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UBC Theses and Dissertations

A biological study of the influence of the Bridge River rapids on the sockeye runs of the Upper Fraser… Killick, Stanley Reginald 1948

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1/S3  A B i o l o g i c a l S t u d y of t h e I n f l u e n c e o f t h e B r i d g e R i v e r R a p i d s on t h e Sockoye Runs of t h e Upper F r a s e r Watersheds by Stanley Reginald K i l l i o k  A T h e s i s s u b m i t t e d i n P a r t i a l F u l f i l m e n t of The Requirements f o r the Degree o f MASTER OF SCIENCE I N AGRICULTURE i n t h e Department of ZOOLOGY  The U n i v e r s i t y o f B r i t i s h Columbia APRIL* 1948  S7  A B i o l o g i c a l Study o f the I n f l u e n c e o f the B r i d g e R i v e r Rapids on the Sockeye Huns o f the Upper F r a s e r  Watershed. by Stanley Reginald K i l l i c k .  •ABSTRACT The s i g n i f i c a n c e o f o b s t r u c t e d passage o f sockeye up the F r a s e r r i v e r was n o t r e a l i z e d f u l l y u n t i l , the v e r y  dlsast-  erous e f f e c t ^ o f H e l l ' s Gate were r e v e a l e d by the i n t e r n a t i o n a l - P a c i f i c Salmon F i s h e r i e s Commission  i n 1941;  ance of the H e l l ' s Gate o b s t r u c t i o n was  A f t e r the i m p o r t -  e s t a b l i s h e d , evidence  on t h e c o n d i t i o n s at the B r i d g e R i v e r R a p i d s were r e v i e w e d and a s t u d y commenced i n 1942.  These R a p i d s a r e l o c a t e d on the  F r a s e r r i v e r , 76 m i l e s n o r t h o f H e l l ' s Gate and must be passed by a l l the sockeye r a c e s d e s t i n e d f o r t h e upper F r a s e r w a t e r shed.  The Rapids c o n s i s t of two s e p a r a t e f a l l s , and have been  r e p o r t e d t o have caused d i f f i c u l t and b l o c k passage t o salmon as e a r l y as 19IS. The s t u d y , commenced by the Commission  i n 1942,  was  o u t l i n e d to determine the d i r e c t i n f l u e n c e of the R a p i d s on the c u r r e n t sockeye p o p u l a t i o n s and t o make such adjustments i n the contour o f the itapids as to a l l o w u n o b s t r u c t e d  passage  o f salmon at a l l water l e v e l s , s h o u l d b l o c k a d e c o n d i t i o n s be revealed.  The problem i n v o l v e d f o u r s e p a r a t e t a g g i n g e x p e r i -  ments from 1942 t o 1946.  No t a g g i n g was  done i n 1943.  The r e s u l t s of t h e v a r i o u s experiments  revealed that  Or  the sockeye ?*ere d e l a y e d art s e r i o u s l y b l o c k e d m  some y e a r s  d u r i n g low water l e v e l s o c c u r r i n g i n September and October. The l a t e - r u n n i n g C h l l k o and S t e l l a k o sockeye were t h e o n l y r a c e s t h a t were e f f e c t e d as the o t h e r runs t o the S t u a r t , Bowr o n and H o r s e f l y d i s t r i c t s pas.sed t h r o u g h t h e R a p i d s  early i n  the summer when the water l e v e l s were h i g h . A f t e r the c o m p l e t i o n of t h e a n a l y s i s o f t h e t a g g i n g experiments up t o 1945, a recommendation, t h a t two f i s h w a y s be c o n s t r u c t e d at t h e K a p i d s , was s u b m i t t e d f o r t h e c o n s i d e r a t i o n o f the Commission.  The i n s t a l l a t i o n o f f i s h w a y s was ap-  proved and t h e i r c o n s t r u c t i o n completed 1946.  f o r t h e salmon runs o f  The e f f i c i e n c y of t h e f i s h w a y s w ^ e  and a complete recorded.  t e s t e d i n t h a t year  change i n the p a t t e r n o f t a g s r e c o v e r i e s was  Whereas, b l o c k c o n d i t i o n s were p r e v i o u s l y shown by  sudden i n c r e a s e s i n the number o f tags r e c o v e r e d below the R a p i d s ; p r a c t i c a l l y no tags were r e c o v e r e d below d u r i n g low water p e r i o d s a f t e r t h e f i s h w a y s were b u i l t .  The same methods  o f a n a l y s i s t h a t were used t o determine b l o c k c o n d i t i o n s were . r e p e a t e d i n 1946 t o t e s t t h e f i s h w a y s and i n each case a n o t i c e a b l e improvement i n passage was r e c o r d e d ;  Therefore, i t  was c o n c l u d e d t h a t t h e f i s h w a y s b u i l t a t the B r i d g e H j v e r Kapi d s were s u c c e s s f u l i n p a s s i n g sockeye salmon, t h r o u g h t h e p r e v i o u s l y known b l o c k p e r i o d s t h a t were r e v e a l e d by t a g g i n g i n 1942j 1944 and 1945.  Frontpiece G e n e r a l view o f t h e lower and upper f a l l s a t the B r i d g e R i v e r R a p i d s l o o k i n g upstream. September 6, .Vater l e v e l RI gauge - 655 f e e t .  1944.  CONTENTS I  INTRODUCTION  1  II  REVIEW OF LITERATURE ......................... v.. R e p o r t s o f J . P. Babcock ............................ (1) C o n d i t i o n o f sockeye salmon i n Seton Creek i n 1912. ........ (2) O b s e r v a t i o n s a t t h e R a p i d s 1912 and 1925 ...... Dominion F i s h e r i e s r e p o r t .............. i . (1) No cohoe salmon p r e s e n t i n the Upper F r a s e r watershed .......... (2) F l u c t u a t i o n s i n t h e Seton Creek p o p u l a t i o n s ... I n v e s t i g a t i o n s o f t h e I n t e r n a t i o n a l P a c i f i c Salmon F i s h e r i e s Commission (1) R e p o r t s of H. S. Tremper . *................... (2) B u l l e t i n #1 - W. F. Thompson ...................  3 3  -  3 4 5 5 5 7 7 8  I I I METHODS 10 Method and l o c a t i o n o f t a g g i n g ...................... 10 Water l e v e l s ....•* 11 Theory o f c o n d u c t i n g a t a g g i n g experiment to. e v a l u a t e blockades ................ » 11 IV  RESULTS ........................... • Number o f Sockeye tagged 1942 - 1946 Section'A - Evidence of o b s t r u c t i o n from t h e a n a l y s i s o f t a g g i n g 1942 - 1945 (a) F i s h i n g i n t e n s i t y and r a c e s o f sockeye ........ CI)  1942  .... *......... i  .........  13 13 14 14 16  (2) 1944 .... ;. 18 " (3) 1945 18 (b) P e r c e n t a g e r e c o v e r y o f tags below and above t h e Rapids 20 (1) 1942 ....... r . 2 1 (2) 1944 23 (3) 1945 25 (c) Time out b e f o r e r e c o v e r y o f tags below ........ 27 (1) 1942 .................. ............... 28 (2) 1944 30 (3) 1945 .. 30 (d) i n f l u e n c e o f water l e v e l s on percentage r e c o v e r y below.......................................... 33 (1) 1942 . . . . . . . . . . . . 3 5 (2) 1944 . 35 (3) 1945 i . 37 The e f f e c t o f H e l l ' s Gate 39 Summation o f the evidence o f d i f f i c u l t and b l o c k conditions 45 Recommendations f o r f1shways 47 S e c t i o n B - The. a n a l y s i s o f t h e 1946 t a g g i n g e x p e r i ment t o t e s t t h e e f f i c i e n c y of t h e f i s h w a y s . 48 (a) F i s h i n g i n t e n s i t y and t h e r a c e s o f sockeye.48 (b) P e r c e n t a g e r e c o v e r y o f t a g s below ahdabove.52  (c) P e r i o d o f d e l a y o f tags below t h e R a p i d s .... 52 (d) Cummulative p e r c e n t a g e o f tags r e c o v e r e d below the Rapi d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 V  SUMMARY AND' CONCLUSIONS 56 B e f o r e t h e f i s h w a y s were c o n s t r u c t e d 57 A f t e r the f i s h w a y s were c o n s t r u c t e d ................. 59  VI ACKNO'ffLSDG'EMENTS ................................ V I I LITERATURE CITED  ... 60 61  % B i o l o g i c a l Study of the I n f l u e n c e of t h e B r i d g e R i v e r R a p l d a on t h e Sockeye Runs of the Upper F r a s e r 'Watershed.  1  by Stanley Reginald K i l l i c k INTRODUCTION The  b i o l o g i c a l and  engineering study of the  Bridge  R i v e r R a p i d s , and subsequent r e m e d i a l measures taken by I n t e r n a t i o n a l P a c i f i c Salmon Commission r e p r e s e n t s the  the sec-  ond major program f o r the r e m o v a l o f s e r i o u s o b s t r u c t i o n s to the m i g r a t i o n o f sockeye salmon w i t h i n the F r a s e r R i v e r w a t e r shed.  The  f i r s t t a s k was  the d i s c o v e r y and  d e f i n i t i o n of  b l o c k a t H e l l ' s Gate and t h e c o n s t r u c t i o n o f f i s h w a y s to pass salmon through The  the  designed  a wide r a n g e o f w a t e r l e v e l s .  s i g n i f i c a n c e o f o b s t r u c t e d passage of sockeye up  the F r a s e r R i v e r was  not r e a l i z e d f u l l y u n t i l the v e r y d i s -  a s t e r o u s e f f e c t s o f H e l l ' s Gate were r e v e a l e d i n 1941.  In  t h a t year i t became apparent t h a t water l e v e l s a c t e d as a major c o n t r o l of the numbers of salmon r e a c h i n g the v a r i o u s spawning grounds. b l o c k was  A f t e r the importance of the H e l l ' s Gate  e s t a b l i s h e d , evidence  R i v e r R a p i d s was  on the c o n d i t i o n s at B r i d g e  r e v i e w e d more t h o r o u g h l y and i t became e v l d r  ent t h a t a s t u d y s h o u l d be a t a r t e d a t t h i s p o i n t I n the summer o f 1943,  the w r i t e r was  immediately.  s t a t i o n e d a t the  Rapids,  and an e x t e n s i v e t a g g i n g program was commenced below and,above the R a p i d s .  T h i s s t u d y was designed t o o b t a i n i n f o r m a t i o n on  the f o l l o w i n g phases o f the problem: (1) Dates of t h e a r r i v a l , peak, and end o f the v a r i o u s runs t h r o u g h t h e R a p i d s . (2) E v i d e n c e  as t o whether sockeye dropped downstream  and e n t e r e d Seton Creek upon b e i n g b l o c k e d a t t h e Rapids. (3) Dates a n d . d u r a t i o n s  of blockades.  (4) P r e c i s e water l e v e l s c a u s i n g blocks.;  ;  (5) I n f l u e n c e o f H e l l ' s Gate on the movements o f sockeye and i t s r e l a t i o n s h i p t o the B r i d g e R i v e r R a p i d s . The problem as d e f i n e d by the Commission was t o d e t ermine t h e d i r e c t i n f l u e n c e o f t h e R a p i d s on the c u r r e n t sockeye p o p u l a t i o n s and to make such adjustments  i n the contour of  the Rapids as t o a l l o w u n o b s t r u c t e d passage o f salmon t o t h e Upper F r a s e r , s h o u l d b l o c k a d e c o n d i t i o n s be r e v e a l e d as a r e s u l t of t h e i r study.  I t i s the purpose o f t h i s paper to pre-  s e n t accumulated'evidence R i v e r Rapids  o f blockade c o n d i t i o n s a t t h e B r i d g e  together with the r e s u l t s obtained a f t e r the  i n s t a l l a t i o n o f the f i s h w a y s i n 1946. R e f e r r i n g t o the map, t h e c r i t i c a l p o s i t i o n o f the B r i d g e R i v e r Rapids i s r e a d i l y n o t e d w i t h r e s p e c t t o a l l t h e F r a s e r R i v e r runs t h a t , spawn above t h e c o n f l u e n c e o f the Thompson R i v e r a t L y t t o n .  A p a r t f r o m t h e t h r e e runs i n t o t h e  Thompson R i v e r watershed ( A d a m s - L i t t l e R i v e r , R a f t and Seymour) a l l t h e sockeye p o p u l a t i o n s o f t h e F r a s e r above H e l l ' s Gate must pass t h r o u g h t h e B r i d g e R i v e r Rapids  except f o r t h e s m a l l  3 Seton-Anders on r u n .  To ssvoid confusion-, i t must be n o t e d t h a t  the Rapids a r e n o t on B r i d g e R i v e r d e s p i t e the name but a r e  on  the F r a s e r p r o p e r , o n e - h a l f m i l e upstream f r o m the mouth o f B r i d g e R i v e r and s i x m i l e s n o r t h o f the town o f L i l l o o e t . R a p i d s c o n s i s t of two s e p a r a t e f a l l s a p p r o x i m a t e l y 900 apart.  These have been d e s i g n a t e d as the " l o w e r " and  f a l l s , b o t h o f w h i c h appear to become d i f f i c u l t for of  feet "upper"  or i m p o s s i b l e  salmon t o ascend d u r i n g c e r t a i n y e a r s when the water the F r a s e r R i v e r becomes low i n . September and  The  level  October.  D e t a i l s on t h e h e i g h t of the drop t h r o u g h the two f a l l s and -a3L o t h e r r e q u i r e d data p e r t a i n i n g t o p r o f i l e s and r i s e and  fall,  of water l e v e l s have been s t u d i e d by the e n g i n e e r i n g d i v i s i o n of  t h e Commission and a r e I n c l u d e d I n an u n p u b l i s h e d  p t by M i l o B e l l (1945).  manuscri-  P l a t e s I and I I i l l u s t r a t e the t u r b -  u l e n c e and drop through the lower and upper f a l l s . REVIEW OF LITERATURE A r e v i e w o f the l i t e r a t u r e and h i s t o r i c a l background of  the B r i d g e R i v e r Rapids has a i d e d m a t e r i a l l y i n d e t e r m i n i n g  the method o f s t u d y and d e f i n i n g the o b j e c t i v e s t o be achieved. U n f o r t u n a t e l y , no p r e c i s e s t u d i e s of the R a p i d s had been undert a k e n p r i o r t o t h e work of the Commission but the sum o f t h e accumulated  e v i d e n c e l e f t l i t t l e doubt t h a t some f a c t o r or  f a c t o r s had i n f l u e n c e d t h e passage o f salmon a t t h i s for  location  many y e a r s .  R e p o r t s o f J . P. Baboock (1) C o n d i t i o n o f sockeye salmon i n Seton Creek i n 1912.  4 I n the r e p o r t of t h e Commissioner of F i s h e r i e s f o r B r i t i s h Columbia f o r 1913, ments :  Babcock made the f o l l o w i n g s t a t e -  "The f i r s t sockeye e n t e r e d our h a t c h e r y w e i r s at the o u t l e t o f Seton Lake on J u l y 35. Between t h a t date and August 17, when t h i s run ended, 3,000 u n u s u a l l y l a r g e prime f i s h had e n t e r e d the w e i r s . On September 1 the s o c k e y e a g a i n began, e n t e r i n g the h a t c h e r y w e i r s , and by the 17th of the month upwards o f 10,000 were impounded i n the s e i n i n g p o o l . The r u n c o n t i n u e d u n t i l October 8. The f i s h which p a s s e d ' t h r o u g h the w e i r s a f t e r September 10 were i n poor c o n d i t i o n , b e i n g b a d l y s c a r r e d about the head and many showed hook and s p e a r wounds. I t was e s t i m a t e d that more t h a n h a l f of t h e f i s h between the 15th and 30th were m u t i l a t e d more or l e s s by hook or s p e a r . Many were so b a d l y waunded t h a t they d i e d . D u r i n g September 6,700 dead sockeye were removed from the w e i r s . " "We a t t r i b u t e the e x c e p t i o n a l l y l a r g e - c o l l e c t ! o n o f sockeye eggs a t the Seton Lake h a t c h e r y t h i s y e a r , and t h e b a t t e r e d and wounded c o n d i t i o n of the f-ish t h a t came t o the s t a t i o n a f t e r September 1 0 t h , t o the low s t a g e of w a t e r i n the F r a s e r R i v e r , which p r e v e n t e d t h e i r p a s s i n g t h r o u g h the canyon h a l f a m i l e above the mouth o f the B r i d g e R i v e r " . I n 1937  and 1940  c o n s i d e r a b l e numbers o f s o c k e y e were  a g a i n found dead and unspawned i n S e t o n C r e e k ,  This  finding  agreed w i t h o b s e r v a t i o n s made i n t h e strBams below H e l l ' s Gate where many salmon were examined d u r i n g b l o c k y e a r s and  found  dead and unspawned, (3) O b s e r v a t i o n s  at the R a p i d s 1913  I n c o n d u c t i o n of Mr.  and  Babcock's r e p o r t on the:jpopulations  i n S e t o n Creek (Cayoosh C r . ) , he made a few on the B r i d g e R i v e r R a p i d s t h e m s e l v e s . R a p i d s i n 1913, Mr.  1935.  actualyobservations  A f t e r a v i s i t t o the  Babcock r e p o r t e d t h a t :  "The r i v e r bed of the F r a s e r where the b l o c k a d e o c c u r r e d i s so narrow and so f i l l e d w i t h p r o j e c t i n g r o c k s , t h a t even d u r i n g o r d i n a r y s t a g e s the water r u s h e d through w i t h s u c h v e l o c i t y as to g i v e the sockeye c o n s i d e r a b l e d i f f i c u l t y i n p a s s i n g . The water was so low t h a t t h e sockeye found t h e i r passage c o m p l e t e l y b l o c k e d by September 10. The w a t e r s of t h e F r a s e r were too d i s c o l o u r e d t o t r a c e t h e movements of t h e s e salmon from the canyon back t o Cayoosh Creek, but the f i s h  5 t h a t r e a c h e d the h a t c h e r y the l a s t of September and t h e f i r s t of October were so s c a r r e d about the head as t o c o n v i n c e anyone who had seen the b r u i s e d f i s h i n the p o o l s below t h e canyon (Rapids) t h a t t h e y r e c e i v e d t h e i r i n j u r i e s t h e r e , and b e i n g u n a b l e t o pass up the F r a s e r had t u r n e d back t o e n t e r the f i r s t a v a i l a b l e l a k e - f e d t r i b u t a r y stream". Upon another v i s i t  es ed;  t o the R a p i d s i n 1925 Babcock  stat'  "At such low s t a g e s of water as e x i s t e d t h e r e t h i s year the f i s h encountered as much d i f f i c u l t y as t h e y d i d a t H e l l * s Gate. They (sockeye) were b l o c k e d f o r two weeks and d u r i n g t h a t time most of them t h a t escaped c a p t u r e by I n d i a n s dropped down-stream and e n t e r e d Cayoosh Creek. F i v e hundred" s o c k e y e e n t e r e d S e t o n . A l l were i n advanced c o n d i t i o n and b e l i e v e d t o be a l l b l o c k e d s o c k e y e . " Dominion F i s h e r i e s R e p o r t s . (1) No Cohoe salmon p r e s e n t i n the Upper F r a s e r watershed. I n r e v i e w i n g some of t h e p e r t i n e n t l i t e r a t u r e i n t h e Dominion F i s h e r i e s r e p o r t I t was found t h a t ishoro. a r o no Cohoe salmon (Oncorhychus k i s u t c h ) have e v e r been r e p o r t e d i n the  upper F r a s e r r i v e r d i s t r i c t ; however, t h e y a r e p r e s e n t i n  the  South Thompson watershed w h i c h i s a c c e s s i b l e w i t h o u t pas-  s i n g through the B r i d g e R i v e r R a p i d s .  The cohoe i s a f a l l - r u n  salmon and would i n e v i t a b l y a r r i v e a t the R a p i d s I n l a t e October and N o v e m b e r i f they passed the Thompson R i v e r  junction.  (2) F l u c t u a t i o n s i n the Seton Creek P o p u l a t i o n s A more d i r e c t i n d i c a t i o n of a b l o c k a d e a t the R a p i d s i s found i n a r e v i e w of the s i z e s o f t h e Seton Creek p o p u l a t ions.  One  i m p o r t a n t c o n s i d e r a t i o n , to be d e s c r i b e d i n t h e  subsequent a n a l y s i s of the t a g g i n g d a t a , was  the t r a c i n g , o f  b l o c k e d sockeye from below B r i d g e R i v e r R a p i d s down t h e F r a s e r and i n t o the Seton-Anders'on w a t e r s h e d . was  I n 1 9 4 2 , t h i s behaviour-  a c t u a l l y proved, by the r e c o v e r y , i n Seton and P o r t a g e c r e e k ,  of  tagged sockeye t h a t were h e l d up by. low water a t t h e R a p i d  d u r i n g September and O c t o b e r .  T h i s phenomenon was  strongly  s u s p e c t e d i n 1912, 1925, 1937 and 1940 by v a r i o u s o b s e r v e r s but l a c k e d p r o o f u n t i l tags c o u l d be t r a c e d from t h e R a p i d s t o Seton c r e e k .  With, the knowledge  o f t h i s movement, i t i s  p o s s i b l e to i n d i c a t e c e r t a i n y e a r s i n the p a s t i n w h i c h b l o c k c o n d i t i o n s must have e x i s t e d a t t h e R a p i d s . The e s t i m a t e d sockeye p o p u l a t i o n s o f Seton Creek have been t a b u l a t e d from the r e c o r d s of the Dominion Department F i s h e r i e s f o r a l l y e a r s from 1901 to 1946  of  (Table I ) . I n  those y e a r s i n w M c h Seton c r e e k had an u n u s u a l l y l a r g e r u n , the  p r e s e n c e o f b l o c k e d sockeye was  the  brood y e a r was  i n d i c a t e d by the f a c t t h a t  too s m a l l t o warrant the g r e a t i n c r e a s e .  F u r t h e r m o r e , t h e r u n f o u r y e a r s l a t e r showed no improvement as a r e s u l t of the i n f l u x o f blocked f i s h . the  Those y e a r s i n w h i c h  p o p u l a t i o n s o f Seton Creek were thus i n c r e a s e d a r e marked  w i t h a double a s t e r i s k  For example,  the y e a r 1937 showed a  p o p u l a t i o n of a p p r o x i m a t e l y 50,000 s o c k e y e , y e t the brood year o f 1933, showed o n l y a r u n o f 100. was  S t i l l more e v i d e n t  the f a c t t h a t the 1941 p o p u l a t i o n s w h i c h s h o u l d be the  progeny o f the 50,000 sockeye I n 1937 c o n s i s t e d o f o n l y 50 salmon.  The b l o c k a t B r i d g e R i v e r R a p i d s must have been s e r -  i o u s i n 1937 as i n d i c a t e d by the S e t o n p o p u l a t i o n .  I n 1942,  when the R a p i d s were under d a i l y o b s e r v a t i o n , tagged sockeye w e r e . t r a c e d back t o Seton but the f i s h were n o t as i n t h a t y e a r as they were i n 1937.  abundant  TABLE I ESTIMATED SOCKEYE POPULATIONS OF SETON CREEK  Year  Population  Year  1,000,000- " 0 971 1,000 200,000 15,000**  1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946  Population  -  1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923  1,000,000 —  •'  90 10,000 30,000 300 200 100 - 200 100 200 0 0 0 0  -• 50 66,000*-*40G 200 700 200 100 100 100 100 400 200 15,000** 50,000** 500 20 2,000** 50 1,000** 800 100 20 75  ** B l o c k a t B r i d g e R i v e r R a p i d s  indicated.  I n v e s t i g a t i o n s by the i n t e r n a t i p n a l P a c i f i c Salmon F i s h e r i e s Commissdon . (1) R e p o r t s  o f H. S; Tremper.  •  The f o l l o w i n g o b s e r v a t i o n s were made by t h e Commissi o n s o b s e r v e r s t a t i o n e d a t t h e R a p i d s i n 1940; "A s l i g h t blockade t o t h e m i g r a t i n g salmon a t B r i d g e R i v e r R a p i d s was e v i d e n t on September 26. T h i s p a r t i a l b l o c k l a s t e d two days. From then (September 28) u n t i l October 4 t h e  8 R a p i d s were a v e r y s e r i o u s o b s t a c l e t o the m i g r a t i n g sockeye. There were l a r g e numbers o f sockeye which were weakened to such a s t a t e t h a t i t d i d n o t seem p o s s i b l e t h a t t h e y c o u l d ascend the R a p i d s i I t then seems o b v i o u s t h a t t h e R a p i d s had a d e t e r ant e f f e c t on l a r g e numbers o f sockeye at c e r t a i n w a t e r l e v e l s . Weak, b a t t e r e d sockeye were observed a t t e m p t i n g the R a p i d s and two days l a t e r , c l e a n e r , f r e s h e r sockeye appeared i n t h e e d d i e s ; " The o b s e r v e r s t a t e s i n c o n c l u s i o n : " I t i s e v i d e n t t h a t the B r i d g e R i v e r R a p i d s r e p r e s e n t s a problem o f n e a r e q u a l magnitude as H e l l ' s G a t e . I t s h o u l d be s t u d i e d i n ' a s i m i l a r manner and w i t h e q u a l v i g o u r i " (2) B u l l e t i n §1 - W. F* Thompson. The above b r i e f r e v i e w of some of the e a r l y h i s t o r y as quoted c h i e f l y from Babcock i s s u f f i c i e n t t o demonstrate t h a t d i f f i c u l t passage a t B r i d g e R i v e r R a p i d s has been e f f e c t i v e f o r many y e a r s .  I n v e s t i g a t i o n conducted by t h e I n t e r n a t i o a f H e l l ' s G a t e f r o m 1939 'to  n a l P a c i f i c Salmon Commission/1942 has f u r t h e r i n d i c a t e d t h a t some i n t e r r u p t i n g f a c t o r s have i n f l u e n c e d the d i s t r i b u t i o n o f the, sockeye r a c e s i n t h e F r a s e r R i v e r system.  Thompson (1945)  d e s c r i b e d the f l u c t u a t i n g p o p u l a t i o n s of the Seton-Anderson watershed and a l s o showed the major d i v i s i o n of t h e sockeye r a c e s i n t o t h e Upper F r a s e r and t h e Thompson a r e a by the r e c o v e r y o f H e l l ' s Gate t a g s on the spawning grounds.  The p a t t e r n  of r a c e s e g r e g a t i o n I n t o the two systems n o t e d above I s an i m p o r t a n t f a c t o r i n the a p p r e c i a t i o n o f the s e r i o u s n e s s of the Bridge River Rapids. R e f e r e n c e may be made t o f i g u r e 21 i n Thompson's r e p o r t where t h e r e c o v e r i e s of H e l l ' s Gate t a g s on t h e v a r i o u s spawning grounds have been p l o t t e d .  From t h i s f i g u r e i t i s  apparent t h a t a t p r e s e n t t h e r e a r e two main d i v i s i o n s of t h e sockeye r u n s w i t h i n t h e F r a s e r R i v e r system.  The f i r s t  divis-  9 ion  p a s s i n g H e l l ' s Gate b e f o r e September 18 i s comprised o f  sockeye g o i n g to the Upper F r a s e r w a t e r s h e d .  The "3econd d i v i -  s i o n passes H e l l ' s Gate a f t e r September 18 and i s d e s t i n e d f o r the South Thompson d i s t r i c t .  W i t h o n l y minor e x c e p t i o n s  this  p a t t e r n o f d i v i s i o n h o l d s t r u e f o r every c y c l e of t»he p r e s e n t day r u n s .  However, t h e h i s t o r y of the Thompson r i v e r r u n s  shown t h a t sockeye f o r m e r l y m i g r a t e d  has  d u r i n g the p e r i o d b e f o r e  September 18 and Thompson'(1945) p r e s e n t s v a r i o u s r e a s o n s f o r t h e i r d e c l i n e almost t o t h e p o i n t . o f complete e x t i n c t i o n . then remains t o be shown what f a c t o r or f a c t o r s c o u l d  It  restrict  the passage of s o c k e y e a f t e r September 18 to the Upper F r a s e r , A s t r o n g c l u e as t o the f a t e of some  of these  late  r u n s t o the Upper F r a s e r i s found i n the sudden appearance o f . l a r g e , unexpected r u n s i n t o the Seton-Anderson watershed* F u r t h e r evidence of t h e o b s t r u c t i o n o f l a t e runs w i l l be brought out i n the a n a l y s i s of the t a g g i n g i n the f o l l o w i n g s e c t i o n s o f t h i s paper. V i t a l evldenoe was  f u r n i s h e d by the i n v e s t i g a t i o n s of  Babcock, Thompson and Tremper i n d i c a t i n g t h a t d i f f i c u l t passage and o f t e n s e r i o u s b l o c k c o n d i t i o n s t o the salmon m i g r a t i n g t o the Upper F r a s e r have been i n e f f e c t f o r many y e a r s .  However,  o n l y the dates o f d i f f i c u l t passage were g i v e n and no  definite  water l e v e l s were a s s i g n e d to the p e r i o d s of s l i g h t d e l a y periods of serious obstruction. adequate d a t a on a c c u m u l a t i o n s  and  Thus, the a p p a r e n t need f o r  of f i s h j  dates o f blockade  and  a c c u r a t e water l e v e l s became e v i d e n t . The d e t e r m i n a t i o n o f the s e r i o u s n e s s o f any  suspected  10 o b s t r u c t i o n t o the m i g r a t i o n o f salmon p r e s e n t s a d i f f i c u l t problem t h a t r e q u i r e s s t u d y f r o m e v e r y p o s s i b l e approach. To d a t e , o n l y l i m i t e d means a r e a v a i l a b l e t o a c c u r a t e l y  determine  d i f f i c u l t passage o f f i s h i n any o t h e r watershed t h a n the Fraser r i v e r .  Thus, the method o f t a g g i n g as employed by t h e  Salmon Commission a t H e l l ' s Gate was used a g a i n a t t h e B r i d g e R i v e r R a p i d s as the b e s t method so f a r a v a i l a b l e f o r s o l v i n g t h i s t y p e o f problem.  C e r t a i n m o d i f i c a t i o n s " a n d adjustments  have been made t o s u i t t h e p a r t i c u l a r c o n d i t i o n s a t the .Rapids but e s s e n t i a l l y the e v i d e n c e o f b l o c k a d e i s I n t e r p r e t e d by t h e pattern of the tag r e c o v e r i e s i METHOD Method and L o c a t i o n o f Tagging The method o f a f f i x i n g t h e t a g s t o t h e sockeye a t t h e R a p i d s was the same as t h a t ' u a e d I n a l l t h e t a g g i n g program conducted by t h e Commission and may be r e f e r r e d . t o i n t h e r e p o r t o f MacKay, Howard and K i l l i c k  (1944).  captured f o r tagging i n I n d i a n d i p n e t s .  The sockeye were  A l l f i s h tagged were  kept out o f t h e water f o r as s h o r t a t i m e as p o s s i b l e and s e l dom more t h a n 45 seconds was r e q u i r e d f o r t h e whole o p e r a t i o n . D e t a i l s on t h e c o n d i t i o n , t o t a l l e n g t h and s c a r s were r e c o r d e d and ;a':.scale sample t a k e n from each  fish;  F i s h i n g s t a t i o n s were l o c a t e d below and above t h e R a p i d s so t h a t comparisons o f t h e f i s h i n g i n t e n s i t i e s and r e c o v e r y o f t a g s c o u l d be made* t o t h e s t a t i o n s below crew.  I n 1944, t a g g i n g was l i m i t e d  t h e R a p i d s o n l y , because o f a reduced  Sockeye were tagged a t b o t h t h e r i g h t and l e f t banks  11 below the f a l l s .  I n the a n a l y s i s o f t h e t a g r e c o v e r i e s i t was  found t h a t t h e r e was no s i g n i f i c a n t d i f f e r e n c e between the numbers o f r e c o v e r i e s f r o m the two banks; t h e r e f o r e , a combina t i o n of b o t h groups o f tags was  used.  Water L e v e l s C o n s i s t e n t water l e v e l r e a d i n g s were r e c o r d e d s i n c e 1942^ from a s i n g l e gauge below the Rapids^ d u r i n g the salmon migrations. for  These r e a d i n g s j t a k e n d a l l y except on Sundays,  the months o f J u l y A u g u s t , September and October w i l l  found a t t h e appendix o f t h i s paper.  D u r i n g the 1944  be  season,  more e x t e n s i v e water l e v e l r e a d i n g s were t a k e n by the Commission  e n g i n e e r s a t t e n s e p a r a t e l o c a t i o n s below and above t h e  R a p i d s on b o t h r i g h t and l e f t  banks-'! The g a u g e u s e d i n the ;  i n t e r p r e t a t i o n o f the b i o l o g i c a l d a t a ^ i s l o c a t e d on the r i g h t bank of t h e r i v e r below t h e l o w e r f a l l s .  (Gauge R l )  As i t was d e s i r a b l e t o have water l e v e l r e a d i n g s f o r y e a r s p r e v i o u s t o 1942, the r a t e o f f l o w of the r i v e r as r e c orded at Jesmond was i n t e r p o l a t e d i n t o gauge r e a d i n g s a t the R a p i d s as f a r backa as 1935.  Jesmond i s l o c a t e d a p p r o x i m a t e l y  30 m i l e s n o r t h o f L l l l o b e t .  F o r the purposes o f the b l o c k -  ade a n a l y s i s , the water l e v e l r e a d i n g s a t t h e R a p i d s as c a l c u l a t e d from Jesmond and c o r r e l a t e d w i t h gauge R l w i l l be used throughout t h i s r e p o r t . Theory o f c o n d u c t i n g a Tagging Experiment t o e v a l u a t e blockades. As i t i s i m p o s s i b l e t o a c t u a l l y observe the salmon  12  w i t h i n the F r a s e r r i v e r , some mark or i d e n t i f i c a t i o n must be a t t a c h e d t o the f i s h i n o r d e r t h a t t h e i r movements may traced,  be  . i n t h i s c a s e , numbered c e l l u l o i d tags were a t t a c h e d  to as many salmon as p o s s i b l e b o t h below and above the s i t e under study*  The  salmon, when caught u n s e l e c t l v e l y ,  tagged  and r e t u r n e d t o the r i v e r , r e p r e s e n t t h e b e s t known means o f d e m o n s t r a t i n g what i s happening t o the p o p u l a t i o n as a whole. I n c o n j u n c t i o n w i t h the t a g g i n g o p e r a t i o n , a c c u r a t e water r e a d i n g s were taken each day and the developement o f any or t u r b u l e n t waters r e c o r d e d .  level falls  I t then remains t o be seen  where and when these tags w i l l be r e c o v e r e d and i n what numbers they w i l l be taken above and below t h e t a g g i n g s i t e * The p l a c e o f r e c o v e r y of t h e tags put on below w i l l considered f i r s t .  be  I n t h i s r e g a r d i t i s q u i t e l o g i c a l t o assume  t h a t i f some tags are r e c o v e r e d above and h £ tags are r e c a p t u r e d a t the p l a c e o f t a g g i n g or a t any downstream p o i n t then t h e s e tagged f i s h have proceeded upstream w i t h o u t d i f f i c u l t y . I t i s e q u a l l y l o g i c a l t o r e a s o n t h a t I f t h e s e tags were r e c o v ered I n s i g n i f i c a n t numbers a t the p l a c e of t a g g i n g below or at any downstream p o i n t then some f a c t o r has impeded t h e i r g r e s s passed-the  s i t e under s t u d y .  pro  C o n c u r r e n t w i t h the abun-  dance o f tags r e c o v e r e d below, t h e r e may  be a c o r r e s p o n d i n g  s c a r c i t y i n the numbers o f r e c o v e r i e s above* i n a d d i t i o n t o t h e a n a l y s i s of tags put on below, the tags put on above are s t u d i e d .  I f no o b s t r u c t i o n i s i n e f f e c t ,  t h e p a t t e r n o f u p r i v e r r e t u r n s from the t a g g i n g below above s h o u l d be the same.  and  I f on the othec hand an o b s t r u c t i o n  13 o c c u r s , i t has been found t h a t the sockeye tagged.above  during  b l o c k p e r i o d s were r e c o v e r e d i n r e d u c e d numbers on the spawni n g as were those sockeye tagged below d u r i n g the same p e r i o d . I t would appear t h a t an extended d e l a y , caused by the o b s t r u c t i o n , reduced the v i t a l i t y of the f i s h t o such an e x t e n t t h a t , even though some sockeye were a b l e to surmount the R a p i d s and be tagged above, they were u n a b l e t o r e a c h the spawning  grounds.  I f a d i f f e r e n t i a l r e c o v e r y o f tags o c c u r r e d w i t h i n t h e season then an e x p l a i n a t i o n s h o u l d be sought to account f o r the various recovery f l u c t u a t i o n s .  The f i r s t t h i n g t o l o o k f o r i s  u n d o u b t a b l y the i n f l u e n c e of t h e r i v e r t h r o u g h which the salmon must swim*  ThuSj the water l e v e l s have been gauged and  p l o t t e d a g a i n s t the p a t t e r n o f t a g r e c o v e r i e s .  This process  was r e p e a t e d over a p e r i o d o f y e a r s t o f i n d out what r e l a t i o n s h i p e x i s t s between the water l e v e l s and the s u c c e s s o f p a s s age of m i g r a t i n g salmon. RESULTS Number of Sockeye tagged 1942-46 A summary of the t o t a l numbers o f sockeye tagged i s shown i n the f o l l o w i n g t a b l e I I : Year  Tagged below  Tagged above  1942 1944 1945 1946  1173 3341 1980 1808  469 0 931 651  Totals  7301  2041  No. i n crew 3 2 4 4  14  A  Each year the maximum numbers o f sockeye were taeyeu tagged and e v e r y e f f o r t wiss made "to s e c u r e at l e a s t 10 on each day of t a g g i n g .  sockeye  D e t a i l s on the r e l a t i v e abundance o f  tags a p p l i e d throughout the season a r e g i v e n i n the s e c t i o n s on the f i s h i n g Section A ing  intensity.  E v i d e n c e o f o b s t r u c t i o n f r o m the a n a l y s i s o f t a g g -  1942-1945. In  t h i s s e c t i o n of the paper the r e s u l t s o f the t a g g i -  ng experiments f o r t h e y e a r s 1942, ented to show how  and 1945  w i l l be p r e s -  the R a p i d s i n f l u e n c e d the passage of sockeye  salmon to the Upper F r a s e r ; the  1944  The v a r i o u s means o f i l l u s t r a t i n g  d i s t r i b u t i o n o f tags and the numbers o f r e c o v e r i e s  below  and above the Rapids a r e i n c l u d e d f o r each y e a r of t a g g i n g . The r e s u l t s w i l l t h e n be summarized and a g e n e r a l statement g i v e n as t o the s e r i o u s n e s s o f t h e R a p i d s and the recommenda t i o n for. r e m e d i a l measures* RESULTS. (a)  F i s h i n g i n t e n s i t y and Races of sockeye. In  f i g u r e s 1-3  i t i s shown t h a t the sockeye p o p u l a t i o n s  a r r i v i n g a t the B r i d g e R i v e r R a p i d s a r e comprised o f a number of  d i s t i n c t and s e p a r a t e r a c e s .  The s e g r e g a t i o n o f these r a c e s  has been c l e a r l y i l l u s t r a t e d by Thompson (1945) and has been c o n f i r m e d by t h e r e s u l t s of t h e p r e s e n t B r i d g e R i v e r R a p i d s t a g g i n g experiment.  The f i g u r e s i n d i c a t e w h i c h r u n s might  e f f e c t e d by a b l o c k a t the R a p i d s .  be  They a l s o I l l u s t r a t e the  v a r y i n g abundance of sockeye of t h e R a p i d s throughout the f  season and the p e r i o d o f passage or range o f the v a r i o u s r a c e s  15  Figure 1 D a i l y c a t c h e s of sockeye above and below B r i d g e R i v e r R a p i d s p l o t t e d a g a i n s t the water l e v e l s and ranges of the r u n s o f t h e Upper F r a s e r sockeye p o p u l a t i o n i n 1943.  1942  30  10  20  30  10  H STELLAKO GHILKO 4 BOWRON H  STUART  120 DAILY CATCHES Below Above  10  20 JULY.  30  10  20 AUGUST •  30  10  20  30  SEPTEMBER  10 OCTOBER  16 d e s t i n e d f o r the spawning ground of the Upper F r a s e r r i v e r . (1)  1942 W i t h r e f e r e n c e to f i g u r e 1 i t w i l l be noted t h a t t a g -  g i n g commenced on J u l y 10 and ended on October 16.  The  c a t c h e s o f the t a g g i n g crews i n d i c a t e t h a t t h e s e dates i n c l u d e the  f u l l range of the sockeye m i g r a t i o n t o the Upper F r a s e r  r i v e r spawning grounds passed the B r i d g e R i v e r R a p i d s d u r i n g 1942.  F i s h i n g was  c o n t i n u e d to October 28 but no sockeye were  caught a f t e r October 16. I t i s shown t h a t the c a t c h e s were e r r a t i c t h r o u g h J u l y and August and a t no t i m e e x c e p t J u l y 31 were the sockeye abundant. of 21.  However, on September -2 and 3 a sudden, heavy  influx  sockeye o c c u r r e d and l a r g e c a t c h e s were made u n t i l September T h i s abundance of f i s h c o n s i s t e d o f a wave o f b l o c k e d  salmon t h a t were r e l e a s e d from a b l o c k a t H e l l ' s Gate when t h e water l e v e l dropped below 28 f e e t on August 3 1 s t .  These f i s h  then r a n i n t o low water a t B r i d g e River: R a p i d s and l a r g e numb e r s were seen a c c u m u l a t i n g i n the eddy below the l o w e r andupper f a l l s and accounted f o r the heavy c a t c h e s o c c u r l n g i n September;  I t i s i n t e r e s t i n g t o n o t e a sudden i n c r e a s e i n t h e  c a t c h e s about the R a p i d s on September 19 w h i c h c o i n c i d e d w i t h a r i s e i n water l e v e l t o 652.8 f e e t on t h i s d a t e . Comparing  the c a t c h e s of f i s h below and above t h e  R a p i d s on f i g u r e 1, i t was noted t h a t p r a c t i c a l l y no sockeye were t a k e n a t the upper s t a t i o n a f t e r September 22, y e t s o c k eye were s t i l l b e i n g caught i n some numbers below.  I t was  t h i s t i m e t h a t the water l e v e l had dropped below a gauge  at  17  Figure 3 D a i l y c a t c h e s o f sockeye below the B r i d g e R i v e r R a p i d s p l o t t e d a g a i n s t the w a t e r l e v e l s and ranges o f the r u n s of t h e Upper F r a s e r sockeye p o p u l a t i o n s I n 1944.  1944  20 30 STELLAKO H CHILKO BOWRON 200  DAILY CATCHES 80  Below  60  40 20  100 80  60  40  20  0  10  20 JULY  30  10  .20 30 AUGUST  10  20  30  SEPTEMBER  10  18 r e a d i n g o f 650 f e e t and remained low f o r t h e remainder o f t h e season.  I t s h o u l d a l s o he r e a l i z e d t h a t no sockeye tagged a t  the R a p i d s a f t e r September 27 were r e c o v e r e d on the spawning grounds d e s p i t e the f a c t t h a t sockeye were tagged i n s i g n i f i cant numbers up t o October 12. (2) 1944 I n 1944, t h e t a g g i n g was c o n f i n e d t o the s t a t i o n s b e l ow t h e f a l l s .  The f i r s t sockeye were caught and tagged on  J u l y 12 and o p e r a t i o n s were t e r m i n a t e d on September 24.  The  d a i l y c a t c h e s i n 1944 p r e s e n t a markedly d i f f e r e n t p i c t u r e from those o f 1942, but a g a i n t h e i n f l u e n c e o f H e l l a s Gate was r e f lected.  With r e f e r e n c e to u n p u b l i s h e d d a t a c o m p l i e d by G. B.  T a l b o t ( 1 9 4 8 ) o n t h e e f f e c t o f b l o c k a d e , a t H e l l ' s Gate, I t was r e p o r t e d t h a t salmon were d e l a y e d u n t i l August 14 a f t e r w h i c h the  water r o s e s u d d e n l y and good passage was p e r m i t t e d u n t i l  August 25.  T h i s o p e n i n g a t t h e Gate between August 14 - .25  was r e f l e c t e d i n the l a r g e c a t c h e s a t t h e R a p i d s from August 18 t o September 3.  None of the sockeye tagged a f t e r September  17 was r e c o v e r e d on the spawning grounds even though t a g g i n g c o n t i n u e d u n t i l September 24. I t s h o u l d be #oted t h a t t h e 1944 water l e v e l s were h i g h throughout t h e sockeye m i g r a t i o n p e r i o d and no l a r g e accummulation o f f i s h was observed below t h e R a p i d s . (3) 1945 A crew o f f o u r men commenced f i s h i n g a t t h e R a p i d s on J u l y 5*  The f i r s t c a t c h o f sockeye o c c u r r e d on J u l y 7 when  4 sockeye were tagged.  As f a r as was p o s s i b l e t o d e t e r m i n e ,  19  Figure 5 D a i l y c a t c h e s of sockeye above and below the B r i d g e R i v e r R a p i d s p l o t t e d a g a i n s t the water l e v e l s and ranges o f the r u n s o f the Upper F r a s e r sockeye p o p u l a t i o n s i n .1945.  1945  WATER LEVELS BRR  30  \ STELLAKO ^ H  CHILKO  MIDDLE RIVER  H HORSEFLY -I -I  BOWRON EARLY STUART  120  DAILY CATCHES Below Above  JULY  AUGUST  SEPTEMBER  so no sockeye were t a k e n a t t h e R a p i d s b e f o r e J u l y 7. the  sockeye r u n i n c r e a s e d and 25 sockeye were tagged on t h a t  day* the  On J u l y 8  C o n s i s t e n t t a g g i n g c o n t i n u e d from J u l y 8 t o the end o f salmon m i g r a t i o n on October 24. The c a t c h e s made by t h e t a g g i n g crews below and above  the R a p i d s have been p l o t t e d s e p a r a t e l y t o i l l u s t r a t e the e f f e c t s o f p o s s i b l e b l o c k s o f salmon below the f a l l s ;  Obser-  i n g t h e d a i l y oatches above and below t h e R a p i d s i t i s seen t h a t t h e b u l k o f the sockeye were caught d u r i n g J u l y a n d August.  The good c a t c h e s made d u r i n g J u l y were a t t r i b u t e d t o t h e  S t u a r t Lake r u n and t o a l e s s e r e x t e n t t h e Bowron s o c k e y e ; The l a r g e s t c a t c h e s were made between August 10 and August 16 when the  peak o f t h e C h i l k o r u n was p a s s i n g t h r o u g h . From August 20 t o 30, t h e c a t c h e s were poor and no  l a r g e r u n o f f i s h appeared a f t e r t h a t d a t e .  One p o i n t o f  major i m p o r t a n c e was t h e f a c t t h a t no l e n g t h y b r e a k s o c c u r r e d i n the c a t c h e s a t t h e R a p i d s t h i s y e a r as o f t e n happened i n t h e past.  T h i s s t e a d y passage o f sockeye was c r e d i t e d t o t h e  improved passage a t H e l l ' s Gate. The most i m p o r t a n t c o n c l u s i o n drawn from f i g u r e 3 i s t h a t no sockeye tagged a t the R a p i d s a f t e r September  12 were  r e c o v e r e d f r o m t h e spawning grounds o f t h e Upper F r a s e r , d e s p i t e t h e f a c t t h a t sockeye were s t i l l b e i n g tagged a t t h e R a p i d s u n t i l October 5.  I t would t h e r e f o r e appear t h a t t h e  R a p i d s were b l o c k e d a f t e r September  12. (Water l e v e l on Sept-  ember 12 - 651 f e e t ) . (b)  P e r c e n t a g e R e c o v e r y o f Tags Below and Above the p K a  l d 3  t  21 The r e c o v e r y o f t h e tags was d i v i d e d i n t o two main groups; namely, r e c o v e r i e s below and r e c o v e r i e s above t h e Rapids.  The r e c o v e r i e s below t h e R a p i d s were tags r e c o v e r e d  i m m e d i a t e l y below t h e R a p i d s or a t any downstream p o i n t ;  The  r e c o v e r i e s above were made m o s t l y on the n o r t h e r n spawning ground b u t i n c l u d e s m a l l numbers o f r e c o v e r i e s from I n d i a n f i s h i n g s t a t i o n s l o c a t e d a l o n g t h e r o u t e o f t h e salmon m i g r a tion.  The t o t a l r e c o v e r y o f tags was broken down i n t o the  number o f each d a y s tagged sockeye t h a t were r e c o v e r e d f  e i t h e r below or above and a r e p r e s e n t e d as p e r c e n t a g e s i n figures 4 - 6 .  ,  I n the e a r l i e r s e c t i o n o f t h i s paper d e a l i n g w i t h t h e t h e o r y o f t a g g i n g i t was s t a t e d t h a t i f no t a g s were r e c o v e r e d below the t a g g i n g l o c a t i o n then t h e passage of salmon c o u l d be r e g a r d e d as b e i n g u n o b s t r u c t e d ;  However, i f tags were r e -  c a p t u r e d below, then they s h o u l d be s t u d i e d as t o abundance, time out and t h e i r r e l a t i o n s h i p t o the w a t e r - l e v e l s . The f i g u r e s on the percentage r e c o v e r y o f tags below a n d above t h e Rapids i l l u s t r a t e the; f l u c t u a t i o n s o c c u r r i n g throughout t h e season, but t h e e x t e n t o f t h e d e l a y o c c u r r i n g b e f o r e t h e tags were a c t u a l l y r e c o v e r e d is. n o t shown. be d e a l t w i t h l a t e r , (1)  T h i s f a c t o r o f time  will  ( s e e pages 27.-33}  1942 The f l u c t u a t i n g p a t t e r n o f the r e c o v e r y o f t h e tags  put on i n 1942 i s i l l u s t r a t e d i n f i g u r e 4 i ) .  I t i s seen t h a t ~  some sockeye were r e c a p t u r e d below the R a p i d s throughout t h e whole season.  I t i s a l s o noted t h a t t h e p e r c e n t a g e o f r e c o v -  22  Figure 4 Percentage r e c o v e r i e s of tags  from  each day o f t a g g i n g as r e c o v e r e d above and below t h e B r i d g e R i v e r Rapids  194S.  B l a n k columns r e p r e s e n t days when l e s s than 10 sockeye were tagged.  1942  640' 10  • 20  ' 30  1  1  10  20  JULY  0 10  20.  r  30  AUGUST  30  10  20  10  20  30 10  SEPTEMBER  30  10  20  OCTOBER  30 10  Date o f Tagging a t R i g h t Bank Above  10  20 • 30 JULY  10  20  AUGUST  30  10  20  30  SEPTEMBER  Date o f Tagging a t R i g h t Bank Below  10 OCTOBER  23 e r y below, f l u c t u a t e s , , w i d e l y ' f r o m 0 t o 68% f o r any one day o f tagging.  Through J u l y and August the number o f r e c o v e r i e s  was  f a i r l y u n i f o r m except f o r s l i g h t i n c r e a s e s i n r e c o v e r y on J u l y 26 and 29 and August 17*  On August 24 and 31 the number of r e -  c o v e r i e s i n c r e a s e d ; but the samples were t o o s m a l l t o w a r r e n t consideration.  However, commencing on September 2, wide  u a t i o n s became apparent*  fluct-  i t appears that the number o f r e c o v -  e r i e s i n c r e a s e d as the water dropped below the 650 f o o t water l e v e l on September 2,4 and 7*  W i t h the sudden r i s e i n w a t e r  l e v e l t o 652.8 f e e t between September 17-19 ow decreased*  the r e c a p t u r e s b e l -  By September 20 the water a g a i n dropped  below  the 650 f o o t mark and remained low f o r the remainder o f t h e season.  With the onset o f low water the number o f r e c o v e r i e s  below the R a p i d s i n c r e a s e d r a p i d l y and the presence o f a b l o c k became a p p a r e n t . The i n f l u e n c e o f the c r i t i c a l water l e v e l s around t h e 650 f o o t l e v e l was a l s o r e f l e c t e d i n t h e p a t t e r on the r e c o v e r ies above the R a p i d s *  C o r r e s p o n d i n g t o the r i s e i n water  above 650 f e e t t h e r e was  level  a r i s e i n the p e r c e n t a g e r e c o v e r y o f  tags above and._a s i m i l a r r e d u c t i o n i n the r e c o v e r i e s  below.  I t i s the a s s o c i a t i o n of t h e s e t h r e e f a c t o r s t h a t p r o v i d e s some o f the b a s i c e v i d e n c e i n t h e d e f i n i t i o n o f the p r e s e n c e o f a blockade at the Rapids*  T h i s alone,, however, i s n o t s u f f i c i e n t  e v i d e n c e as i t must be known how  l o n g the f i s h were out b e f o r e  b e i n g r e c a p t u r e d below t h e p l a c e o f o b s t r u c t i o n . (2)  1944 The r e c o v e r i e s made d u r i n g 1944 a r e p l o t t e d & n f i g u r e  5* A g a i n the p e r c e n t a g e s f l u c t u a t e w i d e l y throughout the s e a son e s p e c i a l l y through J u l y to the m i d d l e of August; No a s s o c i a t i o n s jvarsi noted between t h e r e c o v e r i e s below and above  24  Figure 5 P e r c e n t a g e r e c o v e r i e s o f t a g s from each day o f t a g g i n g as r e c o v e r e d above and below t h e Bridge R i v e r Rapids  1944.  B l a n k columns r e p r e s e n t days when l e s s than 10 sockeye were tagged.  1944  WATER LEVEL  670 660 650  10  20  30  10  1(  20  30  % RECOVERED ABOVE 60 40 20 0  10  20  30  10  20  30  I  L  10  T—  20  r  30  6*0 RECOVERED BELOW 60 40 20 0  10 . 20 JULY  30  10  20 AUGUST  30  10  20  30  SEPTEMBER  Date o f Tagging Below Rapids  85 the R a p i d s u n t i l . t h e end o f August and d u r i n g September;  Com-  mencing on August 18, i t i s shown t h a t a s t e a d y i n c r e a s e o c c u r r e d i n the r e c o v e r i e s below and a c o r r e s p o n d i n g d e c l i n e i n t h e r e c o v e r i e s above.  The r e c o v e r i e s i n d i c a t e t h a t some sockeye  tagged a f t e r August 30 were d e l a y e d l o n g enough t o have p r e v e n t e d them from r e a c h i n g t h e spawning  grounds.  A f t e r Sept-  ember 5 t h e s m a l l p e r c e n t a g e r e c o v e r e d above became evident*, however,the  b u l k o f t h e sockeye passed t h r o u g h the R a p i d s  August 18 to September 3.  from  During this, p e r i o d a high percentage  o f r e c o v e r i e s was made above; t h e r e f o r e , o n l y a s m a l l p r o p o r t i o n o f t h e r u n s was e f f e c t e d by the R a p i d s a t t h e end o f t h e season. As w i l l be shown l a t e r i n t h e a n a l y s i s o f t h e d a t a on t h e days-out b e f o r e r e c a p t u r e o f the f i s h below t h e R a p i d s , t h e salmon were n o t s e r i o u s l y d e l a y e d d u r i n g t h e 1944 season d e s p i t e t h e volume of r e c o v e r i e s  below;  (3) 1945 R e f e r r i n g t o f i g u r e 6 i t i s seen t h a t a r a d i c a l change o c c u r r e d i n t h e p a t t e d of t a g r e c o v e r i e s t a k e n above and below t h e R a p i d s i n 1945;  I t was found t h a t t h e r e was cons-  i d e r a b l e v a r i a t i o n i n the. d a i l y p e r c e n t a g e r e c o v e r y o f t a g s above t h e R a p i d s .  However, t h i s v a r i a t i o n was not caused by  the b l o c k c o n d i t i o n s a l o n e , b u t a l s o depends on t h e e x t e n t and e f f i c i e n c y o f t h e r e c o v e r y o p e r a t i o n s on t h e v a r i o u s spawning grounds.  T h i s i s b e s t i l l u s t r a t e d by t h e h i g h p e r c e n t a g e  r e c o v e r i e s made above t h e R a p i d s i n J u l y on t h e sockeye r u n t o S t u a r t l a k e where a p p r o x i m a t e l y 80$ of t h e dead f i s h were  r  Figure 6 P e r c e n t a g e r e c o v e r i e s of t a g s from each day o f t a g g i n g as r e c o v e r e d above and below the Bridge R i v e r Rapids  1945.  Blank columns r e p r e s e n t days 'when l e s s than 10 sockeye were tagged*  10  20  '  30  10  20  30  10  20  30  % I  RECOVERED BELOW  JULY  AUGUST  SEPTEMBER  Dates o f Tagging Below Lower Rapids  27 examined. I n c o n t r a s t o n l y about 25$ o f t h e C h i l k o sockeye which pass /through t h e R a p i d s I n August were examined on t h e spawning grounds*  Were the s m a l l sample o f dead f i s h a t C h i l k o n o t  taken i n t o account i t would be s u s p e c t e d t h a t the August r u n of salmon were s u b j e c t t o a heavy m o r t a l i t y .  Low p e r c e n t a g e  r e c o v e r y o f tags below d u r i n g b o t h J u l y and August  indicates  good passage; t h e r e f o r e the v a r y i n g p e r c e n t a g e r e c o v e r y above i s i n f l u e n c e d m o s t l y by t h e v a r i a t i o n i n a b i l i t y t o r e c o v e r _ tagged f i s h on t h e spawning grounds. Having accounted f o r t h e v a r i a t i o n s i n t a g r e c o v e r y d u r i n g J u l y and August, we f i n d g r e a t l y r e d u c e d r e c o v e r i e s i n September f a r below what c o u l d have been r e c o v e r e d on t h e spawning grounds had t h e tagged f i s h passed t h e R a p i d s . D i r e c t l y c o r r e s p o n d i n g t o t h e d e c l i n i n g r e c o v e r i e s above, were t h e r a p i d l y i n c r e a s i n g p e r c e n t a g e s r e c o v e r i e s o f tags below. t h i s same time t h e water l e v e l had dropped below  At  the 650 f o o t  mark. In  c o n t r a s t t o the r e c o v e r i e s above, t h e p e r c e n t a g e  of r e c a p t u r e s below was low d u r i n g J u l y and August* a good ascent o f the Salmon t h r o u g h t h e R a p i d s . were few below  indicating  Recaptures  the R a p i d s d u r i n g t h e p a s s i n g o f t h e main p a r t  of t h e C h i l k o r u n .  I t was n o t u n t i l September 5 t h a t t h e  h i g h e r p e r c e n t a g e s of tags were r e c o v e r e d .  From September 5  to t h e end o f t h e s e a s o n , the d a i l y p e r c e n t a g e o f r e c a p t u r e s below the R a p i d s was h i g h and b l o c k c o n d i t i o n s were I n e f f e c t * (c)  Time out b e f o r e r e c o v e r y o f tags below.  28 The v a r y i n g abundance o f tagged sockeye r e c o v e r e d below the R a p i d s and the l e n g t h o f the d e l a y p e r i o d b e f o r e tags were r e c o v e r e d i s shown on f i g u r e s 7-9.' tag  the  Each r e c o v e r e d  i s r e p r e s e n t e d by a s t r a i g h t l i n e drawn f r o m t h e date  of  r e c o v e r y on the r i g h t to the date o f t a g g i n g on t h e l e f t .  The  numbers of r e c a p t u r e s below the f a l l s were few d u r i n g open p e r i o d s a t the Rapids^ a l s o , the tags t h a t were r e c o v e r e d o n l y been out a few days;  had  When p e r i o d s o f d i f f i c u l t y and  block  o c c u r , t h e number o f r e c a p t u r e s w i l l be l a r g e and the number of days out b e f o r e r e c a p t u r e w i l l be extended.  The r e c a p t u r e s  are  p l o t t e d a g a i n s t the w a t e r l e v e l s t o show when the open and closed periods occuri (1)  1942 Upon a n a l y s i s o f F i g u r e 7, i t i s e v i d e n t t h a t t h e  vc  r e c a p t u r e s d u r i n g August were few, i n d i c a t i n g good passage o f salmon through at  the R a p i d s .  F o l l o w i n g the drop i n water l e v e l s  the end o f August, H e l l * s Gate opened and a l a r g e r u n o f  sockeye a r r i v e d a t the R a p i d s on September 3.  By t h i s  date  the water a t the R a p i d s had dropped below the 650 f o o t l e v e l and t h e sockeye found passage up-stream d i f f i c u l t .  Between  September 3 and September 17 the numbers o f r e c a p t u r e d salmon g r e a t l y i n c r e a s e d and the sockeye were s u b j e c t e d t o a d e l a y of 1 t o 6 days or an average o f a p p r o x i m a t e l y sockeye dropped downstream and period.  3 days.  Two  tagged  e n t e r e d Seton Creek d u r i n g t h i s  Water l e v e l s below 648 f e e t were most s e r i o u s and  p e r i o d of d e l a y became much g r e a t e r when t h i s l e v e l was  the  reached  29  Figure 7 P e r i o d s o f d e l a y as shown by tagged r e c a p t u r e d below t h e R a p i d s .  fish  The l i n e s a r e  p l o t t e d . f r o m the d a t e o f r e c o v e r y on the r i g h t to date o f t a g g i n g on the l e f t .  Broken  lines  r e p r e s e n t tags r e c o v e r e d f r o m Seton and P o r t a g e Creeks,  1942.  1942  TAG RECOVERIES AT POINT OF TAGGING BELOW BRIDGE RIVER RAPIDS  10  20  JULY  30  10  20  ' AUGUST  30  10  20  3Q  SEPTEMBER  10,  20  30  OCTOBER .  30 The b l o c k remained i n t o October and an a d d i t i o n a l 9 sockeye dropped downstream and were r e c o v e r e d i n S e t o n Creek d u r i n g the month* (see -f-igure 7)  The r i s e i n w a t e r l e v e l  during  October would have r e l i e v e d the b l o c k c o n d i t i o n s somewhat had i t o c c u r r e d e a r l i e r i n the season*  By t h i s d a t e t h e s o c k -  eye were so weakened t h a t f u r t h e r m i g r a t i o n was (2)  unlikely.  1944 I t has a l r e a d y been demonstrated i n f i g u r e 5j t h a t  a c o n s i d e r a b l e number o f tagged s o c k e y e were r e c o v e r e d below the R a p i d s ; however, the l a p s e o f t i m e from the date o f t a g g i n g t o date o f r e c o v e r y was s h o r t i n most cases as shown i n f i g u r e 8.  Only a few of t h e f i s h r e c a p t u r e d below the R a p i d s had been  out f o r more than 2 or 3 d a y s .  The f i r s t s i g n of any d e l a y  o c c u r r e d on August 6 at which t i m e the l o w e r e a s t bank was d i f f i c u l t to ascend. (Water l e v e l 657 f e e t ) .  An 18 f o o t r i s e  i n water l e v e l between August 14 and August 18 p e r m i t t e d a l l d delayed sockeye t o pass upstream.  A s h o r t d e l a y commenced on  September 1 and l a s t e d u n t i l September 8; however, t h e s e sockeye d i s a p p e a r e d w i t h o u t a r i s e i n water l e v e l *  In general,  a s l i g h t ' d i f f i c u l t y t o m i g r a t i n g sockeye o c c u r r e d a t a water l e v e l of a p p r o x i m a t e l y 658 f e e t i n (3)  1944.  1945 Observing the p a t t e r n of r e c o v e r i e s i n f i g u r e 9 i t  becomes apparent t h a t a r e l a t i v e l y good passage of salmon o c c u r r e d d u r i n g J u l y and August.  Some e v i d e n c e o f d e l a y and  a c c u m u l a t i o n was i n d i c a t e d w h i c h may have been caused by  diff-  i c u l t passage on the e a s t bank, e.g. August 10 and August  26.  31  Figure 8 P e r i o d s of d e l a y as shown by tagged r e c a p t u r e d below t h e R a p i d s .  fish  The l i n e s are  p l o t t e d from, t h e date of r e c o v e r y on the r i g h t t o date o f t a g g i n g on the l e f t .  1944.  1944  TAG RECOVERIES AT POINT OF TAGGING BELOW BRIDGE RIVER RAPIDS  T  10  1  20  JULY  I  1  1  30  10  20  AUGUST  1  30  I  10  I  20  1  30  SEPTEMBER  1  10  I  1  20  30  OCTOBER  32  Figure 9 P e r i o d s o f d e l a y as shown by tagged f i s h r e c a p t u r e d below the R a p i d s .  The  lines  are  p l o t t e d from the date o f r e c o v e r y on the r i g h t t o date o f t a g g i n g on t h e l e f t .  1945.  1945  TAG RECOVERIES AT POINT OF.TAGGING BELOW BRIDGE RIVER RAPIDS  10  20  JULY  30  10  20  AUGUST  30  10  20  30  SEPTEMBER  10  20  30  OCTOBER  33 The most i m p o r t a n t c o n c l u s i o n to be drawn from f i g u r e 9 i s t h e e f f e c t of the o b s t r u c t i o n on the salmon d u r i n g September*  Commencing September 5 and even more apparent on  September 8 a b l o c k c o n d i t i o n was i n d i c a t e d by the l a r g e numbe r s o f r e c a p t u r e s and the extended p e r i o d o f d e l a y .  The w a t e r  dropped below the 650 f o o t l e v e l on September 4 and except f o r s l i g h t r i s e t o l e s s than 651 f e e t between September 11 and September 15 the water c o n t i n u e d to drop t h r o u g h the remainder o f the season* (d) i n f l u e n c e o f Water L e v e l s on P e r c e n t a g e Recovery  Below  I t may be r e a l i z e d from the t a g g i n g a n a l y s i s p r e s ented so f a r t h a t one method alone can n o t be r e l i e d upon t o i l l u s t r a t e the t o t a l e f f e c t o f a b l o c k .  The method used t o  show the v a r y i n g p e r c e n t a g e r e c o v e r i e s below  the R a p i d s  was  u s e f u l but d i d n o t e s t a b l i s h the d u r a t i o n of t h e d e l a y b e f o r e t h e tagged sockeye were r e c o v e r e d .  The second method used t o  demonstrate t h e time o f the b l o c k , by means of t h e l i n e g r a p h , p r o v i d e d i n f o r m a t i o n on the d u r a t i o n o f t h e d e l a y but d i d n o t a l l o w f o r the d i f f e r e n c e s i n ' t h e numbers of tags a p p l i e d on the d i f f e r e n t days*  I t was n e c e s s a r y t o combine t h e two t y p e s o f  a n a l y s i s t o show c l e a r l y how  the v a r i o u s water l e v e l s  influence  t h e passage o f sockeye t h r o u g h the R a p i d s . I n f i g u r e s 10-12, the water l e v e l s have been groups ed i n t o 5 f o o t i n t e r v a l s so t h a t the samples w i l l be  sufficien-  t l y l a r g e t o demonstrate what o c c u r s as the water l e v e l drops* The l i n e between t h e p o i n t s i s a c t u a l l y a r e v e r s e d c u m u l a t i v e c u r v e and was  e s t a b l i s h e d by s u b t r a c t i n g one days r e c o v e r y o f  34  Figure Percentage  10  r e c o v e r y o f a l l tags put on  below and r e c o v e r e d below the R a p i d s d i f f e r e n t water l e v e l s .  at  The percentage  recovery  of tags out f o r v a r y i n g number o f days i s a l s o shown.  194E.  1942  1  1 2  2  3  3 4  4  DAYS OUT 5 6 7 B 9 1 0 - 1 5 - 2 0 20 r  56  7 8  9 1 0 - 1 5 - 2 0 20  !  1  35 tags f r o m the a c c u m u l a t i o n o f a l l those taken i n c l u d i n g t h e day t o be s u b t r a c t e d . - F o r example, i n 1942 a t t h e 650-646 f o o t water l e v e l , 23.2$ o f a l l the t a g s put on were e v e n t u a l l y r e c o v e r e d below t h e R a p i d s .  The.number o f tags t h a t were o n l y  1 day out then s u b s t r a c t e d , l e a v i n g 21.5$ of the t a g s out g.t l e a s t 2 days.  T h i s procedure was c o n t i n u e d u n t i l i t was seen  t h a t 2.6$ o f t h e tags were out f o r more t h a n 20 days. The s i g n i f i c a n c e o f t h i s type o f f i g u r e i s t h a t the percentage  o f t h e r e c o v e r y i s r e a d i l y n o t e d f o r a l l tags and  a l s o t h e percentage beoaeen.  o f r e c o v e r y f o r a l l p e r i o d s o f d e l a y can  T h i s i s i m p o r t a n t because a b l o c k was o n l y s e r i o u s  when a d e l a y o f c o n s i d e r a b l e l e n g t h was caused. l i n e dropped t o a low percentage  Thus i f t h e  a f t e r a d e l a y o f o n l y one o r  two days t h e n no s e r i o u s damage w i l l be l i k e l y to, o c c u r * (1)  1942 • Observing  the f i g u r e 10 i t appears t h a t t h e r e was  no d e l a y above water l e v e l s of.665 f e e t ; Some d i f f i c u l t y i n the passage o f sockeye o c c u r r e d d u r i n g w a t e r - l e v e l s 665-651, and s e r i o u s d e l a y i n s i g n i f i c a n t numbers o c c u r r e d i n t h e 650-646 levels.  The h i g h p e r c e n t a g e  o f r e c o v e r i e s and t h e e x t e n t o f  d e l a y below 650 f e e t appeared t o be the c r i t i c a l s t a g e i n t h e passage o f sockeye i n 1942.  T h i s confirmed the conclusions  r e a c h e d by the o t h e r methods o f a n a l y s i s . (2) 1944 The average water l e v e l s were h i g h i n 1944 and no s e r i o u s . d e l a y was n o t e d a t t h e R a p i d s ; y e t , a c o n s i d e r a b l e number o f t a g s were r e c a p t u r e d below t h e R a p i d s .  The p a t t e r n  36  F i g u r e 11 Percentage r e c o v e r y o f a l l tags p u t on below and r e c o v e r e d below t h e R a p i d s a t d i f f e r e n t water l e v e l s .  The percentage r e c o v e r y of tags  out f o r v a r y i n g number o f days i s a l s o shown.  1944.  1944  DAYS OUT 1 2  3  4  5 6  7 8  9 10-15-20 20 + 665-66 1  -  * °—-o  . 66O-65 6  655-65 1  i  12  t  i  3  i  i  4 5  i  r  6  7  I  1  1  I  i  '  7 8 9 10-15-20 20  of these r e c o v e r i e s i s showng on f i g u r e 11.  The r a n g e of water  l e v e l s through the s e a s o n was s m a l l a n d a t no time d u r i n g t h e sockeye m i g r a t i o n d i d t h e water l e v e l drop below 650 f e e t . Some d e l a y was e v i d e n t between water l e v e l s 660-651 f e e t b u t o n l y up t o a p e r i o d o f 4 days.  I t i s considered that  although  i t would be i d e a l t o have a b s o l u t e l y no d e l a y , t h e c o n d i t i o n s i n 1944 w o u l d not cause s e r i o u s harm. (3)  1945 The  extreme range o f w a t e r - l e v e l s were found i n 1945.  Above t h e water l e v e l o f 655 o n l y a few tagged sockeye were r e c o v e r e d below the R a p i d s .  W i t h few e x c e p t i o n s , these  ye were r e c o v e r e d w i t h i n 3 days.  socke-  Between 655-650 some d i f f i c -  u l t y was shown; however, o n l y a s m a l l p e r c e n t a g e o f t h e s o c k e y e were d e l a y e d l o n g e r than 5 days.  The most s i g n i g l c a n t i n f l u e -  nce o f s e r i o u s o b s t r u c t i o n was e v i d e n t I n the water l e v e l s o f 650-646 and 645-641.  D u r i n g t h e s e p e r i o d s , s l i g h t l y over 3 4 $  of a l l tags p u t on were r e c o v e r e d below the R a p i d s . i m p o r t a n t was the entent o f t h e d e l a y o f t h e s e sockeye*  Equally  obstructed  The curves do n o t drop t o t h e base l i n e r a p i d l y ,  i l l u s t r a t i n g t h a t a c o n s i d e r a b l e number o f sockeye were d e l a y e d f o r a l o n g p e r i o d o£ t i m e , (see f i g u r e 12) On the b a s i s o f these i l l u s t r a t i o n s i t was e v i d e n t t h a t some f a c t o r was i n f l u e n c i n g t h e success sockeye through  the R a p i d s .  o f passage o f  F u r t h e r , i t was e v i d e n t t h a t  t h e r e was a d i f f e r e n t i a l e f f e c t on t h e degree of passage d u r i n g d i f f e r e n t water l e v e l s .  Some d i f f i c u l t y was i l l u s t r a t e d  during  water l e v e l s above 650 f e e t vrtien d e l a y s o f 3 t o 5 days were  38  F i g u r e 12 P e r c e n t a g e r e c o v e r y o f a l l tags put on below and r e c o v e r e d below t h e R a p i d s water l e v e l s .  at d i f f e r e n t  The percentage r e c o v e r y o f tags out  f o r v a r y i n g number o f days i s a l s o shown.  1945.  1945  DAYS OUT g  3 4  1 2  5 6  7 $ ?  3  10-15-20,20*  665-66I  0 3  66O-656  0 5h 0 30 25 20 15 h 10 5 0 645-641  30 25 20 15 10 5 0  —1  1  1 2 3  r-  1  1  4 5  r  1  6 7J  r  1— 1  1  r~—S—  9 10-15-20 20  39 found; howeverj the major p e r i o d s of o b s t r u c t i o n o c c u r r e d below the  650 f o o t w a t e r l e v e l and were apparent i n e a c h o f the  methods o f a n a l y s i s *  I t t h e n remained to be shown what would  happen a f t e r t h e f i s h w a y s were i n s t a l l e d f o r the passage of the  1946 r u n o f sockeye salmon*  The E f f e c t o f H e l l ' s  Gate  I t has been s t a t e d i n the i n t r o d u c t i o n to t h i s paper t h a t t h e r e was the p o s s i b i l i t y t h a t a d e l a y o f sockeye at H e l l ' s Gate may have weakened the salmon to. s u c h an e x t e n t t h a t t h e y would be u n a b l e t o pass t h e t u r b u l e n t w a t e r s o f t h e R a p i d s l o c a t e d 76 m i l e s upstream.  I t might be f u r t h e r sugges-  ted  t h a t , a f t e r the c o n s t r u c t i o n o f t h e ' H e l l ' s ' G a t e f i s h w a y s ^  the  u n o b s t r u c t e d sockeye would be s u f f i c i e n t l y s t r o n g t o o v e r -  come the d i f f i c u l t waters of the R a p i d s above*  While t h i s  p o s s i b i l i t y existed-^ a d e f i n i t e statement of the s e r i o u s n e s s of  the R a p i d s c o u l d n o t be made on the b a s i s of the 1942  1944 d a t a *  and  I t remained t o be seen what the c i r c u m s t a n c e s would  be d u r i n g the season o f 1945 a t which time the H e l l ' s Gate f i s h w a y s would be n e a r l y complete.  The a n a l y s i s o f each t a g -  g i n g experiment a t the R a p i d s has been p r e s e n t e d and i t was e v i d e n t t h a t d i f f i c u l t and b l o c k a d e c o n d i t i o n s p e r s i s t e d a t t h e R a p i d s d u r i n g the 1945 season t o the same or g r e a t e r e x t e n t than t h o s e o c c u r r i n g i n 1942 and 1944.  Thus i t was  concluded  t h a t even w i t h improved passage o f sockeye t h r o u g h H e l l ' s Gate, the  b l o c k s t a g e s a t the R a p i d s remained as s e r i o u s as they had  i n previous years.  Upon t h e c o m p l e t i o n of the a n a l y s i s , o f the  1945 d a t a , recommendations f o r f i s h w a y s a t the R a p i d s were  40 first  submitted. T h i s problem of d e f i n i n g o b s t r u c t i o n c o n d i t i o n s  any p o i n t above a p r e v i o u s  at  o b s t r u c t i o n p o i n t f u r t h e r downstream  i s s u f f i c i e n t l y i m p o r t a n t to w a r r a n t b r i e f d i s c u s s i o n and i n c l u s i o n o f f i g u r e s 13 and 14.  I f i t i s reasoned t h a t  the the  salmon were weakened a t the f i r s t b a r r i e r s u f f i c i e n t l y t o a c t as t h e i r o n l y cause of d e l a y at a second b a r r i e r , then i t must be demonstrated what weakening has  occurred  groups of salmon were thus e f f e c t e d .  and which group or  I f i t can be shown t h a t  weakened f i s h were always h e l d up at the second o b s t r u c t i o n s t r p n g f i s h were n e v e r d e l a y e d , then i t i s p r o b a b l e t h a t second l o c a t i o n w o u l d not be a s e r i o u s f a c t o r when the l o c a t i o n had been c l e a r e d .  and  the  first  I t i s equally probable that i f  p r e v i o u s l y weakened f i s h d i d pass the second b a r r i e r a t c e r t a i n times and t h a t b o t h weakened and s t r o n g f i s h were d e l a y e d a t other t i m e s t h e n each b a r r i e r r e p r e s e n t s  an independent f a c t o r .  To demonstrate the c i r c u m s t a n c e s between b a r r i e r #1  a t H e l l ' s Gate and  b a r r i e r #2  at the Bridge R i v e r Rapids,  two measurements o f p o s s i b l e weakness of the salmon have been investigated.  I n an e a r l i e r u n p u b l i s h e d r e p o r t ( K i l l i c k 1945),  the c o n d i t i o n of the sockeye, r e c o r d e d by t h e t a g g e r s as "green", " p i n k " and  " r e d ' % was  analysed.  I t was  t h a t t h e r e were few  salmon i n " r e d " c o n d i t i o n and  found t h a t that  f i s h n o t e d as "green" a n d . " p i n k " were e q u a l l y d e l a y e d water l e v e l s below 650  feet.  I t was  the during  a l s o n o t e d t h a t t h e maj-  o r i t y of the tagged sockeye t h a t dropped downstream from the Rapids during blocked  s t a g e s and  entered  Seton and P o r t a g e  t  41 c r e e k s were i n "green" c o n d i t i o n when tagged. However, t h i s measure o f the weakness or s t r e n g t h o f the salmon i s open t o c r i t i c i s i m , inasmuch as the appearance  of " g r e e n " and " p i n k "  sockeye may not a c t u a l l y r e p r e s e n t t h e i r t r u e c o n d i t i o n ; A second and more p o s i t i v e c r i t e r i o n o f t h e c o n d i t i o n of the sockeye when t h e y a r r i v e a t the R a p i d s i s the number o f days i t t a k e s f o r the salmon t o t r a v e l between H e l l ' s Gate the  Rapids.  est  time t o a r r i v e a t the R a p i d s .  and  Weakened f i s h w i l l be t h o s e f i s h t a k i n g the l o n g -  The f i g u r e s 13 and 14 i l l u s t r a t e the number of days r e q u i r e d f o r sockeye t o pass from H e l l ' s Gate t o the Highway' b r i d g e l o c a t e d s i x m i l e s below the R a p i d s .  H e l l ' s Gate t a g s  r e c o v e r e d a t the R a p i d s themselves have been p l o t t e d m  a sep-  a r a t e m a n u s c r i p t but a r e n o t used h e r e as i t i s i m p o s s i b l e t o d i s t i n g u i s h between the time enroute and t h e time of d e l a y below the R a p i d s .  As t h e r e i s no r e a s o n t o s u s p e c t d e l a y s , dur-  i n g any water l e v e l s , between the Highway b r i d g e and t h e i R a p i d s i t was  c o n c l u d e d t h a t the days - out p r e s e n t e d on the f i g u r e s  r e p r e s e n t j w i t h i n a few h o u r s , m i g r a t i o n r a t e t o t h e R a p i d s ; O b s e r v i n g f i g u r e 13 f o r t h e y e a r 1942, i t i s apparent t h a t a wide range i n t h e speed o f m i g r a t i o n from 3 t o 49  days  was r e q u i r e d f o r sockeye t o t r a v e l f r o m H e l l ' s Gate t o the H i ghway b r i d g e *  F i s h a r r i v i n g a t the b r i d g e up t o August 10 were  out 12 days or l e s s and were c o n s i d e r e d to be i n good p h y s i c a l condition;  A f t e r August 10 and d u r i n g September, a consider-;  a b l e number of sockeye were out a l o n g time b e f o r e r e a c h i n g the Highway B r i d g e and t h e s e salmon were p o s s i b l y weakened by a d e l a y below H e l l ' s Gate;  However, sockeye  were  42  Figure  15  The m i g r a t i o n r a t e of sockeye tagged a t H e l l ' s Gate and r e c o v e r e d a t the Highway b r i d g e a t L i l l o o e t , 1942 and  1944.  19^2 T  r  M-0 £> 30 o %20 •«  ... _ - - - V.  10  o *  10  20  30  10  JULY  _  _  o  12.22  _  o*  20  30  10  AUGUST  20  30  SEPTEMBER  DATES OF RECOVERY  i  r  ->  :  r  ho EH  O  30  CO _ f  —.——  ......... ,  4  10 10  20  30 JULY  10  20  30  AUGUST DATES OF RECOVERY  10  26  30~  SEPTEMBER  13.5lJ-  43 not  o b s t r u c t e d a t t h e R a p i d s i n August as t h e y s h o u l d have  been i f weak f i s h a r e s u s p e c t e d o f b e i n g d e l a y e d a t the second barrier.  F u r t h e r , t h e r e was a b l o c k a t t h e R a p i d s d u r i n g  September and i t e f f e c t e d a l l f i s h whether p r e v i o u s l y d e l a y e d or  not.  By t h e p a t t e r n of t h e days out o f f i s h from H e l l ' s  Gate i n 1942, i t appears d o u b t f u l t h a t the b l o c k a t t h e R a p i d s was the r e s u l t o f o n l y t h e p r e s e n c e of weakened sockeye as these were p r e s e n t d u r i n g the f u l l month o f August when no e v i d e n c e o f a b l o c k was o c c u r r e d a t the R a p i d s . In ers  1944-, the d a t a were n o t c o n c l u s i v e as t h e numb-  o f r e c o v e r i e s were s m a l l ; however, i t does appear t h a t the  sockeye a r r i v i n g a f t e r August 24 were p r e v i o u s l y d e l a y e d s u f f i c i e n t l y t o cause some weakening.  Low b l o c k l e v e l s were n o t  encountered a t t h e R a p i d s i n t h a t y e a r . The season o f 1945 was o f major i m p o r t a n c e i n the f i n a l d e f i n i t i o n o f t h e B r i d g e R i v e r R a p i d s o b s t r u c t i o n as t h e f i s h w a y s a t H e l l ' s Gate were i n o p e r a t i o n d u r i n g t h a t y e a r * The p o s s i b i l i t y e x i s t e d t h a t , w i t h the improved passage o f sockeye t h r o u g h the Gate,^ t h e R a p i d s would no l o n g e r a c t as an o b s t a c l e to the salmon*  The f a c t t h a t the passage t h r o u g h  H e l l ' s Gate i n 1945 was improved has been c l e a r l y demonstrated by d a t a on f i l e i n the l a b o r a t o r y of t h e I n t e r n a t i o n a l P a c i f i c Salmon Commission. T h i s improvement passage was r e f l e c t e d d e f i n i t e l y i n the more c o n c e n t r a t e d p a t t e r n o f q u i c k r e c o v e r i e s of H e l l ' s Gate t a g s a t the Highway B r i d g e as shown i n f i g u r e 14.  D e s p i t e the improved passage and c o n d i t i o n o f sockeye  a f t e r H e l l ' s Gate was r e m e d i e d , i t was found t h a t b l o c k con-  44  Figure  14  The m i g r a t i o n r a t e o f sockeye tagged a t H e l l ' s Gate and r e c o v e r e d a t the Highway b r i d g e a t L i l l o o e t . 1945 and  1946.  19^5  o CQ  •*  •  «•  10  •*  -  1.0  20  30  8.59  • •• 0  •  •1 •••  •  • • • ••  •  •  • 10  20  • 10  30  20  AUGUST  JULY  30  SEPTEMBER  DATES OF RECOVERY  19^6 •  i  1  1  1  1  1  1  r-  • •  S o 30  •  CQ  •  •  g 20  10  * L0  •  • •• • • • • * • jo." ~.V • * •  20  JULY  30  10  20  •• 30  AUGUST DATES OF RECOVERY  —  10  - g.55  •A - • 20  30  SEPTEMBER  45 d i t i o n a s t i l l p e r s i s t e d a t t h e R a p i d s i n 1945; I t was then e v i d e n t t h a t even when no p r e v i o u s d e l a y has been encountered by t h e sockeye a t a downstream p o i n t t h e y s t i l l were u n a b l e t o pass t h e R a p i d s d u r i n g c e r t a i n low water l e v e l s s t a g e s r i n g i n September and O c t o b e r  occur-  4  The means o f t h e number o f days-out throughout t h e season was a l s o s i g n i f i c a n t *  Whereas i n 1942 and 1944 i t took  on average o f 12.22 and 13.54 days f o r s o c k e y e tagged a t H e l l ' s Gate t o r e a c h t h e Highway B r i d g e , i t r e q u i r e d o n l y 8.59 and 8.55 days t o cover t h i s same d i s t a n c e i n 1945 and 1946* llhe p a t t e r n o f t h e r a t e o f m i g r a t l o n f r o m H e l l ' s Gate  to t;he Highway B r i d g e d u r i n g 1946 has been i n c l u d e d as  an a d d i t i o n a l check on the H e l l ' s Gate f i s h w a y s *  F i g u r e 14  I l l u s t r a t e s t h a t the b u l k o f t h e s r o c k e y e passed u n d e l a y e d between the two p o i n t s t h e same as they had i n 1945. The number o f days r e q u i r e d f o r the m i g r a t i o n d u r i n g 1945 and 1946 show a r e m a r k a b l e s i m i l a r i t y ; thus i t was p o s s i b l e t o compare the B r i d g e R i v e r t a g g i n g r e s u l t s f o r t h e s e two y e a r s  without  q u e s t i o n as t o t h e c o n d i t i o n o f the salmon. Summation o f t h e evidence  o f d i f f i c u l t and b l o c k c o n d i t i o n s .  I n r e v i e w i n g the evidence o f d i f f i c u l t and b l o c k c o n d i t i o n s a t t h e B r i d g e R i v e r R a p i d s j i t must be r e a l i z e d t h a t , as y e t , t h e r e i s no s i n g l e t e s t s u f f i c i e n t l y a c c u r a t e t o produce t h e r e q u i r e d answers t o t h e problem. from every p o s s i b l e s o u r c e must be c o n s i d e r e d .  Information Thus, t h e  r e v i e w o f t h e l i t e r a t u r e was p r e s e n t e d t o express of e a r l i e r i n v e s t i g a t o r s .  the opinions  The a n a l y s i s o f t h e t a g g i n g programs "  of 1942,  1944  and 1945  46 f o l l o w s and r e p r e s e n t s the more e x t e n -  s i v e s t u d y , the r e s u l t s o f w h i c h f o r m the b a s i s f o r p r e c i s e c o n c l u s i o n s and the recommendation o f a s o l u t i o n to t h e problem. Three y e a r s o f t a g g i n g were r e q u i r e d b e f o r e a  de-  f i n i t e statement c o u l d be made r e g a r d i n g the s u c c e s s o f passage o f sockeye salmon through  the R a p i d s .  I n 1942,  direct  obser-  v a t i o n s and the p a t t e r n o f t a g r e t u r n s p o i n t e d s t r o n g l y t o a s t a t e of s e r i o u s o b s t r u c t i o n d u r i n g low water l e v e l s .  In  1944,  water l e v e l s remained h i g h d u r i n g the sockeye m i g r a t i o n making i t i m p o s s i b l e t o t e s t the r e s u l t s o b t a i n e d i n 1942 water s t a g e s ;  The  t a g g i n g conducted d u r i n g 1945  during  s u p p l i e d the  f i n a l answers by c o n f i r m i n g e a r l i e r s u s p i c i o n s and  avoiding  the p o s s i b i l i t y t h a t H e l l ' s Gate was a f a c t o r i n the o f a b l o c k a t the  low  definition  Rapids.  V a r i o u s methods o f a n a l y s i n g the t a g g i n g d a t a have been employed t o t e s t the presence of o b s t r u c t e d passage; and i n each case the p e r i o d s o f d e l a y and b l o c k o c c u r a t the same water l e v e l s i n each y e a r . Upon summarizing e a c h method o f a n a l y s i s i t was found t h a t above w a t e r l e v e l s o f 665 f e e t l e s s than 1% of the sockeye were d e l a y e d  l o n g e r than 1 day below the  Rapids.  Below 665 f e e t and above 650 f e e t , up t o 10% of the sockeye were d e l a y e d a t l e a s t 1 day; however, o n l y 5$ of the f i s h were d e l a y e d f r o m 2 to 4 d a y s .  Delays o f o v e r 20 days were r e c o r d -  ed f o r a few i n d i v i d u a l s d u r i n g w a t e r l e v e l s between 665 but n o t i n s u f f i c i e n t numbers t o be i m p o r t a n t .  These w a t e r  650  47 l e v e l s were c l a s s e d as d i f f i c u l t and were c o n s i d e r e d i n t h e recommendations f o r t h e i n s t a l l a t i o n o f f i s h w a y s . Water l e v e l s below 650 f e e t were then  considered  and a r e m a r k a b l e change i n t h e p a t t e r n o f t a g r e t u r n s was noted.' The r e c o v e r y o f tags below the R a p i d s i n c r e a s e d t o as h i g h as 34% o f a l l tags a p p l i e d . corresponding  Recoveries  above the R a p i d s showed a  d e c l i n e and i t was apparent fchat b l o c k c o n d i t i o n s  were i n e f f e c t .  The p e r i o d o f d e l a y was extended and sockeye  were t r a c e d from below t h e R a p i d s down i n t o Seton and P o r t a g e creeks.  The numbers o f sockeye r e a c h i n g t h e spawning-grounds  dropped t o n e a r l y z e r o d u r i n g the extended b l o c k p e r i o d s i n 1942  and 1945. E v e r y method o f a n a l y s i s showed t h e same  r e s u l t s and c l e a r l y i l l u s t r a t e d t h a t water l e v e l s below 650 f e e t a t t h e R a p i d s were c r i t i c a l and a c t e d as a s e r i o u s b a r r i e r to  t h e sockeye salmon m i g r a t i n g t o t h e spawning grounds o f t h e  Upper F r a s e r w a t e r s h e d . Recommendations f o r f j s h w a y s . A summary r e p o r t on the t a g g i n g experiments f o r t h e years 1942, 1944 and 1945 was s u b m i t t e d f o r t h e c o n s i d e r a t i o n o f t h e Commission i n t h e f a l l o f 1945. I n c l u d e d i n t h i s r e p o r t , was a recommendation t h a t f i s h w a y s be c o n s t r u c t e d a t t h e Rapids, t o pass salmon d u r i n g p e r i o d s o f d i f f i c u l t and b l o c k water l e v e l s .  I t was proposed t h a t f i s h w a y s be b u i l t a t b o t h  the lower and upper R a p i d s and t h a t they s h o u l d f u n c t i o n from a top l e v e l o f 665 f e e t t o a bottom l e v e l o f 642 f e e t . c a r e f u l c o n s i d e r a t i o n o f t h e b i o l o g i c a l evidence  After  and the  r e s u l t s o f an e x t e n s i v e e n g i n e e r i n g s u r v e y t h e proposed  fish-  48 ways were approved*  C o n s t u c t i o n o f the f l s h w a y s was  started  i n the s p r i n g o f 1946 and completed f o r the salmon runs of that year. S e c t i o n B--  The a n a l y s i s of the 1946 t a g g i n g experiment. t o  t e s t , the e f f i c i e n c y o f the f j s h w a y a . The f i s h w a y s , shown i n p l a t e s I I I and 17, were c o n s t r u c t e d e a r l y i n t h e s p r i n g o f 1946;  They were d e s i g n e d  t o p e r m i t u n o b s t r u c t e d passage o f sockeye salmon t o the Upper F r a s e r spawning g r o u n d s . t h r o u g h the e n t i r e p e r i o d o f t h e sockeye salmon m i g r a t i o n .  To t e s t t h e i r e f f i c i e n c y ,  i t was  nec-  e s s a r y to r e p e a t the e a r l i e r t a g g i n g experiments and r e c o r d any changes i n t h e p a t t e r n o f t a g r e t u r n s .  The r e s u l t s o f t h e  1946 t a g g i n g a t the R a p i d s a r e p r e s e n t e d and i n c l u d e each method of s t u d y used i n the e a r l i e r  programs.  (a) F i s h i n g i n t e n s i t y and the r a c e s of sockeye The v a r y i n g abundance o f sockeye as caught a t the R a p i d s i s shown i n f i g u r e 15.  The c a t c h e s made by t h e t a g g i n g  crews below and above the R a p i d s have been p l o t t e d s e p a r a t e l y . I t was n o t e d t h a t the peaks o f abundance o f sockeye c o r r e s p o n d c l o s e l y t o m i d - p o i n t s . o f the passage o f the d l f f e r en#£r*uns.  The peaks of the runs as they o c c u r r e d at the  R a p i d s were as f o l l o w s :  S t u a r t - J u l y 27 j Bowron-August 3,  C h i l k o - A u g u s t 17, S t e l l a k o - September 3. The time o f passage of the v a r i o u s r u n s was  determ-  i n e d f r o m the B r i d g e R i v e r t a g s t h a t were a c t u a l l y r e c o v e r e d on the spawning grounds at the Rapids.  and t r a c e d back t o t h e d a t e o f t a g g i n g  O b s e r v i n g t h e ranges of the r u n s and t h e d a i l y  49  F i g u r e 15 D a l l y c a t c h e s of sockeye above and below the B r i d g e R i v e r R a p i d s p l o t t e d a g a i n s the water l e v e l s and ranges o f the Upper F r a s e r sockeye r u n s i n 1946  1946  H STELLAKO H  GHILKO  BOWRON H STUART 120  DAILY CATCHES Below — — Above  100 80 60 40 20 0  — i  10 !  20 JULY  r  30  10  20 AUGUST  30  10  20  30  SEPTEMBER  50 c a t c h e s , i t was n o t e d t h a t t h e r e were no extended p e r i o d s o f poor c a t c h e s f o l l o w e d by a mass o f f i s h as has o c c u r r e d i n t h e p a s t when H e l l ' s Gate d e l a y e d passage. Catches above t h e R a p i d s , dropped almost t o z e r o d u r i n g September, i n s m a l l numbers.  y e t sockeye were s t i l l b e i n g caught  below  I t would appear t h a t the d e c l i n e i n t h e  catches above i n d i c a t e d a b l o c k a t t h e R a p i d s , however i t was found t h a t sockeye tagged a t t h e R a p i d s d u r i n g September below t h e 650 f o o t water l e v e l succeeded i n r e a c h i n g t h e n o r t h e r n spawning ground.  I t was then r e a l i z e d t h a t a comparison o f  the abundances i n the c a t c h e s above and below t h e R a p i d s cannot be r e l i e d up t o measure the s u c c e s s o f passage. Sockeye tagged on t h e l a s t day o f t a g g i n g , September 28, were r e c o v e r e d on t h e S t e l l a k o r i v e r d i s t r i c t , 15)  (see f i g u r e  T h i s f i n d i n g was i n d i r e c t c o n t r a s t t o the p a t t e r n o f  r e c o v e r i e s i n 1945 when n o t a s i n g l e tagged sockeye was r e c o v ered from the spawning grounds o f t h e Upper F r a s e r r i v e r  after  September 12 (water l e v e l - 6 5 0 f e e t ) , a l t h o u g h sockeye were tagged a t t h e R a p i d s u n t i l October 5.  I t would  therefore i n 1946  -  appear t h a t t h e sockeye were n o t b l o c k e d below t h e R a p i d s / d e s p i t e t h e f a c t t h a t t h e water l e v e l dropped below t h e b l o c k l e v e l o f 650 f e e t on September 1 1 , and c o n t i n u e d t o r e m a i n low throughout t h e remainder o f the s e a s o n .  T h i s was t h e f i r s t  time s i n c e b i o l o g i c a l s t u d i e s were s t a r t e d a t t h e R a p i d s t h a t tagged sockeye from below t h e f a l l s were r e c o v e r e d on t h e n o r t h e r n ground a f t e r c o n t i n u o u s b l o c k c o n d i t i o n s were i n effect.  51 Figure  16  P e r c e n t a g e r e c o v e r i e s o f tags from each day o f t a g g i n g as r e c o v e r e d above and below t h e B r i d g e Klver Kapids 1946.  B l a n k columns r e p r e s e n t  days when l e s s than 10 sockeye were tagged.  1946  53 (b) P e r c e n t a g e r e c o v e r y o f taga below and above the Rapids. A comparison o f the water l e v e l s and t a g s r e c o v e r i e s f o r 1945 and 1946 p r o v i d e s a s t r i k i n g i l l u s t r a t i o n as t o what o c c u r r e d a f t e r the f i s h w a y s were i n s t a l l e d .  The water  levels  were s i m i l a r f o r the two y e a r s ; t h e r e f o r e the p e r i o d s o f b l o c k , i  as r e f l e c t e d by the r e c o v e r y of tags above and below t h e R a p i d s , s h o u l d have been a p p r o x i m a t e l y the same; such was not the c a s e . I n 1945, t h e r e c o v e r y of tagged sockeye below the R a p i d s i n c r e ased n o t i c e a b l y w i t h the advent o f low water below 650; whereas i n 1946j p r a c t i c a l l y no tagged sockeye were r e c o v e r e d below d u r i n g s i m i l a r low water l e v e l c o n d i t i o n s . ( F i g u r e 1 6 ) . i n a l l y e a r s p r e v i o u s t o the c o n s t r u c t i o n of the f i s h w a y s , t h e r e had been a d i s t i n c t i n c r e a s e i n the p e r c e n t a g e r e c o v e r y of tags below the R a p i d s and a c o r r e s p o n d i n g d e c r e a s e i n t h e p e r c e n t a g e r e c o v e r i e s above when the water l e v e l below 650 f e e t .  dropped  Such was not the case a f t e r the f i s h w a y s were  put i n and h i g h r e c o v e r i e s above p e r s i s t e d d e s p i t e a drop i n water l e v e l down as low as 643.4 f e e t by September 38.  Thus,  i t was found t h a t the p a t t e r n o f r e c o v e r i e s of tags above and below the R a p i d s had d i s t i n c t l y changed and sockeye were a b l e t o pass undelaye:d through t h e R a p i d s a t water l e v e l s below 650 f o o t water l e v e l .  the  Good a s c e n t was r e c o r d e d d u r i n g water  l e v e l s down as low as 643.4 f e e t . (c) P e r i o d of d e l a y o f tags below the R a p i d s . I n s t u d y i n g the t a g r e t u r n s f o r 1946 on f i g u r e 17, i t was found t h a t few tagged sockeye were r e t a k e n below the  53  Figure  17.  P e r i o d s o f d e l a y as shown by f i s h r e c a p t u r e d below the R a p i d s .  tagged The  lines  are p l o t t e d from the date of r e c o v e r y on r i g h t t o date of t a g g i n g on the l e f t ,  the  1946.  WATER LEVELS 1946  i  r  TAG RECOVERIES AT PLACE OF TAGGING BELOW BRIDGE RIVER RAPIDS  10  20 . 30  JULY  10  20  ; AUGUST  30  10  20  30  SEPTEMBER  54 f a l l s w h i c h i n d i c a t e d u n o b s t r u c t e d passage w i t h o n l y chance r e c a p t u r e s b e i n g made on t h e same day as t h e y were tagged; Passage i n August appears t o be f r e e from d e f i n i t e b l o c k p e r i o d s . However, some d e l a y was caused the sockeye-about. August I E * T t was on t h i s date t h a t t h e e a s t bank o f the lower f a l l s ed t o become d i f f i c u l t  appear-  t o ascend and t h e d e l a y i n d i c a t e d , p r o -  b a b l y r e p r e s e n t s t h e time i t took f o r t h e sockeye t o overcome the e a s t bank f a l l s o r t o c r o s s over t h e west bank where t h e f i s h w a y was f u n c t i o n i n g . The most s t r i k i n g f e a t u r e shown on f i g u r e 17 i s the few r e c a p t u r e s o c c u r r i n g i n September when t h e water dropped t o below 650 f e e t on September 11* tagged a l l through  level  Sockeye were b e i n g  September below t h e R a p i d s and had t h e f i s h -  ways n o t been i n o p e r a t i o n , r e c a p t u r e s would have p r o b a b l y reached  a maximum d u r i n g t h i s month* ( s e e f i g u r e s 7 and 9)  ( ) Cumulative d  p e r c e n t a g e o f tags r e c o v e r e d below t h e  R a p i d s a t d i f f e r e n t water l e v e l s . - F i g u r e 18 The r e c o v e r i e s below t h e R a p i d s i n 1946 have been p l o t t e d e x a c t l y t h e same as those f o r p r e v i o u s y e a r s .  When  o b s e r v i n g a l l r e c o v e r i e s i t appears t h a t t h e r e was some d e l a y between 665 - 656; however, when o n l y those r e c o v e r i e s out 3 days or more were c o n s i d e r e d , t h e r e were no s i g n i f i c a n t numbers o f sockeye r e c a p t u r e d below throughout the e n t i r e season* Of g r e a t e s t s i g n i f i c a n c e was t h e d r a s t i c change i n t h e p a t t e r n o f r e c o v e r i e s below 650. f e e t *  I n 1943 and 1945 t h e r e c o v e r i e s  55  F i g u r e 18, P e r c e n t a g e r e c o v e r y o f a l l tags p u t on below and r e c o v e r e d below the Rapids a t d i f f e r e n t water l e v e l s .  The percentage r e c o v e r y o f tags  out f o r v a r y i n g number o f days i s a l s o shown. 1946  1946  DAYS OUT 12  34  56  7 8  9 10-15-20 20 + 670-6 66  5 0 5  665-6 61  \ >  0  O  0  C  660-6 56  5  -  0 655-6 51  5 0  65O-6 46 5 0  o  645-6 41 5" 12  34  5 6  7 8  1  1  9 10-15-20 20  56 below 650 f e e t were numerous and p e r i o d s o f extended d e l a y were r e c o r d e d ; however, i n 1946 t h e r e were no tags r e c o v e r e d  from  t a g g i n g i n t h e l e v e l s 650 - 646 and p r a c t i c a l l y none r e c o v e r e d between 645-641.  I t was e v i d e n t t h a t whereas a b l o c k p r e v i o u s -  l y o c c u r r e d below 650 f e e t b e f o r e t h e f i s h w a y s were i n s t a l l e d , the passage was almost c o m p l e t e l y c l e a r e d a f t e r t h e f i s h w a y s were c o n s t r u c t e d . SUMMARY AND CONCLUSIONS D i s c u s s i o n and i n v e s t i g a t i o n on t h e success of t h e upstream m i g r a t i o n o f a d u l t sockeye salmon w i t h i n the F r a s e r f i v e r watershed has been o f v i t a l i n t e r e s t f o r a t l e a s t t h e l a s t f o r t y - f i v e years.  H e l l ' s Gate a t t r a c t e d p a r t i c u l a r a t t e n -  t i o n i n the y e a r s 1913 t o 1915 b u t the e x t e n t t o w h i c h water l e v e l s a c t e d as a major c o n t f i o l of the numbers o f salmon r e a c h i n g the v a r i o u s n o r t h e r n spawning grounds was n o t r e a l i z e d u n t i l 1941.  As soon as t h e I n t e r n a t i o n a l P a c i f i c Salmon Com-  m i s s i o n became aware o f the g r e a t l o s s e s o f salmon a t H e l l ' s Gate then a l l the e v i d e n c e on t h e c o n d i t i o n s a t the B r i d g e R i v e r R a p i d s were r e v i e w e d was was  commenced a t t h e Rapids t o determine  ^ t h o r o u g h l y and a b i o l o g i c a l s t u d y i n 1942.  The purpose^ o f t h i s  t h e d i r e c t i n f l u e n c e o f the R a p i d s  study  on t h e  c u r r e n t sockeye p o p u l a t i o n s and t o recommend such measures as to p r o v i d e u n o b s t r u c t e d p a s s a g e . f o r salmon s h o u l d b l o c k a d e  con-  d i t i o n s be r e v e a l e d . A program o f t a g g i n g was o u t l i n e d and c a r r i e d on i n 1942.  The 1942 experiment  was r e p e a t e d i n 1944 a n d the r e s u l t s  r e p o r t e d f o r each o f these y e a r s .  I t was t h e n thought  that  57 t h e delayed passage o f salmon a t H e l l ' s Gate might have been a factor m  the c o n d i t i o n s a t t h e R a p i d s ; t h e r e f o r e , a t h i r d  t a g g i n g program was conducted a t t h e R a p i d s a f t e r t h e f i s h w a y s a t H e l l ' s Gate has been c o n s t r u c t e d . 1945  At the conclusion of the  s t u d y , i t was apparent t h a t d i f f i c u l t passage and b l o c k  c o n d i t i o n s were s t i l l e f f e c t i v e a t the R a p i d s and two f i s h w a y s were recommended.  A f t e r c a r e f u l consideration of the b i o l o g i -  c a l and e n g i n e e r i n g r e p o r t s on the R a p i d s ,  t h e recommendations  were approved^, and the two f i s h w a y s c o n s t r u c t e d i n t h e s p r i n g " o f 1946. A f o u r t h t a g g i n g experiment was conducted i n t h e summer o f 1946, t o t e s t the e f f e c l e n c y o f t h e f i s h w a y s .  This  paper p r e s e n t s t h e most p e r t i n e n t facfis r e v e a l e d by t h e a n a l y s i s o f each o f t h e f o u r t a g g i n g The  most i m p o r t a n t  experiments. c o n c l u s i o n s a r e o u t l i n e d below:  A..-Before t h e f i s h w a y s were c o n s t r u c t e d . (1) A r e v i e w of t h e r e p o r t s o f J . P. Babcock i n d i c a t e d o  t h a t s e r i o u s b l o c k c o n d i t i o n s e x i s t e d a t the R a p i d s as e a r l y as 1912.  He s t a t e d t h a t t h e sockeye e n t e r i n g Seton Creek l a t e  i n t h e season were b a t t e r e d and wounded a f t e r b e i n g b l o c k e d a t the  Rapids. (2) The f a c t t h a t no cohoe have y e t been found i n t h e  upper F r a s e r may be a t t r i b u t e d t o b l o c k c o n d i t i o n s a t t h e Rapids. (3) The i r r e g u l a r f l u c t u a t i o n s i n t h e Seton Creek sockeye p o p u l a t i o n s t r o n g l y i n d i c a t e t h a t b l o c k c o n d i t i o n s a t t h e Rapids have been e f f e c t i v e f o r many y e a r s . (4) F i g u r e 21 i n B u l l e t i n N o . l o f the i n t e r n a t i o n a l  58 P a c i f i c Salmon Commission  shows t h a t t h e r e a r e two main d i v -  i s i o n s o f sockeye runs w i t h i n the upper F r a s e r r i v e r system. The f i r s t d i v i s i o n passes H e l l ' s Gate b e f o r e September 18 and goes t o the Upper F r a s e r w h i l e the second d i v i s i o n passes the Gate a f t e r September 18 and goes to t h e Thompson d i s t r i c t * Thompson s u g g e s t s t h a t b l o c k s d u r i n g September and October, at the  B r i d g e R i v e r , R a p i d s may have p r e v e n t e d the occurance of a  f a l l r u n o f sockeye i n the upper (5)  Fraser.  B l o c k c o n d i t i o n s were i n d i c a t e d below the 650  foot  water l e v e l i n 1942 and 1945 when t h e d a i l y c a t c h e s above the Rapids became poor w h i l e f a i r catches, were s t i l l b e i n g made below. (6)  A l o s s o f sockeye f.r,omthe S t e l l a k o and C h l l k o r u n s  was i n d i c a t e d i n 1942 and 1945. below 650 f e e t , sockeye were  A f t e r the water l e v e l  dropped  s t i l l b e i n g tagged a t t h e R a p i d s  u n t i l October 12 i n 1942 and October 5 i n 1945; y e t , none o f the sockeye tagged a f t e r September 27 i n 1942 and September 12 i n 1945 were r e c o v e r e d from t h e spawning grounds.' A l o s s o f the l a s t p a r t o f the C h l l k o r u n was i n d i c a t e d i n 1944; however o n l y a s m a l l p o r t i o n o f the r u n was  effected.  (7) . The p e r c e n t a g e r e c o v e r y o f tags below  the R a p i d s  i n c r e a s e d r a p i d l y i n 1942 and 1945 d u r i n g w a t e r l e v e l s 650 f e e t .  below  R e c o v e r i e s o f tags above-.the R a p i d s showed a c o r r e s -  ponding d e c l i n e d u r i n g t h e s e same water l e v e l s ; , . (8)  Less t h a n 1% of the sockeye were d e l a y e d l o n g e r than  1 day when the water l e v e l s a t the R a p i d s were above 665 f e e t .  59 (9)  /  Below ©65 f e e t and above 650 f e e t , up t o 10$ of the  sockeye were d e l a y e d a t l e a s t 1 day; however, o n l y 5% o f the f i s h were d e l a y e d f r o m 2 t o 4 days* (10) When the water l e v e l dropped below 650 f e e t , the r e c o v e r y of tags below the R a p i d s i n c r e a s e d t o as h i g h as  34$  of a l l f i s h tagged. (11)  D u r i n g extended p e r i o d s o f b l o c k , sockeye tagged  a t t h e R a p i d s were r e c o v e r e d i n Seton arid P o r t a g e Greeks. ' (12)  The numbers o f tagged sockeye r e a c h i n g the spawn-  i n g ground dropped t o n e a r l y z e r o d u r i n g the b l o c k p e r i o d s o f 1942 and  1945.  (13)  Fishvmys were recommended t o p r o v i d e passage f o r  salmon d u r i n g the low water p e r i o d .  These were c o n s t r u c t e d by  the Commission i n 1946. (14)  A f t e r s t u d y i n g the m i g r a t i o n times from Hell*!s  Gate t o the Highway B r i d g e l o c a t e d 6 m i l e s below the R a p i d s , I t was c o n c l u d e d t h a t the R a p i d s would a c t as a b a r r i e r t o s a l mon  i r r e s p e c t i v e o f a p r e v i o u s b l o c k a t H e l l ' s Gate*  B - A f t e r the Fjshways were c o n s t r u c t e d . (1)  A f t e r the f l s h w a y s a t ths; R a p i d s were b u i l t f o r the  salmon r u n s o f 1946 i t was found t h a t sockeye tagged d u r i n g water l e v e l s below 650 f e e t were n o t r e c o v e r e d below* (2)  Up t o the l a s t day of t a g g i n g , sockeye were r e c o v e r -  ed on the n o r t h e r n spawning (3)  grounds*  Sockeye were known t o have passed t h r o u g h the R a p i d s  undelayed even when the water l e v e l dropped as low as 643.4 f e e t * t• ;  60 (4)  Between•water'levels  s t i l l remained;  665 - 656 f e e t a s l i g h t  delay  however, when o n l y tags out more than 3 days  were c o n s i d e r e d the number o f r e c o v e r i e s became i n s i g n i f i c a n t * (5)  Wo tags were r e c o v e r e d below t h e R a p i d s from t a g g -  i n g i n l e v e l s 650-646 f e e t and p r a c t i c a l l y none r e c o v e r e d between 645-641* (6)  From t h e sum o f the 1946 a n a l y s i s i t was concluded  t h a t d i f f i c u l t passage above 650 f e e t was r e l i e v e d and p r e v i o u s b l o c k c o n d i t i o n s below 650 f e e t ' were c o m p l e t e l y remedied a f t e r the f i s h w a y s were c o n s t r u c t e d . i  ACKNO WLEDGEMBNT3 The w r i t e r wishes  t o express h i s a p p r e c i a t i o n t o  Mr'. B. M. Brennan, D i r e c t o r o f t h e i n t e r n a t i o n a l P a c i f i c Salmon F i s h e r i e s Commission, f o r p e r m i s s i o n t o u s e t h e m a t e r i a l cont a i n e d i n t h i s paper and t o Dr. R. Yan Cleve f o r h i s c r i t l s i m of t h e m a n u s c r i p t .  I n a d d i t i o n , t h e author i s i n d e b t e d t o D r .  Wi A. Clemens f o r h i s encouragement and a d v i c e d u r i n g t h e a n a l y s i s of the data*  S i n c e r e t h a n k s a r e extended  R. I . J a c k s o n f o r t h e development o f t h e p l a t e s .  t o Mr.  LITERATURE CITED Babcock, J . P. 1913• The spawning beds o f t h e F r a s e r . Report o f Commissioner o f F i s h e r i e s f o r B r i t i s h C o l u m b i a . 1912, p . 2 8 .  1926.  The spawning beds o f t h e F r a s e r . Report o f Commissioner o f F i s h e r i e s f o r B r i t i s h C o l u m b i a . 1925. p. 4 1 .  B e l l , M. I945• P r e l i m i n a r y r e p o r t on B r i d g e R i v e r R a p i d s r e m e d i a l work, F r a s e r R i v e r . I n t e r n a t i o n a l P a c i f i c Salmon F i s h e r i e s Commission.. M a n u s c r i p t . Canada. Department o f F i s h e r i e s . • 1901 - 1946.. V a r i o u s f i e l d r e p o r t s on f i l e a t t h e Dominion F i s h e r i e s O f f i c e , New W e s t m i n s t e r , B. C K i l l i c k , S. R. 1945* The o b s t r u c t i o n a t t h e B r i d g e R i v e r R a p i d s . I n t e r n a t i o n a l P a c i f i c Salmon F i s h e r i e s Commission. Manuscript. MacKay, D.C.G., G. V. Howard, and S. R. K i l l i c k . 1944* Sockeye t a g g i n g a t Sooke and Johnstone S t r a i t . I n t e r n a t i o n a l P a c i f i c Salmon F i s h e r i e s Commission. Annual R e p o r t , 1943» p. 21-22. New W e s t m i n s t e r , B.C., T a l b o t , G. B. 1948. A b i o l o g i c a l study o f t h e e f f e c t i v e n e s s o f t h e Hell's Gate f i s h w a y s . I n t e r n a t i o n a l P a c i f i c Salmon F i s h e r i e s Commission." M a n u s c r i p t . Thompson, W. F. 1945. E f f e c t o f t h e o b s t r u c t i o n a t H e l l ' s Gate on t h e sockeye salmon o f t h e F r a s e r R i v e r . International P a c i f i c Salmon F i s h e r i e s Commission. . B u l l e t i n 1, 1945* P. 101-113. New W e s t m i n s t e r , B.. C.  2.  Tremper, H. S. 1940. Season's report f o r the Seton-Anderson watershed. , International P a c i f i c Salmon Fisheries Commission. Manuscript.  Water L e v e l s a t B r i d g e R i v e r R a p i d s - 1942 C a l c u l a t e d from. Jesmond Day  July  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31  666.6 667.0 667.3 668.0 669.1 670.0 670.1 670.1 669,7 670.0 668.0 667.3 666.8 666.4 666.1 665.5 665.5 667.0 667.5 667.7 667.0 666.1 665.5 665.2 665 ;0 664.7 664.1 663.1 662.5 662.0 661.7  August 661.5 660.9 660.5 659.8 659.4 658.9 658.7 658.9 658.9 658.7 658.7 658.7 658.4 658; 2 657.9 656;7 655.8 655; 4 655.6 656.5 657.4 657.9 658.4 657.9 656.9 655.6 654.4 653;9 652.8 651.1 650.0  September 649.5 649.3 649.2 648.8 648.5 648.1 648.1 647.9 649.0 649.3 649*8 649.8 649.5 649.3 649.2 649.0 649; 5 651.5 652.8 650*8 649*6 649.2 649.0 649*0 649.0 648; 7 648.1 647.7 647.1 646.9  October 646.2 646 ;0 645.8 645.6 646.0 647.4 647.1 646*9 647*4 648*3 649.2 650*1 650;0 650 ;0 650.0 649.0 648.1 647.4 646.6 645.6 644.9 644.7 644.5 646 ;0 647.4 647; 6 646*3 645*6 645.6 645.6 645*8  Water L e v e l s a t B r i d g e R i v e r R a p i d s - 1944 C a l c u l a t e d f r o m Jesmond Day 1 3 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31  " July 663.5 663.3 663.0 662.6 661.6 661.0 660.8 660*7 660*5 659.7 659*4 659*1 659.7 660*4 660.7 660 i 5 661.4 663;6 662.1 661 il 660*8 660.8 661*0 661.0 663.3 665*4 664.6 663.2 661.9 661.4  August 661.-0 660.0 658;-8 657.3 656.7 656.5 656*5 656*6 656.5 656.1 655*5 658.2 664.6 670.2 670.1 667.6 664.9 663,"7 663*8 662.6 663.4 661.-6 659.-7 658 .-4 657*0 656*'6 655; 9 657.0 657.-6 657i6  September 658.4 657*9 656*8 656.6 655 *• 7 654*• 9 653*8 653*3 653.0 652.9 653 .-1 653.1 653.0 653.7 652;-7 653*1 654*0 655*1 655*3 654*3 654*1 653*8 654*- 5 653*1 653 s 7 653 i 2 653 i 3 659i6 659 .-7 657 i8  October 656,9 656.6 655.4 655*3 661.7 663*9 665.4 662*5 659*3 656.3 655*3 653.6 653.4 650*7 649.9 649*7 648*9 648; 6 648.3 647.8 647*3 647*0 646*8 646.8 647.3 647*4 647*3 647.0 646.5 646.0 645*5  Water L e v e l s a t B r i d g e R i v e r R a p i d s  1945  C a l c u l a t e d f r o m Jesmond  Day 1. 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30  July 668.4 667.3 666 7 667.0 666<j>2 665.2 0  663.6 663.3 663.2 663.1 663.2 663.8 663.8 663.9 663 „ 2 662.0 660 8 659*8 o  659.4 658.2 658.5 659.1 658.8 658.1 658.2  August 658.0 657.8 656,4 655.2 651.1 655,2 655.0 655.6 656.0 656.1 656 j 7 656.3 655.9 655.5 655,4 655.4 654,6 653.8 653*8 653.3 652.0 651.1 651.3 651.4 651.6 652.6 653,2  September 652.6 651.1 650.2 649.7 649.1 648.6 649.1 649.4 650.5 650.4 650.9 650.4 650.4 649.0 648.4 648.0 647.4 647.8 646.6 645.6 645.3 644.5 643.6 643.3 643.0  October 642.3 642.2 642.5 642.7 642.9 642.7 642.8 647.1 648.2 649.4 647.0 646.8 646.5 646.3 646,0 646.1 645.4 644.3 644.1 643.6 642.4 642.3 641.9 641.7 641.4  1946 Water L e v e l s - Gauge R, I Bridge R i v e r Rapids  Day 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31  July 670.5 670* 1 669; 7 669.9  '  669.5 669.3 669.0 668.6 668.0 668.0 668.7 668.8 668.8 671*4 668.7 667.9 667.4 666.9 666.2 * vj 664;2 664.1 664.3 V--' <,  '..  August 664.3 664.3 664*,5 663.2 661.4 660 * . l 660*3 659.4 658.4 658.9 658*9 658; 8 658.3 658.0 657 i'O 655.7 655*0 655*0 655.2 655.1 655.4 655.0 654.6 654*2 653.6  September 653.5 . 652.5 652.1 651.9 651.8 651.6 651.3 650.5 648.8 . 648,. 3 648.5 647.9 647.7 647.6 647.5 646*9 645.7 645.1 644^. 1 644.2 644.0 643.7 643.4 643.4  October 643.5 643.7 642*4 642.8 642; 5 643.0 641.8 641.5 641.1 640*7 640,* 4 640; 2 639; 9 639,. 8 640.1 640.3 640.2 639*9 639*5 639.2 639.4 639.1 639.4 639.8 640.2 640.4 640.4 640-.8 640.4 640*0 640.7  Plate I I The upper f a l l s a t t h e B r i d g e R i v e r R a p i d s and t h e lower s e c t i o n o f t h e upper f i s h w a y under c o n s t r u c t i o n . March 5, 1946. Water l e v e l R l gauge - 634 f e e t .  P l a t e III The upper f a l l s a t t h e B r i d g e R i v e r Rapids and t h e completed upper f i s h w a y . A p r i l 2 5 , 1946. v/ater l e v e l RI gauge - 647 f e e t .  Plate  IV  G e n e r a l view o f the l o w e r and upper f a l l s at the B r i d g e R i v e r R a p i d s and t h e completed f l s h w a y s . A p r i l 25, 1946. Water l e v e l RI gauge - 647 f e e t .  

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