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Food and feeding habits, maturity and fecundity of spring salmon (Oncorhynchus tshawytscha) and coho… Prakash, Anand 1958

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FOOD AND FEEDING HABITS, MATURITY AND FECUNDITY' OF SPRING SALMON (Oncorhynchus tshawytscha) AND COHO SALMON (Oncorhynchus k i s u t c h ) IN SOUTHERN BRITISH COLUMBIA COASTAL WATERS  by ANAND PRAKASH B.Sc. (Honours), U n i v e r s i t y of D e l h i , M.Sc,  1952.  U n i v e r s i t y of A l l a h a b a d , 1954.  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n t h e Department of Zoology  We accept t h i s t h e s i s as conforming t o the standard r e q u i r e d from the c a n d i d a t e s f o r t h e degree of MASTER OF ARTS  Members of t h e Department of Zoology THE UNIVERSITY OF BRITISH COLUMBIA August  1958  i ABSTRACT Food study based on the stomach content analyses of s p r i n g and coho salmon c o l l e c t e d from v a r i o u s l o c a l i t i e s along the southern B r i t i s h Columbia coast d u r i n g the summer of 1957  r e v e a l e d t h a t h e r r i n g f o l l o w e d by C r u s t a c e a formed  the most important item of the d i e t of the two s p e c i e s .  Coho  salmon e x h i b i t e d more p e l a g i c and v a r i e d d i e t than s p r i n g salmon caught i n the same a r e a .  D e f i n i t e seasonal f l u c t u a t i o n s  i n the c o m p o s i t i o n of food and f e e d i n g i n t e n s i t y were n o t i c e d , c o n s i d e r a b l e amounts of C r u s t a c e a were taken i n e a r l y summer months and a f t e r t h a t f i s h assumed importance. August mark the p e r i o d when the f e e d i n g a c t i v i t y  J u l y and i s intense  In both the s p e c i e s . Q u a l i t a t i v e and q u a n t i t a t i v e d i f f e r e n c e s i n the f e e d i n g c o n d i t i o n s on the east and west c o a s t s of Vancouver I s l a n d warrant the establishment of two food type areas.  The  d i f f e r e n c e s i n growth of f i s h on the two coasts as r e l a t e d to feeding c o n d i t i o n s are d i s c u s s e d .  Although, h e r r i n g i s the  major food item of both s p r i n g and coho salmon, evidences are presented i n support of the hypothesis t h a t a r e d u c t i o n i n h e r r i n g s t o c k abundance due t o p r e d a t i o n would not a f f e c t salmon c a t c h e s . Based on ova measurements and m a t u r i t y index values f i s h have been c l a s s i f i e d  i n t o immature and maturing.  appears t h a t almost a l l coho salmpn a v a i l a b l e t o the  It commercial  f i s h e r y are maturing, s p r i n g catches on the other hand i n c l u d e  l a r g e percentage of both immature and maturing f i s h . Immature and maturing female s p r i n g s d i v i d e at a f o r k l e n g t h of 74 cm.,  cohos do so at an approximate f o r k l e n g t h of 52 cm. A volume method f o r the d e t e r m i n a t i o n  of egg numbers  present i n the ovary has been developed, the average percentage e r r o r between the c a l c u l a t e d and a c t u a l counts being 5«3»  It  was found t h a t the absolute f e c u n d i t y Is p o s i t i v e l y c o r r e l a t e d t o f i s h l e n g t h and n e g a t i v e l y t o egg s i z e but the magnitude of the e f f e c t of f i s h l e n g t h on absolute f e c u n d i t y i s about f o u r times g r e a t e r than that of egg  size.  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of  the requirements f o r an advanced degree at the  University  of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and agree t h a t p e r m i s s i o n f o r e x t e n s i v e f o r s c h o l a r l y purposes may  study.  I further  copying o f t h i s  be granted by the Head of  Department or by h i s r e p r e s e n t a t i v e .  thesis my  I t i s understood  t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r  financial  g a i n s h a l l not be allowed w i t h o u t my w r i t t e n p e r m i s s i o n .  Department of The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada. Date  - iii TABLE OF CONTENTS Page ABSTRACT  i  INDEX OF TABLES  v  INDEX OF FIGURES  vi  ACKNOWLEDGEMENTS  v i i  INTRODUCTION  1  REVIEW OF THE LITERATURE  2  MATERIALS AND METHODS  6  FOOD AND FEEDING HABITS  8  Treatment of samples f o r food study COHO SALMON (Oncorhynchus k l ^ u t c h ) . . * . . . Composition fif Food Monthly f l u c t u a t i o n s i n food c o m p o s i t i o n  8 12 12 17  Food type areas  21  Feeding i n t e n s i t y  25  SPRING SALMON (Oncorhynchus tschawytscha). . Composition of food  27 27  Monthly f l u c t u a t i o n s and f e e d i n g intensity  .  Food type areas  31 33  Comparison of the food of s p r i n g and coho salmon  34  Salmon - h e r r i n g r e l a t i o n s h i p  37  Discussion  41  - iv-  TABLE OF CONTENTS (Cont.) Page MATURITY  45  ,  S t r u c t u r e of the ovary  46  Stages of m a t u r i t y  47  Maturation  51  FECUNDITY D e t e r m i n a t i o n of egg numbers  6l 62  . . . .  C o r r e l a t i o n between egg number and s i z e of f i s h .  64  R e d u c t i o n i n absolute f e c u n d i t y as a 70  f u n c t i o n of egg s i z e SUMMARY  . •  73  REFERENCES  76  APPENDIX  80  - v -  INDEX OF TABLES Table  .  IA - IB.  Number of coho and s p r i n g salmon samples c o l l e c t e d a c c o r d i n g t o area and month . . . . 1 0 - 1 1  II.  Percentage c o m p o s i t i o n of d i e t of t r o l l - c a u g h t coho salmon  III.  Percentage occurrence of d i e t of t r o l l - c a u g h t coho salmon  IV. V. VI. VII.  VIII. IX. X.  Page  Percentage c o m p o s i t i o n of d i e t of t r o l l - c a u g h t s p r i n g salmon Percentage occurrence of d i e t of t r o l l - c a u g h t s p r i n g salmon Maturity  constituents  19  constituents  20  constituents . constituents  index - egg diameter r e l a t i o n s h i p  28 29  .  49  Percentages of gonads i n d i f f e r e n t stages of m a t u r i t y i n t r o l l - c a u g h t f i s h a c c o r d i n g to months  52  Percentage of maturing female s p r i n g salmon i n each 5 cm. s i z e group  57  Percentage of maturing female coho salmon i n each 5 cm. s i z e group  58  Comparison between a c t u a l and egg counts  65  calculated  - vi-  INDEX OF FIGURES Figure I.  Page Map of southern B r i t i s h Columbia coast showing sampling areas  7  2a - 2b. Food organisms of s p r i n g and coho salmon . . . 3.  15-16  Monthly v a r i a t i o n s i n the volume of f i s h and c r u s t a c e a eaten by coho and s p r i n g salmon on the east and west coasts of Vancouver I s l a n d . . .  22  Comparison between the east and west coasts of Vancouver I s l a n d based on percentage composition of f i s h and c r u s t a c e a eaten by coho salmon i n d i f f e r e n t years  24  Monthly v a r i a t i o n s i n the f e e d i n g i n t e n s i t y of s p r i n g and coho salmon i n d i f f e r e n t areas . . .  26  Food of s p r i n g and coho salmon on southern B.C. coast - Percent volume and frequency of occurrence  36  7.  Egg diameter - m a t u r i t y index r e l a t i o n s h i p . . . .  50  8.  Monthly egg s i z e p r o g r e s s i o n i n s p r i n g salmon  9.  Monthly egg s i z e p r o g r e s s i o n i n coho salmon  10.  Percentage of immature and maturing females  4.  5. 6.  . . 54 ...  55  f o r d i f f e r e n t s i z e s and the s i z e at m a t u r i t y . . .  59  II.  Egg diameter - egg number r e l a t i o n s h i p  63  12. 13.  Egg number - f i s h s i z e r e l a t i o n s h i p R e l a t i o n s h i p beti/een egg diameter and r e l a t i v e f e c u n d i t y i n s p r i n g salmon  67 71  - vli AC KNOWLE D GEME NT S T h i s work was. i n i t i a t e d by the w r i t e r w h i l e i n t h e employ of the F i s h e r i e s Research Board of Canada, P a c i f i c B i o l o g i c a l S t a t i o n at Nanaimo, B.C. i n the summer of 1957* P e r m i s s i o n of t h e F i s h e r i e s Research Board t o i n c o r p o r a t e t h e work i n t o t h e s i s form i s g r a t e f u l l y  acknowledged.  The w r i t e r wishes t o extend h i s s i n c e r e thanks and g r a t i t u d e f o r h e l p and guidance which he r e c e i v e d from the f o l l o w i n g persons:  Dr. P. A. L a r k i n , D i r e c t o r , I n s t i t u t e o f  F i s h e r i e s , The U n i v e r s i t y of B r i t i s h Columbia, f o r guidance and u n f a i l i n g encouragement throughout t h e course of t h i s study;  Dr. D. J . M i l n e of t h e P a c i f i c B i o l o g i c a l S t a t i o n ,  Nanaimo, f o r c o n s t r u c t i v e c r i t i c i s m s , s u g g e s t i o n s and prov i d i n g background f o r t h i s work;  Dr. W. S. Hoar f o r going  through the manuscript and o f f e r i n g h i s c r i t i c i s m s ; Dr. F e r r i s Neave and Mr. J . I . Manzer f o r p r o v i d i n g d a t a c o l l e c t e d by the I n t e r n a t i o n a l North P a c i f i c F i s h e r i e s Commission on the food of coho salmon i n t h e h i g h seas. A s s i s t a n c e and f a c i l i t i e s p r o v i d e d by t h e s t a f f of the B i o l o g i c a l S t a t i o n , Nanaimo, i n the v a r i o u s phases of t h i s work i s g r a t e f u l l y  acknowledged.  The w r i t e r i s p a r t i c u l a r l y indebted t o Messrs. L. Ives and R. Lund and many other sport and commercial t r o l l e r s who were r e s p o n s i b l e f o r the c o l l e c t i o n of samples from the east and west c o a s t s of Vancouver I s l a n d .  Thanks  are a l s o extended t o Messrs. K. M u l l e r and E. A. R. B a l l f o r a s s i s t a n c e i n c o l l e c t i o n of t h e F r a s e r and Fuca samples.  -  1 -  INTRODUCTION The importance of S p r i n g salmon (Oncorhynchus tshawytscha): and Coho salmon (0^ k i s u t c h ) i n t h e economy of B r i t i s h Columbia can be judged by the f a c t t h a t f o r the l a s t f i v e years the t o t a l c a t c h of these two s p e c i e s of P a c i f i c salmon has c o n s t i t u t e d about o n e - f o u r t h of t h e t o t a l l a n d i n g s and value of t h e salmon i n B r i t i s h Columbia.  The b u l k of s p r i n g  and coho salmon i s caught by commercial and s p o r t t r o l l  fish-  e r i e s w h i l e the r e s t i s caught by g i l l n e t , purse seine and trap f i s h e r i e s .  Due t o t h e r a p i d growth o f t h e t r o l l i n g f l e e t  i n recent years and i n c r e a s i n g e x p l o i t a t i o n of s p r i n g and coho salmon s t o c k s much concern has been aroused among the commerc i a l and s p o r t fishermen about t h e c o n s e r v a t i o n of both species. The present study formed a p a r t of the g e n e r a l s p r i n g and coho i n v e s t i g a t i o n programme of t h e F i s h e r i e s Research Board of Canada designed to understand more p r e c i s e l y c e r t a i n b i o l o g i c a l aspects e s p e c i a l l y those concerned w i t h f o o d , m a t u r i t y and f e c u n d i t y of these two s p e c i e s d u r i n g t h e i r oceanic e x i s t e n c e .  The growing b e l i e f among salmon t r o l l e r s  on the west coast of Vancouver I s l a n d t h a t commercial  fishing  f o r h e r r i n g i s one of the major causes o f d e c l i n e i n salmon f i s h i n g because of decrease i n i t s food supply a l s o prompted attempts t o a s c e r t a i n more f u l l y the exact relationship.  salmon-herring  Another purpose of the present study was t o  help evaluate the probable e f f i c a c y and f e a s i b i l i t y of  - 2 adopting  new minimum*size r e g u l a t i o n s as a p p l i e d t o s p r i n g  and coho salmon f i s h i n g .  As s p r i n g and coho salmon stocks  are f i s h e d by both the U n i t e d States and Canada, uniform coastwide r e g u l a t i o n s were decided upon by the two c o u n t r i e s at the Conference on c o o r d i n a t i o n o f f i s h i n g r e g u l a t i o n s i n 1957 i n order t h a t such r e g u l a t i o n s may l e a d t o a long term u t i l i z a t i o n of these two v a l u a b l e species of P a c i f i c salmon. The  e f f i c a c y of new minimum s i z e r e g u l a t i o n s depends upon  the extent t o which s m a l l immature f i s h e s can be avoided by commercial t r o l l e r s .  I t was,  t h e r e f o r e , deemed necessary t o  determine p e r t i n e n t f a c t s about m a t u r i t y o f the commercially caught f i s h e s .  REVIEW OF THE LITERATURE Food s t u d i e s of s p r i n g and coho salmon on the P a c i f i c coast of North America have been p a r t i c u l a r l y numerous. Chapman (1936) i n v e s t i g a t e d the food o f s p r i n g and coho salmon o f f the coast o f 'Washington and concluded t h a t p i l c h a r d f o l l o w e d by h e r r i n g and euphausiids  formed the most important  food item f o r s p r i n g salmon, coho salmon on the other hand s u b s i s t e d m a i n l y on euphausiids a l t e r n a t e foods.  He p o i n t e d out t h a t s m a l l f i s h were f e e d i n g  c h i e f l y on euphausiids, euphausiids  - p i l c h a r d and h e r r i n g were  an i n t e r m e d i a t e  group on f i s h and  w h i l e the l a r g e s t f i s h consumed f i s h  only.  S i l l i m a n (1941) attempted t o c o r r e l a t e f l u c t u a t i o n s i n the d i e t of s p r i n g and coho w i t h the t r o l l c a t c h and s t a t e d t h a t  - 3 s p r i n g and coho salmon t a k e n o f f Washington between A p r i l and November, 1938? show two f e e d i n g phases - a f i s h e a t i n g phase and a Crustacea e a t i n g phase.  He showed t h a t s p r i n g and coho  salmon of Neah Bay area and Westport area c o n t a i n e d p i l c h a r d s , h e r r i n g s , anchovies, r o c k f i s h , s m e l t , e u p h a u s i i d s , megalopa l a r v a e , s q u i d s , octopus, amphipods and copepods i n t h e i r stomachs.  S p r i n g and coho salmon of Puget Sound as r e p o r t e d  by K i r k n e s s (1948) were found t o s u b s i s t l a r g e l y on h e r r i n g , candle f i s h and Crustacea.  Coho took a g r e a t e r v a r i e t y of  organisms as food than s p r i n g salmon and t h e e n t i r e d i e t o f both s p e c i e s was composed of p e l a g i c organisms. Food of s p r i n g and coho salmon taken o f f t h e coast of Oregon has been r e p o r t e d by Heg and Van Hyning  (195D*  They p o i n t e d out t h e d i f f e r e n c e s i n food h a b i t s of t h e two s p e c i e s - coho f e e d i n g l a r g e l y on s m a l l p e l a g i c f i s h , crab l a r v a e , euphausiids and s q u i d s , w h i l e s p r i n g feed mainly on f i s h and e u p h a u s i i d s .  Other s i m i l a r s t u d i e s on e i t h e r of t h e  two s p e c i e s have been conducted by G i l b e r t (1913), W i l l i a m s o n (1930), Clemens (1934), Senter (1940), F r a s e r (1946), F o s k e t t  (195D, Shapovalov and T a f t (1954), M i l n e  ( 1 9 5 5 ) , and M a r k e l  (1957). P r i t c h a r d and T e s t e r (1944) s t u d i e d the food of s p r i n g and coho salmon on the B r i t i s h Columbia coast and covered an e x t e n s i v e area from the Queen C h a r l o t t e t s I s l a n d s i n the n o r t h t o the southern t i p of Vancouver I s l a n d .  The  p e r i o d of t h e i r study extended from 1939 t o 1941 and i t was shown t h a t the food of s p r i n g salmon was s i m i l a r i n each of  - 4 the t h r e e y e a r s ; h e r r i n g , p i l c h a r d and sandlance forming the b u l k of the f i s h d i e t and e u p h a u s i i d s , amphipods and crab l a r v a e forming the c r u s t a c e a n d i e t .  Although t h e i r study has  shown c l e a r l y the nature of the food of s p r i n g salmon, n o t h i n g c o u l d be s a i d c o n c l u s i v e l y about the food of coho salmon because of the smallness of the sample s t u d i e d .  A correct  a p p r a i s a l of food and f e e d i n g h a b i t s of a f i s h s p e c i e s depends, besides other t h i n g s , on a random, n o n - s e l e c t i v e sampling method. for  The methods adopted by P r i t c h a r d and T e s t e r (1944)  c o l l e c t i n g samples from d i f f e r e n t areas were h i g h l y  s e l e c t i v e because o n l y those stomachs were t a k e n which c o n t a i n e d any food.  Such sampling, w h i l e good f o r a q u a l i t a t i v e a n a l y s i s  of food Items, p r e j u d i c e s the q u a n t i t a t i v e e s t i m a t i o n t o a considerable extent. as f i l l i n g  The present i n v e s t i g a t i o n may  be regarded  i n some gaps l e f t by e a r l i e r workers and i s l a r g e l y  concerned w i t h the food of t r o l l caught s p r i n g and coho salmon o f f the Southern B r i t i s h Columbia c o a s t . The  s u b j e c t of m a t u r i t y and f e c u n d i t y of s p r i n g and  coho salmon s u f f e r s from an acute poverty of l i t e r a t u r e . Although such s t u d i e s have been conducted by s e v e r a l f e d e r a l and p r o v i n c i a l f i s h e r i e s agencies d i r e c t l y concerned w i t h the c o n s e r v a t i o n of these two s p e c i e s , both i n Canada and the U n i t e d S t a t e s , t h e r e have been r e l a t i v e l y few p u b l i s h e d records which have d e a l t w i t h these aspects i n d e t a i l .  Notable  con-  t r i b u t i o n s i n t h i s f i e l d are from G i l b e r t (1913) and R i c h (1925) who  s t u d i e d the m a t u r i t y of chinook or s p r i n g salmon  i n the ocean.  McGregor ( 1 9 2 2 , 1923)  estimated the number of  - 5eggs i n k i n g salmon and i n d i c a t e d a marked d i f f e r e n c e i n egg counts of Klamath and Sacramento R i v e r r a c e s .  He a l s o  p o i n t e d out a p o s s i b l e s e p a r a t i o n o f t h e r i v e r races o f k i n g salmon i n ocean caught f i s h by means of egg count.  Heave  (1948) p r e s e n t e d t h e average egg count of coho salmon c o l l e c t e d f o r s e v e r a l years a t Cowichan, P o r t John, Namu, and the F r a s e r R i v e r .  S i m i l a r counts have been r e p o r t e d by  Snyder (1921), F o e r s t e r and P r i t c h a r d (1936), Hunter (1948), and ?/ickett (195D«  R e c e n t l y R o u n s e f e l l (1957) has reviewed  the e x i s t i n g l i t e r a t u r e on f e c u n d i t y of P a c i f i c salmon.  MATERIALS AND METHODS Samples f o r the f o o d , m a t u r i t y and f e c u n d i t y study were obtained m a i n l y from those areas around Vancouver  Island  where the commercial f i s h i n g i s most a c t i v e and sampling c o u l d be done w i t h s u f f i c i e n t r e l i a b i l i t y .  Almost a l l the  samples from the east coast and west coast of Vancouver  Island  were o b t a i n e d from commercial and sport t r o l l e r s , w h i l e those from the F r a s e r and the S t r a i t of Juan de Fuca areas were c h i e f l y g i l l - n e t and p u r s e - s e i n e caught f i s h .  Few  samples  were obtained from the t r a p f i s h e r y o p e r a t i n g i n the S t r a i t of Juan de Fuca.  F i s h i n g areas on the east and west coasts of  Vancouver I s l a n d i n c l u d e d B a r k l e y Sound, Clayoquot Sound, Nootka Sound, Kyuquot Sound, Cape Cook, Courtenay, Departure Bay and the s o u t h e r n p o r t i o n of the Gulf of Georgia ( F i g u r e 1.). I n order t o ensure u n i f o r m i t y i n sampling, each c o l l e c t o r was i s s u e d d e f i n i t e i n s t r u c t i o n s (see Appendix A) which were m o d i f i e d from those i s s u e d by P r i t c h a r d and T e s t e r (1944).  The d e t a i l e d procedures used i n a n a l y s i n g f o o d ,  m a t u r i t y and f e c u n d i t y are g i v e n under each s e c t i o n .  Figure 1.  Map of southern B r i t i s h Columbia ooast showing sampling areas referred to i n the text.  - 8 FOOD AND FEEDING HABITS  TREATMENT OF SAMPLES FOR FOOD STUDY The present r e p o r t i s based, on t h e examination of the stomachs o f 659 coho and 551 s p r i n g salmon c o l l e c t e d d u r i n g the p e r i o d May - October, 1957 (Table I ) . Upon r e c e i p t of t h e samples each stomach was examined f o r i t s contents.  Food items were s o r t e d t o t h e lowest catagory t o  which they c o u l d be i d e n t i f i e d .  I n those stomachs where t h e  food items were found i n an advanced s t a t e of d i g e s t i o n , i d e n t i f i c a t i o n was p o s s i b l e o n l y t o t h e g e n e r i c l e v e l by means o f o p e r c l e bones, v e r t e b r a l column, o t o l i t h , appendages etc. The q u a n t i t a t i v e a n a l y s i s was done by t h e v o l u m e t r i c method, i n which t h e volume o f each food i t e m i s expressed as a percentage of the volume of t h e t o t a l stomach contents (Hynes, 1 9 5 0 ) .  Volume of each food item by s p e c i e s was d e t e r -  mined by t h e displacement method i n a measuring  cylinder  graduated t o 0 . 1 cc. and the percentage c a l c u l a t e d .  The  prevalence of each item of food i n the d i e t d u r i n g d i f f e r e n t months was c a l c u l a t e d by t h e occurrence method (Hynes,  1950),  i n which the number of f i s h i n which each food item occurs i s expressed as a percentage of the t o t a l number of f i s h examined.  From I n d i v i d u a l datum monthly averages were c a l c u -  l a t e d and from these the t o t a l percentage composition by volume or occurrence was determined.  - 9 From the q u a l i t a t i v e and q u a n t i t a t i v e aspects of the food study, t r o l l caught samples were d e a l t w i t h s e p a r a t e l y from those caught b y - e i t h e r g i l l net or purse s e i n e . done f o r the f o l l o w i n g (a)  This  was  reasons:  F i s h caught by methods other than t r o l l i n g are not cleaned or dressed soon a f t e r t h e i r c a p t u r e , t h i s b r i n g s about a post-mortem d i g e s t i o n and d e t e r i o r a t i o n of the stomach c o n t e n t s .  Furthermore,  i t i s o f t e n seen t h a t  p u r s e - s e i n e or g i l l - n e t t caught f i s h e s disgorge t h e i r stomach contents i n t h e i r s t r u g g l e to r e l e a s e (b)  themselves.  F i s h i n g i n the S t r a i t of Juan de Fuca and the F r a s e r R i v e r commenced l a t e i n the season and the samples could be procured o n l y a f t e r J u l y ( f o r s p r i n g ) and August ( f o r coho) from these areas. sampling, i t was  I n the absence of a uniform  considered proper to d e a l w i t h such  samples s e p a r a t e l y .  -  10 -  TABLE I . - A Number of samples of coho salmon c o l l e c t e d from v a r i o u s areas I n d i f f e r e n t months of 1957. COHO MONTH  MAY  AREA E.coast V . I . W.coast V . I . Juan de Fuca Fraser River  No. o f F i s h examined 18 — —  2  Mean Fork Length (cm.) 47 52 --  Fork l e n g t h Range (cm.)  -  43 53 51 - 53  —  ——  —•  46  — —  53 58  —  57  41  52 62  40 — 58  —  ——  AUG.  E.coast V . I . W.coast V . I . Juan de Fuca Fraser River  13 85 129  57 64 59  5 45 87 32  49 66 65 68  46  SEPT.  E.coast V . I . W.coast V . I . Juan de Fuca Fraser River  OCT.  Fraser River  81  61  53  92  61  34 — 79  48  JUNE  E.coast V . I . W.coast V . I . Juan de Fuca Fraser River  JULY  E.coast V . I . W,coast V . I . Juan de Fuca Fraser River  SPAWNERS From Adams, H a r r i s o n , Vedder, Robertson, Thatcher, Cowichan and Eagle Rivers. TOTAL  16  55  54  __  —  751  ——  _  -—  59 64  --• 73 —•  52 ~ 66 51 - 74  40  - 71  _ 52 56 - 72 45 - 77 54 — 80  -  80  - 11  -  TABLE I - B. Number of samples of s p r i n g salmon c o l l e c t e d from v a r i o u s areas i n d i f f e r e n t months of 1957. SPRING MONTH  MAY  JUNE  JULY  AUG.  SEPT. OCT.  AREA ;  No. of F i s h examined  — —  64  — —  56 11  16 53  64  38  E.Coast V . I . W.Coast V . I . Juan de Fuca Fraser River  9 35  E. Coast V . I . W.Coast V . I . Juan de Fuca Fraser River E.Coast V . I . W.Coast V . I . Juan de Fuca Fraser River E.Coast V . I . W.Coast V . I . Juan de Fuca Fraser River E.Coast V . I . W.Coast V . I . Juan de Fuca Fraser River Fraser River  SPAWNERS From Adams, H a r r i s o n , Vedder, Robertson, Thatcher, Cowichan and E a g l e Rivers. TOTAL GRAND TOTAL  Mean Fork Fork Length Length (cm.) Range (cm.)  63  71  —  13  __  —  --  54  -  79  90  79 103  -•  96 108  29 57  76  64  66  27 - 95  6 67 36  59  30  71 67  46  5  34 35  26 76  81 78  24 60 46 55  13  81  55  10  83  ^ , ^ -  —  —  66  60  32  — 561  (coho and s p r i n g )  - 1312  23  56  33 48  _  -  79 96 90 90  27  96 106 104  — 99 o n  - 12 COHO SALMON (Oncorhynchus k l s u t c h Walbaum)  COMPOSITION OF FOOD• For t h e sake of convenience i n the a n a l y s i s and i n t e r p r e t a t i o n of t h e d a t a , t h e s t o m a c h c o n t e n t s have been put i n t o t h r e e main c a t a g o r i e s j (1) F i s h , (2) C r u s t a c e a , and (3) M i s c e l l a n e o u s . laneous organisms  The l a s t mentioned  c a t a g o r y of m i s c e l -  c o n s i s t e d of heterogeneous  elements of  o c c a s i o n a l occurrence such as Gastropods, j e l l y - f i s h , p l a n t matter, d e t r i t u s , digested matter, slime. The analysed data of the stomach contents of t r o l l caught coho a r e presented by months I n Tables I I and I I I and summarized i n F i g u r e 6.  The v o l u m e t r i c c o m p o s i t i o n makes i t  evident t h a t f i s h and C r u s t a c e a a r e the most important food items of coho salmon.  The f i s h p o r t i o n of t h e d i e t was l a r g e l y  made up of P a c i f i c h e r r i n g and sandlance, w h i l e Crustacea were represented c h i e f l y by e u p h a u s i i d s , amphipods, and megalopa larvae.  The v a r i o u s food items i d e n t i f i e d from the stomach  contents a r e d i s c u s s e d i n t h e f o l l o w i n g s e c t i o n s : HERRING The P a c i f i c h e r r i n g (Clupea p a l l a s i i Valenciennes) appeared as t h e s i n g l e food i t e m of o u t s t a n d i n g importance t o t r o l l - c a u g h t coho.  They c o n s t i t u t e d 71.6 percent of t h e t o t a l  volume and were present i n 21 percent of t h e specimens examined ( F i g u r e 6.).  Although a l l s i z e s of h e r r i n g were found  i n the stomachs of coho salmon, f i s h measuring  14 t o 23 cm i n  -  13  -  f o r k l e n g t h were found to be most common.  T h i s s i z e range  i n c l u d e s f i s h which are i n t h e i r second, t h i r d and f o u r t h year; t h r e e and f o u r year o l d h e r r i n g make up about 80 t o 90 percent of the commercial c a t c h ( T a y l o r , 1955)• h e r r i n g r a n g i n g from 2.5  Juvenile  t o 9.0 cm i n f o r k l e n g t h were found  most commonly i n the stomachs of specimens c o l l e c t e d from the Departure  Bay area i n the G u l f of Georgia i n May  and June.  SAID LANCE These formed the second most important item i n the fish diet. Girard.  The  s p e c i e s was  i d e n t i f i e d as Ammodytes tobianus  They formed 5»L percent of the t o t a l volume of food  and occurred i n 6 percent of the stomachs.  The  occurrence  of sand lance i n the stomachs of coho salmon i n c e r t a i n a r e a s , p a r t i c u l a r l y along the n o r t h western coast of Vancouver I s l a n d as i n d i c a t e d by P r i t c h a r d and T e s t e r (1944) c o u l d not be established.  They were taken by coho salmon i n almost  every  sampling area on both the east and west coasts of Vancouver Island. OTHER FISHES These i n c l u d e d o c c a s i o n a l specimens of R o c k f i s h (Sebastodes  s p p ) , P a c i f i c Saury ( C o l o l a b i s s a i r a B r e v o o r t ) ,  S t i c k l e b a c k (Gastrosteus a c u l e a t u s L i n n a e u s ) , u n i d e n t i f i a b l e c l u p e i d s and other f i s h remains, forming 3 ' 5  percent of the  t o t a l volume of food items taken and o c c u r r i n g i n 18 percent of the stomachs examined.  - 14 EUPHAUSIIDS E u p h a u s i i d s appeared  as the most Important item i n  the c r u s t a c e a n d i e t of coho o c c u r r i n g i n 13 per cent of the stomachs and making up 8.6 per cent of the t o t a l volume of food consumed.  They were found i n almost a l l areas of t h e  east and west c o a s t s hut were most abundant i n t h e S t r a i t of Georgia showing d e f i n i t e s e a s o n a l trends I n t h e i r occurrence. Two types of euphausiids were d i s t i n g u i s h e d - a r e d or p i n k v a r i e t y and a vuhite v a r i e t y . i d e n t i f i e d as Thysanoessa Euphausia p a c i f l e a .  The r e d v a r i e t y has been  s p i n i f e r a and t h e white v a r i e t y as  The l a t t e r was l a r g e r than t h e r e d and  the average s i z e was about 23 m i l l i m e t e r i n l e n g t h . Most o f the stomachs were found t o c o n t a i n the w h i t e v a r i e t y . AMPHIPODS These formed a s i g n i f i c a n t p o r t i o n of t h e c r u s t a c e a n d i e t d u r i n g e a r l y summer months and l i k e euphausiids were abundant on t h e east coast of Vancouver I s l a n d .  Both H y p e r l i d  and Gammarid amphipods o c c u r r e d i n the d i e t but the l a t t e r were taken most f r e q u e n t l y .  Two d i s t i n c t forms of Gammarid amphi-  pods were encountered, a p u r p l e and an orange pigmented form, the l a t t e r o c c u r r i n g dominantly.  Amphipods appeared i n 15.6  per cent of t h e stomachs forming 5 . 1 per cent of the t o t a l food items taken. MEGALOPA Young crabs and crab megalops c o n s t i t u t e d 5*7 per cent of t h e d i e t of coho salmon and occurred i n 18 per cent of  - 15 -  Pacific  herring  ( Clupea  pallasi).  i  Sand-lance  Figure  2a.  (Ammodytes  Food organisms o f  tobianus).  s p r i n g and coho  salmon.  - 16 -  Euphausiids.  Amphipods.  Crab  megalops.  2b.  Food organisms  ^  of  ^  s p r i n g and  coho  salmon.  - 17 the stomachs.  T h e i r o c c u r r e n c e , l i k e other c r u s t a c e a n forms,  indicated seasonal f l u c t u a t i o n s .  D i f f e r e n t types and s i z e s  of megalopa l a r v a e were found i n the stomach.  Only those  belonging t o Cancer maglster were i d e n t i f i e d . OTHER CRUSTACEA O c c a s i o n a l forms such as i s o p o d s , shrimps, and copepods have been i n c l u d e d i n t h i s c a t a g o r y , none of these items formed a s i g n i f i c a n t p o r t i o n of the d i e t of coho salmon on the east or west coasts o f Vancouver I s l a n d a t any time. They formed 0.1 per cent of t h e t o t a l volume of food consumed and occurred i n 3*3 per cent of t h e stomachs examined. MISCELLANEOUS I n c i d e n t a l food items such as Gastropod  shells,  j e l l y - f i s h , p l a n t matter, d i g e s t e d matter and s l i m e which a r e unimportant from the p o i n t of view of food have been i n t h i s catagory.  included  These items occurred i n 4.7 per cent of the  stomachs forming 0.3 per cent of the t o t a l food volume.  MONTHLY FLUCTUATIONS IN THE FOOD COMPOSITION Monthly f l u c t u a t i o n s i n the amount of v a r i o u s food items consumed are presented i n Table I I . The occurrence of these items d u r i n g d i f f e r e n t months i s g i v e n i n Table I I I . During May and June a l a r g e p o r t i o n of the d i e t of coho salmon was c r u s t a c e a , whereas f i s h assumed major importance as a food i t e m a f t e r June.  T h i s i s i n agreement w i t h  S i l l i m a n (1941) who r e p o r t e d two d i s t i n c t f e e d i n g phases f o r k i n g ( s p r i n g ) and s i l v e r (coho) salmon taken o f f Washington an i n v e r t e b r a t e f e e d i n g phase and a f i s h f e e d i n g phase.  The  a n a l y s i s of h i s data i n d i c a t e d t h a t the f i s h c o l l e c t e d from Westport and Neah Bay areas s u b s i s t e d l a r g e l y on a c r u s t a c e a n d i e t d u r i n g May and June and a f t e r t h a t the salmon depended on f i s h f o r food.  S i l l i m a n suggested that a l t h o u g h these two  phases show c o n s i d e r a b l e o v e r l a p , they are d i s t i n c t enough t o be r e a d i l y r e c o g n i z e d .  S i m i l a r seasonal changes i n the com-  p o s i t i o n of the food have been r e p o r t e d by M e r k e l (1957) i n h i s study of the food h a b i t s of the k i n g salmon i n the v i c i n i t y of San F r a n c i s c o . Of the C r u s t a c e a , amphipods occupied a dominant p l a c e both i n the q u a n t i t y eaten and i n t h e i r prevalence i n the stomachs.  During May and June euphausiids were taken moderately  and megalopa l a r v a e formed a s i g n i f i c a n t item i n June o n l y . A f t e r June the C r u s t a c e a were l a r g e l y r e p l a c e d by f i s h d i e t c h i e f l y composed of P a c i f i c h e r r i n g which reached i t s peak i n August forming 84.4 per cent of the t o t a l volume of food.  In  September f i s h formed 74.7 per cent of the t o t a l food but i n the degree o f p r e v a l e n c e , euphausiids and megalops e q u a l l e d the f i s h .  Sand lance remained r e l a t i v e l y unimportant  or l e s s uniform i n the d i e t f o r the e n t i r e p e r i o d .  and more  - 19 TABLE I I Percentage composition of d i e t c o n s t i t u e n t s of t r o l l - c a u g h t coho salmon from the Vancouver I s l a n d area I n v a r i o u s months of 1957. Diet Constituents  MAY  JUNE  JULY  AUG.  SEPT.  Herring  50.2  33.7  69.3  84.4  69.I  Sandlance  —  1.5  2.6  7.5  4.6  Other F i s h e s  8.5  4.6  9.6  1.1  1.0  Euphausiids  13.6  21.0  0.5  3.9  22.3  Amphipods  23.9  21.0  6.2  1.6  --  Megalops  3.8  18.0  11.3  1.0  2.5  Other c r u s t a c e a  __  0.1  0.1  0.1  0.2  Miscellaneous  --  0.1  0.4  0.4  0.3  Number of Stomachs  20  Total Vol.(cc)  68.2  64  98  98  50  615.8  1038.2  2252.2  782.6  - 20 -  TABLE I I I Percentage occurrence of d i e t c o n s t i t u e n t s i n the stomachs of t r o l l - c a u g h t coho -salmon from Vancouver I s l a n d area I n v a r i o u s months of 1957• F i g u r e s i n b r a c k e t s i n d i c a t e number of stomachs examined. Diet Constituents  MAY  Herring  19-5  Sand lance  Other F i s h e s  Euphausiids  (8)  mm mm  17.1 (7) 9.8  (4)  JUNE  JULY  AUG.  SEPT  6.4  (10)  22.5 (34)  34.8 (39)  30.8 (16)  3.8 (6)  4.6 (7)  12.5  7.7 (4)  18.6 (29)  28.5  9.8 (11)  13.4  4.0 (6)  17.9  28.8 (15:  7.1 (8)  _»  17.3  (21)  (43)  (14)  (20)  7.7  (4)  Amphipods  39.0 (16)  23.7 (37)  12.6  Megalops  12.2 (5)  24.4  21.2 (32)  8.1  (38)  2.4  3.9 (6)  3.3 (5)  3.6  1.9  5-8  3-3 (5)  6.2 (7)  5.8 (3)  Other C r u s t a c e a  Miscellaneous  (1)  (9)  (19)  (9)  (4)  (9)  (1)  -  21  -  , FOOD TYPE AREAS M i l n e (1950) s t a t e d t h a t coho salmon taken I n the S t r a i t of Georgia are s m a l l e r than those caught o f f the west coast of Vancouver  Island.  These s m a l l s i z e d coho are popu-  l a r l y known as 'Bluebacks' and are f i s h e d h e a v i l y from June to September w i t h peak catches i n J u l y and August.  On the  d i f f e r e n c e i n s i z e of i n s i d e and o u t s i d e coho M i l n e commented: Past d a t a from t a g g i n g , f i n - c l i p p i n g and stream i n s p e c t i o n do not p o i n t to the e x i s t e n c e of slow growing s t o c k s i n any p a r t i c u l a r stream but r a t h e r i n d i c a t e t h a t coho salmon from each stream may go to both i n s i d e and o u t s i d e waters. Whether these d i f f e r e n c e s i n s i z e are due to d i f f e r e n t food cond i t i o n s or to stocks w i t h d i f f e r e n t growth r a t e s i s open to c o n j e c t u r e . I f d i f f e r e n t f e e d i n g c o n d i t i o n s are the major f a c t o r , then any d i f f e r e n c e i n the ocean temperatures or n u t r i e n t s a l t s between the two areas may be s i g n i f i c a n t . A c c o r d i n g l y , s p e c i a l emphasis was p l a c e d on the c o l l e c t i o n of simultaneous samples from the S t r a i t of Georgia and the west coast of Vancouver  Island.  Samples obtained from the S t r a i t  of Georgia showed t h a t Crustacea remained c o n s i s t e n t l y dominant throughout the p e r i o d except d u r i n g May and J u l y .  I n those  months a l a r g e number of j u v e n i l e h e r r i n g i n c r e a s e d the percentage of f i s h consumed t o 72 per cent of the t o t a l food volume ( F i g u r e 3).  Amphipods formed the most important  c r u s t a c e a n item of the d i e t of i n s i d e coho, w h i l e euphausiids and crab megalops were next i n order of importance.  The  s i t u a t i o n o f f the west c o a s t , however, was s t r i k i n g l y d i f f e r e n t ( F i g u r e 3).  F i s h remained dominant throughout the p e r i o d i n  the d i e t of coho salmon and very few Crustacea were taken i n the o u t s i d e w a t e r s .  WEST  COAST  SPRING  COHO  IOO-.  SO-4  FISH  604  CRUSTACEA  •  40 ID  204  EAST  COAST COHO  f\j IV)  MAY  J U N J U L AUG  Figure 3.  SEPT  MAY  JUN  J U L AUG  Monthly v a r i a t i o n s i n the volume of f i s h and  Crustacea  eaten by coho and spring salmon on the east and west coasts of Vancouver Island.  SEPT  - 23  -  For the p e r i o d as a whole, the e a s t c o a s t coho ate c h i e f l y Crustacea and west coast coho s u b s i s t e d c h i e f l y on fish.  The f e e d i n g trends showed by coho salmon i n each of  these two r e g i o n s are s u f f i c i e n t l y d i s t i n c t i v e and more or l e s s c o n s i s t e n t to warrant the establishment of two d i s t i n c t food type areas-.  On t h i s b a s i s i t i s p o s s i b l e t h a t the  d i f f e r e n c e s i n growth of 'Blueback' and west coast coho are r e l a t e d t o the d i f f e r e n c e s i n food. The above h y p o t h e s i s i s f u r t h e r supported by the data c o l l e c t e d d u r i n g 1950, 1954, and 1956 as a part of the g e n e r a l s p r i n g and coho salmon i n v e s t i g a t i o n of the F i s h e r i e s Research Board of Canada.  These a l s o show a predominance of  C r u s t a c e a i n t h e d i e t of coho on the east coast of Vancouver I s l a n d as opposed to the west coast where the c h i e f item of food was f i s h ( F i g u r e 4 ) .  S i m i l a r r e s u l t s were r e p o r t e d by  Chapman (1936) i n h i s study of the food h a b i t s of s i l v e r (coho) salmon o f f the coast of Washington.  He found t h a t at Neah Bay  the salmon s u b s i s t e d c h i e f l y on C r u s t a c e a , w h i l e o f f the coast at Westport f i s h formed the dominant food item.  L i k e the east  and west c o a s t s of Vancouver I s l a n d , Neah Bay and "Westport represent two d i s t i n c t oceanographic areas.  IOO  WEST COAST  SO 60 40 UJ  FISH  2  20  o  0  => _l  >  UJ  < i—  2UJ  (J  Q: UJ  C R U S T A C E A  1950  1957  IOO  EAST COAST  8o 6C 4 0 2 0  O 1954  1956  F i g u r e 4.  1957  Percentage  composition of f i s h and crustacea eaten  by coho salmon on the east and west coasts of Vancouver I s l a n d In d i f f e r e n t years.  - 25 FEEDING INTENSITY To show the f l u c t u a t i o n s i n f e e d i n g a c t i v i t y of coho salmon, average volume of food per stomach was each month from May  to September.  calculated for  The f i n a l f i g u r e s were  c o r r e c t e d f o r l e n g t h and were c a l c u l a t e d as the volume of food per 10 cm of f i s h l e n g t h .  Monthly averages f o r the east  and  west coasts which represent two d i f f e r e n t f e e d i n g areas were c a l c u l a t e d s e p a r a t e l y and the r e s u l t s are shown i n F i g u r e C o n s i d e r a b l e d i f f e r e n c e s i n the f e e d i n g of east and west coast coho salmon are apparent.  5*  intensity F i s h caught  i n the G u l f of Georgia showed an i n c r e a s e d f e e d i n g d u r i n g June which took a downward t r e n d t h e r e a f t e r . West coast coho on the other hand, e x h i b i t e d a p r o g r e s s i v e i n c r e a s e i n the f e e d i n g a c t i v i t y from May  to August a f t e r which t h e r e was  i n the amount of food eaten.  a sudden drop  Feeding i n t e n s i t y as r e v e a l e d  the average volume of food per 10 cm. of f i s h l e n g t h was  by  also  c a l c u l a t e d f o r samples obtained from the S t r a i t of Juan de Fuca and the F r a s e r R i v e r i n the l a t e season. a f t e r August was  A decline i n feeding  apparent.  From the data a v a i l a b l e i t i s c l e a r t h a t coho salmon on the west coast feed most a c t i v e l y i n August.  This i n c r e a s e d  f e e d i n g i s probably a s s o c i a t e d w i t h the a c c e l e r a t e d m a t u r i t y d u r i n g the same p e r i o d which w i l l be d i s c u s s e d i n the second s e c t i o n of t h i s paper. About 95 per cent of t r o l l caught coho both from I n s i d e and o u t s i d e waters belong t o age group 3> ( P r i t c h a r d , 1940) 0  - 26 -  Figure 5. Monthly variations i n the feeding intensity of spring and coho salmon i n different areas. Solid lines : mean volume of food per stomach. Dotted lines : mean volume of food per 10 cm. of f i s h length.  - 27 and are on t h e i r spawning m i g r a t i o n .  Reference to F i g u r e 5  w i l l show t h a t t h e r e i s a marked decrease i n the r a t e of f e e d i n g as the f i s h move from the east and west c o a s t s of Vancouver I s l a n d towards i n l a n d f r e s h water streams.  The S t r a i t of Juan  de Fuca samples show f u r t h e r decrease i n f e e d i n g and f i n a l l y when i n October the f i s h enter the F r a s e r R i v e r as spawners t h e r e i s a complete c e s s a t i o n of f e e d i n g .  The c o n t e n t i o n t h a t  the west coast coho show s l a c k f e e d i n g a f t e r August i s f u r t h e r supported by t h e i n c r e a s i n g number of empty stomachs i n the samples.  I t appears t h a t t h i s d e c l i n e i n f e e d i n g a c t i v i t y i s  more a f u n c t i o n of some i n h e r e n t p h y s i o l o g i c a l a c t i v i t y of t h e f i s h at the commencement of m a t u r i t y than t h a t of n o n a v a i l a b i l i t y of s p e c i f i c food Items.  SPRING SALMON (Oncorhynchus tshawytscha  Walbaum)  COMPOSITION OF FOOD The a n a l y s i s and i n t e r p r e t a t i o n o f the data f o r s p r i n g salmon food and f e e d i n g h a b i t s f o l l o w s very c l o s e l y t h e l i n e s adopted f o r t h e food study of coho salmon.  The food of  s p r i n g salmon seems e s s e n t i a l l y s i m i l a r i n i t s general nature to t h a t of coho, except f o r a somewhat r e s t r i c t e d nature of d i e t of the s p r i n g as opposed t o a v a r i e d d i e t of coho. The  analyses of the stomach contents during v a r i o u s  months are presented i n Tables IV and V. and occurrence  Percentage  composition  of d i f f e r e n t food items f o r the e n t i r e p e r i o d  May - September are shown i n F i g u r e 6 .  - 28 TABLE IV Percentage composition of d i e t c o n s t i t u e n t s of t r o l l - c a u g h t s p r i n g salmon from Vancouver I s l a n d area i n v a r i o u s months of 1957.  Diet Constituents  MAY  JUKE  JULY  AUG.  SEPT.  Herring  21.9  46.1  81.8  79.1  98.3  Sand Lance  57.0  18.2  12.2  6.4  1.2  6.0  1.6  3.2  1.0  18.3  25.0  4.1  10.7  0.2  Megalops  0.8  4.0  0.1  --  0.1  Other c r u s t a c e a  0.1  0.7  0.1  0.2  0.2  Miscellaneous  0.7  --  0.1  0.4  0.2  Number of Stomachs  44  69  86  73  37  680.4  1064.9  1939.4  2155.5  1180.6  Other F i s h e s Euphausiids Amphipods  Total V o l (cc)  - 29 TABLE V. Percentage occurrence of d i e t c o n s t i t u e n t s i n the stomach of t r o l l caught s p r i n g salmon from Vancouver I s l a n d area i n v a r i o u s months of'1957. F i g u r e s i n b r a c k e t s i n d i c a t e number of stomachs examined. Diet Constituents  JUNE  JULY  AUG.  SEPT,  7.9 (4)  26.6 (25)  38.2 (34)  46.1 (30)  62.1 (18)  Sand lance  23-5 (12)  13.8 (13)  19.1 (17)  20.0 (13)  Other F i s h e s  11.8 (6)  22.3 (21)  15.7 (14)  9.2 (6)  10.3 (3)  Euphausiids  33.3 (17)  12.8 (12)  11.2 (10)  6.2 (4)  3.5 (1)  5.9  16.0  3.4  --  3-5  (3)  (15)  (3)  Other C r u s t a c e a  7.8 (4)  7«5 (7)  4.5 (4)  Miscellaneous  9.8  1.0 (1)  7.9 (7)  Herring  MAY  Amphipods Megalops  (5)  (1) 6.2 (4) 12.3 (8)  10.3 (3) 10.3 (3)  -  30  -  S p r i n g salmon tend to s u b s i s t l a r g e l y on f i s h w i t h s p e c i a l emphasis on h e r r i n g and sand l a n c e . (Clupea p a l l a s i i ) was  Pacific herring  the most important s i n g l e item of food  c o n s t i t u t i n g 69.2 per cent of the t o t a l volume of food consumed.  Percentage  occurrence of h e r r i n g i n the stomach of  s p r i n g salmon as shown i n F i g u r e 6 i s much g r e a t e r than t h a t i n coho salmon.  The s i z e of h e r r i n g eaten by the s p r i n g salmon  ranged from 4.5  t o 23.7  most commonly taken was  cm.  i n f o r k l e n g t h but the s i z e range  17 to 23 cm.  No t r a c e of p i l c h a r d  found i n any of the stomachs examined, e a r l i e r  was  investigators  have r e p o r t e d p i l c h a r d as an important item of d i e t of s p r i n g salmon (Chapman, 1936, P r i t c h a r d and T e s t e r , 1944). The next most important food i t e m a f t e r P a c i f i c h e r r i n g was  sand lance (Ammodytes tobianus) which formed 17 per  cent of the t o t a l food volume and occurred i n 16.8 per cent of the stomachs.  Sand l a n c e r a n g i n g from 6 to 21 cm. i n t o t a l  l e n g t h were found i n the s p r i n g stomachs. f i s h were found i n i n d i v i d u a l stomachs.  U s u a l l y equal s i z e d There was no  indica-  t i o n of the abundance of sand lance i n any of the sampling as evident from the stomach c o n t e n t s .  areas  P r i t c h a r d and T e s t e r  (1944) r e p o r t e d an abundance of sand lance along the n o r t h western coast of Vancouver I s l a n d . Other m i s c e l l a n e o u s f i s h such as P a c i f i c ( C o l o l a b i s s a i r a ) , R o c k f i s h (Sebastodes  saury  spp), Gray cod (Gadus  macrocephalus T i l e s i u s ) , Sand f i s h (Trichodon t r i c h o d o n T i l e s i u s ) , u n i d e n t i f i e d c l u p e i d s and other f i s h remains formed 3.3 per cent of the t o t a l food eaten and occurred i n 15.2  per  - 31  -  cent of the stomachs. Crustacean d i e t was  composed of e u p h a u s i i d s , young  crabs and crab megalops and m i s c e l l a n e o u s forms.  Euphausiids  were the dominant item i n c r u s t a c e a n d i e t , w h i l e there was complete  a  absence of amphipods i n the d i e t of the s p r i n g  throughout the p e r i o d May  - September.  Euphausiids represented  by Euphausia p a c i f i c a , and Thysanoessa s p i n i f e r a c o n s t i t u t e d 9 per cent of the t o t a l food volume and were found i n 13.4 cent of the stomachs.  Young crabs and megalops of Cancer  magister formed 0 . 9 per cent by volume of the t o t a l food occurred i n 6.7  per  per cent of the stomachs.  c h i e f l y i s o p o d s , occurred i n 6.7  and  Other c r u s t a c e a ,  per cent of the stomachs and  formed 0 . 3 per cent of the t o t a l volume. The catagory of m i s c e l l a n e o u s items represented by gastropod s h e l l s , d i g e s t e d matter and slime c o n t r i b u t e d only 0 . 3 per cent t o the t o t a l volume of food and occurred i n 7*3 per cent stomachs.  A g e n e r a l l a c k of food items l i k e s q u i d s ,  j e l l y - f i s h and other o f f shore f i s h e s was n o t i c e d . items have been r e p o r t e d by e a r l i e r  MONTHLY FLUCTUATIONS M P  These  workers.  FEEDING INTENSITY  Tables IY and V g i v e monthly f i g u r e s which show seasonal trends i n the d i e t composition of s p r i n g salmon.  Con-  s i d e r a b l e q u a n t i t i e s of f i s h , p a r t i c u l a r l y P a c i f i c h e r r i n g were eaten throughout the p e r i o d of i n v e s t i g a t i o n .  September marked  the peak p e r i o d both i n t h e i r prevalence i n the d i e t and the  -  amount eaten. o n l y i n May  32  -  Sand lance dominated the d i e t of s p r i n g salmon  and e s p e c i a l l y i n those samples which were obtained  from B a r k l e y Sound. -A gradual r e d u c t i o n i n the amount of sand lance eaten was  n o t i c e d a f t e r May  and h e r r i n g assumed c o n s i d e r -  able importance, reaching i t s peak i n September when 9 8 . 3 cent of the d i e t was  per  composed of h e r r i n g .  Euphausiids  appeared to be the most important  i n the crustacean p o r t i o n of the d i e t . were taken d u r i n g May  Considerable  item  amounts  and June but a f t e r t h a t a r e d u c t i o n both  i n percentage volume and percentage prevalence was  noticed.  Crab megalops and other C r u s t a c e a d i d not c o n t r i b u t e much to the d i e t as a whole and no a p p r e c i a b l e seasonal trends i n t h e i r occurrence  and composition were n o t i c e a b l e .  In c o n t r a s t  to the coho, the s p r i n g salmon from the east and west coasts of Vancouver I s l a n d showed no t r a c e of amphipods i n t h e i r stomachs i n any month.  T h i s f a c t probably  d i f f e r e n t f e e d i n g behaviour The  of the two  suggests a  species.  f e e d i n g i n t e n s i t y of 538 specimens as c a l c u l a t e d  on the b a s i s of average volume of food per stomach and 10 cm.  of f i s h l e n g t h i s presented  i n F i g u r e 5.  s i z e range of the specimens examined from May  per  As the mean  t o September  was  s m a l l , the curves f o r average volume of food per stomach f o r the whole p e r i o d d i d not show any a p p r e c i a b l e change even a f t e r a d j u s t i n g f o r l e n g t h of the f i s h .  From these curves i t i s  evident t h a t l a r g e q u a n t i t i e s of food were taken o f f the west coast of Vancouver I s l a n d as compared to the east coast. S p r i n g salmon i n the Gulf of Georgia show a s l i g h t downward  - 33 t r e n d i n f e e d i n g a c t i v i t y from May  to J u l y .  A f t e r t h a t the  f e e d i n g Is i n t e n s e and i s , perhaps, due to the abundance of young h e r r i n g i n the 'gulf.  August marks the p e r i o d when the  f e e d i n g i n t e n s i t y reaches i t s peak both f o r the east and west coast s p r i n g .  I n September a c o n s i d e r a b l e drop i s seen on  both the c o a s t s .  Samples obtained from the mouth of the F r a s e r  i n J u l y , August and September a l s o show a d e c l i n i n g f e e d i n g t r e n d a f t e r J u l y which becomes more pronounced i n August and September.  From the evidence a v a i l a b l e i t appears t h a t August  marks the p e r i o d of maximum f e e d i n g o f f the southern coast of B r i t i s h Columbia and a s i g n i f i c a n t d e c l i n e i n f e e d i n g i n t e n s i t y follows thereafter.  FOOD TYPE AREAS The  stomach analyses of the samples c o l l e c t e d from  the east and west coasts of Vancouver I s l a n d , S t r a i t of Juan de Fuca and the F r a s e r give no s u f f i c i e n t l y d i s t i n c t i v e I n d i c a t i o n s t o warrant the establishment  of food type areas.  As  d i s c u s s e d e a r l i e r i n the case of coho salmon, the east and west coasts of Vancouver I s l a n d represent two d i s t i n c t areas which d i f f e r both q u a l i t a t i v e l y and q u a n t i t a t i v e l y w i t h regard to food.  In the case of s p r i n g salmon, however, only q u a n t i t a t i v e  d i f f e r e n c e s i n the amount of food a v a i l a b l e on the two  coasts  are evident ( F i g u r e 5) and there i s h a r d l y anything t o i n d i c a t e t h a t the food of s p r i n g salmon on the two coasts d i f f e r s qualitatively also.  - 34 Samples obtained from the F r a s e r R i v e r showed a predominance o f sand lance i n t h e i r d i e t w i t h p r a c t i c a l l y no case of h e r r i n g being found i n the stomachs.  Crustacea  other hand formed a very s m a l l p o r t i o n of the d i e t .  on the  Juan de  Fuca s p r i n g s were found f e e d i n g l a r g e l y on h e r r i n g and c r u s t a c e a (mainly e u p h a u s i i d s ) w i t h no t r a c e of sand l a n c e . I n view of a r a t h e r u n s p e c i f i c d i e t of s p r i n g salmon i n a p a r t i c u l a r a r e a , i t i s hard t o e s t a b l i s h food type areas as could be done w i t h coho salmon o f the east and west c o a s t s . There are however d e f i n i t e evidences  that l i k e coho, t h e s p r i n g  salmon i n the G u l f o f Georgia are s m a l l e r I n average s i z e than those on the west coast and i t seems reasonable  t o assume t h a t  t h i s s i z e d i f f e r e n c e might be r e l a t e d t o the amount of food a v a i l a b l e i n the two areas.  COMPARISON OF  THE FOOD OF SPRING  AND COHO SALMON  Because both the commercial and sport  troll  f i s h e r i e s catch s p r i n g and coho salmon almost e x c l u s i v e l y , samples obtained from the S t r a i t of Georgia, B a r k l e y Sound, Clayoquot Sound, Nootka Sound, Esperanza I n l e t , Kyuquot Sound and Quatsino Sound areas i n c l u d e d both coho and s p r i n g salmon which were c o l l e c t e d more or l e s s i n the same p e r i o d i n these areas.  T h i s f a c t has not only helped i n the a p p r a i s a l of t h e  food and f e e d i n g h a b i t s of the two species i n a p a r t i c u l a r area i n i t s proper p e r s p e c t i v e but a l s o can be u t i l i z e d to assess how much these two species d i f f e r from each other i n t h e i r  -  35  -  food and f e e d i n g h a b i t s . As mentioned e a r l i e r , the b a s i c d i f f e r e n c e between the d i e t of s p r i n g and coho salmon l i e s i n the f a c t t h a t w h i l e coho tend t o depend on a l a r g e v a r i e t y of food items s p r i n g salmon shows q u i t e c o n s e r v a t i v e  taste.  been r e p o r t e d by P r i t c h a r d and Tester Heg  and Van Hyning ( 1 9 5 D .  S i m i l a r trends have (1944), K i r k n e s s  (1948),  Both the s p r i n g and coho salmon  depend l a r g e l y on f i s h as food.  Nevertheless,  there  are  d e f i n i t e i n d i c a t i o n s t h a t C r u s t a c e a forms an important part of coho's d i e t and t h i s i s p a r t i c u l a r l y t r u e of the east  coast  'Blueback' whose main food i s C r u s t a c e a . W h i l e enough has been brought to l i g h t concerning d i f f e r e n c e s i n food and f e e d i n g h a b i t s of the coho and  spring  salmon, the reasons f o r these d i f f e r e n c e s are s t i l l obscure. Whether these d i f f e r e n c e s are due to s e l e c t i v i t y on the part of f i s h or due  t o a v a i l a b i l i t y of s p e c i f i c items of food c a n  be confirmed by f u r t h e r d e t a i l e d work.  only  Based on the d a t a i n  hand i t seems reasonable to a t t r i b u t e these d i f f e r e n c e s to the depth which the two species i n h a b i t .  A s s o c i a t e d w i t h the coho  t a g g i n g programme of the F i s h e r i e s Research Board of Canada, p r e l i m i n a r y i n v e s t i g a t i o n s on the depth of occurrence of s p r i n g and coho salmon i n r e l a t i o n t o temperature and d i t i o n s were conducted at B a r k l e y Sound i n 1953 I t was  s a l i n i t y con(Milne, 1955).  found t h a t the s p r i n g migrate at greater depths and  seldom caught at the s u r f a c e .  are  Most of them are taken by  troll  l e s s than 10 m i l e s from the shore and around 15 fathoms.  Coho  salmon on the other hand, are caught around 5 fathoms and  less  than 20 m i l e s from the shore thereby showing a more p e l a g i c existence.  PERCENT  F i g u r e 6.  OF  TOTAL  VOLUME  Food of s p r i n g and coho salmon on southern B r i t i s h Columbia coast. S o l i d bars i n d i o a t e per cent volume, p l a i n bars i n d i c a t e frequency of occurrence.  - 37 -  SALMON - HERRING RELATIONSHIP The d a t a presented i n t h i s paper as w e l l as t h e v a r i o u s accounts of food and f e e d i n g h a b i t s of s p r i n g and coho salmon p u b l i s h e d by e a r l i e r workers make i t c l e a r that P a c i f i c h e r r i n g forms a very important item of t h e i r d i e t . T h i s i s p a r t i c u l a r l y t r u e of s p r i n g salmon.  I n view of t h i s  f a c t i t i s p e r t i n e n t t o examine c r i t i c a l l y t h e salmon-herring r e l a t i o n s h i p s i n c e i t i s of g r e a t e s t concern t o salmon t r o l l f i s h e r m e n who have expressed f e a r that a d e c l i n e i n h e r r i n g stocks due t o e x c e s s i v e  e x p l o i t a t i o n might l e a d t o a d e c l i n e  i n o v e r a l l salmon c a t c h on B r i t i s h Columbia coast. I t was p o s s i b l e I n most cases t o r e c o r d the exact l e n g t h of t h e h e r r i n g which had not been d i g e s t e d .  I n cases  where a p a r t i a l d i g e s t i o n bad t a k e n p l a c e , f i s h lengths were estimated  from the v e r t e b r a l columns which were u s u a l l y  recovered i n t a c t .  The a n a l y s i s of the data r e v e a l s that 14 t o  23 cm. f o r k l e n g t h c o n s t i t u t e d the most v u l n e r a b l e s i z e range. T h i s s i z e range i n c l u d e s h e r r i n g few of which are i n t h e i r 2nd year and a m a j o r i t y i n t h e i r 3 r d and 4 t h y e a r s .  Three and four  year o l d h e r r i n g form a s i g n i f i c a n t p o r t i o n of the commercial catches. T a y l o r and M i l n e (1954) i n t h e i r memorandum r e g a r d i n g the p o s s i b l e r e l a t i o n s h i p between the abundance of h e r r i n g and the abundance of s p r i n g salmon o f f the west coast of Vancouver I s l a n d mentioned that i n J u l y 1953) the s i z e of h e r r i n g consumed o f f B a r k l e y Sound ranged from 15 t o 19 cm. i n standard  length.  - 38 They concluded t h a t t h e abundance of s p r i n g salmon i s u n l i k e l y t o be a f f e c t e d by t h e d e c l i n e i n t h e supply of h e r r i n g because the h e r r i n g used as food belong t o those age groups which have not been r e c r u i t e d t o the w i n t e r f i s h e r y .  Present i n v e s t i g a t i o n  r e v e a l s t h a t t h e s p r i n g and coho salmon took mostly l a r g e s i z e d h e r r i n g which p r o b a b l y belong t o age groups I I I and IV and t o a l e s s e r extent t o age group I I . B r i t i s h Columbia t h e r e c r u i t m e n t  I n southern waters of  t o the h e r r i n g f i s h e r y occurs  l a r g e l y a t age I I I and t o a l e s s e r extent at age IV.  The  dominant age group i n the commercial catches i s formed by three year o l d f i s h ( T a y l o r , 1955)•  I t i s t h e r e f o r e evident that the  s p r i n g and coho salmon on t h e southern B r i t i s h Columbia coast depend l a r g e l y on t h a t s i z e of h e r r i n g which forms a dominant p o r t i o n of t h e commercial  catches.  On t h e b a s i s of the above f a c t , i t i s n a t u r a l t o suspect t h a t a decrease i n t h e supply of h e r r i n g might lead t o d r a s t i c • e f f e c t s on t h e salmon p o p u l a t i o n abundance but a c r i t i c a l i n s i g h t of the observations  made so f a r on the food  and f e e d i n g h a b i t s of s p r i n g and coho salmon makes the p o s s i b i l i t y of the above c o n t e n t i o n  somewhat untenable.  Coho salmon,  as shown by s e v e r a l s t u d i e s made so f a r , i s n o t s p e c i f i c i n i t s d i e t and shows a more or l e s s omnivorous behaviour.  Therefore,  from the p o i n t of view of salmon-herring r e l a t i o n s h i p coho does not seem t o p l a y a very s i g n i f i c a n t r o l e .  Spring salmon on the  other hand has been found t o s u b s i s t l a r g e l y on h e r r i n g . Williamson  (1926) s t u d i e d t h e food of s p r i n g salmon on t h e west  coast of Vancouver I s l a n d and found t h a t sand lance formed the  - 39 p r i n c i p a l f o o d , whereas, p i l c h a r d , h e r r i n g , euphausiids and megalops made up t h e r e s t of t h e d i e t .  Chapman (1936) found  t h a t p i l c h a r d f o l l o w e d by h e r r i n g were the most important s i n g l e item i n t h e d i e t of s p r i n g salmon caught o f f the coast of "Washington.  M e r k e l (1957) i n h i s study of the food h a b i t s  of k i n g salmon i n the v i c i n i t y of San F r a n c i s c o r e p o r t e d that Northern anchovy ( E n g r a u l i s mordax) and R o c k f i s h  (Sebastodes  spp) formed t h e dominant item o f d i e t i n 1955* From these s t u d i e s i t i s evident t h a t the food of salmon changes w i t h l o c a l i t y and time (season).  I t seems  t h e r e f o r e , t h a t t h e d i e t of s p r i n g and coho salmon i s more a f u n c t i o n of t h e a v a i l a b i l i t y of s p e c i f i c food items than t h a t of p r e f e r e n c e or s e l e c t i o n on the p a r t of the f i s h .  These f i s h  would feed on any acceptable food organism which i s a v a i l a b l e to the f i s h at t h e time and p l a c e of t h e i r occurrence. Judging by the p l a s t i c i t y of d i e t i n s p r i n g and coho salmon, i t may be concluded t h a t although h e r r i n g forms an important item of t h e d i e t at p r e s e n t , i t does not n e c e s s a r i l y c o n s t i t u t e the o n l y food on which the s p r i n g and coho salmon are dependent.  The h e r r i n g f i s h e r y f l u c t u a t e s and there i s at  present no i n d i c a t i o n o f i t s d e c l i n e due t o o v e r f i s h i n g .  Salmon  t r o l l catches on the other hand a l s o have not shown d e c l i n i n g t r e n d s f o r t h e l a s t few years on B r i t i s h Columbia coast.  It is  t h e r e f o r e hard t o comprehend t h e p o s s i b l e r e l a t i o n s h i p between salmon and h e r r i n g abundance.  I f f o r a moment we suppose t h a t  h e r r i n g i s the o n l y food on which the salmon i s dependent f o r i t s growth, then the r e d u c t i o n i n the supply of t h i s s p e c i f i c  - 40 food w i l l show up i n p a r t i n the gross poundage of the commercial c a t c h and r e t a r d e d growth r a t e of the f i s h i n general.  Furthermore, we have no c o n c l u s i v e evidence that  t h e r e have been changes i n the a v a i l a b i l i t y of salmon i n the absence of abundant stocks of h e r r i n g .  - 41 DISCUSSION I n food s t u d i e s of a f i s h s p e c i e s , the importance of a p a r t i c u l a r food item i s u s u a l l y judged by the amount consumed and a l s o by the'number of stomachs c o n t a i n i n g i t . I f l a r g e number of stomachs c o n t a i n t h a t item, i t i s assumed t h a t e i t h e r there i s an abundance of t h a t p a r t i c u l a r item or a s e l e c t i o n on the part of f i s h .  The data presented i n t h i s  paper as w e l l as the f i n d i n g s of e a r l i e r i n v e s t i g a t o r s l e a d t o the c o n c l u s i o n t h a t a l t h o u g h s p r i n g and coho salmon are e s s e n t i a l l y p i s c i v o r o u s l a t e i n l i f e , they do e x h i b i t considerable p l a s t i c i t y i n t h e i r f e e d i n g h a b i t s and t h e i r p i s c i v o r o u s behaviour i s not confined to one or two species of f i s h . There are i n d i c a t i o n s t h a t the food of s p r i n g and coho salmon changes w i t h the area and w i t h the time i n the same area.  These f l u c t u a t i o n s seem to be more a f u n c t i o n of  changes I n a v a i l a b i l i t y than a p o s s i b l e s e l e c t i o n on the p a r t of the f i s h .  I t i s u s u a l l y assumed t h a t the extent t o which  an organism i s eaten by a f i s h i s contingent  upon i t s  a v a i l a b i l i t y at the time and place where the predator This does not i n any way preclude e x e r c i s e d by the f i s h .  exists.  the p o s s i b i l i t y of s e l e c t i o n  S e l e c t i o n of a food item i s dependent  d i r e c t l y on i t s s^ize, shape, s m e l l and t a s t e and i n d i r e c t l y on the behaviour of the predator.  The food h a b i t s of the east  coast coho may be i n t e r p r e t e d t o some extent i n t h i s l i g h t . As a l r e a d y shown, coho salmon on the east coast of Vancouver I s l a n d s u b s i s t e d c h i e f l y on c r u s t a c e a , w h i l e s p r i n g salmon  - 42 i n the same area were found f e e d i n g on s m a l l f i s h .  It i s  t h e r e f o r e v e r y probable t h a t due t o l i m i t s imposed by the s i z e of coho on the past c o a s t , the f i s h p r e f e r r e d C r u s t a c e a ^ and not l a r g e f i s h .  With the e x c e p t i o n of t h i s case, i t can  be concluded t h a t the changes i n food are r e l a t e d l a r g e l y to changes i n a v a i l a b i l i t y and the a v a i l a b i l i t y of a food item i n i t s t u r n i s dependent on i t s r e l a t i v e d e n s i t y at a p a r t i c u l a r time and p l a c e .  Evidence In support of the above comes  from the s t u d i e s conducted  on the food of coho salmon i n  1956  as a p a r t of the I n t e r n a t i o n a l North P a c i f i c F i s h e r i e s Commission's programme of i n v e s t i g a t i o n s .  P r e l i m i n a r y obser-  v a t i o n s have r e v e a l e d t h a t squids form an important item of the d i e t of coho salmon i n the h i g h seas f o l l o w e d by euphausiids A l l f i s h samples having squids i n t h e i r stomachs were taken f a r out i n the sea and those w i t h euphausiids were caught c l o s e t o the c o a s t . I t has a l r e a d y been shown t h a t the east and west coasts of Vancouver I s l a n d r e p r e s e n t two f e e d i n g areas which are probably d i f f e r e n t so f a r as the amount of food a v a i l a b l e i s concerned.  The west coast i s c h a r a c t e r i s e d by uniform low  temperature, h i g h s a l i n i t y and r i c h n e s s of the n u t r i e n t s a l t s and p l e n t y of food.  The east coast on the other hand presents  q u i t e converse c o n d i t i o n s , v i z . h i g h summer temperature, s a l i n i t y and l e s s food.  low  The d i f f e r e n c e s i n the p r o d u c t i v i t y  # Chapman (1936) and M i l n e (1955)' have r e p o r t e d t h a t l a r g e f i s h tend to depend on a f i s h d i e t mostly, whereas s m a l l f i s h show a p r e f e r e n c e f o r C r u s t a c e a .  - 43 on the two coasts seem l a r g e l y to be i n f l u e n c e d by oceanographic c o n d i t i o n s .  Northwest winds i n summer on the west  coast of Vancouver I s l a n d r e s u l t i n u p w e l l i n g n u t r i e n t r i c h water to the s u r f a c e ?;hich c o u l d be expected to cause higher productivity.  On the east coast on the other hand, r e l a t i v e l y  h i g h f r e s h water i n f l o w d u r i n g summer months r e s u l t s In marked v e r t i c a l s t a b i l i t y i n the water which i n h i b i t s  replenishment  of n u t r i e n t s i n upper l a y e r s and thus reduce the general productivity.  These d i f f e r e n c e s are r e f l e c t e d In part i n the  growth of s p r i n g and coho salmon on the two c o a s t s .  S p r i n g and  coho salmon o f f the east coast of Vancouver I s l a n d are u s u a l l y s m a l l e r than t h e i r c o u n t e r p a r t s on the west coast (Table I ) . Jensen (1948) a l s o r e p o r t e d s i z e d i f f e r e n c e s of s i l v e r  and  C h i n o o k salmon remaining i n Puget Sound and o f f the coast. suggested  He  t h a t t h i s may be due to l a c k of feed In the sound.  S i m i l a r i n d i c a t i o n s are seen i n Chapman's (193&) account  of  the food h a b i t s of coho o f f the coast of Washington. M i l n e (1955) suggested  t h a t e f f e c t i v e n e s s of c e r t a i n  types of l u r e s used i n t r o l l i n g i s probably c l o s e l y a s s o c i a t e d w i t h the s i z e and type of food e a t e n by the f i s h at the time of capture.  Present i n v e s t i g a t i o n has shown q u i t e c o n c l u s i v e l y  t h a t both s p r i n g and coho salmon on the e a s t and west coasts show a g r e a t e r consumption of c r u s t a c e a i n May any other month.  and June than i n  Based on M i l n e ' s observations i t would be  reasonable to i n f e r t h a t d u r i n g c r u s t a c e a e a t i n g phase, t r o l l i n g l u r e s which are s m a l l and resemble moving crustacea. would be more e f f e c t i v e , whereas d u r i n g the f i s h e a t i n g phase the use  _ 44 of l a r g e plugs and spoons might be advantageous. (1941) has a l s o i n d i c a t e d  the p o s s i b i l i t y  Silliman  of a c o r r e l a t i o n  between the salmon t r o l l c a t c h and the amount of f i s h eaten.  - 45  -  MATURITY The m a t u r i t y study i s based on d e t a i l e d examination of o v a r i e s and t e s t e s from 751  coho and 561 s p r i n g salmon.  A f t e r the r e c e i p t of the samples, gonads were cleaned of the attached t i s s u e , weighed, and t h e i r volume determined displacement method.  by  The m a t u r a t i o n of the female s p r i n g and  coho salmon was s t u d i e d by the measurement of ova diameters. The use of ova diameter measurements to demonstrate  the  developmental changes t h a t take p l a c e i n the o v a r i e s p r i o r to spawning was  i n t r o d u c e d by Thompson (1915) I n h i s study  of the P a c i f i c h a l i b u t .  Other i n v e s t i g a t o r s have a l s o used  t h i s method i n m a t u r i t y s t u d i e s of s e v e r a l other marine species ( R i c h , 1925;  C l a r k , 1925,  1929,  1934; S c h a e f e r , 1936;  Olsen  and Merriman, 1946). As the m a t e r i a l f o r the present study was  formalin-  p r e s e r v e d , the ova i n many cases were somewhat d i s t o r t e d from t h e i r s p h e r i c a l shape.  To a v o i d any p o s s i b l e s e l e c t i o n or b i a s  i n measuring the ova and t o compensate f o r the d i s t o r t i o n due to p r e s e r v a t i o n , a procedure s i m i l a r t o t h a t adopted Vladykov (1956) and R i c h (1925) was employed.  The  by  diameters  of 20 ova from d i f f e r e n t r e g i o n s of the o v a r i e s , along whichever axes they l a y s i d e by s i d e i n a row over a V-shaped measuring trough graduated i n m i l l i m e t r e s were taken.  Pre-  l i m i n a r y o b s e r v a t i o n s r e v e a l e d t h a t the development of ova I n d i f f e r e n t r e g i o n s of the ovary i s uniform as evident by remarkable u n i f o r m i t y i n the s i z e of the ova throughout e n t i r e l e n g t h of the ovary.  the  - 46 STRUCTURE OF THE OVARY The o v a r i e s of the s p r i n g and coho salmon are l o c a t e d j u s t above the a l i m e n t a r y canal i n the abdominal cavity.  The two o v a r i e s are u s u a l l y asymmetrical i n l e n g t h  as w e l l as g i r t h .  The r i g h t ovary i s u s u a l l y somewhat l a r g e r  and w i t h more eggs than the l e f t one.  A critical  examination  r e v e a l s t h a t , a l t h o u g h t h e r e i s a remarkable u n i f o r m i t y i n the s i z e of t h e ova throughout the l e n g t h of the ovary, there are ova.  two types of s m a l l eggs which stand out among the maturing The f i r s t type i s d i s t i n g u i s h e d by a few very s m a l l ,  sometimes m i c r o s c o p i c deep orange-coloured bodies present i n between t h e maturing eggs i n the i n t e r - o v a r i a n t i s s u e .  These  have been n o t i c e d i n almost a l l maturing o v a r i e s i n v a r y i n g numbers e s p e c i a l l y near the t e r m i n a l end of the ovary where they occur i n c l u s t e r s .  The second type are s m a l l maturing  ova which have undergone a t r e s i a and have stopped f u r t h e r development and occur as w h i t i s h , i r r e g u l a r l y s c a t t e r e d  eggs.  These seem t o be more common i n the o v a r i e s which have reached an advanced  s t a t e of m a t u r i t y .  Vladykov (1956) n o t i c e d s i m i l a r eggs i n w i l d speckled t r o u t o v a r i e s and c a l l e d the s m a l l e r bodies " R e c r u i t ment s t o c k " and w h i t i s h eggs ' A t r e t i c eggs'.  Ho attempt has  been made i n the present study t o i n v e s t i g a t e or e l u c i d a t e the probable r o l e of these s m a l l eggs.  Regarding a t r e t i c eggs  Vladykov mentioned that the number -of such eggs v a r i e s c o n s i d e r a b l y w i t h the season, l o c a l i t y and food.  An attempt was  - 47 made t o i n v e s t i g a t e the p o s s i b l e v a r i a t i o n s i n the number of such eggs a c c o r d i n g t o areas and the type of food eaten by the f i s h but the r e s u l t s d i d not show any evident r e l a t i o n s h i p . STAGES OF MATURITY The gonads of s p r i n g and coho salmon have been c l a s s i f i e d i n t o three stages of m a t u r i t y on the b a s i s of t h e i r r e l a t i v e degree of development.  I n females, the degree  of development i s r e a d i l y determined as the ova diameter measurements a f f o r d easy and p r a c t i c a l c r i t e r i a of the s t a t e of m a t u r i t y .  I n the case of males, however, no q u a n t i t a t i v e  measure which would p r o v i d e reasonably a c c u r a t e estimates o f r e l a t i v e m a t u r i t y could be found.  Although a r e l a t i o n e x i s t s  between t h e s i z e of the f i s h and the weight of the t e s t e s , v a r i a t i o n s i n the s i z e or weight of the t e s t e s among the f i s h examined were so great t h a t no p r e c i s e d e l i n e a t i o n of t h e i r growth change c o u l d be o b t a i n e d .  For t h i s reason the degree  of m a t u r i t y was determined by c a l c u l a t i n g the " M a t u r i t y index ( K ) " f o r each f i s h .  K i s an e x p r e s s i o n of the r a t i o between  the weight of t h e gonad and the weight of t h e whole f i s h , and i s expressed by the formula  K  W §  =  W f where W and W  f  r e p r e s e n t s the weight of the gonad i n grams  i s the weight of t h e dressed f i s h i n pounds. The use of K as an index of the s t a t e of m a t u r i t y  - 48 i s based on the premise t h a t as the m a t u r i t y advances, the value of K i n c r e a s e s p r o p o r t i o n a t e l y .  Such a trend can be  seen i n m a t u r i t y index - egg s i z e r e l a t i o n s h i p ( F i g u r e 7 and Table V I ) . The  t h r e e d i f f e r e n t stages of m a t u r i t y show con-  s i d e r a b l e g r a d a t i o n i n the degree of development of the gonads and are as f o l l o w s : STAGE I.  Immature.  Testes e l o n g a t e , s l e n d e r , occupying the whole l e n g t h of the body c a v i t y i n the form of t h i n bands. (Upper l i m i t of K f o r males 1.0) Ovaries having a g r a n u l a r appearance, eggs s m a l l i n s i z e not more than 2.0 mm. diameter.  II.  Maturing.  Testes moderately enlarged, u s u a l l y creamy-white i n c o l o u r . (K f o r males over 1.0) Ovaries enlarged w i t h uniform-sized eggs over 2.0 mm. diameter.  Ill,  Mature.  Testes g r e a t l y enlarged, u s u a l l y pale white i n c o l o u r , f i l l i n g most of the body c a v i t y . Ovaries f u l l y enlarged w i t h l a r g e ova f i l l i n g the e n t i r e abdominal c a v i t y . (This stage i s d i s t i n g u i s h e d from Stage I I by the f a c t t h a t the f i s h are e i t h e r i n f r e s h water zone or very c l o s e to i t - t h i s would mean t h a t a l l the f i s h i n Stage I I I w i l l spawn the same year.)  Because of the a r b i t r a r y nature of-the above c l a s s i f i c a t i o n i t i s hard to determine w i t h c e r t a i n t y when a f i s h passes  -  49  -  TABLE V I . R e l a t i o n s h i p between female m a t u r i t y index (K) and egg diameter  COHO  SPRING  M a t u r i t y index (K) Egg Diam. group (mm)  Mean  Range  M a t u r i t y index (K) Mean  Ran ge  2.6  -  3.1  -  3-5  14.2  10.3-19.7  3.6  -  4.0  21.0  12.4 -30.6  13.3  4.1  -  4.5  28.8  13-7-37.0  18.5  11.0 -25.4  5.0  36.3  28.2  -48.7  25.7  16.6  5.5  47.5  35.1  -66.1  31.4  21.5 -42.0  6.0  58.2  42.4  -79.6  40.6  32.9 - 4 4 . 7  6.5  62.8  46.8 -76.7  46.0  30.5  7.0  —  —  56.7  34.5 -74.6  7.5  --  —  60.1  47.9  1.1 1.6 2.1  5.6  -  6.1  -  4.6 5.1  6.6 7.1  -  1.5  3.9  3.2  -  5.2  2.0  1.1 -  3.8  2.0  4.6  3.6  -  7.0  2.9  2.0  -  4.2  2.5  6.7  4.7  -11.0  4.6  3.6  -  6.0  3.0  11.2  6.7  -18.3  7.6  3.9  -10.3  9.4  7.0 -11.3 8.8  -20.6  -32.8  -4.6.2  -74.5  - 50  o  SPRING COHO  o •  o 1  2  1  1  3  4 EGG  Figure 7.  DIAMETER  -i  1  5  6  r  7  M M .  Relationship between egg diameter and maturity index of female spring and ooho salmon.  - 51  -  from one stage of maourity t o t h e o t h e r .  However, the  methods employed t o assess t h e m a t u r a t i o n trends i n males and females appear t o he adequate f o r a c l o s e approximation. A l l males w i t h t e s t e s immature enough t o be considered as of stage I never exceeded 1.0 as t h e i r m a t u r i t y index and f o r t h i s reason 1.0 was taken as the upper l i m i t of K f o r immature males.  S i m i l a r l y by o b s e r v i n g monthly egg-size p r o g r e s s i o n  of female s p r i n g s i t vims found t h a t f i s h w i t h egg diameters over 2 . 0 mm. a r e i n a process of m a t u r a t i o n and w i l l spawn the same year.  probably  On t h i s b a s i s 2 . 0 mm. was taken as t h e  upper egg diameter l i m i t f o r immature females. These c r i t e r i a do not apply so r i g i d l y to coho salmon because a l l of commercially caught f i s h a r e i n stages I I and III.  Table V I I shows the percentages of males and females  i n d i f f e r e n t stages of m a t u r i t y i n t r o l l catches according to months.  I n May, l a r g e numbers of coho salmon were immature but  as the season advanced t h e percentage of mature f i s h e s g r a d u a l l y i n c r e a s e d and d u r i n g August almost 100 per cent o f the f i s h were mature.  The s i t u a t i o n i n t h e case of s p r i n g  salmon was d i f f e r e n t , immature f i s h e s were taken by the t r o l l f i s h e r y throughout the p e r i o d from May t o September - w i t h the e x c e p t i o n of J u l y when 53 per cent of maturing  females  and 67 per cent of maturing males were taken. MATURATION The growth of r i p e n i n g ova was s t u d i e d by means of egg-size p r o g r e s s i o n and frequency of d i s t r i b u t i o n of ova of  -  52  -  TABLE V I I . Percentages of gonads i n d i f f e r e n t stages of m a t u r i t y i n t r o l l - c a u g h t f i s h a c c o r d i n g t o months. F i g u r e s i n b r a c k e t s r e f e r t o number of f i s h observed.  Male  Female Stage Stage II I MAY  JUNE  JULY  AUGUST  SEPT.  S P R I N G  C 0 H 0  MONTHS  100 (13)  Stage Stage II I  —  57  (4)  43 (3)  15  85  (23)  26 (8)  18 (7)  82 (33)  —  3  —  (2)  97 (60)  5 (2)  95 (35)  —  74  (4)  Female Stage Stage II I 64 (14)  36  (8)  Male Stage Stage I II 100 (16) 24 (22) (7)  57 (20)  43 (15)  76  47  (57)  (17)  53  33 67 (14) (28)  100 (34)  60  40 (14)  70  30  (21)  100  83 (15)  17 (3)  69 (9)  31 (4)  (23)  100  (11)  (19)  (14) (6)  - 53 349 coho and 220  s p r i n g salmon by months.  from the east and west coasts of Vancouver  As the samples I s l a n d were  c o l l e c t e d I n more or l e s s the same time, the samples of these two areas have been combined and t h e i r egg-size prog r e s s i o n i s shown i n F i g u r e s 8 and 9.  From the frequency  polygons two t h i n g s are apparent: 1.  A p r o g r e s s i v e i n c r e a s e i n ova diameter w i t h the advancing season.  2.  D i f f e r e n t i a l growth of ova i n the f i s h which w i l l spawn the same year and those which w i l l not. In order to compare the r e l a t i v e growth of  maturing ova, ovary samples of spawners were obtained from the F r a s e r , Adams, H a r r i s o n , Vedder, Eagle and Thatcher R i v e r s which had ova i n t h e i r u l t i m a t e spawning s i z e .  By  t r a c i n g the development of the modes and f o l l o w i n g the growth of maturing ova, i t was p o s s i b l e to d i s t i n g u i s h between immature and maturing females.  Frequency d i s t r i b u t i o n of ova  diameters of s p r i n g salmon c o l l e c t e d from the east and west coasts of Vancouver  I s l a n d , the S t r a i t of Juan de Fuca and the  f r e s h water streams r e v e a l s t h a t the s t o c k a v a i l a b l e to the f i s h e r y s p l i t s i n t o immature and maturing groups at an average egg diameter of 2.1 - 2.5  mm.  (Figure 8).  S t u d i e s conducted  by R i c h (1925) and M i l n e (1954) on the m a t u r i t y of s p r i n g salmon a l s o p o i n t out s i m i l a r s e p a r a t i o n . Based on observat i o n s made on 220 s p r i n g salmon taken o f f B a r k l e y Sound and from the F r a s e r R i v e r g i l l - n e t f i s h e r y , M i l n e showed t h a t a  - 54 -  OCTOBER  III.  •I  (13)  FRESH WATER OCEAN  SEPTEMBER  AUGUST  I.  JULY  (39)  (59)  (S2)  I-  Illi  D  O  1  1  L  O  O  L  1 1  D  1  o  i  11  D  o  m  o  11  m  o  t  1  11  ^ H < 0 < H < O r H < O r - t - £ > r H < O r H t O  EGG Figure 8.  DIAMETER  f  (  i  o  11  JUNE  (35)  M AY  (2 2)  m  i  - H < 0 < - t  M M .  Monthly egg size progression i n 220 spring salmon taken i n 1957. Figures i n brackets refer to number of f i s h examined each month.  t£>  o  mo  m  o m  o 10  o ^  o  •h  qq  oj  co  -<tiTj<  m i o  to  o  *  •  •  •  • • to  •  i«  i  i  *H  vO  r H <D  rH  (D H  i-*  f-(  W W  tO  tO  EGG Figure 9.  i  i t to H  if)  DIAMETER  <o  i i  •  10  •  o  i i  to <H  (O  H  i n <D  <D  c-  MM.  Monthly egg 3ize progression i n 349 coho salmon taken i n 1957. Figures i n brackets r e f e r to number of f i s h examined each month.  - 56 c l e a r s e p a r a t i o n between immature and maturing females can be made above an average egg diameter of 2.7  mm.  and below  2.0  mm. I n c o n t r a s t to s p r i n g salmon, t h e r e i s no c l e a r d i s t i n c t i o n between immature and maturing females i n the case of coho.  T h i s i s due to the f a c t that coho are r e c r u i t e d t o  the f i s h e r y when they are t h r e e years o l d and i n the present case we are d e a l i n g w i t h o n l y one age group which i s i n i t s maturing phase.  F i g u r e 9 i n d i c a t e s that a l l coho salmon w i t h  the e x c e p t i o n of a few ' g r i l s e ' caught i n September by the sport f i s h e r y , w i l l probably spawn the same year.  Another  f e a t u r e n o t i c e a b l e from the frequency polygons p a r t i c u l a r l y i n the case of coho salmon I s the a c c e l e r a t i o n of growth of eggs d u r i n g J u l y and August. I n order to determine the average s i z e at which a s e p a r a t i o n between immature and maturing female s p r i n g and coho salmon c o u l d be based, the data on stages of m a t u r i t y and f o r k l e n g t h s were analysed and t a b u l a t e d (Tables V I I I and I X ) . From these i t i s seen that a l l female s p r i n g  salmon  up t o a f o r k l e n g t h of 60 cm. are Immature and a l l those over 80 cm. are maturing.  I n other words f i s h pass from stage I  to stage I I of m a t u r i t y somewhere between the f o r k lengths 60 - 80 cm.  S i m i l a r l y a l l female coho salmon on both the east  and west c o a s t s under 50 cm. were immature and over 60 were maturing.  cm.  By p l o t t i n g the percentages of maturing and  immature f i s h a g a i n s t s i z e (Figure 10),  i t was found that at  a f o r k l e n g t h of 74 cm. the r a t i o between immature and  -  57  -  TABLE V I I I . Number of immature and maturing and percentage of maturing female s p r i n g s i n each 5 cm s i z e group on the east and west coasts of Vancouver I s l a n d . Fork length (cm)  No. of fish  ' No. of immature  No. of maturing  % maturing  —  40 -  45  3  3  __  46 -  50  3  3  __  -  55  2  2  56 -  60  10  61  -  65  66 71 76  10  — —  — —  32  30  -2  -6  70  28  23  5  18  -  75  22  14  8  37  -  80  34  6  28  82  81 - 85  35  —  35  100  86 -  90  34  —  34  100  91 -  95  15  15  100  7  100  1  100  51  96 -100  7  -105  1  101  — —  -  58 -  TABLE IX Number of immature and maturing and percentage of maturing female cohos i n each 5 cm s i z e group on the east and west coasts of Vancouver I s l a n d . Fork l e n g t h (cm)  No. of fish  ' No. of immature  No. of maturing  % maturing  4  4  46 - 50  15  15  51 - 55  27  13  14  52  56-60  13  5  8  61  7  loo  East Coast 40-45  61 - 65  7  66-70  1  —  1  loo  50-55  10  6  4  40  56 - 60  18  4  14  78  61 - 65  51  —  51  100  66 - 70  32  —  32  100  71 - 75  10  —  10  100  West Coast  FORK  F i g u r e 10.  L E N G T H  CM.  P e r c e n t a g e o f i m m a t u r e and m a t u r i n g female spring and coho s a l m o n f o r d i f f e r e n t at  maturity.  sizes  and the s i z e  -  60  -  maturing female s p r i n g salmon i s 1:1.  Fork l e n g t h of 52  cm. r e p r e s e n t e d such a p o i n t f o r coho salmon. From the 'above account i t i s obvious t h a t t h e r e i s c o n s i d e r a b l e v a r i a b i l i t y w i t h i n narrow l i m i t s between the  l e n g t h s at which m a t u r i t y commences i n d i f f e r e n t  individuals.  For a l l p r a c t i c a l purposes, however, i t would  be reasonable t o set 74 cm. and 52 cm. as the s i z e s e p a r a t i n g immature and maturing s p r i n g and coho salmon respectively.  M i l n e (1954) i n h i s study of the m a t u r i t y  of s p r i n g salmon r e p o r t e d t h a t maturing and immature females are  d i v i d e d at f o r k l e n g t h of approximately 75 cm. (or a  t o t a l l e n g t h of 30 i n c h e s ) . The s i z e at which f i s h can be separated i n t o maturing and immature groups was d i f f i c u l t to i n t e r p r e t i n the  case of male s p r i n g and coho salmon.  I t was found t h a t  even very l a r g e f i s h sometimes had t e s t e s i n immature condition.  Furthermore, the presence of jacks which are  s m a l l p r e c o c i o u s males I n the commercial catches made such a separation d i f f i c u l t .  - 61 FECUNDITY The annual r e c r u i t m e n t t o a f i s h e r y besides other f a c t o r s depends upon the number of f i s h r e a c h i n g the spawning grounds a f t e r escaping the f i s h i n g m o r t a l i t y .  I n determining  the magnitude of the r e c r u i t m e n t to the stock, number of females r e a c h i n g t h e spawning area and t h e i r r e p r o d u c t i v e p o t e n t i a l or ' f e c u n d i t y ' i s of c o n s i d e r a b l e  importance.  F e c u n d i t y , as a p p l i e d t o f i s h e s i s the r e s u l t i n g  balance  between the f a c t o r s r e s p o n s i b l e f o r i n c r e a s e i n egg number and the f a c t o r s which work a g a i n s t t h i s Increase during t h e e n t i r e m a t u r a t i o n c y c l e of t h e o v a r i e s .  One of the major  f a c t o r s d e t e r m i n i n g egg number i s f o i l i c u l a r r e g r e s s i o n i n the o v a r i e s .  The number of o v a r i a n f o l l i c l e s before the  commencement of maturation i s much more than what remains behind a f t e r m a t u r a t i o n .  Therefore, number of eggs d e s t i n e d  to be spawned i s determined  by the number of o v a r i a n f o l l i c l e s  which undergo r e g r e s s i o n ( S c o t t , 1956).  Such regressed  f o l l i c l e s are seen i n the maturing ovary i n the form of s m a l l y o l k l e s s bodies attached t o the i n t e r - o v a r i a n t i s s u e . Yladykov  (1956) r e f e r r e d these bodies as r e c r u i t m e n t stock  which does not c o n t r i b u t e to the t o t a l f e c u n d i t y . T h i s leads us t o d i s t i n g u i s h between three d i f f e r e n t types of f e c u n d i t y . (a)  I n i t i a l Fecundity  r e f e r s t o number of eggs belonging  to maturing, a t r e t i c and recruitment s t o c k s ; the t o t a l number of eggs i n t h i s case i s always higher due t o nonregression of o v a r i a n f o l l i c l e s .  - 62 (°)  Absolute F e c u n d i t y  r e f e r s to the t o t a l number of  mature eggs which are d e s t i n e d to be spawned. (c)  R e l a t i v e Fecundity - —  i n order t o c o r r e c t f o r f i s h  l e n g t h , f e c u n d i t y i s expressed as the number of eggs per cm. of f i s h l e n g t h .  DETERMINATION OF EGG NUMBERS I n determining the number of ova per ovary, a few maturing eggs were separated out of the ovary and dropped one by one i n a measuring t i l l e x a c t l y 1.0  c y l i n d e r graduated t o 0.1 c c .  c c . of f r e s h water was d i s p l a c e d . The  number of eggs d i s p l a c i n g 1 c c . of water was counted and the t o t a l number of eggs present i n the o v a r i e s was estimated by m u l t i p l y i n g the counted number by the t o t a l volume of both the o v a r i e s .  T h i s method i s e s s e n t i a l l y s i m i l a r t o t h a t  adopted by Vladykov  (1956) i n h i s study of the f e c u n d i t y of  w i l d speckled t r o u t except f o r the f a c t t h a t he counted the number of eggs present i n one gram of the ovary weight i n s t e a d of using a v o l u m e t r i c method.  I t was found that as the egg  s i z e i n c r e a s e d , there was a corresponding decrease i n the number of eggs d i s p l a c i n g 1 c c . of water.  This relationship  i s represented i n F i g u r e 11 by a curve which i s based on averages of egg number per c c . displacement of water f o r d i f f e r e n t diameters.  T h i s curve was found t o be very u s e f u l  and p r a c t i c a l i n e s t i m a t i n g the t o t a l number of eggs i n the o v a r i e s when o n l y egg diameter I n m i l l i m e t r e and the t o t a l volume of the o v a r i e s i n cubic centimetres are known.  700  60CH O > >-  500-  O  AOOA  cc. < > O u. u o cc UJ Q.  d Z o  300-  ON 200-J  UJ  IOCH  t 4  EGG  DIAMETER  MM.  Figure 11. Relationship between the diameters of eggs of spring and cftho salmon and their number per cubic centimetre of ovary volume. Based on egg counts of 603 spring and coho salmon.  - 64 To check the accuracy of t h i s method a c t u a l counts were made of ova from 11 f i s h which i n c l u d e d l a r g e and s m a l l females. These counts were then compared w i t h those obtained by the above method.  The c a l c u l a t e d t o t a l s d i f f e r e d from the a c t u a l  counts by amounts v a r y i n g from 1.5 per cent t o 1 0 . 1 per cent. The average percentage e r r o r was 5»3 (Table . X ) .  Although  the egg diameter - egg number r e l a t i o n s h i p curve gives s u f f i c i e n t l y accurate e s t i m a t i o n of the t o t a l number of eggs present i n the o v a r i e s , i t i s , however, l i m i t e d i n i t s a p p l i c a t i o n when we are d e a l i n g w i t h ova l a r g e r than 5 m i l l i m e t r e . T h i s i s due t o the f a c t t h a t beyond 5 mm. l e v e l the curve tends t o become asymptotic.  To o b t a i n counts of ova over  5 mm. i n diameter, i t would be necessary t o t r a n s f o r m t h i s curve i n t o a l o g a r i t h m i c one. •CORRELATION BETWEEN EGG NUMBER AND SIZE OF FISH S e v e r a l i n v e s t i g a t o r s have shown that t h e number of maturing eggs has a p o s i t i v e c o r r e l a t i o n w i t h the s i z e of f i s h . Such a c o r r e l a t i o n can be seen i n the case of s p r i n g and coho salmon ( F i g u r e 1 2 ) .  The values obtained from 25 sets of  o b s e r v a t i o n s i n the case of coho and 15 sets of o b s e r v a t i o n s f o r s p r i n g were u t i l i z e d and by the method of l e a s t squares, the e q u a t i o n which best expresses the r e l a t i o n between l e n g t h and f e c u n d i t y was c a l c u l a t e d .  The r e l a t i o n s h i p seems t o be  of the type Y = a +. bX and the r e g r e s s i o n equations f o r s p r i n g and coho salmon were found t o be:  - 65 TABLE X. Comparison between a c t u a l and c a l c u l a t e d egg counts of 11 s p r i n g and coho females.  Egg diam. (mm)  Actual count  1.5  3582  3332  n r: i 0 J  1.7  2804  2714  3.3  2.3  3885  3705  4.7  2.8  2970  2790  5.7  3.0  2601  2499  4.1  3.6  3074  3180  3.3  3.9  4237  4175  1.5  4.1  5250 '  5020  4.6  4.8  3412  3625  5.9  4.9  5219  4740  10.1  5.0  5136  5564  7.7  Mean  3834  3758  5.3  Calculated count  fo  difference  - 66 Y -  184.42X - 7203  and Y  =  101.9X - 3057 r e s p e c t i v e l y ,  where Y i s the egg number and X represents f o r k l e n g t h of the f i s h .  The number of eggs i n coho salmon v a r i e d from 2064  to 5670, w i t h an average of 3635 eggs.  Spring salmon had a  greater number of eggs v a r y i n g from 3025 to 10,121 w i t h an average of 5604 eggs. F o e r s t e r and P r i t c h a r d (1936) estimated the average 3000.  egg count of coho c o l l e c t e d i n 1934 to be approximately  To compare w i t h other species of P a c i f i c salmon they reduced the egg counts to a common denominator, i . e . the number of eggs per i n c h of f i s h or per pound of f i s h and concluded  that  even w i t h i n a species there i s a s i g n i f i c a n t v a r i a t i o n i n egg number a c c o r d i n g t o s i z e and t h a t egg number - f i s h s i z e r e l a t i o n s h i p may be d i f f e r e n t from year t o year.  Packer (1932)  i n h i s study of brook t r o u t S a l v e l i n u s f o n t i n a l i s s t a t e d t h a t the r e l a t i o n s h i p between number of eggs and l e n g t h of f i s h i s c u r v i l i n e a r i n s t e a d of l i n e a r .  The l a t t e r i s obtained  only  when the logarithms of egg numbers and logarithms of lengths are u t i l i z e d .  S c o t t (1956) advocated t h i s l o g a r i t h m i c t r a n s -  f o r m a t i o n of the data to c a n c e l out the e f f e c t of c o r r e l a t e d mean and v a r i a n c e and thus change the r e l a t i o n s h i p i n t o a l i n e a r form which i s e a s i l y handled by the method of l e a s t squares.  I n the present study, however, the l o g a r i t h m i c t r a n s -  f o r m a t i o n of the data does not seem to serve a u s e f u l purpose because the values on which F i g u r e 12 i s based are obtained only from maturing f i s h r e p r e s e n t i n g a narrow range of f i s h lengths.  - 68 Now the q u e s t i o n worth c o n s i d e r i n g i s how a r e g r e s s i o n equation can be u t i l i z e d i n p r e d i c t i n g egg number f o r d i f f e r e n t f i s h lengths?  S e v e r a l i n v e s t i g a t o r s have pointed out that t h e  egg count f o r the f i s h of same lengths may vary  significantly  according t o r a c e s , l o c a l i t y , year and so on and as such, t h e slope of t h e l i n e r e p r e s e n t i n g egg number - f i s h l e n g t h r e l a t i o n ship may s h i f t i t s p o s i t i o n a c c o r d i n g l y .  Furthermore, the  e f f e c t o f egg s i z e on egg number i n a p a r t i c u l a r species as shown i n the next s e c t i o n may be a s i g n i f i c a n t f a c t o r i n s h i f t i n g the s l o p e .  I n order t o appraise the u t i l i t y of a  r e g r e s s i o n equation f o r p r e d i c t i n g egg number f o r v a r i o u s f i s h lengths i t would be necessary t o take i n t o account the f a c t o r s determining  egg number and f i s h l e n g t h .  Reference has a l r e a d y  been made t o o v a r i a n f o l l i c u l a r r e g r e s s i o n as a f a c t o r d e t e r mining the egg number.  R o u n s e f e l l ( 1 9 5 7 ) using F o e r s t e r and  P r i t c h a r d ' s ( 1 9 4 1 ) data f o r p i n k salmon t r i e d t o show by means of s t a t i s t i c a l treatments t h a t sea temperature i s the p r i n c i p a l f a c t o r i n c o n t r o l l i n g average l e n g t h of the f i s h and t h a t the annual d i f f e r e n c e s i n mean egg count i n pink salmon are a f u n c t i o n o f sea temperature.  S c o t t ( 1 9 5 6 ) I n h i s study of the  e f f e c t of food on the f e c u n d i t y of Kamloops t r o u t provided experimental maturation  evidence that s t a r v a t i o n may cause suppression of  i n l a t e r years of growth and thus a f f e c t f e c u n d i t y . Age of the f i s h may a l s o be an important  affecting fecundity.  factor  R a i t t ( 1 9 3 3 ) reported that f e c u n d i t y i n  haddock depended mainly on the s i z e of the f i s h but the older f i s h of the same l e n g t h had l a r g e r number of eggs.  Recently  - 69 Nagasaki (1958) i n h i s study of the f e c u n d i t y of P a c i f i c h e r r i n g (Clupea p a l l a s l ) i n B r i t i s h Columbia c o a s t a l waters r e p o r t e d t h a t f e c u n d i t y depended mainly on body l e n g t h and t o a l e s s e r extent on age, independently of i t s e f f e c t on body length.  He a l s o found t h a t f e c u n d i t y of h e r r i n g of same body  l e n g t h and the same age was s i g n i f i c a n t l y higher i n n o r t h e r n B r i t i s h Columbia than i n southern.  I n short i t i s reasonable  to assume t h a t egg number i n a f i s h i s an ever f l u c t u a t i n g e n t i t y and the degree of f l u c t u a t i o n depends upon the s e v e r i t y of the s t r e s s imposed by environmental f a c t o r s w i t h i n c e r t a i n limits.  I t i s t h e r e f o r e u n l i k e l y that egg number - f i s h s i z e  r e l a t i o n s h i p e q u a t i o n would be the same f o r d i f f e r e n t y e a r s , l o c a l i t i e s , races, etc.  - 70 REDUCTION IN ABSOLUTE FECUNDITY AS A FUNCTION OF EGG SIZE As the number of eggs per cm. of f i s h l e n g t h i s , besides other f a c t o r s , dependent on the s i z e of the eggs ( F i g u r e 1 3 ) , r e l a t i v e f e c u n d i t y was u t i l i z e d f o r a c o r r e c t a p p r a i s a l of the e f f e c t of egg s i z e on the absolute  fecundity.  In p l o t t i n g the number of eggs per cm. of f i s h l e n g t h against egg diameters,  a negative r e l a t i o n s h i p was found to e x i s t  between the two v a r i a b l e s , i n other words as the egg diameter i n c r e a s e d t h e r e was a decrease i n r e l a t i v e f e c u n d i t y .  Reference  t o s i m i l a r r e d u c t i o n i n the number of eggs as a f u n c t i o n of egg s i z e has been made by Vladykov (1956) and Scott (1956) i n other  species. I n order t o evaluate the mutual r e l a t i o n s h i p between  f e c u n d i t y , f i s h l e n g t h and egg s i z e more thoroughly,  analysis  of m u l t i p l e r e g r e s s i o n (Snedecor, 1957) was done by t a k i n g 25 sets of o b s e r v a t i o n s which covered the e n t i r e range of f i s h lengths and egg diameters i n s p r i n g salmon.  The r e l a t i o n s h i p  between the three v a r i a t e s i s expressed as Y where Y -  =  a • b  y l > 2  X-l * b  y 2 # 1  X  2  number of eggs (absolute f e c u n d i t y ) , Xj_ =  l e n g t h and X  2  =  egg diameter, byx.2 =  regression coefficient  i n standard measure of Y on X-^ independent of X  2  and b  r e g r e s s i o n c o e f f i c i e n t i n standard measure of Y on X independent of X-j_.  fish  2  y 2  ^ =  IOO  EGG  DIAMETER  (mm)  Figure 13. Relationship between eg« diameter and number of eggs per eentiaetre of fish length. Data based on 169 spring salmon, eaoh dot indicates ayerage egg number for each 0.5 mm. diameter group.  - 72 The m u l t i p l e r e g r e s s i o n equation was found t o be Y *  1892 f 59.76 X  x  -  228.0  X  2  which i n d i c a t e s t h a t a p o s i t i v e c o r r e l a t i o n e x i s t s between the number of eggs and f i s h l e n g t h , w h i l e egg number i s n e g a t i v e l y c o r r e l a t e d w i t h egg s i z e . I n order t o estimate the r e l a t i v e importance of X^  and Xg  w i t h regard t o t h e i r independent e f f e c t on Y,  the standard p a r t i a l r e g r e s s i o n c o e f f i c i e n t s ( b ^ b ' y 2 q) were c a l c u l a t e d and compared.  an<  ^  I t was revealed that  the r e l a t i o n s h i p between f i s h l e n g t h and egg number i s about four times g r e a t e r than the e f f e c t of egg s i z e on egg number independent of f i s h l e n g t h .  I t can t h e r e f o r e be concluded  t h a t f e c u n d i t y i n s p r i n g salmon and a l s o i n coho salmon depends mainly upon the body l e n g t h and to a l e s s e r extent on egg s i z e independent of body l e n g t h .  - 73  -  SUMMARY 1.  The  stomach contents of s p r i n g and coho salmon  c o l l e c t e d d u r i n g t h e summer of 1957  from commercial  and  s p o r t f i s h e r i e s o p e r a t i n g i n southern B r i t i s h Columbia c o a s t a l waters V\/ere analyzed.  Fish, chiefly Pacific  h e r r i n g and C r u s t a c e a formed t h e most important  items  of the d i e t of s p r i n g and coho salmon. 2.  Coho salmon appear t o accept a wider v a r i e t y of food i t e m s , p a r t i c u l a r l y those of the p e l a g i c h a b i t a t and feed on whatever acceptable food item i s a v a i l a b l e i n the area at the time.  3.  D e f i n i t e seasonal changes i n the composition of food of coho were observed.  In the e a r l y p a r t of the summer  (May and June), C r u s t a c e a formed the dominant food but l a t e r f i s h replaced Crustacea.  Both i n q u a n t i t y eaten  and prevalence I n the stomachs, amphipods appeared t o be of o u t s t a n d i n g 4.  The  importance.  east and west coasts of Vancouver I s l a n d r e p r e -  sent two d i s t i n c t food type areas w i t h respect t o the amount of food a v a i l a b l e t o coho and s p r i n g salmon and the type of food items o c c u r r i n g .  Crustacea formed the  dominant food of coho salmon on the east c o a s t , w h i l e f i s h was  the dominant food on the west coast.  These  d i f f e r e n t feeding c o n d i t i o n s as a f f e c t i n g the growth of east and west coast coho are d i s c u s s e d i n d e t a i l s . 5.  U n l i k e coho, s p r i n g salmon appear t o be more conservative i n t h e i r feeding habits.  The d i f f e r e n c e s i n the  - 74 d i e t of s p r i n g and coho salmon are perhaps due t o the d i f f e r e n c e s of depth which these two species i n h a b i t ; coho being more p e l a g i c i n i t s f e e d i n g  migration.  Both s p r i n g and coho salmon, p a r t i c u l a r l y those of the west coast show i n t e n s e feeding a c t i v i t y during J u l y and August.  late  A f t e r August the feeding i n t e n s i t y take  a d e c l i n i n g trend. There i s evidence t h a t part of h e r r i n g on which s p r i n g and coho salmon feed belong to that age group which forms a major p o r t i o n of the commercial catches but the past h i s t o r y r e v e a l s that s p r i n g and coho salmon do feed on a l t e r n a t e foods i n the absence of h e r r i n g . There i s no c o n c l u s i v e evidence to show that r e d u c t i o n i n h e r r i n g abundance due t o p r a d a t i o n would lead to a r e d u c t i o n i n salmon catches. Three types of ova were found i n the maturing ovary: (a) Maturing  eggs which are q u i t e uniform i n s i z e through  out t h e ovary and a r e d e s t i n e d t o be spawned, (b) A t r e t i c eggs which are dead maturing eggs o c c u r r i n g as w h i t i s h i r r e g u l a r l y s c a t t e r e d eggs, and (c) Recruitment stock represented  by very s m a l l deep orange coloured y o l k l e s s  bodies attached t o i n t e r - o v a r i a n t i s s u e . Females have been c l a s s i f i e d as immature, maturing and mature on the b a s i s of egg s i z e - ova diameter of 2.0 mm. separates  immature and maturing f i s h .  I n the case of  males the d i s t i n c t i o n between immature and maturing i s based on whether or not the m a t u r i t y index  value  - 75 (gonad wt/dressed f i s h wt) i s over 1.0. 10.  Immature and maturing female s p r i n g s d i v i d e at a f o r k l e n g t h of approximately  74 cm., w h i l e coho do so  at an approximate l e n g t h of 52 cm. 11.  A volume method has been developed f o r d e t e r m i n a t i o n of egg numbers present  i n the ovary.  The c a l c u l a t e d  t o t a l s and a c t u a l counts of eggs show an average percentage e r r o r of 5*312.  By s t a t i s t i c a l treatments i t has been shown t h a t the absolute f e c u n d i t y i s p o s i t i v e l y c o r r e l a t e d w i t h f i s h l e n g t h but n e g a t i v e l y t o egg s i z e .  The magnitude of  the e f f e c t of f i s h l e n g t h on absolute f e c u n d i t y i s about f o u r times g r e a t e r than t h a t of egg s i z e .  - 76 REFERENCES Chapman, W.M. 1936 The p i l c h a r d f i s h e r y of the s t a t e of "Washington i n 1936 w i t h notes on the food of t h e s i l v e r and Chinook salmon o f f the Washington coast. Dept. F i s h . , S t a t e of Wash., B u l l . (36 C) : 1-20. C l a r k , F. N. 1925 The l i f e h i s t o r y o f Leuresthes t e n u i s a n - an a t h e r i n e f i s h w i t h t i d e c o n t r o l l e d spawning h a b i t s . C a l i f . F i s h and Game Comm. F i s h . B u l l . No.10. 51 pp. 1929  The l i f e h i s t o r y of the C a l i f o r n i a Jack smelt. A t h e r i n o p s i s c a l i f o r n i e n s i s . C a l i f . F i s h and Game Comm. F i s h . B u i 1 i No. l6T~23 pp.  1934  M a t u r i t y of the C a l i f o r n i a sardine (Sardina c a e r u l e a ) determined by ova diameter measurements. Calif. D i v . F i s h and Game. F i s h . B u l l . No.42. 49 pp.  Clemens, W. A. 1934 The food of s p r i n g salmon i n Shuswap Lake. Can. F i e l d . N a t u r a l i s t . 4 8 ( 9 ) : 142. F o e r s t e r , R. E. and P r i t c h a r d , A. L. 1936 The egg content of P a c i f i c salmon. Progr. Rept. Pac., 2 8 . : 3-5« F i s h . Res. Bd. Can. F o s k e t t , D. R. 195L Young salmon i n the Nanaimo area. F i s h . Res. Bd. Can., Prog. Rept. P a c , 86. : 18-19. F r a s e r , C. McLean. 1946 Food of f i s h e s . Trans. Roy. Soc. Canada. S e r i e s 3 . 4(5) : 33-39. G i l b e r t , C.H. 1913 Age o f m a t u r i t y of the P a c i f i c coast salmon of the genus Oncorhynchus. B u l l . Bur. F i s h . U.S., 1 9 1 2 . , 3 2 : 1-22. 1913  The salmon o f S w i f t s u r e Bank and the F r a s e r R i v e r sockeye r u n of 1912. Rept. Comm'er F i s h . , 1912, Prov. B r i t . C o l . 14-24.  Heg, R. and J . Van Hyning. 1951 Food of the chinook and s i l v e r salmon taken o f f t h e Oregon coast. Oregon F i s h . Comm. Res. B r i e f s , v o l . 3, No.2, : 32-40.  - 77 -  Hunter, J . G. 1948 N a t u r a l p r o p o g a t i o n of salmon i n the C e n t r a l c o a s t a l area of B r i t i s h Columbia. F i s h . Res. Bd. Can., Prog. Rept. Pac. 77 : 105-106. Hynes, H. B. N. 1950 The food of the f r e s h water s t i c k l e b a c k s (Gastrosteus a c u l e a t u s and Pygosteus p u n g i t i u s ) w i t h a review of methods used i n s t u d i e s of the food of f i s h e s . J . Anim. E c o l . London. 19 :26-58. Jensen, H.M. 1948 Puget Sound salmon i n v e s t i g a t i o n . Wash., Annual. Rept. 1948. : 3 3 .  Dept. F i s h . S t a t e  K i r k n e s s , W. 1948 Food of chinook and s i l v e r salmon of Puget Sound. Dept. F i s h . S t a t e . Wash., Annual. Rept. 1948. : 2 8 - 3 2 . McGregor, E. A. 1922 O b s e r v a t i o n s on the egg y i e l d of Klamath R i v e r King salmon. C a l i f . F i s h & Game. 8 ( 3 ) : I 6 O - I 7 6 . 1923  A p o s s i b l e s e p a r a t i o n of the r i v e r r a c e s of k i n g salmon i n ocean caught f i s h by means of anatomical c h a r a c t e r i s t i c s . C a l i f . F i s h & Game. 9 (4) : 1 3 8 - 1 5 0 .  M e r k e l , T. J . 1957 Food h a b i t s of the k i n g salmon, Oncorhynchus tshawytscha (Walbaum), i n the v i c i n i t y of San F r a n c i s c o , C a l i f o r n i a . C a l i f . F i s h & Game. 43 ( 4 ) : 249-270. M i l n e , D. J . 1950 The d i f f e r e n c e i n t h e growth of coho salmon on the east and west coasts of Vancouver I s l a n d i n 1 9 5 0 . F i s h . Res. Bd. Can., Prog. Rept. Pac. 85 : 80-82. 1954  T r o l l salmon. F i s h . Res. Bd. Can., Pac. B i o l . S t n . , Annual Rept. 1954.  1955  S e l e c t i v i t y of t r o l l i n g l u r e s . Prog. Rept. Pac. 103 : 3 - 5 .  F i s h . Res. Bd. Can.,  Nagasaki, F. 1958 The f e c u n d i t y of P a c i f i c h e r r i n g (Clupea p a l l a s l ) i n B r i t i s h Columbia c o a s t a l waters. J . F i s h . Res. Bd. Can. 15 ( 3 ) : 3 1 3 - 3 3 0 .  Neave, F. 1948 F e c u n d i t y and m o r t a l i t y i n P a c i f i c salmon. Trans. Roy. Soc. Canada., Ser 3 , 42 (sect 5) : 9 7 - 1 0 5 .  - 78 Olsen, Y. H. and D. Merriman 1946 S t u d i e s on the marine resources o f southern New England. TV. The b i o l o g y and economic importance of t h e ocean pout Macrozoarces americanus. Bingham. Oceanogr. C o l l . B u l l . 9. A r t 4. : I E 4 . P r i t c h a r d , A. L. 1940 S t u d i e s on the age of the coho salmon (Oncorhynchus k i s u t c h ) and the s p r i n g salmon (0. tshawytscha) i n B r i t i s h Columbia. Trans. Roy. Soc. Canada. Ser 3, 34 ( s e c t V) : 99-120. P r i t c h a r d , A. L. and A. L . T e s t e r . 1944 Food of s p r i n g and coho salmon i n B r i t i s h Columbia. B u l l . F i s h . Res. Bd. Can., 65 : 1-23. R a i t t , D. S. 1933 The f e c u n d i t y of haddock. F i s h . Res. Bd. S c o t l a n d . , S c i . I n v e s t . , 1932. No. 1 : 3-42. R i c h , W. H. 1925 Growth and degree of m a t u r i t y of Chinook salmon i n the ocean. B u l l . U.S. Bur. F i s h . , 41 : 67 -110. R i c k e r , W. E. 1932 S t u d i e s of speckled t r o u t ( S a l v e l l n u s f o n t i n a l l s ) i n O n t a r i o . Pub. Ont. F i s h . Res. Lab., 44 : 67-110. R o u n s e f e l l , G. A. 1957 F e c u n d i t y of North American salmonidae. U.S. F i s h & W i l d L i f e S e r v i c e . F i s h . B u l l . 122. V o l . 57- » 451-  468.  Schaefer, M. B. 1936 C o n t r i b u t i o n t o t h e l i f e h i s t o r y of the surf smelt (Hypomesus p r e t i o s u s ) i n Puget Sound. Wash. Dept. F i s h . B i o l . Rept. 35B. : 1-45. S c o t t , D. P. 1956 E f f e c t of food q u a n t i t y on the f e c u n d i t y of Kamloop t r o u t Salmo g a l r d n e r l kamloops. Jordan. Ph.D. T h e s i s . Dept. of Z o o l . Univ. B r i t . C o l . Senter, V. E. 1940 Observations on the food of P a c i f i c salmon. P a c i f i c Fishermen. V o l . 38 (4) : 26. Shapovalov, L. and A. 0 . T a f t 1954 The l i f e h i s t o r i e s of the rainbow t r o u t (Salmo g a l r d n e r l g a l r d n e r l ) and s i l v e r salmon (Oncorhynchus kisutchX"with s p e c i a l reference t o Waddell creek, C a l i f o r n i a , and recommendations regarding t h e i r management. C a l i f . F i s h & Game. F i s h . B u l l . , 98 :  1-375.  - 79 S i l l i m a n , R. P. 1941 F l u c t u a t i o n s i n the d i e t of chinook and s i l v e r salmons o f f Washington as r e l a t e d to the t r o l l c a t c h of salmon. Copeia. 2 : 8 0 - 8 7 . Snedecor, G. 1957  W.  S t a t i s t i c a l methods.  The Iowa State College  Press.  Snyder, J . 0 . 1921 How many eggs does a salmon l a y ? C a l i f . F i s h & Game. 7 : 6-3-64. T a y l o r , F. H. C. 1955 The P a c i f i c h e r r i n g (Clupea p a l l a s i ) along the P a c i f i c coast of Canada. I n t e r n a t . North. Pac. F i s h . Comm. B u l l . No. 1 : 1 0 5 - 1 2 8 . T a y l o r , F. H. C. and D. J . M i l n e . 1954 The p o s s i b l e r e l a t i o n s h i p between abundance of h e r r i n g and the abundance of s p r i n g salmon o f f the west coast of Vancouver I s l a n d . Memorandum (Unpublished). F i s h . Res. Bd. Can. Pac. B i o l . S t n . :  1-8.  Thompson, W. F. 1915 A p r e l i m i n a r y r e p o r t on the l i f e h i s t o r y of the h a l i b u t . Rept. Commsr. F i s h . B. C. f o r 1914. : N76-N99. Vladykov, V. D. 1956 F e c u n d i t y of w i l d speckled t r o u t ( S a l v e l i n u s f o n t i n a l i s ) i n Quebec l a k e s . J . F i s h . Res. Bd. Can7~13 (6) : 799-841. W i c k e t t , W. P. 1951 The coho salmon p o p u l a t i o n of N i l e creek. F i s h . Res. Bd. Can. Prog. Rept. P a c , 89 : 8 8 - 8 9 . W i l l i a m s o n , H. C. 1930 Notes on food of s p r i n g salmon. N a t u r a l i s t . 44 (9) : 203-204.  Canadian. F i e l d .  - 80 -  APPENDIX A INSTRUCTIONS ,FOR THE COLLECTION OF STOMACHS AND GONADS OF SPRING AND COHO SALMON Each c o l l e c t o r i s being provided w i t h k i t s made up of one l i v e r can, one quart of f o r m a l i n , and 25 numbered bags. Upon r e c e i p t of t h i s shipment, the bags should be removed and kept s e p a r a t e l y , the f o r m a l i n emptied i n t o the l i v e r can and the can f i l l e d t o approximately one h a l f I t s c a p a c i t y w i t h s a l t or f r e s h water. I n order t o have a r e p r e s e n t a t i v e sample, i t i s suggested t h a t they should be spread throughout the p e r i o d of f i s h i n g by t a k i n g e i t h e r 5 or 10 samples a week.  Fishermen  are asked t o c o l l e c t stomachs and gonads i n an unbiased and random way. I n l a r g e f i s h remove the U-shaped stomach by s e v e r i n g the g u l l e t immediately behind t h e mouth and t h e i n t e s t i n e immediately behind the f i n g e r - l i k e sacs ( p y l o r i c caeca), a l s o remove each r e p r o d u c t i v e organ (gonad) making c e r t a i n t h a t each stomach and gonad i s complete.  I n s m a l l f i s h remove e n t i r e  gut and complete contents of t h e body c a v i t y and place them I n the bag, t i g h t e n the draw s t r i n g and t i e i t around the top of the bag.  I n the book p r o v i d e d r e c o r d the l a b e l number, date  of c a p t u r e , the f i s h i n g l o c a t i o n , the f o r k l e n g t h I n centimetres and at l e a s t 5 s c a l e s from the l e f t side of the f i s h , and any other  remarks.  - 81 I n s e r t t h e bag and contents i n t o the f o r m a l i n s o l u t i o n i n l i v e r can. The k i t . should be considered f u l l when there I s s t i l l enough f o r m a l i n l e f t to cover the bags.  At t h i s time  c l o s e the l i d t i g h t l y - and ship the package f r e i g h t or express c o l l e c t . t o the B i o l o g i c a l S t a t i o n , Nanaimo, B. C.  Please  mark on t h e r e t u r n address so t h a t f u r t h e r equipment and cheque to cover 25 cents payment f o r each sample may be delivered. Your c o n t r i b u t i o n i s o n l y part of a program throughout B r i t i s h Columbia.  The analyses of these should serve as  a b a s i s f o r determining: (1)  The a c t u a l food of s p r i n g and coho salmon taken i n the commercial catches.  (2)  The r e l a t i v e v a l u e of h e r r i n g and shrimp i n the food relationship.  (3)  The degree of m a t u r i t y f o r d i f f e r e n t s i z e s of f i s h  caught.  The i n v e s t i g a t o r s would welcome any data from l o g books or other records which have been c o l l e c t e d I n the past. C r e d i t w i l l be given f o r such data and they w i l l be t r e a t e d as s t r i c t l y c o n f i d e n t i a l . PLEASE NOTE: (a)  Separate marked cans should be used f o r s p r i n g and coho salmon.  (b)  M a i l the envelope provided to B i o l o g i c a l S t a t i o n w i t h i n f o r m a t i o n as to when each k i t i s despatched.  (c)  I f f i s h i s undersized and s m a l l enough to go i n t o the bag, make a s m a l l s l i t i n the underside and i n c l u d e the whole f i s h as the sample.  

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