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Experimental manipulation of stream gravel characteristics related to early survival in pink and chum… Klassen, Herbert David 1984

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EXPERIMENTAL MANIPULATION OF STREAM GRAVEL CHARACTERISTICS RELATED TO EARLY SURVIVAL IN PINK AND CHUM SALMON AND TO F I S H -FORESTRY PROBLEMS IN THE QUEEN CHARLOTTE ISLANDS OF BRITISH COLUMBIA. by HERBERT DAVID KLASSEN B . S c . , U n i v e r s i t y Of B r i t i s h C olumbia,1977 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES F o r e s t r y Department We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1984 © HERBERT DAVID KLASSEN, 1984 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements 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 L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree that permission f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s or her r e p r e s e n t a t i v e s . It i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of F o r e s t r y The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: 26 A p r i l 1984 i i A b s t r a c t Tandem V - s h a p e d g a b i o n w e i r s f o r i m p r o v i n g s p a w n i n g h a b i t a t f o r p i n k ( O n c o r h y n c h u s g o r b u s c h a ) and chum salmon ( 0 . k e t a ) i n l a n d s l i d e - damaged s t r e a m s were i n s t a l l e d and examined i n S a c h s C r e e k , Queen C h a r l o t t e I s l a n d s . Spawner u t i l i z a t i o n , egg s u r v i v a l , as w e l l as s t a b i l i t y and q u a l i t y of g r a v e l s e n t r a p p e d by t h e s t r u c t u r e s were compared t o t h a t of n a t u r a l c o n t r o l s i t e s . Two g a b i o n s i t e s a t 1% s l o p e g r a d i e n t a t t r a c t e d moderate spawner usage w i t h i n weeks of i n s t a l l a t i o n ; a t h i r d g a b i o n s i t e a t a 3% s l o p e g r a d i e n t was beyond t h e u p s t r e a m l i m i t of p i n k and chum salmon but was u t i l i z e d by coho (0. k i s u t c h ) spawners. P i n k salmon egg s u r v i v a l a p p e a r e d h i g h i n t h e f i r s t autumn-w i n t e r s e a s o n a f t e r i n s t a l l a t i o n ( c a . 11% t o t h e "eyed" s t a g e ) w i t h improvement a n t i c i p a t e d a s t h e g a b i o n s i t e s u n d e rgo n a t u r a l s t a b i l i z a t i o n o f s t r e a m b e d c o n f i g u r a t i o n s . G r a v e l s t a b i l i t y a t a l l 3 g a b i o n s i t e s was poor o v e r t h e f i r s t w i n t e r , and e x c e s s i v e s c o u r t h r e a t e n e d t h e i n t e g r i t y of t h e u p s t r e a m , s t e e p e r s l o p e g a b i o n s i t e w i t h i n 1 y e a r . However, t h e 2 g a b i o n s i t e s a t 1% s l o p e g r a d i e n t s u c c e s s f u l l y s t a b i l i z e d g r a v e l o v e r t h e i r s e c o n d s e a s o n o f s t o r m f l o w s t h r o u g h l o c a l r e d u c t i o n s i n s t r e a m b e d s l o p e g r a d i e n t s . The e f f e c t s of g a b i o n s on g r a v e l c o m p o s i t i o n and i n t r a g r a v e l p e r m e a b i l i t y were v a r i a b l e . D e m o n s t r a t e d improvements i n i n t r a g r a v e l d i s s o l v e d oxygen p r o b a b l y r e s u l t e d f r o m c h a n n e l " r o u g h n e s s " added by t h e g a b i o n s . I n t r a g r a v e l d i s s o l v e d oxygen had a s i g n i f i c a n t (p<.05) p o s i t i v e c o r r e l a t i o n w i t h egg s u r v i v a l . H i g h j u v e n i l e coho and s t e e l h e a d (Salmo  g a i r d n e r i ) d e n s i t i e s a t t h e g a b i o n s i t e s ( a v e r a g e 1.6 / m 2 compared t o 0.9 / m2 a t c o n t r o l s i t e s ) i n d i c a t e d h i g h q u a l i t y r e a r i n g h a b i t a t as an a d d i t i o n a l b e n e f i t . A c h i e v e m e n t o f c o s t e f f e c t i v e n e s s ( r e c o v e r y of c o n s t r u c t i o n c o s t s t h r o u g h i n c r e a s e s i n r e t u r n i n g a d u l t p i n k salmon) was a t t a i n a b l e i n g a b i o n s i t e s w e l l u t i l i z e d by s p a w n e r s . The s t a b i l i t y i n s t r e a m b e d c o n f i g u r a t i o n s p r o v i d e d by g a b i o n s i n t h e i r s e c o n d y e a r would be u s e f u l i n r e h a b i l i t a t i n g low g r a d i e n t r e a c h e s of s t r e a m s damaged by l a n d s l i d e s . Recommendations f o r g a b i o n i n s t a l l a t i o n i n c l u d e d r e s t r i c t i o n t o downstream r e a c h e s a t <2% s l o p e g r a d i e n t where moderate t o heavy spawner usage would o c c u r . i v T a b l e of C o n t e n t s A b s t r a c t i i L i s t of T a b l e s v i L i s t of F i g u r e s v i i i Acknowledgement x C h a p t e r I INTRODUCTION 1 C h a p t e r I I THE STUDY AREA 4 C h a p t e r I I I METHODS 10 1. GABION DESCRIPTION 11 2. STUDY S I T E LOCATIONS 11 3. PRE-TREATMENT S I T E ANALYSIS 12 4. GABION CONSTRUCTION AND INSTALLATION 14 1 . TREATMENT S I T E I 19 2. TREATMENT S I T E II 19 3. TREATMENT S I T E I I I 20 5. POST-INSTALLATION S I T E ANALYSIS 20 1. GRAVEL STABILITY 20 2. GRAVEL QUALITY 21 3. STREAMBED CONFIGURATION 2 3 4. SPAWNER UTILIZATION 24 5. EGG SURVIVAL 2 5 6. JUVENILE UTILIZATION 27 C h a p t e r IV RESULTS 28 1 . S I T E STABILITY 28 1 . GRAVEL SCOUR 28 2. GABION S I T E CONFIGURATIONS 32 2. GRAVEL QUALITY 38 1. INTRAGRAVEL DISSOLVED OXYGEN 38 2. INTRAGRAVEL PERMEABILITY 38 3. GRAVEL COMPOSITION 4'4 4. SEDIMENTATION 47 3. SPAWNER UTILIZATION 49 1. OBSERVED SPAWNING 49 2. PROBABILITY-OF-USE 52 4. EGG SURVIVAL 54 V 5. JUVENILE UTILIZATION 60 C h a p t e r V DISCUSSION 65 1 . S I T E STABILITY 66 2. GRAVEL QUALITY 69 1 . T r e a t m e n t S i t e I 71 2. T r e a t m e n t S i t e II 72 3. T r e a t m e n t S i t e I I I 73 3. SPAWNER UTILIZATION 74 4. EGG SURVIVAL 7 7 5. JUVENILE UTILIZATION 80 6. SUMMARY OF POSITIVE AND NEGATIVE EFFECTS OF GABIONS. ..83 7. PRELIMINARY BENEFIT COST ANALYSIS 86 C h a p t e r VI CONCLUSIONS AND RECOMMENDATIONS 95 LITERATURE CITED 99 APPENDIX A - PROBABILITY-OF-USE CRITERIA OF SACHS CREEK PINK REDDS 104 APPENDIX B - CALCULATIONS OF BENEFIT / C O S T ANALYSIS FOR TREATMENT S I T E I I I AT SACHS CREEK 105 APPENDIX C - PHOTOGRAPHIC PLATES OF GABION SITE S AT SACHS CREEK, 1.5 YEARS POST-INSTALLATION, FEBRUARY 1984. ...107 v i L i s t of T a b l e s 1. Depth of G r a v e l S c o u r on Study S i t e s a t Sachs C r e e k Over W i n t e r 1982-83 and 1983-84 29 2. A t - t e s t A n a l y s i s of G r a v e l S c o u r on St u d y S i t e s a t Sachs C r e e k 30 3. Summary o f Streambed G r a d i e n t Changes w i t h G a b i o n I n s t a l l a t i o n on Sachs C r e e k , 1982-83 37 4. Summary o f I n t r a g r a v e l D i s s o l v e d Oxygen and P e r m e a b i l i t y on S t u d y S i t e s a t Sachs C r e e k . 40 5. A t - t e s t A n a l y s i s of I n t r a g r a v e l D i s s o l v e d Oxygen on Stu d y S i t e s a t Sachs C r e e k 42 6. A t - t e s t A n a l y s i s of I n t r a g r a v e l P e r m e a b i l i t y on S t u d y S i t e s a t Sachs C r e e k 43 7. D i s t r i b u t i o n of Salmon Spawning A c t i v i t y on S t u d y S i t e s a t S a c h s C r e e k , F a l l 1982 and 1983 51 8. Summary o f P r o b a b i 1 i t y - o f - U s e by Spawning P i n k Salmon on Stu d y S i t e s a t Sachs C r e e k , 1 Y e a r P o s t G a b i o n I n s t a l l a t i o n 53 9. Summary o f Egg S u r v i v a l on S t u d y S i t e s a t Sachs C r e e k , F a l l and W i n t e r 1982-83 55 10. A t - t e s t A n a l y s i s of Egg S u r v i v a l i n Year 1 on T r e a t m e n t S i t e I I I and i t s C o n t r o l s a t S a c h s C r e e k 58 11. Redd S u p e r i m p o s i t i o n on E g g - s a m p l i n g S t a t i o n s a t S a c h s C r e e k , 1982 59 12. V e r t i c a l D i s t r i b u t i o n of P i n k Salmon Eggs a t S a c h s C r e e k , December 1982 59 13. J u v e n i l e S a l m o n i d Usage of S t u d y S i t e s on Sachs C r e e k , P r e - and P o s t - F l o o d , Summer 1983 61 14. J u v e n i l e S a l m o n i d P o p u l a t i o n Dynamics T h r o u g h t h e 2 Au g u s t 1983 F l o o d a t Sachs C r e e k 62 15. A t - t e s t A n a l y s i s of J u v e n i l e Coho L e n g t h F r e q u e n c i e s on S t u d y S i t e s a t Sachs C r e e k , Summer 1983 63 16. A Summary of t h e E f f e c t s of G a b i o n I n s t a l l a t i o n on M a j o r P h y s i c a l - C h e m i c a l C o n d i t i o n s and t h e i r R e l a t i o n t o S a l m o n i d P r o d u c t i o n i n S a c h s C r e e k 85 v i i 17. Gabion I n s t a l l a t i o n Costs at Sachs Creek. 87 18. Increases i n Returning Pinks Required to O f f s e t I n s t a l l a t i o n Costs f o r Treatment S i t e III at Sachs Creek 9 4 v i i i L i s t of F i g u r e s 1. S t u d y S i t e L o c a t i o n s on S a c h s Creek 6 2. L o n g i t u d i n a l P r o f i l e of S a c h s C r e e k 7 3. E s t i m a t e d Spawner E s c a p e m e n t s a t Sachs C r e e k 8 4. L o g g i n g H i s t o r y of Sachs C r e e k 9 5. G e n e r a l i z e d View of G a b i o n C o n f i g u r a t i o n • 16 6. Flow D i a g r a m of G a b i o n I n s t a l l a t i o n 18 7. P r o c e d u r e f o r P l a c i n g S c o u r M o n i t o r s i n t o t h e Streambed. 22 8. I s o p l e t h s of G r a v e l S c o u r Depth(cm) as I n d i c a t e d by V e r t i c a l E r o s i o n M o n i t o r s a t G a b i o n S i t e s a t S achs C r e e k i n Y e a r 1 and Year 2 31 9. T e m p o r a l Changes i n B a t h y m e t r i c C o n t o u r s (cm) Below an A r b i t r a r y . B e n c h m a r k a t T r e a t m e n t S i t e I a t S a c h s C r e e k . 33 10. T e m p o r a l Changes i n B a t h y m e t r i c C o n t o u r s (cm) Below an A r b i t r a r y Benchmark a t T r e a t m e n t S i t e II a t S a c h s C r e e k . 34 11. T e m p o r a l Changes i n B a t h y m e t r i c C o n t o u r s (cm) Below an A r b i t r a r y Benchmark a t T r e a t m e n t S i t e I I I a t S a c h s C r e e k 35 12. T e m p o r a l Changes i n A v e r a g e A g g r a d a t i o n Above G a b i o n s a t T r e a t m e n t S i t e I , S a c h s C r e e k 36 13. G r a v e l c o m p o s i t i o n of S t u d y S i t e s a t Sachs C r e e k P r e -and P o s t - G a b i o n I n s t a l l a t i o n 45 14. Mean P e r c e n t of P a r t i c l e s L e s s Than 1.2mm and 0.30mm on S t u d y S i t e s a t S achs C r e e k . . . . ." 46 15. S e d i m e n t a t i o n A c c u m u l a t e d i n Sediment T r a p s on S t u d y S i t e s a t S a c h s C r e e k , December 1982 t o March 1983. ...48 16. L o n g i t u d i n a l D i s t r i b u t i o n of A d u l t Salmon i n S a c h s C r e e k , September t o November, 1982 50 17. Accummulated T h e r m a l U n i t s a t Sachs C r e e k Over F a l l and W i n t e r 1982-1983 56 i x 18. J u v e n i l e Coho L e n g t h F r e q u e n c i e s on S t u d y S i t e s a t S a c h s C r e e k , P r e - f l o o d , Summer 1983 ..64 X Ac knowledgement Many i n d i v i d u a l s and a g e n c i e s have c o n t r i b u t e d t o t h i s p r o j e c t . The m a j o r i t y of t h e f u n d i n g d u r i n g t h e c o n s t r u c t i o n p h a s e was p r o v i d e d by t h e i n t e r - a g e n c y s p o n s o r e d F i s h / F o r e s t r y I n t e r a c t i o n Program ( F F I P ) . T h e s e a g e n c i e s i n c l u d e d B.C. M i n i s t r y of F o r e s t s , B.C. M i n i s t r y o f E n v i r o n m e n t , and Canada Department of F i s h e r i e s and O c e a n s . F u n d i n g i n y e a r 2 was t h r o u g h a Program of R e s e a r c h by U n i v e r s i t i e s i n F o r e s t r y (PRUF) g r a n t s p o n s o r e d by t h e C a n a d i a n F o r e s t r y S e r v i c e . O t h e r s i g n i f i c a n t c o n t r i b u t i o n s a r e g r a t e f u l l y a c k n o w l e d g e d : D. K e n d a l l , D. K e n d a l l and Sons, Queen C h a r l o t t e C i t y , ; P. S l a n e y , B.C. F i s h and W i l d l i f e B r a n c h , V a n c o u v e r ; J . C o n n e r s , M a c M i l l a n B l o e d e l , J a s k a t l a D i v i s i o n ; G. B r e n n e n s t u h l and R. F r a n k , Crown F o r e s t s , S a n d s p i t ; F. Beban, W e s t r o c k C o n t r a c t i n g , S a n d s p i t ; and G. D e r k s e n , EPS, V a n c o u v e r . Manpower a s s i s t a n c e so c r i t i c a l t o t h i s p r o j e c t was p r o v i d e d by t h e F i s h e r i e s Employment B r i d g i n g A s s i s t a n c e Program; t h a n k s t o R o b e r t , J o h n , P e r c y , Jo e and Ted f o r h a u l i n g a l l t h o s e r o c k s and t w i s t i n g t h a t w i r e . The i l l u s t r a t i o n s e n c l o s e d were d r a f t e d by F F I P o f f i c e s t a f f p r o v i d e d by t h e D e partment o f F i s h e r i e s and O c e a n s ; t h a n k s t o L. W h i t e , D. D i m o f f , A. B a k k t u s , D. Day and S. P a r k e r . T e c h n i c a l a s s i s t a n c e i n e v a l u a t i n g t h e g a b i o n s was a p p r e c i a t e d o f D. B o u i l l o n , J . E l l i s and M. M o r r i s . H e l p f u l o n - s i t e s u g g e s t i o n s were r e c e i v e d from D r . L. Beaven, L. D u t t a , B. E c c l e s , E. H a r d i n g , J . Lamb, K. Moore, D. T r i p p , and o t h e r s . T h a n k s t o F F I P ' s T e c h n i c a l A d v i s o r y Committee (T. B a k e r , M. B r o w n l e e , A. Cowan, T. D y e r , J . Lamb, K. Moore, L. P o w e l l , J . Schwab, J . W a l k e r , V. W e l l b u r n and D. W i l f o r d ) f o r p r o g r a m d i r e c t i o n and e d i t i n g p r e v i o u s d r a f t s . S i n c e r e a p p r e c i a t i o n f o r a c a d e m i c a d v i c e , t h e g e n e r o u s use of e q u i p m e n t , and e d i t i n g p r e v i o u s d r a f t s i s e x t e n d e d t o my t h e s i s c o m m i t t e e : Dr. T.G. N o r t h c o t e - S u p e r v i s o r , D r . M. F e l l e r , D r . D. G o l d i n g , Dr. G. Hartman, V. P o u l i n , and P. S l a n e y . S p e c i a l t h a n k s t o F F I P p r o g r a m manager, V. P o u l i n , w i t h o u t whom t h i s p r o j e c t would n o t have been p o s s i b l e . 1 I . INTRODUCTION C o a s t a l f o r e s t h a r v e s t i n g and s a l m o n i d f i s h e r i e s have been c o n f l i c t i n g r e s o u r c e u s e s r e c e i v i n g i n c r e a s e d a t t e n t i o n f r o m r e s o u r c e managers and t h e p u b l i c . Lack o f knowledge of h a r v e s t i n g i m p a c t s on t h e f i s h e r i e s r e s o u r c e has s t i m u l a t e d many i n v e s t i g a t i o n s , most n o t a b l y t h e i n t e n s i v e s t u d i e s on the A l s e a w a t e r s h e d , Oregon ( M o r i n g 1975) and on 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 , V a n c o u v e r I s l a n d (Hartman 1982). One p r o b l e m n o t s a t i s f a c t o r i l y d e a l t w i t h i n t h e s e s t u d i e s i s t h e e f f e c t of mass w a s t i n g on t h e f i s h e r i e s r e s o u r c e ( D r . J . H a l l pers.comm.) 1 . S t e e p l a n d l o g g i n g has a c c e l e r a t e d t h e r a t e of l a n d s l i d e s i n t h e c o a s t a l m a i n l a n d ( M e r s e r e a u and D y r n e s s 1972, O ' L o u g h l i n 1972, Swanston and Swanson 1976) and p a r t i c u l a r l y i n t h e Queen C h a r l o t t e I s l a n d s ( G i m b a r v e s k y MS1984, Rood MS 1984, W i l f o r d and Schwab 1982). The n e g a t i v e i m p a c t s of l a n d s l i d e s on f i s h -b e a r i n g s t r e a m s have been q u a n t i f i e d i n Oregon ( E v e r e s t and Meehan 1981), and W a s h i n g t o n ( C e d e r h o l m and S a l o 1979). The most d e s t r u c t i v e t y p e of l a n d s l i d e from a f i s h e r i e s p e r s p e c t i v e i s t h e d e b r i s t o r r e n t , w h i c h d e s t a b i l i z e s s t r e a m s , c a u s i n g t h e o r i g i n a l m e a n d e r i n g c h a n n e l s t o g i v e way t o more c h u t e - l i k e c h a n n e l s d e v o i d of t h e i n t e g r a l l o g s w h i c h p r o v i d e s t r e a m d i v e r s i t y and s t a b i l i z e d p o c k e t s o f spawning g r a v e l s and r e a r i n g a r e a s . The i m p e t u s f o r t h i s s t u d y l i e s i n t h e need t o d e v e l o p a p p l i e d r e s t o r a t i o n t e c h n i q u e s f o r s a l m o n i d spawning s t r e a m s Comment by J . H a l l . IN: G.F. Hartman ( E D . ) . C a r n a t i o n C r e e k Workshop. M a l a s p i n a C o l l e g e , Nanaimo, B.C. A p r i l 1982. P. 401 . 2 damaged by l a n d s l i d e s i n t h e Queen C h a r l o t t e I s l a n d s . Many f a c t o r s c o n t r i b u t e t o low e a r l y s u r v i v a l of p i n k ( O n c o r h y n c h u s g o r b u s c h a ) and chum ( 0 . k e t a ) salmon s t o c k s . Egg t o f r y s u r v i v a l has o f t e n been as low as 5% f o r w i l d s a l m o n i d s ( D i l l 1969, L a n g e r 1974, M c N e i l 1969), owing t o d r o u g h t , p r e d a t o r s , o v e r - p o p u l a t i o n of spawning a r e a s , and s e d i m e n t a t i o n ( B j o r n n 1968, C e d e r h o l m and S a l o 1979, K o s k i 1975, S h e l t o n and P o l l o c k 1966, S l a n e y e t a l . 1977, W i c k e t t 1958). G r a v e l s c o u r has a l s o been shown t o a f f e c t s a l m o n i d egg s u r v i v a l . D u r i n g s t o r m f l o w e v e n t s , e n t i r e s t o c k s of c h i n o o k salmon (0. t s h a w y t s c h a ) have been d e s t r o y e d by s c o u r (Gangmark and B a k k a l a 1960). S i m i l a r l y , M c N e i l (1966) a t t r i b u t e d a 90% l o s s of p i n k and chum salmon eggs t o a s i n g l e s t o r m f l o w e v e n t ; he s u g g e s t e d t h a t m o r t a l i t y was c a u s e d by b o t h m e c h a n i c a l a b r a s i o n and s t r e a m f l u s h i n g a c t i o n w h i c h removed embryos from t h e p r o t e c t i v e g r a v e l . D e b r i s t o r r e n t s and streambank l o g g i n g p r a c t i c e s i n t e n s i f y g r a v e l s c o u r by r e d u c i n g t h e f r e q u e n c y o f " o r g a n i c s t e p s " d e s c r i b e d by Heede ( 1 9 7 2 ) , t h e r e b y i n c r e a s i n g s t r e a m b e d g r a d i e n t s and s t o r m f l o w v e l o c i t i e s . R e d u c t i o n s i n s t a b l e l a r g e o r g a n i c d e b r i s d e c r e a s e d b o t h c h a n n e l " r o u g h n e s s " and abundance of g r a v e l a s s o c i a t e d w i t h t h e d e b r i s (Swanson e t a l . 1976). A d d i t i o n a l s t r e a m b e d i n s t a b i l i t y and d e g r a d a t i o n may have r e s u l t e d from s e d i m e n t s r e l e a s e d from damaged banks or d e p o s i t i o n a l z o n e s o f l a n d s l i d e s . R e c e n t d e v e l o p m e n t s of i n s t r e a m s t r u c t u r e s have s u c c e s s f u l l y p r o d u c e d s t a b i l i z e d s pawning a r e a s ( H a l l and Baker 3 1982). G a b i o n w e i r s ( w i r e c a g e s t h a t a r e p l a c e d i n t o t h e s t r e a m b o t t o m and f i l l e d w i t h s m a l l r o c k ) were one of s e v e r a l s t r e a m r e h a b i l i t a t i o n t e c h n i q u e s recommended f o r e v a l u a t i o n i n t h e Queen C h a r l o t t e I s l a n d s by t h e F i s h / F o r e s t r y I n t e r a c t i o n Program ( F F I P ) 2 ( B u s t a r d MS1983). G a b i o n w e i r s can s t a b i l i z e g r a v e l movement by i m p o u n d i n g g r a v e l s and r e d u c i n g s t o r m f l o w e n e r g y (Gerke MS1974). G a b i o n s have been f o u n d t o r e d u c e s t r e a m b e d g r a d i e n t and t o impound g r a v e l beds w i t h a mean p a r t i c l e s i z e t y p i c a l of s a l m o n i d spawning a r e a s (Moreau 1981). F u r t h e r m o r e t h e d e p t h of g r a v e l s c o u r c a n be r e d u c e d by s u b s e q u e n t r e d u c t i o n s i n s t o r m f l o w s h e a r s t r e s s a t t h e s u r f a c e of t h e impounded g r a v e l s ( L i s l e 1981). The s p e c i f i c o b j e c t i v e s of t h i s s t u d y were t o :1) examine t h e e f f e c t i v e n e s s of g a b i o n s i n i m p r o v i n g g r a v e l q u a l i t y ( d i s s o l v e d o xygen, p e r m e a b i l i t y , g r a v e l c o m p o s i t i o n and d e p t h of s c o u r ) as w e l l as t h e e a r l y s u r v i v a l of p i n k and chum salmon under c o n d i t i o n s t y p i c a l o f t h e Queen C h a r l o t t e I s l a n d s , and 2) i d e n t i f y s pawning g r a v e l c h a r a c t e r i s t i c s r e l a t e d t o e a r l y s u r v i v a l i n p i n k and chum salmon. 2 The F i s h / F o r e s t r y I n t e r a c t i o n P r ogram ( F F I P ) was a m u l t i - a g e n c y s p o n s o r e d i n v e s t i g a t i o n i n t o t h e e x t e n t , c a u s e s and a m e l i o r a t i o n o f l a n d s l i d e damage i n f o r e s t s and s t r e a m s of t h e Queen C h a r l o t t e I s l a n d s . The Program was c o n t r a c t e d t o V.A. P o u l i n & A s s o c i a t e s L t d . o f V a n c o u v e r B.C. One Component of F F I P u n d e r t a k e n by t h e a u t h o r was t o e v a l u a t e g a b i o n s as a r e h a b i l i t a t i o n t e c h n i q u e f o r l a n d s l i d e - d a m a g e d s t r e a m s . 4 I I . THE STUDY AREA Sachs C r e e k on t h e n o r t h e a s t end of Moresby I s l a n d was s e l e c t e d as t h e s t u d y s t r e a m f o r t h i s p r o j e c t . In h i s r e v i e w of s t r e a m r e h a b i l i t a t i o n t e c h n i q u e s f o r F F I P , B u s t a r d (MS1983) recommended Sachs C r e e k f o r g a b i o n e v a l u a t i o n . I t was c o n s i d e r e d t h e most s u i t a b l e s t r e a m f o r s e v e r a l r e a s o n s : i . The s t r e a m l i e s i n c l o s e p r o x i m i t y t o s o u r c e s of manpower, equipment and g r a v e l s u p p l i e s . i i . The s t r e a m was t h e s i t e of p r e v i o u s s a l m o n i d enhancement work by M a c M i l l a n B l o e d e l . Hence, t h e r e was i n t e r e s t i n f u r t h e r r e s t o r a t i o n work t h e r e . i i i . The s t r e a m had a major d e b r i s t o r r e n t i n 1974, d e p o s i t i n g t o n n e s of m a t e r i a l j u s t u p s t r e a m of salmon spawning h a b i t a t . R e l e a s e of e n t r a p p e d s e d i m e n t s a f t e r m e c h a n i c a l r e m o v a l of t h e t e r m i n a l l o g jam by t h e F e d e r a l Department o f F i s h e r i e s and Oceans i n 1978 has s u b s e q u e n t l y d e s t a b i l i z e d t h e s t r e a m as e v i d e n c e d by a c t i v e l a t e r a l c h a n n e l m i g r a t i o n f o r s e v e r a l h u n d r e d m e t e r s downstream. T h i s l a t e r a l e r o s i o n and e x c e s s i v e s e d i m e n t t r a n s p o r t i s s i m i l a r t o many o t h e r l a n d s l i d e - d a m a g e d s t r e a m s . i v . The s t r e a m s i z e i s a c c e p t a b l e f o r i n - s t r e a m work and s t u d i e s , h a v i n g an a v e r a g e w e t t e d w i d t h o f 10 m e t e r s and a summer d i s c h a r g e o f a b o u t 0.07 m 3/sec (2-3 c f s ) . v. The s t r e a m s u p p o r t s s i g n i f i c a n t r u n s of p i n k , chum and coho (O. k i s u t c h ) salmon and a s m a l l r u n of s t e e l h e a d t r o u t (Salmo q a i r d n e r i ) . 5 Sachs C r e e k d r a i n s i n t o S k i d e g a t e I n l e t on the n o r t h e r n end of Moresby I s l a n d and i s about 11 km l o n g w i t h i n a 19 km 2 w a t e r s h e d ( F i g u r e 1 ) . I t s b e d r o c k t y p e i s m a i n l y s e d i m e n t a r y . The s t r e a m b e d s l o p e g r a d i e n t a v e r a g e s 1% f o r t h e l o w e r m o s t 1 km, 2% f o r t h e n e x t 1 km, 3% f o r t h e n e x t 0.5 km, t h e n r i s e s s h a r p l y u p s t r e a m t h r o u g h a canyon ( F i g u r e 2 ) . The s t r e a m d i s c h a r g e a v e r a g e s a b o u t 0.3 m 3/sec (12 c f s ) d u r i n g t h e f a l l w i t h s t o r m f l o w d i s c h a r g e up t o about 65m 3/sec ( 2 3 0 0 c f s ) b a s e d on u n m e t e r e d c a l c u l a t i o n s (Manning's E q u a t i o n ) . From l a t e A u g u s t t h r o u g h November, Sachs C r e e k s u p p o r t s r u n s of a d u l t chum, p i n k and coho salmon s u c c e s s i v e l y . P i n k s and chum spawn i n t h e l o w e r 1.5 km w i t h maximum d e n s i t y from 0.6 km t o 0.8 km above t h e e s t u a r y ( F i g u r e 16). Coho d i s t r i b u t e t h e m s e l v e s more e v e n l y t h r o u g h t h e lower 2.5 km u p s t r e a m t o t h e canyon b a r r i e r . P i n k salmon e x h i b i t a two y e a r c y c l e , w i t h even y e a r s h a v i n g dominant r u n s t y p i c a l of most Queen C h a r l o t t e I s l a n d s s t r e a m s . "Even, y e a r " p i n k salmon e s c a p e m e n t s have h i s t o r i c a l l y r a n g e d from a b o u t 200 t o 30,000 w i t h a mean of a b o u t 4,600 ( F i g u r e 3 ) . R e c e n t e s c a p e m e n t s have been about 3,000 t o 4,000. A d u l t chum e s c a p e m e n t s h i s t o r i c a l l y have r a n g e d from a b o u t 25 t o 1,500; however, t h e y have s e l d o m e x c e e d e d 200 i n t h e p a s t d e c a d e . E s t i m a t e d coho e s c a p e m e n t s have r a r e l y been i n e x c e s s o f 200 a d u l t s . S a c h s C r e e k w a t e r s h e d l i e s m a i n l y w i t h i n M a c M i l l a n B l o e d e l ' s TFL 39, w i t h a b o u t 5% i n Crown F o r e s t ' s TFL 2. About 40 p e r c e n t of t h e w a t e r s h e d has been l o g g e d s i n c e t h e e a r l y 1960's ( F i g u r e 4 ) . 6 FIGURE I ! Site Locations on Sachs Creek. •a r35 DISTANCE UPSTREAM OF ESTUARY (km) FIGURE 2= Longitudinal Profile of Sachs Creek. 8 50 0 0 0 i z UJ CL < O CO UJ < CO Li Q < 10000 5 0 0 0 0 0 0 500 100 50 20 10000 5 0 0 0 0 0 0 500 100 50-20 Even Year 1930 1940 1950 I960 1970 1980 YEAR PINK CHUM FIGURE 3 = Estimated Spawner Escapements at Sachs Creek, Q.C.I, a) Federal Dept. Fisheries and Oceans records. 9 77-7 / ' - • ) A ^ OH f:. 0H\ ^ / ^ . / , ~ N A/ GH76 176-77//iV jr. /•/ M O R E S B Y I S L A N D Scale 1:50,000 i LEGEND 1 km Rivers and Creeks Watershed Boundaries Logged Areas Unlogged Areas FIGURE 4 : Logging History of Sachs Creek. Symbols: e l o g g e d a r e a s H h i g h l e a d RE ... r e g e n e r a t i o n e s t a b l i s h e d P p r o p o s e d lo g g i n g eg: 6H74 y e a r l o g g e d t y p e of lo g g i n g d e p i c t i n g l o g g e d a r e a s , p a s t and p r e s e n t 10 I I I . METHODS T h r e e s i t e s on S achs C r e e k were s e l e c t e d f o r g a b i o n i n s t a l l a t i o n . G a b i o n s were i n s t a l l e d i n p a i r s a t e a c h of t h e 3 t r e a t m e n t s i t e s and were matched w i t h two c o n t r o l s i t e s t o e n a b l e s t a t i s t i c a l e v a l u a t i o n of t h e r e s u l t s . The a p p r o a c h t o e v a l u a t i n g g a b i o n s i n v o l v e d 3 main p h a s e s : i . P r e - i n s t a l l a t i o n s i t e a n a l y s i s , i n c l u d i n g s t r e a m and s i t e s e l e c t i o n , s i t e s u r v e y i n g , i n t r a g r a v e l d i s s o l v e d oxygen and p e r m e a b i l i t y s a m p l i n g . i i . G a b i o n c o n s t r u c t i o n and i n s t a l l a t i o n , i n v o l v i n g 8 men and heavy e q u i p m e n t . i i i . P o s t - i n s t a l l a t i o n s i t e a n a l y s i s , i n c l u d i n g m o n i t o r i n g of salmon spawner u t i l i z a t i o n , c o n f i g u r a t i o n a l c h a n g e s i n g r a v e l , measurements of s u b s t r a t e s t a b i l i t y , g r a v e l q u a l i t y , and salmon egg s u r v i v a l . The p r o j e c t was i n i t i a t e d i n May 1982 w i t h r e c o n n a i s s a n c e s u r v e y s o f p o t e n t i a l s i t e s on v a r i o u s Queen C h a r l o t t e I s l a n d s t r e a m s . F i n a l s i t e s e l e c t i o n , p r e - i n s t a l l a t i o n s a m p l i n g and s u r v e y i n g were c o m p l e t e d i n J u l y 1982. The c o n s t r u c t i o n -i n s t a l l a t i o n p hase was c o n d u c t e d d u r i n g t h e month of A u g u s t 1982. P a r a m e t e r s n o t e d above were r e - m e a s u r e d a t 0.5 y e a r , 1 y e a r , and 1.5 y e a r i n t e r v a l s a f t e r i n s t a l l a t i o n . 11 1. GABION DESCRIPTION G a b i o n s (0.91m h i g h by 0.91m wide) c o n s i s t e d of g a l v a n i z e d s t e e l t w i s t e d mesh (3mm diam., 8cm by 10cm a p e r t u r e ) m a n u f a c t u r e d by M a c c a f e r r i G a b i o n s . C o m b i n a t i o n s of g a b i o n s 1.82m, 2.73m, and 3.64m l o n g were w i r e d t o g e t h e r t o span t h e s t r e a m (page 19). 2. STUDY S I T E LOCATIONS S t u d y s i t e s were s e l e c t e d l a r g e l y u s i n g c r i t e r i a d e v e l o p e d i n N o r t h e r n C a l i f o r n i a (Moreau 1981). In b r i e f , t h e s e c r i t e r i a i n c l u d e d : 1) a d e q u a t e r o a d a c c e s s , 2) a s t r a i g h t s e c t i o n of s t r e a m c h a n n e l , and 3) a wide f l o o d p l a i n w i t h s h a l l o w b a n k s . T h r e e t r e a t m e n t s i t e s were s e l e c t e d - e a c h r e p r e s e n t i n g d i f f e r e n t h a b i t a t c o n f i g u r a t i o n s . T r e a t m e n t S i t e I was l o c a t e d 2300m u p s t r e a m of t h e e s t u a r y a t t h e p o i n t of e g r e s s o f t h e 1974 d e b r i s t o r r e n t ( F i g u r e s 1 and 2) i n a r i f f l e a t t h e t a i l of a p o o l . T r e a t m e n t S i t e I I was s i t u a t e d i n a 60m r i f f l e 950m from th e e s t u a r y . T r e a t m e n t S i t e I I I was i n a d e e p e r , slow moving ( g l i d e ) s e c t i o n of t h e s t r e a m 880m above t h e e s t u a r y . A l l s i t e s met t h e recommended c r i t e r i a and were, c o n s i d e r e d m a r g i n a l spawning h a b i t a t ; i . e . t h e s i t e s l a c k e d s u i t a b l e spawning s u b s t r a t e , h a v i n g mean p a r t i c l e d i a m e t e r s (D50) c o n s i d e r a b l y l a r g e r o r s m a l l e r t h a n t h e 25mm f o u n d i n t h e t o p l a y e r s o f C a r n a t i o n C r e e k chum salmon spawning a r e a s ( S c r i v e n e r and B r o w n l e e 1982) Two c o n t r o l s i t e s were s e l e c t e d f o r e a c h t r e a t m e n t s i t e i n o r d e r t o a p p l y p a i r e d t - t e s t s f o r s t a t i s t i c a l a n a l y s i s . One 12 c o n t r o l ( "A" - poor spawning h a b i t a t ) was s e l e c t e d t o r e s e m b l e t h e p a r t i c u l a r t r e a t m e n t s i t e b e f o r e t h e g a b i o n s were i n s t a l l e d . The s e c o n d c o n t r o l ( "B" - p r i m e spawning h a b i t a t ) was s e l e c t e d a p r i o r i t o r e s e m b l e t h e t r e a t m e n t s i t e a f t e r t h e g a b i o n s were i n s t a l l e d . T h i s was a c c o m p l i s h e d by s e l e c t i n g 20m l o n g r i f f l e s a t t h e t a i l s of p o o l s h a v i n g e i t h e r A) poor spawning c o n d i t i o n s or B) s u i t a b l e water d e p t h , v e l o c i t y and s u b s t r a t e f o r s p a w n i n g . C r i t e r i a f o r s u i t a b l e spawning c o n d i t i o n s a p p r o x i m a t e d h i g h p r o b a b i 1 i t y - o f - u s e v a l u e s (page 24 and A p p e n d i x A ) . O n l y m i n i m a l i n f l u e n c e s o f g a b i o n i n s t a l l a t i o n were a n t i c i p a t e d on t h e s e c o n t r o l s i t e s . Two methods of p a r a m e t e r c o m p a r i s o n between th e t r e a t m e n t and t h e c o n t r o l s i t e s ( b o t h t y p e s A and B of c o n t r o l where p o s s i b l e ) were u s e d . F i r s t l y , mean v a l u e s of t h e v a r i a b l e s were c a l c u l a t e d f o r e a c h s i t e . S e c o n d l y , i n d i v i d u a l sample p o i n t s w i t h i n t h e t r e a t m e n t s i t e s , b a s e d on d i s t a n c e downstream of t h e i n i t i a l p o o l and d i s t a n c e f r o m e i t h e r streambank, were p a i r e d w i t h r e p r e s e n t a t i v e p o i n t s i n t h e c o n t r o l s i t e s . A p o r t a b l e g r i d s y s t e m u s i n g benchmarks on e i t h e r bank f a c i l i t a t e d t h i s c o m p a r i s o n . S t a t i s t i c a l a n a l y s i s u s i n g t h e two t y p e s of c o n t r o l s i t e s p r o v i d e d a more r i g o r o u s c o m p a r i s o n t h a n u s i n g b e f o r e - and a f t e r - c o m p a r i s o n s w i t h o u t c o n t r o l s . 3. PRE-TREATMENT S I T E ANALYSIS I n t r a g r a v e l p e r m e a b i l i t y and d i s s o l v e d oxygen, g r a v e l c o m p o s i t i o n and s t r e a m b e d t o p o g r a p h y were measured p r i o r t o g a b i o n i n s t a l l a t i o n . Measurement o f t h e above v a r i a b l e s was done on a s t r a t i f i e d g r i d s y s t e m r a t h e r t h a n on a randomly 1 3 s e l e c t e d b a s i s . The s t r a t i f i e d d e s i g n e n a b l e d v a l u e s a t p o i n t s i n t r e a t m e n t s i t e s t o be p a i r e d w i t h t h o s e i n c o n t r o l s i t e s f o r t - t e s t a n a l y s i s . I n t r a g r a v e l d i s s o l v e d oxygen was d e t e r m i n e d f r om 18 t o 21 100ml samples p e r s i t e of i n t r a g r a v e l w a t e r e x t r a c t e d from 25cm below t h e g r a v e l s u r f a c e w i t h a s t a i n l e s s s t e e l s y r i n g e . D i s s o l v e d oxygen i n t h e s e water samples was i m m e d i a t e l y measured w i t h r e g u l a r l y c a l i b r a t e d Y e l l o w S p r i n g s I n s t r u m e n t Co. oxygen m e t e r s . S e m i - m i c r o W i n k l e r t i t r a t i o n s (Rand e t a l . 1975) were u s e d f o r f u r t h e r c a l i b r a t i o n of t h e oxygen m e t e r s . I n t r a g r a v e l p e r m e a b i l i t y was measured u s i n g a Mark VI s t a n d p i p e ( T e r h u n e 1958). T h i s t e c h n i q u e o p e r a t e d on t h e p r i n c i p l e of measured f l o w i n t o a p i p e t h r o u g h p e r f o r a t i o n s 25cm below s u b s t r a t e s u r f a c e . The d r i v i n g f o r c e was a n e g a t i v e p r e s s u r e head of 2.5cm, p r o v i d e d by a hand s u c t i o n pump i n t h e p i p e . Between 15 and 21 measurements were made p e r s i t e . S t r e a m bottom c o n t o u r s were d e t e r m i n e d i n o r d e r t o e v a l u a t e c h a n g e s i n t h e i r c o n f i g u r a t i o n a n t i c i p a t e d w i t h g a b i o n p l a c e m e n t . The t r e a t m e n t s i t e e l e v a t i o n s were s u r v e y e d by t h e o d o l i t e ( w i l d ) . Measurements were made on a b o u t 60 s t a t i o n s w i t h i n t h e g r i d s y s t e m s , as w e l l a s on c r o s s s e c t i o n s a t 10m i n t e r v a l s . S t r e a m g r a v e l was sampled a t t h e g a b i o n s i t e s w i t h two t e c h n i q u e s t o e n a b l e c o m p a r i s o n w i t h g r a v e l c o m p o s i t i o n a t t h e s i t e s a f t e r g a b i o n p l a c e m e n t . The s t a t i o n s sampled were s t r a t i f i e d ( u s i n g t h e g r i d system) a c r o s s t h e w i d t h of t h e st r e a m ^ and 2m u p s t r e a m of t h e f u t u r e l o c a t i o n s of l o w e r 1 4 g a b i o n s . F o r p r e - i n s t a l l a t i o n a n a l y s i s , seven g r a v e l samples were t a k e n i n T r e a t m e n t S i t e I I I u s i n g a M c N e i l g r a v e l s a m p l e r ( C e d e r h o l m and S a l o 1979). G r a v e l s a t T r e a t m e n t S i t e II were sample d by two t e c h n i q u e s ; e a c h sample w i t h t h e M c N e i l g r a v e l s a m p l e r was matched w i t h a f r e e z e - c o r e sample ( S c r i v e n e r and B r o w n l e e 1982). G r a v e l c o m p o s i t i o n was a n a l y z e d u s i n g 18 s i e v e s i z e s t o a c c u r a t e l y i n d i c a t e c o m p o s i t i o n of f i n e s . The l a r g e s u b s t r a t e s i z e a t T r e a t m e n t S i t e I ( p r e - i n s t a l l a t i o n ) p r e c l u d e d s a m p l i n g by e i t h e r method. Hence, 4 randomly s e l e c t e d s t a t i o n s a t T r e a t m e n t S i t e I were p h o t o g r a p h e d f o r l a t e r a n a l y s i s . The a n a l y s i s i n v o l v e d c a l c u l a t i n g s u r f a c e p a r t i c l e d i a m e t e r f r e q u e n c i e s from 140 (random) measurements u s i n g t h e p h o t o g r a p h i c s l i d e s p r o j e c t e d t o a c t u a l s i z e . 4. GABION CONSTRUCTION AND INSTALLATION S e l e c t i o n o f a g a b i o n c o n f i g u r a t i o n f o l l o w e d r e v i e w of s e v e r a l t e s t e d i n W a s h i n g t o n , Oregon and C a l i f o r n i a ( A n d e r s o n MS1981, A n d e r s o n and Cameron 1980, E n g e l s MS1975, G e r k e MS1974, Moreau 1981, Ward MS1982). Moreau (1981) i n C a l i f o r n i a f o u n d t h a t a p a i r e d V - s h a p e d c o n f i g u r a t i o n was t h e most s u c c e s s f u l d e s i g n i n t r a p p i n g b e d l o a d s u i t a b l e f o r s a l m o n i d spawning and w i t h s t a n d i n g s t o r m f l o w s . T h i s c o n f i g u r a t i o n was u s e d a t a l l t r e a t m e n t s i t e s i n t h i s s t u d y w i t h some m i n o r m o d i f i c a t i o n s ( F i g u r e 5 ) . S p l a s h a p r o n s were m o d i f i e d t o m a x i m i z e t h e d e p t h o f t h e p l u n g e p o o l c r e a t e d a t t h e downstream edge of t h e g a b i o n s . The m o d i f i c a t i o n was made t o p r e v e n t u n d e r c u t t i n g t h e g a b i o n y e t f a c i l i t a t e a d u l t m i g r a t i o n . The s p l a s h a p r o n s measured 0.30m h i g h by 0.91m wide by 1.82m l o n g and were 1 5 i n s t a l l e d u n d e r n e a t h t h e g a b i o n but e x t e n d i n g a p p r o x i m a t e l y 0.6m beyond th e g a b i o n t o form a s c o u r - r e s i s t a n t p l a t f o r m a t t h e base of t h e g a b i o n apex ( F i g u r e 5 ) . G a b i o n s were p o s i t i o n e d so as t o a l l o w a d u l t salmon m i g r a t i o n but t o p r e v e n t l a t e r a l bank s c o u r (Moreau 1981). The t o p of t h e u p s t r e a m g a b i o n was p o s i t i o n e d 50cm above t h a t of t h e o r i g i n a l s t r e a m b e d . To a c h i e v e t h i s h e i g h t , t h e s t r e a m b e d was e x c a v a t e d t o a d e p t h of 50cm and t o 90cm i n t h e r e g i o n of t h e s p l a s h a p r o n s . The e l e v a t i o n of t h e downstream g a b i o n was c a l c u l a t e d from c r i t e r i a g i v e n by Moreau <1981) and Reeves and R o e l o f s ( 1 9 8 2 ) ; i . e . t h e t o p o f t h e downstream g a b i o n was l e v e l w i t h t h e base of t h e u p s t r e a m one. A l t h o u g h s u r v e y i n g t e c h n i q u e s were u s e d , t h e a c t u a l p l a c e m e n t v a r i e d up t o 10 cm from t h e s e g u i d e l i n e s . G a b i o n t r e n c h e s were e x c a v a t e d t o p r o v i d e an 8cm t o 15cm d r o p a l o n g t h e t o p of t h e g a b i o n s from t h e streambank t o t h e apex, t h u s e n s u r i n g c o n c e n t r a t e d w a t e r f l o w f o r f i s h p a s s a g e d u r i n g c r i t i c a l summer low f l o w s . S i m i l a r l y , h o r i z o n t a l p l a c e m e n t of t h e g a b i o n s f o l l o w e d r e c ommendations by Moreau ( 1 9 8 1 ) . Recommended a n g l e s between the wings of t h e g a b i o n s v a r i e d from 90° t o 120° - t h e s h a r p e r t h e a n g l e , t h e l e s s r e s i s t a n c e t o s t o r m f l o w s . S u f f i c i e n t d i s t a n c e s between t h e g a b i o n s were s e l e c t e d t o e n a b l e p r o p e r e l e v a t i o n a l p o s i t i o n i n g a f t e r a c c o u n t i n g f o r s t r e a m b e d g r a d i e n t s . The g a b i o n ends were b u r i e d up t o 4m i n t h e s t r e a m b a n k s , and p r o t e c t e d by r i p r a p . S p e c i f i c c h a r a c t e r i s t i c s of t h e h o r i z o n t a l p l a c e m e n t were d e s c r i b e d f o r e a c h s i t e on pages 19 and 20. FIGURE 5 I GENERALIZED VIEW OF GABION CONFIGURATION 1 7 To p e r m i t s i t e usage by a l a r g e run of p i n k salmon, a n t i c i p a t e d i n f a l l of 1982, g a b i o n s i t e s were s u r c h a r g e d ( i . e . f i l l e d t o a h e i g h t l e v e l w i t h t h e t o p of t h e g a b i o n s ) w i t h g r a v e l s u i t a b l e f o r s p a w n i n g . A p p r o x i m a t e l y 300m 3 p e r s i t e of u n s o r t e d " r i v e r r u n " g r a v e l was d e l i v e r e d from a n e a r b y q u a r r y . A d d i t i o n a l manpower and heavy equipment were r e q u i r e d i n g a b i o n c o n s t r u c t i o n and i n s t a l l a t i o n . Seven men were s u p p l i e d t h r o u g h t h e F i s h e r i e s Employment B r i d g i n g A s s i s t a n c e Program ( P r o j e c t No. 566); crew s i z e v a r i e d f r o m one t o f i v e d u r i n g t h i s p h a s e . The heavy equipment u s e d t o e x c a v a t e g a b i o n s i t e s was s u p p l i e d by a l o c a l c o n t r a c t o r . The e q u i p m e n t s u p p l i e d i n c l u d e d a 12 y a r d 3 dump t r u c k , a 2 y a r d 3 f r o n t end l o a d e r , a 22 tonne 1 1/4 y a r d 3 b u c k e t e x c a v a t o r and a 3/4 y a r d 3 b u c k e t e x c a v a t o r . G a b i o n c o n s t r u c t i o n and i n s t a l l a t i o n was c a r r i e d o ut i n 20 s t e p s t o m i n i m i z e c o s t l y " i d l e e q u i p m e n t " t i m e ( F i g u r e 6 ) . I n - s t r e a m work was c a r r i e d o ut under g u i d e l i n e s and p e r m i t of t h e l o c a l D e p t . F i s h e r i e s and Oceans and P r o v i n c i a l F i s h and W i l d l i f e o f f i c e s . S t a n d a r d p r o c e d u r e s o u t l i n e d h e r e r e s t r i c t e d work t o l o w - f l o w p e r i o d s and p e r i o d s when t h e r e were no spawning s a l m o n i d s , d e v e l o p i n g eggs or l a r v a e i n t h e s y s t e m . 18 Site preparation a) tree removal b) reference marking Gabion Excavator gains assembly w access to creek Dig upstream trench Fill rock delivered Load and place splash aprons Excavator leaves the stream laterally i Distribute spawning gravel i Back-fill downstream trench ends Spawning gravel delivered Manually sort fill rock and fasten gabion lids In situ final assembly Begin downstream trenching Thread logging cables through gabions Load upstream gabions Manually sort fill rock and fasten gabion lids Load and place downstream splash apron In situ final assembly and thread logging cables through gabions Load downstream gabion Back - fill upstream trench ends FIGURE 6 | FLOW DIAGRAM OF GABION INSTALLATION 19 1. TREATMENT S I T E I . The i n t e r - g a b i o n d i s t a n c e s e l e c t e d f o r t h i s s i t e was 6.5m, l a r g e l y b a s e d on s u i t a b i l i t y of t h e streambank f o r k e y i n g i n t h e g a b i o n s . An a p i c a l a n g l e of 90° was used (Moreau 1981). T h r e e of t h e g a b i o n ends were b u r i e d 2m t o 4m i n t o t h e streambank; t h e f o u r t h was b u t t e d up and c a b l e d t o a s t a b l e l o g 1m i n t o t h e bank. The g a b i o n l e n g t h r e q u i r e d was 43m. An abundant s u p p l y of r i p r a p was a v a i l a b l e on t h i s p r e v i o u s l y d e s t a b i l i z e d s i t e ; h e n c e , a l l t h e banks were l e f t w e l l a r m o u r e d . C o m m e r c i a l l y s o r t e d g a b i o n f i l l r o c k was not r e q u i r e d on t h i s s i t e . 2. TREATMENT S I T E II The i n t e r - g a b i o n d i s t a n c e s e l e c t e d f o r t h i s s i t e was 10.5m w i t h an a p i c a l a n g l e of 9 0 ° . A l l f o u r g a b i o n ends were b u r i e d 3m t o 5m i n t o t h e s t r e a m b a n k . The t o t a l g a b i o n l e n g t h r e q u i r e d was 50m. N a t u r a l r i p r a p was a v a i l a b l e t o p r o t e c t t h e ends of t h e u p s t r e a m g a b i o n o n l y . Bank s c o u r from f a l l 1982 s t o r m f l o w s a t t h e downstream g a b i o n ends not p r o t e c t e d by r i p r a p was l a t e r s t o p p e d by h a n d p l a c i n g l a r g e a l d e r r o o t wads s e c u r e d w i t h l o g g i n g c a b l e s , and r i p r a p . C o m m e r c i a l l y s o r t e d g a b i o n f i l l r o c k (15cm t o 30cm d i a m e t e r ) was r e q u i r e d a t t h i s s i t e , owing t o a l a c k of s u i t a b l e n a t u r a l m a t e r i a l . In a d d i t i o n , 21m 3 of c o m m e r c i a l l y s o r t e d " d r a i n r o c k " of 2cm t o 15cm d i a m e t e r was d i s t r i b u t e d o v e r t h e spawning p l a t f o r m s t o d i l u t e t h e p r o p o r t i o n of f i n e s i n t h e r i v e r r u n g r a v e l s u s e d t o s u r c h a r g e t h e s i t e s . (The f i n e s l e s s t h a n 2.4mm were d i l u t e d t o 9% of g r a v e l c o m p o s i t i o n samples w i t h t h e a d d i t i o n of d r a i n r o c k . The amount 20 of f i n e s was g r e a t e r where no d r a i n r o c k was a p p l i e d - 11% and 19% f o r T r e a t m e n t S i t e s II and I I I r e s p e c t i v e l y ; F i g u r e 13.) 3. TREATMENT SITE I I I An i n t e r - g a b i o n d i s t a n c e of 10.5m was u s e d . The a p i c a l a n g l e of 120° was s e l e c t e d t o e n l a r g e t h e a r e a of spawning p l a t f o r m c r e a t e d by t h e downstream g a b i o n . T h r e e of t h e g a b i o n ends were b u r i e d 2m t o 4m i n t o t h e s treambank. The f o u r t h g a b i o n end was b u t t e d up and c a b l e d o n t o a s t a b l e l o g . The t o t a l g a b i o n l e n g t h r e q u i r e d was 35m. N a t u r a l r i p r a p was l a c k i n g a t t h i s s i t e so t h e s t r e a m b a n k s were i n i t i a l l y l e f t u n p r o t e c t e d . L a t e r a l bank s c o u r d u r i n g f a l l s t o r m f l o w s prompted hand p l a c e m e n t o f r i p r a p a t t h e s e g a b i o n e n d s . 5. POST-INSTALLATION S I T E ANALYSIS 1. GRAVEL STABILITY Depth of g r a v e l s c o u r was c l o s e l y m o n i t o r e d as a measure of g r a v e l s t a b i l i t y i n t h e 3 t r e a t m e n t and 3 o r 4 c o n t r o l s i t e s o v e r t h e w i n t e r of 1982 and t h e f a l l and w i n t e r o f 1983-84. A p p r o x i m a t e l y 20 v e r t i c a l e r o s i o n m o n i t o r s (VEMs) were i n s t a l l e d a t e a c h of t h e s e s i t e s i n December 1982, and a g a i n i n A u g u s t a n d / o r O c t o b e r 1983. The VEMs employed c o n s i s t e d of a column of 8 p e r f o r a t e d p l a s t i c g o l f b a l l s t h r e a d e d t h r o u g h w i t h 100 l b t e s t m o n o f i l a m e n t l i n e . The a s s e m b l y was i n s e r t e d v e r t i c a l l y i n t o t h e g r a v e l w i t h t h e method i l l u s t r a t e d i n F i g u r e 7. A p l a s t i c d i s c a t t h e d i s t a l end of t h e 1.5m l o n g m o n o f i l a m e n t p r e v e n t e d l o s s o f b a l l s r e l e a s e d by s c o u r i n g . The number of b a l l s s c o u r e d o u t of t h e g r a v e l a f t e r a s t o r m f l o w e v e n t was u s e d 21 as a measure of t h e d e p t h of s c o u r a t t h a t l o c a t i o n . The d e p t h s of s c o u r a t i n d i v i d u a l s t a t i o n s a t t r e a t m e n t s i t e s were p a i r e d w i t h t h a t a t c o n t r o l s i t e s f o r t - t e s t a n a l y s i s . 2. GRAVEL QUALITY The q u a l i t y of spawning g r a v e l s impounded by t h e g a b i o n s was examined t h r o u g h o u t t h e p o s t - i n s t a l l a t i o n p e r i o d . I n t r a g r a v e l d i s s o l v e d oxygen measurements (page 12) were t a k e n d u r i n g 1982-83 salmon egg i n c u b a t i o n . T h e s e were r e p e a t e d a l o n g w i t h p e r m e a b i l i t y measurements (page 13) i n summer 1983. S a m p l i n g on t h e g r i d s y s t e m s e n a b l e d p a i r i n g o f s t a t i o n s i n t r e a t m e n t and t h e i r c o n t r o l s i t e s f o r t - t e s t a n a l y s i s . Between 15 and 27 measurements were made a t e a c h s i t e . G r a v e l c o m p o s i t i o n was a n a l y z e d t w i c e a f t e r g a b i o n i n s t a l l a t i o n as f o l l o w s : a) t h r e e g r a v e l , samples were t a k e n from t h e s u r c h a r g e d spawning g r a v e l s a t e a c h of t h e t h r e e t r e a t m e n t s i t e s i m m e d i a t e l y f o l l o w i n g g a b i o n i n s t a l l a t i o n ; and b) f i v e s t a t i o n s were sampl e d a t a l l t r e a t m e n t and c o n t r o l s i t e s 1 y e a r a f t e r i n s t a l l a t i o n (summer 1983) t o d e t e c t c h a n g e s i n g r a v e l c o m p o s i t i o n a t t r i b u t e d t o w i n t e r s t o r m f l o w s and spawner a c t i v i t y . 22 / DRIVING ROD f-I WATER LEVEL DRIVING ROD REMOVED INNER PIPE REMOVED SCOUR .MONITOR INSERTED OUTER PIPE REMOVED A FIGURE 7 PROCEDURE FOR PLACING SCOUR MONITORS THE STREAM BED. INTO 23 S e d i m e n t a t i o n i s d e f i n e d i n t h i s s t u d y as t h e i n f i l t r a t i o n and i m p a c t i o n o f s t r e a m b e d g r a v e l s w i t h f i n e s e d i m e n t s l e s s t h a n 3mm. Between 10 and 16 s e d i m e n t t r a p s were d i s t r i b u t e d p e r s i t e a t t h e 3 t r e a t m e n t s i t e s and a t 5 of t h e c o n t r o l s i t e s t o d e t e c t d i f f e r e n c e s i n s e d i m e n t a t i o n r a t e s between t r e a t m e n t and c o n t r o l s i t e s on S a c h s C r e e k . The t r a p s c o n s i s t e d of wide-mouth 1.5 l i t e r p l a s t i c j a r s f i l l e d w i t h s o r t e d pea g r a v e l l a r g e r t h an 3mm. The t r a p s were b u r i e d f l u s h w i t h t h e s u r f a c e , as d e s c r i b e d by S l a n e y e t a l . ( 1 9 7 7 ) . The t r a p s c o l l e c t e d s e d i m e n t s from December 1982 t o March 1983 and were l a t e r a n a l y z e d by d r y s i e v i n g . About 60% of t h e t r a p s were d e s t r o y e d by s c o u r . A v e r a g e f i n e s e d i m e n t a c c u m u l a t i o n a t t h e t r e a t m e n t s i t e s were g r a p h i c a l l y compared t o t h a t of c o n t r o l s i t e s . 3. STREAMBED CONFIGURATION Stre a m b o t t o m c o n t o u r s of t h e g a b i o n s i t e s were s u r v e y e d w i t h an a u t o m a t i c l e v e l ( Kern) a t s e v e r a l t i m e s a f t e r i n s t a l l a t i o n : a) i m m e d i a t e l y f o l l o w i n g i n s t a l l a t i o n , b) a f t e r w i n t e r s t o r m f l o w s i n F e b r u a r y 1983, c) 1 y e a r a f t e r i n s t a l l a t i o n i n J u l y 1983, and d) a f t e r a s e c o n d c y c l e of w i n t e r s t o r m f l o w s i n F e b r u a r y 1984. An a d d i t i o n a l s u r v e y of T r e a t m e n t S i t e I was made f o l l o w i n g major c h a n g e s i n s t r e a m b e d c o n f i g u r a t i o n c a u s e d by t h e A u g u s t 1983 f l o o d . 24 4. SPAWNER UTILIZATION Two methods of m e a s u r i n g t h e s u i t a b i l t y of t r e a t m e n t s i t e s a s salmon spawning h a b i t a t were examined: 1) t a b u l a t i o n o f salmon spawner a c t i v i t y on a l l c o n t r o l and t r e a t m e n t s i t e s ; and 2) e v a l u a t i o n o f h a b i t a t s u i t a b i l i t y b a s e d on p r o b a b i 1 i t y - o f - u s e (Bovee and C o c h n a u e r 1977) c u r v e s d e v e l o p e d f o r S a c h s C r e e k p i n k s a l m o n . A c t u a l f i s h usage of t h e s i t e s was o b t a i n e d from p l o t t i n g s p awning l o c a t i o n s of spawning o r r e d d - d e f e n d i n g f e m a l e salmon. F i s h p o s i t i o n s u s u a l l y were mapped e v e r y o t h e r day t h r o u g h o u t t h e spawning s e a s o n of 1982 and e v e r y o t h e r week f o r t h e s m a l l e r r u n i n f a l l 1983. A s t a n d a r d f o r m was u s e d i n c o n j u n c t i o n w i t h t h e o n - s i t e r e f e r e n c e g r i d s y s t e m t o f a c i l i t a t e b o t h p l o t t i n g f i s h p o s i t i o n s and l a t e r a n a l y s i s . In a d d i t i o n , t h e u t i l i z e d p o r t i o n of t h e c r e e k was s u r v e y e d e v e r y 7 t o 10 d a y s from September t o December 1982. A p p r o x i m a t e t i m i n g of r u n s , abundance of salmon, and l o n g i t u d i n a l d i s t r i b u t i o n of t h e p i n k , chum, and coho salmon were r e c o r d e d . P r o b a b i l i t y - o f - u s e c u r v e s (Bovee and C o c h n a u e r 1977) were e s t a b l i s h e d f o r p i n k salmon i n O c t o b e r 1982 t o d e t e r m i n e whether c o n d i t i o n s c o n d u c i v e t o t h e i r spawning were f o u n d a t g a b i o n s i t e s . T h e s e c o n d i t i o n s may o r may not be r e l a t e d t o an i n t r a g r a v e l e n v i r o n m e n t r e q u i r e d f o r h i g h egg and a l e v i n s u r v i v a l . P a r a m e t e r s measured on a t o t a l of 230 r e d d s i n c l u d e d a v e r a g e water d e p t h , w a t e r v e l o c i t y a t spawner "nose h e i g h t " (5cm above t h e s u b s t r a t e ) , and s u r f a c e s u b s t r a t e c o m p o s i t i o n (a s u b j e c t i v e e s t i m a t e o f % g r a v e l s (2cm < x < 12cm) and "D50" -25 t h e d i a m e t e r a t w hich 50% of t h e s u r f a c e p a r t i c l e s a r e s m a l l e r or l a r g e r ) . The a v e r a g e p r o b a b i l i t y - o f - u s e c a l c u l a t e d f o r t h e t r e a t m e n t s i t e s was compared t o t h a t of r e s p e c t i v e c o n t r o l s i t e s . 5. EGG SURVIVAL Egg s u r v i v a l s t u d i e s complemented the above s t u d i e s i n two ways: a) t h e y were d e s i g n e d t o d e t e c t d i f f e r e n c e s i n egg m o r t a l i t y r a t e between c o n t r o l and t r e a t m e n t s i t e s t h r o u g h p a i r e d t - t e s t a n a l y s i s ; and b) t h e y e n a b l e d a c o r r e l a t i o n of egg s u r v i v a l r a t e s t o q u a l i t y of g r a v e l as measured by i n t r a g r a v e l d i s s o l v e d oxygen, i n t r a g r a v e l p e r m e a b i l i t y , g r a v e l q u a l i t y , and d e p t h of s c o u r . Egg and a l e v i n d e n s i t i e s were sampled w i t h a h y d r a u l i c egg s a m p l e r ( M c N e i l 1964a). S a m p l i n g s t a t i o n s were s e l e c t e d w i t h r e f e r e n c e t o spawner mapping d a t a ; o n l y s t a t i o n s e x h i b i t i n g a minimum f i s h usage (2 p i n k s p a w n e r - d a y s ) were sampl e d i n o r d e r t o m i n i m i z e s a m p l i n g a r e a s w i t h no e g g s . T h i s c r i t e r i o n p r e c l u d e d s a m p l i n g s i t e s o t h e r t h a n T r e a t m e n t S i t e I I I and i t s two c o n t r o l s i t e s ( I I I A and I I I B ) , owing t o l a c k o f s u f f i c i e n t spawner d e n s i t i e s a t t h e o t h e r s i t e s . About 20 s t a t i o n s p e r s i t e were sampled f o r e a c h s a m p l i n g p e r i o d : 1) a t t h e " eyed" s t a g e i n December 1982, and 2) i m m e d i a t e l y p r i o r t o p i n k f r y "emergence" from t h e g r a v e l i n M a r c h 1983. S a m p l i n g c o n s i s t e d of 0.2m 2 p e r sample and f o u r a d j a c e n t samples p e r s t a t i o n . The eggs and a l e v i n s were e x t r a c t e d t o a d e p t h of 40cm. Egg s a m p l i n g f o r 29 o f t h e December samples was m o d i f i e d t o d e t e r m i n e t h e a p p r o x i m a t e d e p t h t h a t eggs were d e p o s i t e d . T hese 26 were sampled by i n s e r t i n g t h e h y d r a u l i c p r o b e i n t h e g r a v e l i n i n c r e m e n t s of 10cm down t o a maximum of 40 cm. The eggs c o l l e c t e d a f t e r e a c h i n c r e m e n t were a n a l y z e d s e p a r a t e l y . S e l e c t i o n of t h e 29 d e p t h s a m p l e s was b a s e d on whether an a d j a c e n t sample had more t h a n about 20 e g g s . Two methods of c a l c u l a t i n g egg s u r v i v a l ( M c N e i l 1964a) were a p p l i e d t o t h e egg s a m p l i n g d a t a . F i r s t t h e r a t i o of l i v e t o dead eggs samp l e d was us e d as a r e l a t i v e measure of s u r v i v a l t o d a t e - o f - s a m p l i n g . A s e c o n d method was d e v e l o p e d t o e l i m i n a t e t h e b i a s i n s u r v i v a l i n t r o d u c e d f r o m n a t u r a l egg l o s s . T h i s method r e q u i r e d c a l c u l a t i o n of p o t e n t i a l egg d e p o s i t i o n from a d u l t f e c u n d i t i e s , egg r e t e n t i o n , and spawner mapping d a t a . An a v e r a g e spawner l o n g e v i t y of 10 days ( M c N e i l 1964b) was assumed n e c e s s a r y f o r an a v e r a g e d e p o s i t i o n (1,300 eggs; n=l2 " g r e e n " S a c hs C r e e k p i n k salmon f e m a l e s ) . A p a i r e d t - t e s t a n a l y s i s of s u r v i v a l a t i n d i v i d u a l s t a t i o n s was u s e d t o i n d i c a t e d i f f e r e n c e s i n s u r v i v a l r a t e between T r e a t m e n t S i t e I I I and t h a t of i t s two c o n t r o l s i t e s ( I I I A and I I I B ) . S t e p w i s e m u l t i p l e r e g r e s s i o n s (Rao 1973) were run w i t h egg s u r v i v a l a g a i n s t p h y s i c a l p a r a m e t e r s t o examine t h e r e l a t i o n s h i p s between t h e p h y s i c a l e n v i r o n m e n t and egg s u r v i v a l . I n t r a g r a v e l d i s s o l v e d oxygen and p e r m e a b i l i t y , and d e p t h of g r a v e l s c o u r , measured e i t h e r d u r i n g summer 1982 or w i n t e r 1982-83, were run a g a i n s t b o t h i n d i c e s of egg s u r v i v a l a t i n d i v i d u a l s a m p l i n g s t a t i o n s . 27 6. JUVENILE UTILIZATION J u v e n i l e s a l m o n i d s were e n u m e r a t e d on t h e g a b i o n and c o n t r o l s i t e s on S a c hs C r e e k i n summer 1983 t o i n d i c a t e t h e e f f e c t of g a b i o n i n s t a l l a t i o n on s a l m o n i d r e a r i n g h a b i t a t . J u v e n i l e e n u m e r a t i o n i n v o l v e d 2 s a m p l i n g s e s s i o n s s e p a r a t e d by a 2-3 hour p e r i o d w h i c h e n a b l e d marked f i s h from t h e f i r s t s a m p l i n g t o r e t u r n t o t h e i r o r i g i n a l l o c a t i o n s p r i o r t o t h e s e c o n d s a m p l i n g . E a c h s a m p l i n g e n t a i l e d m u l t i p l e (2-3) p a s s e s w i t h b o t h e l e c t r o s h o c k e r ( S m i t h Root, Type V I I I ) and p o l e s e i n e (3m l o n g , 4mm mesh). J u v e n i l e coho and s t e e l h e a d were marked by c a u d a l f i n - c l i p p i n g t o e n a b l e e n u m e r a t i o n by t h e P e t e r s e n s i n g l e c e n s u s mark - r e c a p t u r e t e c h n i q u e . T h e i r f o r k l e n g t h s were measured t o d e t e c t p o s s i b l e d i f f e r e n c e s i n s i z e between t h e g a b i o n and c o n t r o l s i t e s . S t o p n e t s d e l i n e a t e d t h e s t u d y a r e a s d u r i n g s a m p l i n g and t h e r e - o r i e n t a t i o n p e r i o d . A t - t e s t a n a l y s i s b a s e d on u n p a i r e d measurements of i n d i v i d u a l 0+ coho l e n g t h s was made t o d e t e r m i n e d i f f e r e n c e s i n a v e r a g e l e n g t h between t r e a t m e n t and c o n t r o l s i t e s . 28 IV. RESULTS 1 . S I T E STABILITY 1. GRAVEL SCOUR G r a v e l s c o u r a t two of t h e g a b i o n s i t e s (I and I I ) o v e r t h e f i r s t w i n t e r (1982-83) was s i g n i f i c a n t l y g r e a t e r (p<.05, t - t e s t a n a l y s i s ) t h a n a t t h e i r r e s p e c t i v e c o n t r o l s i t e s ( T a b l e s 1 and 2 ) . The a r e a s of c o n c e n t r a t e d g r a v e l s c o u r were g e n e r a l l y on t h e downstream s i d e of t h e l a t e r a l wings of t h e g a b i o n s and i n the h i g h v e l o c i t y c h a n n e l s e s t a b l i s h e d by bank d e f l e c t i o n ( F i g u r e 8 ) . The e x t e n t of t h e bank s c o u r i n t h e s e c o r n e r s prompted r i p r a p p l a c e m e n t a t T r e a t m e n t S i t e s I I and I I I where t h e r e p r e v i o u s l y had been none (pa g e s 19 and 2 0 ) . G r a v e l s c o u r i n y e a r 2 (1983-84) was not as s e v e r e i n g a b i o n and c o n t r o l s i t e s as i n y e a r 1 (1982-83) ( T a b l e 1 ) . However, g r a v e l s c o u r a t t h e l o w e r two t r e a t m e n t s i t e s ( I I and I I I ) d e c r e a s e d more ( f r o m 13cm i n y e a r 1 t o 4.4cm i n y e a r 2) t h a n t h a t o f t h e i r c o n t r o l s i t e s ( I I B , I I I A and I I I B ; from 5.1cm t o 4.5cm). S c o u r was t h e r e f o r e s i m i l a r (p<.05; T a b l e 2) i n t h e l o w e r two t r e a t m e n t ( I I and I I I ) and c o n t r o l s i t e s ( I I B , I I I A and I I I B ) a f t e r t h e i n i t i a l s t a b i l i z a t i o n p e r i o d of one y e a r . G r a v e l s c o u r a t T r e a t m e n t S i t e I , a t a 3% s l o p e g r a d i e n t , a l s o d e c r e a s e d i n y e a r 2 from t h a t i n y e a r 1 ( f r o m an a v e r a g e o f 22cm to 12cm; T a b l e 1 ) . S c o u r a t T r e a t m e n t S i t e I was g r e a t e r t h a n a l l o t h e r s i t e s i n y e a r 2 ( T a b l e 1 ) , and s i g n i f i c a n t l y g r e a t e r than i t s c o n t r o l IB ( T a b l e 2 ) . 29 T a b l e 1 - D e p t h of G r a v e l S c o u r on S t u d y S i t e s a t S achs C r e e k Over W i n t e r 1982-83 and 1983-84. Y e a r 1 1 Y e a r 2 S i t e No. of S t a t i o n s Mon i t o r e d Avg. S c o u r (cm) 2 S t d . Dev. (Sx) No. of S t a t i o n s M o n i t o r e d Avg. S c o u r (cm) S t d . Dev. (Sx) T r e a t m e n t I 18 22 1 3 1 1 1 2 9.5 T r e a t m e n t I I 1 7 1 1 1 2 19 1 . 1 2.4 T r e a t m e n t I I I 19 1 5 1 5 26 6.8 8.2 T o t a l s : 11 & I I I 3 36 1 3 1 3 45 4.4 6.9 I, I I & I I I 54 1 6 1 4 56 5.9 8.0 C o n t r o l IB 1 2 7.0 1 1 9 0.9 2.8 C o n t r o l I I B 1 6 1 . 1 2.9 9 0.5 1 . 4 Cont r o l I I I A 1 5 7.8 8.7 1 3 5.8 6.3 C o n t r o l I I I B N.A. 1 1 9.2 9.5 T o t a l s : IB, I I B , I I I A and I I I B 43 5. 1 8.4 42 4.5 7.0 1. Peak s t o r m f l o w i n Y e a r 1 (1982-83) was 1.32m on s t a f f gauge. Peak s t o r m f l o w i n Y e a r 2 (1983-84) was 1.14m on s t a f f gauge. 2. As i n d i c a t e d by V e r t i c a l E r o s i o n M o n i t o r s . 3. T h e s e s i t e s a r e a t 1% s l o p e g r a d i e n t . 30 T a b l e 2 - A t - t e s t A n a l y s i s of G r a v e l S c o u r on St u d y S i t e s a t Sachs C r e e k . T r e a t m e n t C o n t r o l Mean S t d . Dev. S i t e ( X ) S i t e ( Y ) Y e a r 1 D i f f . 2 o f t D.F. S i g n i f -(X-Y) D i f f . i c a n c e 3 IB 1 2 2.3 3.8 2.6 1 . 1 2.7 9.9 9 7 S i g , S i g , I I I I B 1 2 2.4 0.55 2.0 1 . 5 4.3 1 . 1 1 2 S i g , N.S, I I I I I I A 1 2 0.72 2.5 1.1 14 N.S. 0.23 2.6 0.31 11 N.S. I l l I I I B 2 -0.24 2.7 -0.30 10 N.S, 1. M o n i t o r i n g Year 1 from e a r l y December 1982 t h r o u g h mid-March 1983; M o n i t o r i n g Year 2 from e a r l y September 1983 t h r o u g h l a t e J a n u a r y 1984. 2. V a l u e s of g r a v e l s c o u r (cm) t r a n s f o r m e d by s q u a r e r o o t . 3. p<.05; one t a i l e d p a i r e d t - t e s t ; Ho: X < Y ; HI: X > Y . 3J> FIGURE 8- Isopleths of Gravel Scour Depth (cm) as Indicated by Vertical Erosion Monitors at Gabion Sites at Sachs Creek in Year I and Year 2 . 32 2. GABION S I T E CONFIGURATIONS C o n f i g u r a t i o n of t h e g a b i o n s i t e s c h a n g e d d u r i n g e x p o s u r e t o t h e i r f i r s t w i n t e r (1982-83) s t o r m f l o w s . P o o l s a b o u t 80cm deep formed i n t h e downstream l a t e r a l c o r n e r s from g r a v e l s c o u r ( F i g u r e s 9, 10, and 11). T h i s c r e a t e d two a d d i t i o n a l p o o l -r i f f l e s e q u e n c e s p e r s i t e . T e a r d r o p shaped g r a v e l b a r s formed downstream of g a b i o n a p i c e s i n T r e a t m e n t S i t e s II and I I I . A l t h o u g h t h e g a b i o n s w i t h s t o o d w i n t e r s t o r m f l o w s t h a t r a i s e d t h e water s u r f a c e by 1.1m, an u n s e a s o n a l f l o o d on 2 A u g u s t 1983 ( r a i s i n g t h e water s u r f a c e by 1.2m) c a u s e d T r e a t m e n t S i t e I t o " f a i l " ( i . e . t o change enough t o t h r e a t e n s i t e i n t e g r i t y ) ; a p p r o x i m a t e l y 0.5m of s u b s t r a t e was s c o u r e d away f o r a 30m r e a c h downstream of t h e l o w e r g a b i o n ( F i g u r e 9 ) . A wedge of stre a m b e d s e d i m e n t s w i t h • b o u l d e r s up t o 0.7m diam. i n u n d a t e d t h e s i t e u p s t r e a m of t h e g a b i o n s d u r i n g t h i s f l o o d ( F i g u r e 12); t h i s wedge a v e r a g e d 13cm t h i c k o v e r a 20m d i s t a n c e u p s t r e a m of t h e g a b i o n s . Much of t h i s wedge was s c o u r e d away d u r i n g s t o r m f l o w s i n y e a r 2 ( F i g u r e s 9 and 12). Str e a m b e d c o n f i g u r a t i o n s r e m a i n e d r e l a t i v e l y c o n s t a n t a t t h e low e r 2 t r e a t m e n t s i t e s ( I I and I I I ) o v e r t h e s e c o n d s e a s o n of w i n t e r s t o r m f l o w s ( F i g u r e s 10, and 11). FIGURE 9 • Temporal Changes in Bathymetric Contours (cm) Below an Arbitrary Benchmark at Treatment Site I at Sachs Creek. FIGURE 10 < Temporal Changes In Bathymetric Contours (cm) Below an Arbitrary Benchmark at Treatment Site II at Sachs Creek. FIGURE II • Temporal Changes in Bathymetric Contours (cm) Below an Arbitrary Benchmark at Treatment Site III at Sachs Creek. 36 E u LU O z 2 LU _1 Lkl 20 10 0--10 Flood CGabion Installation • J \ \ \ \ \ v JULY SEPT 1982 JULY AUG. 1983 FEBRUARY 1984 F i g u r e 12 - Temporal Changes i n Average Aggradation Above Gabions at Treatment S i t e I, Sachs Creek. Changes i n l o c a l streambed slope g r a d i e n t s improved the g r a v e l s t a b i l i z i n g a b i l i t y of a l l 3 gabion s i t e s ; the pre-i n s t a l l a t i o n 3 - s i t e average g r a d i e n t of -1.2% ( f a c i n g downstream) decreased to an average g r a d i e n t of +3.1% 1 year p o s t - i n s t a l l a t i o n (Table 3). (Slope i s p o s i t i v e when the bottom of plunge pools are on average at a lower e l e v a t i o n than g r a v e l s entrapped by gabions f u r t h e r downstream.) The August 1983 f l o o d i n c r e a s e d the streambed g r a d i e n t at Treatment S i t e I to -1.9%; however, t h i s was s t i l l a decrease from the p r e - i n s t a l l a t i o n g r a d i e n t of -2.8% (Table 3 ) . 37 T a b l e 3 - Summary of Streambed G r a d i e n t Changes w i t h • G a b i o n I n s t a l l a t i o n on Sachs C r e e k , 1982-83. L o c a t i o n A v e r a g e S l o p e G r a d i e n t ( % ) F a c i n g Downstream S i t e R e l a t i v e P r e - 1 Year P o s t - P o s t - F l o o d To G a b i o n s I n s t a l l a t i o n 1 I n s t a l l a t i o n 2 Aug. 1983 T r e a t U p s t r e a m -3.0 -1.4 -3.2 I Between -2.5 +5.0 +3.0 Downstream -3.0 +4.0 -5.6 A v e r a g e -2.8 +2.5 -1.9 T r e a t U p s t r e a m -0.2 +4.9 11 Between -1.1 +3.1 Downstream -1.1 +0.5 A v e r a g e -0.8 +2.8 T r e a t U p s t r e a m +1.6 +4.8 I I I Between -1.2 +4.2 Downstream 0 +3.3 A v e r a g e +0.1 +4.1 T o t a l : I , II & I I I -1.2 +3.1 1. S u r v e y e d J u l y 1982. 2. S u r v e y e d J u l y 1983. 38 2. GRAVEL QUALITY 1. INTRAGRAVEL DISSOLVED OXYGEN The e f f e c t of g a b i o n i n s t a l l a t i o n on i n t r a g r a v e l d i s s o l v e d oxygen was v a r i a b l e between t r e a t m e n t s and i n c o m p a r i s o n t o c o n t r o l s w i t h i n t r e a t m e n t s ( T a b l e 4 ) . Oxygen l e v e l s a t a c o m b i n a t i o n o f a l l t h r e e t r e a t m e n t s i t e s were s i g n i f i c a n t l y " i m p r o v e d " when compared t o t h a t of t h e c o n t r o l s . i . e . t h e i n t r a g r a v e l d i s s o l v e d oxygen a t t h e g a b i o n s i t e s was not s i g n i f i c a n t l y d i f f e r e n t (p<.05, p a i r e d t - t e s t ) from e i t h e r of t h e i r c o n t r o l s i t e s p r i o r t o i n s t a l l a t i o n but were s i g n i f i c a n t l y g r e a t e r a f t e r i n s t a l l a t i o n ( T a b l e 5 ) . The oxygen l e v e l s o f T r e a t m e n t S i t e s II and I I I b o t h were s i g n i f i c a n t l y i m p r oved a f t e r g a b i o n i n s t a l l a t i o n . The oxygen l e v e l s o f T r e a t m e n t S i t e I d e c r e a s e d a f t e r g a b i o n i n s t a l l a t i o n when compared t o t h a t o f i t s c o n t r o l s i t e s ; t h e a v e r a g e d i s s o l v e d oxygen c o n c e n t r a t i o n a t t h i s g a b i o n s i t e was s i g n i f i c a n t l y g r e a t e r t h a n C o n t r o l S i t e IA p r i o r t o i n s t a l l a t i o n but was not d i f f e r e n t a f t e r i n s t a l l a t i o n ( T a b l e 5 ) . The i n t r a g r a v e l d i s s o l v e d oxygen a t T r e a t m e n t S i t e I r e m a i n e d s i g n i f i c a n t l y g r e a t e r t h a n C o n t r o l S i t e IB b e f o r e and a f t e r i n s t a l l a t i o n ( T a b l e 5 ) . 2. INTRAGRAVEL PERMEABILITY The e f f e c t of g a b i o n i n s t a l l a t i o n on i n t r a g r a v e l p e r m e a b i l i t y a l s o v a r i e d c o n s i d e r a b l y between t h e s i t e s ( T a b l e 4 ) . P e r m e a b i l i t y o f g r a v e l s a t a c o m b i n a t i o n o f T r e a t m e n t S i t e s II and I I I were s i g n i f i c a n t l y (p<.05) i m p r o v e d r e l a t i v e t o C o n t r o l S i t e s I I B and I I I B , and m a i n t a i n e d a s i g n i f i c a n t l y 39 g r e a t e r p e r m e a b i l i t y t h a n t h a t a t C o n t r o l S i t e s I I A and I I I A ( T a b l e 6 ) . The p e r m e a b i l i t y of T r e a t m e n t S i t e I I s i g n i f i c a n t l y i n c r e a s e d f o l l o w i n g g a b i o n i n s t a l l a t i o n (p<.05; T a b l e 6 ) . The p e r m e a b i l i t y o f T r e a t m e n t S i t e I I I a l s o i n c r e a s e d a f t e r g a b i o n i n s t a l l a t i o n ( T a b l e 4 ) . However, t h e p e r m e a b i l i t y a t t h e g a b i o n s i t e was s i g n i f i c a n t l y g r e a t e r t h a n t h a t a t i t s two c o n t r o l s i t e s p r i o r t o g a b i o n i n s t a l l a t i o n , whereas i t was not s i g n i f i c a n t l y g r e a t e r a f t e r i n s t a l l a t i o n ( T a b l e 6 ) . T h i s was p r o b a b l y owing t o a t h r e e f o l d i n c r e a s e i n t h e v a r i a b i l i t y of p e r m e a b i l i t y a t T r e a t m e n t S i t e I I I ( S t a n d a r d D e v i a t i o n ; T a b l e 4 ) . A t T r e a t m e n t S i t e I, t h e s t r e a m s u b s t r a t e was t o o c o a r s e f o r p e r m e a b i l i t y measurements p r i o r t o g a b i o n i n s t a l l a t i o n ; t h e p o s t - i n s t a l l a t i o n measurements i n d i c a t e d t h a t i t s p e r m e a b i l i t y a l s o was not s i g n i f i c a n t l y g r e a t e r t h a n C o n t r o l S i t e IB ( T a b l e 6 ) . S t r e a m s u b s t r a t e o f C o n t r o l S i t e IA r e m a i n e d t o o c o a r s e f o r p e r m e a b i l i t y measurements a t b o t h s a m p l i n g p e r i o d s . 40 T a b l e 4 - Summary of I n t r a g r a v e l D i s s o l v e d Oxygen and P e r m e a b i l i t y on S t u d y S i t e s a t Sachs C r e e k . D i s s o l v e d Oxygen P e r m e a b i l i t y S i t e S a m p l i n g P e r i o d 1 N ( A v e r a g e % o f s r f c e ) S t d . Dev. N A v e r a g e (cm/hr) S t d . Dev. T r e a t Pre 18 88 1 2 N.A. 2 I 0.5 Year 20 86 9.6 N.A. 1 Year 18 92 8.5 1 5 1.8*10 3 1 .3*10 3 C o n t r Pre 18 61 32 N.A. IA 0.5 Year 18 85 1 5 N.A. 1 Year 1 5 96 4.7 N.A. C o n t r P r e 20 24 26 N.A. IB 0.5 Y e a r 18 64 31 N.A. 1 Year 20 43 32 1 5 3.2*10 3 1 .7*10 3 T r e a t P r e 1 9 30 27 1 5 3 . 1 * 1 0 2 2. 1*10 2 11 0.5 Y e a r 23 80 22 N.A. 1 Y e a r 23 65 28 22 2.3*10 3 2.0*10 3 C o n t r P r e 18 54 28 18 2.4*10 2 4. 1 * 10 2 I I A 0.5 Y e a r 23 58 25 N.A. 1 Y e a r 21 45 28 22 6.0*10 2 1 . 2*10 3 C o n t r P r e 20 43 33 21 7.0*10 2 7.4*10 2 I I B 0.5 Y e a r 23 49 28 N.A. 1 Y e a r 23 33 25 24 4.4*10 2 6.2*10 2 T r e a t P r e 1 9 1 3 1 7 1 6 1.5*10 3 5.0*10 2 I I I 0.5 Year 25 72 22 N.A. 1 Year 18 74 1 8 21 2.6*10 3 1.7*10 3 C o n t r P r e 21 60 31 21 7.1*10 2 1.1 * 1O 3 I I I A 0.5 Year 26 46 31 N.A. •1 Y e a r 1 9 44 26 24 2.3*10 3 1.7*10 3 C o n t r P r e 1 8 58 29 1 9 1 .0*10 3 1.4*10 3 I I I B 0.5 Y e a r 27 55 25 N.A. 1 Y e a r 19 47 28 20 1.9*10 3 1 .6*10 3 T o t a l s C o n t i n u e d Next Page. 41 T a b l e 4 c o n t i n u e d . - Summary of I n t r a g r a v e l D i s s o l v e d Oxygen and P e r m e a b i l i t y on S t u d y S i t e s a t S a c h s C r e e k . D i s s o l v e d Oxygen P e r m e a b i l i t y S i t e S a m p l i n g N A v e r a g e S t d . N A v e r a g e S t d • Per i o d 1 ( % o f s r f c e ) Dev. (cm/hr) Dev • T o t a l s : T r e a t 3 P r e 56 43 38 31 8.2*10 2 5.5* 10 2 I, II 0.5 Year 68 79 20 & I I I 1 Y e a r 59 76 23 43 2.4*10 3 1 .8* 10 3 C o n t r 3 P r e 57 58 30 39 5.0*10 2 6.2* 10 2 IA, I I A 0.5 Year 67 60 30 & I I I A 1 Year 55 58 33 46 1.4*10 3 1 .4* 10 3 C o n t r 3 P r e 58 41 32 40 7 . 1 * 1 0 2 8.4* 10 2 I B , I I B 0.5 Year 68 55 29 & I I I B 1 Year 62 41 29 44 1.1*10 3 1 .2* 10 3 1. P r e - i n s t a l l a t i o n s a m p l i n g i n J u l y and A u g u s t 1982; 0.5 y e a r p o s t - i n s t a l l a t i o n s a m p l i n g i n F e b r u a r y and March 1983; 1 y e a r p o s t - i n s t a l l a t i o n s a m p l i n g i n J u l y and August 1983. 2. N.A. = Not A v a i l a b l e 3. T o t a l s f o r p e r m e a b i l i t y i n c l u d e d T r e a t m e n t s II and I I I , and C o n t r o l s I I A , I I I A , I I B and I I I B o n l y . 42 T a b l e 5 - A t - t e s t A n a l y s i s o f I n t r a g r a v e l D i s s o l v e d Oxygen on S t u d y S i t e s a t Sachs C r e e k . T r e a t m e n t C o n t r o l Sample Mean S t d . t D.F. S i g n i f -S i t e (X) S i t e ( Y ) D a t e 1 D i f f . 2 Dev.of i c a n c e 3 (X-Y) D i f f . I IA Pre 20 26 2. 8 1 3 S i g . ( M a r g i n a l 0.5 Year 1 . 1 1 6 0. 30 1 7 N.S. h a b i t a t ) 1 Year -1.6 6. 1 -0. 96 1 2 N.S. I IB Pr e 61 27 8. 9 1 5 S i g . (Pr ime 0.5 Y e a r 22 30 3. 1 1 7 S i g . h a b i t a t ) 1 Year 49 35 6. 0 1 7 S i g II I I A P r e -27 41 -2. 6 1 5 N.S. ( M a r g i n a l 0.5 Y e a r 22 30 3. 5 22 S i g . h a b i t a t ) 1 Year 21 46 2. 1 20 S i g . II I I B P r e - 1 4 45 -1 . 4 18 N.S. (Pr ime 0.5 Y e a r 31 36 4. 1 22 S i g . h a b i t a t ) 1 Year 32 43 3. 4 21 S i g . I I I I I I A P r e -55 28 -8. 3 1 7 N.S. ( M a r g i n a l 0.5 Year 22 38 2. 9 24 S i g . h a b i t a t ) 1 Year 29 30 4. 1 1 7 S i g . I I I I I I B P r e -45 27 -7. 1 1 7 N.S. (Pr ime 0.5 Y e a r 1 5 27 2. 8 25 S i g . h a b i t a t ) 1 Year 24 31 3. 3 1 7 S i g . T o t a l s • I , I A , I I A , 1 1 1 A Pre -24 44 -3. 7 47 N.S. II , ( M a r g i n a l 0.5 Y e a r 1 7 31 4. 3 64 S i g . &I 11 h a b i t a t ) 1 Year 18 36 3. 6 50 S i g . I , I B , I I B , I I I B P r e -2.3 55 -o. 3 52 N.S. II , ( P r i m e 0.5 Y e a r 23 31 5. 8 65 S i g . t i l l h a b i t a t ) 1 Year 35 38 7. 0 57 S i g . 1. P r e - i n s t a l l a t i o n s a m p l i n g i n J u l y and A u g u s t 1982; 0.5 y e a r p o s t - i n s t a l l a t i o n s a m p l i n g i n F e b r u a r y and March 1983; 1 y e a r p o s t - i n s t a l l a t i o n s a m p l i n g i n August 1983. 2. I n t r a g r a v e l oxygen v a l u e s were e x p r e s s e d as p e r c e n t of d i s s o l v e d oxygen of s u r f a c e w a t e r . 3. p<.05; one t a i l e d p a i r e d t - t e s t ; Ho: X < Y ; H1: X > Y . 43 T a b l e 6 - A t - t e s t A n a l y s i s of I n t r a g r a v e l P e r m e a b i l i t y on S t u d y S i t e s a t Sachs C r e e k . T r e a t m e n t C o n t r o l Sample Mean S t d . t S i t e S i t e D a t e 1 D i f f . 2 Dev.of (X) (Y) (X-Y) D i f f . D.F. S i g n i f -i c a n c e IB (Pr ime h a b i t a t ) P r e •8. 1 25 1.3 14 N.S II I I A ( M a r g i n a l h a b i t a t ) Pr e 1 Year 1 .2 1 5 3.2 21 1 .4 3.2 1 3 20 N.S. S i g . II I I B ( P r i m e h a b i t a t ) P r e 1 Year -4.5 1 5 9.3 21 •1.9 3.3 1 4 20 N.S, S i g . I l l I I I A ( M a r g i n a l h a b i t a t ) Pr e 1 Year 5.2 - 0 . 1 8 10 20 2.0 •0.04 1 4 20 S i g . N.S. I l l I I I B (Pr ime h a b i t a t ) P r e 1 Year 5.8 7.5 1 1 18 2. 1 1 .7 1 5 1 7 S i g N.S T o t a l s : I I , I I A & I I I A &III ( M a r g i n a l h a b i t a t ) Pr e 1 Year 3.3 7.3 7.7 22 2.3 2.2 28 41 S i g . S i g . I I , I I B & I I I B P r e 0.87 11 0.42 30 N.S. &I11 ( P r i m e 1 Year 11 20 3.6 38 S i g . h a b i t a t ) 1. P r e - i n s t a l l a t i o n s a m p l i n g i n J u l y and A u g u s t 1982; 1 y e a r p o s t - i n s t a l l a t i o n s a m p l i n g i n June and J u l y 1983 2. I n t r a g r a v e l p e r m e a b i l i t y v a l u e s e x p r e s s e d a s m i s / s e c e n t e r i n g t h e s t a n d p i p e , b e f o r e c o n v e r s i o n t o cm/hr (T e r h u n e 1958). 3. p<.05; one t a i l e d p a i r e d t - t e s t ; Ho: X < Y ; H1: X > Y 44 3. GRAVEL COMPOSITION The c o m p o s i t i o n of g r a v e l s on t h e T r e a t m e n t S i t e s i n Sachs C r e e k c h a n g e d w i t h t h e a d d i t i o n of g r a v e l s from a q u a r r y and a g a i n w i t h a c y c l e of spawning and w i n t e r s t o r m f l o w s . At T r e a t m e n t S i t e I ( 3 % s t r e a m b e d s l o p e g r a d i e n t ) t h e most n o t a b l e c h a n g e s were f o u n d w i t h g r a v e l s between 10mm and 70mm d i a m e t e r , t h e s u i t a b l e r a n g e f o r p i n k and chum salmon s p a w n i n g . The p r o p o r t i o n of t h e s e g r a v e l s i z e s i n c r e a s e d w i t h t h e a d d i t i o n of q u a r r y g r a v e l s , but were r e d u c e d t o a l m o s t t h e low p r o p o r t i o n s f o u n d b e f o r e i n s t a l l a t i o n f o l l o w i n g t h e f l u s h i n g e f f e c t o f w i n t e r s t o r m f l o w s ( F i g u r e 1 3 ) . G r a v e l s 20mm t o 60mm i n d i a m e t e r a t T r e a t m e n t S i t e s II and I I I ( a t a-1% st r e a m b e d s l o p e g r a d i e n t ) a p p e a r e d more abundant 1 y e a r a f t e r i n s t a l l a t i o n t h a n t h o s e b e f o r e i n s t a l l a t i o n ( F i g u r e 1 3 ) . The amount o f f i n e s e d i m e n t s i n t h e g r a v e l e n t r a p p e d by g a b i o n s and measured by g r a v e l sample s i e v i n g v a r i e d between t h e s i t e s . The " f i n e s " i n T r e a t m e n t S i t e I I I d e c r e a s e d more t h a n 50% between p r e - g a b i o n i n s t a l l a t i o n t o 1-year p o s t - i n s t a l l a t i o n ( F i g u r e 1 4); t h i s r e d u c e d t h e f i n e s t o l e v e l s below t h o s e i n b o t h of i t s c o n t r o l s i t e s ( I I I A and I I I B ) . Changes i n f i n e s a t T r e a t m e n t S i t e I I were m i n o r , w i t h l e v e l s r e m a i n i n g s l i g h t l y below i t s c o n t r o l s i t e s ( I I A and I I B ; F i g u r e 1 4 ) . O n l y a minor f l u s h i n g of f i n e s from t h e added q u a r r y g r a v e l s was e v i d e n t a t T r e a t m e n t S i t e I ( F i g u r e 1 4); t h e c o a r s e n a t u r e o f t h e s u b s t r a t e p r i o r t o i n s t a l l a t i o n p r e v e n t e d p r e - and p o s t - i n s t a l l a t i o n c o m p a r i s o n o f t h e f i n e r component of t h e g r a v e l s a t t h i s s i t e . 45 80" 60' 40 SITE I • Pre-Installation (n=l40) o Post-Installation (n=3) A l Year Post-Installation (n=5) A Control IA I982(n=l4l) • Control TA 1983 (n=117) • Control IB (n=5) 20 OOi SITED • Pre-Installation (n=7) o Post-Installation (n=3) A I Year Post-Installation (n=5) • Control HA (n=5) • Control IIB (n=5) 80 60 z 401 IU UJ a. to 20 40 60 •80 Loo rO 20 oz ui in oc •AO < ' W o u €0 g «o PARTICLE DIAMETER (mm) FIGURE 13» Gravel Composition of Study Sites at Sachs Creek Pre- and Post- Gabion Installation. FIGURE 14 '• Mean Percent of Particles Less Than 1.2 and 0.30mm on Study Sites at Sachs Creek. 47 4. SEDIMENTATION The l o s s of most of t h e s e d i m e n t t r a p s ( a l l i n t h e c a s e of T r e a t m e n t S i t e I) t h r o u g h w i n t e r s t o r m f l o w s p r e c l u d e d s t a t i s t i c a l a n a l y s i s of r e s u l t s . F i n e s e d i m e n t ( l e s s t h an 3mm) a c c u m u l a t i o n i n t r a p s a t T r e a t m e n t S i t e II was 40-50% lo w e r t h a n t h a t of i t s two c o n t r o l s i t e s ( I I A and I I B ; F i g u r e 15). F i n e s e d i m e n t a c c u m u l a t i o n a t T r e a t m e n t S i t e I I I r a n g e d from 10-70% h i g h e r t h a n t h a t of i t s two c o n t r o l s i t e s ( I I I A and I I I B ; F i g u r e 15) . D i f f e r e n t s i z e s of " f i n e s " may v a r y i n s e v e r i t y of e f f e c t s on egg s u r v i v a l . I t was not u n t i l t h e p a r t i c l e s i z e examined i n a n o t h e r s t u d y was r e d u c e d t o l e s s t h a n 0.03mm diam. t h a t a 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 was f o u n d between amount of f i n e s and egg t o f r y s u r v i v a l ( S l a n e y e t a l . 1977). F i n e s l e s s t h a n 0.30mm diam. were a n a l y z e d i n b o t h s i e v e d g r a v e l samples ( F i g u r e 14) and s e d i m e n t a c c u m u l a t i o n ( F i g u r e 1 5 ) . The e f f e c t s o f g a b i o n s on t h e amount of f i n e s l e s s t h a n 0.30mm diam. was s i m i l a r t o t h a t d i s c u s s e d above f o r f i n e s l e s s t h a n 1.2mm diam. ( F i g u r e 14) and f o r f i n e s l e s s t h a n 3.0mm diam. ( F i g u r e 1 5 ) . 48 PARTICLE DIAMETER (mm) FIGURE 15! Sedimentation Accumulated in Sediment Traps on Study Sites at Sachs Creek, December 1982 to March 1983. 49 3. SPAWNER UTILIZATION 1. OBSERVED SPAWNING L o n g i t u d i n a l d i s t r i b u t i o n of p i n k and chum spawners i n 1982 ( F i g u r e 16) i n d i c a t e d t h a t t h e g a b i o n l o c a t i o n s were u p s t r e a m of t h e main c o n c e n t r a t i o n of spawners, w i t h T r e a t m e n t S i t e I beyond t h e u p s t r e a m l i m i t s of p i n k and chum s p a w n i n g . Fewer salmon were o b s e r v e d spawning i n 1983 t h a n i n 1982 owing t o 1983 b e i n g an " o f f y e a r " f o r p i n k salmon r u n s and t o t h e s i t e s b e i n g m o n i t o r e d o n l y a b o u t 10% a s o f t e n as i n 1982 ( T a b l e 7 ) . Spawner o b s e r v a t i o n s i n 1983 were i n s u f f i c i e n t f o r s i t e c o m p a r i s o n . The 1982 coho spawner usage of T r e a t m e n t S i t e I was g r e a t e r t han t h a t i n i t s c o n t r o l s (IA and IB; T a b l e 7 ) . T r e a t m e n t S i t e II had more spawning a c t i v i t y t h a n d i d i t s ( m a r g i n a l h a b i t a t ) C o n t r o l S i t e I I A but l e s s t h a n i t s ( p r i m e h a b i t a t ) C o n t r o l S i t e I I B . T r e a t m e n t S i t e I I I had l e s s s p a w n i ng a c t i v i t y t h a n e i t h e r of i t s two c o n t r o l s i t e s ( I I I A and I I I B ; T a b l e 7 ) . The e f f e c t of t h e l o n g i t u d i n a l d i s t r i b u t i o n o f spawners on s i t e usage i s d i s c u s s e d f u r t h e r on page 75. 5 0 PINK U l U l ac o U . o or UJ H U l or ui a. co b Q < Li_ o or ui m z 400 800 1200 1600 DISTANCE ABOVE ESTUARY (m) 2 0 0 0 2400 FIGURE 16 LONGITUDINAL DISTRIBUTION OF ADULT SALMON IN SACHS CREEK, SEPTEMBER TO NOVEMBER, 1982. 51 T a b l e 7 - D i s t r i b u t i o n of Salmon Spawning A c t i v i t y on Stu d y S i t e s a t Sachs C r e e k , F a l l 1982 and 1983. Spawning S i t e H a b i t a t Q u a l i t y D i s t a n c e Above E s t u a r y (m) Sum of 1 Female 9 8 2 Salmon Ac t i v i t y 1 1 9 8 3 Avg. 1 982 D e n s i t y P i n k Chum Coho Z I Pink Chum Coho L (#/m 2) T r e a t m e n t I 2,285 0 0 18 18 0 0 1 1 0 C o n t r o l IA M a r g i n a l 2, 185 0 0 0 0 0 0 1 1 0 C o n t r o l IB P r i m e 1 ,820 0 0 1 4 1 4 0 0 0 0 0 T r e a t m e n t I I 935 1 38 5 7 1 50 1 2 0 3 0.072 C o n t r o l I I A M a r g i n a l 1,100 99 0 7 1 06 0 0 0 0 0.079 C o n t r o l I I B P r i m e 985 342 3 1 2 357 0 0 0 0 0.27 T r e a t m e n t I I I 875 445 27 0 472 0 0 0 0 0.30 C o n t r o l I I I A M a r g i n a l 360 676 67 1 4 757 2 4 0 6 0.53 C o n t r o l I I I B Prime 575 894 1 86 20 1 , 100 5 5 0 10 0.71 1. - 1982 v a l u e s were t h e t o t a l numbers of o b s e r v a t i o n s of f e m a l e salmon spawning o r r e d d - d e f e n d i n g . V a l u e s were t h e t o t a l s of 53 o b s e r v a t i o n d a y s w i t h i n t e r v a l s a v e r a g i n g 1.5 d a y s . I n d i v i d u a l spawners r e m a i n i n g on t h e s i t e were c o u n t e d s e v e r a l t i m e s ( c a . 6) on d i f f e r e n t d a y s . - 1983 v a l u e s were t h e sums o v e r 6 o b s e r v a t i o n d a y s (1-2 week i n t e r v a l s ) ; „ a d d i t i o n a l f i s h spawned on t h e s i t e s , a s e v i d e n c e d by t h e i r r e d d s . 2. P i n k salmon d e n s i t y c a l c u l a t i o n s were b a s e d on 42 o b s e r v a t i o n d a y s w i t h i n a t e m p o r a l range o f 62 d a y s o f p i n k p r e s e n c e on t h e s i t e s . T h e r e f o r e e a c h o b s e r v a t i o n r e p r e s e n t e d an a v e r a g e of 1.5 spawner d a y s . S i n c e p i n k spawners remain on a s i t e an a v e r a g e o f 10 d a y s ( M c N e i l 1964b), e a c h o b s e r v a t i o n r e p r e s e n t 0.15 s p a w n e r s . 52 The s e q u e n c e of spawning a t Sachs C r e e k was f i r s t chum, t h e n p i n k , and f i n a l l y coho salmon. However, t e m p o r a l d i s t r i b u t i o n o f t h e m a j o r i t y of t h e p i n k spawning o v e r l a p p e d w i t h t h e chum and c o h o . Chum spawning r a r e l y o v e r l a p p e d w i t h c o h o . G r a d u a l spawner m i g r a t i o n up t h e s t r e a m was e v i d e n t as t h e l o w e s t s i t e s ( C o n t r o l s I I I A and I I I B ) e x h i b i t e d spawning a b o u t 10 d a y s p r i o r t o T r e a t m e n t S i t e s II and I I I f u r t h e r u p s t r e a m . 2. PROBABILITY-OF-USE T r e a t m e n t S i t e II showed t h e g r e a t e s t s u i t a b i l i t y of spawning h a b i t a t i n c o m p a r i s o n t o t h a t of i t s m a r g i n a l h a b i t a t c o n t r o l ( I I A ) - a d i f f e r e n c e of 440% ( T a b l e 8 ) . T r e a t m e n t S i t e I I I showed g r e a t e r s u i t a b i l i t y t h a n i t s p r i m e h a b i t a t c o n t r o l ( I I I B ) - a d i f f e r e n c e of 13% - but l e s s t h a n i t s " m a r g i n a l h a b i t a t " c o n t r o l ( I I I A ) . P r o b a b i 1 i t y - o f - u s e measurements were made a f t e r T r e a t m e n t S i t e I had " f a i l e d " d u r i n g t h e A u g u s t 1983 f l o o d (page 6 8 ) . T r e a t m e n t S i t e I showed p o o r e r p i n k spawning h a b i t a t t h a n e i t h e r of i t s c o n t r o l s (IA and I B ) . 53 T a b l e 8 -Salmon on Summary of Stu d y S i t e s P r o b a b i 1 i t y - o f - U s e a t S a c h s C r e e k , 1 I n s t a l l a t i o n . by Y e ar Spawning P i n k P o s t G a b i o n S i t e H a b i t a t Q u a l i t y D i s t a n c e Above E s t u a r y (m) S t a t i o n s Sampled (N) A v e r a g e P r o b a b i l i t y T r e a t m e n t I 2,285 33 0.014 C o n t r o l IA M a r g i n a l 2, 185 20 0.052 C o n t r o l IB Pr ime 1 ,820 20 0. 051 T r e a t m e n t I I 935 38 0.052 C o n t r o l I I A M a r g i n a l 1,100 38 0.012 C o n t r o l I I B Prime 985 40 0.15 T r e a t m e n t I I I 875 34 0.11 C o n t r o l I I I A M a r g i n a l 360 31 0.15 C o n t r o l I I I B Pr ime 575 40 0.091 1. A v e r a g e p r o b a b i 1 i t y - o f - u s e was t h e a v e r a g e of t h e p r o d u c t o f t h e p r o b a b i l i t i e s of 4 v a r i a b l e s measured a t e a c h s t a t i o n where t h e i r v a l u e s were d e t e r m i n e d from p r o b a b i 1 i t y - o f - u s e c u r v e s ( A p p e n d i x A ) . N.B. The p r o b a b i 1 i t y - o f - u s e c u r v e s d e s c r i b e d by Bovee and C o c h n a u e r (1977) and e s t a b l i s h e d f o r p i n k salmon i n Sachs C r e e k ( A p p e n d i x A) a r e i n d i c e s o f " s u i t a b i l i t y " r a t h e r t h a n a c t u a l " p r o b a b i l i t y " . T h i s i s owing t o a v a l u e d e r i v e d from a c u r v e i s not one of a g r o u p o f w e i g h t s whose c o l l e c t i v e sum e q u a l s a p r o b a b i l i t y of one. 54 4. EGG SURVIVAL P i n k salmon egg s u r v i v a l s m e a s u r e d i n March were lower t h a n i n December, p a r t i c u l a r l y i n t h e c o n t r o l s i t e s ( T a b l e 9 ) . The d i f f e r e n c e i n s u r v i v a l was p r o b a b l y t h e r e s u l t of some p i n k f r y emergence from t h e g r a v e l s between t h e two s a m p l i n g p e r i o d s . F r y emergence p r i o r t o M a rch s a m p l i n g was s u p p o r t e d by A c c u m u l a t e d T h e r m a l U n i t (ATU) 3 c a l c u l a t i o n s . S a l m o n i d embryo d e v e l o p m e n t was p r o p o r t i o n a l t o w a t e r t e m p e r a t u r e ; between 250 and 400 ATU's were r e q u i r e d f o r t h e d e v e l o p m e n t o f p i n k a l e v i n s from h a t c h i n g t o emergence (G. T a c c o g n a p e r s . comm.) " . I t was assumed t h a t p i n k h a t c h i n g began a b o u t 1 December, as 3% of t h e p i n k embryos sampled between 3 and 8 December i n t h i s s t u d y were r e c e n t l y h a t c h e d . Between h a t c h i n g and t h e embryo s a m p l i n g p e r i o d i n March, t h e ATU v a l u e e x c e e d e d 300 ( F i g u r e 17), s u g g e s t i n g p i n k emergence was underway p r i o r t o M a rch s a m p l i n g . The ATU v a l u e may have been c o n s i d e r a b l y h i g h e r i n t h e i n t r a g r a v e l w a ter t h a n t h a t r e c o r d e d i n t h e s u r f a c e ; s t u d i e s i n C a r n a t i o n C r e e k i n d i c a t e d t h a t a t some l o c a t i o n s , s u b s u r f a c e t e m p e r a t u r e s may be 2.5°C h i g h e r t h a n s u r f a c e w ater d u r i n g much of t h e w i n t e r p e r i o d , w i t h l o c a l measurements a s much as 5.9°C g r e a t e r (Hartman and Leahy 1983). 3 One ATU = one d e g r e e C day; e.g. an a v e r a g e t e m p e r a t u r e f o r 1 day of 5°C y i e l d s an ATU v a l u e = 5. ATU's were a p p r o x i m a t e d by t h e noon t e m p e r a t u r e s , as r e c o r d e d i n S a c h s C r e e k by a c a l i b r a t e d Ryan/Peabody c o n t i n u o u s r e c o r d i n g t h e r m o g r a p h . " G. T a c c o n g a , Community A d v i s o r , S a l m o n i d Enhancement Program, D e p t . F i s h e r i e s and Oceans, Queen C h a r l o t t e C i t y , B.C., p e r s o n a l c o m m u n i c a t i o n . 55 T a b l e 9 - Summary of Egg C r e e k , F a l l S u r v i v a l and W i n t e r on S t u d y S i t e s 1982-83. a t Sachs S i t e S a m p l i n g Per i o d P o t e n t i a l S u r v i v a l 1 R e l a t i v e S u r v i v a l 2 N A v e r a g e S u r v i v a l (%) S t d . Dev. A v e r a g e S u r v i v a l (%) S t d . Dev. T r e a t m e n t I I I Dec. 20 1 1 1 0 95 38 March 1 5 4.3 19 89 37 C o n t r o l I I I A Dec. 20 1 1 1 5 71 36 March 1 7 1 .0 4. 1 1 6 22 C o n t r o l I I I B Dec. 20 7.9 1 4 68 27 March 1 9 1 .6 3.7 39 34 1. S u r v i v a l t o d a t e of p i n k salmon eggs and a l e v i n s from p o t e n t i a l egg d e p o s i t i o n . 2. R e l a t i v e s u r v i v a l o f p i n k , chum and coho salmon L l i v e eggs and a l e v i n s e q u a l s : * 100 p e r c e n t £ L i v e + L Dead 56 350 F i g u r e 1 7 - A c c u m m u l a t e d T h e r m a l U n i t s a t S a c h s C r e e k O v e r F a l l a n d W i n t e r 1 9 8 2 - 1 9 8 3 . A n o t h e r f a c t o r t h a t i n f l u e n c e d t h e M a r c h s u r v i v a l v a l u e s w a s t h e t i m i n g o f e g g d e p o s i t i o n . P i n k s a l m o n s p a w n i n g c o m m e n c e d 1 0 d a y s . l a t e r o n T r e a t m e n t S i t e I I I t h a n a t i t s c o n t r o l s i t e s ( I I I A a n d I I I B ) ; a c o r r e s p o n d i n g l a t e r e m e r g e n c e m a y a c c o u n t f o r s o m e o f t h e h i g h e r s u r v i v a l v a l u e s f o u n d t h e r e i n M a r c h ( T a b l e 9 ) . T h e p r o b a b l e f r y e m e r g e n c e f r o m t h e g r a v e l p r i o r t o t h e M a r c h s a m p l i n g p r e c l u d e d i t s f u r t h e r a n a l y s i s ; o n l y t h e e g g s u r v i v a l t o D e c e m b e r w a s i n c l u d e d i n l a t e r d i s c u s s i o n . 57 A v e r a g e egg s u r v i v a l a p p e a r e d t o be g r e a t e r a t T r e a t m e n t S i t e I I I t h a n a t i t s two c o n t r o l s ( T a b l e 9 ) , but p a i r e d t - t e s t a n a l y s i s i n d i c a t e d t h a t t h i s d i f f e r e n c e was n o t s i g n i f i c a n t (p<.05) f o r e i t h e r t h e r e l a t i v e or t h e p o t e n t i a l s u r v i v a l i n d e x ( T a b l e 10). An "egg c a p a c i t y " f o r p i n k salmon spawning a r e a s was e s t a b l i s h e d from an optimum spawner d e n s i t y of 1 f e m a l e p i n k p e r m 2 ( M c N e i l 1964b). Egg c a p a c i t y was e x c e e d e d i n a l l t h r e e s i t e s sampled, w i t h a p r o p o r t i o n o f p o t e n t i a l d e p o s i t i o n i n e x c e s s of egg c a p a c i t y i n t h e s t a t i o n s sampled r a n g i n g from 10% f o r T r e a t m e n t S i t e I I I t o 30% f o r b o t h of i t s c o n t r o l s ( I I I A and I I I B ; T a b l e 1 1 ) . Egg s u r v i v a l a t i n d i v i d u a l s t a t i o n s was e x a mined i n a s t e p w i s e m u l t i p l e r e g r e s s i o n a n a l y s i s (Rao 1973) t o d e t e c t c o r r e l a t i o n s w i t h i n t r a g r a v e l d i s s o l v e d o x y g e n , i n t r a g r a v e l p e r m e a b i l i t y and d e p t h o f g r a v e l s c o u r . A l t h o u g h no s i g n i f i c a n t (p<.05) m u l t i p l e r e g r e s s i o n s were f o u n d , t h r e e s i m p l e c o r r e l a t i o n s were i n d i c a t e d . S i g n i f i c a n t c o r r e l a t i o n s (p<.05) were f o u n d between the i n d e x o f r e l a t i v e egg s u r v i v a l and t h r e e d i f f e r e n t g r o u p s of i n t r a g r a v e l d i s s o l v e d oxygen measurements: a) a t T r e a t m e n t S i t e I I I i n F e b r u a r y 1983 ( c o r r e l a t i o n c o e f f i c i e n t r=0.54; D.F.=18); b) a t C o n t r o l S i t e I I I A i n A u g u s t 1982 (r=0.48 ; D.F.=18); and c) a t a c o m b i n a t i o n o f T r e a t m e n t S i t e I I I and C o n t r o l S i t e I I I B i n F e b r u a r y 1983 (r=0.41 ; D.F.=37). D u r i n g s a m p l i n g , eggs were f r e q u e n t l y e n c o u n t e r e d w i t h i n 10cm of t h e g r a v e l s u r f a c e . On f u r t h e r e x a m i n a t i o n of 29 d e p t h s a m p l e s , a p p r o x i m a t e l y one h a l f of t h e p i n k eggs were d e p o s i t e d w i t h i n r e a c h of t h e h y d r a u l i c p r o b e when i n s e r t e d i n t h e s u r f a c e 58 20cm of g r a v e l , and t h e o t h e r h a l f when i n s e r t e d between 20cm and 40cm ( T a b l e 12). T a b l e 10 - A . t - t e s t A n a l y s i s of Egg S u r v i v a l i n Year 1 on T r e a t m e n t S i t e I I I and i t s C o n t r o l s a t S a c h s C r e e k . T r e a t m e n t C o n t r o l Type of Mean S t d . t D.F. S i g n i S i t e (X) S i t e (Y) S u r v i v a l 1 D i f f . Dev. i c a n c e (X-Y) 111 I I I A P o t e n t i a l -3.6 1 8 -0.87 18 N.S. R e l a t i v e 0.16 0.50 1 .4 18 N.S. I I I I I I B P o t e n t i a l 1 .0 1 2 0.37 18 N.S. R e l a t i v e 0.14 0.36 1 .7 18 N.S. 1. S u r v i v a l from t i m e of d e p o s i t i o n t o t h e " e y e d " s t a g e i n December 1982 was e x p r e s s e d by two i n d i c e s : i ) P o t e n t i a l s u r v i v a l e q u a l s : (Number o f l i v e p i n k eggs sampled) * t oo p e r c e n t ( P o t e n t i a l Number of p i n k eggs d e p o s i t e d ) i i ) R e l a t i v e s u r v i v a l e q u a l s : (Z l i v e p i n k , chum and coho sampled) * 1 0 o p e r c e n t (E l i v e ) + (Z dead eggs sampled) 2. p<.05; one t a i l e d p a i r e d t - t e s t ; Ho: X < Y ; H1: X > Y . [ t ( a t p<.05 f o r d f = l 8 ) = 1.73] 59 T a b l e 11 - Redd Super i m p o s i t i o n on E g g - s a m p l i n g S t a t i o n s a t Sachs C r e e k , 1982. S t a t i o n s w i t h P e r c e n t of Redd S u p e r i m p o s i t i o n 1 P o t e n t i a l P i n k Egg S i t e D e p o s i t i o n i n by P i n k s by Chum by A l l E x c e s s of P i n k O n l y 2 and C o h o 3 S p e c i e s Egg C a p a c i t y " T r e a t m e n t I I I 4 0 4 10 C o n t r o l I I I A 10 2 12 30 C o n t r o l I I I B 13 8 16 30 1. 19 s t a t i o n s were sampled f o r egg d e n s i t i e s a t e a c h of T r e a t m e n t S i t e I I I and i t s c o n t r o l s . 2. Where p i n k d e n s i t i e s e x c e e d e d 1 f e m a l e p e r m 2, c a l c u l a t e d from 1 r e d d = l 0 f e m a l e spawner d a y s o b s e r v e d . 3. Where chum o r coho spawned o v e r p r e v i o u s p i n k salmon r e d d s . 4. Assuming an optimum egg c a p a c i t y of 1 f e m a l e p i n k p e r m 2 ( M c N e i l 1964b). E f f e c t of s u p e r i m p o s i t i o n by o t h e r s p e c i e s was not i n c l u d e d . T a b l e 12 - V e r t i c a l D i s t r i b u t i o n o f P i n k Salmon Eggs a t Sachs C r e e k , December 1982. Egg D e p t h 1 (cm) L i v e P i n k E g g s 2 Dead Eggs Number P e r c e n t Number P e r c e n t 0 - 1 0 10 - 20 20 - 30 30 - 40 387 31 313 25 279 22 280 22 1 64 1 59 37 67 38 37 9 1 6 0 - 4 0 1,259 100 427 100 1. T h i s was t h e d e p t h t o w h i c h t h e h y d r a u l i c p r o b e was i n s e r t e d . I t was assumed t h a t eggs from below t h i s d e p t h were not drawn t o t h e s u r f a c e by t h e b u b b l i n g a c t i o n o f t h e p r o b e . Eggs below 40cm were not sampled. 2. N = 19 s t a t i o n s . 60 5. JUVENILE UTILIZATION Coho salmon and r a i n b o w t r o u t were the p r e d o m i n a n t j u v e n i l e s a l m o n i d s o c c u r r i n g t h r o u g h o u t summer on t h e s t u d y s i t e s i n S a c h s C r e e k . P i n k and chum salmon f r y m i g r a t e d t o sea soon a f t e r emergence from the g r a v e l i n e a r l y s p r i n g . B e f o r e t h e A u g u s t 1983 f l o o d , t h e d e n s i t i e s of j u v e n i l e coho and r a i n b o w t r o u t were 69% t o 92% h i g h e r i n t h e g a b i o n s i t e s t h a n i n t h e i r r e s p e c t i v e c o n t r o l s i t e s ( T a b l e 13). A f t e r t h i s f l o o d , t h e d e n s i t i e s o f j u v e n i l e s were 91% t o 224% h i g h e r i n t h e g a b i o n s i t e s t h a n i n t h e i r r e s p e c t i v e c o n t r o l s i t e s ( T a b l e 13). The A u g u s t 1983 f l o o d r e d u c e d t h e s e p o p u l a t i o n s between c a . 20% and 80% ( T a b l e 1 3 ) . Many of t h e j u v e n i l e s (16% t o 77%) marked p r i o r t o t h e f l o o d were p r e s e n t a t t h e same s i t e a f t e r w a r d s ( T a b l e 14). G a b i o n s d i d not a p p e a r t o have any c o n s i s t e n t e f f e c t on s u r v i v a l r a t e of marked j u v e n i l e s d u r i n g t h e f l o o d e v e n t ( T a b l e 14). The coho l e n g t h s most f r e q u e n t l y e n c o u n t e r e d were i d e n t i c a l f o r a l l g a b i o n and c o n t r o l s i t e s i n t h e l o w e r 2 km o f S a c h s C r e e k ( F i g u r e 1 8 ) . L a r g e r coho were more abundant t h a n s m a l l e r ones ( s i g n i f i c a n t a t p<.05) i n t h e h i g h e r s l o p e g r a d i e n t s i t e s ( T r e a t m e n t S i t e I and C o n t r o l IA; T a b l e 15 and F i g u r e 18). 61 T a b l e 13 - J u v e n i l e S a l m o n i d Usage of S t u d y S i t e s on Sachs C r e e k , P r e - and P o s t - F l o o d , Summer 1983. Pre - F l o o d ( J u l y ) P o s t - F l o o d ( A u g u s t ) S i t e L o c a t i o n Type R e l a t i v e No. Avg. D e n s i t y 1 No. Avg. D e n s i t y To of of G a b i o n s S i t e s Coho Coho+Rb 2 S i t e s Coho Coho+Rb T r e a t m e n t : U p s t r e a m 3 1.7 1 0.54 Between 3 1.0 2 0.43 Downstream 2 1.3 2 0.96 T o t a l 3 3 1.2 1.6 2 0. 67 1.1 3" 0.53 0.89 C o n t r o l A's ( m a r g i n a l h a b i t a t ) 2 0.59 0.82 2 0.16 0.33 C o n t r o l B's ( p r i m e h a b i t a t ) 3 0.82 0.93 2 0.34 0.56 A l l C o n t r o l s 5 0.73 0.89 4 0.25 0.45 1. D e n s i t y i n f i s h p e r m 2. 2. Rb = Rainbow T r o u t = S t e e l h e a d 3. D a t a from above c a t e g o r i e s were t o t a l l e d t o c a l c u l a t e o v e r a l l d e n s i t i e s a t t h e s i t e s . 4. T h i s t o t a l i n c l u d e s t h e d e n s i t i e s of T r e a t m e n t S i t e I , h e a v i l y damaged by t h e 2 A u g u s t 1983 f l o o d . 62 T a b l e 14 - J u v e n i l e S a l m o n i d P o p u l a t i o n Dynamics T h r o u g h the 2 A u g u s t 1983 F l o o d a t S a c h s C r e e k . L o c a t i o n Change i n R e c u r r e n c e of Marked S i t e R e l a t i v e P o p u l a t i o n D e n s i t y P r e - F l o o d F i s h 2 Type To G a b i o n s Coho Rb 1 T o t a l Coho Rainbow T o t a l T r e a t m e n t s II & I I I Combined: U p s t r e a m -53% 16% Between -61% 55% Downstream -26% 31% T o t a l -51% +26% -36% 36% 77% 42% C o n t r o l s I I A & I I I A ( m a r g i n a l h a b i t a t ) -84% ?" -70% 5 9 % 5 ? 43% C o n t r o l s I I B & I I I B ( p r i m e h a b i t a t ) -21% ? -19% 27% ? 21% T r e a t m e n t I 3 -92% -34% -76% ? 46% 33% 1. N.B. r e c r u i t m e n t o f 0+ r a i n b o w s h a t c h e d i n l a t e s p r i n g was i n c l u d e d i n p o s t - b u t not p r e - f l o o d p o p u l a t i o n e s t i m a t e s . 2. V a l u e s a p p r o x i m a t e t h e p r o p o r t i o n of f i s h f o u n d on a s i t e b e f o r e t h e f l o o d t h a t a r e f o u n d on t h e same s i t e a f t e r t h e f l o o d , where r e c u r r e n c e = ( p r o p o r t i o n of marks i n pop. p o s t - f l o o d ) *100% ( p r o p o r t i o n o f pop. marked p r e - f l o o d ) 3. T r e a t m e n t S i t e I was s e p a r a t e d , owing t o e x t e n s i v e damage a t t h i s h i g h e n e r g y s i t e . 4. Sample s i z e was i n s u f f i c i e n t t o c a l c u l a t e t h e p o p u l a t i o n . . When t r o u t d a t a were added t o coho d a t a , a t o t a l was p o s s i b l e . 5. A r e c u r r e n c e of 59% of t h e coho a t t h e C o n t r o l S i t e s I I A and I I I A was i n c o n f l i c t w i t h t h e e s t i m a t e d 84% r e d u c t i o n i n c o ho p o p u l a t i o n a t t h e s e s i t e s . T h i s may be from e f f e c t s of s a m p l i n g s m a l l p o p u l a t i o n s a f t e r t h e f l o o d ( a b o u t 14 and 42 r e s p e c t i v e l y ) . 63 T a b l e 15 - A t - t e s t A n a l y s i s of J u v e n i l e Coho L e n g t h F r e q u e n c i e s on S t u d y S i t e s a t Sachs C r e e k , Summer 1983. Mean Mean X N L e n g t h Y N L e n g t h t 1 D.F. S i g n i f -(mm) (mm) i c a n c e ' T r e a t I T r e a t I C o n t r IA T r e a t I T r e a t I T r e a t II T r e a t 11 T r e a t I I I T r e a t I I I 62 56 62 56 48 50 62 56 62 56 41 47 41 47 99 47 99 47 C o n t r IA C o n t r IB C o n t r IB T r e a t 11 T r e a t I I I Cont r II A C o n t r I I B 48 66 66 41 99 40 49 50 4.6 108 C o n t r I I I A 26 C o n t r I I I B 26 44 1 1 43 2.0 1 26 44 4.8 112 47 7.3 101 47 8.1 159 79 46 0.88 88 46 0.31 123 47 -0.33 123 S i g . S i g . S i g . S i g . S i g , S i g , N.S, N.S, N.S, 1. C a l c u l a t i o n s of t b a s e d on u n p a i r e d o b s e r v a t i o n s of i n d i v i d u a l 0+ coho salmon l e n g t h s . 2. p<.05; one t a i l e d t - t e s t ; Ho: X < Y ; H1: X > Y 64 40 20 H n=62 Treatment I July 12 40 -i 20 n = 49 I 1 Control IA July 12 I I I 1 40-20 n = 7l Control TB July II I 1 1 — 1 1 — i 40 20H n = 43 I 1 Treatment II July 14 I 1 > o z L U o LU rr u. 40-20 n=4l Control II A July 14 I I 40-20-n = 49 Control IIB July 13 I 1 40 20H n = 103 Treatment III August I I 1 40H 20 n = 27 Control IIIA July 30 I 1 40 20 n=26 Control III B July 31 m . 30-35 36-41 42-47 48-53 54-59 60-65 66-71 72-77 78-83 84-89 LEN6TH (mm) FIGURE 18 J Juvenile Coho Length Frequencies on Study Sites at Sachs Creek, Pre-flood, Summer 1983. 65 V. DISCUSSION To be s u c c e s s f u l f o r s t r e a m r e h a b i l i t a t i o n , g a b i o n w e i r s s h o u l d : i . C r e a t e s t r e a m b e d c o n f i g u r a t i o n s c o n d u c i v e t o a d u l t s a l m o n i d s pawning; i i . T r a p g r a v e l w h i c h i s not s u b j e c t e d t o e x c e s s i v e s c o u r and a g g r a d a t i o n a c t i o n of s t o r m f l o w s ; i i i . T r a p g r a v e l w h i c h has a q u a l i t y c o n d u c i v e t o h i g h e g g - t o - f r y s u r v i v a l . i v . P r o v i d e a p o o l - r i f f l e c o n f i g u r a t i o n s u i t a b l e f o r r e a r i n g j u v e n i l e s a l m o n i d s {coho and s t e e l h e a d ) ; v. E x h i b i t an a c c e p t a b l e b e n e f i t / c o s t e f f e c t i v e n e s s . The f o l l o w i n g d i s c u s s i o n c o n s i d e r s t h e e f f e c t i v e n e s s of g a b i o n w e i r s i n S a c h s C r e e k i n m e e t i n g t h e above c r i t e r i a . B e n e f i t s of g a b i o n i n s t a l l a t i o n i n s t r e a m s d e v a s t a t e d by d e b r i s t o r r e n t s may be more p r o n o u n c e d t h a n i n many s t r e a m s w i t h n a t u r a l l y s u i t a b l e spawning h a b i t a t . In Sachs C r e e k , t h e uppermost g a b i o n s i t e ( I ) was i n a r e g i o n s e v e r e l y a f f e c t e d by th e 1974 d e b r i s t o r r e n t ; t h e downstream g a b i o n s i t e s ( I I and I I I ) d i d riot a p p e a r g r e a t l y a f f e c t e d by t h e d e b r i s t o r r e n t . A l t h o u g h i t was t h e i n t e n t i o n o f t h i s s t u d y t o p r o v i d e r e s u l t s t h a t c o u l d be e x t r a p o l a t e d t o o t h e r l a n d s l i d e - d a m a g e d s t r e a m s , s u c h e x t r a p o l a t i o n c an o n l y be made w i t h c a u t i o n . 66 1. S I T E STABILITY G a b i o n s a t 1% s l o p e g r a d i e n t r e a c h e s i n t h i s s t u d y were b e g i n n i n g t o s t a b i l i z e e n t r a p p e d g r a v e l s i n y e a r 2 a f t e r c o n s i d e r a b l e c h a n g e s i n s i t e m o r p h o l o g y i n y e a r 1. G r a v e l s c o u r and a g g r a d a t i o n was h i g h a t a l l 3 g a b i o n s i t e s d u r i n g s t o r m f l o w s i n t h e f i r s t w i n t e r a f t e r c o n s t r u c t i o n ( T a b l e 1 ) . The changes i n s t r e a m m o r p h o l o g y c a u s e d by g a b i o n i n s t a l l a t i o n i n d u c e d s c o u r and f i l l as t h e s t r e a m a p p r o a c h e d a new e q u i l i b r i u m (Reeves and R o e l o f s 1982). R e - s h a p i n g of g a b i o n s i t e s by s t o r m f l o w s was e x p e c t e d t o d e c r e a s e o v e r t i m e , owing t o s e l f - a r m o u r i n g of s c o u r e d h i g h - f l o w c h a n n e l s t h a t d e v e l o p e d a f t e r g a b i o n i n s t a l l a t i o n . Streambed c o n f i g u r a t i o n s a p p e a r e d t o have a c h i e v e d an e q u i l i b r i u m i n y e a r 2, e s p e c i a l l y e v i d e n t a t t h e s i t e s a t 1% s l o p e g r a d i e n t ( T r e a t m e n t S i t e s II and I I I ; F i g u r e s 10 and 1 1 ) . A s t a t e of dynamic e q u i l i b r i u m was e v i d e n t o v e r some of t h e s t u d y s i t e s when g r a v e l s from f u r t h e r u p s t r e a m r e p l a c e d t h o s e b e i n g s c o u r e d downstream. Dynamic e q u i l i b r i u m r e s u l t e d i n g r a v e l s c o u r b e i n g r e g i s t e r e d by v e r t i c a l e r o s i o n m o n i t o r s a l t h o u g h no n e t change i n st r e a m b e d c o n f i g u r a t i o n o c c u r r e d . A s u c c e s s f u l g a b i o n would r e d u c e t h e d e p t h o f g r a v e l s c o u r t o m i n i m i z e t h e p h y s i c a l r e m o v a l of s a l m o n i d eggs (page 7 8 ) . S u c c e s s i n r e d u c i n g g r a v e l s c o u r was e v i d e n t a t t h e two low e r t r e a t m e n t s i t e s ( I I and I I I ) o v e r t h e s e c o n d s e a s o n of w i n t e r s t o r m f l o w s ; t h e a v e r a g e s c o u r a t T r e a t m e n t S i t e s I I and I I I was ab o u t t h e same as t h e a v e r a g e o f t h e c o n t r o l s i t e s (4-5cm; T a b l e 1 ) . T h i s d e p t h of s c o u r may have d i r e c t l y a f f e c t e d up t o 15% of 67 t h e p i n k eggs (page 7 9 ) . However, m o r t a l i t y t h r o u g h s c o u r was o n l y one of s e v e r a l f a c t o r s t h a t f u r t h e r r e d u c e d p i n k egg s u r v i v a l t o a b o u t 10% ( T a b l e 9 ) . I t would a p p e a r t h a t a t t e m p t i n g t o s t a b i l i z e g r a v e l more t h a n t h e 4-5cm of s c o u r f o u n d i n c o n t r o l s i t e s ( T a b l e 1) may become d e t r i m e n t a l t o o v e r a l l s a l m o n i d egg s u r v i v a l , owing t o t r a d e o f f s w i t h b e n e f i c i a l a s p e c t s of g r a v e l s c o u r . E n g e l s (MS1975) c o n c l u d e d t h a t : " S e e k i n g t o t a l s t a b i l i t y of a g r a v e l bar becomes s e l f -d e f e a t i n g , s i n c e s u c h permanence c a n o n l y be o b t a i n e d by r e d u c i n g s t r e a m v e l o c i t i e s t o a p o i n t where t h e u t i l i t y of a g r a v e l bar as a spawning a r e a i s n e g a t e d due t o i t s b e i n g c o m p l e t e l y b u r i e d under f i n e s a n d and s i l t . The optimum g o a l - t h a t of p r o v i d i n g r e a s o n a b l e s t a b i l i t y w i t h w ater v e l o c i t i e s s t i l l h i g h enough t o p r e v e n t b u r i a l under sa n d and s i l t - r e q u i r e s a p p r o x i m a t i n g t h e n a t u r a l e q u i l i b r i u m c o n d i t i o n n o t e d above [a s t a t e of s e m i - o r d y n a m i c - e q u i l i b r i u m ] . Under s u c h c o n d i t i o n s , g r a d u a l s c o u r of a g r a v e l bed i s c o n s i d e r e d b o t h n e c e s s a r y and n o r m a l , and p e r i o d i c r e p l e n i s h m e n t of t h e g r a v e l s u p p l y must be c o n s i d e r e d as a n o r m a l m a i n t e n a n c e e x p e n s e . " G r a v e l s c o u r a t t h e u p p e r 3% s l o p e g r a d i e n t T r e a t m e n t S i t e I r e m a i n e d above a v e r a g e (12cm) i n y e a r 2. The s u b s t a n t i a l d e c r e a s e i n l o c a l s t r e a m b e d g r a d i e n t s a t t h e g a b i o n s i t e s ( T a b l e 3) p r o b a b l y was r e s p o n s i b l e f o r p a r t of t h e s t a b i l i z a t i o n e f f e c t e v i d e n t a t t h e l o w e r two t r e a t m e n t s i t e s ( I I and I I I ) . By r e d u c i n g t h e l o c a l s l o p e , g a b i o n s r e d u c e t h e s h e a r s t r e s s a t t h e water / g r a v e l i n t e r f a c e , c a u s i n g g r a v e l d e p o s i t i o n ( L i s l e 1981). A l t h o u g h t h e l o c a l s t r e a m b e d g r a d i e n t of T r e a t m e n t S i t e I a l s o d e c r e a s e d a f t e r g a b i o n i n s t a l l a t i o n , t h e h i g h s t o r m f l o w e n e r g y a t t h i s 3% s l o p e g r a d i e n t s i t e was p r o b a b l y s u f f i c i e n t t o p r o d u c e e x c e s s i v e s c o u r even a t t h e s e r e d u c e d l o c a l g r a d i e n t s . 68 Some of t h i s s c o u r i n y e a r 2 may have been i n d u c e d from an e v e n t i n A u g u s t 1983 w h i c h s e v e r e l y c h a n g e d t h e c o n f i g u r a t i o n of T r e a t m e n t S i t e I . " F a i l u r e " a t T r e a t m e n t S i t e I The a p p a r e n t " f a i l u r e " of T r e a t m e n t S i t e I was a c o n s e q u e n c e of n a t u r a l s t r e a m d y n a m i c s i n t h i s p r e v i o u s l y d e s t a b i l i z e d s y s t e m . Two new c h a n n e l s 40m downstream of t h e g a b i o n s were formed, one d u r i n g 1981-82 w i n t e r f l o o d s , t h e s e c o n d d u r i n g 1982-83 w i n t e r f l o o d s . The s t e e p s l o p e g r a d i e n t a t t h e u p s t r e a m end of t h e s e new c h a n n e l s was m a i n t a i n e d by o l d b u r i e d l o g s and b o u l d e r s u n t i l t h e A u g u s t 1983 f l o o d ; t h e s e gave way, r e s u l t i n g i n a more g e n t l e s l o p e g r a d i e n t . The e f f e c t o f t h i s was not u n l i k e " n i c k p o i n t m i g r a t i o n " ( L . Beaven p e r s . comm.) 5 ; t h e s t e e p s l o p e g r a d i e n t ( n i c k p o i n t ) p o r t i o n of t h e s t r e a m c h a n n e l moved p r o g r e s s i v e l y u p s t r e a m as m a t e r i a l s a t t h e b ase of t h i s n i c k p o i n t were washed downstream. T h i s n i c k p o i n t m i g r a t i o n was t e m p o r a r i l y h a l t e d a t t h e l o w e r g a b i o n a t T r e a t m e n t S i t e I . L a c k of t h e s u p p o r t p r o v i d e d p r i o r t o t h e f l o o d by s t r e a m b e d m a t e r i a l a g a i n s t t h e downstream edge of t h i s g a b i o n e n a b l e d t h e g a b i o n t o s t a r t r o l l i n g i n t o i t s now -e n l a r g e d p l u n g e p o o l ( F i g u r e 9 ) ; t h e t h e h e i g h t of t h e w ater f a l l o v e r t h i s l o w e r g a b i o n i n c r e a s e d from t h e p r e v i o u s 40cm t o t h e new h e i g h t o f 90cm. The g a b i o n r e s p o n d e d t o t h e s e c h a n g e s by bowing a b o u t 1m downstream and r o l l i n g a b o u t 20° o f f t h e v e r t i c a l . S h o u l d t h i s g a b i o n and t h e u p s t r e a m one f a i l 5 L. Beaven, F l u v i a l G e o m o r p h o l o g i s t , F i s h / F o r e s t r y I n t e r a c t i o n Program, Queen C h a r l o t t e C i t y , B.C., p e r s o n a l c o m m u n i c a t i o n . 69 p r o g r e s s i v e l y , t h i s n i c k p o i n t w i l l m i g r a t e u p s t r e a m and e n d a n g e r the f o u n d a t i o n o f a l o g b r i d g e 20m above t h e upper g a b i o n . One p r o b l e m w i t h t h e V - s h a p e d g a b i o n c o n f i g u r a t i o n was t h a t o f bank s c o u r . Water c h a n g e d d i r e c t i o n when e n c o u n t e r i n g g a b i o n s , f l o w i n g p e r p e n d i c u l a r l y a c r o s s them. T h i s i n t r o d u c e d a l a t e r a l component, d i r e c t i n g s t r e a m f l o w t o w a r d s t h e banks. S t o r m f l o w s r e s u l t e d i n c o n s i d e r a b l e bank e r o s i o n a t t h e downstream c o r n e r s o f t h e g a b i o n w i n g s . R i p r a p p l a c e m e n t a t s t r a t e g i c p o i n t s a l l e v i a t e d t h i s p r o b l e m a t t h e lower two t r e a t m e n t s i t e s ( I I and I I I ) . The n i c k p o i n t m i g r a t i o n a t t h e upper T r e a t m e n t S i t e I removed r i p r a p , e x p o s i n g t h e two l a t e r a l c o r n e r s t o s u b s e q u e n t e r o s i o n ( F i g u r e 9 ) . 2. GRAVEL QUALITY G a b i o n s i n t h i s s t u d y were s u c c e s s f u l i n c r e a t i n g h i g h q u a l i t y s a l m o n i d embryo and a l e v i n i n c u b a t i o n a l p r o p e r t i e s i n t h e i r e n t r a p p e d g r a v e l s . T hese h i g h q u a l i t y i n c u b a t i o n a l p r o p e r t i e s i n c l u d e d s u i t a b l e : a) i n t r a g r a v e l d i s s o l v e d oxygen c o n t e n t , b) s u b s u r f a c e w a t e r v e l o c i t i e s f o r oxygen p r o v i s i o n and m e t a b o l i c waste r e m o v a l , and c) s a l m o n i d f r y a c c e s s t o s u r f a c e w a t e r s f o r emergence. These p r o p e r t i e s a r e n o t n e c e s s a r i l y t h o s e t h a t a r e c o n d u c i v e t o a d u l t spawning, as d i s c u s s e d i n t h e n e x t s e c t i o n (page 7 4 ) . G a b i o n s f a c i l i t a t e d t h e exchange of s u r f a c e / i n t r a g r a v e l w a t e r s n e c e s s a r y t o meet t h e s e c r i t e r i a by i n c r e a s i n g c h a n n e l r o u g h n e s s . Vaux (1962 and 1968) s u g g e s t e d t h e f a c t o r s t h a t c o n t r o l l e d t h i s i n t e r c h a n g e i n c l u d e d : a) t h e s t r e a m s u r f a c e p r o f i l e , b) g r a v e l p e r m e a b i l i t i e s , c) g r a v e l bed 70 d e p t h , and d) i r r e g u l a r i t y of t h e s t r e a m b e d s u r f a c e . H i s e x a m i n a t i o n of 3 c a s e s of s t r e a m b e d p r o f i l e i n d i c a t e d : a) no i n t e r c h a n g e w i t h a s t r a i g h t s u r f a c e , b) water f l o w e d out of t h e g r a v e l a t a c o n c a v e s u r f a c e , and c) water f l o w e d i n t o t h e g r a v e l a t a c o n v e x s u r f a c e . R e s u l t s of i n t r a g r a v e l oxygen measurements of t h i s s t u d y were i n agreement w i t h t h e above f i n d i n g s of Vaux (1962 and 1968); i n t r a g r a v e l d i s s o l v e d oxygen was m a i n t a i n e d a t a h i g h c o n c e n t r a t i o n a t t h e upper t r e a t m e n t s i t e ( I ) and s i g n i f i c a n t l y i m p r o v e d w i t h g a b i o n i n s t a l l a t i o n a t T r e a t m e n t S i t e s I I and I I I ( T a b l e s 4 and 5 ) . Where t h e r e was o n l y one c o n v e x r e g i o n of t h e s t r e a m p r o f i l e s p e r g a b i o n s i t e p r i o r t o g a b i o n i n s t a l l a t i o n a t t h e t a i l (downstream end) of t h e u p s t r e a m p o o l , t h e r e were t h r e e convex r e g i o n s p e r s i t e a f t e r i n s t a l l a t i o n : a) a t t h e t a i l of t h e i n i t i a l p o o l above t h e u p s t r e a m g a b i o n s , b) a t t h e t a i l of t h e p l u n g e p o o l between t h e g a b i o n s , and c) a t t h e t a i l of t h e p l u n g e p o o l downstream of t h e l o w e r g a b i o n s ( F i g u r e s 9, 10 and 1 1 ) . S t r e a m f l o w t u r b u l e n c e was a n o t h e r f a c t o r f o u n d t o f a c i l i t a t e t h i s s u r f a c e / i n t r a g r a v e l water i n t e r c h a n g e (Vaux 1962, W i c k e t t 1962). T u r b u l e n c e was p r o v i d e d a t t h e g a b i o n s i t e s by t h e p l u n g e o v e r t h e g a b i o n s . G r a v e l c o m p o s i t i o n and i n t r a g r a v e l p e r m e a b i l i t y a r e i n t e r r e l a t e d f a c t o r s w h i c h a f f e c t e d t h e s u p p l y of i n t r a g r a v e l d i s s o l v e d oxygen t o i n c u b a t i n g s a l m o n i d eggs and a l e v i n s . The p r o p o r t i o n of f i n e s e d i m e n t s i n s t r e a m g r a v e l s has been i n v e r s e l y c o r r e l a t e d w i t h i n t r a g r a v e l d i s s o l v e d oxygen ( L a n g e r 1974, M c N e i l 1969, P h i l l i p s 1971, S k a u g s e t 1980). T h i s 71 r e l a t i o n s h i p was a r e s u l t of a r e d u c e d i n t r a g r a v e l p e r m e a b i l i t y (and t h e r e b y r e d u c e d i n t r a g r a v e l water v e l o c i t y ) o b s e r v e d when i n c r e a s e d f i n e s e d i m e n t s f i l l e d i n t r a g r a v e l p o r e s p a c e s ( C o o p e r 1974, W i c k e t t 1962). The n e g a t i v e e f f e c t s of f i n e s e d i m e n t s on s a l m o n i d egg s u r v i v a l have been e x t e n s i v e l y documented ( B j o r n n 1968, C e d e r h o l m and S a l o 1979, Cooper 1974, K o s k i 1975, M e r r e l l 1962, S h e l t o n and P o l l o c k 1966, S l a n e y e t a l . 1977, T a g a r t 1976) and summarized by C e d e r h o l m and S a l o ( 1 9 7 9 ) . In a d d i t i o n t o f i n e s e d i m e n t s r e d u c i n g t h e p e r m e a b i l i t y o f t h e g r a v e l s ( W i c k e t t 1962), t h e y a l s o may o b s t r u c t a c c e s s t o t h e s u r f a c e w a t e r s f o r e m e r g i n g f r y ( S l a n e y e t a l . 1977). The e f f e c t of g a b i o n i n s t a l l a t i o n on t h e c o m p o s i t i o n and p e r m e a b i l i t y of e n t r a p p e d s t r e a m b e d g r a v e l s was not c l e a r l y d e m o n s t r a t e d i n t h i s s t u d y ; improvement of g r a v e l q u a l i t y was i n c o n s i s t e n t b o t h between p a r a m e t e r s measured and between g a b i o n s i t e s , as d i s c u s s e d s e p a r a t e l y below. 1. T r e a t m e n t S i t e I Changes i n g r a v e l q u a l i t y a t T r e a t m e n t S i t e I c o u l d not be d e t e r m i n e d , owing t o t h e c o a r s e n a t u r e of s t r e a m b e d m a t e r i a l s p r i o r t o g a b i o n i n s t a l l a t i o n ; c o a r s e s u b s t r a t e p r e c l u d e d s a m p l i n g of i n t r a g r a v e l p e r m e a b i l i t y and g r a v e l c o m p o s i t i o n b e f o r e g a b i o n i n s t a l l a t i o n . S ediment t r a p a n a l y s i s was a l s o u n a v a i l a b l e , s i n c e a l l t r a p s a t T r e a t m e n t S i t e I were s c o u r e d out d u r i n g w i n t e r s t o r m f l o w s . The q u a l i t y of g r a v e l a t T r e a t m e n t S i t e I one y e a r a f t e r g a b i o n i n s t a l l a t i o n can be compared t o t h a t a t o t h e r s i t e s . The p r o p o r t i o n of f i n e s i n s a m p l e s a t T r e a t m e n t S i t e I was l o w e r 72 t h a n a t f i v e o t h e r s t u d y s i t e s ( F i g u r e 14). On t h e o t h e r hand, T r e a t m e n t S i t e I had more c o a r s e m a t e r i a l t h a n a l l of t h e o t h e r s t u d y s i t e s sampled e x c e p t i t s " m a r g i n a l h a b i t a t " C o n t r o l IA ( F i g u r e 13). P e r m e a b i l i t y one y e a r a f t e r i n s t a l l a t i o n h e r e was above th e a v e r a g e of t h e s i x s i t e s sampled b e f o r e i n s t a l l a t i o n but below t h e a v e r a g e of t h e e i g h t s i t e s sampled one y e a r a f t e r i n s t a l l a t i o n ( T a b l e 4 ) . T h e s e r e s u l t s s u g g e s t t h a t b o t h low f i n e s and low p e r m e a b i l i t y e x i s t e d h e r e a f t e r i n s t a l l a t i o n , i n c o n t r a s t t o t h e o b s e r v a t i o n s of C o o p e r (1974) and W i c k e t t (1962) t h a t a low p r o p o r t i o n of f i n e s r e s u l t i n h i g h p e r m e a b i l i t y . Owing t o t h e h i g h s p a t i a l v a r i a b i l i t y i n g r a v e l c o m p o s i t i o n f o u n d i n s t r e a m b e d s ( S c r i v e n e r and B r o w n l e e 1982) t h e g r a v e l sample s i z e h e r e (n = 5) may have been i n s u f f i c i e n t t o r e p r e s e n t t h e whole s i t e . The p r o b l e m of s e a s o n a l v a r i a b i l i t y i n i n t r a g r a v e l p e r m e a b i l i t y and g r a v e l c o m p o s i t i o n ( S c r i v e n e r and B r o w n l e e 1982) was m i n i m i z e d i n t h e p r e s e n t s t u d y by s a m p l i n g b o t h of t h e s e p a r a m e t e r s d u r i n g t h e summers. 2. T r e a t m e n t S i t e I I T h r e e g r a v e l q u a l i t y p a r a m e t e r s i n d i c a t e d t h a t g a b i o n s i m p r o v e d t h e q u a l i t y of s a l m o n i d egg i n c u b a t i o n h a b i t a t a t T r e a t m e n t S i t e I I . I n t r a g r a v e l p e r m e a b i l i t y and d i s s o l v e d oxygen b o t h i n c r e a s e d a f t e r g a b i o n i n s t a l l a t i o n (page 3 7 ) . Sediment t r a p a n a l y s i s s u g g e s t e d t h e r e was l e s s s e d i m e n t a t i o n h e r e t h a n a t i t s c o n t r o l s i t e s ( I I A and I I B ; F i g u r e 15). These improvements were not r e f l e c t e d i n t h e amount o f f i n e s e d i m e n t s i n g r a v e l s a m p l e s a t t h i s s i t e . No change was d e t e c t e d w i t h g a b i o n i n s t a l l a t i o n , p e r h a p s a r e s u l t of t h e i n i t i a l l y l ower 73 p r o p o r t i o n of f i n e s a t T r e a t m e n t S i t e II b e f o r e g a b i o n i n s t a l l a t i o n t h a n a t most o t h e r s i t e s ( F i g u r e 14). Where t h e p r o p o r t i o n of f i n e s was i n i t i a l l y h i g h , s u c h as a t T r e a t m e n t S i t e I I I , t h e amount of f l u s h i n g by spawning f i s h and g r a v e l s c o u r a v a i l a b l e r e d u c e d f i n e s t o t h e low p r o p o r t i o n s f o u n d a T r e a t m e n t S i t e II ( F i g u r e 14). 3. T r e a t m e n t S i t e I I I T h r e e o f t h e g r a v e l q u a l i t y p a r a m e t e r s measured i n d i c a t e d t h e g a b i o n s a t T r e a t m e n t S i t e I I I r e s u l t e d i n i n c r e a s e d q u a l i t y of i n c u b a t i o n a l h a b i t a t . The f i n e s e d i m e n t s f o u n d i n g r a v e l s amples d e c r e a s e d w i t h g a b i o n i n s t a l l a t i o n ( F i g u r e 14). However, the r e d u c t i o n s i n f i n e s i n g r a v e l s a m p l e s was not i n agreement w i t h s e d i m e n t t r a p r e s u l t s . G r e a t e r f i n e s e d i m e n t a c c u m u l a t i o n was f o u n d i n s e d i m e n t t r a p s a t T r e a t m e n t S i t e I I I when compared t o t h a t of C o n t r o l S i t e s I I I A and I I I B ( F i g u r e 15). T h i s c o n t r a d i c t i o n may be an a r t i f a c t of t h e s e d i m e n t t r a p r e s u l t s . S i n c e many of t h e t r a p s were l o s t from s c o u r i n g , t h o s e r e c o v e r e d and a n a l y z e d were n e c e s s a r i l y i n d e p o s i t i o n a l a r e a s and l o w - s c o u r a r e a s (< 5cm). The h i g h e r s e d i m e n t a c c u m u l a t i o n s a t T r e a t m e n t S i t e I I I may have r e s u l t e d from a h i g h e r p r o p o r t i o n of t r a p s r e c o v e r e d from d e p o s i t i o n a l a r e a s t h a n t h a t of i t s c o n t r o l s i t e s ( I I I A and I I I B ) . B o t h i n t r a g r a v e l p e r m e a b i l i t y and d i s s o l v e d oxygen i n c r e a s e d a f t e r g a b i o n i n s t a l l a t i o n ( T a b l e s 4, 5 and 6 ) . D i f f e r e n t p r o c e s s e s w h i c h a f f e c t g r a v e l q u a l i t y p r o b a b l y were i n t e r a c t i n g on t h e s t u d y s i t e s . N a t u r a l s c o u r and f i l l p r o c e s s e s d u r i n g s t o r m f l o w s s o r t g r a v e l s b e h i n d " r o u g h n e s s 74 e l e m e n t s " such a s g a b i o n s ( L i s l e 1981); d u r i n g t h e r e c e d i n g l i m b of t h e h y d r o g r a p h , u p w e l l i n g b e h i n d s t r e a m o b s t r u c t i o n s keep f i n e s e d i m e n t s i n s u s p e n s i o n w h i l e c o a r s e r g r a v e l s d e p o s i t i n t h e p r e v i o u s l y s c o u r e d a r e a s . The r e d d d i g g i n g p r o c e s s o f spawning salmon a l s o c an r e d u c e t h e p r o p o r t i o n of f i n e s e d i m e n t s i n spawning g r a v e l s ( M c N e i l and A h n e l l 1964, S h a p e l y and B i s h o p 1965). A l t h o u g h s c o u r d u r i n g f r e s h e t s may be s i g n i f i c a n t i n f l u s h i n g f i n e s i n t h e upper 5~6cm (Year2 a v e r a g e ; T a b l e 1), spawning a c t i v i t y may f l u s h g r a v e l s d e e p e r t h a n t h e 25cm i n s e r t i o n d e p t h of t h e p e r m e a b i l i t y s t a n d p i p e . The f l u s h i n g a c t i o n of up t o a b o u t 150 p i n k s p e r s i t e ( T a b l e 7) may be r e p o n s i b l e f o r t h e a p p a r e n t i n c r e a s e s i n p e r m e a b i l i t y o b s e r v e d i n C o n t r o l S i t e s I I I A and I I I B from summer 1982 t o summer 1983. The dominance of t h e even y e a r p i n k r u n a l l o w e d 20 months of f i n e s a c c u m u l a t i o n p r i o r t o t h e 1982 s a m p l i n g b u t o n l y 8 months a c c u m u l a t i o n p r i o r t o 1983 s a m p l i n g . A s i m i l a r s e a s o n a l i n c r e a s e i n p e r m e a b i l i t y w i t h s p a w n ing a c t i v i t y was f o u n d i n C a r n a t i o n C r e e k f o r t h e p r e - l o g g i n g p e r i o d ( S c r i v e n e r and Br o w n l e e 1982). T h i s c o i n c i d e d w i t h a s e a s o n a l t r e n d of d e c r e a s e d f i n e s d u r i n g spawning and w i n t e r s t o r m f l o w s and an a c c u m u l a t i o n o f f i n e s o v e r summer. 3. SPAWNER UTILIZATION The g a b i o n s s u c c e e d e d i n p r o d u c i n g g r a v e l beds s u i t a b l e f o r salmon spawning, as i n d i c a t e d by b o t h spawner o b s e r v a t i o n s and c a l c u l a t e d p r o b a b i 1 i t y - o f - u s e ( p a g e s 49 and 5 2 ) . The o b s e r v e d spawning a c t i v i t y i n d i c a t e d g a b i o n s had v a r i a b l e e f f e c t s on s i t e u sage compared t o c o n t r o l s . T r e a t m e n t S i t e I was u p s t r e a m of 75 p i n k and chum d i s t r i b u t i o n , but had g r e a t e r c oho usage t h a n i t s c o n t r o l s i t e s (IA and IB; T a b l e 7 ) . P i n k usage a t T r e a t m e n t S i t e I I was g r e a t e r t h a n i t s m a r g i n a l c o n t r o l ( I I A ) but l e s s t h a n i t s p r i m e c o n t r o l ( I I B ; T a b l e 7 ) . The g r e a t e r abundance of p i n k and chum spawners i n l o w e r r e a c h e s of S a c h s C r e e k ( F i g u r e 16) was p r o b a b l y the c a u s e of lower o b s e r v e d u t i l i z a t i o n of T r e a t m e n t S i t e I I I t h an i t s c o n t r o l s i t e s ( I I I A and I I I B ; T a b l e 7 ) . The h i g h e r u t i l i z a t i o n of T r e a t m e n t S i t e I I I t h a n T r e a t m e n t S i t e II may be a r e s u l t of t h e " d r a i n r o c k " on t h e l a t t e r s i t e not b e i n g of a s i z e a t t r a c t i v e t o p i n k s p a w n e r s . P r o b a b i l i t y - o f - u s e c a l c u l a t i o n s f o r T r e a t m e n t S i t e s I and I I and t h e i r c o n t r o l s were i n agreement w i t h t h e o b s e r v e d spawning a c t i v i t y ( T a b l e s 7 and 8 ) . However, t h e c a l c u l a t e d p r o b a b i l i t y - o f - u s e f o r T r e a t m e n t S i t e I I I compared t o t h a t of i t s c o n t r o l s was not i n agreement w i t h t h e r e l a t i o n s h i p of o b s e r v e d spawner usage of T r e a t m e n t S i t e I I I compared t o t h a t of i t s c o n t r o l s . Where o b s e r v e d p i n k spawner usage of T r e a t m e n t S i t e I I I was 0.5 t h a t o f i t s c o n t r o l I I I B ( T a b l e 7 ) , i t s c a l c u l a t e d p r o b a b i l i t y - o f - u s e was s l i g h t l y g r e a t e r t h a n t h i s same c o n t r o l ( T a b l e 8 ) . The e x p l a n a t i o n f o r t h i s c o n t r a d i c t i o n p r o b a b l y l i e s i n t h e spawner d i s t r i b u t i o n w i t h i n t h e s t r e a m . L e s s t h a n 0.5 a s many p i n k spawners were a v a i l a b l e t o spawn on T r e a t m e n t S i t e I I I as were a v a i l a b l e a t C o n t r o l S i t e I I I B ( a b o u t 4.8 and 11 f i s h / m r e s p e c t i v e l y ; F i g u r e 1 6 ) . A d j u s t i n g t h e o b s e r v e d u t i l i z a t i o n of T r e a t m e n t S i t e I I I by t h e i n v e r s e of t h e r e l a t i o n s h i p of spawner a v a i l a b i l i t y (2.3) would b r i n g o b s e r v e d u t i l i z a t i o n i n agreement w i t h p r o b a b i l i t y - o f - u s e . S i m i l a r 76 r e l a t i o n s h i p s were f o u n d between T r e a t m e n t S i t e I I I and C o n t r o l S i t e s I I B and I I I A , as e x p l a i n e d below: i . The r a t i o s of o b s e r v e d spawning a c t i v i t y of C o n t r o l S i t e s I I B and I I I A compared t o t h a t of T r e a t m e n t S i t e I I I were 0.90 and 1.8 r e s p e c t i v e l y ( T a b l e 7 ) . i i . The r a t i o s of spawner a v a i l a b i l i t y on C o n t r o l S i t e s I I B and I I I A compared t o T r e a t m e n t S i t e I I I were a b o u t 0.64 and 1.3 r e s p e c t i v e l y ( F i g u r e 1 6 ) . i i i . To a c c o u n t f o r d i f f e r e n c e s i n spawner a v a i l a b i l i t y , t h e r a t i o s of o b s e r v e d spawning a c t i v i t y i n i ) s h o u l d be m u l t i p l i e d by t h e i n v e r s e of t h e r a t i o s of spawner a v a i l a b i l i t y i n i i ) . i v . The r a t i o s o f o b s e r v e d spawner a c t i v i t y , when a d j u s t e d as i n i i i ) , a p p r o x i m a t e t h e r a t i o s of t h e p r o b a b i l i t y -o f - u s e o f C o n t r o l S i t e s I I B and I I I A compared t o t h a t of T r e a t m e n t S i t e I I I ( b o t h a t 1.4; T a b l e 8 ) . T h i s s u g g e s t s t h a t d i s t a n c e u p s t r e a m of t h e e s t u a r y a f f e c t s spawner d i s t r i b u t i o n i n d e p e n d e n t l y of o t h e r p r o b a b i 1 i t y - o f - u s e f e a t u r e s . P r o b a b i 1 i t y - o f - u s e c a l c u l a t i o n s s h o u l d t h e r e f o r e i n c o r p o r a t e d i s t a n c e u p s t r e a m of t h e e s t u a r y as a usage c r i t e r i a . . T r e a t m e n t S i t e I may not have had spawning h a b i t a t s u i t a b l e f o r p i n k salmon ( T a b l e 8 ) , owing t o i t s s t e e p s l o p e g r a d i e n t (3%) and r e s u l t a n t h i g h e n e r g y of s t o r m f l o w s , even i f p i n k and chum spawners c o u l d have r e a c h e d i t ( F i g u r e 7 ) . The l i k e l i h o o d of e v e r c r e a t i n g a r t i f i c i a l s p awning h a b i t a t i n s t e e p g r a d i e n t , upper r e a c h e s o f " f l a s h y " Queen C h a r l o t t e I s l a n d s s t r e a m s i s 77 p o o r . However, i n r e a c h e s h a v i n g l o w e r s l o p e g r a d i e n t s ( 1 % t o 2 % ) , g a b i o n s can c r e a t e h a b i t a t s u i t a b l e f o r p i n k and chum spawn i ng. 4. EGG SURVIVAL G a b i o n s i n t h i s s t u d y d i d not improve e a r l y s u r v i v a l of p i n k and chum salmon i n t h e f i r s t y e a r a f t e r t h e i r i n s t a l l a t i o n . In c o n t r a s t , a s t u d y i n W a s h i n g t o n s u g g e s t e d t h a t g a b i o n s t h e r e i m p r o v e d chum egg s u r v i v a l d u r i n g t h e i r f i r s t y e a r o f o p e r a t i o n (Gerke MS1974). The a v e r a g e p i n k salmon egg s u r v i v a l t o December a t T r e a t m e n t S i t e I I I and i t s two C o n t r o l S i t e s I I I A and I I I B ( 1 1 % , 11%, and 7.9% r e s p e c t i v e l y ; T a b l e 9) l i e w i t h i n t h e r a n g e of o t h e r c o a s t a l s t r e a m s . F r e q u e n t l y , 95% of eggs d e p o s i t e d by p i n k and chum salmon d i e b e f o r e t h e f r y emerge from spawning g r a v e l s ( D i l l 1969, L a n g e r 1974, M c N e i l 1966 and 1969, M e r r e l l 1962). The s u b s t a n t i a l d i f f e r e n c e i n p i n k salmon egg s u r v i v a l c a l c u l a t e d by t h e two i n d i c e s u s e d i n t h i s s t u d y ( r e l a t i v e egg s u r v i v a l was on a v e r a g e 68% h i g h e r t h a n t h e egg s u r v i v a l f r o m p o t e n t i a l egg d e p o s i t i o n ; December v a l u e s , T a b l e 9) i n d i c a t e d a h i g h d e g r e e of egg l o s s from t h e g r a v e l s . The r e l a t i v e s u r v i v a l •index d i d not a c c o u n t f o r t h e s e egg l o s s e s . B o t h b i o l o g i c a l and p h y s i c a l f a c t o r s a f f e c t s a l m o n i d egg s u r v i v a l . B i o l o g i c a l f a c t o r s i n c l u d e p r e d a t i o n by b i r d s , f i s h and i n s e c t s , non-f e r t i l i z a t i o n o f e g g s , and r e d d s u p e r i m p o s i t i o n . Redd s u p e r i m p o s i t i o n egg l o s s e s r e s u l t from l a t e a r r i v a l spawners d i g g i n g new r e d d s on t o p of p r e v i o u s l y c o n s t r u c t e d r e d d s . P h y s i c a l - c h e m i c a l f a c t o r s t h a t a f f e c t s a l m o n i d egg s u r v i v a l 78 i n c l u d e g r a v e l s c o u r and g r a v e l q u a l i t y . E x t r e m e w i n t e r low f l o w s and f r e e z i n g were not c o n s i d e r e d a p r o b l e m i n Sachs C r e e k i n 1982-83. A l l of t h e s e f a c t o r s have s u b s t a n t i a l l y r e d u c e d egg s u r v i v a l i n e v e n t s d e s c r i b e d e l s e w h e r e ( M c N e i l 1969). Redd s u p e r i m p o s i t i o n o c c u r r e d a t ab o u t 70% of t h e s t a t i o n s sampled i n t h e two c o n t r o l s i t e s ( I I I A and I I I B ) and a t ab o u t 20% of t h e s t a t i o n s sampled a t T r e a t m e n t S i t e I I I ( T a b l e 11). T h i s s u g g e s t e d t h a t even f o r an a v e r a g e s i z e p i n k r u n , spawning h a b i t a t was l i m i t i n g a t S a c h s C r e e k . L e s s r e d d s u p e r i m p o s i t i o n o c c u r r e d a t T r e a t m e n t S i t e I I I , p r o b a b l y owing t o i t b e i n g f u r t h e r u p s t r e a m beyond t h e peak d e n s i t y a r e a f o r p i n k spawners ( F i g u r e 1 6 ) . In a d d i t i o n t o t h e p h y s i c a l r e m o v a l o f p r e v i o u s l y spawned e g g s , r e d d s u p e r i m p o s i t i o n a l s o may h a v e : a) s h o c k e d t h e v e r y s e n s i t i v e eggs t h a t had not d e v e l o p e d t o t h e e y e d s t a g e , o r i f t h e eggs were e y e d , b) r e d i s t r i b u t e d them v e r t i c a l l y , making them more v u l n e r a b l e t o s u b s e q u e n t l o s s t h r o u g h g r a v e l s c o u r . Egg l o s s t h r o u g h g r a v e l s c o u r would be r e l a t e d t o t h e d e p t h a t w h i c h t h e eggs were d e p o s i t e d and t h e d e p t h t o which t h e g r a v e l s were s c o u r e d . L i v e eggs were d i s t r i b u t e d f a i r l y e v e n l y down t o a d e p t h of 40cm, but dead eggs were more common near t h e s u r f a c e ( 7 0% i n t h e t o p 20cm; T a b l e 12). O b s e r v a t i o n s from t h e K o d i a k a r c h i p e l a g o s u g g e s t e d t h a t p i n k s t h e r e i n i t i a l l y d e p o s i t e d eggs between 10cm and 25cm (K. Manthey p e r s . comm.) 6 ; a l t e r a t i o n of s i m i l a r d i s t r i b u t i o n s by g r a v e l s c o u r , a g g r a d a t i o n , o r r e d d s u p e r i m p o s i t i o n p r o b a b l y p r o d u c e d t h e 6 K. Manthey, A r e a Management B i o l o g i s t , K o d i a k A r e a , A l a s k a D e p t . F i s h and Game, p e r s o n a l c o m m u n i c a t i o n . 79 d i s t r i b u t i o n f o u n d i n t h i s s t u d y . The p r e d o m i n a n c e of dead eggs nea r t h e s u r f a c e s u g g e s t e d r e d d s u p e r i m p o s i t i o n was a t l e a s t p a r t i a l l y r e s p o n s i b l e , w i t h m o r t a l i t y a c o n s e q u e n c e of t h e j a r r i n g i n v o l v e d . The d e p t h o f g r a v e l s c o u r i n s e v e r a l " f l a s h y " Queen C h a r l o t t e I s l a n d s s t r e a m s t e n d t o be h i g h . P r e l i m i n a r y egg d e p t h measurements by F F I P (page 3) s u g g e s t e d t h a t of t h e 65 s t a t i o n s measured, 15-20% of t h e coho eggs and 30% of t h e chum eggs may have been d i r e c t l y a f f e c t e d by g r a v e l s c o u r (D. T r i p p p e r s . comm.) 7 . G r a v e l s c o u r i n t h e c o n t r o l s i t e s a t Sachs Creek a v e r a g e d 5.1cm o v e r w i n t e r i n y e a r 1 and 4.5cm i n y e a r 2 ( T a b l e 1 ) . G r a v e l s c o u r may t h e r e f o r e have a c c o u n t e d f o r up t o 15% of t h e p i n k egg m o r t a l i t y i n t h e c o n t r o l s i t e s a t Sachs Creek f o r t h e s e y e a r s ( T a b l e 12). A l t h o u g h i t a p p e a r e d t h a t a f t e r 2 y e a r s t h e g a b i o n s h e r e d i d not r e d u c e egg l o s s as a r e s u l t of r e d u c e d g r a v e l s c o u r ( T a b l e 1 ) , t h e q u a l i t y o f t h e g r a v e l f o r i n c u b a t i o n of t h e r e m a i n i n g (>85%) eggs and a l e v i n s was i m p r o v e d by g a b i o n i n s t a l l a t i o n ( T a b l e 16). In t h i s s t u d y , i n t r a g r a v e l d i s s o l v e d oxygen was f o u n d t o be s i g n i f i c a n t l y c o r r e l a t e d w i t h t h e i n d e x of r e l a t i v e egg s u r v i v a l ( T a b l e 1 2 ) . T h i s r e l a t i o n s h i p was n o t d e t e c t e d w i t h t h e i n d e x of s u r v i v a l f r o m p o t e n t i a l d e p o s i t i o n , p r o b a b l y owing t o t h e o v e r w h e l m i n g i n f l u e n c e of egg l o s s (>80%) on t h i s i n d e x ; i . e . oxygen d e p r i v a t i o n a p p e a r e d a s i g n i f i c a n t s o u r c e of m o r t a l i t y t o t h o s e eggs w h i c h had not been p h y s i c a l l y removed from t h e 7 D. T r i p p , B i o l o g i s t , F i s h / F o r e s t r y I n t e r a c t i o n Program, V a n c o u v e r , B.C., p e r s o n a l c o m m u n i c a t i o n . 80 g r a v e l s (<20%). O t h e r v a r i a b l e s s u c h as i n t r a g r a v e l p e r m e a b i l i t y and d e p t h of g r a v e l s c o u r may i n d e e d have a f f e c t e d egg s u r v i v a l i n S a c h s C r e e k , but t h e complex n a t u r e ( w i t h p o s s i b l e s y n e r g i s t i c e f f e c t s ) i n w h i c h a l l t h e s e f a c t o r s i n t e r r e l a t e c o u l d not be m o d eled w i t h th e m u l t i p l e r e g r e s s i o n a n a l y s i s a p p l i e d . 5. JUVENILE UTILIZATION Two main a r e a s of b e n e f i t s were o f f e r e d by g a b i o n s i n t h i s s t u d y : a) an improvement i n p i n k and chum salmon s p a w n i n g / i n c u b a t i o n h a b i t a t , and b) an improvement i n j u v e n i l e coho salmon and r a i n b o w t r o u t ( o r s t e e l h e a d ) r e a r i n g h a b i t a t . S i n c e j u v e n i l e s a l m o n i d d e n s i t i e s were not m e asured p r i o r t o g a b i o n i n s t a l l a t i o n , e v i d e n c e f o r improvement i n r e a r i n g h a b i t a t was i n d i c a t e d t h r o u g h d e d u c t i o n . S u b s t a n t i a l l y h i g h e r j u v e n i l e d e n s i t i e s were f o u n d a t g a b i o n s i t e s t h a n a t c o n t r o l s i t e s ( T a b l e 1 3 ) . H i g h j u v e n i l e d e n s i t i e s a t t h e g a b i o n s i t e s i n t h i s s t u d y were i n agreement w i t h i n c r e a s e d coho d e n s i t i e s a t g a b i o n s i t e s ( h e r e u s e d as c u r r e n t d e f l e c t o r s ) p l a c e d on o t h e r c o a s t a l s t r e a m s (Ward and S l a n e y 1981). The a b i l i t y of g a b i o n s i t e s t o accommodate h i g h e r j u v e n i l e d e n s i t i e s was i n d i c a t e d by t h e l e n g t h f r e q u e n c i e s of t h e 0+ c o h o . In o t h e r s t u d i e s coho s i z e was i n v e r s e l y c o r r e l a t e d t o t h e i r d e n s i t y ( F r a s e r 1969). One c o u l d t h e r e f o r e e x p e c t t h a t coho l e n g t h s a t g a b i o n s i t e s ( h i g h e r j u v e n i l e d e n s i t i e s ) would be l e s s t h an a t t h e c o n t r o l s i t e s ( l o w e r d e n s i t i e s ) . However, coho l e n g t h s a t t h e g a b i o n s i t e s t e n d e d t o be g r e a t e r t h a n a t c o n t r o l s i t e s ( s i g n i f i c a n t l y g r e a t e r t h a n 3 81 of t h e 6 c o n t r o l s i t e s ; p<.05; T a b l e 15 and F i g u r e 18). The a b i l i t y of g a b i o n s i t e s t o accommodate more and l a r g e r j u v e n i l e s s u g g e s t t h a t p h y s i c a l d i f f e r e n c e s a t the s i t e s a r e r e s p o n s i b l e f o r t h i s g r e a t e r u t i l i z a t i o n . I f i t can be shown t h a t g a b i o n s p r o d u c e d t h e s e p h y s i c a l d i f f e r e n c e s , one can c o n c l u d e t h a t g a b i o n s i m p r o v e d r e a r i n g h a b i t a t . S a l m o n i d r e a r i n g h a b i t a t r e q u i r e m e n t s v a r i e d between s p e c i e s and c h a n g e d w i t h s e a s o n . In i n t e r - s p e c i e s t e r r i t o r i a l c o n f r o n t a t i o n s , Hartman (1965) f o u n d t h a t coho were more s u c c e s s f u l i n l o w e r v e l o c i t y " p o o l s " and s t e e l h e a d were more s u c c e s s f u l i n h i g h e r v e l o c i t y " r i f f l e s " . B u s t a r d and N a r v e r (1975a) f o u n d t h a t as s t r e a m t e m p e r a t u r e s d e c r e a s e d i n w i n t e r , t h e s e f e e d i n g p o s i t i o n s d e s c r i b e d by Hartman (1965) were e x c h a n g e d f o r h a b i t a t c l o s e r t o c o v e r . In w i n t e r , 0+ coho were a s s o c i a t e d more w i t h o r g a n i c c o v e r , and 0+ s t e e l h e a d w i t h r u b b l e ( B u s t a r d and N a r v e r 1975b, Ward and S l a n e y 1981). The p r e s e n t s t u d y s u g g e s t e d t h a t g a b i o n s i n c r e a s e d r e a r i n g h a b i t a t d i v e r s i t y b e c a u s e two a d d i t i o n a l p o o l - r i f f l e s e q u e n c e s were c r e a t e d a t e a c h s i t e (page 3 2 ) . T h i s d i v e r s i t y f a c i l i t a t e d i n t e r - s p e c i e s r e s o u r c e p a r t i t i o n i n g by p r o v i d i n g s e p a r a t e a r e a s b e s t s u i t e d f o r e a c h s p e c i e s . At t h e g a b i o n s i t e s b o t h r i p r a p and b o u l d e r r u b b l e below t h e p l u n g e p o o l s p r o v i d e d some w i n t e r h a b i t a t f o r s t e e l h e a d . P l a c e m e n t of b o u l d e r s i n c o a s t a l s t r e a m s has been f o u n d t o improve s t e e l h e a d w i n t e r h a b i t a t (Ward and S l a n e y 1979). The nooks and c r a n n i e s w i t h i n t h e g a b i o n s t r u c t u r e s t h e m s e l v e s s i m i l a r l y p r o v i d e d c o v e r . F o r coho w i n t e r h a b i t a t , g a b i o n s i t e s p r o v i d e d some o r g a n i c d e b r i s c o v e r . However, t h e 82 a d d i t i o n of rootwads a n c h o r e d i n t h e p l u n g e p o o l s would g r e a t l y augment j u v e n i l e coho w i n t e r and summer h a b i t a t (G. Hartman p e r s . comm.) 8 . The f l o o d on 2 August 1983 i n Sachs C r e e k p r o v i d e d an u n e x p e c t e d o p p o r t u n i t y t o examine f l o o d r e l a t e d j u v e n i l e s a l m o n i d p o p u l a t i o n d y n a m i c s . As a n t i c i p a t e d , t h e l a r g e s t d e c r e a s e i n coho p o p u l a t i o n (-92%) o c c u r r e d a t t h e uppermost T r e a t m e n t S i t e I ( T a b l e 14) where e n e r g y of t h e s t o r m f l o w was g r e a t e r t h a n a t o t h e r s i t e s . T h i s was s u g g e s t e d by t h e s t e e p (3%) s l o p e g r a d i e n t and s u b s t a n t i a l c h a n g e s i n s i t e c o n f i g u r a t i o n (page 6 8 ) . The 51% d e c r e a s e i n j u v e n i l e coho p o p u l a t i o n a t t h e o t h e r two t r e a t m e n t s i t e s ( I I and I I I ) was l e s s t h a n t h e 84% d e c r e a s e a t t h e m a r g i n a l c o n t r o l s i t e s ( I I A and I I I A ) but g r e a t e r t h a n t h e 21% d e c r e a s e a t t h e pr i m e spawning h a b i t a t c o n t r o l s i t e s ( I I B and I I B ; T a b l e 14). D e s p i t e t h e s e major c h a n g e s i n coho p o p u l a t i o n s , many j u v e n i l e s resumed t h e i r f e e d i n g s t a t i o n s on t h e same s i t e s a f t e r t h e f l o o d . The p r o p o r t i o n of j u v e n i l e s marked i n t h e p r e - f l o o d s a m p l i n g t h a t were a c c o u n t e d f o r d u r i n g t h e p o s t - f l o o d s a m p l i n g r a n g e d from about 30% t o 60% between t h e s i t e s ( T a b l e 14); t h a t of t h e two g a b i o n s i t e s a g a i n was between t h a t of t h e i r c o n t r o l s i t e s ( T a b l e 14). G. Hartman, C o o r d i n a t o r , C a r n a t i o n C r e e k W a t e r s h e d S t u d i e s , 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. 83 6. SUMMARY OF POSITIVE AND NEGATIVE EFFECTS OF GABIONS. The e f f e c t s of g a b i o n i n s t a l l a t i o n on t h e p h y s i c a l - c h e m i c a l and b i o l o g i c a l p a r a m e t e r s measured on s t u d y s i t e s i n S a c hs C r e e k were b r i e f l y summarized i n T a b l e 16. In r e l a t i o n t o s a l m o n i d p r o d u c t i o n , t h e b e n e f i c i a l e f f e c t s of g a b i o n s on g r a v e l s c o u r and s t r e a m b e d s l o p e g r a d i e n t s o u t w e i g h e d t h e n e g a t i v e 3 t o 1 . S i m i l a r l y , g r a v e l q u a l i t y p a r a m e t e r s showing b e n e f i c i a l e f f e c t s of g a b i o n s o u t w e i g h e d t h o s e w i t h n e g a t i v e by 8 t o 2. In s u m m a r i z i n g t h e e f f e c t s of g a b i o n s on spawner u t i l i z a t i o n ( T a b l e 16), t h e o b s e r v e d spawning u t i l i z a t i o n s were a d j u s t e d f o r l o n g i t u d i n a l spawner d i s t r i b u t i o n (page 7 6 ) . The c a l c u l a t e d p r o b a b i l i t y - o f - u s e was e n t e r e d u n a d j u s t e d . The e f f e c t s of g a b i o n s on s u i t a b i l i t y o f spawning- h a b i t a t was v a r i a b l e w i t h 1 p o s i t i v e i n d i c a t o r , 3 n e u t r a l and 2 n e g a t i v e . B o t h o f t h e egg s u r v i v a l i n d i c e s showed b e n e f i c i a l e f f e c t s of g a b i o n s ( T a b l e 16). The i n d i c a t i o n o f 11 p o s i t i v e t o 3 n e g a t i v e p h y s i c a l - c h e m i c a l e f f e c t s of g a b i o n s ( T a b l e 16) s u g g e s t t h a t f u t u r e egg s u r v i v a l a t g a b i o n s i t e s may be e x p e c t e d t o be g r e a t e r t h a n t h a t o b s e r v e d i n t h i s s t u d y i n t h e f i r s t y e a r o f o p e r a t i o n . S i m i l a r l y , o n l y b e n e f i c i a l e f f e c t s of g a b i o n s on j u v e n i l e s a l m o n i d p r o d u c t i o n were f o u n d by t h i s s t u d y In summing t h e p o s i t i v e and n e g a t i v e a t t r i b u t e s p e r s i t e , T r e a t m e n t S i t e I r a n k e d l o w e s t w i t h 5 p o s i t i v e t o 3 n e g a t i v e i n d i c a t o r s , p r o b a b l y owing t o t h e e f f e c t s of a s t e e p (3%) s l o p e g r a d i e n t . T r e a t m e n t S i t e s II (7 p o s i t i v e t o 1 n e g a t i v e ) and I I I (8 t o 1) i n d i c a t e d t h e r e were s u b s t a n t i a l s i t e improvements w i t h g a b i o n i n s t a l l a t i o n a t t h e s e s i t e s . The o v e r a l l r a t i o o f 20 84 p o s i t i v e t o 5 n e g a t i v e s u g g e s t t h a t g a b i o n s may be an e f f e c t i v e way t o r e h a b i l i t a t e s t r e a m s . However, recommendations f o r f u r t h e r a p p l i c a t i o n may be d e t e r m i n e d by t h e i r c o s t e f f e c t i v e n e s s . 85 T a b l e 16 - A Summary of t h e E f f e c t s of G a b i o n I n s t a l l a t i o n on M a j o r P h y s i c a l - C h e m i c a l C o n d i t i o n s and t h e i r R e l a t i o n t o S a l m o n i d P r o d u c t i o n i n S a c h s C r e e k . P a r a m e t e r T r e a t m e n t I T r e a t m e n t II T r e a t m e n t I I I S i t e S t a b i l i t y : S c o u r ( y e a r 2) S l o p e G r a d i e n t G r a v e l Q u a l i t y : D i s s o l v e d Oxygen P e r m e a b i 1 i t y > c o n t r o l ( - ) r e d u c e d ( + ) d e c r e a s e d ( - ) - c o n t r o l ( - ) r e d u c e d ( + ) i n c r e a s e d ( + ) i n c r e a s e d ( + ) F i n e s S e d i m e n t s i n T r a p s Spawner U t i l i z a t i o n : O b s e r v e d low ( - ) > c n t r l s : c o h o ( + ) - c o n t r o l s ( - ) r e d u c e d ( + ) i n c r e a s e d ( + ) c o n t r o l s ( - ) S i z e s f o r Spawning i n c r e a s e d i n c r e a s e d i n c r e a s e d ( + ) ( + ) ( + ) P r o b a b i l i t y - o f - u s e < c o n t r o l s ( - ) Egg S u r v i v a l : R e l a t i v e Index P o t e n t i a l Index J u v e n i l e U t i l i z a t i o n : D e n s i t y > c o n t r o l s ( +.) P o o l s / R i f f l e s > c o n t r o l s ( + ) same ( - ) < c o n t r o l s ( + ) < c o n t r o l s ( - ) betw'n c n t r l s . ( - ) > c o n t r o l s ( + ) > c o n t r o l s ( + ) l a r g e d e c r e a s e ( + ) > c o n t r o l s ( - ) between c n t r l s ( - ) between c n t r l s ( - ) > c o n t r o l s ( + ) > c o n t r o l s ( + ) > c o n t r o l s ( + ) > c o n t r o l s ( + ) T o t a l s : P o s i t i v e N e u t r a l N e g a t i v e 8 4 1 G r a n d T o t a l : P o s i t i v e = 2 0 N e g a t i v e = 5 86 7. PRELIMINARY BENEFIT COST ANALYSIS The c o s t s o f t h e p r o j e c t were d i v i d e d i n t o 6 c a t e g o r i e s , as l i s t e d i n T a b l e 17. T h e r e was an o b v i o u s t r e n d of d e c r e a s i n g i n s t a l l a t i o n c o s t s w i t h e x p e r i e n c e of i n s t a l l a t i o n ( f r o m $5,200 t o $3,800 t o $3,000; f i r s t t o l a s t ) f o r t h e t h r e e t r e a t m e n t s i t e s . The c o s t p e r meter of g a b i o n i n s t a l l e d s i m i l a r l y d e c r e a s e d w i t h e x p e r i e n c e ( f r o m $l05/m t o $89/m t o $85/m). The c o s t s were n o t r e p r e s e n t a t i v e o f what s h o u l d be e x p e c t e d i n an o p e r a t i o n a l s e n s e . The c o n t r a c t o r employed t o e x c a v a t e t h e s i t e s d i s c o u n t e d h i s equipment t i m e 30 p e r c e n t . The p r o j e c t was b i l l e d a r a t e of $50/hour r a t h e r t h a n t h e n o r m a l $70/hour f o r t h e e x c a v a t o r . C o n s i d e r a b l e c o s t was a l s o s a v e d by u t i l i z i n g s l a c k t i m e on t h e e x c a v a t o r ; t h e e x c a v a t o r o p e r a t o r l o a d e d and h a u l e d g r a v e l d u r i n g t h e p e r i o d s he c o u l d not do i n s t r e a m work. Many c o n t r a c t o r s would have c h a r g e d f o r b o t h m a c h i n e s . R e s u l t a n t c o n t r a c t o r c o s t s , t h e r e f o r e , were e s t i m a t e d a t a b o u t 50% of a c t u a l c o s t s . The p r o j e c t e d n o n - d i s c o u n t e d c o s t s were i n c l u d e d i n T a b l e 17. Manpower f o r g a b i o n c o n s t r u c t i o n was s u p p l i e d t h r o u g h th e F i s h e r i e s Employment B r i d g i n g A s s i s t a n c e Program ( P r o j e c t No. 5 6 6 ) . W h i l e t h i s a s s i s t a n c e made t h i s p r o j e c t p o s s i b l e , c o n s i d e r a b l e r e d u c t i o n i n mandays p r o b a b l y would have o c c u r r e d i f a n o n - " j o b c r e a t i o n " l a b o u r f o r c e had been u s e d . Some l o s s of p r o d u c t i v i t y was a l s o e v i d e n t t h r o u g h s h o r t work d a y s , owing t o e x t e n s i v e t r a v e l t i m e . I t was e s t i m a t e d t h a t t r a i n e d manpower would have c o m p l e t e d t h e j o b i n 2/3 of t h e t i m e e x p e n d e d . A r e a l i s t i c c o s t f o r h i r e d manpower on t h e Queen 87 C h a r l o t t e I s l a n d s would be $80 per day (1982). Using these f i g u r e s , the p r o j e c t e d manpower c o s t s for gabion i n s t a l l a t i o n are given in Table 17. Table 17 - Gabion I n s t a l l a t i o n Costs at Sachs Creek. Treatment S i t e #: I II III TotJ Dates Worked August 1982: 7-23 9- 1 7 24 -29 1) Gabions: Length (m): 43 50 35 1 28 Cost D e l i v e r e d : $ 954 $1,086 $ 882 $ 2,922 1) E x c a v a t i o n : Hours: 15.5 20 1 2 47 @ $50/hour: Cost: $ 775 $1,000 $ 600 $ 2 , 375 3) Spawning G r a v e l : H a u l i n g : Hours: 11.5 1 0 5. 5 27 @ $50/hour:- Cost: $ 575 $ 500 $ 275 $ 1 ,350 D i s t r i b u t i n g : Hours: 5 6 4 1 5 @ $50/hour: Cost: $ 250 $ 300 $ 200 $ 750 4) Equipment T r a n s p o r t : $ 58 $ 58 $ 58 $ 174 5) Sorted Rock-Delivered: $ 0 $ 950 $ 400 $ 1 ,350 6) Labour: Man Days: 27 30 1 4 7 1 @ $45/Man Day: Cost: $1 ,215 $1,350 $ 630 $ 3.195 T o t a l Cost: $3,827 $5,244 $2,985 $12,057 T o t a l Cost per Gabion Length (per m): $ 89 $ 1 05 $ 85 $ 94 P r o j e c t e d C o s t s : C o n t r a c t o r ' s Discount: $1,658 $1,858 $1 , 1 33 $ 4,649 Labour: Man Days: 18 20 10 48 Cost @ $80/day: $1 ,439 $1,600 $ 800 $ 3,840 T o t a l P r o j e c t e d C o s t s : $5,709 $$7352 $4,288 $17,349 88 S e v e r a l h u n d r e d c u b i c m e t e r s of g r a v e l and r o c k were u s e d on t h e g a b i o n s i t e s . The m a j o r i t y of t h i s g r a v e l was d o n a t e d from a n e a r b y M a c M i l l a n B l o e d e l g r a v e l p i t . T h i s m a t e r i a l was u n s o r t e d r i v e r run g r a v e l . I n i t i a l l y , c o n c e r n was e x p r e s s e d t h a t t h e f i n e s component of t h e p i t g r a v e l was h i g h and c o u l d i n f l u e n c e egg s u r v i v a l . To p r e v e n t t h i s , 21 m 3 of s o r t e d " d r a i n , r o c k " (between 2cm and 15cm d i a m e t e r ) was p u r c h a s e d and d i s t r i b u t e d o v e r a p a r t i a l l y s u r c h a r g e d T r e a t m e n t S i t e I I . The h i g h c o s t of t h e d r a i n r o c k ( c a . $600 d e l i v e r e d ) d e t e r r e d f u r t h e r use o f t h i s m a t e r i a l on T r e a t m e n t S i t e s I and I I I . The d r a i n r o c k may have been r e s p o n s i b l e f o r t h e l o w e r p r o p o r t i o n ( d i l u t i o n ) of f i n e s i n t h e s u r c h a r g e d m a t e r i a l s of T r e a t m e n t S i t e II t h a n T r e a t m e n t S i t e s I and e s p e c i a l l y I I I (September 1982; F i g u r e 1 4 ) . The a b i l i t y of t h e s t r e a m t o remove t h e s e f i n e s by t h e J une 1983 s a m p l i n g would s u g g e s t t h a t t h e o v e r a l l d i l u t i o n e f f e c t o f t h i s d r a i n r o c k on egg s u r v i v a l was n e g l i g i b l e . In f i l l i n g t h e g a b i o n s , l o c a l r o c k l a r g e r t h a n 10cm d i a m e t e r was u s e d b e f o r e c o m m e r c i a l l y s o r t e d r o c k was p u r c h a s e d . A l t h o u g h t h e r e was s u f f i c i e n t l o c a l m a t e r i a l a t T r e a t m e n t S i t e I, $350 and $400 w o r t h of s o r t e d r o c k was needed a t T r e a t m e n t S i t e s II and I I I r e s p e c t i v e l y ( T a b l e 17). The c o s t e f f e c t i v e n e s s o f g a b i o n i n s t a l l a t i o n i n S a c h s C r e e k r e m a i n s p r e l i m i n a r y t o d a t e . A l t h o u g h t h e c o s t s a r e known, the i n c r e a s e i n f i s h p r o d u c t i o n and t h e l o n g e v i t y of t h e g a b i o n s a r e n o t . G a b i o n l o n g e v i t y i s d e p e n d e n t on b o t h t h e i n t e g r i t y of t h e s t r u c t u r e and t h e r e s i s t a n c e of t h e w i r e mesh 89 t o a b r a s i o n and r u s t . S i m i l a r s t r u c t u r e s have w i t h s t o o d f l o o d s of 100 y e a r r e t u r n p e r i o d s i n Oregon ( A n d e r s o n 1981). L o n g e v i t y of t h e g a b i o n s i n t h i s s t u d y may be d ependent on t h e l o c a l s l o p e g r a d i e n t of t h e s t r e a m . The dynamic n a t u r e of s t r e a m m o r p h o l o g y i n h i g h e r g r a d i e n t (> 2%) r e a c h e s , e s p e c i a l l y t h o s e r e n d e r e d u n s t a b l e from p o o r s t r e a m s i d e l o g g i n g or d e b r i s t o r r e n t s as a t T r e a t m e n t S i t e I (page 6 8 ) , r e d u c e d t h e l i k e l i h o o d of a d e q u a t e s t r u c t u r e l o n g e v i t y . However, t h e a b i l i t y of s t r u c t u r e s i n t h e 1% s l o p e g r a d i e n t r e a c h e s t o w i t h s t a n d t h e A u g u s t 1983 f l o o d w i t h o u t s h i f t i n g s u g g e s t e d t h a t g a b i o n s a t low s l o p e g r a d i e n t s i t e s may have a l o n g e v i t y of a c o u p l e of d e c a d e s . A b r a s i o n a l s o was more p r e v a l e n t a t t h e h i g h e r g r a d i e n t g a b i o n s i t e i n t h i s s t u d y ( T r e a t m e n t S i t e I) t h a n a t t h e l o w e r g a b i o n s ( T r e a t m e n t S i t e s II and I I I ) . A b r a s i o n was f o u n d o n l y on t h e g a l v a n i z e d c o a t i n g on t h e u p s t r e a m e x p o s e d p o r t i o n s of t h e g a b i o n mesh. R u s t i n g of t h e mesh was not e v i d e n t but may l i m i t t h e u s e f u l l i f e of t h e s t r u c t u r e s . The economic v a l u e s o f some of t h e b e n e f i t s and c o s t s of g a b i o n s were n o t c a l c u l a t e d , owing t o t h e u n c e r t a i n n a t u r e of t h e s e f a c t o r s . One s u c h c o s t was f i n e s e d i m e n t i n p u t d u r i n g g a b i o n c o n s t r u c t i o n . The s u s p e n d e d s e d i m e n t s were e s t i m a t e d t o have e x c e e d e d 400 ppm ( J . Lamb p e r s . comm.) 9 d u r i n g s t r e a m b e d e x c a v a t i o n . S e t t l e m e n t of t h e s e d i m e n t s was r a p i d , w i t h a c c u m u l a t i o n s up t o 2cm deep i n b a c k w a t e r a r e a s i m m e d i a t e l y downstream of t h e s i t e s . T h e s e were f l u s h e d f r o m t h e s y s t e m 9 J . Lamb, H a b i t a t P r o t e c t i o n , D e p t . F i s h e r i e s and Oceans, Nanaimo, B.C. p e r s o n a l c o m m u n i c a t i o n . 90 d u r i n g t h e f i r s t m inor s t o r m f l o w . The e f f e c t s h e r e were s i m i l a r t o t h o s e d e s c r i b e d f o r e x c a v a t i o n i n o t h e r c o a s t a l s t r e a m s by Ward and S l a n e y ( 1 9 7 9 ) . B e n e f i t s of g a b i o n s d e s c r i b e d i n p r e v i o u s s e c t i o n s above i n c l u d e d a n t i c i p a t e d i n c r e a s e s i n s a l m o n i d egg t o f r y s u r v i v a l and i n c r e a s e s i n j u v e n i l e s a l m o n i d summer d e n s i t i e s and r e a r i n g h a b i t a t . In a d d i t i o n , many a d u l t salmon were o b s e r v e d " h o l d i n g " o r r e s t i n g i n water ponded u p s t r e a m of t h e g a b i o n s i n autumn 1982 and 1983. A n o t h e r b e n e f i t may be an i n c r e a s e i n s t r e a m b e n t h o s p r o d u c t i v i t y e x p e c t e d w i t h r i p a r i a n v e g e t a t i o n r e m o v a l d u r i n g g a b i o n i n s t a l l a t i o n ; t h e l o c a l i z e d i n c r e a s e d s u n l i g h t i n p u t t o t h i s n o r t h e r n c o l d - w a t e r s t r e a m may improve a l g a l and b e n t h o s p r o d u c t i o n , p r o v i d i n g more f o o d f o r r e a r i n g j u v e n i l e s a l m o n i d s ( D u b o w i t s 1979). A l t h o u g h g a b i o n s may make s i g n i f i c a n t c o n t r i b u t i o n s t o f i s h p r o d u c t i o n t h r o u g h t h e above d e s c r i b e d b e n e f i t s , i t i s o n l y t h r o u g h a n t i c i p a t e d i n c r e a s e s i n p i n k salmon egg s u r v i v a l t h a t t h e f o l l o w i n g b e n e f i t / c o s t a n a l y s i s was made. The a c t u a l c o s t e f f i c i e n c y o f g a b i o n s would p r o b a b l y be g r e a t e r t h a n t h e f o l l o w i n g a n a l y s i s s u g g e s t s i f t h e o t h e r b e n e f i t s o f g a b i o n s were i n c l u d e d . A b e n e f i t / c o s t a n a l y s i s was made t o d e t e r m i n e what p r o d u c t i o n g o a l s were r e q u i r e d t o o f f s e t g a b i o n c o n s t r u c t i o n c o s t s w i t h s e n s i t i v i t y e x p r e s s e d o v e r t h e i r e x p e c t e d r a n g e s . T r e a t m e n t S i t e I I I was u s e d f o r t h i s a n a l y s i s b e c a u s e : a) i t was the l a s t and hence l e a s t e x p e n s i v e g a b i o n s i t e , h a v i n g t h e b e n e f i t of p r e v i o u s i n s t a l l a t i o n e x p e r i e n c e ; and b) i t had s u f f i c i e n t spawner usage t o e n a b l e egg s a m p l i n g . C r i t e r i a 91 c o n s i d e r e d i n t h e a n a l y s i s a r e o u t l i n e d below. Benef i t s i . P i n k spawner u t i l i z a t i o n of T r e a t m e n t S i t e I I I was 60 f e m a l e s (120 a d u l t s ) i n 1982. A f t e r a d j u s t m e n t f o r e f f e c t s o f l o n g i t u d i n a l spawner d i s t r i b u t i o n , a c t u a l usage of T r e a t m e n t S i t e I I I was i n t e r m e d i a t e between t h a t of i t s c o n t r o l s (page 7 6 ) . Hence, b e n e f i t s from i n c r e a s e d spawner usage were n o t i n c l u d e d i n t h e b e n e f i t / c o s t a n a l y s i s . i i . Egg s u r v i v a l w i t h i n T r e a t m e n t S i t e I I I a p p e a r e d h i g h e r t h a n t h a t of b o t h C o n t r o l S i t e s I I I A and I I I B . I n c r e a s e s i n a v e r a g e egg s u r v i v a l were assumed t o have an e q u a l e f f e c t on i n c r e a s e s o f r e t u r n i n g a d u l t s , ( e . g . A 100% i n c r e a s e i n egg s u r v i v a l w ould y i e l d an a d d i t i o n a l 100% of t h e o r i g i n a l number of f i s h s p awning on t h e s i t e (120 a d u l t s ) r e t u r n i n g as a d u l t s . ) An e x p l o i t a t i o n r a t e f o r a d u l t p i n k salmon r e t u r n i n g t o t h e e a s t c o a s t o f t h e Queen C h a r l o t t e I s l a n d s a v e r a g e d 56% o v e r t h e p a s t 10 y e a r s (S. W r i g h t p e r s . comm.) 1 0 . i i i . C u r r e n t w h o l e s a l e p r i c e s of p i n k salmon were assumed t o be $8.87 p e r p i e c e f o r n e t c a u g h t and $6.00 p e r p i e c e f o r t r o l l c a u g h t i n 1982 d o l l a r s (S. W r i g h t p e r s . comm.). 1 0 T h e s e f i g u r e s were b a s e d on t h e 1976 1 0 S. W r i g h t , E v a l u a t i o n E c o n o m i s t , Department o f F i s h e r i e s and O c e a n s , V a n c o u v e r , B.C., p e r s o n a l c o m m u n i c a t i o n . 92 p r o v i n c e wide c a t c h and a d j u s t e d f o r i n f l a t i o n t o 1982 v a l u e s . Of t h e p i n k salmon c a u g h t i n t h e Queen C h a r l o t t e I s l a n d s a r e a , 96% were net c a u g h t and 4% were t r o l l c a u g h t . The a d j u s t e d w h o l e s a l e p r i c e a v e r a g e d $8.76 p e r p i e c e , i v . Over t h e l i f e s p a n of t h e g a b i o n s , an e q u a l i n c r e a s e i n p i n k a d u l t s was assumed f o r t h c o m i n g e v e r y o t h e r y e a r . A n a l y s i s s e n s i t i v i t y was shown f o r l o n g e v i t i e s o f 6, 12 and 18 y e a r s . C o s t s i . The i n i t i a l c o n s t r u c t i o n c o s t of T r e a t m e n t S i t e I I I p r o j e c t e d t o r e f l e c t r e a l c o s t s was u s e d ($4,288; T a b l e 17). However, c o n s t r u c t i o n c o s t s may c o n t i n u e t o d e c r e a s e .with e x p e r i e n c e . i i . Once i n s t a l l e d , g a b i o n s i t e s were e x p e c t e d t o r e q u i r e no a d d i t i o n a l work and m a i n t e n a n c e c o s t s were assumed z e r o . i i i . S u b s e q u e n t c o s t s i n c l u d e d h a r v e s t i n g and p r o c e s s i n g o f t h e i n c r e a s e i n r e t u r n i n g a d u l t s . H a r v e s t i n g c o s t s i n 1982 d o l l a r s (S. W r i g h t p e r s . comm.) 1 0 were $.61 p e r p i e c e f o r t r o l l c a u g h t and $.19 p e r p i e c e f o r n e t c a u g h t , a v e r a g i n g $.21 p e r p i e c e ( a d j u s t e d f o r p r o p o r t i o n n e t and t r o l l c a u g h t ; p . 9 1 ) . P r o c e s s i n g c o s t s were $2.38 p e r p i e c e f o r t r o l l c a u g h t and $2.75 p e r p i e c e f o r n e t c a u g h t , a v e r a g i n g $2.74 p e r p i e c e . P r o c e s s i n g c o s t s i n c l u d e d a c q u i s i t i o n , i n - p l a n t p r o c e s s i n g , and m a r k e t i n g c o s t s . The combined 93 h a r v e s t i n g and p r o c e s s i n g c o s t s a v e r a g e d $2.95 p e r p i e c e . A d i s c o u n t i n g r a t e of 10 p e r c e n t w i t h s e n s i t i v i t y a t 5 and 15 p e r c e n t was u s e d f o r b o t h c o s t s and b e n e f i t s a c c r u e d o v e r t h e g a b i o n l i f e s p a n s shown. T h i s p r o c e d u r e b r o u g h t f u t u r e v a l u e s t o p r e s e n t v a l u e . I f i n t e r e s t r a t e s were m a i n t a i n e d a t l e v e l s l o w e r t h a n 10 p e r c e n t , t h e f u t u r e n et b e n e f i t s i n d i c a t e d i n t h i s s t u d y would be c o n s e r v a t i v e t o what may be e x p e c t e d ( T a b l e 18). S i m i l a r l y , i f t h e net v a l u e s r o s e as a r e s u l t of p r i c e i n c r e a s e s a f t e r a l l c a p i t a l c o s t s were i n c u r r e d d u r i n g c o n s t r u c t i o n , f u t u r e b e n e f i t s would be g r e a t e r t h a n e x p e c t e d . I n c r e a s e s i n r e t u r n i n g a d u l t p i n k salmon r e q u i r e d t o o f f s e t g a b i o n c o n s t r u c t i o n c o s t s a r e summarized i n T a b l e 18. At a 10 p e r c e n t d i s c o u n t r a t e w i t h a g a b i o n l o n g e v i t y of 12 s e a s o n s , 375 f i s h a d d i t i o n a l t o t h e 120 i n i t i a l l y spawning on the s i t e a r e r e q u i r e d b i e n i a l l y (major p i n k r u n s a r e on even y e a r s o n l y ) . A p r o d u c t i o n of t h i s m a g n i t u d e ( a b o u t 4 t i m e s n a t u r a l s u r v i v a l ) may be a t t a i n a b l e f o r g a b i o n s i t e s , owing t o improvements o f g r a v e l q u a l i t y w i t h a n t i c i p a t e d i n c r e a s e s i n egg t o f r y s u r v i v a l as d i s c u s s e d a b o v e . A c h i e v e m e n t o f c o s t e f f e c t i v e n e s s becomes more p r o b a b l e a t lower i n t e r e s t r a t e s and g r e a t e r l o n g e v i t i e s ( T a b l e 18) and when b e n e f i t s o f g a b i o n s o t h e r t h a n i n c r e a s e s i n p i n k salmon egg t o f r y s u r v i v a l a r e a l s o c o n s i d e r e d . L a c k o f h i g h e r spawner usage of t h e g a b i o n s i t e s ( T a b l e 16) s u g g e s t e d t h a t no b e n e f i t s would be d e r i v e d t h r o u g h e f f e c t s of g a b i o n s on spawning h a b i t a t . However, g a b i o n s i t e s w i t h fewer spawners would r e q u i r e s t i l l g r e a t e r improvements i n egg t o f r y s u r v i v a l 94 t o o f f s e t c o n s t r u c t i o n c o s t s . The a s s u m p t i o n of egg t o f r y s u r v i v a l b e i n g t h e l i m i t i n g f a c t o r i n s m o l t p r o d u c t i o n a p p e a r e d r e a s o n a b l e , owing t o t h e " i m m e d i a t e " seaward m i g r a t i o n o f f r y e m e r g i n g from t h e spawning g r a v e l s . However, m o r t a l i t y i n t h e oc e a n may y i e l d a d i s p r o p o r t i o n a t e l y l o w e r r e t u r n i n a d u l t s f o r i n c r e a s e i n s m o l t p r o d u c t i o n (Peterman 1982). T a b l e 18 - I n c r e a s e s i n R e t u r n i n g P i n k s R e q u i r e d t o O f f s e t I n s t a l l a t i o n C o s t s f o r T r e a t m e n t S i t e I I I a t S a c h s C r e e k . G a b i o n A d d i t i o n a l Number of R e t u r n i n g A d u l t s R e q u i r e d L o n g e v i t y B i e n n i a l l y t o R e c o v e r C o n s t r u c t i o n C o s t s 1 D i s c o u n t R a t e : Number of F i s h R e l a t i v e I n c r e a s e 2 5% 1 0% 1 5% 5% 1 0% 1 5% 6 Y e a r s 418 520 632 348% 433% 527% 12 Y e a r s 273 375 495 228% 312% 413% 18 Y e a r s 217 325 452 1 80% 271% 377% 1. C a l c u l a t i o n s of r e q u i r e d r e t u r n s a r e d i s c u s s e d i n A p p e n d i x B. 2. I n c r e a s e i n p r o d u c t i o n e x p r e s s e d as p e r c e n t o f t h e i n i t i a l 120 spawners on t h e s i t e i n 1982. 95 V I . CONCLUSIONS AND RECOMMENDATIONS G a b i o n w e i r s met t h e f i v e c r i t e r i a r e q u i r e d of a s u c c e s s f u l s t r e a m r e h a b i l i t a t i o n t e c h n i q u e a s o u t l i n e d e a r l y i n t h e Di s c u s s i on : i . G a b i o n w e i r s s u r c h a r g e d w i t h g r a v e l c r e a t e d s t r e a m b e d c o n f i g u r a t i o n s y i e l d i n g moderate q u a l i t y spawning h a b i t a t f o r p i n k and chum salmon i n s i t e s a t 1% s l o p e g r a d i e n t r e a c h e s . T h i s was d e m o n s t r a t e d t h r o u g h b o t h o b s e r v e d spawner usage and c a l c u l a t e d p r o b a b i 1 i t y - o f -u s e . A l t h o u g h a n o t h e r s i t e a t 3% s l o p e g r a d i e n t was u t i l i z e d by coho spawners, i t was not s u i t a b l e f o r p i n k s p a w n e r s . i i . L o n g i t u d i n a l p i n k salmon d i s t r i b u t i o n was i n d e p e n d e n t of o t h e r p r o b a b i l i t y - o f - u s e f e a t u r e s . F u t u r e s i t e e v a l u a t i o n s s h o u l d i n c l u d e d i s t a n c e u p s t r e a m of t h e e s t u a r y as a p r o b a b i l i t y - o f - u s e c r i t e r i o n . i i i . S t a b i l i t y of g r a v e l s e n t r a p p e d by t h e g a b i o n s a t t h e two 1% s l o p e g r a d i e n t s i t e s was d e m o n s t r a t e d i n y e a r 2 a f t e r c o n s i d e r a b l e s i t e r e - s h a p i n g by s t o r m f l o w s i n y e a r 1. However, t h e s h o r t d u r a t i o n of t h i s s t u d y p r e c l u d e d c o n c l u s i o n s on g r a v e l s t a b i l i t y a t g a b i o n s i t e s d u r i n g major s t o r m f l o w e v e n t s . The g a b i o n s i t e a t 3% s l o p e g r a d i e n t f a i l e d t o s t a b i l i z e g r a v e l s , owing t o t h e h i g h e n e r g y o f s t o r m f l o w s t h e r e . i v . Q u a l i t y of t h e s u r c h a r g e d and n a t u r a l g r a v e l s e n t r a p p e d by t h e g a b i o n s i t e s was c o n d u c i v e t o h i g h egg t o f r y s u r v i v a l . I n t r a g r a v e l d i s s o l v e d oxygen and 96 g r a v e l c o m p o s i t i o n measurements i n d i c a t e d e i t h e r i m p r o v e d or good i n c u b a t i o n a l h a b i t a t . However, i n t r a g r a v e l p e r m e a b i 1 i t y and s e d i m e n t a t i o n measurements were i n c o n s i s t e n t i n e v a l u a t i n g t h i s h a b i t a t . The a p p a r e n t " s t a b i l i t y " a t t h e g a b i o n s i t e s a t 1% s l o p e g r a d i e n t i n y e a r 2 s u g g e s t e d t h a t t h e h i g h egg s u r v i v a l d e m o n s t r a t e d h e r e d u r i n g an " u n s t a b l e " y e a r 1 would y i e l d s u b s t a n t i a l i n c r e a s e s i n t h e f u t u r e . v. J u v e n i l e s a l m o n i d r e a r i n g h a b i t a t was c r e a t e d w i t h t h e d e v e l o p m e n t of 2 a d d i t i o n a l p o o l / r i f f l e s e q u e n c e s p e r g a b i o n s i t e . The good q u a l i t y of t h i s h a b i t a t was d e m o n s t r a t e d by h i g h j u v e n i l e d e n s i t i e s a t t h e g a b i o n s i t e s ( a v e r a g e 1.6 p e r m 2) compared t o t h e c o n t r o l s i t e s ( a v e r a g e 0.9 p e r m 2 ) . v i . P r e l i m i n a r y b e n e f i t / c o s t a n a l y s i s p r o j e c t e d r e q u i r e d i n c r e a s e s i n p i n k salmon p r o d u c t i o n f o r v a r i o u s g a b i o n l o n g e v i t i e s ( e . g . a b o u t a 300% i n c r e a s e o v e r a l o n g e v i t y of 12 y e a r s ) . C o s t e f f e c t i v e n e s s may be a t t a i n a b l e , e s p e c i a l l y a t l o w e r i n t e r e s t r a t e s and g r e a t e r g a b i o n l o n g e v i t i e s , owing t o t h e e f f e c t s o f h i g h q u a l i t y and s t a b i l i t y of g r a v e l s e n t r a p p e d a t t h e g a b i o n s i t e s i n i n c r e a s i n g egg s u r v i v a l ; no b e n e f i t s were d e r i v e d from spawner u s a g e . Recommendations f o r f u t u r e a p p l i c a t i o n of g a b i o n w e i r s a d a p t e d from t h e 8 c r i t e r i a r e v i e w e d by Moreau (1981) a r e as f o l l o w s : 97 i . S e l e c t a s t r a i g h t s t r e a m s e c t i o n . i i . S e l e c t a s e c t i o n w i d e r t h a n a v e r a g e c h a n n e l w i d t h . i i i . The s t r e a m r e a c h s h o u l d have g r a d u a l l y s l o p i n g b a n k s , p r e f e r a b l y w i t h an o v e r f l o w ( f l o o d ) p l a i n . i v . L o c a l c h a n n e l s l o p e s h o u l d be s l i g h t . v . S i t e s u b s t r a t e s h o u l d be s l i g h t l y l a r g e r t h a n d e s i r e d . v i . The t a i l of a p o o l i s s u i t a b l e i f t h e c r i t e r i a above a r e met. v i i . The s i t e must have good a c c e s s . v i i i . Where w e i r s a r e t o be p l a c e d i n s e r i e s , p l a c e t h e downstream w e i r s u c h t h a t t h e t o p o f t h e downstream w e i r i s l e v e l w i t h t h e base o f t h e u p s t r e a m w e i r . A d d i t i o n a l r ecommendations s u g g e s t e d by t h i s s t u d y i n c l u d e : i x . S e l e c t downstream r e a c h e s w i t h i n peak d i s t r i b u t i o n s o f spawning p i n k s a l m o n . x. L i m i t s t r e a m b e d s l o p e g r a d i e n t s t o < 2% (as i n i v above) i n " f l a s h y " c o a s t a l s t r e a m s , above w h i c h s t o r m f l o w e n e r g i e s d e p o s i t u n s u i t a b l y l a r g e b o u l d e r s ; p i n k and chum r a r e l y spawn i n t h e s e s t e e p e r r e a c h e s . x i . G e n e r o u s l y r i p r a p t h e banks a t and below t h e p o i n t s t o w h i c h t h e g a b i o n s a r e keyed t o p r e v e n t l a t e r a l bank s c o u r a r o u n d t h e ends of t h e g a b i o n s . x i i . The i n t e r g a b i o n d i s t a n c e s h o u l d e q u a l a t l e a s t 1 . 5 t i m e s t h e w e t t e d w i d t h of t h e s t r e a m t o a l l o w s u f f i c i e n t l e n g t h o f p l u n g e p o o l u p s t r e a m of t h e e n t r a p m e n t a r e a o f t h e downstream g a b i o n . 98 x i i i . S p l a s h a p r o n s a r e more u s e f u l i n t h e l a t e r a l wing r e g i o n s than n e a r t h e apex of t h e g a b i o n s . T h i s i s owing t o t h e l a t e r a l component of t h e f l o w p e r p e n d i c u l a r a c r o s s t h e g a b i o n s d i r e c t i n g f l o w away from t h e a p i c e s and t o t h e r e s u l t a n t downstream g r a v e l b a r s a b u t t i n g t h e a p i c e s . x i v . F u r t h e r r e s e a r c h may be b e s t d i r e c t e d i n " f i n e t u n i n g " g a b i o n c o n f i g u r a t i o n s t o m a x i m i z e a r e a s o f p r i m e spawning h a b i t a t . xv. Low c o s t p r o c e d u r e s f o r m i n i m i z i n g s u s p e n d e d s e d i m e n t r e l e a s e d u r i n g i n s t r e a m e x c a v a t i o n s h o u l d be d e v e l o p e d . x v i . S i t e c o n s t r u c t i o n s h o u l d be d u r i n g an " o f f " p i n k y e a r t o a l l o w r e - s h a p i n g of one y e a r o f s t o r m f l o w s t o s t a b i l i z e t h e s i t e p r i o r t o heavy spawner u s a g e . 99 LITERATURE CITED A n d e r s o n , J.W. MS198'I. Anadromous f i s h p r o j e c t s 1981. USDI B u r e a u Land Mgmt., Coos Bay D i s t r i c t , O r e g o n . A n d e r s o n , J.W., and J . J . Cameron 1980. The use of g a b i o n s t o improve a q u a t i c h a b i t a t . USDI B u r e a u L a n d Mgmt. T e c h . Note No. 342. B j o r n n , T.C. 1968. S u r v i v a l and emergence of t r o u t and salmon f r y i n v a r i o u s g r a v e l - s a n d m i x t u r e s . IN: L o g g i n g and Salmon Forum, A l a s k a D e p t . 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F i s h e r y R e s e a r c h Rep. No. 9. 1 02 O ' L o u g h l i n , C.L. 1972. A p r e l i m i n a r y s t u d y of l a n d s l i d e s i n th e c o a s t m o u n t a i n s of s o u t h w e s t e r n B r i t i s h C o l u m b i a . IN: H.O. S l a y m a k e r and H.J. McPherson [ e d s . ] . M o u n t a i n G e o m o r p h o l o g y . B.C. G e o g r a p h i c a l S e r i e s 14:101-111. Peterman, R. 1982. N o n l i n e a r r e l a t i o n between s m o l t s and a d u l t s i n B a b i n e Lake s o c k e y e salmon ( O n c o r h y n c h u s n e r k a ) and i m p l i c a t i o n s f o r o t h e r salmon p o p u l a t i o n s . Can. J . F i s h . A q u a t . S c i . 39:904-913. Rand, M.C., A.E. G r e e n b e r g , and M.J. T a r a s 1975 [ e d s . ] . S t a n d a r d Methods f o r t h e E x a m i n a t i o n of Water and  Wastewater . Am. Pub. H e a l t h A s s n . W a s h i n g t o n , D . C , 14th E d i t i o n . Rao, C R . 1973. L i n e a r S t a t i s t i c a l I n f e r e n c e and i t s A p p l i c a t i o n s . W i l e y , New Y o r k , 2nd E d i t i o n . R e e v e s , G.H. and T.D. R o e l o f s 1982. R e h a b i l i t a t i n g and e n h a n c i n g s t r e a m h a b i t a t : f i e l d a p p l i c a t i o n s . IN: W.R. Meehan [ e d . ] I n f l u e n c e of F o r e s t and R a n g e l a n d Management on Anadromous F i s h H a b i t a t i n W e s t e r n N o r t h A m e r i c a . USDA F o r . S e r v . Gen. T e c h . Rep. PNW-140. Rood, K.M. MS1984. L o g g i n g l a n d u s e and mass w a s t i n g i n t h e Queen C h a r l o t t e I s l a n d s . F i s h / F o r e s t r y I n t e r a c t i o n Program, V a n c o u v e r , B.C. i n p r e p . S c r i v e n e r , J . C , and M.J. Bro w n l e e 1982. An a n a l y s i s of C a r n a t i o n C r e e k g r a v e l - q u a l i t y d a t a , 1973-1981. IN: G.F. Hartman [ e d . ] . P r o c e e d i n g s o f t h e C a r n a t i o n C r e e k Workshop; a t e n y e a r r e v i e w . F e b r . 24-26, M a l a s p i n a C o l l e g e , Nanaimo, B.C. S h a p e l y , P.S., and D.M. B i s h o p 1965. S e d i m e n t a t i o n i n a salmon s t r e a m . J . F i s h . Res. B o a r d Can. 2 2 ( 4 ) : 9 1 9 - 9 2 8 . S h e l t o n , J.M., and R.D. P o l l o c k 1966. S i l t a t i o n and egg s u r v i v a l i n i n c u b a t i o n c h a n n e l s . T r a n s . Amer. F i s h . S o c. 9 5 ( 2 ) : 1 8 3 - 1 8 7 . S l a n e y , P.A., T.G. H a l s e y , and A.F. T a u t z 1977. E f f e c t s of f o r e s t h a r v e s t i n g p r a c t i c e s on spawning h a b i t a t of s t r e a m s a l m o n i d s i n C e n t e n n i a l C r e e k w a t e r s h e d , B r i t i s h C o l u m b i a . B.C. F i s h W i l d l i f e B r . , F i s h . Mgmt. Rep. No. 73. Swanson, F . J . , G.W. L i e n k a e m p e r , and J.R. S e d e l l 1976. H i s t o r y , p h y s i c a l e f f e c t s and management i m p l i c a t i o n s o f l a r g e o r g a n i c d e b r i s i n w e s t e r n Oregon s t r e a m s . USDA F o r . S e r v . Gen. T e c h . Rep. PNW-56. Swanston, D.N., and F . J . Swanson 1976. Timber h a r v e s t i n g , mass e r o s i o n and s t e e p l a n d f o r e s t g e o m o r p h o l o g y i n t h e P a c i f i c N o r t h w e s t . IN: D.R. C o a t e s [ e d . ] . G eomorphology and 1 03 E n g i n e e r i n g , Dowden, H u t c h i n s o n and Ross I n c . p. 199-221 . T a g a r t , J.V. 1976. The s u r v i v a l from egg d e p o s i t i o n t o emergence o f coho salmon i n t h e C l e a r w a t e r R i v e r , J e f f e r s o n C o u n t y , W a s h i n g t o n . MSc. t h e s i s , U n i v . W a s h i n g t o n . T e r h u n e , L.D.B. 1958. The Mark VI g r o u n d w a t e r s t a n d p i p e f o r m e a s u r i n g seepage t h r o u g h salmon spawning g r a v e l . J . F i s h . Res. B o a r d Can. 15(5):1027-1063. Vaux, W.G. 1962. I n t e r c h a n g e of s t r e a m and i n t e r g r a v e l water i n a salmon spawning r i f f l e . U.S. F i s h W i l d l i f e S e r v . , S p e c . Rep. F i s h . No. 405. Vaux, W.G. 1968. I n t r a g r a v e l f l o w and i n t e r c h a n g e i n a s t r e a m b e d . U.S. F i s h W i l d l i f e S e r v . , F i s h . B u l l . 66:479-489. Ward, B.R., and P.A. S l a n e y 1979. E v a l u a t i o n of i n - s t r e a m enhancement s t r u c t u r e s f o r t h e p r o d u c t i o n of j u v e n i l e s t e e l h e a d t r o u t and coho salmon i n t h e Keough R i v e r ; p r o g r e s s 1977 and 1978. B.C. M i n . E n v i r o n . , F i s h . T e c h . C i r c . No. 45. Ward, B.R., and-P.A. S l a n e y 1981. F u r t h e r e v a l u a t i o n s of s t r u c t u r e s f o r t h e improvement of s a l m o n i d r e a r i n g h a b i t a t i n c o a s t a l s t r e a m s of B r i t i s h C o l u m b i a . IN: P r o p a g a t i o n , Enhancement, and R e h a b i l i t a t i o n of Anadromous S a l m o n i d P o p u l a t i o n s and H a b i t a t Symposium, O c t 15-17, Humboldt S t a t e U n i v . , A r e a t a C a l i f . Ward, W.H. MS1982. P a t r i c k C r e e k f i s h h a b i t a t improvement. D e l N o r t e C o u n t y , C a l i f o r n i a . USDA F o r . S e r v . S i x R i v e r s N a t i o n a l F o r e s t , FY 1982. W i c k e t t , W.P. 1958. The r e v i e w of c e r t a i n e n v i r o n m e n t a l f a c t o r s a f f e c t i n g t h e p r o d u c t i o n of p i n k and chum sa l m o n . J . F i s h . Res. B o a r d Can. 15:1103-1126. W i c k e t t , W.P. 1962. E n v i r o n m e n t a l v a r i a b i l i t y and r e p r o d u c t i o n p o t e n t i a l s o f p i n k salmon i n B r i t i s h C o l u m b i a . IN: N.J. W i l i m o v s k y [ e d . ] . Symposium on P i n k Salmon. 1960. H.R. M a c M i l l a n L e c t . S e r i e s , U n i v . B r i t i s h C o l u m b i a , V a n c o u v e r . W i l f o r d , D . J . , a n d J.W. Schwab 1982. S o i l mass movements i n t h e R e n n e l l Sound a r e a , Queen C h a r l o t t e I s l a n d s , B r i t i s h C o l u m b i a . IN: P r o c . C a n a d i a n H y d r o l o g y Symp. on H y d r o l o g i c a l P r o c e s s e s on F o r e s t e d A r e a s . F r e d e r i c t o n , N.B., June 1982. CH 1 1 . 40 60 80 100 % GRAVEL DEPTH (cm) 0 20 40 60 VELOCITY (cm/sec) APPENDIX A = Probability-of-use Criteria of Sachs Creek Pink Redds (n = 230). 1 05 APPENDIX B - CALCULATIONS OF BENEFIT / COST ANALYSIS FOR TREATMENT S I T E I I I AT SACHS CREEK The i n c r e a s e i n p i n k salmon p r o d u c t i o n r e q u i r e d t o o f f s e t i n i t i a l g a b i o n c o n s t r u c t i o n c o s t s was d e r i v e d below. The a v e r a g e w h o l e s a l e p r i c e of $8.76 p e r p i e c e l e s s t h e a v e r a g e h a r v e s t i n g and p r o c e s s i n g c o s t s of $2.95 p e r p i e c e y i e l d s a n e t b e n e f i t of $5.81 p e r p i e c e ( d i s c u s s i o n and a s s u m p t i o n s on pages 91 and 9 2 ) . D i s c o u n t r a t e s of 5, 10 and 15 p e r c e n t were a p p l i e d t o a l l v a l u e s i n c u r r e d a f t e r y e a r z e r o t o b r i n g f u t u r e v a l u e s t o p r e s e n t w o r t h . A l l v a l u e s were i n 1982 d o l l a r s . Y e a r 1 Net B e n e f i t s p e r F i s h A d d i t i o n a l F i s h R e q u i r e d p e r Spawning Y e a r t o R e c o v e r C o s t s 1 H a r v e s t e d 2 R e t u r n i n g 3 D i s c o u n t R a t e : 5% 10% 15% 5% 10% 15% 5% 10% 15% 0 $ 0 $ o $ o 2 5. 27 4 .80 4 .39 4 4 . 78 3 .97 3 .32 6 4. 34 3 .28 2 .51 8 3. 93 2 .71 1 .90 $18. 32 $14 .76 $12 . 12 1 0 $ 3. 57 $ 2 .24 $1 .44 1 2 3. 24 1 .85 1 .09 1 4 2. 93 1 .53 .82 $28. 06 $20 .38 $15 .47 1 6 $ 2. 66 $ 1 .26 $ .62 18 2. 41 1 .05 .47 20 2. 1 9 .86 .36 $35. 32 $23 .55 $16 .92 234 1 53 291 354 418 520 632 210 277 273 375 495 121 182 253 217 325 452 1. P i n k salmon a d u l t s r e t u r n i n g i n y e a r x a r e t h e p r o g e n y of spawners i n y e a r x-2. M a j o r p i n k r u n s a r e on even y e a r s o n l y . 2. The i n i t i a l g a b i o n c o s t s ($4,288) were d i v i d e d by t h e sum of net b e n e f i t s p e r f i s h f o r t h e d e s i r e d number of y e a r s t o c a l c u -l a t e how many a d u l t s a d d i t i o n a l t o t h e t h e i n i t i a l 120 would be r e q u i r e d t o be h a r v e s t e d p e r spawning y e a r t o r e c o v e r c o n s t r u c -t i o n c o s t s . e.g. A f t e r d i s c o u n t i n g a t 10 p e r c e n t f o r 14 y e a r s t h e n e t b e n e f i t s of one f i s h e v e r y spawning y e a r ($20.38) y i e l d a r e q u i r e m e n t of ($4,288 / $20.38 =) 210 f i s h e v e r y o t h e r y e a r . 106 APPENDIX B - c o n t i n u e d . 3.The number of a d d i t i o n a l f i s h r e q u i r e d f o r h a r v e s t a r e a d j u s t e d t o a c c o u n t f o r an e x p l o i t a t i o n r a t e of 56%. e.q. 210 / .56 = 375. 107 APPENDIX C - PHOTOGRAPHIC PLATES OF GABION SITES AT SACHS CREEK,  1.5 YEARS POST-INSTALLATION, FEBRUARY 1984. T r e a t m e n t S i t e I : Note t h e e n l a r g e d w a t e r f a l l o v e r the downstream g a b i o n (a r e s u l t of " n i c k p o i n t m i g r a t i o n " ) . L a r g e s i z e of s u b s t r a t e was a c o n s e q u e n c e of t h e h i g h e n e r g y a t t h i s 3% s l o p e g r a d i e n t s i t e . T r e a t m e n t S i t e I : The downstream l e f t g a b i o n wing t h a t r e s p o n d e d t o t h e above changes by bowing c a . 1m downstream and r o l l i n g c a . 20° i n t o the p l u n g e p o o l . 1 08 T r e a t m e n t S i t e I I : T r e a t m e n t S i t e I I : L o o k i n g u p s t r e a m . Note t h e g r a v e l bar f o r m e d downstream of t h e g a b i o n s . 109 T r e a t m e n t S i t e I I I : Note s c o u r e d bank on f a r s i d e and r i p r a p p l a c e m e n t where g a b i o n s were keyed i n t o t h e bank. The water l e v e l a t t h i s s i t e was r a i s e d by s p r u c e blowdowns a t t o p of p h o t o g r a p h and s u b s e q u e n t u p s t r e a m g r a v e l b a r f o r m a t i o n . T r e a t m e n t S i t e I I I : L o o k i n g u p s t r e a m , t h e o l d l o g jam a t t h e b o t t o m of p h o t o g r a p h i s d e f l e c t i n g t h e s t r e a m , r e s u l t i n g i n a deep s c o u r p o o l i n f r o n t of i t . 

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