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An experimental examination of behavioural isolation between sockeye salmon and kokanee, the anadromous… Foote, Christopher J. 1987

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AN EXPERIMENTAL EXAMINATION OF BEHAVIOURAL ISOLATION BETWEEN SOCKEYE SALMON AND KOKANEE, THE ANADROMOUS AND NON-ANADROMOUS FORMS OF ONCORHYNCHUS NERKA by CHRISTOPHER J . FOOTE B.Sc. U n i v . o f T o r o n t o , T o r o n t o 1977 M.Sc. U n i v . o f M a n i t o b a , W i n n i p e g 1979 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES (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 a s 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 UNIVERSITY OF BRITISH COLUMBIA November 1987 © C h r i s t o p h e r J . F o o t e , 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of 2. o O \ & V The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date fitc, a °\ \<\ E > DE-6(3/81) i i ABSTRACT The g e n e t i c r e l a t i o n s h i p of anadromous ( s o c k e y e salmon) and non-anadromous (kokanee) O n c o r h y n c h u s n e r k a was examined i n c o n j u n c t i o n w i t h t h e b r e e d i n g b e h a v i o u r o f t h e two forms t o d e t e r m i n e : (1) i f t h e r e i s e v i d e n c e of g e n e t i c d i v e r g e n c e between t h e forms where t h e y spawn s y m p a t r i c a l l y ; (2) i f s u c h d i v e r g e n c e i s a s s o c i a t e d w i t h s i g n i f i c a n t p r e m a t i n g i s o l a t i o n between t h e forms and; (3) i f p r e m a t i n g i s o l a t i o n r e s u l t s d i r e c t l y from t h e s i z e d i f f e r e n c e between t h e forms ( s o c k e y e a r e much l a r g e r t h a n kokanee a t m a t u r i t y ) . B o t h s e x e s e x h i b i t spawning t e r r i t o r i a l i t y ; f e m a l e s e s t a b l i s h and d e f e n d p a r t i c u l a r n e s t s i t e s u n t i l d e a t h o r d i s p l a c e m e n t , males d e f e n d a c c e s s t o s p e c i f i c f e m a l e s from o t h e r m a l e s u n t i l t h e f e m a l e has spawned o u t , t h e y a r e d i s p l a c e d , o r l e a v e t o compete f o r a d d i t i o n a l m ates. S i z e and p r i o r a c c e s s t o r e s o u r c e s (mates a n d / o r s p e c i f i c a r e a s ) a r e s i g n i f i c a n t f a c t o r s i n i n t r a s e x u a l a g g r e s s i o n i n b o t h s e x e s , w i t h s i z e t h e m a j o r f a c t o r i n males and p r i o r a c c e s s t h e m a j o r f a c t o r i n f e m a l e s . F e m a l e s a c c o m p a n i e d by m a l e s l a r g e r t h a n t h e m s e l v e s l o s e w e i g h t a t a f a s t e r r a t e t h a n t h o s e a c c o m p a n i e d by m a l e s s m a l l e r t h a n t h e m s e l v e s . W e i g h t l o s s i s r e l a t e d t o egg l o s s , i n d i c a t i n g f e m a l e s spawn a t a f a s t e r r a t e when a c c o m p a n i e d by l a r g e m a l e s . M a l e mate p r e f e r e n c e depends on t h e s i z e of t h e m a l e . M a l e s of v a r i o u s s i z e s p r e f e r f e m a l e s of t h e i r own s i z e o r l a r g e r o v e r f e m a l e s s m a l l e r t h a n t h e m s e l v e s . In c o n t r a s t , a l l s i z e s of m a l e s t e s t e d d e m o n s t r a t e d no p r e f e r e n c e between f e m a l e s o f t h e i r own s i z e and t h o s e l a r g e r . L a r g e m a l e s , w h i c h have t h e w i d e s t r a n g e o f p o t e n t i a l mates ( b e c a u s e o f male i n t r a s e x u a l c o m p e t i t i o n and f e m a l e c h o i c e ) , a r e t h e most s e l e c t i v e and s m a l l m a l e s , w h i c h have t h e n a r r o w e s t r a n g e o f p o t e n t i a l mates, a r e t h e l e a s t s e l e c t i v e . T h e r e were s i g n i f i c a n t d i f f e r e n c e s i n a l l e l e f r e q u e n c i e s between s y m p a t r i c a l l y s p a w n ing s o c k e y e and k o k anee. However, t h e r e were no c o n s i s t e n t d i f f e r e n c e s between s o c k e y e and kokanee a t any of f i v e p o l y m o r p h i c l o c i e xamined. The e x t e n t of g e n e t i c d i f f e r e n t i a t i o n between s y m p a t r i c forms a p p e a r s t o be l e s s t h a n t h a t between n e i g h b o u r i n g p o p u l a t i o n s o f t h e same form, j u d g i n g from an e x a m i n a t i o n of a l l e l e f r e q u e n c i e s a n d / o r a l l e l e c o m p o s i t i o n s . T h e r e was e x t e n s i v e a s s o r t a t i v e m a t i n g by form between s o c k e y e and kokanee, w h i c h was n o t t o t a l l y a c c o u n t e d f o r by t h e l a r g e s i z e d i f f e r e n c e . In t h e two s y s t e m s examined, m a l e s p r e f e r r e d t o mate w i t h f e m a l e s o f t h e i r own f o r m . In s o c k e y e , s u c h p r e f e r e n c e s a r e e x p e c t e d b e c a u s e o f t h e s i z e d i f f e r e n c e between f o r m s . In kokanee, s u c h p r e f e r e n c e s a r e not e x p e c t e d b a s e d on s i z e a l o n e , s u g g e s t i n g t h e e v o l u t i o n of p r e m a t i n g i v i s o l a t i n g mechanisms. The d e g r e e o f p r e m a t i n g i s o l a t i o n 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 t h e e x t e n t of g e n e t i c d i v e r g e n c e between s y m p a t r i c f o r m s . The r e s u l t s of t h i s s t u d y a r e r e l a t e d t o e x i s t i n g models o f s y m p a t r i c s p e c i a t i o n t o h y p o t h e s i z e t h a t s o c k e y e and kokanee have d i v e r g e d i n s y m p a t r y . The p r o b a b l e d i f f e r e n c e s i n s e l e c t i o n between t h e m a r i n e and f r e s h w a t e r e n v i r o n m e n t s c o u p l e d w i t h t h e a s s o r t a t i v e m a t i n g r e s u l t i n g f r o m t h e i r s i z e d i f f e r e n c e may have c a u s e d s u b s e q u e n t g e n e t i c d i v e r g e n c e . T h i s d i v e r g e n c e a p p e a r s t o have been f o l l o w e d by t h e e v o l u t i o n o f p r e m a t i n g i s o l a t i o n . V TABLE OF CONTENTS ABSTRACT i i L I S T OF TABLES x L I S T OF FIGURES x i i ACKNOWLEDGEMENTS x i x INTRODUCTION 1 C h a p t e r 1: E x p e r i m e n t a l e x a m i n a t i o n o f spawning t e r r i t o r i a l i t y i n salmon 6 I n t r o d u c t i o n 6 1. An e x p e r i m e n t a l e x a m i n a t i o n of t h e m a t i n g s y s t e m i n kokanee 8 Methods 8 A. C h r o n o l o g y of s e t t l e m e n t on t h e spawning g r o u n d s 12 B. An e x p e r i m e n t a l e x a m i n a t i o n of t e r r i t o r i a l i t y i n m a l e s and f e m a l e s 12 C. The e f f e c t of c o m p e t i t o r s on t h e commencement of t e r r i t o r i a l i t y i n kokanee 16 R e s u l t s 16 A. C h r o n o l o g y o f s e t t l e m e n t on t h e spawning g r o u n d s 17 B. An e x p e r i m e n t a l e x a m i n a t i o n of t e r r i t o r i a l i t y i n m a l e s and f e m a l e s 17 C. The e f f e c t of c o m p e t i t o r s on t h e commencement o f t e r r i t o r i a l i t y 34 2. The e f f e c t s of s i z e and p r i o r a c c e s s i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n 39 Methods 39 A. P r e f e r r e d s pawning s i t e s 39 B. The e f f e c t s o f s i z e i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n 40 C. The e f f e c t of p r i o r a c c e s s i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n 40 R e s u l t s 41 A. P r e f e r r e d s pawning s i t e s 41 B. S i z e i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n 50 C. The e f f e c t of p r i o r a c c e s s i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n 53 3. E f f e c t s of s i z e and p r i o r r e s i d e n c e i n male i n t r a s e x u a l c o m p e t i t i o n 55 M ethods 55 R e s u l t s 58 A. S i z e i n male i n t r a s e x u a l c o m p e t i t i o n 58 B. P r i o r a c c e s s i n male i n t r a s e x u a l c o m p e t i t i o n ...61 C. The i n t e r a c t i o n of s i z e and p r i o r a c c e s s 62 D. F a c t o r s i n v o l v e d i n t h e a d v a n t a g e a s s o c i a t e d w i t h p r i o r a c c e s s 63 D i s c u s s i o n 66 F emale t e r r i t o r i a l i t y 66 M a l e t e r r i t o r i a l b e h a v i o u r 69 C o m p a r i s o n of spawning t e r r i t o r i a l i t y i n m a l e s and f e m a l e s 73-v i i CHAPTER 2: Female mate c h o i c e i n salmon 76 I n t r o d u c t i o n .76 Methods 78 R e s u l t s 80 D i s c u s s i o n 86 E v i d e n c e of f e m a l e p r e f e r e n c e f o r l a r g e m a l e s 86 P o s s i b l e a d a p t i v e s i g n i f i c a n c e o f f e m a l e mate c h o i c e .88 CHAPTER 3: M a l e mate c h o i c e d e p e n d e n t on male s i z e i n salmon 91 I n t r o d u c t i o n 91 Methods 94 R e s u l t s 99 A. Mate s e l e c t i o n o f s m a l l m a l e s when g i v e n a c h o i c e between s m a l l f e m a l e s o f s l i g h t l y d i f f e r e n t s i z e ..99 B. Mate s e l e c t i o n of s m a l l and medium s i z e d m a l e s g i v e n a c h o i c e between s m a l l and medium f e m a l e s ..107 C. Mate s e l e c t i o n o f • s m a l l and medium s i z e d m a l e s g i v e n a c h o i c e between s m a l l and l a r g e f e m a l e s ...107 D. Mate s e l e c t i o n of medium and l a r g e m a l e s when g i v e n a c h o i c e between medium and l a r g e f e m a l e s ..108 E. The e f f e c t o f c o m p e t i t i o n on s m a l l male c h o i c e ...108 Female r e s p o n s e t o t h e p r e s e n t a t i o n of m a l e s 109 D i s c u s s i o n 111 E v i d e n c e t h a t male c h o i c e depends on male s i z e 111 P o s s i b l e a d a p t i v e s i g n i f i c a n c e o f s i z e d e p e n d e n t male mate c h o i c e 116 The p a t t e r n of a s s o c i a t i o n of m a l e s and f e m a l e s on v i i i t h e spawning g r o u n d s 118 C o m p a r i s o n o f male c h o i c e i n salmon and o t h e r f i s h e s 120 CHAPTER 4: A b i o c h e m i c a l g e n e t i c e x a m i n a t i o n of s o c k e y e salmon and kokanee . . 123 I n t r o d u c t i o n 123 Methods 126 R e s u l t s 133 A n n u a l v a r i a t i o n i n a l l e l e f r e q u e n c i e s 133 C o m p a r i s o n of s y m p a t r i c s o c k e y e and kokanee i n t h r e e l a k e s y s t e m s 134 O v e r a l l c o m p a r i s o n of s o c k e y e and kokanee i n B r i t i s h C o l u m b i a 139 D i s c u s s i o n 143 The r e l a t i o n s h i p of s o c k e y e and kokanee 143 G e n e t i c d i f f e r e n t i a t i o n between s y m p a t r i c s o c k e y e and kokanee .148 P o s s i b l e s y m p a t r i c o r i g i n of s o c k e y e and kokanee ....150 CHAPTER 5: An e x p e r i m e n t a l e x a m i n a t i o n of a s s o r t a t i v e m a t i n g between s o c k e y e salmon and kokanee 154 I n t r o d u c t i o n 154 1. A s s o r t a t i v e m a t i n g between s o c k e y e salmon and kokanee 157 Methods 157 R e s u l t s 158 2. Kokanee and s o c k e y e male c h o i c e i n t h e p r e s e n c e and a b s e n c e of c o m p e t i t o r s 162 Methods 162 R e s u l t s 165 A. M a l e c h o i c e i n t h e a b s e n c e o f c o m p e t i t o r s 165 B. Kokanee and j a c k s o c k e y e male c h o i c e i n t h e p r e s e n c e o f a l a r g e s o c k e y e male 177 C. Kokanee and j a c k male c h o i c e i n t h e p r e s e n c e o f a l a r g e s o c k e y e and a male o f t h e i r own s i z e ..178 D. C o m p a r i s o n o f t h e b e h a v i o u r of kokanee m a l e s t o w a r d s s o c k e y e f e m a l e s i n P i e r r e and Narrows c r e e k s 180 E . C o m p a r i s o n of t h e sneak b e h a v i o u r of kokanee ..males from P i e r r e and Narrows c r e e k s 185 3. F a c t o r s i n v o l v e d i n d e t e r m i n i n g t h e a t t r a c t i v e n e s s o f kokanee and s o c k e y e f e m a l e s t o m a l e s 186 Methods 186 R e s u l t s 190 D i s c u s s i o n 196 P r o x i m a t e mechanisms i n v o l v e d i n a s s o r t a t i v e m a t i n g .196 E v i d e n c e of a form e f f e c t i n kokanee male c h o i c e ....198 P o s s i b i l i t y t h a t t h e form e f f e c t i n male c h o i c e a r o s e f r o m s e l e c t i o n f o r p r e m a t i n g i s o l a t i o n 199 C o n c l u s i o n s 207 L i t e r a t u r e c i t e d 212 X L I S T OF TABLES T a b l e 1. The mean s i z e and s i z e r a n g e o f f i s h e s u s e d i n t e r r i t o r i a l i t y e x p e r i m e n t s 21 T a b l e 2. The mean number o f d i g s and a g g r e s s i v e b e h a v i o u r s d i s p l a y e d by 25 m a l e s and f e m a l e s when t h e s e x e s were h e l d t o g e t h e r and s e p a r a t e l y 22 T a b l e 3. C o m p a r i s o n of t h e i n t e r s e x u a l a g g r e s s i v e b e h a v i o u r o f males and f e m a l e s 28 T a b l e 4. The mean f o r k l e n g t h s and s i z e g r o u p s o f f e m a l e s and males u s e d i n t h e e x a m i n a t i o n of male mate c h o i c e , p l u s a summary of t h e c h o i c e s made i n f i v e e x p e r i m e n t s 100 T a b l e 5. The mean number and d i f f e r e n c e i n d i g s p e r f o r m e d by t h e s m a l l e s t and l a r g e s t f e m a l e s i n t h e f i v e c h o i c e e x p e r i m e n t s 110 T a b l e 6. The l o c a t i o n and form of 0^ n e r k a p o p u l a t i o n s sampled and t h e r e s u l t s of e l e c t r o p h o r e s i s a t f i v e p o l y m o r p h i c l o c i 129 T a b l e 7. Enzymes and t i s s u e s u s e d t o i n v e s t i g a t e g e n e t i c v a r i a t i o n i n s o c k e y e salmon and kokanee 131 x i T a b l e 8. R e s u l t s o f a n a l y s i s of v a r i a n c e t o d e t e r m i n e t h e s o u r c e s of v a r i a t i o n i n a l l e l e f r e q u e n c i e s a t t h r e e p o l y m o r p h i c l o c i 142 T a b l e 9. D i s t r i b u t i o n of 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 gene d i v e r s i t y a t t h r e e p o l y m o r p h i c l o c i among 29 c o l l e c t i o n s 146 T a b l e 10. The t o t a l number o f kokanee and s o c k e y e o b s e r v e d i n P i e r r e C r e e k , B a b i n e Lake, and Narrows C r e e k , T a k l a L a k e , on d i f f e r e n t o c c a s i o n s o v e r t h e c o u r s e o f t h e spawning r u n s , p l u s t h e r a t i o s of t h e number o f kokanee and s o c k e y e m a l e s a t t e n d i n g i n d i v i d u a l f e m a l e s of t h e two forms ...159 T a b l e 11. The f r e q u e n c y d i s t r i b u t i o n and t h e mean number of c o u r t s h i p d i s p l a y s p e r f o r m e d by i n d i v i d u a l m a l e s o f e a c h of f o u r s i z e c l a s s e s w i t h i n d i v i d u a l s o c k e y e and kokanee f e m a l e s o v e r t e n m i n u t e s o f o b s e r v a t i o n i n an e x p e r i m e n t a l a r e n a 193 T a b l e 12. The d i f f e r e n c e i n t h e number of d i g s p e r f o r m e d by e i g h t s o c k e y e and e i g h t kokanee f e m a l e s when i n t h e a l t e r n a t i n g p r e s e n c e of m a l e s o f e a c h o f two s i z e c l a s s e s 195 X I 1 L I S T OF FIGURES Figure 1. The design of experimental arenas used in the examination of spawning t e r r i t o r i a l i t y in kokanee 10 Figure 2. The number of males and females holding positions in three 4 by 4 m designated areas of the Meadow Creek spawning channel, over the course of the run in September, 1984 18 Figure 3. Mean distance between successive positions held by 25 males and 25 females that were held (A) separate from the opposite sex and (B) together with the opposite sex 23 Figure 4. Total intrasexual aggressive a c t i v i t y over 30 minutes of observation by 25 males and 25 females that were held (A) separate from and (B) together with the opposite sex 2 5 Figure 5. Areas in which individual females, kept apart from males, spent most of their time over (A) five days of undisturbed observation and (B), l a t e r , over one and one half days of repeated displacement 30 Figure 6. Areas in which individual females, in the presence of males, spent most of their time over (A) three days of undisturbed observation and (B) l a t e r , xi i i over one day of repeated displacement 32 Figure 7. Areas in which individual males, kept apart from females, spent most of their time over (A) fiv e days of undisturbed observation and (B) l a t e r , over one and one half days repeated displacement 35 Figure 8. Areas in which individual males, in the presence of females, spent most of their time over (A) three days of undisturbed observation and (B) l a t e r , over one day of, repeated displacement 37 Figure 9. Positions held by 'large' and 'small' kokanee females accompanied by males in arenas 1 and 2... 42 Figure 10. Positions occupied by females (A) before females were removed from the preferred area and (B) five hours after they were removed 46 Figure 11. Positions occupied by females (A) before females were removed from the non-preferred area (B) five hours after they were removed 48 Figure 12. Difference between the number of females from two test groups which were able to hold positions within the preferred spawning area. (A) 'Large' and 'small' females competed for access to preferred po s i t i o n s . (B) Incumbent females competed against xiv immigrant females for access to preferred posit ions.... 51 Figure 13. Difference between test groups in the number of males which held dominant positions beside females, for each of three separate experiments. (A) 'Large* males competed against 'small' males for access to females. (B) Males with four hours prior access to females competed against similar sized immigrant males. (C) 'Small' males with four hours prior access to females competed against 'large' immigrant males 59 Figure 14. Difference between test groups in the number of males which held dominant positions beside females, for each of two experiments. (D) Males which had recently been with females competed against males which had not recently been with females for access to novel females in novel surroundings. (E) Males which had previously been with females competed against males which had not recently been with females for novel females in surroundings familiar only to the f i r s t group of males 64 Figure 15. The weight loss by females accompanied by (A) 'large' males and (B) 'small' males over 18 hours..81 Figure 16. The relationship between subjective scores of female body cavity distension and weight loss 84 XV F i g u r e 17. Male c h o i c e d e p e n d e n t on male s i z e as i n d i c a t e d by t h e median ( + 9 5 % CI) of t h e d i f f e r e n c e i n t i m e s p e n t n e a r a c h o i c e o f two f e m a l e s i n f i v e e x p e r i m e n t s 101 F i g u r e 18. Male c h o i c e d e p e n d e n t on male s i z e as i n d i c a t e d by t h e mean d i f f e r e n c e ( + 95% C I ) i n t o t a l c o u r t s h i p d i s p l a y s p e r f o r m e d t o a c h o i c e of two f e m a l e s i n f i v e e x p e r i m e n t s ....103 F i g u r e 19. Male c h o i c e d e p e n d e n t on t h e s i z e d i f f e r e n c e between t h e t e s t male and ' t h e s m a l l e s t p r e s e n t e d f e m a l e 105 F i g u r e 20. Measure o f a t t r a c t i v e n e s s o f f e m a l e s t o ma l e s b a s e d on t h e i r r e l a t i v e s i z e s 114 F i g u r e 21. L o c a t i o n and f o r m o f n e r k a p o p u l a t i o n s s a m p l e d f o r e l e c t r o p h o r e s i s 127 F i g u r e 22. Phenograms b a s e d on measurements of g e n e t i c s i m i l a r i t y a t t h r e e t o f i v e p o l y m o r p h i c l o c i f o r t h e t h r e e s y s t e m s examined where s o c k e y e and kokanee spawn sympatr i c a l l y 1 36 F i g u r e 23. Phenograms o f t h e r e l a t i o n s h i p among of s o c k e y e salmon and kokanee p o p u l a t i o n s b a s e d on measurements o f g e n e t i c s i m i l a r i t y a t t h r e e p o l y m o r p h i c X V I l o c i 140 Figure 24. Hierarchy used in gene d i v e r s i t y analysis of sockeye salmon and kokanee 144 Figure 25. Kokanee and sockeye male choice between kokanee and sockeye females in the absence (A) and presence of competitors (B, C) in Pierre Creek, as indicated by the median of the difference in time spent near the females 166 Figure 26. Kokanee and sockeye male choice between kokanee and sockeye salmon females in the absence (A) and presence (B, C) of competitors in Pierre Creek', as indicated by the mean difference in the t o t a l number of courtship displays performed 168 Figure 27. The regression of Dig Difference (digs by sockeye - digs by kokanee) between paired sockeye and kokanee females on the size of the male present in Pierre Creek 171 Figure 28. Kokanee male choice between kokanee and sockeye females in the absence (A) and presence (B, C) of competitors in Narrows Creek as indicated by the median of the difference in time spent' near the females 173 x v i i F i g u r e 29. Kokanee male c h o i c e between kokanee and s o c k e y e f e m a l e s i n t h e a b s e n c e (A) and p r e s e n c e (B, C) o f c o m p e t i t o r s i n Narrows C r e e k as i n d i c a t e d by t h e d i f f e r e n c e i n t h e t o t a l number o f c o u r t s h i p d i s p l a y s p e r f o r m e d t o f e m a l e s of t h e two f o r m s 175 F i g u r e 30. The t i m e kokanee m a l e s i n P i e r r e and Narrows C r e e k s s p e n t n e a r s o c k e y e f e m a l e s i n t h e a b s e n c e (A) and p r e s e n c e (B, C) o f c o m p e t i t o r s o v e r t e n m i n u t e s of o b s e r v a t i o n • 181 F i g u r e 31. The number o f c o u r t s h i p d i s p l a y s kokanee m a l e s i n P i e r r e and Narrows C r e e k s p e r f o r m e d t o s o c k e y e f e m a l e s i n t h e a b s e n c e (A) and p r e s e n c e (B, C) o f c o m p e t i t o r s o v e r t e n m i n u t e s o f o b s e r v a t i o n 183 F i g u r e 32. The amount t i m e (A) kokanee m a l e s i n P i e r r e and Narrows c r e e k s s p e n t n e a r s o c k e y e f e m a l e s and t h e number o f c o u r t s h i p d i s p l a y s (B) p e r f o r m e d when no o t h e r c h o i c e was a v a i l a b l e o v e r t e n m i n u t e s of o b s e r v a t i o n i n an e x p e r i m e n t a l a r e n a 187 F i g u r e 33. The a t t r a c t i v e n e s s o f s o c k e y e (a) and kokanee (b) f e m a l e s t o s o c k e y e and kokanee m a l e s as i n d i c a t e d by t h e t o t a l t i m e i n d i v i d u a l m a l e s s p e n t n e a r them when no o t h e r c h o i c e was a v a i l a b l e o v e r t e n m i n u t e s o f o b s e r v a t i o n i n an e x p e r i m e n t a l a r e n a 191 x v i i i F i g u r e 34. The a t t r a c t i v e n e s s o f s o c k e y e f e m a l e s t o kokanee males i n P i e r r e and Narrows c r e e k s as compared t o t h a t e x p e c t e d b a s e d s o l e l y on t h e s i z e d i f f e r e n c e between t h e forms 204 x i x ACKNOWLEDGEMENTS I w i s h t o t h a n k my s u p e r v i s o r , D r . P. A. L a r k i n , f o r h i s a d v i c e , s u p p o r t and encouragement t h r o u g h o u t a l l s t a g e s o f t h i s work. I am i n d e b t e d t o D r s . C. C. L i n d s e y , J . D. M c P h a i l , C. C. Wood and D. P. Swain f o r t h e r e h e l p i n t h e p r e p a r a t i o n of t h i s t h e s i s . R. W i t h l e r i s g r a t e f u l l y a c k n o w l e d g e d f o r i n t r o d u c i n g me t o t h e p r o b l e m . Numerous f r i e n d s h e l p e d i n t h e p r e p a r a t i o n of p a r t s of t h i s t h e s i s , i n p a r t i c u l a r , J . E a d i e , B. A n h o l t , M. L a P o i n t e , S. C o u r t e n a y , E. T a y l o r , A. B l a c h f o r d , G. Brown and D. H a l l . The f i e l d h e l p of D. P. Swain, M. L a P o i n t e , A. B r e t t , D. H a l l , C. Wood, W. Luedke, S. R u s h f o r t h - G u i n n and, i n p a r t i c u l a r , B. G u i n n i s g r a t e f u l l y a c k n o w l e d g e d . H. A d r u s a k , L. F l e c k and J . H u t c h i n s o n of t h e F i s h and W i l d l i f e B r a n c h o f t h e B r i t i s h C o l u m b i a Department of t h e E n v i r o n m e n t a r e t h a n k e d f o r t h e i r c o n s t a n t h e l p and s u p p o r t . I thank G. Brown f o r making t h e f i n i s h i n g of t h i s t h e s i s an e n j o y a b l e e x p e r i e n c e . T h i s r e s e a r c h was f u n d e d t h r o u g h a NSERC o p e r a t i n g g r a n t t o P. A. L a r k i n and a F i s h e r i e s and Oceans r e s e a r c h g r a n t t o C. C. Wood. P e r s o n a l f u n d i n g was s u p p l i e d t h r o u g h NSERC and 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 p o s t - g r a d u a t e s c h o l a r s h i p s . T h i s r e s e a r c h was done i n memory of James Delmar F o o t e . The s u p p o r t of h i s b r o t h e r , E l d o n F o o t e , w i l l a l w a y s be a p p r e c i a t e d . 1 INTRODUCTION N a t u r a l s e l e c t i o n c an be d i v i d e d i n t o two components, r e l a t e d t o t h e a b i l i t y t o s u r v i v e and t h e a b i l i t y t o r e p r o d u c e . S e x u a l s e l e c t i o n was d e s c r i b e d by D a r w i n (1871) as t h e e v o l u t i o n a r y p r o c e s s a r i s i n g from v a r i a b i l i t y i n t h e a b i l i t y t o r e p r o d u c e . A n i m a l s p o s s e s s i n g c h a r a c t e r s w h i c h by t h e s e means l e a d t o t h e p r o d u c t i o n of more o f f s p r i n g t h a t c o n t r i b u t e t o t h e n e x t g e n e r a t i o n a r e s e l e c t e d o v e r o t h e r s . The c h a r a c t e r s s e l e c t e d a r e t h o s e t h a t c o n f e r an a d v a n t a g e i n i n t r a s e x u a l c o m p e t i t i o n and t h o s e t h a t l e a d t o t h e s e l e c t i o n of h i g h q u a l i t y m a t e s . The f a c t o r s i n v o l v e d i n s e x u a l s e l e c t i o n w i t h i n s p e c i e s and t h o s e i n v o l v e d i n s e l e c t i o n f o r r e p r o d u c t i v e i s o l a t i o n between s p e c i e s c an be c l o s e l y r e l a t e d . In b o t h c a s e s s e l e c t i o n f a v o u r s i n d i v i d u a l s w h i c h make t h e " c o r r e c t " mate c h o i c e . W i t h i n s p e c i e s t h i s means t h e h i g h e s t q u a l i t y mates; between s p e c i e s " c o r r e c t " means s e l e c t i n g t h e r i g h t s p e c i e s . The r e p r o d u c t i v e s u c c e s s of i n d i v i d u a l s making t h e wrong c h o i c e i n b o t h s i t u a t i o n s may be s i m i l a r , t h a t i s , c l o s e t o z e r o . The q u e s t i o n a r i s e s : does a c o n t i n u u m e x i s t between t h e two s e l e c t i v e f o r c e s ? T h a t i s , i s i t p o s s i b l e f o r t h e e f f e c t s of s e x u a l s e l e c t i o n t o r e s u l t i n s e l e c t i o n f o r r e p r o d u c t i v e i s o l a t i o n ? I f s o , t h e s t u d y of s e x u a l s e l e c t i o n may c o n s t i t u t e an e x a m i n a t i o n o f t h e p r o c e s s of s p e c i a t i o n . 2 Maynard S m i t h (1966) d e s c r i b e d s i t u a t i o n s i n w h i c h t h e p o t e n t i a l f o r t h i s phenomenon e x i s t s . S t a b l e p o l y m o r p h i s m s ( m a i n t a i n e d by d i s r u p t i v e s e l e c t i o n ) between a l l e l e s t h a t a d a p t i n d i v i d u a l s t o d i f f e r e n t e c o l o g i c a l n i c h e s a r e t h e o r e t i c a l l y p o s s i b l e i n h e t e r o g e n e o u s e n v i r o n m e n t s . I f a s t a b l e p o l y m o r p h i s m a r i s e s t h i s i s l i k e l y t o be f o l l o w e d by t h e e v o l u t i o n of r e p r o d u c t i v e i s o l a t i o n between t h e morphs. B o t h of t h e s e p r e d i c t i o n s have been v e r i f i e d i n s t u d i e s on D r o s o p h i l a . Thoday and h i s c o l l e a g u e s d e m o n s t r a t e d t h a t d i s r u p t i v e s e l e c t i o n c a n c r e a t e and m a i n t a i n p o l y m o r p h i s m s i n a . . p o p u l a t i o n even i n t h e f a c e o f m a s s i v e gene f l o w (Thoday 1959; Thoday and Boam 1959; M i l l i c e n t and Thoday 1961). In a d d i t i o n , d i s r u p t i v e s e l e c t i o n was r e s p o n s i b l e f o r t h e e v o l u t i o n of c o m p l e t e r e p r o d u c t i v e i s o l a t i o n i n one s t u d y (Thoday and G i b s o n 1962) and p a r t i a l i s o l a t i o n i n numerous o t h e r s ( e . a,. Dobzhansky et_ a l . 1976; C r o s s l e y 1974; R i c e 1985; K o e p f e r 1987). The r e q u i r e m e n t s n e c e s s a r y f o r t h e e v o l u t i o n of a p o l y m o r p h i s m v i a d i s r u p t i v e s e l e c t i o n a r e s e v e r e . Maynard S m i t h (1966) p r e s e n t e d two m a n d a t o r y c o n d i t i o n s : 1) t h e d e n s i t y d e p e n d e n t f a c t o r s r e g u l a t i n g p o p u l a t i o n s i z e must o p e r a t e s e p a r a t e l y w i t h i n t h e two n i c h e s and; 2) t h e s e l e c t i v e a d v a n t a g e s a s s o c i a t e d w i t h b e i n g a d a p t e d t o a p a r t i c u l a r n i c h e must be l a r g e . The a d v a n t a g e s n e c e s s a r y a r e g r e a t l y r e d u c e d i f t h e r e i s a an i n i t i a l h i g h d e g r e e of a s s o r t a t i v e m a t i n g by form. 3 S a l m o n i d s d i s p l a y c h a r a c t e r s n e c e s s a r y f o r t h e e v o l u t i o n of r e p r o d u c t i v e i s o l a t i o n i n s y m p a t r y . T h e r e a r e s t r o n g s e l e c t i v e f o r c e s a c t i n g on p o p u l a t i o n s ( e . g_. R a l e i g h 1967; Brannon 1972; Bams 1976; R i d d e l l and L e g g e t 1981; R i d d e l l e t a l . 1981). Homing t o p a r e n t a l spawning g r o u n d s r e s u l t s i n r e d u c e d gene f l o w among p o p u l a t i o n s ( e . c[. L i n d s e y e t a_l. 1959; Hartman and R a l e i g h 1964; M c C l e a v e 1967; A l t u k h o v 1982). B e h a v i o u r a l a n d / o r m o r p h o l o g i c a l p o l y m o r p h i s m s e x i s t i n numerous s t o c k s ( e . g_. R i c k e r 1938, 1940, 1972; N o r t h c o t e 1962; R a l e i g h 1967; Hanson and S m i t h 1967; M c C a r t 1970; K e l s o e t a l . 1981). F i n a l l y , i n d e p e n d e n t p o p u l a t i o n r e g u l a t i o n a p p e a r s p r o b a b l e i n many of t h e above e x a m p l e s . The P a c i f i c salmon O n c o r h y n c h u s n e r k a o c c u r s i n two f o r m s , t h e anadromous s o c k e y e salmon and t h e non-anadromous kokanee. S o c k e y e spend a y e a r (and sometimes more) i n l a k e s b e f o r e m i g r a t i n g t o t h e o c e a n , t y p i c a l l y s p e n d i n g two t o f o u r y e a r s i n t h e ocean b e f o r e r e t u r n i n g t o p o p u l a t i o n s p e c i f i c spawning g r o u n d s u s u a l l y e i t h e r i n o r t r i b u t a r y t o l a k e s . Kokanee spend t h e i r whole l i f e ( t y p i c a l l y 3 t o 5 y e a r s ) i n l a k e s . At m a t u r i t y , s o c k e y e salmon a r e much l a r g e r t h a n kokanee (two t o t h r e e t i m e s as long)-, m a i n l y b e c a u s e of t h e g r e a t e r p r o d u c t i v i t y o f t h e m a r i n e e n v i r o n m e n t . T h e s e forms o c c u r t o g e t h e r and s e p a r a t e l y . Where t h e y o c c u r t o g e t h e r , spawning u s u a l l y o c c u r s i n d i f f e r e n t l o c a l i t i e s a t d i f f e r e n t t i m e s . In a few l o c a l i t i e s , s o c k e y e and kokanee spawn i n t h e same p l a c e a t t h e same t i m e . 4 B o t h anadromous and non-anadromous i n d i v i d u a l s c a n g i v e r i s e t o t h e o p p o s i t e f o r m ( F o e r s t e r 1947; R i c k e r 1959, 1972; S c o t t 1984), p r e s e n t i n g t h e p o s s i b i l i t y t h a t one form may have g i v e n r i s e t o t h e o t h e r i n sy m p a t r y on numerous o c c a s i o n s . Where t h e y spawn s y m p a t r i c a l l y t h e r e i s a l a r g e d e g r e e of a s s o r t a t i v e m a t i n g by s i z e and form; s o c k e y e males mate a l m o s t e x c l u s i v e l y w i t h s o c k e y e f e m a l e s and kokanee males a t t e m p t t o mate w i t h f e m a l e s o f b o t h forms (Hanson and S m i t h 1967; Mc C a r t 1970). B e c a u s e of t h e i r s m a l l s i z e , kokanee m a l e s a r e u s u a l l y r e s t r i c t e d t o s u b o r d i n a t e sneak p o s i t i o n s i n t h e male spawning h i e r a r c h y when i n p u r s u i t of s o c k e y e f e m a l e s . T h i s a s s o r t a t i v e m a t i n g by form, i n a s s o c i a t i o n w i t h t h e p r o b a b l e l a r g e s e l e c t i v e d i f f e r e n c e s between t h e m a r i n e and l a c u s t r i n e e n v i r o n m e n t s (see R i c k e r 1940), c r e a t e s t h e p o s s i b i l i t y f o r s y m p a t r i c g e n e t i c d i v e r g e n c e f o l l o w e d by t h e e v o l u t i o n of p r e m a t i n g i s o l a t i n g mechanisms i n t h e manner d e s c r i b e d i n numerous t h e o r e t i c a l m o d e l s ( e . c[. Maynard S m i t h 1966; R o s e n z w e i g 1978; Pimm 1979; R i c e 1984). The r e p r o d u c t i v e and g e n e t i c r e l a t i o n s h i p of s o c k e y e salmon and kokanee i s examined i n t h i s t h e s i s . T h r e e major q u e s t i o n s a r e a d d r e s s e d . F i r s t , what f a c t o r s a r e i n v o l v e d i n s e x u a l s e l e c t i o n w i t h i n f o r m s ? To answer t h i s , I e x p e r i m e n t a l l y examine t h e n a t u r e o f t h e 0. n e r k a m a t i n g s y s t e m , p a y i n g s p e c i a l a t t e n t i o n t o t h e e f f e c t s of s i z e w i t h f o r m s . In c h a p t e r 1, t h e n a t u r e o f spawning t e r r i t o r i a l i t y i n kokanee i s examined. In 5 c h a p t e r s 2 and 3, f e m a l e and male mate c h o i c e , r e s p e c t i v e l y , a r e e x a m i n e d . S e c o n d , what i s t h e g e n e t i c r e l a t i o n s h i p between s o c k e y e and kokanee i n B r i t i s h C o l u m b i a ? More s p e c i f i c a l l y , i s t h e r e e v i d e n c e o f s y m p a t r i c g e n e t i c d i v e r g e n c e between forms? To answer t h i s , I e l e c t r o p h o r e t i c a l l y compare s o c k e y e and kokanee p o p u l a t i o n s i n B r i t i s h C o l u m b i a , from l o c a l i t i e s where t h e y spawn e i t h e r s e p a r a t e l y o r s y m p a t r i c a l l y ( C h a p t e r 4 ) . F i n a l l y , i s t h e r e any e v i d e n c e o f t h e e v o l u t i o n of p r e m a t i n g i s o l a t i n g mechanisms between s y m p a t r i c s o c k e y e salmon and kokanee? To answer t h i s , t h e r e p r o d u c t i v e r e l a t i o n s h i p of s o c k e y e salmon and kokanee w h i c h spawn s y m p a t r i c a l l y i n two s y s t e m s a r e compared t o : (1) t h a t e x p e c t e d ( C h a p t e r s 1 t h r o u g h 3) b a s e d on t h e s i z e d i f f e r e n c e between t h e f o r m s ; (2) e a c h o t h e r and; (3) t o t h e d e g r e e of b i o c h e m i c a l g e n e t i c d i v e r g e n c e o b s e r v e d between s y m p a t r i c forms i n t h e two s y s t e m s . 6 CHAPTER 1 EXPERIMENTAL EXAMINATION OF SPAWNING TERRITORIALITY IN SALMON I n t r o d u c t i o n The spawning b e h a v i o u r of s a l m o n i d s has been e x t e n s i v e l y s t u d i e d ( e . cj. Needham and T a f t 1934; J o n e s and K i n g 1952; F a b r i c u s and G u s t a f s o n 1954; J o n e s 1959; Hanson and -Smith 1967; Hartman 1969; M c C a r t 1970; T a u t z and G r o o t 1975; C a m p b e l l 1977; Newcombe and Hartman 1980; S c h r o d e r 1981, 1982; van den Berghe 1984; G r o s s 1985; S a r g e n t et. a l . 1986; Maekawa and O n o z a t o 1986). Many o f t h e s e s t u d i e s have d e a l t w i t h t h e d e s c r i p t i o n of p a i r f o r m a t i o n and spawning b e h a v i o u r , w h i l e o t h e r s , n o t a b l y Hanson and S m i t h ( 1 9 6 7 ) , S c h r o d e r (1981, 1982), van den Berghe (1984) and Maekawa and O n o z a t o ( 1 9 8 6 ) have a t t e m p t e d t o document, and examine t h e f a c t o r s c o n t r i b u t i n g t o v a r i a n c e i n r e p r o d u c t i v e s u c c e s s of e a c h of t h e s e x e s . F o r t h e most p a r t , t h e s e l a t e r s t u d i e s have c o n c e n t r a t e d on male b e h a v i o u r , a l t h o u g h t h e r e i s g r o w i n g i n t e r e s t i n t h e f a c t o r s c o n t r i b u t i n g t o v a r i a t i o n i n f e m a l e r e p r o d u c t i v e s u c c e s s ( S c h r o d e r 1981; van den Berghe 1984; van den Berghe and G r o s s 1984). The s a l m o n i d m a t i n g s y s t e m has been c h a r a c t e r i z e d as. one i n whi c h f e m a l e s compete f o r t e r r i t o r i e s ( spawning s i t e s ) and males compete f o r d i r e c t a c c e s s t o f e m a l e s ( S c h r o d e r 1981; G r o s s 1985; S a r g e n t et_ a_l. 1986). T h i s c h a r a c t e r i z a t i o n i s ' d e r i v e d from numerous o b s e r v a t i o n s t h a t o n l y f e m a l e s p a r t i c i p a t e i n t h e 7 c o n s t r u c t i o n and d e f e n s e of t h e n e s t s i t e , w h i l e m a l e s move from f e m a l e t o f e m a l e t h r o u g h o u t t h e i r s pawning l i f e t i m e . Some s t u d i e s have p o i n t e d t o t h e e x i s t e n c e of male spawning t e r r i t o r i a l i t y , c e n t e r e d a r o u n d f e m a l e s a n d / o r h i g h q u a l i t y n e s t s i t e s (Hanson and S m i t h 1967; Hartman 1969; M c C a r t 1970; J o n s s o n and H i n d a r 1982) . A g g r e s s i v e b e h a v i o u r has been o b s e r v e d i n b o t h s e x e s , w i t h t h e m a j o r i t y of a g g r e s s i v e a c t s d i r e c t e d i n t r a s e x u a l l y (Hanson and S m i t h 1967; Mc C a r t 1970; S c h r o d e r 1981, 1982). In m a l e s , outcome of i n t r a s e x u a l c o m p e t i t i o n a p p e a r s t o be d e c i d e d l a r g e l y by t h e r e l a t i v e s i z e s o f c o m p e t i n g i n d i v i d u a l s ; l a r g e m a l e s d o m i n a t e s m a l l males i n c o m p e t i t i o n f o r a c c e s s t o f e m a l e s ( e. cj. Hanson and S m i t h 1967; M c C a r t 1970; C a m p b e l l 1977; S c h r o d e r 1981). In f e m a l e s , t h e e f f e c t s of s i z e i n i n t r a s e x u a l c o m p e t i t i o n a r e l a r g e l y unknown. J o n s s o n and H i n d a r (1982) s u g g e s t e d t h a t s i z e i s an i m p o r t a n t f a c t o r i n d e t e r m i n i n g t h e spawning d i s t r i b u t i o n of d i f f e r e n t s i z e d morphs of A r c t i c c h a r r , S a l v e l i n u s a l p i n u s . S i m i l a r l y , van den Berghe (1984) c o n c l u d e d t h a t s i z e was a f a c t o r i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n i n coho sa l m o n , 0. k i s u t c h . L i t t l e s u p p o r t i n g e v i d e n c e was p r e s e n t e d i n e i t h e r s t u d y . In an e x p e r i m e n t a l s t u d y on f e m a l e i n t r a s e x u a l c o m p e t i t i o n , S c h r o d e r (1981) f o u n d no e v i d e n c e t o s u g g e s t s i z e was a f a c t o r i n d e t e r m i n i n g t h e outcome of f e m a l e a g g r e s s i v e i n t e r a c t i o n s , c o n c l u d i n g t h a t p r i o r r e s i d e n c e was t h e major f a c t o r . P r i o r r e s i d e n c e has n o t been c o n s i d e r e d i n male i n t r a s e x u a l c o m p e t i t i o n . 8 In t h i s c h a p t e r , I p r e s e n t e x p e r i m e n t a l r e s u l t s p e r t a i n i n g t o t h e e x i s t e n c e and n a t u r e of spawning t e r r i t o r i a l i t y i n male and f e m a l e kokanee and t h e f a c t o r s w h i c h i n f l u e n c e t h e outcome of i n t r a s e x u a l c o m p e t i t i o n i n b o t h s e x e s . I t h e n compare and c o n t r a s t t h e spawning b e h a v i o u r o f t h e s e x e s and r e l a t e t h e s e f i n d i n g s t o t h e e v o l u t i o n of t h e s a l m o n i d m a t i n g s y s t e m . Brown's (1975) d e f i n i t i o n o f t e r r i t o r i a l i t y i s u s e d : a t e r r i t o r y i s a f i x e d a r e a from w h i c h i n t r u d e r s a r e e x c l u d e d by some c o m b i n a t i o n of a d v e r t i s e m e n t , t h r e a t , o r a t t a c k . J _ . An e x p e r i m e n t a l e x a m i n a t i o n o f t h e mat i n g s y s t e m i n kokanee Methods In t h i s f i r s t of t h r e e major s e t s of e x p e r i m e n t s , I examine th e n a t u r e o f spawning t e r r i t o r i a l i t y i n kokanee. I f i r s t p r e s e n t a summary of t h e methods common t o most of t h e e x p e r i m e n t s and t h e n p r e s e n t t h e s p e c i f i c methods p e r t a i n i n g t o the e x a m i n a t i o n of t h e m a t i n g s y s t e m i n kokanee. A l l e x p e r i m e n t s were u n d e r t a k e n i n t h e Meadow C r e e k spawning c h a n n e l , s i t u a t e d a t t h e n o r t h end of K o o t e n a y L a k e , B. C. , d u r i n g September 1982-1984 ( s e e V e r n o n (1957) f o r a d e s c r i p t i o n o f K o o t e n a y L a k e kokanee. Meadow C r e e k s u s t a i n s t h e l a r g e s t kokanee spawning r u n i n K o o t e n a y Lake and p o s s i b l y t h e 9 w o r l d , w i t h spawning p o p u l a t i o n s o f t e n e x c e e d i n g one m i l l i o n ) . Most e x p e r i m e n t s were c a r r i e d out i n e n c l o s e d a r e n a s ( F i g . 1 ) , f i v e by f i v e , f o u r by f i v e , o r f o u r by f o u r m e t e r s ( d e p e n d i n g on t h e e x p e r i m e n t ) , c o n s t r u c t e d of 0.9 cm c h i c k e n w i r e f e n c i n g . Two a r e n a s , s e p a r a t e d from e a c h o t h e r by 1 m, were e n c l o s e d w i t h i n a l a r g e r f e n c e d a r e a t o l i m i t i n t e r a c t i o n of f i s h i n an a r e n a from t h o s e i n t h e a d j a c e n t a r e n a and t h o s e spawning n a t u r a l l y i n t h e s t r e a m . L a r g e w h i t e r o c k s were p l a c e d on t h e f l o o r of e a c h a r e n a a t one meter i n t e r v a l s . T h e s e were u s e d t o r e c o r d t h e i n d i v i d u a l p o s i t i o n s of f i s h o v e r t i m e . A l l kokanee u s e d i n e x p e r i m e n t s were i n d i v i d u a l l y t a g g e d . In t h e e x a m i n a t i o n of t e r r i t o r i a l i t y t a g s were i n d i v i d u a l l y c o l o u r c o d e d 0.5 by 2 cm p l a s t i c s t r i p s , sewn i n t o t h e a n t e r i o r b ase of t h e d o r s a l f i n w i t h s u r g i c a l t h r e a d . F o r s t u d i e s on i n t r a s e x u a l c o m p e t i t i o n , c o l o u r c o d e d 2 cm F l o y d a r t t a g s were u s e d , a t t a c h e d e i t h e r t o t h e a n t e r i o r or p o s t e r i o r base of t h e d o r s a l f i n . The s t u d y of t h e kokanee m a t i n g s y s t e m c o n s i s t e d of t h r e e e x p e r i m e n t s t h a t examined w h i c h r e s o u r c e s a r e n e c e s s a r y t o evoke male and f e m a l e i n t r a s e x u a l c o m p e t i t i o n , and, p o s s i b l y , t e r r i t o r i a l i t y . In t h e f i r s t , I m o n i t o r e d t h e c h r o n o l o g y of a r r i v a l and s e t t l i n g o f m a l e s and f e m a l e s i n t o t h r e e 4 by 4 m marked a r e a s . Second, t h e b e h a v i o u r of males and f e m a l e s was compared i n t h e e x p e r i m e n t a l a r e n a s , when t h e s e x e s were h e l d s e p a r a t e l y and t o g e t h e r . The t h i r d e x p e r i m e n t compared t h e t i m e g u r e 1. The d e s i g n of e x p e r i m e n t a l a r e n a s u s e d i n t h e e x a m i n a t i o n of s p a w ning t e r r i t o r i a l i t y i n kokanee. e x a c t d i m e n s i o n s of t h e a r e n a v a r i e d s l i g h t l y between e x p e r i m e n t s . \ \ \ \ \ \ S T R E A M F L O W -4 m-4m /////////// S T R E A M B A N K 1 2 i t t o o k f i s h t o e s t a b l i s h s pawning s i t e s i n t h e spawning c h a n n e l where numerous f i s h were a l r e a d y p r e s e n t t o t h e t i m e i t t o o k f i s h t o e s t a b l i s h s pawning s i t e s i n t h e a r e n a s , where no a d d i t i o n a l f i s h were p r e s e n t . A. C h r o n o l o g y o f s e t t l e m e n t on t h e spawning g r o u n d s At 1700 h o u r s on e a c h day f o r a f o u r week p e r i o d , I r e c o r d e d t h e number and sex of e a c h f i s h h o l d i n g p o s i t i o n i n e a c h of t h r e e 4 by 4 m d e s i g n a t e d a r e a s . F i s h swimming t h r o u g h t h e marked a r e a s were not r e c o r d e d . B. An e x p e r i m e n t a l e x a m i n a t i o n of t e r r i t o r i a l i t y i n m a l e s and  f e m a l e s T w e n t y - f i v e r i p e (and i n t h e c a s e of f e m a l e s , unspawned) f e m a l e s and m a l e s were s e l e c t e d from s c h o o l s of kokanee ( i n w h i c h f i s h a r e n o t a g g r e s s i v e o r t e r r i t o r i a l ) , i n d i v i d u a l l y t a g g e d and p l a c e d i n an a r e n a w i t h ( p a i r e d ) or w i t h o u t an e q u a l number of t h e o p p o s i t e sex ( u n p a i r e d ) . The b e h a v i o u r o f e a c h f i s h was m o n i t o r e d o v e r a t h r e e t o f i v e day p e r i o d ( d e p e n d i n g on th e w e a t h e r ; f i v e d a y s f o r t h e u n p a i r e d t r e a t m e n t p e r f o r m e d i n i n c l e m e n t weather and t h r e e d a y s f o r t h e p a i r e d t r e a t m e n t ) . The p o s i t i o n of e a c h f i s h was r e c o r d e d a t a p p r o x i m a t e l y two hour i n t e r v a l s , s i x t o s e v e n t i m e s d u r i n g d a y l i g h t of e a c h day (we a t h e r p e r m i t t i n g ) . The i n d i v i d u a l b e h a v i o u r of e a c h f i s h was r e c o r d e d d u r i n g 15 two m i n u t e o b s e r v a t i o n p e r i o d s w h i c h were 13 s p a c e d r e l a t i v e l y e v e n l y o v e r t h e c o u r s e o f t h e t h r e e t o f i v e day t r e a t m e n t . A l l f i s h were o b s e r v e d w i t h i n one hour o f e a c h o t h e r d u r i n g e a c h o f t h e 15 o b s e r v a t i o n p e r i o d s , w i t h t h e i n d i v i d u a l o r d e r of o b s e r v a t i o n r a n d o m i z e d between p e r i o d s . Two o b s e r v e r s were u s e d . W i t h i n e a c h o b s e r v a t i o n p e r i o d , e a c h o b s e r v e r was r e s t r i c t e d t o r e c o r d i n g t h e b e h a v i o u r o f one sex, w i t h t h e sex o b s e r v e d s w i t c h e d between p e r i o d s t o c o n t r o l f o r p o s s i b l e d i f f e r e n c e s between o b s e r v e r s . The b e h a v i o u r s r e c o r d e d were: c h a s e s , b i t e s , l a t e r a l d i s p l a y s , T - d i s p l a y s , and d i g g i n g . T hese b e h a v i o u r s were d e f i n e d as f o l l o w s : 1) C h a s e s - any r a p i d d i r e c t a p p r o a c h t o w a r d s a n o t h e r f i s h , o f t e n e n d i n g i n c o n t a c t of t h e two f i s h e s . 2) B i t e s - open mouth a t t a c k s , a l w a y s i n v o l v i n g c o n t a c t and u s u a l l y p r e c e d e d by a c h a s e . 3) L a t e r a l D i s p l a y s - p a r a l l e l body p r e s e n t a t i o n s i n w h i c h t h e a b d o m i n a l f i n s a r e l o w e r e d and t h e d o r s a l f i n r a i s e d , w i t h t h e body s l i g h t l y i n c l i n e d ( h e a d up, t a i l down). The d i s p l a y i s u s u a l l y p e r f o r m e d i n tandem by two i n d i v i d u a l s w h i l e swimming u p s t r e a m and p a r a l l e l t o one a n o t h e r ( s e p a r a t e d by 5 cm t o 1 m). 4) T - D i s p l a y s - p e r p e n d i c u l a r body p r e s e n t a t i o n s i n w h i c h t h e d i s p l a y i n g f i s h h o l d s i t s ' body a t an a n g l e t o t h e c u r r e n t (45-90 ) and t h e f i s h d i r e c t l y downstream from i t . The d i s p l a y i n g f i s h t h e n d r i f t s w i t h t h e c u r r e n t , u s u a l l y d i s p l a c i n g t h e downstream f i s h . T h i s i s s i m i l a r t o " b a c k - p e d a l i n g " d e s c r i b e d by J o n e s (1959) and Hanson and S m i t h ( 1 9 6 7 ) , and has been d e s c r i b e d by Hartman (1969) and named by S c h r o d e r (1981 ). 5) D i g g i n g - i n f e m a l e s , c o n s i s t i n g of a s e r i e s o f s t r o n g body 1 4 f l e x u r e s w h i l e t u r n e d on one s i d e . T h i s d i g g i n g c r e a t e s a n e s t d e p r e s s i o n i n t h e g r a v e l i n w h i c h eggs a r e e v e n t u a l l y d e p o s i t e d ( T a u t z and G r o o t 1975). Some t e r r i t o r i a l f e m a l e s were o b s e r v e d t o d i g i n t h e n e s t s of o t h e r f e m a l e s w h i l e t h o s e f e m a l e s were i n v o l v e d i n o t h e r a g g r e s s i v e i n t e r a c t i o n s . The f u n c t i o n of t h i s d i g g i n g i s u n c l e a r . D i g g i n g - i n m a l e s , o c c u r r i n g i n two f o r m s . The a g g r e s s i v e d i g c o n s i s t s of a dominant male (one c o u r t i n g a f e m a l e ) l o w e r i n g i t s body t o t h e s u b s t r a t e , r o l l i n g on i t s s i d e , and making a s e r i e s of body f l e x u r e s w h i c h c a r r y i t u p s t r e a m and push g r a v e l downstream. T h i s b e h a v i o u r i s o n l y done when sneak m a l e s a p p r o a c h from t h e r e a r . The a p p r o a c h of t h e sneak males a p p e a r s t o be e l l i c i t e d by t h e dominant male l o w e r i n g i t s e l f i n t o t h e n e s t , as has been d e m o n s t r a t e d i n s t u d i e s of r a i n b o w t r o u t , S. g a i r d n e r i , spawning b e h a v i o u r (Newcombe and Hartman 1980). T h i s s u g g e s t s t h e k i c k i n g of g r a v e l by t h e dominant male i s an a n t i - s n e a k a g g r e s s i v e b e h a v i o u r as a p p r o a c h i n g s n e a k s a r e f a c e d w i t h a shower of g r a v e l i n what o t h e r w i s e would be a p r o t e c t e d p o s i t i o n from a t t a c k (_i. e. b e h i n d t h e dominant m a l e ) . However, i t i s not known i f t h i s b e h a v i o u r a f f e c t s t h e r e p r o d u c t i v e s u c c e s s of sneak m a l e s . The c o u r t s h i p d i g i s a s h o r t d u r a t i o n d i g p e r f o r m e d by males w h i l e c o u r t i n g f e m a l e s and o c c u r s i n t h e p r e s e n c e or a b s e n c e of a d d i t i o n a l m a l e s . I t i n v o l v e s r e p e a t e d s t r i k i n g t h e c u a d a l f i n a g a i n s t t h e s u b s t r a t e w h i l e t h e male m a i n t a i n s i t s u p r i g h t p o s i t i o n . L i t t l e g r a v e l i s d i s p l a c e d , s u g g e s t i n g t h i s b e h a v i o u r i s not a s s o c i a t e d w i t h n e s t c o n s t r u c t i o n . 15 The a c t i v i t y p a t t e r n s ( b e h a v i o u r s and movement) of m a l e s and f e m a l e s i n t h e two t r e a t m e n t s ( p a i r e d and u n p a i r e d ) were compared w i t h a two-way Anova m o d e l . A p r i o r i m u l t i p l e c o m p a r i s o n s were p e r f o r m e d w i t h t h e L e a s t S i g n i f i c a n t D i f f e r e n c e s t e s t . Two s e t s of d a t a were a n a l y s e d : t h e a v e r a g e d i s t a n c e between s u c c e s s i v e p o s i t i o n s f o r e a c h f i s h and t h e t o t a l number of a g g r e s s i v e b e h a v i o u r s p e r f i s h o b s e r v e d i n 30 m i n u t e s of o b s e r v a t i o n . The f r e q u e n c y o f p e r f o r m a n c e of b e h a v i o u r s was compared between t h e p a i r e d and u n p a i r e d t r e a t m e n t s w i t h i n e a c h sex and t h e n between s e x e s u s i n g t h e C h i s q u a r e d c o n t i n g e n c y t e s t . I n t e r s e x u a l a g g r e s s i v e a c t i v i t y between m a l e s and f e m a l e s i n t h e p a i r e d t r e a t m e n t was compared u s i n g t h e s t u d e n t s T - t e s t . A p<0.05 l e v e l of s i g n i f i c a n c e was u s e d t h r o u g h o u t t h e t h e s i s . To d e t e r m i n e i f t h e a g g r e s s i v e a c t i v i t i e s of m a l e s and f e m a l e s were a s s o c i a t e d w i t h p a r t i c u l a r a r e a s ( u n p a i r e d ) or mates and a r e a s ( p a i r e d ) a l l f i s h were r e p e a t e d l y d i s p l a c e d from t h e i r p o s i t i o n s (by s c r u b b i n g t h e a r e n a f e n c e w i t h h a r d b r i s t l e b r u s h e s ) . The p o s i t i o n s e a c h f i s h h e l d 30, 60, 90, and 120 m i n u t e s a f t e r d i s p l a c e m e n t were r e c o r d e d , a f t e r w h i c h t h e whole p r o c e s s was . r e p e a t e d . In t h e u n p a i r e d t r e a t m e n t , males and f e m a l e s were d i s p l a c e d from t h e i r p o s i t i o n s a t o t a l of n i n e t i m e s o v e r t h e c o u r s e of a day and a h a l f , d u r i n g w h i c h 30 p o s i t i o n o b s e r v a t i o n s were r e c o r d e d f o r e a c h f i s h . S i m i l a r l y , i n t h e p a i r e d t r e a t m e n t , t h e f i s h were d i s p l a c e d f i v e t i m e s o v e r 16 t h e c o u r s e o f one day, d u r i n g w h i c h 20 p o s i t i o n s were r e c o r d e d f o r e a c h f i s h . I f m a l e s a n d / o r f e m a l e s do d e f e n d s p e c i f i c r e s o u r c e s , t h e y a r e e x p e c t e d t o r e t u r n t o t h e s e r e s o u r c e s a f t e r d i s p l a c e m e n t . I f t h e y d e f e n d o n l y a s p a c e a r o u n d t h e m s e l v e s and n o t a s p e c i f i c r e s o u r c e , t h e y a r e n o t e x p e c t e d t o r e t u r n t o t h e i r f o r m e r p o s i t i o n s f o l l o w i n g d i s p l a c e m e n t . C. The e f f e c t of c o m p e t i t o r s on t h e commencement o f  t e r r i t o r i a l i t y i n kokanee To t e s t whether space was l i m i t i n g on t h e spawning g r o u n d s , 25 males and 25 f e m a l e s were c o l l e c t e d from s c h o o l s of kokanee, t a g g e d t o i d e n t i f y t h e i r sex and r e l e a s e d back i n t o t h e s t r e a m . At t h e same t i m e , an e q u a l number of i n d i v i d u a l s i n s i m i l a r p h y s i c a l c o n d i t i o n were c a p t u r e d , t a g g e d , and p l a c e d i n an empty e x p e r i m e n t a l a r e n a ( s e e E x p e r i m e n t B ) . E a c h day an o b s e r v e r w a l k e d t h e spawning c h a n n e l and r e c o r d e d whether t a g g e d i n d i v i d u a l s were h o l d i n g p o s i t i o n on t h e spawning g r o u n d s or whether t h e y were moving a b o u t or i n s c h o o l s . The t o t a l number of m ales and f e m a l e s w h i c h had e s t a b l i s h e d spawning s i t e s a f t e r t h r e e days i n e a c h t r e a t m e n t were compared. R e s u l t s 1 7 A. C h r o n o l o g y of s e t t l e m e n t on t h e spawning g r o u n d s Kokanee began e s t a b l i s h i n g p o s i t i o n s d u r i n g t h e f i r s t week of September i n e a c h o f t h e t h r e e a r e a s m o n i t o r e d i n t h e s p a w n ing c h a n n e l ( F i g . 2 ) . The number o f kokanee m a i n t a i n i n g p o s i t i o n i n a l l a r e a s i n c r e a s e d o v e r t h e month, l e v e l i n g o f f a t t h e end of t h e spawning r u n i n l a t e September. The sex r a t i o of kokanee w h i c h h e l d p o s i t i o n s w i t h i n t h e s e a r e a s was skewed t o w a r d m a l e s e a r l y i n September but c o n v e r g e d t o w a r d e q u a l i t y o v e r t h e t h r e e and one h a l f weeks o f o b s e r v a t i o n . D u r i n g t h e t i m e i n w h i c h males were more numerous t h a n f e m a l e s , m a l e s were a g g r e s s i v e t o w a r d e a c h o t h e r , and f a i r l y e v e n l y s p a c e d a c r o s s t h e a r e a s . They d i d not c l u s t e r a r o u n d t h e few spawning f e m a l e s p r e s e n t . B. An e x p e r i m e n t a l e x a m i n a t i o n of t e r r i t o r i a l i t y i n m a l e s and  f e m a l e s The b e h a v i o u r of m a l e s and f e m a l e s was examined i n e x p e r i m e n t a l a r e n a s , w i t h t h e s e x e s h e l d s e p a r a t e l y ( u n p a i r e d ) and t o g e t h e r ( p a i r e d ) . I f males a n d / o r f e m a l e s a r e s o l e l y t e r r i t o r i a l of n e s t s i t e r e s o u r c e s , t h e n t h e y a r e e x p e c t e d t o compete amongst t h e m s e l v e s f o r t h e s e r e s o u r c e s b o t h i n t h e p r e s e n c e and a b s e n c e o f t h e o p p o s i t e s e x . S i t e s p e c i f i c i n t r a s e x u a l a g g r e s s i o n would be e v i d e n c e o f s u c h t e r r i t o r i a l i t y . In c o n t r a s t , i f males a n d / o r f e m a l e s a r e s o l e l y t e r r i t o r i a l of mates, t h e n t h e y would be e x p e c t e d t o compete among t h e m s e l v e s 18 F i g u r e 2. The number o f m a l e s and f e m a l e s h o l d i n g p o s i t i o n s i n t h r e e 4 by 4 m d e s i g n a t e d a r e a s o f t h e Meadow C r e e k spawning c h a n n e l , o v e r t h e c o u r s e o f t h e r u n i n September, 1 984. 20 o n l y i n t h e p r e s e n c e of t h e o p p o s i t e sex and e x h i b i t i o n s of i n t r a s e x u a l c o m p e t i t i o n would be e x p e c t e d t o be s i t e a n d / o r mate s p e c i f i c and p e r s i s t e n t o v e r t i m e . The s i z e r a n g e o f f i s h e s ( f o r k l e n g t h s ) u s e d i n e a c h t r e a t m e n t a r e g i v e n i n T a b l e 1 . The mean d i s t a n c e between s u c c e s s i v e p o s i t i o n s h e l d by i n d i v i d u a l f i s h (MDP) was s i g n i f i c a n t l y d i f f e r e n t between t h e s e x e s and between t r e a t m e n t s ( p a i r e d o r u n p a i r e d ) ( T a b l e 2; p < 0 . 0 0 l ) . On a v e r a g e , f e m a l e s moved ab o u t l e s s t h a n m a l e s i n b o t h t r e a t m e n t s and m a l e s and f e m a l e s w h i c h were p a i r e d w i t h t h e o p p o s i t e sex t e n d e d t o move ab o u t l e s s t h a n t h o s e w h i c h were kept s e p a r a t e from t h e o p p o s i t e sex ( F i g . 3 ) . F e m a l e s moved a b o u t s i g n i f i c a n t l y l e s s t h a n m a l e s when t h e s e x e s were h e l d s e p a r a t e l y ( p < 0 . 0 0 l ) , but t h e r e was no s i g n i f i c a n t d i f f e r e n c e i n t h e movement of t h e s e x e s when t h e y were h e l d t o g e t h e r (p>0.6). W i t h i n s e x , m a l e s w h i c h were h e l d t o g e t h e r w i t h f e m a l e s moved a b o u t s i g n i f i c a n t l y l e s s t h a n m a l e s w h i c h were h e l d i n t h e a b s e n c e of f e m a l e s ( p < 0 . 0 0 l ) . A l t h o u g h p a i r e d f e m a l e s t e n d e d t o move a b o u t l e s s t h a n u n p a i r e d f e m a l e s , t h e d i f f e r e n c e was not s i g n i f i c a n t (p<0.07). The t o t a l a g g r e s s i v e , a c t i v i t y of f i s h e s d i f f e r e d s i g n i f i c a n t l y between t h e s e x e s (p<0.001) but not between t r e a t m e n t s ( p a i r e d and u n p a i r e d ) ( p > 0 . 1 5 ; F i g . 4 ) . The i n t e r a c t i o n o f sex and p a i r i n g was s i g n i f i c a n t (p<0.05). F e m a l e s d i s p l a y e d fewer a g g r e s s i v e b e h a v i o u r s t h a n males i n b o t h t r e a t m e n t s (p<0.05). W i t h i n s e x e s , f e m a l e s i n t h e p r e s e n c e of \ 21 Table 1. Mean fork l e n g t h s , weights and s i z e ranges (+SE) of males and females used. L e t t e r d e s i g n a t i o n s a r e : m,f=sex; U=unpaired t e s t group ( i . e. sexes s e p a r a t e d ) ; PA=paired t e s t group; S=small s i z e ; L=large s i z e ; P=prior a c c e s s ; NP= without p r i o r access; WF=males which were r e c e n t l y with females; WOF=males not r e c e n t l y with females; WA=males p r e v i o u s l y i n area and; WOA=males not p r e v i o u s l y with females or i n a r e a . Exp. Test Mean Range Mean Range Sex Group Fork Length N Weight N lb m U 21.3 (0.2) 19.3-23.2 25 m PA 21.3 (0.2) 19.6-24.5 25 f U 21.0 (0.2) 18.9-22.6 25 f PA 20.8 (0.2) 19.2-23.7 24 2b f S 19.7 (0.1) 17.7-20.9 165 78.6 (0 .8) 56 .1-97.5 1 58 L 22.5 (0.1) 21 .5-29.4 165 112.3 ( 1 .8) 84 .7-250.0 165 2c f SP 19.6 (0.1 ) 18.3-20.6 60 76.8 ( 1 .3) 58 .2-95.9 54 LP 22.2 (0.1 ) 21.5-28.7 60 108.0 (2 .2) 84 .7-221.3 60 SNP 19.4 (0.1) 17.7-20.5 60 76.9 ( 1 .2) 57 .2-94.4 59 LNP 22.4 (0.1 ) 21 .5-27.8 60 1 12.2 (2 .5) 90 .9-216.6 60 3a m S 20. 1 (0.1 ) 18.5-20.7 70 76.3 (0 .9) 58 .5-88.8 56 L 22. 1 (0.1) 21 .5-24.6 70 102.2 ( 1 .3) 81 .9-138.9 56 3b m P 20.3 (0.0) 20.0-20.5 70 80.6 (0 .6) 69 .6-93.7 70 NP 20.3 (0.0) 20.1-20.5 70 80.5 (0 .6) 71 .4-93.2 70 3c m SP 20. 1 (0.1) 18.1-20.8 70 76.7 (0 .8) 57 .8-92.0 56 LNP 22. 1 (0.1 ) 21 .5-24.0 70 1 04. 1 ( 1 .4) 83 .1-138.0 56 3d m WF 20.3 (0.0) 20.1-20.5 56 82.6 (0 .5) 76 .2-92.3 56 WOF 20.3 (0.0) 20.1-20.4 56 82.3 (0 .7) 73 .3-94.5 56 3e m WA 20.3 (0.0) 20.1-20.4 56 86. 1 (0 .6) 75 .2-96.2 56 WOA 20.3 (0.0) 20.1-20.4 56 83.3 (0 .5) 74 .9-91 .0 56 22 Table 2. The mean number of d i g s and a g g r e s s i v e behaviours d i s p l a y e d by 25 males and 25 females over 30 minutes of ob s e r v a t i o n when held together with an equal number of the opposite sex (T) and when h e l d separate from the o p p o s i t e sex (S), over three to f i v e days i n an experimental arena. The means of the mean d i s t a n c e between s u c c e s s i v e p o s i t i o n s (MDP) (+SE) hel d by each f i s h over three to f i v e days are a l s o p r e s e n t e d . Males Females Dig Chase B i t e L a t e r a l T T o t a l (SE) MDP (SE) D i s p l a y D i s p l a y s 0.4 18.4 2.4 18.4 6.0 45.7 (4.5) 1.78 (.01) T 1 .3 22.8 4.6 15.4 6.6 50.6 (5.0) 0.93 (.01) » S 2.3 22.9 2.8 4.2 2.9 35. 1 (4.3) 1.10 (.01) T 8.0 13.4 3.6 1 .0 0.9 26.5 (3.1) 0.86 ( .01) 23 F i g u r e 3. Mean d i s t a n c e between s u c c e s s i v e p o s i t i o n s h e l d by 25 m a l e s and 25 f e m a l e s t h a t were h e l d (A) s e p a r a t e from t h e o p p o s i t e sex o v e r f i v e d a y s and (B) t o g e t h e r w i t h t h e o p p o s i t e sex o v e r t h r e e d a y s of o b s e r v a t i o n i n an e x p e r i m e n t a l a r e n a . 24 8 -i A) Sexes he ld s e p a r a t e l y u c QJ D CT CD C_ Ll_ 6 A A A 2 A o J I I 1 1 1 1 1 1 0 . 0 0 . 5 1 . 0 1 .5 2 . 0 2 . 5 3 . 0 io n B) Sexes he ld toge ther B A 6 A 4 A 2 A o J SBS t t i M M I 1 I 1 1 1 1 0 . 0 0 . 5 1 . 0 1 .5 2 . 0 2 . 5 3 . 0 Mean Dist a n c e Between P o s i t i o n s Held by I n d i v i d u a l F i s h over Days In an Arena (m) Hi) - Females [3 " Males F i g u r e 4. T o t a l a g g r e s s i v e a c t i v i t y o v e r 30 m i n u t e s o f o b s e r v a t i o n by 25 m a l e s and 25 f e m a l e s t h a t were h e l d s e p a r a t e f r o m t h e o p p o s i t e sex f o r f i v e d a y s and (B) t o g e t h e r w i t h t h e o p p o s i t e sex f o r t h r e e d a y s i n an e x p e r i m e n t a l a r e n a . 26 14 i A) Sexes he ld s e p a r a t e l y tp io i B) Sexes he ld toge ther a -6 -4 H 2 H 0 20 40 60 80 100 120 140 Total Number of Aggressive Behaviours Displayed over 30 Minutes of Observation in an Arena = Females ^ = Males 27 m a l e s d i s p l a y e d fewer a g g r e s s i v e b e h a v i o u r s t h a n f e m a l e s h e l d s e p a r a t e l y f r o m m a l e s (p<0.05). The d e c r e a s e i n a g g r e s s i v e a c t i v i t y i n t h e p r e s e n c e of m a l e s was a s s o c i a t e d w i t h a s i g n i f i c a n t i n c r e a s e i n t h e amount of n e s t c o n s t r u c t i o n ( d i g g i n g ) o b s e r v e d ( p < 0 . 0 0 l ) , s u c h t h a t t h e t o t a l f e m a l e a c t i v i t y l e v e l s (sum of d i g g i n g and a g g r e s s i v e b e h a v i o u r s ) d i d not d i f f e r s i g n i f i c a n t l y between t r e a t m e n t s (p>0.15). T h e r e was no s i g n i f i c a n t d i f f e r e n c e i n t h e a g g r e s s i v e a c t i v i t y of males between t r e a t m e n t s (p>0.4). To f u r t h e r compare male and f e m a l e b e h a v i o u r , a g g r e s s i v e b e h a v i o u r s were d i v i d e d i n t o two c a t e g o r i e s : " D i r e c t A c t i o n s " , t h o s e w h i c h i n v o l v e d d i r e c t a s s a u l t s on o t h e r i n d i v i d u a l s ( c h a s e s and b i t e s ) and " D i s p l a y s " , b e h a v i o u r s w h i c h i n v o l v e d l a t e r a l o r p e r p e n d i c u l a r body p r e s e n t a t i o n s w h i c h i n t h e m s e l v e s d i d not i n v o l v e d i r e c t p h y s i c a l c o n t a c t w i t h t h e r e c e i v e r ( l a t e r a l d i s p l a y s and T - d i s p l a y s ) . T h e r e were no s i g n i f i c a n t d i f f e r e n c e s w i t h i n s e x e s between t r e a t m e n t s i n t h e r e l a t i v e f r e q u e n c y o f p e r f o r m a n c e o f e i t h e r D i r e c t A c t i o n s o r D i s p l a y s (p>0.3; T a b l e 2 ) , but t h e r e were g r e a t d i f f e r e n c e s between t h e s e x e s i n t h e r e l a t i v e f r e q u e n c y of D i r e c t A c t i o n s and D i s p l a y s (p<0.005). Male a c t i v i t y was d i v i d e d n e a r l y e q u a l l y between D i r e c t A c t i o n s and D i s p l a y s but f e m a l e a c t i v i t y i n v o l v e d m a i n l y (83%) D i r e c t A c t i o n s . F e m a l e s were more a g g r e s s i v e t o w a r d s males t h a n males t o w a r d f e m a l e s (T-t e s t , p<0.001; T a b l e 3 ) . D i r e c t A c t i o n s composed t h e m a j o r i t y 28 Table 3. Comparison of the mean i n t e r s e x u a l a g g r e s s i v e behaviour of 25 male and 25 female female kokanee observed for 30 minutes each over three days i n an experimental arena. Chase B i t e L a t e r a l ' T T o t a l (SE) % T o t a l D i s p l a y D i s p l a y A g g r e s s i o n Males 3.6 0.7 0.8 0.9 5.9 (0.8) 11.1% Females 8.2 1.9 1.0 0.9 12.4 (1.1) 31.9% 29 o f i n t e r s e x u a l i n t e r a c t i o n s o f b o t h s e x e s . T h e r e were s i g n i f i c a n t d i f f e r e n c e s i n movement (MDP) among f e m a l e s i n b o t h t h e p a i r e d and u n p a i r e d t r e a t m e n t (One-way a n o v a , p < 0 . 0 0 l ) . The MDP f o r p a i r e d f e m a l e s , a v e r a g e d o v e r 21 o b s e r v a t i o n s t a k e n o v e r t h r e e d a y s , r a n g e d between 0.12 and 1.77 m. The MDP f o r u n p a i r e d f e m a l e s , a v e r a g e d o v e r 31 o b s e r v a t i o n s t a k e n o v e r 5 d a y s , r a n g e d between 0.39 and 1.91 m. In b o t h t r e a t m e n t s , t h e m a j o r i t y of f e m a l e s h e l d t o p a r t i c u l a r a r e a s , w h i c h t h e y a g g r e s s i v e l y d e f e n d e d ( F i g s . 5a and 6 a ) . Some f e m a l e s f a i l e d t o e s t a b l i s h f i x e d p o s i t i o n s . The d e g r e e t o w h i c h f e m a l e s h e l d t o s p e c i f i c p o s i t i o n s depended on whether m a l e s were p r e s e n t or a b s e n t . In t h e a b s e n c e of m a l e s , f e m a l e s moved a r o u n d more w i t h i n g i v e n a r e a s , and r e t u r n e d l e s s s p e c i f i c a l l y when d i s p l a c e d . In t h e p r e s e n c e of m a l e s , t h e m a j o r i t y of f e m a l e s h e l d t o s p e c i f i c l o c a t i o n s and r e t u r n e d p r e c i s e l y t o t h o s e p o s i t i o n s when d i s p l a c e d ( F i g s . 5b and 6 b ) . T h e r e were s i g n i f i c a n t d i f f e r e n c e s i n movement (MDP) among mal e s i n b o t h p a i r e d and u n p a i r e d t r e a t m e n t s (One-way a n o v a , P<0.001). In t h e u n p a i r e d t r e a t m e n t , t h e MDP r a n g e d between 0.85 and 2.35 m. In t h e p a i r e d t r e a t m e n t , t h e mean d i s t a n c e s between p o s i t i o n s were s u b s t a n t i a l l y s m a l l e r , r a n g i n g from 0.18 t o 1.81 m. Male movement was l o c a l i z e d i n b o t h c a s e s , a l t h o u g h much more so i n t h e p r e s e n c e o f f e m a l e s . Some m a l e s , i n t h e a b s e n c e of f e m a l e s , a g g r e s s i v e l y m a i n t a i n e d p o s i t i o n s w i t h i n g i v e n a r e a s o v e r d a y s . The g e n e r a l a r e a s o c c u p i e d by f i v e of 30 F i g u r e 5. A r e a s i n w h i c h i n d i v i d u a l f e m a l e s , kept a p a r t from m a l e s , s p e n t most o f t h e i r t i m e o v e r (A) f i v e d a y s of u n d i s t u r b e d o b s e r v a t i o n and ( B ) , l a t e r , o v e r one and one h a l f d a y s o f r e p e a t e d d i s t u r b a n c e s (and d i s p l a c e m e n t s from t h e i r p o s i t i o n s ) i n an e x p e r i m e n t a l a r e n a . E a c h f i s h i s i d e n t i f i e d by l e t t e r . G r e a t e r d e n s i t y of t h e s h a d i n g of a r e a s i n d i c a t e s h i g h e r rank of t h e f e m a l e i n t o t a l a c t i v i t y (summ of d i g g i n g and a g g r e s s i v e a c t i v i t i e s ) . The p a r e n t h e s i z e d number b e s i d e e a c h l e t t e r i n d i c a t e s t h e p e r c e n t a g e of t o t a l o b s e r v a t i o n s i n w h i c h t h e f e m a l e was o b s e r v e d w i t h i n t h e d e s i g n a t e d a r e a . A) P o s i t i o n s of Females Over F i v e Days B ) P o s i t i o n s of Females A f t e r Repeated Displacement 0 1 2 3 4 5 Dis tance From Fr 0 1 2 3 4 5 ont of Arena (m) 32 F i g u r e 6. A r e a s i n w h i c h i n d i v i d u a l f e m a l e s , i n t h e p r e s e n c e o f m a l e s , s p e n t most o f t h e i r t i m e o v e r (A) t h r e e d a y s of u n d i s t u r b e d o b s e r v a t i o n and (B) l a t e r , o v e r one day r e p e a t e d d i s t u r b a n c e (and d i s p l a c e m e n t from t h e i r p o s i t i o n s ) i n an e x p e r i m e n t a l a r e n a . See l e g e n d t o F i g . 5 f o r f u r t h e r d e t a i l s . A) Pos i t i o n s of Females B) Positions of Females After Over Three Days Repeated Displacement J I I I I I 1 1 I I I L 0 1 2 3 4 5 Dis tance From Fr 0 1 2 3 4 5 ont of Arena (m) 34 t h e s i x most a g g r e s s i v e m a l e s i n t h e u n p a i r e d t r e a t m e n t a r e shown i n F i g . 7. T h e s e m a l e s r a n g e d w i t h i n s m a l l but o f t e n o v e r l a p p i n g a r e a s d u r i n g t h e m a j o r i t y of t h e o b s e r v a t i o n p e r i o d s and r e t u r n e d , f a i r l y p r e c i s e l y t o t h e s e a r e a s when r e p e a t e d l y d i s p l a c e d . In t h e p r e s e n c e o f f e m a l e s , m a l e s c o u r t i n g f e m a l e s l a r g e l y e x c l u d e d o t h e r m a l e s from t h e i r d i r e c t v i c i n i t y , and r e t u r n e d t o t h e i r p o s i t i o n s , a t t e n d i n g t h e same f e m a l e , a f t e r r e p e a t e d d i s p l a c e m e n t ( F i g . 8 ) . Some m a l e s a d o p t e d sneak p o s i t i o n s b e h i n d p a i r s and u s u a l l y r e t u r n e d t o t h e i r sneak p o s i t i o n s b e h i n d t h e same f e m a l e a f t e r d i s p l a c e m e n t . C. The e f f e c t of compet i t o r s on t h e commencement of  t e r r i t o r i a l i t y Kokanee r e l e a s e d back i n t o t h e crowded spawning c h a n n e l e s t a b l i s h e d p o s i t i o n s a t a much s l o w e r r a t e t h a n t h o s e p l a c e d i n t o an e x p e r i m e n t a l a r e n a (38 of 50 d e f e n d e d p o s i t i o n s i n t h e a r e n a as compared t o 3 of 19 o b s e r v e d i n t h e c h a n n e l a f t e r t h e same t h r e e day p e r i o d ; C h i - s q u a r e d t e s t , p < 0 . 0 0 l ) . Most of t h e 16 t a g g e d kokanee w h i c h d i d not e s t a b l i s h spawning p o s i t i o n s i n t h e c h a n n e l o v e r t h r e e d a ys were o b s e r v e d i n s c h o o l s o f kokanee, u p s t r e a m from t h e i r r e l e a s e p o i n t . The p o s i t i o n of s c h o o l s (sometimes c o n s i s t i n g o f o v e r 10,000 f i s h ) i n t h e s t r e a m r e m a i n e d c o n s t a n t o v e r d a y s , u s u a l l y i n p o o l s o r back e d d i e s , even t h o u g h t h e i n d i v i d u a l f i s h making up t h e s c h o o l s moved. T h i s s u g g e s t s t h a t t h e s c h o o l s d i d not move as a u n i t , but r a t h e r t h a t i n d i v i d u a l f i s h o r s m a l l g r o u p s of f i s h moved 35 F i g u r e 7 . A r e a s i n w h i c h i n d i v i d u a l m a l e s , kept s e p a r a t e from f e m a l e s , s p e n t most o f t h e i r t i m e o v e r (A) f i v e d a y s of u n d i s t u r b e d o b s e r v a t i o n and (B) l a t e r , o v e r one and one h a l f d a y s r e p e a t e d d i s t u r b a n c e s (and d i s p l a c e m e n t s from p o s i t i o n s ) i n an e x p e r i m e n t a l a r e n a . The p o s i t i o n s o f o n l y f i v e of t h e most a g g r e s s i v e males a r e shown. See l e g e n d t o F i g . 5 f o r f u r t h e r d e t a i l s . A) P o s i t i o n s of Males Over Five Days B) Positions of Males A f t e r Repeated Displacement D i s t a n c e From F r o n t of Arena (m) 37 F i g u r e 8. A r e a s i n w h i c h i n d i v i d u a l m a l e s , i n t h e p r e s e n c e of f e m a l e s , s p e n t most o f t h e i r t i m e o v e r (A) t h r e e d a y s o f u n d i s t u r b e d o b s e r v a t i o n and (B) l a t e r , o v e r one day of r e p e a t e d d i s t u r b a n c e (and d i s p l a c e m e n t from t h e i r p o s i t i o n s ) i n an e x p e r i m e n t a l a r e n a . The l e t t e r "S" b e s i d e p a r t i c u l a r m a l e s i n d i c a t e s t h a t t h e y s p e n t t h e m a j o r i t y of t h e i r t i m e a t t e m p t i n g t o sneak f e r t i l i z a t i o n s from f e m a l e s a t t e n d e d by o t h e r m a l e s . See l e g e n d t o F i g . 5 f o r f u r t h e r d e t a i l s . 00 ro A) P o s i t i o n s of Males B) P o s i t i o n s of Males A f t e r Over Three Days Repeated Displacement 0 1 2 3 4 5 0 1 2 3 4 5 Dis tance From Front of Arena (m) 39 u p s t r e a m from s c h o o l t o s c h o o l . 2. The e f f e c t s o f s i z e and p r i o r a c c e s s i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n Methods A. P r e f e r r e d spawning s i t e s The e f f e c t s of s i z e and p r i o r a c c e s s i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n were t e s t e d i n two 5 by 5 m e x p e r i m e n t a l a r e n a s i n Meadow C r e e k spawning c h a n n e l i n September, 1983. I t was f i r s t n e c e s s a r y t o d e t e r m i n e w h i c h a r e a s of t h e a r e n a s were p r e f e r r e d by f e m a l e s and whether t h e p r e f e r r e d a r e a s d i f f e r e d between " s m a l l " and " l a r g e " i n d i v i d u a l s (The s i z e r a n g e s of f e m a l e s u s e d a r e g i v e n i n T a b l e 1 ) . ' P r e f e r r e d a r e a s ' were d e t e r m i n e d by a l l o w i n g d i f f e r e n t numbers of f e m a l e s of e a c h s i z e c l a s s (5, 10, 15, 20; r e p e a t e d t w i c e f o r e a c h s i z e g r o u p , 200 f e m a l e s i n t o t a l ) , a c c o m p a n i e d by an e q u a l number of m a l e s , t o e s t a b l i s h p o s i t i o n s ( n e s t s i t e s ) i n e a c h e x p e r i m e n t a l a r e n a o v e r an 8 t o 14 hour p e r i o d . At t h e end of a p e r i o d , t h e p o s i t i o n of e a c h f e m a l e , a l o n g w i t h d a t a on whether i t was (1) a c c o m p a n i e d by a male, (2) h o l d i n g p o s i t i o n and (3) c o n s t r u c t i n g a n e s t ( d i g g i n g ) , were r e c o r d e d . ' P r e f e r r e d a r e a s ' were c o n s i d e r e d t o be t h o s e i n h a b i t e d by f e m a l e s a t t e n d e d by m a l e s . 40 B. The e f f e c t s of s i z e i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n In e a c h of 11 t r i a l s , 15 l a r g e and 15 s m a l l r i p e unspawned and i n d i v i d u a l l y t a g g e d f e m a l e s were i n t r o d u c e d s i m u l t a n e o u s l y i n t o A r e n a 2 (downstream) a t 1800 h o u r s and a l l o w e d t o compete f o r p o s i t i o n s o v e r a 24 hour p e r i o d . The p o s i t i o n of e a c h f e m a l e (and whether i t was h o l d i n g p o s i t i o n ) was r e c o r d e d t w i c e , a t 0800 h o u r s on t h e f o l l o w i n g m o r n i n g and a g a i n a t 1730 h o u r s . 'Winners' of f e m a l e c o m p e t i t i o n t r i a l s were j u d g e d t o be t h o s e f e m a l e s t h a t h e l d p o s i t i o n s w i t h i n t h e ' p r e f e r r e d a r e a ' d u r i n g b o t h t h e dawn and dusk o b s e r v a t i o n p e r i o d s . To d e r i v e an i n d e p e n d e n t s c o r e f o r e a c h t r i a l , t h e number of s m a l l f e m a l e s t h a t h e l d p o s i t i o n s i n t h e p r e f e r r e d a r e a was s u b t r a c t e d from t h e number of l a r g e f e m a l e s w h i c h d i d s o . C. The e f f e c t of p r i o r a c c e s s i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n In e a c h of f o u r t r i a l s , 30 f e m a l e s (15 l a r g e and 15 s m a l l ; t h o s e from t r i a l s 4, 6, 8 and 10 o f t h e s i z e e x p e r i m e n t ) , were t a k e n from a r e n a 2 a t 1800 h o u r s , i n t r o d u c e d i n t o a r e n a 1, and a l l o w e d t o e s t a b l i s h n e s t s i t e s o v e r a 24 h o u r p e r i o d . The p o s i t i o n of e a c h o f t h e s e f e m a l e s was r e c o r d e d t w i c e d u r i n g t h i s 24 hour p e r i o d . At t h e end of t h e 24 hour p e r i o d , 30 f e m a l e s (15 l a r g e and 15 s m a l l ; t h o s e from t r i a l s 5, 7, 9 and 11) were t a k e n from a r e n a 2, p l a c e d i n a r e n a 1, and a l l o w e d t o compete w i t h t h e incumbent f e m a l e s o v e r a 24 hour p e r i o d . The s u c c e s s of t h e i m m i g r a n t f e m a l e s i n e s t a b l i s h i n g t e r r i t o r i e s was 41 measured by s u b t r a c t i n g t h e number o f i m m i g r a n t f e m a l e s (no p r i o r a c c e s s ) h o l d i n g p o s i t i o n s i n t h e p r e f e r r e d a r e s f r o m t h e number of incumbent ( t h o s e w i t h p r i o r a c c e s s ) f e m a l e s d o i n g s o . The d a t a from e a c h e x p e r i m e n t were a n a l y s e d u s i n g t h e W i l c o x o n m a tched p a i r s s i g n e d rank t e s t (one t a i l e d ) . The matched p a i r s i n t h i s e x p e r i m e n t a r e t h e n o n - i n d e p e n d e n t outcomes o f e a c h t r i a l ( t h a t i s , whether o r n o t a f i s h h e l d p o s i t i o n w i t h i n t h e p r e f e r r e d spawning a r e a of t h e a r e n a ) . R e s u l t s A. P r e f e r r e d spawning s i t e s L a r g e and s m a l l kokanee f e m a l e s a t t e n d e d by m a l e s e s t a b l i s h e d n e s t s i t e s i n t h e same g e n e r a l v i c i n i t y i n b o t h e x p e r i m e n t a l a r e n a s . P o s i t i o n s i n t h e downstream, o f f s h o r e p o r t i o n s o f e a c h a r e n a were a l w a y s o c c u p i e d ( F i g . 9 ) , i n d e p e n d e n t of t h e number o f f e m a l e s p r e s e n t . As f e m a l e d e n s i t y i n c r e a s e d , f e m a l e s e s t a b l i s h e d p o s i t i o n s s l i g h t l y u p s t r e a m o f t h i s p r e f e r r e d . a r e a . The o f f s h o r e p o r t i o n s o f e a c h a r e n a were t h e a r e a s of maximal water v e l o c i t y . Water l e f t e a c h a r e n a t h r o u g h b o t h t h e r e a r f e n c e and t h e l o w e r r e a c h e s of t h e o u t e r f e n c e . T h i s r e s u l t e d i n a a d i s t i n c t d e v i a t i o n of t h e c u r r e n t t o w a r d s t h e o f f s h o r e f e n c e i n t h e downstream o f f s h o r e p o r t i o n of e a c h a r e n a (as d e m o n s t r a t e d by p l o t t i n g t h e c o u r s e o f r e l e a s e d dye) . 42 F i g u r e 9. P o s i t i o n s h e l d by ' l a r g e ' and ' s m a l l ' kokanee f e m a l e s w h i c h were a c c o m p a n i e d by m a l e s i n a r e n a s 1 and 2. The p o s i t i o n s o f f e m a l e s t h a t were not a c c o m p n a i e d by males a r e shown. The d o t t e d l i n e s e n c l o s e an a r e a where o v e r 85% o f f e m a l e s of b o t h s i z e g r o u p s e s t a b l i s h e d n e s t s i t e s . Dis tance from Side of Arena (m) 44 To b r o a d l y d e l i n e a t e t h e a r e a s p r e f e r r e d as spawning s i t e s by f e m a l e s , a s e c t i o n of e a c h a r e n a i n w h i c h t h e m a j o r i t y of f e m a l e s e s t a b l i s h e d n e s t s i t e s was v i s u a l l y i d e n t i f i e d ( F i g . 9 ) . The s u b j e c t i v e b o u n d a r i e s of t h e s e " p r e f e r r e d a r e a s " were s u p p o r t e d by n e a r e s t n e i g h b o u r a n a l y s e s of t h e p o s i t i o n s o f a l l a t t e n d e d f e m a l e s . The " p r e f e r r e d a r e a " took up j u s t o v e r one h a l f t h e t o t a l p o s s i b l e spawning a r e a i n e a c h a r e n a (13.5 and 12.8 s q u a r e m e t e r s of a r e n a 1 and 2, r e s p e c t i v e l y ) . In a r e n a 1, 63 o f t h e 66 l a r g e f e m a l e s (95%) and 58 of 64 s m a l l f e m a l e s (91%) a t t e n d e d by m a l e s e s t a b l i s h e d n e s t s i t e s w i t h i n t h e " p r e f e r r e d a r e a " . In a r e n a 2, 54 o f 60 l a r g e f e m a l e s (90%) and 56 of 64 s m a l l f e m a l e s (88%) a t t e n d e d by males e s t a b l i s h e d n e s t s i t e s w i t h i n t h e " p r e f e r r e d a r e a " . The m a j o r i t y of f e m a l e n e s t c o n s t r u c t i o n ( d i g g i n g ) was o b s e r v e d w i t h i n t h e " p r e f e r r e d a r e a s " . In a r e n a 1, a l l 19 l a r g e f e m a l e s and 20 o f 22 s m a l l f e m a l e s o b s e r v e d c o n s t r u c t i n g n e s t s ( d i g g i n g ) , d i d so w i t h i n t h e " p r e f e r r e d a r e a " . In a r e n a 2, 24 o f 26 l a r g e f e m a l e s and 21 o f 24 s m a l l f e m a l e s o b s e r v e d d i g g i n g , d i d so w i t h i n t h e " p r e f e r r e d a r e a " . To v e r i f y t h a t t h e " p r e f e r r e d a r e a " o f e a c h a r e n a was p r e f e r r e d , and competed f o r , by f e m a l e s , I t w i c e ( w i t h s e p a r a t e g r o u p s of f e m a l e s , no males p r e s e n t ) removed f e m a l e s from t h e " p r e f e r r e d a r e a " of a r e n a 1 and r e c o r d e d t h e p o s i t i o n s of t h e r e m a i n i n g f e m a l e s f i v e h o u r s l a t e r ( t h e " p r e f e r r e d a r e a " r e f e r r e d t o h e r e i s s m a l l e r t h a n t h a t d e s c r i b e d above, as i t was 45 r o u g h l y e s t i m a t e d i n t h e f i e l d w i t h o u t t h e a i d of t h e d a t a on f e m a l e p o s i t i o n i n g t h a t were t h e n b e i n g c o l l e c t e d ) . I a l s o removed f e m a l e s t h a t h e l d p o s i t i o n s o u t s i d e t h e " p r e f e r r e d a r e a " on one o c c a s i o n and s i m i l a r l y r e c o r d e d t h e p o s i t i o n s o f t h e r e m a i n i n g f e m a l e s . A f t e r t h e f e m a l e s h o l d i n g t e r r i t o r i e s w i t h i n t h e " p r e f e r r e d a r e a " were removed, t h e a r e a was a l w a y s r e - o c c u p i e d by f e m a l e s e m i g r a t i n g f r o m t h e n o n - p r e f e r r e d a r e a ( F i g . 1 0 ) . O ver t h e two t r i a l s , 21 f e m a l e s were removed from t h e " p r e f e r r e d a r e a " and 22 o t h e r f e m a l e s moved i n t o and e s t a b l i s h e d p o s i t i o n s w i t h i n t h i s a r e a o v e r t h e c o u r s e of f i v e h o u r s . F i v e o f t h e i m m i g r a n t f e m a l e s were o b s e r v e d c o n s t r u c t i n g n e s t s ( d i g g i n g ) . In c o n t r a s t , few f e m a l e s e m i g r a t e d from t h e " p r e f e r r e d a r e a " t o t h e o u t l y i n g a r e a s a f t e r f e m a l e s were removed from t h e s e 'non-p r e f e r r e d ' a r e a s ( F i g . 1 1 ) . Of t h e f i v e f e m a l e s t h a t l e f t t h e " p r e f e r r e d a r e a " , t h r e e moved t o p o s i t i o n s j u s t beyond t h e b o u n d a r i e s , and two l e f t t h e a r e a c o m p l e t e l y . The e x a m i n a t i o n o f p o s i t i o n s e s t a b l i s h e d by spawning p a i r s , s u p p o r t e d by d a t a from t h e r e m o v a l e x p e r i m e n t , d e m o n s t r a t e s t h a t f e m a l e s p r e f e r r e d t o e s t a b l i s h n e s t s i t e s i n t h e o u t e r , downstream p o r t i o n s of t h e e x p e r i m e n t a l a r e n a s and t h a t f e m a l e i n t e r a c t i o n s l i m i t e d t h e number of f e m a l e s w h i c h c o u l d do s o . In t h e f o l l o w i n g e x p e r i m e n t s , " w i n n e r s " of f e m a l e i n t r a s e x u a l c o m p e t i t i o n f o r n e s t s s i t e s were j u d g e d as t h o s e i n d i v i d u a l s w h i c h m a i n t a i n e d p o s i t i o n s w i t h i n t h e " p r e f e r r e d a r e a " o v e r t h e 46 F i g u r e 10. P o s i t i o n s o c c u p i e d by f e m a l e s i n a r e n a 1 (A) b e f o r e f e m a l e s were removed from t h e p r e f e r r e d a r e a and f i v e h o u r s a f t e r (B) f e m a l e s were removed from t h e p r e f e r r e d a r e a . A) Positions Before Females Removed From Preferred Area B) Positions After Females Removed From Preferred Area 1 2 3 4 5 0 1 2 3 4 D i s t a n c e from F r o n t of Arena (m) females l e f t in arena; 0 - females removed from arena 48 F i g u r e 11. P o s i t i o n s o c c u p i e d by f e m a l e s i n a r e n a 1 (A) b e f o r e f e m a l e s were removed f r o m t h e n o n - p r e f e r r e d a r e a (B) f i v e h o u r s a f t e r f e m a l e s were removed from t h e n o n - p r e f e r r e d a r e a . A) Positions Before Females B) Positions After Females Hemoved From Non-Preferred Area Removed From Non-Preferred Area *! * * * * o *k * * j * * * 1 * * o u i ! * * * ! * *# ! * * * ! * : * U - _ _ _ _ _ _ — _ _ _ _ _ _ _ _ _ LJ ** o o o o o ° - i i i i t i * 0 1 2 3 4 5 0 1 2 3 4 5 D i s t a n c e from F r o n t of Arena (m) * - fem a l e s l e f t i n arena; 0 - females removed from arena 50 c o u r s e of 24 hour t r i a l s . B. S i z e i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n L a r g e f e m a l e s (14% l o n g e r , 43% h e a v i e r ; T a b l e 1) d o m i n a t e d s m a l l f e m a l e s i n c o m p e t i t i o n f o r p r e f e r r e d s i t e s i n 9 of 11 t r i a l s i n a r e n a 2 (p<0.05; F i g . 1 2 a ) . In o n l y one t r i a l was t h e number of s m a l l f e m a l e s h o l d i n g p o s i t i o n w i t h i n t h e p r e f e r r e d a r e a g r e a t e r t h a n t h e number of l a r g e f e m a l e s i n t h e same a r e a . In one o t h e r t r i a l , t h e numbers of l a r g e and s m a l l f e m a l e s i n t h e p r e f e r r e d a r e a were e q u a l . On a v e r a g e , 64% (6.6 + 0.5SE p e r t r i a l ) of f e m a l e s t h a t m a i n t a i n e d p o s i t i o n s w i t h i n t h e p r e f e r r e d a r e a were o f t h e l a r g e g r o u p and 36% (3.7 + 0.6) were o f t h e s m a l l g r o u p . The e f f e c t of s i z e was m a i n t a i n e d when f e m a l e s were t r a n s f e r r e d t o a r e n a 1 and a l l o w e d t o re-compete f o r p o s i t i o n s o v e r 24 h o u r s (number of l a r g e f e m a l e s h o l d i n g p o s i t i o n i n p r e f e r r e d a r e a minus t h e number of s m a l l f e m a l e s h o l d i n g p o s i t i o n ; i n t h e f o u r t r i a l s = 8, 2, 5, 7; p=0.05). On a v e r a g e , 9.8 (0.8SE) l a r g e and 4.3 (0.6) s m a l l f e m a l e s m a i n t a i n e d p o s i t i o n i n t h e p r e f e r r e d a r e a . The m a j o r i t y (71%) of l a r g e (26 of 39) and s m a l l (13 o f 16) f e m a l e s w h i c h h e l d p r e f e r r e d t e r r i t o r i e s i n a r e n a 1 p r e v i o u s l y h e l d p r e f e r r e d t e r r i t o r i e s i n a r e n a 2. Of t h e r e m a i n i n g 16 f e m a l e s , 11 had p r e v i o u s l y h e l d p o s i t i o n i n t h e p r e f e r r e d a r e a of a r e n a 2 d u r i n g one of t h e two o b s e r v a t i o n p e r i o d s . The r e p e a t a b i l i t y of t h e r e s u l t s a t t h e 51 F i g u r e 12. The d i f f e r e n c e between t h e number of f e m a l e s from two t e s t g r o u p s w h i c h were a b l e t o h o l d p o s i t i o n s w i t h i n t h e p r e f e r r e d spawning a r e a . (A) In 11 t r i a l s , g r o u p s of 15 ' l a r g e ' and 15 ' s m a l l ' f e m a l e s competed f o r a c c e s s t o p r e f e r r e d p o s i t i o n s o v e r 24 h o u r s . (B) In f o u r t r i a l s , g r o u p s of 30 f e m a l e s (15 ' l a r g e ' and 15 ' s m a l l ' ) w h i c h had p r e v i o u s a c c e s s t o t h e p r e f e r r e d p o s i t i o n s competed a g a i n s t a s i m i l a r number and s i z e r a n g e of f e m a l e s f o r a c c e s s t o p r e f e r r e d p o s i t i o n s o v e r 24 h o u r s . 52 -2 0 2 4 6 8 10 12 Number of Incumbent Females minus Number of Immigrant Females in Preferred Spawning Area 53 i n d i v i d u a l l e v e l d e m o n s t r a t e s t h a t t h e r e i s s i g n i f i c a n t v a r i a t i o n among i n d i v i d u a l s i n t h e a b i l i t y t o a c q u i r e t e r r i t o r i e s t h a t i s not a c c o u n t e d f o r by s i z e d i f f e r e n c e s a l o n e . C. The e f f e c t of p r i o r a c c e s s i n f e m a l e i n t r a s e x u a l c o m p e t i t i o n Incumbent f e m a l e s ( t h o s e w i t h 24 hour p r i o r a c c e s s ) d o m i n a t e d i m m i g r a n t s i n i n t e n s e c o m p e t i t i o n f o r p r e f e r r e d n e s t i n g s i t e s i n a l l f o u r t r i a l s (p=0.05; F i g . 12b). Of t h e 62 f e m a l e s m a i n t a i n i n g p o s i t i o n w i t h i n t h e p r e f e r r e d a r e a , 49 (79%) had been i n t h e a r e n a 24 h o u r s p r i o r t o t h e a d d i t i o n of t h e i m migrant f e m a l e s . R e l a t i v e s i z e was not a f a c t o r i n d e t e r m i n i n g w h i c h incumbent f e m a l e s were a b l e t o m a i n t a i n t h e i r t e r r i t o r i e s . The number of s m a l l incumbent f e m a l e s h o l d i n g p r e f e r r e d p o s i t i o n s i n c r e a s e d from 16 t o 19 a f t e r t h e a d d i t i o n of t h e s e c o n d g r o u p of f e m a l e s and t h e number of l a r g e incumbent f e m a l e s d e c r e a s e d from 39 t o 30. T h e r e was no s i g n i f i c a n t d i f f e r e n c e between t h e number of p r e f e r r e d p o s i t i o n s a t t a i n e d by l a r g e and s m a l l i m m i g r a n t f e m a l e s . The sample s i z e s were s m a l l and i t i s p o s s i b l e t h a t l a r g e f e m a l e s p o s s e s s an a d v a n t a g e on t h e a v e r a g e o v e r s m a l l f e m a l e s i n e s t a b l i s h i n g p o s i t i o n s w i t h i n an a l r e a d y i n h a b i t e d a r e a . L a r g e i m m i g r a n t f e m a l e s h e l d 8 p r e f e r r e d p o s i t i o n s compared t o t h e 5 h e l d by s m a l l i m m i g r a n t f e m a l e s . Of t h e 49" f e m a l e s w i t h p r i o r a c c e s s w h i c h h e l d p o s i t i o n s w i t h i n t h e p r e f e r r e d a r e a , 42 (85.7%; 27 of 30 l a r g e , 15 of 19 54 s m a l l ) h e l d p o s i t i o n s i n t h e p r e f e r r e d a r e a d u r i n g t h e day p r i o r t o t h e i n t r o d u c t i o n of t h e i m m i g r a n t f e m a l e s . Of t h e r e m a i n i n g s e v e n f e m a l e s , f i v e (10.2%) h e l d p o s i t i o n s i n t h e p r e f e r r e d a r e a d u r i n g o n l y t h e p r e v i o u s e v e n i n g o b s e r v a t i o n p e r i o d and two were n e v e r o b s e r v e d h o l d i n g p o s i t i o n s w i t h i n t h e p r e f e r r e d a r e a . T h e s e r e s u l t s d e m o n s t r a t e t h a t t h e a d v a n t a g e o f p r i o r a c c e s s i s a c c r u e d from h o l d i n g s p e c i f i c p o s i t i o n s ( p r i o r r e s i d e n c e ) and not s i m p l y from an a s s o c i a t i o n w i t h a r e n a s u r r o u n d i n g s . The e f f e c t s of p r i o r a c c e s s were a l s o a p p a r e n t i n t h e c o m p a r i s o n o f t h e number o f incumbent and i m m i g r a n t f e m a l e s o b s e r v e d w i t h i n 1.25 m of t h e s t r e a m bank ( u s u a l l y s c h o o l i n g ) d u r i n g b o t h t h e AM and PM o b s e r v a t i o n p e r i o d s . In a l l f o u r t r i a l s , i m m i g r a n t f e m a l e s were t h e m a j o r i t y of t h e s c h o o l i n g f i s h e s (number of f e m a l e s w i t h o u t p r i o r i t y minus number o f f e m a l e s w i t h p r i o r i t y s c h o o l i n g n e a r bank i n t h e f o u r t r i a l s 11, 9, 5, 2; o n e - t a i l e d W i l c o x o n t e s t , p=0.05). -Of t h e 51 f e m a l e s ( f r o m a t o t a l o f 240) w h i c h c o n s i s t e n t l y h e l d t o t h e s t r e a m edge (where t h e y would be u n l i k e l y t o a t t r a c t m a l e s ) , 38 (74%) were i m m i g r a n t s (17 l a r g e , 21 s m a l l ) ; whereas o n l y 13 (26%) were r e s i d e n t s (3 l a r g e , 10 s m a l l ) . The number o f r e s i d e n t f e m a l e s s c h o o l i n g n e a r t h e s t r e a m bank was l i t t l e a f f e c t e d by t h e d o u b l i n g i n number o f f e m a l e s p r e s e n t . Summed o v e r t h e f o u r t r i a l s , 10 incumbent f e m a l e s (1 l a r g e , 9 s m a l l ) m a i n t a i n e d p o s i t i o n n e a r t h e s t r e a m bank b e f o r e t h e a d d i t i o n o f th e i m m i g r a n t f e m a l e s ; o n l y 13 (3 l a r g e , 10 s m a l l ) h e l d t o t h e s t r e a m bank a f t e r t h e i r a d d i t i o n . 55 The s l i g h t d e c r e a s e i n t h e number of p r e f e r r e d t e r r i t o r i e s (56 t o 49) h e l d by r e s i d e n t f e m a l e s , c o u p l e d w i t h t h e m a r g i n a l i n c r e a s e i n t h e number of r e s i d e n t f e m a l e s s c h o o l i n g n e a r t h e s t r e a m bank (10 t o 13) a f t e r t h e number of f e m a l e s i n t h e a r e n a was d o u b l e d d e m o n s t r a t e s t h a t p r i o r a c c e s s t o p r e f e r r e d spawning a r e a s g r e a t l y i n c r e a s e s t h e c h a n c e s t h a t f e m a l e s w i l l be a b l e t o win f u t u r e c o m p e t i t i o n s f o r p o s i t i o n s w i t h i n t h o s e a r e a s . 3_. E f f e c t s of s i z e and p r i o r r e s i d e n c e i n male i n t r a s e x u a l c o m p e t i t i o n Methods S i z e , p r i o r a c c e s s and t h e i n t e r a c t i o n of t h e s e two f a c t o r s i n male i n t r a s e x u a l c o m p e t i t i o n were examined i n t h r e e e x p e r i m e n t s d u r i n g September, 1984. F o r e a c h of 10 t r i a l s , s e v e n t e r r i t o r i a l unspawned f e m a l e s were e s t a b l i s h e d i n a 4 by 4 m e x p e r i m e n t a l a r e n a . The f e m a l e s were s e l e c t e d i n t h e m o r n i n g from t w e l v e f e m a l e s w h i c h had been p l a c e d i n t h e a r e n a on t h e p r e v i o u s e v e n i n g and a l l o w e d t o compete f o r t e r r i t o r i e s . O n l y f e m a l e s w h i c h h e l d d e f e n d e d p o s i t i o n s were s e l e c t e d ( f e m a l e s .•-w i t h o u t n e s t s i t e s a r e u n a t t r a c t i v e t o males ( S c h r o d e r 1982; F i g . 9 ) , t h u s m i n i m i z i n g d i f f e r e n c e s i n f e m a l e t e r r i t o r i a l i t y w i t h i n and between t r i a l s . M a l e s were s e l e c t e d , measured ( f o r k l e n g t h ) , w e ighed and 56 t a g g e d on t h e eve o f a c o m p e t i t i o n t r i a l and h e l d o v e r n i g h t i n 1.5 m f i n e s c r e e n c a g e s i n t h e c r e e k . The mean l e n g t h s and w e i g h t s of a l l male s i z e g r o u p s f o r e a c h e x p e r i m e n t a r e p r e s e n t e d i n T a b l e 1. A l l males s e l e c t e d were s e x u a l l y r i p e and i n e x c e l l e n t p h y s i c a l c o n d i t i o n . One hour a f t e r t h e r e m o v a l of t h e e x c e s s f e m a l e s i n t h e m o r n i n g , m a l e s were i n t r o d u c e d i n t o t h e a r e n a c o n t a i n i n g t h e s e v e n t e r r i t o r i a l f e m a l e s . In t h e " s i z e " e x p e r i m e n t , 14 m a l e s , s e v e n ' l a r g e ' and s e v e n ' s m a l l ' were i n t r o d u c e d s i m u l t a n e o u s l y . In t h e " p r i o r a c c e s s " e x p e r i m e n t , s e v e n s m a l l m a l e s were i n i t i a l l y i n t r o d u c e d and f o u r h o u r s l a t e r s e v e n a d d i t i o n a l s m a l l m a l e s were a d d e d . In t h e " i n t e r a c t i o n " e x p e r i m e n t ( s i z e x p r i o r a c c e s s ) s e v e n s m a l l m a l e s were i n t r o d u c e d , and f o u r h o u r s l a t e r s e v e n l a r g e m a l e s were i n t r o d u c e d . The p o s i t i o n of e a c h male ( w i t h r e s p e c t t o f e m a l e s ) was r e c o r d e d f o u r h o u r s a f t e r a l l f i s h were f i r s t i n t h e a r e n a t o g e t h e r . The f o u r male p o s i t i o n s s c o r e d were: (1) 'dominant' (male c l o s e s t t o t h e f e m a l e ) ; (2) ' c o m p e t i t o r ' (where two m a l e s were c o m p e t i n g f o r a c c e s s t o a f e m a l e w i t h no c l e a r d o m i n a n t ) ; (3) 'sneak' ( m a l e s w h i c h h e l d p o s i t i o n b e h i n d a m a t i n g p a i r ) and; (4) ' l o n e r ' (males n o t i n v o l v e d w i t h any f e m a l e ) . A l l f i s h were r e l e a s e d a t t h e end o f e a c h t r i a l and were not u s e d i n s u b s e q u e n t t r i a l s or e x p e r i m e n t s . An i n d e p e n d e n t s c o r e was g e n e r a t e d f o r e a c h t r i a l t o 57 q u a n t i f y t h e outcome o f i n t r a s e x u a l c o m p e t i t i o n . T h i s was done by s u b t r a c t i n g t h e number of m a l e s o f one g r o u p ( s m a l l , no p r i o r a c c e s s ) w h i c h h e l d d o m i n a n t p o s i t i o n s from t h e number o f t h o s e of t h e o t h e r g r o u p ( l a r g e , p r i o r a c c e s s ) w h i c h h e l d dominant p o s i t i o n s . M a l e s w h i c h were c l a s s i f i e d as ' c o m p e t i t o r s ' were g i v e n h a l f s c o r e s , r e f l e c t i n g t h e f a c t t h a t two m a l e s were e v e n l y matched i n c o m p e t i t i o n f o r a c c e s s t o a f e m a l e . L e s s t h a n f i v e p e r c e n t of a l l m a l e s o b s e r v e d were c l a s s i f i e d as ' c o m p e t i t o r s ' . The W i l c o x o n matched p a i r s s i g n e d rank t e s t was u s e d t o a n a l y s e t h e d a t a w i t h i n e x p e r i m e n t s and t h e Mann Wh i t n e y U t e s t was u s e d i n c o m p a r i s o n s between e x p e r i m e n t s . I t became a p p a r e n t t h a t p r i o r a c c e s s t o f e m a l e s a f f o r d e d m a l e s an a d v a n t a g e i n s u b s e q u e n t c o m p e t i t i o n f o r a c c e s s t o f e m a l e s . M a l e s may g a i n an a d v a n t a g e i n c o m p e t i t i o n s i m p l y by h a v i n g been p r e v i o u s l y a s s o c i a t e d w i t h f e m a l e s . A l t e r n a t i v e l y , an a s s o c i a t i o n w i t h a p h y s i c a l t e r r i t o r y w h i l e w i t h f e m a l e s may g i v e m a l e s an a d v a n t a g e i n f u t u r e c o m p e t i t i o n f o r a c c e s s t o new f e m a l e s a r r i v i n g i n t h e a r e a . Two e x p e r i m e n t s were d e s i g n e d t o t e s t t h e s e p o s s i b i l i t i e s . The m e t h o d o l o g i e s were s i m i l a r t o t h e p r e v i o u s t h r e e e x p e r i m e n t s . In t h e f i r s t e x p e r i m e n t , s e v e n m a l e s were g i v e n a c c e s s t o one g r o u p of t e r r i t o r i a l f e m a l e s f o r f o u r h o u r s . The m a l e s were t h e n s e i n e d from t h e a r e n a , and p l a c e d i n a l a r g e water f i l l e d c a n a l o n g w i t h s e v e n m a l e s of t h e same s i z e , w h i c h had not r e c e n t l y been w i t h f e m a l e s . A f t e r a few m i n u t e s , a l l were 58 r e l e a s e d s i m u l t a n e o u s l y i n t o a n o t h e r a r e n a w i t h s e v e n n o v e l t e r r i t o r i a l f e m a l e s , and a l l o w e d t o compete f o r f o u r h o u r s . In t h e s e c o n d e x p e r i m e n t , i n e a c h of two a r e n a s s e v e n m a l e s were g i v e n f o u r h o u r s p r i o r a c c e s s t o s e v e n f e m a l e s and t h e n b o t h t h e m a l e s and f e m a l e s were s e i n e d from t h e two a r e n a s . Seven f e m a l e s from e a c h a r e n a were i n t r o d u c e d i n t o t h e o t h e r a r e n a . The m a l e s t a k e n from e a c h a r e n a were s u p p l e m e n t e d by s e v e n n o v e l m a l e s of s i m i l a r s i z e and i n t r o d u c e d i n t o t h e a r e n a t h e y had p r e v i o u s l y o c c u p i e d . Thus, i n e a c h of e i g h t t r i a l s , s e v e n m a l e s were f a c e d w i t h s e v e n new f e m a l e s and s e v e n new m a l e s i n an a r e n a t h e y had p r e v i o u s l y o c c u p i e d w i t h s e v e n o t h e r f e m a l e s f o r f o u r h o u r s . R e s u l t s A. S i z e i n male i n t r a s e x u a l c o m p e t i t i o n L a r g e m a l e s (10% l o n g e r , 35% h e a v i e r ; T a b l e 1) d o m i n a t e d s m a l l males i n c o m p e t i t i o n f o r a c c e s s t o f e m a l e s i n a l l t e n t r i a l s i n w h i c h males of b o t h s i z e g r o u p s were i n t r o d u c e d s i m u l t a n e o u s l y i n t o t h e a r e n a (p<0.005; F i g . 1 3 a ) . Of t h e 66 (of a p o s s i b l e 70) f e m a l e s a t t e n d e d by males a t t h e end of a l l t r i a l s , 50.5 (76.5%; h a l f s c o r e s were g i v e n t o males c l a s s i f i e d a s ' c o m p e t i t o r s ' ) were a c c o m p a n i e d by l a r g e m a l e s and 15.5 (23.5%) were a c c o m p a n i e d by s m a l l m a l e s . Most m a l e s a t t e n d e d o n l y a s i n g l e f e m a l e ( 6 2 ) , a l t h o u g h two l a r g e m a l e s d e f e n d e d 59 F i g u r e 13. D i f f e r e n c e between t e s t g r o u p s i n t h e number of m ales w h i c h h e l d dominant p o s i t i o n s b e s i d e f e m a l e s , f o r e a c h of t h r e e s e p a r a t e e x p e r i m e n t s c o n s i s t i n g of 10 f o u r hour t r i a l s . (A) ' L a r g e ' m a l e s competed a g a i n s t ' s m a l l ' males f o r a c c e s s t o f e m a l e s . (B) M a l e s w i t h f o u r h o u r s p r i o r a c c e s s t o f e m a l e s competed a g a i n s t s i m i l a r s i z e d i m m i g r a n t m a l e s f o r a c c e s s t o f e m a l e s . (C) ' S m a l l ' m a l e s w i t h f o u r h o u r s p r i o r a c c e s s t o f e m a l e s competed a g a i n s t ' l a r g e ' i m m i g r a n t m a l e s . 60 U c CD c r c_ Li. 4 3 2 • 1 « A) Factor: SIZE 4 i 3 • 2 • 0 J - 8 - 6 - 4 - 2 0 2 4 6 8 Number of Large Males with Females minus Number of Small Males with Females B) Factor: PRIOR ACCESS - 8 - 6 - 4 - 2 0 2 4 6 8 Number of Incumbent Males with Females minus Number of Immigrant Males with Females 4 3 • 2 • 1 C) Factor: SIZE * PRIOR ACCESS - 8 - 6 - 4 - 2 0 2 4 6 8 Number of Large Immigrant Males with Females minus Number of Small Incumbent Males with Females 61 a c c e s s t o two a d j a c e n t f e m a l e s s i m u l t a n e o u s l y . S m a l l m a l e s were f i f t e e n t i m e s more l i k e l y t o a d o p t sneak p o s i t i o n s t h a n l a r g e m a l e s (15 of 70 v e r s u s 1 of 7 0 ) . M a l e s t e n d e d t o s t a y w i t h p a r t i c u l a r f e m a l e s . T h i r t y - f o u r of t h e 45 l a r g e m a l e s (76%) t h a t were o b s e r v e d w i t h f e m a l e s a f t e r b o t h f o u r and e i g h t h o u r s , r e m a i n e d w i t h t h e same f e m a l e . S i m i l a r l y , 11 o f t h e 13 s m a l l m a l e s (85%) t h a t were o b s e r v e d w i t h f e m a l e s on b o t h o c c a s i o n s r e m a i n e d w i t h t h e same f e m a l e . Of t h e 9 m a l e s w h i c h assumed sneak p o s i t i o n s a f t e r b o t h 4 and 8 h o u r s , 5 (56%) m a i n t a i n e d t h e i r p o s i t i o n b e h i n d t h e same f e m a l e . B. P r i o r a c c e s s i n male i n t r a s e x u a l c o m p e t i t i o n M a l e s w i t h f o u r h o u r s p r i o r a c c e s s t o f e m a l e s d o m i n a t e d i n t r o d u c e d m a l e s of t h e same s i z e i n c o m p e t i t i o n f o r a c c e s s t o f e m a l e s i n a l l t e n t r i a l s ( p < 0 . 0 l ; F i g . 13b). Of t h e 66 a t t e n d e d f e m a l e s , 47.5 (72%) were a c c o m p a n i e d by m a l e s w i t h p r i o r a c c e s s . A l l males w i t h f e m a l e s d e f e n d e d a c c e s s t o s i n g l e f e m a l e s o n l y . T h e r e was no d i f f e r e n c e between g r o u p s i n t h e number of m a l e s w h i c h a d o p t e d sneak p o s i t i o n s b e h i n d f e m a l e s . In t o t a l , s e v e n m a l e s w i t h p r i o r a c c e s s (10%) and 11 males w i t h o u t p r i o r a c c e s s (15.7%) a d o p t e d sneak p o s i t i o n s . F i f t y t h r e e o f t h e 70 f e m a l e s were a t t e n d e d by m a l e s i m m e d i a t e l y b e f o r e t h e a d d i t i o n of t h o s e w i t h no p r i o r a c c e s s . F o u r h o u r s l a t e r , m ales w i t h p r i o r a c c e s s s t i l l a t t e n d e d 48.5 62 f e m a l e s . Thus, t h e a d d i t i o n o f more m a l e s had l i t t l e e f f e c t on t h e number o f male w i t h p r i o r a c c e s s t h a t a t t e n d e d f e m a l e s . T h i r t y f i v e o f 47 m a l e s w i t h p r i o r a c c e s s (75%) t h a t were o b s e r v e d w i t h f e m a l e s i n a dominant r o l e i m m e d i a t e l y b e f o r e t h e a d d i t i o n of t h e o t h e r m a l e s and t h a t c o u r t e d f e m a l e s f o u r h o u r s l a t e r ( i n any r o l e ) r e m a i n e d w i t h t h e same f e m a l e . The m a j o r i t y (34) r e t a i n e d t h e i r d ominant p o s i t i o n . S i m i l a r l y , m a l e s w h i c h a d o p t e d sneak p o s i t i o n s t e n d e d t o s t a y w i t h t h e same f e m a l e a f t e r t h e a d d i t i o n of t h e o t h e r m a l e s (2 of 3 ) . C. The i n t e r a c t i o n of s i z e and p r i o r a c c e s s T h e r e was no s i g n i f i c a n t d i f f e r e n c e between t h e a d v a n t a g e a s s o c i a t e d w i t h s i z e and t h a t a s s o c i a t e d w i t h p r i o r a c c e s s when t h e f a c t o r s were examined s e p a r a t e l y ( c o m p a r i s o n of t h e r e s u l t s of t h e two p r e v i o u s e x p e r i m e n t s ; p > 0 . 4 ) . The e f f e c t s of s i z e a p p r o a c h e d s i g n i f i c a n c e o v e r p r i o r a c c e s s when s m a l l males were g i v e n f o u r h o u r s p r i o r a c c e s s t o f e m a l e s b e f o r e t h e a d d i t i o n of l a r g e m a l e s (p<.1; F i g . 1 3 c ) . T h i r t y - e i g h t of t h e 65 a t t e n d e d f e m a l e s were a c c o m p a n i e d by l a r g e m ales w i t h no p r i o r a c c e s s whereas o n l y 27 were a c c o m p a n i e d by s m a l l m a l e s w i t h f o u r h o u r s p r i o r a c c e s s . The e f f e c t s of s i z e were s t r o n g l y e v i d e n t when t h e p o s i t i o n i n g o f s m a l l m a l e s r e l a t i v e t o f e m a l e s was compared i m m e d i a t e l y b e f o r e t h e a d d i t i o n of l a r g e m ales and f o u r h o u r s 63 l a t e r . The number of s m a l l m a l e s h o l d i n g dominant p o s i t i o n s was n e a r l y h a l v e d (53 t o 2 7 ) , whereas the number o f s m a l l sneak m a l e s n e a r l y t r i p l e d (6 t o 17) and t h e number of s m a l l m a l e s a l o n e more t h a n d o u b l e d (12 t o 2 6 ) ( p < 0 . 0 5 ) . T h i r t y - o n e of 35 s m a l l m a l e s (79%) t h a t were a s s o c i a t e d w i t h f e m a l e s i n dominant r o l e s b e f o r e t h e a d d i t i o n o f t h e l a r g e m a l e s and w h i c h were o b s e r v e d w i t h f e m a l e s f o u r h o u r s l a t e r ( i n any r o l e ) r e m a i n e d w i t h t h e same f e m a l e . E i g h t of t h e f o r m e r l y d o m i n a n t s m a l l males were f o r c e d i n t o sneak r o l e s w i t h t h e f e m a l e s t h e y p r e v i o u s l y c o u r t e d . S i m i l a r l y , 75% (3 o f 4) of m a l e s t h a t a d o p t e d s u b o r d i n a t e sneak p o s i t i o n s b e f o r e t h e a d d i t i o n of t h e l a r g e m a l e s r e m a i n e d w i t h t h e same f e m a l e . D. F a c t o r s i n v o l v e d i n t h e a d v a n t a g e a s s o c i a t e d w i t h p r i o r  a c c e s s M a l e s t h a t were i n t h e p r e s e n c e of f e m a l e s f o r f o u r h o u r s f a r e d no b e t t e r t h a n males w i t h no r e c e n t e x p e r i e n c e w i t h f e m a l e s i n c o n t e s t s f o r a c c e s s t o n o v e l f e m a l e s i n n o v e l l o c a l i t i e s (p>0.6; F i g . 14a). O n l y 28 of t h e 54 a t t e n d e d f e m a l e s (52%) were a c c o m p a n i e d by m a l e s w h i c h had r e c e n t l y been w i t h o t h e r f e m a l e s . T h e r e f o r e , s i m p l y b e i n g w i t h f e m a l e s d i d n o t n o t i c e a b l y i n c r e a s e t h e c h a n c e s of a male i n f u t u r e c o m p e t i t i o n s f o r a c c e s s t o n o v e l f e m a l e s . M a l e s t h a t were r e t u r n e d t o t h e a r e n a t h e y had p r e v i o u s l y 64 F i g u r e 14. D i f f e r e n c e between t e s t g r o u p s i n t h e number o f males w h i c h h e l d dominant p o s i t i o n s b e s i d e f e m a l e s , f o r e a c h of two e x p e r i m e n t s c o n s i s t i n g of e i g h t f o u r hour t r i a l s . (D) M a l e s w h i c h had i m m e d i a t e l y p r e v i o u s l y been w i t h f e m a l e s competed a g a i n s t m a l e s w h i c h had n o t r e c e n t l y been w i t h f e m a l e s f o r a c c e s s t o n o v e l f e m a l e s i n n o v e l s u r r o u n d i n g s . (E) M a l e s w h i c h had p r e v i o u s l y been w i t h f e m a l e s competed a g a i n s t males w h i c h had n o t r e c e n t l y been w i t h f e m a l e s f o r a c c e s s t o n o v e l f e m a l e s i n s u r r o u n d i n g s f a m i l i a r t o t h e f i r s t g r o u p of m a l e s . 65 3 2 1 0 D) Factor: RECENT EXPOSURE TO FEMALES -B -6 -4 -2 B u c OJ D cr c_ Number of Males with Females that had Recent Exposure to Females minus Number of Males with Females that had no Recent Exposure to Females 4 3 i 2 1 0 E) Factor: PRIOR ACCESS TO ARENA -B -6 -4 -2 B Number of Males Courting Females that had Previous Exposure to Arena (and other females) minus Number of Males with Females that had no Previous Exposure to Arena 66 o c c u p i e d w i t h one s e t o f f e m a l e s d o m i n a t e d i n e x p e r i e n c e d m a l e s i n c o m p e t i t i o n f o r a c c e s s t o n o v e l f e m a l e s (36 t o 14 o v e r a l l ; p<.02; F i g . 14b). A f t e r t h e i r t e m p o r a r y r e m o v a l , m a l e s w i t h p r i o r a c c e s s t e n d e d t o r e t u r n t o t h e i r p r e v i o u s p o s i t i o n s . The mean d i s t a n c e between p o s i t i o n s o f m a l e s w i t h p r i o r a c c e s s t h a t h e l d dominant p o s i t i o n s b o t h b e f o r e and a f t e r t h e r e m o v a l of t h e f e m a l e s t h e y were c o u r t i n g and t h e i n t r o d u c t i o n of n o v e l f e m a l e s and m a l e s was o n l y 0.59 m ( 0 . 0 8 S E , n=30), a mean d i s t a n c e c o m p a r a b l e t o t h a t of m a l e s w h i c h were l e f t u n d i s t u r b e d w i t h f e m a l e s ( T a b l e 2 ) . The e f f e c t of p r i o r a c c e s s t o an a r e a was s i g n i f i c a n t l y d i f f e r e n t f r o m t h e e f f e c t of immediate p r e v i o u s e x p e r i e n c e w i t h f e m a l e s ( p < 0 . 0 2 ) . These r e s u l t s d e m o n s t r a t e t h a t a t l e a s t p a r t , i f n o t a l l , of t h e a d v a n t a g e s a s s o c i a t e d w i t h p r i o r a c c e s s i n mal e s a r e a c c r u e d from a s i t e s p e c i f i c a s s o c i a t i o n w i t h t h e p h y s i c a l e n v i r o n m e n t . D i s c u s s i o n Female t e r r i t o r i a l i t y F e m a l e s a g g r e s s i v e l y a t t e m p t t o e x c l u d e o t h e r f e m a l e s from t h e i r n e a r v i c i n i t y b o t h i n t h e p r e s e n c e and a b s e n c e of m a l e s . The l o c a t i o n s d e f e n d e d a r e s p e c i f i c . F e m a l e s r e m a i n e d i n t h e same p l a c e f o r s e v e r a l d a y s and r e t u r n e d t o t h e i r p o s i t i o n s a f t e r r e p e a t e d d i s p l a c e m e n t s . The s e l e c t i o n and t e r r i t o r i a l 67 d e f e n s e of spawning s i t e s b o t h i n t h e t h e p r e s e n c e and a b s e n c e o f m a l e s (_i. e. b e f o r e any egg d e p o s i t i o n ) s u g g e s t s t h a t f e m a l e s i n i t i a l l y d e f e n d p o s i t i o n s as s i t e s f o r f u t u r e egg d e p o s i t i o n and, l a t e r , d e f e n d them t o p r o t e c t t h e i r d e v e l o p i n g p r o g e n y . F e m a l e s a r e s e l e c t i v e i n t h e i r c h o i c e o f s p a w ning s i t e s , u s u a l l y p r e f e r r i n g a r e a s of p a r t i c u l a r c u r r e n t v e l o c i t y and g r a v e l c o m p o s i t i o n ( b o t h d e p e n d e n t on s i z e o f f e m a l e ) , and u p w e l l i n g o r b e n d i n g c u r r e n t s ( F a b r i c u s and G u s t a f s o n 1954; Hartman 1969; M c C a r t 1970; T a u t z and G r o o t 1975; J o n s s o n and H i n d a r 1982; S c h r o d e r 1982). Such s e l e c t i v i t y h e l p s e n s u r e t h a t t h e embryos w i l l r e c e i v e s u f f i c i e n t oxygen d u r i n g d e v e l o p m e n t (Brannon 1972; K o s k i 1975; T a u t z and G r o o t 1975; T a p p e l and B j o r n n 1983). S u b s t a n t i a l and r e p e a t a b l e n e s t s i t e s e l e c t i v i t y was e v i d e n t i n t h i s s t u d y . The p r e f e r r e d s i t e s i n a r e n a s n e a r t h e s t r e a m bank were i n t h e q u a d r a n t s t h a t were f u r t h e s t downstream and away from t h e s t r e a m bank, a r e a s t y p i f i e d by t h e h i g h e r water v e l o c i t i e s and t h e g r e a t e r b e n d i n g and u p w e l l i n g o f c u r r e n t s . Hence, kokanee f e m a l e t e r r i t o r y p r e f e r e n c e s w i t h i n t h e a r e n a s were s e e m i n g l y r e l a t e d t o t h e i n c u b a t i o n q u a l i t i e s o f t h e a r e a s s e l e c t e d . T e r r i t o r i a l b e h a v i o u r i n f e m a l e s can be r e l a t e d t o t h e n e c e s s i t y t o e s t a b l i s h and d e f e n d n e s t s i t e s i f t h e y a r e t o a c h i e v e a s i g n i f i c a n t measure of r e p r o d u c t i v e s u c c e s s . I t t a k e s between 80 and 140 days f o r 0. n e r k a eggs t o h a t c h and t h e young spend s e v e r a l more months b e f o r e e m e r g i n g from t h e g r a v e l 68 ( F o e r s t e r 1968). Eggs w h i c h a r e n o t b u r i e d b e n e a t h t h e g r a v e l a r e v u l n e r a b l e t o m e c h a n i c a l shock ( S m i r n o v 1955), egg p r e d a t i o n ( J o n e s and K i n g 1952; van den B e r g h e 1984; Maekawa and O n o z a t o 1986) and c l i m a t i c d i s t u r b a n c e s ( H o l t b y and H e a l e y 1986) and a r e u n l i k e l y t o s u r v i v e . T e r r i t o r i a l b e h a v i o u r i n f e m a l e s i s f u r t h e r p r o m o t e d by t h e v a r i a b i l i t y i n i n c u b a t i o n q u a l i t y among a r e a s i n t h e s t r e a m ( K o s k i 1975), and t h e o f t e n l i m i t e d number of n e s t i n g s i t e s a v a i l a b l e ( e . cj. M c N e i l 1964; van den Berghe 1984; see Exp. 1c and 3 b ) . F e m a l e s t h a t s u c c e s s f u l l y compete f o r , e s t a b l i s h , spawn i n , and d e f e n d h i g h q u a l i t y n e s t s i t e s w i l l have g r e a t e r r e p r o d u c t i v e s u c c e s s . A g g r e s s i v e f e m a l e i n t r a s e x u a l i n t e r a c t i o n s have been o b s e r v e d p r e v i o u s l y i n P a c i f i c salmon (Hanson and S m i t h 1967; M c C a r t 1970; T a u t z 1977; S c h r o d e r 1981, 1982; van den B e r g h e 1984). T a u t z (1977) c o n c l u d e d t h a t f e m a l e a g g r e s s i v e i n t e r a c t i o n s l i m i t t h e number o f f e m a l e s w h i c h c a n e s t a b l i s h spawning s i t e s a t any one t i m e . In my e x p e r i m e n t s , f e m a l e i n t e r a c t i o n s l i m i t e d t h e number of f e m a l e s w h i c h c o u l d e s t a b l i s h p o s i t i o n s b o t h i n e x p e r i m e n t a l e n c l o s u r e s and i n t h e w i l d . Non-t e r r i t o r i a l f e m a l e s t a k e n from t h e w i l d q u i c k l y e s t a b l i s h e d t e r r i t o r i e s when p l a c e d i n a r e n a s i n w h i c h no o t h e r f e m a l e s were p r e s e n t . In c o n t r a s t , n o n - t e r r i t o r i a l f e m a l e s r e l e a s e d back i n t o t h e w i l d , o r i n t o a r e n a s c o n t a i n i n g t e r r i t o r i a l f e m a l e s , u s u a l l y r e m a i n e d n o n - t e r r i t o r i a l ( s c h o o l i n g ) . When f e m a l e s were 69 removed from p r e f e r r e d s p a w n ing a r e a s , t h e i r l o c a l i t i e s were a l m o s t i m m e d i a t e l y f i l l e d by o t h e r f e m a l e s . Female s i z e i s a l s o a f a c t o r i n d e t e r m i n i n g t h e r a t e a t w h i c h f e m a l e s e s t a b l i s h t e r r i t o r i e s . L a r g e f e m a l e s a c c o u n t e d f o r 64% of t h e f e m a l e s h o l d i n g t e r r i t o r i e s w i t h i n p r e f e r r e d a r e a s o f t h e e x p e r i m e n t a l a r e n a s , when i n c o m p e t i t i o n w i t h an e q u a l number o f s m a l l f e m a l e s . However, once a f e m a l e has e s t a b l i s h e d a t e r r i t o r y , she i s u n l i k e l y t o be d i s p l a c e d u n t i l n e a r d e a t h , i n d e p e n d e n t of s i z e ( F i g . 12b). The s t r o n g e f f e c t of p r i o r r e s i d e n c e has p r e v i o u s l y been n o t e d i n A t l a n t i c salmon (Salmo s a l a r ) ( J o n e s 1959), coho salmon ( 0 . k i s u t c h ) (van den Be r g h e 1984), and documented i n chum salmon ( 0 . k e t a ) ( S c h r o d e r 1981, 1982). M a l e t e r r i t o r i a l b e h a v i o u r Kokanee male b e h a v i o u r d i f f e r s m a r k e d l y i n t h e p r e s e n c e and a b s e n c e of f e m a l e s . In t h e p r e s e n c e of f e m a l e s , males o f t e n s t a y e d w i t h p a r t i c u l a r f e m a l e s f o r s e v e r a l d a y s , a g g r e s s i v e l y p r e v e n t i n g a c c e s s t o t h e s e f e m a l e s by o t h e r m a l e s , a b e h a v i o u r w h i c h has been r e p o r t e d i n t h e w i l d (Needham and T a f t 1934; Hanson and S m i t h 1967). M a l e s c o n s i s t e n t l y r e t u r n e d t o t h e f e m a l e s t h e y c o u r t e d a f t e r t h e y were d i s p l a c e d from t h e i r p o s i t i o n , d e m o n s t r a t i n g t h a t s p e c i f i c r e s o u r c e s and p e r h a p s p a r t i c u l a r f e m a l e s a r e d e f e n d e d . M a l e s r e t u r n e d t o p r e v i o u s p o s i t i o n s even a f t e r t h e f e m a l e s t h e y were c o u r t i n g were removed. 70 In t h e a b s e n c e of any f e m a l e s , males a g g r e s s i v e l y h o l d t o g e n e r a l a r e a s and r e t u r n t o them when d i s p l a c e d b u t t h e y do not t e n d t o s u c c e s s f u l l y e x c l u d e o t h e r m a l e s from t h e i r v i c i n i t y , as t h e y do when f e m a l e s a r e p r e s e n t . M a l e s do n o t compete amongst t h e m s e l v e s s o l e l y f o r d i r e c t a c c e s s t o f e m a l e s , a s i s sometimes s u g g e s t e d ( S c h r o d e r 1981, 1982; G r o s s 1985; S a r g e n t e t a l . 1986). W h i l e male i n t r a s e x u a l c o m p e t i t i o n i n t h e a b s e n c e of f e m a l e s d o e s not r e s u l t i n t h e e x c l u s i o n of o t h e r m a l e s , t h e a s s o c i a t i o n w i t h an a r e a a p p e a r s t o i n c r e a s e t h e c h a n c e s t h a t incumbent m a l e s w i l l win c o m p e t i t i o n s f o r a c c e s s t o f e m a l e s moving i n t o t h a t a r e a . M a l e s w i t h p r i o r a c c e s s t o an a r e n a (and a s e t of f e m a l e s ) d o m i n a t e d i m m i g r a n t m a l e s i n c o m p e t i t i o n f o r a c c e s s t o immig r a n t f e m a l e s . T h i s may e x p l a i n why m a l e s o f t e n outnumber f e m a l e s e a r l y i n salmon spawning r u n s ( e . g_. L o r z and N o r t h c o t e 1965; J o h n s o n 19.80), and why many m a l e s e s t a b l i s h p o s i t i o n s on t h e spawning g r o u n d s p r i o r t o t h e a r r i v a l o f f e m a l e s ( F i g . 2 ) . The a b s e n c e of d e f i n i t i v e male t e r r i t o r i a l b e h a v i o u r i n t h e a b s e n c e of f e m a l e s c an be r e l a t e d t o i n t e n s e l e v e l s of male c o m p e t i t i o n and t h e l o n g p e r i o d (weeks) o v e r w h i c h s e x u a l l y a c t i v e f e m a l e s a r e a v a i l a b l e . T e r r i t o r i a l d e f e n s e by m a l e s of r e s o u r c e s n e c e s s a r y t o f e m a l e s i s common i n polygamous m a t i n g s y s t e m s ( e . £ . Howard 1978; W e l l s 1977; S e a r c y 1979; F r i c k e 1980), b ut i s not e c o n o m i c a l l y f e a s i b l e i n m a t i n g s y s t e m s i n w h i c h t h e d i s t r i b u t i o n o f r e s o u r c e s n e c e s s a r y t o f e m a l e s i s e x t r e m e l y clumped (Emlen and O r i n g 1977). C l u m p i n g of f e m a l e s 71 l e a d s t o a c l u m p i n g of m a l e s , w h i c h can p r o h i b i t i v e l y i n c r e a s e t h e c o s t s f o r m a l e s of m a i n t a i n i n g r e s o u r c e t e r r i t o r i e s , w h i l e w a i t i n g f o r f e m a l e s . When t h e c o s t s of m a i n t a i n i n g r e s o u r c e t e r r i t o r i e s a r e t o o l a r g e , m a l e s o f t e n g a t h e r a r o u n d t h e r e s o u r c e s n e c e s s a r y f o r f e m a l e s , and compete amongst t h e m s e l v e s f o r d i r e c t a c c e s s t o a r r i v i n g f e m a l e s ( e . £ . D a v i e s and H a l l i d a y 1979). T h i s a p p e a r s t o be t h e c a s e i n P a c i f i c s almon, where t h e c l u m p i n g of f e m a l e s i n p o p u l a t i o n s p e c i f i c s p a w n i n g l o c a t i o n s i s e x t r e m e and male i n t r a s e x u a l c o m p e t i t i o n i s i n t e n s e . Two f a c t o r s promote i n t e n s e male i n t r a s e x u a l c o m p e t i t i o n i n s a l m o n . F i r s t , f e m a l e s a r e a l i m i t i n g r e s o u r c e t o m a l e s . W h i l e sex r a t i o s a r e u s u a l l y f a i r l y even i n salmon spawning p o p u l a t i o n s ( e . £ . Hanson and S m i t h 1967; F o e r s t e r 1968; S a r g e n t e t a l . 1986), t h e o p e r a t i o n a l sex r a t i o i s s t r o n g l y skewed t o w a r d s m a l e s ( S c h r o d e r 1981), b e c a u s e m a l e s a r e s e x u a l l y a c t i v e t h r o u g h o u t t h e i r whole spawning l i f e t i m e , whereas f e m a l e s a r e ' o n l y s e x u a l l y a c t i v e u n t i l t h e y have l a i d a l l of t h e i r e g g s . M a l e s must compete w i t h o t h e r m a l e s t o g a i n and m a i n t a i n c l o s e a c c e s s t o f e m a l e s . The i n t e n s i t y of t h i s c o m p e t i t i o n i s l i k e l y e x a g g e r a t e d b e c a u s e t h e t o t a l l i f e t i m e r e p r o d u c t i v e e f f o r t of P a c i f i c salmon m a l e s o c c u r s o v e r a s i n g l e s h o r t p e r i o d of t i m e . S e l e c t i o n has p r o b a b l y f a v o u r e d h i g h a g g r e s s i o n l e v e l s and d e c r e a s e d t h e p r o b a b i l i t y t h a t m ales w i l l abandon a l l c o m p e t i t i o n s f o r a c c e s s t o f e m a l e s . The s t r o n g t e r r i t o r i a l b e h a v i o u r e x h i b i t e d by m a l e s t h a t 72 a r e c o u r t i n g f e m a l e s c a n be r e l a t e d t o t h e n e c e s s i t y f o r m a l e s t o g a i n c l o s e a c c e s s t o i n d i v i d u a l f e m a l e s p r i o r t o s p a w n i n g . F e r t i l i z a t i o n i s e x t e r n a l and f e m a l e n e s t s i t e s a r e u s u a l l y i n open a r e a s , c r e a t i n g an o p p o r t u n i t y f o r numerous males t o p a r t i c i p a t e i n t h e spawning a c t ( e . g_. J o n e s and K i n g 1952; Hanson and S m i t h 1967; C a m p b e l l 1977; J o n s s o n and H i n d a r 1982; G r o s s 1985; J o n s s o n 1985). M a l e s w h i c h h o l d t h e p o s i t i o n c l o s e s t t o t h e f e m a l e ( d o m i n a n t p o s i t i o n ) i m m e d i a t e l y p r i o r t o spawning u s u a l l y f e r t i l i z e t h e l a r g e m a j o r i t y o f eggs l a i d ( S c h r o d e r 1982; Chebanov e t a l . 1983; Maekawa and O n o z a t o 1986). The b e n e f i t s t o males of w i n n i n g c o m p e t i t i o n s f o r c l o s e a c c e s s t o f e m a l e s a r e c l e a r . The b e n e f i t s o f m a i n t a i n i n g t h i s p o s i t i o n f o r some t i m e ( t e r r i t o r i a l i t y ) , a p p e a r t o be d e r i v e d from t h e spawning b e h a v i o u r of f e m a l e s . Salmon f e m a l e s l a y t h e i r eggs i n a s e r i e s o f c l o s e l y s i t u a t e d n e s t s ( u s u a l l y t h r e e i n k o k a n e e ) . Spawning e v e n t s a r e b r i e f ( s e c o n d s ) , and may be s e p a r a t e d by h o u r s t o d a y s . To e n s u r e t h e y a r e p r e s e n t a t t h e time o f spawning, m a l e s must d e f e n d t h e i r dominant p o s i t i o n s f o r a p r o t r a c t e d p e r i o d . Numerous f i e l d s t u d i e s have documented s i z e a s a f a c t o r i n male i n t r a s e x u a l c o m p e t i t i o n (Hanson and S m i t h 1967; Hartman 1969; M c C a r t 1970; C a m p b e l l 1977). In t h e e x p e r i m e n t s h e r e r e p o r t e d , on a v e r a g e , a 10% d i f f e r e n c e i n l e n g t h more t h a n t r i p l e d t h e c h a n c e s t h a t l a r g e males would p r e v a i l o v e r s m a l l m a l e s when v y i n g f o r a c c e s s t o f e m a l e s . S m a l l m a l e s a t t e m p t t o r e d u c e t h e i r l o s s e s by becoming s n e a k s t o spawning p a i r s . By 73 c o n t r a s t w i t h f e m a l e s , p r i o r a c c e s s d i d not o v e r r i d e t h e e f f e c t s of s i z e i n m a l e s . W h i l e a s l i t t l e a s f o u r h o u r s p r e v i o u s r e s i d e n c e c o n f e r r e d a l a r g e a d v a n t a g e t o e q u a l s i z e d c o m p e t i t o r s , t h e e f f e c t was l a r g e l y n e g a t e d when immig r a n t m a l e s were l a r g e r . However, b e c a u s e f e m a l e a t t r a c t i v e n e s s t o m a l e s i n c r e a s e s a s t h e y n e a r spawning ( S c h r o d e r 1982; H u t c h i n g and Myers 1985; p e r s . obs. ), p r i o r a c c e s s p r o b a b l y a l l o w s m a l e s t o m a i n t a i n t h e i r p o s i t i o n r e l a t i v e t o t h e f e m a l e d u r i n g b r i e f p u l s e s of e x a g g e r a t e d f e m a l e a t t r a c t i v e n e s s . C o m p a r i s o n of spawning t e r r i t o r i a l i t y i n m a l e s and f e m a l e s The e x p r e s s i o n of t e r r i t o r i a l i t y d i f f e r s m a r k e d l y between t h e s e x e s . M a l e s t e m p o r a r i l y d e f e n d ( h o u r s t o d a y s ) a c c e s s t o p a r t i c u l a r f e m a l e s and t h e a r e a s t h e y o c c u p y whereas f e m a l e s a t t e m p t t o d e f e n d t h e i r t e r r i t o r i e s ( n e s t s i t e s ) u n t i l d e a t h . The d i f f e r e n c e i n b e h a v i o u r can be r e l a t e d t o t h e p o t e n t i a l f o r m a l e s t o f e r t i l i z e many more eggs t h a n a s i n g l e f e m a l e c a n p r o d u c e . H a v i n g spawned w i t h a f e m a l e , a male has t h e o p t i o n o f r e m a i n i n g w i t h t h e f e m a l e and d e f e n d i n g t h e d e v e l o p i n g embryos or of l e a v i n g t o s e a r c h f o r a d d i t i o n a l mates. The c o s t t o m a l e s of l e a v i n g t h e i r a l r e a d y p r o t e c t e d embryos ; a r e s m a l l i n c o m p a r i s o n t o t h e p o t e n t i a l g a i n s of m a t i n g w i t h a d d i t i o n a l f e m a l e s . The p r e s e n c e o v e r a p e r i o d o f t i m e of numerous s e x u a l l y a c t i v e f e m a l e s makes i t l i k e l y t h a t d e p a r t i n g m a l e s w i l l e n c o u n t e r o t h e r s e x u a l l y a c t i v e f e m a l e s . In a d d i t i o n , m a l e s w h i c h d o m i n a t e t h e c o m p e t i t i o n f o r a c c e s s t o one f e m a l e 74 a r e l i k e l y t o p o s s e s s p h y s i c a l a n d / o r b e h a v i o u r a l c h a r a c t e r i s t i c s ( s i z e , a g g r e s s i o n ) w h i c h enhance t h e i r c h a n c e s o f g a i n i n g a c c e s s t o o t h e r f e m a l e s . The d i f f e r e n t w e i g h t i n g of t h e e f f e c t s of s i z e and p r i o r r e s i d e n c e i n i n t r a s e x u a l c o m p e t i t i o n i n m a l e s and f e m a l e s c a n a l s o be r e l a t e d t o t h e d i f f e r e n t r e p r o d u c t i v e s t r a t e g i e s of t h e s e x e s . F e m a l e s i n v e s t a l a r g e amount o f e n e r g y i n r e l a t i v e l y few eggs, w h i c h t h e y d e p o s i t i n c l o s e l y s i t u a t e d n e s t s and s u b s e q u e n t l y d e f e n d u n t i l t h e y a r e d i s p l a c e d o r d i e . L o s s of a t e r r i t o r y by a f e m a l e t h a t i s as y e t unspawned means, a t t h e l e a s t , s e a r c h i n g and c o m p e t i n g f o r a new n e s t s i t e , f u r t h e r l i m i t i n g t h e e n e r g y a v a i l a b l e f o r n e s t c o n s t r u c t i o n and p r o t e c t i o n ; a t t h e most, i t means l e a v i n g d e v e l o p i n g p r o g e n y u n d e f e n d e d , and a t r i s k o f n e s t s u p e r i m p o s i t i o n by o t h e r f e m a l e s ( J o n e s 1959; M c N e i l 1964; van den Berghe 1984). In c o n t r a s t , m a l e s i n v e s t l i t t l e i n t h e i r o f f s p r i n g . They n e i t h e r p r o t e c t t h e f e m a l e from o t h e r f e m a l e s , nor r e m a i n w i t h a f e m a l e t o p r o t e c t t h e n e s t . M a l e s s p r e a d t h e i r r e p r o d u c t i v e r i s k by a t t e m p t i n g t o mate w i t h many f e m a l e s o v e r t h e c o u r s e of t h e s p a w n ing s e a s o n . The c o s t s of l o s i n g i n d i v i d u a l c o n t e s t s a r e f a r g r e a t e r f o r f e m a l e s t h a n f o r m a l e s . Thus f e m a l e s a r e e x p e c t e d , and o b s e r v e d , t o be much more r e l u c t a n t t o r e l i n q u i s h t h e i r p o s i t i o n s t h a n m a l e s when f a c e d w i t h s i m i l a r p r e s s u r e s . The d i f f e r e n c e i n e x p r e s s i o n of a g g r e s s i v e b e h a v i o u r s between males and f e m a l e s may have e v o l v e d i n r e s p o n s e t o t h e 75 r e p r o d u c t i v e needs of e a c h s e x . In m a l e s , where s i z e i s a major f a c t o r i n d e t e r m i n i n g t h e outcome o f i n t r a s e x u a l c o m p e t i t i o n , body d i s p l a y s form a l a r g e p a r t of t h e b e h a v i o u r a l r e p e r t o i r e . In f e m a l e s , where p r i o r r e s i d e n c e a p p e a r s t o d e c i d e t h e outcome of most i n t r a s e x u a l i n t e r a c t i o n s , d i s p l a y s f o r m o n l y a s m a l l p a r t of a g g r e s s i v e b e h a v i o u r s . The p r o p e n s i t y t o d i s p l a y may be e x a g g e r a t e d i n m a l e s b e c a u s e t h e y c a n a f f o r d t o l o s e i n d i v i d u a l c o m p e t i t i o n s , and may r e d u c e t h e r i s k o f i n j u r y by r e s p o n d i n g t o and t r a n s m i t t i n g d i s p l a y s . B e c a u s e t h e c o s t s of l o s i n g i n d i v i d u a l c o m p e t i t i o n s a r e g r e a t i n f e m a l e s , p a r t i c u l a r l y t h o s e w h i c h have a l r e a d y commenced spawning, t e r r i t o r i a l f e m a l e s a r e l e s s l i k e l y t h a n males t o r e s p o n d t o d i s p l a y s o r t h r e a t s . The s a l m o n i d m a t i n g s y s t e m i s more complex t h a n t h a t p r e v i o u s l y s u g g e s t e d . B o t h s e x e s e x p r e s s t e r r i t o r i a l i t y , a l t h o u g h i n d i f f e r e n t forms and f o r d i f f e r e n t l e n g t h s o f t i m e . The d i f f e r e n c e s between s e x e s i n t e r r i t o r i a l i t y , e x p r e s s i o n s o f a g g r e s s i v e b e h a v i o u r and f a c t o r s w h i c h d e t e r m i n e t h e outcome of i n t r a s e x u a l c o m p e t i t i o n s a p p e a r t o have e v o l v e d i n r e s p o n s e t o d i f f e r e n t p o r t f o l i o s of e n e r g y i n v e s t m e n t . The d e t e r m i n a n t s o f t h e amounts o f e n e r g y i n v e s t m e n t a r e p r o b a b l y r e l a t e d t o t h e c lumped d i s t r i b u t i o n o f n e c e s s a r y r e s o u r c e s , and t h e a v a i l a b l e r e p r o d u c t i v e o p t i o n s . 76 CHAPTER 2 FEMALE MATE CHOICE IN SALMON I n t r o d u c t i o n Mate c h o i c e d e s c r i b e s a l l i n s t a n c e s i n w h i c h d i f f e r e n t i a l m a t i n g s u c c e s s i n one sex i s due t o p r e f e r e n c e s e x h i b i t e d by t h e o p p o s i t e sex ( S e a r c y 1982; H a l l i d a y 1983). F e m a l e s a r e g e n e r a l l y c o n s i d e r e d t o be more s e l e c t i v e of mates t h a n m a l e s b e c a u s e t h e y a r e l i m i t e d i n t h e number of eggs t h e y c a n p r o d u c e and t h e number of young t h e y c an r a i s e . M a l e s a r e o f t e n l i m i t e d o n l y by t h e number of f e m a l e s t h e y c a n i n s e m i n a t e ( D a r w i n 1871; Bateman 1948; O r i a n s 1969; T r i v e r s 1972). T h e r e f o r e , numerous s i t u a t i o n s e x i s t where i t pays m a l e s t o be i n d i s c r i m i n a t e by c o m p a r i s o n w i t h f e m a l e s . Female mate c h o i c e c an depend on a v a r i e t y o f f a c t o r s , f o r some o f w h i c h t h e r e p r o d u c t i v e g a i n s t h r o u g h d i s c r i m i n a t i n g c h o i c e a r e r e a d i l y a p p a r e n t and f o r o t h e r s of w h i c h t h e y a r e n o t . The c h o i c e o f mates on t h e b a s i s of t h e r e s o u r c e s t h e y h o l d ( t e r r i t o r i e s ) , t h e n u p t i a l g i f t s t h e y p r e s e n t , and t h e p a r e n t a l a b i l i t y t h e y i n d i c a t e ( e . g_. c o u r t s h i p f e e d i n g ) , c a n l e a d t o i n c r e a s e d r e p r o d u c t i v e s u c c e s s f o r s e l e c t i v e f e m a l e s ( s e e S e a r c y 1982 f o r r e v i e w ) . In m a t i n g s y s t e m s where males i n v e s t o n l y t h e i r gametes i n t h e i r p r o g e n y , as i n salmon, immediate b e n e f i t s o f f e m a l e mate c h o i c e a r e not o b v i o u s ( s e e B r a d b u r y and G i b s o n 1983). I t has been a r g u e d t h a t s u c h c h o i c e 77 may be b a s e d on p h y s i c a l a n d / o r b e h a v i o u r a l c h a r a c t e r i s t i c s w h i c h r e f l e c t t h e g e n e t i c f i t n e s s of p o t e n t i a l mates ( e . g_. B o r g i a 1979; T h o r n h i l l and A l c o c k 1983). C o m p e t i t i o n among m a l e s f o r a c c e s s t o f e m a l e s can l i m i t t h e c h o i c e s a v a i l a b l e t o f e m a l e s ( e . g_. D a v i e s and H a l l i d a y 1979; Cox 1981; Diamond 1981). However, even where r e s t r i c t e d by male c o m p e t i t i o n , f e m a l e s may e x e r t some c o n t r o l o v e r w h i c h i n d i v i d u a l s t h e y mate w i t h ( D a v i e s and H a l l i d a y 1977; F a i r c h i l d 1981; Cox 1981; H a l l i d a y 1983). In t h e s e m e l p a r o u s P a c i f i c s almon, f e m a l e s a r e t e r r i t o r i a l of n e s t s i t e s and males compete f o r a c c e s s t o f e m a l e s and t h e a r e a s s u r r o u n d i n g them ( C h a p t e r 1 ) . The outcome of male i n t r a s e x u a l c o m p e t i t i o n depends l a r g e l y on t h e r e l a t i v e s i z e s o f c o m p e t i n g m a l e s (Hanson and S m i t h 1967; C h a p t e r 1), and n o t , a p p a r e n t l y , on t h e b e h a v i o u r o f f e m a l e s . W h i l e f e m a l e s a r e o f t e n r e s t r i c t e d i n t h e d i r e c t c h o i c e of m a l e s , t h e r e i s e v i d e n c e t o s u g g e s t t h a t t h e y p r e f e r t o spawn w i t h l a r g e m a l e s . Hanson and S m i t h (1967) and H a n k i n and M c K e l v e y (1985) have o b s e r v e d t h a t P a c i f i c salmon f e m a l e s a t t a c k s m a l l m a l e s more f r e q u e n t l y t h a n t h e y a t t a c k l a r g e m a l e s . M c C a r t (1970) and S c h r o d e r (1981) have documented t h a t f e m a l e s a c c o m p a n i e d by m ales l a r g e r t h a n t h e m s e l v e s spawn more r a p i d l y t h a n f e m a l e s a c c o m p a n i e d by m a l e s s m a l l e r t h a n t h e m s e l v e s . In t h i s c h a p t e r , I e x p e r i m e n t a l l y examine t h e spawning r a t e 78 of kokanee f e m a l e s a c c o m p a n i e d by males of d i f f e r e n t s i z e s , t o t e s t t h e h y p o t h e s i s t h a t f e m a l e s v a r y t h e i r r a t e o f spawning d e p e n d e n t on t h e s i z e o f c o u r t i n g m a l e s . Methods Ten t e r r i t o r i a l , r i p e , 'medium' s i z e d f e m a l e s (20.5 t o 21.0 cm f o r k l e n g t h ) of known w e i g h t were p l a c e d i n e a c h o f two 4 by 4 m a d j a c e n t e x p e r i m e n t a l a r e n a s . To one a r e n a 10 ' s m a l l ' m a l e s (17.0 t o 19.0 cm f o r k l e n g t h ) were added; t o t h e o t h e r 10 ' l a r g e ' m ales (22.0 t o 25.1 cm). The f i s h were l e f t t o g e t h e r f o r 18 h o u r s , a f t e r w h i c h a l l were removed and t h e f e m a l e s w e i g h e d . T h i s p r o c e d u r e was r e p e a t e d s i x t i m e s , a l t e r n a t i n g t h e s i z e g r o u p of m a l e s p r e s e n t e d between a d j a c e n t a r e n a s t o c o n t r o l f o r p o s s i b l e d i f f e r e n c e s i n spawning r a t e a s s o c i a t e d w i t h t h e d i f f e r e n t a r e n a s ( o f w h i c h t h e r e was no d i f f e r e n c e ) . The d a t a on f e m a l e w e i g h t l o s s (egg d e p o s i t i o n ) were u s e d t o t e s t t h e h y p o t h e s i s t h a t f e m a l e s a c c o m p a n i e d by m a l e s l a r g e r t h a n t h e m s e l v e s spawned a g r e a t e r number of eggs (_i. e. l o s t more w e i g h t ) o v e r t h e 18 hour p e r i o d t h a n f e m a l e s a c c o m p a n i e d by m a l e s s m a l l e r t h a n t h e m s e l v e s . The e x p e r i m e n t was c o n d u c t e d i n t h e Meadow C r e e k spawning c h a n n e l a t t h e n o r t h end of K o o t e n a y Lake, d u r i n g September 1984. The f e m a l e s were c a r e f u l l y s e l e c t e d f r o m o v e r 1,000 e x a m i n e d . To commence e a c h t r i a l , 30 f e m a l e s were s e l e c t e d from a c o l l e c t i o n o f a n e s t h e t i z e d (MS-22) f e m a l e s , weighed and 79 i n d i v i d u a l l y t a g g e d (2 cm F l o y d a r t t a g s ) . T h e s e f e m a l e s were a l l o w e d t o r e c o v e r from t h e a n e s t h e t i c f o r a t l e a s t one h o u r , w h i l e b e i n g k e p t i n 1.5 m s q u a r e s c r e e n h o l d i n g chambers i n t h e s t r e a m . A t 17:00 h o u r s , t h e f e m a l e s were randomly d i v i d e d i n t o two g r o u p s o f 15, r e l e a s e d i n t o t h e two e x p e r i m e n t a l a r e n a s and a l l o w e d t o e s t a b l i s h t e r r i t o r i e s o v e r n i g h t . To m i n i m i z e d i f f e r e n c e s among f e m a l e s i n r e a d i n e s s t o spawn, t e n t e r r i t o r i a l f e m a l e s were i d e n t i f i e d a t 900 h o u r s on t h e f o l l o w i n g m o r n i n g , and t h e 5 e x c e s s f e m a l e s removed ( f e m a l e s r e a d i l y spawn o n l y i f t h e y have e s t a b l i s h e d n e s t s i t e s ) . The r e m a i n i n g t e n f e m a l e s were t h e n l e f t u n d i s t u r b e d u n t i l 17:00 h o u r s . A t t h i s t i m e , t e n t a g g e d m a l e s o f one of two s i z e g r o u p s ( ' l a r g e ' and ' s m a l l ' ) were i n t r o d u c e d i n t o t h e a r e n a and a l l o w e d t o r e m a i n w i t h t h e f e m a l e s f o r 18 h o u r s . P r i o r t o t h e c o m p l e t i o n o f e a c h t r i a l , t h e p o s i t i o n o f e a c h male r e l a t i v e t o t h e f e m a l e s was r e c o r d e d ('dominant', ' c o m p e t i t o r ' , 'sneak', ' a l o n e ' ) . A f t e r t h i s , a l l f e m a l e s were s e i n e d from t h e a r e n a , a n e s t h e t i z e d and w e i g h e d . The w e i g h t o f e a c h f e m a l e a t t h e end o f e a c h t r i a l was s u b t r a c t e d f r o m i t s i n i t i a l w e i g h t t o d e t e r m i n e t o t a l f e m a l e w e i g h t l o s s . The d a t a on f e m a l e w e i g h t l o s s were e x a m i n e d by two methods: f i r s t by a s s u m i n g t h e b e h a v i o u r of e a c h f e m a l e was i n d e p e n d e n t of t h e b e h a v i o u r of a l l o t h e r f e m a l e s t h e y were h e l d w i t h (Mann W h i t n e y U t e s t ) and; s e c o n d , by a s s u m i n g non-i n d e p e n d e n c e o f f e m a l e spawning b e h a v i o u r b o t h w i t h i n and between a r e n a s ( W i l c o x o n s i g n e d rank matched p a i r t e s t ) . In 80 t h i s l a t t e r t e s t , t h e w e i g h t l o s s o f a l l f e m a l e s w i t h i n an a r e n a was summed and t h e t o t a l w e i g h t l o s t by f e m a l e s a c c o m p a n i e d by s m a l l m a l e s p e r t r i a l was s u b t r a c t e d from t h e t o t a l w e i g h t l o s t by f e m a l e s a c c o m p a n i e d by l a r g e m a l e s i n t h e a d j a c e n t a r e n a . T h i s m e t h o d o l o g y c o n t r o l l e d f o r p o s s i b l e d i f f e r e n c e s between t r i a l s due t o c l i m a t i c c o n d i t i o n s , by d e r i v i n g s i n g l e s c o r e s f o r g r o u p s o f f e m a l e s r u n a t t h e same t i m e . To d e t e r m i n e i f f e m a l e w e i g h t l o s s was r e l a t e d t o egg l o s s , s u b j e c t i v e s c o r e s of f e m a l e body c a v i t y d i s t e n s i o n were r e c o r d e d f o r e a c h f e m a l e . The s e v e n s c o r e s r a n g e d from 0 t o 30, a t i n t e r v a l s of 5 (0 v e r y d i s t e n d e d ( f u l l of e g g s ) ; 30 = not d i s t e n d e d (no eggs l e f t i n body c a v i t y ) ) . T h e s e s u b j e c t i v e s c o r e s were compared t o t h e w e i g h t l o s s measurements t o d e t e r m i n e i f t h e r e was a r e l a t i o n s h i p between t h e w e i g h t l o s t by i n d i v i d u a l f e m a l e s and t h e i r body c a v i t y d i s t e n s i o n . R e s u l t s Female kokanee a c c o m p a n i e d by l a r g e m a l e s o v e r an 18 hour p e r i o d l o s t more w e i g h t t h a n f e m a l e s a c c o m p a n i e d by s m a l l m a l e s (p<0,.05; F i g . 1 5 ) . On a v e r a g e , f e m a l e s a c c o m p a n i e d by l a r g e m a l e s l o s t 5.3 g (0.5SE) and f e m a l e s a c c o m p a n i e d by s m a l l m a l e s l o s t 3.8g ( 0 . 5 S E ) , a d i f f e r e n c e c o r r e s p o n d i n g t o a p p r o x i m a t e l y 10% of t h e w e i g h t o f t h e egg mass of a medium s i z e d f e m a l e . In a l l 6 t r i a l s , f e m a l e s a c c o m p a n i e d by m a l e s w h i c h were l a r g e r t h a n t h e m s e l v e s l o s t more w e i g h t i n t o t a l t h a n f e m a l e s 81 F i g u r e 15. The w e i g h t l o s s by f e m a l e s a c c o m p a n i e d by (A) ' l a r g e ' m a l e s and (B) ' s m a l l ' m a l e s . 82 83 a c c o m p a n i e d by m a l e s s m a l l e r t h a n t h e m s e l v e s , i n d e p e n d e n t of t h e a r e n a o c c u p i e d (mean d i f f e r e n c e i n w e i g h t l o s s o f t e n f e m a l e s 14.95 + 3.84SE g; p<0.05). Some f e m a l e s g a i n e d w e i g h t between t h e two w e i g h i n g s w i t h i n a t r i a l , s u g g e s t i n g measurement e r r o r , p r o b a b l y a r i s i n g f r o m s a m p l i n g i n t h e f i e l d under v a r i a b l e weather c o n d i t i o n s and from t a k i n g wet w e i g h t s of f e m a l e s . I t i s p r o b a b l e t h a t t h i s s a m p l i n g e r r o r was e q u a l between g r o u p s . Female w e i g h t l o s s was r e l a t e d t o egg l o s s . S u b j e c t i v e s c o r e s o f f e m a l e body c a v i t y d i s t e n s i o n were s t r o n g l y r e l a t e d t o t h e w e i g h t l o s t by e a c h f e m a l e ( p < 0 . 0 0 l ; F i g . 1 6 ) . A n a l y s i s of body d i s t e n s i o n d a t a showed t h a t f e m a l e s a c c o m p a n i e d by s m a l l m a l e s had more d i s t e n d e d abdomens a t t h e end of t h e p e r i o d ( c l o s e r t o t h e z e r o s c o r e w h i c h i n d i c a t e s no egg l o s s ) t h a n f e m a l e s a c c o m p a n i e d by l a r g e m a l e s (Mann Wh i t n e y U t e s t ; p<0.05). The d i f f e r e n c e i n w e i g h t l o s s between th e g r o u p s o f f e m a l e s was n o t a c c o u n t e d f o r by a s i g n i f i c a n t d i f f e r e n c e i n t h e number of f e m a l e s a t t e n d e d by m a l e s i n e a c h t r e a t m e n t . F o r t y - n i n e of 60 and 44 o f 60 f e m a l e s were a t t e n d e d by l a r g e and s m a l l m a l e s , r e s p e c t i v e l y , a t t h e end of t h e 18 hour t r i a l ( C h i s q u a r e d c o n t i n g e n c y t e s t ; p>0.25). 84 F i g u r e 16. The r e l a t i o n s h i p between s u b j e c t i v e s c o r e s o f f e m a l e body c a v i t y d i s t e n s i o n (0 = f u l l y d i s t e n d e d ; 30 = empty) and w e i g h t l o s s . 85 Weight L o s s by Females (g) i CJ1 _L_ O _L_ CJI _L_ O _ l _ 171 _L_ o H i i i i i i infHiiini + + CJI H > CJ Q. O 3 M . CD O D a co n-ro D CO o 03 n o i CD CJI + -H-f- Mil I II I III + + \ \ \ \ \ + + + Htf \ \ ++ + + ro o +++ ro CJI II o m + -H- • \ 1 111 II + CO O 86 D i s c u s s i o n E v i d e n c e of f e m a l e p r e f e r e n c e f o r l a r g e males P r e v i o u s e x p e r i m e n t a l s t u d i e s on f e m a l e mate c h o i c e i n salmon have d e m o n s t r a t e d t h a t f e m a l e s v a r y t h e i r r a t e of spawning d e p e n d i n g on t h e s i z e of t h e a c c o m p a n y i n g male. M c C a r t (1970) d e m o n s t r a t e d t h a t s o c k e y e f e m a l e s p a i r e d w i t h ( l a r g e ) s o c k e y e m a l e s spawned much f a s t e r t h a n s o c k e y e f e m a l e s a c c o m p a n i e d by ( s m a l l ) kokanee m a l e s ( s e e a l s o C h a p t e r 5 ) . S c h r o d e r (1981) d e m o n s t r a t e d t h a t chum salmon f e m a l e s a c c o m p a n i e d by male's l a r g e r t h a n t h e m s e l v e s spawned more r a p i d l y t h a n f e m a l e s p a i r e d w i t h m a l e s s m a l l e r t h a n t h e m s e l v e s . Female p r e f e r e n c e f o r r e l a t i v e l y l a r g e m a l e s has a l s o been i n d i c a t e d i n s t u d i e s of f e m a l e i n t e r s e x u a l a g g r e s s i o n . Salmon f e m a l e s have been shown t o a t t a c k m a l e s s m a l l e r t h a n t h e m s e l v e s more o f t e n t h a n t h e y a t t a c k m a l e s l a r g e r t h a n t h e m s e l v e s (Hanson and S m i t h 1967; H a n k i n and M c K e l v e y 1985). However, t h e a t t a c k e d m a l e s i n t h e s e s t u d i e s p r o b a b l y o c c u p i e d s u b o r d i n a t e p o s i t i o n s i n male h i e r a r c h i e s , and f e m a l e a g g r e s s i o n may have been d i r e c t e d t o w a r d s s u b o r d i n a t e m a l e s , and not n e c e s s a r i l y t o w a r d s s m a l l m a l e s , per s e . In e i t h e r c a s e , a g g r e s s i o n may not r e f l e c t f e m a l e c h o i c e . T h i s b e h a v i o u r may be an a t t e m p t t o l i m i t s pawning i n t e r f e r e n c e by m a l e s , o r i t may s i m p l y r e s u l t f r o m a c a s e o f m i s t a k e n i d e n t i t y ; s u b o r d i n a t e m a l e s o f t e n a d o p t " f e m a l e " c o l o u r p a t t e r n s ( S c h r o d e r 1981; p e r s . o b s . ) and 87 f e m a l e s a r e a g g r e s s i v e t o w a r d s o t h e r f e m a l e s ( C h a p t e r 1 ) . T h e r e i s no e v i d e n c e t o s u g g e s t t h a t f e m a l e s a g g r e s s i v e l y d r i v e o f f s m a l l m a l e s when no o t h e r m a l e s a r e p r e s e n t . In t h i s s t u d y , kokanee f e m a l e s a c c o m p a n i e d by m a l e s l a r g e r t h a n t h e m s e l v e s l o s t w e i g h t a t a g r e a t e r r a t e t h a n f e m a l e s a c c o m p a n i e d by m a l e s s m a l l e r t h a n t h e m s e l v e s . T h i s i s a d d i t i o n a l e v i d e n c e t h a t f e m a l e s v a r y t h e i r r a t e o f spawning d e p e n d i n g on t h e s i z e of t h e a c c o m p a n y i n g male, b e c a u s e f e m a l e w e i g h t l o s s was d i r e c t l y a t t r i b u t a b l e t o egg l o s s ( F i g . 16), and egg l o s s was p r o b a b l y r e l a t e d t o spawning b e h a v i o u r . Female i n t r a s e x u a l c o m p e t i t i o n c an c a u s e egg l o s s ( p e r s . o b s . ), but t h i s does not a p p e a r t o a c c o u n t f o r t h e d i f f e r e n c e s o b s e r v e d h e r e . The d e n s i t y of f e m a l e s i n t h e a r e n a s was not g r e a t , m i n i m i z i n g a g g r e s s i v e i n t e r a c t i o n s among f e m a l e s . Female salmon a p p e a r t o v a r y t h e i r r a t e o f spawning d e p e n d i n g on t h e s i z e ( r e l a t i v e t o t h e m s e l v e s ) of t h e a c c o m p a n y i n g male, and n o t on b e h a v i o u r a l c h a r a c t e r i s t i c s a s s o c i a t e d w i t h s i z e . S c h r o d e r (1981) d e m o n s t r a t e d t h a t t h e r e were no s i g n i f i c a n t d i f f e r e n c e s i n spawning b e h a v i o u r between r e l a t i v e l y l a r g e and s m a l l chum salmon m a l e s w h i c h c o u l d a c c o u n t f o r t h e d i f f e r e n c e he o b s e r v e d i n f e m a l e s p a w ning r a t e . S i m i l a r l y , I f o u n d t h a t t h e r e was no s i g n i f i c a n t d i f f e r e n c e i n t h e t o t a l number of f e m a l e s a t t e n d e d by l a r g e and s m a l l males t h a t c o u l d a c c o u n t f o r t h e o b s e r v e d d i f f e r e n c e s i n w e i g h t l o s s . 88 S c h r o d e r (1981) s u g g e s t e d t h a t f e m a l e s a f f e c t mate c h o i c e by e l i c i t i n g c o n t i n u e d c o m p e t i t i o n among m a l e s when t h e y a r e a c c o m p a n i e d by m a l e s s m a l l e r t h a n t h e m s e l v e s , d o i n g so by s l o w i n g t h e i r s pawning r a t e and t h u s i n c r e a s i n g t h e c h a n c e t h a t s m a l l incumbent males w i l l be d i s p l a c e d by l a r g e r m a l e s . The p r o b a b i l i t y t h a t a s m a l l male w i l l be d i s p l a c e d i n c r e a s e s w i t h t i m e f o r t h r e e r e a s o n s : f i r s t , t h e r e i s g r e a t and c o n t i n u e d c o m p e t i t i o n f o r a c c e s s t o f e m a l e s ( e . g_. Hanson and S m i t h 1967; S c h r o d e r 1981); s e c o n d , l a r g e f e m a l e s a t t r a c t l a r g e m a l e s ( C h a p t e r 3) and; f i n a l l y , s i z e i s a major f a c t o r i n male i n t r a s e x u a l c o m p e t i t i o n i n salmon, l a r g e l y o u t w e i g h i n g a d v a n t a g e s a c c r u e d t h r o u g h p r i o r a c c e s s ( C h a p t e r 1 ) . P o s s i b l e a d a p t i v e s i g n i f i c a n c e of f e m a l e mate c h o i c e Female p r e f e r e n c e f o r l a r g e m a l e s i n salmon i s p r o b a b l y n o t r e l a t e d t o any immediate b e n e f i t s a s s o c i a t e d w i t h s i z e i n m a l e s . M a l e s p r o v i d e n e i t h e r p r o t e c t i o n nor r e s o u r c e s t o t h e f e m a l e s t h e y accompany o r t o t h e i r p r o g e n y . F e r t i l i z a t i o n e f f i c i e n c y , i n t h e a b s e n c e of c o m p e t i t o r s , a p p e a r s u n a f f e c t e d by male s i z e i n salmon ( M c C a r t 1970; H u t c h i n g and Myers 1985). F e m a l e s may a c h i e v e l o n g t e r m b e n e f i t s t h r o u g h p r e f e r e n c e f o r l a r g e m a l e s i f s i z e i s a h e r i t a b l e c h a r a c t e r , b e c a u s e l a r g e s i z e c o n f e r s an a d v a n t a g e i n male and f e m a l e i n t r a s e x u a l s pawning c o m p e t i t i o n ( C h a p t e r 1) and a t o t h e r t i m e s i n t h e l i f e h i s t o r y ( e . c[. F o e r s t e r 1968; H e a l e y 1982; West and L a r k i n 89 1987). The e x i s t e n c e o f s i g n i f i c a n t a d d i t i v e g e n e t i c v a r i a t i o n f o r g r o w t h i n s a l m o n i d s ( R i c k e r 1981; K i n g h o r n 1983) s u g g e s t s t h a t mate s e l e c t i o n b a s e d on s i z e may r e s u l t i n i n c r e a s e d f i t n e s s of t h e p r o g e n y . W h i l e t h e r e a s o n s f e m a l e s p r e f e r l a r g e m a l e s a r e u n c l e a r , i t i s p r o b a b l e t h a t t h i s p r e f e r e n c e i s n o t f r e e of c o s t s . F e m a l e s a p p e a r t o i n c r e a s e t h e r i s k s o f r e p r o d u c t i v e f a i l u r e t h r o u g h t h e i r d i s c r i m i n a t i o n a g a i n s t s m a l l m a l e s . P a c i f i c salmon f e m a l e s have o n l y l i m i t e d and f i n i t e e n e r g y r e s e r v e s t o d e v o t e t o r e p r o d u c t i o n . T h e i r e n e r g y r e s e r v e s a r e d i v i d e d among t h e needs of m a i n t a i n i n g b o d i l y f u n c t i o n s , f i n d i n g a n e s t s i t e , c o n s t r u c t i n g and spawning i n s e v e r a l a d j a c e n t n e s t s , and d e f e n d i n g t h e n e s t s i t e f r o m o t h e r f e m a l e s b e f o r e and a f t e r s p a w n i n g . I t seems p r o b a b l e t h a t by d e l a y i n g s p a w n i n g , a f e m a l e i n c r e a s e s t h e c o s t s of n e s t d e f e n s e b e f o r e spawning c o m p l e t i o n , and t h u s d e c r e a s e s t h e e n e r g y a v a i l a b l e f o r l a t e r n e s t d e f e n s e , a t t h e same t i m e i n c r e a s i n g t h e r i s k of f a i l i n g t o c o m p l e t e spawning, e i t h e r b e c a u s e of d i s p l a c e m e n t by o t h e r f e m a l e s o r d e a t h . In c o n c l u s i o n , f e m a l e kokanee a p p e a r t o v a r y t h e i r r a t e o f spawning d e p e n d i n g on t h e s i z e o f t h e c o u r t i n g male, spawning more r e a d i l y w i t h l a r g e m a l e s . On a v e r a g e , l a r g e m a l e s w i l l s p e nd l e s s t i m e w i t h i n d i v i d u a l f e m a l e s t h a n s m a l l m a l e s and hence w i l l have more t i m e and e n e r g y t o mate w i t h a d d i t i o n a l f e m a l e s . C o u p l e d w i t h t h e a d v a n t a g e of s i z e i n i n t r a s e x u a l 90 c o m p e t i t i o n , f e m a l e mate c h o i c e may have a s i g n i f i c a n t e f f e c t on male m a t i n g s u c c e s s , i n c r e a s i n g t h e d i s p a r i t y between s m a l l and l a r g e m a l e s w i t h i n p o p u l a t i o n s . 91 CHAPTER 3 MALE MATE CHOICE DEPENDENT ON MALE SIZE IN SALMON I n t r o d u c t i o n Mate c h o i c e and i n t r a s e x u a l c o m p e t i t i o n a r e major components of s e x u a l s e l e c t i o n . The outcome of i n t r a s e x u a l c o m p e t i t i o n i s u s u a l l y d e c i d e d by t h e r e l a t i v e s t r e n g t h s o f t h e c o m p e t i t o r s , w h i c h can o f t e n be u n a m b i g u o u s l y measured by t h e i r r e l a t i v e s i z e ( e . c[. K o d r i c - B r o w n 1977; Howard and K l u g e 1985; B a r l o w e t a_l. 1986; M c L a i n and B o r o m i s a 1987). In c o n t r a s t , mate c h o i c e i s u s u a l l y c o n s i d e r e d t o be i n d e p e n d e n t o f t h e p h y s i c a l c h a r a c t e r i s t i c s o f t h e sex making t h e c h o i c e ; c r i t e r i a of c h o i c e s u c h as mate s i z e , dominance and p a r e n t a l c a r e a b i l i t y a r e u s u a l l y n o t c o n s i d e r e d d e p e n d e n t on t h e c h a r a c t e r i s t i c s of t h o s e s e l e c t i n g mates i n e m p i r i c a l s t u d i e s of mate c h o i c e ( s e e S e a r c y 1982; H a l l i d a y 1983). Mate c h o i c e b a s e d on i n b r e e d i n g a v o i d a n c e i s a r a r e example of c h o i c e d e p e n d e n t on r e l a t i v e c h a r a c t e r s between t h e s e x e s ( e . g_. B a t e s o n 1983; S m i t h and A y a s s e 1987). The number of mates a v a i l a b l e t o i n d i v i d u a l s o f t e n d i f f e r s among members o f a p o p u l a t i o n b e c a u s e of t h e e f f e c t s of i n t r a s e x u a l c o m p e t i t i o n ( e . g_. Le Boeuf 1974;. Howard 1978; D a v i e s and H a l l i d a y 1979; Downhower e t a_l. 1983; M c L a i n and B o r o m i s a 1987). W h i l e t h e r e i s much e v i d e n c e t o s u g g e s t t h a t s u c h c o m p e t i t i o n can l e a d t o t h e e v o l u t i o n of a l t e r n a t i v e 92 s t r a t e g i e s f o r s e e k i n g mates ( e . cj. Howard 1978; D a v i e s and H a l l i d a y 1979; R u b e n s t e i n 1980; Dunbar 1982; Dominey 1984; G r o s s 1985), t h e r e i s l i t t l e e v i d e n c e t o s u g g e s t i t c a n l e a d t o t h e e v o l u t i o n o f v a r y i n g s t r a t e g i e s of mate p r e f e r e n c e (what mates a r e p r e f e r r e d ) . Where t h e r e a r e immediate s e l e c t i v e a d v a n t a g e s a s s o c i a t e d w i t h d i s c r i m i n a t i n g c h o i c e , a l l i n d i v i d u a l s , i n d e p e n d e n t o f t h e i r r e l a t i v e s t r e n g t h , a r e u s u a l l y assumed t o p r e f e r t h e same p o t e n t i a l mates. However, i n t r a s e x u a l c o m p e t i t i o n can c a u s e t h e e x p e c t e d v a r i a n c e i n r e p r o d u c t i v e s u c c e s s t o d i f f e r among members o f t h e sex i n q u e s t i o n i f t h e y mated a t random w i t h f e m a l e s a v a i l a b l e t o them. F o r example, i f t h e s t r o n g e s t i n d i v i d u a l s have t h e w i d e s t range o f p o t e n t i a l mates (by v i r t u e o f t h e i r c o m p e t i t i v e s u p e r i o r i t y a n d / o r p r e f e r e n c e by t h e o p p o s i t e sex; e. g_. Hanson and S m i t h 1967; Le Boeuf 1974; B u r l e y 1977; Cox 1981) t h e n t h e v a r i a n c e i n t h e e x p e c t e d r e p r o d u c t i v e s u c c e s s of t h e s e i n d i v i d u a l s i f t h e y mated a t random i s l i k e l y t o be g r e a t e r t h e n t h a t of t h e weakest i n d i v i d u a l s . S i m p l y , t h e s t r o n g e s t i n d i v i d u a l s c o u l d p o t e n t i a l l y mate w i t h t h e h i g h e s t and l o w e s t q u a l i t y mates whereas t h e weakest i n d i v i d u a l s a r e u s u a l l y l i m i t e d t o t h e l o w e s t q u a l i t y mates. C o n s e q u e n t l y , t h e s t r o n g e s t i n d i v i d u a l s w i t h i n a sex may be e x p e c t e d t o be more s e l e c t i v e of mates, h a v i n g more t o g a i n t h r o u g h s u c h s e l e c t i v i t y . Thus, s e l e c t i o n m i g ht be e x p e c t e d t o f a v o u r mate c h o i c e s t r a t e g i e s t h a t a r e b a s e d not o n l y on t h e a b s o l u t e c h a r a c t e r s of p o t e n t i a l mates but a l s o on t h e r e l a t i v e s t r e n g t h of t h e c h o o s i n g i n d i v i d u a l . 93 P r e v i o u s work on male c h o i c e i n f i s h e s , i n c l u d i n g salmon, s u g g e s t s t h a t m a l e s , i n d e p e n d e n t o f s i z e , p r e f e r t h e l a r g e s t of a v a i l a b l e f e m a l e s , p r o b a b l y b e c a u s e of t h e s t r o n g r e l a t i o n s h i p between f e m a l e s i z e and f e c u n d i t y (Hanson and S m i t h 1967; M c C a r t 1970; J o n s s o n and H i n d a r 1982; Downhower and Brown 1981; Rowland 1982; L o i s e l l e 1982; S a r g e n t e t a l . 1986; B e r g l u n d e t a l . 1986). However, t h e r e i s c o n s i d e r a b l e e v i d e n c e t o s u g g e s t t h e range of a v a i l a b l e mates i n c r e a s e s w i t h male s i z e i n f i s h e s b e c a u s e of t h e e f f e c t s o f s i z e i n male i n t r a s e x u a l c o m p e t i t i o n (Hanson and S m i t h 1967; K o d r i c - B r o w n 1977; F r i c k e 1980; T h r e s h e r and Moyer 1983; Downhower e_t a_l. 1983) and f e m a l e p r e f e r e n c e f o r l a r g e a n d / o r c o m p e t i t i v e l y s u p e r i o r m a l e s ( S c h r o d e r 1981; Downhower e_t a l . 1983; B e r g l u n d e t a l . 1986). T h e r e f o r e , we m i g h t e x p e c t t o see v a r i a b l e mate c h o i c e s t r a t e g i e s d ependent on male s i z e i n f i s h e s . In a s e r i e s of f i v e e x p e r i m e n t s , I t e s t e d whether kokanee m a l e s ( w h i c h spawn s e p a r a t e l y from s o c k e y e ) s e l e c t f e m a l e s b a s e d on t h e i r a b s o l u t e s i z e o r on t h e i r s i z e r e l a t i v e t o t h a t of t h e male. I f male c h o i c e has e v o l v e d i n r e s p o n s e t o t h e v a r i a n c e i n mate q u a l i t y of a v a i l a b l e f e m a l e s r a t h e r t h a n t o t h e v a r i a n c e i n mate q u a l i t y of a l l f e m a l e s , male s e l e c t i v i t y s h o u l d i n c r e a s e w i t h i n c r e a s i n g male s i z e i n sa l m o n . 94 Methods Male c h o i c e was examined i n two s e p a r a t e kokanee p o p u l a t i o n s i n s o u t h e a s t e r n B r i t i s h C o l u m b i a : Meadow C r e e k , t r i b u t a r y t o K o o t e n a y Lake and P a s s C r e e k , t r i b u t a r y t o Arrow L a k e . T h e s e p o p u l a t i o n s p r o v i d e d a l a r g e s i z e r a n g e of spawning kokanee. M a l e s and f e m a l e s were b r o a d l y c a t e g o r i z e d i n t o t h r e e s i z e g r o u p s : s m a l l (19-27 cm, a l l measurements a r e of f o r k l e n g t h ) ; medium (28-40 cm); and l a r g e (41-52 cm). In f o u r e x p e r i m e n t s (A,B,C and D) males o f one or two s i z e g r o u p s were p r e s e n t e d w i t h a c h o i c e o f two t e r r i t o r i a l but d i f f e r e n t s i z e d f e m a l e s . The s i z e s o f m a l e s and f e m a l e s u s e d v a r i e d among e x p e r i m e n t s . A f i f t h e x p e r i m e n t (E) examined t h e e f f e c t o f male c o m p e t i t i o n on p r e f e r e n c e by t h e s m a l l e s t m a l e s . S m a l l males were g i v e n a c h o i c e between e i t h e r a s m a l l f e m a l e o r a l a r g e f e m a l e a c c o m p a n i e d by a l a r g e m a l e . E x p e r i m e n t s A and B were c o n d u c t e d a t Meadow C r e e k and t h e r e s t were c o n d u c t e d a t Pass C r e e k . E s t i m a t e s of mean f e c u n d i t i e s of f e m a l e s u s e d were d e r i v e d f r o m a r e g r e s s i o n o f egg number on f e m a l e f o r k l e n g t h f o r K o o t e n a y Lake kokanee (Log (egg number) = 3.09 Log ( f o r k l e n g t h ) 1.75, n=68, R = 90.5, p<0.001; M i n i s t r y of E n v i r o n m e n t , P r o v i n c e o f B r i t i s h C o l u m b i a , u n p u b l i s h e d d a t a ) . The r e l a t i o n s h i p of egg number and f e m a l e f o r k l e n g t h has not been measured i n P a s s C r e e k kokanee, but was assumed t o be s i m i l a r t o th e r e l a t i o n s h i p between f e c u n d i t y and s i z e i n t h e n e a r b y (<100 95 km) K o o t e n a y Lake kokanee p o p u l a t i o n s . A l l e x p e r i m e n t s were c o n d u c t e d i n t h e spawning s t r e a m s i n two 4 x 4 m e x p e r i m e n t a l a r e n a s c o n s t r u c t e d of c h i c k e n w i r e i n a r e a s o f good spawning g r a v e l and water f l o w . The a r e n a s were e n c l o s e d w i t h i n a l a r g e r pen t o l i m i t i n t e r a c t i o n s o f t e s t f i s h w i t h f r e e - s w i m m i n g f i s h i n t h e c r e e k s . The a r e n a s were l a r g e r e l a t i v e t o f e m a l e spawning r e q u i r e m e n t s ( T a u t z 1977), m i n i m i z i n g p o s s i b l e d i f f e r e n c e s i n t e r r i t o r y q u a l i t y between f e m a l e s . P a i n t e d w h i t e r o c k s were p l a c e d i n e a c h a r e n a t o d e l i n e a t e a 1 m g r i d . F e m a l e s u s e d i n t h e e x p e r i m e n t s were c h o s e n t o m i n i m i z e d i f f e r e n c e s i n t h e i r spawning r e a d i n e s s , a f a c t o r i n male c h o i c e ( S c h r o d e r 1981; H u t c h i n g s and Myers 1985). O n l y f e m a l e s w h i c h d i s p l a y e d t e r r i t o r i a l d e f e n s e o f n e s t s i t e s i n t h e a r e n a s were u s e d i n t h e e x p e r i m e n t s . They were s e l e c t e d by p l a c i n g 2-4 f e m a l e s of e a c h of two s i z e g r o u p s i n t h e a r e n a s on t h e n i g h t b e f o r e a t e s t . Most e s t a b l i s h e d t e r r i t o r i e s o v e r n i g h t and commenced n e s t c o n s t r u c t i o n . In t h e m o r n i n g , one t e r r i t o r i a l f e m a l e o f e a c h s i z e g r o u p was s e l e c t e d and t h e o t h e r s were r e l e a s e d . D u r i n g t h e e x p e r i m e n t s , t h e number of d i g g i n g b o u t s ( n e s t c o n s t r u c t i o n movements) p e r f o r m e d by e a c h of t h e two f e m a l e s i n t h e a r e n a was r e c o r d e d t o m o n i t o r p o s s i b l e d i f f e r e n c e s i n f e m a l e a c t i v i t y . A f e m a l e d i g g i n g bout c o n s i s t s of a r a p i d s e r i e s of body f l e x u r e s e a c h c u l m i n a t i n g i n t h e s c r a p i n g of t h e t a i l o v e r a s m a l l l e n g t h of s u b s t r a t e as t h e 96 f e m a l e moves s l i g h t l y u p s t r e a m . A f t e r e a c h d i g g i n g b o u t , t h e f e m a l e moves o r d r i f t s downstream t o h e r o r i g i n a l p o s i t i o n and u s u a l l y s u r v e y s h e r n e s t ( ' p r o b i n g ' ; M c C a r t 1969; T a u t z and G r o o t 1975) b e f o r e commencing a n o t h e r d i g g i n g bout ( s e e M c C a r t 1969 f o r a d e t a i l e d d e s c r i p t i o n o f t h e d i g g i n g b e h a v i o u r o f 0. n e r k a ) . M a l e s t o be t e s t e d were s e i n e d from t h e s t r e a m i m m e d i a t e l y b e f o r e t h e t e s t s . C a p t u r e and t r a n s p o r t of males a p p e a r e d t o have m i n i m a l e f f e c t on male b e h a v i o u r , as most showed an immediate and c o n t i n u e d i n t e r e s t in., t h e f e m a l e s a f t e r t h e i r i n t r o d u c t i o n i n t o t h e a r e n a s . F o r male c h o i c e t r i a l s , a s i n g l e male was i n t r o d u c e d i n t o an a r e n a w i t h two t e r r i t o r i a l f e m a l e s and a l l o w e d t o become o r i e n t e d f o r 10 m i n u t e s . B e h a v i o u r r e l a t i v e t o e a c h f e m a l e was t h e n r e c o r d e d d u r i n g two f i v e m i n u t e o b s e r v a t i o n p e r i o d s s e p a r a t e d by a s e v e n m i n u t e i n t e r v a l . At t h e c o m p l e t i o n o f e a c h t r i a l , m a l e s were removed from t h e a r e n a s , t h e i r f o r k l e n g t h s measured and t h e n t h e y were r e l e a s e d . Male c h o i c e d i d not d i f f e r between t h e f i v e m i n u t e o b s e r v a t i o n , p e r i o d s and t h e r e s u l t s were combined f o r a n a l y s e s . To q u a n t i f y male p r e f e r e n c e , t i m e s p e n t n e a r t h e f e m a l e s ( ' n e a r n e s s t i m e ' ) and t h e number of male ' c o u r t s h i p d i s p l a y s ' d i r e c t e d t o w a r d e a c h f e m a l e were r e c o r d e d . N e a r n e s s t i m e was d e f i n e d as t h e t i m e a male s p e n t w i t h i n 25 cm of a f e m a l e , p l u s 97 t h e t i m e i t was o r i e n t e d t o t h e f e m a l e when a t d i s t a n c e s f r o m 25 cm t o 1 m. A male was c o n s i d e r e d ' o r i e n t e d ' t o a f e m a l e when i t s head was p o i n t e d t o w a r d t h e f e m a l e o r when t h e male r e a c t e d t o f e m a l e movements when l a t e r a l o r s l i g h t l y u p s t r e a m of t h e f e m a l e . I f t h e male went f a r t h e r t h a n 1m from t h e f e m a l e , t i m i n g was recommenced when t h e male a p p r o a c h e d t o w i t h i n 25 cm. The t i m i n g c r i t e r i o n was d e r i v e d from numerous o b s e r v a t i o n s t h a t male salmon u s u a l l y r e m a i n w i t h i n 1 m w h i l e c o u r t i n g f e m a l e s (Hanson and S m i t h 1967; G r o s s 1985; C h a p t e r 1 ) . The male was r e q u i r e d t o a p p r o a c h w i t h i n 25 cm t o r e d u c e s u b j e c t i v i t y i n t i m i n g ' i n t e r e s t ' . The ' n e a r n e s s t i m e ' r u l e was m o d i f i e d s l i g h t l y f o r t h e c o m p e t i t i o n e x p e r i m e n t ( E ) . B e c a u s e t h e p r e s e n c e of a l a r g e male o f t e n r e s t r i c t e d c l o s e a c c e s s t o t h e l a r g e f e m a l e , t h e r e q u i r e m e n t t h a t t h e male must a p p r o a c h w i t h i n 25 cm f o r t i m i n g t o be commenced was d r o p p e d and a l l t i m e o r i e n t e d t o t h e f e m a l e when w i t h i n 1m was r e c o r d e d . The c o u r t s h i p d i s p l a y s r e c o r d e d were ' a p p r o a c h e s ' ( i n c l u d i n g q u i v e r s ) , ' c r o s s o v e r s ' and ' d i g s ' ( M c C a r t 1969; T a u t z and G r o o t 1975). D i g g i n g b o u t s by m a l e s have n o t p r e v i o u s l y been c o n s i d e r e d a s c o u r t s h i p d i s p l a y s i n 0. n e r k a but r a t h e r a s ' d i s p l a c e m e n t a c t i v i t i e s ' ( M c C a r t 1969). However, I do not a g r e e w i t h t h i s i n t e r p r e t a t i o n . S i n c e male d i g g i n g ( o f t h e t y p e r e c o r d e d ; see C h a p t e r 1) i s a b e h a v i o u r e x p r e s s e d o n l y when w i t h f e m a l e s , I b e l i e v e i t i s a p p r o p r i a t e t o c l a s s i t a s a c o u r t s h i p d i s p l a y , i n t h e same manner t h a t t h e o t h e r d i s p l a y s p e r f o r m e d s o l e l y i n t h e p r e s e n c e o f f e m a l e s a r e c l a s s e d a s c o u r t s h i p d i s p l a y s . M a l e d i g g i n g i s an i n f r e q u e n t b e h a v i o u r (<3% of t o t a l 98 b e h a v i o u r s ) and i t s i n c l u s i o n a s a c o u r t s h i p b e h a v i o u r d i d not a f f e c t t h e outcome of any s t a t i s t i c a l t e s t s . The f r e q u e n c i e s o f a l l c o u r t s h i p d i s p l a y s were p o s i t i v e l y c o r r e l a t e d and t h e d a t a were combined f o r a n a l y s e s . P r e f e r e n c e o f a male f o r a f e m a l e was e x p r e s s e d i n two ways: f i r s t , a s t h e d i f f e r e n c e between t h e t o t a l n e a r n e s s t i m e w i t h t h e l a r g e s t f e m a l e and t h e t o t a l n e a r n e s s t i m e w i t h t h e s m a l l e s t f e m a l e (Time D i f f e r e n c e ) ; and s e c o n d , as t h e d i f f e r e n c e i n t h e number of c o u r t s h i p d i s p l a y s p e r f o r m e d w i t h t h e l a r g e s t and s m a l l e s t f e m a l e s ( D i s p l a y D i f f e r e n c e ) . D i f f e r e n c e s c o r e s were c a l c u l a t e d f o r e a c h male b e c a u s e t h e t i m e s p e n t n e a r one f e m a l e and t h e number of d i s p l a y s d i r e c t e d t o h e r were not i n d e p e n d e n t of t h e t i m e and d i s p l a y s r e c o r d e d w i t h t h e o t h e r f e m a l e . W i t h i n male s i z e g r o u p s , p r e f e r e n c e was t e s t e d u s i n g t h e W i l c o x o n s i g n e d r a n k s t e s t on t h e Time D i f f e r e n c e d a t a and t h e p a i r e d s t u d e n t ' s t - t e s t on t h e D i s p l a y D i f f e r e n c e d a t a . Between male s i z e g r o u p s , p r e f e r e n c e s were compared u s i n g t h e Mann W h i t n e y U - t e s t f o r Time D i f f e r e n c e d a t a and a two sample t -t e s t f o r D i s p l a y d i f f e r e n c e d a t a ( a l l t e s t s were t w o - t a i l e d ) . 99 R e s u l t s The mean s i z e s and number o f (1) f e m a l e p a i r s p r e s e n t e d and (2) m a l e s t e s t e d f o r e a c h of t h e f i v e e x p e r i m e n t s a r e g i v e n i n T a b l e 1. A summary o f t h e Time D i f f e r e n c e and D i s p l a y D i f f e r e n c e r e s u l t s f o r e a c h e x p e r i m e n t a r e p r e s e n t e d i n F i g s . 17 and 18. The Time D i f f e r e n c e and D i s p l a y D i f f e r e n c e d a t a i n d i c a t e d t h e same p r e f e r e n c e by g i v e n s i z e d m a l e s w i t h i n e a c h e x p e r i m e n t . T h e s e p r e f e r e n c e s a r e summarized i n T a b l e 1. A. Mate s e l e c t i o n of s m a l l m a l e s when g i v e n a c h o i c e between  s m a l l f e m a l e s of s i i g h t l y d i f f e r e n t s i z e When g i v e n a c h o i c e between f e m a l e s s l i g h t l y l a r g e r and s l i g h t l y s m a l l e r t h a n t h e m s e l v e s , s m a l l kokanee males d i s p l a y e d more t o and s p e n t more t i m e n e a r t h e l a r g e r f e m a l e s (p<0.00l f o r Time D i f f e r e n c e ; p<0.005 f o r D i s p l a y D i f f e r e n c e ) . The d e g r e e o f p r e f e r e n c e , measured i n n e a r n e s s t i m e , f o r t h e l a r g e s t f e m a l e 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 t h e d i f f e r e n c e i n s i z e between t h e male and t h e s m a l l e s t f e m a l e ( r = 0.289, n = 116, p < 0 . 0 l ; F i g . 1 9 ) . In c o n t r a s t , t h e r e was no s i g n i f i c a n t c o r r e l a t i o n between t h e p r e f e r e n c e of m a l e s and t h e d i f f e r e n c e between t h e i r own s i z e and t h a t of t h e l a r g e s t f e m a l e s ( r = -0.092; p>0.5). To examine f u r t h e r t h e r e l a t i o n s h i p between male p r e f e r e n c e and t h e s i z e o f t h e male r e l a t i v e t o t h e s m a l l e s t f e m a l e , males were s p l i t i n t o two s i z e g r o u p s . The s i z e g r o u p s were 100 Table 4. The mean fork lengths (cm; +SE) and s i z e groups of t e r r i t o r i a l females used and kokanee males t e s t e d , plus a summary of the choices made i n f i v e experiments. Experiment Mean FL of females , Mean FL Choice smallest l a r g e s t . nl of males n2 A 19.5 +0.1 S(S) 22.3 +0.1 S(L) 36 21.2 +0.1 S 116 S(L) 21.4 +0.2 S 29.2 +1.0 M 5 21.4 +0.2 S 21 none B 21.7 +0.1 S 30.7 +0.7 M 6 31.7 +0.3 M 15 M 26.6 +0.7 S 47.3 +0.6 L 5 27.0 +0.3 S 20 none C 24.1 +1.5 S 46.3 +0.7 L 2 34.8 +0.1 M 10 L 35.5 +0.3 M 47.6 +1.2 L 2 34.5 +0.5 M 10 none D 35.1 +0.1 M 47.4 +,0.8 L 3 46.6 +0.5 L 10 L E 24.4 +0.6 S 46.2 +0.3 L 4 26.4 +0.5 S 14 S S, M, and L correspond to Small, Medium and Large s i z e groups. S(S) and S(L) correspond to the small and large subsets of the small s i z e group i n Experiment A only. n1 = the number of female p a i r s used; n2 = the number of males t e s t e d . 101 F i g u r e 17. M a l e c h o i c e d e p e n d e n t on male s i z e a s i n d i c a t e d by t h e median (+ 95% CI) of t h e d i f f e r e n c e i n t i m e s p e n t n e a r a c h o i c e o f f e m a l e s . The symbols r e p r e s e n t t h e c h o i c e o f f e m a l e s ( i n w h i t e , on t h e o u t s i d e o f t h e v e r t i c a l a x e s ) p r e s e n t e d t o m a l e s ( i n b l a c k , a t t h e median i n t h e d i f f e r e n c e i n t i m e s p e n t n e a r t h e l a r g e s t and s m a l l e s t f e m a l e s o f a c h o i c e o v e r t e n m i n u t e s of o b s e r v a t i o n i n an e x p e r i m e n t a l a r e n a ) . The s i z e of t h e symbols a r e p r o p o r t i o n a l t o t h e mean s i z e s o f t h e f i s h u s e d . A s c a l e of a c t u a l s i z e s a p p e a r s i n t h e upper l e f t c o r n e r o f t h e f i g u r e . M a l e s were t e s t e d i n d i v i d u a l l y i n a l l e x p e r i m e n t s , e x c e p t E, where a l a r g e male was p a i r e d w i t h t h e l a r g e f e m a l e d u r i n g t h e t e s t i n g of s m a l l male c h o i c e . The p r e s e n c e of t h e l a r g e male i s i n d i c a t e d on t h e o u t s i d e of t h e r i g h t v e r t i c a l a x i s . M ale s y m b o l s t o t h e r i g h t of t h e b r o k e n l i n e i n d i c a t e p r e f e r e n c e f o r t h e l a r g e s t of a c h o i c e of f e m a l e s , t h o s e t o t h e l e f t i n d i c a t e p r e f e r e n c e f o r t h e s m a l l e s t o f a c h o i c e of f e m a l e s . Note t h a t i n e x p e r i m e n t A t h e s m a l l e s t f e m a l e s , on t h e l e f t , a r e o n l y s l i g h t l y s m a l l e r t h a n t h e l a r g e s t p r e s e n t e d f e m a l e s , on t h e r i g h t (means o f 19.5 v e r s u s 22.3 cm). 102 103 F i g u r e 18. M a l e c h o i c e d e p e n d e n t on male s i z e as i n d i c a t e d by t h e mean d i f f e r e n c e (+ 95% CI) i n t o t a l c o u r t s h i p d i s p l a y s p e r f o r m e d t o a c h o i c e o f two f e m a l e s i n f i v e s e p a r a t e e x p e r i m e n t s . See F i g . 17 f o r a d e s c r i p t i o n o f symbols and l a y o u t of f i g u r e . 104 S M A L L E S T F E M A L E fl B D E o - 4 0 - 2 0 - 0 - f -L A R G E S T F E M A L E 30 -20 -10 0 10 20 30 C o u r t s h i p D i s p l a y D i f f e r e n c e 105 F i g u r e 19. Mal e c h o i c e d e p e n d e n t on t h e s i z e d i f f e r e n c e between t h e t e s t male and t h e s m a l l e s t p r e s e n t e d f e m a l e i n e x p e r i m e n t A. P o i n t s t o t h e r i g h t o f t h e v e r t i c a l b r o k e n l i n e a r e t h o s e of m a l e s g r e a t e r t h a n t h e mean (1.63cm) s i z e d i f f e r e n c e between t e s t m ales and t h e s m a l l e s t f e m a l e s . P o i n t s above t h e b r o k e n h o r i z o n t a l l i n e i n d i c a t e i n d i v i d u a l male p r e f e r e n c e o f t h e l a r g e s t of a p r e s e n t e d p a i r of f e m a l e s . Note t h a t r e l a t i v e l y few m a l e s w h i c h were g r e a t e r t h a n 1.63cm l a r g e r t h a n t h e s m a l l e s t f e m a l e s p e n t t h e m a j o r i t y o f t h e i r t i m e n e a r t h e s m a l l e s t f e m a l e ( l o w e r r i g h t q u a d r a t ) . 106 I o I cn o o •1 L T i m e D i f f e r e n c e (s) i .U o o I IU o o ro o o o o O) o o LO 3 0) o o o o o I CD 3 cn OJ rf *— CD to TI 3 O 0) T (-< 7C CD r -T| fl) O D "3 CO TT rf 3 r -CD 2 13 M-CO D rf C zr cn n — O IU o o o o o o o o o o o o o A o o 1 n o ro CD to n I .OQCJ . o o o o o o d o oo I o o o o o o o o o o o o o o o o o 00 o o o o cn o 1 07 d e t e r m i n e d by s u b t r a c t i n g t h e s i z e o f t h e s m a l l e s t f e m a l e from t h e s i z e of e a c h male, and th e n by d i v i d i n g t h e m a l e s i n t o two g r o u p s ( s l i g h t l y s m a l l e r , s l i g h t l y l a r g e r ) a t t h e mean (1.63 cm) of t h i s s i z e d i f f e r e n c e . The s l i g h t l y l a r g e r m a l e s showed a s t r o n g p r e f e r e n c e f o r t h e l a r g e s t f e m a l e ( p < 0 . 0 0 0 l , n=54, f o r Time ( F i g . 19) and D i s p l a y D i f f e r e n c e s ) . In c o n t r a s t , t h e s l i g h t l y s m a l l e r m a l e s showed no p r e f e r e n c e among t h e f e m a l e s p r e s e n t e d (p> 0 . 4 , n = 62 f o r Time and D i s p l a y D i f f e r e n c e s ) . B. Mate s e l e c t i o n o f s m a l l and medium s i z e d m a l e s g i v e n a c h o i c e between s m a l l and medium f e m a l e s S m a l l kokanee males showed no p r e f e r e n c e between s m a l l and medium s i z e d f e m a l e s i n n e a r n e s s t i m e or c o u r t s h i p d i s p l a y s (p>0.3 f o r Time D i f f e r e n c e ; p>0.05 f o r D i s p l a y D i f f e r e n c e ) . In c o n t r a s t , medium s i z e d m a l e s showed a p r e f e r e n c e f o r medium f e m a l e s i n b o t h c h o i c e c r i t e r i a (p<0.05). The two s i z e s of m a l e s d i f f e r e d s i g n i f i c a n t l y i n Time D i f f e r e n c e (p<0.05) but n o t i n D i s p l a y D i f f e r e n c e (p>0.05). C. Mate s e l e c t i o n of s m a l l and medium s i z e d m a l e s g i v e n a c h o i c e  between s m a l l and l a r g e f e m a l e s S m a l l kokanee m a l e s showed no p r e f e r e n c e between t h e s m a l l and l a r g e f e m a l e s i n e i t h e r n e a r n e s s t i m e or d i s p l a y s (p>0.6 f o r Time D i f f e r e n c e ; p>0.1 f o r D i s p l a y D i f f e r e n c e ) . In c o n t r a s t , medium s i z e d m a l e s showed a s t r o n g p r e f e r e n c e f o r l a r g e f e m a l e s 108 (p< 0 . 0 l f o r Time D i f f e r e n c e ; p<0 .00 l f o r D i s p l a y D i f f e r e n c e ) . The p r e f e r e n c e o f s m a l l and medium s i z e d m a l e s d i f f e r e d s i g n i f i c a n t l y (p< 0 . 0 0 l f o r Time D i f f e r e n c e ; p<0 .0 l f o r D i s p l a y D i f f e r e n c e ) . D. Mate s e l e c t i o n of medium and l a r g e m ales when g i v e n a c h o i c e  between medium and l a r g e f e m a l e s Medium males showed no p r e f e r e n c e when g i v e n a c h o i c e between f e m a l e s of t h e i r own s i z e and t h o s e much l a r g e r (p>0.9 f o r Time D i f f e r e n c e ; p>0.2 f o r D i s p l a y D i f f e r e n c e ) . In c o n t r a s t , l a r g e m a l e s showed a s t r o n g p r e f e r e n c e f o r t h e l a r g e f e m a l e s (p<0.05 f o r Time and D i s p l a y D i f f e r e n c e ) . The p r e f e r e n c e s of l a r g e and medium males were s i g n i f i c a n t l y d i f f e r e n t f o r b o t h c h o i c e c r i t e r i a (p< 0 . 0 5 ) . E. The e f f e c t of c o m p e t i t i o n on s m a l l male c h o i c e The s m a l l e s t m a l e s i n Pa s s C r e e k , w h i c h showed no p r e f e r e n c e between s m a l l a nd l a r g e f e m a l e s i n t h e a b s e n c e of c o m p e t i t i o n , p r e f e r r e d t h e s m a l l f e m a l e s when t h e l a r g e f e m a l e was a t t e n d e d by a l a r g e male (p<0 .05 f o r Time D i f f e r e n c e ; p< 0 . 0 l f o r D i s p l a y D i f f e r e n c e ) . 109 Female r e s p o n s e t o t h e p r e s e n t a t i o n o f m a l e s In a l l e x p e r i m e n t s , w i t h t h e e x c e p t i o n o f E x p e r i m e n t A, t h e r e was no s i g n i f i c a n t d i f f e r e n c e i n t h e d i g g i n g b e h a v i o u r of f e m a l e s ( T a b l e 5 ) . D i s c o u n t i n g t h e e x c e p t i o n , t h i s s u g g e s t s t h a t t h e o b s e r v e d male c h o i c e c a n be r e l a t e d t o t h e s i z e o f t h e p r e s e n t e d f e m a l e s and not t o d i f f e r e n t s t a t e s o f f e m a l e a c t i v i t y . S i n c e t h e r a t e of f e m a l e d i g g i n g i s p r o b a b l y r e l a t e d t o f e m a l e r e s p o n s i v e n e s s t o m a l e s i n salmon ( M c C a r t 1970; S c h r o d e r 1981; C h a p t e r 5 ) , t h e s e r e s u l t s s u g g e s t t h e d i f f e r e n t s i z e s o f f e m a l e s were e q u a l l y r e c e p t i v e t o t h e p r e s e n t e d m a l e s . In e x p e r i m e n t A t h e l a r g e s t f e m a l e s dug s i g n i f i c a n t l y f a s t e r t h a n t h e s m a l l e s t f e m a l e s . The d i f f e r e n c e i n t h e d i g g i n g r a t e between f e m a l e s was o p p o s i t e t o t h a t e x p e c t e d on t h e b a s i s of f e m a l e c h o i c e a l o n e . In salmon, f e m a l e s d i g f a s t e r when a c c o m p a n i e d by males l a r g e r t h a n t h e m s e l v e s t h a n when a c c o m p a n i e d by m a l e s s m a l l e r t h a n t h e m s e l v e s ( M c C a r t 1970; S c h r o d e r 1981; C h a p t e r 5 ) . In e x p e r i m e n t A, t h e t e s t m a l e s were s m a l l e r t h a n t h e l a r g e f e m a l e s and l a r g e r t h a n t h e s m a l l f e m a l e s , s u g g e s t i n g t h a t s m a l l e r f e m a l e s s h o u l d have" been more r e c e p t i v e t h a n l a r g e r f e m a l e s t o t h e p r e s e n t a t i o n of t h e males (s e e C h a p t e r 2 ) . Thus, t h e g r e a t e r r a t e of d i g g i n g by t h e l a r g e r f e m a l e s may be r e l a t e d t o g r e a t e r male i n t e r e s t and not s o l e l y t o f e m a l e c h o i c e . 110 T a b l e 5. The mean number and D i f f e r e n c e (+SE) i n d i g s p e r f o r m e d by the s m a l l e s t and l a r g e s t f e m a l e s over t e n m i n u t e s of o b s e r v a t i o n i n i n an e x p e r i m e n t a l a r e n a i n f i v e c h o i c e e x p e r i m e n t s . E x p e r i m e n t Mean number of d i g s by f e m a l e s D i f f e r e n c e Male s i z e s m a l l e s t l a r g e s t N g r o u p P A 3.86 S(S) 7.99 S( L ) -4.13 +0.71 1 16 S <0.001 B 0.05 S 0.00 M 0.05 +0.05 21 s >0.3 1 .47 S 2.33 M -0.86 + 1 .60 15 M >0.6 C 3.85 s 0.05 L 3.80 + 2.30 20 S >0. 1 1 .50 s 1.10 L 0.40 +0.65 10 M >0.5 D 4.30 M 2.50 L 1 .80 + 1 .92 10 M >0.3 1 .20 M 1.10 L 0.10 + 1 .09 10 L >0.9 E 4.00 S 2.43 L 1 .57 + 2.41 14 S >0.5 see T a b l e 4 f o r l e t t e r d e s i g n a t i o n . 111 D i s c u s s i o n E v i d e n c e t h a t male c h o i c e depends on male s i z e P r e v i o u s s t u d i e s on male c h o i c e i n f i s h e s s u g g e s t m a l e s r e s p o n d t o t h e a b s o l u t e s i z e o f f e m a l e s , p r e f e r r i n g t h e l a r g e , hence more f e c u n d , f e m a l e s (Rowland 1982; L o i s e l l e 1982; Downhower and Brown 1981; S a r g e n t e t a l . 1986; B e r g l u n d e t a l . 1986). The r e s u l t s o f t h i s s t u d y show t h a t t h e s i z e of t h e f e m a l e r e l a t i v e t o t h a t of t h e male can a l s o be an i m p o r t a n t f a c t o r i n male c h o i c e . M a l e p r e f e r e n c e f o r l a r g e f e m a l e s i n kokanee i n c r e a s e d w i t h i n c r e a s i n g male s i z e . The s m a l l e s t males d i d n o t d i s c r i m i n a t e between f e m a l e s o f t h e i r own s i z e and t h o s e s u b s t a n t i a l l y l a r g e r , even where t h e r e was a t h r e e f o l d d i f f e r e n c e i n f e m a l e f e c u n d i t y . Medium s i z e d m a l e s p r e f e r r e d l a r g e o v e r s m a l l f e m a l e s but d i d not d i s c r i m i n a t e between f e m a l e s o f t h e i r own s i z e and t h o s e l a r g e r . L a r g e m a l e s p r e f e r r e d l a r g e o v e r medium s i z e d f e m a l e s , i n d i c a t i n g o n l y l a r g e m a les f i n d l a r g e f e m a l e s more a t t r a c t i v e t h a n a l l o t h e r f e m a l e s . (I d i d not a t t e m p t t o d e m o n s t r a t e t h a t l a r g e m ales p r e f e r l a r g e f e m a l e s o v e r s m a l l f e m a l e s . However, t h i s p r e f e r e n c e was a p p a r e n t and formed t h e b a s i s of E x p e r i m e n t E ) . Had a b s o l u t e s i z e been t h e major f a c t o r i n male c h o i c e a l l m a l e s w o u l d have been e x p e c t e d t o p r e f e r t h e l a r g e s t f e m a l e s , y e t t h i s was c l e a r l y n ot t h e c a s e . The s i z e d e p e n d e n t n a t u r e o f male mate c h o i c e o b s e r v e d does 1 1 2 not a p p e a r t o r e s u l t f r o m p r e v i o u s c o n d i t i o n i n g on t h e spawning g r o u n d s . Medium and l a r g e s i z e d f e m a l e s a r e e x t r e m e l y r a r e i n Meadow C r e e k ( p r o b a b l y l e s s t h a n 1 i n 1,000 f e m a l e s ) , whereas a l l s i z e s o f m a l e s and f e m a l e s a r e common i n P a s s C r e e k ( p e r s . o b s . ). T h i s means t h a t t h e s m a l l m a l e s t e s t e d i n Meadow C r e e k were f a r l e s s l i k e l y t o have had p r e v i o u s e x p e r i e n c e w i t h l a r g e r i n d i v i d u a l s t h a n t h o s e t e s t e d i n Pa s s C r e e k , y e t t h e p a t t e r n of mate p r e f e r e n c e o b s e r v e d i n t h e two s t r e a m s was s i m i l a r . M a l e s o f a l l s i z e s g i v e n a c h o i c e between f e m a l e s t h e i r own s i z e and t h o s e l a r g e r d e m o n s t r a t e d no c o n s i s t e n t p r e f e r e n c e between a v a i l a b l e f e m a l e s ( F i g s . 17, 18 and 19). The a t t r a c t i v e n e s s of f e m a l e s t o ma l e s i s s t r o n g l y i n f l u e n c e d by f e m a l e a c t i v i t y p a t t e r n s ( S c h r o d e r 1982). Non-t e r r i t o r i a l f e m a l e s a r e l a r g e l y u n a t t r a c t i v e t o m a l e s . In my e x p e r i m e n t s , I c o n t r o l l e d f o r d i f f e r e n c e s i n t e r r i t o r i a l i t y between f e m a l e s ( s e e methods) and m o n i t o r e d t h e i r n e s t c o n s t r u c t i o n b e h a v i o u r ( d i g g i n g ) t o d e t e r m i n e i f t h e r e were f i n e s c a l e d i f f e r e n c e s i n f e m a l e a c t i v i t y w h i c h c o u l d a c c o u n t f o r t h e o b s e r v e d male p r e f e r e n c e s . Female d i g g i n g r a t e s were s i m i l a r i n most e x p e r i m e n t s ( T a b l e 2 ) , wh i c h s u g g e s t s t h a t d i f f e r e n c e s i n f e m a l e a c t i v i t y do not a c c o u n t f o r t h e male mate p r e f e r e n c e s o b s e r v e d . I r e a c h e d t h e same c o n c l u s i o n i n t h e e x a m i n a t i o n of male c h o i c e between s o c k e y e salmon and kokanee ( C h a p t e r 5 ) . In t h a t s t u d y , a l l s i z e s of m a l e s f o u n d t h e l a r g e , s o c k e y e f e m a l e s a t t r a c t i v e , i n d e p e n d e n t of t h e v a r y i n g s o c k e y e f e m a l e r e s p o n s e , whereas o n l y t h e s m a l l e r m a l e s f o u n d t h e s m a l l , kokanee f e m a l e s 1 1 3 a t t r a c t i v e . The d i s c r i m i n a t i o n a g a i n s t r e l a t i v e l y s m a l l f e m a l e s , s i m i l a r t o t h a t o b s e r v e d i n t h e p r e s e n t s t u d y , was e v i d e n t b o t h when a c h o i c e of f e m a l e s was a v a i l a b l e and when i t was n o t . A measure of f e m a l e a t t r a c t i v e n e s s b a s e d on s i z e of t h e f e m a l e r e l a t i v e t o t h e male may be g e n e r a t e d by c o n s i d e r i n g t h e p r e f e r r e d f e m a l e i n e a c h c h o i c e e x p e r i m e n t as 100% ( f u l l y ) a t t r a c t i v e . The d e g r e e of a t t r a c t i v e n e s s o f t h e n o n - p r e f e r r e d f e m a l e may t h e n be e x p r e s s e d by d i v i d i n g t h e mean t i m e s p e n t n e a r t h e n o n - p r e f e r r e d f e m a l e by t h e mean t i m e s p e n t n e a r t h e p r e f e r r e d f e m a l e . The r e s u l t i n g measure i s a s y m m e t r i c . F e m a l e s a p p e a r t o i n c r e a s e i n a t t r a c t i v e n e s s t o males as t h e y i n c r e a s e i n s i z e up t o t h a t of t h e male ( F i g . 2 0 ) . Beyond t h e l e n g t h o f the male a l l f e m a l e s a r e e q u a l l y a t t r a c t i v e . T h i s p a t t e r n was e v i d e n t o v e r t h e s m a l l e s t ( E x p e r i m e n t A) as w e l l a s t h e l a r g e s t s i z e r a n g e s ( E x p e r i m e n t s C and D) of f i s h e s e x amined. A s i m i l a r p a t t e r n of a t t r a c t i v e n e s s of f e m a l e s was e v i d e n t i n t h e e x a m i n a t i o n o f kokanee and s o c k e y e male c h o i c e ( C h a p t e r 5 ) . Note t h a t t h i s measure of a t t r a c t i o n d o e s n o t r e s u l t f r o m any r e l a t i o n s h i p between f e r t i l i z a t i o n e f f i c i e n c y and r e l a t i v e s i z e of p a r t n e r s i n s a l m o n i d s . A l l m a l e s , i n d e p e n d e n t o f t h e i r s i z e , a r e e q u a l l y c a p a b l e of s u c c e s s f u l l y f e r t i l i z i n g t h e eggs o f l a r g e f e m a l e s i n t h e a b s e n c e o f c o m p e t i t i o n ( M c C a r t 1970; H u t c h i n g s and Myers 1985; Maekawa and O n o z a t o 1986). T h i s measure of a t t r a c t i o n s u g g e s t s male c h o i c e i n salmon 1 1 4 F i g u r e 20. Measure of a t t r a c t i v e n e s s of f e m a l e s t o m a l e s b a s e d on t h e i r r e l a t i v e s i z e s . See t e x t f o r method o f c a l c u l a t i o n of % a t t r a c t i o n . The c o m b i n a t i o n s of l e t t e r s c o r r e s p o n d i n o r d e r t o : 1) t h e e x p e r i m e n t (A, B, C, D); 2) t h e s i z e g r o u p o f males t e s t e d (S, M, L ) ; and 3) t h e s i z e g r o u p of t h e f e m a l e s i n q u e s t i o n (S, M, L, S ( S ) , S(D). See T a b l e 1 f o r l e t t e r d e s i g n a t i o n . Note t h a t f o r e a c h e x p e r i m e n t and male s i z e g r o u p t e s t e d t h e r e a r e two s i z e g r o u p s of f e m a l e s f o r w h i c h % a t t r a c t i o n i s c a l c u l a t e d . The l i n e t h r o u g h t h e p o i n t s was f i t t e d by e y e . 0 . 4 0 . 6 0 . 8 1 . 0 1 . 2 1 . 4 1 . 6 1 . 8 2 . 0 Female Fork L e n g t h / Male F o r k L e n g t h 1 1 6 i n v o l v e s a v a r i a t i o n o f d e c i s i o n s s u g g e s t e d by ' t h r e s h o l d ' m o d e l s o f mate c h o i c e ( J a n e t o s 1980; W i t t e n b e r g e r 1983). F o r e a c h male, f e m a l e s i n c r e a s e i n a t t r a c t i v e n e s s w i t h i n c r e a s i n g s i z e u n t i l t h e y r e a c h a t h r e s h o l d i n a t t r a c t i v e n e s s a t t h e m a l e ' s own s i z e . The i n t e r e s t i n g f e a t u r e of male c h o i c e i n salmon i s t h a t t h e t h r e s h o l d l e v e l v a r i e s d e p e n d e n t on male s i z e and hence t h e s e l e c t i o n p r e s s u r e f o r i n c r e a s e d f e m a l e s i z e g e n e r a t e d by male c h o i c e w i l l be l o w e r t h a n p r e d i c t e d i n models of mate s e l e c t i o n b a s e d on a b s o l u t e s i z e or r e l a t i v e s i z e w i t h i n t h e sex b e i n g s e l e c t e d ( e . £. Lande 1981; K i r k p a t r i c 1982; S e g e r 1985; H e i s l e r 1985). As l o n g as t h e r e a r e s m a l l m a l e s i n salmon p o p u l a t i o n s s m a l l f e m a l e s w i l l have a t l e a s t some males w h i c h f i n d them f u l l y a t t r a c t i v e . P o s s i b l e a d a p t i v e s i g n i f i c a n c e of s i z e d e p e n d e n t male mate  c h o i c e The r a p i d i n c r e a s e i n t h e a t t r a c t i v e n e s s of f e m a l e s w i t h i n c r e a s i n g f e m a l e s i z e ( w h i c h a r e s m a l l e r t h a n a male i n s i z e ) c o r r e s p o n d s t o t h e i n c r e a s e i n r e p r o d u c t i v e p o t e n t i a l w i t h s i z e i n f e m a l e s . R e p r o d u c t i v e p o t e n t i a l i n c r e a s e s w i t h s i z e i n f e m a l e s a l m o n i d s b e c a u s e of t h e s t r o n g r e l a t i o n s h i p between body s i z e and f e c u n d i t y , egg s i z e ( W a l l a c e and A a s j o r d 1984), p a r e n t a l c a r e (van den Berghe and G r o s s 1984), and c o m p e t i t i v e a b i l i t y ( C h a p t e r 1 ) . F e m a l e s s m a l l e r t h a n a male a r e u s u a l l y a v a i l a b l e f o r m a t i n g on t h e spawning g r o u n d s b e c a u s e t h e y t e n d t o be c o u r t e d by s m a l l e r , d i s p l a c e a b l e males (Hanson and S m i t h 1 1 7 1967; M c C a r t 1970; C a m p b e l l 1977; J o n s s o n and H i n d a r 1982). T h a t m a l e s p r e f e r t h e l a r g e r f e m a l e s when g i v e n a c h o i c e between f e m a l e s s m a l l e r t h a n t h e m s e l v e s and t h o s e s i m i l a r t o t h e i r own s i z e , s u g g e s t s t h a t s e l e c t i o n f a v o u r s males t h a t t a k e a d v a n t a g e of t h e g r e a t e r r e p r o d u c t i v e p o t e n t i a l o f l a r g e r f e m a l e s . The p l a t e a u i n a t t r a c t i v e n e s s of f e m a l e s l a r g e r t h a n a male does not c o r r e s p o n d t o t h e s t r o n g p o s i t i v e r e l a t i o n s h i p between f e m a l e s i z e and r e p r o d u c t i v e p o t e n t i a l . However, f e m a l e s a r e not e q u a l l y a v a i l a b l e t o a l l m a l e s on t h e spawning g r o u n d s ( s e e r e f e r e n c e s a b o v e ) . The l a r g e r a f e m a l e i s t h a n a male t h e l o w e r t h e p r o b a b i l i t y t h a t a male w i l l s u c c e s s f u l l y c o u r t h e r . The a v a i l a b i l i t y of r e l a t i v e l y l a r g e f e m a l e s d e c r e a s e s w i t h i n c r e a s i n g f e m a l e s i z e f o r two r e a s o n s . F i r s t , r e l a t i v e l y l a r g e f e m a l e s a t t r a c t r e l a t i v e l y l a r g e m a l e s , w h i c h p o s s e s s a s t r o n g a d v a n t a g e i n c o m p e t i t i o n f o r a c c e s s t o f e m a l e s . Second, f e m a l e s a c c o m p a n i e d by males w h i c h a r e s m a l l e r t h a n t h e m s e l v e s t a k e a l o n g e r t i m e t o spawn t h a n when a c c o m p a n i e d by m a l e s of t h e i r own s i z e o r l a r g e r (McCart 1970; S c h r o d e r 1981; C h a p t e r s 2 and 5 ) . T h i s f e m a l e b e h a v i o u r i n c r e a s e s t h e t i m e f o r l a r g e r m a l e s t o f i n d l a r g e f e m a l e s and d i s p l a c e s m a l l e r m a l e s ( S c h r o d e r 1981; C h a p t e r 2 ) . Once d i s p l a c e d , m a l e s may l e a v e t o s e a r c h f o r o t h e r female.s, o r t h e y may become ' s n e a k s ' t o t h e spawning p a i r . As ' s n e a k s ' t h e y u s u a l l y f e r t i l i z e o n l y a s m a l l p r o p o r t i o n of t h e f e m a l e ' s eggs ( S c h r o d e r 1981; Chebanov e t a l . 1983; Maekawa and O n o z a t o 1986). T h e r e f o r e , t h e p l a t e a u i n f e m a l e a t t r a c t i v e n e s s may have e v o l v e d as a r e s u l t o f a t r a d e o f f between i n c r e a s i n g 1 18 r e p r o d u c t i v e p o t e n t i a l w i t h s i z e i n f e m a l e s and t h e i r d e c r e a s i n g a v a i l a b i l i t y . I t i s w e l l known t h a t t h e m a g n i t u d e o f v a r i a t i o n i n t h e q u a l i t y of mates i s an i m p o r t a n t f a c t o r i n t h e e v o l u t i o n of v a r y i n g s t r a t e g i e s o f mate c h o i c e b o t h between s e x e s and between s p e c i e s ( T r i v e r s 1972; P a r k e r 1983). Even where t h e r e i s l i m i t e d p a r e n t a l i n v e s t m e n t by one sex ( u s u a l l y m a l e s ) , i f t h e v a r i a t i o n i n mate q u a l i t y i n t h e o p p o s i t e sex i s g r e a t , mate c h o i c e may e v o l v e ( P a r k e r 1983). In salmon, m a l e s i n v e s t l i t t l e i n t h e i r o f f s p r i n g but t h e r e i s g r e a t v a r i a b i l i t y i n f e m a l e q u a l i t y . The e v i d e n c e p r e s e n t e d h e r e s u g g e s t s t h a t male c h o i c e i n salmon has e v o l v e d i n r e s p o n s e t o v a r i a t i o n i n a v a i l a b l e f e m a l e q u a l i t y r a t h e r t h a n t h e v a r i a n c e i n a b s o l u t e f e m a l e q u a l i t y as i s o f t e n c o n s i d e r e d i n e m p i r i c a l s t u d i e s o f mate c h o i c e ( s e e S e a r c y 1982; H a l l i d a y 1983). Male s e l e c t i v i t y i n c r e a s e s w i t h i n c r e a s i n g male s i z e i n s a l m o n , as d o e s t h e r a n g e i n s i z e of p o t e n t i a l mates. The s m a l l e s t m a l e s a r e t h e l e a s t s e l e c t i v e , h a v i n g t h e n a r r o w e s t r a n g e o f p o t e n t i a l mates, whereas t h e l a r g e s t m ales a r e t h e most s e l e c t i v e , h a v i n g t h e w i d e s t range o f p o t e n t i a l m ates. The p a t t e r n o f a s s o c i a t i o n of m a l e s and f e m a l e s on t h e spawning  g r o u n d s The e v i d e n c e t h a t male mate p r e f e r e n c e i s d e p e n d e n t on male s i z e i s c o n s i s t e n t w i t h two p a t t e r n s of a s s o c i a t i o n between male 119 and f e m a l e salmon on t h e spawning g r o u n d s . F i r s t , i t i s common i n salmon f o r t h e number of m a l e s a r o u n d f e m a l e s t o i n c r e a s e w i t h i n c r e a s i n g f e m a l e s i z e (Hanson and S m i t h 1967; M c C a r t 1970; C a m p b e l l 1977; J o n s s o n and H i n d a r 1982; S a r g e n t e t a l . 1986). P r e v i o u s s t u d i e s have s u g g e s t e d t h i s i n d i c a t e s a l l m a l e s p r e f e r t h e l a r g e s t f e m a l e s ( M c C a r t 1970; S a r g e n t e t a l . 1986). My r e s u l t s s u g g e s t an a l t e r n a t i v e i n t e r p r e t a t i o n . S i m p l y , t h a t as f e m a l e s i z e i n c r e a s e s , t h e s i z e r a n g e (and number) o f males w h i c h f i n d t h e s e f e m a l e s f u l l y a t t r a c t i v e a l s o i n c r e a s e s . S m a l l f e m a l e s a r e f u l l y a t t r a c t i v e t o o n l y t h e s m a l l e s t m a l e s , whereas l a r g e f e m a l e s a r e f u l l y a t t r a c t i v e t o a l l m a l e s . T h e r e f o r e , t h e s e r e s u l t s p r e d i c t l a r g e f e m a l e s s h o u l d a t t r a c t more m a l e s , i n a c c o r d a n c e w i t h t h e p a t t e r n o b s e r v e d i n n a t u r e , even t h o u g h l a r g e f e m a l e s a r e a c t u a l l y p r e f e r r e d o v e r a l l o t h e r f e m a l e s o n l y by l a r g e m a l e s . Second, i n salmon t h e s e x e s o f t e n p a i r a s s o r t a t i v e l y by s i z e (Hanson and S m i t h 1967; M c C a r t 1970; C a m p b e l l 1977; J o n s s o n and H i n d a r 1982). My r e s u l t s s u g g e s t a d e g r e e of a s s o r t a t i v e m a t i n g by s i z e i s e x p e c t e d t h r o u g h male c h o i c e d e p e n d e n t on male s i z e . S m a l l m a l e s a r e e q u a l l y l i k e l y t o mate w i t h f e m a l e s t h e i r own s i z e and l a r g e r when g i v e n a c h o i c e , whereas -large m a l e s a r e u n l i k e l y t o mate w i t h f e m a l e s s m a l l e r t h a n t h e m s e l v e s . A s s o r t a t i v e m a t i n g by s i z e i s f u r t h e r augmented by male i n t r a s e x u a l c o m p e t i t i o n . Once a l a r g e male has p a i r e d w i t h a l a r g e f e m a l e , a c c e s s by s m a l l e r m a l e s i s r e s t r i c t e d , i n c r e a s i n g t h e p r o b a b i l i t y t h a t s m a l l males w i l l mate w i t h f e m a l e s n e a r e r 120 t h e i r own s i z e . The r e s u l t s o f e x p e r i m e n t E s u p p o r t t h i s i n t e r p r e t a t i o n . S m a l l m a l e s d e m o n s t r a t e d no p r e f e r e n c e between s m a l l and l a r g e f e m a l e s i n t h e a b s e n c e o f c o m p e t i t o r s but p r e f e r r e d s m a l l f e m a l e s when l a r g e f e m a l e s were a c c o m p a n i e d by a l a r g e m a l e s . Female c h o i c e and f e m a l e i n t r a s e x u a l c o m p e t i t i o n a l s o l i k e l y c o n t r i b u t e t o a s s o r t a t i v e m a t i n g i n salmon ( S c h r o d e r 1981; J o n s s o n and H i n d a r 1982; C h a p t e r s 1, 2 and 5 ) . C o m p a r i s o n o f male c h o i c e i n salmon and o t h e r f i s h e s S i z e d e p e n d e n t ..male mate p r e f e r e n c e s have n o t been documented i n s t u d i e s on f i s h e s , a l t h o u g h i t i s s t r o n g l y s u g g e s t e d i n c i c h l i d s ( B a r l o w 1968; McKaye 1986). I b e l i e v e t h e r e a r e two r e a s o n s f o r t h i s . F i r s t , t o my knowledge, t h e q u e s t i o n has not p r e v i o u s l y been e x p e r i m e n t a l l y a d d r e s s e d . S e c o n d , t h e m a t i n g s y s t e m of f i s h e s p r e v i o u s l y e x p e r i m e n t a l l y examined a r e s i m i l a r t o e a c h o t h e r and d i f f e r e n t from t h a t o f s a l m o n . In m o t t l e d s c u l p i n s , C o t t u s b a i r d i , t h r e e - s p i n e d s t i c k l e b a c k s , G a s t e r o s t e o u s a c u l e a t u s , and p u p f i s h , C y p r i n o d o n  m a c u l a r i u s c a l i f o r n i e n s i s , t h e m a l e s e s t a b l i s h and d e f e n d t e r r i t o r i e s w h i c h females. a p p r o a c h f o r s p a w n i n g . M a l e s p r e f e r e n t i a l l y c o u r t t h e l a r g e s t f e m a l e s . C o u r t s h i p i s b r i e f , and f e m a l e s l e a v e t h e t e r r i t o r y i m m e d i a t e l y a f t e r s pawning (Downhower and Brown 1981; Rowland 1982; L o i s e l l e 1982; S a r g e n t e t a l . 1986). S i m i l a r l y , i n p i p e f i s h e s ( F a m i l y S y n g n a t h i d a e ) , f e m a l e s a p p r o a c h males on t h e i r s m a l l homeranges ( G r o n e l l 1984) and males p r e f e r e n t i a l l y s e l e c t t h e l a r g e r of a p p r o a c h i n g 121 f e m a l e s w i t h w h i c h t h e y spawn a f t e r a r e l a t i v e l y b r i e f c o u r t s h i p p e r i o d ( B e r g l u n d e t a l . 1986). I n salmon, f e m a l e s a r e t e r r i t o r i a l and ma l e s u s u a l l y a p p r o a c h f e m a l e s f o r spa w n i n g . C o u r t s h i p i s e x t e n d e d , o f t e n f o r d a y s , and w h i l e m a l e s w i l l l e a v e f e m a l e s a f t e r a s i n g l e spawning most a p p e a r t o r e m a i n w i t h t h e f e m a l e u n t i l she has c o m p l e t e d h e r spawning ( a p p r o x i m a t e l y 2-4 sp a w n i n g s i n k o k a n e e ) . T h e r e f o r e w h i l e p r e f e r e n c e f o r t h e l a r g e s t f e m a l e may r e s u l t i n immediate r e p r o d u c t i v e s u c c e s s i n s t i c k l e b a c k s , s c u l p i n s , p u p f i s h and p i p e f i s h , t h e same i s not t r u e i n salmon, where e x t e n d e d c o u r t s h i p and d i r e c t c o m p e t i t i o n f o r a c c e s s t o f e m a l e s i n c r e a s e t h e p r o b a b i l i t y t h a t s m a l l m a l e s w i l l u l t i m a t e l y be d i s p l a c e d when i n p u r s u i t o f t h e l a r g e s t f e m a l e s . C h o i c e d e p e n d e n t on i n d i v i d u a l a b i l i t y t o o b t a i n mates ( s i z e ) a p p e a r s a d v a n t a g e o u s i n t h e s e m e l p a r o u s P a c i f i c salmon m a t i n g s y s t e m , where t i m e and e n e r g y a r e e x t r e m e l y l i m i t e d , r a p i d l y d i m i n i s h i n g r e s o u r c e s ( s e e van den B e r g h e and G r o s s 1986). I f male c h o i c e were d e p e n d e n t on f e m a l e a b s o l u t e s i z e (_i. e. c o m p a r i s o n s among f e m a l e s , i n d e p e n d e n t of male s i z e ) , a l l mal e s would seek out t h e l a r g e s t a v a i l a b l e f e m a l e s ('best o f n' s t r a t e g y ) . In d o i n g s o , a l l but t h e l a r g e s t m a l e s would f a c e t h e r i s k o f l e a r n i n g t h r o u g h c o s t l y e x p e r i e n c e o f t h e l i m i t e d a v a i l a b i l i t y of l a r g e f e m a l e s . The c o s t s of s u c h s e a r c h i n g would be i n v e r s e l y r e l a t e d t o male s i z e ; t h e s m a l l e s t m a l e s would end up s e a r c h i n g t h e most b e f o r e b e i n g d i s p l a c e d t o t h e s m a l l e s t f e m a l e s . By s e l e c t i n g mates d e p e n d e n t on t h e i r a b i l i t y 1 22 t o o b t a i n mates ( i _ . e. t h e i r own s i z e ) , i n d i v i d u a l male salmon r e d u c e t h e i r s e a r c h i n g c o s t s and t h u s i n c r e a s e t h e t i m e and e n e r g y a v a i l a b l e t o be s p e n t i n c o u r t s h i p and d e f e n s e o f a c c e s s t o f e m a l e s . 1 23 CHAPTER 4 A BIOCHEMICAL GENETIC COMPARISON OF SOCKEYE SALMON AND KOKANEE I n t r o d u c t i o n The P a c i f i c salmon Q n c o r h y n c h u s n e r k a o c c u r s i n two d i s t i n c t f o r m s , t h e anadromous s o c k e y e salmon and t h e non-anadromous kokanee. S o c k e y e salmon t y p i c a l l y s p e n d t h e i r f i r s t y e a r of l i f e ( sometimes l o n g e r ) i n a l a k e b e f o r e m i g r a t i n g t o t h e o c ean whereas kokanee r e m a i n i n a l a k e t h r o u g h o u t t h e i r l i f e t i m e . S o c k e y e u s u a l l y a t t a i n a t l e a s t t w i c e t h e l e n g t h o f kokanee a t m a t u r i t y , l a r g e l y b e c a u s e of t h e d i f f e r e n c e i n p r o d u c t i v i t y between t h e m a r i n e and f r e s h w a t e r e n v i r o n m e n t s ( F o e r s t e r 1968). S o c k e y e salmon and kokanee p o p u l a t i o n s o c c u r e i t h e r t o g e t h e r or s e p a r a t e l y ( R i c k e r 1940; N e l s o n 1968a). Where t h e y o c c u r s y m p a t r i c a l l y , spawning u s u a l l y o c c u r s i n s e p a r a t e l o c a l i t i e s and a t d i f f e r e n t t i m e s ( R i c k e r 1940; N e l s o n 1968a). In a few l o c a l i t i e s s o c k e y e and kokanee spawn i n t h e same p l a c e a t t h e same t i m e ( R i c k e r 1940; Hanson and S m i t h 1967; M c C a r t 1970). I t i s g e n e r a l l y a c c e p t e d t h a t kokanee have o r i g i n a t e d f r o m s o c k e y e on numerous i n d e p e n d e n t o c c a s i o n s ( R i c k e r 1940, 1959, 1972; N e l s o n 1968a; Behnke 1972). T h i s c o n c l u s i o n i s s u p p o r t e d t h r o u g h an e x a m i n a t i o n o f t h e d i s t r i b u t i o n of t h e two forms ( R i c k e r 1940; N e l s o n 1968a) and by o b s e r v a t i o n s ' t h a t non-anadromous p o p u l a t i o n s of 0. n e r k a have a p p e a r e d a f t e r s o c k e y e 124 salmon were i n t r o d u c e d t o l a k e s p r e v i o u s l y b a r r e n of t h e s p e c i e s ( R i c k e r 1959, 1972; S c o t t 1984). I t seems more p r o b a b l e t h a t kokanee i n J a p a n , S i b e r i a , and w e s t e r n N o r t h A m e r i c a ( i n c l u d i n g V a n c o u v e r I s l a n d ) have a r i s e n l a r g e l y f r o m t h e m a r i n e d i s p e r s a l o f s o c k e y e salmon f o l l o w i n g t h e r e t r e a t o f t h e W i s c o n s i n c o n t i n e n t a l i c e masses, t h a n t h a t t h e y have a r i s e n s o l e l y t h r o u g h t h e f r e s h w a t e r d i s p e r s a l of kokanee. T h e r e i s e v i d e n c e o f g e n e t i c d i v e r g e n c e between s y m p a t r i c s o c k e y e and kokanee p o p u l a t i o n s ( N e l s o n 1968b; M c C a r t 1970) and v a r i o u s mechanisms have been p r o p o s e d t o a c c o u n t f o r t h i s . S e l e c t i v e p r e s s u r e s i n f r e s h w a t e r and m a r i n e e n v i r o n m e n t s p r o b a b l y d i f f e r g r e a t l y , p r o m o t i n g g e n e t i c d i f f e r e n t i a t i o n between t h e forms ( R i c k e r 1940). G e n e t i c d i f f e r e n t i a t i o n i s f u r t h e r p r o m o t e d by t h e t e n d e n c y o f s y m p a t r i c s o c k e y e and kokanee t o spawn i n s e p a r a t e l o c a t i o n s a t d i f f e r e n t t i m e s , l i m i t i n g gene f l o w between t h e forms ( R i c k e r 1940). Where spawning i s c o i n c i d e n t , gene f l o w i s p r o b a b l y g r e a t l y r e s t r i c t e d t h r o u g h a s s o r t a t i v e m a t i n g by form, a s s o c i a t e d w i t h t h e g r e a t s i z e d i f f e r e n c e between mature s o c k e y e and kokanee (Hanson and S m i t h 1967; M c C a r t 1970; F o o t e and L a r k i n , i n p r e s s ) . S o c k e y e m a l e s mate a l m o s t e x c l u s i v e l y w i t h s o c k e y e f e m a l e s , whereas kokanee m a l e s mate e i t h e r w i t h kokanee f e m a l e s o r a t t e m p t t o f e r t i l i z e t h e eggs of s o c k e y e f e m a l e s by " s n e a k i n g " . In t h i s s t u d y , t h e r e s u l t s o f an e l e c t r o p h o r e t i c c o m p a r i s o n of s y m p a t r i c and a l l o p a t r i c s o c k e y e and kokanee p o p u l a t i o n s i n 1 25 B r i t i s h C o l u m b i a a r e u s e d t o a d d r e s s q u e s t i o n s c o n c e r n i n g t h e r e c e n t a n c e s t r y and g e n e t i c s i m i l a r i t y o f t h e two f o r m s . I f d i f f e r e n t i a t i o n has been r e c e n t , s o c k e y e and kokanee s h o u l d be v e r y s i m i l a r g e n e t i c a l l y . I f one o r b o t h forms have g i v e n r i s e t o t h e o t h e r form on numerous o c c a s i o n s t h e n s o c k e y e and kokanee s h o u l d be g e n e t i c a l l y i n t e r r e l a t e d r a t h e r t h a n members of two d i s t i n c t g e n e t i c l i n e a g e s . A d d i t i o n a l l y , i f kokanee have a r i s e n i n s y m p a t r y w i t h s o c k e y e , s y m p a t r i c s o c k e y e and kokanee may be e x p e c t e d t o be g e n e t i c a l l y more s i m i l a r t o e a c h o t h e r t h a n t h e y a r e t o t h e i r r e s p e c t i v e forms i n o t h e r l a k e s . S o c k e y e and kokanee p o p u l a t i o n s were sampled from t h r o u g h o u t B r i t i s h C o l u m b i a , i n c l u d i n g t h r e e l o c a l i t i e s where t h e forms spawn s y m p a t r i c a l l y . S y m p a t r i c g e n e t i c d i f f e r e n t i a t i o n would seem t o be t h e l e a s t l i k e l y i n l o c a l i t i e s where s o c k e y e and kokanee spawn s y m p a t r i c a l l y b e c a u s e o f t h e g r e a t o p p o r t u n i t y f o r gene f l o w between t h e f o r m s . G e n e t i c d i f f e r e n t i a t i o n i n t h e s e l o c a l i t i e s would s u g g e s t t h a t mechanisms i n a d d i t i o n t o s e g r e g a t i o n t o d i f f e r e n t s pawning g r o u n d s a r e i m p o r t a n t i n t h e g e n e t i c d i f f e r e n t i a t i o n o f s a l m o n i d p o p u l a t i o n s . 126 Methods Kokanee and s o c k e y e were e a c h c o l l e c t e d from 11 and 12 l o c a l i t i e s , r e s p e c t i v e l y , i n B r i t i s h C o l u m b i a ( F i g . 21, T a b l e 6 ) . F i v e p o p u l a t i o n s were sample d a n n u a l l y f o r two o r t h r e e y e a r s . A l l s a m p l e s , w i t h t h e e x c e p t i o n s of t h o s e from C u l t u s and Cowichan l a k e s and Okanogan R i v e r , were c o l l e c t e d w i t h g a f f s and s m a l l s e i n e s i n s t r e a m s where f i s h were s p a w n i n g . S o c k e y e s m o l t s were c o l l e c t e d by t r a p i n t h e o u t l e t o f C u l t u s L a k e . Kokanee were c a p t u r e d w i t h a m i d - w a t e r t r a w l i n Cowichan L a k e . E l e c t r o p h o r e t i c d a t a f o r t h e Okanogan R i v e r s o c k e y e were t a k e n from U t t e r e_t a l . ( 1 9 8 4 ) . Where spawning p o p u l a t i o n s were s m a l l (<10,000 f i s h ) , m a i n l y m o r i b u n d o r f r e s h l y dead s p e c i m e n s were c o l l e c t e d . Where s o c k e y e and kokanee spawned s y m p a t r i c a l l y , t h e y were d i s t i n g u i s h e d by s i z e ; most s o c k e y e were g r e a t e r t h a n 45 cm f o r k l e n g t h and kokanee r a n g e d from 16-28 cm. J a c k s o c k e y e ( p r e c o c i o u s m a l e s ) were r a r e i n t h e p o p u l a t i o n s sampled and were g r e a t e r t h a n 30 cm f o r k l e n g t h . H e a r t , l i v e r , eye and m u s c l e t i s s u e s were c o l l e c t e d from f r e s h l y k i l l e d f i s h , o r r a r e l y , from t h o s e r e c e n t l y dead as j u d g e d f r om r e d n e s s of t h e g i l l s . Samples were p l a c e d on i c e i m m e d i a t e l y and f r o z e n a s q u i c k l y a s p o s s i b l e , u s u a l l y w i t h i n 12 h o u r s of c o l l e c t i o n , and s t o r e d a t -40 C u n t i l a s s a y e d . Samples were a s s a y e d e l e c t r o p h o r e t i c a l l y u s i n g s t a n d a r d e x t r a c t i o n and g e l t e c h n i q u e s ( e . £ . May e t a_l. 1979). The s y s t e m of n o m e n c l a t u r e s u g g e s t e d by A l l e n d o r f and U t t e r (1979) was u s e d t o F i g u r e 21. The l o c a t i o n and form o f 0. n e r k a p o p u l a t i o n s sampled f o r e l e c t r o p h o r e s i s . P o p u l a t i o n numbers c o r r e s p o n d t o t h o s e i n T a b l e 6. 128 o> CN1 T a b l e 6 . A l l e l e f r e q u e n c i e s a t p o l y m o r p h i c l o c i f o r s o c k e y e and kokanee p o p u l a t i o n s sampled in B r i t i s h C o l u m b i a S i t e Form Yr PGM-1 N PGM-2 N LDH-4 N GL-2 N ALAT N (100) (100) (100) (115) (85) (100) (91) (100) (108) (95) C o a s t a l P o p u l a t i o n s 1. C o w i c h a n L . K 85 0 . 460 150 0 .840 150 1 .000 0 .000 0, ,000 150 2 . C u l t u s L. S 85 0 . 147 158 0 .837 95 1 .000 0 .000 0. ,000 99 3 . Chewhat L . S 85 0 . 375 100 0 .865 100 1 .000 0 .000 0. .000 100 Upper F r a s e r R i v e r P o p u l a t i o n s 4 . H o r s e f l y R. S 85 0 . 624 93 0 .805 100 1 .000 0 .000 0, .000 100 0 .995 96 0. .330 0. ,569 0. .000 0. 101 94 5. E a g l e R. K 86 0 . 348 99 0 .828 99 1 .000 0 .000 0. OOO 99 1 .000 99 0. ,505 0. ,111 0. . 354 0. 030 99 6 . L . Shuswap R . S 83 0 . 414 99 0 .842 101 0 .995 0 .005 0. ,000 97 1 , .000 80 0. , 172 0. 754 0. .030 0. ,045 67 7 . K 83 0 . 132 76 0 .842 76 0 .987 0 .006 0. ,006 77 1 , .000 78 0. 355 0. , 158 0, ,480 0. 007 99 K 86 0 . 142 53 0 . 783 53 0 .991 0 .009 0. .000 58 0. ,336 0. 052 0, .586 0. 026 58 8 . M. Shuswap R . S 86 0 . 583 144 0 .870 142 0 .993 0 .007 0. ,000 145 1 . .000 141 0. . 132 0. .688 0, ,066 0. 115 144 9 . T a k l a L. K 82 0 . 357 77 0 .903 77 1 .000 0 .000 0. ,000 76 K 83 0 . 340 38 V 0 .865 381 1 .000 0 .000 0. .000 300 K 85 0 . 367 124 0 .846 123 1 .000 0 .OOO 0. ,000 124 0 .992 1 19 0. 721 0. , 1 19 0 .000 0. , 160 122 10. , T a k l a L. S 83 0 . 467 83 0 .837 83 1 .OOO 0 .000 0. .000 79 S 85 0 . 588 97 0. .813 96 1 .000 0 .000 0. ,000 97 1 , .000 100 0. , 149 0. ,819 0, .000 0. ,032 94 C o l u m b i a R i v e r P o p u l a t i o n s 1 1 . . Meadow C r . K 83 0 . 586 151 0. .870 151 0, .993 0 .003 0. .003 151 12 . . R e d f i s h C r . K 83 0 . 595 42 0 .964 42 0, .977 0 .023 0. .000 38 13 . Arrow L . K 85 0 . 575 100 0 .910 100 1. .000 0 .000 0. ,000 98 0, .995 100 0. ,360 0, .615 0 .000 0. ,025 100 14 . . Okanogan R. S -- 0 . 493 71 0. .782 71 1, .000 0. .000 0. ,000 72 1 , .000 62 0. ,285 0. ,590 0, .007 0. ,000 72 15 . , Skaha L . K 83 0 . 284 88 0, .875 88 1, .000 0 .000 0. ,000 85 Skeena R i v e r P o p u l a t i o n s ( B a b i n e Lake) 16. F u l t o n R. S 85 0 . 158 291 0. .776 290 0. .973 0 .017 0. ,010 293 17 . T ach ek C r . S 85 0 . 290 50 0. .800 50 0. .940 0. .010 0. .050 50 18 . K 85 0 . 238 103 0. .607 103 0, .861 0 .000 0. , 139 102 1 . .000 35 0. ,500 0. .390 0 .000 0. , 1 10 41 19. P i e r r e C r . s 84 0 . 215 100 0, .735 100 0. .968 0 .016 0. .016 94 s 85 0 . 202 94 0, .766 94 0. .953 0 .010 0. ,036 92 0, .989 91 0. ,529 0. .382 0 .006 0. .082 85 20. P i e r r e C r . K 84 0 . 270 1 1 1 0. .698 1 1 1 0. .850 0 .000 0. 150 1 10 K 85 0 . 228 1 14 0. .702 1 14 0, .870 0 .004 0. , 126 1 15 0. .980 74 0. ,649 0. ,299 0, .000 0. .052 77 21 . T w a i n C r . K 85 o. 239 92 0. .678 101 0, . 865 0 .005 0. , 130 95 22 . s 85 0 . 214 103 0. .830 103 0, .971 0 .010 0. ,019 103 23 . P i n k u t C r . s 85 0 . 231 193 0 .725 193 0. .972 0 .005 0. ,025 198 1 30 d e s i g n a t e l o c i and a l l e l e s ( T a b l e 7 ) , t h e same n o m e n c l a t u r e has been p r e v i o u s l y u s e d f o r s o c k e y e salmon p o p u l a t i o n s ( G r a n t e t a l . 1980; U t t e r e t a l . 1984; Wilmot and B u r g e r 1985). A few samp l e s were a s s a y e d a t 24 l o c i b u t t h e m a j o r i t y were a s s a y e d a t a s u b s e t of 4 o r 8 l o c i known t o be p o l y m o r p h i c i n a t l e a s t some s o c k e y e and kokanee p o p u l a t i o n s . A l l 27 samples were a s s a y e d a t Pgm-1, Pgm-2, Ldh-4, and A a t - 3 and 16 were a l s o a s s a y e d a t Ada-2, P g i and Sdh. In a d d i t i o n , 12 o f t h e s e samples were r e a s s a y e d a t G l - 2 and A l a t ( p r e v i o u s l y d e s i g n a t e d G p t -2 ; t h i s l o c u s had been t o o d i f f i c u l t t o s c o r e r e l i a b l y u n t i l a new s t a i n i n g p r o c e d u r e was d e v e l o p e d by P. A e b e r s o l d ( N o r t h w e s t and A l a s k a F i s h e r i e s C e n t e r , 2725 M o n t l a k e B o u l e v a r d E a s t , S e a t t l e , WA 98112, p e r s . comm. t o C. C. Wood, P a c i f i c B i o l o g i c a l S t a t i o n , Nanaimo, B . C . ) . D i f f e r e n c e s i n g e n o t y p e f r e q u e n c i e s between y e a r s and among p o p u l a t i o n s were t e s t e d by l i k e l i h o o d r a t i o (_i. e. , G - t e s t , S o k a l and R o h l f 1981) f o r i n d i v i d u a l l o c i and a l l l o c i c o n s i d e r e d s i m u l t a n e o u s l y ( u s i n g m o d i f i e d c r i t i c a l v a l u e s f o r m u l t i p l e c o m p a r i s o n s ) . G e notype f r e q u e n c i e s w i t h i n p o p u l a t i o n s were compared w i t h t h o s e e x p e c t e d under H a r d y - W e i n b e r g e q u i l i b r i u m u s i n g t h e C h i - s q u a r e d g o o d n e s s - o f - f i t t e s t . A l l e l e f r e q u e n c i e s a t e i t h e r t h r e e t o f i v e p o l y m o r p h i c l o c i , d e p e n d i n g on t h e s a m p l e s , were u s e d t o c o n s t r u c t s i m i l a r i t y phenograms u s i n g t h e u n b i a s e d g e n e t i c i d e n t i t y s t a t i s t i c ( N e i 1978) and t h e u n w e i g h t e d p a i r g r o u p methods ( S n e a t h and S o k a l 1973). 131 Tabl e 7. Enzymes and t i s s u e s used to i n v e s t i g a t e g e n e t i c v a r i a t i o n i n sockeye salmon and kokanee. B u f f e r s used were (AC) an amine c i t r a t e b u f f e r d e s c r i b e d by C l a y t o n and T r e t i a k (1972), (RW) a T r i s , c i t r i c a c i d , l i t h i u m hydroxide, and b o r i c a c i d b u f f e r d e s c r i b e d by Ridgway et. a l . (1970), and (MF) a T r i s , b o r i c a c i d , EDTA b u f f e r , d e s c r i b e d by Markert and Faulhaber (1965). Enzyme T i s s u e Locus B u f f e r A s p a r t a t e aminotransferase Eye Aat-1 ,2 AC Adenosine deaminase Muscle Ada-2 AC A l a n i n e aminotransferase Muscle A l a t (Gpt -2) MF P e p t i t d a s e ( g l y c y l l e u c i n e s u b s t r a t e ) Eye Gl-2 MF L a c t a t e Dehydrogenase L i v e r Ldh-4 RW Phosphoglucoisomerase Muscle Pgi RW Phosphoglucomutase Heart Pgm- 1 AC Phosphoglucomutase Muscle Pgm-2 RW S o r b i t o l dehydrogenase L i v e r Sdh RW Superoxide dismutase Muscle Sod RW 1 32 V a r i a t i o n i n a l l e l e f r e q u e n c i e s ( a r c s i n e s q u a r e - r o o t t r a n s f o r m e d ) was i n v e s t i g a t e d u s i n g Method 3 o f H e n d e r s o n (1953) f o r t h e f o l l o w i n g ANOVA m o d e l : Y = u + F + D + F*D + L , + S , + e ,„ i j k l m i j i j j k j k l i j k l m where: Y i s t h e t r a n s f o r m e d v a l u e of t h e i n d i v i d u a l i j k l m o b s e r v a t i o n o f a l l e l i c f r e q u e n c y ; u i s t h e o v e r a l l mean v a l u e ; F i s t h e f i x e d e f f e c t o f l i f e - h i s t o r y t y p e ( i = 1-2, s o c k e y e i o r k o k a n e e ) ; D i s t h e random e f f e c t due t o d r a i n a g e ( j = 1-4, j C o l u m b i a , Skeena, upper F r a s e r and C o a s t a l - i n c l u d i n g Lower F r a s e r R i v e r and V a n c o u v e r I s l a n d ) ; F * 0 ^ i s t h e e f f e c t of t h e i n t e r a c t i o n between t y p e and d r a i n a g e ; L^ k i s t h e random e f f e c t of l a k e w i t h i n d r a i n a g e ; S ^ i s t h e random e f f e c t o f spawning s i t e w i t h i n l a k e ; and t h e e r r o r t e r m e / i s t h e e f f e c t o f i j k l m a n n u a l v a r i a b i l i t y w i t h i n spawning s i t e s . The s i g n i f i c a n c e o f d i f f e r e n c e s i n a l l e l e f r e q u e n c i e s between s o c k e y e and kokanee was examined by an F t e s t of t h e "f o r m " mean s q u a r e d i v i d e d by t h e " f o r m - d r a i n a g e " i n t e r a c t i o n , e a c h w i t h a s i n g l e d e g r e e o f f r e e d o m due t o t h e u n b a l a n c e d d e s i g n . A l l o t h e r e f f e c t s were c o n s i d e r e d random, and t h e i r i n d i v i d u a l c o n t r i b u t i o n s t o t h e t o t a l p h e n o t y p i c v a r i a n c e were e s t i m a t e d by d i v i s i o n o f t h e a p p r o p r i a t e v a r i a n c e component by t h e sum of t h e d r a i n a g e , t y p e - d r a i n a g e i n t e r a c t i o n , l a k e , s i t e , and e r r o r v a r i a n c e components. A l l e l e f r e q u e n c y v a r i a t i o n was a l s o examined i n a 133 c o m p l e t e l y n e s t e d gene d i v e r s i t y a n a l y s i s (GDA) ( N e i 1973; C h a k r a b o r t y 1980). In t h i s model, s o c k e y e and kokanee spawning s y m p a t r i c a l l y were t r e a t e d a s d i f f e r e n t " f o r m s " of 0. n e r k a , w i t h form n e s t e d w i t h i n spawning s i t e s . D e v i a t i o n s f r o m a l l e l e f r e q u e n c i e s e x p e c t e d under p a n m i x i a due t o e a c h l e v e l of p o p u l a t i o n s u b d i v i s i o n were measured u s i n g s C h a k r a b o r t y ' s (1980) GDA mod e l : H T = H w + H Y + H s + H L + H n + H p where: H T i s t h e t o t a l d i v e r s i t y among and w i t h i n s i t e s ; H w i s th e d i v e r s i t y w i t h i n s i n g l e s a m p l e s ; i s t h e d i v e r s i t y among y e a r s w i t h i n s i t e s ; H_ i s t h e d i v e r s i t y between s o c k e y e and kokanee w i t h i n s i t e s ; H i s t h e d i v e r s i t y among spawning s i t e s w i t h i n l a k e s ; H i s t h e d i v e r s i t y among l a k e s w i t h i n d r a i n a g e s ; J-i and H i s t h e d i v e r s i t y among d r a i n a g e s . R e s u l t s A n n u a l v a r i a t i o n i n a l l e l e f r e q u e n c i e s F i v e o f t h e l o c i a s s a y e d were p o l y m o r p h i c i n some o f t h e kokanee and s o c k e y e p o p u l a t i o n s examined ( T a b l e 6 ) . Th e s e were Pgm-1, Pgm-2, Ldh-4, A l a t and G l - 2 . The o b s e r v e d g e n o t y p e f r e q u e n c i e s d i d not d i f f e r s i g n i f i c a n t l y (p>0.05) from t h o s e e x p e c t e d under H a r d y - W e i n b e r g e q u i l i b r i u m i n any of t h e p o p u l a t i o n s s a m p l e d . In a d d i t i o n , t h e r e were no s i g n i f i c a n t d i f f e r e n c e s i n g e n o t y p e f r e q u e n c i e s o v e r y e a r s a t any of t h e 134 i n d i v i d u a l l o c i examined, o r f o r a l l l o c i combined, f o r t h e t h r e e kokanee ( T a k l a L a k e ; P i e r r e C r e e k , B a b i n e L a k e ; Lower Shuswap R i v e r ) and two s o c k e y e ( T a k l a L a k e ; P i e r r e C r e e k , B a b i n e L a k e ) p o p u l a t i o n s sampled r e p e a t e d l y ( T a b l e 6 ) . T h i s s u g g e s t s t h a t t h e g e n e t i c s t r u c t u r e of 0. n e r k a p o p u l a t i o n s i s s t a b l e o v e r r e l a t i v e l y s h o r t t i m e p e r i o d s . A c c o r d i n g l y , t h e e l e c t r o p h o r e t i c i n f o r m a t i o n o v e r y e a r s w i t h i n p o p u l a t i o n s was p o o l e d f o r most s u b s e q u e n t c o m p a r i s o n s among p o p u l a t i o n s . C o m p a r i s o n of s y m p a t r i c s o c k e y e and kokanee i n t h r e e l a k e  s y s t e m s S o c k e y e from t h r e e s t r e a m s i n B a b i n e Lake where s o c k e y e spawn s y m p a t r i c a l l y w i t h kokanee ( P i e r r e , Twain and Tachek c r e e k s ) and from two l a r g e r s y s t e m s where spawning kokanee a r e a b s e n t ( F u l t o n R i v e r and P i n k u t C r e e k ) showed no e v i d e n c e of g e n e t i c d i f f e r e n t i a t i o n a t any o f t h e t h r e e p o l y m o r p h i c l o c i e x amined (p>0.05). S i m i l a r l y , t h e r e was no e v i d e n c e of d i f f e r e n t i a t i o n • among t h e kokanee p o p u l a t i o n s a t any of t h e t h r e e t o f i v e p o l y m o r p h i c l o c i examined (p>0.05). In c o n t r a s t , t h e r e were s i g n i f i c a n t d i f f e r e n c e s between s o c k e y e and kokanee i n a l l s y s t e m s where t h e y spawn s y m p a t r i c a l l y (p<0.05). In Twain and Tachek c r e e k s , s o c k e y e and kokanee d i f f e r e d s i g n i f i c a n t l y i n g e n o t y p e f r e q u e n c i e s a t Pgm-2 and Ldh-4, whereas i n P i e r r e C r e e k d i f f e r e n t i a t i o n was s i g n i f i c a n t a t o n l y L d h - 4 ( a l t h o u g h t h e d i r e c t i o n of d i f f e r e n c e a t Pgm-2 was s i m i l a r t o t h a t o b s e r v e d i n t h e o t h e r s ) . Thus, t h e r e were h i g h 1 35 s i m i l a r i t i e s w i t h i n forms and c o n s i s t e n t d i f f e r e n c e s between f o r m s a c r o s s t h e B a b i n e Lake spawning l o c a l i t i e s s ampled ( F i g . 2 2 ) . S o c k e y e spawning i n t h e p r e s e n c e of kokanee were no more s i m i l a r t o kokanee t h a n were s o c k e y e s p a wning i n t h e i r a b s e n c e . Kokanee and s o c k e y e were sampled from t h r e e l o c a l i t i e s i n t h e Shuswap L a k e s y s t e m : t h e M i d d l e Shuswap R i v e r where spawning kokanee a r e a b s e n t ; t h e Lower Shuswap R i v e r where t h e forms spawn s y m p a t r i c a l l y and; E a g l e R i v e r where t h e forms spawn s y m p a t r i c a l l y but s o c k e y e a r e r a r e (and n o t s a m p l e d ) . S i g n i f i c a n t d i f f e r e n c e s e x i s t a t Pgm-1 between t h e t h e M i d d l e and Lower Shuswap R i v e r s o c k e y e p o p u l a t i o n s (p<0.05). S i m i l a r l y , s i g n i f i c a n t d i f f e r e n c e s e x i s t a t b o t h Pgm-1 and M a t between t h e Lower Shuswap R i v e r and E a g l e R i v e r kokanee p o p u l a t i o n s (p<0.05). However, t h e r e were g r e a t e r d i f f e r e n c e s between s o c k e y e and kokanee t h a n between p o p u l a t i o n s w i t h i n f o r m ( F i g . 2 2 ) . The f r e q u e n c y of Pgm-1 100 were c o n s i s t e n t l y h i g h e r , and t h o s e o f M a t 91 and 108 c o n s i s t e n t l y l o w e r , i n s o c k e y e as compared t o kokanee p o p u l a t i o n s i n t h e Shuswap Lake d r a i n a g e ( p < 0 . 0 l ) . S o c k e y e and kokanee from Narrows C r e e k , T a k l a L a k e , sampled o v e r two and t h r e e y e a r s r e s p e c t i v e l y , were c o n s i s t e n t l y d i f f e r e n t a t Pgm-1 (p<0.05) and M a t (p<0.0O ( M a t was examined o n l y i n 1985). Narrows C r e e k kokanee e x p r e s s e d t h e M a t 91 a l l e l e i n t h e h i g h e s t f r e q u e n c y o b s e r v e d i n t h i s s t u d y whereas 136 F i g u r e 22 . Phenograms b a s e d on measurements o f g e n e t i c s i m i l a r i t y f o r e a c h of t h e s y s t e m s examined where s o c k e y e and kokanee spawn s y m p a t r i c a l l y : B a b i n e L a k e ; Shuswap Lake and; T a k l a L a k e . Phenograms b a s e d on d a t a t a k e n from f i v e p o l y m o r p h i c l o c i ( a l l l a k e s ) a r e drawn i n s o l i d l i n e s , t h o s e b a s e d on t h r e e p o l y m o r p h i c l o c i o n l y ( B a b i n e Lake) a r e drawn i n b r o k e n l i n e s . CO Form Population K Narrows Cr. Narrows Cr. a co CO 3 sz CO K Lower Shuswap R. K Eagle R. S Lower Shuswap R. S Middle Shuswap R. S Pinkut Cr. S Pierre Cr. S Fulton R. 0 C n co OQ 'L I •1 K Tachek Cr. Twain Cr. K Tachek Cr. K Twain Cr. Pierre Cr. o o-d d ci o o> o d o o" d Amuepi 0U9U90 sj9N 138 s o c k e y e had t h e h i g h e s t o b s e r v e d f r e q u e n c y of M a t 100. As a r e s u l t , g e n e t i c d i f f e r e n t i a t i o n between forms i n T a k l a Lake was g r e a t e r t h a n t h a t f o r o t h e r s y m p a t r i c s o c k e y e and kokanee p o p u l a t i o n s ( F i g . 2 2 ) . In summary, t h e r e were s i g n i f i c a n t and c o n s i s t e n t g e n e t i c d i f f e r e n c e s between s y m p a t r i c a l l y spawning s o c k e y e salmon and kokanee i n a l l s y s t e m s examined. W i t h i n s y s t e m s , t h e e x t e n t of g e n e t i c d i f f e r e n t i a t i o n w i t h i n forms was a l w a y s l e s s t h a n t h a t o b s e r v e d between f o r m s , but t h e e x t e n t of t h i s d i f f e r e n t i a t i o n v a r i e d g r e a t l y between l a k e s . W h i l e s y m p a t r i c sockeye. and kokanee d i f f e r e d c o n s i s t e n t l y i n a l l e l e f r e q u e n c i e s , t h e y s h a r e d t h e same a l l e l e s a t t h e l o c i e x a m i n e d . T h i s i n d i c a t e s g r e a t e r s i m i l a r i t y between s y m p a t r i c forms t h a n t h a t s u g g e s t e d t h r o u g h t h e use of N e i ' s g e n e t i c i d e n t i t y , w h i c h compares o n l y d i f f e r e n c e s i n a l l e l e f r e q u e n c i e s and not t h e p r e s e n c e or a b s e n c e of a l l e l e s . F o r example, a l l s o c k e y e and kokanee p o p u l a t i o n s sampled from t h e Shuswap Lake s y s t e m e x p r e s s e d t h e A l a t 108 a l l e l e , w h i c h was l a r g e l y a b s e n t from a l l o t h e r l o c a l i t i e s ( T a b l e 6 ) . S i m i l a r l y , a l l s o c k e y e and kokanee p o p u l a t i o n s sampled from B a b i n e Lake e x p r e s s e d t h e Ldh-4 85: a l l e l e , a l s o l a r g e l y a b s e n t o u t s i d e t h i s s y s t e m (Tabl-e 6; W i t h l e r 1985). T a k l a Lake s o c k e y e and kokanee e x p r e s s e d t h e same a l l e l e c o m p o s i t i o n s a t t h e l o c i examined, a l t h o u g h t h e y d i s p l a y e d none u n i q u e t o t h e s y s t e m . 1 39 O v e r a l l c o m p a r i s o n o f s o c k e y e and kokanee i n B r i t i s h C o l u m b i a 0. n e r k a p o p u l a t i o n s from a c r o s s B r i t i s h C o l u m b i a c l u s t e r i n t o two b r o a d g r o u p s ( F i g . 2 3 ) . One c l u s t e r i n c l u d e s a l l s o c k e y e and kokanee p o p u l a t i o n s sampled f r o m t h e upper F r a s e r and C o l u m b i a R i v e r w a t e r s h e d s ( w i t h t h e e x c e p t i o n of Skaha Lake and Lower Shuswap R i v e r k o k a n e e ) . The o t h e r c l u s t e r i n c l u d e s t h e s o c k e y e and kokanee p o p u l a t i o n s o f B a b i n e L a k e (Skeena R i v e r s y s t e m ) . The t h r e e c o a s t a l 0. n e r k a p o p u l a t i o n s examined a r e s p l i t between t h e two c l u s t e r s , w i t h C u l t u s Lake s o c k e y e c l u s t e r i n g c l o s e l y w i t h B a b i n e Lake s o c k e y e and Cowichan Lake kokanee, and Cheewhat Lake s o c k e y e c l u s t e r i n g w i t h upper F r a s e r and C o l u m b i a R i v e r 0. n e r k a p o p u l a t i o n s . T h e r e i s no o b v i o u s s e p a r a t i o n among p o p u l a t i o n s b a s e d on form ( s o c k e y e or k o k a n e e ) . The b r o a d g r o u p i n g of C o l u m b i a and upper F r a s e r R i v e r 0. n e r k a p o p u l a t i o n s , c o u p l e d w i t h t h e s e p a r a t i o n of t h e Skeena R i v e r p o p u l a t i o n s ( B a b i n e Lake) and t h e s p l i t t i n g of c o a s t a l p o p u l a t i o n s between t h e g r o u p s i s v e r y s i m i l a r t o t h a t r e p o r t e d by U t t e r e t a_l. (1984) i n t h e i r e x t e n s i v e g e o g r a p h i c e x a m i n a t i o n of s o c k e y e salmon a t 50 l o c i . The g e n e t i c r e l a t i o n s h i p - o f s o c k e y e and kokanee was i n v e s t i g a t e d u s i n g a n a l y s i s of v a r i a n c e on a l l e l e f r e q u e n c i e s a t t h r e e l o c i . T h e r e were no s i g n i f i c a n t d i f f e r e n c e s between forms i n a l l e l e f r e q u e n c i e s a t Pgm-1, Pgm-2 or Ldh-4 a l l e l e s ( T a b l e 8 ) . D i f f e r e n c e s among d r a i n a g e s y s t e m s and t h e i n t e r a c t i o n o f d r a i n a g e s y s t e m and form a c c o u n t e d f o r most of t h e o b s e r v e d F i g u r e 23. Phenograms o f t h e r e l a t i o n s h i p among o f s o c k e y e salmon and kokanee p o p u l a t i o n s b a s e d on measurements of g e n e t i c s i m i l a r i t y a t t h r e e p o l y m o r p h i c l o c i . Form Population A rf K Arrow L. K N. Kootenay L. K W. Kootenay L. S Middle Shuswap R. S Horsefly R. S Okanogan R. K Cowichan L. S Takla L. K Takla L. S Chewatt L. K . Eagle R. S Lower Shuswap R. K Skaha L. S Tachek Cr. S Twain Cr. 4 -t S Cultus L. K Lower Shuswap R. S Fulton R. S Pinkut Cr. S Pierre Cr. K Tachek Cr. K Twain Cr. K Pierre Cr. 6 d 6 o o AHiuepi ouauep SJ©N 142 Table 8. Percentage v a r i a t i o n i n a l l e l e f r e q u e n c i e s of 23 sockeye salmon and kokanee p o p u l a t i o n s accounted for by sources of v a r i a t i o n i n c l u d e d i n an ANOVA model. Source % of T o t a l V a r i a t i o n Pgm- -1 100 Pgm-2 100 Ldh-4 100 1 15 85 e r r o r 5. ,31 18. ,26 1 . .87 8, .91 2, .35 (among years) s i t e s 12, .67 0. ,00 1 , .22 46, .55 0, .56 lakes 25. , 1 4 0. ,00 0. .00 1 , .55 0, .00 drainage 17, .05 38. ,14 29, .35 0, .00 14, .96 form * drainage 39, .84 43. ,60 67, .56 42, .99 82, .13 form 0, .78 0. ,50 1 , .09 0, .68 1 , .04 143 v a r i a n c e i n a l l e l e f r e q u e n c i e s . T h e s e r e s u l t s i n d i c a t e t h a t i t i s n o t p o s s i b l e t o c l a s s i f y 0. n e r k a p o p u l a t i o n s as s o c k e y e o r kokanee s o l e l y from knowledge o f t h e a l l e l e f r e q u e n c i e s a t t h e l o c i a s s a y e d , but c l a s s i f i c a t i o n m i ght be p o s s i b l e g i v e n knowledge o f t h e d r a i n a g e s y s t e m s a m p l e d . T h e s e c o n c l u s i o n s a r e s u p p o r t e d by t h e more l i m i t e d d a t a f o r A l a t and G l - 2 , w h i c h a l s o d i s p l a y e d no c o n s i s t e n t d i f f e r e n c e s between s o c k e y e and kokanee. Gene d i v e r s i t y a n a l y s i s ( N e i 1973) y i e l d e d s i m i l a r r e s u l t s . On a v e r a g e , o v e r 90% o f t h e v a r i a t i o n i n a l l e l e f r e q u e n c i e s a t t h e t h r e e p o l y m o r p h i c l o c i a s s a y e d was due t o v a r i a t i o n w i t h i n p o p u l a t i o n s ( F i g . 2 4 ) . D i f f e r e n c e s among d r a i n a g e s y s t e m s were c o n s i s t e n t l y t h e s e c o n d g r e a t e s t s o u r c e of v a r i a t i o n a t e a c h l o c u s , f o l l o w e d u s u a l l y by d i f f e r e n c e s among l a k e s , between forms and among y e a r s ( T a b l e 9 ) . D i s c u s s i o n The r e l a t i o n s h i p of s o c k e y e and kokanee S o c k e y e and kokanee o c c u r n a t u r a l l y i n J a p a n , Kamchatka, A l a s k a , B r i t i s h C o l u m b i a ( i n c l u d i n g V a n c o u v e r I s l a n d ) and t h e n o r t h w e s t e r n U n i t e d S t a t e s ( N e l s o n 1968a; R i c k e r 1972; S c o t t and Crossman 1973). I t seems l i k e l y t h a t s o c k e y e o r i g i n a l l y c o l o n i z e d t h e s e d i v e r s e r e g i o n s and s u b s e q u e n t l y gave r i s e t o non-anadromous p o p u l a t i o n s ( kokanee) ( R i c k e r 1940; N e l s o n 1968a) . 1 44 F i g u r e 24. H i e r a r c h y u s e d i n gene d i v e r s i t y a n a l y s i s o f s o c k e y e salmon and kokanee. P e r c e n t a g e s i n r i g h t column a r e t h e a v e r a g e p r o p o r t i o n s o v e r t h r e e l o c i o f t o t a l g e n e t i c v a r i a t i o n o c c u r r i n g a t d i f f e r e n t l e v e l s . P o p u l a t i o n numbers c o r r e s p o n d t o t h o s e i n T a b l e 6. Skeena Columbia Upper Fraser Coastal 3.57% 1.86% 0.97% 1.16% 0.11% Within 22 23 17 18 21 22 19 10 20 20 13 14 15 11 12 i 8 6 7 7 * 10 10 9 9 9 1 2 3 92 .35% 146 Table 9. Percenatge d i s t r i b u t i o n of e l e c t r o p h o r e c t i c a l l y d e t e c t a b l e gene d i v e r s i t y at three polymorphic l o c i among 29 c o l l e c t i o n s of sockeye salmon and kokanee. Source of V a r i a t i o n Pgm-1 R e l a t i v e Gene D i v e r s i t y Pgm-2 Ldh-4 Mean With i n 89.35 96.10 96.13 92.35 populat ions Among years 0.12 0.09 0.02 0.11 Among forms 1 .38 0.81 1.16 1.16 Among s i t e s 1 .55 0.20 0.44 0.97 Among la k e s 3.07 0.40 0.04 1 .86 Among drain a g e s 4.52 2.39 2.22 3.57 147 The p r e s e n t s t u d y s u p p o r t s t h e s e c o n c l u s i o n s r e g a r d i n g t h e p o l y p h y l e t i c r e l a t i o n s h i p between s o c k e y e salmon and kokanee. T h e r e were no c o n s i s t e n t e l e c t r o p h o r e t i c d i f f e r e n c e s between s o c k e y e and kokanee i n B r i t i s h C o l u m b i a by w h i c h t h e forms c o u l d be s e p a r a t e d . T h e r e were g r e a t e r d i f f e r e n c e s among 0. n e r k a p o p u l a t i o n s among d r a i n a g e s than t h e r e were between s o c k e y e and kokanee. T h e r e f o r e , i t seems u n l i k e l y t h a t t h e e x i s t i n g s o c k e y e and kokanee p o p u l a t i o n s i n B r i t i s h C o l u m b i a a r e d e r i v e d from s e p a r a t e g e n e t i c l i n e a g e s . The anadromous and non-anadromous forms o f o t h e r s a l m o n i d s a l s o a p p e a r t o have g i v e n r i s e t o one a n o t h e r on numerous o c c a s i o n s t h r o u g h o u t t h e i r r a n g e . Nordeng (1983) d e m o n s t r a t e d t h a t b o t h anadromous and non-anadromous forms of A r c t i c c h a r , S a l v e l i n u s a l p i n u s , c an p r o d u c e anadromous and non-anadromous p r o g e n y , t h e p r o p e n s i t y t o do so d e p e n d i n g on p a r e n t a l form and e n v i r o n m e n t a l c o n d i t i o n s . J o h n s o n (1980) compared t h e d i s t r i b u t i o n of anadromous and non-anadromous s t o c k s of a r c t i c c h a r , and c o n c l u d e d t h a t one f o r m gave r i s e t o t h e o t h e r on numerous o c c a s i o n s t h r o u g h o u t t h e s p e c i e s ' r a n g e . S i m i l a r l y , O s i n o v (1984) c o n c l u d e d t h a t anadromous and non-anadromous forms forms of brown t r o u t , Salmo t r u t t a i n U.S.S.R. were " i n t e r c h a n g e a b l e " . S u p p o r t i n g t h i s , Ryman (1983) d e m o n s t r a t e d t h a t anadromous and non-anadromous brown t r o u t Salmo t r u t t a from Sweden were not members of d i s t i n c t g e n e t i c l i n e a g e s . A l l e n d o r f (1975) f o u n d t h a t anadromous ( s t e e l h e a d ) and non-anadromous 148 r a i n b o w t r o u t p o p u l a t i o n s , S. g a i r d n e r i , were g e n e t i c a l l y i n t e r r e l a t e d . S t a h l (1987) d e m o n s t r a t e d t h a t non-anadromous and anadromous A t l a n t i c s almon, S. s a l a r , w i t h i n b r o a d g e o g r a p h i c r e g i o n s were g e n e t i c a l l y more s i m i l a r t o e a c h o t h e r t h a n t h e y were t o t h e i r r e s p e c t i v e forms between r e g i o n s . G e n e t i c d i f f e r e n t i a t i o n between s y m p a t r i c s o c k e y e and kokanee G e n e t i c d i f f e r e n t i a t i o n among l o c a l p o p u l a t i o n s of s a l m o n i d s has been documented on numerous o c c a s i o n s i n a v a r i e t y of s a l m o n i d s p e c i e s ( e . g_. V e r n o n 1957; F r o s t 1965; Ryman et-a l . 1979; F e r g u s o n and Mason 1981; P a r k i n s o n 1984; O s i n o v 1984; W i lmot and B u r g n e r 1985; C r o z i e r and F e r g u s o n 1986; H i n d a r e_t a l . 1986; Campton and U t t e r 1987). Such d i f f e r e n t i a t i o n i s commonly a t t r i b u t e d t o t h e v i r t u a l i s o l a t i o n among p o p u l a t i o n s w h i c h r e s u l t s f r o m a c c u r a t e homing t o s e p a r a t e s p a w ning g r o u n d s ( p h i l o p a t r y ) ( e . £ . V e r n o n 1957; Hartman and R a l e i g h 1964; F r o s t 1965; Behnke 1972; Ryman e_t §_1. 1979; C r o z i e r and F e r g u s o n 1986), c o u p l e d w i t h t h e e f f e c t s o f g e n e t i c d r i f t ( A l l e n d o r f and P h e l p s 1981; Campton and U t t e r 1987). However, g e n e t i c d i f f e r e n c e s between s y m p a t r i c s o c k e y e and kokanee a r e d i f f i c u l t t o e x p l a i n s o l e l y on t h e s e g r o u n d s . G e n e t i c d i f f e r e n c e s e x i s t between t h e forms even where t h e y spawn p r e d o m i n a n t l y i n t h e same p l a c e a t t h e same t i m e , i n d i c a t i n g i s o l a t i o n t h r o u g h homing t o s e p a r a t e spawning a r e a s c a n n o t a c c o u n t f o r o b s e r v e d d i f f e r e n c e s between f o r m s . B e c a use spawning p o p u l a t i o n s of 0. n e r k a a t my s t u d y s i t e s were u s u a l l y l a r g e (>1,000 t o 1 49 >500,000 i n d i v i d u a l s ) , d i f f e r e n c e s between forms a r e n o t l i k e l y t o have a r i s e n from r e c e n t g e n e t i c d r i f t , a l t h o u g h h i s t o r i c a l b o t t l e n e c k e f f e c t s c a n n o t be r u l e d o u t . I t i s i m p r o b a b l e t h a t t h e o b s e r v e d d i f f e r e n c e s a r e due t o s a m p l i n g e r r o r o r y e a r l y v a r i a t i o n as my sample s i z e s were l a r g e and r e p l i c a t e d . I t i s n o t y e t c l e a r how g e n e t i c d i f f e r e n c e s between s y m p a t r i c a l l y spawning s o c k e y e and kokanee o r i g i n a t e o r how t h e y a r e m a i n t a i n e d . M c C a r t (1970) c o n c l u d e d t h a t s o c k e y e and kokanee spawning i n t h e s m a l l t r i b u t a r i e s t o B a b i n e Lake were p a r t of t h e same p o l y m o r p h i c p o p u l a t i o n . He n o t e d t h a t s o c k e y e and kokanee i n t e r m i x e d on t h e spawning g r o u n d s and t h a t kokanee males ( l i k e j a c k s o c k e y e m a l e s ) showed a s t r o n g p r o p e n s i t y t o a c t as " s n e a k s " t o spawning s o c k e y e p a i r s , s u g g e s t i n g t h a t s i g n i f i c a n t i n t e r b r e e d i n g o c c u r r e d between t h e f o r m s . M c C a r t (1970) d e m o n s t r a t e d kokanee m a l e s f e r t i l i z e d t h e eggs of s o c k e y e f e m a l e s i n t h e a b s e n c e o f c o m p e t i t i o n and showed t h a t t h e p r o g e n y o f s u c h c r o s s e s were f u l l y v i a b l e i n h a t c h e r y c o n d i t i o n s . However, t h e p r e s e n t e l e c t r o p h o r e t i c c o m p a r i s o n of s o c k e y e and kokanee c l e a r l y d e m o n s t r a t e s g e n e t i c d i f f e r e n t i a t i o n between forms i n B a b i n e L a k e t r i b u t a r i e s . D e s p i t e a p p a r e n t i n t e r b r e e d i n g , t h e r e i s an e f f e c t i v e r e s t r i c t i o n i n gene f l o w between s o c k e y e and kokanee t h a t i n d i c a t e s t h e y do not c o n s t i t u t e a s i n g l e p o l y m o r p h i c p o p u l a t i o n . 150 P o s s i b l e s y m p a t r i c o r i g i n o f s o c k e y e and kokanee The o b s e r v e d g e n e t i c s i m i l a r i t y between p o p u l a t i o n s o f s o c k e y e and kokanee i n B a b i n e , T a k l a and Shuswap l a k e s s t r o n g l y i n d i c a t e s t h a t , i n e a c h c a s e , one f o r m has a r i s e n from t h e o t h e r i n s y m p a t r y . The p l a u s i b i l i t y o f s y m p a t r i c d i v e r g e n c e i s s u p p o r t e d by knowledge of t h e b i o l o g y o f 0. n e r k a . N a t i v e and i n t r o d u c e d p o p u l a t i o n s o f s o c k e y e salmon a r e known t o have g i v e n r i s e t o non-anadromous i n d i v i d u a l s ( R i c k e r 1938, 1940, 1959, 1972; S m i r n o v 1959; K r o k h i n 1967; K r o g i u s 1981) and i n some c a s e s s e l f - s u s t a i n i n g p o p u l a t i o n s ( R i c k e r 1959; S c o t t 1984). S i m i l a r l y , kokanee a r e known t o be a b l e t o g i v e r i s e t o s o c k e y e ( F o e r s t e r 1947). However, t h e r e i s no c o n c l u s i v e e v i d e n c e t h a t t h e g e n e t i c s i m i l a r i t i e s o b s e r v e d between forms w i t h i n l a k e s a r e t h e r e s u l t s y m p a t r i c d i v e r g e n c e . O t h e r mechanisms can be p r o p o s e d t o a c c o u n t f o r t h e p a t t e r n s of s i m i l a r i t y o b s e r v e d . The • forms may have e v o l v e d i n a l l o p a t r y and s u b s e q u e n t l y i n t r o g r e s s e d a n d / o r have been s u b j e c t e d t o c o n v e r g e n t s e l e c t i o n p r e s s u r e s i n s y m p a t r y . However, n e i t h e r of t h e s e a l t e r n a t i v e h y p o t h e s e s a p p e a r s t o be t e n a b l e . I f i n t r o g r e s s i o n between t h e forms had o c c u r r e d , one would e x p e c t t o f i n d g r e a t e r g e n e t i c s i m i l a r i t y between s o c k e y e and kokanee where t h e y spawn s y m p a t r i c a l l y t h a n where t h e y spawn i n s e p a r a t e l o c a l i t i e s w i t h i n t h e same l a k e b e c a u s e o f t h e o p p o r t u n i t y f o r c o n t i n u i n g i n t r o g r e s s i o n . The e x t e n s i v e c o m p a r i s o n of B a b i n e Lake s o c k e y e and kokanee spawning p o p u l a t i o n s p r o v i d e s no e v i d e n c e of s u c h c o n t i n u i n g i n t r o g r e s s i o n . S o c k e y e t h a t spawn i n t h e a b s e n c e o f 151 kokanee i n F u l t o n R i v e r and P i n k u t C r e e k were g e n e t i c a l l y i n d i s t i n g u i s h a b l e from s o c k e y e t h a t spawn s y m p a t r i c a l l y w i t h kokanee i n P i e r r e , Twain and Tachek c r e e k s . S i m i l a r l y , i n t h e Shuswap Lak e s y s t e m , s o c k e y e t h a t spawn s y m p a t r i c a l l y w i t h kokanee i n t h e Lower Shuswap R i v e r a r e g e n e t i c a l l y no more s i m i l a r t o kokanee t h a n s o c k e y e t h a t spawn i n t h e a b s e n c e of kokanee i n t h e M i d d l e R i v e r s y s t e m . I t seems even more i m p r o b a b l e t h a t c o n v e r g e n t s e l e c t i o n p r e s s u r e s w i t h i n l a k e s c o u l d a c c o u n t f o r t h e o b s e r v e d g e n e t i c s i m i l a r i t y of. s y m p a t r i c s o c k e y e and kokanee, s i n c e a l l e l e s a t t h e l o c i e x a mined a r e g e n e r a l l y c o n s i d e r e d t o be n e u t r a l or n e a r l y n e u t r a l t o s e l e c t i o n ( e . g_. Ryman 1983). A l t e r n a t i v e l y , i f t h e s e a l l e l e s a r e not s e l e c t i v e l y n e u t r a l , and c o n v e r g e n t s e l e c t i o n p r e s s u r e s were r e s p o n s i b l e f o r t h e o b s e r v e d g e n e t i c s i m i l a r i t y , one might e x p e c t 0. n e r k a p o p u l a t i o n s i n n e i g h b o u r i n g l a k e s t o be g e n e t i c a l l y s i m i l a r as w e l l . B a b i n e L a k e , i n t h e Skeena d r a i n a g e , and T a k l a L a k e , i n t h e F r a s e r D r a i n a g e , a r e s e p a r a t e d by a d i s t a n c e of l e s s t h a n 100 km and a r e m o r p h o m e t r i c a l l y s i m i l a r ; t h e y o c c u r i n t h e same c l i m a t i c zone and have s i m i l a r g e o l o g i c a l and c o l o n i z a t i o n h i s t o r i e s , and f i s h s p e c i e s ^ c o m p o s i t i o n s ( L i n d s e y and M c P h a i l 1986). The p h y s i c a l and b i o t i c s i m i l a r i t i e s between l a k e s s h o u l d g i v e r i s e t o s i m i l a r s e l e c t i v e r e g i m e s and, i n t h e a b s e n c e o f f o u n d e r e f f e c t s , s o c k e y e and kokanee i n t h e two l a k e s m i g h t be e x p e c t e d t o be g e n e t i c a l l y and p h e n o t y p i c a l l y s i m i l a r . In f a c t , v e r y s u b s t a n t i a l d i f f e r e n c e s were f o u n d b o t h i n a l l e l e f r e q u e n c i e s 1 52 and a l l e l e c o m p o s i t i o n s among s o c k e y e and kokanee p o p u l a t i o n s i n T a k l a and B a b i n e l a k e s . M o r e o v e r , s y m p a t r i c s o c k e y e and kokanee i n T a k l a L a k e show g r e a t e r d i f f e r e n c e s i n a l l e l e f r e q u e n c i e s and g i l l r a k e r c o u n t s ( N e l s o n 1968b) t h a n do t h o s e i n B a b i n e L a k e . T h e s e r e s u l t s s u g g e s t t h a t l a c u s t r i n e s e l e c t i o n p r e s s u r e s a l o n e do not a c c o u n t f o r t h e g e n e t i c s i m i l a r i t y o b s e r v e d between s y m p a t r i c f o r m s . T h i s s t u d y , t o g e t h e r w i t h p r e v i o u s s t u d i e s of anadromous and non-anadromous 0. n e r k a o c c u r r i n g i n s y m p a t r y , s u g g e s t s t h a t g e n e t i c a l l y i s o l a t e d p o p u l a t i o n s o f s o c k e y e and kokanee have a r i s e n i n s y m p a t r y , p r o b a b l y on numerous o c c a s i o n s t h r o u g h o u t t h e s p e c i e s ' r a n g e . The s y m p a t r i c o r i g i n o f d i f f e r e n t f orms f o l l o w e d by g e n e t i c d i v e r g e n c e i s t h e o r e t i c a l l y p o s s i b l e ( e . g_. Maynard S m i t h 1966; R o s e n z w e i g 1978; Pimm 1979; R i c e 1984) but i t s o c c u r r e n c e i n n a t u r e i s e x t r e m e l y d i f f i c u l t t o s u b s t a n t i a t e and w i d e l y d i s p u t e d (Mayr 1970; Futuyma and Mayer 1980; T e m p l e t o n 1981). The b i o l o g y o f 0. n e r k a meets two c r i t i c a l r e q u i r e m e n t s o f models f o r s y m p a t r i c s p e c i a t i o n . F i r s t , t h e s e l e c t i v e p r e s s u r e s e x p e r i e n c e d by anadromous and non-anadromous i n d i v i d u a l s a r e p r o b a b l y v e r y d i f f e r e n t , and would be e x p e c t e d t o promote t h e g e n e t i c d i v e r g e n c e o f t h e forms ( R i c k e r 1940). Second, r a t h e r s t r i c t a s s o r t a t i v e m a t i n g by form would o c c u r w i t h i n a s i n g l e g e n e r a t i o n o f t h e s y m p a t r i c o r i g i n o f t h e forms b e c a u s e o f t h e g r e a t s i z e d i f f e r e n c e between them a t m a t u r i t y . Even w i t h i n f o r m s , a s s o r t a t i v e m a t i n g by s i z e i s c o n s p i c u o u s i n w i l d p o p u l a t i o n s (Hanson and S m i t h 1967; C h a p t e r 3 ) . S t r o n g 153 a s s o r t a t i v e m a t i n g g r e a t l y f a c i l i t a t e s g e n e t i c d i f f e r e n t i a t i o n c a u s e d by s e l e c t i o n (Maynard S m i t h 1966). Once d i f f e r e n c e s o f s e l e c t i v e v a l u e have a c c r u e d , " h y b r i d s " would l i k e l y have l o w e r f i t n e s s t h a n e i t h e r " p u r e " s o c k e y e o r kokanee. Such s e l e c t i o n c a n l e a d t o t h e e v o l u t i o n o f p r e m a t i n g e t h o l o g i c a l i s o l a t i n g mechanisms (Maynard S m i t h 1966), w h i c h may p a r t i a l l y a c c o u n t f o r t h e p r e m a t i n g i s o l a t i o n o b s e r v e d between s o c k e y e and kokanee i n B a b i n e Lake t r i b u t a r i e s ( C h a p t e r 5 ) . In P i e r r e C r e e k , kokanee m a l e s p r e f e r t o mate w i t h kokanee f e m a l e s r a t h e r t h a n w i t h t h e l a r g e r , and more f e c u n d , s o c k e y e f e m a l e s . In c o n c l u s i o n , r e c e n t work d e s c r i b i n g e c o l o g i c a l , m o r p h o l o g i c a l and b i o c h e m i c a l d i f f e r e n t i a t i o n o f s y m p a t r i c forms i n s a l m o n i d s s u g g e s t s t h a t d i v e r g e n c e i n sympatry i s p o s s i b l e and may be w i d e s p r e a d ( J o h n s o n 1980; S a v v a i t o v a 1980; B a l o n 1980; B a l o n and Penczak 1980; H i n d a r e t a l . 1986). T h i s s t u d y p r o v i d e s f u r t h e r e v i d e n c e t o s u p p o r t t h i s h y p o t h e s i s . 1 54 CHAPTER 5 AN EXPERIMENTAL EXAMINATION OF ASSORTATIVE MATING BETWEEN SOCKEYE SALMON AND KOKANEE I n t r o d u c t i o n Numerous t h e o r e t i c a l models have examined t h e c o n d i t i o n s u n d e r w h i c h s y m p a t r i c s p e c i a t i o n i s p o s s i b l e (Maynard S m i t h 1966; R o s e n z w e i g 1978; Pimm 1979; R i c e 1984). A g e n e r a l t e n e t of t h e s e s t u d i e s i s t h a t g e n e t i c d i f f e r e n t i a t i o n c an r e s u l t when p o l y m o r p h i s m s a r e m a i n t a i n e d by d i s r u p t i v e s e l e c t i o n . Such d i f f e r e n t i a t i o n w i l l p r o b a b l y l e a d t o s e l e c t i o n f o r r e p r o d u c t i v e i s o l a t i o n . F a c t o r s t h a t promote an i n i t i a l d e g r e e of a s s o r t a t i v e m a t i n g between forms g r e a t l y f a c i l i t a t e t h e p r o c e s s . However, w h i l e s y m p a t r i c s p e c i a t i o n i s a p o s s i b l e outcome of d i s r u p t i v e s e l e c t i o n , t h e r e i s l i t t l e e m p i r i c a l e v i d e n c e of i t s o c c u r r e n c e i n n a t u r e (Futuyma and Mayer 1980; W e s t - E b e r h a r d 1986). The anadromy/non-anadromy p o l y m o r p h i s m o f s a l m o n i d s e x h i b i t s many of t h e e l e m e n t s n e c e s s a r y f o r models o f s y m p a t r i c s p e c i a t i o n . The p o l y m o r p h i s m has a g e n e t i c b a s i s (Neave 1944; Nordeng 1983), but one form can r e a d i l y g i v e r i s e t o t h e o t h e r ( R i c k e r 1972; Nordeng 1983; S c o t t 1984). Where t h e anadromous and non-anadromous forms spawn s y m p a t r i c a l l y , t h e r e i s a h i g h d e g r e e of a s s o r t a t i v e m a t i n g (Neave 1944; Hanson and S m i t h 1967; M c C a r t 1970). F i n a l l y , t h e s e l e c t i v e d i f f e r e n c e s between t h e 1 55 m a r i n e and f r e s h w a t e r e n v i r o n m e n t s a r e p r o b a b l y e x t r e m e ( R i c k e r 1940). In a s s o c i a t i o n w i t h t h e s e f a c t o r s , t h e r e i s g r o w i n g e v i d e n c e o f s y m p a t r i c g e n e t i c d i v e r g e n c e between anadromous and non-anadromous s a l m o n i d s (Neave 1944; N e l s o n 1968b; M c C a r t 1970; Nordeng 1983; C h a p t e r 4) The a s s o r t a t i v e m a t i n g o b s e r v e d between anadromous and non-anadromous s a l m o n i d s may r e s u l t f r o m t h e p h e n o t y p i c d i f f e r e n c e s between t h e f o r m s , most n o t a b l y s i z e (anadromous s a l m o n i d s a r e u s u a l l y much l a r g e r a t m a t u r i t y t h a n non-anadromous i n d i v i d u a l s ) . A s s o r t a t i v e m a t i n g by s i z e has been documented i n many a n i m a l s , i n c l u d i n g salmon ( e . g_. Hanson and S m i t h 1967; L i c h t 1976; D a v i e s and H a l l i d a y 1977; M c L a i n 1982; M a l m q v i s t 1983; Snead and A l c o c k 1985; Howard and K l u g e 1 9 8 5 ; McKaye 1986; M c L a i n and B o r o m i s a 1987). A d d i t i o n a l l y , a s s o r t a t i v e m a t i n g may r e s u l t from s e l e c t i o n f o r r e p r o d u c t i v e i s o l a t i o n between t h e fo r m s , i n a s s o c i a t i o n w i t h t h e i r g e n e t i c d i v e r g e n c e . V a r y i n g d e g r e e s of a s s o r t a t i v e m a t i n g , r a n g i n g from c o m p l e t e t o none a t a l l , have r e s u l t e d from d i s r u p t i v e s e l e c t i o n and g e n e t i c d i v e r g e n c e i n l a b o r a t o r y s t u d i e s on D r o s o p h i l a ( e . c[. Thoday and G i b s o n 1962; C r o s s l e y 1974; Dobzhansky e t a l . 1976; S p e i s s and W i l k e 1984; R i c e 1985; K o e p f e r 1987). Thus t h e a s s o r t a t i v e m a t i n g o b s e r v e d between anadromous and non-anadromous s a l m o n i d s may be t h e p r o d u c t o f f a c t o r s i n v o l v e d i n s e x u a l s e l e c t i o n a n d / o r f a c t o r s i n v o l v e d i n s e l e c t i o n f o r p r e m a t i n g i s o l a t i o n . To d e t e r m i n e i f a s s o r t a t i v e m a t i n g between anadromous and 1 56 non-anadromous s a l m o n i d s r e s u l t s from t h e s i z e d i f f e r e n c e between t h e forms a l o n e o r a d d i t i o n a l p r e m a t i n g i s o l a t i n g mechanisms, I r a n a s e r i e s o f male c h o i c e e x p e r i m e n t s on t h e anadromous ( s o c k e y e salmon) and non-anadromous (kokanee) forms o f O n c o r h y n c h u s n e r k a from two spawning l o c a l i t i e s , P i e r r e C r e e k t r i b u t a r y t o B a b i n e Lake and Narrows C r e e k , t r i b u t a r y t o T a k l a L a k e . T h r e e mechanisms c o u l d a c c o u n t f o r t h e a s s o r t a t i v e m a t i n g o b s e r v e d between s o c k e y e and kokanee. F i r s t , a s s o r t a t i v e m a t i n g may r e s u l t f r o m male i n t r a s e x u a l c o m p e t i t i o n , s u c h t h a t l a r g e r m a l e s o u t c o m p e t e s m a l l e r males f o r a c c e s s t o t h e ( p o s s i b l y ) p r e f e r r e d l a r g e f e m a l e s , as has been s u g g e s t e d by Hanson and S m i t h ( 1 9 6 7 ) , M c C a r t (1970) and J o n s s o n and H i n d a r ( 1 9 8 2 ) . In s u c h c a s e s , a s s o r t a t i v e m a t i n g s h o u l d b r e a k down i n t h e a b s e n c e of c o m p e t i t o r s f o r mates. Second, a s s o r t a t i v e m a t i n g may o c c u r b e c a u s e of male c h o i c e d e p e n d e n t on male s i z e i n salmon'. In kokanee, male s e l e c t i v i t y i n c r e a s e s w i t h male s i z e ; s m a l l m a l e s do n o t d i s c r i m i n a t e between s m a l l and l a r g e f e m a l e s whereas l a r g e m ales s t r o n g l y p r e f e r l a r g e f e m a l e s ( C h a p t e r 3 ) . I f t h i s same mechanism a c c o u n t s f o r a s s o r t a t i v e m a t i n g between s o c k e y e and kokanee, we e x p e c t t o f i n d male c h o i c e dependent on male s i z e b u t , as w i t h i n kokanee, we do not e x p e c t t o f i n d t h a t m a l e s of any s i z e ( o r form) p r e f e r t h e s m a l l e s t f e m a l e s (kokanee) o v e r t h e l a r g e s t f e m a l e s ( s o c k e y e ) . F i n a l l y , a s s o r t a t i v e m a t i n g may r e s u l t from mate c h o i c e d e p e n d e n t on t h e form ( s o c k e y e o r kokanee) of p o t e n t i a l mates. I f so, we e x p e c t t o f i n d t h a t 157 kokanee m a l e s p r e f e r kokanee o v e r s o c k e y e f e m a l e s when g i v e n a c h o i c e , b o t h i n t h e p r e s e n c e and a b s e n c e of c o m p e t i t i o n . Mate c h o i c e d e p e n d e n t on form may be e v i d e n c e o f b e h a v i o u r a l c h a r a c t e r d i s p l a c e m e n t i n a s s o c i a t i o n w i t h s e l e c t i o n f o r p r e m a t i n g i s o l a t i o n between s o c k e y e and kokanee. The s t u d y i s i n t h r e e p a r t s . F i r s t , I document t h e d e g r e e o f a s s o r t a t i v e m a t i n g between s o c k e y e and kokanee i n P i e r r e and N arrows c r e e k s . S econd, I examine male c h o i c e i n b o t h t h e p r e s e n c e and a b s e n c e of male c o m p e t i t o r s . F i n a l l y , i n P i e r r e C r e e k , t h e f a c t o r s t h a t d e t e r m i n e t h e a t t r a c t i v e n e s s of f e m a l e s t o m a l e s a r e examined. The r e s u l t s i n d i c a t e t h a t a s s o r t a t i v e m a t i n g i n 0. n e r k a i s n o t s i m p l y t h e r e s u l t o f i n t r a s e x u a l c o m p e t i t i o n o r male c h o i c e d e p e n d e n t on male s i z e ; r a t h e r I p r e s e n t e v i d e n c e t h a t a s s o r t a t i v e m a t i n g between s o c k e y e and kokanee i s a t l e a s t p a r t i a l l y b a s e d on form, and t h u s p o s s i b l y t h e r e s u l t o f s e l e c t i o n f o r r e p r o d u c t i v e i s o l a t i o n between t h e f o r m s . J _ . A s s o r t a t i v e mat i n g between s o c k e y e salmon and kokanee Methods To examine t h e p a t t e r n of a s s o c i a t i o n of s o c k e y e salmon and kokanee i n P i e r r e C r e e k , B a b i n e L a k e , and Narrows C r e e k , T a k l a L a k e , I c o n d u c t e d s t r e a m s i d e o b s e r v a t i o n s d e t a i l i n g t h e s t r u c t u r e of male spawning a g g r e g a t i o n s a r o u n d s o c k e y e and 158 kokanee f e m a l e s . On A u g u s t 2, 5 and 15, 1984 I c o u n t e d t h e t o t a l numbers o f s o c k e y e and kokanee i n P i e r r e C r e e k and r e c o r d e d t h e number of s o c k e y e and kokanee m a l e s a s s o c i a t e d w i t h a r e p r e s e n t a t i v e sample o f 206 t e r r i t o r i a l s o c k e y e f e m a l e s and 119 t e r r i t o r i a l kokanee f e m a l e s . Kokanee m a l e s i n P i e r r e C r e e k r a n g e d from 21 t o 26 cm f o r k l e n g t h ; s o c k e y e m a l e s r a n g e d from 30 t o 67 cm f o r k l e n g t h . On A u g u s t 5, 6, 7 and 9, 1983, I c o u n t e d t h e t o t a l number o f s o c k e y e and kokanee i n Narrows C r e e k and r e c o r d e d t h e number o f s o c k e y e and kokanee a s s o c i a t e d w i t h a r e p r e s e n t a t i v e sample of 302 t e r r i t o r i a l s o c k e y e f e m a l e s and 100 t e r r i t o r i a l kokanee f e m a l e s . Kokanee males i n Narrows C r e e k r a n g e d from 17 t o 20 cm f o r k l e n g t h ; s o c k e y e m a l e s r a n g e d from 55 t o 66 cm f o r k l e n g t h . M a l e s a s s o c i a t e d w i t h f e m a l e s m a i n l y a d o p t e d one o f two b e h a v i o u r s ; t h e y were e i t h e r d ominant t o o t h e r c o u r t i n g m a l e s , a s s u m i n g a p o s i t i o n d i r e c t l y l a t e r a l t o t h e r e a r f l a n k s of a f e m a l e , or t h e y were s u b o r d i n a t e , 'sneak' m a l e s , a s s u m i n g p o s i t i o n s b e h i n d o r b e s i d e a f e m a l e and d o m i n a n t m a l e . In a few c a s e s t h e r e was o n g o i n g c o m p e t i t i o n f o r t h e dominant p o s i t i o n ( t h e p o s i t i o n c l o s e s t t o t h e f e m a l e ) . R e s u l t s In P i e r r e C r e e k , B a b i n e L a k e , no s o c k e y e males were o b s e r v e d c o u r t i n g t h e 119 t e r r i t o r i a l kokanee f e m a l e s s e l e c t e d f o r o b s e r v a t i o n . Kokanee f e m a l e s were a l m o s t a l w a y s c o u r t e d by a s i n g l e kokanee male ( T a b l e 1 0 ) . In o n l y two c a s e s were kokanee f e m a l e s o b s e r v e d t o have more t h a n one kokanee male i n 159 T a b l e 10. The t o t a l number of kokanee and s o c k e y e o b s e r v e d i n P i e r r e C r e e k , B a b i n e L a k e , and N a r r o w s C r e e k , T a k l a L a k e on t h r e e and f o u r d a t e s , r e s p e c t i v e l y . Mean m a l e / f e m a l e r a t i o s a r e shown f o r kokanee m a l e s a s s o c i a t e d w i t h kokanee f e m a l e s (K) and s o c k e y e f e m a l e s ( S ; most w i t h s o c k e y e m a l e s ) and f o r s o c k e y e m a l e s i n n o n - d o m i n a n t ( s n e a k ) p o s i t i o n s t o s o c k e y e p a i r s ( S P ; s o c k e y e f e m a l e s w i t h s o c k e y e m a l e s ) . A l l r e p e a t e d m e a s u r e s a r e p r e s e n t e d w i t h s t a n d a r d e r r o r s and sa m p l e s i z e s i n p a r e n t h e s e s . Number Mean M a l e / F e m a l e R a t i o D a t e S o c k e y e Kokanee Kokanee/K Kokanee/S S o c k e y e / S P P i e r r e C r . Aug. 2 710 5178 - 3 .45 ( 0 . 40,29) 0. 14 ( 0 . 08,22) Aug. 5 1293 10629 1 .03 ( 0 . 00,76) 2 .49 ( 0 . 20,86) 0. 07 ( 0 . 03,67) Aug. 15 4553 9295 1 .00 ( 0 . 00,43) 2 .46 ( 0 . 15,91) 0. 19 ( 0 . 04,80) N a r r o w s C r , Aug. 5 131 593 - 0 .91 ( 0 . 22,21) 0. 05 ( 0 . 05,19) Aug. 6 199 1335 - 1 . 1 1 ( 0 . 14,55) 0. 00 ( 0 . 00,36) Aug. 7 281 1300 1 .20 ( 0 . 13,10) 1 .15 ( 0 . 14,91) 0. 01 ( 0 . 02,64) Aug. 9 316 2557 0.94 ( 0 . 04,90) 1 .24 ( 0 . 09,134) 0. 02 ( 0 . 02,86) 160 a t t e n d a n c e . In c o n t r a s t , a l m o s t a l l (191 o f 206) t e r r i t o r i a l s o c k e y e f e m a l e s had an e n t o u r a g e t h a t i n c l u d e d s e v e r a l kokanee m a l e s . U n l e s s no s o c k e y e m a l e s were p r e s e n t , kokanee m a l e s a s s o c i a t e d w i t h s o c k e y e f e m a l e s assumed s u b o r d i n a t e r o l e s i n t h e c o u r t s h i p h i e r a r c h y . The r a t i o o f kokanee m a l e s t o s o c k e y e f e m a l e s d e c r e a s e d o v e r t h e p e r i o d o f o b s e r v a t i o n (ANOVA, P<0.01). T h i s d e c r e a s i n g r a t i o may c o i n c i d e w i t h an i n c r e a s e i n th e p r o p o r t i o n o f kokanee f e m a l e s i n t h e kokanee run o v e r t i m e , a s has been o b s e r v e d i n o t h e r kokanee p o p u l a t i o n s ( L o r z and N o r t h c o t e 1965). S o c k e y e males w h i c h assumed s u b o r d i n a t e r o l e s t o s o c k e y e p a i r s were much l e s s numerous t h a n s u b o r d i n a t e kokanee m a l e s and t h e r a t i o of s o c k e y e males t o f : s o c k e y e p a i r s d i d n o t change s i g n i f i c a n t l y o v e r t i m e (ANOVA, p > 0 . l 0 ) . W h i l e no s o c k e y e males were o b s e r v e d c o u r t i n g t h e kokanee f e m a l e s s e l e c t e d f o r o b s e r v a t i o n i n P i e r r e C r e e k , a few o f t h e s m a l l e s t s o c k e y e m a l e s ( j a c k s ; 30-41 cm) were o b s e r v e d c o u r t i n g kokanee f e m a l e s a t o t h e r t i m e s . To r o u g h l y e s t i m a t e t h e p r o p o r t i o n o f j a c k s t h a t a c c o m p a n i e d kokanee f e m a l e s , I r e c o r d e d t h e p o s i t i o n s of a r e p r e s e n t a t i v e sample of j a c k males on A u g u s t 15. Of t h e 44 j a c k s o b s e r v e d , o n l y 9.5% (4) were o b s e r v e d c o u r t i n g kokanee f e m a l e s , w h i l e t h e r e s t assumed sneak p o s i t i o n s b e h i n d s o c k e y e p a i r s (38) o r were a l o n e ( 2 ) . M c C a r t (1970) o b s e r v e d t h a t o n l y 6% of j a c k m a l e s c o u r t e d kokanee f e m a l e s i n F o u r M i l e C r e e k , a n o t h e r t r i b u t a r y t o B a b i n e L a k e , s u g g e s t i n g t h a t t h e l i m i t e d i n t e r e s t of s o c k e y e m a l e s i n kokanee f e m a l e s i s a r e l a t i v e l y c o n s t a n t f e a t u r e o f t h e r e l a t i o n s h i p between 161 s o c k e y e and kokanee i n B a b i n e L a k e . In Narrows C r e e k , T a k l a L a k e , no s o c k e y e m a l e s were o b s e r v e d c o u r t i n g t h e 100 kokanee f e m a l e s s e l e c t e d f o r o b s e r v a t i o n . In a d d i t i o n , I n e v e r saw any s o c k e y e m a l e s c o u r t i n g kokanee f e m a l e s i n my numerous w a l k s o f t h e c r e e k i n 1983 and 1985, s u g g e s t i n g t h a t s o c k e y e male p a i r i n g s w i t h kokanee f e m a l e s a r e r a r e e v e n t s i n Narrows C r e e k , i f t h e y o c c u r a t a l l . T e r r i t o r i a l kokanee f e m a l e s were a l m o s t a l w a y s a t t e n d e d by a s i n g l e kokanee m a l e . Of t h e 100 t e r r i t o r i a l kokanee f e m a l e s o b s e r v e d , 90 were c o u r t e d by kokanee m a l e s and t e n were a l o n e . O n l y s e v e n of t h e 90 c o u r t e d f e m a l e s were a t t e n d e d by two kokanee m a l e s . S o c k e y e f e m a l e s were u s u a l l y a t t e n d e d by a s i n g l e s o c k e y e male ( o n l y f o u r of 301 s o c k e y e f e m a l e s were a t t e n d e d by more t h a n one s o c k e y e m a l e ) , and a s m a l l number of kokanee m a l e s . In c o n t r a s t t o P i e r r e C r e e k , a s i g n i f i c a n t p e r c e n t a g e o f s o c k e y e f e m a l e s were n o t a t t e n d e d by any kokanee males (33.6% v e r s u s 7.2% i n P i e r r e C r e e k ) . The number o f kokanee m a l e s a t t e n d i n g i n d i v i d u a l s o c k e y e f e m a l e s was s m a l l and d i d n o t change s i g n i f i c a n t l y o v e r t i m e (p>0.5). The d e g r e e of a s s o r t a t i v e m a t i n g by form i n P i e r r e C r e e k and Narrows C r e e k o v e r t h e c o u r s e o f t h e spawning run was even g r e a t e r t h a n t h a t o b s e r v e d d u r i n g t h e i n d i v i d u a l w a l k s o f t h e s t r e a m , as t h e spawning r u n s of kokanee and s o c k e y e d i d not c o m p l e t e l y o v e r l a p i n e i t h e r c r e e k . In P i e r r e C r e e k , t h e kokanee spawning run was much s h o r t e r t h a n t h e s o c k e y e r u n . On 162 Aug. 2 8 t h , 5,315 s o c k e y e were c o u n t e d i n t h e c r e e k (and more were seen e n t e r i n g ) , w h i l e o n l y 200 n e a r l y dead kokanee were o b s e r v e d . No s i g n i f i c a n t r u n s o f kokanee i n t o t h e c r e e k were o b s e r v e d p a s t Aug. 1 4 t h . In Narrows C r e e k , t h e s o c k e y e run s t a r t s and ends e a r l i e r t h a n t h e kokanee r u n . S o c k e y e f i r s t a r r i v e i n Narrows C r e e k d u r i n g t h e l a s t week i n J u l y t o t h e f i r s t week i n A u g u s t , w i t h t h e run u s u a l l y c o m p l e t e by t h e t h i r d week i n A u g u s t ( I n t e r n a t i o n a l P a c i f i c Salmon Commission u n p u b l i s h e d r e p o r t s ) . Kokanee do n o t b e g i n a r r i v i n g u n t i l t h e f i r s t week i n A u g u s t and t h e r u n p e r s i s t s a t l e a s t u n t i l t h e f i r s t week i n September (no o b s e r v a t i o n s were made p a s t t h i s t i m e ) ( p e r s . o b s . ). 2. Kokanee and s o c k e y e male c h o i c e i n t h e p r e s e n c e and a b s e n c e of compet i t o r s Methods T h e r e i s a h i g h d e g r e e o f a s s o r t a t i v e m a t i n g between s o c k e y e and kokanee i n P i e r r e C r e e k and Narrows C r e e k . Here I t e s t t h e h y p o t h e s e s t h a t a s s o r t a t i v e m a t i n g i s t h e r e s u l t o f (1) male i n t r a s e x u a l c o m p e t i t i o n , (2) male c h o i c e d e p e n d e n t on male s i z e a n d / o r (3) male c h o i c e d e p e n d e n t on t h e form o f t h e f e m a l e (see i n t r o d u c t i o n f o r how t o d i f f e r e n t i a t e between h y p o t h e s e s ) . Kokanee and s o c k e y e male c h o i c e between s o c k e y e and kokanee f e m a l e s was examined i n e x p e r i m e n t a l a r e n a s under t h e f o l l o w i n g 1 63 c o m p e t i t i v e s i t u a t i o n s : A) no c o m p e t i t o r s p r e s e n t ; B) a l a r g e s o c k e y e male p r e s e n t , p a i r e d w i t h t h e s o c k e y e f e m a l e ; and C ) , as i n B, b u t two m a l e s of t h e t y p e t e s t e d were added s i m u l t a n e o u s l y . Kokanee ( i n P i e r r e and Narrows c r e e k s ) and t h r e e s i z e g r o u p s of s o c k e y e m a l e s ( i n P i e r r e C r e e k ) were t e s t e d i n e x p e r i m e n t A, whereas kokanee ( i n P i e r r e and Narrows c r e e k s ) and j a c k s o c k e y e ( i n P i e r r e C r e e k ) m a l e s o n l y were t e s t e d i n e x p e r i m e n t s B and C. The t h r e e s i z e g r o u p s o f s o c k e y e m a l e s i n P i e r r e C r e e k were: 1) j a c k s (31-41 cm); 2) medium (42-51 cm) and l a r g e (52-67 cm). The t h r e e s i z e g r o u p s c o r r e s p o n d r o u g h l y t o t h r e e y e a r o l d s , f o u r y e a r o l d s and f o u r and f i v e y e a r o l d s , r e s p e c t i v e l y , a c c o r d i n g t o t h e s i z e and age d a t a p r e s e n t e d i n Hanson and S m i t h ( 1 9 6 7 ) . The s m a l l e r f o u r y e a r o l d s (medium s o c k e y e m a l e s ) were d e s i g n a t e d as an i n d i v i d u a l s i z e g r o u p b e c a u s e , l i k e j a c k m a l e s , t h e y had no c o r r e s p o n d i n g s i z e c l a s s of s o c k e y e f e m a l e s . U n l i k e j a c k m a l e s , medium m a l e s were s i m i l a r i n a p p e a r a n c e t o t h e l a r g e s o c k e y e m a l e s , w i t h hooked jaws, a p r o m i n e n t d o r s a l hump and b r i g h t r e d c o l o u r . J a c k males were d u l l r e d i n c o l o u r and d i d not have t h e o b v i o u s d o r s a l humps and hooked jaws o f l a r g e r m a l e s . J a c k m a l e s and medium s i z e d m a l e s were a b s e n t i n Narrows C r e e k . M a l e s t o be t e s t e d were added s i n g l y ( e x p e r i m e n t s A and B) or i n p a i r s ( e x p e r i m e n t C) t o a f o u r by f o u r meter e n c l o s u r e i n th e s p a w n i ng s t r e a m c o n t a i n i n g a t e r r i t o r i a l kokanee and a t e r r i t o r i a l s o c k e y e f e m a l e ( e i t h e r a t t e n d e d (B, C) o r not a t t e n d e d (A) by a l a r g e s o c k e y e m a l e ) . The b e h a v i o u r s r e c o r d e d 164 f o r e a c h male w i t h r e s p e c t t o e a c h f e m a l e o v e r t e n m i n u t e s o f o b s e r v a t i o n (two f i v e m i n u t e p e r i o d s s e p a r a t e d by a s e v e n m i n u t e p e r i o d ) were ' n e a r n e s s t i m e ' and c o u r t s h i p d i s p l a y s . N e a r n e s s t i m e was d e f i n e d as a l l t h e t i m e a male s p e n t w i t h i n 25 cm o f a f e m a l e p l u s o n l y t h e t i m e i t was o r i e n t e d t o t h e f e m a l e a t d i s t a n c e s up t o 1m away from h e r . To r e d u c e s u b j e c t i v i t y i n what I c a l l e d ' o r i e n t e d ' , a male had t o f i r s t a p p r o a c h w i t h i n 25 cm f o r any t i m i n g t o be commenced. T i m i n g was s t o p p e d when t h e male l e f t t h e 1m range o r was j u d g e d t o be no l o n g e r o r i e n t e d t o t h e f e m a l e when w i t h i n t h e 1m r a n g e , and recommenced o n l y when t h e male a p p r o a c h e d t o w i t h i n 25 cm. The n e a r n e s s t i m e r u l e was m o d i f i e d s l i g h t l y i n e x p e r i m e n t s B and C where a n o t h e r male was p r e s e n t i n t h e a r e n a , b e c a u s e t h i s p r e s e n c e o f t e n r e s t r i c t e d c l o s e a c c e s s t o p a r t i c u l a r f e m a l e s . In t h e s e e x p e r i m e n t s a l l t i m e o r i e n t e d t o a f e m a l e w i t h i n 1m was r e c o r d e d and t h e 25 cm commencement r u l e was d r o p p e d . C o u r t s h i p d i s p l a y s c o n s i s t e d o f a p p r o a c h e s ( i n c l u d i n g q u i v e r s ) , c r o s s o v e r s and d i g s ( s e e M c C a r t 1969 f o r d e s c r i p t i o n of male d i g g i n g and T a u t z and G r o o t 1975 f o r a d e s c r i p t i o n of q u i v e r s and c r o s s o v e r s ) . A l l d i s p l a y s were p o s i t i v e l y c o r r e l a t e d w i t h one a n o t h e r and lumped f o r a n a l y s e s . Female d i g g i n g b e h a v i o u r was a l s o r e c o r d e d d u r i n g t h e two f i v e m i n u t e o b s e r v a t i o n p e r i o d s . A ' d i g ' c o n s i s t e d o f a s e r i e s o f s t r o n g body f l e x u r e s w h i l e t u r n e d on one s i d e . C h o i c e was d e t e r m i n e d by a n a l y s e s o f t h e d i f f e r e n c e i n t i m e s p e n t n e a r t h e two f e m a l e s (Time D i f f e r e n c e ) and by t h e d i f f e r e n c e i n t h e number o f c o u r t s h i p d i s p l a y s p e r f o r m e d t o e a c h 165 o f t h e f e m a l e s ( D i s p l a y D i f f e r e n c e ) ( s e e C h a p t e r 3 f o r f u r t h e r d e t a i l s ) . R e s u l t s A. Male c h o i c e i n t h e a b s e n c e of compet i t o r s In P i e r r e C r e e k , B a b i n e L a k e , c h o i c e d i f f e r e d s i g n i f i c a n t l y among t h e f o u r s i z e c l a s s e s of males when p r e s e n t e d t o a s o c k e y e and a kokanee f e m a l e ( K r u s k a l - W a l l i s n o n - p a r a m e t r i c ANOVA, P<0.001 f o r Time D i f f e r e n c e and D i s p l a y D i f f e r e n c e ; F i g s . 25a and 2 6 b ) . Kokanee males s p e n t more t i m e near t h e kokanee f e m a l e (p<0.05) whereas a l l t h r e e s i z e c l a s s e s of s o c k e y e m a l e s s p e n t more t i m e n e a r t h e s o c k e y e f e m a l e (p<0.05; i n t h i s and a l l s u b s e q u e n t w i t h i n male s i z e g r o u p c o m p a r i s o n s Time D i f f e r e n c e d a t a were a n a l y z e d by W i l c o x o n matched p a i r s s i g n e d r a n k t e s t and D i s p l a y D i f f e r e n c e d a t a were a n a l y z e d by p a i r e d t - t e s t ) . S i m i l a r d i f f e r e n c e s were f o u n d i n c o u r t s h i p d i s p l a y s , e x c e p t t h a t j a c k s o c k e y e d i d not d i s p l a y s i g n i f i c a n t l y more t o e i t h e r t y p e of f e m a l e (p>0.3). O v e r a l l , 13 of 20 kokanee m a l e s s p e n t more t i m e n e a r t h e kokanee f e m a l e , whereas, 12 of 16 j a c k s , a l l medium (10) and a l l l a r g e (8) s o c k e y e m a l e s s p e n t more t i m e n e a r t h e s o c k e y e f e m a l e . M u l t i p l e c o m p a r i s o n s ( n o n - p a r a m e t r i c e x t e n s i o n of T u k e y ' s t e s t ; see Zar 1984) r e v e a l e d kokanee d i f f e r e d f r o m a l l s i z e s o f s o c k e y e m a l e s i n b o t h Time D i f f e r e n c e and D i s p l a y D i f f e r e n c e (p<0.05). No s i g n i f i c a n t d i f f e r e n c e s i n t h e t i m e and d i s p l a y s c o r e s were f o u n d among t h e s o c k e y e m a l e s . 1 66 F i g u r e 25. Kokanee and s o c k e y e male c h o i c e between kokanee and s o c k e y e f e m a l e s i n t h e a b s e n c e (A) and p r e s e n c e of c o m p e t i t o r s (B, C) i n P i e r r e C r e e k , as i n d i c a t e d by t h e median d i f f e r e n c e i n t i m e (+ 95% CI) s p e n t n e a r f e m a l e s o f t h e two f o r m s . The symbols r e p r e s e n t t h e c h o i c e of f e m a l e s ( i n w h i t e , kokanee on t h e o u t s i d e of t h e l e f t v e r t i c a l a x i s , s o c k e y e on t h e o u t s i d e o f t h e r i g h t v e r t i c a l a x i s ) p r e s e n t e d t o kokanee ( i n b l a c k ) and t h r e e s i z e c l a s s e s o f s o c k e y e m a l e s ( s t r i p e d , a t t h e median i n t h e d i f f e r e n c e i n t i m e t h e y s p e n t n e a r a f e m a l e of e a c h o f t h e two forms o v e r t e n m i n u t e s o f o b s e r v a t i o n i n an e x p e r i m e n t a l a r e n a ) . The h e i g h t o f t h e symbols i s p r o p o r t i o n a l t o t h e mean f o r k l e n g t h of t h e f e m a l e s p r e s e n t e d and m a l e s t e s t e d . A s c a l e of a c t u a l s i z e s i s p r e s e n t e d i n t h e upper l e f t of t h e f i g u r e . No male c o m p e t i t o r s were p r e s e n t i n e x p e r i m e n t A; a l l s i z e g r o u p s o f males were t e s t e d s e p a r a t e l y and i n d i v i d u a l l y . The male c o m p e t i t o r s p r e s e n t i n e x p e r i m e n t s B and C a r e d e p i c t e d , a l o n g w i t h th e f e m a l e s t h e y a t t e n d e d , on t h e o u t s i d e of t h e a x e s . In e x p e r i m e n t B, a l a r g e s o c k e y e male was p a i r e d w i t h t h e l a r g e s o c k e y e f e m a l e d u r i n g t h e s e p a r a t e and i n d i v i d u a l t e s t i n g of kokanee and j a c k s o c k e y e c h o i c e . In e x p e r i m e n t C, w h i c h a d d i t i o n a l m ales were p r e s e n t d epended on t h e t y p e of male t e s t e d . F o r kokanee, an a d d i t i o n a l kokanee male was p a i r e d w i t h t h e kokanee f e m a l e and a l a r g e s o c k e y e male was p a i r e d w i t h t h e s o c k e y e f e m a l e . F o r j a c k s o c k e y e , a l a r g e s o c k e y e and an a d d i t i o n a l j a c k s o c k e y e male a t t e n d e d t h e s o c k e y e f e m a l e and t h e kokanee f e m a l e was u n a t t e n d e d . Symbols t o t h e r i g h t of t h e b r o k e n l i n e i n d i c a t e p r e f e r e n c e f o r t h e s o c k e y e f e m a l e , t h o s e t o t h e l e f t i n d i c a t e p r e f e r e n c e f o r t h e kokanee f e m a l e . 1 68 Figure 26. Kokanee and sockeye male choice between kokanee and sockeye salmon females in the absence ( A ) and presence ( B , C) of competitors in Pierre Creek, as indicated by the mean difference (+ 95% CI) in the t o t a l number of courtship displays performed to females of the two forms. See F i g . 25 for an explanation of the layout. 169 1 70 However, t h e d i f f e r e n c e s c o r e s o b s c u r e d t h e f a c t t h a t 55% (9 o f 16) o f j a c k m a l e s d i s p l a y e d t o t h e kokanee f e m a l e p r e s e n t whereas none of t h e medium (0 of 8) and l a r g e s o c k e y e m a l e s (0 o f 10) d i d . S i m i l a r l y , w h i l e kokanee m a l e s d i s p l a y e d more t o kokanee f e m a l e s t h r o u g h o u t t h e t r i a l s , 70% (14 o f 20) o f them d i d d i s p l a y t o t h e s o c k e y e f e m a l e p r e s e n t . Kokanee f e m a l e s spawned o n l y w i t h kokanee (1,20; number of spawnings o b s e r v e d , number o f m a l e s t e s t e d ) and j a c k (2,16) m a l e s whereas s o c k e y e f e m a l e s spawned w i t h j a c k ( 3 , 1 6 ) , medium (2,8) and l a r g e s o c k e y e m a l e s ( 3 , 1 0 ) . The d i f f e r e n c e i n t h e number of d i g s p e r f o r m e d by t h e s o c k e y e and kokanee f e m a l e s was p o s i t i v e l y d e p e n d e n t on t h e s i z e of t h e male p r e s e n t (r=0.64, n=22, p < 0 . 0 l ; F i g . 2 7 ) , s u g g e s t i n g f e m a l e s may a l s o have e x e r t e d a c h o i c e . However, f e m a l e d i g g i n g r a t e was a l s o p r o b a b l y r e l a t e d t o male i n t e r e s t w h i c h was c o n f o u n d e d w i t h t h e male s i z e g r o u p s . In Narrows C r e e k , T a k l a L a k e , kokanee m a l e s showed a s t r o n g p r e f e r e n c e f o r t h e kokanee f e m a l e when g i v e n a c h o i c e between a s o c k e y e and a kokanee f e m a l e (p<0.005 f o r Time D i f f e r e n c e and - D i s p l a y D i f f e r e n c e ; F i g s . 28 and 2 9 ) . N i n e t e e n of 20 m a l e s t e s t e d s p e n t more time n e a r and d i s p l a y e d more t o t h e kokanee f e m a l e . T h e r e was no s i g n i f i c a n t d i f f e r e n c e i n t h e d i g g i n g r a t e of t h e s o c k e y e and kokanee f e m a l e s u s e d (p>0.1; mean number o f d i g s 171 g u r e 27. The r e g r e s s i o n of D i g D i f f e r e n c e ( d i g s by s o c k e y e -d i g s by kokanee) between p a i r e d s o c k e y e and kokanee f e m a l e s on t h e s i z e of t h e male p r e s e n t i n P i e r r e C r e e k . K = kokanee m a l e s ; J = j a c k s o c k e y e m a l e s ; M = medium s o c k e y e m a l e s ; L = l a r g e s o c k e y e m a l e s . The d a t a a r e t a k e n o n l y from t h e f i r s t t i m e a f e m a l e p a i r was p r e s e n t e d w i t h a t e s t male t o i n s u r e i n d e p e n d e n c e . One o b s e r v a t i o n f o r j a c k m a l e s was e x c l u d e d from t h e a n a l y s i s , as t h e s o c k e y e f e m a l e spawned and t h e m a j o r i t y o f her d i g s were n e s t c o v e r i n g , v e r s u s c o n s t r u c t i n g , i n n a t u r e . 172 173 F i g u r e 28. Kokanee male c h o i c e between kokanee and s o c k e y e f e m a l e s i n t h e a b s e n c e (A) and p r e s e n c e (B, C) of c o m p e t i t o r s i n Narrows C r e e k , as i n d i c a t e d by t h e median i n d i f f e r e n c e between (+ 95% C I ) i n t h e t i m e s p e n t n e a r t h e f e m a l e s . See F i g . 25 f o r an e x p l a n a t i o n o f t h e l a y o u t . 174 KOKANEE FEMALE / •0 fl r 40 20 L 0 B Kokan** | 1 1 1 1 1 m . i . -600 -400 -200 0 200 400 Time D i f f e r e n c e (s) 80CKEYE FEMALE Sockeye 600 "»•'• 175 F i g u r e 29. Kokanee male c h o i c e between kokanee and s o c k e y e salmon f e m a l e s i n t h e a b s e n c e (A) and p r e s e n c e (B, C) o f c o m p e t i t o r s i n Narrows C r e e k , a s i n d i c a t e d by t h e mean d i f f e r e n c e (+ 95% CI) i n t h e t o t a l number o f c o u r t s h i p d i s p l a y s p e r f o r m e d t o f e m a l e s o f t h e two f o r m s . See F i g . 25 f o r an e x p l a n a t i o n o f t h e l a y o u t of t h e f i g u r e . 176 KOKANEE FEMALE Kokanee male C o u r t s h i p D i s p l a y D i f f e r e n c e 177 p e r s o c k e y e f e m a l e p e r t e n m i n u t e s = 3.4 + 1.4SE, mean number o f d i g s p e r kokanee f e m a l e p e r t e n m i n u t e s = 5.0 + 1.8SE). Two s p a w n i n g s were o b s e r v e d , once e a c h w i t h a s o c k e y e and kokanee f e m a l e . B. Kokanee and j a c k s o c k e y e male c h o i c e i n t h e p r e s e n c e of a l a r g e s o c k e y e male In P i e r r e C r e e k , j a c k s o c k e y e and kokanee m a l e s be h a v e d i n the o p p o s i t e manner when p r e s e n t e d w i t h a c h o i c e of a s o c k e y e p a i r and a kokanee f e m a l e ( F i g s . 25b and 26b; p < 0 . 0 0 l ; Mann-Whi t n e y U t e s t f o r Time D i f f e r e n c e d a t a , t - t e s t f o r D i s p l a y D i f f e r e n c e d a t a ) . E i g h t e e n of 20 kokanee m a l e s s p e n t more t i m e n e a r and 19 o f 20 d i s p l a y e d more t o kokanee f e m a l e s ( p < 0 . 0 0 O . S i x t e e n of 20 j a c k m a l e s s p e n t more t i m e n e a r ( p < 0 . 0 0 l ) , and 9 of 20 d i s p l a y e d more t o t h e s o c k e y e f e m a l e s (7 j a c k s d i s p l a y e d t o n e i t h e r f e m a l e ) (p<0.05). T h e s e r e s u l t s were q u a l i t a t i v e l y s i m i l a r t o t h o s e o b t a i n e d when no l a r g e s o c k e y e male was p r e s e n t . Q u a n t i t a t i v e l y , o n l y t h e D i s p l a y D i f f e r e n c e s c o r e s o f kokanee m a l e s d i f f e r e d s i g n i f i c a n t l y between e x p e r i m e n t s , w i t h kokanee d i s p l a y i n g more t o kokanee f e m a l e s when a l a r g e s o c k e y e male was p r e s e n t (p<0.05). Kokanee males spawned f o u r t i m e s w i t h kokanee f e m a l e s t h r o u g h o u t t h e 20 t r i a l s but d i d n o t p a r t i c i p a t e i n t h e two s o c k e y e p a i r s p a w n i n g s . J a c k s o c k e y e m a l e s d i d n o t spawn w i t h kokanee f e m a l e s t h r o u g h o u t t h e 20 t r i a l s but p a r t i c i p a t e d i n one 178 o f t h e two s o c k e y e p a i r s p a w n i n g s . In Narrows C r e e k , kokanee m a l e s showed a s t r o n g p r e f e r e n c e f o r kokanee f e m a l e s when g i v e n a c h o i c e between a l o n e kokanee f e m a l e and a s o c k e y e p a i r (p<0.00l f o r b o t h Time D i f f e r e n c e and D i s p l a y D i f f e r e n c e ; F i g s . 28b and 2 9 b ) . E i g h t e e n of 20 m a l e s t e s t e d s p e n t more t i m e n e a r and d i s p l a y e d more t o t h e kokanee f e m a l e . One male a p p r o a c h e d n e i t h e r f e m a l e t h r o u g h o u t t h e t r i a l , w h i l e t h e o t h e r s p e n t more t i m e n e a r t h e s o c k e y e f e m a l e but d i s p l a y e d t o n e i t h e r f e m a l e . S i x s p a w n i n g s were o b s e r v e d , t w i c e between kokanee p a i r s and f o u r t i m e s between s o c k e y e p a i r s . Kokanee m a l e s d i d n o t p a r t i c i p a t e i n any of t h e s o c k e y e s p a w n i n g s . C. Kokanee and j a c k male c h o i c e i n t h e p r e s e n c e of a l a r g e  s o c k e y e and a male of t h e i r own s i z e In P i e r r e C r e e k , t h e p r e s e n c e o f a s i m i l a r s i z e d c o m p e t i t o r r e s u l t e d i n a s w i t c h i n b e h a v i o u r by t h e ' l o s i n g ' kokanee male but not by t h e ' l o s i n g ' j a c k male (where ' l o s i n g ' i s d e f i n e d as s p e n d i n g a l e s s e r amount of t i m e w i t h t h e kokanee f e m a l e f o r kokanee m a l e s and w i t h t h e s o c k e y e f e m a l e f o r j a c k s ; F i g s . 25c and 2 6 c ) . S i x t e e n o f t w e n t y kokanee l o s e r s s p e n t most t i m e w i t h t h e s o c k e y e f e m a l e (p<0.05), and 12 o f 20 d i s p l a y e d more o f t e n t o t h e s o c k e y e f e m a l e (p>0.3). C o u r t s h i p d i s p l a y s t o b o t h kokanee and s o c k e y e f e m a l e s were r e s t r i c t e d by t h e p r e s e n c e of 179 o t h e r m a l e s . J a c k l o s e r s d i d not d i s p l a y more t o o r spend s i g n i f i c a n t l y more t i m e w i t h e i t h e r kokanee o r s o c k e y e f e m a l e s ( p > 0 . l ) . However, i n g e n e r a l t h e y o r i e n t e d t o w a r d t h e s o c k e y e f e m a l e s , but o f t e n r e m a i n e d o u t s i d e t h e 1 m t i m i n g range ( n o t e t h a t t h e r e were a l r e a d y two s o c k e y e m a l e s u s u a l l y w i t h i n t h i s r a n g e ) . O n l y one o f t e n j a c k s t e s t e d d e m o n s t r a t e d a c o n s i s t e n t i n t e r e s t i n t h e kokanee f e m a l e i n b o t h Time and D i s p l a y D i f f e r e n c e s c o r e s . T h e r e was no s i g n i f i c a n t d i f f e r e n c e between th e b e h a v i o u r of kokanee and j a c k ' l o s e r s ' i n e i t h e r Time o r D i s p l a y D i f f e r e n c e (p>0.2). No spawnings were o b s e r v e d between t h e kokanee f e m a l e and kokanee m a l e s but kokanee males d i d p a r t i c i p a t e as s n e a k s i n a l l f o u r s p a w n i n g s between t h e s o c k e y e p a i r t h r o u g h o u t t h e 20 t r i a l s . Kokanee s n e a k s d i s a p p e a r e d b e n e a t h t h e spawning s o c k e y e p a i r a t t h e moment o f spawning and r e m a i n e d t h e r e u n t i l spawning was c o m p l e t e . No spawnings were o b s e r v e d d u r i n g t h e t e n t r i a l s of j a c k s o c k e y e male c h o i c e . In Narrows C r e e k , t h e p r e s e n c e of a s i m i l a r s i z e d c o m p e t i t o r d i d n o t a f f e c t t h e p r e f e r e n c e of kokanee males f o r kokanee f e m a l e s . Kokanee ' l o s e r s ' s p e n t s i g n i f i c a n t l y more time n e a r t h e kokanee f e m a l e t h a n n e a r t h e s o c k e y e f e m a l e (p<0.005) but d i d not d i s p l a y more t o e i t h e r t y p e of f e m a l e (p>0.25; F i g s . 28c and 2 9 c ) . In t o t a l , 14 o f t h e 20 kokanee ' l o s e r s ' s p e n t more t i m e n e a r t h e kokanee f e m a l e t h a n t h e y d i d n e a r t h e s o c k e y e f e m a l e . T h r e e s p e n t no t i m e n e a r e i t h e r f e m a l e and 180 t h r e e s p e n t most tim e n e a r t h e s o c k e y e f e m a l e . Two s p a w n i n g s were o b s e r v e d , b o t h i n v o l v i n g a kokanee f e m a l e and t h e dominant kokanee m a l e . In n e i t h e r c a s e d i d t h e kokanee ' l o s e r ' p a r t i c i p a t e . D. C o m p a r i s o n of t h e b e h a v i o u r of kokanee m a l e s t o w a r d s s o c k e y e  f e m a l e s i n P i e r r e and Narrows c r e e k s I t was a p p a r e n t t h a t kokanee f e m a l e s were a t t r a c t i v e t o kokanee m a l e s i n b o t h P i e r r e and Narrows c r e e k s . In c o n t r a s t , t h e a t t r a c t i v e n e s s of s o c k e y e f e m a l e s t o kokanee m a l e s a p p e a r e d t o d i f f e r between c r e e k s . Kokanee m a l e s i n P i e r r e C r e e k s w i t c h e d t h e i r p r e f e r e n c e t o s o c k e y e f e m a l e s when f a c e d w i t h c o m p e t i t i o n f o r a c c e s s t o kokanee f e m a l e s , whereas kokanee m a l e s i n Narrows C r e e k m a i n t a i n e d a p r e f e r e n c e f o r k o k a n e e f e m a l e s . To f u r t h e r c o n t r a s t t h e a t t r a c t i v e n e s s of s o c k e y e f e m a l e s t o kokanee m a l e s i n b o t h s y s t e m s , I compared t h e t i m e kokanee m a l e s i n P i e r r e and Narrows c r e e k s s p e n t n e a r s o c k e y e f e m a l e s and t h e number of c o u r t s h i p d i s p l a y s t h e y p e r f o r m e d t o them i n e a c h of t h e t h r e e p r e v i o u s e x p e r i m e n t s . In a l l e x p e r i m e n t s , T a k l a Lake kokanee m a l e s s p e n t s i g n i f i c a n t l y l e s s t i m e n e a r and p e r f o r m e d fewer c o u r t s h i p d i s p l a y s t o s o c k e y e f e m a l e s t h a n d i d B a b i n e Lake kokanee m a l e s (Mann W h i t n e y U t e s t ; p < 0 . 0 l ; F i g s . 30 and 3 1 ) . The g r e a t e r a t t r a c t i v e n e s s of s o c k e y e f e m a l e s t o B a b i n e kokanee m a l e s 181 F i g u r e 30. C o m p a r i s o n of t h e t i m e kokanee m a l e s i n P i e r r e and Narrows C r e e k s s p e n t n e a r s o c k e y e f e m a l e s i n t h e a b s e n c e (A) and p r e s e n c e (B, C) of c o m p e t i t o r s . See F i g . 25 f o r a d e s c r i p t i o n o f e x p e r i m e n t a l c o n d i t i o n s . 182 20 1BH 10 5 0 20 15 ^  10 5 0 20 15 1CH 5 0 A) No Competitors MR 200 400 B) Sockeye Male Present 600 800 200 400 600 C) Sockeye and Kokanee Male Present BOO 0 200 400 600 BOO Time spent w i t h i n 1 m of Sockeye Female (s) i ^ - P i e r r e Cr.. Babine L.; E3 " Narrows Ck., Takla L. 183 F i g u r e 31. C o m p a r i s o n o f t h e number of c o u r t s h i p d i s p l a y s kokanee m a l e s i n P i e r r e and Narrows c r e e k s p e r f o r m e d t o s o c k e y e f e m a l e s i n t h e a b s e n c e (A) and p r e s e n c e (B, C) of c o m p e t i t o r s . See F i g . 25 f o r a d e s c r i p t i o n o f e x p e r i m e n t a l c o n d i t i o n s . 184 >» CJ c CD D CJ CD C_ LL 20 15 10 5 0 J A) No Competitors KWIWJ 20 15 10 5 0 0 10 20 B) Sockeye Male Present -T-4 —r— 8 i 30 i 12 0 2 6 10 2 Q C) Sockeye and Kokanee Males Present 15 10 5 0 J 40 14 0 2 4 6 8 10 12 14 C o u r t s h i p D i s p l a y s to Sockeye Female • P i e r r e Cr.. Babine L. 0- NarrowB Cr., Takla L. 185 s u g g e s t e d by t h e s e r e s u l t s c o r r e s p o n d s t o s t r e a m o b s e r v a t i o n s ( T a b l e 10). On a v e r a g e , s o c k e y e f e m a l e s i n P i e r r e C r e e k , B a b i n e L a k e , had many more kokanee m a l e s a s s o c i a t e d w i t h them t h a n d i d s o c k e y e f e m a l e s i n Narrows C r e e k , T a k l a Lake ( p < 0 . 0 0 l ) , even t h o u g h t h e r a t i o o f kokanee t o s o c k e y e was h i g h e r i n Narrows C r e e k . E. C o m p a r i s o n of t h e sneak b e h a v i o u r of kokanee males from  P i e r r e and Narrows c r e e k s To compare t h e p r o p e n s i t y of kokanee males i n P i e r r e and Narrows c r e e k s t o become s n e a k s t o s o c k e y e p a i r s , s i n g l e kokanee m a l e s were p l a c e d i n an a r e n a c o n t a i n i n g o n l y a s o c k e y e p a i r and t h e i r b e h a v i o u r was m o n i t o r e d as i n p r e v i o u s e x p e r i m e n t s . Kokanee were t e s t e d o v e r two y e a r s i n Narrows C r e e k (19 m a l e s were t e s t e d i n 1983, 14 i n 1985) and i n a s i n g l e y e a r i n P i e r r e C r e e k ( 1 9 8 5 ) . T h e r e was no s i g n i f i c a n t d i f f e r e n c e between y e a r s i n N arrows C r e e k i n t h e b e h a v i o u r of kokanee males when p r e s e n t e d t o a s o c k e y e p a i r (p>0.80 f o r n e a r n e s s t i m e and c o u r t s h i p d i s p l a y s ) . T h e s e d a t a were p o o l e d f o r c o m p a r i s o n w i t h P i e r r e C r e e k kokanee. T h e r e were s t r i k i n g d i f f e r e n c e s i n t h e b e h a v i o u r of T a k l a and B a b i n e kokanee t o w a r d s s o c k e y e p a i r s i n b o t h n e a r n e s s t i m e and t o t a l c o u r t s h i p d i s p l a y s (Mann Whitney U - t e s t ; p<0.000l; 186 F i g . 3 2 ) . A l l 18 B a b i n e kokanee m a l e s t e s t e d became s n e a k s t o t h e s o c k e y e p a i r p r e s e n t . T h i r t e e n o f t h e s e m a l e s s p e n t g r e a t e r t h a n 83% o f t h e i r t i m e (>500 s e c o n d s ) w i t h i n one meter of t h e s o c k e y e f e m a l e . In c o n t r a s t , o n l y 5 o f t h e 33 m a l e s t e s t e d i n T a k l a Lake e x h i b i t e d even weak sneak b e h a v i o u r t o w a r d s t h e s o c k e y e p a i r . None o f t h e T a k l a L a k e kokanee s p e n t more t h a n 66% o f t h e i r t i m e (>400 s e c o n d s ) w i t h i n 1 m o f t h e s o c k e y e f e m a l e . S i m i l a r l y , 78% (14) of B a b i n e kokanee p e r f o r m e d a t l e a s t one c o u r t s h i p b e h a v i o u r ( a l m o s t a l l were r u s h e s ( a p p r o a c h e s ) under t h e abdomen of t h e f e m a l e ) , whereas o n l y 15% (5) d i d so i n Narrows C r e e k . _3. F a c t o r s i n v o l v e d i n d e t e r m i n i n g t h e a t t r a c t i v e n e s s o f  kokanee and s o c k e y e f e m a l e s t o m a l e s Methods Female a t t r a c t i v e n e s s t o males may depend on one o r a c o m b i n a t i o n of t h e f o l l o w i n g t h r e e f a c t o r s : a) a b s o l u t e s i z e of f e m a l e ; b) f o r m ( s o c k e y e o r kokanee) o f f e m a l e and; c) r e l a t i v e s i z e of t h e f e m a l e t o t h e male. I f f e m a l e a b s o l u t e s i z e . i s t h e c r i t e r i o n o f male c h o i c e , t h e n t h e a t t r a c t i v e n e s s - o f f e m a l e s s h o u l d be i n d e p e n d e n t o f male s i z e . I f t h e form o f t h e f e m a l e i s t h e s o l e c r i t e r i o n of c h o i c e , m a l e s s h o u l d be a t t r a c t e d o n l y t o f e m a l e s o f t h e i r own f o r m . F i n a l l y , i f r e l a t i v e s i z e o f t h e f e m a l e t o t h e male i s a c r i t e r i a of c h o i c e , t h e a t t r a c t i v e n e s s o f kokanee f e m a l e s s h o u l d d e c l i n e w i t h i n c r e a s i n g male s i z e and 187 F i g u r e 32. The amount t i m e (A) kokanee m a l e s i n P i e r r e and Narrows c r e e k s s p e n t n e a r s o c k e y e f e m a l e s and t h e number of c o u r t s h i p d i s p l a y s (B) p e r f o r m e d when no o t h e r c h o i c e was a v a i l a b l e o v e r t e n m i n u t e s of o b s e r v a t i o n i n an e x p e r i m e n t a l a r e n a . 188 A) u c OJ cr OJ c_ 25 -j 20 -15 • 10 • 5 • 0 -30 -1 25 -20 -15 -10 • 5 -0 -0 200 400 600 800 Time Spent Near (im) Sockeye Female (s) B) 4 6 B —i 10 C o u r t s h i p D i s p l a y s t o Sockeye Female 77[ " Narrows Cr., Takla L.; ||| - P i e r r e Cr.. Babine L. 189 s o c k e y e f e m a l e s s h o u l d be a t t r a c t i v e t o a l l m a l e s ( s e e C h a p t e r 3 ) . To t e s t among t h e s e a l t e r n a t i v e s i n P i e r r e C r e e k , 12 ma l e s of e a c h s i z e c l a s s were t e s t e d i n d i v i d u a l l y w i t h e i t h e r a s i n g l e t e r r i t o r i a l s o c k e y e or kokanee f e m a l e i n t h e e x p e r i m e n t a l a r e n a . Methods were t h e same as i n t h e p r e v i o u s c h o i c e e x p e r i m e n t s e x c e p t t h a t i n t h i s c a s e no c h o i c e was a v a i l a b l e as o n l y a s i n g l e t e r r i t o r i a l f e m a l e was p r e s e n t . To l o o k f o r p o s s i b l e d i f f e r e n c e s i n f e m a l e r e s p o n s e t o mal e s of d i f f e r e n t s i z e s , e a c h f e m a l e was a l t e r n a t e l y p r e s e n t e d w i t h males o f two s i z e c l a s s e s . R a t e s o f d i g g i n g ( n e s t c o n s t r u c t i o n ) and spawning were r e c o r d e d . The two s i z e c l a s s e s u s e d were e i t h e r kokanee and medium s o c k e y e m a l e s or j a c k and l a r g e s o c k e y e m a l e s . E a c h f e m a l e was u s e d f o r 6 t r i a l s i n t o t a l , t h r e e t r i a l s w i t h e a c h of t h e two s i z e c l a s s e s o f m a l e s . Fo r m a l e s , d a t a on n e a r n e s s t i m e were a n a l y z e d w i t h a two-way e x t e n s i o n of K r u s k a l - W a l l i s n o n - p a r a m e t r i c ANOVA. The b e h a v i o u r d a t a were a n a l y z e d by two-way ANOVA a f t e r a Log (x + 1) t r a n s f o r m a t i o n . The s e t o f o r t h o g o n a l c o n t r a s t s i n b o t h c a s e s were: c o m p a r i s o n s between t h e two t y p e s o f f e m a l e s f o r e a c h of t h e f o u r s i z e c l a s s e s o f m a l e s ; c o m p a r i s o n of kokanee and j a c k m a l e s ; c o m p a r i s o n of medium and l a r g e m a l e s and a c o m p a r i s o n of kokanee and j a c k m a l e s a s a g r o u p w i t h medium and l a r g e m a l e s as a g r o u p . D a t a on f e m a l e b e h a v i o u r were a n a l y z e d by f i r s t s u b t r a c t i n g 190 t h e number o f d i g s p e r f o r m e d i n t h e p r e s e n c e of t h e t h r e e s m a l l m ales f r o m t h e number p e r f o r m e d i n t h e p r e s e n c e of t h e t h r e e l a r g e m a l e s ( t o g e t a s i n g l e i n d e p e n d e n t s c o r e f o r e a c h f e m a l e ) . The d a t a were t h e n s u b j e c t e d t o a two-way ANOVA w i t h f e m a l e t y p e and male p a i r t y p e as t h e i n d e p e n d e n t v a r i a b l e s . R e s u l t s T h e r e were s i g n i f i c a n t d i f f e r e n c e s : 1) w i t h i n male g r o u p s (between f e m a l e t y p e ) i n t h e t i m e s p e n t n e a r t h e s o c k e y e and kokanee f e m a l e s ; 2) among male g r o u p s i n t h e t i m e s p e n t n e a r and d i s p l a y s t o e i t h e r t y p e o f f e m a l e ; and 3) i n t h e i n t e r a c t i o n between male g r o u p s and f e m a l e t y p e i n t h e t i m e s p e n t n e a r and d i s p l a y s p e r f o r m e d t o f e m a l e s ( p < 0 . 0 l ; F i g . 33, T a b l e 1 1 ) . The major d i f f e r e n c e s i n r e s p o n s e t o t h e f e m a l e s l a y between t h e g r o u p of kokanee and j a c k s o c k e y e m a l e s and t h e g r o u p of medium and l a r g e s o c k e y e m a l e s ( p < 0 . 0 0 l ) . S o c k e y e f e m a l e s were a t t r a c t i v e t o males of a l l s i z e c l a s s e s ( F i g . 3 3 a ) . A l l m a l e s , e x c e p t two kokanee m a l e s , s p e n t a t l e a s t 40% of t h e i r t i m e n e a r t h e s o c k e y e f e m a l e (one o f t h e e x c e p t i o n a l kokanee m a l e s was o r i e n t e d t o t h e f e m a l e t h r o u g h o u t t h e t r i a l but r e m a i n e d m o s t l y j u s t o u t s i d e t h e 1m t i m i n g a r e a ) . E i g h t y - n i n e p e r c e n t of a l l m a l e s d i s p l a y e d t o t h e s o c k e y e f e m a l e s . In c o n t r a s t , kokanee f e m a l e s were a t t r a c t i v e t o a l l kokanee and j a c k s o c k e y e m a l e s , but t o few medium and l a r g e s o c k e y e m a l e s ( F i g . 3 3 b ) . A l l kokanee and j a c k males s p e n t most o f t h e i r t i m e n e a r t h e kokanee f e m a l e s and d i s p l a y e d t o them, but most medium and l a r g e m a l e s 191 F i g u r e 33. The a t t r a c t i v e n e s s of s o c k e y e (a) and kokanee (b) f e m a l e s t o s o c k e y e and kokanee m a l e s as i n d i c a t e d by t h e t o t a l t i m e i n d i v i d u a l m ales s p e n t near them when no o t h e r c h o i c e was a v a i l a b l e o v e r t e n m i n u t e s of o b s e r v a t i o n i n an e x p e r i m e n t a l a r e n a . See F i g . 27 f o r l e t t e r d e s i g n a t i o n . a. Sockeye Females 600 <n 500 A Q ) r-l 400 ro E Q ) L L 300 c to OJ 200 0 ) E •ri IOO H oH J J MM^ jj M H M M LL L L K K 01 0 ) f—i ro E Q J U. c_ ro OJ z OJ E •ri 600 -500 -400 300 200 100 -0 -1 1 b. Kokanee Females vLlUU J J K M * J J MM M M V M w L L L L L • 20 —r-30 - i — 40 50 60 Male Fork Length (cm) 70 193 Table 11. The frequency d i s t r i b u t i o n and mean number of c o u r t s h i p d i s p l a y s performed by 12 males of each of four s i z e c l a s s e s with i n d i v i d u a l sockeye and kokanee females over ten minutes of observation i n an experimental arena. Male S i z e Class Female S i z e C l a s s 1 kokanee -5 6-15 16-25 >25 sockeye 1-5 6-15 16-25 >25 kokanee 2 2 jack 1 2 medium 9 1 1 large 10 1 3 5 29.7) 2 4 4 1 8 47.3| 7 3 1 3.51 1 4 2 1 2.8 | 2 6 3 11.2 10.6 24.8 5.5 1 94 s p e n t l i t t l e t i m e n e a r t h e kokanee f e m a l e s and o n l y a few of e a c h s i z e c l a s s d i s p l a y e d t o them. Those l a r g e s o c k e y e males w h i c h d i d r e s p o n d t o t h e kokanee f e m a l e s were t h e s m a l l e s t of t h e i r c l a s s . Kokanee f e m a l e s spawned o n l y once w i t h kokanee m a l e s , f o u r t i m e s w i t h j a c k s o c k e y e m a l e s and n e v e r w i t h medium and l a r g e s o c k e y e m a l e s . S o c k e y e f e m a l e s spawned f i v e t i m e s w i t h medium m a l e s and once w i t h a l a r g e male compared t o once w i t h a kokanee male and z e r o t i m e s w i t h j a c k m a l e s . The d i g g i n g b e h a v i o u r of s o c k e y e and kokanee f e m a l e s d i f f e r e d s i g n i f i c a n t l y (p<0.01; T a b l e 1 2 ) . S o c k e y e f e m a l e s dug more when c o u r t e d by medium and l a r g e m ales t h a n by kokanee and j a c k m a l e s , but kokanee f e m a l e s dug more o f t e n i n t h e p r e s e n c e of kokanee and j a c k m a l e s . The r a t e of s o c k e y e d i g g i n g can be r e l a t e d t o s o c k e y e f e m a l e p r e f e r e n c e f o r r e l a t i v e l y l a r g e m a l e s as a l l s i z e s of males a c t i v e l y c o u r t e d t h e s o c k e y e f e m a l e s . I t i s i m p o r t a n t t o n o t e t h a t t h e v a r y i n g s o c k e y e f e m a l e r e s p o n s e d i d not m a r k e d l y a f f e c t t h e i r a t t r a c t i v e n e s s t o kokanee and t h e t h r e e s i z e g r o u p s o f s o c k e y e m a l e s . T h i s d e m o n s t r a t e s t h a t f e m a l e c h o i c e (as i n d i c a t e d by t h e r a t e o f n e s t c o n s t r u c t i o n ) does not d i c t a t e male c h o i c e i n s o c k e y e and kokanee.. Kokanee f e m a l e d i g g i n g c a n n o t be r e l a t e d d i r e c t l y t o kokanee f e m a l e p r e f e r e n c e f o r kokanee and j a c k m a l e s as most of t h e medium and l a r g e m a l e s d i d not r e s p o n d t o t h e p r e s e n c e o f kokanee f e m a l e s . T a b l e 12. The d i f f e r e n c e i n t h e number of d i g s (+SE) p e r f o r m e d by e i g h t s o c k e y e and e i g h t kokanee f e m a l e s when i n t h e a l t e r n a t i n g p r e s e n c e of t h r e e i n d i v i d u a l males of each of two s i z e c l a s s e s , o v e r one hour of o b s e r v a t i o n i n an e x p e r i m e n t a l a r e n a . Female t y p e Male s i z e c l a s s p a i r Kokanee Sockeye kokanee and medium s o c k e y e "3,5 (2.9) 19.3 (5.5) j a c k and l a r g e s o c k e y e -15.3 (8.5) 13.8 (8.4) The d i f f e r e n c e i n d i g s was c a l c u l a t e d by s u b t r a c t i n g the t o t a l number of d i g g i n g b o u t s p e r f o r m e d i n t h e p r e s e n c e of t h e s m a l l e s t male from t h o s e w i t h t h e l a r g e s t male. 196 D i s c u s s i o n P r o x i m a t e mechanisms i n v o l v e d i n a s s o r t a t i v e mat i n g T h e r e i s a s t r i k i n g d e g r e e o f a s s o r t a t i v e m a t i n g by form between s o c k e y e and kokanee i n b o t h P i e r r e and Narrows c r e e k s . S o c k e y e m a l e s mate a l m o s t e x c l u s i v e l y w i t h s o c k e y e f e m a l e s whereas kokanee males mate w i t h b o t h kokanee and s o c k e y e f e m a l e s . B e c a u s e of t h e i r s m a l l s i z e kokanee m a l e s a r e r e s t r i c t e d t o s u b o r d i n a t e , sneak r o l e s i n t h e spawning of s o c k e y e p a i r s . T h i s p a t t e r n of m a t i n g i s a p p a r e n t l y s t a b l e o v e r y e a r s and l o c a l i t i e s i n B a b i n e Lake (Hanson and S m i t h 1967; M c C a r t 1970) and o v e r y e a r s i n T a k l a Lake ( p e r s . o b s . ). I n c r e a s e d f e r t i l i z a t i o n e f f i c i e n c y has been s u g g e s t e d as a f a c t o r i n t h e e v o l u t i o n of a s s o r t a t i v e m a t i n g of a m p h i b i a n s and f i s h e s ( D a v i e s and H a l l i d a y 1977; M a l m q v i s t 1983). T h i s does not a c c o u n t f o r t h e a s s o r t a t i v e m a t i n g by form (and s i z e ) o b s e r v e d i n s a l m o n i d s , as s m a l l non-anadromous and l a r g e anadromous m a l e s a r e e q u a l l y c a p a b l e of f e r t i l i z i n g l a r g e f e m a l e s , i n t h e a b s e n c e of c o m p e t i t i o n (McCart 1970; H u t c h i n g s and Myers 1985). M a l e i n t r a s e x u a l c o m p e t i t i o n has been s u g g e s t e d as t h e major f a c t o r b e h i n d a s s o r t a t i v e m a t i n g between d i f f e r e n t s i z e c l a s s e s and forms (anadromous and non-anadromous) of s a l m o n i d s (Hanson and S m i t h 1967; M c C a r t 1970; J o n s s o n and H i n d a r 1982). 1 97 T h e s e s t u d i e s assumed a l l m a l e s p r e f e r r e d t h e l a r g e s t f e m a l e s w h i c h i s u n l i k e l y t o be t h e c a s e ( s e e C h a p t e r 3 ) . My r e s u l t s show t h a t male c o m p e t i t i o n i s n o t t h e d i r e c t c a u s e o f a s s o r t a t i v e m a t i n g between s o c k e y e and kokanee, as a s s o r t a t i v e m a t i n g o c c u r r e d i n t h e a b s e n c e o f c o m p e t i t o r s i n b o t h P i e r r e and Narrows c r e e k s ( F i g s . 25, 26, 28 and 2 9 ) . W i t h an i n c r e a s e i n th e number o f males p r e s e n t i n t h e e x p e r i m e n t a l a r e n a s , a s s o r t a t i v e m a t i n g d i d n o t i n c r e a s e between forms as p r e d i c t e d by t h e c o m p e t i t i o n h y p o t h e s i s , b ut d e c r e a s e d i n P i e r r e C r e e k and r e m a i n e d t h e same i n Narrows C r e e k . B a b i n e kokanee m a l e s , w h i c h p r e f e r r e d kokanee f e m a l e s i n t h e a b s e n c e o f c o m p e t i t i o n , s w i t c h e d t h e i r p r e f e r e n c e t o s o c k e y e f e m a l e s o n l y when d e n i e d a c c e s s t o kokanee f e m a l e s . T h i s s w i t c h i n p r e f e r e n c e a p p e a r s t o a c c o u n t f o r t h e numerous kokanee m a l e s a t t e n d i n g i n d i v i d u a l s o c k e y e f e m a l e s i n P i e r r e C r e e k , as a l m o s t a l l t h e t e r r i t o r i a l kokanee f e m a l e s were a t t e n d e d by kokanee m a l e s ( T a b l e 10). T a k l a kokanee males d i d n o t s w i t c h t h e i r p r e f e r e n c e t o s o c k e y e f e m a l e s when d e n i e d a c c e s s t o kokanee f e m a l e s , c o n s i s t e n t w i t h t h e r e l a t i v e l y few kokanee m a l e s o b s e r v e d a t t e n d i n g s o c k e y e f e m a l e s i n Narrows C r e e k ( T a b l e 10). Complementary male and f e m a l e c h o i c e a p p e a r t o be t h e major f a c t o r s p r o m o t i n g a s s o r t a t i v e m a t i n g between s o c k e y e and kokanee. I n d i v i d u a l s of b o t h s e x e s f i n d members of t h e o p p o s i t e sex of t h e i r own form h i g h l y a t t r a c t i v e . Kokanee f e m a l e s a r e h i g h l y r e c e p t i v e t o kokanee m a l e s as a r e s o c k e y e f e m a l e s t o s o c k e y e males ( F i g . 27; T a b l e 1 2 ) . In B a b i n e L a k e , o n l y kokanee 198 f e m a l e s and j a c k s o c k e y e m a l e s a p p e a r s t r o n g l y and m u t u a l l y r e c e p t i v e between f o r m s . Even i n t h i s c a s e , j a c k s o c k e y e s t r o n g l y p r e f e r s o c k e y e o v e r kokanee f e m a l e s when g i v e n a c h o i c e ( F i g s . 25 and 2 6 ) . I o b s e r v e d no e v i d e n c e of m u t u a l r e c e p t i v i t y between s o c k e y e and kokanee i n Narrows C r e e k , p o s s i b l y b e c a u s e of t h e v i r t u a l a b s e n c e of s m a l l ( j a c k ) s o c k e y e m a l e s . E v i d e n c e of a form e f f e c t i n kokanee male c h o i c e I showed i n C h a p t e r 3 t h a t w i t h i n kokanee, o v e r a s i z e r ange a p p r o a c h i n g t h a t between s o c k e y e and kokanee i n B a b i n e and T a k l a l a k e s , male c h o i c e depended on t h e r e l a t i v e s i z e s of f e m a l e s t o m a l e s . M a l e s c h o s e f e m a l e s of t h e i r own s i z e o r l a r g e r ; l a r g e m a l e s c h o s e l a r g e f e m a l e s ; s m a l l m a l e s c h o s e s m a l l or l a r g e f e m a l e s w i t h e q u a l f r e q u e n c y . In t h e c h o i c e s between forms i n t h i s s t u d y , t h e p r e f e r e n c e of s o c k e y e m a l e s f o r s o c k e y e f e m a l e s can be a c c o u n t e d f o r by s i m i l a r male c h o i c e d e p e n d e n t on t h e s i z e of t h e f e m a l e r e l a t i v e t o t h a t o f t h e male. The a t t r a c t i v e n e s s of kokanee f e m a l e s t o s o c k e y e m a l e s d e c l i n e d r a p i d l y w i t h i n c r e a s i n g male s i z e i n B a b i n e Lake ( F i g s . 25, 26 and 3 3 ) . However, t h e p r e f e r e n c e o f kokanee m a l e s f o r kokanee f e m a l e s c a n n o t so be e x p l a i n e d . From t h e r e s u l t s w i t h i n kokanee, kokanee m a l e s would be p r e d i c t e d n o t t o d i s c r i m i n a t e between kokanee and s o c k e y e f e m a l e s . Thus t h e p r e f e r e n c e o f kokanee m a l e s f o r kokanee f e m a l e s i n b o t h P i e r r e and Narrows c r e e k s i n d i c a t e s t h a t kokanee male c h o i c e depends on f e m a l e f o r m . T h i s was p a r t i c u l a r l y c l e a r i n Narrows C r e e k , where 199 kokanee m a l e s d i s p l a y e d l i t t l e i n t e r e s t i n becoming s n e a k s t o s o c k e y e p a i r s , even i n t h e a b s e n c e o f any o t h e r c h o i c e . In P i e r r e C r e e k , t h e s u g g e s t i o n Of a form e f f e c t i n kokanee male c h o i c e i s s u p p o r t e d by t h e c o m p a r i s o n o f kokanee and j a c k s o c k e y e c h o i c e . Even t h o u g h kokanee and j a c k m a l e s a r e r e s t r i c t e d t o t h e same c h o i c e o f mates on t h e spawning g r o u n d s , t h a t i s t o be d o m i n a n t s t o kokanee f e m a l e s o r s n e a k s t o s o c k e y e p a i r s , t h e i r c h o i c e d i f f e r s . G i v e n a c h o i c e between a s o l e kokanee f e m a l e and a s o c k e y e p a i r i n t h e e x p e r i m e n t a l a r e n a s , j a c k s o c k e y e m a l e s s t r o n g l y p r e f e r r e d t h e s o c k e y e w h i l e kokanee m a l e s s t r o n g l y p r e f e r r e d t h e kokanee f e m a l e ( F i g s . 25 and 2 6 ) . T h i s b e h a v i o u r a l d i f f e r e n c e i s not e x p l a i n e d by a d i f f e r e n c e i n s n e a k i n g a b i l i t y between kokanee and j a c k s o c k e y e m a l e s . In s a l m o n , t h e s m a l l e s t m a l e s ( i n t h i s c a s e kokanee) a r e t h o u g h t t o p o s s e s s an a d v a n t a g e i n sneak b e h a v i o u r b e c a u s e of t h e i r a b i l i t y t o g a i n c l o s e a c c e s s t o f e m a l e s p r i o r t o ( G r o s s 1985) and d u r i n g spawning ( J o n e s and K i n g 1952; M c C a r t 1970; G r o s s 1985). In t h i s s t u d y , B a b i n e kokanee m a l e s were a b l e t o sneak d i r e c t l y b e n e a t h and between spawning s o c k e y e whereas j a c k m a l e s , b e c a u s e of t h e i r l a r g e r s i z e , were r e s t r i c t e d t o p o s i t i o n s b e s i d e t h e spawning s o c k e y e p a i r . P o s s i b i l i t y t h a t t h e form e f f e c t i n male c h o i c e a r o s e f r o m  s e l e c t i o n f o r p r e m a t i n g i s o l a t i o n The e v o l u t i o n of r e p r o d u c t i v e i s o l a t i n g mechanisms between 200 s y m p a t r i c forms i n p o l y m o r p h i c p o p u l a t i o n s w i l l p r o b a b l y o c c u r o n l y i f t h e r e a r e s t r o n g s e l e c t i v e d i f f e r e n c e s between t h e e n v i r o n m e n t s t h e forms o c c u p y ( e . g_. Maynard S m i t h 1966; R o s e n z w e i g 1978; Pimm 1979; R i c e 1984). As a d a p t i v e g e n e t i c d i f f e r e n c e s a c c u m u l a t e between f o r m s , t h e f i t n e s s o f p r o g e n y o f between f o r m c r o s s e s w i l l d e c r e a s e , t h u s p r o m o t i n g t h e e v o l u t i o n o f p r e m a t i n g i s o l a t i n g mechanisms. At p r e s e n t , t h e r e i s no d i r e c t e v i d e n c e o f s e l e c t i o n a g a i n s t t h e p r o g e n y o f s o c k e y e -kokanee m a t i n g s but i t i s p r o b a b l e t h a t s u c h s e l e c t i o n e x i s t s , a s t h e s e l e c t i o n p r e s s u r e s of t h e m a r i n e and l a c u s t r i n e e n v i r o n m e n t s p r o b a b l y d i f f e r g r e a t l y ( s e e R i c k e r 1940). D i f f e r e n c e s i n s e l e c t i o n o p e r a t i n g on s o c k e y e and kokanee a r e i n d i c a t e d by t h e i r g e n e t i c d i v e r g e n c e i n v e r t e b r a numbers and a l l o z y m e f r e q u e n c i e s i n B a b i n e L a k e , and by t h e i r d i v e r g e n c e i n g i l l r a k e r number and a l l o z y m e f r e q u e n c i e s i n T a k l a Lake ( v e r t e b r a l c o u n t c o m p a r i s o n s have n o t been made on T a k l a s o c k e y e and k o k a n e e ) . M c C a r t (1970) f o u n d t h a t t h e v e r t e b r a numbers d i f f e r e d s i g n i f i c a n t l y between B a b i n e s o c k e y e and kokanee. T h e s e d i f f e r e n c e s were m a i n t a i n e d i n c o n t r o l l e d r e a r i n g e x p e r i m e n t s . V e r t e b r a l v a r i a t i o n w i t h i n p o p u l a t i o n s o f f i s h e s has r e c e n t l y been d e m o n s t r a t e d t o be a d a p t i v e (Swain and L i n d s e y 1984). N e l s o n (1968b) showed t h a t T a k l a Lake kokanee and s o c k e y e d i f f e r e d s i g n i f i c a n t l y i n g i l l r a k e r number. G i l l r a k e r number i s an i n h e r i t e d t r a i t i n t h e f a m i l y S a l m o n i d a e ( S v a r d s o n 1970), and d i v e r g e n c e i n g i l l r a k e r number i n s y m p a t r i c p o p u l a t i o n s i s u s u a l l y a s s o c i a t e d w i t h e c o l o g i c a l d i v e r g e n c e ( e . g. L i n d s e y 1963; B o d a l y 1979). The f r e q u e n c i e s o f a few 201 a l l o z y m e s a l s o d i f f e r s i g n i f i c a n t l y between s o c k e y e and kokanee i n P i e r r e C r e e k , B a b i n e L a k e , and i n Narrows C r e e k , T a k l a L a k e and t h e s e d i f f e r e n c e s a r e m a i n t a i n e d o v e r y e a r s ( C h a p t e r 4 ) . The e v o l u t i o n of g e n e t i c d i f f e r e n t i a t i o n and r e p r o d u c t i v e i s o l a t i o n i n sympatry i s g r e a t l y f a c i l i t a t e d by an i n i t i a l d e g r e e of a s s o r t a t i v e m a t i n g between forms (Maynard S m i t h 1966). Most models and examples o f t h e e v o l u t i o n of r e p r o d u c t i v e i s o l a t i o n between forms have s u g g e s t e d b r e e d i n g h a b i t a t d i f f e r e n t i a t i o n as t h e p r e d o m i n a n t f a c t o r p r o m o t i n g s u c h i n i t i a l a s s o r t a t i v e m a t i n g ( e . £ . Maynard S m i t h 1966; Bush 1975; T a u b e r and T a u b e r 1977; McKaye 1980; R i c e 1984, 1985; R a u s h e r 1984). I have d e m o n s t r a t e d t h a t p h y s i c a l f a c t o r s ( i n t h i s c a s e s i z e ) a s s o c i a t e d w i t h t h e p o l y m o r p h i s m can a l s o r e s u l t i n a s i g n i f i c a n t d e c r e a s e i n gene f l o w between f o r m s . Gene f l o w i s r e s t r i c t e d between s i z e c l a s s e s w i t h i n s o c k e y e salmon and kokanee b e c a u s e of a s s o r t a t i v e m a t i n g by s i z e (Hanson and S m i t h 1967; C h a p t e r 3 ) . A s s o r t a t i v e m a t i n g by s i z e w i t h i n forms i s p a r t l y a c o n s e q u e n c e o f male c h o i c e d e p e n d e n t on male s i z e and male i n t r a s e x u a l c o m p e t i t i o n ( C h a p t e r s 1 and 3 ) . Female mate c h o i c e and f e m a l e i n t r a s e x u a l c o m p e t i t i o n a l s o p r o b a b l y promote a s s o r t a t i v e m a t i n g w i t h i n forms (Hanson and S m i t h 1967; S c h r o d e r 1981; J o n s s o n and H i n d a r 1982; C h a p t e r 2 ) . As s u c h , gene f l o w i s e x p e c t e d t o be even f u r t h e r r e s t r i c t e d between s o c k e y e and kokanee, as t h e s i z e d i f f e r e n c e between forms i s f a r g r e a t e r t h a n t h a t f o u n d w i t h i n f o r m s . S i n c e t h i s s i z e d i f f e r e n c e i s l a r g e l y e n v i r o n m e n t a l l y i n d u c e d ( F o e r s t e r 1947; R i c k e r 1938, 202 1940, 1959, 1972; S c o t t 1984), t h e i n i t i a l p r o d u c t i o n of b o t h anadromous and non-anadromous i n d i v i d u a l s w i t h i n a p o p u l a t i o n w i l l r e s u l t i n a s e v e r e r e s t r i c t i o n i n gene f l o w between forms b e f o r e any g e n e t i c d i f f e r e n t i a t i o n has o c c u r r e d . Such an i n i t i a l s e v e r e r e s t r i c t i o n i n gene f l o w a c c o m p a n i e d by s t r o n g d i s r u p t i v e s e l e c t i o n , may have l e d t o t h e o b s e r v e d g e n e t i c d i f f e r e n t i a t i o n o f s o c k e y e and kokanee i n B a b i n e and T a k l a l a k e s , and t h u s t o t h e e v o l u t i o n of t h e o b s e r v e d p r e m a t i n g i s o l a t i n g between t h e f o r m s . I f so, t h i s i n d i c a t e s s e x u a l s e l e c t i o n may promote g e n e t i c d i v e r g e n c e and p o s s i b l y s p e c i a t i o n between s y m p a t r i c p o p u l a t i o n s of a n i m a l s i n a d d i t i o n t o i t s p o s s i b l e r o l e i n t h e r a p i d a l l o p a t r i c s p e c i a t i o n of a n i m a l s ( s e e Lande 1981; W e s t - E b e r h a r d 1983, 1986). The i d e a t h a t a p o l y m o r p h i s m may r e s u l t i n a s u b s t a n t i a l d e c r e a s e i n gene f l o w between forms i s not new. The i m p r i n t i n g of p a r e n t a l and s i b c o l o u r morphs i s a n o t h e r c h a r a c t e r a s s o c i a t e d w i t h p o l y m o r p h i s m s w h i c h can l e a d t o a s s o r t a t i v e m a t i n g and p o s s i b l y s y m p a t r i c s p e c i a t i o n i n c i c h l i d f i s h e s ( K o s s w i g 1947; S i e p e n and C r a p on de C a p r o n a 1986). F i n a l l y , i t has been a r g u e d t h a t t h e e v o l u t i o n o f p r e m a t i n g i s o l a t i o n t h r o u g h mate c h o i c e i s g r e a t l y r e s t r i c t e d i n n a t u r e b e c a u s e of complex g e n e t i c c h a n g e s r e q u i r e d i n t h e manner i n w h i c h i n d i v i d u a l s s e l e c t mates ( F e l s e n s t e i n 1981; Sved 1981a, 1981b). U n l e s s t h e r e i s some i n i t i a l l i n k a g e d i s e q u i l i b r i u m between g e n e ( s ) c o d i n g f o r a s s o r t a t i v e m a t i n g by form and t h o s e 203 under s e l e c t i o n t h e r e can be no i s o l a t i o n between s u b p o p u l a t i o n s . In t h e c a s e of s o c k e y e salmon and kokanee, l i t t l e c hange i n kokanee male c h o i c e i s r e q u i r e d t o p r o d u c e s i g n i f i c a n t p r e m a t i n g i s o l a t i o n between s o c k e y e and kokanee i n l o c a l i t i e s where t h e forms spawn s y m p a t r i c a l l y . In t h i s c a s e , t h e l i n k a g e i s not c h r o m o s o n a l but s i z e a s s o c i a t e d . Where s e p a r a t e , s m a l l kokanee m a l e s d e m o n s t r a t e d no p r e f e r e n c e between f e m a l e s t h e r e own s i z e and t h o s e much l a r g e r ( a p p r o a c h i n g s o c k e y e f e m a l e s i z e ; C h a p t e r 3 ) . The s l i g h t r e d u c t i o n i n t h e a t t r a c t i v e n e s s of s o c k e y e f e m a l e s t o kokanee m a l e s i n B a b i n e Lake r e s u l t e d i n kokanee f e m a l e s b e i n g t h e most a t t r a c t i v e and s i g n i f i c a n t a s s o r t a t i v e m a t i n g by form ( F i g . 3 4 ) . The f u r t h e r r e d u c t i o n i n t h e a t t r a c t i v e n e s s of s o c k e y e f e m a l e s t o kokanee m a l e s i n T a k l a L a k e, i n a s s o c i a t i o n w i t h t h e g r e a t e r g e n e t i c d i v e r g e n c e ( s e e C h a p t e r 4 ) , may s i m p l y r e p r e s e n t an a d d i t i o n a l s t e p i n t h e p r o c e s s of t h e e v o l u t i o n of p r e m a t i n g i s o l a t i o n . T h us, t h e e v o l u t i o n of a form e f f e c t i n kokanee male c h o i c e does not a p p e a r t o i n v o l v e a major change i n t h e manner i n w h i c h m a l e s s e l e c t mates, but r a t h e r an a d j u s t m e n t i n t h e manner i n w h i c h t h e y r e s p o n d t o f e m a l e s o f p a r t i c u l a r s i z e s , a b e h a v i o u r a l c h a r a c t e r i s t i c s e e m i n g l y amenable t o s e l e c t i o n w i t h i n forms ( s e e C h a p t e r 3 ) . In c o n c l u s i o n , I have p r e s e n t e d b e h a v i o u r a l e v i d e n c e t o s u g g e s t a s s o r t a t i v e m a t i n g between s o c k e y e and kokanee i n P i e r r e and Narrows c r e e k s i s , i n p a r t , t h e r e s u l t o f male mate c h o i c e d e p e n d e n t on form. Male i n t r a s e x u a l c o m p e t i t i o n and male mate 204 F i g u r e 34 . The a t t r a c t i v e n e s s of s o c k e y e f e m a l e s t o kokanee ma l e s i n P i e r r e C r e e k , B a b i n e Lake (*B') and Narrows C r e e k , T a k l a Lake ('T') as compared t o t h a t e x p e c t e d b a s e d on t h e s i z e a l o n e . o CM Female F o r k L e n g t h / M a l e F o r k L e n g t h 206 c h o i c e d e p e n d e n t on male s i z e do n o t d i r e c t l y a c c o u n t f o r t h e p r e f e r e n c e of kokanee m a l e s f o r kokanee f e m a l e s i n b o t h s y s t e m s . I have a r g u e d t h a t s u c h form d e p e n d e n t c h o i c e may have e v o l v e d as a r e s u l t of s e l e c t i o n a g a i n s t t h e ' h y b r i d s ' o f t h e two f o r m s . S u p p o r t i n g t h i s h y p o t h e s i s , I d e m o n s t r a t e d ( C h a p t e r 4) t h a t s y m p a t r i c s o c k e y e and kokanee p o p u l a t i o n s a r e g e n e t i c a l l y d i v e r g e n t , s u g g e s t i n g s t r o n g s e l e c t i o n e x i s t s a g a i n s t ' h y b r i d s ' . Such s e l e c t i o n , i n a s s o c i a t i o n w i t h t h e a s s o r t a t i v e m a t i n g by s i z e and t h u s form ( C h a p t e r 1 t o 3 ) , c a n l e a d t o t h e e v o l u t i o n of p r e m a t i n g i s o l a t i o n . Some d e g r e e of p r e m a t i n g i s o l a t i o n was o b s e r v e d i n b o t h B a b i n e and T a k l a L a k e s . The knowledge o f t h e b i o l o g y o f 0. n e r k a , and t h e g e n e t i c s i m i l a r i t y between s y m p a t r i c f o r m s , s u g g e s t s t h a t s o c k e y e and kokanee may have d i v e r g e d i n s y m p a t r y , t h u s l e a d i n g t o t h e p o s s i b i l i t y of s y m p a t r i c s p e c i a t i o n . S i n c e B a b i n e and T a k l a l a k e s have been d e g l a c i a t e d f o r l e s s t h a n 10,000 y e a r s ( L i n d s e y and M c P h a i l 1986), i t i s p o s s i b l e t h a t t h e p r o c e s s e s o f g e n e t i c d i f f e r e n t i a t i o n and e v o l u t i o n of r e p r o d u c t i v e i s o l a t i o n between s o c k e y e salmon and kokanee a r e o n g o i n g i n b o t h s y s t e m s . 207 CONCLUSIONS The e v o l u t i o n of p r e m a t i n g i s o l a t i n g mechanisms between s o c k e y e salmon and kokanee i s c o n s i s t e n t w i t h m o d els of s y m p a t r i c s p e c i a t i o n ( e . g_. Maynard S m i t h 1966; R i c e 1984). As has been o b s e r v e d i n o t h e r s a l m o n i d s ( e . £ . I v a n k o v e t al. 1981; Nordeng 1983), e i t h e r form c an g i v e r i s e t o t h e o t h e r ( R i c k e r 1938, 1940, 1959, 1972; F o e r s t e r 1947; S c o t t 1984). The s e l e c t i v e p r e s s u r e s e x p e r i e n c e d by s o c k e y e and kokanee p r o b a b l y d i f f e r g r e a t l y ( see R i c k e r 1940). F o r example, s o c k e y e u n d e r t a k e e x t e n s i v e m i g r a t i o n s t o and t h r o u g h o u t t h e n o r t h P a c i f i c Ocean, a f t e r w h i c h t h e y r e t u r n t o t h e i r p o p u l a t i o n s p e c i f i c s pawning g r o u n d s . The e n e r g y demands of t h e s e m i g r a t i o n s a r e g r e a t ( e . g_. Mommsen e_t a l . 1980), g e n e r a t i n g s t r o n g s e l e c t i o n on swimming p e r f o r m a n c e ( e . c.. R i c k e r 1972). In c o n t r a s t , kokanee u n d e r g o no e x t e n s i v e m i g r a t i o n s , a l l e v i a t i n g t h e need t o a l l o c a t e l a r g e e n e r g y s t o r e s f o r m i g r a t i o n and p r o b a b l y d e c r e a s i n g t h e s e l e c t i v e p r e s s u r e s a s s o c i a t e d w i t h p r o l o n g e d a r d u o u s m i g r a t i o n s . A d i f f e r e n c e i n swimming p e r f o r m a n c e i s i n d i c a t e d by t h e r e l a t i v e i n a b i l i t y of kokanee t o n a v i g a t e b a r r i e r s compared t o s o c k e y e ( S e e l e y and McCammon 1966). F r e s h w a t e r p a r a s i t e i n f e s t a t i o n r a t e s ~ ( S a l m i n c o l a ) d i f f e r between s o c k e y e and kokanee, w i t h kokanee t h e more r e s i s t a n t ( R i c k e r 1938). T h i s s u g g e s t s kokanee have d e v e l o p e d s p e c i f i c d e f e n s e s not n e c e s s a r y t o s o c k e y e , as S a l m i n c o l a a r e l o s t upon e n t e r i n g s a l t w a t e r ( R i c k e r 1940). G e n e t i c d i f f e r e n c e s w h i c h a c c r u e b e c a u s e of s e l e c t i v e 208 d i f f e r e n c e s between e n v i r o n m e n t s may p e r s i s t b e c a u s e of t h e h i g h d e g r e e o f a s s o r t a t i v e m a t i n g by s i z e , and hence by f o r m ( C h a p t e r s 1, 2, 3 and 5 ) . T h a t g e n e t i c d i f f e r e n c e s do p e r s i s t between forms was c l e a r l y e v i d e n t i n t h e g e n e t i c e x a m i n a t i o n o f a l l o z y m e f r e q u e n c i e s ( C h a p t e r 4 ) . A d a p t i v e g e n e t i c d i f f e r e n t i a t i o n p r o m o t e s t h e e v o l u t i o n o f p r e m a t i n g i s o l a t i n g mechanisms. P r e m a t i n g i s o l a t i o n was o b s e r v e d between s o c k e y e and kokanee i n two s e p a r a t e s y s t e m s , w i t h t h e d e g r e e o f i s o l a t i o n p o s i t i v e l y c o r r e l a t e d t o t h e d e g r e e o f g e n e t i c d i f f e r e n t i a t i o n ( C h a p t e r 5 ) . Two f a c t o r s a p p e a r c r i t i c a l f o r s u c h s y m p a t r i c d i v e r g e n c e t o o c c u r : t h e r e must be p a r t i c u l a r e c o l o g i c a l c o n d i t i o n s i f two forms of one s p e c i e s a r e t o o c c u r t o g e t h e r and; mechanisms must e x i s t by w h i c h one form c an g i v e r i s e t o t h e o t h e r . T h e r e a r e numerous examples o f t h e s y m p a t r i c o c c u r r e n c e o f two v e r y s i m i l a r forms w i t h i n t h e F a m i l y S a l m o n i d a e ( e . g_. L i n d s e y 1963, 1981; I v a n k o v e t a l . 1981; J o n s s o n 1985; H i n d a r e t a l . 1986). The s y m p a t r i c o c c u r r e n c e of two forms a p p e a r s t o be d i r e c t l y t i e d t o t h e p r e v a i l i n g e n v i r o n m e n t a l c o n d i t i o n s . C i s c o e s (genus C o r e g o n u s , subgenus L e u c i c h t h y s ) n o r m a l l y o c c u p y t h e p e l a g i c zone of l a k e s , f e e d i n g on z o o p l a n k t o n w i t h t h e i r numerous l o n g f i n e g i l l r a k e r s . Where c i s c o e s a r e a b s e n t , l a k e w h i t e f i s h ( C o r e g o n u s c l u p e a f o r m i s ) n o r m a l l y a b e n t h i c f e e d e r , t y p i c a l l y have h i g h e r g i l l r a k e r c o u n t s ( L i n d s e y 1981), and i n i n some l a k e s o c c u r i n two d i s c r e t e h i g h and low g i l l r a k e r forms 209 ( L i n d s e y 1963; B o d a l y 1979). T h e s e two forms of w h i t e f i s h o c c u p y t h e p e l a g i c and b e n t h i c z o n e s , w h i c h a r e n o r m a l l y o c c u p i e d by c i s c o e s and w h i t e f i s h , r e s p e c t i v e l y . S i m i l a r l y , dwarf and n o r m a l s i z e d non-anadromous A r c t i c c h a r o c c u r s y m p a t r i c a l l y i n many Norwegian l a k e s , t h e i r c o - o c c u r r e n c e a p p a r e n t l y r e s t r i c t e d t o l a k e s deep enough t o have a w e l l o x y g e n a t e d h y p o l i m n i o n ( H i n d a r and J o n s s o n 1982). C h e r r y salmon ( 0 . masu) e x i s t i n b o t h anadromous and non-anadromous f o r m s , w h i c h may o c c u r t o g e t h e r o r s e p a r a t e l y ( I v a n k o v e t a l . 1981). The c o - e x i s t e n c e of t h e two forms i s t i e d t o t h e p r o d u c t i v i t y of t h e f r e s h w a t e r e n v i r o n m e n t , t h e g r e a t e r t h e p r o d u c t i v i t y t h e more p r o b a b l e t h a t t h e two forms w i l l c o - e x i s t . The s y m p a t r i c o c c u r r e n c e of s o c k e y e salmon and kokanee a p p e a r s t i e d t o b o t h l a k e p r o d u c t i v i t y and t h e p r e s e n c e of c o m p e t i t o r s . Kokanee a r e a b s e n t from most c o a s t a l l a k e s c o n t a i n i n g s o c k e y e salmon i n B r i t i s h C o l u m b i a ( R i c k e r 1940; N e l s o n 1968a; K. H y a t t , P a c i f i c B i o l o g i c a l S t a t i o n , Nanaimo, p e r s . comm. ). These l a k e s a r e t y p i f i e d by low p r o d u c t i v i t y and s m a l l s o c k e y e s m o l t s i z e s ( H y a t t and S t o c k n e r 1 9 8 5 ) , s u g g e s t i n g f o o d r e s o u r c e s may not be g r e a t enough t o s u p p o r t two s y m p a t r i c f o r m s . F o o d l i m i t a t i o n i n c o a s t a l l a k e s i s p r o b a b l y f u r t h e r e x a g g e r a t e d by t h e p r e s e n c e o f l i m n e t i c t h r e e s p i n e s t i c k l e b a c k s , G. a c u l e a t u s , w h i c h compete d i r e c t l y f o r z o o p l a n k t o n (Manzer 1976). In c o n t r a s t , kokanee a r e p r e s e n t i n a l m o s t a l l of t h e c e n t r a l i n t e r i o r s o c k e y e salmon l a k e s on t h e F r a s e r R i v e r s y s t e m ( N e l s o n 1968a; G o o d l a d e t a l . 1974), l a k e s t y p i f i e d by h i g h e r 210 z o o p l a n k t o n p r o d u c t i v i t y , l a r g e r s o c k e y e s m o l t s i z e s , and t h e a b s e n c e of s t i c k l e b a c k s ( G o o d l a d e_t a l . 1974), G i v e n t h e n e c e s s a r y b i o t i c c o n d i t i o n s , kokanee a p p e a r a b l e t o p e r s i s t i n a l a k e u t i l i z e d by j u v e n i l e s o c k e y e salmon ( o r v i c e v e r s a ) . R i c k e r (1938, 1940) o u t l i n e d a mechanism by w h i c h kokanee c o u l d d i v e r g e f r o m s o c k e y e i n s y m p a t r y . S o c k e y e salmon g i v e r i s e t o non-anadromous p r o g e n y ( m a i n l y m a l e s , c a l l e d ' r e s i d u a l s ' by R i c k e r , t h e non-anadromous p r o g e n y of anadromous p a r e n t s ) , w h i c h R i c k e r s u g g e s t e d m i g h t be p r e c u r s o r s of kokanee. I t has s i n c e been d e m o n s t r a t e d t h a t c r o s s e s between r e s i d u a l s a r e v i a b l e ( S m i r n o v 1959), and t h a t s o c k e y e i n t r o d u c e d i n t o l a k e s p r e v i o u s l y b a r r e n of 0. n e r k a can g i v e r i s e t o s e l f s u s t a i n i n g non-anadromous p o p u l a t i o n s ( R i c k e r 1959; S c o t t 1984). T h e s e f a c t s , i n c o n j u n c t i o n w i t h t h e h i g h g e n e t i c s i m i l a r i t y between s o c k e y e and kokanee and t h e s i m i l a r d i s t r i b u t i o n o f t h e forms s u p p o r t t h e c o n t e n t i o n t h a t s o c k e y e have g i v e n r i s e t o kokanee on numerous o c c a s i o n s ( s e e C h a p t e r 4 ) . The s t r o n g male b i a s i n r e s i d u a l s s u g g e s t s t h e y p a r t i c i p a t e as s n e a k s t o s o c k e y e p a i r s . ' S n e a k i n g ' i s a a l t e r n a t i v e r e p r o d u c t i v e s t r a t e g y common amongst s a l m o n i d s , by w h i c h ( u s u a l l y ) s m a l l m ales p a r t i c i p a t e i n t h e s p a w n ing of l a r g e r p a i r s ( s e e C h a p t e r 1 ) . U n l i k e m a l e s , f e m a l e s do not a p p e a r a b l e t o sneak s p a w n i n g s ; t h e y must e s t a b l i s h t e r r i t o r i e s and a t t r a c t m a l e s t o r e p r o d u c e . S i n c e m a l e s d i s c r i m i n a t e a g a i n s t f e m a l e s s m a l l e r t h a n t h e m s e l v e s , s m a l l f e m a l e s a r e u n l i k e l y t o a t t r a c t 21 1 mates i n t h e a b s e n c e of s m a l l males ( s e e C h a p t e r s 3 and 5 ) . Hence s m a l l non-anadromous f e m a l e s a r e u n l i k e l y t o p e r s i s t a s a t y p e i n t h e a b s e n c e o f non-anadromous m a l e s . However, once s m a l l non-anadromous m a l e s e x i s t i n t h e p o p u l a t i o n , p e r p e t u a t e d by t h e i r a b i l i t y f o r sneak f e r t i l i z a t i o n , s m a l l non-anadromous f e m a l e s w i l l be a b l e t o a t t r a c t some m a l e s , i n c r e a s i n g t h e i r r e p r o d u c t i v e c h a n c e s . Once r e s i d u a l m a l e s commence spawning w i t h r e s i d u a l f e m a l e s , t h e p r o d u c t i o n of non-anadromous p r o g e n y from non-anadromous p a r e n t s (_i. e. kokanee) i s p o s s i b l e , g i v e n a p r o p e n s i t y t o p r o d u c e non-anadromous p r o g e n y . The p r o p e n s i t y t o p r o d u c e non-anadromous p r o g e n y i s a p p a r e n t i n t h e p e r p e t u a t i o n of non-anadromous p o p u l a t i o n s , o r i g i n a l l y d e r i v e d f r o m s o c k e y e i n t r o d u c t i o n s ( e . g_. S c o t t 1984). F a c t o r s i n v o l v e d i n s e x u a l s e l e c t i o n would t h e n l e a d t o a s s o r t a t i v e m a t i n g by s i z e and form ( o u t l i n e d i n C h a p t e r 5 ) , t h u s i n c r e a s i n g t h e l i k e l i h o o d of g e n e t i c d i v e r g e n c e between f o r m s , w h i c h may l e a d t o t h e e v o l u t i o n o f p r e m a t i n g i s o l a t i n g mechanisms and u l t i m a t e l y t o s p e c i a t i o n . I c o n c l u d e t h a t s o c k e y e have g i v e n r i s e t o kokanee i n d e p e n d e n t l y i n many p l a c e s w h i c h combine r e l a t i v e l y h i g h p r o d u c t i v i t y w i t h t h e a b s e n c e of c o m p e t i t o r s , and t h a t t h e .p r o c e s s c a n o c c u r s y m p a t r i c a l l y t h r o u g h t h e c o m b i n a t i o n of sneak spawning by s m a l l m a l e s and of a s s o r t a t i v e m a t i n g w i t h r e s p e c t t o s i z e . 212 LITERATURE CITED A l l e n d o r f , F. W. 1975. 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