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The influence of temperature, salinity, and dissolved oxygen on juvenile salmon distributions in a nearshore… Mesa, Kathryn A. 1985

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THE INFLUENCE OF TEMPERATURE, SALINITY, AND DISSOLVED OXYGEN ON JUVENILE SALMON DISTRIBUTIONS IN A NEARSHORE ESTUARINE ENVIRONMENT by KATHRYN A. MESA B . S c , U n i v . of M a n i t o b a , 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA F e b r u a r y 1985 © K a t h r y n A. Mesa, 1985 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of ~EZOO\OCJ y  The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date A p l S /WVS i i ABSTRACT T h i s study examines the e f f e c t s of a low oxygen environment, i n c o n c e r t with f l u c t u a t i n g temperature and s a l i n i t y c o n d i t i o n s , on the nearshore depth d i s t r i b u t i o n s (0-1 m) and f l o o d t i d e movements of j u v e n i l e chinook (Oncorhynchus  tshawytscha) and chum (O. keta) salmon. Comparisons are made between an u n p o l l u t e d and a sewage p o l l u t e d e s t u a r i n e i n t e r t i d a l f l a t i n the F r a s e r R i v e r e s t u a r y , B r i t i s h Columbia, the p o l l u t e d area being c h a r a c t e r i z e d by the r e g u l a r occurrence of low d i s s o l v e d oxygen l e v e l s . R e s u l t s are based on 380 beach seine samples taken between A p r i l and June of 1984. In g e n e r a l , chum and chinook salmon of i n c r e a s i n g l e n g t h were captured i n i n c r e a s i n g depths, though t h i s p a t t e r n was m o d i f i e d by seasonal changes i n water temperature. Low d i s s o l v e d oxygen c o n d i t i o n s i n deeper waters may have been r e s p o n s i b l e f o r the presence of l a r g e r , and o f t e n s l u g g i s h l y swimming f i s h i n h i g h e r oxygenated s u r f a c e water l a y e r s or i n shallow waters near the shore. In both areas, the r i s k of a e r i a l p r e d a t i o n was h i g h . On a f l o o d t i d e , the l i k e l i h o o d of c a p t u r i n g a chinook salmon was reduced as temperatures i n c r e a s e d and oxygen l e v e l s ' decreased. A combination of avoidance behaviour and a r e g u l a r i t y i n the movement p a t t e r n s of chinook onto the study area i n the l a t e r stages of the f l o o d t i d e may account f o r t h e i r r a r e occurrence i n low oxygen c o n c e n t r a t i o n s (<6 mg/1) and high temperatures (>20 ° C ) . F i s h m o r t a l i t i e s were most l i k e l y to occur on the ebb t i d e when f i s h were f o r c e d i n t o waters of low i i i oxygen content by the drainage p a t t e r n s c h a r a c t e r i s t i c of the p o l l u t e d study a r e a . Though wide ranges i n s a l i n i t y were recorded on both t i d a l f l a t s , t h i s f a c t o r was not s t r o n g l y c o r r e l a t e d to Chinook d i s t r i b u t i o n s . However, s i g n i f i c a n t l y higher s a l i n i t y l e v e l s i n the u n p o l l u t e d area may account f o r the g r e a t e r numbers of chum salmon captured t h e r e . An understanding of the i n f l u e n c e of e s t u a r i n e water q u a l i t y c o n d i t i o n s on the d i s t r i b u t i o n of j u v e n i l e salmonids may a s s i s t i n the i d e n t i f i c a t i o n of s i g n i f i c a n t sources of m o r t a l i t y i n t h e i r e a r l y marine l i f e . T h i s knowledge i s p a r t i c u l a r l y important i n the e v a l u a t i o n of water q u a l i t y changes as caused by human a c t i v i t y . i v TABLE OF CONTENTS ABSTRACT i i LIST OF TABLES v i LIST OF FIGURES v i i i ACKNOWLEDGEMENTS X INTRODUCTION 1 D e s c r i p t i o n of the study s i t e 6 GENERAL METHODS 12 S t a t i s t i c a l a n a l y s i s 17 E n v i r o n m e n t a l parameters 17 Presence/absence a n a l y s i s 17 RESULTS 21 E n v i r o n m e n t a l parameters 21 Temperature 21 S a l i n i t y 28 D i s s o l v e d oxygen 35 F i s h c a t c h 45 Depth d i s t r i b u t i o n s 48 Temporal d i s t r i b u t i o n s 58 Presence/absence r e s u l t s 60 Chinook salmon 64 May 64 June 72 Chum salmon 85 May 85 Other s p e c i e s 91 O b s e r v a t i o n s on f i s h s t r e s s and b i r d p r e d a t i o n 91 DISCUSSION 97 Depth d i s t r i b u t i o n s 97 Temperature 100 D i s s o l v e d oxygen 101 G e n e r a l i n f l u e n c e s of water q u a l i t y on f i s h presence..105 D i s s o l v e d oxygen and temperature 107 Temperature 110 S a l i n i t y 112 D i s t r i b u t i o n of f i s h i n the study a r e a 113 Temporal movements 116 Summary 118 R e f e r e n c e s C i t e d 122 APPENDIX 1. A s s o c i a t i o n of p h y s i c a l measurements w i t h s e i n e h a u l s •. 129 APPENDIX 2. Net performance t e s t : two person v e r s u s one person beach s e i n i n g 130 APPENDIX 3. A n a l y s i s of v a r i a n c e r e s u l t s f o r t e m p e r a t u r e , s a l i n i t y and oxygen 132 APPENDIX 4. Water q u a l i t y v a l u e s a s s o c i a t e d w i t h s t a r r y f l o u n d e r s , arrow g o b i e s , and P a c i f i c s t a g h o r n s c u l p i n s .135 LIST OF TABLES Ta b l e 1. D e s c r i p t i o n of samp l i n g s t a t i o n s 10 T a b l e I I . S p e c i e s l i s t 46 T a b l e I I I . T o t a l numbers c a p t u r e d and CPUE of s a l m o n i d s p e c i e s 47 T a b l e IV. Numbers of salmon i n each l e n g t h c a t e g o r y and depth f o r a l l months and s t a t i o n s combined 48 Ta b l e V. Numbers of chi n o o k and chum salmon i n each l e n g t h c a t e g o r y and depth ( p o l l u t e d and u n p o l l u t e d a r e a ) 51 T a b l e V I . Numbers of chinook and chum salmon i n each l e n g t h c a t e g o r y f o r each month 52 Ta b l e V I I . Depth d i s t r i b u t i o n s of common s p e c i e s 57 T a b l e V I I I . Mean c a p t u r e t i m e s of c h i n o o k and chum salmon 61 Tab l e IX. L o g i s t i c r e g r e s s i o n r e s u l t s f o r presence/absence a n a l y s i s of c h i n o o k and chum salmon.. 62 T a b l e X. Q u a l i t a t i v e summary of l o g i s t i c r e g r e s s i o n r e s u l t s 63 T a b l e X I . Maximum and minimum water q u a l i t y v a l u e s a s s o c i a t e d w i t h the presence of chum and chinook salmon i n the p o l l u t e d and u n p o l l u t e d a r e a s 65 T a b l e X I I . F r e q u e n c i e s of temperature/oxygen c o m b i n a t i o n s o c c u r r i n g i n May 69 Ta b l e X I I I . Mean p e r c e n t a g e a i r s a t u r a t i o n v a l u e s and mean s a l i n i t i e s a s s o c i a t e d w i t h temperature/oxygen c o m b i n a t i o n s o c c u r r i n g i n May 71 Ta b l e XIV. F r e q u e n c i e s of temperature/oxygen c o m b i n a t i o n s o c c u r r i n g i n June.... 84 v i i T a b l e XV. Mean percentage a i r s a t u r a t i o n v a l u e s and mean s a l i n i t i e s a s s o c i a t e d w i t h temperature/oxygen c o m b i n a t i o n s o c c u r r i n g i n May 86 Tab l e XVI. Water q u a l i t y measurements from S t a t i o n 1, May 1984 95 LIST OF FIGURES F i g u r e 1. L o c a t i o n of st u d y a r e a 3 F i g u r e 2. L o c a t i o n of s a m p l i n g s t a t i o n s a l o n g Iona j e t t y 7 F i g u r e 3. I l l u s t r a t i o n of the 3 s a m p l i n g depths 13 F i g u r e 4. Mean monthly t e m p e r a t u r e s a t each s t a t i o n 22 F i g u r e 5. Maximum and minimum t e m p e r a t u r e s r e c o r d e d on each sample day a t each s t a t i o n 24 F i g u r e 6. Temperatures r e c o r d e d from 3 sample depths on an ebb and f l o o d t i d e , J u l y 24 26 F i g u r e 7. Mean monthly s a l i n i t i e s a t each s t a t i o n 29 F i g u r e 8. Maximum and minimum s a l i n i t y v a l u e s r e c o r d e d on each sample day a t each s t a t i o n 31 F i g u r e 9. Example of s a l i n i t y changes on a d a i l y f l o o d c y c l e a t s t a t i o n s 3 and 4 i n June 33 F i g u r e 10. Mean monthly s a l i n i t i e s a t each s t a t i o n 36 F i g u r e 11. Maximum and minimum d i s s o l v e d oxygen l e v e l s r e c o r d e d on each sample day a t each s t a t i o n 38 F i g u r e 12. Example of r i s e i n oxygen l e v e l s on a f l o o d t i d e a t the p o l l u t e d s t a t i o n s 40 F i g u r e 13. Example of f a l l and r i s e of oxygen l e v e l s on an ebb and f l o o d t i d e a t the p o l l u t e d s t a t i o n s 42 F i g u r e 14. Mean f o r k l e n g t h s of p i n k , chum and chinook salmon found i n each sample d e p t h 49 F i g u r e 15. D i s s o l v e d oxygen c o n c e n t r a t i o n s and c o r r e s p o n d i n g depth d i s t r i b u t i o n of sockeye salmon a t s t a t i o n 1 53 F i g u r e 16. Chinook salmon c a p t u r e s on a s i n g l e f l o o d t i d e ix c y c l e 58 F i g u r e 17. Temperature/oxygen p r o b a b i l i t y s u r f a c e f o r May (depth 3, p o l l u t e d s i d e of the j e t t y ) 67 F i g u r e 18. Temperature/oxygen p r o b a b i l i t y s u r f a c e f o r May (depth 3, u n p o l l u t e d s i d e of the j e t t y ) 73 F i g u r e 19. Captures of chinook salmon i n r e l a t i o n to s a l i n i t y values recorded i n the p o l l u t e d and u n p o l l u t e d areas i n May 75 F i g u r e 20. Histogram of s a l i n i t y l e v e l s recorded i n June and the p r o b a b i l i t y of a chinook salmon o c c u r r i n g i n each l e v e l 78 F i g u r e 21. Histogram of s a l i n i t y v a l u e s recorded i n the p o l l u t e d and u n p o l l u t e d areas i n May 80 F i g u r e 22. Temperature/oxygen p r o b a b i l i t y s u r f a c e f o r June (depth 3, u n p o l l u t e d s i d e of the j e t t y 82 F i g u r e 23. Histogram of oxygen v a l u e s recorded i n May and the p r o b a b i l i t y of a chum salmon o c c u r r i n g i n each l e v e l 87 F i g u r e 24. T o t a l numbers of chum salmon captured i n r e l a t i o n to d i s s o l v e d oxygen c o n c e n t r a t i o n s 89 F i g u r e 25. Captures of chum salmon i n r e l a t i o n t o s a l i n i t y l e v e l s recorded i n the p o l l u t e d and u n p o l l u t e d areas i n May 92 X ACKNOWLEDGEMENTS I would l i k e t o thank the members of my committee, Dr. Linds-ey, Dr. B i r t w e l l , and Dr. N o r t h c o t e , f o r t h e i r guidance and comments on my t h e s i s . My deepest a p p r e c i a t i o n goes t o Helene Crepeau f o r h e l p i n g me wade t h r o u g h the s t a t i s t i c a l mire of my r e s u l t s and t o a l l members of the B i o - S c i e n c e s Data Center f o r t h e i r a s s i s t a n c e and encouragement. S p e c i a l thanks go t o the s t a f f a t the Iona I s l a n d Sewage Treatment P l a n t f o r t h e i r c o o p e r a t i o n and c o n c e r n f o r my s a f e t y , t o my f r i e n d s a t the Canadian C o a s t g u a r d H o v e r c r a f t s t a t i o n f o r c o n v e y i n g me t o my study s i t e i n s t y l e , t o K e l l y W i l l e t , Grant Pogson, A l y r e C h i a s s o n , and Margaret Mesa f o r t h e i r a s s i s t a n c e w i t h f i e l d work, and t o C h r i s Foote f o r the l o a n of h i s n e t . A l s o , Grant Pogson's a s s i s t a n c e w i t h the t h e s i s ' i l l u s t r a t i o n s . w a s g r e a t l y a p p r e c i a t e d . The monetary support of NSERC, the Anne V a l l e e e c o l o g i c a l fund, Dr. L i n d s e y , and the 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 i s g r a t e f u l l y acknowledged. 1 INTRODUCTION Many s t u d i e s on s a l m o n i d use of e s t u a r i n e a r e a s have been s t i m u l a t e d by the p o s s i b i l i t y t h a t j u v e n i l e P a c i f i c salmon ( Oncorhynchus) may s u f f e r heavy m o r t a l i t i e s i n t h e i r e a r l y marine l i f e ( P a r k e r 1962). Research on j u v e n i l e chum (0. keta) and chinook salmon (0. t s h a w y t s c h a ) i n the i n s h o r e a r e a s of the F r a s e r R i v e r e s t u a r y i n B r i t i s h Columbia ( i n c l u d i n g marsh a r e a s , t i d a l c h a n n e l s , t i d a l f l a t s and low t i d e r e f u g e s ) have f o c u s e d p r i m a r i l y on the food h a b i t s and s h o r t term abundances of these two s p e c i e s (Dunford 1975, Levy et a l . 1979, Levy and N o r t h c o t e 1982, Gordon and L e v i n g s 1984). A l t h o u g h the p h y s i c a l v a r i a b i l i t y of e s t u a r i n e environments (Kinne 1967), and n e a r s h o r e i n t e r t i d a l a r e a s i n p a r t i c u l a r (Davenport 1982) i s w e l l known, t h e r e i s l i t t l e i n f o r m a t i o n a v a i l a b l e on • how salmonids respond t o c h a n g i n g water q u a l i t y c o n d i t i o n s i n n a t u r a l s i t u a t i o n s . Such f l u c t u a t i o n s may o f t e n put c o n s t r a i n t s on the h a b i t a t s a v a i l a b l e t o f i s h f o r purposes of f e e d i n g and p r e d a t o r a v o i d a n c e ( N o r t h c o t e 1978). The responses of j u v e n i l e s a l m o n i d s t o v a r i a t i o n s i n temperature ( B r e t t 1952), s a l i n i t y (Houston 1957, Baggerman 1960, M c l n e r n e y 1964) and d i s s o l v e d oxygen (Whitmore et a l . 1960, Hoglund 1961, Warren et a l . 1973) have been examined i n l a b o r a t o r y s i t u a t i o n s and i t i s o b v i o u s t h a t t h e s e f a c t o r s can p l a y an i m p o r t a n t r o l e i n i n f l u e n c i n g t h e i r movements, d i s t r i b u t i o n s , abundances and s u r v i v a l i n the n a t u r a l environment. A few f i e l d s t u d i e s have i n d i c a t e d t h a t j u v e n i l e salmon d i s t r i b u t i o n s or abundances a r e c o r r e l a t e d t o temperature 2 and/or s a l i n i t y (eg. Mason 1974, B i r t w e l l 1977, Healey 1980, S t r a t y and J a e n i c k e 1980, Bax e t a l . 1980, Iwata and Komatsu 1984) and B i r t w e l l (1977) has shown t h a t v a r i a t i o n s i n low d i s s o l v e d oxygen c o n c e n t r a t i o n s may a f f e c t the depth d i s t r i b u t i o n s of c h i n o o k salmon i n the water column. I t i s not known which of these t h r e e f a c t o r s , i f any, p l a y s a dominant r o l e i n d e t e r m i n i n g salmon d i s t r i b u t i o n s . The o b j e c t i v e of t h i s s t u d y i s t o t e s t how a low oxygen e n v i r o n m e n t , i n c o n c e r t w i t h n a t u r a l l y o c c u r r i n g f l u c t u a t i o n s i n t e m p e r a t u r e and s a l i n i t y l e v e l s , can a f f e c t the n e a r s h o r e depth d i s t r i b u t i o n s and t e m p o r a l movements of j u v e n i l e c hinook and chum salmon on an i n t e r t i d a l s a n d f l a t . Data were c o l l e c t e d on a p o l l u t e d and u n p o l l u t e d a r e a s e p a r a t e d by a 4.4 km l o n g j e t t y . The p o l l u t e d a r e a , l o c a t e d i n the F r a s e r R i v e r e s t u a r y near Iona I s l a n d ( f i g u r e 1 ) , i s c h a r a c t e r i z e d by f r e q u e n t d e p r e s s i o n s i n d i s s o l v e d oxygen t h a t accompany the d i s c h a r g e of m u n i c i p a l waste ( B i r t w e l l e t a l . 1983). C o n s e q u e n t l y , the responses of s a l m o n i d s t o h y p o x i c c o n d i t i o n s c o u l d be examined on a r e g u l a r b a s i s . Sampling was performed on a f l o o d t i d e when l a r g e changes i n a l l water q u a l i t y f a c t o r s , caused by t i d a l e m e r s i o n , c o u l d be r e l a t e d t o the e a r l y movements of s a l m o n i d s onto the i n t e r t i d a l f l a t s . Data were a n a l y s e d by a presence/absence method which gave the p r o b a b i l i t y or r i s k t h a t a salmon would o c c u r i n a p a r t i c u l a r c o m b i n a t i o n of water q u a l i t y c o n d i t i o n s . T h i s s t u d y p l a c e s emphasis on examining the d i s t r i b u t i o n s of chum and chinook salmon i n r e l a t i o n t o a low oxygen e n v i r o n m e n t . Changes i n n a t u r a l d i s s o l v e d oxygen regimes a r e 3 F i g u r e 1. L o c a t i o n of study a r e a . Iona j e t t y on S t u r g e o n Bank, B r i t i s h Columbia. 4 5 o f t e n o b s e r v e d i n e s t u a r i n e a r e a s where human a c t i v i t y p r e v a i l s . For i n s t a n c e , r e d u c t i o n s i n d i s s o l v e d oxygen have been found i n l o g s t o r a g e a r e a s (Levy et a l . 1982) and i n the v i c i n i t y of p u l p m i l l e f f l u e n t d i s c h a r g e s ( P a r k e r and S i b e r t 1973). N a t u r a l l y o c c u r r i n g h y p o x i c a r e a s due t o p l a n k t o n blooms and b a c t e r i a l r e s p i r a t i o n ( D a v i s 1975) a r e o f t e n more t r a n s i e n t phenomena but s t i l l may a l t e r f i s h d i s t r i b u t i o n p a t t e r n s and r e s u l t i n f i s h k i l l s ( S t e i m l e and Sindermann 1978). I n f o r m a t i o n on how j u v e n i l e salmon respond t o water q u a l i t y cues may be a v a l u a b l e c o n s i d e r a t i o n i n the i d e n t i f i c a t i o n and p r e s e r v a t i o n of e s s e n t i a l salmon h a b i t a t (Dorcey et a l . 1978). 6 DESCRIPTION OF THE STUDY SITE The h i g h i n t e r t i d a l f l a t s i n v e s t i g a t e d comprise a s m a l l p o r t i o n of Sturgeon Bank, a 7000 ha f o r e s h o r e a r e a of the F r a s e r R i v e r E s t u a r y i n B r i t i s h Columbia. The study s i t e i s l o c a t e d seaward of the Iona I s l a n d Sewage Treatment P l a n t between the m i d d l e and n o r t h arms of the F r a s e r R i v e r ( f i g u r e 1 ) . The Iona p l a n t began o p e r a t i o n s i n 1963 and i s d e s i g n e d f o r p r i m a r y t r e a t m e n t of sewage o n l y . Average dry weather f l o w i s 4.62 m 3/sec or a p p r o x i m a t e l y 400,000 m 3/day. P r i m a r y treatment c a p a c i t y i s 14.7 m 3/sec and maximum wet weather f l o w i s 17.7 m 3/sec. The p o l l u t e d t i d a l f l a t i s t r a v e r s e d by a 7 km dredged c h a n n e l (1 t o 3 m depth a t low t i d e ) which conveys e f f l u e n t westward t o the deeper waters of G e o r g i a S t r a i t . E f f l u e n t from the p l a n t g e n e r a l l y moves seaward on an ebb and s m a l l f l o o d t i d e but landward on a l a r g e f l o o d t i d e (Drinnan and C l a r k 1980). S u r f a c e water a d j a c e n t t o Sturgeon Bank shows a p e r s i s t e n t n orthward f l o w (Tabata et a l . 1971) but a 4.4 km rock j e t t y bounds the e f f l u e n t c h a n n e l on i t s n o r t h e r n s i d e and p r e v e n t s sewage from d i s p e r s i n g over l a r g e a r e a s of s h o r e l i n e ( f i g u r e 2 ) . Thus, a h i g h l y c o n t r a s t i n g ' c l e a n e r ' a r e a i s m a i n t a i n e d d i r e c t l y n o r t h of the p o l l u t e d study a r e a . T h i s a r e a cannot be c o n s i d e r e d p o l l u t i o n f r e e as water may f l o w around the end of the j e t t y i n m i c r o c i r c u l a t i o n p a t t e r n s (Tabata e t a l . 1971). However, f o r s i m p l i c i t y the a r e a n o r t h of the j e t t y w i l l be r e f e r r e d t o as the u n p o l l u t e d s i t e . The t i d e s i n the a r e a a r e of the mixed, s e m i d i u r n a l type ure 2. L o c a t i o n of s a m p l i n g s t a t i o n s a l o n g Iona j e t t y . 1=seaward, p o l l u t e d s t a t i o n ; 2=landward, p o l l u t e d s t a t i o n ; 3=seaward, u n p o l l u t e d s t a t i o n ; 4=landward, u n p o l l u t e d s t a t i o n . The approximate p o s i t i o n of the t i d a l f r o n t a t a low t i d e h e i g h t of 1.4 m or l e s s i s i n d i c a t e d by the hachured l i n e . a p p r o x i m a t e s c a l e ( m e t e r s ) 9 which i n d i c a t e a d a i l y c y c l e of two complete t i d a l o s c i l l a t i o n s w i t h marked i n e q u a l i t i e s i n the times and h e i g h t s of s u c c e s s i v e h i g h or low w a t e r s . C u r r e n t speeds on Sturgeon Bank may r e a c h speeds up t o 3.5 knots (Tabata et a l . 1971). The study a r e a i s g e n t l y s l o p i n g w i t h the d i s t a n c e from the Iona I s l a n d s h o r e l i n e t o the lower l i m i t s of the t i d a l bank b e i n g about 5.8 km (Otte and L e v i n g s 1975). P h y s i c a l c h a r a c t e r i s t i c s of the sediments near the e f f l u e n t c h a n n e l were d e s c r i b e d by B.C. Research (1973,1975,1978). Sediments near the Iona I s l a n d s h o r e l i n e a re muddy, i n c r e a s i n g i n sand c o n t e n t i n a seaward d i r e c t i o n ( w e s t ) . Much of the f i n e s i l t and mud i n t h i s a r e a i s d e p o s i t e d by the F r a s e r R i v e r . The a r e a e x t e n d i n g 500 m a l o n g the e f f l u e n t c h a n n e l and 350 m south from the o u t f a l l i s d e f i n e d as h e a v i l y p o l l u t e d (no b e n t h i c l i f e ) and i s c h a r a c t e r i z e d by e x t e n s i v e s l u d g e d e p o s i t s . The sediments on the n o r t h s i d e of the j e t t y a r e c o a r s e r g r a i n e d sands which may r e f l e c t a lower s i l t d e p o s i t i o n r a t e from the F r a s e r R i v e r due t o the i n t e r v e n i n g j e t t y ( L e v i n g s and C o u s t a l i n 1975). V e g e t a t i o n i s r e s t r i c t e d t o the s h o r e l i n e of Iona I s l a n d and c o n s i s t s p r i m a r i l y of sedges (Carex sp.) ( L e v i n g s and C o u s t a l i n 1975). For t h i s s t u d y , two p a i r s of complementary s t a t i o n s were e s t a b l i s h e d a t d i f f e r e n t d i s t a n c e s from the o u t f a l l on e i t h e r s i d e of the Iona j e t t y ( f i g u r e 2 ) . The s t a t i o n d e s c r i p t i o n s a r e summarized i n t a b l e 1. At low, s l a c k t i d e the s h o r e l i n e a t t h e seaward s t a t i o n s (1 and 3) r e p r e s e n t e d the t i d a l f r o n t . The f l o o d i n g t i m e s of a l l s t a t i o n s v a r i e d a c c o r d i n g t o the d u r a t i o n 10 TABLE I D e s c r i p t i o n of s t a t i o n s S t a t i o n D i s t a n c e from S t a t i o n Slope of Time t o S u b s t r a t e sewage exposed beach f l o o d type o u t f a l l (km) ( t i d e h t . (degrees) ( h r s . i n m ) a f t e r low s l a c k ) 1 ( p o l l u t e d ) 4.3 1 .4 1.7 1-2 80% 20% sand mud 2 ( p o l l u t e d ) 2.7 8.0 1.7 3.5-4 50% 50% sand mud 3 ( u n p o l l u t e d ) 4.3 1 .4 1 .6 1-2 100% sand 4 ( u n p o l l u t e d ) 2.7 8.0 1 .6 3.5-4 1 00% sand 11 and range of t i d a l maxima and minima f o r a g i v e n day but f e l l w i t h i n the ranges noted i n t a b l e 1. 12 GENERAL METHODS F i s h were c a p t u r e d a t d i f f e r e n t depth i n t e r v a l s u s i n g a one-person beach s e i n i n g t e c h n i q u e . Temperature, s a l i n i t y and d i s s o l v e d oxygen l e v e l s were r e c o r d e d c o i n c i d e n t a l l y t o r e l a t e t o f i s h p r e s e n c e . P r e l i m i n a r y s a m p l i n g and o b s e r v a t i o n s on f l o o d t i d e movements and depth d i s t r i b u t i o n s of sa l m o n i d s took p l a c e from May t o J u l y i n 1983. However, the m a j o r i t y of the d a t a p r e s e n t e d i n t h i s t h e s i s were o b t a i n e d from A p r i l t o June, 1984. A t o t a l of 380 beach s e i n e samples were taken over 34 days. Sampling p r o c e d u r e was as f o l l o w s : At low t i d e h e i g h t s of 1.4 m the beaches a t the seaward s t a t i o n s were s u f f i c i e n t l y exposed f o r s a m p l i n g . On any s i n g l e day, o n l y two s t a t i o n s on one s i d e of the j e t t y were sampled (due t o manpower r e s t r i c t i o n s ) . Sampling would b e g i n a t a seaward s t a t i o n and t e r m i n a t e upon f l o o d i n g of t h a t s t a t i o n ( w i t h i n 2 hours a f t e r low s l a c k t i d e ) . Sampling was then c o n t i n u e d i n a s i m i l a r f a s h i o n a t the c o r r e s p o n d i n g landward s t a t i o n ( f r o m 2-4 hours a f t e r low s l a c k t i d e ) . A p p r o x i m a t e l y 6 beach s e i n e h a u l s were taken a t each s t a t i o n , each day. At each s t a t i o n , measurements of t e m p e r a t u r e , s a l i n i t y and d i s s o l v e d oxygen were t a k e n a t depths of .05, .25, .5 and 1.0 m b e f o r e and a f t e r e v e r y s e t of 3 beach s e i n e h a u l s . The 3 beach s e i n e samples were taken from the d i s c r e t e depth i n t e r v a l s 0 t o .24 m (d e p t h 1 ) , .25 t o .49 m (depth 2) and .5 t o 1.0 m (depth 3) i n the same o r d e r ( f i g u r e 3 ) . Times were noted f o r a l l samples and p h y s i c a l measurements. W i t h i n 2 d a y s , the o p p o s i t e s i d e of j e t t y was sampled a t s i m i l a r 1 3 F i g u r e 3. I l l u s t r a t i o n of the 3 sa m p l i n g depths. Depth 1=0-.24 m; depth 2=.25-.49 m; depth 3=.5-1.0 m. D i s t a n c e s not t o s c a l e . 15 t i m e s r e l a t i v e t o s l a c k low t i d e . S i m i l a r low t i d e h e i g h t s were sampled an e q u a l number of tim e s i n both a r e a s throughout the summer. The t i d e h e i g h t s were c a t e g o r i z e d as 1.0-1.4 m ( 1 ) , .7-.9 m (2) and 0-.6 m ( 3 ) . Temperature and s a l i n i t y measurements were made w i t h a YSI Model 33 c o n d u c t i v i t y meter. D i s s o l v e d oxygen c o n c e n t r a t i o n s were r e c o r d e d u s i n g a YSI Model 57 d i s s o l v e d oxygen meter which was a i r c a l i b r a t e d p r i o r t o use each day. At water depths g r e a t e r than .25 m a l l p h y s i c a l measurements were taken a t both the t o p and bottom of the water column. The proce d u r e used t o c o r r e l a t e e n v i r o n m e n t a l measurements t o the sample depths i s g i v e n i n appendix 1. S o l u b i l i t y v a l u e s of d i s s o l v e d oxygen a t the r e c o r d e d t emperature and s a l i n i t y l e v e l s were c a l c u l a t e d u s i n g the e q u a t i o n g i v e n by T r u e s d a l e and Gameson (1957). Beach s e i n i n g was conducted w i t h a p o l e s e i n e (5.2 m l o n g , 2.0 m h i g h w i t h a.1 cm s t r e t c h e d mesh) c o n v e r t e d f o r one person use by the method o u t l i n e d by Campana (1982). The t e c h n i q u e u t i l i z e s a 3 m l o n g spacer bar t o keep the s e i n e mouth open and the net i s p u l l e d a l o n g by a 15m rope c o n n e c t e d t o t h i s b a r . Each depth i n t e r v a l was sampled by p u l l i n g the s e i n e p a r a l l e l t o shore f o r 100 m. Each s e i n e h a u l r e p r e s e n t s a u n i t of e f f o r t w i t h r e f e r e n c e t o c a t c h per u n i t e f f o r t (CPUE) r e s u l t s . When samp l i n g depth 2 or 3, c a t c h o v e r l a p s from a r e a s o t h e r than the sample depth of i n t e r e s t were m i n i m i z e d by not a n c h o r i n g the s e i n e u n t i l the s t a r t of a sample. Samples were completed by p u l l i n g the net c l o s e t o the o p e r a t o r and w a l k i n g d i r e c t l y i n f r o n t of the n e t opening t o sh o r e . E x a m i n a t i o n of o v e r l a p e r r o r 16 i n terms of s p e c i e s and numbers of f i s h caught i n improper depths was done by a n c h o r i n g an empty net a t the minimum depth of a depth i n t e r v a l (eg. a t .25 m of the .25-.49 m d e p t h ) , and p u l l i n g the s e i n e t o the s h o r e . The c a t c h i n t h i s s e i n e h a u l was then compared t o the o v e r a l l c a t c h of a r e g u l a r s e i n e h a u l i n t h a t d epth i n t e r v a l . T h i s t e s t i n d i c a t e d o n l y the depth d i s t r i b u t i o n s of s c h o o l i n g s p e c i e s such as sa n d l a n c e (Ammodytes  h e x a p t e r u s ) and h e r r i n g ( C l u p e a harengus p a l l a s i ) c o u l d not be a d e q u a t e l y r e p r e s e n t e d . A c o m p a r i s o n of the one per s o n method of s a m p l i n g v e r s u s t h a t of a two person p o l e s e i n e (appendix 2) i n d i c a t e d t h a t t h e r e were no d i f f e r e n c e s i n the s p e c i e s caught by the two beach s e i n i n g methods but each s p e c i e s was not always p r e s e n t i n comparable s e i n e h a u l s . A l s o , the two per s o n method t y p i c a l l y caught a l a r g e r number of f i s h i n depth 1. Of s i x comparable s e t s of s e i n e h a u l s (taken i n s i m i l a r d e p t h s ) a s i n g l e s e t (.5-1.0 m depth) r e v e a l e d s i g n i f i c a n t d i f f e r e n c e s between the s i z e c l a s s d i s t r i b u t i o n s of s t a r r y f l o u n d e r . P e r i o d i c ( i n f i e l d ) comparisons of the f i s h s p e c i e s c a p t u r e d by s i n g l e p e r s o n beach s e i n e s ( a l l depths combined) w i t h the c a t c h of 8 m beach s e i n e nets a l s o r e v e a l e d no d i f f e r e n c e s . For each s e i n e h a u l , f i s h l e s s than 10 cm i n l e n g t h were p l a c e d i n t o 10% f o r m a l i n f o r subsequent i d e n t i f i c a t i o n and l e n g t h / w e i g h t measurements i n t h e l a b o r a t o r y . Both f o r k and s t a n d a r d l e n g t h measurements were made t o the n e a r e s t mm and we i g h t s were r e c o r d e d t o the n e a r e s t .01 grams. S t a n d a r d l e n g t h s of S t a r r y f l o u n d e r ( P l a t i c h t h y s s t e l l a t u s ) and P a c i f i c s t a g h o r n s c u l p i n s ( L e p t o c o t t u s armatus) g r e a t e r than 10 cm were 1 7 made i n the f i e l d ( t o the n e a r e s t .5 cm) and the f i s h were r e l e a s e d a t a p o i n t away from the s a m p l i n g s t a t i o n . S t a t i s t i c a l a n a l y s i s E n v i r o n m e n t a l parameters The water q u a l i t y d a t a p r e s e n t e d i n the s e c t i o n on e n v i r o n m e n t a l parameters were c o l l e c t e d i n 1984. For each month ( A p r i l , May and J u n e ) , each of the water q u a l i t y parameters ( t e m p e r a t u r e , s a l i n i t y , and d i s s o l v e d oxygen) was examined f o r s i g n i f i c a n t d i f f e r e n c e s w i t h r e s p e c t t o d i s t a n c e (landward or seaward s t a t i o n s ) , s i d e ( p o l l u t e d or u n p o l l u t e d s t a t i o n s ) , t i d a l h e i g h t ( c a t e g o r i e s 1, 2 and 3 ) , and depth ( c a t e g o r i e s 1, 2 and 3) u s i n g a n a l y s i s of v a r i a n c e ( l o g t r a n s f o r m a t i o n of t e m p e r a t u r e , s a l i n i t y and oxygen). The r e s u l t s a r e t a b u l a t e d i n appendix 3. Tukey's t e s t was used t o examine the means of f a c t o r s w i t h s i g n i f i c a n t e f f e c t s on the water q u a l i t y p a r a m e t e r s . Presence/absence a n a l y s i s L o g i s t i c r e g r e s s i o n a n a l y s i s was used t o c a l c u l a t e the maximum l i k e l i h o o d e s t i m a t e s of the parameters which p r o v i d e d the b est e x p l a n a t i o n r e g a r d i n g the presence of chum and c h i n o o k salmon i n a sample. S e l e c t i o n of a presence/absence method of a n a l y s i s v e r s u s a method which r e l i e d on the t o t a l numbers of f i s h caught (eg. a n a l y s i s of v a r i a n c e ) was based on the h i g h 18 p r o p o r t i o n of samples which had a z e r o c a t c h . A t r a n s f o r m a t i o n of c o u n t s w i t h a l a r g e number of z e r o s may l e a d t o swamping of the d a t a ( M c u l l a g h and N e l d e r 1983). In a b i n a r y approach where the dependent v a r i a b l e i s r e p r e s e n t e d as 1=present or 0=absent, the i n f o r m a t i o n p r o v i d e d by the z e r o c a t c h i s not l o s t . L o g i s t i c r e g r e s s i o n employs the l o g i t t r a n s f o r m a t i o n ( l n ( p / 1 - p ) ) which s a t i s f i e s the c o n d i t i o n of n o r m a l i t y f o r p r o p o r t i o n d a t a on a 0 t o 1 s c a l e . M c u l l a g h and N e l d e r (1983) and Breslow and Day (1980) o u t l i n e the t h e o r y b e h i n d l o g i s t i c r e g r e s s i o n and p r o v i d e examples f o r i t s use. The l o g i s t i c r e g r e s s i o n e q u a t i o n i s where the p r o b a b i l i t y of the dependent v a r i a b l e y i s r e l a t e d t o a s e r i e s of k independent r e g r e s s i o n v a r i a b l e s x=(x ,...x ). a r e p r e s e n t s the p r o b a b i l i t y of presence or absence w i t h z e r o r e g r e s s i o n v a r i a b l e s w h i l e exp(0 ) i s the f r a c t i o n by which the p r o b a b i l i t y i n c r e a s e s or d e c r e a s e s f o r every u n i t change i n x ( B r e s l o w and Day 1980). The independent v a r i a b l e s may be c a t e g o r i c a l or c o n t i n u o u s (Baker and N e l d e r 1980). The f o l l o w i n g independent v a r i a b l e s were examined i n a s s o c i a t i o n w i t h the presence or absence of c h i n o o k and chum salmon at Iona I s l a n d . 1. DISTANCE = seaward (1) and landward (2) s t a t i o n s . 19 2. SIDE = p o l l u t e d ( s i d e 1) and u n p o l l u t e d ( s i d e 2) s t a t i o n s . 3. DEPTH = depth 1 (0-.24 m) , depth 2 (.25-.49 m) and depth 3 (.5-1.0 m). 4. TIDE = t i d e h e i g h t c a t e g o r i e s (1=1.0-1.4 m, 2=.7-.9 m and 3=0-.6 m) 5. TEMPERATURE (°C) 6. "SALINITY (%•) 7. DISSOLVED OXYGEN (mg/1) 8. PERCENT SATURATION (of d i s s o l v e d oxygen) Each v a r i a b l e or c o m b i n a t i o n of v a r i a b l e s may d e f i n e a c a t e g o r y f o r which the p r o b a b i l i t y of presence or absence of a s p e c i e s may be made. An a r c s i n e t r a n s f o r m a t i o n was performed on the p e r c e n t a g e a i r s a t u r a t i o n v a l u e s p r i o r t o a n a l y s i s . The c o n t i n u o u s v a r i a b l e s ( t e m p e r a t u r e , s a l i n i t y , d i s s o l v e d oxygen and p e r c e n t a g e a i r s a t u r a t i o n ) were s c a l e d by d i v i d i n g each v a l u e i n a d a t a s e t by i t s s t a n d a r d d e v i a t i o n , a l l o w i n g the r e l a t i v e importance of the terms t o be judged by the s i z e of the e s t i m a t o r . P o s i t i v e e s t i m a t o r s i n d i c a t e t h a t the p r o b a b i l i t y of a presence or absence i n c r e a s e s w i t h i n c r e a s i n g v a l u e s of t h a t e s t i m a t o r . N e g a t i v e v a l u e s i n d i c a t e the c o n v e r s e s i t u a t i o n . The l o g i s t i c r e g r e s s i o n program used i s p a r t of the GLIM ( g e n e r a l i z e d l i n e a r m o d e l l i n g ) package from the R o y a l S t a t i s t i c a l S o c i e t y . The p r o c e d u r e r e q u i r e s i n i t i a l l y f i t t i n g 20 the main v a r i a b l e s and c h o o s i n g t h o s e w i t h e s t i m a t o r s g r e a t e r than t w i c e t h e a s s o c i a t e d s t a n d a r d e r r o r ( S E ) . I f the v a l u e e q u i v a l e n t t o t w i c e the SE exceeds the e s t i m a t o r , then the e s t i m a t o r i n c l u d e s z e r o and i s e x c l u d e d from the r e s u l t s . I n t e r a c t i o n terms a r e a s s e s s e d by f i t t i n g them one a t a time t o the main e f f e c t s model and, a g a i n , r e t a i n i n g o n l y those w i t h s i g n i f i c a n t e s t i m a t o r s . The a p p r o p r i a t e n e s s of the f i n a l models p r e s e n t e d i n t h i s s tudy were then checked by an e x a m i n a t i o n of the s t a n d a r i z e d r e s i d u a l s p l o t t e d a g a i n s t one of the c o n t i n u o u s c o v a r i a t e s not i n c l u d e d i n the model (Baker and N e l d e r 1980). 21 RESULTS E n v i r o n m e n t a l parameters Temperature Temperatures g r a d u a l l y i n c r e a s e d t hroughout the sa m p l i n g season ( f i g u r e 4) but the most s t r i k i n g event was the sudden drop i n water t e m p e r a t u r e s a t the end of June (1984) c o i n c i d e n t w i t h a week of c o o l weather and r a i n . S t a t i o n s 2 and 4 were emersed f o r a p p r o x i m a t e l y 8 d a y l i g h t hours on a l l s a m p l i n g days. As e x p e c t e d , the water t e m p e r a t u r e s a t the landward s t a t i o n s were s i g n i f i c a n t l y h i g h e r (p<.05) than those of the c o r r e s p o n d i n g seaward s t a t i o n s i n a l l months. Both landward s t a t i o n s e x p e r i e n c e d l a r g e r ranges i n temperature than e i t h e r seaward s t a t i o n ( f i g u r e 5 ) . The mean water t e m p e r a t u r e s a t a l l depths were s i g n i f i c a n t l y d i f f e r e n t from each o t h e r w i t h i n each month (p<.0l) w i t h the h i g h e s t mean temp e r a t u r e o c c u r r i n g i n depth 1 and d e c r e a s i n g w i t h i n c r e a s i n g d e p t h s . On a d a i l y b a s i s , the l a r g e s t t e m p e r a t u r e changes u s u a l l y o c c u r r e d between depth 1 and depth 2 (example i n f i g u r e 6 ) . Near low s l a c k t i d e ( t i m e 0) tempe r a t u r e s i n the t h r e e depths began d i v e r g i n g w i t h the g r e a t e s t h e a t i n g o c c u r r i n g i n depth 1. The l o n g p e r i o d of emersion f o r s t a t i o n 2 r e s u l t e d i n a maximum temperature range of 21 t o 28.5 °C o c c u r r i n g w i t h i n 20 m of shore 3 hours a f t e r the s t a r t of a f l o o d t i d e . Once t h e beach was c o v e r e d by wa t e r , t e m p e r a t u r e s began d r o p p i n g a g a i n . In A p r i l , water t e m p e r a t u r e s on h i g h e r low t i d e s (.9-1.4 m) 22 F i g u r e 4. Mean monthly t e m p e r a t u r e s a t each s t a t i o n . Means are g i v e n f o r the middle of A p r i l (day 15) and the b e g i n n i n g (day 5 ) , middle (day 15) and end (day 25) of May and June. S t a t i o n s 1 and 3 (seaward s t a t i o n s ) r e p r e s e n t the sampling p e r i o d from 0-2 hours a f t e r low s l a c k t i d e and s t a t i o n s 2 and 4 (landward s t a t i o n s ) were sampled from 2-4 hours a f t e r low s l a c k t i d e . 24 22\ ro co 24 F i g u r e 5. Maximum and minimum te m p e r a t u r e s r e c o r d e d on each sample day a t each s t a t i o n . The h o r i z o n t a l l i n e s a t 15 °C s e r v e as a i d s f o r c o m p a r a t i v e r e f e r e n c e s between s t a t i o n s . The landward s t a t i o n s (2 and 4) e x p e r i e n c e l a r g e r d a i l y f l u c t u a t i o n s i n temperature than the seaward s t a t i o n s (1 and 3 ) . 30 26 2 0 1 6 1 0 6 0 Station 1 A p r i l May J u n • 3<M S tat ion 3 1 0 6 A p r i l 1 Ma^ ' Tu~n"e ' ' Stat 1 ion 2 1 I i 1 i 1. • i < • : • -Stat ion 4 A p r i l May June ro 26 F i g u r e 6. Temperatures r e c o r d e d ebb and f l o o d t i d e , J u l y 24 2=.25-.49 m; depth 3=.5-1.0 p o l l u t e d s t a t i o n ) f l o o d s a t low s l a c k t i d e ( t i m e 0) and hours a f t e r low, s l a c k t i d e from 3 sample depths on an Depth 1=0-.24 m; depth m. S t a t i o n 1 (seaward, a p p r o x i m a t e l y 2 hours a f t e r s t a t i o n 2 f l o o d s a t about 4 28 were s i g n i f i c a n t l y c o o l e r (p<.00l) than by t i d a l h e i g h t s from .7-.9 m by about 2 °C. In both May and June, t i d e s a f f e c t e d t e m p e r a t u r e s d i f f e r e n t l y on the two s i d e s of the j e t t y . The o n l y o b v i o u s t r e n d was t h a t temperatures tended t o be h i g h e r i n the p o l l u t e d a r e a f o r any g i v e n t i d a l h e i g h t . T i d a l h e i g h t had no s i g n i f i c a n t e f f e c t on temperature i n J u l y . S a l i n i t y Mean s a l i n i t i e s dropped from about 17 °/00 i n A p r i l t o 3-9 % i n June ( f i g u r e 7 ) . The drop i n s a l i n i t i e s i n June were c o i n c i d e n t w i t h the peak of s p r i n g f r e s h e t f o r the F r a s e r R i v e r . For a g i v e n s i d e of the j e t t y , average s a l i n i t i e s f o l l o w e d a v e r y s i m i l a r p a t t e r n but the n o r t h s i d e s a l i n i t i e s were always s i g n i f i c a n t l y h i g h e r than on the south s i d e ( A p r i l p < . 0 l ) . The v a r i a t i o n i n s a l i n i t y v a l u e s a s s o c i a t e d w i t h d i f f e r e n t s i d e s of the j e t t y showed i n t e r a c t i o n s w i t h t i d e i n June and t i d e and d i s t a n c e i n May. No p a t t e r n s c o u l d be d e t e c t e d i n the s e v a r i a t i o n s . The range of obse r v e d s a l i n i t y v a l u e s was t y p i c a l l y g r e a t e r on the n o r t h s i d e " of the j e t t y , p a r t i c u l a r l y i n June ( f i g u r e 8 ) . A n a l y s i s of v a r i a n c e showed t h a t average s a l i n i t i e s of a l l depths i n June were s i g n i f i c a n t l y d i f f e r e n t from each o t h e r (p<.05) w i t h a p a t t e r n of d e c r e a s i n g s a l i n i t i e s w i t h i n c r e a s i n g d e p t h s . In June, s a l i n i t i e s on the n o r t h s i d e of the j e t t y o f t e n d e c r e a s e d w i t h time w i t h i n a s i n g l e t i d a l c y c l e ( f i g u r e s 9 ) . A l l 3 . depths f o l l o w e d a s i m i l a r p a t t e r n and o c c u p i e d o n l y a narrow s a l i n i t y range a t a g i v e n t i m e . 29 F i g u r e 7. Mean monthly s a l i n i t i e s a t each s t a t i o n . Means are g i v e n f o r the m i d d l e of A p r i l (day 15) and the b e g i n n i n g (day 5 ) , m i d d l e (day 15) and end (day 25) of May and June. S t a t i o n s 1 and 3 (seaward s t a t i o n s ) r e p r e s e n t the s a m p l i n g p e r i o d from 0-2 hours a f t e r low s l a c k t i d e and s t a t i o n s 2 and 4 (landward s t a t i o n s ) were sampled from 2-4 hours a f t e r low s l a c k t i d e . 31 F i g u r e 8. Maximum and minimum s a l i n i t y v a l u e s r e c o r d e d on each sample day a t each s t a t i o n . The h o r i z o n t a l l i n e s at 10 % serve' as a i d s f o r c o m p a r a t i v e r e f e r e n c e s between s t a t i o n s . 2 5 2 0 1 5 1 0-6-0 Stat ion 1 — 1 . I r-A p r i l May J u n e 2 5-2 0 1 6 1 0 6 0 Stat ion 3 A p r i l May J u n e 2 5 Stat ion 2 2 0 1 5 I 1 0 t i l 1 I 5 0 A p r i l May J u n e Stat ion 4 l l A p r i l May J u n e 33 F i g u r e 9. Examples of s a l i n i t y changes on a d a i l y f l o o d c y c l e a t s t a t i o n s 3 and 4 i n June. Depth 1=0-.24 m; depth 2=.25-.49 m; depth 3=.5-1.0 m. S t a t i o n 3 (seaward, u n p o l l u t e d s t a t i o n ) f l o o d s a t a p p r o x i m a t e l y 2 hours a f t e r low s l a c k t i d e (time 0) and s t a t i o n 4 (la n d w a r d , u n p o l l u t e d s t a t i o n ) f l o o d s a t about 4 hours a f t e r low, s l a c k t i d e . o ro o ro 35 D i s s o l v e d oxygen Mean d i s s o l v e d oxygen (D.O.) c o n c e n t r a t i o n s a t the p o l l u t e d s t a t i o n s (1 and 2) were t y p i c a l l y (but not always) below c o n c e n t r a t i o n s a t the u n p o l l u t e d s t a t i o n s ( f i g u r e 10). Both p o l l u t e d s t a t i o n s f o l l o w e d the same p a t t e r n w i t h average D.O. l e v e l s d r o p p i n g below 7 mg/1 towards the end of May and June. At the u n p o l l u t e d s t a t i o n s D.O. c o n c e n t r a t i o n s peaked a t the end of May w i t h average v a l u e s e x c e e d i n g 9 mg/1. S t a t i o n 3 e x h i b i t e d a more v a r i a b l e oxygen regime than i t s c o r r e s p o n d i n g landward s t a t i o n w i t h average v a l u e s d i p p i n g below the p o l l u t e d s i d e i n mid-May as w e l l as a t the end of June. A n a l y s i s of v a r i a n c e i n d i c a t e d t h a t " s i d e " was the o n l y s i g n i f i c a n t f a c t o r a f f e c t i n g oxygen v a l u e s i n A p r i l and May w i t h h i g h e r l e v e l s o c c u r r i n g i n the u n p o l l u t e d a r e a as e x p e c t e d . In June, oxygen c o n c e n t r a t i o n s on the n o r t h s i d e of the j e t t y were h i g h e s t on t i d e s above .9 m and de c r e a s e d s i g n i f i c a n t l y (p<.0|) w i t h each lower t i d a l h e i g h t c a t e g o r y . Mean oxygen c o n c e n t r a t i o n s on a l l t i d e h e i g h t s on the n o r t h s i d e exceeded the so u t h s i d e . In 1983, o b s e r v a t i o n s of d i s s o l v e d oxygen c o n c e n t r a t i o n s below 5 mg/1 on the p o l l u t e d t i d a l f l a t began on May 12 and c o n t i n u e d throughout the remainder of the sa m p l i n g p e r i o d (end of J u l y ) . I n 1984, w i t h two e x c e p t i o n s , a l l days sampled on the p o l l u t e d t i d a l f l a t a f t e r and i n c l u d i n g May 29 d i s p l a y e d D.O. l e v e l s below 5 mg/1 ( t o t a l = l 3 o c c a s i o n s ) ( f i g u r e 11). Oxygen l e v e l s on t h e p o l l u t e d t i d a l f l a t r o s e and f e l l i n c h a r a c t e r i s t i c p a t t e r n s ( f i g u r e s 12 and 13). The te m p e r a t u r e d a t a which c o r r e s p o n d s t o f i g u r e 13 were p r e s e n t e d i n f i g u r e 6. 36 F i g u r e 10. Mean monthly d i s s o l v e d oxygen c o n c e n t r a t i o n s a t each s t a t i o n . Means a r e g i v e n f o r the m i d d l e of A p r i l (day 15) and the b e g i n n i n g (day 5 ) , m i d d l e (day 15) and end (day 25) of May and June. S t a t i o n s 1 and 3 (seaward s t a t i o n s ) r e p r e s e n t the samp l i n g p e r i o d from 0-2 hours a f t e r low s l a c k t i d e and s t a t i o n s 2 and 4 (landward s t a t i o n s ) were sampled from 2-4 hours a f t e r low s l a c k t i d e . 38 F i g u r e 11. Maximum and minimum d i s s o l v e d oxygen v a l u e s r e c o r d e d on each sample day a t each s t a t i o n . The h o r i z o n t a l l i n e s a t 6 mg/1 s e r v e d a i d s f o r c o m p a r a t i v e r e f e r e n c e s between s t a t i o n s . S t a t i o n s 1 and 2 ( p o l l u t e d s t a t i o n s ) e x h i b i t t y p i c a l l y g r e a t e r oxygen ranges than s t a t i o n s 3 and 4 ( u n p o l l u t e d s t a t i o n s ) . Station 1 A p r i l May June Station 3 j r ' i ,•' L A p r i l 1 May ' June Stat ion 2 1, 1 ' 11 1 1 1 T~: 1 » 1 — Stat ion 4 I A p r i l 1 May ' J une 40 F i g u r e 12. T y p i c a l example of the r i s e i n oxygen l e v e l s on a f l o o d t i d e a t the p o l l u t e d s t a t i o n s (1 and 3 ) . Depth 1=0-.24 m; depth 2=.25-.49 m; depth 3=.5-1.0 m. 42 F i g u r e 13. Example of the f a l l and r i s e i n oxygen l e v e l s on an ebb and f l o o d t i d e a t the p o l l u t e d s t a t i o n s on J u l y 24. S t a t i o n 1 (seaward, p o l l u t e d ) ; s t a t i o n 2 (landward, p o l l u t e d ) . See t e x t f o r e x p l a n a t i o n . 43 44 A d e s c r i p t i o n of the g e n e r a l oxygen c y c l e o b s e r v e d on the l a t e ebb and e a r l y f l o o d t i d a l s t a g e s i n the p o l l u t e d a r e a ( s t a t i o n s 1 and 2) i s as f o l l o w s : A p p r o x i m a t e l y f o u r hours b e f o r e low s l a c k t i d e , d e c l i n i n g oxygen l e v e l s a r e r e c o r d e d i n depth 3. Water w i t h a h i g h e r oxygen c o n t e n t near the j e t t y d r a i n s i n t o the a l r e a d y low oxygen waters of the e f f l u e n t c h a n n e l on the ebbing t i d e . The h y p o x i c water i n the c h a n n e l p r o b a b l y r e p r e s e n t s the westward movement of e f f l u e n t t h a t has been p o o l e d near the o u t f a l l by the p r e v i o u s f l o o d w a t e r s . As the t i d e approaches i t s l o w e s t p o i n t (time 0 i n f i g u r e 13) and water l e v e l s have receded t o the banks of the e f f l u e n t c h a n n e l , depth 3 e x h i b i t s v e r y low oxygen c o n c e n t r a t i o n s . H i g h e r oxygen l e v e l s may be r e c o r d e d i n depth 1 depending on how f a r the t i d e has dropped and t h e d i s t a n c e of t h i s d e pth from the sewage c h a n n e l . A l s o , wind and wave a c t i o n may o f t e n r e s u l t i n oxygen l e v e l s e x c e e d i n g 5 mg/1 i n depth 1 w h i l e lower depths a r e s t i l l e x p e r i e n c i n g l e v e l s below 2 mg/1. At low s l a c k t i d e , the oxygen l e v e l s at b o t h the landward and seaward s t a t i o n s a r e t y p i c a l l y a t a minimum. Oxygen l e v e l s a t the seaward s t a t i o n appear t o d e c l i n e i n a manner s i m i l a r t o the landward s t a t i o n but w i t h a d e f i n i t e l a g t i m e . On a f l o o d t i d e , water renewal b e g i n s a t the c e n t e r of the e f f l u e n t c h a n n e l . Water t h a t i s both c o o l e r and h i g h e r i n oxygen c o n t e n t i n i t i a l l y f l o w s over the deoxygenated l a y e r i n the e f f l u e n t c h a n n e l . T i d a l m i x i n g of the two water masses p r o b a b l y o c c u r s . The r i s e i n oxygen l e v e l s on a f l o o d t i d e i s s w i f t . At the seaward s t a t i o n , oxygen c o n c e n t r a t i o n s r i s e above 45 6 mg/1 w i t h i n 45 t o 75 minutes a f t e r low s l a c k t i d e . The renewal time i s u s u a l l y l o n g e r on lower low t i d e h e i g h t s . At the landward s t a t i o n oxygen l e v e l s b e g i n i n c r e a s i n g s w i f t l y a t 2.5 t o 3 hours a f t e r low t i d e . F i s h c a t c h A l t o g e t h e r , 29 s p e c i e s of f i s h were c a p t u r e d a t the study s i t e i n 1984, 8 of which were c o n s i d e r e d r a r e ( l e s s than 3 o c c u r r e n c e s i n the whole s a m p l i n g p e r i o d ) ( t a b l e I I ) . The predominant s p e c i e s were s t a r r y f l o u n d e r ( P l a t i c h t h y s s t e l l a t u s ), arrow g o b i e s ( C l e v e l a n d i a i o s ) , and P a c i f i c s t a g h o r n s c u l p i n s ( L e p t o c o t t u s armatus) o c c u r r i n g i n 75.5 % , 65 % and 60 % of the t o t a l s e i n e h a u l s r e s p e c t i v e l y . Of the s a l m o n i d s , j u v e n i l e c h i n o o k and chum salmon were the most common s p e c i e s c a p t u r e d i n the study a r e a ( t a b l e I I I ) . Peak numbers were r e c o r d e d f o r chum salmon i n May and i n June f o r c h i n o o k . Chinook were o c c a s i o n a l l y o b s e r v e d i n the a r e a i n J u l y but numbers were not r e c o r d e d . For J u l y 1983, CPUE f o r chin o o k was low. P i n k salmon were most abundant i n A p r i l (1984) and coho salmon were o n l y c a p t u r e d i n May. J u v e n i l e sockeye were p r e s e n t m a i n l y i n J u l y of 1983. In May, h i g h e s t CPUE v a l u e s f o r chi n o o k salmon were r e c o r d e d a t the p o l l u t e d s t a t i o n s . In June, l o w e s t numbers of chi n o o k were caught a t the landward p o l l u t e d s t a t i o n . Chum were most commonly caught i n the u n p o l l u t e d a r e a i n both May and June. P i n k salmon were found a t a l l s t a t i o n s i n A p r i l but h i g h e s t CPUE v a l u e s a r e f o r the n o r t h s i d e of the j e t t y . I n 46 Ta b l e I I S p e c i e s l i s t f o r A p r i l , May and June (1984) Common name Chinook salmon Sockeye salmon* P i n k salmon Coho salmon Chum salmon P a c i f i c h e r r i n g S h i n e r p e r c h P a c i f i c s a n d l a n c e S u r f smelt 3-spine s t i c k l e b a c k P a c i f i c s t a g h o r n s c u l p i n S t a r r y f l o u n d e r Arrow goby C r e s c e n t gunnel P a c i f i c snake p r i c k l e b a c k T i d e p o o l s c u l p i n Sharpnose s c u l p i n S a n d s o l e B u f f a l o s c u l p i n Saddleback gunnel P r i c k l y s c u l p i n * E n g l i s h s o l e N o r t h e r n anchovy* Saddleback s c u l p i n * K e l p g r e e n l i n g E u l a c h o n * S n a i l f i s h ( s p . ) * Padded s c u l p i n * Bay p i p e f i s h * S c i e n t i f i c name Oncorhynchus tshawytscha Oncorhynchus nerka Oncorhynchus gorbuscha Oncorhynchus k i s u t c h Oncorhynchus k e t a Clupea harengus p a l l a s i Cymatogaster a g g r e g a t a Ammodytes h e x a p t e r u s Hypomesus p r e t i o s u s p r e t i o s u s G a s t e r o s t e u s a c u l e a t u s L e p t o c o t t u s armatus P l a t i c h t h y s s t e l l a t u s C l e v e l a n d i a i o s P h o l i s l a c t a Lumpenus s a g i t t a O l i g o c o t t u s maculosus C l i n o c o t t u s a c u t i c e p s P s e t t i c h t h y s m e l a n o s t i c u s Enophrys b i s o n P h o l i s o r n a t a C o t t u s a s p e r P a r o p h r y s v e t u l u s E n g r a u l i s mordax mordax O l i g o c o t t u s r i m e n s i s Hexagrammos decagrammus T h a l e i c h t h y s p a c i f i c u s L i p a r i s (sp.) A r t e d i u s f e n e s t r a l i s Syngnathus g r i s e o l i n e a t u s * r a r e s p e c i e s w i t h l e s s t han 3 o c c u r r e n c e s i n each month May, p i n k salmon were caught o n l y i n the u n p o l l u t e d a r e a . 47 TABLE I I I CPUE and t o t a l numbers of sa l m o n i d s caught near Iona I s l a n d i n 1984 and J u l y 1983. T o t a l numbers a r e g i v e n i n p a r e n t h e s e s . Month S t a t i o n Chinook Chum Pi n k Coho A p r i l 1 .22 (4) 0 .11 (2) 0 2 .60 (9) .53 (8) .20 (2) 0 3 . 12 (3) .58 (15) .35 (9) 0 4 .26 (5) .83 (15) .89 (16) 0 May 1 .62 (29) .85 (40) 0 .17 (8) 2 .80 (28) .34 (12) 0 .03 (1 ) 3 .48 (20) 2.24 (94) .29 (12) .10 (4) 4 .53 (18) .76 (26) .15 (5) .03 (1) June 1 1 .61 (45) .04 (1) 0 0 2 .93 (28) .03 (1) 0 0 3 1 .23 (53) .44 (19) 0 0 4 1 .73 (75) .31 (13) 0 0 J u l y (1983) 1 0 (0) 0 0 0 2 .06 (1) 0 0 0 3 .17 (2) 0 0 0 4 . 1 1 (2) 0 0 0 48 Depth d i s t r i b u t i o n s Chinook salmon showed a d i s t i n c t l e n g t h / d e p t h d i s t r i b u t i o n p a t t e r n ( t a b l e I V ) . F i s h of l e s s than 5 cm l e n g t h o c c u r r e d i n a l l 3 depths but the g r e a t e s t numbers were c a p t u r e d i n depth 2. T a b l e IV Numbers of salmon i n each l e n g t h c a t e g o r y and depth f o r a l l months and s t a t i o n s combined. Depth 1=0-.24 m., depth 2= .25-.49 m and depth 3=.5-1.0 m. (1984) Fork Length Chinook Chum Pin k C a t e g o r y Depth Depth Depth (cm) 1 2 3 1 2 3 1 2 3 3-3.95 2 2 1 15 23 7 11 23 11 4-4.95 9 28 8 8 81 23 5-5.95 1 14 1 4 50 24 6-6.95 33 34 5 5 7-7.95 5 29 2 8-8.95 5 29 9-11.5 1 31 S i m i l a r numbers of f i s h of 5-7 cm l e n g t h s were c a p t u r e d i n depths 2 and 3 and f i s h g r e a t e r than 7 cm were most f r e q u e n t l y c a p t u r e d i n depth 3. F i s h l o n g e r than 9 cm were r a r e l y caught i n water l e s s than .5 m deep. T h i s p a t t e r n of ch i n o o k depth d i s t r i b u t i o n s was s i m i l a r f o r the p o l l u t e d and u n p o l l u t e d sample a r e a s ( t a b l e V ) . In A p r i l , c h i n o o k salmon were of a mean l e n g t h of l e s s than 4.5 cm and s i m i l a r numbers were c a p t u r e d i n each of the 3 depths ( f i g u r e 14). The g r e a t e s t numbers of ch i n o o k were i n the 4-5 cm l e n g t h range ( t a b l e V I ) . In May, the l e n g t h s of c a p t u r e d c h i n o o k ranged from 3.7-11.4 cm ( t a b l e V I ) . In p a r t i c u l a r , an 49 F i g u r e 14. Mean f o r k l e n g t h s of p i n k , chum and c h i n o o k salmon found i n each sample depth i n A p r i l , May and June. Depth 1=0-.24 m; depth 2=.25-.49 m; d e p t h 3=.5-1.0 m. 95 % c o n f i d e n c e i n t e r v a l s f o r the means and t o t a l numbers of each s p e c i e s c a p t u r e d a r e p r e s e n t e d . 10f Apr i l 10- May 8H 6-3 o l Tt1 2 2 s t a o-L 1 2 3 Depth 1 2 Depth 101 June *3 • 1 4 M 1 0 (90 • 8 e 1 4 to KEY • C h i n o o k ( 1 9 8 4 ) 0 C h i n o o k ( 1 • • • ) # Chum • P ink 1 2 3~ Depth t n o 51 T a b l e V Numbers of salmon i n each l e n g t h c a t e g o r y and depth f o r the p o l l u t e d and u n p o l l u t e d s i d e s of the j e t t y . Depth 1=0-.24 m., depth 2=.25-.49 m and depth 3=.5-1.0 m. (1984) Fork Chinook Chum Length P o l l u t e d U n p o l l u t e d P o l l u t e d U n p o l l u t e d Category Depth Depth Depth Depth (cm) 1 2 3 1 2 3 1 2 3 1 2 3 3-3.95 1 2 1 1 0 0 1 7 3 14 1 6 4 4-4.95 2 1 3 7 7 15 1 1 18 1 2 7 63 1 1 5-5.95 1 7 6 7 8 9 7 41 1 7 6-6.95 1 3 1 4 20 20 1 5 4 7-7.95 21 28 24 33 2 8-8.95 2 1 1 3 18 9-11.5 1 5 1 1 6 i n c r e a s e i n mean l e n g t h (above 6 cm) was noted f o r chinook c a p t u r e d i n depth 3 and t h e r e was no o v e r l a p between the s t a n d a r d d e v i a t i o n s of mean l e n g t h s f o r depths 2 and 3 ( f i g u r e 14). In June, depths 2 and 3 were a g a i n o c c u p i e d by f i s h of a s i m i l a r mean l e n g t h (6-7 cm) and a s i n g l e f i s h of l e s s than 5.5 cm l e n g t h was o b s e r v e d i n depth 1. The l a t t e r o b s e r v a t i o n was r e c o r d e d a t s t a t i o n 2 d u r i n g a p e r i o d of c o o l , r a i n y weather. Chum salmon o c c u r r e d most commonly i n l e n g t h c a t e g o r i e s of l e s s than 6 cm, and f o l l o w e d l e n g t h / d e p t h d i s t r i b u t i o n p a t t e r n s s i m i l a r t o c h i n o o k ( t a b l e I V ) . Very few chum salmon were c a p t u r e d i n d e p t h 1 of the p o l l u t e d a r e a i n r e l a t i o n t o the u n p o l l u t e d a r e a , however, the t o t a l number of chum c a p t u r e d i n the p o l l u t e d a r e a was a l s o low ( t a b l e V ) . No chum were c a p t u r e d i n depth 3 i n A p r i l ( f i g u r e 14). In May, chum were found i n a l l 3 depths w i t h peak numbers o c c u r r i n g i n depth 2. In June, no chum salmon were c a p t u r e d i n depth 1 even though t h e i r mean l e n g t h s were s t i l l l e s s than 5.5 cm. 52 P i n k salmon g r e a t e r than 4 cm were not observed i n the n e a r s h o r e a r e a . T h i s s p e c i e s was found i n a l l 3 depths i n A p r i l and May, w i t h g r e a t e s t numbers b e i n g c a p t u r e d i n depth 2. Only 5 p i n k s were c a p t u r e d i n the p o l l u t e d area ( t a b l e I I I ) , 2 of which were c a p t u r e d i n depth 2, and 2 i n depth 3. For a l l months combined, the c o r r e l a t i o n between l e n g t h and depth f o r chinook salmon was .49. W i t h i n months, o n l y May showed a s i g n i f i c a n t l e n g t h / d e p t h c o r r e l a t i o n of .66. There were no s i g n i f i c a n t l e n g t h c o r r e l a t i o n s w i t h depth f o r chum salmon i n any month. TABLE VI Numbers of c h i n o o k and chum salmon i n each l e n g t h c a t e g o r y f o r each month (1984). Fork Length Category (cm) A p r i l Chinook Chum May Chinook Chum June Chinook Chum 3-3.95 3 20 2 22 0 2 4-4.95 17 14 24 89 4 9 5-5.95 1 3 1 4 54 14 17 6-6.95 1 2 6 55 4 7-7.95 12 1 94 1 8-8.95 6 27 9-9.95 1 4 5 10-10.95 8 2 11-11.95 3 2 In 1984, t h e r e were no s i g n i f i c a n t d i f f e r e n c e s between the o v e r a l l mean l e n g t h s of j u v e n i l e salmon caught i n the p o l l u t e d and u n p o l l u t e d a r e a . Mean l e n g t h s of chinook salmon c a p t u r e d i n June, 1983 were p r e s e n t e d i n f i g u r e 14 t o c o n t r a s t w i t h the 1984 d a t a . At s t a t i o n 1, 5 salmon w i t h a mean l e n g t h g r e a t e r than 6 53 cm were p r e s e n t i n depth 1. The f i s h were c a p t u r e d on a s i n g l e day when low oxygen l e v e l s ( l e s s than 2 mg/1) were r e c o r d e d a t depths 2 and 3. S t r o n g s o u t h winds and c o r r e s p o n d i n g heavy wave a c t i o n r e s u l t e d i n c o n s i d e r a b l y h i g h e r oxygen l e v e l s ( g r e a t e r than 6 mg/1) i n depth 1. A s i m i l a r event was r e c o r d e d i n J u l y of 1983 when low oxygen c o n d i t i o n s p r e v a i l e d i n depths 2 and 3 ( f i g u r e 15). T h i s t i m e , sockeye salmon w i t h a mean l e n g t h of 4.5 cm were observed swimming i n 3-5 cm of water a t s t a t i o n 1 (water temperature = 18 °C, s a l i n i t y = 2.2 % 0 ) . Many of t h e s e f i s h moved s l u g g i s h l y and were e a s i l y caught by hand. When the d i s s o l v e d oxygen c o n c e n t r a t i o n s rose t o 4 mg/1 i n a l l depths the f i s h swam n o t i c e a b l y f a s t e r and d i s a p p e a r e d from the s h a l l o w water. A p p r o x i m a t e l y 150 g u l l s and herons were engaged i n a c t i v e f e e d i n g i n the area a t t h i s time (but I c o u l d not d i s c e r n the n a t u r e of t h e i r prey i t e m s ) . Other o b s e r v a t i o n s on l e n g t h / d e p t h d i s t r i b u t i o n s were made on the s o u t h s i d e of the sewage c h a n n e l i n May 1983. On two c o n s e c u t i v e days, s c h o o l s of 5-10 chinook salmon were seen a c t i v e l y swimming i n 5 cm of water. The f i s h appeared t o be f o l l o w i n g the a d v a n c i n g water f r o n t of the f l o o d t i d e . Fork l e n g t h s of c a p t u r e d c h i n o o k were a l l l e s s than 5 cm. P h y s i c a l measurements of t e m p e r a t u r e , s a l i n i t y and oxygen on the f i r s t day were 20 °C, 3 %«and 4.9 mg/1 r e s p e c t i v e l y . On the second day, measurements were 20 °C, 12 % 0 a n d 7.5 mg/1 r e s p e c t i v e l y . No d i f f e r e n c e s i n the swimming b e h a v i o u r of f i s h were noted between the two days. 54 F i g u r e 15. D i s s o l v e d oxygen c o n c e n t r a t i o n s and c o r r e s p o n d i n g d e p th d i s t r i b u t i o n of sockeye salmon a t s t a t i o n 1 (seaward, p o l l u t e d ) . See t e x t f o r e x p l a n a t i o n . Depth 1=0-.24 m; depth 2=.25-.49 m; depth 3=.5-1.0 m. 56 An o v e r a l l p i c t u r e of the depth d i s t r i b u t i o n s of common s p e c i e s caught a t each sample s t a t i o n i n 1984 i s p r e s e n t e d i n t a b l e V I I . Common s p e c i e s were d e f i n e d as o c c u r r i n g i n 50 % or more of the t o t a l s e i n e h a u l s i n a p a r t i c u l a r month. For a l l months, o n l y s i x s p e c i e s were c o n s i d e r e d common i n depth 1 w i t h arrow g o b i e s and P a c i f i c s t a g h o r n s c u l p i n s p r e d o m i n a t i n g . These two s p e c i e s were a l s o c a p t u r e d w i t h s i m i l a r f r e q u e n c y i n depths 2 and 3. Chum salmon were among the more f r e q u e n t l y caught s p e c i e s a t s t a t i o n 4, depth 1 i n A p r i l . There were no commonly o c c u r r i n g s p e c i e s i n depth 1 of s t a t i o n 2 i n A p r i l and s t a t i o n 3 i n May. A range of 1 t o 9 s p e c i e s was c o n s i d e r e d common i n depths 2 and 3 (of d i f f e r e n t s t a t i o n s ) . P i n k and chum salmon were f r e q u e n t l y c a p t u r e d a t s t a t i o n 4, depth 2 i n A p r i l . Chinook salmon were caught i n both depths 2 and 3 a t v a r i o u s s t a t i o n s i n a l l months. Sharpnose s c u l p i n s were p r e s e n t p r i m a r i l y i n depth 2 whereas c r e s c e n t gunnels and s t i c k l e b a c k s o c c u r r e d o n l y i n depth 3. Temporal d i s t r i b u t i o n s R e s u l t s of p r e l i m i n a r y s a m p l i n g i n 1983 suggested t h a t c h i n o o k salmon may show d i s t i n c t a r r i v a l t i m e s a t the p o l l u t e d , seaward s t a t i o n ; the term " a r r i v a l t i m e " i m p l y i n g t h a t the f i s h were moving onto the i n t e r t i d a l a r e a and swimming p r i m a r i l y i n a seaward t o landward d i r e c t i o n . Once the s e f i s h have passed by a g i v e n s t a t i o n they were not l i k e l y t o be c a p t u r e d i n the sa m p l i n g p e r i o d s used i n t h i s s t u d y . The r e s u l t s i n f i g u r e 16, o b t a i n e d i n mid June, i n d i c a t e d a peak i n c a p t u r e s o c c u r r e d 2.25 57 TABLE V I I Most common* s p e c i e s found a t each s t a t i o n (1-4) i n depths 1, 2, and 3 i n A p r i l , May and June (1984). A p r i l May June Depth Spec i e s 1 2 3 4 1 2 3 4 1 2 3 4 1 Surf smelt X X X S t a r r y f l o u n d e r x X X X Chum salmon X Arrow goby X X X X X X P a c i f i c s t a g -horn s c u l p i n X X X X X X X Sharpnose s c u l p i n X 2 Surf smelt X X X X X S t a r r y f l o u n d e r X X X X X X X X X X X X E n g l i s h s o l e X X X X X Chinook salmon X X 3-spine s t i c k l e -back X X X X X X P i n k salmon X Chum salmon X Sandlance X X P a c i f i c s t a g -horn s c u l p i n X X X X X X X X X Arrow goby X X X X X X X X X H e r r i n g X X X X X Sharpnose s c u l p i n X S h i n e r p e r c h X X X 3 S t a r r y f l o u n d e r X X X X X X X X X X X X Arrow goby X X X X X X X E n g l i s h s o l e X X X X Chinook salmon X X X X X X X Surf smelt X X H e r r i n g X X X X X X X C r e s c e n t gunnel X P a c i f i c snake p r i c k l e b a c k X X X S h i n e r p e r c h X X X X 3-spine s t i c k l e -back X X X X P a c i f i c s t a g h o r n s c u l p i n X X X X X X Sandlance X *common s p e c i e s a r e those t h a t o c c u r r e d i n a t l e a s t 50 % of the samples taken a t a s t a t i o n f o r a g i v e n month. 58 F i g u r e 16. Chinook salmon c a p t u r e s a t s t a t i o n 1 on a s i n g l e f l o o d t i d e c y c l e . (June 14, 1983). C o r r e s p o n d i n g d i s s o l v e d oxygen l e v e l s a r e g i v e n . See t e x t f o r e x p l a n a t i o n . 60 hours a f t e r s l a c k t i d e (oxygen=8.4 mg/1, temperature=18 °C and s a l i n i t y = 4 . 5 %„ ). Samples were taken over the whole 0 t o 1 m de p t h . The oxygen l e v e l a t s l a c k t i d e (6 mg/1) was not low i n r e l a t i o n t o normal l e v e l s o b s e r v e d f o r t h i s month (<3mg/l). In 1984, sa m p l i n g a t the seaward s t a t i o n s u s u a l l y took p l a c e from 0 t o 1.5 hours a f t e r low s l a c k t i d e , a s u f f i c i e n t p e r i o d t o r e c o r d oxygen l e v e l s above 7 mg/1 on the p o l l u t e d s i d e of the j e t t y . Comparisons of chum salmon c a p t u r e times i n May showed s i g n i f i c a n t d i f f e r e n c e s were p r e s e n t between each p a i r of seaward and landward s t a t i o n s ( p < . 0 l , MWU t e s t ) . The chum salmon on the p o l l u t e d s i d e of the j e t t y were caught an average of 19 minutes e a r l i e r than chum i n the u n p o l l u t e d a r e a ( t a b l e V I I I ) . There were no s i g n i f i c a n t d i f f e r e n c e s i n the c a p t u r e t i m e s of chi n o o k between the p o l l u t e d and u n p o l l u t e d p a i r s of s t a t i o n s i n e i t h e r May or June. However, the mean a r r i v a l t i m e s of chinook salmon g r e a t e r than 6 cm were s i g n i f i c a n t l y l a t e r than s m a l l e r chinook (p<.05, MWU t e s t ) . P resence/absence r e s u l t s The b i n a r y method of l o g i s t i c r e g e s s i o n was used t o d i s c e r n t h o s e f a c t o r s or c o m b i n a t i o n of f a c t o r s s i g n i f i c a n t l y a s s o c i a t e d (but not n e c e s s a r i l y c a u s a l l y r e l a t e d ) w i t h the presence of chum and c h i n o o k salmon i n the study a r e a . The f i n a l r e s u l t s a r e g i v e n i n t a b l e IX and r e i t e r a t e d q u a l i t a t i v e l y i n t a b l e X. Parameters were c o n s i d e r e d s i g n i f i c a n t i f t w i c e t h e i r SE ( s t a n d a r d e r r o r ) d i d not exceed the parameter e s t i m a t e . I f the SE was too l a r g e , t h i s was an i n d i c a t i o n t h a t the parameter was TABLE V I I I Means of c a p t u r e times (hours a f t e r f l o o d ) and water q u a l i t y p arameters a s s o c i a t e d w i t h c h i n o o k and chum salmon i n 1984. S t a n d a r d e r r o r s of c a p t u r e t i m e s a r e g i v e n i n p a r e n t h e s e s . Spec Month S t a t - Capture Temp S a l i n - Oxygen % S a t -- i e s i o n time °C i t y % mg/1 u r a t i o n Chinook May 1 0.96(.16) 14.5 1 1 . 1 8.11 87.9 3 1.16(.26) 15.2 1 1 .4 8.65 95.1 2 3.01(.08) 17.7 10 . 1 7.45 85.4 4 3.01(.23) 16.8 13 .4 9.24 1 06. 1 June 1 1.12(.17) 16.3 2 .6 8.26 89.0 3 0.84(.16) 17.4 5 .2 7.18 79.4 2 3.03(.14) 19.0 4 .4 6.53 73.8 4 2.97(.12) 17.2 7 .8 7.85 87.7 Chum May 1 0.61(.17) 17.1 7 .9 6.32 70.7 3 0.93(.19) 16.0 1 1 .6 7.57 84.3 2 2.78(.15) 16.8 1 1 .6 6.51 77.0 4 3.11(.15) 17.2 1 4 .0 9.08 105.3 June 3 0.78(.24) 17.6 6 .8 7.04 79.1 4 3.22(.18) 18.9 8 .0 9.03 104.4 62 Ta b l e IX L o g i s t i c r e g r e s s i o n r e s u l t s f o r presence/absence a n a l y s i s of c h i n o o k and chum salmon i n May and June of 1984. Spec i e s Month Parameter E s t i m a t e SE Chinook May a 42.07 1 5.66 s i d e ( 2 ) -1 .53 .51 de p t h ( 2 ) 2.06 .71 de p t h ( 3 ) 3.01 .74 oxygen -8.59 2.70 temp. -8.20 2.88 temp*oxygen 1 .61 .50 Chum May s i d e ( 2 ) 1.71 .56 de p t h ( 2 ) 1 .24 .53 oxygen -0.66 .26 Chinook June a 23.11 8.39 de p t h ( 2 ) 3.45 1.10 d e p t h ( 3 ) 4.12 1.10 temp. -4.32 1 .43 s a l i n i t y -1.12 .34 oxygen -5.68 2.37 temp*oxygen 1 .02 .41 a poor p r e d i c t o r of f i s h p r e s e n c e . a r e p r e s e n t s the p r o b a b i l i t y of a s p e c i e s b e i n g p r e s e n t w i t h z e r o r e g r e s s i o n v a r i a b l e s (a was a l s o not i n c l u d e d i n the f i n a l r e s u l t s i f the SE exceeded the parameter e s t i m a t e ) . Temperature, oxygen and s a l i n i t y ( c o n t i n u o u s f a c t o r s ) were s c a l e d (see s e c t i o n on s t a t i s t i c a l a n a l y s i s ) so t h a t the l a r g e s t parameter e s t i m a t o r c o u l d be i n t e r p r e t e d as c o n t r i b u t i n g t h e most t o the p r o b a b i l i t y of a salmon b e i n g p r e s e n t . For t h e c o n t i n u o u s f a c t o r s and f o r i n c r e a s i n g l e v e l s of each c a t e g o r i c a l f a c t o r (eg. s i d e 1, s i d e 2 ) , n e g a t i v e e s t i m a t o r s i n d i c a t e d e c r e a s i n g p r o b a b i l i t i e s of a s p e c i e s o c c u r r i n g and p o s i t i v e e s t i m a t o r s i n d i c a t e i n c r e a s i n g p r o b a b i l i t i e s . The e s t i m a t o r of the f i r s t l e v e l of each s i g n i f i c a n t c a t e g o r i c a l parameter (eg. depth 1, s i d e 1) i s an i m p l i e d "0" . I t must be emphasized t h a t the p r o b a b i l i t i e s 63 TABLE X Q u a l i t a t i v e summary of p r o b a b i l i t i e s a s s o c i a t e d w i t h chinook and chum salmon d i s t r i b u t i o n s a t d i f f e r e n t parameter c o m b i n a t i o n s and l e v e l s (1984). S p e c i e s Parameter and l e v e l P r o b a b i 1 i t y of o c c u r r e n c e i n May P r o b a b i l i t y of o c c u r r e n c e i n June Chinook low oxygen (3-6 mg/1) medium temp (16-19°C) h i g h h i g h low oxygen (3-6 mg/1) h i g h temp (20-28 C) low low h i g h oxygen (>6 mg/1) low temp (10-15 C) low -h i g h oxygen (>6 mg/1) medium temp (16-19"C) h i g h h i g h d e pth (1,2 or 3) h i g h e r w i t h i n c r e a s i n g d e p th h i g h e r w i t h i n c r e a s i n g depth p o l l u t e d s i d e h i g h e r no d i f f e r e n c e u n p o l l u t e d s i d e lower no d i f f e r e n c e h i g h s a l i n i t y (>=6 %<> ) no d i f f e r e n c e lower low s a l i n i t y (<6 % 0 ) no d i f f e r e n c e h i g h e r Chum low oxygen (<6 mg/1) h i g h oxygen (>6 mg/1) d e p t h (1,2 or 3) h i g h low h i g h e s t i n de p t h 2 -64 g e n e r a t e d by the l o g i s t i c r e g r e s s i o n e q u a t i o n a r e a d e s c r i p t i o n of the data c o l l e c t e d and are a f u n c t i o n of t h e sample s i z e s r e c o r d e d f o r each f a c t o r l e v e l . The p r o b a b i l i t i e s w i l l be d e s c r i b e d and d i s c u s s e d as i n c r e a s i n g or d e c r e a s i n g t r e n d s i n s t e a d of a c t u a l p r o b a b i l i t y v a l u e s . Chinook salmon May In May 1984, the p r o b a b i l i t y of a c h i n o o k b e i n g p r e s e n t was " e x p l a i n e d " by oxygen, t e m p e r a t u r e , s i d e , d e pth ( g r e a t e s t p r o b a b i l i t y i n depth 3) and an oxygen/temperature i n t e r a c t i o n term ( t a b l e I X ) . Chinook salmon were p r e s e n t i n 28 % of the t o t a l samples, and of t h e s e , 62 % were taken i n the p o l l u t e d s t u d y area ( t a b l e X I ) . The temperature/oxygen i n t e r a c t i o n term i n d i c a t e d t h a t the r e l a t i o n s h i p between t h e s e two f a c t o r s changed w i t h the l e v e l s c o n s i d e r e d . Examined s i n g l y , the oxygen term was o n l y s l i g h t l y l a r g e r than the t e m p e r a t u r e e s t i m a t o r which suggested the two f a c t o r s were of s i m i l a r importance. These r e s u l t s are best d e s c r i b e d by e x a m i n i n g f i g u r e 17, the temperature/oxygen p r o b a b i l i t y s u r f a c e f o r d e p t h 3, s i d e 1. The p r o b a b i l i t i e s g i v e n f o r the shaded a r e a s of the f i g u r e must be viewed as p r e d i c t i v e v a l u e s o n l y as t h e s e c o m b i n a t i o n s of temperature and oxygen were not r e c o r d e d i n t h e study a r e a ( t a b l e X I I ) . The r e m a i n i n g temperature and oxygen v a l u e s r e p r e s e n t a l l v a l u e s r e c o r d e d on the p o l l u t e d and u n p o l l u t e d s i d e of the j e t t y i n May. 65 TABLE XI Summary of the water q u a l i t y c o n d i t i o n s r e c o r d e d i n A p r i l , May and June, 1984; o v e r a l l , and f o r samples c o n t a i n i n g s a l m o n i d s . P = p o l l u t e d ; U = u n p o l l u t e d . Month S p e c i e s or a l l days No. of samples Temperature (°C) S a l i n i t y °/oo P U P U P U A l l days mean 33 44 12.7 13.0 15.2 17.3 med. 12.3 12.8 15.2 17.1 max. 19.8 16.4 18.6 23.8 min. 10.6 10.7 12.0 11.8 Chinook mean 8 4 12.4 12.7 15.0 18.1 med. 11.9 12.2 15.0 17.4 max. 14.8 14.8 15.7 21 .2 min. 11.1 11.5 14.5 16.3 Chum mean 2 12 14.2 13.7 15.4 16.7 med. 14.2 13.7 15.4 16.5 max. 14.8 16.4 15.9 21.3 min. 13.5 11.5 14.8 11.8 A l l days mean 82 76 17.4 16.2 10.2 12.5 med. 17.5 15.6 9.8 12.7 max. 26.5 23.8 18.3 17.5 min. 10.8 13.3 5.9 17.4 Chinook mean 28 17 16.4 15.9 7.8 12.5 med. 16.2 15.9 8.1 12.7 max. 21 .3 18.5 9.3 17.5 min. 10.9 13.5 3.8 17.4 Chum mean 1 2 22 17.3 16.6 9.6 12.8 med. 17.3 16.6 8.1 13.3 max. 19.8 20.8 14.1 17.5 min. 14.4 13.7 7.2 7.5 A l l days mean 58 85 19.8 18.1 5.4 8.4 med. 19.7 17.5 4.9 8.0 max. 28.3 28.3 12.0 14.9 min. 15.6 14.8 2.1 3.3 Chinook mean 18 26 18.2 17.2 3.9 7.1 med. 18.3 17.5 3.3 7.0 max. 21.8 21 .5 9.5 11.8 min. 15.6 14.8 2.1 3.3 Chum mean 2 9 20.0 17.9 5.0 7.8 med. 20.0 17.8 5.0 5.7 max. 21 .8 21 .5 5.1 12.6 min. 18.2 15.5 4.9 4.6 May 66 TABLE XI ( c o n t 1 ) Summary of the water q u a l i t y c o n d i t i o n s r e c o r d e d i n A p r i l , May and June, 1984; o v e r a l l , and f o r samples c o n t a i n i n g s a l m o n i d s . P = p o l l u t e d ; U = u n p o l l u t e d . Month S p e c i e s or No. of D i s s o l v e d P e r c e n t a l l days samples Oxygen mg/1 S a t u r a t i o n (%) P U P U P U May A l l days mean 33 44 6. ,98 9. 32 74. 5 101 . ,5 med. 7. .03 9. 25 74. 1 100. ,9 max. 9. ,57 10. 25 102. 2 117. ,5 min. 4. ,30 8. 20 44. ,7 86. ,0 Chinook mean 8 4 6. ,89 9. 28 73. , 1 100. ,5 med. 6. ,73 9. 30 70. ,0 100. ,3 max. 8. ,23 9. 50 89. ,0 103. ,9 min. 5. ,55 9. 00 57. ,2 97. ,2 Chum mean 2 12 7. ,15 9. 54 79. ,5 104. ,9 med. 7. ,15 9. 98 79. ,5 108. .7 max. 7. ,56 10 .2 86. ,0 117. .5 min. 6. ,73 8 .3 73. ,0 88. .0 A l l days mean 82 76 7. ,07 8. 72 80. ,2 98. .7 med. 7. ,41 8. 93 84. ,7 101 , .2 max. 10. ,05 9. 70 110. ,7 110, .7 min. 2. .59 5. 86 30. ,0 65, .4 Chinook mean 28 17 7. .76 8. 79 87. .2 98, .5 med. 8. ,07 9. 04 90. ,0 101, .9 max. 9. .30 9. 52 109. ,5 110, .7 min. 3. .79 5. 86 43. , 1 65, .4 Chum mean 1 2 22 6, .17 8. 53 71 . 3 97, . 1 med. 6. .61 8. 91 72. ,5 102, . 1 max. 7. .80 9. 52 87. .2 110, .7 min. 3. .45 6. 10 40. ,9 68, .7 A l l days mean 58 85 6, .09 7. 76 69. .9 87, .8 med. 6, .05 7. 44 72. .7 84, .7 max. 8. .99 13. 10 101. .2 149, .4 min. 3. .05 3. 60 30. .0 42, .2 Chinook mean 18 26 7, .22 7. 37 80. .9 82, .0 med. 7, .49 7. 18 81 . .4 82, .3 max. 8, .99 13. 10 101 . .2 143, .3 min. 4. .38 3. 60 50. .9 42, .2 Chum mean 2 9 6, .40 8. 01 74, .5 91 , .0 med. 6, .40 7. 53 74, .5 82, .8 max. 6. .74 1 1 .2 80. .8 128, . 1 min. 6, .06 6. 01 68. .2 67, .2 67 F i g u r e 17. Temperature/oxygen p r o b a b i l i t y s u r f a c e f o r chinook salmon i n May (depth 3, p o l l u t e d s i d e of the j e t t y ) . Shaded a r e a s r e p r e s e n t t h o s e temperature/oxygen c o m b i n a t i o n s which were not r e c o r d e d i n the s t u d y a r e a . See t e x t f o r e x p l a n a t i o n . AlHiqBqoJd 69 Ta b l e X I I T o t a l f r e q u e n c i e s of temperature/oxygen c o m b i n a t i o n s r e c o r d e d i n May (1984). Number of samples i n which chinook salmon were p r e s e n t i s g i v e n i n p a r e n t h e s e s . Temp. (°C) <3.0 3-3.9 4-4.9 D i s s o l v e d oxygen (mg/1) 5-5.9 6-6.9 7-7.9 8-8.9 >=9.0 < 1 2 . 0 0 0 0 0 0 0 4(2) 4 12-13.9 0 0 0 0 0 0 6 8(2) 14-15.9 0 1(1) 0 1(1) 1(1) 5(1 ) 13(6) 22(7) 16-17.9 0 0 2 2(1 ) 8(1 ) 13(5) 15(6) 10(4) 18-19.9 1 1 4 3 2(1 ) 5(2) 4(2) 2(1 ) 20-21.9 0 1 0 2 1 2(1 ) 4 0 22-23.9 0 1 1 1 1 4 1 0 24-25.9 0 0 0 0 1 0 0 0 >26 0 0 0 1 0 0 0 0 70 At oxygen l e v e l s from 2-6 mg/1, the p r o b a b i l i t y of a c h i n o o k salmon b e i n g p r e s e n t d e c r e a s e d as t e m p e r a t u r e s i n c r e a s e d from 14-18 °C ( f i g u r e 17) and mean p e r c e n t a g e a i r s a t u r a t i o n v a l u e s ranged from 43-65 % ( t a b l e X I I I ) . From 18-26 °C, the p r o b a b i l i t y of a chinook presence was almost n i l , and the c o r r e s p o n d i n g percentage a i r s a t u r a t i o n v a l u e s ranged from 30-71 % ( t a b l e X I I I ) . As the oxygen l e v e l s r o s e above 6 mg/1, the p r o b a b i l i t y of a c h i n o o k o c c u r r i n g i n t e m p e r a t u r e s above 18 °C i n c r e a s e d ( f i g u r e 17). The mean pe r c e n t a g e s a t u r a t i o n v a l u e s of d i s s o l v e d oxygen a l s o showed a t y p i c a l l y i n c r e a s i n g p a t t e r n w i t h i n c r e a s i n g oxygen and temperature l e v e l s ( t a b l e X I I I ) . Oxygen l e v e l s above 6 mg/1 were r e c o r d e d f a r more f r e q u e n t l y than lower oxygen l e v e l s ( t a b l e X I I ) . At h i g h oxygen l e v e l s (above 6 mg/1) and t e m p e r a t u r e s below 16 °C, the p r o b a b i l i t y of a chinook salmon o c c u r r i n g was low. Temperatures below 16 °C were r e c o r d e d p r i m a r i l y i n e a r l y May when s a l i n i t y l e v e l s were h i g h e r (13-16 %o ) but not v e r y d i f f e r e n t from o t h e r samples when ch i n o o k salmon were p r e s e n t ( t a b l e X I I I ) . The p r o b a b i l i t y of a salmon b e i n g p r e s e n t i n c r e a s e d s i g n i f i c a n t l y (p<.05) as the t e m p e r a t u r e s rose t o 19 °C (and oxygen c o n c e n t r a t i o n s were g r e a t e r than 6 mg/1). F u r t h e r u n i t changes i n temperature d i d not change p r o b a b i l i t i e s s i g n i f i c a n t l y a t t h i s l e v e l . The area on the s u r f a c e ( f i g u r e 17) where a l l i n c r e a s i n g and d e c r e a s i n g p r o b a b i l i t i e s converged may be i n t e r p r e t e d as the temperature/oxygen c o m b i n a t i o n s a t which c h i n o o k salmon had the h i g h e s t p r o b a b i l i t y of o c c u r r i n g . In May, t h i s o c c u r r e d near a 71 T a b l e X I I I Mean pe r c e n t a g e a i r s a t u r a t i o n v a l u e s and mean s a l i n i t i e s g i v e n i n p a r e n t h e s e s f o r the t e m p e r a t u r e / oxygen c o m b i n a t i o n s r e c o r d e d i n May (1984). Temp. (°C) <3.0 3-3. 9 4-4. 9 D i s s o l v e d oxygen (mg/1) 5-5.9 6-6.9 7-7.9 8-8.9 >=9. 0 <1 2.0 0 0 0 0 0 0 89.4 99. 9 (0) (0) (0) (0) (0) (0) (15.7) (13. 0) 12-13. 9 0 0 0 0 0 0 94.2 100. 4 (0) (0) (0) (0) (0) (0) (16.0) (13. 4) 14-15. 9 0 43. 1 0 65.4 74. 1 81.5 95.2 1 02. 3 (0) (7. 6) (0) (11.6) (10.7) (11.8) (13.5) (11. 9) 16-17. 9 0 0 47. 5 63.0 72.6 85.0 97. 1 104. 9 (0) (0) (7. 5) (10.5) (9.8) (10.2) (10.6) (14. 4) 18-19. 9 30.0 40. 9 58. 2 64.0 73.0 87.0 104.7 110. 1 (7.7) (8. 3) (7. 9) (7.6) (9.8) (7.7) (15.4) (12. 8) 20-21 . 9 0 40. 8 0 65.6 80.5 90.2 105.8 0 (0) (8. 2) (0) (7.8) (6.5) (11.6) (16.4) (0) 22-23. 9 0 46. 3 63. 2 62.7 84.0 95.8 109.5 0 (0) (8. 8) (9. 8) (8.3) (9.8) (13.6) (18.0) (0) 24-25. 9 0 0 0 0 79.3 0 0 0 (0) (0) (0) (0) (8.8) (0) (0) (0) >26 0 0 0 71 .0 0 0 0 0 (0) (0) (0) (7.3) (0) (0) (0) (0) 72 temperature of 16 °C and an oxygen l e v e l of 8 mg/1. The mean per c e n t a g e a i r s a t u r a t i o n was around 97 % ( t a b l e X I I I ) . I f the n e g a t i v e parameter e s t i m a t o r f o r the u n p o l l u t e d s i d e of the j e t t y ( s i d e 2, t a b l e IX) i s s u b s t i t u t e d i n t o the l o g i s t i c r e g r e s s i o n e q u a t i o n , the r e l a t i o n s h i p between temperature and oxygen remains the same but the p r o b a b i l i t i e s of a c h i n o o k o c c u r r i n g a r e lower ( f i g u r e 18). S a l i n i t y was not a s s o c i a t e d w i t h the presence of chinook salmon i n May and the mean v a l u e s w i t h i n which they were caught were not s i g n i f i c a n t l y d i f f e r e n t between the n o r t h and south s i d e s of the j e t t y (11.2 %,and 12.7 % r e s p e c t i v e l y ) ( t a b l e X I ) . Chinook salmon were found over a wide range of s a l i n i t i e s (7.6 t o 18.3 %<> ) on both s i d e s of the j e t t y ( f i g u r e 19). June In June, chinook salmon were p r e s e n t i n 31 % of the t o t a l s e i n e h a u l s . The p r o b a b i l i t y of a chinook b e i n g p r e s e n t was " e x p l a i n e d " by d e p t h , s a l i n i t y , t e m p e r a t u r e , oxygen and a temperature/oxygen i n t e r a c t i o n term ( t a b l e I X ) . There were no d i f f e r e n c e s i n c h i n o o k salmon presence between the two s i d e s of the j e t t y or between the seaward and landward s t a t i o n s . For s i m p l i c i t y , s a l i n i t y was examined s e p a r a t e l y from the temperature and oxygen terms. As i n May, c h i n o o k salmon were most commonly c a p t u r e d i n depth 3. S a l i n i t y v a l u e s r e c o r d e d i n June ranged from 2-15 °/0O . Chinook were found over t h i s whole range but more f r e q u e n t l y i n lower s a l i n i t y water ( f i g u r e 2 0 ) . The h i g h e s t p r o b a b i l i t i e s of 73 F i g u r e 18. Temperature/oxygen p r o b a b i l i t y s u r f a c e f o r chinook salmon i n May (depth 3, u n p o l l u t e d s i d e of the j e t t y ) . Shaded a r e a s r e p r e s e n t t h o s e temperature/oxygen c o m b i n a t i o n s which were not r e c o r d e d i n the s t u d y a r e a . See t e x t f o r e x p l a n a t i o n . A i m q e q o J d 75 F i g u r e 19. H i s t o g r a m of s a l i n i t y v a l u e s r e c o r d e d i n the p o l l u t e d and u n p o l l u t e d a r e a s i n May. Shaded a r e a s the graph r e p r e s e n t number of o c c u r r e n c e s of c h i n o o k salmon at each s a l i n i t y l e v e l . Number of occurrences 0 5 10 15 20 25 77 chinook b e i n g p r e s e n t were a s s o c i a t e d w i t h s a l i n i t i e s of 2-6 % 0 . The f r e q u e n c y of o c c u r r e n c e f o r each s a l i n i t y l e v e l i l l u s t r a t e d i n the same f i g u r e shows t h a t v a l u e s from 4-9 % w e r e r e l a t i v e l y common. A l a r g e number of these low s a l i n i t y v a l u e s were r e c o r d e d i n the p o l l u t e d a r e a ( f i g u r e 21) S a l i n i t y had a s m a l l e r e s t i m a t o r than e i t h e r temperature or oxygen and t h e r e f o r e e x p l a i n e d l e s s of the v a r i a b i l i t y a s s o c i a t e d w i t h chinook c a p t u r e s . P r o b a b i l i t i e s f o r the temperature/oxygen r e l a t i o n s h i p p i c t u r e d i n f i g u r e 22 were g e n e r a t e d u s i n g a l l s i g n i f i c a n t parameter e s t i m a t o r s f o r June i n c l u d i n g the terms f o r depth 3 and s a l i n i t y . The s a l i n i t y term was a s s i g n e d the mean v a l u e a s s o c i a t e d w i t h chinook presence i n June (5.8 %o ). See the t e x t d e s c r i p t i o n of f i g u r e 17 f o r i n f o r m a t i o n on the o r i g i n of temperature/oxygen c o m b i n a t i o n s used i n f i g u r e 22. The temperature/oxygen p r o b a b i l i t y s u r f a c e ( f i g u r e 22) showed the same g e n e r a l t r e n d s as f o r May w i t h some d i f f e r e n c e s o c c u r r i n g a t the p o i n t s of i n c r e a s i n g and d e c r e a s i n g p r o b a b i l i t i e s . The minimum temperature r e c o r d e d i n June (14.8 °C) was 4 °C h i g h e r than f o r May (10.8 °C) ( t a b l e X I ) . At a l l oxygen l e v e l s from 3 t o 8 mg/1, the p r o b a b i l i t y of a c h i n o o k b e i n g p r e s e n t d e c r e a s e d w i t h i n c r e a s i n g t e m p e r a t u r e s . In p a r t i c u l a r , a t t e m p e r a t u r e s above 20 °C and oxygen l e v e l s of 3-6 mg/1, c h i n o o k were g e n e r a l l y a b s e n t . Temperatures above 22 °C were r e c o r d e d i n f r e q u e n t l y ( t a b l e X I V ) . The g r e a t e s t d e c l i n e i n p r o b a b i l i t i e s o c c u r r e d i n the temperature i n c r e a s e from 17 t o 19 °C. At oxygen l e v e l s above 8 mg/1, a l l p e r c e n t a g e s a t u r a t i o n 78 F i g u r e 20. H i s t o g r a m of s a l i n i t y v a l u e s r e c o r d e d i n June and the p r o b a b i l i t y of a c h i n o o k salmon o c c u r r i n g i n each l e v e l . The s i n g l e c u r v e d l i n e r e p r e s e n t s the p r o b a b i l i t y v a l u e s g e n e r a t e d by the l o g i s t i c r e g r e s s i o n a n a l y s i s . The shaded a r e a s of t h e graph r e p r e s e n t the a c t u a l number of o c c u r r e n c e s of c h i n o o k salmon a t each s a l i n i t y l e v e l . s a o u e j j n o o o jo jequinN 80 F i g u r e 21. H i s t o g r a m of s a l i n i t y v a l u e s r e c o r d e d i n the p o l l u t e d and u n p o l l u t e d a r e a s i n June. Shaded a r e a s the graph r e p r e s e n t number of o c c u r r e n c e s of c h i n o o k salmon a t each s a l i n i t y l e v e l . 1 8 82 F i g u r e 22. Temperature/oxygen p r o b a b i l i t y s u r f a c e f o r c h i n o o k salmon i n June (depth 3, u n p o l l u t e d s i d e of the j e t t y ) . Shaded a r e a s r e p r e s e n t those temperature/oxygen c o m b i n a t i o n s which were not r e c o r d e d i n the study a r e a . See t e x t f o r e x p l a n a t i o n . 83 84 T a b l e XIV T o t a l f r e q u e n c i e s of temperature/oxygen c o m b i n a t i o n s r e c o r d e d i n June ( 1984 ) . Number of samples i n which c h i n o o k salmon were p r e s e n t i s g i v e n i n p a r e n t h e s e s . Temp. (•c) <3.0 3-3.9 D i s s o l v e d (mg/1) 4 -4 .9 5 -5.9 6 oxygen - 6 . 9 7 - 7 . 9 8 -8.9 > = 9.0 < 1 2 . 0 0 0 0 0 0 0 0 0 12-13.9 0 0 0 0 0 0 0 0 14-15.9 0 0 0 2 (1 ) 3(2) 3 (3 ) 6(4) 1 1(2) 16-17.9 0 0 3(1) 5(1 ) 5(4) 15(8) 5(2) 9(1 ) 18-19.9 0 5(1 ) 2 7(1 ) 7(1 ) 8 (4 ) 5(2) 4 20 -21.9 0 5 4(2) 2 4(2) 5(2) 1 0 22 -23.9 0 1 1 0 4 o - 0 0 24 -25 .9 0 0 2 1 2 1 0 0 >26 0 1 0 2 2 0 0 0 85 v a l u e s exceeded 90 % ( t a b l e XV) and c h i n o o k salmon had r e l a t i v e l y h i g h p r o b a b i l i t i e s of b e i n g p r e s e n t . Chinook had the h i g h e s t p r o b a b i l i t i e s of b e i n g p r e s e n t near a temperature of 17 °C and oxygen c o n c e n t r a t i o n s from 8-9 mg/1. The mean pe r c e n t a g e s a t u r a t i o n of t h i s d i s s o l v e d oxygen l e v e l was around 97 % ( t a b l e XV). The l a r g e r v a l u e of the oxygen e s t i m a t o r ( t a b l e V I I I ) i n d i c a t e s i t had a g r e a t e r e f f e c t than temperature i n d e s c r i b i n g the p r e s e n c e of chinook salmon. Chum salmon May At t h e i r peak abundance i n May, chum salmon were p r e s e n t i n 22 % of the t o t a l s e i n e h a u l s and t h e i r p r e s e n c e c o u l d be d e s c r i b e d by the depth, s i d e and oxygen terms. Chum were p r e s e n t most o f t e n i n depth 2 on the u n p o l l u t e d s i d e of the j e t t y . There was no s i g n i f i c a n t e s t i m a t o r f o r depth 3. The h i g h e s t p r o b a b i l i t i e s of chum salmon presence were i n reduced oxygen l e v e l s t h a t had a low fr e q u e n c y of o c c u r r e n c e ( f i g u r e 2 3 ) . However, t h e t o t a l number of chum salmon caught i n low oxygen water (<5 mg/1) was low and the g r e a t e s t number were p r e s e n t i n median oxygen c o n c e n t r a t i o n s (6-8 mg/1) ( f i g u r e 2 4 ) . The mean p e r c e n t a g e s a t u r a t i o n of oxygen a s s o c i a t e d w i t h chum salmon i n May was 88.0 % (sd=l7.6) f o r a l l s t a t i o n s and 97.0 % (sd=11.7) f o r t h e u n p o l l u t e d s i d e o n l y ( t a b l e X I ) . S a l i n i t y was not a p r e d i c t o r of chum salmon presence i n May. However, b o t h the mean and median s a l i n i t i e s w i t h i n which 86 T a b l e XV Mean p e r c e n t a g e a i r s a t u r a t i o n v a l u e s and mean s a l i n i t i e s g i v e n i n p a r e n t h e s e s f o r the t e m p e r a t u r e / oxygen c o m b i n a t i o n s r e c o r d e d i n June (1984). Temp. C O <3.0 3-3. 9 4-4. 9 D i s s o l v e d oxygen (mg/1) 5-5.9 6-6.9 7-7.9 8-8. 9 >=9. 0 <12. 0 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 12-13 .9 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 14-15 .9 0 (0) 0 (0) 0 (0) 56.9 (9.1 ) 70.3 (8.1 ) 82.0 (5.1) 90. (6. 4 3) 113. (9. 8 8) 16-17 .9 0 (0) 0 (0) 48. (6. 5 8) 60.0 (4.4) 70.8 (5.4) 81.3 (5.5) 96. (9. 7 3) 121. (11. 0 9) 18-19 .9 0 (0) 42. (5. 7 8) 52. (9. 8 5) 64.9 (8.2) 76.4 (6.5) 88.4 (7.4) 97. (6. 4 2) 113. (12. 9 3) 20-21 .9 0 (0) 32. (5. 5 4) 53. (4. 9 2) 68.5 (5.7) 81 .6 (7.0) 89.3 (6.0) 97. (6. 1 0) 0 (0) 22-23 .9 0 (0) 39. (2. 1 6) 49. (4. 9 2) 0 (0) 76.0 (5.7) 0 (0) 0 (0) 0 (0) 24-25 .9 0 (0) 0 (0) 59. (4. 6 8) 73.9 (3.3) 85.3 (9.7) 96.0 (5.7) 0 (0) 0 (0) >26 0 (0) 47. (5. 0 7) 0 (0) 69.7 (6.4) 87.8 (12.3) 0 (0) 0 (0) 0 (0) 87 F i g u r e 23. H i s t o g r a m of oxygen v a l u e s r e c o r d e d i n May and the p r o b a b i l i t y of a chum salmon o c c u r r i n g i n each l e v e l . The s i n g l e c u r v e d l i n e r e p r e s e n t s the p r o b a b i l i t y v a l u e s g e n e r a t e d by the l o g i s t i c r e g r e s s i o n a n a l y s i s . The shaded a r e a s of the graph r e p r e s e n t the a c t u a l number of o c c u r r e n c e s of chum salmon a t each oxygen l e v e l . C O C O 89 F i g u r e 24. T o t a l number of chum salmon c a p t u r e d i n r e l a t i o n t o d i s s o l v e d oxygen c o n c e n t r a t i o n s (May). 90 40-c o E CO ta E 3 o CO l _ CD E 35-30 25-20-15-10 5-J ! 4 6 8 10 D i s so l ved oxygen (mg/l) 12 91 chum were found were s i g n i f i c a n t l y d i f f e r e n t (p<.0l) between the u n p o l l u t e d and p o l l u t e d s i d e s of the j e t t y ( t a b l e XI and f i g u r e 25) c o r r e s p o n d i n g t o the s i g n i f i c a n t l y lower s a l i n i t i e s r e c o r d e d i n the p o l l u t e d a r e a o v e r a l l . In June, o n l y a few chum salmon were caught on the n o r t h s i d e of the j e t t y i n mean and median s a l i n i t i e s of 7.8 and 5.7 % o r e s p e c t i v e l y . O v e r a l l mean s a l i n i t i e s (chum p r e s e n t and ab s e n t ) on the n o r t h s i d e of the j e t t y dropped from 13.4 % 0 i n May t o 8.42 % i n June ( t a b l e X I ) . Other s p e c i e s A summary of the means and ranges of water q u a l i t y parameters (1984 r e s u l t s ) r e c o r d e d a t the time of c a p t u r e of the most commonly caught s p e c i e s , s t a r r y f l o u n d e r , P a c i f i c s t a g h o r n s c u l p i n s and arrow g o b i e s , i s g i v e n i n appendix 4. These 3 s p e c i e s were f r e q u e n t l y c a p t u r e d i n the e a r l y s t a g e s of the f l o o d t i d e when oxygen c o n c e n t r a t i o n s were most l i k e l y t o be d e p r e s s e d . O c c a s i o n a l y , s t r e s s e d and dead f i s h were o b s e r v e d when h y p o x i c c o n d i t i o n s p r e v a i l e d i n the e f f l u e n t c h a n n e l . O b s e r v a t i o n s on f i s h s t r e s s and b i r d p r e d a t i o n a t Iona I s l a n d (1984) O b s e r v a t i o n s of s t r e s s e d f i s h on the p o l l u t e d t i d a l f l a t a t Iona I s l a n d were r e c o r d e d p r i m a r i l y on the ebb and low s l a c k t i d a l s t a g e s when d i s s o l v e d oxygen c o n c e n t r a t i o n s were low. These e v e n t s were g e n e r a l l y accompanied by heavy b i r d p r e d a t i o n ( p r i m a r i l y by Great B l u e Herons and g u l l s ) . The f o l l o w i n g i s a 92 F i g u r e 25. H i s t o g r a m of s a l i n i t y v a l u e s r e c o r d e d i n the p o l l u t e d and u n p o l l u t e d a r e a s i n May. Shaded a r e a s of the graph r e p r e s e n t number of o c c u r r e n c e s of chum salmon at each s a l i n i t y l e v e l . in -o -1 Polluted area 4 6 B 1 0 1 2 14 1 6 1 8 2 0 Salinity CO Unpolluted area o «- in _ w o _ in -o -1 It i 1 1 1 1— i 1 1 i 6 8 1 0 1 2 1 4 1 6 1 6 2 0 2 2 Salinity ('/-) to 94 b r i e f d e s c r i p t i o n of o b s e r v a t i o n s made d u r i n g these p e r i o d s . On May 29 (1984), a p p r o x i m a t e l y 20 herons and 250 g u l l s were observed a c t i v e l y f e e d i n g a l o n g the s h o r e l i n e at s t a t i o n 1 (seaward, p o l l u t e d s t a t i o n ) . A s i n g l e dead chum salmon was found on the beach and s e v e r a l dead P a c i f i c snake p r i c k l e b a c k s , s m a l l s t a r r y f l o u n d e r and h e r r i n g were p u l l e d up i n beach s e i n e s (0 t o 1 m of w a t e r ) . Some f i s h c a p t u r e d i n the 0-.24 m depth e x h i b i t e d v e r y s l u g g i s h b e h a v i o u r i n c l u d i n g 2 coho salmon ( a p p r o x i m a t e l y 9 cm s t a n d a r d l e n g t h ) , s t a r r y f l o u n d e r , s c u l p i n s and c r a b s . On t h i s day, winds were 5 t o 7 knots from the n o r t h w e s t , c l o u d c o v e r was v a r i a b l e and a i r temperatures were 20-23 °C. Water q u a l i t y ( t e m p e r a t u r e , s a l i n i t y and oxygen) l e v e l s a r e shown i n t a b l e XVI. On J u l y 26 and 27 (1984), hundreds of s t r e s s e d and dead f i s h were obser v e d a t s t a t i o n 1. At 1.5 hours b e f o r e low s l a c k t i d e on J u l y 26 (0945 s t a n d a r d time) and 2.5 hours b e f o r e low s l a c k t i d e on J u l y 27 (1030 ST), many f i s h ( s t a r r y f l o u n d e r , h e r r i n g , s h i n e r p e r c h and P a c i f i c s t a g h o r n s c u l p i n s ) were seen skimming a l o n g the water s u r f a c e as they moved i n a seaward d i r e c t i o n . These f i s h appeared d i s o r i e n t e d and o f t e n swam among the r o c k s of the j e t t y where they became s t r a n d e d by the e b b i n g t i d e . F i s h e x h i b i t i n g s u r f a c i n g b e h a v i o u r were s l u g g i s h and e a s i l y caught by hand. Large numbers of herons and g u l l s were f e e d i n g on t h e s e f i s h . There was e v i d e n c e t h a t few salmon were p r e s e n t i n the study a r e a a t t h i s time as f o u r 200 m beach s e i n e h a u l s on the p r e v i o u s day ( u s i n g a 15 m s e i n e ) had y i e l d e d o n l y 3 c h i n o o k salmon. 95 TABLE XVI Water q u a l i t y measurements a t s t a t i o n 1, May 29, 1984. (Time = hours a f t e r f l o o d ; depth 1 = 0-.24 m, depth 2 = .25-.49 m, depth 3 = .5-1.0 m). Time Depth (m) Temperature C O S a l i n i t y (%) D i s s o l v e d (mg/1) -.22 1 19.7 8.3 3.45 2 18.3 7.7 1 .85 3 17.5 7.7 2.94 .67 1 21.0 8.2 3.38 2 19.3 7.6 3.33 3 18.3 7.5 4.65 1 .53 1 19.5 8.3 6.78 2 1 8.8 8.0 6.62 3 18.5 8.0 6.75 On J u l y 26, winds were from the s o u t h e a s t (about 3 k n o t s ) , the sky was o v e r c a s t and a i r t e m p e r a t u r e s ranged from 18-20 °C. D i s s o l v e d oxygen c o n c e n t r a t i o n s a t s t a t i o n 1 ranged from .3-1.9 mg/1, water t e m p e r a t u r e s were 19 °C and s a l i n i t y was 7 % 0 . On J u l y 27, winds were a g a i n from the s o u t h e a s t (same sp e e d ) , t h e r e was no c l o u d and a i r temp e r a t u r e s ranged from 19-24 °C. D i s s o l v e d oxygen c o n c e n t r a t i o n s ranged from .1-1.6 mg/1 a t the end of the j e t t y , s a l i n i t y was 8 % 0 a n d water t e m p e r a t u r e s were 18.5 °C. On two o c c a s i o n s , J u l y 12 and 24, o b s e r v a t i o n s on b i r d f e e d i n g were made 4 hours b e f o r e low s l a c k t i d e . Thousands of g u l l s and herons were seen f e e d i n g i n the c e n t e r of the e f f l u e n t c h a n n e l near s t a t i o n 2 ( l a n d w a r d , p o l l u t e d s t a t i o n ) . Many of the g u l l s brought t h e i r p r e y t o the. s h o r e l i n e i n d i c a t i n g t h a t p r i m a r i l y s m a l l f l o u n d e r s were b e i n g eaten (or perhaps t h i s s p e c i e s of f i s h i s not as e a s i l y swallowed by b i r d s i n f l i g h t ) . As the ebb t i d e p r o g r e s s e d , the f e e d i n g b i r d s moved as a f l o c k 96 down the c e n t e r of the e f f l u e n t c h a n n e l towards the sea. T h i s p a t t e r n of b i r d f e e d i n g appeared t o f o l l o w the seaward movement of low oxygen water as d e s c r i b e d e a r l i e r i n the s e c t i o n on e n v i r o n m e n t a l p a r a m e t e r s . At low t i d e , the m a j o r i t y of b i r d s had moved beyond the j e t t y and o n l y a few herons remained f e e d i n g a l o n g the s h o r e l i n e of the e f f l u e n t c h a n n e l . On r e g u l a r s a m p l i n g days b e g i n n i n g a t low s l a c k t i d e , the l a t t e r o b s e r v a t i o n was the t y p i c a l p a t t e r n of b i r d d i s t r i b u t i o n r e c o r d e d . I t i s not known i f the f e e d i n g p a t t e r n d e s c r i b e d f o r the ebb t i d e was a d a i l y o c c u r r e n c e . O c c a s s i o n a l l y on a f l o o d t i d e , l a r g e numbers of b i r d s c o n g r e g a t e d i n the n a t u r a l d r a i n a g e c h a n n e l s on the south s i d e of the e f f l u e n t c h a n n e l but they never e x h i b i t e d the same degree of a c t i v i t y r e c o r d e d on the ebb t i d e . B i r t w e l l et a l . (1983) has r e c o r d e d s i m i l a r o b s e r v a t i o n s of s t r e s s e d f i s h i n the p o l l u t e d a r e a a t Iona I s l a n d . 97 DISCUSSION The comparison of a p o l l u t e d and u n p o l l u t e d i n t e r t i d a l a r e a i n t h i s study s e r v e s t o i l l u s t r a t e the n e a r s h o r e d i s t r i b u t i o n s of j u v e n i l e chum and c h i n o o k salmon i n r e l a t i o n t o t e m p e r a t u r e , s a l i n i t y and d i s s o l v e d oxygen. The o c c u r r e n c e s of these two s p e c i e s a r e d i s c u s s e d w i t h r e f e r e n c e t o depth d i s t r i b u t i o n s , t e m p o r a l movements and p h y s i c a l v a r i a b i l i t y of the environment. Depth d i s t r i b u t i o n s The o b s e r v e d depth d i s t r i b u t i o n s of f i s h may r e f l e c t the i n f l u e n c e of a l a r g e c o m b i n a t i o n of b i o l o g i c a l (eg. c o m p e t i t i v e i n t e r a c t i o n s , food a v a i l a b i l i t y , p r e d a t o r s ) and p h y s i c a l (eg. f i s h l e n g t h , water q u a l i t y ) f a c t o r s (Edwards and S t e e l e 1968, Gibson 1973, S h i r v e l l and Dungey 1983). Only f i s h l e n g t h and water q u a l i t y were examined i n t h i s s t u d y . D i s c r e t e d epth s a m p l i n g i n 0 t o 1 m of water i n d i c a t e d t h a t 'nearshore' f o r j u v e n i l e s a l m o n i d s may be i n as l i t t l e as 5 cm of water a t the a d v a n c i n g f r o n t of a f l o o d t i d e but the g r e a t e s t c o n c e n t r a t i o n of f i s h o c c u r r e d i n .25 t o 1.0 m of water. Depths used by f i s h were r e l a t e d t o l e n g t h and may have been m o d i f i e d by s e a s o n a l t e m p e r a t u r e changes. I t i s p o s s i b l e t h a t the numbers of salmon caught i n depth 1 (0-.24 m) were u n d e r e s t i m a t e d by the one-p e r s o n beach s e i n i n g t e c h n i q u e (see appendix 1 ) , however, t h i s s h o u l d not a f f e c t the g e n e r a l l e n g t h / d e p t h r e l a t i o n s h i p s o b s e r v e d . I t s h o u l d be noted t h a t f i s h u s i n g the depth i n t e r v a l s as d e f i n e d f o r t h i s s t u d y (the d e f i n i t i o n s g i v i n g t h e minimum and maximum depths of a g i v e n i n t e r v a l ) may a l s o be 98 d i s t r i b u t e d v e r t i c a l l y w i t h i n the water column (e.g. s u r f a c e or bottom w a t e r s ) . T h i s type of v e r t i c a l d i s t r i b u t i o n was not examined except i n c o n t e x t of s u r f a c e b r e a k i n g b e h a v i o u r ( l a t e r d i s c u s s i o n ) . In f r e s h w a t e r , stream environments water depth i s c o n s i d e r e d an i m p o r t a n t m i c r o h a b i t a t f e a t u r e i n d e t e r m i n i n g s a l m o n i d d i s t r i b u t i o n s ( E v e r e s t and Chapman 1972, E g g l i s h a w and S h a c k l e y 1982, Rimmer e t a l . 1984). S h i r v e l l and Dungey (1983) summarized t h a t m i c r o h a b i t a t p r e f e r e n c e s were p r i m a r i l y a f u n c t i o n of f i s h s i z e . T h i s g e n e r a l r u l e appears t o h o l d f o r the depth d i s t r i b u t i o n s of chinook salmon i n n e a r s h o r e e s t u a r i n e environments as w e l l . As l e n g t h i n c r e a s e d , t h e r e was a c l e a r s h i f t of j u v e n i l e c h i n o o k t o deeper samp l i n g d e p t h s . F i s h w i t h a f o r k l e n g t h of l e s s than 5 cm were found i n a l l t h r e e depth i n t e r v a l s sampled but o c c u r r e d p r i m a r i l y i n depth 2 (.25-.49 m). F i s h g r e a t e r than 7 cm o c c u r r e d i n l a r g e r numbers i n depth 3 (.5-1.0 m) and no f i s h above 5 cm was caught i n d e p t h 1 except on c e r t a i n o c c a s i o n s when low d i s s o l v e d oxygen c o n d i t i o n s p r e v a i l e d . The l e n g t h / d e p t h s e g r e g a t i o n observed i n t h i s s tudy a g r e e s w i t h the broader o b s e r v a t i o n s by Myers (1980) and L e v i n g s (1982) t h a t s m a l l e r c h i n o o k f r y use beach h a b i t a t s whereas l a r g e r f i s h a r e found f u r t h e r o f f s h o r e i n deeper w a t e r s . E v e r e s t and Chapman (1972) showed a s i m p l e c o r r e l a t i o n of 0.65 between summer c h i n o o k l e n g t h s (3.2 - 11.7 cm t o t a l l e n g t h ) and depth ( g r e a t e s t d e n s i t i e s i n .6-.75 m of water) i n Idaho streams. They found t h a t as c h i n o o k grew the f i s h tended t o p r e f e r deeper and f a s t e r w a t e r s . Water v e l o c i t i e s were not 99 measured a t the s i t e of the p r e s e n t s t u d y but the c a p t u r e s of l a r g e chinook were a s s o c i a t e d w i t h the ad v a n c i n g s t a g e s of the f l o o d t i d e when c u r r e n t s had g r e a t l y i n c r e a s e d . A s i g n i f i c a n t c o r r e l a t i o n between f i s h l e n g t h and depth o c c u r r e d o n l y i n May ( c o r r e l a t i o n = . 6 6 ) w i t h l e n g t h s r a n g i n g from 3.7 t o 11.4 cm ( f o r k l e n g t h ) . In June l e n g t h s s t i l l ranged from 4.8 t o 10.2 cm but l i t t l e d epth s e g r e g a t i o n o c c u r r e d , p r o b a b l y as the m a j o r i t y of f i s h caught were i n the 6-8 cm range. The depth d i s t r i b u t i o n s of b o t h p i n k and chum salmon were s i m i l a r t o c h i n o o k f o r the same l e n g t h c a t e g o r i e s . A l l t h r e e s p e c i e s d i s p l a y e d peak abundances i n depth 2 f o r s i z e c l a s s e s of l e s s than 4 cm. No p i n k s of g r e a t e r than 4 cm f o r k l e n g t h were caught i n the stu d y a r e a . T h i s a g r e e s w i t h the o b s e r v a t i o n s of Le B r a s s e u r and P a r k e r (1964) t h a t t h e movement of p i n k salmon away from the s h o r e l i n e o c c u r s a t l e n g t h s of 4.5-5.5 cm. The absence of a s i g n i f i c a n t l e n g t h / d e p t h c o r r e l a t i o n f o r chum salmon i n 0 t o 1 m of water was not unexpected. The m a j o r i t y of chum caught were w i t h i n a narrow l e n g t h range of 4-6 cm and the s m a l l numbers of l a r g e r f i s h p r e s e n t were d i s t r i b u t e d e v e n l y among depths 2 and 3. The f a c t t h a t few chum salmon over 6 cm l e n g t h were c a p t u r e d might i n d i c a t e t h a t t h e i r movement away from the s h o r e l i n e i s a l s o r e l a t e d t o a s p e c i f i c l e n g t h . However, i n Hood C a n a l (Washington), Bax e t a l . (1983) found a wide range of f o r k l e n g t h s among chum salmon j u v e n i l e s caught ,by beach s e i n e s and s u r f a c e townets s u g g e s t i n g t h e r e were no d i s t i n c t s i z e ranges a t which the f r y moved away from beach a r e a s . They i n d i c a t e d t h a t the d i s t r i b u t i o n s of chum f r y 100 r e l a t i v e t o the s h o r e l i n e may be d e t e r m i n e d by a c o m b i n a t i o n of f a c t o r s i n c l u d i n g f i s h l e n g t h and season. Temperature The i n f o r m a t i o n p r e s e n t e d i n t h i s s t u d y suggested t h a t s a l m o n i d s of l e n g t h s l e s s than 5 cm were c a p a b l e of u s i n g water depths of l e s s than .25 m. However, the c a p t u r e of r e l a t i v e l y few salmon i n t h i s depth (0-.24 m), d e s p i t e t h e abundance of s u i t a b l e s i z e d f i s h , may be p a r t i a l l y e x p l a i n e d i n terms of s e a s o n a l u t i l i z a t i o n of the d e p t h . In A p r i l , p i n k , chum and c h i n o o k salmon of l e s s than 5 cm l e n g t h were d i s t r i b u t e d e v e n l y among depths 1 and 2. In May, g r e a t e s t numbers of chinook and chum salmon i n t h i s l e n g t h c l a s s were p r e s e n t i n depth 2. In June, when o n l y chum salmon e x h i b i t e d an o v e r a l l mean l e n g t h of l e s s than 5 cm, t h i s s p e c i e s d i d not occur i n depth 1. A l s o , chum salmon numbers no l o n g e r peaked i n depth 2 (as i n May) and were d i s t r i b u t e d more e v e n l y among depths 2 and 3. D u r i n g a c o o l r a i n y p e r i o d i n l a t e June (1984), mean water t e m p e r a t u r e s i n depth 1 dropped t o 16 °C from normal d a i l y averages of 18-25 °C and a chinook salmon of l e s s than 5 cm l e n g t h was once a g a i n c a p t u r e d i n depth 1. I t appears as i f t h e r e i s a s h i f t of s m a l l f i s h t o deeper water c o r r e s p o n d i n g t o the onset of warmer months and i n c r e a s i n g water t e m p e r a t u r e s . The narrow u t i l i z a t i o n of d e p t h 1 i s f u r t h e r i l l u s t r a t e d by the f a c t t h a t arrow g o b i e s and P a c i f i c s t a g h o r n s c u l p i n s were the most common f i s h c a p t u r e d h e r e . Both s p e c i e s a r e h i g h l y r e s i s t a n t t o extreme c o n d i t i o n s of t emperature and s a l i n i t y ( M o r r i s 1960, C a r t e r 1965 c i t e d i n 101 Hart 1973). D i s s o l v e d oxygen From A p r i l t o June i n 1984, the l e n g t h / d e p t h r e l a t i o n s h i p s of chinook salmon were s i m i l a r f o r the p o l l u t e d and u n p o l l u t e d s t a t i o n s . T h i s suggested t h a t the l e n g t h / d e p t h p a t t e r n s observed i n 1984 c o u l d be viewed c o l l e c t i v e l y as r e g u l a r events and s e r v e as a c o n t r a s t t o i r r e g u l a r i t i e s i n s a l m o n i d depth d i s t r i b u t i o n s r e c o r d e d i n 1983. On a t l e a s t two o c c a s i o n s i n June and J u l y of 1983 (.5 hours b e f o r e low t i d e ) , the o c c u r r e n c e s of v e r y low d i s s o l v e d oxygen l e v e l s (<1 mg/1) i n depths 2 and 3 of s t a t i o n 1 were accompanied by the presence of chinook and sockeye f r y a t the beach/water i n t e r f a c e where h i g h e r oxygen c o n c e n t r a t i o n s p r e v a i l e d . The uniqueness of the depth d i s t r i b u t i o n s i n both s i t u a t i o n s was demonstrated by the complete absence of a l l f i s h i n deeper water and the ease w i t h which the salmon were caught by hand. In a d d i t i o n , the mean l e n g t h s of c h i n o o k salmon caught i n depth 1 exceeded 6 cm whereas i n 1984, a l l salmon caught i n depth 1 were s m a l l e r . D u r i n g t h i s p e r i o d , l a r g e numbers of herons and g u l l s were f e e d i n g a c t i v e l y a t the w a t e r s edge. Though the n a t u r e of t h e i r food items c o u l d not be d i s c e r n e d , i t seems l o g i c a l t h a t the s l u g g i s h salmon would be e a s i l y c a p t u r e d prey i t e m s . A s i m i l a r type of h o r i z o n t a l depth d i s p l a c e m e n t owing t o the r e g u l a r o c c u r r e n c e of low d i s s o l v e d oxygen l e v e l s i n deeper waters has been r e c o r d e d i n M o b i l e Bay, Alabama (May 1973). E x t e n s i v e a r e a s of bottom water i n t h i s G u l f of Mexico e s t u a r y 102 s u f f e r oxygen d e p l e t i o n i n summer due t o s a l i n i t y s t r a t i f i c a t i o n i n s i n k s and by s p o i l from c o n s t r u c t i o n of a s h i p c h a n n e l . P e r i o d i c a l l y , the h y p o x i c bottom water i s d i r e c t e d a g a i n s t the beach by a c o m b i n a t i o n of wind and f l o o d t i d e c u r r e n t s f o r c i n g hundreds of l a r g e f i s h i n t o the s h a l l o w s . On two o t h e r o c c a s i o n s i n the c o u r s e of t h i s study ( d u r i n g May, 1983), s m a l l s c h o o l s of chinook were o b s e r v e d swimming i n 5 cm of water a t the a d v a n c i n g t i d a l f r o n t . I t i s d e b a t a b l e whether depth d i s p l a c e m e n t had o c c u r r e d i n t h i s s i t u a t i o n . The c h i n o o k d i d not appear s t r e s s e d and were d i f f i c u l t t o c a p t u r e but owing t o the p r o x i m i t y of the sewage c h a n n e l i t i s p o s s i b l e t h a t the depth c h o i c e of the salmon had been a f f e c t e d by unmeasured f a c t o r s (eg. sewage, low d i s s o l v e d oxygen c o n c e n t r a t i o n s i n i n a c c e s i b l e d e p t h s ) . However, a l l c a p t u r e d chinook were l e s s than 5 cm l o n g which agreed w i t h the 1984 l e n g t h c a t e g o r i e s a s s o c i a t e d w i t h depth 1. I t i s noteworthy t h a t Healey (1980) a l s o r e c o r d e d chinook salmon c a p t u r e s i n as l i t t l e as a few c e n t i m e t e r s of water. Other s t u d i e s documenting v e r t i c a l changes i n the depth d i s t r i b u t i o n of f i s h i n response t o low d i s s o l v e d oxygen c o n c e n t r a t i o n s i n c l u d e Lewis (1970) on c y p r i n o d o n t o i d s , P e t r o s k y and Magnuson (1973) on Esox l u c i u s , P e r c a f l a v e s c e n s and Lepomis  m a c r o c h i r u s , B i r t w e l l (1977) on 0. t s h w a t s c h a , Gee (1978) on g r e a t p l a i n s f i s h e s , and Kramer and McClure (1982) on t r o p i c a l f i s h e s . S u r f a c e water l a y e r s o f t e n c o n t a i n h i g h e r l e v e l s of d i s s o l v e d oxygen owing t o a t m o s p h e r i c d i f f u s i o n , and t h u s upward movements by f i s h a r e p r o b a b l y a d a p t i v e ( P e t r o s k y and Magnuson 103 1973). Once at the s u r f a c e , f i s h may engage i n a q u a t i c s u r f a c e r e s p i r a t i o n (use of the oxygenated l a y e r a t the a i r - w a t e r i n t e r f a c e ) (Lewis 1970, Kramer e t a l . 1983). D u r i n g J u l y (1984) of t h i s s t u d y , o n l y s h i n e r p e r c h , s t a r r y f l o u n d e r , P a c i f i c s t a g h o r n s c u l p i n s and h e r r i n g were o b s e r v e d skimming a l o n g the s u r f a c e of the h y p o x i c w a t e r s i n the e f f l u e n t c h a n n e l . T h i s response was not noted f o r any salmonids p o s s i b l y because v e r y few salmon were p r e s e n t i n the a r e a d u r i n g t h i s month. A l s o , the main o c c u r r e n c e s of s u r f a c i n g b e h a v i o u r seemed t o t a k e p l a c e on ebb t i d e s and the b u l k of s a m p l i n g d u r i n g peak p e r i o d s of salmon presence was c a r r i e d out on f l o o d t i d e s . Chinook salmon a r e p r o b a b l y c a p a b l e of the s u r f a c i n g response as s u g g e s t e d by o b s e r v a t i o n s made by H i g l e y and Bond (1973) d u r i n g p e r i o d s of h i g h t e m p e r a t u r e s and low oxygen c o n d i t i o n s i n a r e s e r v o i r . F o r c e d changes i n depth d i s t r i b u t i o n may remove f i s h from h y p o x i c w a t e r s , but movement t o the s u r f a c e or t o s h a l l o w water may a l s o i n c r e a s e t h e i r s u s c e p t i b i l i t y t o a e r i a l p r e d a t i o n . In a l a b o r a t o r y s t u d y , Kramer et a l . (1983) showed how the r i s k of c a p t u r e f o r a f i s h i n c r e a s e d w i t h p r o x i m i t y t o the water s u r f a c e . In the p r e s e n t s t u d y , t h e r e were many i n d i c a t i o n s t h a t g u l l s and herons were c o n g r e g a t i n g i n the p o l l u t e d a rea t o f e e d on s t r e s s e d f i s h swimming i n s u r f a c e w a t e r s . In a study of f e e d i n g b e h a v i o u r by Great B l u e Herons at Iona I s l a n d , Krebs (1974) observed t h i s s p e c i e s engaged i n "a t e r n - l i k e h o v e r i n g over deep water p u n c t u a t e d by o c c a s i o n a l swoops t o c a p t u r e f i s h near the s u r f a c e " and " o c c a s i o n a l l y saw b i r d s p i c k i n g up dead 104 f i s h which had been s t r a n d e d on the mud by the o u t g o i n g t i d e . " S i m i l a r o b s e r v a t i o n s were made i n the p r e s e n t s t u d y , but o n l y d u r i n g p e r i o d s of low oxygen c o n d i t i o n s . Krebs' o b s e r v a t i o n s may be an i n d i c a t i o n t h a t f i s h s t r e s s u l t i m a t e l y r e l a t e d t o the presence of the sewage o u t f a l l has been o c c u r r i n g i n the a r e a f o r many y e a r s . Large numbers of b i r d s a r e p r o b a b l y a t t r a c t e d t o the p o l l u t e d a rea a t Iona I s l a n d by enhanced f e e d i n g o p p o r t u n i t i e s owing t o the d i p o s a l of o r g a n i c waste and the r e g u l a r o c c u r r e n c e of low oxygen c o n d i t i o n s . C o n s e q u e n t l y , s m a l l j u v e n i l e salmonids u t i l i z i n g the s h a l l o w water near the t i d a l f r o n t may be f a c e d w i t h i n c r e a s e d r i s k s of b i r d p r e d a t i o n i n a p o l l u t e d over an u n p o l l u t e d environment, even i n the absence of low oxygen c o n d i t i o n s . In a d d i t i o n t o the p r e d a t o r y h a z a r d , movements of f i s h i n t o s u r f a c e waters may have p h y s i o l o g i c a l consequences. For i n s t a n c e , i n the Somass R i v e r e s t u a r y , B r i t i s h C o l u m b i a , B i r t w e l l (1977) noted t h a t the movement of j u v e n i l e c h i n o o k salmon t o s u r f a c e water l a y e r s ( i n response t o low oxygen c o n d i t i o n s i n deeper depths) exposed the f i s h t o e l e v a t e d t e m p e r a t u r e s and v a r i a b l e d i l u t i o n s of k r a f t p u l p m i l l e f f l u e n t . S i m i l a r l y , sewage e f f l u e n t a t Iona I s l a n d i s d i s p e r s e d w i t h i n the upper p a r t of the water column p r o v i d i n g a t o x i c h a z a r d t o f i s h moving i n these l a y e r s ( B i r t w e l l e t a l . 1983). 105 G e n e r a l i n f l u e n c e s of water q u a l i t y on f i s h presence E s t u a r i n e i n t e r t i d a l f l a t s a r e g e n e r a l l y viewed as i m p o r t a n t f e e d i n g grounds f o r j u v e n i l e f i s h of many s p e c i e s (Gibson 1973, M i l l e r and Dunn 1980). These a r e a s become a v a i l a b l e t o f i s h o n l y upon immersion. Wide f l u c t u a t i o n s i n water q u a l i t y w i l l t y p i c a l l y accompany the advance of f l o o d w aters (Davenport 1982) and o f t e n r e s u l t i n extreme c o n d i t i o n s which may, a t l e a s t t e m p o r a r i l y , c o n s t r a i n the movements of f i s h . F l o o d t i d e f l u c t u a t i o n s of tem p e r a t u r e , s a l i n i t y and oxygen showed some c y c l i c t r e n d s a t the study s i t e . V a r i a b i l i t y i n temperature and s a l i n i t y regimes on both s i d e s of the j e t t y were r e l a t e d t o changing s e a s o n a l c o n d i t i o n s , r i v e r r u n - o f f volumes, t i d a l h e i g h t s and p o s i t i o n on the t i d a l f l a t (seaward and landward s t a t i o n s ) . The source of massive r e d u c t i o n s i n d i s s o l v e d oxygen was p r i m a r i l y a n t h r o p o g e n i c w i t h r e c o r d e d c o n c e n t r a t i o n s b e i n g a s t r o n g f u n c t i o n of t i m e . The g r e a t e s t d e p r e s s i o n s i n d i s s o l v e d oxygen c o n c e n t r a t i o n s were r e c o r d e d a t low s l a c k t i d e but the a c t u a l l e v e l s v a r i e d w i t h t i d a l h e i g h t and l o c a l weather c o n d i t i o n s . The Iona j e t t y had the e f f e c t of r e s t r i c t i n g water movement p a t t e r n s on the t i d a l f l a t such t h a t the b u l k of low oxygen o b s e r v a t i o n s were c o n f i n e d t o the s o u t h ( p o l l u t e d ) s i d e of the j e t t y . H i g h e r s a l i n i t i e s were r e c o r d e d on the n o r t h ( u n p o l l u t e d ) t i d a l f l a t as the j e t t y a f f e c t e d t h e p a t t e r n s of f r e s h w a t e r f l o w from the middle arm of the F r a s e r R i v e r . F i s h which a r e found i n such a heterogenous and changing environment may e i t h e r t o l e r a t e water q u a l i t y v a r i a t i o n s or move 106 t o a more h o s p i t a b l e a r e a ( M i l l e r and Dunn 1980). The s t r a t e g y used w i l l a f f e c t the t i m e s when a f i s h i s p r e s e n t or absent. The wide ranges of t e m p e r a t u r e , s a l i n i t y and oxygen r e c o r d e d i n the beach h a b i t a t s of the h i g h i n t e r t i d a l a r e a a t Iona I s l a n d p r o v i d e d the grounds f o r a n a t u r a l experiment i n f i s h r e s p o n s e s t o the environment. However, i n a f i e l d s i t u a t i o n , the number of p o s s i b l e c o m b i n a t i o n s of water q u a l i t y f a c t o r s and f a c t o r l e v e l s which c o u l d be r e l a t e d t o f i s h p r e s e n ce i s v e r y l a r g e . Thus, the p r i m a r y l i m i t a t i o n of t h i s s t udy was the v a r i a b l e and o f t e n s m a l l numbers of samples which were o b t a i n e d f o r p a r t i c u l a r water q u a l i t y l e v e l s o r c o m b i n a t i o n s d e s p i t e a r e a s o n a b l e amount of e f f o r t . Data of t h i s form can be s u c c e s s f u l l y a n a l y s e d u s i n g a l o g i s t i c r e g r e s s i o n model which p r o v i d e s a q u a n t i f i e d d e s c r i p t i o n of t h e main f e a t u r e s of the d a t a and a l l o w s p r e d i c t i o n s t o be made f o r c a t e g o r i e s i n which s c a n t i n f o r m a t i o n i s a v a i l a b l e (Breslow and Day 1980). U s i n g l o g i s t i c r e g r e s s i o n , p r o b a b i l i t i e s were a s s i g n e d t o those f a c t o r c o m b i n a t i o n s t h a t were most h i g h l y a s s o c i a t e d w i t h the presence of chum and c h i n o o k salmon. The t r e n d s i l l u s t r a t e d t h r o u g h t h i s t e c h n i q u e may be viewed as a form of r i s k a n a l y s i s i n terms of the a b i l i t y of a f i s h t o d e a l w i t h b oth the n a t u r a l and sewage r e l a t e d v a r i a t i o n on the t i d a l f l a t s . 107 D i s s o l v e d oxygen and temperature D i s s o l v e d oxygen l e v e l s have a d i r e c t b e a r i n g on the a b i l i t y of an a q u a t i c system t o support l i f e . T o l e r a n c e of low oxygen c o n d i t i o n s tends t o be c o r r e l a t e d w i t h h a b i t a t , so t h a t f i s h n o r m a l l y o c c u p y i n g w e l l - o x y g e n a t e d water a r e l e s s t o l e r a n t of low l e v e l s than f i s h e n c o u n t e r i n g i t p e r i o d i c a l l y ( D a v i s 1975). J u v e n i l e s a l m o n i d s p r o b a b l y r a r e l y encounter a r e a s e x h i b i t i n g d e p r e s s e d oxygen l e v e l s , t h e r e f o r e t h e i r response t o such c o n d i t i o n s as caused by sewage p o l l u t i o n or o t h e r human a c t i v i t y i s a m a t t e r of c o n c e r n . In both May and June of 1984, d i f f e r e n c e s i n the environment between the p e r i o d s when chi n o o k were p r e s e n t and absent was p a r t i a l l y d e s c r i b e d by a temperature/oxygen i n t e r a c t i o n term. An i n t e r a c t i v e r e l a t i o n s h i p between t h e s e two f a c t o r s i s b o t h p h y s i c a l l y v a l i d and b i o l o g i c a l l y i m p o r t a n t ; as temperature i n c r e a s e s the oxygen c o n t e n t of water drops owing t o reduced s o l u b i l i t y , and p r o g r e s s i v e l y h i g h e r p e r c e n t a g e s a t u r a t i o n s of d i s s o l v e d oxygen are r e q u i r e d t o f u l f i l l the oxygen r e q u i r e m e n t s of f i s h ( D a v i s 1975). The r e l a t i o n s h i p between t e m p e r a t u r e and oxygen was s i m i l a r f o r both months but the p o i n t s of i n c r e a s i n g and d e c r e a s i n g p r o b a b i l i t i e s s h i f t e d t o s l i g h t l y h i g h e r temperature and oxygen v a l u e s i n June. The p r i m a r y cause of these s h i f t s can be a t t r i b u t e d t o t h e 4 °C d i f f e r e n c e between the minimum temperature v a l u e r e c o r d e d i n each month. In May and June, the h i g h e s t p r o b a b i l i t y of c a p t u r i n g a chinook salmon o c c u r r e d a t s i m i l a r temperature/oxygen c o m b i n a t i o n s (16-17 °C and 8-9 mg/1) and 108 s i m i l a r p e r c e n t a g e s a t u r a t i o n v a l u e s (97 % ) . At the g i v e n t e m p e r a t u r e s , these oxygen l e v e l s were between D a v i s ' (1975) c r i t e r i a l e v e l A and B of i d e a l oxygen c o n d i t i o n s f o r anadramous marine s a l m o n i d s . L e v e l A r e p r e s e n t s oxygen l e v e l s c l o s e t o f u l l s a t u r a t i o n where few members of a f i s h p o p u l a t i o n a r e l i k e l y t o e x h i b i t s i g n s of oxygen d i s t r e s s . At l e v e l B, some degree of r i s k may e x i s t i f the oxygen minimum p e r i o d i s p r o l o n g e d beyond a few h o u r s . The t o t a l number of samples a s s o c i a t e d w i t h oxygen c o n c e n t r a t i o n s below 6 mg/1 was not l a r g e , however, some t r e n d s r e l a t e d t o c h i n o o k salmon presence were s t i l l a p p a r e n t . In both May and June, c o m b i n a t i o n s of oxygen and temperature a s s o c i a t e d w i t h low p r o b a b i l i t i e s of chinook salmon o c c u r r i n g ranged from 2-6 mg/1 and 22-28 °C r e s p e c t i v e l y . When • t e m p e r a t u r e s dropped below 20 °C and oxygen l e v e l s ranged from 2-8 mg/1, the p r o b a b i l i t i e s of a c h i n o o k salmon b e i n g p r e s e n t i n c r e a s e d . These r e s u l t s may be compared t o the l a b o r a t o r y e x p e r i m e n t s of Whitmore et a l . ( i 9 6 0 ) who found t h a t at summer te m p e r a t u r e s of 16.5 t o 25.5 °C c h i n o o k salmon showed s t r o n g a v o i d a n c e of oxygen c o n c e n t r a t i o n s l e s s than 4.5 mg/1 but no a v o i d a n c e of 6 mg/1. Reduced a v o i d a n c e of low oxygen c o n c e n t r a t i o n s was shown a t autumn or lower t e m p e r a t u r e s r a n g i n g from 6.5-18 °C. In the p r e s e n t s t u d y , the r e l a t i v e absence of chinook salmon from a r e a s of low oxygen c o n c e n t r a t i o n s i s o n l y s u g g e s t i v e t h a t the f i s h were e x h i b i t i n g some t y p e of a v o i d a n c e b e h a v i o u r i n response t o h y p o x i c c o n d i t i o n s . However, an o b s e r v a t i o n made i n mid-June 1984 p r o v i d e d e v i d e n c e t h a t low d i s s o l v e d oxygen c o n c e n t r a t i o n s 109 below 6 mg/1 c o u l d a f f e c t c h i n o o k movements onto the i n t e r t i d a l a r e a . On t h i s day, mean d i s s o l v e d oxygen c o n c e n t r a t i o n s at both s t a t i o n s on the u n p o l l u t e d s i d e of the j e t t y were below 6 mg/1 at low s l a c k t i d e . Oxygen l e v e l s a t the seaward s t a t i o n d i d not r e a c h 8 mg/1 u n t i l 2 hours a f t e r low s l a c k t i d e . T h i s r i s e i n oxygen l e v e l s t o 8 mg/1 c o r r e s p o n d e d t o an immediate c a p t u r e of chinook salmon, a p p r o x i m a t e l y one hour a f t e r the normal d a i l y c a p t u r e t i m e . At the landward s t a t i o n oxygen l e v e l s d i d not r i s e above 6.5 mg/1 i n the s a m p l i n g p e r i o d , and no salmon were caught i n t h a t t i m e . The absence of salmon a t t h i s s t a t i o n was a unique o c c u r r e n c e . A l l o b s e r v a t i o n s of c h i n o o k salmon showing a l t e r e d depth d i s t r i b u t i o n s i n r e l a t i o n t o low oxygen c o n c e n t r a t i o n s were made p r i o r t o low t i d e . These salmon may have f a i l e d t o e x i t the e f f l u e n t c h a n n e l on an e b b i n g t i d e and were thus caught i n a s l u g of h y p o x i c water moving seaward or were swept i n t o the e f f l u e n t c h a n n e l from ' c l e a n e r ' waters v i a one of the s e v e r a l d r a i n a g e c h a n n e l s i n the p o l l u t e d a r e a ( B i r t w e l l e t a l . 1983). The p a t t e r n s of water movement on an ebb t i d e whereby oxygen l e v e l s i n the l o w e s t depths drop f i r s t may have then d i r e c t e d these f i s h i n t o the s h a l l o w s . The c h i n o o k salmon which m i g r a t e i n t o the a r e a on a f l o o d t i d e seem t o have a ' c h o i c e ' of moving i n t o the low oxygen a r e a or w a i t i n g f o r more f a v o r a b l e c o n d i t i o n s . In o r d e r t o a c c u r a t e l y a s s e s s the impact of low oxygen c o n d i t i o n s on salmon p o p u l a t i o n s i n the p o l l u t e d a r e a , s a m p l i n g must be done on ebb t i d a l s t a g e s t o d e t e r m i n e when the m a j o r i t y of t h e s e f i s h a r e l e a v i n g the i n t e r t i d a l . 1 10 D i s s o l v e d oxygen was t h e o n l y water q u a l i t y parameter a s s o c i a t e d w i t h chum salmon d i s t r i b u t i o n s ( i n May). The l o g i s t i c r e g r e s s i o n r e s u l t s s uggested t h a t chum salmon had a h i g h p r o b a b i l i t y of o c c u r r e n c e i n water w i t h an oxygen c o n c e n t r a t i o n below 5 mg/1. In May, the f r e q u e n c y w i t h which th e s e oxygen l e v e l s were r e c o r d e d was low, thus the s e r i o u s n e s s of the s i t u a t i o n i s d i f f i c u l t t o a s s e s s . C o n s i d e r i n g the d i s c r e p a n c i e s i n the o b s e r v e d c a p t u r e times of chum between the two s i d e s of the j e t t y ( e a r l i e r on the p o l l u t e d s i d e ) combined w i t h t h e i r o c c a s i o n a l p r e s e n c e i n low oxygen c o n c e n t r a t i o n s , the f a c t s a r e s u g g e s t i v e t h a t chum salmon have some r i s k of o c c u r r i n g i n degraded oxygen c o n d i t i o n s . However, i n terms of numbers, the m a j o r i t y of chum salmon were caught i n the u n p o l l u t e d i n t e r t i d a l i n water which was 97.0 % s a t u r a t e d a t a mean te m p e r a t u r e of 16.6 °C. As noted e a r l i e r f o r ch i n o o k salmon, t h i s s a t u r a t i o n l e v e l of oxygen ( a t the g i v e n t e m perature) r e p r e s e n t s a s a f e l e v e l (between l e v e l s A and B) f o r anadramous marine s a l m o n i d s ( D a v i s 1975). Temperature F i s h a r e e c t o t h e r m i c organisms which may c o n t r o l t h e i r body temperature by r e s p o n d i n g b e h a v i o u r a l l y t o t h e r m a l s t i m u l i . Thus, t e m p e r a t u r e i s o f t e n r e g a r d e d as a major f a c t o r a f f e c t i n g the d i s t r i b u t i o n of f i s h ( e g . B r e t t 1952, Reynolds 1977). In the absence of low oxygen c o n d i t i o n s i n the st u d y a r e a , temperature appeared t o have a l a r g e e f f e c t on salmon d i s t r i b u t i o n s . E a r l i e r i n the d i s c u s s i o n , the i n f l u e n c e of 111 temperature on the s e a s o n a l depth c h o i c e of j u v e n i l e s a l m o n i d s was d e s c r i b e d . Healey (1980) made a s i m i l a r type of o b s e r v a t i o n i n which chinook salmon i n the Nanaimo e s t u a r y ( B r i t i s h Columbia) may have d i s c o n t i n u e d use of s h a l l o w e r water t o a v o i d h i g h t e m p e r a t u r e s t h a t o c c u r r e d on sunny days. D u r i n g May (1984) of the p r e s e n t s t u d y , c h i n o o k salmon a l s o had a low p r o b a b i l i t y of o c c u r r i n g i n te m p e r a t u r e s below 14 °C a l t h o u g h oxygen c o n c e n t r a t i o n s were above 8 mg/1. The m a j o r i t y of t h e s e low t e m p e r a t u r e s were r e c o r d e d i n e a r l y May when ch i n o o k salmon were not y e t abundant. However, i t i s not known whether the low abundances were c a u s a l l y r e l a t e d t o low te m p e r a t u r e s . S a l i n i t y l e v e l s i n t h i s p e r i o d ranged from 13-16 %o and were not d i f f e r e n t from o t h e r p e r i o d s when chi n o o k were p r e s e n t . Chinook salmon d i s t r i b u t i o n s a r e not r e s t r i c t e d t o 'warmer' waters as i n d i c a t e d by t h e i r p resence i n the Somass R i v e r e s t u a r y i n t e m p e r a t u r e s as low as 9 °C ( B i r t w e l l 1977) and i n the F r a s e r R i v e r e s t u a r y at 5 °C ( B i r t w e l l , u n p u b l i s h e d d a t a ) . S t r a t y and J a e n i c k e (1980) made an i n t e r e s t i n g o b s e r v a t i o n r e g a r d i n g sockeye salmon movements i n B r i s t o l Bay, Oregon. They i n d i c a t e d t h a t p r e f e r e n c e f o r warmer te m p e r a t u r e s may c o n t r i b u t e t o the c o n c e n t r a t i o n of sockeye i n near s h o r e v e r s u s o f f s h o r e w a t e r s d u r i n g t h e i r seaward m i g r a t i o n . The warmer i n s h o r e t e m p e r a t u r e s may s e r v e t o enhance growth and t h u s i n c r e a s e the s u r v i v a l of the sockeye. I t i s p o s s i b l e t h a t the t i m i n g of j u v e n i l e c h i n o o k movements from the i n s h o r e marsh a r e a s of the F r a s e r R i v e r a r e r e l a t e d s i m i l a r l y t o i n c r e a s i n g sea t e m p e r a t u r e s i n t h e ne a r s h o r e i n t e r t i d a l a r e a s . 1 1 2 B r e t t (1952) d e t e r m i n e d the u l t i m a t e upper l e t h a l t e m p e r a t u r e s f o r chinook and chum salmon as b e i n g 25.1 °C and 23.8 °C r e s p e c t i v e l y . In the p r e s e n t s t u d y , both s p e c i e s were absent from t e m p e r a t u r e s above 21.8 °C. S i m i l a r l y , i n the Somass e s t u a r y , B i r t w e l l (1977) d i d not c a t c h c h i n o o k salmon i n temper a t u r e s above 22.5 °C or chum salmon above 20 °C ( B i r t w e l l , u n p u b l i s h e d d a t a ) . I n c o n t r a s t , the maximum temperatures a s s o c i a t e d w i t h j u v e n i l e salmon i n the i n n e r marsh a r e a s of the F r a s e r R i v e r a r e lower than f o r the o u t e r e s t u a r y (chum, 16.0 °C; c h i n o o k , 19.4 °C; B i r t w e l l , u n p u b l i s h e d d a t a ) . S a l i n i t y Of the water q u a l i t y v a r i a b l e s examined, s a l i n i t y had the weakest a s s o c i a t i o n w i t h c h i n o o k salmon p r e s e n c e . T h i s i s not s u r p r i s i n g c o n s i d e r i n g the h i g h s a l i n i t y t o l e r a n c e of t h i s s p e c i e s and t h e i r c a p a c i t y f o r r a p i d a c c l i m a t i o n (Wagner et a l . 1969). A r e l a t i o n s h i p between c h i n o o k presence and s a l i n i t y o c c u r r e d o n l y i n June when average s a l i n i t i e s i n the t h r e e sample depths were s i g n i f i c a n t l y d i f f e r e n t . Chinook had the h i g h e s t p r o b a b i l i t y of o c c u r r i n g i n depth 3 where the low e s t mean s a l i n i t y p r e v a i l e d . S i n c e s a l i n i t y l e v e l s i n the study a r e a tended t o decrease w i t h i n c r e a s i n g time a f t e r low s l a c k t i d e , i t i s p o s s i b l e t h a t t h i s was o n l y a c o i n c i d e n t a l r e l a t i o n s h i p r e s u l t i n g from the r e g u l a r a r r i v a l t i m e s of chinook onto the i n t e r t i d a l . However, the a b i l i t y of j u v e n i l e salmon t o p o s i t i o n themselves i n s a l i n i t y g r a d i e n t s may a l s o be a p o t e n t i a l l y u s e f u l way f o r salmon t o o r i e n t t h e m s e l v e s i n the 1 1 3 c o m p l e x i t y of the e s t u a r i n e environment (Mclnerney 1964). Chinook movements guided by lower s a l i n i t i e s may be a d a p t i v e as the h i g h t e m p e r a t u r e s and low oxygen c o n d i t i o n s which p r e v a i l i n the e a r l y s t a g e s of the f l o o d t i d e would be a v o i d e d . There 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 chum salmon presence and s a l i n i t y i n t h i s s t u d y . However, the mean s a l i n i t y w i t h i n which chum salmon were caught (11.7 %o) agreed w i t h the f i e l d o b s e r v a t i o n s of Iwata and Komatsu (1984) t h a t m i g r a t i n g chum f r y appear t o p r e f e r i s o t o n i c e s t u a r i n e waters (12 %o ). Chum salmon f r y have s t r o n g p r e f e r e n c e s f o r seawater (Houston 1957, Mclnerney 1964) and thus the c o n c e n t r a t i o n of chum salmon on the n o r t h v e r s u s south s i d e of the j e t t y ( i n t h i s s t udy) may have been r e l a t e d t o the h i g h e r median s a l i n i t i e s which p r e v a i l e d i n the n o r t h e r n a r e a . I t i s a l s o p o s s i b l e t h a t the r e d u c t i o n of chum salmon numbers i n the n e a r s h o r e area i n June was r e l a t e d t o the 5 /Sodrop i n o v e r a l l mean s a l i n i t i e s t o 8.4 % i n the i n t e r t i d a l a r e a . D i s t r i b u t i o n of f i s h i n the st u d y a r e a When ch i n o o k salmon were p r e s e n t i n both May and June, r e c o r d e d c a p t u r e t i m e s , oxygen c o n c e n t r a t i o n s and temperatures were not s i g n i f i c a n t l y d i f f e r e n t between the two s i d e s of the j e t t y . Mean s a l i n i t i e s a s s o c i a t e d w i t h the presence of chi n o o k salmon were not s i g n i f i c a n t l y d i f f e r e n t between the two s i d e s of the j e t t y i n May, but were s i g n i f i c a n t l y d i f f e r e n t i n June. In bo t h months, lower mean s a l i n i t i e s p r e v a i l e d i n the p o l l u t e d a r e a . In view of the s e f a c t s , the water q u a l i t y f a c t o r s 1 1 4 examined do not suggest an e x p l a n a t i o n f o r why chinook salmon were p r e s e n t i n t w i c e as many samples i n the p o l l u t e d v e r s u s u n p o l l u t e d a r e a i n May w h i l e no d i f f e r e n c e s were noted between the two a r e a s i n June. I t i s p o s s i b l e t h a t the h i g h e r p r o b a b i l i t y of chinook salmon o c c u r r i n g i n the p o l l u t e d a r e a i n May was r e l a t e d t o the e x i s t e n c e of the Iona j e t t y as a p h y s i c a l b a r r i e r t o f i s h movement. D u r i n g May, peak d e n s i t i e s of j u v e n i l e c h i n o o k salmon o c c u r i n the i n n e r marsh a r e a s of the F r a s e r R i v e r (Levy and N o r t h c o t e 1982). Salmon o c c u p y i n g the m i d d l e arm of the F r a s e r may move f r e e l y onto the s o u t h study a r e a but must move around the Iona j e t t y t o r e a c h the n o r t h e r n t i d a l f l a t . The movements of c h i n o o k away from the i n n e r marsh h a b i t a t s t o the o u t e r e s t u a r y i n June (Levy and N o r t h c o t e 1982) may d e c r e a s e the p r o b a b i l i t y of d i f f e r e n t i a l use of the two study a r e a s on a f l o o d i n g t i d e . Compared t o May, June was c h a r a c t e r i z e d by s i g n i f i c a n t l y warmer t e m p e r a t u r e s and c o n s i s t e n t l y lower oxygen c o n c e n t r a t i o n s a t the s t a r t of the f l o o d t i d e . In June, the numbers of f i s h caught were l o w e s t a t the landward p o l l u t e d s t a t i o n but the chance of c a t c h i n g a c h i n o o k (even a s i n g l e f i s h ) was the same f o r a l l s t a t i o n s . Avoidance of the p o l l u t e d a r e a seems t o have o c c u r r e d as a r e d u c t i o n i n the t o t a l numbers of salmon caught r a t h e r than a decrease i n the number of samples a salmon was p r e s e n t i n . B i r t w e l l e t a l . (1983) a l s o r e c o r d e d s i g n i f i c a n t l y lower c a t c h e s of c h i n o o k on the p o l l u t e d i n t e r t i d a l f l a t w i t h i n two hours of h i g h t i d e . S i n c e mean oxygen c o n c e n t r a t i o n s and t e m p e r a t u r e s a t which c h i n o o k were caught i n t h i s s t u d y were not 1 1 5 s i g n i f i c a n t l y d i f f e r e n t between May and June, i t would appear t h a t the ch i n o o k may have been a v o i d i n g some unmeasured f a c t o r a s s o c i a t e d w i t h the sewage o u t f a l l . The r e l a t i v e l y low numbers of chum salmon caught d u r i n g the study may have been r e l a t e d t o the time of s a m p l i n g . Gordon and L e v i n g s (1984) i n d i c a t e d t h a t chum salmon were o f t e n more abundant a t h i g h e r t i d e l e v e l s . I f t h i s i s the c a s e , then an assessment of chum salmon response t o water q u a l i t y v a r i a t i o n s might be more m e a n i n g f u l (and s u c c e s s f u l ) i f d a t a were o b t a i n e d on t i d a l h e i g h t s above those examined i n t h i s s t u d y . Low t i d e h e i g h t s and d i s t a n c e a l o n g the j e t t y had no e f f e c t on the p r o b a b i l i t i e s of ch i n o o k and chum salmon b e i n g p r e s e n t d e s p i t e the s i g n i f i c a n t c o n t r i b u t i o n of t h e s e f a c t o r s t o v a r i a b i l i t y i n water q u a l i t y measurements. The absence of e f f e c t s may be p a r t i a l l y due t o t h e narrow ranges of t i d e and d i s t a n c e examined i n t h i s s t u d y . A l s o , t h e i r s i g n i f i c a n t e f f e c t s on water q u a l i t y may not have been of a s u f f i c i e n t magnitude t o a f f e c t the p r e s e n c e of f i s h f o r any one t i d e or d i s t a n c e c a t e g o r y . With r e f e r e n c e t o d i s t a n c e o n l y , l o c a t i o n d i f f e r e n c e s i n s a l m o n i d p r e s e n c e were l a r g e l y a s s o c i a t e d w i t h the p o l l u t e d or u n p o l l u t e d s i d e of the j e t t y . On whichever s i d e chum or chi n o o k were more commonly p r e s e n t , use of b o t h seaward and landward s t a t i o n s was s i m i l a r . O b v i o u s l y , d i s t a n c e would a l s o have an e f f e c t on the t i m e s of f i s h c a p t u r e depending on the speed w i t h which f i s h moved from the seaward t o the landward s t a t i o n s on an a d v a n c i n g t i d e . 1 16 Temporal movements Chinook salmon on the p o l l u t e d t i d a l f l a t were t y p i c a l l y c a p t u r e d i n waters w i t h an oxygen c o n t e n t above 6 mg/1. I f the " a r r i v a l t i m e s " or movement of the s e f i s h onto the study a r e a were s i m p l y a f u n c t i o n of h i g h oxygen c o n c e n t r a t i o n s , one might expect t h a t c a p t u r e times would v a r y w i t h changing c o n d i t i o n s (eg. e a r l i e r c a p t u r e times on days when oxygen c o n d i t i o n s were not d e p r e s s e d ) . However, the mean c a p t u r e t i m e s of chinook a t the p o l l u t e d and u n p o l l u t e d s t a t i o n s were s i m i l a r and d i d not d i f f e r between May and June even though oxygen c o n d i t i o n s i n May d i d not show the d a i l y d e p r e s s i o n s o b s e r v e d i n June. These f a c t s suggest t h a t the d a i l y t i m i n g of chi n o o k a r r i v a l s onto the i n t e r t i d a l was not u l t i m a t e l y d e t e r m i n e d by water q u a l i t y , but i n s t e a d , r e p r e s e n t e d a more p r e d i c t a b l e b e h a v i o u r p a t t e r n s y n c h r o n i z e d by some o t h e r exogenous f a c t o r . As a f u r t h e r example, on a s i n g l e sampling o c c a s i o n i n June (1983) the peak c a p t u r e time f o r chinook a t the p o l l u t e d seaward s t a t i o n was r e c o r d e d as 2 hours a f t e r low s l a c k t i d e . Over the whole s a m p l i n g p e r i o d , the v a l u e s of temperature and oxygen were not i n the ranges a v o i d e d by chinook i n 1984 and t h u s , were p r o b a b l y not l i m i t i n g f a c t o r s t o t h e i r movement. A p o s s i b l e e x p l a n a t i o n of the corre s p o n d e n c e i n a r r i v a l t i m e s between s t a t i o n s and months i s t h a t t h i s i s how l o n g i t t a k e s the f i s h t o t r a v e l from a low t i d e r e f u g e on Sturgeon Bank. The e x i s t e n c e of t h i s type of r e f u g e was d i s c u s s e d by Healey (1980) and L e v i n g s (1982). G r a d i e n t s i n water q u a l i t y parameters or c u r r e n t d i r e c t i o n s may s e r v e as cues i n t h i s type of m i g r a t i o n . On o c c a s i o n s when low 1 17 oxygen c o n c e n t r a t i o n s and warm te m p e r a t u r e s a r e p r e v a l e n t , the lower l i m i t s of the f i r s t c h inook c a p t u r e s appear t o be d e t e r m i n e d water q u a l i t y . A p e r i o d i c i t y i n s a l m o n i d movement w i t h r e s p e c t t o t h e i r c a p t u r e t i m e s was a l s o demonstrated by Levy e t a l . (1979) and Levy and N o r t h c o t e (1982) i n the e x i t of c h i n o o k , chum and p i n k salmon from marsh t i d a l c h a n n e l s . P i n k s tended t o abandon the c r e e k s 2 and 3 hours a f t e r h i g h t i d e wheras most chum and c h i n o o k w a i t e d t i l l the d e w a t e r i n g phase of the c h a n n e l a t low t i d e . L e v i n g s (1982) sampled a low t i d e r e f u g e c l o s e t o the a f o r e m e n t i o n e d marsh a r e a s and r e c o r d e d i n c r e a s e d abundance of c h i n o o k on f a l l i n g t i d e s . The d i s a p p e a r a n c e of f i s h from the marsh h a b i t a t s c o r r e s p o n d e d w i t h the h i g h e r c a t c h e s f a r t h e r o f f s h o r e . Mason (1974) and Healey (1979) d e s c r i b e d the movements of j u v e n i l e chum salmon i n i n t e r t i d a l a r e a s as t i d e -r e l a t e d . In the Nanaimo e s t u a r y chum f r y would r e t r e a t i n t o t i d a l c r e e k s a t low t i d e and d i s p e r s e t o a p o r t i o n of the e s t u a r y 2000 m away on a h i g h t i d e (Healey 1979). Some o t h e r s p e c i e s of f i s h d i s p l a y i n g timed movements i n r e l a t i o n t o t i d a l s tage i n c l u d e w i n t e r f l o u n d e r ( T y l e r 1971), sand g o b i e s (Gibson and Hesthagen 1981), a n c h o v i e s ( R e i s and Dean 1981) and p l a i c e ( Gibson 1973). B e h a v i o u r a l rhythms of t i d a l p e r i o d i c i t y a re q u i t e common i n f i s h o c c u p y i n g the i n t e r t i d a l zone (Schwassmann 1971). 118 Summary In t h i s s tudy the depth d i s t r i b u t i o n s and temporal movements of chi n o o k and chum salmon were compared between a (sewage) p o l l u t e d and u n p o l l u t e d i n t e r t i d a l f l a t . The i n f o r m a t i o n p r e s e n t e d p r o v i d e s some i n s i g h t i n t o the i n f l u e n c e of water q u a l i t y on h a b i t a t use by j u v e n i l e s a l m o n i d s . The p o l l u t e d and u n p o l l u t e d a r e a s a r e s e p a r a t e d by a 4.4 km l o n g j e t t y . At s t a t i o n s i n the p o l l u t e d a r e a , h i g h t e m p e r a t u r e s i n c o n c e r t w i t h low oxygen c o n c e n t r a t i o n s were t y p i c a l l y r e c o r d e d i n the e a r l y s t a g e s of f l o o d i n g . Chinook salmon moving onto the i n t e r t i d a l on a f l o o d t i d e d i d not have a h i g h p r o b a b i l i t y of o c c u r r i n g i n a r e a s where d i s s o l v e d oxygen c o n c e n t r a t i o n s were l e s s than 6 mg/1 and t e m p e r a t u r e s were g r e a t e r than 20 °C. T h e i r low o c c u r r e n c e i n the s e c o n d i t i o n s c o u l d be e x p l a i n e d by a c o m b i n a t i o n of a v o i d a n c e b e h a v i o u r and as a c o r r e l a t i o n w i t h the rhy t h m i c t i m i n g of t h e i r movements onto the i n t e r t i d a l i n h i g h e r oxygenated f l o o d w a t e r s ( i n l a t e r s t a g e s of the f l o o d t i d e ) . Chinook salmon u t i l i z e d a broad range of s a l i n i t y l e v e l s i n the study a r e a (2.1-23.8 7°°) but a r e l a t i o n s h i p w i t h low s a l i n i t y water (< 6 %«) was r e v e a l e d i n June. S i n c e s a l i n i t y l e v e l s i n the a r e a d e c r e a s e d w i t h i n c r e a s i n g time a f t e r the f l o o d t i d e , t h i s r e l a t i o n s h i p may a l s o r e s u l t from a c o i n c i d e n c e w i t h the t i m i n g of c h i n o o k movements onto t h e i n t e r t i d a l . Chum salmon were not abundant on the t i d a l h e i g h t s sampled and they d i d not show the same p e r i o d i c i t y of movement d i s p l a y e d by c h i n o o k . A c c o r d i n g l y , water q u a l i t y c o n d i t i o n s were not 119 s t r o n g l y a s s o c i a t e d w i t h t h e i r d i s t r i b u t i o n s . The m a j o r i t y of chum salmon were caught i n the u n p o l l u t e d a r e a but those found on the p o l l u t e d s i d e of the j e t t y had some r i s k of o c c u r r i n g i n degraded oxygen c o n d i t i o n s . The u n p o l l u t e d a r e a was c h a r a c t e r i z e d by s i g n i f i c a n t l y h i g h e r s a l i n i t y l e v e l s than the p o l l u t e d a r e a . T h i s s a l i n i t y d i f f e r e n c e may have been one f a c t o r i n f l u e n c i n g l a r g e r numbers of chum salmon t o u t i l i z e the a r e a on the n o r t h s i d e of the j e t t y ( u n p o l l u t e d a r e a ) . The r e d u c t i o n i n numbers of chum salmon i n the u n p o l l u t e d a r e a i n June c o r r e s p o n d e d t o a 5 drop i n the average s a l i n i t y l e v e l ( t o about 8 % 0 ) . E x a m i n a t i o n of the f i n e d e p th d i s t r i b u t i o n s of j u v e n i l e salmon i n 0 t o 1 m of water i n d i c a t e d t h a t depth use was a s s o c i a t e d w i t h f i s h l e n g t h and p o s s i b l y m o d i f i e d by t e m p e r a t u r e . Chum, chinook and p i n k salmon of e q u a l s i z e had s i m i l a r d e p th d i s t r i b u t i o n s . Chinook salmon l e n g t h s ranged from 3.6 t o 11.4 cm; chum salmon of l e s s than 6 cm l e n g t h were most common i n t h e n e a r s h o r e a r e a but reached l e n g t h s up t o 7.4 cm; p i n k salmon l e n g t h s d i d not exceed 3.9. In t h e absence of low oxygen c o n d i t i o n s , salmon of l e s s than 5 cm f o r k l e n g t h were o f t e n p r e s e n t i n water depths of l e s s than .25 m but the l a r g e s t numbers were c a p t u r e d i n .25 t o .5 m of wate r . Salmon i n a l e n g t h range of 5 t o 7 cm were c a p t u r e d i n s i m i l a r numbers i n the .25-.49 m and .5-1.0 m depth i n t e r v a l s . Salmon g r e a t e r than 7 cm were caught p r i m a r i l y i n the .5 t o 1.0 m d e p t h . On o c c a s i o n when d i s s o l v e d oxygen c o n c e n t r a t i o n s i n the p o l l u t e d a r e a were low, j u v e n i l e salmon were observed swimming i n s h a l l o w 120 water a t the beach/water i n t e r f a c e where h i g h e r oxygen l e v e l s p r e v a i l e d . These f i s h , e x h i b i t i n g v e r y s l u g g i s h swimming b e h a v i o u r , were p r o b a b l y h i g h l y s u s c e p t i b l e t o b i r d p r e d a t i o n . The movements and d i s t r i b u t i o n of f i s h a r e u s u a l l y not governed by a s i n g l e p h y s i c a l or b i o l o g i c a l f a c t o r , but r a t h e r a c o m b i n a t i o n of numerous i n t e r a c t i v e and m o d i f y i n g i n f l u e n c e s (Kinne 1967). B i o t i c f a c t o r s such as f e e d i n g and p r e d a t o r a v o i d a n c e may p r o v i d e the m o t i v a t i o n f o r p a r t i c u l a r movements ( N o r t h c o t e 1978) but th e s e may be c o n s t r a i n e d by a b i o t i c f a c t o r s such as oxygen, t e m p e r a t u r e , and s a l i n i t y . B i o t i c f a c t o r s were not examined i n t h i s s t u d y ; of the a b i o t i c f a c t o r s , oxygen and temperature had the g r e a t e s t i n f l u e n c e on salmon, w i t h extreme c o n d i t i o n s s e r v i n g t o a l t e r t h e i r l e n g t h / d e p t h d i s t r i b u t i o n p a t t e r n s or p o s s i b l y i n h i b i t i n g t h e i r movements onto the i n t e r t i d a l . S a l i n i t y d i d not appear t o g r e a t l y i n f l u e n c e the d i s t r i b u t i o n s of chinook salmon. However, the c o n c e n t r a t i o n of chum salmon on the u n p o l l u t e d s i d e of the j e t t y and t h e i r d i s a p p e a r a n c e from the study a r e a i n June were b o t h e v e n t s c o r r e s p o n d i n g t o s a l i n i t y v a r i a t i o n s . As an assessment of the impact of sewage d i s p o s a l on the i n t e r t i d a l a r e a a t Iona I s l a n d , the r e s u l t s from t h i s s tudy i n d i c a t e t h a t f i s h moving onto the t i d a l f l a t s on a f l o o d t i d e had a low p r o b a b i l i t y of o c c u r r i n g i n water of low oxygen c o n t e n t . However, the o c c a s i o n a l r e c o r d s of s t r e s s e d ( s l u g g i s h swimming b e h a v i o u r , a l t e r e d d e pth d i s t r i b u t i o n s , s u r f a c i n g b e h a v i o u r ) salmon and o t h e r s p e c i e s suggested t h a t the c o n d i t i o n s on ebb t i d a l s t a g e s were d e t r i m e n t a l t o f i s h 121 s u r v i v a l . In the p o l l u t e d a r e a , the presence of s e v e r a l n a t u r a l c r e e k s which d r a i n c l e a n waters from the h i g h i n t e r t i d a l i n t o the h y p o x i c w a t e r s of the e f f l u e n t c h a n n e l may c o n t r i b u t e t o a l a r g e p r o p o r t i o n of the observed f i s h s t r e s s . As water l e v e l s f a l l on an e b b i n g t i d e , f i s h p r e s e n t i n these n a t u r a l c r e e k s do not have an a l t e r n a t i v e t o e n t e r i n g the e f f l u e n t c h a n n e l . A l s o , the l a r g e b i r d p o p u l a t i o n i n the p o l l u t e d a r e a may be a s i g n i f i c a n t s o u r c e of m o r t a l i t y t o j u v e n i l e salmon p r e s e n t i n the s h a l l o w w a t e r s of the n e a r s h o r e environment. 1 22 REFERENCES CITED B.C. R e s e a r c h . 1973. E n v i r o n m e n t a l s t u d i e s a t Iona I s l a n d . 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T r u e s d a l e , G.A., and A.L.H. Gameson. 1957. The s o l u b i l i t y of oxygen i n s a l i n e w a t e r . J . Cons. i n t . E x p l o r . Mer 22:163-1 66. T y l e r , A.V. 1971. Surges of w i n t e r f l o u n d e r , P s e u d o p l e u r o n e c t e s  americanus, i n t o the i n t e r t i d a l zone. J . F i s h . Res. Board Can. 28:1727-1723. Wagner, H.H., F.P. Conte, and J.L. F e s s l e r . 1969. Development of osmotic and i o n i c r e g u l a t i o n i n two r a c e s of ch i n o o k salmon Oncorhynchus t s h a w y t s c h a . Comp. Biochem. P h y s i o l . 29:325-341. Warren, C.E., P. D o u d o r o f f , and D.L. Shumway. 1973. Development of d i s s o l v e d oxygen c r i t e r i a f o r f r e s h w a t e r f i s h . U.S. E n v i r o n . P r o t . Agency, Washington D.C, Rep. EPA-R3-73-019 : 2 l p . Whitmore, CM., G.E. Warren, and P. D o u d o r o f f . 1960. Avoidance r e a c t i o n s of s a l m o n i d s and c e n t r a c h i d f i s h e s t o low oxygen c o n c e n t r a t i o n s . T r a n s . Am. F i s h . Soc. 89:17-26. 129 APPENDIX 1 A s s o c i a t i o n of p h y s i c a l measurements w i t h s e i n e h a u l s Water q u a l i t y measurements were taken b e f o r e and a f t e r each se t of t h r e e beach s e i n e s i n .05, .25, .5, and 1.0 m of water. At depths g r e a t e r than .25 m, a l l measurements were taken a t the to p and bottom of the water column. A c o m b i n a t i o n of two p h y s i c a l measurements from the above depths were averaged t o g i v e a s i n g l e v a l u e f o r each of the t h r e e s e i n e h a u l s made. Water q u a l i t y i n depth 1 was d e s c r i b e d by measurements from .05 and .25 m, depth 2 was a s s o c i a t e d w i t h measurements from .25 and .5 m and de p t h 3 was r e p r e s e n t e d by measurements from .5 and 1.0 m. S i n c e t h e r e was a time l a g of about 40 minutes between any two s e t s of water q u a l i t y measurements, the averaged v a l u e s c l o s e s t i n time t o any g i v e n s e i n e h a u l were a s s o c i a t e d w i t h t h a t s e i n e h a u l . I f a s e i n e h a u l was c l o s e s t t o the mi d d l e of a time i n t e r v a l , then the mean of the b e f o r e and a f t e r p h y s i c a l measurements were taken as the a s s o c i a t e d v a l u e . T h i s was n e c e s s a r y as t h e r e were o f t e n l a r g e d i f f e r e n c e s i n the v a l u e s of two c o n c u r r e n t s e t s of p h y s i c a l measurements. The r e l a t i o n s h i p between t h e s e two s e t s of measurements was assumed t o be l i n e a r . 130 APPENDIX 2 Net performance t e s t : two person v e r s u s one person beach s e i n i n g To a s s e s s the performance of my one person sampling method, c a t c h e s were compared from a s e r i e s of one and two person beach s e i n e s taken i n depth 1 (0-.24 m) , depth 2 (.25-.49 m), and depth 3 (.5-1.0 m). For the one person t e c h n i q u e a spacer bar f l o a t s on t h e water i n f r o n t of the net o p e n i n g , which may r e s u l t i n c e r t a i n s p e c i e s or s i z e c l a s s e s of f i s h b e i n g e x c l u d e d from the c a t c h . There i s no such o b s t r u c t i o n of the net opening when beach s e i n i n g w i t h two p e o p l e . The performance t e s t was c a r r i e d out a t s t a t i o n 4 (landward, u n p o l l u t e d s t a t i o n ) which i s c h a r a c t e r i z e d by a r e l a t i v e l y l o n g , s t r a i g h t s e c t i o n of beach. Two a d j a c e n t , 50 m s e c t i o n s of beach were marked o f f . The s a m p l i n g p r o c e d u r e c o n s i s t e d of t a k i n g a two person s e i n e h a u l i n a s i n g l e depth i n t e r v a l of one 50 m s e c t i o n and then a one person s e i n e h a u l i n the same depth i n t e r v a l i n the next s e c t i o n . Each comparable depth i n the two s e c t i o n s was s e i n e d i n a s i n g l e d i r e c t i o n t o m i n i m i z e d i f f e r e n c e s i n f i s h c a t c h r e l a t e d t o c u r r e n t e f f e c t s . Each depth i n t e r v a l i n each s e c t i o n was sampled t w i c e , once by each method. S i z e c l a s s d i s t r i b u t i o n s of s t a r r y f l o u n d e r and p a c i f i c s t a g h o r n s c u l p i n s caught by the two s a m p l i n g methods were compared u s i n g the t w o - t a i l e d Kolmogorov-Smirnov (K-S) two sample t e s t ( S i e g e l 1956). F l o u n d e r and s c u l p i n s were chosen f o r the comparison because of t h e i r l a r g e s i z e ranges which 131 occur i n the study a r e a (about 2-30 cm). The K-S t e s t i s a. t e s t of whether two independent samples have been drawn from the same p o p u l a t i o n or from p o p u l a t i o n s w i t h the same d i s t r i b u t i o n . The t w o - t a i l e d t e s t i s s e n s i t i v e t o any k i n d of d i f f e r e n c e i n the d i s t r i b u t i o n s from w h i c h the two samples were drawn, such as d i f f e r e n c e s i n c e n t r a l tendency, d i s p e r s i o n or skewness. O v e r a l l , t h e r e were no d i f f e r e n c e s i n the s p e c i e s caught by the two beach s e i n i n g methods even though each s p e c i e s was not always p r e s e n t i n comparable s e i n e s . Only i n d e p t h 1 were the numbers of f i s h caught by the one person method t y p i c a l l y l e s s than the numbers o b t a i n e d by the two person method ( t a b l e 1) but t h e r e were no s i g n i f i c a n t d i f f e r e n c e s (p<.05) between the s i z e c l a s s d i s t r i b u t i o n s of th e s e f i s h . S i g n i f i c a n t d i f f e r e n c e s between s i z e c l a s s d i s t r i b u t i o n s were p r e s e n t o n l y f o r s t a r r y f l o u n d e r i n one of the two comparisons of the .5-1.0 m de p t h . The one person method appears t o be a r e a s o n a b l e means of d e t e r m i n i n g which s p e c i e s and s i z e c l a s s e s of f i s h a r e p r e s e n t i n a g i v e n depth i n t e r v a l . The advantage of t h i s method i s t h a t f i s h s ampling can be done w i t h o u t f i e l d a s s i s t a n c e . F i s h s p e c i e s and t o t a l numbers of f i s h o b t a i n e d by one and T a b l e 1 two person beach s e i n e s . Depth S p e c i e s T o t a l no. of f i s h (sum of 2 samples) (m) 1 p e r s o n 2 person method method 0-.24 P a c i f i c s t a g - 12 28 horn s c u l p i n S t a r r y f l o u n d e r 12 18 Arrow goby 6 28 S h i n e r p e r c h 1 3 H e r r i n g 10 6 S u r f smelt 0 38 .25-.49 P a c i f i c s t a g - 19 7 horn s c u l p i n S t a r r y f l o u n d e r 25 31 Arrow goby 4 4 S h i n e r p e r c h 29 28 H e r r i n g 11 12 3-spine s t i c k l e - 6 1 back S u r f smelt 2 26 Chinook salmon 0 2 .5-1.0 P a c i f i c s t a g - 25 24 horn s c u l p i n S t a r r y f l o u n d e r 34 24 Arrow goby 25 17 S h i n e r p e r c h 27 34 H e r r i n g 241 82 3-spine s t i c k l e - 0 1 1 back Chinook salmon 3 5 E n g l i s h s o l e 1 1 133 Appendix 3a R e s u l t s from the a n a l y s i s of v a r i a n c e of te m p e r a t u r e d a t a ; mean squares and p r o b a b i l i t i e s a s s o c i a t e d w i t h F - r a t i o t e s t s . (* p<.05, **p<.0l, ***p<.00O Source A p r i l May June MS DF F MS DF F MS DF F D i s t a n c e .03 1 6.41* .70 1 44.28*** .33 1 20.00*** S i d e .02 1 3.39 .17 1 10.85*** .29 1 17.23*** Depth .09 2 16.39*** .27 2 17.22*** .13 2 7.92** T i d e .49 1 90.69*** .27 2 17.15*** .02 2 1 .08 S i d e * T i d e - - .10 2 6.13* . 1 7 2 10.00*** R e s i d u a l .01 65 .02 1 42 - .02 127 -T o t a l 77 1 57 142 134 Appendix 3b R e s u l t s from the a n a l y s i s of v a r i a n c e of s a l i n i t y d a t a ; mean sq u a r e s and p r o b a b i l i t i e s a s s o c i a t e d w i t h F - r a t i o t e s t s . (* p<.05, **p<.0l, ***p<.00l) Source A p r i l MS DF F MS May DF F June MS DF F D i s t a n c e .002 1 .08 .01 1 0, . 1 6 .64 1 4. 56* S i d e .26 1 10 .67** 2.95 1 49, .84*** 8.91 1 63. 50*** Depth .01 2 .29 .04 2 .59 .48 2 3. 42* T i d e .03 1 1 .34 .41 2 7, .01 ** .62 2 4 .42* S i d e * T i d e - - .61 2 1 0, .47*** 1.15 2 8 . 20*** D i s t * T i d e - - .22 2 3, .66* - - -R e s i d u a l .02 65 .06 1 40 - . 1 4 127 -T o t a l 77 1 57 1 42 135 Appendix 3c R e s u l t s from the a n a l y s i s of v a r i a n c e of oxygen d a t a ; mean squares and p r o b a b i l i t i e s a s s o c i a t e d w i t h F - r a t i o t e s t s . (* p<.05, **p<.0l, ***p<.00l) Source A p r i l MS DF May MS DF MS June DF F D i s t a n c e .01 S i d e 1.85 Depth 0.001 T i d e .34 S i d e * T i d e -R e s i d u a l .02 65 T o t a l 77 1 .38 1 88.76*** 2 .05 1 16.26 .01 1 0.26 .27 1 3.67 2.28 1 49.85*** 2.13 1 28.92*** .06 2 1.25 .12 2 1.56 .09 2 1.96 .35 2 4.68* - - - .71 2 9.59*** .05 142 - .07 127 157 142 136 Appendix 4 Means and ranges of water q u a l i t y parameters a s s o c i a t e d w i t h arrow g o b i e s , P a c i f i c s t a g h o r n s c u l p i n s and s t a r r y f l o u n d e r s i n May and June of 1984. Month Parameter Arrow goby P a c i f i c S t a r r y s t a g h o r n f l o u n d e r s c u l p i n May No. of samples 113 98 125 Temperature (°C) mean(SE) 17.3(.3) 17.3(.3) 16.6(2.6) max. 24.8 24.8 23.3 min. 10.9 10.8 10.8 % of samples i n temp > 22 °C 6.2 5.1 2.4 S a l i n i t y (%) mean(SE) 11.5(.3) 11.8(.4) 11.8(.3) max. 19.3 19.5 19.3 min. 5.9 6.5 7.2 Oxygen (mg/1) mean (SE) 7.62(1.64) 7.84(.16) 7.87(.14) max. 9.8 10.05 9.80 min. 2.6 3.38 2.59 % of samples i n oxygen < 6 mg/1 12.0 11.0 10.4 P e r c e n t s a t u r a t i o n mean(SE) 87.2(1.7) 89.8(1.7) 89.0(1.5) max. 109.5 110.7 110.7 min. 30.0 83.7 30.0 June No. of samples 102 131 110 Temperature C°C) mean(SE) 19.0(.3 ) 18.7(.3 ) 18.7( . 3) max. 28.3 28.3 28.3 min. 14.8 14.8 14.8 % of samples i n temp > 2 2 ° C 9.8 8.4 8.2 S a l i n i t y ( % > o ) mean(SE) 7 . K . 3 ) 7.4(.3) 7.2(.3) max. 14.9 14.9 14.9 min. 2.3 2.1 2.1 Oxygen (mg/1) mean(SE) 6.93(.23) 7.22(.19) 7.26(.19) max. 13.10 13.10 13.10 min. 3.05 3.05 3.22 % p r e s e n t i n oxygen <6 mg/1 11.7 9.2 18.0 P e r c e n t s a t u r a t i o n mean(SE) 78.9(2.5) 82.0(2.1) 82.7(2.1) max. 149.4 49.4 149.4 min. 30.0 30.0 39.1 

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