o g r a p h y of g e n e t i c v a r i a t i o n i n the f a m i l y Salmonidae. Canad. Tech. Rept. F i s h . Aquat. S c i . 1098:1-161. 79 APPENDIX 1 Percentage of time spent performing each behaviour for each MIS experiment ( d e s c r i p t i o n s of the behaviours are found i n Table 2.) A. P i l o t Experiment (9 days of o b s e r v a t i o n , 10 days d u r a t i o n , 3 minute o b s e r v a t i o n p e r i o d s per f i s h , 29 f i s h per po p u l a t i o n ) Nathan Creek Hope Slough Behaviour NULL 37.9 50.6 SWIM AGAINST MIRROR 56.6 38.4 HEADS UP WIG-WAG 0.2 1 .6 HORIZONTAL WIG-WAG 0.2 1 .0 HEADS DOWN WIG-WAG 0.0 0.2 DORSAL FIN ERECTION 0.9 8.1 SUBMISSION 1 .2 0.1 B. R e p l i c a t e Experiment (10 days of o b s e r v a t i o n , 20 days d u r a t i o n , 2 minute observat ion p e r i o d s per f i s h , 30 f i s h per po p u l a t i o n ) Nf x : Nm Hf x Hm Nf x Hm Hf x Nm Behaviour NULL 86.7 71.7 77.3 79.2 SWIM AGAINST MIRROR 10.8 22.6 18.4 15.3 HEADS UP WIG-WAG 0.1 0.3 0.5 1 . 1 HORIZONTAL WIG-WAG 0.1 0.1 0.1 0.2 HEADS DOWN WIG-WAG 0.0 0.0 0.0 0.0 DORSAL FIN ERECTION 1.6 4.6 3.4 3.2 SUBMISSION 0.7 0.7 0.3 1 .0 C. Wild F i s h Experiment (7 days of o b s e r v a t i o n , 14 days d u r a t i o n , 2 minute o b s e r v a t i o n p e r i o d s per f i s h , 60 f i s h per p o p u l a t i o n ) Nathan Creek Hope Slough Behaviour NULL 57.3 59.8 SWIM AGAINST MIRROR 33.3 28.8 HEADS UP WIG-WAG 2.9 2.9 HORIZONTAL WIG-WAG 0.3 0.8 HEADS DOWN WIG-WAG 0.0 0.0 DORSAL FIN ERECTION 4.3 6.0 SUBMISSION 1.8 1.5 

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