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Some aspects of the winter ecology of juvenile salmonids with reference to possible habitat alteration… Bustard, David R. 1973

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SOME ASPECTS OF THE WINTER ECOLOGY OP JUVENILE SALMONIDS WITH REFERENCE TO POSSIBLE HABITAT ALTERATION BY LOGGING IN CARNATION CREEK, VANCOUVER ISLAND by DAVID R. BUSTARD B.Sc. (Forest Biology), University of B r i t i s h Columbia, 1970 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE (Forest Hydrology) in the Faculty of Forestry We accept th i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA November 1973 In presenting t h i s thesis in 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 U n i v e r s i t y 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 a v a i l -able for reference and study. I further agree that permission for extensive copying of t h i s thesis for s c h o l a r l y purposes may be granted by the Head of my Department or by his representatives. I t i s understood that copying or p u b l i c a t i o n 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 Forestry The University of B r i t i s h Columbia Vancouver 8, Canada. Date i ABSTRACT Juvenile coho, steelhead, and cutthroat trout commonly spend from one to three or more years in coastal streams before migrating to the sea. Much of t h i s time i s spent i n streams during the winter, making a study of these f i s h e s ' winter habitat requirements, d i s t r i b u t i o n , behavior, and the possible influences of stream habitat a l t e r a t i o n on them a useful undertaking. Some physical c h a r a c t e r i s t i c s of areas selected by juvenile coho and steelhead were observed by snorkeling in a small west coast of Vancouver Island stream between September 1972 and A p r i l 1973. Observations revealed that with lowering water temperatures from 9°C to 2°C coho and older steelhead tended to move into deeper water while most steelhead fry remained in shallow, marginal sections of the stream. As water temperatures dropped in the winter, juvenile f i s h fed less and moved closer to areas o f f e r i n g low water v e l o c i t i e s and cover. Steelhead fry were most often found under rubble while coho and older steelhead were most often found within upturned roots and under logs. Results from f i s h traps located on the lower ends of two small tributary streams indicated that juvenile coho, steelhead and cutthroat trout moved upstream into these t r i b u t a r i e s in the l a t e f a l l . Overwinter s u r v i v a l of coho in one tributary was 3-6 times as great as the estimated sur v i v a l of coho in the main stream. Together the two t r i b u t a r i e s c o n t r i b u t e d between 15 and 25 per cent to the t o t a l coho smolt production of the l a r g e r system. A s e r i e s of experiments comparing coho and c u t t h r o a t preference f o r a l t e r n a t i v e h a b i t a t types i n s i d e p o o l areas as may occur before and a f t e r stream disturbance were c a r r i e d out during the w i n t e r . Both coho and c u t t h r o a t demonstrated a strong preference f o r bay areas o f f e r i n g overhanging bank cover as opposed to bays without cover, and f o r bays o f f e r i n g c l e a n rubble s u b s t r a t e as opposed to s i l t e d rubble s u b s t r a t e . The impacts of timber h a r v e s t i n g on o v e r w i n t e r i n g f i s h as suggested by the r e s u l t s from the underwater o b s e r v a t i o n s , winter movements, and the s i d e p o o l experiments are discussed and management recommendations are made. i i i TABLE OF CONTENTS Page TABLE OF CONTENTS i i i LIST OF FIGURE S . . . . . . . . . . . . . . . . . . . . i v ACKNOWLEDGEMENTS . . . . . x INTRODUCTION 1 PART I . WINTER ECOLOGY OF JUVENILE COHO AND STEELHEAD -DESCRIPTION OF STUDY AREA . 6 A. C a r n a t i o n Creek . 6 B. 750 and 1600 Creeks 8 MATERIALS AND METHODS . . . . . . . . . 13 A. W i n t e r O b s e r v a t i o n s o f J u v e n i l e Coho and S t e e l h e a d . 13 1. I n t e n s i v e H a b i t a t Survey 13 2. E x t e n s i v e H a b i t a t Survey . 15 3. L i m i t a t i o n s o f Underwater O b s e r v a t i o n s . . . 16 B. W i n t e r Movements o f J u v e n i l e Coho and S t e e l h e a d 17 A. W i n t e r O b s e r v a t i o n s o f J u v e n i l e Coho and S t e e l h e a d . . . . . . . . . . . . . . . . . . 20 1. Water Depth and V e l o c i t y . . . . . . . . . . 20 2. W i n t e r Cover . . . . . . . . . . . . . . . . 27 3. W i n t e r F e e d i n g and H i d i n g B e h a v i o r . . . . . 33 B. W i n t e r Movements o f J u v e n i l e Coho and S t e e l h e a d 34 1. 750 C r e e k . . . . . . . . . . . . . . . . . 35 2. 1600 C r e e k . . . . . . . . . . . . . . . . . 37 C . Summary . . . . . . . . . . . . . . . 42 i v Page PART I I . HABITAT PREFERENCES OF COHO AND TROUT . . . . 43 DESCRIPTION OF STUDY AREA 43 MATERIALS AND METHODS . 44 1. Design of Sidepools . . . . . . 44 2. Experimental F i s h . 48 3. T r i a l Procedure . „ 50 4. Experimental Conditions . . . 51 RESULTS 52 1. J u v e n i l e Coho Cover Preference . 52 2. J u v e n i l e Cutthroat Cover Preference . . . . . . . 54 DISCUSSION . . 57 A. Winter H i d i n g and I t s Adaptive Values 57 B. P h y s i c a l C h a r a c t e r i s t i c s of Wintering Areas . . . 59 1. Water Depth and V e l o c i t y 59 2. Winter Cover and I t s S u r v i v a l I m p l i c a t i o n s . . 61 C. A l t e r a t i o n of Winter Cover . . . . . . . . . . . . 68 D. Conclusions . . . . . ' 70 MANAGEMENT RECOMMENDATIONS „ . . . . . . < • • . . . . . . . 7 2 LITERATURE CITED . . . . . . . . « . . « . * . . » . * o 74 APPENDICES . . . . . . • . ' » • • o « . . « o ' * o « . * « * 78 LIST OF FIGURES FIGURE PAGE 1. L o c a t i o n o f the C a r n a t i o n Creek w a t e r s h e d and s t u d y s e c t i o n s ( S c a l e s 1:50,000) 7 2. A. C a r n a t i o n Creek a t 1300 m. Note e x t e n s i v e g r a v e l b a r s and abundance o f c o v e r . B. C a r n a t i o n Creek n e a r 2600 m. Note l a r g e r s u b s t r a t e and u p t u r n e d r o o t s . . . . . . . . . . 9 3. D r i e d c h a n n e l o f 750 Creek d u r i n g e a r l y September. Photo t a k e n from j u s t above t h e t r a p s 11 4. M e a s u r i n g w a t e r d e p t h (A) and w a t e r v e l o c i t y (B) . . 1 4 5. Upstream and downstream t r a p p i n g d e v i c e s on 1600 Creek (A) and 750 Creek ( B ) . Photo was t a k e n i n September 1972 w h i l e 750 Creek was s t i l l d r y . 18 6. Depth o f w a t e r s e l e c t e d by j u v e n i l e coho and s t e e l -head a t w a t e r t e m p e r a t u r e s o f 7°C o r l e s s . . . . 21 7. Water d e p t h d i s t r i b u t i o n o f j u v e n i l e coho and s t e e l -head a t d i f f e r e n t w a t e r t e m p e r a t u r e s . Dots and c i r c l e s r e p r e s e n t mean de p t h o f f i s h f o r a l l o b s e r v a t i o n s w i t h i n t h e degree i n t e r v a l . V e r t i c a l l i n e s r e p r e s e n t s t a n d a r d d e v i a t i o n s and a s s o c i a t e d numbers i n d i c a t e the sample s i z e . R e g r e s s i o n l i n e s were d e r i v e d from N o b s e r v a t i o n s . ( * s i g n i f i c a n t a t p=.05, * * s i g n i f i c a n t a t p=.01, NS n o t s i g n i f i c a n t a t p=.05) . . . . . . . . . . 22 8. F o c a l p o i n t w a t e r v e l o c i t i e s s e l e c t e d by j u v e n i l e coho and s t e e l h e a d a t w a t e r t e m p e r a t u r e s o f 7°C v i FIGURE PAGE 9. Maximum a r e a w a t e r v e l o c i t i e s s e l e c t e d by j u v e n i l e coho and s t e e l h e a d a t w a t e r t e m p e r a t u r e s o f 7°C or l e s s . . . . 25 10. F o c a l p o i n t and maximum a r e a w a t e r v e l o c i t i e s s e l e c t e d by age 0 and age 1+ s t e e l h e a d p l o t t e d a g a i n s t v/ater t e m p e r a t u r e . Streatnflows were between 0.3 and 0.7 mVsec f o r a l l measurements. Dots and c i r c l e s r e p r e s e n t mean w a t e r v e l o c i t i e s w i t h i n the 0.5 degree i n t e r v a l based on a sample s i z e i n d i c a t e d by t h e a s s o c i a t e d numbers. R e g r e s s i o n l i n e s were d e r i v e d from N o b s e r v a -t i o n s 26 11. D i s t a n c e t o c o v e r o f j u v e n i l e coho and s t e e l h e a d a t d i f f e r e n t w a t e r t e m p e r a t u r e s . Dots and c i r c l e s r e p r e s e n t mean c o v e r d i s t a n c e f o r a l l o b s e r v a -t i o n s w i t h i n the one degree i n t e r v a l based on a sample s i z e i n d i c a t e d by t h e a s s o c i a t e d numbers. R e g r e s s i o n l i n e s were d e r i v e d from N o b s e r v a -t XOX1S o t t ^ e o o c A t f A O W A t f e o o ^ v o o ^ 28 12. D i s t a n c e t o c o v e r s e l e c t e d by j u v e n i l e coho and s t e e l h e a d a t w a t e r t e m p e r a t u r e s o f 7°C o r l e s s . 29 13. Cover t y p e s s e l e c t e d by j u v e n i l e coho and s t e e l -head a t w a t e r t e m p e r a t u r e s o f 7°C o r l e s s . . . . 30 14. P h y s i c a l c h a r a c t e r i s t i c s o f s u b s t r a t e w i n t e r i n g a r e a s s e l e c t e d by age 0 s t e e l h e a d (based on 43 o b s e r v a t i o n s ) . . . . . . . . . . . . . 32 v i i FIGURE PAGE 15. (Top) Monthly upstream and downstream movements of juvenile coho in 750 Creek. Totals from March do not include recently emerged f r y . . . 36 16. (Bottom) Length frequency d i s t r i b u t i o n of juvenile coho in 750 Creek. Data are lumped for 4-mm length intervals for the September to December and January to May periods 36 17. (Top) Monthly upstream and downstream movements of juvenile coho in 1600 Creek. Totals from March do not include recently emerged f r y . . . 38 18. (Bottom) Length frequency d i s t r i b u t i o n of juvenile coho in 1600 Creek. Data are lumped for 4-mm length intervals for the September to December and January to May periods 38 19. (Top) Monthly upstream and downstream movements of juvenile steelhead and cutthroat i n 1600 Creek. Totals are for trout greater than 60 mm in length . . . . . . . . . . . . . . . . 40 20. (Bottom) Length frequency d i s t r i b u t i o n of juvenile steelhead and cutthroat in 1600 Creek. Data are lumped i n 10-mm in t e r v a l s for the period September 1972 through May 1973 . . . . 40 21. Orientation of sidepools with respect to each other and to Dick Creek 45 22. Basic design of sidepools . . . . . . . 46 v i i i FIGURE PAGE 23. A. S i d e p o o l o f f e r i n g bays w i t h o v e r h a n g i n g bank c o v e r o r no c o v e r . Overhang i s r a i s e d and up-s i d e down t o show r o o t mass. Water l e v e l s were e x c e p t i o n a l l y low when t h i s photo was t a k e n . B. S i d e p o o l o f f e r i n g bays w i t h c l e a n o r s i l t e d r u b b l e . . . . . . . . . 47 24. The p e r c e n t a g e o f coho c h o o s i n g a l t e r n a t i v e c o v e r t y p e s (A and B) i n t h e s i d e p o o l s when n o t p e r m i t t e d a c c e s s t o D i c k Creek ( o b l i g a t o r y r e s i d e n c e ) and when p e r m i t t e d a c c e s s t o D i c k Creek ( v o l u n t a r y r e s i d e n c e ) . The p e r c e n t a g e o f coho r e m a i n i n g i n t h e s i d e p o o l s a f t e r b e i n g p e r m i t t e d a c c e s s t o t h e c r e e k i s i n d i c a t e d above the a r r o w s , and t h e i r d i s t r i b u t i o n i n t h e s i d e p o o l s i s shown i n t h e c i r c l e s on t h e r i g h t . The f i g u r e s a r e f o r two t e m p e r a t u r e c a t e g o r i e s ( i n d i c a t e d below t h e a r r o w s ) , and each r e p r e -s e n t s a c o m b i n a t i o n o f d a t a from f o u r t r i a l s on two s i d e p o o l s . . . . . . . . . . . . . . . . 53 25. The p e r c e n t a g e o f c u t t h r o a t c h o o s i n g a l t e r n a t i v e c o v e r t y p e s i n t h e s i d e p o o l s when n o t p e r m i t t e d a c c e s s t o D i c k Creek ( o b l i g a t o r y r e s i d e n c e ) and when p e r m i t t e d a c c e s s t o D i c k Creek ( v o l u n t a r y \ r e s i d e n c e ) . The p e r c e n t a g e o f c u t t h r o a t r e m a i n -i n g i n t h e s i d e p o o l s a f t e r b e i n g p e r m i t t e d a c c e s s t o the c r e e k i s i n d i c a t e d above t h e arr o w s , and t h e i r d i s t r i b u t i o n i n t h e s i d e p o o l s is shown in the circles on the right. Each figure represents a combination of data from four t r i a l s on two sidepools X ACKNOWLEDGEMENTS I w i s h t o thank my t h e s i s s u p e r v i s o r , D r. Bob W i l l i n g -t o n f o r the s u p p o r t and encouragement he p r o v i d e d t h r o u g h o u t t h i s s t u d y . The i n t e r e s t , e n t h u s i a s m , and c o n s t r u c t i v e c r i t i c i s m s p r o v i d e d by Dr. D a v i d N a r v e r o f t h e P a c i f i c B i o l o g i c a l S t a t i o n a r e s i n c e r e l y a p p r e c i a t e d , and i t i s a p l e a s u r e t o acknowledge Dr. J i m H a l l o f Oregon S t a t e U n i v e r s i t y f o r h i s h e l p f u l a d v i c e and s t i m u l a t i n g d i s c u s s i o n s d u r i n g t h e e a r l y phases o f my r e s e a r c h . I am i n d e b t e d t o t h e o t h e r two members o f my committee. D r. Tom N o r t h c o t e and Dr. J.P. Kimmins, f o r t h e i r a s s i s t a n c e , and t o Bruce Andersen, Bob Hooton, D i c k Leahy, C h a r l i e S c r i v e n e r and D a v i d W i l f o r d whose c o o p e r a t i o n i n the f i e l d c o n t r i b u t e d n o t a b l y t o t h i s s t u d y . T h i s r e s e a r c h was made p o s s i b l e t h r o u g h f u n d i n g p r o v i d e d by t h e N a t i o n a l R e s e a r c h C o u n c i l o f Canada and t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a . Accommodation, equipment, and u n p u b l i s h e d i n f o r m a t i o n was p r o v i d e d by t h e Department o f Environment and some o f the f i e l d a s s i s t a n c e was made a v a i l a b l e by the B.C. F i s h and W i l d l i f e B r a n c h . 1 INTRODUCTION I n c o a s t a l B r i t i s h Columbia coho salmon (Oncorhynchus  k i s u t c h ) , s t e e l h e a d (Salmo g a i r d n e r i ) , and c o a s t a l c u t t h r o a t t r o u t (S_. c l a r k i ) commonly occupy s m a l l e r streams f o r s e v e r a l y e a r s b e f o r e m i g r a t i n g t o s e a . C o a s t a l c u t t h r o a t r e s i d e p e r m a n e n t l y i n many s t r e a m s . An e s s e n t i a l , b u t n e g l e c t e d phase o f f i s h e r i e s r e s e a r c h , i s the s t u d y o f t h e w i n t e r h a b i t a t r e q u i r e m e n t s o f t h e s e s a l m o n i d s . E v e r e s t (1969) noted t h a t young s t e e l h e a d i n an Idaho s t r e a m may spend 21 o f t h e i r f i r s t 35 months o f s t r e a m r e s i d e n c e o v e r w i n t e r i n g , and o n l y 14 months g r o w i n g . T h i s o v e r w i n t e r i n g p e r i o d i n many p a r t s o f B r i t i s h Columbia i s ' a l s o l e n g t h y , making a s t u d y o f s a l m o n i d w i n t e r h a b i t a t r e q u i r e m e n t s p a r t i c u l a r l y d e s i r a b l e . W i n t e r i s r e g a r d e d as a p e r i o d o f c o n s i d e r a b l e m o r t a l i t y f o r j u v e n i l e s a l m o n i d s i n h a b i t i n g streams c h a r a c t e r i z e d by low w a t e r t e m p e r a t u r e s w i t h accompanying snow, i c e or f r e s h e t c o n d i t i o n s . The a p p a r e n t causes o f m o r t a l i t y may be d i v e r s e . For example, Reimers (1963) and Hunt (1969) s u g g e s t t h a t i n -adequate n u t r i t i o n d u r i n g t h e w i n t e r r e s u l t s i n p h y s i o l o g i c a l s t r e s s e s i n d u c i n g d e a t h i n weaker i n d i v i d u a l s . O v e r w i n t e r m o r t a l i t i e s may r e s u l t from s e v e r e s t r e a m f l o w f l u c t u a t i o n s (Hartman, 1965; Elwood and Waters, 1969), s u b s u r f a c e i c e and c o l l a p s i n g snow (Tack, 1938; Needham, M o f f e t , and S l a t e r , 1945; M a c i o l e k and Needham, 1952; and Needham and J o n e s , 1959), or p r e d a t i o n by b i r d s , mammals, and o t h e r f i s h . These r e p o r t s s u g g e s t t h a t c o n d i t i o n s w i t h i n a s t r e a m d u r i n g t h e w i n t e r have*'an i m p o r t a n t i n f l u e n c e on the a b i l i t y o f a stream t o produce f i s h . 2 Man's a c t i v i t i e s , and i n c o a s t a l B r i t i s h C o l u m b i a , t i m b e r h a r v e s t i n g i n p a r t i c u l a r , may s i g n i f i c a n t l y a l t e r c o n d i t i o n s w i t h i n a s t r e a m . S a t i s f a c t o r y i n s i g h t i n t o t h e s p e c i f i c n a t u r e and magnitude o f man's impact on o v e r w i n t e r i n g f i s h does n o t e x i s t , b u t i t i s e s s e n t i a l f o r i n t e g r a t e d r e s o u r c e management. T h i s weakness r e s u l t s p a r t i a l l y from a l a c k o f adequate q u a n t i t a t i v e means o f d e s c r i b i n g changes i n p h y s i c a l h a b i t a t i n d uced by t i m b e r h a r v e s t i n g . However, a good u n d e r s t a n d i n g o f the o v e r w i n t e r h a b i t a t r e q u i r e m e n t s o f f i s h i s a l s o e s s e n t i a l b e f o r e the e f f e c t s o f h a b i t a t a l t e r a -t i o n can be e v a l u a t e d a d e q u a t e l y . A number o f s t u d i e s ( L i n d r o t h , 1955a; Hartman, 1963 and 1965; Edmundson, E v e r e s t , and Chapman, 1968; and Chapman and B j o r n n , 1969) i n d i c a t e t h a t when w a t e r t e m p e r a t u r e s d r o p t o near f r e e z i n g , j u v e n i l e s a l m o n i d s become r e l a t i v e l y i n -a c t i v e and e x h i b i t a c h a r a c t e r i s t i c h i d i n g r e s p o n s e . D u r i n g t h i s p e r i o d , f e e d i n g a c t i v i t y i s r e d u c e d or s t o p p e d a l t o -g e t h e r . Reimers (1957) has shown t h a t young t r o u t a t low v/ater t e m p e r a t u r e s may s u r v i v e many months w i t h o u t f o o d . S p e c i f i c h a b i t a t t y p e s appear t o be i m p o r t a n t and i t has been shown t h a t i n some s i t u a t i o n s i f s u i t a b l e w i n t e r c o v e r i s n o t a v a i l a b l e , f i s h w i l l move i n t o o t h e r a r e a s w h i c h do p r o v i d e c o v e r ( B j o r n n , 1971; M o r r i l , 1972). Two s t u d i e s i n p a r t i c u l a r p r o v i d e v a l u a b l e i n f o r m a t i o n w i t h r e s p e c t t o o v e r w i n t e r i n g s a l m o n i d s . Hartman (19S5) examined the d i s t r i b u t i o n and b e h a v i o r o f u n d e r y e a r 1 i n g coho and s t e e l h e a d i n t h r e e r i v e r systems i n c o a s t a l B r i t i s h C o l umbia. P a r t i a l l y c o n t r o l l e d s t r e a m aquarium s t u d i e s were 3 used t o p r o v i d e c o m p l i m e n t a r y i n f o r m a t i o n . Hartman's work i n d i c a t e d t h a t a l t h o u g h coho and s t e e l h e a d b o t h o c c u p i e d p o o l s i n t h e w i n t e r , they u t i l i z e d d i f f e r e n t m i c r o h a b i t a t s , w i t h coho most commonly found under l o g jams and o v e r h a n g i n g banks and s t e e l h e a d most o f t e n under b o u l d e r s . I n a r e a s where l o g jam c o v e r was a b s e n t , a pronounced r e d u c t i o n i n coho and s t e e l h e a d d e n s i t y o c c u r r e d d u r i n g t h e w i n t e r . I n b o t h s p e c i e s , a g g r e s s i o n was low. Hartman d i d n o t measure d e t a i l e d p h y s i c a l c h a r a c t e r i s t i c s o f coho and s t e e l h e a d o v e r w i n t e r i n g a r e a s . E v e r e s t (1969), however, measured the bottom and s u r f a c e w a t e r v e l o c i t i e s , s u b s t r a t e s i z e , and w a t e r d e p t h o f o v e r -w i n t e r i n g a r e a s u t i l i z e d by s t e e l h e a d and c h i n o o k salmon (O. t s h a w y t s c h a ) i n two l a r g e Idaho s t r e a m s . E v e r e s t i n d i c a t e d t h a t s t e e l h e a d and c h i n o o k o n l y u t i l i z e d a r e a s w i t h l a r g e b o u l d e r s . Both s t u d i e s i n d i c a t e d t h a t j u v e n i l e s a l m o n i d s occupy d i f f e r e n t h a b i t a t a r e a s i n t h e summer t h a n i n t h e w i n t e r . Some p r e l i m i n a r y u nderwater o b s e r v a t i o n s by t h e a u t h o r i n s e v e r a l s m a l l c o a s t a l streams d u r i n g 1972 s u p p o r t e d H a r t -man's and E v e r e s t ' s c o n c l u s i o n s t h a t young s a l m o n i d s o c c u p i e d d i f f e r e n t h a b i t a t s i n t h e w i n t e r t h a n i n t h e summer, and t h a t l o g jams and r u b b l e were i m p o r t a n t s o u r c e s o f w i n t e r c o v e r . However, t h e s e o b s e r v a t i o n s s u g g e s t e d t h a t o t h e r t y p e s o f h a b i t a t i n the s t r e a m system were a l s o i m p o r t a n t t o o v e r -w i n t e r i n g f i s h , and t h a t c e r t a i n p h y s i c a l c h a r a c t e r i s t i c s made some o v e r w i n t e r i n g a r e a s more d e s i r a b l e t h a n o t h e r s . I t was a p p a r e n t t h a t more d e t a i l e d q u a n t i t a t i v e i n f o r m a t i o n o f the b e h a v i o r , d i s t r i b u t i o n , and p h y s i c a l c h a r a c t e r i s t i c s i m p o r t a n t t o o v e r w i n t e r i n g coho and t r o u t i n s m a l l n u r s e r y streams would be u s e f u l . 4 The underwater o b s e r v a t i o n s i n d i c a t e d t h a t many m a r g i n a l bays and i s o l a t e d s i d e p o o l s , as w e l l as v e r y s m a l l b u t a c c e s -s i b l e t r i b u t a r i e s were e x t e n s i v e l y used by j u v e n i l e s a l m o n i d s d u r i n g t h e w i n t e r . U n d e r s t a n d i n g t h e importance o f t h e s e a r e a s t o o v e r w i n t e r i n g f i s h i s c o n s i d e r e d u s e f u l f o r s t r e a m management c o n s i d e r a t i o n s . S i n c e many o f t h e s e s i d e p o o l s and t r i b u t a r i e s may d r y up and a r e u n i m p o r t a n t f i s h h a b i t a t i n t h e summer, they a r e h i g h l y s u s c e p t i b l e t o damage from t i m b e r h a r v e s t i n g . P h y s i c a l bank damage and sediment a c c u m u l a t i o n s w i t h i n the c h a n n e l s u b s t r a t e a r e two p o t e n t i a l problems a r i s i n g from l o g g i n g o p e r a t i o n s a d j a c e n t t o t h e s e a r e a s . T h i s s t u d y had t h r e e p r i m a r y o b j e c t i v e s : 1. To q u a n t i t a t i v e l y d e s c r i b e some o f t h e p h y s i c a l c h a r a c t e r i s t i c s o f o v e r w i n t e r i n g a r e a s i n a coho and s t e e l h e a d n u r s e r y s t r e a m i n c o a s t a l B r i t i s h C o l u m b i a . 2. To e v a l u a t e the r o l e o f two s m a l l t r i b u t a r i e s i n p r o v i d i n g w i n t e r r e f u g e f o r young s a l m o n i d s i n t h i s n u r s e r y s t r e a m . 3 . To e x p e r i m e n t a l l y compare coho and t r o u t p r e f e r e n c e f o r a l t e r n a t i v e h a b i t a t t y p e s i n s i d e p o o l a r e a s s i m u l a t i n g c o n d i t i o n s b e f o r e and a f t e r s t r e a m d i s t u r b a n c e by l o g g i n g . The a l t e r n a t i v e h a b i t a t t y p e s were: a) s i d e p o o l s w i t h or w i t h o u t o v e r h a n g i n g banks, and b) s i d e p o o l s w i t h c l e a n or s i l t e d r u b b l e sub-s t r a t e . 5 The study i s r e p o r t e d i n two s e c t i o n s . The f i r s t d e a l s w i t h f i e l d o b s e r v a t i o n s of the w i n t e r e c o l o g y o f j u v e n i l e coho and s t e e l h e a d and i n c l u d e s p h y s i c a l measurements of o v e r w i n t e r -ing areas u t i l i z e d by j u v e n i l e salmonids as w e l l as a b e h a v i o r a l d e s c r i p t i o n o f salmonid a c t i v i t y a t v a r y i n g water termperatures and flows as determined by underwater o b s e r v a t i o n s . J u v e n i l e salmonid movements i n and out o f two s m a l l t r i b u t a r y areas d u r i n g the w i n t e r are r e p o r t e d i n t h i s f i r s t s e c t i o n . The second s e c t i o n deals w i t h the e x p e r i m e n t a l r e s u l t s o f s i d e p o o l t r i a l s comparing coho and t r o u t p r e f e r e n c e f o r h a b i t a t a l t e r n a -t i v e s t h a t may occur b e f o r e and a f t e r stream d i s t u r b a n c e . 6 PART I . WINTER ECOLOGY OF JUVENILE COHO AND STEELHEAD DESCRIPTION OF STUDY AREA A s m a l l Vancouver I s l a n d coho and t r o u t n u r s e r y s t r e a m ( C a r n a t i o n Creek) and two o f i t s t r i b u t a r i e s (750 and 1600 Creeks) were s t u d i e d ( F i g . 1 ) . The C a r n a t i o n Creek w a t e r s h e d i s t he s i t e o f a l o n g term s t u d y e x a m i n i n g t h e e f f e c t s o f t i m b e r h a r v e s t i n g on t h e f o r e s t e c o s y s t e m . E i g h t a g e n c i e s from t h e F e d e r a l and P r o v i n c i a l Governments as w e l l as a major f o r e s t i n d u s t r i a l c o r p o r a t i o n a r e i n v o l v e d i n t h e p r o j e c t . A. C a r n a t i o n Creek The C a r n a t i o n Creek v/ater shed i s a p p r o x i m a t e l y 10 km 2 and d r a i n s i n t o B a r k l e y Sound on the wes t c o a s t o f Vancouver I s l a n d . The w a t e r s h e d c o n s i s t s o f an overmature w e s t e r n hemlock (Tsuga h e t e r o p h y l l a ) , a m a b a l i s f i r ( A b i e s a m a b a l i s ) , and w e s t e r n r e d c e d a r (Tjiuja^ p l i c a t a ) f o r e s t , h a l f o f w h i c h i s s c h e d u l e d t o be logged w i t h i n the n e x t 10 y e a r s . I n a d d i t i o n t o the above s p e c i e s , S i t k a s p r u c e ( P i c e a s i t c h e n s i s ) , r e d a l d e r ( A l n u s r u b r a ) , s a l m o n b e r r y (Rubus s p e c t a b l i s ) , and s t i n k c u r r a n t ( R i b e s bracteosuiTi ) a r e commonly found a l o n g t h e s t r e a m s . The l o w e s t 3.5 km of C a r n a t i o n Creek i s a c c e s s i b l e t o anadromous f i s h , and i s u t i l i z e d by coho and chum (O.Jketa) salmon, and s t e e l h e a d and c u t t h r o a t t r o u t . A r e s i d e n t p o p u l a -t i o n o f two s p e c i e s o f s c u l p i n s ( C o t t u s a l e u t i c u s and C. asper) i s a l s o p r e s e n t i n t h i s s e c t i o n . The upper r e g i o n o f F i g . 1 . L o c a t i o n o f t h e C a r n a t i o n C r e e k w a t e r s h e d a n d s t u d y s e c t i o n s ( S c a l e : 1 : 5 0 , 0 0 0 ) . 8 t h e C a r n a t i o n Creek system s u p p o r t s a p o p u l a t i o n o f r e s i d e n t c u t t h r o a t t r o u t . The w a t e r s h e d i s l o c a t e d i n an a r e a o f h i g h a n n u a l p r e c i p i t a t i o n (275-450 cm), w i t h most o f i t o c c u r r i n g as r a i n -f a l l between October and A p r i l . S t r e a m f l o w f l u c t u a t e s v i o l e n t l y w i t h i n s h o r t time p e r i o d s and has ranged from 0.03 raVsec (1 c f s ) d u r i n g the l a t e summer p e r i o d t o o v e r 20 mVsec (700 c f s ) d u r i n g peak w i n t e r f r e s h e t s . The mean d a i l y d i s c h a r g e f r o m " l a t e September 1972 t h r o u g h May 1973 i s g i v e n i n Appendix I . C a r n a t i o n Creek drops a p p r o x i m a t e l y 60 m i n t h e l o w e s t 2.5 km (2.4 p e r c e n t s l o p e ) . The s u b s t r a t e i n t h i s s e c t i o n ranges from s m a l l g r a v e l t o r u b b l e up t o 30 cm i n d i a m e t e r , and e x t e n s i v e g r a v e l b a r s s u g g e s t t h a t c o n s i d e r a b l e s u b s t r a t e movement o c c u r s d u r i n g f r e s h e t s . U p turned t r e e r o o t s , f a l l e n t r e e s , o v e r h a n g i n g b anks, and s m a l l a c c u m u l a t i o n s o f d e b r i s a r e common t h r o u g h o u t t h e s t u d y a r e a ( F i g . 2 ) . Maps o f two i n t e n s i v e l y s u r v e y e d s e c t i o n s o f C a r n a t i o n Creek a r e p r e s e n t e d i n Appendix I I and show the l o c a t i o n s o f o v e r h a n g i n g banks, l o g s , and u p t u r n e d r o o t s , p r o v i d i n g an i n d i c a t i o n o f t h e i r abundance i n t y p i c a l s e c t i o n s o f C a r n a t i o n C r e e k . B. 750 and 1600 Creeks Two t r i b u t a r y streams o f C a r n a t i o n Creek were s t u d i e d as p o t e n t i a l j u v e n i l e s a l m o n i d w i n t e r i n g a r e a s . One s t r e a m e n t e r s the mainstem o f C a r n a t i o n Creek 750 m above t h e e s t u a r y (750 Creek) and t h e second 1600 m above the e s t u a r y (1600 C r e e k ) . 9 g r a v e l bars and abundance of cover. B. Carn-a t i o n Creek near 2600 m. Note l a r g e r substrate and upturned r o o t s . 10 The f i r s t t r i b u t a r y c o n s i s t s of a s e r i e s of i n t e r c o n -nected mud substrate pools formed behind o l d , deserted beaver dams. I t dra i n s an area of approximately 14 h e c t a r e s . Winter flows are g e n e r a l l y l e s s than 0.03 raVsec (1 c f s ) , however v i s u a l estimates suggest flows as high as approximately 3 0.2 m /sec (7 c f s ) occur during peak w i n t e r f r e s h e t s . The lowest 100 m of the creek i s u t i l i z e d by young salmonids a t higher flows but i s dry during the l a t e summer ( F i g . 3 ) . Adjacent v e g e t a t i o n c o n s i s t s p r i m a r i l y of western hemlock, w i t h an understory of salmonberry and t a l l blue huckleberry (Vaccinium o v a l i f o l i u m ) . The second t r i b u t a r y , 1600 Creek, i s l a r g e r than 750 Creek and dr a i n s an area of approximately 22 h e c t a r e s . The channel i s more defined than 750 Creek and c o n s i s t s of long pool s e c t i o n s of mud and organic matter s u b s t r a t e and s h o r t r i f f l e s e c t i o n s w i t h small g r a v e l s u b s t r a t e . This stream flows throughout the year and peak flows as high as 0.6 mVsec (20 cf s ) probably occur during w i n t e r f r e s h e t s . The lowest 500 m of 1600 Creek i s a c c e s s i b l e to salmonids and a d u l t coho and c u t t h r o a t spawn i n i t and young coho and c u t t h r o a t use i t as a nursery area throughout the year. Red a l d e r , western hem-lo c k , s t i n k c u r r a n t , and salmonberry are found adjacent 1600 Creek. The midday water temperatures o f Carnation Creek and the two t r i b u t a r i e s from l a t e September 1972 through May 1973 are given i n Appendix I . Temperatures i n Carnation Creek reached a maximum of 13°C i n the l a t e summer and dropped to 2°C f o r s h o r t periods d u r i n g the w i n t e r . Some surface i c e F i g . 3 . Dried channel of 750 Creek during e a r l y September. Photo taken from j u s t above the t r a p s . 12 forms i n back channels dur i n g the c o l d e s t p e r i o d s . Water temperatures remained l e s s than 6°C from December through A p r i l . Temperatures i n 750 Creek f l u c t u a t e d more than i n the main creek, w h i l e temperatures i n 1600 Creek were c o n s i s t e n t l y warmer than the other two streams throughout the w i n t e r . For example, on January 10, 1973, midday water temperatures were 3.5°C, 2.0°C, and 0.5°C f o r 1600, Carnation, and 750 Creeks r e s p e c t i v e l y . 13 MATERIALS AND METHODS A. W i n t e r O b s e r v a t i o n s o f J u v e n i l e Coho and S t e e l h e a d 1• I n t e n s i v e H a b i t a t Survey Coho and s t e e l h e a d m i c r o h a b i t a t i n f o r m a t i o n was c o l -l e c t e d by s n o r k e l i n g o b s e r v a t i o n s i n t h e l o w e s t 2800 m o f C a r n a t i o n Creek from September 1972 t o A p r i l 1973. To sample a s e c t i o n o f s t r e a m , t h e a u t h o r e n t e r e d the w a t e r downstream and c a r e f u l l y worked up t o a p o i n t where an u n d i s t u r b e d f i s h or a g g r e g a t i o n o f f i s h was o b s e r v e d . F i s h were v i s u a l l y s e p a r a t e d by s p e c i e s i n t o age 0 and age 1+ g r o u p s . Coho and s t e e l h e a d i n t h e i r f i r s t w i n t e r (age 0) c o u l d be r e a d i l y i d e n t i f i e d , b u t s t e e l h e a d i n t h e i r second and t h i r d w i n t e r s c o u l d n o t be s e p a r a t e d from each o t h e r by s i g h t and were d e s i g n a t e d as age I+. F i s h o b s e r v a t i o n s were made between 1000 and 1600 hours and were r e s t r i c t e d t o s t r e a m -f l o w s l e s s t h a n 3 mVsec (105 c f s ) . An underwater l i g h t was used f o r s e a r c h i n g l o g jams and i n o t h e r p o o r l y l i g h t e d a r e a s . A m e t a l r o d was used t o o v e r -t u r n r o c k s and probe f o r f i s h w i t h i n t h e s u b s t r a t e . A f t e r o b s e r v i n g a f i s h f o r 1-5 m i n u t e s , i t s most f r e -quent l o c a t i o n o r f o c a l p o i n t (wickham, 1967) was marked w i t h a l e a d w e i g h t and p h y s i c a l c h a r a c t e r i s t i c s o f i t s h a b i t a t were measured ( F i g . 4 ) . Coho were o f t e n found i n c l o s e a g g r e g a t i o n s , and a c o u n t o f the number o f f i s h i n t h e a g g r e g a t i o n as w e l l as p h y s i c a l c h a r a c t e r i s t i c s o f t h e i r h a b i t a t were o b t a i n e d . 14 F i g . 4. Measuring water depth (A) and water v e l o c i t y (B). 15 Water d e p t h and v e l o c i t y , s u b s t r a t e s i z e , d i s t a n c e t o s u i t a b l e c o v e r , and type o f c o v e r were r e c o r d e d f o r e a c h o b s e r v a t i o n . Water v e l o c i t i e s , b o t h f o c a l p o i n t v e l o c i t y and maximum s u r r o u n d i n g a r e a v e l o c i t y w i t h i n 0.3 m o f t h e p o i n t o f o b s e r v a -t i o n f o r age 0 and w i t h i n 0.6 m f o r age 1+ f i s h were measured t o t h e n e a r e s t c e n t i m e t e r p e r second w i t h M i d g e t B e n t z e l c u r r e n t speed tubes s i m i l a r t o t h o s e d e s c r i b e d by E v e r e s t (1967). These i n s t r u m e n t s were s u i t a b l e f o r m e a s u r i n g c u r r e n t s between 15 and 120 cm/sec. T o t a l s t r e a m d i s c h a r g e ( w e i r measurements) and w a t e r t e m p e r a t u r e ( r e c o r d i n g , thermograph) i n f o r m a t i o n was o b t a i n e d a t the b e g i n n i n g and end o f e a ch o b s e r v a t i o n p e r i o d from a permanent h y d r o l o g i c a l i n s t a l l a t i o n m a i n t a i n e d a t S t a t i o n B ( F i g . 1 ) . Upturned t r e e r o o t s , l o g s , overhanging banks w i t h and w i t h o u t r o o t s , o v e r h a n g i n g b r u s h , d e b r i s ( i e . , s m a l l , temporary a c c u m u l a t i o n s o f branches and s n a g s ) , r u b b l e , and t u r b u l e n t s u r f a c e water c o n s t i t u t e d p o t e n t i a l a r e a s of c o v e r . F i s h more t h a n 2 m from c o v e r were a s s i g n e d t o a 'no cover', c a t e g o r y . Coho were more p r e v a l e n t t h a n s t e e l h e a d i n the s t u d y s e c t i o n s and o b s e r v a t i o n s were made on a t o t a l o f 1311 age 0 coho, 351 age 1+ coho, 122 age 0 s t e e l h e a d , and 167 age 1+ s t e e l h e a d . 2. E x t e n s i v e H a b i t a t Survey D u r i n g the c o u r s e o f t h i s s t u d y , a number o f o t h e r c o a s t a l B r i t i s h Columbia streams were b r i e f l y examined i n the w i n t e r and some r e f e r e n c e t o the j u v e n i l e coho, s t e e l h e a d and c u t t h r o a t d i s t r i b u t i o n s i n them i s i n c l u d e d . i n the d i s c u s s i o n . 16 I n F e b r u a r y and March 1972 P a t o n Creek was examined by s n o r k e l -i n g w h i l e w a t e r t e m p e r a t u r e s were between 2°C and 4°C. P a t o n Creek i s a t r i b u t a r y o f the Seymour R i v e r , n o r t h o f Vancouver, B.C. The S a r i t a R i v e r , near C a r n a t i o n Creek ( F i g . 1 ) , was examined u s i n g s n o r k e l i n g o b s e r v a t i o n s i n O c t o b e r 1972 (7°~11°C) and i n F e b r u a r y 1973 (4°C). These streams b o t h have p o p u l a t i o n s o f j u v e n i l e s t e e l h e a d and coho. O b s e r v a t i o n s o f t h e d i s t r i b u -t i o n o f c u t t h r o a t d u r i n g the w i n t e r were made on R i t h e r d o n Creek ( F i g . 1) w h i l e e l e c t r o f i s h i n g t r o u t t o be used i n t h e s i d e p o o l e x p e r i m e n t s . R i t h e r d o n Creek c o n t a i n e d o n l y c u t t h r o a t t r o u t and was examined i n J a n u a r y and F e b r u a r y 1973 wh i l e w a t e r tem p e r a t u r e s were between 2°C and 3°C. 3. L i m i t a t i o n s o f Underwater O b s e r v a t i o n s A l t h o u g h s n o r k e l i n g has been used by o t h e r w o r k e r s w h i l e e x a m i n i n g young s a l m o n i d d i s t r i b u t i o n i n r e l a t i o n t o t h e i r h a b i t a t (Hartman, 1965; Edmundson ejb a lU, 1968; E v e r e s t , 1969; G r i f f i t h , 1971), i t has never p r e v i o u s l y been used t o t h e same e x t e n t as i n t h i s s t u d y f o r making w i n t e r o b s e r v a t i o n s . A s h o r t d i s c u s s i o n o f t h e problems a s s o c i a t e d w i t h w i n t e r u n d e r -w a t e r o b s e r v a t i o n s i s a p p r o p r i a t e . A n o t i c e a b l e d i f f e r e n c e between summer and w i n t e r u n d e r -w a t e r o b s e r v a t i o n s was the g r e a t e r tendency f o r t h o s e f i s h n o t w i t h i n c o v e r t o s c u r r y t o c o v e r when approached i n t h e w i n t e r . T h i s more pronounced f r i g h t r e a c t i o n n e c e s s i t a t e s v e r y s l o w , c a r e f u l movements when a p p r o a c h i n g f i s h . J u v e n i l e f i s h d u r i n g the summer a r e u s u a l l y more a g g r e s s i v e , l e s s e a s i l y f r i g h t e n e d , and t h e r e f o r e e a s i e r t o o b s e r v e . 17 H i d i n g f i s h t end t o seek t h e d a r k e s t a r e a s a v a i l a b l e , t w i s t i n g b e h i n d r o o t s and t a k i n g on t h e c o l o u r o f t h e i r s u r r o u n d i n g s , making them d i f f i c u l t t o f i n d . H i g h e r d i s c h a r g e s and a s s o c i a t e d t u r b i d i t i e s d u r i n g t h e w i n t e r l i m i t the p e r i o d s and c o n d i t i o n s o f o b s e r v a t i o n s . A f i n a l comment on t h e use o f s n o r k e l i n g f o r o b s e r v i n g f i s h d u r i n g the w i n t e r i s t h a t when w a t e r t e m p e r a t u r e s a r e l e s s than 4°C, an o b s e r v e r e x p e r i e n c e s s e v e r e c o l d , sometimes a f t e r l e s s t h a n 1/2 h r i n the s t r e a m . A c o l d d i v e r t e n d s t o c o l l e c t d a t a h a s t i l y , p r o b a b l y l e a d i n g t o g r e a t e r e r r o r s i n measurements made a t low w a t e r t e m p e r a t u r e s . B. W i n t e r Movements o f J u v e n i l e Coho and T r o u t F i s h t r a p d e v i c e s a t t h e l o w e r end o f 750 and 1600 Creeks ( F i g . 1) were used t o a s s e s s upstream and downstream s a l m o n i d movements. The t r a p s c o n s i s t e d o f a w i r e mesh (6 mm) fence w h i c h d i v e r t e d m i g r a n t s i n t o s c r e e n e d f u n n e l t r a p s ( F i g . 5 ) . Rocks were p l a c e d i n t h e t r a p s t o p r o v i d e escape c o v e r f o r t h e s m a l l e r f i s h . A d e b r i s - c a t c h i n g f e n c e o f c h i c k e n w i r e was c o n s t r u c t e d above th e 1600 Creek f e n c e . The t r a p s were checked d a i l y . F o r k l e n g t h s o f a l l f i s h were measured t o the n e a r e s t m i l l i m e t e r and p a s s e d i n the d i r e c t i o n o f movement, i n d i c a t e d by t h e i r c a p t u r e . Water t e m p e r a t u r e s were o b t a i n e d from d a i l y r e a d i n g s a t t r a p l o c a t i o n s and from a Ryan thermograph i n 1600 C r e e k . S t a f f gauges i n -d i c a t i n g w a t e r l e v e l a t the two f e n c e s were r e a d d a i l y . 18 F i g . 5 . Upstream and downstream t r a p p i n g devices on 1600 Creek (A) and 750 Creek ( B ) . Photos were taken i n September 1972 w h i l e 750 Creek was s t i l l dry. Data c o l l e c t e d a t t h e f i s h t r a p s were t a b u l a t e d as t o t a l number o f coho, s t e e l h e a d , and c u t t h r o a t m i g r a n t s p e r month. The l e n g t h f r e q u e n c y d i s t r i b u t i o n s o f m i g r a n t s f o r two p e r i o d s , September t o December and J a n u a r y t o May, were c a l c u l a t e d based on 4-mm f o r k l e n g t h i n t e r v a l s f o r coho and 10~mm i n t e r v a l s f o r t r o u t . Because o f t h e i r s i m i l a r a p p e a r -ance, no a t t e m p t was made t o s e p a r a t e s t e e l h e a d and c u t -t h r o a t f r y w h i c h were l e s s t h a n 60 mm i n l e n g t h . 20 RESULTS A. W i n t e r O b s e r v a t i o n s o f J u v e n i l e Coho and S t e e l h e a d 1. Water Depth and V e l o c i t y 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 mean de p t h s o f w a t e r o c c u p i e d by j u v e n i l e coho and s t e e l h e a d d u r i n g t h e w i n t e r were found ( P i g . 6 ) . Age 0 coho were found i n a v a r i a b l e range o f depths g r e a t e r t h a n 15 cm (x=73 cm). Age 1+ coho and s t e e l -head a l s o o c c u p i e d a v a r i e t y o f w a t e r d e p t h s , b u t f a v o r e d deeper w a t e r (x=89 cm and 90 cm r e s p e c t i v e l y ) t h a n coho f r y ( t - t e s t , p < . 0 1 ) . S t e e l h e a d f r y u s u a l l y s e l e c t e d much s h a l l o w e r r e a c h e s o f the s t r e a m (x=32 cm) t h a n coho and o l d e r s t e e l h e a d . More t h a n 20 p e r c e n t o f the s t e e l h e a d f r y were found i n l e s s t han 15 cm o f w a t e r , i n c l u d i n g a number o f f r y under s u b s t r a t e i n w a t e r l e s s t h a n 5 cm deep. Ko s t e e l h e a d f r y were o b s e r v e d i n the ' g r e a t e r than 105 cm' d e p t h c a t e g o r y f a v o r e d by t h e o l d e r coho and s t e e l h e a d . S i g n i f i c a n t n e g a t i v e c o r r e l a t i o n s (p<.01) were o b t a i n e d between w a t e r t e m p e r a t u r e s (8.5°C and l e s s ) and w a t e r d e p t h o c c u p i e d by coho and age 1+ s t e e l h e a d ( F i g . 7 ) , i n d i c a t i n g t h a t as water t e m p e r a t u r e s d r o p i n t h e l a t e f a l l and w i n t e r coho and age 1+ s t e e l h e a d move i n t o deeper r e a c h e s o f t h e s t r e a m . No s i g n i f i c a n t c o r r e l a t i o n o f t h i s t y p e e x i s t e d f o r the age 0 s t e e l h e a d . Coho were u s u a l l y l e s s c l o s e l y a s s o c i a t e d w i t h t h e s t r e a n b ottom t h a n s t e e l h e a d and t h e i r average d i s t a n c e from the s t r e a n bottom was 25 and 27 cm f o r age 0 and age 1+ coho r e s p e c t i v e l y . 21 DEPTH O F WATER 60 40 A 20 X CO A G E 0 C O H O N = 1274 A G E 0 S T E E L H E A D N = 78 60 40 H 20 A G E 1+ C O H O N = 298 o •o I o o o A G E 1+ S T E E L H E A D N = 122 I o i I »o o O •O I r o i D E P T H O F W A T E R (CM) F i g . 6. Depth o f wat e r s e l e c t e d by j u v e n i l e coho and s t e e l h e a d a t w a t e r t e m p e r a t u r e s o f 7°C o r l e s s 2 2 DEPTH OF W A T E R O--.-O A G E 0 C O H O N = 1311. r = - 0 . 3 5 * * -© © A G E 1 + C O H O N = 3 5 1 . r = - 0 . 4 3 * * y '= 13 5.0 - 9.76 x y'= 116.9 " 9 . 2 0 x T E M P E R A T U R E 150 U I X I— a. LU Q LU t— < 100 H O-.-.-o A G E 0 S T E E L H E A D N = 1 2 2 , r = 0 . 0 5 N S © © A G E 1 + S T E E L H E A D N = 1 6 7 , r = - 0 . 4 9 * * T E M P E R A T U R E ° C F i g . 7 . W a t e r d e p t h d i s t r i b u t i o n o f j u v e n i l e c o h o a n d s t e e l -h e a d a t d i f f e r e n t w a t e r t e m p e r a t u r e s . D o t s a n d c i r -c l e s r e p r e s e n t m e a n d e p t h o f f i s h f o r a l l o b s e r v a t i o n s w i t h i n t h e d e g r e e i n t e r v a l . V e r t i c a l l i n e s r e p r e s e n t s t a n d a r d d e v i a t i o n s a n d a s s o c i a t e d n u m b e r s i n d i c a t e t h e s a m p l e s i z e . R e g r e s s i o n l i n e s w e r e d e r i v e d f r o m N o b s e r v a t i o n s . ( * s i g n i f i c a n t a t p = . 0 5 , * * s i g n i f i -c a n t a t p = . 0 1 , N S n o t s i g n i f i c a n t a t p - . 0 5 ) 23 The average distance of steelhead from the stream bottom was 5 cm for age 0 steelhead and 12 cm for age 1+ steelhead. F i g . 8 shows the d i s t r i b u t i o n of f o c a l point v e l o c i t i e s and F i g . 9 shows the maximum surrounding area v e l o c i t i e s a t which coho and steelhead were observed. The figures indicate that at low water temperatures both age groups of coho and steelhead were most commonly found at points where the water ve l o c i t y was less than 15 cm/sec. An examination of the v e l o c i t i e s in the area surrounding the coho and steelhead indicates that most of the f i s h were found i n the low v e l o c i t y water. T h i s is most obvious for age 0 coho where nearly 80 per cent of the f i s h were observed to be in low v e l o c i t y water. Mean focal point and maximum area v e l o c i t i e s for age 0 and age 1+ steelhead at various water temperatures a r e shown in F i g . 10. Only measurements taken during mcde.rate stream-flows (0.3 to 0.7 tnVsec or approximately 10 to 25 cfs) are included in t h i s comparison because of apparent v a r i a b i l i t y in f i s h a c t i v i t y r e s u l t i n g from very low or high flows. S i n c e the current meters were not suitable for measuring low water v e l o c i t i e s (water v e l o c i t i e s less than 15 cm/sec were recorded as zero) the mean water v e l o c i t i e s presented in F i g . 9 do not represent the true mean v e l o c i t i e s . W i t h t h i s point i n mind, these r e s u l t s should be used to indicate trends rather than actual values. For both ages o f steelhead, f o c a l point and maximum v e l o c i t i e s in surrounding areas tended to increase s i g n i f i c a n t l y with r i s i n g temperatures i n the range above 4°C. So r e l a t i o n s h i p between water v e l o c i t y occupied by coho and 24 F O C A L P O I N T V E L O C I T I E S 100 n X co 80 60 40 20 0 O 1 0 0 O 80 60 40 A 20 A G E 0 C O H O N = 12 74 A G E 0 S T E E L H E A D N = 78 A G E 1+ C O H O ! N = 298 A G E 1+ S T E E L H E A D N = 122 r ~ CO WATER V E L O C I T Y ( C M / S E C ) F i g . 8 . F o c a l p o i n t w a t e r v e l o c i t i e s s e l e c t e d b y j u v e n i l e c o h o a n d s t e e l h e a d a t w a t e r t e m p e r a t u r e s o f 7 ° C o r l e s s . 25 MAXIMUM A R E A VELOCITIES 100 80 6 0 40 X CO 20 0 O i o o 80 6 0 40 20 -f A G E 0 C O H O N = 12 74 MIL-A G E 0 S T E E L H E A D N = 78 1 A G E 1+COHO N = 298 A G E 1 + S T E E L H E A D N = 122 i o I o m 7 o W A T E R V E L O C I T Y ( C M / S E C ) F i g . 9 . M a x i m u m a r e a w a t e r v e l o c i t i e s s e l e c t e d b y j u v e n i l e c o h o a n d s t e e l h e a d a t w a t e r t e m p e r a t u r e s o f 7 ° C o r l e s s . 60-, MAXIMUM AREA V E L O C I T I E S w -o—-oAGE 0 STEELHEAD N = 36, r = 0.49** </>5o- © — © A G E 1 + STEELHEAD N = 66 © r = 0.52** o T E M P E R A T U R E ° C F i g . 1 0 . F o c a l p o i n t a n d m a x i m u m a r e a w a t e r v e l o c i t i e s s e l e c t e d b y a g e 0 a n d a g e .1+ s t e e l h e a d p l o t t e d a g a i n s t . w a t ^ r t e m p e r -a t u r e . S t r e a m f l o w s w e r e b e t w e e n 0 . 3 a n d 0 . 7 m ° / s e c f o r a l l m e a s u r e m e n t s . D o t s a n d c i r c l e s r e p r e s e n t m e a n w a t e r v e l o c i t i e s ' w i t h i n t h e 0 . 5 d e g r e e i n t e r v a l b a s e d o n a s a m p l e s i z e i n d i c a t e d b y t h e a s s o c i a t e d n u m b e r s . R e g r e s s i o n l i n e s w e r e d e r i v e d f r o m N o b s e r v a t i o n s . 27 water temperature was i n d i c a t e d from the m i c r o h a b i t a t informa-t i o n except t h a t a t water temperatures l e s s than 4°C the mean water v e l o c i t i e s s e l e c t e d by coho were between 0 and 15 cm/sec. 2. Winter Cover As water temperatures dropped from 9<>C to 2°C, coho and steelhead moved c l o s e r t o o b j e c t s p r o v i d i n g cover ( F i g . 11). When water temperatures became very low, feeding a c t i v i t y was reduced, and n e a r l y a l l f i s h were found e i t h e r w i t h i n or very near ( l e s s than 1 m) cover ( F i g . 12). F i s h found w i t h i n cover were h e a v i l y pigmented and s t r o n g l y photonegative when the beam from an underwater lamp was d i r e c t e d towards them. Upturned t r e e r o o t s and logs were the -most common type of cover used by both age groups of coho and by age 1+ s t e e l -head ( F i g . 13). Deep pools were o f t e n formed around these roots and l o g s , and the combination of deep, slow water and good cover made these s e c t i o n s o f the stream important w i n t e r -ing areas, p a r t i c u l a r l y f o r the o l d e r f i s h . Overhanging banks and d e b r i s m a t e r i a l such as branches and s m a l l snags were a l s o used as winter cover. However only those overhanging banks t h a t had a s s o c i a t e d r o o t complexes were u t i l i z e d . These r o o t s may be p r o v i d i n g the d i s t i n c t v i s u a l and t a c t i l e r e ference p o i n t s which Hartman (1963) i n d i c a t e d were important i n r e g u l a t i n g brown t r o u t (Salmo t r u t t a ) d i s t r i b u t i o n . Few instances o f t u r b u l e n t white water occurred i n the study s e c t i o n s , and most of those t h a t d i d were not used by young salmonids f o r w i n t e r cover. Flooded bush such as salmonberry and s t i n k c u r r a n t D I S T A N C E TO C O V E R 28 150 - 1 at > o u O UJ U z < i o o H 50 H o o A G E 0 STEELHEAD N = 122,r = 0 . 3 3 * * ® © A G E 1 + S T EEL H E A D N = 167,r = 0.1 8 * F i g . 1 1 . TEMPERATURE U C • D i s t a n c e t o c o v e r o f j u v e n i l e c o h o a n d s t e e l h e a d a t d i f f e r e n t w a t e r t e m p e r a t u r e s . D o t s a n d c i r c l e s r e p r e -s e n t m e a n c o v e r d i s t a n c e f o r a l l o b s e r v a t i o n s w i t h i n t h e o n e d e g r e e i n t e r v a l b a s e d o n a s a m p l e s i z e i n d i -c a t e d b y t h e a s s o c i a t e d n u m b e r s . R e g r e s s i o n l i n e s w e r e d e r i v e d f r o m N o b s e r v a t i o n s . 29 DISTANCE TO C O V E R 80 " A G E 0 COHO (N =12 74) 60 -40 -C O 20 -} L L . 0 - j L L . o 80 -| AGE 1+ COHO 60 - (N = 298) 40 -20 - - r 1 j 1 0 " z s § o o i n o *— CN o o 1 7 I I o A i o o O w o "> D I S T A N C E TO A G E 0 STEELHEAD (N = 78) AGE 1+ STEELHEAD (N= 122) X | - - <N O) H; 0 I I I A > o o o $ ^ o £ C O V E R (CM) F i g . 1 2 . D i s t a n c e t o c o v e r s e l e c t e d b y j u v e n i l e c o h o a n d s t e e l h e a d a t w a t e r t e m p e r a t u r e s o f 7 ° C o r l e s s . 3 0 C O V E R T Y P E S 60 • 40 • 20 • AGE 0 C O H O (N = 1274) x to I 0 ' A G E 0 STEELHEAD (N = 78) o 60-40 • AGE 1+ C O H O (N = 298) 20 4 AGE 1+- STEELHEAD (N=122) o o o o z < CD o z o z < X a: tu > o x </> CO O z o z < X ex UJ > o < x z o z o o C£ D LLI z 3 o o 1/1 X ry Z to CO < z> LU CO CO Q O O z z o o z z < < X I Oi > > o o < X z o z F i g . 1 3 . C o v e r t y p e s s e l e c t e d . b y j u v e n i l e c o h o a n d s t e e l h e a d a t w a t e r t e m p e r a t u r e s o f 7 ° C o r l e s s . 31 p r o v i d e d some c o v e r f o r coho, e s p e c i a l l y i n b a c k w a t e r p o o l s and t r i b u t a r y a r e a s . S i d e p o o l s p r o v i d e d s u i t a b l e c o v e r and p r o t e c t i o n from s e v e r e w i n t e r f r e s h e t s . F o r example, a s i d e p o o l ( a p p r o x i m a t e l y 10 m^  w i t h a maximum d e p t h o f 25 cm) l o c a t e d 50 ra from t h e C a r n a t i o n e s t u a r y was e l e c t r o f i s h e d i n e a r l y J a n u a r y 1973 and 54 coho were removed from i t . When t h i s p o o l was e l e c t r o f i s h e d a g a i n i n e a r l y March, a n o t h e r 20 coho were o b t a i n e d . D u r i n g t h e summer, t h i s p o o l i s d r y and n o t i m p o r t a n t f i s h h a b i t a t . Rubble was t h e p r i n c i p a l s o u r c e o f c o v e r f o r age 0 s t e e l h e a d , and h a l f o f the f r y o b s e r v e d a t w a t e r t e m p e r a t u r e s o f 7°C or l e s s were e i t h e r v e r y c l o s e t o o r under r u b b l e . Upturned r o o t s , l o g s , o v e r h a n g i n g banks and d e b r i s m a t e r i a l a l s o p r o v i d e d some c o v e r f o r s t e e l h e a d f r y . Some p h y s i c a l c h a r a c t e r i s t i c s o f t h e a r e a s where s t e e l -head f r y were found i n t h e s u b s t r a t e a r e shown i n F i g . 14. More than h a l f the f r y were found under r o c k s l e s s t h a n 15 cm and r o c k s as s m a l l as 10 cm p r o v i d e d c o v e r as l o n g as t h e r e were s u i t a b l e i n t e r s t i c e s between the r o c k s t o a l l o w f o r f i s h movement. The r u b b l e s e l e c t e d by s t e e l h e a d f r y f o r w i n t e r c o v e r was u s u a l l y i n s h a l l o w w a t e r , c l o s e t o t h e margin o f the s t r e a m . The w a t e r v e l o c i t y above t h e r u b b l e was u s u a l l y l e s s t h a n 15 cm/sec. There were s e v e r a l i n s t a n c e s where more than one age 0 s t e e l h e a d was found under t h e same r o c k . Only f o u r a p p a r e n t l y age 1+ s t e e l h e a d were found h i d i n g under r u b b l e , and none appeared t o be more t h a n 80 mm i n l e n g t h . O l d e r age groups o f s t e e l h e a d were commonly found under b o u l d e r s i n t h e S a r i t a R i v e r , a l a r g e s t r e a m a d j a c e n t t o C a r n a t i o n Creek, 32 100 < LU 80 -X p LU LU 1— 6 0 -CO o LU 40 -o < OF 20 -c> SUBSTRATE SIZE I I 10 I 15 l < 1 0 I l I I I I 15 I 20 20 | 25 I I I | I l > 3 0 | 25 I 30 I I S U B S T R A T E D I A M E T E R ( C M ) I O O n < W 8 0 X LU LU I— CO O LU o < 60 40 O 20 H WATER DEPTH I 0 | 15 | 30 | I I I | I | I | >45 I | 15 | 30 | 45 | | D E P T H O F W A T E R ( C M ) 100 < LU X CO LU o < LL. o 80 6 0 40 20 MAXIMUM OVERHEAD VELOCITY | 0 | 15 I 30 | | | l I l I I l > 4 5 l I 15 I 30 I 45 I ] W A T E R V E L O C I T Y ( C M / S E C ) F i g . 1 4 . P h y s i c a l c h a r a c t e r i s t i c s o f s u b s t r a t e w i n t e r i n g a r e a s s e l e c t e d b y a g e 0 s t e e l h e a d ( b a s e d o n 4 3 o b s e r v a t i o n s ) and c u t t h r o a t i n o l d e r age c l a s s e s were found under b o u l d e r s i n upper R i t h e r d o n Creek, a n o t h e r nearby s t r e a m . I n R i t h e r d o n Creek, c u t t h r o a t a l s o u t i l i z e d l o g jams, u p t u r n e d r o o t s , and s m a l l a c c u m u l a t i o n s o f d e b r i s f o r c o v e r . Very few coho were found under r u b b l e i n C a r n a t i o n Creek, a l t h o u g h coho f r y d i d u t i l i z e r u b b l e f o r w i n t e r c o v e r i n P a t o n Creek. 3. W i n t e r F e e d i n g and H i d i n g B e h a v i o r When w a t e r t e m p e r a t u r e s were above 7°C, most f i s h i n C a r n a t i o n Creek were a c t i v e and f e e d i n g . I n w a t e r between 4°C and 7°C coho and s t e e l h e a d v a r i e d between b e i n g a c t i v e and i n a c t i v e depending on stream c o n d i t i o n s . For example, a t w a t e r t e m p e r a t u r e s o f 7°C and s t r e a m f l o w s o f 0.03 m-Vsec (1 c f s ) , v i r t u a l l y no s t e e l h e a d f r y c o u l d be o b s e r v e d above t h e sub-s t r a t e . When s t r e a m f l o w s i n c r e a s e d i n November, s t e e l h e a d f r y were obse r v e d m a i n t a i n i n g p o s i t i o n s i n moderate c u r r e n t s and a c t i v e l y f e e d i n g , even though w a t e r t e m p e r a t u r e s were n e a r l y a degree C e n t i g r a d e l o w e r . Many coho were s t i l l v i s i b l e and f e e d i n g t h r o u g h o u t November and e a r l y December w h i l e w a t e r t e m p e r a t u r e s were s t i l l above 5°C. D u r i n g p e r i o d s o f h i g h e r f l o w s (1.5 t o 3.0 mVsec o r 53 t o 105 c f s ) , coho f a v o r e d back eddy a r e a s formed b e h i n d upturned r o o t s and f a l l e n l o g s . F i s h i n t h e s e a r e a s most o f t e n f a c e d downstream i n t o the e d d y i n g w a t e r t o f e e d . D u r i n g January and F e b r u a r y , few coho and s t e e l h e a d were observed i n open a r e a s . Even a f t e r i n t e n s i v e s e a r c h i n g w i t h a l i g h t under l o g s and r o o t s , few f i s h c o u l d be l o c a t e d . Coho were g e n e r a l l y more a c t i v e a t lo w e r w a t e r t e m p e r a t u r e s 34 than steelhead, and some were observed feeding a t water temp-e r a t u r e s as low as 2.5°C. At 3°- 4°C, 10 o f 46 j u v e n i l e s t e e l -head observed v/ere feeding. S l i g h t l y more than two t h i r d s of the t o t a l 370 f i s h t h a t were observed a t water temperatures below 4°C were h i d i n g . Since the underwater observations presumably favored those f i s h t h a t were v i s i b l e , and s i n c e the v i s i b l e f i s h were u s u a l l y the 'feeders', the p r o p o r t i o n of h i d i n g f i s h should probably be higher than i n d i c a t e d . - No j u v e n i l e steelhead were ever observed feeding a t low water temperatures i n the S a r i t a R i v e r where the f r y entered the s u b s t r a t e i n e a r l y October a t water temperatures between 7°C and 8°C, and remained there i n t o the f o l l o w i n g s p r i n g . Observations i n the S a r i t a suggest t h a t steelhead i n the o l d e r age c l a s s e s entered the su b s t r a t e l a t e r than the f r y . B. Winter Movements of J u v e n i l e Coho and Steelhead F i s h movements i n the two t r i b u t a r y streams, 750 and 1600 Creeks from September 1972 to the end of May 1973 are reported i n t h i s s e c t i o n of the study. Although s c u l p i n move-ments (mainly C. a l e u t i c u s w i t h some C. asper) i n and out o f both systems occurred throughout the study p e r i o d , they are not included i n t h i s r e p o r t . Traps were i n o p e r a t i v e f o r f i v e days duri n g December and January i n 1600 Creek and f o r one day i n December i n 75 0 Creek due to washouts r e s u l t i n g from high flows combined w i t h organic d e b r i s b u i l d u p on the fences. Longer trapping records of coho and t r o u t i n the two creek systems are re q u i r e d before r e l i a b l e estimates o f move-ments and overwinter s u r v i v a l i n the systems can be made. 35 1 . 750 Creek The 750 Creek system was used p r i m a r i l y by coho and -> s c u l p i n s , w i t h o n l y two t r o u t moving i n t o i t t h r o u g h o u t t h e w i n t e r . M o n t h l y t o t a l s o f the movements o f j u v e n i l e coho th r o u g h the t r a p s a r e p r e s e n t e d i n F i g . 15. E x c e p t f o r a few i s o l a t e d p o o l s , 750 Creek was d r y t h r o u g h o u t most o f September and a l l o f October . A s m a l l m i g r a t i o n o f coho i n t o t h e c r e e k o c c u r r e d d u r i n g a s t o r m i n l a t e September and t h r e e o f t h e s e f i s h were l a t e r found dead i n a d r i e d p o o l j u s t above the t r a p s . D u r i n g the p e r i o d from September t o May, 355 coho moved i n t o 750 Creek and 271 moved o u t (76 p e r c e n t s u r v i v a l ) . The upstream movements o c c u r r e d p r e d o m i n a n t l y i n November and December, w h i l e a s t e a d y downstream movement o c c u r r e d from F e b r u a r y t h r o u g h May w i t h a peak o f over 60 coho i n one day d u r i n g a f r e s h e t i n l a t e May. N e a r l y a l l up and down movements o c c u r r e d when w a t e r t e m p e r a t u r e s were g r e a t e r t h a n 6°C. h breakdown o f t h e l e n g t h f r e q u e n c y d i s t r i b u t i o n o f t h e m i g r a n t s ( F i g . 16) i s g i v e n f o r t h e September t o December and f o r the J a n u a r y t o May p e r i o d s . I n t h e September t o December p e r i o d , upstream m i g r a n t s (x=54.1 mm) were s m a l l e r t h a n down-stream m i g r a n t s (x=61.5 mm). I f t h e 65-70 mm range i s t a k e n as t h e a p p r o x i m a t e s e p a r a t i n g p o i n t between age 0 and age 1+ coho f o r t h i s p e r i o d 1 , 48 (17 p e r c e n t o f t o t a l ) o f the up-s t r e a m m i g r a n t s were age 1+ and 231 (83 p e r c e n t ) were age 0. 3-From s c a l e r e a d i n g i n f o r m a t i o n f o r coho o b t a i n e d i n September and November 1972, Dr. D. N a r v e r , P a c i f i c B i o l o g i c a l S t a t i o n , Nanaimo, B. C. 3 6 MONTHLY C O H O AAOVEMENTS-750 CREEK 80 60 O X O u 40 20 ac 0 IJJ CO 5 20 H 40 60 80 J G2 O C T S E P T J A N N O V F E B D E C APR MAR 101 MAY 5 < OO Cu < OO Z O Q L E N G T H FREQUENCY DISTRIBUTIONS S E P T - D E C X = 54.1 M M N = 279 X = 61.5 M M N= 54 ' FORK ( M M ) ° ^ : 1 2 0 LENGTH 4 0 J A N - MAY X= 6 2 . 5 M M N= 76 X= 6 4 . 5 M M N=217 F i g . 1 5 . ( T o p ) M o n t h l y u p s t r e a m a n d d o w n s t r e a m m o v e m e n t s o f j u v e n i l e c o h o i n 7 5 0 C r e e k . T o t a l s f r o m M a r c h d o n o t i n c l u d e r e c e n t l y e m e r g e d f r y . F i g . 1 6 . ( B o t t o m ) L e n g t h f r e q u e n c y d i s t r i b u t i o n o f j u v e n i l e c o h o i n 7 5 0 C r e e k . D a t a a r e l u m p e d f o r 4 - m m l e n g t h i n t e r v a l s f o r t h e S e p t e m b e r t o D e c e m b e r a n d J a n u a r y t o M a y p e r i o d s . 37 Downstream m i g r a n t s d u r i n g t h i s p e r i o d had a h i g h e r p r o p o r -t i o n o f y e a r l i n g s , and i n c l u d e d 20 age 1+ coho (37 p e r c e n t ) and 34 age 0 coho (63 p e r c e n t ) . Upstream and downstream m i g r a n t s i n the J a n u a r y t o May p e r i o d had r e l a t i v e l y s i m i l a r mean f o r k l e n g t h s o f 62.5 mm and 64.5 mm r e s p e c t i v e l y . No a t t e m p t was made t o d i s t i n g u i s h t h e i r age c l a s s e s due t o t h e wide v a r i a b i l i t y i n l e n g t h - a g e r e l a t i o n s h i p s f o r t h i s p e r i o d . 2.' 1600 Creek Coho, s t e e l h e a d , c u t t h r o a t , and s c u l p i n movements i n and o ut o f 1600 Creek o c c u r r e d t h r o u g h o u t t h e p e r i o d from September t o May. No a t t e m p t was made t o examine s i z e d i f f e r -ences o f m i g r a n t t r o u t a t d i f f e r e n t seasons because o f t h e low numbers o f f i s h moving downstream. a) Coho Movements A t o t a l o f 224 j u v e n i l e coho moved upstream and 471 moved downstream d u r i n g the s t u d y p e r i o d ( P i g . 1 7 ) . S u r v i v a l e s t i m a t e s based on t r a p i n f o r m a t i o n c o u l d n o t be made s i n c e 1600 Creek s e r v e s as a summer r e a r i n g h a b i t a t f o r coho and c u t t h r o a t . D u r i n g the September t o December p e r i o d e q u a l numbers (179) o f coho moved up and down t h r o u g h t h e t r a p s . However, downstream m i g r a n t s (292) f a r outnumbered upstream m i g r a n t s (45) i n the J a n u a r y t o May p e r i o d . The peak o f the o u t m i g r a t i o n o c c u r r e d i n e a r l y May when 66 coho moved o u t on a s i n g l e day. An e x a m i n a t i o n o f t h e l e n g t h f r e q u e n c y d i s t r i b u t i o n o f the m i g r a n t s ( F i g . 18) i n d i c a t e s t h a t t h e September t o December downstream m i g r a n t s (x=46.2 mm) were c o n s i d e r a b l y s m a l l e r t h a n 38 MONTHLY COHO MOVE ME NTS-1600 CREEK 801 60-O 40-x O <J 20-O 0-Z 40-60-80-OCT DEC J A N FEB APR N O V SEPT MAR cn MAY 5 < LU C£ I— CO Q_ 3 < LU co Z o LENGTH FREQUENCY DISTRIBUTIONS SEPT - DEC X= 5 6 . 8 M M N= 179 X= 46.2 M M N= 179 20 10 0 F O R K (MM? ^ L E N G T H Q 20H 40 J J A N - M A Y X= 63.1 M M N = 4 5 X= 6 6 . 9 M M N= 292 2 < L U at t— iO 4 < L U at (-<S) Z o Q F i g . 1 7 . ( T o p ) M o n t h l y u p s t r e a m a n d d o w n s t r e a m m o v e m e n t s o f j u v e n i l e c o h o i n 1 5 0 0 C r e e k . T o t a l s f r o m M a r c h d o n o t i n c l u d e r e c e n t l y e m e r g e d f r y . F i g . 1 8 . ( B o t t o m ) L e n g t h f r e q u e n c y d i s t r i b u t i o n o f j u v e n i l e c o h o i n 1 5 0 0 C r e e k . D a t a a r e l u m p e d f o r 4 - m m l e n g t h i n t e r v a l s f o r t h e . S e p t e m b e r t o D e c e m b e r a n d J a n u a r y t o M a y p e r i o d s . upstream m i g r a n t s (x=56.8 mm). I f t h e 65-70 mm range i s a g a i n used t o s e p a r a t e t h e age 0 from th e age 1+ coho, t h e n t h e down-stream m i g r a n t s i n c l u d e d o n l y 12 age 1+ coho (7 per c e n t ) as compared t o 41 age 1+ coho (23 p e r c e n t ) i n t h e upstream m i g r a n t s . The predominance o f s m a l l age 0 coho i n t h e 1600 Creek downstream m i g r a t i o n d i f f e r s from t h e o u t m i g r a t i o n o f l a r g e r f i s h i n 750 Creek. U n l i k e 750 Creek, 1600 Creek p r o -v i d e d summer r e a r i n g h a b i t a t f o r coho. Many o f t h e s m a l l e r c o h o - i n 1600 Creek were pass e d t h r o u g h t h e t r a p s i n September and t h e s e movements may be t h e r e s u l t o f t e r r i t o r i a l d i s p l a c e -ment p r o b a b l y s t i l l o c c u r r i n g i n the c r e e k d u r i n g t h e low September f l o w s . Upstream and downstream m i g r a n t s i n t h e January t o May p e r i o d s had mean l e n g t h s o f 63.1 mm and 66.9 mm r e s p e c t i v e l y , however no a t t e m p t was made t o s e p a r a t e age c l a s s e s because o f v a r i a b l e l e n g t h - a g e r e l a t i o n s h i p s f o r t h i s p e r i o d . b) T r o u t Movements D u r i n g the s t u d y p e r i o d , 50 j u v e n i l e s t e e l h e a d ( >60 mm) moved upstream i n t o 1600 Creek and 18 moved downstream ( F i g . 1 9 ) . A l l b u t t h r e e o f the s t e e l h e a d o b t a i n e d i n t h e t r a p s were between 60 mm and 160 mm i n l e n g t h , a l t h o u g h one s t e e l h e a d 232 mm l o n g was p a s s e d upstream ( F i g . 2 0 ) . Most o f the upstream movements o c c u r r e d i n November and December. An e s t i m a t i o n o f t h e o v e r w i n t e r s u r v i v a l o f j u v e n i l e s t e e l h e a d i n 1600 Creek i s o f q u e s t i o n a b l e v a l u e . Even s m a l l l o s s e s o f s t e e l h e a d due t o d e l a y e d m o r t a l i t i e s r e s u l t i n g from t r a p p i n g and h a n d l i n g , o r escapes d u r i n g p e r i o d s when t h e t r a p s were n o n - o p e r a t i o n a l c o u l d l e a d t o c o n s i d e r a b l e v a r i a t i o n i n 40 MONTHLY TROUT M O V E M E N TS -1600 CREEK 30-1 20H X to 1 0 -co z S T E E L H E A D C U T T H R O A T SEPT O C T N O V J A N FEB APR M A Y D E C M A R < I O - " L E N G T H F R E Q U E N C Y D I S T R I B U T I O N S 15 X w 10H Z3 60 5 -J 3 S T E E L H E A D X = 107 .0 M M N = 5 0 15 io H FORK C U T T H R O A T X = 1 4 7. 8 M M N = 6 5 u 100 140 180 2 2 0 L E N G T H J — J 1 — I • i ' " " " " i " ; " F Ti''" ' — i ( M M ) 60 1 0 0 , 4 0 1 8 0 2 2 0 0 Ys- 110.5 M M N= 18 5 -J X = 128.1 M M N= 8 < o. 4 < UJ or i— i n Z o o F i g . 19. (Top) Monthly upstream and downstream movements of j u v e n i l e steelhead and c u t t h r o a t i n 1600 Creek. T o t a l s are f o r t r o u t g r e a t e r than 60 mm i n l e n g t h . F i g . 20. (Bottom) Length frequency d i s t r i b u t i o n of j u v e n i l e steelhead and c u t t h r o a t i n 1600 Creek. Data are lumped i n 10-mm len g t h i n t e r v a l s f o r the p e r i o d September 1972 through May 1973. 41 any s u r v i v a l e s t i m a t e . A l s o , a p r o b l e m d i s t i n g u i s h i n g j u v e n i l e s t e e l h e a d and c u t t h r o a t from e a c h o t h e r i n t h e e a r l y p a r t o f the s t u d y caused some e r r o r . Based on l e n g t h measurements, i t appears t h a t some o f t h e downstream m i g r a n t s were f i s h w h i c h had s p e n t l e s s t h a n one week i n 1600 C r e e k . These f i s h s h o u l d n o t be i n c l u d e d i n a s u r v i v a l e s t i m a t e . Even a f t e r a l l o w i n g f o r v a r i a b i l i t y due t o t h e s e f a c t o r s , i t a p p e a r s t h a t t h e s u r v i v a l o f j u v e n i l e s t e e l h e a d i n 1600 Creek was p o o r , w i t h p r o b a b l y l e s s t h a n 25 p e r c e n t o f t h o s e f i s h w h i c h moved i n t o the c r e e k i n the l a t e f a l l and e a r l y w i n t e r l e a v i n g i n t h e s p r i n g . E l e c t r o f i s h i n g 300 m o f 1600 Creek i n J u l y 1973, i n d i c a t e d t h a t no s t e e l h e a d remained i n t h e c r e e k d u r i n g t h e summer. D u r i n g the p e r i o d from September t o May, 65 c u t t h r o a t ( >60 mm) moved upstream and o n l y 8 moved downstream t h r o u g h the t r a p s on 1600 Creek ( F i g . 19). The peak upstream c u t -t h r o a t movement, as w i t h the s t e e l h e a d , o c c u r r e d i n November. Upstream c u t t h r o a t m i g r a n t s were l a r g e r t h a n s t e e l h e a d m i g r a n t s (x=147.8 mm as compared t o x=107.0 mm) and the l a r g e s t c u t -t h r o a t was n e a r l y 250 mm i n l e n g t h ( F i g . 20). Presumably, the l a r g e r c u t t h r o a t s spawn i n 1600 Creek d u r i n g the w i n t e r . T h i s was s u b s t a n t i a t e d by mature eggs c o n t a i n e d i n a 240 mm female found dead i n the t r a p s . S i n c e e l e c t r o f i s h i n g i n J u l y 1973 i n d i c a t e d t h a t , u n l i k e s t e e l h e a d , c u t t h r o a t remained i n 1600 Creek i n t h e summer, an e s t i m a t e o f w i n t e r s u r v i v a l based on the t r a p r e s u l t s would be m e a n i n g l e s s . Few t r o u t l e s s t h a n 60 mm i n l e n g t h moved t h r o u g h t h e t r a p s d u r i n g t h e s t u d y p e r i o d , and i n a l l , t h e r e were o n l y e i g h t upstream and e i g h t downstream m i g r a n t s . 42 C Summary Underwater observations suggest some o f the p h y s i c a l c h a r a c t e r i s t i c s of areas u t i l i z e d by coho and steelhead d u r i n g the w i n t e r , and r e s u l t s from the traps on the two t r i b u t a r i e s i n d i c a t e t h a t some coho and t r o u t move i n t o these t r i b u t a r i e s d uring the f a l l and e a r l y w i n t e r . Because of the apparent importance o f s i d e p o o l areas t o o v e r wintering f i s h and the high s u s c e p t i b i l i t y o f these areas t o damage from l o g g i n g , experiments were conducted on sidepools s i m u l a t i n g c o n d i t i o n s as they may occur before and a f t e r stream d i s t u r b a n c e . The n a t u r a l stream h a b i t a t d i d not present the opp o r t u n i t y f o r t e s t i n g such c o n d i t i o n s , so a s e r i e s of a r t i f i c i a l s i d epools were cons t r u c t e d and experiments were c a r r i e d out on them. The second p a r t of t h i s study describes these experimental f a c i l i t i e s and the methods of comparing j u v e n i l e coho and c u t t h r o a t preference f o r a l t e r -n a t i v e h a b i t a t types. The r e s u l t s of the f i e l d observations w i l l be discussed i n the l i g h t of the r e s u l t s from the s i d e -pool experiments. 43 PART I I . HABITAT PREFERENCES OF COHO AND TROUT DESCRIPTION OF STUDY AREA Experiments comparing coho and c u t t h r o a t preferences f o r a l t e r n a t i v e h a b i t a t types i n s i d e p o o l areas were c a r r i e d out on Dick Creek, a stream which enters the Carnation e s t u a r y ( F i g ; 1 ) . The Dick Creek watershed i s approximately 1.2 km 2 and contains a sm a l l lake ( s e v e r a l ha 2) i n i t s headwaters. No streamflow measurements were made on Dick Creek, but v i s u a l estimates suggest discharge v a r i e s from about 2 mVsec (approx-imately 70 c f s ) during peak w i n t e r flows t o j u s t a t r i c k l e d uring the l a t e summer. During the experimental p e r i o d from October 1972 t o March 1973, the maximum water temperatures reached 9°C and minimum temperatures dropped to near 0°C f o r short periods of c l e a r c o l d days and low f l o w s . A w a t e r f a l l l i m i t s f i s h access t o the lowest 500 m of the creek, where the s u b s t r a t e i s predominantly la r g e g r a v e l and rubble up to 30 cm. 44 MATERIALS AND METHODS 1. D e s i g n o f S i d e p o o l s Four e x p e r i m e n t a l s i d e p o o l s were c o n s t r u c t e d a d j a c e n t t o a l o n g r i f f l e s e c t i o n l o c a t e d 250 m up D i c k Creek ( F i g . 2 1 ) . Each s i d e p o o l was c o n s t r u c t e d from 1.9 cm t h i c k plywood and p l a c e d i n an e x c a v a t e d p i t c o n n e c t e d t o t h e c r e e k b y an e n t r a n c e a r e a . The s i d e p o o l s were 2.4 m l o n g , 1.2 m w i d e , 0.6 m deep, had a plywood bottom, and were d i v i d e d i n h a l f (bays) i n o r d e r t o o f f e r a l t e r n a t i v e c o v e r c h o i c e s t o e x p e r i -m e n t a l f i s h ( F i g . 2 2 ) . S l i d i n g s c r e e n g a t e s c o n t r o l l e d a c c e s s from the e n t r a n c e a r e a t o the bays and t o D i c k C reek. Two s i d e p o o l s were d e s i g n e d t o t e s t t h e e f f e c t o f remov-i n g o v e r h a n g i n g banks on t h e c h o i c e o f o v e r w i n t e r i n g a r e a s . Plywood, c u t d i a g o n a l l y and p l a c e d 0.4 m above th e p o o l f l o o r p r o v i d e d bank c o v e r on one s i d e o f e a c h bay. A dense system o f i n t e r t w i n i n g r o o t s a t t a c h e d t o t h e base o f t h e plywood p r o v i d e d c o v e r w i t h i n the o v e r h a n g i n g bank ( F i g . 2 3 ) . The a l t e r n a t i v e c h o i c e t o t h e o v e r h a n g i n g bank was a b a r r e n bay. The o t h e r two s i d e p o o l s were d e s i g n e d t o t e s t t h e e f f e c t o f s i l t d e p o s i t i o n w i t h i n r u b b l e s u b s t r a t e on c h o i c e o f o v e r -w i n t e r i n g a r e a s . A 5 cm deep base l a y e r o f g r a v e l and f o r t y r o c k s 15-30 cm i n d i a m e t e r were p l a c e d i n each bay. One hundred l i t r e s o f sediment were p l a c e d i n one bay o f e a c h s i d e p o o l and were s u f f i c i e n t t o f i l l most o f the spaces between the r o c k s ( F i g . 2 3 ) . A l l s i d e p o o l s were c o v e r e d w i t h 2.5 cm c h i c k e n w i r e t o p r e v e n t a v i a n o r mammalian p r e d a t i o n on e x p e r i m e n t a l f i s h . 45 F i g . 21. O r i e n t a t i o n o f s i d e p o o l s w i t h r e s p e c t t o e a c h o t h e r a n d t o D i c k C r e e k . 46 F i g . 2 2 . B a s i c d e s i g n o f s i d e p o o l s . 47 F i g . 23. A. Sidepool o f f e r i n g bays w i t h overhanging bank cover or no cover. Overhang i s r a i s e d and upside down to show root mass, v/ater l e v e l s were e x c e p t i o n a l l y low when t h i s photo was taken. B. Sidepool o f f e r i n g bays w i t h c l e a n or s i l t e d r u b ble. 48 2. Experimental F i s h J u v e n i l e coho used i n the experiments were obtained from the lower 200 m of Carnation Creek and Dick Creek. Five hund-red coho f r y were seined i n September and used i n e i g h t p r e -l i m i n a r y t r i a l s and i n the f i r s t two coho t r i a l s . In e a r l y January, 300 coho were captured by e l e c t r o f i s h i n g and used i n the l a s t s i x coho t r i a l s . Most coho t r i a l s used a mixture of naive and 'experienced' i n d i v i d u a l s ( i e . , f i s h used i n previous t e s t s ) . The coho t r i a l s c a r r i e d out i n October and January used predominantly naive f i s h whereas the t r i a l s i n November, December, February and March were comprised of a higher p r o -p o r t i o n of !experienced' f i s h . Few f i s h were used i n more than two t r i a l s , and a minimum of two weeks was allowed before any f i s h was reused i n a t r i a l . J u v e n i l e c u t t h r o a t t r o u t used i n the experiments were obtained by e l e c t r o f i s h i n g from Ritherdon Creek i n September, January, and February. Although some 'experienced' c u t t h r o a t were used (mainly i n the l a s t t r i a l ) , the c u t t h r o a t t r i a l s used predominantly naive i n d i v i d u a l s . J u v e n i l e steelhead t r o u t were not s u f f i c i e n t l y abundant i n Carnation Creek t o provide a source of experimental f i s h and were not introduced from another stream system due to p o s s i b l e g e n e t i c and p o p u l a t i o n c o m p l i c a t i o n s . Since j u v e n i l e steelhead and c u t t h r o a t appear to have s i m i l a r m i c r o h a b i t a t requirements (Hartman and G i l l , 1968), c u t t h r o a t were thought t o be a reasonable a l t e r n a t i v e . The coho and c u t t h r o a t t h a t were obtained i n September were held i n two 1 m2 screened pens i n Dick Creek u n t i l used i n the t r i a l s . These f i s h were l o s t d u r i n g a f r e s h e t i n 49 December and a l l f i s h o b t a i n e d a f t e r t h i s time were k e p t i n two 230 l i t r e a q u a r i a s u p p l i e d w i t h a c o n s t a n t s o u r c e o f D i c k Creek w a t e r . W h i l e h e l d i n pens and a q u a r i a , f i s h were f e d r a t i o n s o f Oregon M o i s t P e l l e t a d j u s t e d f o r w a t e r t e m p r a t u r e and f i s h s i z e . Coho used i n t h e t r i a l s ranged from 36-81 mm i n l e n g t h and c u t t h r o a t ranged from 41-92 mm i n l e n g t h . S c a l e r e a d i n g i n d i c a t e d t h a t a l l e x p e r i m e n t a l f i s h were age 0 e x c e p t f o r a b o u t 10 s m a l l y e a r l i n g c u t t h r o a t . The s i z e range and mean f o r k l e n g t h s o f a l l f i s h used i n t h e e x p e r i m e n t s a r e g i v e n i n Appendix I I I . The number o f coho used i n t h e ; t r i a l s was changed from 40 (14/m 2) t o 20 (7/m 2) f i s h p e r s i d e p o o l f o l l o w i n g the t h i r d t r i a l . Twenty c u t t h r o a t p e r s i d e p o o l were used i n a l l t r o u t t r i a l s . A v a i l a b l e i n f o r m a t i o n i n the l i t e r a t u r e and p e r s o n a l o b s e r v a t i o n s s u g g e s t t h a t these d e n s i t i e s were h i g h b u t n o t u n r e a s o n a b l e f o r o v e r w i n t e r i n g coho and t r o u t . For example, Hartman (1965) r e p o r t e d up t o 7.3 coho/m 2 d u r i n g the w i n t e r i n the upper C h i l l i w a c k R i v e r and coho d e n s i t i e s o f 5.4/m2 were found by the a u t h o r i n a 10 m s i d e p o o l o f C a r n a t i o n Creek i n January (p. 31)„ A g g r e g a t i o n s o f up t o 75 coho w i t h i n an a r e a o f s e v e r a l square meters were ob s e r v e d d u r i n g t h e w i n t e r i n C a r n a t i o n Creek. T r o u t d e n s i t i e s d u r i n g t h e w i n t e r appear t o be l o w e r t h a n coho d e n s i t i e s . Hartman (1965) r e p o r t e d maximum t r o u t d e n s i t i e s of about 100 s t e e l h e a d / 1 0 0 m2, and L i n d r o t h (1955a) r e p o r t e d brown t r o u t d e n s i t i e s o f 3-4 f i s h / m o f s t r e a m bank. I n t h i s s t u d y , t e n c u t t h r o a t o f s e v e r a l age groups were 50 c o l l e c t e d by e l e c t r o f i s h i n g i n a s i d e p o o l o f about 2 m^  i n R i t h e r d o n Creek. 3. T r i a l P r o c e d u r e On the f i r s t day o f each t r i a l , e x p e r i m e n t a l f i s h were p l a c e d i n the s i d e p o o l e n t r a n c e a r e a s a t 0830 h r , and a l l o w e d f r e e a c c e s s t o e i t h e r bay b u t n o t t o D i c k Creek from 0930 h r o f day 1 t o 0930 h r o f day 2. At t h i s time t h e g a t e s were c l o s e d , and i n t h e case o f t h e c l e a n - s i l t e d r u b b l e s i d e p o o l s , the r o c k s were l i f t e d . The n e x t morning t h e f o u r s i d e p o o l s were e l e c t r o f i s h e d and a l l f i s h found i n each bay o f the s i d e -p o o l s were a n a e t h e s i z e d , counted and measured t o t h e n e a r e s t m i l l i m e t e r . The r u b b l e was r e p l a c e d i n t h e s i d e p o o l s and t h e f i s h were r e t u r n e d t o t h e i r r e s p e c t i v e b a y s . T h i s ended the f i r s t h a l f o f t h e t r i a l s . A t 0930 h r o f day 4, a l l g a t e s were opened a l l o w i n g the f i s h f r e e a c c e s s i n t o D i c k Creek f o r a 24-hr p e r i o d . Then, the g a t e s were c l o s e d , t h e r u b b l e l i f t e d , and the number and s i z e s o f f i s h r e m a i n i n g i n each bay was d e t e r m i n e d by e l e c t r o f i s h i n g . E l e c t r o f i s h i n g was n o t e f f e c t i v e i n r e c o v e r i n g f i s h i n the c l e a n - s i l t e d r u b b l e s i d e p o o l s u n l e s s t h e r u b b l e was removed b e f o r e h a n d . 1 A 24-hr p e r i o d between removing t h e ^ E l e c t r o f i s h i n g was e f f e c t i v e i n r e c o v e r i n g 98% o f a l l f i s h used i n t h e t r i a l s . O v e r a l l m o r t a l i t y r e s u l t i n g from e l e c t r o f i s h i n g , a n a e s t h e t i c , h a n d l i n g , and o t h e r causes was 2% o f the 12 t r i a l s . 51 rubble and e l e c t r o f i s h i n g was required to allow time for the water to clear, so a complete t r i a l , c onsisting of two phases, took six days. Eight preliminary time t r i a l s c a r r i e d out in October indicated that 24 hours was a reasonable time period to allow experimental f i s h to choose between the bays and between the sidepools and Dick Creek (Appendix IV) . 4. Experimental Conditions Maximum water temperatures and water l e v e l s for each t r i a l are presented in Appendix V. Water temperatures were obtained from a Ryan thermograph i n Dick Creek and were checked frequently with thermometer readings. Water l e v e l was read from a s t a f f gauge located i n one of the sidepools. A t o t a l of 12 t r i a l s were run between November and March, with eight of them using coho and four of them cutthroat. Stream conditions were variable, however the t r i a l s were con-ducted so that moderate to high and low streamflows were about equally represented. The coho t r i a l s were conducted under a wider range of temperatures than the cutthroat t r i a l s * Since stream observa-tions in Carnation Creek indicated that coho were more active above 5°C than below, results of coho preferences at water temperatures above and below 5°C have been separated for comparison. No attempt was made to look at the e f f e c t s of temperature on cutthroat cover preference since a l l of the t r i a l s were at less than 6°C. 52 RESULTS Periodic observations of the f i s h in the sidepools during the winter indicated that when allowed access to the bays, groups of f i s h i n i t i a l l y 'wandered' in and out of both sides, j u s t i f y i n g t h e i r choice of bays being c a l l e d a 'prefer-ence '. 1. Juvenile Coho Cover Choice Juvenile coho demonstrated a consistent preference for the bays o f f e r i n g overhanging bank cover as opposed to those v/ithout bank cover (Fig. 24) . Only one t r i a l did not indicate t h i s preference for cover (Appendix VI), but i t was c a r r i e d out in early November when water temperatures were 9°C, the highest temperatures of any t r i a l s (Appendix V) . When given the option of either remaining in the sidepools or of moving into Dick Creek (phase two of the t r i a l s ) , a greater percentage of the coho remained i n the sidepools at lower water tempera-tures than at higher temperatures. In both temperature regimes, only 3-4 per cent of the t o t a l number of coho o r i g -i n a l l y in the sidepools remained in the barren side as compared to 48-70 per cent remaining in the overhanging bank s i d e . Bays o f f e r i n g clean rubble substrate were preferred to bays o f f e r i n g s i l t e d rubble ( F i g . 24 and Appendix VII), p a r t i c u l a r l y at lower water temperatures. When given the option of e i t h e r remaining i n the sidepools or of moving int o Dick Creek, more coho remained at lower temperatures than at higher temperatures. In both temperature regimes, a greater 53 COHO COVER CHOICE O B L I G A T O R Y R E S I D E N C E V O L U N T A R Y R E S I D E N C E A 34 F i g . 2 4 . T h e p e r c e n t a g e o f c o h o c h o o s i n g a l t e r n a t i v e c o v e r t y p e s ( A a n d B) i n t h e s i d e p o o l s w h e n n o t p e r m i t t e d , a c c e s s t o D i c k C r e e k ( o b l i g a t o r y r e s i d e n c e ) a n d w h e n p e r m i t t e d a c c e s s t o D i c k C r e e k ( v o l u n t a r y r e s i d e n c e ) . T h e p e r c e n t a g e o f c o h o r e m a i n i n g i n t h e s i d e p o o l s a f t e r b e i n g p e r m i t t e d a c c e s s t o t h e c r e e k i s i n d i c a t e d a b o v e t h e a r r o w s , a n d t h e i r d i s t r i b u t i o n i n t h e s i d e p o o l s i s s h o w n i n t h e c i r c l e s o n t h e r i g h t . T h e f i g u r e s a r e f o r t w o t e m p e r a t u r e c a t e g o r i e s ( i n d i c a t e d b e l o w t h e a r r o w s ) , a n d e a c h f i g u r e r e p r e s e n t s a c o m b i n a t i o n o f d a t a f r o m f o u r t r i a l s i n t w o s i d e p o o l s . 54 percentage of the t o t a l number of coho o r i g i n a l l y i n the sidepools remained in the bays o f f e r i n g clean rubble than in the s i l t e d rubble. At warmer temperatures, the preference was not as obvious, but was s t i l l s t a t i s t i c a l l y s i g n i f i c a n t ( t - t e s t , p < .01) . These t r i a l s indicate that some form of cover was required by juvenile coho during most t r i a l conditions. Cover requirements were lower at moderate water temperatures (5°-9°C) than at cold water temperatures (less than 5°C) . The high percentage of coho remaining in the overhang-ing bank cover side of the pools suggests that the bank cover bay areas were providing s u i t a b l e habitat for coho during the la t e f a l l and winter period. I f the overhanging banks were not present, very few coho used the bays. Fewer coho remained in the bays o f f e r i n g rubble sub-strate cover (52 per cent at 2°-5°C and 18 per cent at 5°-9°C) than in those providing overhanging bank cover (73 per cent at 2°-5°C and 42 per cent at 5°-9°C), e s p e c i a l l y at warmer temperatures. Few coho remained in the bays where the spaces between the rubble were f i l l e d with f i n e s , suggesting that rubble substrate in sidepool areas may be used by juvenile coho during the late f a l l and winter periods, but that the sub-strate must have adequate i n t e r s t i c e s to provide sui t a b l e cover. 2. Juvenile Cutthroat Cover Choice Juvenile cutthroat trout showed a strong preference for bays o f f e r i n g overhanging bank cover as opposed to no cover ( P i g . 25). In two o f the four t r i a l s , a l l o f the e x p e r i -mental f i s h chose the overhanging bank s i d e (Appendix V I I I ) . When g i v e n the o p t i o n o f e i t h e r remaining i n the s i d e p o o l s or o f moving i n t o Dick Creek, 46 per c e n t o f the c u t t h r o a t remained, but o n l y one per c e n t o f these f i s h s t a y e d i n the b a r r e n s i d e . C u t t h r o a t p r e f e r r e d bays o f f e r i n g c l e a n r u b b l e sub-s t r a t e t o those o f f e r i n g s i l t e d r u b b l e . N e a r l y h a l f o f the o r i g i n a l c u t t h r o a t i n the s i d e p o o l s remained when allowed access t o Dick Creek, and a l l but one were found i n the c l e a n rubble bays. The r e s u l t s i n d i c a t e t h a t a t low water temperatures, c u t t h r o a t used e i t h e r overhanging banks or r u b b l e s u b s t r a t e to p r o v i d e c o v e r . S i d e p o o l areas w i t h o u t bank cover, or where the r u b b l e was clogged w i t h f i n e sediment m a t e r i a l were u t i l i z e d by only a s m a l l p r o p o r t i o n o f the c u t t h r o a t . CUTTHROAT COVER CHOICE O B L I G A T O R Y R E S I D E N C E V O L U N T A R Y R E S I D E N C E 92 F i g . 2 5 . T h e p e r c e n t a g e o f c u t t h r o a t c h o o s i n g a l t e r n a t i v e . c o v e r t y p e s i n t h e s i d e p o o l s w h e n n o t p e r m i t t e d a c c e s s t o D i c k C r e e k ( o b l i g a t o r y r e s i d e n c e ) a n d w h e n p e r m i t t e d a c c e s s t o D i c k C r e e k ( v o l u n t a r y r e s i d e n c e ) . T h e p e r c e n t a g e o f c u t t h r o a t r e m a i n -i n g i n t h e s i d e p o o l s a f t e r b e i n g p e r m i t t e d a c c e s s t o t h e c r e e k i s i n d i c a t e d a b o v e t h e a r r o w s , a n d t h e i r d i s t r i b u t i o n i n t h e s i d e p o o l s i s s h o w n i n t h e c i r c l e s o n t h e r i g h t . E a c h f i g u r e r e p r e -s e n t s a c o m b i n a t i o n o f d a t a f r o m f o u r t r i a l s o n t w o s i d e p o o l s . 57 DISCUSSION A. W i n t e r H i d i n g and I t s A d a p t i v e V a l u e s J u v e n i l e coho and s t e e l h e a d i n C a r n a t i o n Creek undergo major b e h a v i o r a l changes b e g i n n i n g i n e a r l y O c t o b e r . W i t h d e c r e a s i n g w a t e r t e m p e r a t u r e s , t h e s e f i s h t e n d t o spend more o f t h e i r time h i d i n g . T h i s i n c r e a s e d h i d i n g w i t h l o w e r w a t e r t e m p e r a t u r e s i s c h a r a c t e r i s t i c o f j u v e n i l e s a l m o n i d s , and has been d i s c u s s e d i n some d e t a i l by Chapman and B j o r n n ( 1 9 6 9 ) . O b s e r v a t i o n s t h r o u g h o u t t h e f a l l and w i n t e r i n C a r n a t i o n Creek s u g g e s t t h a t s h o r t e r day l e n g t h d i d n o t have an i m p o r t a n t i n f l u e n c e on the h i d i n g b e h a v i o r o f j u v e n i l e coho and s t e e l -head. For example, many o f the s t e e l h e a d f r y w h i c h were h i d i n g i n the s u b s t r a t e i n mid O c t o b e r were a c t i v e l y f e e d i n g i n November and e a r l y December. Hartman (1965) was a b l e t o induce s t e e l h e a d and coho t o h i d e i n a s t r e a m aquarium by l o w e r i n g the water t e m p e r a t u r e even though he m a i n t a i n e d d a y -l e n g t h a t a c o n s t a n t 12 h r s . S i m i l a r l y , by m a i n t a i n i n g a c o n s t a n t 13 h r d a y l e n g t h , Chapman and B j o r n n (1969) showed t h a t t h e number o f y e a r l i n g s t e e l h e a d h i d i n g i n r u b b l e c o v e r was d i r e c t l y r e l a t e d t o w a t e r t e m p e r a t u r e . A l t h o u g h temperature was a major f a c t o r i n d u c i n g t h e h i d i n g response i n f i s h i n C a r n a t i o n Creek, s t r e a m d i s c h a r g e a l s o appeared t o have a s i g n i f i c a n t i n f l u e n c e on f i s h a c t i v i t y , e s p e c i a l l y a t w a t e r t e m p e r a t u r e s between 4°C and 8°C. When s t r e a m f l o w s were low, coho and s t e e l h e a d were more i n c l i n e d t o h i d e even though w a t e r t e m p e r a t u r e s were the same or c o l d e r . 58 This increased a c t i v i t y may r e f l e c t an increase i n a v a i l a b i l -i t y of food organisms or an increase i n p r o t e c t i o n from preda-t i o n provided by f a s t e r and more t u r b i d water. The h i d i n g behavior demonstrated by the j u v e n i l e salmonids i n c o l d water probably has a number o f adaptive value s . F i r s t , a f i s h spending the w i n t e r i n a stream a t near f r e e z i n g water temperatures has a lower metabolism, reduced food requirements, and l e s s energy a v a i l a b l e f o r a c t i v i t y . Hartman (1968) found t h a t d u r i n g p e r i o d s when the water temp-eratures were below 7.8°C the growth r a t e of coho and steelhead was g e n e r a l l y very depressed. Reimers (1957), i n c o n t r o l l e d feeding experiments, found t h a t i t takes young rainbow t r o u t up t o 70 hrs to completely d i g e s t hard-bodied i n s e c t s a t water temperatures between 0°C and 1°C. He f e l t t h a t the amount of nourishment t r o u t can o b t a i n from a v a i l a b l e food i n near f r e e z i n g water i s c o n t r o l l e d p r i m a r i l y by the r a t e o f a s s i m i l a -t i o n r a t h e r than by the r a t e of f e e d i n g . By h i d i n g d u r i n g periods of lowest temperatures, j u v e n i l e salmonids may avoid the u n p r o f i t a b l e expenditure of energy necessary t o maintain a feeding s t a t i o n from which they may not d e r i v e s u f f i c i e n t nourishment. A second adaptive value o f the h i d i n g response o f j u v e n i l e salmonids i s t h a t i t may provide a means of a v o i d i n g predation d u r i n g a p e r i o d of lower a c t i v i t y and reduced swim-ming a b i l i t y . For example, mergansers and k i n g f i s h e r s may take a heavy t o l l of young f i s h ( L i n d r o t h , 1955b; E l s o n , 1962). One would suspect t h a t young salmonids would be more s u s c e p t i b l e prey d u r i n g the w i n t e r than the summer unless some h i d i n g behavior i s demonstrated. 59 Another p o s s i b l e a d a p t i v e v a l u e o f t h e h i d i n g r e s p o n s e i s t h a t i t may reduce d i s p l a c e m e n t d u r i n g f r e s h e t s . That s u c h d i s p l a c e m e n t does o c c u r has been d e m o n s t r a t e d by Onodera and Ueno (1961) and s u g g e s t e d by Chapman (1965). P h y s i c a l c o n d i -t i o n s i n C a r n a t i o n Creek d u r i n g a w i n t e r f r e s h e t a r e s e v e r e . A t v e r y h i g h d i s c h a r g e s , t u r b i d c o n d i t i o n s reduce v i s i b i l i t y d r a s t i c a l l y . Poor v i s i b i l i t y , c o u p l e d w i t h i n c r e a s e d w a t e r v e l o c i t i e s and an i m p a i r e d swimming a b i l i t y i n c o l d w a t e r , make i t e s s e n t i a l f o r f i s h t o f i n d c o v e r i n a p r o t e c t e d l o c a -t i o n . B. P h y s i c a l C h a r a c t e r i s t i c s o f W i n t e r i n g Areas For b o t h coho and s t e e l h e a d , w a t e r d e p t h , w a t e r v e l o c i t y , and t h e p r e s e n c e o f c o v e r proved t o be i m p o r t a n t f a c t o r s i n d e t e r m i n i n g w h i c h s e c t i o n s o f t h e s t r e a m were s e l e c t e d as o v e r -w i n t e r i n g a r e a s . 1. Water Depth and V e l o c i t y As w a t e r t e m p e r a t u r e s dropped d u r i n g t h e f a l l and e a r l y w i n t e r , coho and o l d e r s t e e l h e a d moved i n t o d eeper w a t e r ( F i g . 7 ) . T h i s tendency f o r f i s h t o move i n t o p o o l s i n t h e w i n t e r was demonstrated by Hartman (1965) u s i n g a s t r e a m a q u a r i -um o f f e r i n g s e c t i o n s o f v a r y i n g d e p t h s . In Hartman's e x p e r i -ments, u n d e r y e a r l i n g coho and s t e e l h e a d showed a s t r o n g p r e f e r e n c e f o r t h e d e e p e s t d e p t h g r a d i e n t a t l o w e s t w a t e r t e m p e r a t u r e s . Most s t e e l h e a d f r y i n C a r n a t i o n Creek chose s h a l l o w m a r g i n a l a r e a s f o r o v e r w i n t e r i n g i n the s u b s t r a t e . E v e r e s t (1969), however, found s t e e l h e a d under s u b s t r a t e a t a v a r i e t y 60 o f v/ater d e p ths and s u g g e s t e d t h a t w a t e r d e p t h and overh e a d v e l o c i t y were n o t i m p o r t a n t i n d e t e r m i n i n g o v e r w i n t e r i n g a r e a s . L i n d r o t h (1955a), w h i l e e x a m i n i n g t h e w i n t e r d i s t r i b u -t i o n o f young s a l m o n i d s i n a l a r g e Swedish r i v e r , found b o t h A t l a n t i c salmon (Salmo s a l a r ) and brown t r o u t w i t h i n the s u b -s t r a t e . The brown t r o u t were found a l o n g the margin o f t h e r i v e r i n w a t e r l e s s t h a n 30 cm deep, and o f t e n under r o c k s t h a t were b r e a k i n g the w a t e r s u r f a c e . They were r a r e l y found i n a r e a s o f s t i l l w a t e r . The A t l a n t i c salmon were found under t h e s u b s t r a t e i n deeper w a t e r t h a n t h e t r o u t . F o r f i s h t h a t do n o t e n t e r t h e s u b s t r a t e i n t h e w i n t e r , s uch as most o f t h e coho and o l d e r s t e e l h e a d i n C a r n a t i o n Creek, deep p o o l s o f f e r the advantages o f c o v e r and reduced w a t e r v e l o c i t i e s . S m a l l e r f i s h o v e r w i n t e r i n g w i t h i n the s u b s t r a t e may o b t a i n t h e s e advantages from t h e r o c k s o v e r h e a d . I n t h e s m a l l r u b b l e t y p i c a l o f C a r n a t i o n Creek, s t e e l -head f r y were n o t found deep i n t h e s u b s t r a t e as has been r e p o r t e d i n o t h e r r i v e r systems (Edmundson e t a l . , 1968; E v e r e s t , 1 9 6 9 ) 0 Some o f t h e s h a l l o w a r e a s used by t h e s t e e l -head f r y i n C a r n a t i o n Creek were d r y d u r i n g low w i n t e r f l o w s . F r y h i d i n g i n t h e s e a r e a s must s h i f t l o c a t i o n w i t h c h a n g i n g d i s c h a r g e . For example, i n J a n u a r y , two s t e e l h e a d f r y were found i n stream l o c a t i o n s w h i c h had been d r y the p r e v i o u s week. E v e r e s t (1969) s u g g e s t s t h a t once f i s h move i n t o t h e s u b s t r a t e f o r the w i n t e r , no subsequent movements o c c u r . I n c o l d e r streams v / i t h l e s s f l u c t u a t i n g w i n t e r f l o w s t h a n C a r n a -t i o n Creek, such as E v e r e s t ' s Idaho s t r e a m s , t h i s may be t h e c a s e . There was a tendency f o r s t e e l h e a d t o be found i n l o w e r v e l o c i t y w a t e r w i t h d e c r e a s i n g t e m p e r a t u r e s ( F i g . 1 0 ) . T h i s would be e x p e c t e d s i n c e f e e d i n g a c t i v i t y i s r e d u c e d i n c o l d w a t e r . Such a r e l a t i o n s h i p was n o t d e m o n s t r a t e d f o r coho, p r o b a b l y f o r two r e a s o n s . F i r s t , most coho t e n d t o occupy lower v e l o c i t y p o o l a r e a s the y e a r r o u n d . T h e r e f o r e t h e change i n s e l e c t e d w a t e r v e l o c i t i e s w i t h d e c r e a s i n g w a t e r t e m p e r a t u r e s was not as o b v i o u s as f o r s t e e l h e a d . Second, the c u r r e n t meters were n o t s e n s i t i v e enough t o d e t e c t d i f f e r -ences between th e 'low v e l o c i t y ' f e e d i n g a r e a s and t h e 'no v e l o c i t y * h i d i n g a r e a s . 2. W i n t e r Cover and I t s S u r v i v a l i m p l i c a t i o n s . A t low w a t e r t e m p e r a t u r e s , s u i t a b l e c o v e r a r e a s p r o v e d t o be c r i t i c a l and few f i s h were found more t h a n 1 m from p o t e n t i a l c o v e r . Hartman (1965) o b s e r v e d t h e c l o s e a s s o c i a t i o n o f u n d e r y e a r l i n g coho and s t e e l h e a d f o r a r e a s o f overhead c o v e r d u r i n g the w i n t e r i n t h e upper C h i l l i w a c k R i v e r . He used a s t r e a m aquarium t o demonstrate t h e i n c r e a s i n g a s s o c i -a t i o n o f young f i s h w i t h s h e l t e r a r e a s a t l o w e r i n g temperatures-(Hartraan, 1963 and 1965). O b s e r v a t i o n s o f young f i s h i n C a r n a t i o n Creek agree w i t h Hartman's c o n c l u s i o n s t h a t s t e e l -head and coho f r y seek d i f f e r e n t c o v e r t y p e s i n t h e w i n t e r , w i t h coho f r y s e l e c t i n g l o g s , r o o t s and bank c o v e r a r e a s and s t e e l h e a d f r y p r e f e r r i n g r u b b l e a r e a s . A l t h o u g h o l d e r s t e e l -head o f t e n s e l e c t e d the same t y p e s o f c o v e r as coho, t h e y appeared t o u t i l i z e them i n a d i f f e r e n t manner. For example, o l d e r s t e e l h e a d were u s u a l l y found c l o s e r t o t h e bottom than coho, i n deeper p o o l s t h a n the coho f r y , and a l m o s t n e v e r a s s o c i a t e d w i t h sidepools or bay areas as many of the. coho were. Although some coho stayed i n the bays c o n t a i n i n g r u b b l e s u b s t r a t e , the higher numbers s t a y i n g i n the bays w i t h over-hanging banks suggests t h a t coho p r e f e r bank cover to rubble s u b s t r a t e cover. Stream observations a l s o i n d i c a t e d t h a t rubble was not commonly s e l e c t e d as w i n t e r cover by coho, and i n f a c t Ruggles (1966) found t h a t when he added 'patio b l o c k s ' to the g r a v e l l e d bottom of a stream channel, the channel's c a p a c i t y t o hold young coho over the w i n t e r was a c t u a l l y r e -duced . In Carnation Creek, many of the coho tended to move i n t o flooded areas d u r i n g the e a r l y w i n t e r . The importance of such movements might vary, depending on the s e v e r i t y of wi n t e r c o n d i t i o n s i n the stream. I f the w i n t e r has long dry pe r i o d s , then coho s u r v i v a l i n these areas might be low as a r e s u l t of d r y i n g of the e a r l i e r flooded areas . Dead coho f r y were found i n d r i e d pools i n 750 Creek duri n g an extended period without r a i n f o l l o w i n g a freshet, i n September. I f the wi n t e r i s severe w i t h frequent major f r e s h e t s , then coho s u r v i v a l i n the main channel may be low, and these flooded pools and small t r i b u t a r i e s may be the areas of highest coho overwinter s u r v i v a l . For instance, i n March 1972, underwater observations i n d i c a t e d there were extremely low d e n s i t i e s of coho i n the main Carnation Creek channel, e s p e c i a l l y i n the the lower 1000 m. Sidepools and t r i b u t a r i e s , p a r t i c u l a r l y 1600 Creek, contained much higher d e n s i t i e s of young f i s h . These observations were made f o l l o w i n g a per i o d of severe e a r l y s p r i n g f r e s h e t s . 63 The timing of floods i n r e l a t i o n to body c o n d i t i o n may be an important f a c t o r i n determining j u v e n i l e salmonid over-w i n t e r s u r v i v a l and probably warrants f u t u r e examination. Reimers (1953) showed t h a t h i g h e s t w i n t e r m o r t a l i t i e s o f young t r o u t occurred i n the l a t e w i n t e r and e a r l y s p r i n g when t h e i r body c o n d i t i o n was poorest. Some p r e l i m i n a r y examinations by Dr. Narver (pers. comm.)^ have suggested t h a t coho f r y i n Carnation Creek have low body l i p i d reserves i n the l a t e w i n t e r and e a r l y s p r i n g as compared to e a r l y f a l l . One would suspect t h a t severe floods during t h i s e a r l y s p r i n g period would be most damaging to f i s h i n poorer c o n d i t i o n . The s u r v i v a l of j u v e n i l e coho i n 75 0 Creek (76 per cent) dur i n g the 1972-73 w i n t e r was co n s i d e r a b l y higher than t h a t estimated f o r coho i n the whole Carnation Creek system f o r the previous two win t e r s (12 and 24 per cent f o r age 0 coho and approximately 50 per cent f o r age 1+ c o h o ) . 2 Thick, over-hanging vegetation and broad slow pools a f f o r d e d p r o t e c t i o n from p r e d a t i o n and displacement during the w i n t e r . That over 200 coho, many of them p o t e n t i a l smolts, s u r v i v e d the wi n t e r i n t h i s 100 m s e c t i o n of i n t e r m i t t e n t pools i s i n d i c a t i v e of t h i s type of environment's p o t e n t i a l value t o coho p r o d u c t i o n . The 300 y e a r l i n g coho l e a v i n g 1600 Creek between February and May i s f u r t h e r evidence of the productive c a p a c i t y of some very s m a l l streams. Of the approximately 2000 coho smolts 1 P a c i f i c B i o l o g i c a l S t a t i o n , Nanaimo, B.C. 2 S u r v i v a l estimates d e r i v e d from 1971 and 1972 f a l l and s p r i n g j u v e n i l e coho p o p u l a t i o n estimates and s p r i n g out-mig r a t i o n i n f o r m a t i o n , Dr. Narver, P a c i f i c B i o l o g i c a l S t a t i o n , Nanaimo, B.C. 64 l e a v i n g C a r n a t i o n Creek i n 1973, the two s m a l l t r i b u t a r i e s t h a t were s t u d i e d c o n t r i b u t e d between 15 and 25 p e r c e n t o f 3 the t o t a l . I f the number o f coho o v e r w i n t e r i n g i n t h e lower ends o f a l l the a c c e s s i b l e i n t e r m i t t e n t streams and b a c k -w a t e r s o f C a r n a t i o n Creek were known, the r e l a t i v e i m p o r t a n c e o f t h e s e a r e a s as compared t o t h e main s t r e a m c h a n n e l f o r o v e r w i n t e r i n g coho would be h i g h . The m i g r a t i o n o f j u v e n i l e coho o u t o f C a r n a t i o n Creek and i n t o 750 and 1600 Creeks d u r i n g t h e f a l l i s n o t u n i q u e t o t h i s s ystem. A movement o f j u v e n i l e coho o u t o f a r i v e r i n t o a t r i b u t a r y s t r e a m i n the f a l l has been d e s c r i b e d by S k e e s i c k (1970). He found a c o n s i s t e n t f a l l m i g r a t i o n o f l a r g e j u v e -n i l e coho o u t o f W i l s o n R i v e r i n t o S p r i n g Creek i n Oregon. Based on t h e r e c o v e r y o f marked f i s h , t h e o v e r w i n t e r s u r v i v a l of the immigrant coho i n S p r i n g Creek averaged 63 per c e n t o v e r a 10 y e a r p e r i o d . The f a l l u p stream m i g r a n t s w h i c h s u r v i v e d t o t h e s m o l t s t a g e a v e r a g e d 14 mm l o n g e r a t e m i g r a -t i o n t h a n s m o l t s w h i c h had s p e n t t h e i r e n t i r e l i v e s i n S p r i n g Creek. I t was s p e c u l a t e d t h a t t h e l a r g e r r i v e r was p r o v i d i n g good summer r e a r i n g h a b i t a t (thus t h e l a r g e j u v e n i l e coho) b u t n o t s u i t a b l e a r e a s t o escape the t u r b u l e n t w i n t e r f r e s h e t s (thus the m i g r a t i o n ) . S k e e s i c k n o t e s s i m i l a r f a l l movements o f coho i n t o t r i b u t a r i e s i n two o t h e r s t r e a m systems i n Oregon. 3The maximum'estimate, 25%, would o c c u r i f a l l o f t h e coho w h i c h l e f t the t r i b u t a r i e s from J a n u a r y onward were s m o l t s . The minimum e s t i m a t e , 15%, would o c c u r i f a l l coho g r e a t e r t h a n 60 mm i n l e n g t h w h i c h l e f t the t r i b u t a r i e s from F e b r u a r y onward were s m o l t s . 65 Steelhead f r y u t i l i z e d d i f f e r e n t w i n t e r cover than age 1+ steelhead i n Carnation Creek. Rubble i n the 10-25 cm range was s e l e c t e d by steelhead f r y , whereas o l d e r steelhead p r e f e r r e d to hide i n upturned roots and under logs and d e b r i s . Everest (1969) i n d i c a t e d j u v e n i l e steelhead of s e v e r a l age groups were found only under rubble l a r g e r than 40 cm i n diameter and Hartman (1965) found t h a t most steelhead i n the upper C h i l l i w a c k R i v e r were under 20-40 cm r o c k s . The sub-s t r a t e of Carnation Creek was sm a l l e r than i n the r i v e r systems i n which Everest and Hartman were working, and t h i s might account f o r some of the d i f f e r e n c e s i n the choice of winter h a b i t a t by age 1+ st e e l h e a d . I t i s p o s s i b l e t h a t rubble i n Carnation Creek i s too s m a l l to provide adequate h i d i n g places f o r the l a r g e r f i s h . Older age c l a s s e s of steelhead and c u t t h r o a t were found i n the l a r g e r s u b s t r a t e of the S a r i t a R i v e r and Ritherdon Creek. Two species of Cottidae are common i n Carnation Creek. During, the w i n t e r p e r i o d , C. a l e u t i c u s ( u s u a l l y y e a r l i n g and older f i s h ) were commonly found i n pools under the same s i z e d s u b s t r a t e as the steelhead f r y . Steelhead f r y and s c u l p i n s were never found under the same rocks, and i n s i t u a t i o n s where both species might be present i n high numbers, competition f o r rubble cover d u r i n g the w i n t e r might occur. The movements of age 1+ steelhead i n t o 1600 Creek during November and December suggests t h a t these f i s h were unable to f i n d s u i t a b l e w i n t e r cover i n the main channel and so were searching elsewhere. Other s t u d i e s have reported a f a l l movement of steelhead both i n and out of t r i b u t a r i e s . 66 Skeesick (1970) mentions a movement i n October of 450 j u v e n i l e steelhead (60 t o 200 mm i n length) i n t o a s m a l l stream coming from the E l k R i v e r hatchery i n Oregon. Large migrations of steelhead and chinook out of t r i b u t a r y streams w i t h poor w i n t e r cover i n t o l a r g e r streams w i t h good boulder cover have been de s c r i b e d by Chapman and Bjornn (1969) and Bjornn (1971) . Because of s i g n i f i c a n t groundwater i n p u t s , water temperatures i n 1600 Creek were c o n s i s t e n t l y higher than"in Carnation Creek throughout the w i n t e r (Appendix I ) . This warmer water may have a t t r a c t e d steelhead i n t o 1600 Creek. Hunt (1969) found t h a t the overwinter s u r v i v a l of f i n g e r l i n g brook t r o u t ( S a l v e l i n u s f o n t i n a l i s ) was higher d u r i n g w i n t e r s w i t h warmer water temperatures. Most j u v e n i l e steelhead spend two or three w i n t e r s i n Carnation Creek before s m o l t i n g . S u r v i v a l of steelhead from the l a t e summer f r y to the smolt stage, based on three years population data f o r Carnation Creek, i s l e s s than 10 per c e n t . 4 S u r v i v a l of steelhead from the l a t e summer f r y to age 1+ stage (estimated 17 and 15 per cent f o r the w i n t e r s of 1970-71 and 1971-72 r e s p e c t i v e l y ) i s extremely low. The estimated s u r v i v a l o f steelhead from the l a t e summer age in-to midsummer age 11+ i s higher (28 and 39 per cent f o r the same winters r e s p e c t i v e l y ) than f o r the f r y . These apparently high m o r t a l i t y rates along w i t h the low s u r v i v a l estimates of o l d e r j u v e n i l e steelhead i n 1600 Creek p o i n t t o the w i n t e r 4From p o p u l a t i o n estimates and outmigration records f o r Carnation Creek, 1971-73, Dr. Narver, P a c i f i c B i o l o g i c a l S t a t i o n , Nanaimo, B. C. p e r i o d as being the most c r u c i a l p eriod to steelhead d u r i n g t h e i r stream residence phase i n streams s i m i l a r to Carna-t i o n Creek. The very poor s u r v i v a l of j u v e n i l e s t e e l h e a d , p a r t i c u l a r l y f r y , may r e f l e c t the a v a i l a b i l i t y of s u i t a b l e w i n t e r cover i n Carnation Creek. Steelhead f r y chose s m a l l rubble, often l e s s than 15 cm i n diameter. This s m a l l sub-s t r a t e may prove to be hazardous d u r i n g extreme w i n t e r f r e s h e t s when f r y may be crushed beneath moving rubble. C. Lyons (pers. comm.) has found damaged and diseased steelhead f r y i n e a r l y s p r i n g i n some east coast Vancouver I s l a n d streams. He suggests t h a t these f i s h may have been damaged by the g r i n d i n g a c t i o n of s h i f t i n g s u b s t r a t e . Perhaps the l a c k of l a r g e r and more s t a b l e boulder areas coupled w i t h extreme w i n t e r f r e s h e t s may be a major f a c t o r c o n t r i b u t i n g t o the heavy winter m o r t a l i t i e s of steelhead f r y i n Carnation Creek. That o l d e r steelhead used rubble f o r cover i n other stream systems, but not i n Carnation Creek, suggests t h a t the s m a l l rubble was not s u i t a b l e and they were forced t o use l e s s s u i t a b l e types of w i n t e r c o v e r . This may help t o account f o r the poor s u r v i v a l of o l d e r j u v e n i l e s t e e l h e a d . For comparison, Hunt (1969) found the mean overwinter s u r v i v a l of f i n g e r l i n g brook t r o u t i n Lawrence Creek, Wisconsin, was 54 per cent and t h a t during the 11 years o f study, overwinter s u r v i v a l v a r i e d by as much as 200 per cent, depending upon the s e v e r i t y of w i n t e r and the c o n d i t i o n of the f i s h going i n t o the w i n t e r . B r i t i s h Columbia F i s h and W i l d l i f e Branch, Nanaimo, B.C. 68 C. A l t e r a t i o n of Winter Cover The s i d e p o o l experiments c l e a r l y demonstrated the need by coho and c u t t h r o a t f o r w i n t e r cover, whether overhanging banks or c l e a n rubble s u b s t r a t e . The very low numbers of f i s h i n i t i a l l y choosing and remaining i n the sidepools c o n t a i n i n g no bank cover or s i l t e d rubble a t low water temperatures i n d i c a t e d t h a t these types o f areas were not p r o v i d i n g s u i t -able w i n t er cover. These r e s u l t s agree w i t h underwater observations i n Carnation Creek which i n d i c a t e d t h a t n e a r l y a l l f i s h were found c l o s e l y a s s o c i a t e d w i t h cover. The p r e -ference of coho f o r bank cover over rubble cover and the use of bank cover and rubble s u b s t r a t e by c u t t h r o a t a l s o agree w i t h underwater and e l e c t r o f i s h i n g o b s e r v a t i o n s . A number of s t u d i e s c a r r i e d out i n other parts of North America have demonstrated the importance of s h e l t e r areas t o f i s h s u r v i v a l . McCrimmon (1954) found the s u r v i v a l of A t l a n t i c salmon f i n g e r l i n g s was much lower i n experimental stream s e c t i o n s where the substrate was h e a v i l y s i l t e d than where i t was c l e a n , and accounted the d i f f e r e n c e to a l o s s of s h e l t e r to escape cover from l a r g e r predatory f i s h . R e f e r r i n g to t h e i r surveys of C a l i f o r n i a streams, Cordone and K e l l e y (1961) suggested t h a t i n streams where sediment was deposited i n the spaces between rubble, s h e l t e r f o r t r o u t was reduced. They f e l t t h i s may be l i m i t i n g these streams' production of l a r g e r t r o u t . Hunt (1971) demonstrated t h a t adding overhang-ing bank cover and i n c r e a s i n g the number of pools i n Lawrence Creek r e s u l t e d i n a decrease of brook t r o u t overwinter 69 m o r t a l i t i e s to n e a r l y h a l f of t h e i r o r i g i n a l l e v e l . Removal of overhanging v e g e t a t i o n and banks r e s u l t e d i n a decrease i n the t r o u t p o p u l a t i o n of a s m a l l Montana stream (Boussu, 1954), and Saunders and Smith (1962), by i n c r e a s i n g the number of h i d i n g places i n a s m a l l stream, n e a r l y doubled the p o p u l a t i o n of brook t r o u t over age I . The experiments c a r r i e d out w i t h the simulated s i d e -p o o l s , along w i t h underwater observations suggest the consequences of c e r t a i n p h y s i c a l a l t e r a t i o n s to these p o t e n t i a l l y important w i n t e r i n g areas. Logging o p e r a t i o n s , channel clearance and s t r a i g h t e n i n g , and road c o n s t r u c t i o n a c t i v i t i e s adjacent t o stream areas may r e s u l t i n bank damage (Anderson, 1971; Burns, 1972; and Narver, 1972), and a l t e r s e c t i o n s of streams from the experimental 'bank cover' s i t u a t i o n to the 'no bank cover' s i t u a t i o n . Increased sediment loads i n streams f o l l o w i n g l ogging operations have been w e l l documented and mainly a t t r i -buted to poor road designs ( J e f f r e y , 1968; F r e d r i k s e n , 1970; Megahan and Kidd, 1972), s l a s h b u r n i n g (Brown, 1971), and bank e r o s i o n of d i s t u r b e d streambanks (Anderson, 1971; Burns, 1972). The marginal areas used by steelhead and c u t t h r o a t f o r w i n t e r cover, because of t h e i r lower water v e l o c i t i e s , are a l s o the reaches of the stream most s u s c e p t i b l e t o sediment d e p o s i t i o n . In the experiments, v i r t u a l l y no t r o u t remained i n the s i l t e d rubble, presumably because i t d i d not c o n t a i n s u i t a b l e i n t e r s t i c e s f o r f i s h t o hide i n . While examining the substrate i n Carnation Creek, no f i s h were found i n rubble plugged w i t h f i n e r sands and pebbles. This need f o r adequate spaces has been observed by Everest (1969). 70 The s i d e p o o l e x p e r i m e n t s p e r m i t t e d v o l i t i o n a l r e s i d e n c e o f f i s h . S i n c e n e a r l y a l l f i s h l e f t t he bays w i t h no bank c o v e r o r s i l t e d r u b b l e , one would s u s p e c t t h e s e f i s h w o u l d a v o i d s t r e a m s e c t i o n s s i m i l a r l y l a c k i n g i n c o v e r . What t h e s e t r i a l s do n o t i n d i c a t e i s whether o r n o t f i s h would s u r v i v e i f t h e y were n o t g i v e n t h e o p t i o n o f moving t o a l t e r n a t i v e a r e a s . D. C o n c l u s i o n s Streambank p r o t e c t i o n measures f o r f i s h streams t h e s i z e o f C a r n a t i o n Creek and l a r g e r a r e , i n t h e f u t u r e , a n t i c i -p a t e d t o be p a r t o f the s t a n d a r d f o r e s t management p l a n . However, i t i s d i f f i c u l t t o v i s u a l i z e adequate p r o t e c t i o n f o r streams t h e s i z e o f the two t r i b u t a r i e s w h i c h were examined i n t h i s s t u d y . One o f t h e streams was d r y t h r o u g h o u t t h e summer, and t h e . o t h e r had summer f l o w s o f about .003 m 3/sec (0.1 c f s ) . Mundie (1969) has d i s c u s s e d the v a l u e o f s m a l l streams t o coho p r o -d u c t i o n and D e w i t t (1955), Lowry (1965), and Hartman and G i l l (1968) have i n d i c a t e d the importance o f v e r y s m a l l streams t o c u t t h r o a t p r o d u c t i o n . L a t e summer low f l o w s i n s m a l l t r i b -u t a r i e s d i s g u i s e the p o t e n t i a l p r o d u c t i v e c a p a c i t i e s o f s u c h streams t o t h e f i s h e r y . A t p r e s e n t , such streams o f t e n a r e no t c o n s i d e r e d when d e s i g n i n g and c a r r y i n g out h a r v e s t i n g o p e r a t i o n s , y e t t h e s e a re t h e a r e a s most s u s c e p t i b l e t o damage. The ease w i t h w h i c h s m a l l t r i b u t a r i e s , b a c k w a t e r s , and s i d e p o o l s o f l a r g e r streams may be o v e r l o o k e d i n management p l a n s and o f t e n t i m e s i r r e v e r s i b l y damaged by l o g g i n g o p e r a t i o n s 7 1 i s alarming. The r o l e of c e r t a i n o f these areas i n the s u r v i v a l of young coho and t r o u t may be so s u b t l e t h a t i t can only be recognized a f t e r c a r e f u l study d u r i n g c e r t a i n periods of the year. Streamflow f l u c t u a t i o n s a l l o w i n g only p e r i o d i c access t o c e r t a i n areas, and the c l o s e a s s o c i a t i o n o f f i s h f o r cover a t low water temperatures, complicates h a b i t a t e v a l u a t i o n of these stream systems. Unless we recognize the very important r o l e of cover areas i n the overwinter s u r v i v a l of coho and t r o u t , and the r o l e t h a t many of the t i n y t r i b u t a r i e s , backwaters, s i d e p o o l s , and bank areas of a stream system play i n p r o v i d i n g t h i s cover, many of our present p r o t e c t i o n measures o f t e n designed t o p r o t e c t salmonid spawning and summer r e a r i n g h a b i t a t w i l l be wasted. 72 MANAGEMENT RECOMMENDATIONS On the b a s i s of t h i s study i t i s suggested t h a t the f o l l o w i n g recommendations be incorporated i n t o management planning f o r f i s h h a b i t a t p r o t e c t i o n . 1. Do not remove r o o t s , logs and s m a l l accumulations of d e b r i s m a t e r i a l from a stream unless i t presents a b a r r i e r to f i s h m i g r a t i o n . This m a t e r i a l provides cover, an important component of j u v e n i l e coho and t r o u t w i n t e r h a b i t a t . On the subject of w i n t e r cover Hartman (1968) s t a t e s : "Stable and p r o t e c t i v e l o g jams provide good w i n t e r cover f o r f i s h * However, . t h i s does not mean t h a t mats of logging d e b r i s which f l u s h out and are c a r r i e d away w i t h f r e s h e t s provide good r e a r i n g h a b i t a t . " In Carnation Creek, a d u l t steelhead, coho and chum salmon a l s o u t i l i z e d the cover provided by upturned r o o t s , l o g jams, and overhanging banks, p a r t i c u l a r l y a t lower streamflows. 2. Encourage the p r o t e c t i o n of the stream environment by r e t a i n i n g streambank v e g e t a t i o n and y a r d i n g away from f i s h streams. The marginal areas of a stream are most important f o r o verwintering coho and t r o u t and should be t r e a t e d accord-i n g l y . As w e l l as the streambanks, these marginal areas in c l u d e reaches of the stream flooded during higher flows such as back-water pools and the lower ends of ephemeral streams. Although some of these s m a l l e r streams may not have a spawning popula-t i o n of f i s h , they may be u t i l i z e d d uring some periods of the year. The argument th a t a s t r i p of t r e e s l e f t adjacent to streams w i l l o f t e n times blow down loses some of i t s e f f e c t i v e -ness i f one views these t r e e s (plus roots) as p r o v i d i n g s t a b l e cover f o r f i s h . C o nsideration should be given t o s m a l l streams to ensure that access by j u v e n i l e f i s h i n t o them i s not r e s t r i c t e d by d e b r i s jams or by poor c u l v e r t designs or l o c a t i o n s . Improv-ing or c r e a t i n g access i n t o c e r t a i n of these backwaters and small t r i b u t a r i e s might a c t u a l l y increase the p r o d u c t i v e c a p a c i t y of streams where t h i s type of h a b i t a t i s l a c k i n g . 3. Since c l e a n rubble s u b s t r a t e i s necessary f o r over-w i n t e r i n g steelhead and c u t t h r o a t , sediment loads i n a stream should be kept to a minimum, e s p e c i a l l y i n streams which do not f l u s h f r e q u e n t l y . Methods of minimizing sediment pro d u c t i o n from logging and road c o n s t r u c t i o n such as o u t l i n e d i n Rothwell (1971) should be incorporated i n t o management p l a n s . Research i n t o p o t e n t i a l improvement of t r o u t w i n t e r h a b i t a t by adding lar g e rubble to areas which do not have good cover should be encouraged. For example, adding l a r g e angular rock t o stream channels along roads and r a i l r o a d s may be improving f i s h w i n t e r h a b i t a t i n these areas (Everest, 1969). LITERATURE CITED Anderson, H.W. 1971. R e l a t i v e c o n t r i b u t i o n s o f se d i m e n t from s o u r c e a r e a s and t r a n s p o r t p r o c e s s e s , p. 55-63. I n : J.T. K r y g i e r and J.D. H a l l ( E d s . ) , F o r e s t Land Uses and Stream Environment Symposium, Oregon S t a t e U n i v e r s i t y . B j o r n n , T.C. 1971. T r o u t and salmon movements i n two Idaho streams as r e l a t e d t o t e m p e r a t u r e , f o o d , s t r e a m f l o w , c o v e r , and p o p u l a t i o n d e n s i t y . T r a n s . Amer. F i s h . S o c , 1 0 0 ( 3 ) : 423-438. Boussu, M.F. 1954. R e l a t i o n s h i p between t r o u t p o p u l a t i o n s and c o v e r on a s m a l l s t r e a m . J o u r . W i l d l . Mgmt., 18: 229-239. Brown, G.W. and J.T. K r y g i e r . 1971. 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The i n f l u e n c e s o f i n -o r g a n i c sediment on t h e a q u a t i c l i f e o f s t r e a m s . C a l i f . F i s h and Game, 47: 189-228. DeWitt, J.W. 1954. A s u r v e y o f the c o a s t c u t t h r o a t t r o u t , Salmo c l a r k i c l a r k i R i c h a r d s o n , i n C a l i f o r n i a . C a l i f . F i s h and Game, 40_: 329-335. Edmundson, E. and F.H. E v e r e s t and D.W. Chapman. 1968. Perman ence of s t a t i o n i n j u v e n i l e c h i n o o k salmon and s t e e l h e a d t r o u t . J . F i s h . Res. Bd. Canada, 25_(7) : 1453-1464. E l s o n , P.F. 1962. P r e d a t o r - p r e y r e l a t i o n s h i p s between f i s h -e a t i n g b i r d s and A t l a n t i c salmon. B u l l . F i s h . Res. Bd. Canada, No. 133, 87 p. Elwood, J.W. and T.F. Water s . 1969. E f f e c t s o f f l o o d s on food consumption and p r o d u c t i o n r a t e s o f a s t r e a m b r o o k t r o u t p o p u l a t i o n . T r a n s . Amer. F i s h . 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Comparative b e h a v i o r and h a b i t a t u t i l i z a -t i o n o f b r o o k t r o u t and c u t t h r o a t t r o u t i n s m a l l streams i n n o r t h e r n Idaho. J . F i s h . Res. Bed. Canada, 29 (3) : 265-273. Hartman, G.F. 1963. O b s e r v a t i o n s on b e h a v i o r o f j u v e n i l e brown t r o u t i n a st r e a m aquarium d u r i n g the w i n t e r and s p r i n g . J . F i s h . Res. Bd. Canada, 2J0(3): 769-787. , 1965. The r o l e o f b e h a v i o r i n the e c o l o g y and i n t e r a c t i o n o f u n d e r y e a r l i n g coho salmon (Qncorhynchus  k i s u t c h ) and s t e e l h e a d t r o u t (Salmo g a i r d n e r i ) . ~~J~. F i s h . Res. Bd. Canada, 22_: 1035-1081. , 1968. Growth r a t e and d i s t r i b u t i o n o f some f i s h e s i n the C h i l l i w a c k , South A l o u e t t e , and Salmon R i v e r s . B.C. F i s h and W i l d l . B r a n c h , Mgmt. P u b l . No. 11, 33 p. Hartman, G.F. and C.A. G i l l . 1968. D i s t r i b u t i o n s o f j u v e n i l e s t e e l h e a d and c u t t h r o a t t r o u t (Salmo g a i r d n e r i and S. c l a r k i c l a r k i ) w i t h i n streams i n s o u t h w e s t e r n B r i t i s h C o l umbia. J . F i s h . Res. Bd. Canada, 25_(1) : 33-48. Hunt, R.L. 1969. O v e r w i n t e r s u r v i v a l o f w i l d f i n g e r l i n g b r ook t r o u t i n Lawrence Creek, W i s c o n s i n . J . F i s h . Res. Bd. Canada, 26_: 1473-1483. , 1971. Responses o f a br o o k t r o u t p o p u l a t i o n t o h a b i t a t development i n Lawrence Creek. Tech. B u l l . No. 48. W i s . Dep. Nat. Resour., Madison, Wis. J e f f r e y , W.W. 1968. Watershed management problems i n B r i t i s h C o l umbia: a f i r s t a p p r a i s a l . Water R e s o u r c e s B u l l . 4(3) : 58-70. L i n d r o t h , A. 1955a. D i s t r i b u t i o n , t e r r i t o r i a l b e h a v i o u r and movements o f sea t r o u t f r y i n the R i v e r I n d a l s a l v e n . R ept. I n s t . F r e s h w a t e r Res. D r o t t n i n g h o l m , 36_: 104-119. , 1955b. Mergansers as salmon and t r o u t p r e d a t o r s i n t h e R i v e r I n d a l s a l v e n . I b i d . , 36: 126-132. 76 Lowry, G.R. 1965. Movement o f c u t t h r o a t t r o u t , Salmo c l a r k i  c l a r k i R i c h a r d s o n , i n t h r e e Oregon c o a s t a l s t r e a m s . T r a n s . Amer. F i s h . Soc., 94: 334-338. M a c i o l e k , J.A. and P.R. Needham. 1952. E c o l o g i c a l e f f e c t s o f w i n t e r c o n d i t i o n s on t r o u t and t r o u t foods i n C o n v i c t Creek, C a l i f o r n i a , 1951. T r a n s . Amer. F i s h . S o c , 81: 202-217. McCrimmon, H.R. 1954. Stream s u t i d e s on p l a n t e d A t l a n t i c salmon. J . F i s h . Res. Bd. Canada, 11,(4): 362-403. Megahan, W.F. and W.J. K i d d . 1972. E f f e c t s o f l o g g i n g and l o g g i n g r o a d s on e r o s i o n and sedim e n t d e p o s i t i o n from s t e e p t e r r a i n . J o u r n a l o f F o r e s t r y , 70(3) : 136-141. M o r r i l , C.F. 1972. M i g r a t i o n r e s p o n s e o f j u v e n i l e Chinook salmon t o s u b s t r a t e s and t e m p e r a t u r e s . M.S. t h e s i s , U n i v e r s i t y o f I d a h o 0 27 p. Mundie, J.H. 1969. E c o l o g i c a l i m p l i c a t i o n s o f t h e d i e t o f j u v e n i l e coho i n s t r e a m s , p. 135-152. I n : T.G. N o r t h -c o t e ( E d . ) , Symposium on Salmon and T r o u t i n Streams. H.R. M a c M i l l a n L e c t u r e s i n F i s h e r i e s . U n i v e r s i t y o f B r i t i s h C o lumbia, Vancouver. N a r v e r , D.W. 1972. A s u r v e y o f some p o s s i b l e e f f e c t s o f l o g g i n g on two e a s t e r n Vancouver I s l a n d s t r e a m s . F i s h . Res. Bd. Canada, Tech. R e p o r t No. 323, 55 p. Needham, P.R. and A.C. J o n e s . 1959. Flow, t e m p e r a t u r e , s o l a r r a d i a t i o n , and i c e i n r e l a t i o n t o a c t i v i t i e s o f f i s h e s i n Sagehen Creek, C a l i f o r n i a . E c o l o g y 40_(3) : 465-474. Needham, P.R. and J.W. M o f f e t and D.W. S l a t e r . 1945. F l u c t u a -t i o n s i n w i l d brown t r o u t p o p u l a t i o n s i n C o n v i c t Creek, C a l i f o r n i a . J o u r . W i l d l . Mgmt., 9 ( 1 ) : 9-25. Onodera, K. and T. Ueno. 1961. On t h e s u r v i v a l o f t r o u t f i n g e r -l i n g s s t o c k e d i n a mountain b r o o k . I I . S u r v i v a l r a t e measured and s c o u r i n g e f f e c t o f f l o o d as a cause o f m o r t a l i t y . B u l l . J a p . Soc. S c i . F i s h . 27_: 530-557. Reimers, N. 1957. Some a s p e c t s o f the r e l a t i o n between s t r e a m foods and t r o u t s u r v i v a l . C a l i f . F i s h and Game, 43_(1) : 43-69. , 1963. Body c o n d i t i o n , w a t e r t e m p e r a t u r e , and o v e r -w i n t e r s u r v i v a l o f h a t c h e r y - r e a r e d t r o u t i n C o n v i c t Creek, C a l i f o r n i a . T r a n s . Amer. F i s h . S o c , 92_(1) : 39-47. R o t h w e l l , R.L. 1971. Watershed management g u i d e l i n e s f o r l o g g i n g and road c o n s t r u c t i o n . Can. F o r e s t S e r v . I n f o r . R e p o r t A-X-42, F o r e s t Res. Lab., Edmonton, A l t a . 77 Ruggles, C P . 1966. Depth and v e l o c i t y as a f a c t o r i n stream r e a r i n g and production of j u v e n i l e coho salmon. Can. F i s h . C u l t . 3J3: 35-53. Saunders, J.W. and M.W. Smith. 1962. P h y s i c a l a l t e r a t i o n o f stream h a b i t a t to improve brook . t r o u t p r o d u c t i o n . Trans. Amer. F i s h . S o c , 91_(2) : 185-188. Skeesick, D.G. 1970. The f a l l immigration of j u v e n i l e coho salmon i n t o a s m a l l t r i b u t a r y . Res. Rept. F i s h Comm. Oregon 2_(1) : 90-95. Tack, E. 1938. Trout m o r t a l i t y from the formation of suspended i c e c r y s t a l s . F i s c h e r e i - Z e i t u n g 41: 42. (Rev. i n Prog. F i s h . C u l t . , 1937-1938, No. 37: 26T. Wickham, M.G. 1967. P h y s i c a l m i c r o h a b i t a t of t r o u t . M.S. t h e s i s , Colorado State U n i v e r s i t y , 42 p. cms 9 -8 -7 -6 -5 -4 -3 -2 -1 -0 M E A N D A I L Y D I S C H A R G E r300 K200 c fs f-700 10 9-i 8 7 " 6 -5 4 -3 -2 1 W A T E R T E M P E R A T U R E C A R N A T I O N CREEK 1600 C R E E K 750 CREEK — i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 20 O C T 10 20 N O V 10 20 D E C 10 20 JAN 10 20 F E B 10 20 MAR 10 20 APR 10 20 MAY 10 20 A p p e n d i x I . M e a n d a i l y d i s c h a r g e i n C a r n a t i o n C r e e k a t B w e i r a n d m i d d a y w a t e r -t e m p e r a t u r e s i n C a r n a t i o n , 1 6 0 0 , a n d 7 5 0 C r e e k s f r o m S e p t e m b e r 2 0 , 1 9 7 2 , t o M a y . 2 0 , 1 9 7 3 . co 79 A p p e n d i x I I . C r o s s s e c t i o n a l v i e w s o f t w o s e c t - i o n s o f C a r n a t i o n C r e e k i n d i c a t i n g t h e l o c a t i o n o f o v e r h a n g i n g b a n k s , l o g s , a n d u p t u r n e d r o o t s . S m a l l a c c u m u l a t i o n s o f d e b r i s a n d o v e r h a n g i n g b u s h a r e n o t s h o w n . S t r e a m -f l o w a t t h e t i m e o f s u r v e y i n g w a s 2 . 5 c f s . A d a p t e d f r o m m a p s p r o v i d e d b y t h e D e p a r t m e n t o f E n v i r o n m e n t , F i s h e r i e s S e r v i c e . S c a l e : l " = 2 0 l . Appendix I I I . Mean fork l e n g t h and s i z e range of f i s h used i n the s i d e p o o l experiments. Date When Used T r i a l Mean Fork Length Range Sample Size Coho Oct. 16 t o Oct. 28 Nov. 7 Dec. 2 Jan. 14 Feb. 2 Feb. 16 Mar. 6 Mar. 12 Mar. 19 P r e l i m i n a r y Time T r i a l s C l C2 C3 C4 C5 C6 C7 C8 (mm) 45.2 45.9 50.5 51.2 51.8 54.2 53 .2 59.1 58.4 (mm) 37-67 36-66 39-65 39-70 39-67 39-73 43-73 45-76 41-81 318 78 154 158 79 79 80 77 79 Cutthroat Nov. 18 Jan. 26 Feb. 22 Mar. 1 T l T2 T3 T4 60.8 63.9 63.4 62.6 41-75 49-91 45-91 45-92 80 78 79 80 81 A p p e n d i x I V . T h e p e r c e n t a g e o f j u v e n i l e c o h o c h o o s i n g o v e r -h a n g i n g b a n k c o v e r a t v a r i o u s t i m e i n t e r v a l s ( A ) a n d t h e p e r c e n t a g e c h o o s i n g t o r e m a i n i n t h e s i d e p o o l s w h e n a l l o w e d a c c e s s t o D i c k C r e e k . a t t w o t i m e i n t e r v a l s ( B ) . D o t s r e p r e s e n t m e a n s b a s e d o n t w o r e p l i c a t e s o f 4 0 f i s h a n d t h e c i r c l e r e p r e s e n t s a m e a n b a s e d o n f o u r r e p l i c a t e s o f 4 0 f i s h . 90 - I 0 24 ' 48 72 TIME (HRS) 82 Appendix V. Date, maximum and minimum water temperatures and water depths, and number of f i s h - p e r s i d e -pool f o r a l l of the s i d e p o o l experiments. Water Water F i s h Temp. Depth Per T r i a l Species Date (°C) (cm) Po o l P r e l i m . Coho Oct. 16 6.0-8.0 10-13 40 Time t o T r i a l s Oct. 28 CI Coho Nov. 7-12 8.0-9.0 20-34 40 C2 Dec. 2-7 2.5-5.0 15-17 40 C3 Jan. 14-19 2.8-5.5 27-47 40 C4 Feb. 2-7 2.9-4.4 17-22 20 C5 Feb. 16-21 4.1-4.6 12-22 20 C6 Mar. 6-11 5.0-6.0 15-26 20 C7 Mar. 12-17 5.1-6.1 17-22 20 C8 Mar. 19-24 5.0-5.7 18-32 20 T l Cutthroat Nov. 18-23 4.5-5.6 12-13 20 T2 II Jan. 26-31 3.5-5.4 17-27 20 T3 II Feb. 22-27 3.5-4.9 13-15 20 T4 II Mar. 1-6 5.8 20-30 20 83 Appendix VI. The percentage of j u v e n i l e coho choosing the bays o f f e r i n g overhanging bank cover as opposed t o those o f f e r i n g barren bays. OBIGATORY RESIDENCE means coho were not permitted access to Dick Creek and VOLUNTARY RESIDENCE means coho were permitted access t o Dick Creek. Figures are f o r two temperature c a t e g o r i e s . OBLIGATORY RESIDENCE Over-hanging Bank T r i a l Cover Barren Cover Barren T o t a l * C2 97 3 95 5 C3 82 18 95 5 2.5-5.0°C C4 95 5 60 40 C5 79 21 100 0 85 2 87 43 0 43 67 15 82 72 5 77 84 0 84 55 0 55 79 0 79 71 5 76 Mean 87.9 12.1 69.5 3.4 72.9 C l 50 50 45 55 C6 90 10 5.1°-9.0°C 100 0 C7 100 0 100 0 C8 95 5 95 5 95 9 104 52 7 59 40 5 45 50 0 50 35 0 35 42 5 47 30 5 35 37 0 37 Mean 84.4 15.6 47.6 3.9 51.5 VOLUNTARY RESIDENCE Over-hang ing Bank *% Based on T o t a l Numbers of F i s h I n i t i t a l l y i n Side p o o l s . 84 Appendix V I I . The p e r c e n t a g e o f j u v e n i l e coho c h o o s i n g t h e bays o f f e r i n g c l e a n r u b b l e as opposed t o t h o s e o f f e r i n g s i l t e d r u b b l e . OBLIGATORY RESIDENCE means coho v/ere n o t p e r m i t t e d a c c e s s t o D i c k Creek and VOLUNTARY RESIDENCE means coho were p e r m i t t e d a c c e s s t o D i c k Creek. F i g u r e s a r e f o r two t e m p e r a t u r e c a t e g o r i e s . COHO OBLIGATORY RESIDENCE VOLUNTARY RESIDENCE C l e a n S i l t e d C l e a n S i l t e d T r i a l Rubble Rubble Rubble Rubble T o t a l C2 81 19 43 6 49 - 74 26 26 0 26 C3 77 23 28 24 52 97 3 23 8 31 2 .5-5.0°C C4 79 21 42 0 42 100 0 30 5 35 C5 100 0 63 0 63 95 5 40 0 40 Mean 87.9 12.1 36.9 5.4 42.3 CI 74 26 24 14 38 65 35 0 21 21 .1^9.0°C C6 95 5 10 0 10 5 42 58 16 0 16 C7 85 15 10 0 10 25 75 5 0 5 C8 81 19 21 16 37 63 37 5 5 10 Mean 66.2 33.8 11.4 7.0 18.4 85 Appendix V I I I . The p e r c e n t a g e o f j u v e n i l e c u t t h r o a t c h o o s i n g the bays o f f e r i n g o v e r h a n g i n g bank c o v e r as opposed t o those o f f e r i n g b a r r e n bays and t h e p e r c e n t a g e c h o o s i n g t h e bays o f f e r i n g c l e a n r u b b l e s u b s t r a t e as opposed t o s i l t e d s u b s t r a t e . OBLIGATORY RESIDENCE means f i s h were n o t p e r -m i t t e d a c c e s s t o D i c k Creek and VOLUNTARY RESIDENCE means f i s h were p e r m i t t e d a c c e s s t o D i c k Creek. A l l t r i a l s were c a r r i e d o u t a t w a t e r t e m p e r a t u r e s l e s s t h a n 6°C. CUTT1 IROAT OBLIGATORY RESIDENCE VOLUNTARY RESIDENCE Overhanging B a r r e n Overhanging B a r r e n T r i a l Bank Cover P o o l Bank Cover P o o l T o t a l T l 70 30 65 0 65 90 10 60 0 60 T2 100 0 35 0 35 100 0 45 0 45 T3 95 5 35 5 40 80 20 15 0 15 T4 ' 100 0 60 0 60 100 0 47 0 47 Mean 91.9 8.1 45.2 0.6 45.8 C l e a n S i l t e d C l e a n S i l t e d Rubble Rubble Rubble Rubble T o t a l T l 89 11 89 0 89 95 5 53 0 53 T2 100 0 26 6 31 95 5 58 0 58 T3 82 18 24 0 24 65 35 10 0 10 T4 100 0 63 0 63 100 0 37 0 37 Mean 90.8 9.2 44.8 0.8 45.6 

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