Science, Faculty of
Zoology, Department of
DSpace
UBCV
Kingston, Gary
Master of Science - MSc
University of British Columbia
This thesis investigated variation in egg size with size of the female parent in Pacific herring, Clupea harengus pallasi (Valenciennes), and the effect of this variation on subsequent larval growth and survival. Egg weight was found to increase markedly with length or weight of the female; larger females had mean egg weights up to 50% greater than those observed in the smaller females. Differences in egg size had no effect on fertilization rate, incubation time, or hatching success, contrary to some of the other findings in the literature. Total weight at hatch, that is, the weight of the larvae and yolk combined, was highly correlated with original egg weight. Larvae from larger eggs generally had more yolk at hatch, grew more quickly on the yolk reserves, and took longer to reach complete yolk absorption. The net result was that small differences in size at hatch were amplified and larvae from larger eggs were substantially longer and heavier at yolk absorption than larvae of the same age from smaller eggs. Under starvation conditions, larvae from larger eggs survived 4 to 5 days longer than larvae from smaller eggs at 9.1 °C. The magnitude of this difference was temperature dependent. When fed an Artemia diet larvae from smaller eggs and larvae from larger eggs had similar growth rates regardless of when feeding was initiated. Trends in survival with egg size were not significant except when feeding was initiated early. In this case, survival declined significantly as egg size increased. Implications of these results in terms of fisheries management are discussed.
EGG S I Z E VARIATION IN PACIFIC HERRING, CLUPEA HARENGUS PALLASI (VALENCIENNES), AND ITS EFFECTS ON LARVAL GROWTH AND SURVIVAL by GARY KINGSTON . S c . ( h o n ) , U n i v e r s i t y o f V i c t o r i a , V i c t o r i a , 1976 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department o f Z o o l o g y ) We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA Au g u s t 1983 (c) G a r y K i n g s t o n , 1983 I n 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 o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e 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 a n d s t u d y . I f u r t h e r a g r e e 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 c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e h e a d o f my d e p a r t m e n t o r by h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d 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 . D e p a r t m e n t o f The U n i v e r s i t y o f B r i t i s h C o l u m b i a 1956 Main Mall V a n c o u v e r , Canada V6T 1Y3 i DE-6 (3/81) i i ABSTRACT T h i s t h e s i s i n v e s t i g a t e d v a r i a t i o n i n egg s i z e w i t h s i z e o f t h e f e m a l e p a r e n t i n P a c i f i c h e r r i n g , C l u p e a h a r e n g u s p a l l a s i ( V a l e n c i e n n e s ) , and t h e e f f e c t o f t h i s v a r i a t i o n on s u b s e q u e n t l a r v a l g r o w t h and s u r v i v a l . Egg w e i g h t was f o u n d t o i n c r e a s e m a r k e d l y w i t h l e n g t h o r w e i g h t of t h e f e m a l e ; l a r g e r f e m a l e s had mean egg w e i g h t s up t o 50% g r e a t e r t h a n t h o s e o b s e r v e d i n t h e s m a l l e r f e m a l e s . D i f f e r e n c e s i n egg s i z e had no e f f e c t on f e r t i l i z a t i o n r a t e , i n c u b a t i o n t i m e , o r h a t c h i n g s u c c e s s , c o n t r a r y t o some o f t h e o t h e r f i n d i n g s i n t h e l i t e r a t u r e . T o t a l w e i g h t a t h a t c h , t h a t i s , t h e w e i g h t o f t h e l a r v a e and y o l k c o m b i n e d , was h i g h l y c o r r e l a t e d w i t h o r i g i n a l egg w e i g h t . L a r v a e f r o m l a r g e r e ggs g e n e r a l l y had more y o l k a t h a t c h , grew more q u i c k l y on t h e y o l k r e s e r v e s , and t o o k l o n g e r t o r e a c h c o m p l e t e y o l k a b s o r p t i o n . The n e t r e s u l t was t h a t s m a l l d i f f e r e n c e s i n s i z e a t h a t c h were a m p l i f i e d and l a r v a e f r o m l a r g e r eggs were s u b s t a n t i a l l y l o n g e r and h e a v i e r a t y o l k a b s o r p t i o n t h a n l a r v a e o f t h e same age f r o m s m a l l e r e g g s . Under s t a r v a t i o n c o n d i t i o n s , l a r v a e f r o m l a r g e r eggs s u r v i v e d 4 t o 5 d a y s l o n g e r t h a n l a r v a e f r o m s m a l l e r eggs a t 9.1 °C. The m a g n i t u d e o f t h i s d i f f e r e n c e was t e m p e r a t u r e d e p e n d e n t . When f e d an A r t e m i a d i e t l a r v a e f r o m s m a l l e r eggs and l a r v a e f r o m l a r g e r eggs had s i m i l a r g r o w t h r a t e s r e g a r d l e s s o f when f e e d i n g was i n i t i a t e d . T r e n d s i n s u r v i v a l w i t h egg s i z e were n o t s i g n i f i c a n t e x c e p t when f e e d i n g was i n i t i a t e d e a r l y . I n t h i s c a s e , s u r v i v a l d e c l i n e d s i g n i f i c a n t l y a s egg s i z e i n c r e a s e d . I m p l i c a t i o n s o f t h e s e r e s u l t s i n terms o f s h e r i e s management a r e d i s c u s s e d . i v TABLE OF CONTENTS ABSTRACT i i L I S T OF TABLES v i L I S T OF FIGURES v i i ACKNOWLEDGEMENTS i x I n r o d u c t i o n . ' 1 I n t r a s p e c i f i c V a r i a t i o n i n Egg S i z e 1 Egg S i z e and L a r v a l S u r v i v a l 4 Female S i z e and L a r v a l S u r v i v a l 6 M a t e r i a l s and Methods 9 Yea r 1 ( 1980) 10 Y e a r 2 (1981) 13 R e s u l t s 15 Female S i z e and Egg S i z e 15 Egg S i z e E f f e c t s 20 F e r t i l i z a t i o n r a t e 20 I n c u b a t i o n Time 22 H a t c h i n g S u c c e s s 24 S i z e and C o n d i t i o n a t H a t c h .... 24 Ra t e and e f f i c i e n c y o f y o l k u t i l i z a t i o n 33 Growth 43 S t a r v e d L a r v a e 43 F e d L a r v a e 46 M o r t a l i t y 54 S t a r v e d L a r v a e 54 F e d L a r v a e .. 58 D i s c u s s i o n 63 G e n e r a l 63 L a r v a l S u r v i v a l 69 I m p l i c a t i o n s f o r F i s h e r i e s Management 72 E c o l o g i c a l R e l a t i o n s h i p s 74 L i t e r a t u r e C i t e d 77 v i L I S T OF TABLES T a b l e 1. P r e v i o u s s t u d i e s 3 T a b l e 2. Egg s i z e and f e m a l e s i z e 15 T a b l e 3. A n a l y s i s of c o v a r i a n c e 18 T a b l e 4. Egg s i z e and gonad p o s i t i o n 20 T a b l e 5. S i z e a t h a t c h and o r i g i n a l egg w e i g h t 28 T a b l e 6. Y o l k c o n v e r s i o n e f f i c i e n c i e s 43 v i i L I S T OF FIGURES F i g u r e 1. Mean egg w e i g h t and f e m a l e w e i g h t 16 F i g u r e 2. Mean Egg w e i g h t and f e m a l e l e n g t h 17 F i g u r e 3. Egg s i z e and f e r t i l i z a t i o n r a t e 21 F i g u r e 4. I n c u b a t i o n t i m e and egg s i z e 23 F i g u r e 5. H a t c h i n g s u c c e s s and egg s i z e 25 F i g u r e 6. Y o l k volume and Y o l k w e i g h t 27 F i g u r e 7. H a t c h l e n g t h and egg w e i g h t 29 F i g u r e 8. T o t a l w e i g h t a t h a t c h and egg w e i g h t 30 F i g u r e 9. Y o l k and l a r v a l w e i g h t a t h a t c h 31 F i g u r e 10. C o n d i t i o n a t h a t c h and egg w e i g h t 32 F i g u r e 11. Y o l k u t i l i z a t i o n and egg w e i g h t 35 F i g u r e 12. Changes i n y o l k w e i g h t o v e r t i m e 36 F i g u r e 13. C a l c u l a t i o n o f y o l k c o n v e r s i o n e f f i c i e n c i e s .... 38 F i g u r e 14. C o n v e r s i o n e f f i c i e n c y and egg w e i g h t 40 F i g u r e 15. L a r v a l w e i g h t a t c o m p l e t e y o l k a b s o r p t i o n 41 F i g u r e 16. L a r v a l l e n g t h a t c o m p l e t e y o l k a b s o r p t i o n ...... 42 F i g u r e 17. Growth i n l e n g t h o f s t a r v e d l a r v a e 44 F i g u r e 18. Growth i n w e i g h t of s t a r v e d l a r v a e 45 F i g u r e 19. L a r v a l l e n g t h and w e i g h t r e l a t e d t o egg s i z e ... 47 F i g u r e 20. Growth i n l e n g t h and f e e d i n g t r e a t m e n t s 50 F i g u r e 21. Growth i n w e i g h t i n d i f f e r e n t f e e d i n g t r e a t m e n t s 52 F i g u r e 22. Growth r a t e and egg s i z e 55 F i g u r e 23. F i n a l l e n g t h and egg s i z e 56 v i i i F i g u r e 24. S t a r v a t i o n t i m e and egg s i z e 57 F i g u r e 25. M o r t a l i t y c u r v e s and egg s i z e 59 F i g u r e 26. S t a r v a t i o n t i m e and t e m p e r a t u r e 60 F i g u r e 27. P e r c e n t s u r v i v a l i n f e d l a r v a e 61 i x ACKNOWLEDGEMENTS I would l i k e t o thank my s u p e r v i s o r , D r . N . J . W i l i m o v s k y , f o r f i n a n c i a l s u p p o r t and v a l u a b l e a d v i c e d u r i n g t h e c o u r s e of th e r e s e a r c h . I would a l s o l i k e t o thank p e r s o n n e l a t 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 i n Nanaimo where most o f t h e l a b work was c a r r i e d o u t , e s p e c i a l l y D r . D o u g l a s Hay f o r t h e use of h i s l a b f a c i l i t i e s a nd f o r h e l p f u l d i s c u s s i o n s a t many p o i n t s d u r i n g t h e s t u d y . T h i s p r o j e c t was s u p p o r t e d by f u n d s from t h e Department o f F i s h e r i e s and Oceans and from D r . W i l i m o v s k y ' s NSERC g r a n t . P e r s o n a l s u p p o r t was p r o v i d e d by an NSERC p o s t g r a d u a t e f e l l o w s h i p . 1 INRODUCTION I n t r a s p e c i f i c V a r i a t i o n i n Egg S i z e I n t r a s p e c i f i c v a r i a t i o n i n egg s i z e h as been o b s e r v e d i n many s p e c i e s of f i s h , y e t t h e c a u s e s and e f f e c t s o f t h i s v a r i a t i o n have been g i v e n l i t t l e a t t e n t i o n t o d a t e (Hempel, 1979). B a g e n a l (1971) l i s t e d t h e v a r i a t i o n i n egg s i z e f o r 46 s p e c i e s o f m a r i n e f i s h e s . D i f f e r e n c e s i n egg volume, e x p r e s s e d a s t h e p e r c e n t d i f f e r e n c e between s m a l l e s t and l a r g e s t e g g s , r a n g e d from a s low as 4.5% i n Pegusa l a s c a r i s t o as h i g h a s 404% i n E n g r a u l i s e n c r a s i c o l u s . V a r i a t i o n i n egg s i z e i s i m p o r t a n t b e c a u s e i t may i n f l u e n c e t h e g r o w t h and s u r v i v a l o f t h e r e s u l t a n t l a r v a e ( B l a x t e r and Hempel, 1963; B l a x t e r , 1969; H u n t e r , 1 9 8 0 ) . I n t r a s p e c i f i c d i f f e r e n c e s i n egg s i z e d e r i v e p r i n c i p a l l y f r o m t h r e e s o u r c e s . T h e s e a r e : (1) d i f f e r e n c e s between s t o c k s s u c h as t h o s e d i f f e r e n c e s f o u n d between w i n t e r - s p r i n g s p a w n i n g and summer-autumn spawning s t o c k s o f A t l a n t i c h e r r i n g (Hempel and B l a x t e r , 1967). T h e s e d i f f e r e n c e s a p p e a r t o be r e l a t e d t o t h e t i m e o f y e a r d u r i n g w h i c h s p awning t a k e s p l a c e , w h i c h d e t e r m i n e s t o some e x t e n t t h e amount of f o o d a v a i l a b l e t o t h e l a r v a e ( B a g e n a l , 1971). (2) c h a n g e s i n egg s i z e w i t h i n a s t o c k w h i c h o c c u r o v e r a spawning s e a s o n as has been d e m o n s t r a t e d f o r A t l a n t i c m a c k e r e l , Scomber scombrus (Ware, 1977), and a v a r i e t y o f o t h e r s p e c i e s : P l e u r o n e c t e s p l a t e s s a , S o l e a s o l e a , and M e r l a n g u s m e r l a n g u s ( B a g e n a l , 1971). D u r i n g a p r o t r a c t e d spawning p e r i o d , a s h i f t 2 i s g e n e r a l l y o b s e r v e d where l a r g e r eggs a r e p r o d u c e d i n t h e w i n t e r or e a r l y s p r i n g and p r o g r e s s i v e l y s m a l l e r eggs a r e p r o d u c e d as spawning a p p r o a c h e s t h e summer months. L i k e t h e d i f f e r e n c e s f o u n d between s t o c k s o f A t l a n t i c h e r r i n g , t h i s v a r i a t i o n i s t h o u g h t t o be a d a p t i v e s i n c e l a r g e r eggs s h o u l d r e s u l t i n l a r g e r l a r v a e w i t h g r e a t e r s u r v i v a l p o t e n t i a l when f o o d p r o d u c t i o n i s low, as i s t h e c a s e i n t h e w i n t e r months (Hempel, 1979). A c c o r d i n g t o B a g e n a l ( 1 9 7 1 ) , t h e d e c r e a s e i n egg s i z e i s not a s s o c i a t e d w i t h t r e n d s i n s e a t e m p e r a t u r e o r s a l i n i t y , ,and he c o n c l u d e s t h a t i t i s a b i o l o g i c a l phenomenon. B l a x t e r (1969) s u g g e s t s t h a t low f e c u n d i t y and l a r g e egg s i z e o f w i n t e r spawning A t l a n t i c h e r r i n g a r e a d a p t a t i o n s t o r e d u c e d f o o d s u p p l y and p r e d a t o r p o p u l a t i o n s . (3) v a r i a t i o n i n egg s i z e r e f l e c t s v a r i a t i o n i n m a t e r n a l s i z e : l a r g e r f e m a l e s o f t e n have l a r g e r e g g s . T h a t y o u n g e r f e m a l e s i n a s t o c k may p r o d u c e s m a l l e r eggs t h a n o l d e r o r l a r g e r i n d i v i d u a l s has been d e m o n s t r a t e d f o r a number of s p e c i e s ( t a b l e 1 ) . The p o s i t i v e c o r r e l a t i o n o f egg s i z e w i t h f i s h s i z e has been f o u n d i n most of t h e f i s h s t o c k s i n v e s t i g a t e d , a l t h o u g h t h e r e l a t i o n s h i p i s l e s s a p p a r e n t i n h i g h l y f e c u n d m a r i n e s p e c i e s (Hempel, 1979). F o r example, t h e r e l a t i o n s h i p i s v a r i a b l e b o t h i n A t l a n t i c c o d and i n A t l a n t i c h e r r i n g . B l a x t e r and Hempel (1966) c o n c l u d e d f o r h e r r i n g t h a t more d a t a a r e needed t o e s t a b l i s h whether d i f f e r e n c e s t h e y o b s e r v e d were c o n s i s t e n t . In c a s e s where s i g n i f i c a n t r e s u l t s were o b t a i n e d t h e r e l a t i o n s h i p was p r i m a r i l y d e p e n d e n t on t h e s m a l l e r egg s i z e s f o u n d i n r e c r u i t s pawners. Schopka (1971) f o u n d a r e l a t i o n s h i p i n N o r t h 3 T a b l e 1. P r e v i o u s s t u d i e s t h a t have r e l a t e d egg s i z e and f e m a l e s i z e , showing t h e s p e c i e s and t h e n a t u r e of t h e r e l a t i o n s h i p ( n . s - n o n - s i g n i f i c a n t a t t h e 0.05 l e v e l ) . Spec i e s S t u d y R e l a t i o n s h i p A r g e n t i n e a n c h o v y C i e c h o m s k i , 1966 P o s i t i v e A t l a n t i c c o d O o s t h u z e n and Daan, 1974 P o s i t i v e , n . s . Grauman, 1973 P o s i t i v e S c h o pka, 1971 V a r i a b l e A t l a n t i c h e r r i n g B l a x t e r and Hempel, 1963 V a r i a b l e S c h o p k a , 1971 P o s i t i v e K r i v o b o k e t a l , 1971 P o s i t i v e Toom, 1958 P o s i t i v e A t l a n t i c salmon Pope e t a l , 1961 P o s i t i v e Brown t r o u t H a r d y , 1967 P o s i t i v e C a r p H u l a t a e t a l , 1974 P o s i t i v e A n i s i m o v a , 1956 C a s p i a n r o a c h N i k o l s k i i , 1963 P o s i t i v e C h i n o o k salmon F o w l e r , 1972 P o s i t i v e D o g f i s h Templeman, 1944 P o s i t i v e F l o u n d e r S o l e m d a l , 1967 V a r i a b l e L a r g e m o u t h b a s s L a u r e n c e , 1969 P o s i t i v e Medaka S t a n l e y , 1977 None P a c i f i c h e r r i n g J o n e s , 1972 P o s i t i v e , n . s . P l a i c e B a g e n a l , 1971 P o s i t i v e Q u e e n f i s h D e M a r t i n i and F o u n t a i n , P o s i t i v e 1980 Rainbow t r o u t S c o t t , 1962 None G a l l , 1974 P o s i t i v e S o c k e y e salmon R o u n s e f e l l , 1957 P o s i t i v e S t e e l h e a d B u l k l e y , 1967 P o s i t i v e S u r f s m e l t S t a n l e y , 1977 P o s i t i v e T e x a s d a r t e r Hubbs e t a l , 1968 None T i l a p i a P e t e r s , 1963 P o s i t i v e Sea c o d between egg s i z e and l e n g t h o f t h e mother, w h i l e i n I c e l a n d i c c o d t h e r e l a t i o n s h i p was w i t h age o f t h e m o ther. In B a l t i c c o d , t h e r e was no c o r r e l a t i o n of egg s i z e w i t h l e n g t h o r age. O o s t h u z e n and Daan (1974) f o u n d no s i g n i f i c a n t r e l a t i o n s h i p i n N o r t h Sea c o d , w h i l e Grauman (1973) f o u n d a p o s i t i v e r e l a t i o n s h i p i n B a l t i c s t o c k s . In s p i t e o f t h e s e c o n t r a d i c t o r y f i n d i n g s , t h e phenomenon of i n c r e a s i n g egg s i z e w i t h f e m a l e s i z e i s g e n e r a l l y w e l l e s t a b l i s h e d . I n a few 4 i n s t a n c e s i t a p p e a r s t h a t egg s i z e may d e c l i n e s l i g h t l y i n v e r y o l d spawners ( K r i v o b a k e t a l . , 1971). Egg S i z e and L a r v a l S u r v i v a l D i f f e r e n c e s i n egg w e i g h t a r e m a i n l y due t o d i f f e r e n c e s i n t h e q u a n t i t y o f y o l k ( P e t e r s , 1963). L a r g e r eggs p r o d u c e l a r g e r l a r v a e w i t h g r e a t e r y o l k r e s e r v e s a t h a t c h t h a n t h o s e f r o m s m a l l e r eggs ( B l a x t e r and Hempel, 1963; B a g e n a l , 1 9 7 1 ; Toom, 1958). L a r g e r eggs might c o n f e r a s u r v i v a l a d v a n t a g e on t h e l a r v a e i n one o r a c o m b i n a t i o n o f t h r e e ways: (1) L a r g e r l a r v a e w i t h g r e a t e r y o l k r e s e r v e s may have a l o n g e r t i m e t o s t a r v a t i o n and t h e r e f o r e may be a b l e t o s u r v i v e f o r l o n g e r p e r i o d s b e f o r e e n c o u n t e r i n g f o o d . (2) L a r g e r l a r v a e , once f o o d h a s been e n c o u n t e r e d , may f e e d more e f f i c i e n t l y due t o h i g h e r swimming s p e e d s , g r e a t e r r e a c t i v e d i s t a n c e s , and a l a r g e r gape. (3) L a r g e r l a r v a e may be b e t t e r a b l e t o a v o i d p r e d a t i o n due t o h i g h e r swimming s p e e d s and g r e a t e r p h y s i c a l s i z e . The f i r s t o f t h e s e t h r e e p o i n t s i s s u p p o r t e d by B l a x t e r and Hempel (1963, 1966), who f o u n d t h a t l a r g e r eggs d i d r e s u l t i n l o n g e r t i m e s t o s t a r v a t i o n . T h i s was t r u e f o r eggs o f w i d e l y d i f f e r e n t s i z e s t a k e n f r o m d i f f e r e n t r a c e s o r s t o c k s o f A t l a n t i c h e r r i n g . W i t h i n a r a c e , d i f f e r e n c e s i n egg s i z e were n o t a s g r e a t and t h e l a r v a e h a t c h i n g f r o m l a r g e r eggs d i d n o t s u r v i v e l o n g e r t h a n t h o s e f r o m s m a l l e r eggs under s t a r v a t i o n c o n d i t i o n s . T h i s was p r e s u m a b l y due t o t h e h i g h e r m e t a b o l i c demands o f t h e 5 l a r g e r l a r v a e . B a g e n a l ( 1 9 6 9 ) , s t u d y i n g brown t r o u t , Salmo t r u t t a , f o u n d t h a t l a r g e f r y d e r i v e d from l a r g e eggs s u r v i v e d l o n g e r w i t h o u t f o o d t h a n s m a l l f r y from s m a l l e g g s . The same was t r u e o f j a c k m a c k e r e l l a r v a e ( T h e i l a c k e r , 1980). On t h e o t h e r hand, S t a n l e y (1977) and C i e c h o m s k i ( 1 9 6 6 ) , w o r k i n g w i t h medaka and A r g e n t i n e a n c h o v y r e s p e c t i v e l y , f o u n d t h a t t h e s i z e of t h e egg had no d e t e c t a b l e e f f e c t on s u r v i v a l t i m e s of l a r v a e d e p r i v e d o f f o o d . The e f f e c t s o f egg s i z e on g r o w t h and s u r v i v a l of f e d l a r v a e i n h a t c h e r y s i t u a t i o n s have been i n v e s t i g a t e d i n r a i n b o w t r o u t ( G a l l , 1974) and c h i n o o k salmon ( F o w l e r , 1972). Growth, a t l e a s t i n t h e e a r l y s t a g e s , was o b s e r v e d t o be h i g h l y c o r r e l a t e d w i t h o r i g i n a l egg s i z e . Growth o f f e d c a r p l a r v a e a l s o a p p e a r s t o be d e p e n d e n t on egg w e i g h t ( H u l a t a e t a l , 1976). On t h e o t h e r hand, F o w l e r (1972) f o u n d i n t h r e e s e p a r a t e r u n s t h a t t o t a l m o r t a l i t y was s i g n i f i c a n t l y h i g h e r i n l a r v a e d e r i v e d f r o m l a r g e e g g s . O b s e r v a t i o n s of swimming s p e e d , r e a c t i v e d i s t a n c e , and gape a l l show t h e s e p a r a m e t e r s t o be p o s i t i v e l y c o r r e l a t e d w i t h l a r v a l s i z e ( H u n t e r , 1972; B l a x t e r , 1969; B l a x t e r and Hempel, 1963). U n f o r t u n a t e l y , t h e l a t t e r s t u d i e s c o n f o u n d t h e e f f e c t s o f age and s i z e s i n c e c o n c l u s i o n s were drawn u s i n g l a r v a e o f d i f f e r e n t a g e s . S t u d i e s o f p r e d a t i o n on f i s h l a r v a e a r e r a r e . L i l l e l u n d and L a s k e r (1971) f o u n d t h a t s e v e r a l s p e c i e s o f m a r i n e c o p e p o d s were e f f i c i e n t p r e d a t o r s of a n c h o v y l a r v a e , but t h a t swimming and e s c a p e a b i l i t y i n c r e a s e d a s t h e l a r v a e grew. T h e i l a c k e r a n d L a s k e r (1974) t e s t e d t h e a b i l i t y of E u p h a u s i a p a c i f i c a t o 6 c a p t u r e a n c h o v y l a r v a e . A g a i n , t h e c a p t u r e s u c c e s s was r e d u c e d when o l d e r , more a c t i v e l a r v a e were i n t r o d u c e d . T h e s e s t u d i e s a l s o c o n f o u n d t h e e f f e c t s o f age and s i z e and many of t h e d i f f e r e n c e s between l a r g e r and s m a l l e r l a r v a e can be a t t r i b u t e d t o l e a r n i n g o r d e v e l o p m e n t a l e f f e c t s . B a g e n a l (1969) examined t h e e f f e c t s of egg s i z e on brown t r o u t l a r v a e under r e l a t i v e l y n a t u r a l c o n d i t i o n s u s i n g c a g e s embedded i n a s t r e a m . The l a r v a e were s u b j e c t t o n a t u r a l v a r i a t i o n s i n p h y s i c a l c o n d i t i o n s and f o o d a v a i l a b i l i t y , but n o t t o p r e d a t i o n . T r o u t f r y s u r v i v a l was s i g n i f i c a n t l y g r e a t e r i n f r y d e r i v e d f r o m l a r g e r e g g s . B a g e n a l b e l i e v e d t h i s m i ght be due p r i m a r i l y t o c o m p e t i t i o n f o r s p a c e among l a r g e r and s m a l l e r l a r v a e r a t h e r t h a n d i f f e r e n c e s i n f e e d i n g c a p a b i l i t i e s o r s t a r v a t i o n t i m e s . 220 Female S i z e and L a r v a l S u r v i v a l I f y o u n g e r o r s m a l l e r f e m a l e s p r o d u c e s m a l l e r eggs w h i c h r e s u l t i n l e s s v i a b l e l a r v a e , t h e n i t i s l i k e l y t h a t t h e y o u n g e r f e m a l e spawners i n a s t o c k p r o d u c e l e s s v i a b l e l a r v a e . T h i s has been s u g g e s t e d by a number of a u t h o r s ( N i k o l s k i i , 1963; B l a x t e r and Hempel, 1963; S t a n l e y , 1977), but has r e c e i v e d l i t t l e i n t e r e s t f r o m o t h e r i n v e s t i g a t o r s . S i n c e t h e e f f e c t o f a f i s h e r y i s t o l o w e r t h e a v e r a g e age o f t h e s t o c k , l e s s v i a b l e egg p r o d u c t i o n i n y o u n g e r f i s h c o u l d c o n c e i v a b l y have s e r i o u s e f f e c t s on r e c r u i t m e n t beyond t h o s e due t o c h a n g e s i n t o t a l egg p r o d u c t i o n . B r i d g e r (1960, 1961; c i t e d by P a r r i s h and S a v i l l e , 7 1965) p o s t u l a t e d s u c h an e f f e c t f o r A t l a n t i c h e r r i n g . He f o u n d a s t r o n g c o r r e l a t i o n between t h e spawning p o t e n t i a l o f f i s h 5 y e a r s o r o l d e r and t h e number of l a r v a e p r o d u c e d . When t h e e n t i r e s t o c k was c o n s i d e r e d , t h e r e a p p e a r e d t o be no r e l a t i o n s h i p . L i k e w i s e , Ponomarenko ( 1 9 7 3 ) , w o r k i n g w i t h A t l a n t i c c o d , f o u n d t h a t when r e c r u i t spawners a r e p r e d o m i n a n t i n t h e spawning s t o c k , t h e p r o b a b i l i t y o f t h e a p p e a r a n c e of a s t r o n g y e a r c l a s s i s v e r y s l i g h t , even i f t h e spawning p o p u l a t i o n i s l a r g e . The p r o b a b i l i t y o f a s t r o n g y e a r c l a s s was p o s i t i v e l y r e l a t e d t o t h e p r o p o r t i o n o f t h e s t o c k made up o f r e p e a t s p a w n e r s . Ponomarenko c o n c l u d e d t h a t s m a l l e r f e m a l e s p r o d u c e l e s s v i a b l e o f f s p r i n g . Ponomarenko and N i k o l s k i i (1963) b o t h s u g g e s t e d t h a t t h e r e c r u i t spawners c o n s t i t u t e a r e s e r v e , w h i c h c a n c o n t r i b u t e i n a s i g n i f i c a n t way t o r e c r u i t m e n t o n l y u n d e r v e r y f a v o r a b l e c o n d i t i o n s . Hempel and B l a x t e r (1967) c o n c l u d e d , however, t h a t t h e a g e - o r s i z e - s p e c i f i c e f f e c t on l a r v a l , s u r v i v a l i n A t l a n t i c h e r r i n g was n e g l i g i b l e b a s e d on a maximum o b s e r v e d egg s i z e d i f f e r e n c e o f 14% between young r e c r u i t s and o l d e r s pawners, and t h a t i t was u n l i k e l y t h a t a s i g n i f i c a n t m a t e r n a l e f f e c t on l a r v a l s u r v i v a l e x i s t e d . T h i s c o n c l u s i o n seems p r e m a t u r e i n l i g h t o f t h e a v a i l a b l e i n f o r m a t i o n . The p r e s e n t s t u d y i n v e s t i g a t e s t h e r e l a t i o n s h i p between f e m a l e s i z e , egg s i z e , and l a r v a l g r o w t h and s u r v i v a l i n a s t o c k o f P a c i f i c h e r r i n g , C l u p e a h a r e n g u s p a l l a s i . The h y p o t h e s i s t h a t age o r s i z e of t h e f e m a l e a f f e c t s l a r v a l s u r v i v a l i s r e f o r m u l a t e d a s t h r e e s t a t e m e n t s : 8 ( 1 ) In P a c i f i c herring, Clupea harengus p a l l a s i , larger females have s i g n i f i c a n t l y larger eggs at spawning than do younger indi v i d u a l s . (2) Under starvation conditions, larvae derived from larger eggs have a larger size, faster growth, and longer survival times than larvae from smaller eggs. (3) Under a variety of delayed feeding regimes larvae from larger eggs have a greater capacity to withstand starvation, and higher growth and survival rates than larvae from smaller eggs. 9 MATERIALS AND METHODS A l l e x p e r i m e n t s were c a r r i e d o u t a t 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 i n Nanaimo, B.C. R i p e h e r r i n g were o b t a i n e d from Nanoose Bay i n 1980 and from D e p a r t u r e Bay i n 1981. In b o t h c a s e s , t h e h e r r i n g were o b t a i n e d from s e i n e r s engaged i n t e s t s e t s p r i o r t o t h e o p e n i n g of t h e r o e f i s h e r y . H e r r i n g were d i p n e t t e d f r o m t h e p u r s e d s e i n e n e t and p l a c e d i n o x y g e n a t e d h o l d i n g t a n k s on b o a r d a n o t h e r v e s s e l . The f i s h were t h e n t r a n s p o r t e d t o P.B.S. and h e l d i n l a r g e c i r c u l a r t a n k s s u p p l i e d w i t h f l o w t h r o u g h s e a w a t e r t a k e n from D e p a r t u r e Bay. R i p e m a l e s and f e m a l e s were s e l e c t e d from t h e l a r g e r g r o u p i n s u c h a way as t o p r o v i d e a s wide a r a n g e of s i z e s as p o s s i b l e . E a c h f i s h was sampled f o r s t a n d a r d l e n g t h and w e i g h t , and s c a l e s were t a k e n f o r a g i n g . A sample o f eggs was t a k e n from e a c h f e m a l e by a p p l y i n g g e n t l e p r e s s u r e t o t h e abdomen, t h e r e b y f o r c i n g eggs o u t t h r o u g h t h e g e n i t a l o p e n i n g . A minimum of 50 eggs were t a k e n f r o m e a c h f e m a l e and f i x e d i n 4% f o r m a l i n . A d d i t i o n a l s a m p l e s were t a k e n from f i v e f e m a l e s and d r y egg w e i g h t s d e t e r m i n e d w i t h o u t p r e s e r v a t i o n f o r c o m p a r i s o n w i t h f i x e d d r y w e i g h t s . Eggs were a l s o s a m p l e d from e i g h t d i f f e r e n t gonad p o s i t i o n s i n t h r e e f e m a l e s t o c o n f i r m t h a t egg s i z e i s i n d e p e n d e n t o f p o s i t i o n i n t h e gonad. Eggs were d r i e d on g l a s s s l i d e s a t 90 d e g r e e s f o r 24 h o u r s and weighed i n d i v i d u a l l y on a Cahn m i c r o b a l a n c e a c c u r a t e t o 1 ng. D r y w e i g h t i s b e l i e v e d t o be t h e b e s t measure o f egg s i z e as b o t h d i a m e t e r and volume a r e dynamic q u a n t i t i e s w h i c h change m a r k e d l y f o l l o w i n g f e r t i l i z a t i o n ( B l a x t e r , 1969) and d e p e n d t o some e x t e n t on t h e p a s t o s m o t i c 10 h i s t o r y o f t h e f e m a l e ( S o l e m d a l , 1967). The m e t h o d o l o g y i n v o l v e d i n f e r t i l i z a t i o n and i n c u b a t i o n o f t h e eggs i s s t r a i g h t f o r w a r d a n d w e l l d e s c r i b e d e l s e w h e r e ( A l d e r d i c e and V e l s o n , 1978). The a d h e s i v e eggs were s q u e e z e d from t h e f e m a l e o n t o l a b e l l e d g l a s s s l i d e s i n narrow l i n e s . T h ese were t h e n f e r t i l i z e d w i t h a sperm s o l u t i o n o b t a i n e d by r e m o v i n g t h e t e s t e s f r o m s e v e r a l m a l e s and m i x i n g t h e c o n t e n t s w i t h s e a w a t e r . The g l a s s s l i d e s w i t h f e r t i l i z e d eggs were t h e n p l a c e d i n r a c k s i n t h e water t a b l e f o r i n c u b a t i o n . L a r v a l e x p e r i m e n t s were c o n d u c t e d i n a q u a r i a p l a c e d i n w a t e r t a b l e s t o m a i n t a i n c o n s t a n t w a t e r t e m p e r a t u r e . Y e a r J_ (1 980) In y e a r 1, f o r t y f e m a l e s o v e r as wide a r a n g e o f s i z e as p o s s i b l e were u s e d a s s o u r c e s o f r i p e e g g s . E a c h f i s h was sampled as n o t e d above and a p p r o x i m a t e l y 2000 eggs f r o m e a c h f e m a l e were f e r t i l i z e d on g l a s s s l i d e s . The f e r t i l i z a t i o n s u c c e s s was d e t e r m i n e d t h e n e x t day by c o u n t i n g a p p r o x i m a t e l y 300 eggs under a d i s s e c t i n g m i c r o s c o p e and n o t i n g t h e number w h i c h were u n f e r t i l i z e d . U n f e r t i l i z e d eggs a r e e a s i l y d i s t i n g u i s h e d by a b s e n c e o f c l e a v a g e and f a i l u r e t o f o r m t h e p e r i v i t e l l i n e s p a c e . T h e r e i s no s w e l l i n g i n u n f e r t i l i z e d eggs and t h e r e f o r e t h e y a r e s i g n i f i c a n t l y s m a l l e r t h a n f e r t i l i z e d e g g s . The d e v e l o p m e n t o f t h e l a r v a e was m o n i t o r e d d a i l y . One o r two d a y s b e f o r e t h e i n i t i a t o n o f h a t c h t h e eggs f r o m e a c h f e m a l e were p l a c e d i n s e p a r a t e c o n t a i n e r s . The p e r c e n t h a t c h was 11 e s t i m a t e d by c o u n t i n g a r e p r e s e n t a t i v e number o f eggs d a i l y f o l l o w i n g t h e f i r s t day of h a t c h i n g . Eggs t h a t had h a t c h e d out were d e t e c t e d by t h e p r e s e n c e o f empty s h e l l s a t t a c h e d t o t h e g l a s s s l i d e . When i t a p p e a r e d t h a t no f u r t h e r h a t c h i n g would o c c u r , t h e s l i d e s were removed from t h e c o n t a i n e r s and t h e f i n a l h a t c h e s t i m a t e d . . On t h e 17th day f o l l o w i n g f e r t i l i z a t i o n , o r 2 d a y s a f t e r t h e main h a t c h , 100 l a r v a e f r o m e a c h f e m a l e were p l a c e d i n s e p a r a t e 1 l i t e r c o n t a i n e r s on t h e w ater t a b l e . The c o n t a i n e r s were n o t a e r a t e d s i n c e B l a x t e r and Hempel (1963) f o u n d t h a t l a r v a e l i v e d l o n g e r i n u n a e r a t e d j a r s . T h i s s e t o f c o n t a i n e r s was u s e d t o e s t i m a t e t h e m o r t a l i t y of t h e l a r v a e under s t a r v a t i o n c o n d i t i o n s . Dead l a r v a e i n e a c h c o n t a i n e r were removed and c o u n t e d d a i l y . Dead l a r v a e a r e w h i t e and opaque and e a s i l y d e t e c t e d on t h e b o t t o m o f t h e c o n t a i n e r s when h e l d a g a i n s t a d a r k b a c k g r o u n d . The t o t a l number o f d ead l a r v a e was u s e d t o c o n f i r m t h e i n i t i a l number p r e s e n t . The h a t c h i n g c o n t a i n e r s were a d j u s t e d t o c o n t a i n a p p r o x i m a t e l y t h e same number o f l a r v a e and t h e s e were sampled p e r i o d i c a l l y t o e s t i m a t e g r o w t h and y o l k u t i l i z a t i o n . Commencing on t h e f i r s t day o f h a t c h , 10 l a r v a e p e r day were sampled f r o m e a c h c o n t a i n e r , a n a e s t h e t i z e d w i t h MS222, and p r e s e r v e d i n 4% f o r m a l i n s o l u t i o n . A n a e s t h e t i z a t i o n b e f o r e p r e s e r v a t i o n p r e v e n t s e x c e s s i v e b e n d i n g o f t h e l a r v a e and f a c i l i t a t e s l a t e r measurement. F r e s h d r y w e i g h t s were a l s o m e a sured on s e v e r a l o c c a s i o n s f o r c o m p a r i s o n w i t h f i x e d d r y w e i g h t s . 12 T h r o u g h o u t t h e e x p e r i m e n t , t e m p e r a t u r e s were m o n i t o r e d d a i l y . M i n o r d i f f e r e n c e s between c o n t a i n e r s c o u l d be e l i m i n a t e d by a d j u s t i n g t h e water f l o w i n t h e water t a b l e . S a l i n i t i e s were c h e c k e d p e r i o d i c a l l y and water l o s t t o e v a p o r a t i o n r e p l a c e d w i t h d i s t i l l e d w a t e r . The p r e s e r v e d m a t e r i a l s were a n a l y z e d a t U.B.C. f o l l o w i n g c o m p l e t i o n o f t h e e x p e r i m e n t s . F i x e d l a r v a e were r i n s e d b r i e f l y a nd p l a c e d on g l a s s s l i d e s p r e v i o u s l y t r e a t e d w i t h a s i l i c o n compound, * S i l i c l a d ' , w h i c h f a c i l i t a t e d r e m o v a l o f t h e l a r v a e f o r w e i g h i n g f o l l o w i n g d r y i n g . E a c h l a r v a e was measured f o r l e n g t h , f r o m t h e t i p o f t h e s n o u t t o t h e end of t h e n o t o c h o r d , as w e l l as l e n g t h and h e i g h t o f t h e y o l k . Y o l k volume was c a l c u l a t e d as an a p p r o x i m a t i o n t o t h e volume o f a s p h e r o i d , where; V = ( 7 r/6)lh 2 T h i s a p p r o x i m a t i o n has been u s e d f o r m e r l y by B l a x t e r and Hempel (1963) and by H o w e l l ( 1 9 8 0 ) . The y o l k s a c was d i s s e c t e d away from t h e body and b o t h were d r i e d f o r 24 h o u r s a t 90° C, t h e n c o o l e d i n a d e s i c c a t o r and w e i g h e d on a Cahn m i c r o b a l a n c e t o t h e n e a r e s t 1 jug. E h r l i c h (1974) f o u n d t h a t d r i e d l a r v a e g a i n e d an a d d i t i o n a l 1% w e i g h t d u r i n g w e i g h i n g due t o a b s o r p t i o n o f a t m o s p h e r i c w a t e r . 13 Y e a r 2 (1981) In t h e s e c o n d y e a r o f t h e s t u d y , g r o w th and m o r t a l i t y o f t h e l a r v a e was examined u n d e r a v a r i e t y o f d e l a y e d f e e d i n g r e g i m e s . Eggs and t h e same i n f o r m a t i o n c o l l e c t e d i n y e a r 1, i n c l u d i n g gonad w e i g h t and c a r c a s s w e i g h t , were t a k e n from 28 f e m a l e s . Eggs were f e r t i l i z e d from 10 f e m a l e s r e p r e s e n t i n g t h e b r o a d e s t r a n g e o f a v a i l a b l e s i z e s . In y e a r 2, t h e eggs were e x t r u d e d o n t o n i t e x s c r e e n s m e a s u r i n g 30 * 45 cm t h e r e b y g r e a t l y i n c r e a s i n g t h e number o f f e r t i l i z e d eggs p e r f e m a l e . The f e r t i l i z a t i o n p r o c e d u r e and t h e means of e s t i m a t i n g f e r t i l i z a t i o n r a t e , i n c u b a t i o n t i m e , and h a t c h i n g s u c c e s s f o l l o w e d t h e m e t h o d o l o g y g i v e n i n y e a r 1. The l a r v a e were h e l d i n 18 l i t e r a q u a r i a w i t h 750 l a r v a e p e r a q u a r i u m . F o u r t r e a t m e n t s were u s e d : s t a r v e d , f i r s t f e d on day 15, f i r s t f e d on day 17, and f i r s t f e d on day 20. S i n c e t h e mean day o f h a t c h i n y e a r 2 was 12 d a y s f o l l o w i n g f e r t i l i z a t i o n t h e f i r s t f e e d i n g t o o k p l a c e 3 d a y s f o l l o w i n g h a t c h i n g . The l a r v a e were f e d A r t e m i a n a u p l i i from eggs i n c u b a t e d a t 28-29 0 C f o r 24 h o u r s . E a c h a q u a r i u m r e c e i v e d a p p r o x i m a t e l y 20,000 n a u p l i i p e r day or r o u g h l y 1.1 n a u p l i i p e r m l . Werner and B l a x t e r (1980) f o u n d f o r A t l a n t i c h e r r i n g t h a t A r t e m i a d e n s i t i e s e x c e e d i n g 0.1-0.3 p e r ml d i d n o t r e s u l t i n i n c r e a s e d g r o w th o r s u r v i v a l . L i k e w i s e , H a e g e l e and Outram (1978) f o u n d no improvement i n g r o w t h or s u r v i v a l of P a c i f i c h e r r i n g l a r v a e when t o t a l d a i l y r a t i o n e x c e e d e d 7500 n a u p l i i p e r day i n 8 l i t e r t a n k s . I t i s t h e r e f o r e assumed t h a t l a r v a l f o o d was i n e x c e s s a t a l l t i m e s f r o m commencement of f e e d i n g . A r t e m i a d e n s i t i e s 1 4 were p r o b a b l y h i g h e r t h a n 1.1 p e r ml as t h e r e were a l w a y s n a u p l i i r e m a i n i n g i n t h e t a n k f r o m t h e p r e v i o u s d a y ' s f e e d i n g . Dead A r t e m i a and l a r v a e were s i p h o n e d from t h e b o t t o m of t h e t a n k d a i l y and t h e dead l a r v a e c o u n t e d f o r e s t i m a t i o m of l a r v a l m o r t a l i t y . In o r d e r t o e s t i m a t e s i z e and gr o w t h , 20 l a r v a e p e r day f o r t h e f i r s t 7 d a y s f o l l o w i n g h a t c h and 20 l a r v a e e v e r y s e c o n d day t h e r e a f t e r were c o l l e c t e d f r o m e a c h t a n k and p r e s e r v e d . The s u b s e q u e n t a n a l y s i s of p r e s e r v e d samples was i d e n t i c a l t o y e a r 1. The e x p e r i m e n t was t e r m i n a t e d when t h e f e d l a r v a e r e a c h e d 32 d a y s o f a g e . A s e c o n d s e t o f e x p e r i m e n t s was i n i t i a t e d s u b s e q u e n t t o c o m p l e t i o n o f t h e f i r s t . I t was o r i g i n a l l y p l a n n e d t o r e p e a t t h e f e e d i n g e x p e r i m e n t u s i n g n a t u r a l p l a n k t o n l e s s t h a n 200 n i n s i z e a s a f o o d s o u r c e . I t was b e l i e v e d t h a t t h i s m i ght overcome some o f t h e l i m i t a t i o n s o f u s i n g A r t e m i a . U n f o r t u n a t e l y , a f t e r 10 d a y s o f p l a n k t o n tows i t became a p p a r e n t t h a t s u f f i c i e n t p l a n k t o n i n t h e d e s i r e d s i z e r a n g e was n o t a v a i l a b l e and t h e e x p e r i m e n t was t e r m i n a t e d . The ade q u a c y o f A r t e m i a a s a f o o d s o u r c e f o r h e r r i n g l a r v a e i s d i s c u s s e d i n a s u b s e q u e n t s e c t i o n of t h e t h e s i s . 15 RESULTS Female S i z e and Egg S i z e Egg s i z e , e x p r e s s e d as d r y w e i g h t , 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 l e n g t h o r w e i g h t o f t h e f e m a l e . The r e l a t i o n s h i p s between -egg w e i g h t and f e m a l e w e i g h t , and egg w e i g h t and f e m a l e s t a n d a r d l e n g t h , a r e shown i n f i g u r e s 1 and 2 r e s p e c t i v e l y . The r e s u l t s of r e g r e s s i o n a n a l y s e s a r e g i v e n i n t a b l e 2. The d a t a f r o m b o t h y e a r s have been combined i n t h e f i n a l r e g r e s s i o n s i n c e a n a l y s i s o f c o v a r i a n c e shows no s i g n i f i c a n t d i f f e r e n c e between s l o p e s o r i n t e r c e p t s i n d i f f e r e n t y e a r s ( t a b l e 3 ) . The d r y w e i g h t s g i v e n a r e t h o s e of eggs p r e v i o u s l y f i x e d i n 4% f o r m a l i n . F i v e s e t s o f f i x e d and f r e s h d r y w e i g h t s were compared. The f i x e d d r y w e i g h t s a v e r a g e d 5.1% l e s s t h a n f r e s h d r y w e i g h t s . T a b l e 2. R e s u l t s o f r e g r e s s i o n a n a l y s e s o f mean egg w e i g h t (ug) a s a f u n c t i o n o f f e m a l e s i z e , e x p r e s s e d b o t h as w e i g h t (g) and l e n g t h (cm). The i n d i c a t e d p r o b -a b i l i t y i s t h e p r o b a b i l i t y t h a t s l o p e = 0 . V a r i a b l e S o u r c e I n t e r c e p t S l o p e r 2 F n P W e i g h t Y e a r 1 183 .543 .594 67 .2 48 .000 Y e a r 2 189 .507 .541 30 .6 28 .000 T o t a l 185 .527 .571 98 .5 76 .000 L e n g t h Y e a r 1 17 11.2 .515 49 .9 49 .000 Y e a r 2 29 10.7 .551 31 .9 28 .000 T o t a l 22 11.0 .528 84 .0 77 .000 A l t h o u g h t h e r e g r e s s i o n s a r e h i g h l y s i g n i f i c a n t , t h e y o n l y a c c o u n t f o r a b o u t 55% o f t h e o b s e r v e d v a r i a t i o n i n mean egg 16 i i i i i i i i i i i i i i i i 50 100 150 200 Female Weight (g) F i g u r e 1. The r e l a t i o n s h i p between mean egg w e i g h t and f e m a l e w e i g h t f o r y e a r s 1 and 2. The r e g r e s s i o n l i n e s f o r e a c h y e a r a r e n o t s i g n i f i c a n t l y d i f f e r e n t a n d t h e d a t a a r e combi n e d t o o b t a i n t h e l i n e o f b e s t f i t shown. i 7 16 18 20 22 24 Female Length (cm) F i g u r e 2. The r e l a t i o n s h i p between mean egg w e i g h t and f e m a l e l e n g t h f o r y e a r s 1 and 2. The r e g r e s s i o n l i n e s f o r e a c h y e a r a r e not s i g n i f i c a n t l y d i f f e r e n t a n d t h e d a c a a r e combined t o o b t a i n t h e l i n e o f b e s t f i t shown. 18 T a b l e 3. R e s u l t s of a n a l y s i s of c o v a r i a n c e p e r f o r m e d on r e g r e s s i o n l i n e s of mean egg w e i g h t as a f u n c t i o n of f e m a l e s i z e , e x p r e s s e d b o t h as l e n g t h and w e i g h t . T h e r e i s no s i g n i f i c a n t d i f f e r e n c e between t h e two y e a r s ( a n a l y s i s a c c o r d i n g t o S n e d e c o r and C o c h r a n , 1967). V a r i a b l e H y p o t h e s i s F dF P W e i g h t S l o p e s a r e e q u a l I n t e r c e p t s a r e e q u a l .112 .116 1 ,72 1 ,73 >.25 >.25 L e n g t h s l o p e s a r e e q u a l I n t e r c e p t s a r e e q u a l .027 . 182 1 ,73 1 ,74 >.25 >.25 s i z e . The l a r g e r s c a t t e r of p o i n t s a r o u n d t h e r e g r e s s i o n l i n e s r e p r e s e n t i n d i v i d u a l d i f f e r e n c e s , e i t h e r i n f e e d i n g h i s t o r y and t h e r e f o r e t h e amount of e n e r g y a v a i l a b l e f o r r e p r o d u c t i o n , o r i n t h e way t h a t i n d i v i d u a l f i s h b a l a n c e f e c u n d i t y and egg s i z e . The s m a l l e s t egg w e i g h t r e c o r d e d was 151 ug and t h e l a r g e s t was 325 ug. The eggs f r o m t h e l a r g e s t f e m a l e s a r e up t o 50% l a r g e r t h a n t h o s e f r o m s m a l l e r f e m a l e s . T h i s d i f f e r e n c e i s s u b s t a n t i a l when compared w i t h t h e maximum 14% d i f f e r e n c e f o u n d between o l d e r and r e c r u i t i n g f e m a l e s i n s t o c k s o f A t l a n t i c h e r r i n g ( B l a x t e r and Hempel, 1967). B l a x t e r a n d Hempel a l s o f o u n d t h a t p o s i t i v e c o r r e l a t i o n s between egg w e i g h t and f e m a l e s i z e were s i g n i f i c a n t o n l y i f egg w e i g h t s from new r e c r u i t s were i n c l u d e d i n t h e d a t a . Egg w e i g h t s d i d not i n c r e a s e as m a r k e d l y w i t h f e m a l e s i z e i n t h e l a r g e r s i z e c l a s s e s . In t h i s s t u d y , t h e egg w e i g h t i n c r e a s e s a t a c o n s t a n t r a t e w i t h t h e s i z e o f t h e f e m a l e . R e c e n t l y , i n v e s t i g a t o r s a t 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 have d e r i v e d egg w e i g h t s f o r a number of P a c i f i c h e r r i n g s t o c k s u s i n g i n f o r m a t i o n on gonad w e i g h t and f e c u n d i t y f o r d i f f e r e n t 19 s i z e d f i s h . P r e l i m i n a r y r e s u l t s i n d i c a t e t h a t a l l of t h e s t o c k s d e m o n s t r a t e a p o s i t i v e r e l a t i o n s h i p between egg s i z e and f e m a l e s i z e (Hay, pers.comm.). P r e v i o u s work by A n o k h i n a (1971) s u g g e s t s t h a t f a t c o n t e n t o r c o n d i t i o n o f h e r r i n g m i g h t i n some way i n f l u e n c e egg s i z e . T h e r e f o r e t h e c o n d i t i o n f a c t o r o f t h e f e m a l e was compared t o egg s i z e , where; C o n d i t i o n F a c t o r = b o d y w e i g h t / d e n g t h ) 3 - 2 3 * 1 0 3 The e x p o n e n t , 3.23, was d e r i v e d as t h e s l o p e of t h e l e n g t h -w e i g h t r e l a t i o n s h i p when l o g w e i g h t was p l o t t e d a g a i n s t l o g l e n g t h ( r = . 9 7 9 ) . T h e r e was no s i g n i f i c a n t r e l a t i o n s h i p between c o n d i t i o n f a c t o r and egg s i z e ( r 2 = . 0 0 3 , p=.79). V a r i a t i o n i n egg s i z e w i t h i n i n d i v i d u a l f e m a l e s was c o n s i d e r a b l y l e s s t h a n between f e m a l e s : t h e r a n g e i n egg w e i g h t was a b o u t 30 ug and t h e s t a n d a r d d e v i a t i o n o f e a c h sample o f 30 eggs v a r i e d between 5 and 8 Mg. The 95% c o n f i d e n c e i n t e r v a l s f o r t h e mean w e i g h t were n o r m a l l y w i t h i n p l u s o r minus 2.9 ug o f t h e e s t i m a t e d v a l u e . T h e r e was no s i g n i f i c a n t d i f f e r e n c e i n egg s i z e between sa m p l e s t a k e n from d i f f e r e n t p o s i t i o n s i n t h e gonad ( t a b l e 4 ) . 20 T a b l e 4. R e s u l t s of a two-way a n a l y s i s o f v a r i a n c e . The two f a c t o r s a r e gonad p o s i t i o n , one o f e i g h t l o c a t i o n s i n t h e gonads from w h i c h eggs were t a k e n , and f i s h , w h i c h of t h r e e f i s h t h e samples were t a k e n f r o m . S o u r c e o f V a r i a t i o n SS DF MS T o t a l 1,296,362 719 C e l l s 1 ,255,203 23 gonad p o s i t i o n 820 7 1 17 f i s h number 1,252,345 2 626,172 i n t e r a c t i o n 2,038 1 4 1 46 E r r o r 41,159 696 59 H: Egg s i z e does not v a r y between d i f f e r e n t l o c a t i o n s i n t h e gonad. F=1.98 DF=7,696 P > .05 H a c c e p t e d H: Egg s i z e does n o t v a r y between f i s h . F=10,600 DF=2,696 P « .001 H r e j e c t e d Egg S i z e E f f e c t s F e r t i l i z a t i o n r a t e F e r t i l i z a t i o n r a t e i s n o t a f f e c t e d by egg s i z e ( f i g u r e 3) o r by t h e s i z e of t h e f e m a l e . I n y e a r 1, t h e o v e r a l l r a t e o f f e r t i l i z a t i o n was 91.6%; t h e l o w e s t v a l u e o b s e r v e d was 85.4% and t h e h i g h e s t was 97.1%. In y e a r 2, t h e o v e r a l l f e r t i l i z a t i o n r a t e was 81.3% and more v a r i a b l e . The l o w e s t v a l u e r e c o r d e d was 70.6% and t h e h i g h e s t was 92.2%. 2 1 100i 90 CO CC 80 60-1 • A A A A A A + A A A Year 1 A Year 2 150 200 250 Mean Egg Weight (ug) 300 F i g u r e 3. P e r c e n t n o t a p p e a r F e r t i l i z a t i o n y e a r . f e r t i l i z a t i o n and egg w e i g h t . T h e r e d o e s t o be a r e l a t i o n s h i p between t h e two. r a t e i s s l i g h t l y l o w e r o v e r a l l i n t h e s e c o n d 22 I n c u b a t i o n Time H a t c h i n g of t h e l a r v a e o c c u r e d o v e r a p e r i o d o f 3 t o 4 d a y s i n a p a t t e r n s i m i l a r t o t h a t d e s c r i b e d by A l d e r d i c e and V e l s o n ( 1 9 7 1 ) . H a t c h i n g t o o k p l a c e d u r i n g t h e d a r k h o u r s and t h e number o f l a r v a e h a t c h e d was e s t i m a t e d e a c h m o r n i n g . The i n c u b a t i o n t i m e i s h e r e d e f i n e d as t h e mean day of h a t c h . B l a x t e r and Hemple (1963) d e f i n e d i n c u b a t i o n t i m e as t h e t i m e f r o m f e r t i l i z a t i o n t o 50% h a t c h . The two methods g i v e s i m i l a r r e s u l t s . I n c u b a t i o n t i m e between y e a r s v a r i e d s i n c e t h e water s y s t e m t e m p e r a t u r e was s l i g h t l y h i g h e r i n y e a r 2. D u r i n g t h e f i r s t y e a r t h e s e a w a t e r s y s t e m a v e r a g e d 9.1 C and t h e t o t a l i n c u b a t i o n t i m e was 15.5 d a y s ; i n t h e s e c o n d y e a r t h e s e a w a t e r s y s t e m a v e r a g e d 9.9 C and t h e t o t a l i n c u b a t i o n t i m e was 12.4 d a y s . T h e s e v a l u e s c o r r e s p o n d w i t h t h o s e f o u n d by A l d e r d i c e and V e l s o n (1971) f o r P a c i f i c h e r r i n g i n c u b a t e d a t v a r i o u s t e m p e r a t u r e s , a l t h o u g h t h e i n c u b a t i o n t i m e d u r i n g t h e s e c o n d y e a r i s somewhat l o w e r t h a n m i g h t be e x p e c t e d . The i n c u b a t i o n t i m e d i d n o t depend i n any way on s i z e o f t h e egg and i t i s a p p a r e n t t h a t m i n o r t e m p e r a t u r e d i f f e r e n c e s w ould have a much more d r a m a t i c e f f e c t t h a n egg s i z e ( f i g u r e 4 ) . I t s h o u l d be n o t e d t h a t i n c u b a t i o n t i m e s m easured i n t h e l a b o r a t o r y may have l i t t l e c o r r e s p o n d a n c e w i t h t h o s e o b s e r v e d i n t h e s e a . In t h e l a b t h e eggs a r e i n c a l m w a t e r b a t h s , w h i l e i n t h e s e a t h e y a r e e x p o s e d t o a v a r i e t y o f c o n d i t i o n s s u c h as a i r d r y i n g and wave t u r b u l e n c e . H a n d l i n g o r v i b r a t i o n o f h e r r i n g eggs d e f i n i t e l y c a u s e s h a t c h i n g t o o c c u r e a r l i e r t h a n might be 23 16H 15J in > •D • A A ^ A A A A / A 9.1 °C <u 14 ^ E i — c o 18 13-] J 3 3 O c 12 9.9° C — ' 1 1 1 I I i i i i i i i i i 150 200 250 300 Mean Egg Weight (ug) F i g u r e 4. I n c u b a t i o n t i m e and mean egg w e i g h t . T h e r e i s no r e l a t i o n s h i p between t h e two q u a n t i t i e s . Two s e t s o f d a t a a r e shown f o r two d i f f e r e n t i n c u b a t i o n t e m p e r a t u r e s ; Y e a r 1, 9.1 C; Y e a r 2, 9.9 C. 24 e x p e c t e d o t h e r w i s e ( M a r l i a v e , 1975; Hay, pers.comm.). S i n c e t h i s i s t h e u s u a l c a s e under n a t u r a l c o n d i t i o n s , h a t c h i n g i n t h e sea l i k e l y o c c u r s e a r l i e r t h a n i n t h e l a b . H a t c h i n g S u c c e s s H a t c h i n g s u c c e s s i s t h e p e r c e n t a g e o f eggs i n i t i a l l y f e r t i l i z e d t h a t h a t c h o u t . Knowing t h e i n i t i a l number o f eggs f e r t i l i z e d , t h i s q u a n t i t y was e s t i m a t e d by c o u n t i n g t h e number of d e a d embryos r e m a i n i n g i n s i d e t h e egg c a s e s a f t e r h a t c h i n g was c o m p l e t e . H a t c h i n g s u c c e s s was d e t e r m i n e d f o r y e a r 1 o n l y . The a v e r a g e h a t c h r a t e was 70% w i t h v a l u e s r a n g i n g from 35.2% t o 93.6%. T h e r e was no r e l a t i o n s h i p between h a t c h i n g s u c c e s s and egg s i z e ( f i g u r e 5 ) . J o n e s (1972) f o u n d some i n d i c a t i o n o f a r e l a t i o n s h i p between t h e s e two q u a n t i t i e s ; eggs f r o m s m a l l e r f e m a l e s had a l o w e r s u r v i v a l r a t e f r o m f e r t i l i z a t i o n t o h a t c h . S i z e and C o n d i t i o n a t H a t c h D u r i n g t h e f i r s t y e a r o f t h e s t u d y , l a r v a e were p r e s e r v e d i n 4% f o r m a l i n s o l u t i o n p r e p a r e d u s i n g d i s t i l l e d w a t e r . T h i s s a l i n i t y of p r e s e r v a t i v e r e s u l t s i n minimum s h r i n k a g e of l a r v a e i n t e r m s o f l e n g t h (Hay, 1982). Samples o f l a r v a e were measured f r e s h and a f t e r f i x a t i o n . I n 25 f i x e d s a m p l e s , t h e a v e r a g e s h r i n k a g e i n l e n g t h was 3.7%. Changes i n d r y w e i g h t were much l a r g e r , t h o u g h r e l a t i v e l y c o n s t a n t . In 5 s a m p l e s , t h e f i x e d d r y w e i g h t a v e r a g e d 35.6% l o w e r t h a n f r e s h d r y w e i g h t o f l a r v a e from 25 2 0 0 2 5 0 3 0 0 M e a n E g g W e i g h t (ug ) F i g u r e 5. T o t a l p e r c e n t h a t c h and mean egg w e i g h t f o r y e a r 1 o n l y . T h e r e i s no r e l a t i o n s h i p between t h e two q u a n t i t i e s . 26 t h e same g r o u p . D u r i n g t h e s e c o n d y e a r , an a t t e m p t was made t o r e d u c e t h i s w e i g h t d i f f e r e n c e by u s i n g a f o r m a l i n s o l u t i o n o f 15 p p t s a l i n i t y , w h i c h B l a x t e r and Hempel (1966) r e p o r t e d would r e s u l t i n a w e i g h t d i f f e r e n c e o f -0.4 t o 0.5%. In t h e p r e s e n t s t u d y , t h e o b s e r v e d w e i g h t l o s s was 22% w h i c h prompted a s e r i e s o f e x p e r i m e n t s e x a m i n i n g w e i g h t l o s s d u r i n g f i x a t i o n i n f o r m a l i n s o l u t i o n s of d i f f e r e n t c o n c e n t r a t i o n s and s a l i n i t i e s . The r e s u l t s of t h e s e e x p e r i m e n t s a r e summarized i n Hay and K i n g s t o n ( i n p r e s s ) . B r i e f l y , as s a l i n i t y i n c r e a s e s , w e i g h t l o s s d e c r e a s e s and s h r i n k a g e i n l e n g t h i n c r e a s e s . The w e i g h t s o f y o l k and l a r v a e p r e s e n t e d i n t h i s s t u d y a r e f i x e d d r y w e i g h t s . T h e i l a c k e r and D o r s e y (1980) a l s o f o u n d t h a t f o r m a l i n p r e s e r v a t i o n c a u s e d a 30% d e c r e a s e i n d r y w e i g h t o f l a r v a l s a r d i n e and p r e s e r v a t i o n i n e t h y l a l c o h o l d e c r e a s e d d r y w e i g h t s o f P a c i f i c m a c k e r e l by 50%. Y o l k volumes a r e o f t e n e s t i m a t e d i n l a r v a l s t u d i e s owing t o t h e d i f f i c u l t y of o b t a i n i n g a c t u a l y o l k w e i g h t s . B o t h q u a n t i t i e s were measured i n t h i s s t u d y and compared. Y o l k volume a p p e a r s t o be a r e l i a b l e e s t i m a t o r o f y o l k w e i g h t ( f i g u r e 6) s i n c e t h e d e g r e e o f c o r r e l a t i o n between t h e two p a r a m e t e r s i s h i g h ( r 2 = . 9 4 9 ) . The e x a c t n a t u r e o f t h e r e l a t i o n s h i p v a r i e s w i t h t h e s a l i n i t y o f t h e f i x a t i v e . S e v e r a l p a r a m e t e r s were measured f o r l a r v a e on t h e day o f h a t c h ; t a k e n t o be t h e 15th day i n y e a r 1 and t h e 12th day i n y e a r 2. L e n g t h , t o t a l w e i g h t , l a r v a l body w e i g h t , and y o l k w e i g h t were me a s u r e d . Y o l k w e i g h t / body w e i g h t r a t i o was c a l c u l a t e d as w e l l , as t h e c o n d i t i o n f a c t o r u s e d by B l a x t e r 27 0.2H O.H O.O' 20 40 Yolk Weight (ug) 60 F i g u r e 6. The r e l a t i o n s h i p between t h e mean y o l k volume, m e a s u r e d as t h e volume o f a s p h e r o i d , and t h e mean y o l k w e i g h t . The d a t a a r e f r o m y e a r 2 o f t h e s t u d y f o r l a r v a e f i x e d i n 15 p p t s a l i n i t y , 4% f o r m a l i n . 28 ( 1 9 6 5 ) , where; C o n d i t i o n F a c t o r = body w e i g h t / l e n g t h 3 * 10 The r e l a t i o n s h i p between t h e s e p a r a m e t e r s a t h a t c h and o r i g i n a l egg w e i g h t a r e shown i n f i g u r e s 7 t h r o u g h 10 and t h e a p p r o p r i a t e s t a t i s t i c a l a n a l y s e s a r e summarized i n t a b l e 5. A s t r o n g T a b l e 5. R e s u l t s of r e g r e s s i o n a n a l y s e s o f s e v e r a l p a r a m e t e r s a t t h e t i m e o f h a t c h i n g as a f u n c t i o n o f t h e i n i t i a l egg w e i g h t . The a n a l y s i s i s p e r f o r m e d s e p a r a t e l y f o r e a c h y e a r . Day of h a t c h i s t h e 15th day f o l l o w i n g f e r t i l i z a t i o n i n y e a r 1 and t h e 12th day i n y e a r 2. The p r o b a b i l i t i e s g i v e n a r e p r o b a b i l i t y t h a t t h e s l o p e of r e g r e s s i o n l i n e e q u a l s z e r o . V a r i a b l e S o u r c e I n t e r c e p t S l o p e r 2 F n P L e n g t h Y e a r 1 7 .9 .0018 .048 .799 18 .385 Y e a r 2 5 .7 .0069 .341 4. 1 4 10 .076 T o t a l Y e a r 1 1 3 .0 .313 .697 36 .9 18 .000 W e i g h t Y e a r 2 -1. .5 .532 .914 84 .8 10 .000 Y o l k Y e a r 1 -5 .7 .111 .225 4. 35 1 7 .054 W e i g h t Y e a r 2 -21 .7 .269 .433 6. 10 10 .039 L a r v a l Y e a r 1 23 .8 .185 .462 12. 87 17 .003 W e i g h t Y e a r 2 19 . 1 .267 .483 7. 48 10 .039 C o n d i t i o n Y e a r 1 0. 65 .002 .233 4. 53 17 .050 F a c t o r Y e a r 2 1 . 91 .001 .021 • 17 10 .687 Y o l k / Y e a r 1 .082 .001 .073 1 . 18 17 .295 l a r v a e Y e a r 2 . 1 83 .001 .069 0. 59 10 .463 p o s i t i v e c o r r e l a t i o n i s a p p a r e n t between t h e t o t a l w e i g h t a t h a t c h and egg w e i g h t ( f i g u r e 8) and t h e r e l a t i o n s h i p i s h i g h l y s i g n i f i c a n t . Y o l k w e i g h t and l a r v a l body w e i g h t a t h a t c h i n g a r e 29 e 7. The r e l a t i o n s h i p between mean l e n g t h a t h a t c h and o r i g i n a l egg w e i g h t f o r b o t h y e a r s . The l i n e s o f b e s t f i t a r e shown even t h o u g h t h e r e g r e s s i o n s a r e n o t s i g n i f i c a n t . The l o w e r l e n g t h s i n y e a r 2 may r e f l e c t t h e e a r l i e r h a t c h i n t h a t y e a r . 30 F i g u r e 8. The r e l a t o n s h i p between t o t a l w e i g h t , t h a t i s , l a r v a l body w e i g h t and y o l k w e i g h t c o m b i n e d , and o r i g i n a l egg w e i g h t . The r e g r e s s i o n s a r e h i g h l y s i g n i f i c a n t . H i g h e r v a l u e s i n y e a r 2 a r e due t o e a r l i e r h a t c h and a h i g h e r s a l i n i t y of p r e s e r v a t i v e . 31 160 200 240 280 320 Egg Weight (ug) 160 200 240 280 320 Egg Weight (ug) F i g u r e 9. The r e l a t i o n s h i p s between l a r v a l w e i g h t a t h a t c h and mean egg w e i g h t , a n d y o l k w e i g h t a t h a t c h and mean egg w e i g h t . S o l i d t r i a n g l e s a r e d a t a p o i n t s f r o m t h e f i r s t y e a r o f t h e s t u d y , o p en t r i a n g l e s a r e from t h e s e c o n d y e a r . 32 2.4 u 2.0 A A ' A A A C o 1.6 o o • A 1.2 160 200 240 280 Egg Weight Cug) 320 '5 75 > ra —i \ '53 O > .6 .4 A • A A A .2 160 200 240 280 Egg Weight (ug) 320 F i g u r e 10. The r e l a t i o n s h i p s b e t w e e n c o n d i t i o n f a c t o r a t h a t c h a n d egg w e i g h t , a n d t h e y o l k / l a r v a l w e i g h t r a t i o a t h a t c h and egg w e i g h t . S o l i d t r i a n g l e s a r e d a t a f r o m y e a r 1, open t r i a n g l e s f r o m y e a r 2. 33 a l s o s i g n i f i c a n t l y c o r r e l a t e d w i t h egg w e i g h t , a l t h o u g h t h e r e l a t i o n s h i p i s not as c l e a r as t h a t f o r y o l k and l a r v a l w e i g h t c o m b i n ed. T h i s i s l i k e l y due t o s l i g h t l y d i f f e r e n t r a t e s of d e v e l o p m e n t between d i f f e r e n t s e t s of e g g s . A l t h o u g h t h e t o t a l w e i g h t i s d e p e n d e n t on o r i g i n a l egg w e i g h t , d i f f e r e n t p r o p o r t i o n s o f t h e i n i t i a l y o l k mass may be u t i l i z e d r e s u l t i n g i n c o r r e s p o n d i n g v a r i a t i o n s i n l a r v a l body w e i g h t . I f y o l k w e i g h t i s i n c l u d e d as an i n d e p e n d e n t v a r i a b l e i n t h e r e g r e s s i o n o f body w e i g h t as a f u n c t i o n of egg w e i g h t , t h e r 2 a l m o s t d o u b l e s . The body w e i g h t a t h a t c h i s t h e r e f o r e d e p e n d e n t on egg w e i g h t and on t h e amount o f y o l k w h i c h has been u t i l i z e d t o t h e p o i n t of h a t c h . L e n g t h , c o n d i t i o n f a c t o r , and y o l k w e i g h t / l a r v a l w e i g h t r a t i o a r e n o t s i g n i f i c a n t l y r e l a t e d t o egg w e i g h t a t t h e t i m e o f h a t c h , a l t o u g h t h e r e g r e s s i o n o f l e n g t h on egg w e i g h t i s a l m o s t s i g n i f i c a n t i n y e a r 2. T h e s e r e s u l t s d i f f e r f r o m t h o s e f o u n d by B l a x t e r and Hempel (1963, 1966) f o r d i f f e r e n t s t o c k s of A t l a n t i c h e r r i n g , where l e n g t h and y o l k w e i g h t / l a r v a l w e i g h t r a t i o were r e l a t e d t o o r i g i n a l egg w e i g h t . R a t e and e f f i c i e n c y o f y o l k u t i l i z a t i o n The r a t e o f y o l k u t i l i z a t i o n was e s t i m a t e d b o t h a s a d e c r e a s e i n w e i g h t and d e c r e a s e i n volume p e r d a y . The s l o p e o f t h e r e g r e s s i o n o f y o l k volume and w e i g h t on age i n d a y s was t a k e n as t h e b e s t e s t i m a t e o f y o l k u t i l i z a t i o n r a t e . R a t e s e s t i m a t e d f r o m volumes a r e c o n s i d e r e d more a c c u r a t e s i n c e a g r e a t e r number of o b s e r v a t i o n s were a v a i l a b l e . The a v e r a g e r a t e 34 i n y e a r 1 was .036 mm 3/day and r a n g e d from .018 t o as h i g h a s .088 mm 3/day. The o v e r a l l r a t e i n y e a r 2 was .040 mm 3/day and r a n g e d f r o m .023 t o .074 mm 3/day. The s l i g h t l y h i g h e r a v e r a g e r a t e i n y e a r 2 i s t o be e x p e c t e d g i v e n t h e h i g h e r t e m p e r a t u r e s i n t h a t y e a r . The r e l a t i o n s h i p between y o l k u t i l i z a t i o n r a t e and t h e i n i t i a l egg w e i g h t i s shown i n f i g u r e 11. I t i s e v i d e n t f r o m t h e f i g u r e t h a t l a r g e r l a r v a e f r o m l a r g e r e ggs consume t h e i r y o l k a t a h i g h e r r a t e t h a n s m a l l e r l a r v a e f r o m s m a l l e r e g g s . T h i s i s due t o t h e g r e a t e r m e t a b o l i c r e q u i r e m e n t s o f t h e l a r g e r l a r v a e . Even s o , l a r v a e f r o m t h e l a r g e r eggs g e n e r a l l y t a k e l o n g e r t o c o m p l e t e y o l k a b s o r p t i o n , a s shown i n f i g u r e 12. T h i s g e n e r a l i z a t i o n i s l e s s e v i d e n t i n t h e s e c o n d y e a r o f t h e s t u d y . Under c o n d i t i o n s of h i g h e r t e m p e r a t u r e , l a r g e r l a r v a e may n o t e x h i b i t l o n g e r t i m e s t o c o m p l e t e y o l k a b s o r p t i o n , a s was r e p o r t e d by T h e i l a c k e r (1980) f o r j a c k m a c k e r e l l a r v a e . B l a x t e r (1969) d e f i n e s y o l k c o n v e r s i o n e f f i c i e n c y a s ; E f f i c i e n c y = d r y w e i g h t i n c r e m e n t o f body * 100 d r y w e i g h t d e c r e m e n t o f y o l k T h i s d e f i n i t i o n assumes t h a t y o l k i s n o t s t o r e d i n t e r n a l l y i n t h e body a s i s t h e c a s e i n p l a i c e ( S h e l b o u r n e , 1957). I t i s t h e p e r c e n t a g e o f t h e y o l k t h a t ends up as l a r v a l t i s s u e . T h i s q u a n t i t y h a s been c a l c u l a t e d i n o t h e r s t u d i e s f r o m d r y w e i g h t ( B l a x t e r a nd Hempel, 1966) and from c a l o r i c c o n t e n t s of y o l k and l a r v a e ( L a s k e r , 1962). I n t h e p r e s e n t s t u d y , t h e e f f i c i e n c y was e s t i m a t e d a s t h e s l o p e o f t h e r e g r e s s i o n between l a r v a l w e i g h t and y o l k w e i g h t f o r a l l p a i r s o f o b s e r v a t i o n s ( f i g u r e 1 3 ) . The 35 oo 16 12-160 200 240 280 320 Egg Weight CugJ n T3 E E .08H .06 .04-1 .02H o ~ o o 160 200 240 280 320 Egg Weight Cugi F i g u r e 11. The r e l a t i o n s h i p between t h e r a t e o f y o l k u t i l i z a t i o n and mean egg w e i g h t . L a r g e r l a r v a e f r o m l a r g e r eggs a b s o r b t h e i r y o l k a t a h i g h e r r a t e t h a n s m a l l e r l a r v a e f r o m s m a l l e r e g g s . S o l i d c i r c l e s a r e d a t a f r o m y e a r 1, open c i r c l e s a r e d a t a from y e a r 2. 36 F i g u r e 1 2 . The r e l a t i o n s h i p between y o l k s i z e and egg w e i g h t as i t c h a n g e s o v e r t i m e i n y e a r 1. Numbers i n t h e upper l e f t hand c o r n e r s o f t h e boxes a r e t h e number o f d a y s from f e r t i l i z a t i o n . I t i s a p p a r e n t from t h e f i g u r e t h a t l a r v a e f r o m s m a l l e r eggs have a s h o r t e r p e r i o d t o c o m p l e t e y o l k a b s o r p t i o n . 40 '5 * 20 1 o >-15 16 111 17 * * * 18 1 t 1 1 19 E E CO E 3 o > o .5-.4 .3 .2 .1 • .0 • • • * « • ,1 1 140 220 300 140 220 300 140 220 300 140 Egg Weight Cug) 220 300 140 220 300 38 u r e 13. The r e l a t i o n s h i p between l a r v a l w e i g h t a n d y o l k w e i g h t . An example f r o m y e a r 2 t o d e m o n s t r a t e how e f f i c i e n c y i s c a l c u l a t e d i n t h i s s t u d y . The l i n e shown i s t h e GM f u n c t i o n a l r e g r e s s i o n l i n e as d e f i n e d by R i c k e r ( 1 9 7 3 ) . I t s s l o p e i s e q u i v e l e n t t o t h e r a t i o o f t h e d r y w e i g h t i n c r e m e n t o f t h e b o d y / d r y w e i g h t d e c r e m e n t o f y o l k . T h e r e f o r e , t h e s l o p e * 100 = e f f i c i e n c y a s d e f i n e d by B l a x t e r ( 1 9 6 9 ) . The Y - i n t e r c e p t r e p r e s e n t s t h e p o i n t a t w h i c h t h e y o l k w e i g h t e q u a l s z e r o , w h i c h i s e q u i v e l e n t t o t h e w e i g h t a t c o m p l e t e y o l k a b s o r p t i o n . 39 s l o p e r e p r e s e n t s t h e g a i n i n l a r v a l t i s s u e p e r u n i t l o s s o f y o l k w e i g h t . The s l o p e i n t h i s c a s e i s t h a t of t h e GM f u n c t i o n a l r e g r e s s i o n l i n e as s p e c i f i e d by R i c k e r (1973) s i n c e t h e f u n c t i o n a l r e l a t i o n s h i p between t h e two v a r i a b l e s i s d e s i r e d . T h i s r e g r e s s i o n l i n e a l s o g i v e s t h e b e s t e s t i m a t e of l a r v a l w e i g h t a t c o m p l e t e y o l k a b s o r p t i o n from t h e Y - i n t e r c e p t , o r t h e w e i g h t o f t h e l a r v a e when t h e w e i g h t o f t h e y o l k becomes z e r o . S i m i l a r l y , t h e l e n g t h o f t h e l a r v a e a t t h e c o m p l e t i o n o f y o l k a b s o r p t i o n can be e s t i m a t e d a s t h e Y - i n t e r c e p t o f t h e r e g r e s s i o n o f l e n g t h on y o l k v o l u m e . C o n v e r s i o n e f f i c i e n c y , and l e n g t h and w e i g h t a t y o l k a b s o r p t i o n were e s t i m a t e d as o u t l i n e d a b o v e . T h e r e a p p e a r s t o be no r e l a t i o n s h i p between e f f i c i e n c y and egg s i z e ( f i g u r e 14; t a b l e 6 ) , c o n t r a r y t o t h e f i n d i n g s o f B l a x t e r and Hempel ( 1 9 6 6 ) . The e f f i c i e n c i e s i n b o t h y e a r s a r e s i m i l a r and a v e r a g e a p r o x i m a t e l y 70%. T h i s compares w i t h 77 t o 79% f o r s a r d i n e l a r v a e , S a r d i n o p s c a e r u l a ( L a s k e r , 1962), 46.9 t o 67.9% f o r s o l e , S o l e a s o l e a ( F l u c h t e r and P a n d i a n , 1968), and 50 t o 60% f o r A t l a n t i c h e r r i n g ( B l a x t e r and Hempel, 1966). L e n g t h and w e i g h t a t y o l k a b s o r p t i o n a r e b o t h s t r o n g l y and p o s i t i v e l y c o r r e l a t e d t o egg s i z e ( f i g u r e s 15 and 16; t a b l e 6 ) . L a r v a e f r o m t h e l a r g e r eggs a r e up t o 30% h e a v i e r and 15% l o n g e r t h a n l a r v a e f r o m s m a l l e r eggs a t t h e t i m e of c o m p l e t e y o l k a b s o r p t i o n . 40 c a> u i_ a> a. >» o c a> o H — HI 100, 80\ 60\ 40H O o o 20 220 240 260 280 300 Egg Weight Cug) Fi g u r e 14. The r e l a t i o n s h i p between yolk c o n v e r s i o n e f f i c i e n c y and egg s i z e . There i s no c o r r e l a t i o n (see t a b l e 6). S o l i d c i r c l e s are year 1 data, open c i r c l e s are year 2 data. 41 220 240 260 Egg Weight CugD 280 300 F i g u r e 15. The r e l a t i o n s h i p between l a r v a l w e i g h t a t c o m p l e t e y o l k a b s o r p t i o n and egg w e i g h t . The r e g r e s s i o n i s h i g h l y s i g n i f i c a n t . S o l i d boxes a r e y e a r 1 d a t a , open b o x e s a r e y e a r 2 d a t a . 42 9.8-1 1 6 0 180 200 220 240 260 280 300 320 Egg Weight Cpg) F i g u r e 16. The r e l a t o n s h i p between l a r v a l l e n g t h a t c o m p l e t e y o l k a b s o r p t i o n and egg w e i g h t . The r e g r e s s i o n i s h i g h l y s i g n i f i c a n t ( s e e t a b l e 6 ) . S o l i d boxes a r e y e a r 1 d a t a , open boxes a r e y e a r 2 d a t a . 43 T a b l e 6. R e l a t i o n s h i p s between y o l k c o n v e r s i o n e f f i c i e n c y , l e n g t h and w e i g h t a t y o l k a b s o r p t i o n , and o r i g i n a l egg w e i g h t . The p r o b a b i l i t y g i v e n i s t h e p r o b a b i l i t y t h a t t h e s l o p e of t h e r e g r e s s i o n l i n e e q u a l s z e r o . V a r i a b l e Y e a r I n t e r c e p t S l o p e r 2 F n P L e n g t h 1 6.5 .0102 .87 72.9 1 3 .000 2 5.4 .0130 .90 74.9 10 .000 Weight 1 9.9 .292 .82 69.7 13 .000 2 16.9 .365 .87 54.5 10 .000 C o n v e r s i o n 1 1.1 -.0014 .09 1 . 1 13 .312 E f f i c i e n c y 2 1.1 -.0016 .28 3.1 10 .115 Growth S t a r v e d L a r v a e Under c o n d i t i o n s o f s t a r v a t i o n , t h e g r o w t h o f l a r v a e i s v a r i a b l e d e p e n d i n g on o r i g i n a l egg s i z e . F i g u r e s 17 a n d 18 show g r o w t h i n l e n g t h and w e i g h t f o r a v a r i e t y o f egg s i z e s i n y e a r 1. D a t a from y e a r 2 show i d e n t i c a l t r e n d s . M i n o r d i f f e r e n c e s i n l e n g t h become m a g n i f i e d a s t h e l a r v a e f r o m t h e l a r g e r eggs grow ; f a s t e r and f o r a l o n g e r p e r i o d o f t i m e s i n c e t h e y o l k r e s e r v e s l a s t s l i g h t l y l o n g e r . The maximum l e n g t h o b s e r v e d i s h i g h l y c o r r e l a t e d w i t h egg s i z e ( y e a r 1, r 2 = . 8 2 , P=.000; y e a r 2, r 2 = . 6 6 , P=.008). L a r v a e f r o m t h e s m a l l e s t egg s i z e , 167 ug, showed a l m o s t no g r o w t h i n t e r m s o f l e n g t h . The g r o w t h c u r v e s shown h e r e a r e c h a r a c t e r i s t i c o f s t a r v e d l a r v a e . Growth i s r a p i d u n t i l c o m p l e t e y o l k a b s o r p t i o n , a t w h i c h p o i n t l e n g t h becomes more o r l e s s c o n s t a n t and may even d e c l i n e . F i g u r e 18 shows t h e a c c o m p a n y i n g c h a n g e s i n l a r v a l w e i g h t f o r t h e same f o u r g r o u p s o f s t a r v e d l a r v a e . W e i g h t i n c r e a s e s 44 7.5 7.0- _ 1 5 1 7 ™ 21 ' 23 25 27 ' 29 Age Cdays from fert i l izat ion) F i g u r e 17. Changes i n l e n g t h w i t h age f o r l a r v a e f r o m a v a r i e t y o f egg s i z e s . The mean egg w e i g h t i s shown i n b r a c k e t s f o l l o w i n g e a c h g r o w th c u r v e . A r r o w s i n d i c a t e c o m p l e t e y o l k a b s o r p t i o n . 45 Age Cdays from ferti l ization) F i g u r e 18. Changes i n l a r v a l d r y w e i g h t ( y o l k s removed) w i t h age f o r l a r v a e from a v a r i e t y o f egg s i z e s . The mean egg w e i g h t i s shown i n b r a c k e t s f o l l o w i n g e a c h c u r v e . A r r o w s i n d i c a t e c o m p l e t e y o l k a b s o r p t i o n . 46 u n t i l t h e y o l k i s c o m p l e t e l y a b s o r b e d and t h e n d e c l i n e s r a p i d l y w i t h an a c c o m p a n y i n g d e c l i n e i n c o n d i t i o n o f t h e l a r v a e . I n t h e c a s e of t h e l a r v a e from t h e 167 ug eggs, t h e r e i s a c o n t i n u o u s d e c l i n e i n w e i g h t f o l l o w i n g h a t c h . I t i s l i k e l y t h a t m e t a b o l i c r e q u i r e m e n t s e x c e e d t h e e n e r g y a v a i l a b l e f r o m t h e y o l k and no i n c r e m e n t i n l a r v a l t i s s u e i s o b s e r v e d . As w i t h l e n g t h , t h e maximum o b s e r v e d w e i g h t i s h i g h l y c o r r e l a t e d w i t h egg s i z e ( y e a r 1, r 2 = . 7 7 , P=.000; y e a r 2, r 2 = . 8 7 , p=.000). F i g u r e 19 e m p h a s i z e s t h e s e r e l a t i o n s h i p s and d e m o n s t r a t e s how t h e y change w i t h t i m e f o r y e a r 1. A g a i n , d a t a f r o m t h e s e c o n d y e a r show i d e n t i c a l p a t t e r n s . I n i t i a l l y , t h e r e l a t i o n s h i p s o f l a r v a l l e n g t h and w e i g h t w i t h egg w e i g h t a r e n o t c l e a r , e s p e c i a l l y i n t h e c a s e o f l e n g t h . However t h e c o r r e l a t i o n becomes more p r o n o u n c e d w i t h t i m e . One might s p e c u l a t e t h a t t h e s o o n e r f o o d becomes a v a i l a b l e , t h e l e s s marked i s t h e f e e d i n g a d v a n t a g e e n j o y e d by l a r g e r l a r v a e from l a r g e r e g g s . I n y e a r 1, l a r v a e f r o m l a r g e r eggs were a l m o s t t w i c e as h e a v y as l a r v a e o f t h e same age f r o m s m a l l e r eggs a t t h e p o i n t when l a r v a l s i z e d i f f e r e n c e s were maximum. T h i s o c c u r e d when l a r g e r l a r v a e were j u s t c o m p l e t i n g y o l k a b s o r p t i o n w h i l e s m a l l e r l a r v a e had c o m p l e t e d y o l k a b s o r p t i o n a day o r two e a r l i e r and had a l r e a d y begun t o d e c l i n e i n w e i g h t . F e d L a r v a e D u r i n g t h e s e c o n d s e t o f e x p e r i m e n t s , l a r v a e were e x p o s e d t o f o u r d i f f e r e n t f e e d i n g r e g i m e s : f i r s t f e d on day 15, o r t h r e e d a y s a f t e r h a t c h when y o l k a b s o r p t i o n was i n c o m p l e t e ; f i r s t f e d 47 F i g u r e 1 9 . The r e l a t i o n s h i p s between l a r v a l l e n g t h and w e i g h t , and egg s i z e a t v a r i o u s t i m e s i n t h e e x p e r i m e n t f o r y e a r 1. Numbers i n t h e upper l e f t hand c o r n e r s o f t h e b o x e s a r e t h e number o f d a y s f r o m f e r t i l i z a t i o n . When d i f f e r e n c e s a r e g r e a t e s t , l a r v a e from l a r g e r eggs may be up t o 90% h e a v i e r and 20% l o n g e r t h a n l a r v a e of t h e same age from s m a l l e r e g g s . 49 on day 17, when c o m p l e t e y o l k a b s o r p t i o n had o c c u r e d ; f i r s t f e d on day 20, d e l a y e d f e e d i n g ; and f i n a l l y , no f e e d i n g or s t a r v a t i o n . F i g u r e s 20 and 21 show combined r e s u l t s and how l e n g t h and w e i g h t change o v e r t i m e under t h e above f e e d i n g c o n d i t i o n s . As e x p e c t e d , t h e l a r g e s t l a r v a e were t h o s e f e d e a r l i e s t on day 15. L a r v a e f e d a s l a t e a s day 20 s t i l l a p p e a r e d c a p a b l e o f f e e d i n g and i n c r e a s i n g i n s i z e , a l t h o u g h a t t h e t e r m i n a t i o n o f t h e e x p e r i m e n t t h e y were much s m a l l e r t h a n l a r v a e f e d e a r l i e r . I n c e r t a i n i n d i v i d u a l c a s e s , t h e f i n a l s i z e a t t h e end o f t h e e x p e r i m e n t was g r e a t e r f o r t h o s e l a r v a e f i r s t f e d 17 da y s a f t e r f e r t i l i z a t i o n t h a n f o r t h o s e f i r s t f e d on t h e 15th day. The i n i t i a l l a g i n g r o w t h a f t e r i n i t i a t i o n o f f e e d i n g i s p r o b a b l y due t o low c a p t u r e s u c c e s s when l a r v a e a r e f i r s t p r e s e n t e d w i t h f o o d . A t l a n t i c h e r r i n g l a r v a e were s u c c e s s f u l i n c a p t u r i n g o n l y 6% o f t h e f o o d p a r t i c l e s a t w h i c h a s t r i k e was made d u r i n g i n i t i a l f e e d i n g t r i a l s , but f e e d i n g s u c c e s s i n c r e a s e d r a p i d l y i n s u b s e q u e n t t r i a l s ( B l a x t e r and S t a i n e s , 1971). F i g u r e 22 shows t h e a v e r a g e g r o w t h d u r i n g t h e e x p e r i m e n t i n mm/day f o r t h e f o u r t r e a t m e n t s . T h e r e a p p e a r s t o be no r e l a t i o n s h i p between egg s i z e and growth r a t e o f t h e l a r v a e . S m a l l e r l a r v a e must be a t l e a s t a s s u c c e s s f u l i n f e e d i n g a s l a r g e r l a r v a e , even when f e e d i n g i s d e l a y e d t o 20 d a y s f o l l o w i n g f e r t i l i z a t i o n . Growth r a t e s i n l a r v a e f i r s t f e d on day 15 were c o m p a r a b l e w i t h H a e g e l e and Outram's (1978) f i g u r e s f o r l a r v a l P a c i f i c h e r r i n g g r o w t h o f .089 t o .179 mm/day, d e p e n d i n g on t y p e and c o n c e n t r a t i o n o f f o o d . The f i n a l l e n g t h s o f t h e l a r v a e i n 50 F i g u r e 20. A v e r a g e g r o w t h i n l e n g t h o f l a r v a e where f e e d i n g i s i n i t i a t e d on d i f f e r e n t d a y s . 52 F i g u r e 21. A v e r a g e growth i n w e i g h t o f l a r v a e where f e e d i n g i s i n i t i a t e d on d i f f e r e n t d a y s . Fed 15 Days from Ferti l ization w 54 r e l a t i o n t o egg s i z e f o r t h e d i f f e r e n t t r e a t m e n t s i s shown i n f i g u r e 23. The marked d i f f e r e n c e s o b s e r v e d f o r s t a r v e d l a r v a e a r e n o t a p p a r e n t i n l a r v a e f i r s t f e d on day 15 and a r e l e s s e v i d e n t i n l a r v a e f i r s t f e d on day 17. M i n o r v a r i a t i o n s i n g r o w t h r a t e s e v e n t u a l l y a l l o w some o f t h e s m a l l e r l a r v a e t o c a t c h up and some of t h e l a r g e r l a r v a e t o f a l l b e h i n d . T h u s , when f e e d i n g i s i n i t i a t e d on a f u l l r a t i o n A r t e m i a d i e t , l a r v a e f r o m l a r g e r eggs do n o t seem t o have an a d v a n t a g e , i n t e r m s of g r o w t h r a t e , o v e r l a r v a e f r o m s m a l l e r eggs even when f e e d i n g i s d e l a y e d up t o 20 d a y s f o l l o w i n g f e r t i l i z a t i o n (8 d a y s f o l l o w i n g h a t c h ) . In a d d i t i o n t o t h e a b o v e , 20 l a r v a e from e a c h egg s i z e were p l a c e d i n s e p a r a t e c o n t a i n e r s f o r 2 h o u r p e r i o d s and a l l o w e d t o f e e d on h i g h c o n c e n t r a t i o n s o f A r t e m i a . A f t e r t h i s 2 h o u r s had e l a p s e d , t h e l a r v a e were removed and t h e number of n a u p l i i i n e a c h l a r v a l g u t c o u n t e d . T h e r e was no d i f f e r e n c e i n f e e d i n g s u c c e s s o f l a r v a e from d i f f e r e n t s i z e d e g g s . However, t h e e x t r e m e v a r i a b i l i t y of t h e d a t a makes i t d i f f i c u l t t o draw any f i r m c o n c l u s i o n . M o r t a l i t y S t a r v e d L a r v a e Mean s t a r v a t i o n t i m e s a r e s t r o n g l y and p o s i t i v e l y c o r r e l a t e d w i t h o r i g i n a l egg w e i g h t ( r 2 = . 5 9 5 , P=.000) ( f i g u r e 2 4 ) . S u r v i v a l c u r v e s f o r l a r v a e g r o u p e d a c c o r d i n g t o egg s i z e e x h i b i t t h e t y p i c a l p a t t e r n o f m o r t a l i t y i n h e r r i n g l a r v a e and t h e 55 0.3 0.2 >. 0.1 jo E E a 0.0 ca DC 0.3 o C3 0.2 0.1 0.0 I Starved Fed 20 • • • • • • • • • • • • • • • • • • Fed 17 Fed 15 • • * * • • • • • • • • • 200 240 280 200 240 Egg Weight Cug) 280 F i g u r e 22. Growth r a t e s o f l a r v a e i n r e l a t i o n t o egg s i z e . T r e a t m e n t i s shown i n t h e u p p e r l e f t c o r n e r o f e a c h box. 56 13. O* 11.0 9.0 E o> 7.0 0) 13.0 11.0 9.0 7.0 Starved Fed 20 • • • • • • • • • • • • Fed 17 Fed 15 • • • • • • • • • • • • • • • • • • 200 240 280 200 240 280 Egg Weight cpg) F i g u r e 23. F i n a l l e n g t h s of l a r v a e i n r e l a t i o n t o egg s i z e . T r e a t m e n t i s shown i n t h e u p p e r l e f t c o r n e r o f e a c h box. 57 175 200 225 250 275 300 Egg Weight Cug} F i g u r e 24. The r e l a t i o n s h i p between mean day o f s t a r v a t i o n and egg s i z e . S t a r v a t i o n t i m e i s s t r o n g l y c o r r e l a t e d w i t h egg s i z e . 58 r e l a t i v e d i f f e r e n c e s between egg s i z e s ( F i g u r e 2 5 ) . L a r v a e from t h e l a r g e s t eggs l a s t f o r a p p r o x i m a t e l y 3 d a y s l o n g e r t h a n l a r v a e f r o m t h e s m a l l e s t e g g s . A s i d e f r o m dependence on i n i t i a l y o l k r e s e r v e s , s t a r v a t i o n t i m e i s s t r o n g l y a f f e c t e d by t e m p e r a t u r e ( F i g u r e 2 6 ) . The t h r e e s t a r v a t i o n e x p e r i m e n t s were ru n under s l i g h t l y d i f f e r e n t t e m p e r a t u r e s due t o i n c r e a s e s i n t h e t e m p e r a t u r e o f t h e s e a w a t e r s y s t e m . An i n c r e a s e i n t e m p e r a t u r e o f 1 d e g r e e c a u s e s a c o r r e s p o n d i n g d e c r e a s e i n s u r v i v a l t i m e o f a p p r o x i m a t e l y f o u r d a y s . T h u s , i n c r e a s e s i n t e m p e r a t u r e i n t h e s e a would s i g n i f i c a n t l y d e c r e a s e t h e amount o f t i m e a v a i l a b l e f o r a l a r v a e t o f i n d f o o d . F e d L a r v a e The p e r c e n t s u r v i v a l f o r e a c h egg s i z e and e a c h o f t h e t h r e e f e e d i n g t r e a t m e n t s a r e g i v e n i n f i g u r e 27. The r e l a t i o n s h i p between p e r c e n t s u r v i v a l and egg s i z e i s s i g n i f i c a n t f o r t h e l a r v a e f i r s t f e d on t h e 15th day f o l l o w i n g f e r t i l i z a t i o n ( r 2 = . 5 2 0 , P=.018). The c o r r e l a t i o n i s a n e g a t i v e one; s u r v i v a l d e c r e a s i n g s l i g h t l y w i t h i n c r e a s i n g egg s i z e . In t h e c a s e o f l a r v a e f e d i n i t i a l l y on t h e 17th day f o l l o w i n g f e r t i l i z a t i o n , t h e r e l a t i o n s h i p i s p o s i t i v e , b ut n o t s t a t i s t i c a l l y s i g n i f i c a n t ( r 2 = . 2 0 5 , p = . 2 2 l ) . 59 16 18 20 22 24 26 28 30 32 34 Days from Ferti l ization F i g u r e 25. S u r v i v a l o f l a r v a e g r o u p e d a c c o r d i n g t o egg w e i g h t . 60 Days from Ferti l ization F i g u r e 26. Combined s u r v i v a l c u r v e s f o r r u n s a t t h r e e d i f f e r e n t t e m p e r a t u r e s . An i n c r e a s e o f 1 d e g r e e d e c r e a s e s t i m e t o s t a r v a t i o n by a p p r o x i m a t e l y 4 d a y s . 6 1 F i g u r e 27. P e r c e n t s u r v i v a l t o t h e 32nd day f o l l o w i n g f e r t i l i z a t i o n a s a f u n c t i o n o f egg s i z e f o r t h e t h r e e d i f f e r e n t f e e d i n g r e g i m e s . Fed 15 Fed 17 Fed 20 JL-JL. 190 210 230 250 270 290 Egg Weight Cug) 63 DISCUSSION G e n e r a l In t h e s t o c k of P a c i f i c h e r r i n g i n v e s t i g a t e d i n t h i s s t u d y , eggs from l a r g e r f e m a l e s were up t o 50% h e a v i e r t h a n eggs from s m a l l e r i n d i v i d u a l s . T h i s f e m a l e s i z e - e g g s i z e r e l a t i o n s h i p has been c o n f i r m e d f o r o t h e r s t o c k s o f P a c i f i c h e r r i n g (Hay; u n p u b l i s h e d d a t a ) . Egg s i z e i s n o t r e l a t e d t o c o n d i t i o n f a c t o r of t h e f e m a l e . In any of t h e f e m a l e s i z e c a t e g o r i e s , t h e range o f mean egg s i z e s i s q u i t e l a r g e s u g g e s t i n g t h a t o t h e r f a c t o r s a r e i m p o r t a n t i n d e t e r m i n i n g f i n a l egg w e i g h t . P e r h a p s i n d i v i d u a l f e e d i n g h i s t o r i e s o r v a r i a t i o n s i n t h e way i n d i v i d u a l f i s h b a l a n c e f e c u n d i t y and egg s i z e a c c o u n t s f o r t h e o b s e r v e d v a r i a t i o n . Egg s i z e does not a f f e c t f e r t i l i z a t i o n r a t e , i n c u b a t i o n t i m e , o r h a t c h i n g s u c c e s s . A s s u m i n g t h a t s p a w n i n g i s more o r l e s s s y n c h r o n o u s w i t h i n a s t o c k o f h e r r i n g , t h e n f o r a g i v e n number o f eggs t h e number o f l a r v a e p r o d u c e d and t h e t i m e t h a t t h e y w i l l h a t c h i s i n d e p e n d e n t o f egg s i z e . T h e r e f o r e , any e f f e c t on v i a b i l i t y must be r e l a t e d t o d i f f e r e n c e s i n l a r v a l c h a r a c t e r i s t i c s a t h a t c h and t h e e f f e c t s of t h e s e d i f f e r e n c e s on e v e n t s s u b s e q u e n t t o h a t c h i n g . Ware (1975) d e r i v e d a r e l a t i o n s h i p i n w h i c h i n c u b a t i o n t i m e i n c r e a s e s w i t h egg s i z e . A c o r r e l a t i o n was shown between egg s i z e and t e m p e r a t u r e s u c h t h a t a t l o w e r t e m p e r a t u r e s i t was a d v a n t a g e o u s f o r f i s h t o p r o d u c e l a r g e r e g g s . Ware d i d n o t , however, i m p l y t h a t egg s i z e had a d i r e c t e f f e c t on i n c u b a t i o n t i m e . S i n c e t h e n , s e v e r a l 64 a u t h o r s have c o n c l u d e d t h a t i n c u b a t i o n t i m e i s d e p e n d e n t on egg s i z e i n t h e same way t h a t i t i s d e p e n d e n t on t e m p e r a t u r e ( T h e i l a c k e r and D o r s e y , 1980; H u n t e r , 1980). T h e s e c o n c l u s i o n s a p p e a r t o be b a s e d on a m i s i n t e r p r e t a t i o n of Ware's r e s u l t s . B l a x t e r and Hempel (1963) and C i e c h o m s k i ( 1 9 6 6 ) , w o r k i n g w i t h A t l a n t i c h e r r i n g and A r g e n t i n e a n c h o v y r e s p e c t i v e l y , a l s o f o u n d t h a t i n c u b a t i o n t i m e was i n d e p e n d e n t of t h e s i z e of t h e e g g . The combined w e i g h t of t h e l a r v a and t h e y o l k a t h a t c h i s s t r o n g l y d e p e n d e n t on o r i g i n a l egg w e i g h t . L a r g e r egg s i z e t h e r e f o r e p r o v i d e s f o r g r e a t e r body w e i g h t a t h a t c h , g r e a t e r y o l k r e s e r v e a t h a t c h o r , i n most c a s e s , b o t h of t h e s e a d v a n t a g e s . F o l l o w i n g t h e h a t c h , any d i f f e r e n c e s between l a r v a l body w e i g h t o r l e n g t h i n c r e a s e r a p i d l y . D i s p a r i t i e s t h a t were n o t l a r g e o r a b s e n t i n t h e c a s e of l e n g t h , become m a g n i f i e d . S i n c e l a r g e r l a r v a e t e n d t o t a k e l o n g e r t o r e a c h t h e p o i n t o f c o m p l e t e y o l k a b s o r p t i o n t h e y c a n grow f o r a l o n g e r t i m e on t h e i r y o l k r e s e r v e s . In a d d i t i o n , y o l k c o n v e r s i o n e f f i c i e n c y i s i n d e p e n d e n t of egg s i z e , a t l e a s t i n t h e p e r i o d f o l l o w i n g h a t c h . T h i s means t h a t t h e f i n a l s i z e o f t h e l a r v a e a t y o l k a b s o r p t i o n , i n t e r m s of l e n g t h as w e l l as w e i g h t , i s s t r o n g l y d e p e n d e n t on t h e o r i g i n a l w e i g h t o f t h e e g g . The p o i n t o f c o m p l e t e y o l k a b s o r p t i o n i s more c r i t i c a l e c o l o g i c a l l y t h a n t h e t i m e of h a t c h as i t marks t h e t i m e when t h e l a r v a e must s h i f t from endogenous t o exogenous f e e d i n g . The s u c c e s s o r f a i l u r e o f t h i s p r o c e s s i s b e l i e v e d by many t o e x e r t a m a j o r i n f l u e n c e on t h e e v e n t u a l s i z e o f t h e y e a r c l a s s e n t e r i n g t h e f i s h e r y ( H j o r t , 1926; T h e i l a c k e r 65 and D o r s e y , 1980). A f t e r t h i s p e r i o d of maximum l a r v a l l e n g t h and w e i g h t , i f f o o d i s n o t a v a i l a b l e , t h e l e n g t h r e m a i n s c o n s t a n t o r d e c r e a s e s s l i g h t l y , w h i l e t h e w e i g h t d e c l i n e s a t a c o n s t a n t and r e l a t i v e l y r a p i d r a t e as t h e l a r v a l t i s s u e i s i t s e l f c a t a b o l i z e d . The c o n d i t i o n o f t h e l a r v a e a l s o f a l l s a c c o r d i n g l y . T h r o u g h o u t t h i s s t a r v a t i o n p e r i o d , however, l a r v a e from l a r g e r eggs m a i n t a i n t h e i r a d v a n t a g e i n t e r m s o f l e n g t h and w e i g h t . The l a r v a e f r o m t h e l a r g e r eggs a l s o d e m o n s t r a t e a g r e a t e r r e s i s t a n c e t o s t a r v a t i o n t h a n l a r v a e f r o m s m a l l e r e g g s , s u r v i v i n g f o r up t o t h r e e d a y s l o n g e r w i t h o u t f o o d . T h i e l a c k e r ( 1 9 8 0 ) , w o r k i n g w i t h j a c k m a c k e r e l l a r v a e , f o u n d t h a t l a r v a e f r o m l a r g e r eggs s t a r v e d more s l o w l y and l i v e d f o r one day l o n g e r w i t h o u t f o o d t h a n l a r v a e from s m a l l e r e g g s . More i m p o r t a n t t h a n t h e p o i n t o f s t a r v a t i o n i s t h e p o i n t a t w h i c h t h e l a r v a i s f u n c t i o n a l l y i n c a p a b l e of f e e d i n g . T h i s p o i n t i s t e r m e d t h e " p o i n t o f no r e t u r n " or PNR by B l a x t e r and Hempel ( 1 9 6 3 ) . In A t l a n t i c h e r r i n g l a r v a e , t h e PNR o c c u r s a t a b o u t 75% of t h e t i m e from h a t c h t o s t a r v a t i o n r e g a r d l e s s o f egg s i z e ( B l a x t e r and Hempel, 1963). A s s u m i n g a PNR o f a p p r o x i m a t e l y 75% of s t a r v a t i o n t i m e , l a r v a e from l a r g e r eggs m i g h t be f u n c t i o n a l l y c a p a b l e o f f e e d i n g up t o 25 d a y s f o l l o w i n g f e r t i l i z a t i o n (10 d a y s f o l l o w i n g h a t c h ) , w h i l e l a r v a e from s m a l l e r eggs would be i n c a p a b l e o f f e e d i n g 23 d a y s a f t e r f e r t i l i z a t i o n (8 d a y s f o l l o w i n g h a t c h ) . T h e s e f i g u r e s a r e o n l y v a l i d f o r t h e t e m p e r a t u r e r e g i m e under w h i c h t h e above e x p e r i m e n t s were r u n . A t h i g h e r t e m p e r a t u r e s t h e s t a r v a t i o n 66 t i m e s w o u l d be s h o r t e r and t h e t i m e d i f f e r e n t i a l s between PNR's f o r l a r g e r v e r s u s s m a l l e r l a r v a e would be d e c r e a s e d . A t l o w e r t e m p e r a t u r e s , t h e r e v e r s e would be t r u e . Thus, t h e r e m ight e x i s t a 'time window' o r l i m i t e d p e r i o d o f t i m e where s m a l l e r l a r v a e a r e i n c a p a b l e of f e e d i n g w h i l e l a r v a e from l a r g e r eggs a r e c a p a b l e o f f e e d i n g , g r o w i n g , and, u l t i m a t e l y , s u r v i v i n g . T h i s s t u d y a l s o i n v e s t i g a t e d t h e e f f e c t of egg s i z e on t h e s u b s e q u e n t a b i l i t y o f t h e l a r v a e t o f e e d and grow a f t e r v a r y i n g p e r i o d s o f s t a r v a t i o n . I t seems r e a s o n a b l e t o assume t h a t l a r v a e f r o m s m a l l e r eggs would be a t a d i s a d v a n t a g e once f o o d became a v a i l a b l e due t o s l o w e r swimming s p e e d s , s h o r t e r r e a c t i v e d i s t a n c e s , and s m a l l e r g a p e s . T h i s d i s a d v a n t a g e s h o u l d be r e f l e c t e d i n d i f f e r e n t g r o w t h r a t e s o f l a r v a e f r o m s m a l l and l a r g e eggs under i d e n t i c a l f e e d i n g c o n d i t i o n s . On t h e o t h e r hand, l a r v a e f r o m s m a l l e ggs a b s o r b t h e i r y o l k more q u i c k l y and may be r e a d y t o f e e d e a r l i e r t h a n l a r v a e f r o m l a r g e r e g g s . T h i s w o u l d p r o v e a d v a n t a g e o u s i f f o o d became a v a i l a b l e soon a f t e r h a t c h i n g o c c u r e d . The g r o w t h r a t e s o b s e r v e d f o r f e d l a r v a e were q u i t e v a r i a b l e and i n d e p e n d e n t o f b o t h t h e i n i t i a l s i z e o f t h e l a r v a e and i n i t i a l egg w e i g h t . The f i n a l s i z e s o f l a r v a e f i r s t f e d 15 d a y s a f t e r f e r t i l i z a t i o n were n o t r e l a t e d t o egg w e i g h t . T h i s r e s u l t w o u l d l i k e l y h o l d f o r t h e o t h e r t r e a t m e n t s a s w e l l i f t h e e x p e r i m e n t s had been e x t e n d e d f o r a l o n g e r p e r i o d . Even i n l a r v a e f e d as l a t e a s t h e 2 0 t h day f o l l o w i n g f e r t i l i z a t i o n , o r 8 days f o l l o w i n g h a t c h i n g , s m a l l e r l a r v a e grew as w e l l o r even b e t t e r t h a n l a r v a e f r o m t h e l a r g e r e g g s . I t may be t h a t an even 67 l a t e r day o f f i r s t f e e d i n g , one w h i c h f e l l w i t h i n t h e PNR 'window' d i s c u s s e d above, would be n e c e s s a r y t o d e m o n s t r a t e d i f f e r e n c e s i n t h e a b i l i t y of t h e l a r v a e t o r e c o v e r and grow. In r a i n b o w t r o u t , f i n g e r l i n g s f r o m o l d e r f e m a l e s grew 20% f a s t e r t h a n t h o s e from two y e a r o l d f e m a l e s under i d e n t i c a l f e e d i n g c o n d i t i o n s ( G a l l , 1974). The f a c t t h a t A r t e m i a n a u p l i i were e x c l u s i v e l y u s e d a s a f o o d s o u r c e may have a s i g n i f i c a n t b e a r i n g on t h e r e s u l t s o b t a i n e d . The a b i l i t y o f f i s h l a r v a e t o grow and s u r v i v e i s v e r y much d e p e n d e n t on t h e t y p e o f f o o d p a r t i c l e a v a i l a b l e . R e s u l t s o b t a i n e d u s i n g A r t e m i a may d i f f e r f r o m r e s u l t s o b t a i n e d u s i n g o t h e r f o o d s o u r c e s due t o d i f f e r e n c e s i n p a r t i c l e s i z e , swimming c a p a b i l i t y o f t h e p r e y , and v i s i b i l i t y . A r t e m i a i s a l a r g e , h i g h l y p i g m e n t e d , and t h e r e f o r e h i g h l y v i s i b l e p r e y i t e m . I t i s a l s o a s l o w e r p r e y t h a n t h e n a u p l i i and c o p e p o d i t e s t h a t h e r r i n g l a r v a e p r e y on i n t h e n a t u r a l e n v i r o n m e n t ( R o s e n t h a l and Hempel, 1970). B o t h t h e v u l n e r a b i l i t y of A r t e m i a and t h e h i g h p r e y d e n s i t i e s i n t h e a q u a r i a may have p r o v i d e d t h e l a r v a e from t h e s m a l l e r eggs w i t h optimum c o n d i t i o n s f o r f e e d i n g and g r o w t h . H a e g e l e and Outram ( 1 9 7 8 ) , i n t h e i r e x p e r i m e n t s w i t h P a c i f i c h e r r i n g l a r v a e , o b t a i n e d t h e h i g h e s t i n i t i a l s u r v i v a l r a t e s w i t h A r t e m i a n a u p l i i , a f a c t w h i c h t h e y a t t r i b u t e d t o t h e h i g h v i s i b i l i t y and low m o b i l i t y of t h e p r e y . R o s e n t h a l and Hempel (1980) a l s o r e c o r d e d t h e b e s t f e e d i n g s u c c e s s of A t l a n t i c h e r r i n g l a r v a e i n a p u r e p l a n k t o n o f A r t e m i a l a r v a e . Use o f n a t u r a l p l a n k t o n by H a e g e l e a n d Outram l e d t o a much h i g h e r i n i t i a l m o r t a l i t y r a t e as t h e l a r v a e l e a r n e d more s l o w l y t o 68 c a p t u r e t h e l e s s v i s i b l e and h i g h l y m o b i l e p r e y . R e p e a t e x p e r i m e n t s were p l a n n e d i n y e a r 2 u s i n g n a t u r a l p l a n k t o n as a f o o d s o u r c e , b u t s u f f i c i e n t p l a n k t o n i n t h e a p p r o p r i a t e s i z e i n t e r v a l was n o t a v a i l a b l e a t t h e r e q u i r e d t i m e . T h e r e f o r e g e n e r a l c o n c l u s i o n s c o n c e r n i n g r e l a t i v e f e e d i n g c a p a b i l i t i e s of d i f f e r e n t s i z e d l a r v a e a r e d i f f i c u l t t o make. I t a p p e a r s t h a t g i v e n optimum c o n d i t i o n s , s m a l l e r l a r v a e f r o m s m a l l e r eggs c a n grow as q u i c k l y or more q u i c k l y t h a n l a r g e r l a r v a e f r o m l a r g e r e ggs, even when f e e d i n g has been c o n s i d e r a b l y d e l a y e d . I n i t i a l f e e d i n g on t h e f i f t e e n t h day f o l l o w i n g f e r t i l i z a t i o n l e d t o a s i g n i f i c a n t l y h i g h e r m o r t a l i t y among l a r v a e f r o m l a r g e r e g g s . F o w l e r (1972) f o u n d s i m i l a r r e s u l t s f o r c h i n o o k s a l m o n . In t h r e e s e p a r a t e e x p e r i m e n t s , m o r t a l i t y i n l a r g e r e gged l a r v a e was h i g h e r t h a n i n s m a l l e r l a r v a e f r o m s m a l l e r eggs f e d on a s t a n d a r d h a t c h e r y d i e t . I n t h i s s t u d y , t h e s m a l l e r l a r v a e had a b s o r b e d a l l o f t h e i r y o l k by t h e f i f t e e n t h day f o l l o w i n g f e r t i l i z a t i o n w h i l e l a r v a e f r o m l a r g e r eggs s t i l l h ad some y o l k r e m a i n i n g . I t seems f e a s i b l e t h a t p r e m a t u r e e x p o s u r e t o f o o d c o u l d l e a d t o le s s , s u c c e s s f u l f e e d i n g i n l a r v a e w i t h i n c o m p l e t e y o l k a b s o r p t i o n t h a n t h a t o b s e r v e d i n l a r v a e w h i c h have a b s o r b e d a l l of t h e i r y o l k . I n t h i s way, t h e l a r v a e w i t h i n c o m p l e t e y o l k a b s o r p t i o n would o b t a i n a l o w e r r e t u r n f o r a g i v e n amount o f e n e r g y expended. T h i s p o s s i b l y e x p l a i n s h i g h e r s u r v i v a l r a t e s o b s e r v e d i n l a r v a e f r o m s m a l l e r eggs w h i c h a r e e x p o s e d t o f o o d a t an e a r l y s t a g e i n d e v e l o p m e n t . I t m i g h t be e x p e c t e d t h a t d i f f e r e n c e s i n e a r l y f e e d i n g a b i l i t y 69 would a l s o show up i n g r o w t h r a t e s . S i n c e t h i s i s n o t t h e c a s e , i t seems l i k e l y t h a t t h e e a r l i e r f e e d i n g a f f e c t s n o t t h e f e e d i n g r a t e and t h e r e f o r e growth r a t e , b ut t h e p r o p o r t i o n of t h e l a r v a e t h a t a c t u a l l y make t h e t r a n s i t i o n from endogenous t o exogenous f e e d i n g . I f t h e l a r v a e i s s u c c e s s f u l i n making t h e t r a n s i t i o n , t h e n f e e d i n g s u c c e s s and g r o w t h r a t e i s s i m i l a r between d i f f e r e n t s i z e d l a r v a e . V a r i a b i l i t y i n t h e s u r v i v a l r a t e s i n t h e o t h e r two f e e d i n g t r e a t m e n t s make i t v e r y d i f f i c u l t t o draw c o n c l u s i o n s , t h o u g h s u r v i v a l r a t e a p p e a r s t o i n c r e a s e w i t h egg s i z e i n l a r v a e f i r s t f e d 17 d a y s f o l l o w i n g f e r t i l i z a t i o n . L a r v a l S u r v i v a l As p r e v i o u s l y s t a t e d , s u r v i v a l and g r o w t h may be a f f e c t e d by (1) s u s c e p t i b i l i t y t o p r e d a t i o n , (2) s t a r v a t i o n t i m e , and (3) f e e d i n g a b i l i t y once f o o d has been l o c a t e d . The d e g r e e t o w h i c h l a r g e r l a r v a e may be more s u c c e s s f u l i n a v o i d i n g p r e d a t i o n t h a n s m a l l e r l a r v a e o f t h e same age was n o t s t u d i e d i n t h i s t h e s i s . The number of p o t e n t i a l p r e d a t o r s o f h e r r i n g l a r v a e i s q u i t e l a r g e and i n c l u d e s o t h e r f i s h s p e c i e s , b o t h a d u l t s and j u v e n i l e s , a s w e l l a s a i n v e r t e b r a t e p l a n k t e r s s u c h as c t e n o p h o r e s , e u p h a u s i i d s , c o p e p o d s , and amphipods. T h e r e i s some e v i d e n c e t h a t m o r t a l i t y r a t e due t o p r e d a t i o n i s d e p e n d e n t on p a r t i c l e s i z e (Ware, 1975). As s i z e i n c r e a s e s , p r e d a t i o n m o r t a l i t y may a l s o d e c r e a s e s i m p l y due t o a d e c l i n e i n t h e number o f p o t e n t i a l p r e d a t o r s . L a r g e r l a r v a e may be s t r o n g e r and s l i g h t l y f a s t e r t h a n s m a l l e r l a r v a e w h i c h w o u l d 70 c o n f e r an a d v a n t a g e a g a i n s t some of t h e s m a l l e r i n v e r t e b r a t e p r e d a t o r s i n t e r m s o f t h e i r a b i l i t y t o s t a y away o r b r e a k f r e e when c a u g h t . L i l l e l u n d and L a s k e r ( 1 9 7 1 ) , w o r k i n g w i t h c o p e p o d p r e d a t o r s , and T h e i l a c k e r and L a s k e r ( 1 9 7 4 ) , w o r k i n g w i t h e u p h a s i i d s , f o u n d t h a t l a r g e r a n c h o v y l a r v a e were c a u g h t and e a t e n l e s s f r e q u e n t l y han s m a l l e r l a r v a e . L a r g e r l a r v a e a r e a l s o c o n s i d e r a b l y more c a p a b l e o f a v o i d i n g p l a n k t o n n e t s (Hempel, 1979). In c o n t r a s t , i t has been d e m o n s t r a t e d t h a t some f i s h p r e d a t o r s may a c t i v e l y s e l e c t t h e l a r g e r o f a g r o u p o f f o o d i t e m s (Ware, 1972). T h e r e f o r e , l a r g e r l a r v a e may be more v u l n e r a b l e t o c e r t a i n p r e d a t o r s . L a r v a e under c o n d i t i o n s where f o o d i s a b u n d a n t q u i c k l y grow t o a p o i n t where i n i t i a l s i z e d i f f e r e n c e s a r e o b s c u r e d . T h e r e f o r e , i f egg s i z e does a f f e c t t h e p r e d a t i o n r a t e e x p e r i e n c e d by t h e l a r v a e , i t i s l i k e l y t o be an e f f e c t o f s h o r t d u r a t i o n . T h i s i s n o t t o s a y t h a t i t may n o t have i m p o r t a n t c o n s e q u e n c e s , however, i t i s n o t p o s s i b l e t o a d d r e s s t h i s p o i n t f u r t h e r w i t h t h e e v i d e n c e a v a i l a b l e t o d a t e . The s e c o n d c o n s i d e r a t i o n i s t h e s t a r v a t i o n t i m e , o r t h e amount o f t i m e t h e l a r v a e has i n w h i c h t o e n c o u n t e r f o o d . L a r v a e f r om l a r g e r eggs do have l o n g e r t i m e s t o s t a r v a t i o n and p r o b a b l y l o n g e r t i m e s t o PNR. P l a n k t o n on w h i c h t h e l a r v a e f e e d may be d i s t r i b u t e d i n t h e s e a a s a u n i f o r m m i x t u r e o r as d i s c r e t e p a t c h e s w h i c h v a r y i n d e n s i t y and d i s t a n c e o f s e p a r a t i o n d e p e n d i n g on b i o l o g i c a l and p h y s i c a l o c e a n o g r a p h i c f a c t o r s . S i n c e t h e l a t t e r p r e y d i s t r i b u t i o n i s most l i k e l y , i t i s p r o b a b l e t h a t t h e l a r v a e ' s e a r l y s u r v i v a l depends upon 71 l o c a t i n g a f o o d p a t c h of s u f f i c i e n t s i z e and d e n s i t y . Many s t u d i e s have shown t h a t a v e r a g e d e n s i t i e s o f f o o d i n t h e s e a a r e not a d e q u a t e t o meet t h e o r e t i c a l r e q u i r e m e n t s o b t a i n e d from m o d e ls o r f r o m l a b o r a t o r y e x p e r i m e n t s . T h i s l e a d s t o t h e h y p o t h e s i s t h a t l a r v a e a r e d e p e n d e n t on s m a l l s c a l e p a t c h i n e s s o f f o o d ( H u n t e r , 1980). L a s k e r (1975) has f o u n d v e r y e x t e n s i v e p a t c h e s of Gymnodinium o f f t h e c o a s t o f C a l i f o r n i a c a p a b l e o f s u s t a i n i n g l a r v a l a n c h o v y . The s t a r v a t i o n of m a r i n e f i s h l a r v a e a f t e r y o l k a b s o r p t i o n i s b e l i e v e d by many t o be one of t h e p r i n c i p l e c a u s e s of l a r v a l f i s h m o r t a l i t y ( T h e i l a c k e r , 1980). I f t h i s i s i n d e e d t h e c a s e , t h e n i t seems l i k e l y t h a t l a r v a e f r o m l a r g e r eggs may have some a d v a n t a g e i n t h a t t h e y have a l o n g e r t i m e i n w h i c h t o e n c o u n t e r f o o d . Once l a r v a e have e n c o u n t e r e d f o o d , t h e r e may a l s o be d i f f e r e n c e s i n t h e f e e d i n g e f f i c i e n c y of l a r v a e f r o m l a r g e and s m a l l e g g s . From r e s u l t s o b t a i n e d i n t h i s s t u d y , s m a l l e r l a r v a e seem as c a p a b l e of f e e d i n g on A r t e m i a n a u p l i i a t h i g h d e n s i t i e s as l a r g e r s i b l i n g s and i n i t i a l s i z e d i f f e r e n c e s q u i c k l y become o b s c u r e d as t h e l a r v a e grow. I t i s not p o s s i b l e t o s a y what m i g h t happen under c o n d i t i o n s o f l o w e r f o o d d e n s i t y o r d i f f e r e n t f o o d i t e m s . L a r g e r l a r v a e a r e l i k e l y t o have a t l e a s t a s l i g h t a d v a n t a g e i n terms o f f e e d i n g . I t f o l l o w s t h a t d u r i n g y e a r s o f h i g h f o o d p r o d u c t o n , w i t h s m a l l between p a t c h d i s t a n c e s and h i g h f o o d d e n s i t i e s , any d i s c r e p a n c i e s between l a r v a e from l a r g e and s m a l l eggs would q u i c k l y d i s a p p e a r and l a r g e r l a r v a e would have l i t t l e s u r v i v a l a d v a n t a g e . In y e a r s o f low f o o d p r o d u c t i o n , o r when spawning i s 72 o u t o f p h a s e w i t h f o o d p r o d u c t i o n , t h e a d v a n t a g e o f l a r g e r l a r v a e f r o m l a r g e r eggs m i g h t become m a g n i f i e d . I f t h i s l i n e o f r e a s o n i n g i s c o r r e c t , t h e n i t may be t h a t s m a l l e r eggs s e r v e as a r e s e r v e and o n l y make s i g n i f i c a n t c o n t r i b u t i o n s t o r e c r u i t m e n t when c o n d i t i o n s f o r l a r v a l s u r v i v a l a r e o p t i m a l a s p o s t u l a t e d by N i k o l s k i i (1963) and Ponomarenko ( 1 9 7 3 ) . On t h e o t h e r hand, i f c o n d i t i o n s a r e v e r y f a v o r a b l e , s m a l l e r l a r v a e from s m a l l e r eggs m i g h t even be a b l e t o f e e d e a r l i e r t h a n l a r g e r l a r v a e due t o e a r l i e r y o l k a b s o r p t i o n and t h u s e x p e r i e n c e h i g h e r s u r v i v a l . T h e r e i s some i n d i c a t i o n t h a t s u c h i s t h e c a s e f r o m t h e r e s u l t s -o b t a i n e d h e r e . I m p l i c a t i o n s f o r F i s h e r i e s Management H j o r t (1926) f i r s t p r o p o s e d what i s now r e f e r e d t o a s t h e ' c r i t i c a l p e r i o d ' c o n c e p t . He b e l i e v e d t h a t t h e a v a i l a b i l i t y o f f o o d a t t h e t i m e o f t r a n s i t i o n f r o m endogenous t o exogenous f e e d i n g d e t e r m i n e d l a r v a l s u r v i v a l and y e a r c l a s s s i z e . May (1974) o f f e r s a good r e v i e w o f t h e c r i t i c a l p e r i o d c o n c e p t . S i n c e H j o r t ' s t i m e t h e c r i t i c a l p e r i o d has come t o mean any p o i n t d u r i n g t h e f i s h ' s l i f e h i s t o r y where t h e p o t e n t i a l e x i s t s f o r a l t e r a t i o n o f y e a r c l a s s s i z e . Most a u t h o r s b e l i e v e t h a t f o r m a r i n e s p e c i e s , t h e most i m p o r t a n t e f f e c t on y e a r c l a s s s i z e o c c u r s when m o r t a l i t y i s h i g h e s t , w h i c h i s v e r y e a r l y i n t h e l a r v a l s t a g e . A c c o r d i n g t o R o s e n t h a l and H e m p e l ( 1 9 7 0 ) , t h e c a u s e s o f i n a d e q u a t e r e c r u i t m e n t and f l u c t u a t i o n s i n y e a r c l a s s s t r e n g t h a r e t o be f o u n d d u r i n g t h e f i r s t y e a r o f l i f e . They a l s o s u g g e s t t h a t s h o r t a g e o f p l a n k t o n i c f o o d d u r i n g an e a r l y 73 c r i t i c a l s t a g e j u s t a f t e r t h e r e s o r p t i o n o f t h e y o l k sac r e s u l t s i n p o o r r e c r u i t m e n t i n h e r r i n g . I t seems r e a s o n a b l e t o c o n s i d e r t h i s e a r l y s t a g e as a t l e a s t one o f t h e p o i n t s where y e a r c l a s s s i z e i s i n f l u e n c e d . G i v e n t h a t egg s i z e i n f l u e n c e s e a r l y s u r v i v a l and g r o w t h , and t h a t e a r l y s u r v i v a l a f f e c t s r e c r u i t m e n t , any c o r r e l a t i o n of egg s i z e w i t h f e m a l e s i z e becomes i m p o r t a n t i n t e r m s o f t h e c o n t r i b u t i o n of d i f f e r e n t s i z e d i n d i v i d u a l s t o t h e s i z e o f t h e y e a r c l a s s . S i n c e t h e e f f e c t o f most f i s h e r i e s i s t o l o w e r t h e a v e r a g e age and s i z e o f i n d i v i d u a l s i n t h e s t o c k , r e c r u i t m e n t may be a f f e c t e d by an o v e r a l l d e c r e a s e i n v i a b i l i t y o f t h e l a r v a e p r o d u c e d , even i f t h e t o t a l q u a n t i t y o f eggs r e m a i n s h i g h . T h i s i d e a has been p r e s e n t e d by a number of a u t h o r s , e s p e c i a l l y i n t h e S o v i e t l i t e r a t u r e ( N i k o l s k i i , 1963; Pomonarenko, 1973), and e l s e w h e r e ( B r i d g e r , 1960, 1961; C u s h i n g and B r i d g e r , 1964; B l a x t e r and Hempel, 1963; S t a n l e y , 1977). The i d e a was l a r g e l y d i s m i s s e d by B l a x t e r and Hempel on t h e b a s i s o f t h e i r e x p e r i m e n t a l r e s u l t s . They f o u n d a maximum i n c r e a s e i n egg s i z e f r o m r e c r u i t s t o o l d e r A t l a n t i c h e r r i n g o f 14% and c o n c l u d e d t h a t d i f f e r e n c e s o f t h i s m a g n i t u d e a r e n o t i m p o r t a n t . They may have r e a c h e d d i f f e r e n t c o n c l u s i o n s , however, i f t h e y had o b s e r v e d l a r g e r egg s i z e d i f f e r e n c e s s u c h as t h o s e seen i n t h i s s t u d y . I t i s u n l i k e l y t h a t t h e e x i s t e n c e o f t h i s phenomenon w i l l be c o n f i r m e d o r d e n i e d by f u r t h e r l a b o r a t o r y e x p e r i m e n t a t i o n . Work t o d a t e has d e m o n s t r a t e d t h a t t h e p o s s i b i l i t y o f an e f f e c t e x i s t s and s h o u l d p e r h a p s be g i v e n c o n s i d e r a t i o n . . The most 74 p r o d u c t i v e d i r e c t i o n i n t e r m s o f f u r t h e r u n c o v e r i n g t h e r e l a t i o n s h i p i s p r o b a b l y t h a t u s e d by a number of i n v e s t i g a t o r s i n t h e p a s t ( B r i d g e r , 1960, 1961; Ponomarenko, 1973) where age o r s i z e c o m p o s i t i o n o f t h e s t o c k i s t a k e n i n t o a c c o u n t as a f a c t o r i n t h e s t o c k r e c r u i t m e n t r e l a t i o n s h i p . In t h i s way i t m i g h t be p o s s i b l e t o d e t e r m i n e t h e e f f e c t of t h e p r o p o r t i o n o f l a r g e r i n d i v i d u a l s i n t h e s t o c k on t h e p r o b a b i l i t y o f t h e p r o d u c t i o n o f a l a r g e y e a r c l a s s . A n o t h e r p o s s i b i l i t y w ould be t o c o n d u c t a s t u d y under more n a t u r a l c o n d i t i o n s s u c h a s B a g e n a l (1969) d i d f o r brown t r o u t . The a p p l i c a t i o n o f t h i s l a t t e r a p p r o a c h t o t h e m a r i n e s i t u a t i o n , however, w o u l d be much more d i f f i c u l t . E c o l o g i c a l R e l a t i o n s h i p s I f s m a l l e r eggs a r e l e s s v i a b l e t h a n l a r g e r e g g s , t h e n why do s m a l l e r f i s h p r o d u c e s m a l l e r e g g s ? A t a g i v e n l e v e l o f r e p r o d u c t i v e e f f o r t , t h e g o n a d a l mass may be d i v i d e d up i n a way s u c h t h a t egg s i z e and f e c u n d i t y a r e i n v e r s e l y r e l a t e d . In o t h e r words, s m a l l e r f i s h c o u l d p r o d u c e l a r g e r eggs a s do t h e o l d e r i n d i v i d u a l s o f t h e s t o c k , but o n l y a t t h e e x p e n s e o f a l o w e r e d f e c u n d i t y . F a c t o r s d e t e r m i n i n g egg s i z e w i t h i n a s p e c i e s a r e l a r g e l y unknown. S v a r d s o n (1949) e x t e n d e d L a c k ' s (1948) i d e a s c o n c e r n i n g l i t t e r s i z e i n b i r d s and mammals t o f i s h . As he p o i n t e d o u t , i f t h e r e were no r e l a t i o n s h i p between egg s i z e and l a r v a l s u r v i v a l , s e l e c t i o n w o u l d f a v o r h i g h e r f e c u n d i t y and s m a l l e r egg s i z e . A mechanism w h i c h c o u n t e r b a l a n c e s t h i s 75 t e n d e n c y t o w a r d s g r e a t e r numbers of s m a l l e r eggs i s n e c e s s a r y . F o r t h i s r e a s o n , S v a r d s o n b e l i e v e d t h a t l a r g e r egg s i z e r e s u l t e d i n i n c r e a s e d l a r v a l s u r v i v a l . S i n c e t h a t t i m e , i n v e s t i g a t o r s have t e n d e d t o r e g a r d h i g h egg numbers as c o m p e n s a t i o n f o r heavy p r e d a t i o n . A t t h e same t i m e , i n d i v i d u a l eggs must be l a r g e enough, t h a t i s have s u f f i c i e n t y o l k , t o g i v e t h e l a r v a e a r e a s o n a b l e c h a n c e o f a v o i d i n g s t a r v a t i o n . S i n c e f e c u n d i t y and egg s i z e a r e n e g a t i v e l y c o r r e l a t e d , t h e o p p o s i n g f o r c e s o f s t a r v a t i o n and p r e d a t i o n a r e t h o u g h t t o o p e r a t e t o g e t h e r t o d e t e r m i n e t h e optimum d i v i s i o n o f t h e r e p r o d u c t i v e p o t e n t i a l i n t e r m s o f s i z e and numbers o f eggs (Hempel and B l a x t e r , 1966; H u n t e r , 1980). T h i s l e a d s d i r e c t l y t o t h e q u e s t i o n as t o why t h e optimum egg s i z e a p p e a r s t o i n c r e a s e w i t h i n c r e a s i n g f i s h s i z e w i t h i n a s p e c i e s . I t i s p o s s i b l e t h a t as t h e gonad w e i g h t i n c r e a s e s , o r t h e amount o f e n e r g y a v a i l a b l e f o r r e p r o d u c t i o n i n c r e a s e s , t h e optimum a l l o c a t i o n i n t e r m s o f egg s i z e m i g h t change s i m p l y due t o t h e r a p i d i n c r e a s e i n f e c u n d i t y . A t some p o i n t , i t seems r e a s o n a b l e t h a t i t become l e s s a d v a n t a g e o u s f o r t h e i n d i v i d u a l t o p r o d u c e more eggs and i n s t e a d t o i n c r e a s e t h e s i z e o r s u r v i v a l v a l u e o f an i n d i v i d u a l e g g . Put a n o t h e r way, optimum egg number and s i z e m i g h t s h i f t s l i g h t l y i n r e s p o n s e t o a v a i l a b l e r e p r o d u c t i v e mass. The optimum d i v i s i o n w ould be t h e one t h a t m a x i m i z e d t h e numbers o f o f f s p r i n g w h i c h r e a c h e d r e p r o d u c t i v e a g e . Even t h o u g h s m a l l e r eggs m i g h t i n d i v i d u a l l y h ave a s l i g h t l y l o w e r p r o b a b i l i t y o f s u r v i v i n g , a g r e a t e r number of eggs of t h i s s m a l l e r s i z e would be p r o d u c e d , a l l o w i n g a h i g h e r m o r t a l i t y r a t e . 77 LITERATURE CITED A l d e r d i c e , D.F. and F . P . J . V e l s o n . 1971. Some e f f e c t s o f s a l i n i t y and t e m p e r a t u r e on e a r l y d e v e l o p m e n t o f . P a c i f i c h e r r i n g ( C l u p e a p a l l a s i ) . J . F i s h . Res. B o a r d Can. 28: 1545-1562. A l d e r d i c e , D.F. and F . P . J . V e l s o n . 1978. E f f e c t s o f s h o r t t e r m s t o r a g e o f gametes on f e r t i l i z a t i o n of P a c i f i c h e r r i n g e g g s . H e l g o l . W i s s . M e e r e s . 31:485-498. A n i s i m o v a , I.M. 1956. Some a s p e c t s o f t h e i n c u b a t i o n o f c a r p spawn i n r e l a t i o n t o age o f t h e p a r e n t s . I z v . Mosk. R y b n o v o d n o m e l i o r . O p y t n . S t a n t s i i . J_. A n o k h i n a , L . E . 1971. M a t u r a t i o n o f B a l t i c and W h i t e Sea h e r r i n g w i t h s p e c i a l r e f e r e n c e t o v a r i a t i o n s i n f e c u n d i t y and egg d i a m e t e r . Rapp. P.-v. Cons. Reun. I n t . E x p l o r . Mer. 160: 12-17. B a g e n a l , T.B. 1969. R e l a t i o n s h i p between egg s i z e and f r y s u r v i v a l i n brown t r o u t , Salmo t r u t t a L. J . F i s h . B i o l . 1: 349-353. B a g e n a l , T.B. 1971. The i n t e r r e l a t i o n of t h e s i z e o f f i s h e g g s , t h e d a t e o f spawning, and t h e p r o d u c t i o n c y c l e ( M a r i n e and f r e s h w a t e r ) . J . F i s h . B i o l . 3:207-209. B l a x t e r , J.H.S. The f e e d i n g of h e r r i n g l a r v a e and t h e i r e c o l o g y i n r e l a t i o n t o f e e d i n g . R e p t . C a l i f . Coop. Oceanog. F i s h e r i e s I n v e s t . 10:79-88. B l a x t e r , J.H.S. 1969. D e v e l o p m e n t : eggs and l a r v a e . I_n W.S. Hoar and D . J . R a n d a l l [ e d s ] . F i s h P h y s i o l o g y 3:177-252. Academic P r e s s , N.Y. B l a x t e r , J.H.S. and K.F. E h r l i c h . 1974. Changes i n b e h a v i o r d u r i n g s t a r v a t i o n o f h e r r i n g and p l a i c e l a r v a e . In J.H.S. B l a x t e r [ e d ] . The E a r l y L i f e H i s t o r y o f F i s h . S p r i n g e r -V e r l a g . 78 B l a x t e r , J.H.S. and G. Hempel. 1963. The i n f l u e n c e o f egg s i z e on h e r r i n g l a r v a e ( C l u p e a h a r e n g u s L.) J . Con. Perm. I n t . E x p l o r . Mer. 28:211-230. B l a x t e r , J.H.S. and G. Hempel. 1966. U t i l i z a t i o n of y o l k ^ b y h e r r i n g l a r v a e . J . Mar. B i o l . A s s o c . U.K. 46:219-234. B l a x t e r , J.H.S. and M.E. S t a i n e s . 1971. Fo o d s e a r c h i n g p o t e n t i a l i n m a r i n e f i s h l a r v a e . I_n D . J . C r i s p [ e d ] F o u r t h E u r o p e a n M a r i n e B i o l o g y Symposium. U n i v e r s i t y P r e s s , C a m b r i d g e . B r i d g e r , J . P . 1960. On t h e r e l a t i o n s h i p between s t o c k , l a r v a e , and r e c r u i t s i n t h e "Downs" h e r r i n g . C o n s. I n t . E x p l o r . Mer., H e r r i n g Comm. Pap. 159,9pp. B r i d g e r , J . P . 1961. On f e c u n d i t y and l a r v a l abundance o f Downs h e r r i n g . F i s h e r y I n v e s t , S e r . 2: 23(3) . B u l k l e y , R.V. 1967. F e c u n d i t y o f s t e e l h e a d t r o u t , Salmo g a i r d n e r i , f r o m A l s e a r i v e r , O r e g o n . J . F i s h . R es. B o a r d Can. 24:917-926. C i e c h o m s k i , J.D. 1966. Development o f t h e l a r v a e and v a r i a t i o n s i n t h e s i z e o f t h e eggs o f A r g e n t i n e a n c h o v y , E n g r a u l i s a n c h o i t a Hubbs and M a r i n i . J . Cons. Perm. I n t . E x p l o r . Mer. 30:281-290. C u s h i n g , D.H. and J . P . B r i d g e r . 1964. The p r e s e n t s t a t e o f t h e B r i d g e r h y p o t h e s i s r e l a t i n g l a r v a l m o r t a l i t y o f h e r r i n g t o r e c r u i t m e n t . I n t . Coun. E x p l o r . Sea, CM 1964, Doc. No. 99, 6pp. D e M a r t i n i , E . E . and R.K. F o u n t a i n . 1980. O v a r i a n c y c l i n g f r e q u e n c y and b a t c h f e c u n d i t y i n t h e q u e e n f i s h , S e r i p h u s p o l i t u s : a t t r i b u t e s r e p r e s e n t a t i v e o f s e r i a l s pawning f i s h e s . F i s h . B u l l . 79:547-555. E h r l i c h , K.F. 1974. C h e m i c a l c h a n g e s d u r i n g g r o w t h and s t a r v a t i o n o f h e r r i n g l a r v a e , p.301-323. I_n J.H.S. B l a x t e r [ e d ] The E a r l y L i f e H i s t o r y o f F i s h . S p r i n g e r - V e r l a g , N.Y. 79 F l u c h t e r , J . and T . J . P a n d i a n . 1968. R ate and e f f i c i e n c y o f y o l k u t i l i z a t i o n i n d e v e l o p i n g eggs of t h e s o l e , S o l e a s o l e a . H e l g o l . w i s s . M e e r e s . 18:53-60. F o w l e r , L.G. 1972. Growth and m o r t a l i t y o f f i n g e r l i n g c h i n o o k salmon as a f f e c t e d by egg s i z e . P r o g . F i s h . C u l t . 34:66-9. G a l l , G.A.E. 1974. I n f l u e n c e o f s i z e of eggs and age of f e m a l e on h a t c h a b i l i t y and g r o w t h i n r a inbow t r o u t . C a l i f . F i s h Game 60:26-35. Grauman, G.B. 1973. I n v e s t i g a t i o n o f f a c t o r s i n f l u e n c i n g f l u c t u a t i o n s i n abundance of B a l t i c c o d . Rapp. P.-v. C o n s. Reun. I n t . E x p l o r . Mer. 164:186-198. H a e g e l e , C.W. and D.N. Outram. 1978. The e f f e c t s of d i e t and r a t i o n on t h e g r o w t h and s u r v i v a l of P a c i f i c h e r r i n g ( C l u p e a h a r e n g u s p a l l a s i ) l a r v a e . Canada, F i s h . . Mar. S e r v . T e c h . R e p t . 767. H a r d y , C . J . 1967. The f e c u n d i t y o f brown t r o u t f r o m s i x C a n t e r b u r y s t r e a m s . New Z e a l a n d D e p t . F i s h e r i e s T e c h . R e p t . 22:1-14. Hay, D. 1982. F i x a t i o n s h r i n k a g e o f h e r r i n g l a r v a e : e f f e c t s o f s a l i n i t y , f o r m a l i n c o n c e n t r a t i o n , and o t h e r f a c t o r s . Can. J . F i s h . A q u a t . S c i . 39:1138-1143. Hempel, G. 1979. E a r l y L i f e H i s t o r y o f M a r i n e F i s h ; t h e Egg S t a g e . U n i v e r s i t y o f W a s h i n g t o n Sea G r a n t P u b l i c a t i o n . Hempel, G. and J.H.S. B l a x t e r . 1967. Egg w e i g h t i n A t l a n t i c h e r r i n g . J . Con... Perm. I n t . E x p l o r . Mer. 31 :1 70-1 95. H j o r t , J . 1926. F l u c t u a t i o n s i n t h e y e a r c l a s s e s o f i m p o r t a n t f o o d f i s h e s . J . Con. Perm. I n t . E x p l o r . Mer. _1_:5-38. H o w e l l , W.H. 1980. T e m p e r a t u r e e f f e c t s on g r o w t h and y o l k u t i l i z a t i o n i n t h e y e l l o w t a i l f l o u n d e r , Limanda f e r r u g i n e a , y o l k - s a c l a r v a e . F i s h . B u l l . 78:731-740. 80 Hubbs, C , M.M.- S t e v e n s o n , and A.E. Peden. 1968. F e c u n d i t y and egg s i z e i n two c e n t r a l T e x a s d a r t e r p o p u l a t i o n s . S o u t h w e s t e r n N a t u r a l i s t 13:301-324. H u l a t a , G., R. Moav, and G. W o h l f a r t h . 1974. The r e l a t i o n s h i p of gonad s i z e and egg s i z e t o w e i g h t and age i n t h e E u r o p e a n and C h i n e s e r a c e s o f t h e common c a r p , C y p r i n u s c a r p i o L. J . F i s h . B i o l . 6:745-758. H u l a t a , G., R. Moav, and G. W o h l f a r t h . 1976. The e f f e c t s o f m a t e r n a l s i z e , r e l a t i v e h a t c h i n g t i m e and d e n s i t y o f s t o c k on g r o w t h r a t e o f f r y i n t h e E u r o p e a n and C h i n e s e r a c e s o f t h e common c a r p . J . F i s h . B i o l . 9:499-513. H u n t e r , J.R. 1972. Swimming and f e e d i n g b e h a v i o r o f l a r v a l a n c h o v y , E n g r a u l i s mordax. U.S. F i s h . B u l l . 70:821-838. H u n t e r , J.R. 1980. The f e e d i n g b e h a v i o r and e c o l o g y o f m a r i n e f i s h l a r v a e . I_n J . E . B a r d a c h [ e d ] P r o c e e d i n g s o f t h e C o n f e r e n c e on t h e P h y s i o l o g i c a l and B e h a v i o r a l M a n i p u l a t i o n o f Food F i s h a s P r o d u c t i o n and Management T o o l s . I n t e r n a t i o n a l C e n t e r f o r L i v i n g A q u a t i c R e s o u r c e s Management, M a n i l l a . J o n e s , B.C. 1972. E f f e c t o f i n t e r t i d a l e x p o s u r e on s u r v i v a l and embyonic d e v e l o p m e n t o f P a c i f i c h e r r i n g spawn. J . F i s h . Res. B o a r d Can. 29:1119-1124. K r i v o b o k , M.N., O.I. T a r k o v s k a y a , and A.A. K a r a s i k o v a . 1971. Q u a l i t y o f eggs o f B a l t i c h e r r i n g of v a r i o u s s i z e s , age g r o u p s and f e c u n d i t y . F i s h . Res. B o a r d Can. T r a n s . S e r . No.1628. L a c k , D. 1948. The s i g n i f i c a n c e o f l i t t e r s i z e . J . Anim. E c o l . 17:45-50. L a s k e r , R. 1962. E f f i c i e n c y and r a t e of y o l k u t i l i z a t i o n by d e v e l o p i n g embryos and l a r v a e o f t h e P a c i f i c s a r d i n e , S a r d i n o p s c a e r u l a ( G i r a r d ) . J . F i s h . R es. B o a r d Can. 19: 867-875. 81 L a s k e r , R. 1975. F i e l d c r i t e r i a f o r s u r v i v a l of a n c h o v y l a r v a e : t h e r e l a t i o n between i n s h o r e c h l o r o p h y l l maximum l a y e r s and s u c c e s s f u l f i r s t f e e d i n g . F i s h . B u l l . , U.S. 73:453-462. L a u r e n c e , G.C. 1969. The e n e r g y e x p e n d i t u r e o f l a r g e m o u t h b a s s , M i c r o p t e r u s s a l m o i d e s , d u r i n g y o l k a b s o r p t i o n . T r a n s . Am. F i s h . S o c . 98:398-405. L i l l e l u n d , K. and R. L a s k e r . 1971. L a b o r a t o r y p r e d a t i o n by m a r i n e c o p e p o d s on f i s h l a r v a e . F i s h . B u l l . , U.S. 69:655-667. M a r l i a v e , J.B. 1975. The b e h a v i o r a l t r a n s f o r m a t i o n f r o m t h e p l a n k t o n i c l a r v a l s t a g e o f some m a r i n e f i s h e s r e a r e d i n t h e l a b o r a t o r y . Ph.D. T h e s i s , D e p a r t m e n t o f Z o o l o g y , U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r , B r i t i s h C o l u m b i a . May, R.C. 1974. L a r v a l m o r t a l i t y i n m a r i n e f i s h e s and t h e c r i t i c a l p e r i o d c o n c e p t . I_n J.H.S. B l a x t e r [ e d ] The E a r l y L i f e H i s t o r y o f F i s h . S p r i n g e r - V e r l a g , N.Y., New Y o r k . N i k o l s k i i , G.V. 1963. The e c o l o g y of F i s h e s . Academic P r e s s . O o s t h u i z e n , E . and N. Daan. 1974. Egg f e c u n d i t y and m a t u r i t y o f N o r t h Sea c o d , Gadus morhua. N e t h e r . J . Sea Res. 8:378-397. P a r r i s h , B.B. and A. S a v i l l e . 1965. The b i o l o g y of N.E. A t l a n t i c h e r r i n g p o p u l a t i o n s . Oceanog. Mar. B i o l . Rev. 3:323-373. P e t e r s , H.M. 1963. E i z a h l , E i g w i c h t , und G e l e g e e n t w i c k l u n g i n d e r g a t t u n g T i l a p i a ( C i c h l i d a e , T e l e o s t e i ) . I n t e r n . Rev. Ges. H y d r o b i o l . 48:547-576. Ponomarenko, Y.P. 1973. On a p r o b a b l e r e l a t i o n between age c o m p o s i t i o n o f spawning s t o c k and abundance o f t h e y e a r c l a s s e s o f c o d i n t h e B a r e n t s S e a . Rapp. P.-v. Cons. Reun. E x p l o r . Mer. 164:186-198. 82 Pope, J.A., D.H. M i l l s , and W.M. S h e a r e r . 1961. The f e c u n d i t y of A t l a n t i c salmon (Salmo s a l a r L i n n . ) . F r e s h w a t e r Salmon F i s h e r i e s Res., S c o t l a n d 26:1-12. R i c k e r , W.E. 1973. L i n e a r r e g r e s s i o n i n f i s h e r y r e s e a r c h . J . F i s h . R e s . B o a r d Can. 30:409-439. R o s e n t h a l , H. and G. Hempel. 1970. E x p e r i m e n t a l s t u d i e s i n f e e d i n g and f o o d r e q u i r e m e n t s o f h e r r i n g l a r v a e ( C l u p e a h a r e n g u s L.) I_n J.H. S t e e l e [ e d ] M a r i n e Food C h a i n s , U n i v . C a l i f . P r e s s , B e r k e l e y , C a l i f o r n i a . R o u n s e f e l l , G.A. 1957. F e c u n d i t y of N o r t h A m e r i c a n s a l m o n i d a e . F i s h . B u l l . , U.S. 57:451-468. S c h o p k a , S.A. 1971. V e r g l e i c h e n d e u n t e r s u c h u n g e n z u r f o r t p f l a n z u n g s r a t e b e i h e r i n g s und k a b e l j a u p o p u l a i o n e n (C. h a r e n g u s L. und Gadus morhua L . ) . B e r . d t . w i s s . Komm. M e e r e s f o r s c h 22:31-79. S c o t t , D.P. 1962. E f f e c t o f f o o d q u a n t i t y on f e c u n d i t y of t h e r a i n b o w t r o u t , Salmo g a i r d n e r i . J . F i s h . R e s . B o a r d Can. 19:717-724. S n e d e c o r , G.W. and W.G. C o c h r a n . 1967. S t a t i s t i c a l M ethods, 6 t h ed. Iowa S t a t e U n i v e r s i t y P r e s s , Iowa. S h e l b o u r n e , J . E . 1957. The f e e d i n g and c o n d i t i o n o f p l a c e l a r v a e i n good and bad p l a n k t o n p a t c h e s . J . Mar. B i o l . A s s . U.K. 36:539-552. S o l e m d a l , P. 1967. The e f f e c t o f s a l i n i t y on b u o y a n c y , s i z e , and d e v e l o p m e n t of f l o u n d e r e g g s . S a r s i a 29:431-442. S t a n l e y , R.D. 1977. The e f f e c t o f egg s i z e on s i z e and v i a b i l i t y o f newly h a t c h e d medaka ( O r y z i a s l a t i p e s ) and s u r f s m e l t (Hypomesus p r e t i o s u s p r e t i o s u s ) . M.Sc. T h e s i s , D e partment o f Z o o l o g y , U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r , B r i t i s h C o l u m b i a . 83 S v a r d s o n , G. 1949. N a t u r a l s e l e c t i o n and egg number i n f i s h . Rep. I n s t . F r e s h w a t . Res. D r o t t n i n g h o l m 29:115-122. Templeman, W. 1944. The l i f e h i s t o r y of t h e s p u r d o g f i s h , S q u a l u s a c a n t h u s , and t h e v i t a m i n A v a l u e s o f d o g f i s h l i v e r o i l . R es. B u l l . D i v . F i s h e r y R e s o u r c e s , N e w f o u n d l a n d 15:1-102. T h e i l a c k e r , G.H. 1980. E f f e c t o f f e e d i n g h i s t o r y and egg s i z e on t h e m o r p h o l o g y of j a c k m a c k e r e l , T r a c h u r u s s y m m e t r i c u s , l a r v a e . Rapp. P.-v. Reun. Cons. I n t . E x p l o r . Mer. 178:432-440. T h e i l a c k e r , G.H., and K. D o r s e y . 1980. L a r v a l f i s h d i v e r s i t y , a summary o f l a b o r a t o r y and f i e l d r e s e a r c h . FAO, I n t e r g o v e r n m e n t a l O c e a n o g r a p h i c Commision, Workshop R e p o r t No. 28. T h e i l a c k e r , G.H., and R. L a s k e r . 1974. L a b o r a t o r y s t u d i e s o f p r e d a t i o n by e u p h a u s i i d s h r i m p s on f i s h l a r v a e . Ln J.H.S. B l a x t e r [ ed] The E a r l y L i f e H i s t o r y o f F i s h , p.287-299. S p r i n g e r - V e r l a g , B e r l . Toom, M.M. 1958. E x p e r i m e n t s i n t h e i n c u b a t i o n o f B a l t i c h e r r i n g e g g s . T r u d y VNIRO 34:19-29. Ware, D.M. 1972. P r e d a t i o n s by r a i n b o w t r o u t (Salmo g a i r d n e r i ) : t h e i n f l u e n c e o f h u n g e r , p r e y d e n s i t y , and p r e y s i z e . J . F i s h . R es. B o a r d Can. 29:1193-1201. Ware, D.M. 1975. R e l a t i o n between egg s i z e , g r o w t h , and n a t u r a l m o r t a l i t y o f l a r v a l f i s h . J . F i s h . R es. B o a r d Can. 32: 2503-2512. Ware, D.M. 1977. Spawning t i m e and egg s i z e o f A t l a n t i c m a c k e r e l , Scomber scombrus, i n r e l a t i o n t o t h e p l a n k t o n . J . F i s h . Res. B o a r d Can. 34:2308-2315. Werner, R.G. and J.H.S. B l a x t e r . 1980. Growth and s u r v i v a l o f l a r v a l h e r r i n g ( C l u p e a h a r e n g u s ) i n r e l a t i o n t o p r e y d e n s i t y . Can. J . F i s h . A q u a t . S c i . 37:1063-1069.
Thesis/Dissertation
eng
Zoology
Vancouver : University of British Columbia Library
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
Graduate
Egg size variation in Pacific herring, Clupea harengus pallasi (Valenciennes), and its effects on larval growth and survival
Text