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Selective mortality of juvenile sockeye (Oncorhynchus nerka) in Babine Lake determined from body-otolith… West, Cameron John 1983

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SELECTIVE MORTALITY OF JUVENILE SOCKEYE ( O n c o r h y n c h u s n e r k a ) IN BABINE LAKE DETERMINED FROM BODY—OTOLITH RELATIONSHIPS by CAMERON JOHN WEST B.Sc., U n i v e r s i t y of B r i t i s h C o l u m b i a , 1976 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Dep a r t m e n t of Z o o l o g y ) We a c c e p t t h i s t h e s i s as c o n f o r m i n g to the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA September 1983 (c) Cameron John W e s t ( 1983 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library shall make i t 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 i s understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of ^ e>& Co The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date DE-6 (3/81) ABSTRACT The p r e s e n c e of d i f f e r e n t i a l growth and m o r t a l i t y was i n v e s t i g a t e d among j u v e n i l e s o c k e y e ( O n c o r h y n c h u s n e r k a ) i n B a b i n e L a k e . Emergent f r y were c o l l e c t e d from the r i v e r s and a r t i f i c i a l spawning c h a n n e l s of the F u l t o n R i v e r and P i n k u t C r e e k systems i n May and e a r l y June of 1979. J u v e n i l e samples were t o w - n e t t e d from B a b i n e Lake i n J u l y , A u g u st and September, and s m o l t samples were c o l l e c t e d i n May and June of the f o l l o w i n g y e a r a t the o u t l e t of the B a b i n e - N i l k i t k w a l a k e s y s tern. F o r k l e n g t h s and the d i m e n s i o n s of s a g i t t a o t o l i t h s were mea s u r e d . O r t h o g o n a l p o l y n o m i a l s f i t t e d to Ln f o r k l e n g t h v e r s u s Ln o t o l i t h s i z e between the s t a g e s of f r y emergence and s m o l t m i g r a t i o n were s i g m o i d w i t h r ^ v a l u e s of 0.97 to 0.98. S i g n i f i c a n t s t o c k d i f f e r e n c e s were fo u n d among l i n e a r r e g r e s s i o n s of Ln f o r k l e n g t h v e r s u s Ln t o t a l o t o l i t h l e n g t h of emergent f r y from F u l t o n R i v e r , P i n k u t Creek and the t h r e e a r t i f i c i a l spawning c h a n n e l s . G r o u p i n g of F u l t o n v e r s u s P i n k u t or of r i v e r v e r s u s c h a n n e l s o u r c e s was not o b v i o u s . An a v e r a g e r e g r e s s i o n was c a l c u l a t e d f o r g e n e r a l use w i t h emergent f r y from the main l a k e p o p u l a t i o n . I n s t a n t a n e o u s growth r a t e of f r y i n e a r l y J u l y was p o s i t i v e l y c o r r e l a t e d w i t h f o r k l e n g t h . The d i s t r i b u t i o n s of emergent f o r k l e n g t h b a c k - c a l c u l a t e d from j u v e n i l e and s m o l t samples i n d i c a t e d h i g h e r m o r t a l i t y r a t e s among f r y w i t h s m a l l e r f o r k l e n g t h s a t emergence. The t i m i n g of the s e l e c t i v e m o r t a l i t y was between mid-August and s m o l t m i g r a t i o n i n the f o l l o w i n g s p r i n g . The a s s o c i a t i o n of s m a l l e r i n i t i a l body s i z e w i t h i n c r e a s e d p r o b a b i l i t y of p a r a s i t i z a t i o n by the c e s t o d e E u b o t h r ium s a l v e l i n i , s u b s e q u e n t s l o w e r growth and the e f f e c t on the s i z e d i s t r i b u t i o n of the y e a r c l a s s i s d i s c u s s e d . TABLE OF CONTENTS i v Page T I T L E PAGE i ABSTRACT i i TABLE OF CONTENTS i v LIST OF FIGURES v i LI S T OF TABLES v i i i ACKNOWLEDGEMENTS X INTRODUCTION 1 GENERAL METHODS 7 F i s h C o l l e c t i o n and P r e s e r v a t i o n 7 O t o l i t h Removal and S t o r a g e 9 O t o l i t h P r e p a r a t i o n and P h o t o g r a p h i n g 10 O t o l i t h Measurements 12 FORK LENGTH VERSUS OTOLITH SIZE RELATIONSHIPS 20 R e l a t i o n s h i p s Between F r y Emergence and Smolt M i g r a t i o n 19 R e l a t i o n s h i p s f o r Emergent F r y 24 S t o c k D i f f e r e n c e s a t Emergence 26 GROWTH RATE IN BABINE LAKE 32 SELECTIVE MORTALITY IN BABINE LAKE 36 T o t a l O t o l i t h L e n g t h a t Emergence 36 F o r k L e n g t h a t Emergence 42 F o r k L e n g t h V e r s u s T o t a l O t o l i t h L e n g t h 49 V GENERAL DISCUSSION 53 SUMMARY 58 LITERATURE CITED 60 v i L I S T OF FIGURES F i g u r e Page 1. Map of B a b i n e Lake, B r i t i s h C o l u m b i a 2 2. Sockeye s m o l t v e r s u s f r y p r o d u c t i o n i n the main b a s i n of B a b i n e Lake (1961 t o 1980 b r o o d y e a r s ) 4 3. D i s t a l f a c e of a g e n e r a l i z e d s o c k e y e s m o l t s a g i t t a 14 4. P o s t e r i o r r a d i i a t 1 4 0 ° , 160° and 200° from an e m i g r a t i n g s o c k e y e s m o l t 16 5. T o t a l o t o l i t h l e n g t h of s a g i t t a from s o c k e y e a t e m i g r a t i n g s m o l t and emergent f r y s t a g e s 16 6. R e l a t i o n s h i p s between Ln f o r k l e n g t h v e r s u s Ln o t o l i t h " a d i u s a t 1 4 0 ° , 160° and 2 0 0 ° , and Ln t o t a l o t o l i t h "•ength f o r 1 978 b r o o d s o c k e y e between the s t a g e s of emergent f r y and e m i g r a t i n g sub-2 s m o l t from the B a b i n e Lake system, B.C. 21 7. R e s i d u a l s from the 6 t h o r d e r o r t h o g o n a l p o l y n o m i a l r e g r e s s i o n s of Ln f o r k l e n g t h on Ln o t o l i t h r a d i u s a t 140°, 160° and 2 0 0 ° , and Ln t o t a l o t o l i t h l e n g t h 22 8. P r e d i c t i v e r e g r e s s i o n s of Ln f o r k l e n g t h v e r s u s Ln t o t a l o t o l i t h l e n g t h of emergent so c k e y e f r y from the F u l t o n R i v e r and P i n k u t C r e e k systems 27 9. R e s i d u a l s from the a v e r a g e p r e d i c t i v e l i n e a r r e g r e s s i o n of Ln f o r k l e n g t h v e r s u s Ln t o t a l o t o l i t h l e n g t h , f o r emergent s o c k e y e f r y from the F u l t o n R i v e r and P i n k u t C r e e k systems 27 Mean f o r k l e n g t h s of 1978 and 1965 b r o o d s o c k e y e from f r y emergence to s m o l t e m i g r a t i o n from B a b i n e L a k e . V e r t i c a l b a r s r e p r e s e n t two s t a n d a r d d e v i a t i o n s on e i t h e r s i d e of the mean Mean f o r k l e n g t h s of the 1978 b r o o d s o c k e y e f r y o v e r the 20 day p e r i o d p r i o r to c a p t u r e i n J u l y ( c e n t r a l c a p t u r e d a t a = J u l y 1 2 ) . Numbers i n b r a c k e t s i n d i c a t e sample s i z e *. I n s t a n t a n e o u s d a i l y growth r a t e s i n r e l a t i o n to Ln f o r k l e n g t h o v e r the 20 days p r i o r to c a p t u r e ( c e n t r a l c a p t u r e d a t e = J u l y 12) o f the 1978 b r o o d s o c k e y e i n Babin e Lake H i s t o g r a m s of the r e l a t i v e f r e q u e n c i e s of t o t a l o t o l i t h l e n g t h (um) a t emergence d u r i n g : f r y emergence, mid-J u l y , m i d - A u g u s t , mid-September and a t the sub-2 s m o l t e m i g r a t i o n from the main b a s i n of B a b i n e Lake, B.C S e l e c t i v i t y of t o t a l o t o l i t h l e n g t h a t emergence (Te) between the f r y and s m o l t s t a g e s ( r e l a t i v e f r e q u e n c y of s m o l t Te / r e l a t i v e f r e q u e n c y of f r y Te) H i s t o g r a m s of the r e l a t i v e f r e q u e n c i e s of f o r k l e n g t h (mm) a t emergence d u r i n g : f r y emergence, m i d - J u l y , m i d -August, mid-September and a t the sub-2 s m o l t emi-g r a t i o n from the main b a s i n of B a b i n e Lake, B.C S e l e c t i v i t y of f o r k l e n g t h a t emergence (Fe) between the f r y and s m o l t s t a g e s ( R e l a t g i v e f r e q u e n c y of s m o l t Fe / r e l a t i v e f r e q u e n c y of f r y Fe) Ln f o r k l e n g t h (mm) a t emergence v e r s u s Ln t o t a l o t o l i t h l e n g t h (um) a t emergence f o r s o c k e y e a t f r y emergence, m i d - J u l y , m i d - A u g u s t , mid-September and a t the sub-2 s m o l t e m i g r a t i o n from the main b a s i n of Babin e Lake, B.C B i v a r i a t e means and 95 p e r c e n t c o n f i d e n c e e l l i p s e s of the Ln f o r k l e n g t h (mm) v e r s u s Ln t o t a l o t o l i t h l e n g t h d i s t r i b u t i o n s a t emergence v i i i L I S T OF TABLES T a b l e Page O r t h o g o n a l p o l y n o m i a l c o e f f i c i e n t s f o r the r e l a t i o n -s h i p s between Ln f o r k l e n g t h (mm) v e r s u s Ln o t o l i t h r a d i u s ( m i c r o n s ) a t 1 4 0 ° , 160° and 200 ° , and Ln t o t a l o t o l i t h l e n g t h ( m i c r o n s ) f o r soc k e y e between the s t a g e s of emergent f r y and e m i g r a t i n g sub-2 s m o l t from the 1978 b r o o d , B a b i n e Lake, B.C 23 P r e d i c t i v e (P) and F u n c t i o n a l (F) r e g r e s s i o n s of n o s e - f o r k l e n g t h (mm) on f i v e o t o l i t h d i m e n s i o n s (um); C r o s s S e c t i o n a l A r e a ( A ) ; T o t a l O t o l i t h L e n g t h ( T L ) ; and, P o s t e r i o r R a d i i (R) a t 1 4 0 ° , 160° and 200° f o r emergent s o c k e y e f r y from the F u l t o n R i v e r and P i n k u t C r e e k s y s t e m s . . . . . . . . . . . 25 P r e d i c t i v e r e g r e s s i o n s f o r the r e l a t i o n s h i p between Ln f o r k l e n g t h and Ln t o t a l o t o l i t h l e n g t h a t f i v e f r y s o u r c e s on the B a b i n e Lake s y s t e m . S l o p e s and means t h a t a r e u n d e r l i n e d a r e not s i g n i f i c a n t l y d i f f e r e n t from each o t h e r ( S c h e f f e s m u l t i p l e range t e s t , p=.05). Aver a g e main l a k e r e g r e s s i o n i s c a l c u l a t e d from the combined f r y s o u r c e s , w e i g h t e d by r e l a t i v e f r y p r o d u c t i o n 29 D i s t r i b u t i o n s of t o t a l o t o l i t h l e n g t h a t emergence (Te) f o r w e i g h t e d emergent f r y samples, o b s e r v e d tow samples i n J u l y , A u g u s t and September, and w e i g h t e d s m o l t samples from the B a b i n e s m o l t t r a p . A l l samples a r e from the 1978 b r o o d of the B a b i n e Lake main b a s i n s o c k e y e 38 F r y to s m o l t s u r v i v a l (s) and i n s t a n t a n e o u s m o r t a l i t y r a t e ( z ) o f s o c k e y e f r y w i t h t o t a l o t o l i t h l e n g t h s a t emergence above and below the mean of the 1978 b r o o d . . . 40 P r e d i c t i v e l i n e a r r e g r e s s i o n s of f o r k l e n g t h a t c a p t u r e ( F c ) v e r s u s t o t a l o t o l i t h l e n g t h a t c a p t u r e (Tc) f o r the 1978 b r o o d s o c k e y e a t : f r y emergence, m i d - J u l y , mid-August, mid-September and a t the sub-2 s m o l t e m i g r a t i o n from the main b a s i n of B a b i n e Lake 42 i x 7. D i s t r i b u t i o n s of f o r k l e n g t h (mm) a t emergence f o r w e i g h t e d emergent f r y samples, o b s e r v e d tow samples i n J u l y , A u g u st and September, and w e i g h t e d s m o l t samples from the B a b i n e s m o l t t r a p . A l l samples a r e from the 1978 b r o o d of the B a b i n e Lake main b a s i n s o c k e y e . See t e x t f o r w e i g h t i n g p r o c e d u r e s 45 F r y to s m o l t s u r v i v a l (s) and i n s t a n t a n e o u s m o r t a l i t y r a t e ( z ) of s o c k e y e f r y w i t h emergent f o r k l e n g t h s above and below the mean of the 1978 b r o o d 46 9. Mean f o r k l e n g t h a t emergence (Fe) and mean t o t a l o t o l i t h l e n g t h a t emergence (Te) of the f r y and s m o l t p o p u l a t i o n s , and of the f r y p o p u l a t i o n when samples w i t h f o r k l e n g t h s l e s s than 30.5 mm a r e removed and when samples w i t h t o t a l o t o l i t h l e n g t h s l e s s t h a n 480 m i c r o n s are removed 51 X ACKNOWLEDGEMENTS I would l i k e t o e x p r e s s my most s i n c e r e g r a t i t u d e to Dr. P.A. L a r k i n f o r h i s s u p p o r t and g u i d a n c e of t h i s t h e s i s . I a l s o w i s h to thank D r . T.G. N o r t h c o t e and Dr. C . J . W a l t e r s f o r t h e i r c r i t i c a l and h e l p f u l r e v i e w s . My th a n k s to M o i r a G r e a v e n , G a i l Sugden and M a t t Foye f o r t h e i r d i l i g e n c e and f i n e work w i t h the s a m p l e s . My p a r t i c u l a r t h a n k s to H e l e n Hahn f o r her s u p p o r t and encouragement, and to my w i f e Kim f o r her p a t i e n c e . F i n a n c i a l s u p p o r t was p r o v i d e d by the B r i t i s h C o l u m b i a Sportsmans Fund and by the Department of F i s h e r i e s and Oceans, Canada. S p e c i a l t h a n k s to Mr. R.M.J. G i n e t z and to Mr. E.A. P e r r y of the Department of F i s h e r i e s and Oceans f o r a l l o w i n g me to c a r r y o ut the M a s t e r s program w h i l e i n t h e i r employ. 1 INTRODUCTION The p u r p o s e of t h i s s t u d y was to a s c e r t a i n , by means of b a c k - c a l c u l a t i o n methods u s i n g p e r i o d i c growth r i n g s of s a g i t t a o t o l i t h s , the e f f e c t of emergent body s i z e on the s u b s e q u e n t s u r v i v a l of s o c k e y e ( O n c o r h y n c h u s n e r k a ) f r y i n B a b i n e Lake ( f i g . 1 ) . S i z e s e l e c t i v e m o r t a l i t y has been i n v e s t i g a t e d i n the e a r l y l i f e h i s t o r y of s e v e r a l s p e c i e s of j u v e n i l e s a l m o n i d s . P a r k e r (1971) s u g g e s t e d t h a t e a r l y m a r i n e m o r t a l i t y of j u v e n i l e p i n k ( O n c o r h y n c h u s q o r b u s c h a ) and chum (O n c o r h y n c h u s ke t a ) salmon due to p r e d a t i o n by j u v e n i l e coho ( O n c o r h y n c h u s k i s u t c h ) was b i a s e d t o w a r d s the s m a l l e r i n d i v i d u a l s of the p r e y p o p u l a t i o n . H e a l e y (1982) has a l s o d e m o n s t r a t e d s i z e s e l e c t i v e m o r t a l i t y d u r i n g the e a r l y m a r i n e l i f e of j u v e n i l e chum salmon and c o n s i d e r e d p r e d a t i o n a l i k e l y c ause of m o r t a l i t y . B i l t o n e t a l . (1 982) have f o u n d an optimum window f o r time and s i z e of r e l e a s e f o r s u r v i v a l of coho s m o l t s r e l e a s e d from h a t c h e r i e s and s u s p e c t f o o d s u p p l y and p r e d a t i o n to be major f a c t o r s o p e r a t i n g on j u v e n i l e s u r v i v a l . R e l e a s e s of c h i n o o k ( O n c o r h y n c h u s t s h a w y t s c h a ) and coho j u v e n i l e s from h a t c h e r i e s have a l s o i n d i c a t e d t h a t l a r g e r i n d i v i d u a l s s u r v i v e a t h i g h e r r a t e s . The e a r l y l i f e h i s t o r y of j u v e n i l e s o c k e y e salmon has been s t u d i e d i n t e n s i v e l y , p a r t i c u l a r i l y i n C u l t u s and B a b i n e Lake, 2 F i g u r e 1 Map of B a b i n e Lake and g e o g r a p h i c l o c a t i o n i n B r i t i s h C o l u m b i a . 3 b u t most s t u d i e s have p r o v i d e d o n l y i n c i d e n t a l i n f o r m a t i o n on s i z e s e l e c t i v e m o r t a l i t y . R e l e a s e s of marked j u v e n i l e s i n C u l t u s Lake ( F o e r s t e r , 1938) d i d not i n d i c a t e any d i f f e r e n c e i n s u r v i v a l between the w i l d p o p u l a t i o n and the l a r g e r i n d i v i d u a l s of the r e a r e d marked g r o u p s . E v i d e n c e s u g g e s t s however, t h a t i n c r e a s e d s u r v i v a l of the r e a r e d p o p u l a t i o n to the m i g r a n t s t a g e may have been o f f s e t by an i n c r e a s e i n the i n c i d e n c e of r e s i d u a l i s m ; i n d i v i d u a l s who r e m a i n i n the l a k e and m a t u r e . P r e d a t i o n on j u v e n i l e s o c k e y e has a l s o been i n v e s t i g a t e d i n C u l t u s Lake ( R i c k e r , 1941; F o e r s t e r and R i c k e r , 1941) but the s t u d i e s d i d not i n v e s t i g a t e d i f f e r e n t i a l m o r t a l i t y w i t h i n y e a r c l a s s e s , a l t h o u g h i n c r e a s e d p r e d a t i o n on i n d i v i d u a l s b e c a u s e of t h e i r s m a l l e r s i z e i s h y p o t h e s i z e d . Boyce ( u n p u b l i s h e d ) a t t e m p t e d to s t u d y t h e r e l a t i o n s h i p between the i n i t i a l s i z e of f r y a t l a k e e n t r y and s u b s e q u e n t s u r v i v a l i n B a b i n e l a k e by m a r k i n g a r t i f i c i a l l y r e a r e d s o c k e y e f r y b u t c o m p l i c a t i o n s due to d i s e a s e o u t b r e a k s a r e t h o u g h t to have c a u s e d s e v e r e m o r t a l i t y among the t e s t g r o u p s . The dependence of j u v e n i l e s o c k e y e s u r v i v a l on the a v a i l a b l e f o o d s u p p l y i n B a b i n e Lake i s me n t i o n e d by R a n k i n (1977) b u t the mechanism of m o r t a l i t y was not i n v e s t i g a t e d . A f i n - c l i p p i n g s t u d y by McDonald (1969) on the 1965 b r o o d a t B a b i n e Lake i s p e r h a p s the b e s t s o u r c e of i n f o r m a t i o n on d i f f e r e n t i a l m o r t a l i t y among j u v e n i l e s o c k e y e . 4 Emergent f r y from F u l t o n R i v e r and F u l t o n spawning c h a n n e l no.1 were f i n - c l i p p e d and r e c o v e r e d t h r o u g h o u t t h e i r one y e a r l a k e r e a r i n g p e r i o d and as s m o l t when th e y m i g r a t e d from B a b i n e L a k e . A l t h o u g h i n i t i a l s i z e d i f f e r e n c e s between the two g r o u p s p e r s i s t e d to the s m o l t s t a g e , s u r v i v a l r a t e s of the two g r o u p s were s i m i l a r . F i g u r e 2 shows t h a t f r y - t o - s m o l t s u r v i v a l i n B a b i n e Lake i s h i g h l y v a r i a b l e . I t a l s o s u g g e s t s t h a t a t medium l e v e l s of f r y p r o d u c t i o n s i m i l a r to t h a t of the 1978 b r o o d , a d d i t i o n a l f r y p r o d u c t i o n above the p r e - B a b i n e Development l e v e l s does not l e a d t o i n c r e a s e d s m o l t o u t p u t s . T h i s type of r e s p o n s e to i n c r e a s e d f r y numbers, a s w i t c h i n g - o v e r r e s p o n s e by p r e d a t o r s from 200-co UJ < 150H O 1 100-UJ 5 50H PRE - DEVELOPMENT POST - DEVELOPMENT 197S brood \ . 6 9 ,62 . 6 7 S M . 6 3 , 7 0 . 74 . 7 5 • * * . 61 50 100 150 200 250 MAIN LAKE FRY (x1E6) F i g u r e 2 Sockeye s m o l t v e r s u s f r y p r o d u c t i o n i n the Main B a s i n o f B a b i n e Lake (1961 to 1980 b r o o d y e a r s ) . 5 a l t e r n a t e p r e y s o u r c e s to i n c r e a s e d numbers of s o c k e y e f r y has been d i s c u s s e d by R i c k e r ( 1 9 4 1 ) . I n c r e a s e d s u r v i v a l r a t e s a t h i g h e r f r y p r o d u c t i o n l e v e l s may a l s o r e p r e s e n t a swamping of the l a k e ' s p r e d a t o r p o p u l a t i o n . The p r e s e n c e of d e p e n s a t o r y m o r t a l i t y a t medium l e v e l s of f r y p r o d u c t i o n . In l i g h t of the i n v e s t i g a t i o n s on o t h e r s p e c i e s , the p r e s e n c e of d e p e n s a t o r y p r e d a t i o n may s u g g e s t t h a t d i f f e r e n t i a l m o r t a l i t y does o c c u r on s o c k e y e i n B a b i n e Lake a t medium l e v e l s o f f r y p r o d u c t i o n . The a bsence of s i z e - d e p e n d e n t m o r t a l i t y among the 1965 b r o o d , the l o w e s t f r y p r o d u c t i o n y e a r r e c o r d e d , i s not i n c o n s i s t e n t w i t h R i c k e r ' s t h e o r y of p r e d a t o r s s w i t c h i n g t o a l t e r n a t e s o u r c e s i n the a b s e n c e of a d e q u a t e f r y numbers. The i n i t i a l d i s t r i b u t i o n s of body s i z e of the j u v e n i l e and s m o l t p o p u l a t i o n s i n t h i s s t u d y were b a c k - c a l c u l a t e d from b o d y - o t o l i t h r e l a t i o n s h i p s d e t e r m i n e d f o r the 1978 s o c k e y e b r o o d i n B a b i n e L a k e . B a c k - c a l c u l a t i o n of body s i z e from p e r i o d i c r i n g s i n the h a r d p a r t s of f i s h has been documented by s e v e r a l a u t h o r s . Reviews of v a r i o u s b a c k - c a l c u l a t i o n t e c h n i q u e s a r e g i v e n by H i l e ( 1 9 7 0 ) , B a g e n a l and T e s c h (1978) and C a r l a n d e r ( 1 9 8 1 ) . The use of d a i l y growth r i n g s i n the s a g i t t a o t o l i t h s o f f i s h has become an e s t a b l i s h e d t e c h n i q u e f o r s i z e d e t e r m i n a t i o n ( J o n s s o n and S t e n s e t h , 1977; M a r s h a l l and P a r k e r , 1982; N e i l s o n and Geen, 1982; S t r u h s a k e r and Uchiyama, 1979; W i l d and Foreman, 1980; W i l s o n , 1981; W i l s o n and L a r k i n , 1 9 8 2 ) . 6 B a b i n e Lake was s e l e c t e d as the s t u d y a r e a f o r an i n v e s t i g a t i o n of d i f f e r e n t i a l m o r t a l i t y among j u v e n i l e s o c k e y e . B a b i n e i s the l a r g e s t l a k e of the Skeena R i v e r system w h i c h , as a whole, r a n k s s e c o n d i n B r i t i s h C o l u m b i a as a p r o d u c e r of s o c k e y e salmon. Due to the i m p o r t a n c e of the B a b i n e system ( S h e p a r d and W i t h l e r , 1958; L a r k i n and McDonald, 1968), e n u m e r a t i o n f a c i l i t i e s e x i s t to p r o v i d e a c c u r a t e e s t i m a t e s of a d u l t and s m o l t p o p u l a t i o n s f o r management of the B a b i n e s t o c k s . I t i s a l s o the s i t e of the B a b i n e Lake Development P r o j e c t (Anon, 1965; H e s k i n , 1967; G i n e t z , 1977; West, 1978) which p r o d u c e s most of the f r y to the B a b i n e s y s t e m . F r y e n u m e r a t i o n and q u a l i t y m o n i t o r i n g programs c a r r i e d out a t the d e v e l o p m e n t p r o j e c t p r o v i d e d the o p p o r t u n i t y to e s t i m a t e the s i z e d i s t r i b u t i o n of the i n i t i a l f r y p o p u l a t i o n i n B a b i n e L a k e . 7 GENERAL METHODS F i s h C o l l e c t i o n and P r e s e r v a t i o n Samples were c o l l e c t e d i n the main b a s i n and spawning t r i b u t a r i e s of the B a b i n e Lake s y s t e m . F o r t h i s s t u d y , the main b a s i n r e g i o n i s c o n s i d e r e d to be the B a b i n e Lake system minus the N o r t h Arm and N i l k i t k w a Lake r e g i o n . The 1978 b r o o d was sampled i n the s p r i n g of 1979 a t emergence, d u r i n g the summer l a k e r e s i d e n c y p e r i o d and the f o l l o w i n g s p r i n g a t m i g r a t i o n from th e l a k e as o n e - y e a r o l d (sub 2) s m o l t s . S t r a t i f i e d s a m p l i n g of emergent f r y was c a r r i e d out a t f i v e f r y s o u r c e s ; the F u l t o n R i v e r , F u l t o n spawning c h a n n e l no.1, F u l t o n spawning c h a n n e l no.2, P i n k u t Creek and t h e P i n k u t spawning c h a n n e l . F i f t y f r y were t a k e n r a n d o m l y from each s o u r c e n e a r the peak of the n i g h t l y m i g r a t i o n t h r e e t i m e s weekly, t h r o u g h o u t the p e r i o d of m i g r a t i o n (May - e a r l y J u n e ) . A f t e r l e n g t h and w e i g h t measurements were t a k e n , the f r y were p r e s e r v e d i n 70% e t h a n o l f o r s u b s e q u e n t s a m p l i n g of o t o l i t h s . E s t i m a t e s of the number of f r y m i g r a t i n g n i g h t l y from each s o u r c e were p r o v i d e d by the f r y e n u m e r a t i o n programs of the Department of F i s h e r i e s and O c e a n s . The n i g h t l y m i g r a t i o n e s t i m a t e s were used to c a l c u l a t e w e i g h t e d d i s t r i b u t i o n s from the s t r a t i f i e d f r y s a m p l e s . 8 J u v e n i l e s were t o w - n e t t e d from B a b i n e Lake i n m i d - J u l y , A u g u s t and September of 1979. The n e t was a 2-meter s q u a r e mouth mid-water t r a w l , d e s i g n e d by the Lake F e r t i l i z a t i o n D i v i s i o n of the S a l m o n i d Enhancement Program ( G j e r n e s , 1 9 7 8 ) . The n e t was towed i n an S - p a t t e r n by a s i n g l e b o a t from a d i s t a n c e of 60 meters and f i s h e d a t a d e p t h of 2 m e t e r s . A Furuno echo sounder was used as an a i d to d e t e c t f i s h and s e l e c t l i k e l y t o w - n e t t i n g s i t e s . At each j u v e n i l e s a m p l i n g p e r i o d , t o w - n e t t i n g was c a r r i e d o u t t h r o u g h o u t the main b a s i n . P r e v i o u s s t u d i e s by McDonald (1969) had d e t e r m i n e d t h a t f r y i n i t i a l l y m i g r a t e s o u t h w a r d i n the main b a s i n , t h e n d i s t r i b u t e t h e m s e l v e s r a n d o m l y by mid-Summer; by f a l l t h e y a r e c o n c e n t r a t e d i n the n o r t h end of t h e b a s i n . The t o w - n e t t i n g samples r e f l e c t e d t h i s m i g r a t i o n p a t t e r n but were i n a d e q u a t e to a t t e m p t to make i n f e r e n c e s as to the p o p u l a t i o n d e n s i t y e x c e p t f o r the most g e n e r a l of a r e a s . The p e r i o d i m m e d i a t e l y a f t e r dusk was u s u a l l y the most p r o d u c t i v e b u t t o w - n e t t i n g was o f t e n c a r r i e d out from dusk t o dawn. C a t c h e s were i m m e d i a t e l y p l a c e d i n 70% e t h a n o l f o r e x a m i n a t i o n a t a l a t e r d a t e and the time and l o c a t i o n n o t e d . The r e p r e s e n t a t i v e n e s s of the tow samples i s q u e s t i o n a b l e . Even thou g h samples were t a k e n t h r o u g h o u t the l a k e , the r e l a t i v e l y s m a l l s a m p l i n g e f f o r t i n v o l v e d may have been c o n c e n t r a t e d on the head o r t a i l ends of m i g r a t i n g s c h o o l s of j u v e n i l e s and hence may be b i a s e d to s m a l l e r or l a r g e r i n d i v i d u a l s . 9 Smolt samples were c o l l e c t e d t h r o u g h o u t the s m o l t m i g r a t i o n from the B a b i n e system i n l a t e May and e a r l y June of 1980. Samples were t a k e n a t the B a b i n e Lake s m o l t t r a p , l o c a t e d a t the o u t l e t of the B a b i n e - N i l k i t k w a Lake system where a s m o l t e n u m e r a t i o n and s a m p l i n g program i s c a r r i e d out a n n u a l l y by the D e p a r t m e n t of F i s h e r i e s and O c e a n s . F i f t y s m o l t s t a k e n r a n d o m l y from e v e r y second n i g h t ' s c a t c h were p r e s e r v e d i n 70% e t h a n o l f o r e x a m i n a t i o n a t a l a t e r d a t e . As w i t h the f r y s a m p l i n g , n i g h t l y m i g r a t i o n e s t i m a t e s from the s m o l t e n u m e r a t i o n program were used to w e i g h t the samples t o c a l c u l a t e the l e n g t h d i s t r i b u t i o n s of the main l a k e s m o l t p o p u l a t i o n . O t o l i t h Removal and S t o r a g e F o r k l e n g t h s were measured to the n e a r e s t 0.5 mm and b o t h s a g i t t a o t o l i t h s were removed from each sample. Two d i s s e c t i o n methods were used to remove the o t o l i t h s , d e p e n d i n g on the s i z e of the f i s h . F o r t h o s e l e s s t h an a p p r o x i m a t e l y 40 mm, t h e v e n t r a l d i s s e c t i o n method d e s c r i b e d by W i l s o n (1981) was most s u i t a b l e . The f i s h was h e l d i n an i n v e r t e d p o s i t i o n and the o p e r c u l a r p l a t e s removed, e x p o s i n g the g i l l s t r u c t u r e s . The o t o l i t h s were t h e n t e a s e d from the s a c c u l u s on the t i p of a p r o b e . F o r l a r g e r f i s h (40-90 mm) d i s s e c t i n g s c i s s o r s were used to s p l i t the head a l o n g the l o n g i t u d i n a l a x i s e x p o s i n g on e i t h e r s i d e the s a g i t t a e which c o u l d be removed w i t h f o r c e p s . T h i s method was f a s t and v e r y few o t o l i t h s were damaged. O t o l i t h s 10 were c l e a n e d of membranes and s t o r e d i n the w e l l s of M i c r o T e s t 3034 t i ssue c u l t u r e p l a t e s • The M i c r o t e s t p l a t e c o n v e n i e n t l y h o l d s 60 numbered w e l l s which can be s e a l e d by p l a c i n g a s q u a r e o f 1/16 i n c h p l e x i g l a s s o v e r the w e l l s and h o l d i n g i t i n p l a c e w i t h a p i e c e of sponge between the p l e x i g l a s s and the c o v e r l i d . E l a s t i c bands a b o u t the c o n t a i n e r s p r e v e n t e d a c c i d e n t a l o p e n i n g . Wet s t o r a g e i n 70% e t h a n o l was used i n i t i a l l y b u t l a t e r abandoned when i t was r e a l i z e d t h a t e x p o s u r e to a i r was n o t d e s t r u c t i v e and d i d not i n v o l v e p e r i o d i c r e f i l l i n g to r e p l a c e e v a p o r a t i v e l o s s . O t o l i t h P r e p a r a t i o n and P h o t o g r a p h i n g L e f t o r r i g h t o t o l i t h s were randomly s e l e c t e d f o r o b s e r v a -t i o n and measurement. Two methods were used to p r e p a r e o t o l i t h s f o r p h o t o g r a p h i n g . F r y o t o l i t h s were a t t a c h e d to m i c r o s c o p e s l i d e s , s u l c a l s u r f a c e upwards, w i t h an a c r y l i c a d h e s i v e ( C r a z y G l u e ) f o r c o n v e n i e n c e of h a n d l i n g and to m a i n t a i n an even p l a n e when g r i n d i n g . When r e q u i r e d , mounted o t o l i t h s c o u l d be removed by s o a k i n g i n a c e t o n e which l i f t e d the g l u e from the s l i d e s u r f a c e . F o r a l l b u t the emergent f r y o t o l i t h s , r e m o v a l of o v e r b u r d e n was r e q u i r e d and was done by hand, u s i n g a s i n t e r e d g l a s s p l a t e and carborundum No. 50 aluminum o x i d e powder mixed w i t h water as 11 a l a p p i n g compound. These methods were a d e q u a t e b ut c a r e and a t t e n t i o n was needed to keep the g r i n d i n g p l a n e e v e n . A s e c o n d and s u p e r i o r method d e v e l o p e d by N e i l s o n and Geen (1981) was used f o r the l a r g e r u n d e r y e a r l i n g tow and s m o l t s a m p l e s . Heat s e n s i t i v e g l u e which c o u l d be removed by the a p p l i c a t i o n of s m a l l amounts of h e a t was used to mount the o t o -l i t h s on g l a s s s l i d e s . The s l i d e s were h e l d i n a j i g s u p p o r t e d on t h r e e l e g s which c o u l d be moved o v e r the g r i n d i n g s u r f a c e . T h i s m a i n t a i n e d an even g r i n d i n g p l a n e and c o n s t a n t p r e s s u r e on the g r i n d i n g s u r f a c e . M y l a r g r i n d i n g s h e e t s of 25 and 0.5 m i c r o n g r i t were used i n p l a c e of the carborundum powder. P r i o r to p h o t o g r a p h i n g , mounted o t o l i t h s were c l e a r e d i n g l y c e r o l . The time r e q u i r e d f o r the a p p e a r a n c e of r i n g s and the p e r i o d f o r which t h e y are v i s i b l e i s r e l a t e d to o t o l i t h s i z e . The s m a l l o t o l i t h s of f r y p r o d u c e d maximum r i n g c o u n t s a f t e r a p p r o x i m a t e l y s i x h o u r s of c l e a r i n g , and would b e g i n to o v e r -c l a r i f y i n a n o t h e r s i x . The c l e a r i n g p r o c e s s c o u l d be r e v e r s e d by s o a k i n g the mount i n e t h a n o l . The l a r g e s m o l t o t o l i t h s r e q u i r e d s e v e r a l days to c l e a r , b u t remained r e a d a b l e f o r a much l o n g e r p e r i o d . Because of t h i s v a r i a b i l i t y , s t a n d a r d p e r i o d s f o r c l e a r i n g were used f o r optimum d i s p l a y of r i n g s b e f o r e p h o t o g r a p h i n g . F r y o t o l i t h s were c l e a r e d f o r 4 t o 6 h o u r s , j u v e n i l e samples c l e a r e d f o r 24 h o u r s and s m o l t o t o l i t h s from 2 t o 3 d a y s . 12 Two c a m e r a - m i c r o s c o p e systems were u s e d . The m a j o r i t y of o t o l i t h s were p h o t o g r a p h e d t h r o u g h an Olympus t r i n o c u l a r compound m i c r o s c o p e w i t h a W i l d 35 mm a u t o m a t i c camera, u s i n g t r a n s m i t t e d l i g h t and Kodak P a n a t o m i c - X ASA 32 f i l m . A p p r o x i m a t e l y 20% of the f r y samples were p h o t o g r a p h e d w i t h a Z e i s s I k o n camera on a Z e i s s compound m i c r o s c o p e . M a g n i f i -c a t i o n s of 50x and 200x were used on the Olympus system and 64x and 160x were used on the Z e i s s s y s t e m . N e g a t i v e s were mounted i n 35 mm s l i d e h o l d e r s and p r o j e c t e d w i t h an Opus p h o t o g r a p h i c e n l a r g e r (x10) o r a 35 mm s l i d e p r o j e c t o r ( x 1 3 . 2 ) . O t o l i t h Measurements The s a g i t t a o t o l i t h s of s o c k e y e f r y a r e s p e c i e s d i s t i n c t i v e b u t t h e i r shape v a r i e s between i n d i v i d u a l f i s h , and the s a g i t t a o t o l i t h s i n a s i n g l e f i s h may have d i f f e r e n t s h a p e s . To s t a n d -a r d i z e measurements between samples, a g e n e r a l i z e d o t o l i t h was used to d e f i n e common r e f e r e n c e p o i n t s when m e a s u r i n g o t o l i t h d i m e n s i o n s . The t e r m i n o l o g y i s t h a t used by P a n n e l l a ( 1 9 8 1 ) . The t y p i c a l s a g i t t a of a j u v e n i l e s o c k e y e i s l a t e r a l l y c o mpressed and e l l i p t i c a l from the d i s t a l s i d e ( f i g . 3 ) . The l o n g a x i s i s o r i e n t e d a l o n g t h a t of the f i s h w i t h t h e r o s t r u m a n t e r i o r and p o s t r o s t r u m p o s t e r i o r . The convex p r o x i m a l s i d e i s d i v i d e d by the s u l c u s a c u s t i c u s , a s u l c a l g roove c o n t a i n i n g 13 n e r v e a t t a c h m e n t s . On the d i s t a l f a c e the s u l c a l g roove i s seen t e r m i n a t i n g as i n f l e c t i o n s a l o n g the s a g i t t a m a r g i n , a n t e r o -d o r s a l l y as the e x c i s u r a and p o s t e r i o r l y as t h e p o s t c a u d a l t r o u g h . A l o n g the l o n g i t u d i n a l a x i s of the o t o l i t h p r o p e r a r e t h r e e major n u c l e i r e f e r r e d to by some a u t h o r s ( N e i l s o n and Geen, 1982) as p r i m o r d i a . A d d i t i o n a l minor n u c l e i (2-5) may be f o u n d n e a r b y , a n t e r i o r l y a l o n g the l o n g i t u d i n a l a x i s . R a d i a l bands c a u s e d by the i n t e r s e c t i o n of domes of c o n c e n -t r i c growth a r e u s u a l l y p r e s e n t . They p r o v i d e cues to the p o s i t i o n of the major n u c l e i and o r i e n t a t i o n of the v e r t i c a l and h o r i z o n t a l a x e s . The bands, sometimes c u r v e d , a r e p e r p e n d i c u l a r t o the r i n g s of growth and c o n v e r g e toward t h e i r r e s p e c t i v e n u c l e i . The a n t e r o - d o r s a l band which i n t e r s e c t s the e x c i s u r a i s p a r t i c u l a r l y u s e f u l . I t i n d i c a t e s the p o s i t i o n of the e x c i s u r a on s a g i t t a e d i s p l a y i n g no i n f l e c t i o n or d o u b l e i n f l e c t i o n s on the m a r g i n . For p u r p o s e s of r e f e r e n c e , the a n g l e of r a d i a l measurement was d e f i n e d i n compass d e g r e e s as i n d i c a t e d i n f i g u r e 3. V a r i o u s o t o l i t h measurements a r e d e s c r i b e d i n the l i t e r a -t u r e . C o m p a r i s o n s between s t u d i e s a r e o f t e n d i f f i c u l t however, b e c a u s e r e l a t i o n s h i p s a r e s p e c i e s and age s p e c i f i c , and d i f f e r e n t o t o l i t h d i m e n s i o n s a r e u s e d . 14 J o n s s o n and S t e n s e t h (1979) compared t h r e e p o s t e r i o r r a d i i of the s a g i t t a o t o l i t h s of Brown T r o u t (Salmo t r u t t a L.) w i t h f i s h l e n g t h . S e l e c t i n g the r a d i i which gave the b e s t c o r r e l a t i o n , s i x r e g r e s s i o n models were examined i n c l u d i n g a f o u r t h o r d e r p o l y n o m i a l e q u a t i o n . Campana ( p e r s . comm.) has r e l a t e d the l e n g t h of s t a r r y f l o u n d e r s ( P l a t i c h t h y s g t e l l a t u s ) t o t h r e e l i n e a r measurements of the o t o l i t h : t o t a l l e n g t h , c e n t r a l n u c l e u s to p o s t e r i o r edge and p e r i p h e r a l n u c l e u s to p o s t e r i o r edge. W i l d and Foreman (1980) c o n s i d e r e d t h r e e l o c a t i o n s of o t o l i t h s of a d u l t y e l l o w f i n tuna (Thunnus F i g u r e 3 D i s t a l f a c e of a g e n e r a l i z e d s o c k e y e s m o l t s a g i t t a . 15 a l b a c a r e s) and s k i p j a c k tuna (Katsuwonus p e l a m i s ) ; t h e v e n t r a l edge below the p r i m o r d i u m , the p o s t r o s t r u m and the r o s t r u m . N e i l s o n and Geen (1982) w o r k i n g on c h i n o o k ( O n c o r h y n c h u s  t s h a w y t s c h a ) j u v e n i l e s have used the t o t a l l e n g t h of the o t o l i t h minus the l e n g t h of the r o s t r u m . W i l s o n and L a r k i n (1982) w o r k i n g w i t h s o c k e y e ( O n c o r h y n c h u s n e r k a ) f r y measured a d o r s a l p o s t e r i o r r a d i u s a t 40° from the l o n g i t u d i n a l a x i s . The a x i s was d e f i n e d as the l i n e p a s s i n g from the t i p of t h e r o s t r u m t h r o u g h the p o s t e r i o r n u c l e u s . Hence, a s t a n d a r d and w i d e l y a c c e p t e d o t o l i t h measurement i s not a p p a r e n t . In t h i s s t u d y , f i v e o t o l i t h d i m e n s i o n s were i n v e s t i g a t e d . R a d i i were measured from the p o s t e r i o r major n u c l e u s a t 1 4 0 ° , 160° and 200° ( f i g . 4 ) . The f o u r t h d i m e n s i o n was t o t a l l e n g t h , d e f i n e d as the d i s t a n c e a l o n g the l o n g i t u d i n a l a x i s , from the p o i n t p e r p e n d i c u l a r to the r o s t r a l i n f l e c t i o n to the i n t e r -s e c t i o n of the a x i s and the p o s t e r i o r edge ( f i g . 5 ) . The i n t e r s e c t i o n was used r e g a r d l e s s of the p r e s e n c e of p o s t e r i o r l o b e s e x t e n d i n g p a s t the i n t e r s e c t i o n , or whether the p o s t c a u d a l t r o u g h was not c e n t e r e d on the a x i s . The f i f t h measurement was a s i m p l e e s t i m a t e of c r o s s s e c t i o n a l a r e a . S i x t e e n r a d i i a t 22.5° i n t e r v a l s were measured from the c e n t e r n u c l e u s and the a r e a s of the e n c l o s e d t r i a n g l e s summed. T h i s measurement c o u l d be more e a s i l y made by p l a n i m e t r y or by d i g i t i z i n g on a computer g r a p h i c s t a b l e t . F o r the number of samples i n v o l v e d i n t h i s s t u d y however, the above method was a d e q u a t e . F i g u r e 4 P o s t e r i o r r a d i i a t 140°, 160° and 200° from an e m i g r a t i n g s o c k e y e s m o l t . T O T A L O T O L I T H L E N G T H — S M O L T FRY— F i g u r e 5 T o t a l o t o l i t h l e n g t h of s a g i t t a from s o c k e y e a t e m i g r a t i n g s m o l t and emergent f r y s t a g e s . 17 The f o u r t h measurement i s t h a t d e s c r i b e d by N e i l s o n and Geen (1981) as " t o t a l o t o l i t h l e n g t h minus t h e r o s t r u m " . The r a d i a l measurement a t 140° i s s i m i l a r to t h a t used by W i l s o n and L a r k i n (1982) , b u t the l o n g i t u d i n a l a x i s from w h i c h i t i s measured i s s l i g h t l y d i f f e r e n t , b e i n g d e f i n e d by the p o s i t i o n s of the c e n t e r n u c l e i and not the t i p of the r o s t r u m . D i m e n s i o n s of the e n l a r g e d images were measured to the n e a r e s t m i l l i m e t e r , g i v i n g an a v e r a g e p r e c i s i o n of a b o u t 0.7 p e r c e n t . The second measurement e r r o r was i n d e t e r m i n i n g the e x a c t p o s i t i o n of the n u c l e i . U s i n g a r i g o r o u s measurement p r o c e d u r e , the s m a l l e s t r a d i i c o u l d be e s t i m a t e d w i t h 95 p e r c e n t c o n f i d e n c e l i m i t s of 1 to 2 p e r c e n t , e q u i v a l e n t to about 2 to 3 m i c r o n s , from t h r e e i n d e p e n d e n t measurements. The f o l l o w i n g p r o c e d u r e was used to d e f i n e the p o s i t i o n of n u c l e i and the s a g i t t a axes p r i o r to m e a s u r i n g t o t a l l e n g t h and r a d i i : - A t e m p l a t e w i t h v e r t i c a l and h o r i z o n t a l axes p l u s the t h r e e r a d i i was p o s i t i o n e d under the p r o j e c t e d image w i t h the v e r t i c a l a x i s of the t e m p l a t e p a s s i n g t h r o u g h the c e n t e r n u c l e u s and a l i g n e d w i t h the v e r t i c a l a x i s of t h e o t o l i t h . R a d i a l bands were u s e f u l i n d e f i n i n g t h e e x a c t p o s i t i o n of the n u c l e u s and the v e r t i c a l a x i s . 1 8 - The t e m p l a t e was then moved v e r t i c a l l y to p o s i t i o n i t s h o r i z o n t a l a x i s t h r o u g h the c e n t e r n u c l e u s , d e f i n i n g the l o n g i t u d i n a l a x i s of the o t o l i t h . - To measure p o s t e r i o r r a d i i , the t e m p l a t e was t h e n moved l a t e r a l l y , p o s i t i o n i n g i t s o r i g i n a t the p o s t e r i o r n u c l e u s . In some o t o l i t h s t h i s n u c l e u s was not c l e a r l y d e f i n e d . P o s t e r i o r r a d i a l bands, c o n v e r g i n g towards the n u c l e u s would t h e n be used t o e s t i m a t e the e x a c t l o c a t i o n of the n u c l e u s . R a d i a l measurements were then r e a d d i r e c t l y from s c a l e d r a d i i on the t e m p l a t e . - T o t a l o t o l i t h l e n g t h measurements were made by moving the t e m p l a t e l a t e r a l l y , p o s i t i o n i n g the v e r t i c a l a x i s t h r o u g h the r o s t r a l i n f l e c t i o n and m e a s u r i n g from the t e m p l a t e o r i g i n to the i n t e r s e c t i o n of the l o n g i t u d i n a l a x i s and the edge of the p o s t r o s t r u m . F o r o t o l i t h s d i s p l a y i n g m u l t i p l e or no r o s t r a l i n f l e c t i o n s , an e q u i v a l e n t p o i n t was e s t i m a t e d by t h e i n t e r s e c t i o n of the d o r s o - a n t e r i o r r a d i a l band and the o t o l i t h e dge. 19 FORK LENGTH VERSUS OTOLITH SIZE RELATIONSHIPS R e l a t i o n s h i p s from F r y Emergence to Smolt M i g r a t i o n G e n e r a l p o l y n o m i a l s were d e r i v e d to d e s c r i b e the dependence of f o r k l e n g t h on o t o l i t h s i z e f o r s o c k e y e between the s t a g e s of f r y and s m o l t . Over the one y e a r i n t e r v a l from f r y to s m o l t , the form of the f o r k l e n g t h v e r s u s o t o l i t h r a d i i o r t o t a l o t o l i t h l e n g t h r e l a t i o n s h i p i s s i g m o i d . The d a t a were t r a n s f o r m e d by n a t u r a l l o g a r i t h m s and f i t t e d w i t h s t e p w i s e o r t h o g o n a l p o l y n o m i a l s , w i t h r e j e c t i o n of s u c c e s s i v e powers s e t a t a p r o b a b i l i t y of 0.01. T h i s r e s u l t e d i n 8 t h to 12th o r d e r e q u a t i o n s w i t h some c o e f f i c i e n t s a p p r o a c h i n g m a g n i t u d e s of 10 to the f o u r t e e n t h power. The r e g r e s s i o n s which were h i g h l y s i g n i f i c a n t w i t h R^ v a l u e s r a n g i n g from 0.97 t o 0.98 b u t were u n w i e l d y b e c a u s e of the number of terms and r o u n d i n g e r r o r s . The h i g h o r d e r of the p o l y n o m i a l s was c a u s e d by the complex-i t y of the r e l a t i o n s h i p s and the l a r g e sample s i z e s . Each r e l a t i o n s h i p between f o r k l e n g t h and o t o l i t h r a d i u s c o n t a i n e d a t o t a l of 480 f r y , j u v e n i l e and s m o l t s a m p l e s . The t o t a l o t o l i t h l e n g t h r e g r e s s i o n , i n c l u d i n g d a t a from the i n v e s t i g a t i o n of s t o c k s p e c i f i c r e l a t i o n s h i p s a t emergence, used a p p r o x i m a t e l y 1200 s a m p l e s . When the p o t e n t i a l o r d e r or number of v a r i a b l e s i s l a r g e (K>10) and the number of d a t a p o i n t s i s much l a r g e r (5K t o 10K) t h e n " o v e r f i t t i n g " may o c c u r ( D r a p e r and S m i t h , 1 9 6 6 ) . 20 P r o v i d e d t h a t a l l i m p o r t a n t terms have been i n c l u d e d and the above c o n d i t i o n s a r e met, a d d i t i o n a l terms w i l l c o n t i n u e to be added as t h e r e s i d u a l mean s q u a r e s t a b i l i z e s a r o u n d t h e t r u e p o p u l a t i o n v a r i a n c e . T h i r d o r d e r o r t h o g o n a l p o l y n o m i a l s f i t t e d to the t r a n s f o r m e d d a t a s e t s were s i g n i f i c a n t w i t h R2 v a l u e s of a p p r o x i m a t e l y 0.94. They were d i s c a r d e d however, as p l o t s of the r e s i d u a l s a g a i n s t o t o l i t h s i z e showed p e r i o d i c b i a s e s . S i x t h o r d e r o r t h o g o n a l p o l y n o m i a l s a r e p r e s e n t e d as a compromise of manageable c o e f f i c i e n t s w i t h s u i t a b l y d i s t r i b u t e d r e s i d u a l s f o r p r e d i c t i v e i n f e r e n c e ( t a b l e 1 ) . The r e l a t i o n -s h i p s a r e s i g n i f i c a n t (p<.01) w i t h R 2 v a l u e s r a n g i n g from 0.97 t o 0.98. The p o l y n o m i a l s a r e shown f i t t e d to the d a t a i n f i g u r e 6. The r e s i d u a l s p l o t t e d a g a i n s t r a d i i and t o t a l l e n g t h a r e shown i n f i g u r e 7. The r e s i d u a l s a r e e v i d e n t l y n o r m a l l y d i s t r i b u t e d a r o u n d the a x i s and show no marked non-random t r e n d s . The c o m p l e x i t y i m p l i e d by t h e s e r e l a t i o n s h i p s may be a c o n -sequence of the range of l i f e h i s t o r y phases t h a t a r e i n c l u d e d . M o r p h o l o g i c a l changes a r e e a s i l y seen as newly emerged f r y a b s o r b the l a s t of t h e i r y o l k and b e g i n a c t i v e f e e d i n g i n the l a k e . Marked changes i n the body l e n g t h to w e i g h t r e l a t i o n s h i p t a k e p l a c e between the t i m e s of l a k e e n t r y and e m i g r a t i o n . 21 5.0 '&5 . 6 0 65 7.0 75 Ln (OTOLITH (um)) F i g u r e 6 R e l a t i o n s h i p s ' between Ln f o r k l e n g t h v e r s u s Ln o t o l i t h r a d i u s a t 140°, 160° and 2 0 0 ° , and Ln t o t a l o t o l i t h l e n g t h f o r 1978 b r o o d s o c k e y e be-tween the s t a g e s of emergent f r y and e m i g r a t i n g s m o l t s from the B a b i n e Lake system, B.C. 22 e e o LU _ J or o UJ co o < ZD 9 co LU or +0.2 o.o -0.2 +0.2 0.0 -0.2 +0.2 0.0 -0.2 + 0.2 0.0 -0.2 H 140° RADIUS 160° RADIUS 200° RADIUS h TOTAL OTOLITH LENGTH J 1 I L -I 1 I L J 1 I l_ 5.0 5.5 6.0 65 Ln (OTOLITH (um)) 7.0 7.5 F i g u r e 7 R e s i d u a l s from 6 t h o r d e r o r t h o g o n a l p o l y n o m i a l r e g r e s s i o n s of Ln n o s e - f o r k l e n g t h on Ln o t o l i t h r a d i u s a t 1 4 0 ° , 160° and 2 0 0 ° , and Ln t o t a l o t o l i t h l e n g t h . 23 A l l o m e t r i c growth of the o t o l i t h a l s o o c c u r s as the p o s t e r i o r l o b e s e x t e n d . A s y n c h r o n o u s growth between the a x i a l body l e n g t h and o t o l i t h r a d i u s was not i n v e s t i g a t e d b u t i s a n o t h e r p o s s i b l e c a u s e of the c o m p l e x i t y of t h e b o d y - o t o l i t h r e l a t i o n s h i p . S t o c k s p e c i f i c r e l a t i o n s h i p s may a l s o have c a u s e d i r r e g -u l a r i t i e s i n the r e l a t i o n s h i p . J u v e n i l e s were sampled t h r o u g h o u t the main b a s i n of the l a k e b u t the t o w - n e t t i n g T a b l e 1 O r t h o g o n a l p o l y n o m i a l c o e f f i c i e n t s f o r the r e l a t i o n -s h i p s between Ln f o r k l e n g t h (mm) v e r s u s Ln o t o l i t h r a d i u s ( m i c r o n s ) a t 140°, 160° and 2 0 0 ° , and Ln t o t a l o t o l i t h l e n g t h ( m i c r o n s ) f o r s o c k e y e between the s t a g e s of emergent f r y and e m i g r a t i n g sub-2 s m o l t from the 1978 b r o o d , B a b i n e Lake, BC. O r d e r c o n s t a n t 1 2 3 4 5 6 R 2 Sy*x R a d i u s 1 40° -193382.89 193507.04 -80506.644 17825.906 •221 5 .6265 146.57611 -4.0324030 0.9740 0.2496 R a d i u s 160° -21 0289.34 210537.62 -87647.458 19421.103 -2415 .8643 159.96699 -4.4051 223 0.9726 0.2527 R a d i u s 200° -1 29298 . 33 1 30508 .35 -54758.770 12225.728 •1 531 .9535 102.15684 •2.8324161 0.9751 0 .2466 T o t a l O t o l i t h l e n g t h -3 1 1595. 70 280521.51 -1 05070.85 20958.907 -2348 .3730 140.14400 •3 .4801885 0.9823 0.2256 24 s u r v e y s were not e x t e n s i v e . Changes i n t o w - n e t t i n g e f f i c i e n c y and non-random d i s t r i b u t i o n s of s t o c k s w i t h i n the l a k e c o u l d have b i a s e d the r e p r e s e n t a t i o n of i n d i v i d u a l s t o c k s . S t o c k s p e c i f i c r e l a t i o n s h i p s were t e s t e d among the f i v e s o u r c e s of emergent f r y ( n e x t s e c t i o n ) . R e l a t i o n s h i p s f o r Emergent F r y The 6 t h o r d e r p o l y n o m i a l s d e r i v e d p r e v i o u s l y a r e s u i t a b l e f o r use w i t h j u v e n i l e s o c k e y e i n B a b i n e Lake b u t f o r emergent f r y and s m o l t s , n e a r the ends of the o b s e r v e d s i z e r a n g e s , t h e y a r e n o t s u f f i c i e n t l y d e s c r i p t i v e of the v a r i a b i l i t y . At emergence the b o d y - o t o l i t h r e l a t i o n s h i p s a r e nea r l i n e a r . F o r t h i s r e a s o n , s i m p l e l i n e a r r e g r e s s i o n s were i n v e s t i g a t e d f o r emergent f r y . Sub-samples of 71 f r y were s e l e c t e d r andomly from the F u l t o n R i v e r and P i n k u t C r e e k f r y s a m p l e s . T o t a l o t o l i t h l e n g t h s , c r o s s s e c t i o n a l a r e a and p o s t e r i o r r a d i i a t 140°, 160° and 200° were t r a n s f o r m e d w i t h n a t u r a l l o g a r i t h m s and f i t t e d by l e a s t s q u a r e s p r e d i c t i v e and g e o m e t r i c mean f u n c t i o n a l r e g r e s s i o n s ( R i c k e r , 1973) shown i n t a b l e 2. A l l f i v e o t o l i t h d i m e n s i o n s were s i g n i f i c a n t l y c o r r e l a t e d w i t h f o r k l e n g t h b u t t h e r e were d i f f e r e n c e s i n t h e ease of measurement and the goodness of f i t . C r o s s s e c t i o n a l a r e a i s 25 the b e s t e s t i m a t o r of f o r k l e n g t h f o r emergent s o c k e y e f r y (p<.001) w i t h an R 2 v a l u e of 0.5190. However, i t i s the most t e d i o u s measurement to make and not a l l o t o l i t h s d i s p l a y the ( r e q u i r e d ) c o n t i n u o u s emergence c h e c k . The p o s t e r i o r r a d i i r e g r e s s i o n s were s i g n i f i c a n t (p<.01) b u t R v a l u e s were o n l y i n the range of 0.11 to 0.14. For i n v e s t i -g a t i o n s such as growth r a t e s o v e r s h o r t p e r i o d s , t h e y a r e T a b l e 2 P r e d i c t i v e (P) and F u n c t i o n a l (F) r e g r e s s i o n s of n o s e -f o r k l e n g t h (mm) on f i v e o t o l i t h d i m e n s i o n s (um); C r o s s S e c t i o n a l A r e a ( A ) ; T o t a l O t o l i t h L e n g t h ( T ) ; and, P o s t e r i o r R a d i i (R) a t 1 4 0 ° , 160° and 200° f o r emergent s o c k e y e f r y from the F u l t o n R i v e r and P i n k u t Creek s y s t e m s . O t o l i t h D i m e n s i o n R e g r e s s i o n n C S . C S . A r e a A r e a T o t a l L e n g t h T o t a l L e n g t h R a d i u s R a d i u s 140' 1 40' R a d i u s 160° R a d i u s 160° R a d i u s 200° R a d i u s 200° L n ( L ) = 0.3220 + 0.2514 * Ln(A) (P) 0.5219* 71 L n ( L ) =-0.8510 + 0.3480 * Ln(A) (F) L n ( L ) = 1 .6447 + 0.2842 * L n ( T ) (P) 0. 2501* 71 L n ( L ) =-0.1001 + 0.5683 * L n ( T ) (F) L n ( L ) = 2.3081 + 0.1992 * Ln(R) (P) 0.1427* 71 L n ( L ) = 0.5269 + 0.5274 * Ln(R) (F) L n ( L ) = 2.4879 + 0.1659 * Ln(R) (P) 0.1140* 71 L n ( L ) = 0.7194 + 0.4914 * Ln(R) (F) L n ( L ) = 2.3730 + 0.1878 * Ln(R) (P) 0.1271* 69 L n ( L ) = 0.5406 + 0.5267 * Ln(R) (F) * P<.01 26 p r a c t i c a l r e l a t i o n s h i p s to use be c a u s e s p e c i f i c growth r i n g s need not be t r a c e d a r ound the o t o l i t h . T o t a l o t o l i t h l e n g t h was s e l e c t e d as the most s u i t a b l e d i m e n s i o n f o r b a c k - c a l c u l a t i n g s i z e a t emergence. The r2 v a l u e i s o n l y 0.2501 b u t i t i s u s e f u l f o r e s t i m a t i n g the mean Ln f o r k l e n g t h of d i s t r i b u t i o n s of s a m p l e s . I t i s a l s o an easy measurement to make as the emergence check i s r e a d a b l e a t the e x c i s u r a and p o s t - c a u d a l g r o o v e on most o t o l i t h s . S t o c k D i f f e r e n c e s a t Emergence S t o c k d i f f e r e n c e s i n the b o d y - o t o l i t h r e l a t i o n s h i p s a t emergence were t e s t e d u s i n g t o t a l o t o l i t h l e n g t h a t emergence. A p p r o x i m a t e l y 25 f r y were t a k e n from each s o u r c e , t h r e e t i m e s w e e k l y , o v e r the p e r i o d of f r y m i g r a t i o n . T o t a l o t o l i t h l e n g t h s o f t h o s e samples not p h o t o g r a p h e d were measured d i r e c t l y under a compound m i c r o s c o p e w i t h an o c u l a r m i c r o m e t e r . F o r k l e n g t h and t o t a l o t o l i t h l e n g t h d a t a from each f r y s o u r c e were t r a n s f o r m e d w i t h n a t u r a l l o g a r i t h m s and f i t t e d by l e a s t s q u a r e s p r e d i c t i v e r e g r e s s i o n s ( f i g . 8 ) . A n a l y s i s of c o v a r i a n c e r e v e a 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 among the b o d y - o t o l i t h r e l a t i o n s h i p s of the v a r i o u s f r y s o u r c e s . S c h e f f e s m u l t i p l e range t e s t i n d i c a t e d two homogeneous s u b s e t s among the c o v a r i a t e s l o p e s and 4 s u b s e t s among the mean f o r k 27 E E x r-CD TZ. LU cr F i g u r e 8 3.5 3.4 3.3 3.2 Fulton River Fulton Chan 1 Fulton Chan 2 Pinkut Creek Pinkut Channel Average Regression J -53 55 6j0 6.1 62 6.3 Ln (TOTAL OTOLITH LENGTH (um)) 6.4 P r e d i c t i v e r e g r e s s i o n s of Ln f o r k l e n g t h v e r s u s Ln t o t a l o t o l i t h l e n g t h of emergent s o c k e y e f r y from t h e F u l t o n R i v e r and P i n k u t C r e e k s y s t e m s . E E _l X +0.2 < I-g 2 0 0 on g -0.2 Q 58 59 60 6.1 62 63 64 Ln (TOTAL OTOLITH LENGTH (um)) F i g u r e 9 R e s i d u a l s from the a v e r a g e p r e d i c t i v e l i n e a r r e g r e s s i o n of Ln f o r k l e n g t h v e r s u s Ln t o t a l o t o l i t h l e n g t h , f o r emergent so c k e y e f r y from the F u l t o n R i v e r and P i n k u t Creek s y s t e m s . 28 l e n g t h s ( t a b l e 3 ) . G r o u p i n g of c h a n n e l v e r s u s r i v e r or F u l t o n v e r s u s P i n k u t s t o c k s was not o b v i o u s . S t o c k d i f f e r e n c e s among the b o d y - o t o l i t h r e l a t i o n s h i p s a t emergence e x i s t . However, the means to i d e n t i f y j u v e n i l e and s m o l t samples by s t o c k does not e x i s t f o r t h i s s t u d y , p r e c l u d i n g t h e use of s t o c k s p e c i f i c r e l a t i o n s h i p s . T h e r e f o r e , an a v e r a g e r e g r e s s i o n was c a l c u l a t e d f o r the t o t a l p o p u l a t i o n of main b a s i n f r y . Mean f o r k l e n g t h and t o t a l o t o l i t h l e n g t h a t emergence of t h e main l a k e f r y p o p u l a t i o n were e s t i m a t e d by summing the means f o r e ach f r y s o u r c e , w e i g h t e d by the r e l a t i v e 1978 b r o o d f r y p r o d u c t i o n ( e q . 1 ) . F r y p r o d u c t i o n by t h o s e main l a k e s t r e a m spawners n o t s t u d i e d was assumed to be e q u a l to 233 f r y p e r spawner and t h e i r b o d y - o t o l i t h r e l a t i o n s h i p s assumed to be s i m i l a r to t h o s e from P i n k u t C r e e k (McDonald, p e r s . comm.). The combined r e g r e s s i o n c o e f f i c i e n t was a w e i g h t e d mean of the d i f f e r e n t s o u r c e s ( e q . 2 ) . The combined i n t e r c e p t was c a l c u l a t e d u s i n g w e i g h t e d mean f o r k and t o t a l o t o l i t h l e n g t h s from each s o u r c e ( e q . 3 ) . The r e s u l t i n g a v e r a g e r e g r e s s i o n was h i g h l y s i g n i f i c a n t (p<.001, t a b l e 3 ) . R e s i d u a l s from the a v e r a g e r e g r e s s i o n , ( f i g . 9 ) a p p e a r e d to be homogeneous and n o r m a l l y d i s t r i b u t e d T a b l e 3 P r e d i c t i v e r e g r e s s i o n s f o r the r e l a t i o n s h i p between Ln f o r k l e n g t h and Ln t o t a l o t o l i t h l e n g t h a t f i v e f r y s o u r c e s on the B a b i n e Lake s y s t e m . S l o p e s and means t h a t a r e u n d e r l i n e d are not s i g n i f i c a n t l y d i f f e r e n t from each o t h e r ( S c h e f f e s m u l t i p l e range t e s t , p=.05). Average main l a k e r e g r e s s i o n i s c a l c u l a t e d from the combined f r y s o u r c e s , w e i g h t e d by r e l a t i v e f r y p r o d u c t i o n . S o u r c e i n t e r c e p t s l o p e (b) P i n k u t C h a n n e l 2 .38017 0.15850 F u l t o n R i v e r 1 .86284 0 .24940 F u l t o n Chan. 2 1.96408 0.23500 P i n k u t Creek 1 . 26758 0.34607 F u l t o n Chan. 1 0.87015 0.40849 Main Lake 1 . 52293 0.30493 Sy*x R2 t ( b ) p(b=0) 0.03523 0.0856 3.18 < .01 1 1 0 0.03096 0 .2265 6.67 <.001 154 0.03152 0.1572 6.39 < . 001 221 0.03716 0.2633 7.86 < .001 175 0.04537 0.3577 9.35 < .001 159 0.03717 0.215 2 14.97 < .001 81 9 Sou r c e mean y P i n k u t C hannel 3.34716 F u l t o n Chan. 1 3.37263 P i n k u t Creek 3.38095 F u l t o n R i v e r 3.39146 F u l t o n Chan. 2 3.40723 Main Lake 3.38786 Sy 0.03667 0.05643 0.04318 0.03509 0.03426 0.04603 3 0 a r o u n d the x - a x i s . L o s s of p r e c i s i o n by use of the a v e r a g e r e g r e s s i o n was n o t g r e a t : t h e mean i n c r e a s e i n s t a n d a r d d e v i a t i o n from r e g r e s s i o n , w e i g h t e d by r e l a t i v e f r y p r o d u c t i o n , was l e s s t han 2 per c e n t f o r each s t o c k . B a c k - c a l c u l a t i o n e r r o r s due to s t o c k d i f f e r e n c e s can be e s t i m a t e d from f i g u r e 8. The a v e r a g e r e g r e s s i o n u n d e r - e s t i m a t e s l e n g t h a t emergence i n s t o c k s f o r which the r e l a t i o n s h i p l i e s above the a v e r a g e r e g r e s s i o n and o v e r - e s t i m a t e s l e n g t h s f o r t h o s e below, by an amount e q u a l to the d i f f e r e n c e between the F c = E PK * F f c TC = E PK * T k ( e q . l ) PK _ E — E (F.. - P ) (T., - T ) k s k i l k c l k b c = (eq.2) £ — E (T . , - T ) 2 k S k i l k c a c . = F c " b c * T c ( e < 3 " 3 ) where p k — s k = n" ' I "* N k — F r y p r o d u c t i o n a t s o u r c e k n k = F r y samples a t s o u r c e k F i k = Emergent f o r k l e n g t h i a t s o u r c e T i k = Emergent t o t a l o t o l i t h l e n g t h i a t s o u r c e k 31 p r e d i c t e d v a l u e s a t any g i v e n t o t a l o t o l i t h l e n g t h . The l a r g e s t e r r o r s a r e a s s o c i a t e d w i t h the P i n k u t spawning c h a n n e l s t o c k , w hich has the r e l a t i o n s h i p most d i f f e r e n t from the a v e r a g e r e g r e s s i o n . However, the b i a s ( o v e r e s t i m a t e d f o r k l e n g t h s ) i s n o t c r i t i c a l when w o r k i n g w i t h l a r g e random samples from the j u v e n i l e and s m o l t p o p u l a t i o n s , b e c a u s e the c h a n n e l p r o d u c e d o n l y 7.5 p e r c e n t of the main l a k e f r y p o p u l a t i o n i n 1979. 3 2 GROWTH RATE IN BABINE LAKE F o r k l e n g t h s of the main l a k e f r y p o p u l a t i o n f o r the 1965 (McDonald, 1969) and the 1978 b r o o d s ar e p l o t t e d from emergence t o s m o l t m i g r a t i o n i n f i g u r e 10. The growth p a t t e r n of the two b r o o d s i s s i m i l a r . In e ach, the range of f o r k l e n g t h s i n c r e a s e d d r a m a t i c a l l y d u r i n g the e a r l y l a k e r e a r i n g p e r i o d , i n d i c a t i n g a l a r g e v a r i a t i o n among the growth r a t e s of i n d i v i d u a l f r y . Some o f the J u l y f r y d i s p l a y e d h i g h growth r a t e s w h i l e o t h e r s showed l i t t l e i n c r e a s e s o v e r May s i z e s . 0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 D A Y S O F G R O W T H F R O M M A Y 1 = D A Y 1 F i g u r e 10 Mean f o r k l e n g t h s of 1978 and 1965 b r o o d s o c k e y e from f r y emergence to s m o l t e m i g r a t i o n from B a b i n e L a k e . V e r t i c a l b a r s r e p r e s e n t two s t a n d a r d d e v i a t i o n s on e i t h e r s i d e of the mean. 33 The mean f o r k l e n g t h d u r i n g the s p r i n g d i d not i n c r e a s e by c o m p a r i s o n w i t h the s u b s e q u e n t growth o v e r the summer months. The range of f o r k l e n g t h s d i d not change g r e a t l y o v e r the summer or w i n t e r p e r i o d s . McDonald f o u n d h i g h e r growth r a t e s d u r i n g the e a r l y l a k e r e a r i n g p e r i o d among the l a r g e r F u l t o n r i v e r f r y t h a n among the s m a l l e r c h a n n e l f r y . The dependence of growth r a t e on f i s h s i z e i n e a r l y J u l y was i n v e s t i g a t e d f o r the 1978 b r o o d . The d a i l y g rowth r i n g s i n the o t o l i t h s of the J u l y tow samples were measured o v e r the 20 days p r i o r to c a p t u r e . F o r k l e n g t h s were t h e n b a c k - c a l c u l a t e d u s i n g the 6 t h o r d e r p o l y n o m i a l d e r i v e d p r e v i o u s l y f o r 140° r a d i i ( e q . 4 ) . D e v i a t i o n s from the p r e d i c t i v e f u n c t i o n a t the time of c a p t u r e were assumed to be c o n s t a n t o v e r the b a c k - c a l c u l a t e d p e r i o d and e s t i m a t e d as Ln f o r k l e n g t h a t c a p t u r e minus the p r e d i c t e d Ln f o r k l e n g t h a t c a p t u r e . Ln F t = f ( T t ) + Ln Fc - f ( T c ) (eq.4) where f ( x ) = 6th o r d e r p o l y n o m i a l of Ln f o r k l e n g t h v e r s u s Ln t o t a l o t o l i t h l e n g t h F t F o r k l e n g t h t days b e f o r e c a p t u r e Fc F o r k l e n g t h a t c a p t u r e T t T o t a l o t o l i t h l e n g t h t days b e f o r e c a p t u r e Tc T o t a l o t o l i t h l e n g t h a t c a p t u r e 34 A p l o t of the i n d i v i d u a l growth c u r v e s i s c o n f u s i n g , t h e r e f o r e the samples were the n grouped i n t o 1 mm i n t e r v a l s of f o r k l e n g t h a t c a p t u r e and the a v e r a g e b a c k - c a l c u l a t e d f o r k l e n g t h s p l o t t e d o v e r time ( f i g . 1 1 ) . F i g u r e 11 Mean f o r k l e n g t h s of the 1978 b r o o d s o c k e y e f r y o v e r the 20 day p e r i o d p r i o r to c a p t u r e i n J u l y ( c e n t r a l c a p t u r e d a t a = J u l y 1 2 ) . Numbers i n b r a c k e t s i n d i c a t e sample s i z e . 35 The o r d e r l y d i v e r g e n c e of the growth c u r v e s and the low i n c i d e n c e of c r o s s i n g - o v e r s u g g e s t s t h a t a r e l a t i o n s h i p e x i s t s between i n s t a n t a n e o u s growth r a t e and Ln f o r k l e n g t h , and a c c o r d i n g l y a m a i n t e n a n c e of a h i e r a r c h y of l e n g t h s w i t h i n the f r y p o p u l a t i o n . The c o r r e l a t i o n of i n s t a n t a n e o u s d a i l y growth r a t e s and Ln f o r k l e n g t h i n f i g u r e 12 was s i g n i f i c a n t ( r 2 = 0.6142) . w < pt, a fr 3 o oi o H < a CO D O w 2 < 2 < EH CO 2 0 . 0 1 5 o.oio H 0 . 0 0 5 H o.o H 3 . 0 -i 1 1 r - 1 1 1 r 3.2 3 . 4 3.6 3.8 L n ( F O R K L E N G T H ( m m ) ) F i g u r e 12 I n s t a n t a n e o u s d a i l y growth r a t e s i n r e l a t i o n to Ln f o r k l e n g t h o v e r the 20 days p r i o r to c a p t u r e ( c e n t r a l c a p t u r e d a t e = J u l y 12) o f the 1978 b r o o d s o c k e y e i n B a b i n e L a k e . 36 SELECTIVE MORTALITY IN BABINE LAKE T o t a l O t o l i t h L e n g t h a t Emergence T o t a l o t o l i t h l e n g t h a t emergence (Te) was compared among the f r y , j u v e n i l e and s m o l t p o p u l a t i o n s . The d i s t r i b u t i o n s of t o t a l o t o l i t h l e n g t h a t emergence of the d a i l y f r y samples were w e i g h t e d by the number of m i g r a t i n g f r y ( e q . 5 ) . The r e s u l t i n g d i s t r i b u t i o n s of each f r y s o u r c e were then summed to e s t i m a t e the d i s t r i b u t i o n of t o t a l o t o l i t h l e n g t h a t emergence of the main l a k e f r y p o p u l a t i o n ( e q . 6 ) . P ( f ) i j k * N ( f ) j k " T ( f ) i k ( e * - 5 ) where P ( f ) . . , = F r a c t i o n o f f r y w i t h T. on day j 1 3 k . 1 a t s o u r c e k N(f ) = Number o f f r y on day j a t s o u r c e k D k T ( f ) . , = Number o f f r y w i t h T. a t s o u r c e k i k 1 and I P (f ) . ., = 1 i j T = T o t a l o t o l i t h l e n g t h a t emergence T ( f ) . = I ( T ( f ) .. * W, ) (eq.6) 1 k i k k where T (f) . 1 = Number o f f r y w i t h T, i n the l a k e 37 The d a i l y s m o l t d i s t r i b u t i o n s of t o t a l o t o l i t h l e n g t h a t emergence were w e i g h t e d by the d a i l y m i g r a t i o n numbers and summed to e s t i m a t e the d i s t r i b u t i o n of t o t a l o t l i t h l e n g t h s a t emergence of the main b a s i n s m o l t p o p u l a t i o n ( e q . 7 ) . The o b s e r v e d d i s t r i b u t i o n s of the tow samples were not m o d i f i e d . P(s) . . * N(s) . = T ( s ) . (eq.7) 13 3 1 where P ( s ) . . = F r a c t i o n o f smolt w i t h T. on day j ID 1 N ( s ) j _ j= Number o f s m o l t s on day j T ( s ) . = Number o f s m o l t s w i t h T. 1 1 and E P ( s ) . . = 1 i j l J T = T o t a l o t o l i t h l e n g t h a t emergence The r e s u l t i n g t o t a l o t o l i t h l e n g t h d i s t r i b u t i o n s a r e g i v e n i n t a b l e 4. An abundance of s m a l l o t o l i t h s o b s e r v e d i n J u l y d i d not a p pear i n the e s t i m a t e d main l a k e f r y p o p u l a t i o n , and t h i s was p a r t of a t r e n d f o r s m a l l o t o l i t h s to d i s a p p e a r between the f r y and s m o l t s t a g e s ( f i g . 1 3 ) . Between the f r y and s m o l t s t a g e s the r e l a t i v e f r e q u e n c y of o t o l i t h s w i t h emergent t o t a l o t o l i t h l e n g t h s s m a l l e r than the mean of the f r y p o p u l a t i o n d e c r e a s e d from 47.5 t o 11.3 per c e n t a t the s m o l t s t a g e ( t a b l e 5 ) . T a b l e 4 D i s t r i b u t i o n s of t o t a l o t o l i t h l e n g t h a t emergence (Te) f o r w e i g h t e d emergent f r y samples, tow samples i n J u l y , August and September, and w e i g h t e d s m o l t samples from the B a b i n e s m o l t t r a p . A l l samples from the 1978 brood of the B a b i n e Lake main b a s i n s o c k e y e . T o t a l O t o l i t h L e n g t h a t Emergence Weighted F r y Sample s no. % Observed Tows Ju l y Aug Sept Weighted Smolt Sample s no. % 330 - 345 1 345 - 360 2 0.299 2 1 360 - 375 3 0.398 3 1 2 375 - 390 8 0.996 2 2 0 390 - 405 19 2.291 1 2 2 2 2.6 1.532 405 - 420 41 4.980 5 3 1 1 . 4 0. 81 7 420 - 435 68 8.366 6 2 5 2. 3 1 . 328 435 - 450 178 21.912 7 7 2 4.6 2.656 450 - 465 1 26 15.538 9 1 2 6 15.8 9.193 465 - 480 159 19.622 5 6 9 15.8 9.193 480 - 495 1 30 16.036 4 4 1 0 32.2 18.692 495 - 51 0 46 5.67 7 2 5 7 46.9 27 .27 3 51 0 - 525 22 2.689 4 2 6 29 . 7 17.262 525 - 540 6 0 .697 1 2 9 14.4 8.376 540 - 555 4 0.498 2 3 5.3 3.064 555 - 570 1 1 . 0 0.613 mean 458. 1 435. 4 460. 1 482 . 0 493 . 6 v a r i a n c e 182.5 2130. 8 1971 .4 1772.4 904. 8 n 81 2 63 52 62 1 7 2 39 20 H > 10 u z u 3 cr o i 20 as B . 10 CD > J 2 0 ca as 10-2 0 H 10 H MAIN L A K E SMOLT M I D - S E P T E M B E R r n n - 1 M I D - A U G U S T H=L M I D - J U L Y MAIN L A K E F R Y 1 — r 300 330 360 390 420 450 ' 480 SO 540 570 600 TOTAL OTOLITH L E N G T H (um) AT E M E R G E N C E F i g u r e 13 H i s t o g r a m s of the r e l a t i v e f r e q u e n c i e s of t o t a l o t o l i t h l e n g t h (um) a t emergence d u r i n g : f r y emergence, m i d - J u l y , m i d - A u g u s t , mid-September and a t the sub-2 s m o l t e m i g r a t i o n , f o r the 1978 b r o o d s o c k e y e from the main b a s i n of B a b i n e Lake, B.C. 40 F r y s u r v i v a l s from the two h a l v e s of the emergent t o t a l o t o l i t h l e n g t h d i s t r i b u t i o n were 8.9 p e r c e n t and 63.6 p e r c e n t . The r e s u l t i n g s h i f t i n the mean t o t a l o t o l i t h l e n g t h from 458.1 t o 493.6 m i c r o n s ( f r y to s m o l t ) was h i g h l y s i g n i f i c a n t (p<.001). T a b l e 5 F r y to s m o l t s u r v i v a l (s) and i n s t a n t a n e o u s m o r t a l i t y r a t e ( z ) o f s o c k e y e f r y w i t h t o t a l o t o l i t h l e n g t h s a t emergence above and below the mean of the 1978 b r o o d . T o t a l O t o l i t h F r y Smolt S u r v . I n s t a n t . L e n g t h a t r a t e m o r t a l i t y Emergence % m i l l i o n s % m i l l i o n s (s) r a t e ( z ) < mean 47.5 59.4 11.3 5.3 0.089 2.4166 > mean 52.5 65.6 88.7 41.7 0.636 0.4531 t o t a l 100.0 125.0 100.0 47.0 R i c k e r (1969) p r o v i d e s an i n d e x of the i n t e n s i t y of s e l e c t i o n ( r ) which compares i n s t a n t a n e o u s m o r t a l i t y r a t e s of the p a r t s of a p o p u l a t i o n w i t h i n one p r o b a b l e e r r o r (0.6745s) on e i t h e r s i d e of the mean ( e q . 8 ) . T h i s i s e q u i v a l e n t to the d i f f e r e n c e i n a v e r a g e i n s t a n t a n e o u s m o r t a l i t y r a t e s between t h e two h a l v e s of the d i s t r i b u t i o n i f the i n s t a n t a n e o u s m o r t a l i t y r a t e i s a l i n e a r f u n c t i o n of the i n d e p e n d e n t v a r i a b l e . The c a l c u l a t e d r of the t o t a l o t o l i t h l e n g t h a t emergence from f r y t o s m o l t s t a g e i s : 1.349 d / s 1.349 * (458.1 - 493.6) / 13.51 -3.55 ( i n d e x of r e l a t i v e s e l e c t i v i t y ) (eq.8) The d i f f e r e n c e i n the o b s e r v e d i n s t a n t a n e o u s m o r t a l i t y r a t e s f o r the two h a l v e s of t h e d i s t r i b u t i o n i n t a b l e 5 was (0.4531 - 2.4166) = -1.9635 which i s d i f f e r e n t from the c a l c u -l a t e d v a l u e of -3.55. T h i s d i s c r e p a n c y i s due to the f a i l u r e of the d a t a to meet the u n d e r l y i n g a s s u m p t i o n of the i n d e x - a l i n e a r change i n the i n s t a n t a n e o u s m o r t a l i t y r a t e ( z ) o v e r the r a n g e of the i n d e p e n d e n t v a r i a b l e . The i n t e n s i t y of n e g a t i v e s e l e c t i o n a g a i n s t the s m a l l e r o t o l i t h s i s c o n s t a n t and i n t e n s e up to 485 m i c r o n s , s l i g h t l y beyond the mean t o t a l o t o l i t h l e n g t h ( f i g . 1 4 ) . F i g u r e 14 S e l e c t i v i t y of t o t a l o t o l i t h l e n g t h a t emergence (Te) between the f r y and s m o l t s t a g e s ( r e l a t i v e f r e q u e n c y of s m o l t Te / r e l a t i v e f r e q u e n c y of f r y T e ) . 42 F o r k L e n g t h a t Emergence Ln f o r k l e n g t h a t emergence (Fe) was b a c k - c a l c u l a t e d from Ln t o t a l o t o l i t h l e n g t h . To p r e v e n t d i v e r g e n c e n e a r the ends of t h e o b s e r v e d range of Ln t o t a l o t o l i t h l e n g t h , t h e 6 t h o r d e r p o l y n o m i a l was r e p l a c e d w i t h p r e d i c t i v e l i n e a r r e g r e s s i o n s c a l c u l a t e d from the d a t a of each s a m p l i n g p e r i o d ( t a b l e 6 ) . S i n c e the form of the r e l a t i o n s h i p i s l i n e a r a t each s a m p l i n g p e r i o d , and the d a t a a r e n o r m a l l y d i s t r i b u t e d a r o u n d the r e g r e s s i o n l i n e s , t h e i r use i s v a l i d f o r b a c k - c a l c u l a t i o n p u r p o s e s . The a v e r a g e r e g r e s s i o n c a l c u l a t e d p r e v i o u s l y f o r the main l a k e f r y p o p u l a t i o n was used as the p r e d i c t i v e f u n c t i o n f o r Ln t o t a l o t o l i t h l e n g t h a t emergence and the a p p r o p r i a t e r e g r e s s i o n f o r each l i f e h i s t o r y s t a g e ( t a b l e 6) was used f o r the f u n c t i o n of Ln f o r k l e n g t h v e r s u s Ln t o t a l o t o l i t h l e n g t h a t c a p t u r e . T a b l e 6 P r e d i c t i v e l i n e a r r e g r e s s i o n s of Ln f o r k l e n g t h a t c a p t u r e ( F c ) v e r s u s Ln t o t a l o t o l i t h l e n g t h a t c a p t u r e (Tc) f o r the 1978 b r o o d s o c k e y e a t : f r y emergence, m i d - J u l y , m i d - A u g u s t , mid-September and a t the sub-2 s m o l t e m i g r a t i o n from the main b a s i n of B a b i n e L a k e . L i f e H i s t o r y S t a g e P r e d i c t i v e R e g r e s s i o n F r y Emergence L n ( F e ) 1 .39577 + 0. 32543 * L n ( T e ) m i d - J u l y L n ( F c ) = -4 .08384 + 1 . 19502 * L n ( T c ) mid-Aug L n ( F c ) -2 .43577 + 0. 95689 * L n ( T c ) m i d - S e p t L n ( F c ) -1 .14453 + 0. 76759 * L n ( T c ) Smolt L n ( F c ) 0 .77640 + 0. 49969 * L n ( T c ) n o t e : Fe = Fc and Te = Tc f o r emergent f r y 43 Ln f o r k l e n g t h a t emergence (Fe) o f the j u v e n i l e and s m o l t samples was b a c k - c a l c u l a t e d from Ln emergent t o t a l o t o l i t h l e n g t h ( e q . 9 ) . D e v i a t i o n s of each sample from the p r e d i c t i v e r e g r e s s i o n a t the t i m e of c a p t u r e were assumed t o be c o n s t a n t o v e r the range of Ln t o t a l o t o l i t h l e n g t h , as i n e q u a t i o n 4. A c o r r e c t i o n (C) was i n c l u d e d to remove b i a s c a u s e d by s e l e c t i v e m o r t a l i t y . S e l e c t i o n on s m a l l e r emergent f r y c a u s e s the d i s t r i b u t i o n of s u r v i v o r s and the r e s u l t i n g p r e d i c t i v e r e g r e s s i o n to s h i f t upwards, b i a s i n g the d e v i a t i o n of o b s e r v e d f o r k l e n g t h s from the p r e d i c t e d f o r k l e n g t h downwards. Hence, the e f f e c t i s s i m i l a r to L e e ' s phenomena but i n the o p p o s i t e d i r e c t i o n . Based on the a s s u m p t i o n t h a t d e v i a t i o n s from the p r e d i c t i v e r e l a t i o n s h i p a r e c o n s t a n t f o r each sample, C c a n be e s t i m a t e d by the mean emergent f o r k l e n g t h of the j u v e n i l e o r Ln Fe = f ( T e ) + Ln Fc - f ( T c ) + C (eq.9) where f ( T e ) = P r e d i c t e d Ln Fe from r e g r e s s i o n of Ln Fe v e r s u s Ln Te f ( T c ) = P r e d i c t e d Ln Fc from r e g r e s s i o n of Ln Fc v e r s u s Ln Tc Te = T o t a l o t o l i t h l e n g t h a t emergence Tc = T o t a l o t o l i t h l e n g t h a t c a p t u r e Fe = F o r k l e n g t h a t emergence Fc = F o r k l e n g t h a t c a p t u r e C = Mean Ln Fe of the f r y p o p u l a t i o n minus the mean Ln Fe of s u r v i v i n g p o p u l a t i o n 44 s m o l t d i s t r i b u t i o n minus the mean f o r k l e n g t h of the i n i t i a l f r y p o p u l a t i o n . The d i s t r i b u t i o n of emergent f o r k l e n g t h s f o r the main l a k e f r y p o p u l a t i o n was c a l c u l a t e d from the s t r a t i f i e d f r y samples u s i n g the same p r o c e d u r e as f o r the d i s t r i b u t i o n of t o t a l o t o l i t h l e n g t h s a t emergence (eq.5 & 6 ) . The s t r a t i f i e d samples of s m o l t s were p o o l e d and grouped i n t o 0.5 mm i n t e r v a l s of f o r k l e n g t h a t c a p t u r e . The d i s t r i b u t i o n of emergent f o r k l e n g t h s w i t h i n each i n t e r v a l was then w e i g h t e d by the d i s t r i b u t i o n of f o r k l e n g t h s of the main l a k e s m o l t s ( e q . 1 0 ) . B a c k - c a l c u l a t e d d i s t r i b u t i o n s of emergent f o r k l e n g t h f o r the tow samples were no t m o d i f i e d . The r e s u l t i n g d i s t r i b u t i o n s of f o r k l e n g t h a t emergence a r e g i v e n i n t a b l e 7. * N(s) . F e ( s ) , (eq.10) where F r a c t i o n of smolts with Fe. and Fc. N ( s) j Fe (s) Number of smolts with Fc. Number of smolts with Fe. Fe Fork l e n g t h at emergence Fc Fork l e n g t h at capture and E P (s) . . i j 1 3 1 T a b l e 7 D i s t r i b u t i o n s of f o r k l e n g t h (mm) a t emergence f o r w e i g h t e d emergent f r y samples, o b s e r v e d tow samples i n J u l y , A u g u s t and September, and w e i g h t e d s m o l t samples from the B a b i n e s m o l t t r a p . A l l samples a r e from the 1978 b r o o d of the B a b i n e Lake main b a s i n s o c k e y e . See t e x t f o r w e i g h t i n g p r o c e d u r e s . F o r k L e n g t h a t Emergence (mm ) Weighted F r y no, Observed Tows Ju l y Aug S e p t Weighted s m o l t s no, 23 - 24 1 24 - 25 4 1 25 - 26 2 . 4 0 . 3 2 2 1 26 - 27 6.5 0.8 7 2 4 1 . 3 0.7 27 - 28 27 .6 3.4 6 6 4 1 . 8 1 . 1 28 - 29 122.6 15.1 8 8 8 8.9 5 . 2 29 - 30 241 . 2 29 .7 1 1 8 9 16.2 9.4 30 - 31 261 . 5 32.2 1 2 6 1 1 23.5 13.7 31 - 32 121.0 14.9 7 6 1 0 39 .6 23.0 32 - 33 28 . 4 3.5 2 6 6 40. 6 23.6 33 - 34 0 . 8 0.1 1 3 2 18.1 10.5 34 - 35 2 2 11.6 6.7 35 - 36 0 2 6.1 3.6 36 - 37 0 1 1 . 6 1 . 0 37 - 38 0 2 38 - 39 1 mean 29 .55 28 .84 30.00 30.62 31.08 v a r i a n c e 1.352 5.025 6.586 7.013 3.841 n 81 2 61 51 62 172 46 H i s t o g r a m s of the r e l a t i v e f r e q u e n c i e s of emergent f o r k l e n g t h s a t each s a m p l i n g p e r i o d ( f i g . 1 5 ) i n d i c a t e s e l e c t i o n a g a i n s t f r y w i t h s m a l l emergent f o r k l e n g t h s . The i n c r e a s e i n mean f o r k l e n g t h from 29.55 to 31.08 mm between the f r y and s m o l t s t a g e s was s i g n i f i c a n t (p<.001). F r y to sm o l t s u r v i v a l s o f the two h a l v e s of the d i s t r i b u t i o n above and below the mean emergent f o r k l e n g t h of the f r y a r e 51.5 p e r c e n t and 12.7 p e r c e n t r e s p e c t i v e l y ( t a b l e 8 ) . T a b l e 8 F r y to s m o l t s u r v i v a l (s) and i n s t a n t a n e o u s m o r t a l i t y r a t e ( z ) of s o c k e y e f r y w i t h emergent f o r k l e n g t h s above and below the mean of the 1978 b r o o d . F o r k L e n g t h a t Emergence < mean > mean t o t a l F r y Smolt 35.9 64 . 1 100.0 m i 1 l i ons 44 . 8 80 . 2 125.0 % 12.2 87 . 8 100.0 m i l l i o n s 5 . 7 41.3 47.0 Sur v. r a t e (s) 0.127 0.515 Ins t a n t . m o r t a l i t y r a t e ( z ) 2.0617 0.6637 The o b s e r v e d d i f f e r e n c e between the i n s t a n t a n e o u s m o r t a l i t y r a t e s o f the two h a l v e s of the f o r k l e n g t h d i s t r i b u t i o n i s (0.6637 - 2.0617) = -1.398. R i c k e r ' s c a l c u l a t e d i n d e x between the two h a l v e s i s -1.775. The agreement between the c a l c u l a t e d and o b s e r v e d i n d i c e s of s e l e c t i o n on f o r k l e n g t h i s c l o s e r t h a n f o r t o t a l o t o l i t h l e n g t h . The lower o b s e r v e d i n d e x however, i n d i c a t e s t h a t s e l e c t i o n a g a i n s t f o r k l e n g t h does n o t change l i n e a r l y o v e r the range of f o r k l e n g t h s and t h a t the i n t e n s i t y y 4 7 20-10 -20 H 10 A o z 3 20-o LU rr > LU rr 20 10 4 2 0 H io H n — i — r 22 24 MAIN L A K E SMOLT M I D - S E P T E M B E R M I D - A U G U S T MID-JULY MAIN L A K E F R Y ft " I — I — I — I — I 34 36 38 26 28 30 32 40 TOTAL OTOLITH L E N G T H (um) AT E M E R G E N C E F i g u r e 15 H i s t o g r a m s of the r e l a t i v e f r e q u e n c i e s of f o r k l e n g t h s (mm) a t emergence d u r i n g : . f r y emergence, m i d - J u l y , m i d - A u g u s t , mid-September and a t the sub-2 s m o l t e m i g r a t i o n f o r the 1978 b r o o d s o c k e y e from the main b a s i n of B a b i n e Lake, B.C. 48 of s e l e c t i o n r e m a i n s h i g h o v e r the range of the s m a l l e r f o r k l e n g t h s . P l o t t i n g an e s t i m a t e of s e l e c t i v i t y , the r a t i o of r e l a t i v e f r e q u e n c y of s m o l t to t h a t of the f r y p o p u l a t i o n , o v e r i n t e v a l s of emergent t o t a l o t o l i t h l e n g t h i n d i c a t e s t h a t " m o r t a l i t y i s i n t e n s e up to about 31 mm emergent f o r k l e n g t h ( f i g . 1 6 ) . F O R K L E N G T H AT E M E R G E N C E (mm) F i g u r e 16 S e l e c t i v i t y of f o r k l e n g t h a t emergence (Fe) between the f r y and s m o l t s t a g e s ( R e l a t i v e f r e q u e n c y of s m o l t Fe / r e l a t i v e f r e q u e n c y of f r y F e ) . •4 9 F o r k L e n g t h V e r s u s T o t a l O t o l i t h L e n g t h D i s t r i b u t i o n s of Ln f o r k l e n g t h a t emergence v e r s u s Ln t o t a l o t o l i t h l e n g t h a t emergence a r e shown f o r each s a m p l i n g p e r i o d i n f i g u r e 17. The t r e n d of r e m o v a l of f r y w i t h s m a l l t o t a l o t o l i t h l e n g t h s and s m a l l f o r k l e n g t h s a t emergence i s o b v i o u s . However, the c o r r e l a t i o n between body and o t o l i t h s i z e r a i s e s the q u e s t i o n : Is s e l e c t i o n a g a i n s t the two p a r a m e t e r s i n d e p e n d e n t or does s e l e c t i o n a g a i n s t one p a r a m e t e r c a u s e an a p p a r e n t s e l e c t i o n a g a i n s t the o t h e r ? A s i m p l e e x e r c i s e was c a r r i e d o ut to t e s t the i n d e p e n d e n c e of s e l e c t i o n on each c h a r a t e r i s t i c . R e c o r d s of f r y w i t h t o t a l o t o l i t h l e n g t h s l e s s than 480 m i c r o n s were s e l e c t i v e l y removed. The mean t o t a l o t o l i t h l e n g t h and f o r k l e n g t h of the r e m a i n i n g samples were then w e i g h t e d by the r e l a t i v e p r o d u c t i o n of t h e i r r e s p e c t i v e f r y s o u r c e s . The mean t o t a l o t o l i t h l e n g t h a t emergence of the a d j u s t e d main l a k e f r y p o p u l a t i o n was s i m i l a r t o t h a t o f the s m o l t p o p u l a t i o n , b u t o n l y 48 p e r c e n t of t h e s h i f t i n mean f o r k l e n g t h between the f r y and s m o l t s t a g e s was a c c o u n t e d f o r ( t a b l e 9 ) . P e r f o r m i n g the c o n v e r s e o p e r a t i o n by r e m o v i n g a l l r e c o r d s of f r y w i t h f o r k l e n g t h s l e s s t h an 30.5 mm s h i f t e d the mean f o r k l e n g t h c l o s e to t h a t of the s m o l t s b u t c a u s e d o n l y 43 p e r c e n t of the o b s e r v e d s h i f t i n t o t a l o t o l i t h l e n g t h . Thus, i t c a n n o t be shown t h a t s e l e c t i v e m o r t a l i t y o p e r a t e s o n l y on emergent f o r k l e n g t h or on emergent t o t a l 5 0 LU O z LU o rr LU 2 LU E E C3 Z LU rr O LL 0 5 -a*-3 3 -a2-as a4-33-32-3 5 - ) 3 4 U 2 -3 2 -35-34-33-0 2 -as-a4-3 3 -32 SMOLT MID-SEPTEMBER MID-AUGUST M I D - J U L Y FMf EMERGENCE 5J8 5 3 6J0 6.1 8 2 6 3 6.4 L N ( T O T A L O T O L I T H L E N G T H ( u m ) A T E M E R G E N C E ) 6 2 LF i g u r e 17 Ln f o r k l e n g t h (mm) a t emergence and Ln t o t a l o t o l i t h l e n g t h (um) a t emergence f o r s o c k e y e a t f r y emergence, m i d - J u l y , m i d - A u g u s t , mid-September and a t the sub-2 s m o l t e m i g r a t i o n from the main b a s i n of B a b i n e L a k e , B.C. Arrows i n d i c a t e means. 51 o t o l i t h l e n g t h . T a b l e 9 Mean f o r k l e n g t h a t emergence (Fe) and mean t o t a l o t o l i t h l e n g t h a t emergence (Te) o f the f r y and s m o l t p o p u l a t i o n s , and of the f r y p o p u l a t i o n when samples w i t h f o r k l e n g t h s l e s s t h an 30.5 mm a r e removed and when samples w i t h t o t a l o t l i t h l e n g t h l e s s t h a n 480 m i c r o n s (um) a r e removed. Main Lake Mean Mean P o p u l a t i o n Te Fe F r y 29.55 458.1 Smolt 31.08 493.6 F r y w i t h Te > 30.5 mm 30.92 473.4 F r y w i t h Fe > 480 um 30.28 493.1 The b i v a r i a t e means of the d i s t r i b u t i o n s a r e p l o t t e d i n f i g u r e 18. The 95 p e r c e n t c o n f i d e n c e e l l i p s e s have been c a l c u l a t e d from p r i n c i p a l components a n a l y s i s ( S o k a l and R o h l f , 1969). B e f o r e e x a m i n i n g the c o n f i d e n c e r e g i o n s , b i a s of the tow-net samples i n m i d - J u l y , m i d - A u g u s t and mid-September s h o u l d be c o n s i d e r e d . The p o s i t i o n of the m i d - J u l y mean below t h a t of the emergent f r y p o p u l a t i o n i s q u e s t i o n a b l e . Even i f the s i z e of the f r y from the u n s t u d i e d s t r e a m s was o v e r e s t i m a t e d by a s s u m i n g t h a t t h e y were s i m i l a r to t h o s e from P i n k u t C r e e k, they a r e too few i n numbers to c a u s e the o b s e r v e d s h i f t i n mean s i z e . B i a s e d tow-net s a m p l i n g i s a more p r o b a b l e e x p l a n a t i o n of the 52 s m a l l s i z e of the f r y i n the m i d - J u l y sample. I— o to z Z LU LU e> _ i as L U ^ z: a: L U o u. h-a 4 -a 3 -a2-M I D - A U G U S T M I D - S E P T E M B E R 5:8 5.9 6.0 6.1 T 62 63 6.4 LN (TOTAL OTOLITH LENGTH (um) AT EMERGENCE) F i g u r e 18 B i v a r i a t e means and 95 p e r c e n t c o n f i d e n c e e l l i p s e s of the Ln f o r k l e n g t h (mm) v e r s u s Ln t o t a l o t o l i t h l e n g t h d i s t r i b u t i o n s a t emergence. The September mean i s mid-way between the A u g u s t and s m o l t s a m p l e s , s u g g e s t i n g t h a t the p r o c e s s of s e l e c t i v e m o r t a l i t y i s b e g i n n i n g by m i d - A u g u s t and i s h a l f c o m p l e t e d by mid-September. However, c o n s i d e r i n g the p o s s i b l e s a m p l i n g b i a s of the tow samples, the o n l y s i g n i f i c a n t s t a t e m e n t to be made i s t h a t the mid - A u g u s t mean i s s i m i l a r to t h a t of the f r y sample and d i f f e r e n t from the s m o l t . The mid-September mean may be s i m i l a r t o the mean i n A u g u s t or a t the s m o l t s t a g e . 53 GENERAL DISCUSSION D i f f e r e n t i a l growth and l a r g e i n c r e a s e s i n the v a r i a t i o n of f i s h s i z e were f o u n d i n the e a r l y r e a r i n g p e r i o d of j u v e n i l e s o c k e y e i n B a b i n e L a k e . S e v e r a l a u t h o r s have i n v e s t i g a t e d growth i n the f i r s t y e a r of r e a r i n g and the e f f e c t s of growth and c o m p e t i t i o n on the e v e n t u a l s i z e of f i s h w i t h i n a y e a r c l a s s . D i s c u s s i o n s of growth d i s p a r i t y b e g i n w i t h an e x p l a n a t i o n of the v a r i a t i o n i n spawning time, g e n e t i c d e t e r m i n a t i o n , egg s i z e and e n v i r o n m e n t a l c o n d i t i o n s and o t h e r such t h i n g s which a f f e c t the i n i t i a l v a r i a t i o n i n body s i z e . The e f f e c t s of c a n n i b a l i s m and p r e d a t i o n on s u b s e q u e n t growth and v a r i a t i o n a r e t h e n m e n t i o n e d and most i n v o l v e r a t i o n and the r e l a t i v e a b i l i t y of members w i t h i n a y e a r c l a s s to o b t a i n p r e y . D e A n g e l i s and C o u t a n t (1979) f o u n d t h a t under c o n d i t i o n s of s u r p l u s r a t i o n , the a v e r a g e growth r a t e of s m a l l m o u t h b a s s p o p u l a t i o n s was c o n s t a n t w i t h time and t h a t the growth r a t e of i n d i v i d u a l s was i n d e p e n d e n t o f f i s h s i z e and n o r m a l l y d i s t r i b u t e d . Under c o m p e t i t i v e c o n d i t i o n s however, the adv a n t a g e of l a r g e body s i z e and the d e c r e a s i n g a v a i l a b i l i t y of r a t i o n to the s m a l l e r members of a p o p u l a t i o n has been found to i n c r e a s e the v a r i a b i l i t y of body s i z e and to * ca u s e b i m o d a l s i z e d i s t r i b u t i o n s among l a r g e m o u t h b a s s ( S h e l t o n e t . a l . , 1979; Timmons and S h e l t o n , 1980; D e A n g e l i s and C o u t a n t , 1982). 54 In e a r l y J u l y , the l i n e a r dependance of growth r a t e on f o r k l e n g t h and the sudden i n c r e a s e i n v a r i a b i l i t y of f o r k l e n g t h s u g g e s t t h a t c o m p e t i t i o n f o r r a t i o n s may be t a k i n g p l a c e . Under t h e s e c o n d i t i o n s growth d e p e n s a t i o n can o c c u r , t h a t i s ; l a r g e r i n d i v i d u a l s w i l l grow f a s t e r t han the s m a l l e r i n d i v i d u a l s , m a i n t a i n i n g the r e l a t i v e h e i r a r c h y of s i z e s and i n c r e a s i n g t h e v a r i a b i l i t y of the l e n g t h d i s t r i b u t i o n . The e f f e c t of r a t i o n on the b o d y - o t o l i t h r e l a t i o n s h i p may be a s o u r c e of e r r o r i n the s t u d y of e a r l y growth r a t e s . M a r s h a l l and P a r k e r (1982) f o u n d s i g n i f i c a n t d i f f e r e n c e s between t h e s l o p e s of the r e l a t i o n s h i p s of s t a r v e d and f e d g r o u p s of j u v e n i l e s o c k e y e of s i m i l a r s i z e . When s t a r v e d f o r two to t h r e e weeks, the r e l a t i o n s h i p of f o r k l e n g t h to o t o l i t h d i a m e t e r d e v e l o p e d a lower s l o p e . T h i s was b e l i e v e d to be a s h o r t term r e p o n s e to s t a r v a t i o n b u t the e f f e c t of r a t i o n on t h e r e l a t i o n s h i p m i g h t a f f e c t r e s u l t s . Hence, i f the c o r r e l a t i o n of J u l y growth r a t e and f o r k l e n g t h was b r o u g h t a b o u t by c o m p e t i t i o n f o r f o o d and s t a r v e d f i s h d e v e l o p e d a b o d y - o t o l i t h r e l a t i o n s h i p w i t h a lower s l o p e , t h e n the use of an a v e r a g e r e l a t i o n s h i p would u n d e r e s t i m a t e the growth of the f a s t g r o w i n g f i s h and o v e r e s t i m a t e t h a t of the s m a l l slow g r o w i n g f i s h . T h i s b i a s would o n l y have made the d i s p a r i t y of the e s t i m a t e d growth r a t e s c o n s e r v a t i v e . The e f f e c t of p r e d a t i o n and s t a r v a t i o n c o u l d b i a s the 55 e s t i m a t e of f o r k l e n g t h s a t emergence upwards. C o n s t a n t r e m o v a l of s m a l l i n d i v i d u a l s from the p o p u l a t i o n by s e l e c t i v e p r e d a t i o n would cause the n e x t i n d i v i d u a l s i n t u r n to become " s m a l l " i n r e l a t i o n to the p o p u l a t i o n . S t a r v a t i o n v i a c o m p e t i t i o n f o r a d i m i n i s h i n g f o o d s u p p l y would then r e s u l t i n s m a l l e r f i s h b e i n g a s s o c i a t e d w i t h l a r g e r o t o l i t h s and c a u s i n g s u b s e q u e n t o v e r - e s t i m a t i o n of emergent f o r k l e n g t h s of s m a l l f r y i n the b a c k - c a l c u l a t i o n p r o c e s s . S e l e c t i v e m o r t a l i t y was f o u n d to a c t a g a i n s t f r y w i t h s m a l l ^ o r k l e n g t h s and s m a l l t o t a l o t o l i t h l e n g t h s a t Emergence. S e l e c t i o n b a s e d on o t o l i t h s i z e i s u n l i k e l y but t h e emergence c h e c k s were measured d i r e c t l y and d i s t r i b u t i o n s of emergent f o r k l e n g t h from the s m o l t samples a r e u n l i k e l y to be b i a s e d u n l e s s the w e i g h t i n g p r o c e s s of the n i g h t l y samples was i n e r r o r . c e l e c t i o n a g a i n s t o t o l i t h s i z e i s more l i k e l y r e l a t e d to some o t h e r body c h a r a c t e r i s t i c a s s o c i a t e d w i t h o t o l i t h s i z e such as endomorphy, the r a t i o of s k e l e t a l s t r u c t u r e to body s i z e . F o r k l e n g t h and o t o l i t h s i z e a r e c o r r e l a t e d but s e l e c t i o n c a n n o t be shown to a c t i n d e p e n d e n t l y on one c h a r a c t e r i s t i c a l o n e . The t i m i n g of s e l e c t i v e m o r t a l i t y of f r y w i t h s m a l l o t o l i t h s and of l e s s e r l e n g t h a p p e a r s to be between mid-August and the f o l l o w i n g s p r i n g . One h y p o t h e s i s of d e l a y e d m o r t a l i t y r e l a t e d t o emergence c h a r a c t e r i s t i c s and the e a r l y r e a r i n g p e r i o d i n v o l v e s p a r a s i t i z a t i o n by the c e s t o d e E u b o t h r i u m s a l v e l i n i . B6 The p a r a s i t e i s i n g e s t e d a l o n g w i t h copepods which a r e an i n t e r m e d i a t e h o s t of the p a r a s i t e and a major f o o d i t e m of j u v e n i l e s o c k e y e . The p a r a s i t e i s t h e n r e l e a s e d i n t o the i n t e s t i n e of the j u v e n i l e s o c k e y e which i s the t e r m i n a l h o s t , and l o d g e s i t s e l f i n the p y l o r i c c a e c a , a b s o r b i n g n u t r i e n t s from f o o d p a s s i n g t h r o u g h the i n t e s t i n e of the s o c k e y e and r e d u c i n g the growth r a t e of the f i s h . Boyce (1974) f o u n d t h a t the E u b o t h r i u m i n f e c t i o n r a t e d e c l i n e d s h a r p l y as the f o r k l e n g t h of s o c k e y e i n c r e a s e d above the 36 t o 45 mm r a n g e . P r e s u m a b l y , e i t h e r the i n t e s t i n a l t r a c t and p y l o r i c c a e c a were by then too l a r g e to a l l o w the p a r a s i t e t o wedge i t s e l f i n t o the end of the p y l o r i c c a e c a or the f r y may have d e v e l o p e d by then immune systems to cope w i t h the p a r a s i t e . Boyce (1977) d i s c u s s e s how p a r a s i t i z a t i o n g e n e r a l l y r e d u c e s the a b i l i t y of i n f e c t e d j u v e n i l e s to w i t h s t a n d s t r e s s b u t i n f e c t e d j u v e n i l e s may s u r v i v e to the s m o l t s t a g e . B i l t o n and R o b b i n s (1971) f o u n d t h a t j u v e n i l e s o c k e y e i n November c o u l d w i t h s t a n d up to twenty weeks of s t a r v a t i o n w i t h o u t undue m o r t a l i t y . However, p a r a s i t i z a t i o n c o u l d cause m o r t a l i t y among the i n f e c t e d j u v e n i l e s by r e d u c i n g the growth r a t e and a l l o w i n g s e l e c t i v e p r e d a t i o n to remove the i n f e c t e d f i s h . The i m p l i c a t i o n f o r s u r v i v a l i s t h a t f a s t e r growing f r y and f r y which ar e i n i t i a l l y l a r g e r would s u c c e s s f u l l y compete f o r 57 r a t i o n s , g r o w i n g more q u i c k l y and s p e n d i n g l e s s time i n the s i z e r ange s u s c e p t i b l e to p a r a s i t i z a t i o n . C o n t i n u e d h i g h e r growth r a t e s would then l e a d to i n c r e a s e d s u r v i v a l t h r o u g h a v o i d a n c e of p r e d a t i o n m o r t a l i t y . 58 SUMMARY The r e l a t i o n s h i p between f o r k l e n g t h and o t o l i t h s i z e , and d i f f e r e n t i a l growth and m o r t a l i t y based on emergent c h a r a c t e r i s t i c s was i n v e s t i g a t e d f o r the 1978 b r o o d s o c k e y e from the main b a s i n of B a b i n e L a k e . The b o d y - o t o l i t h r e l a t i o n s h i p of s o c k e y e between the s t a g e s of f r y emergence and s m o l t m i g r a t i o n i s a complex c u r v e f o r which 6 t h o r d e r o r t h o g o n a l p o l y n o m i a l s were d e r i v e d f o r b a c k - c a l c u l a t i n g f o r k l e n g t h s from t o t a l o t o l i t h l e n g t h and t h r e e o t o l i t h r a d i i . L i n e a r r e g r e s s i o n s of f o r k l e n g t h on f i v e o t o l i t h d i m e n s i o n s were d e r i v e d f o r emergent f r y . In o r d e r of d e c r e a s i n g s i g n i f i c a n c e the o t o l i t h d i m e n s i o n s a r e : 1) c r o s s s e c t i o n a l a r e a ; 2) t o t a l o t o l i t h l e n g t h ; 3) 140° r a d i u s ; 4) 200° r a d i u s ; and, 5) 160° r a d i u s . S i g n i f i c a n t d i f f e r e n c e s were found among the f o r k l e n g t h v e r s u s t o t a l o t o l i t h l e n g t h r e l a t i o n s h i p s of emergent f r y from d i f f e r e n t s o u r c e s . No g r o u p i n g of F u l t o n v e r s u s P i n k u t or r i v e r v e r s u s c h a n n e l s o u r c e s was o b v i o u s . A combined p r e d i c t i v e r e g r e s s i o n was d e r i v e d f o r use w i t h the t o t a l main b a s i n f r y p o p u l a t i o n . 59 The mean growth r a t e of the j u v e n i l e p o p u l a t i o n i s lower i n the s p r i n g t h an i n the summer. I n d i v i d u a l J u l y growth r a t e s a r e p o s i t i v e l y c o r r e l a t e d w i t h f o r k l e n g t h . T h i s may be due to c o m p e t i t i o n f o r p r e y and c o u l d c a u s e growth d e p e n s a t i o n , e x p l a i n i n g the i n c r e a s e d v a r i a n c e of l e n g t h i n the e a r l y s p r i n g . S e l e c t i v e m o r t a l i t y was found to o p e r a t e a g a i n s t j u v e n i l e s w i t h s m a l l f o r k l e n g t h s as emergent f r y and a g a i n s t j u v e n i l e s w i t h s m a l l emergent t o t a l o t o l i t h l e n g t h s or some c h a r a c t e r i s t i c a s s o c i a t e d w i t h s m a l l o t o l i t h s . The t i m i n g of s e l e c t i v e m o r t a l i t y based on emergent c h a r a c t e r i s t i c s a p p e a r s to o c c u r between mid-August and the n e x t s p r i n g . A h y p o t h e s i s of d e l a y e d m o r t a l i t y i n v o l v i n g p a r a s i t i z a t i o n by the c e s t o d e E u b o t h r ium s a l v e l i n i and s u b s e q u e n t p r e d a t i o n m o r t a l i t y of j u v e n i l e s o c k e y e i s d i s c u s s e d . 60 LITERATURE CITED Anon. 1965. P r o p o s e d s o c k e y e salmon d e v e l o p m e n t program f o r B a b i n e L a k e . Canada. D e p t . of F i s h e r i e s . P a c i f i c a r e a and F i s h e r i e s R e s e a r c h B o a r d . r e p o r t 1965-9. 53 pp . B a g e n a l , T.B. and F.W. T e s c h . 1978. Age and Growth, i n : IBP Handbook no. 3, 3 r d ed., Methods f o r a s s e s s m e n t of f i s h p r o d u c t i o n i n f r e s h w a t e r s . T.B. B a g e n a l ( e d . ) . pp. 101 - 136. B l a c k w e l l s c i e n t i f i c p u b l i c a t i o n s , O x f o r d . B i l t o n , H.T. and G.L. R o b b i n s . 1971. Response of young s o c k e y e salmon ( O n c o r h y n c h u s n e r k a ) t o p r o l o n g e d p e r i o d s of s t a r v a t i o n . J . F i s h . Res. Bd. Can. 28: 1757-1761. Boyce, N.P.J. 1974. B i o l o g y of E u b o t h r ium s a l v e l i n i ( C e s t o d a : P s e u d o p h y l l i d e a ) a p a r a s i t e of j u v e n i l e s o c k e y e salmon ( O n c o r h y n c h u s n e r k a ) o f B a b i n e Lake, B r i t i s h C o l u m b i a . J . F i s h . Res. Board Can. 31: 1735-1742. Boyce, N.P.J. 1977. E f f e c t s of a p a r a s i t e , E u b o t h r ium s a l v e l i n i ( C e s t o d a : P s e u d o p h y l l i d e a ) , on the r e s i s t a n c e of j u v e n i l e s o c k e y e salmon ( O n c o r h y n c h u s n e r k a ) , to z i n c . J . F i s h . Res. Board Can. 34: 706-709. C a r l a n d e r , K.D. 1981. C a u t i o n on the use of t h e r e g r e s s i o n method of b a c k - c a l c u l a t i n g l e n g t h s from s c a l e m easurements. F i s h e r i e s , 6: 2-4. D e A n g e l i s , D.L. and C C . C o u t a n t . 1979. Growth r a t e s and s i z e d i s t r i b u t i o n s of f i r s t - y e a r s m a l l m o u t h b a s s p o p u l a t i o n s : Some c o n c l u s i o n s from e x p e r i m e n t s and a model. T r a n s . Am. F i s h . Soc. 108: 137-141. D e A n g e l i s , D.L. and C.C. C o u t a n t . 1982. G e n e s i s of b i m o d a l s i z e d i s t r i b u t i o n s i n s p e c i e s c o h o r t s . T r a n s . Am. F i s h . Soc. 111: 384-388. D r a p e r , N.R. and H. S m i t h . 1966. A p p l i e d R e g r e s s i o n a n a l y s i s . John W i l e y & Son, L t d . , New York, N.Y. F o e r s t e r , R.E. 1938. M o r t a l i t y t r e n d among young s o c k e y e salmon ( O n c o r h y n c h u s n e r k a ) d u r i n g v a r i o u s s t a g e s of l a k e r e s i d e n c e . J . F i s h . Res. Board Can. 4: 184-191. F o e r s t e r , R.E. and W.E. R i c k e r . 1941. The e f f e c t of r e d u c t i o n of p r e d a c e o u s f i s h on s u r v i v a l of young s o c k e y e salmon a t C u l t u s L a k e . J . F i s h . Res. Board Can. 5: 315-336 61 G i n e t z , R.M.J. 1977. A r e v i e w of the B a b i n e Lake Development P r o j e c t , 1961-1977. Canada D e p t . o f F i s h e r i e s . T e c h n i c a l R e p o r t S e r i e s No. t-77-6. G j e r n e s , T. 1979. A p o r t a b l e midwater t r a w l i n g system f o r use i n remote l a k e s . Can. F i s h . Mar. S e r v . T e c h . r e p . No. 888. 13 pp. H e a l e y , M.C. 1982. T i m i n g and r e l a t i v e i n t e n s i t y of s i z e -s e l e c t i v e m o r t a l i t y of j u v e n i l e chum salmon ( O n c o r h y n c h u s ke t a ) d u r i n g e a r l y sea l i f e . Can. J . F i s h . A q u a t . S c i . 39: 952-957. H e s k i n , B.A. 1967. The B a b i n e Lake Development Program f o r s o c k e y e salmon. Canada D e p t . o f F i s h e r i e s R e p t . 3, 1 5pp . H i l e , R. 1970. B o d y - s c a l e r e l a t i o n and c a l c u l a t i o n of growth i n f i s h e s . T r a n s . Am. F i s h . Soc. 99: 468-474. J o n s s o n , B. and N.C. S t e n s e t h . 1977. A method f o r e s t i m a t i n g f i s h l e n g t h from o t o l i t h s i z e . D r o t t n i n g h o l m : I n s t , of F r e s h w a t e r R e s e a r c h , R e p o r t No.56, pp: 81-86. L a r k i n , P.A. and J.G. McDonald. 1968. F a c t o r s i n the p o p u l a t i o n b i o l o g y of the sockeye salmon of the Skeena R i v e r . J . Anim. E c o l . 37:229-258. M a r s h a l l , S.L. and S.S. P a r k e r . 1982. P a t t e r n i d e n t i f i c a t i o n i n the m i c r o s t r u c t u r e of s o c k e y e salmon ( O n c o r h y n c h u s  n e r k a ) o t o l i t h s . Can. J . F i s h . A q u a t . S c i . 39: 542-547. McDonald, J.G. 1969. D i s t r i b u t i o n , g r o w t h , and s u r v i v a l of s o c k e y e f r y ( O n c o r h y n c h u s n e r k a ) p r o d u c e d i n n a t u r a l and a r t i f i c i a l s t r e a m e n v i r o n m e n t s . J . F i s h . Res. Board Can. 26: 229-267. N e i l s o n , J.D. and G.H. Geen. 1982. O t o l i t h s of c h i n o o k salmon ( O n c o r h y n c h u s t s h a w y t s c h a ) : D a i l y growth i n c r e m e n t s and f a c t o r s i n f l u e n c i n g t h e i r p r o d u c t i o n . Can. J . F i s h . A q u a t . S c i . 39: 1340-1347. P a n n e l l a , G. 1980. Growth p a t t e r n s i n f i s h s a g i t t a e , p.519-560. i n (D.C. Rhoads and R.A. L u t z eds.) S k e l e t a l growth of a q u a t i c o r g a n i s m s : b i o l o g i c a l r e c o r d s of e n v i r o n m e n t a l change. Plenum P r e s s , New York, NY. P a r k e r , R.R. 1971. S i z e s e l e c t i v e p r e d a t i o n among j u v e n i l e s a l m o n i d f i s h e s i n a B r i t i s h C o l u m b i a i n l e t . J . F i s h . Res. Board Can. 28: 1503-1510. 62 R a n k i n , D.P. 1977. I n c r e a s e d p r e d a t i o n by j u v e n i l e s o c k e y e salmon ( O n c o r h y n c h u s n e r k a Walbaum) r e l a t i v e to changes i n m a c r o z o o p l a n k t o n abundance i n B a b i n e Lake, B r i t i s h C o l u m b i a . MSc. T h e s i s . D e p t . o f Z o o l o g y . U n i v . of B.C. 101 pp. R i c k e r . W.E. 1941. The c o n s u m p t i o n of young s o c k e y e salmon by p r e d a c e o u s f i s h . J . F i s h . Res. Board Can. 5: 293-313. R i c k e r , W.E. 1969. E f f e c t s of s i z e - s e l e c t i v e m o r t a l i t y and s a m p l i n g b i a s on e s t i m a t e s of growth, m o r t a l i t y , p r o d u c t i o n , and y i e l d . J . F i s h . Res. Board Can. 26: 479-541. R i c k e r , W.E. 1973. L i n e a r r e g r e s s i o n s i n f i s h e r y r e s e a r c h . J . F i s h . Res. Board Can. 30: 409-434. S h e l t o n , W.L., W.D. D a v i e s , T.A. K i n g and T . J . Timmons. 1979. V a r i a t i o n i n t h e growth of the i n i t i a l y e a r c l a s s of l a r g e m o u t h b a s s i n West P o i n t r e s e r v o i r , Alabma and G e o r g i a . T r a n s . Am. F i s h . Soc. 108: 142-149. S h e p a r d , M.P. and F . C W i t h l e r . 1958. Spawning s t o c k s i z e and r e s u l t a n t p r o d u c t i o n f o r Skeena s o c k e y e . J . F i s h . Res. Board Can. 15: 1007-1025 <=okal, R.R. and F . J . R o h l f . 1969. B i o m e t r y . The p r i n c i p l e s and p r a c t i c e of s t a t i s t i c s i n b i o l o g i c a l r e s e a r c h . W.H. Freeman and Company. San F r a n s i c o . S t r u h s a k e r , P. and J.H. U c h i y a m a . 1979. Age and growth of the nehu, S t o l e p h o r u s p u r p u r e u s ( P i s c e s : E n g r a u l i d a e ) , from the H a w a i i a n I s l a n d s as i n d i c a t e d by d a i l y growth i n c r e m e n t s of s a g i t t a e . F i s h . B u l l . , U.S. 74: 9-17. Timmons, T.T. and W.L. S h e l t o n . 1980. D i f f e r e n t i a l growth of l a r g e m o u t h b a s s i n West P o i n t R e s e r v o i r , A l a b a m a - G e o r g i a . T r a n s . Am. f i s h . Soc. 109: 176-186. C . J . 1978. A r e v i e w of the B a b i n e Lake D e v e l o p m e n t P r o j e c t 1961 - 1977. Canada D e p t . of F i s h e r i e s , T e c h n i c a l R e p o r t s e r i e s No. 812. A. and T . J . Foreman. 1980. The r e l a t i o n s h i p between o t o l i t h i n c r e m e n t s and time f o r y e l l o w f i n and s k i p j a c k t u n a marked w i t h t e t r a c y c l i n e ( i n E n g l i s h and S p a n i s h ) . I n t e r - A m e r . T r o p . Tuna Comm., B u l l . , 17: 509-557. W i l s o n , K.H. 1981. D a i l y r i n g s i n o t o l i t h s of s o c k e y e salmon ( O n c o r h y n c h u s n e r k a ) and t h e i r r e l a t i o n s h i p to g r o w t h . MSc. T h e s i s . U n i v . of B.C. D e p t . of Z o o l o g y . 53 pp. West, W i l d , 63 W i l s o n , K.H., and P.A. L a r k i n . 1982. D a i l y growth r i n g s i n the o t o l i t h s of j u v e n i l e s o c k e y e salmon ( O n c o r h y n c h u s  n e r k a ) . Can. J . F i s h . A q u a t . S c i . 37: 1495-1498. 

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