Open Collections

UBC Theses and Dissertations

UBC Theses Logo

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

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1948_A4 K4 B4.pdf [ 6.7MB ]
Metadata
JSON: 831-1.0106970.json
JSON-LD: 831-1.0106970-ld.json
RDF/XML (Pretty): 831-1.0106970-rdf.xml
RDF/JSON: 831-1.0106970-rdf.json
Turtle: 831-1.0106970-turtle.txt
N-Triples: 831-1.0106970-rdf-ntriples.txt
Original Record: 831-1.0106970-source.json
Full Text
831-1.0106970-fulltext.txt
Citation
831-1.0106970.ris

Full Text

1/S3 S7 A B i o l o g i c a l Study of the Influence of the Bridge R i v e r Rapids on the Sockoye Runs of the Upper F r a s e r Watersheds by S t a n l e y Reginald K i l l i o k A Thesis submitted 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 of MASTER OF SCIENCE IN AGRICULTURE i n the Department of ZOOLOGY The U n i v e r s i t y of B r i t i s h Columbia APRIL* 1948 A B i o l o g i c a l Study o f the Influence of  the Bridge R i v e r Rapids on the Sockeye Huns of the  Upper Fraser 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 of obstructed passage of sockeye up the Fraser 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 very d l s a s t -erous e f f e c t ^ o f H e l l ' s Gate were revealed 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; A f t e r the import-ance of the H e l l ' s Gate o b s t r u c t i o n was e s t a b l i s h e d , evidence on the c o n d i t i o n s at the Bridge R i v e r Rapids were reviewed and a study commenced i n 1942. These Rapids are l o c a t e d on the Fraser r i v e r , 76 m i l e s n o r t h of H e l l ' s Gate and must be passed by a l l the sockeye races destined f o r the upper Fraser water-shed. The Rapids c o n s i s t of two separate f a l l s , and have been reported to have caused d i f f i c u l t and block passage to salmon as e a r l y as 19IS. The study, 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 Rapids on the current sockeye populations and to make such adjustments i n the contour of the itapids as to allow unobstructed passage of salmon at a l l water l e v e l s , should blockade c o n d i t i o n s be re v e a l e d . The problem i n v o l v e d four separate tagging e x p e r i -ments from 1942 to 1946. No tagging was done i n 1943. The r e s u l t s of the va r i o u s experiments r e v e a l e d that Or the sockeye ?*ere delayed art s e r i o u s l y blocked m some years during 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 the only races that were e f f e c t e d as the other runs to the S t u a r t , Bow-ron and H o r s e f l y d i s t r i c t s pas.sed through the Rapids e a r l y i n the summer when the water l e v e l s were high. A f t e r the completion of the a n a l y s i s of the tagging experiments up to 1945, a recommendation, that two fishways be constructed at the Kapids, was submitted f o r the considera-t i o n of the Commission. The i n s t a l l a t i o n of fishways was ap-proved and t h e i r c o n s t r u c t i o n completed f o r the salmon runs of 1946. The e f f i c i e n c y of the fishways w^e tested i n t h a t year and a complete change i n the p a t t e r n of tag s r e c o v e r i e s was recorded. Whereas, block c o n d i t i o n s were p r e v i o u s l y shown by sudden increases i n the number of tags recovered below the Rapids; p r a c t i c a l l y no tags were recovered below during low water periods a f t e r the fishways were b u i l t . The same methods of a n a l y s i s that were used to determine b l o c k c o n d i t i o n s were . repeated i n 1946 t o t e s t the fishways and i n each case a n o t i c e a b l e improvement i n passage was recorded; Therefore, i t was concluded that the fishways b u i l t at the Bridge Hjver Kap-i d s were s u c c e s s f u l i n passing sockeye salmon, through the p r e v i o u s l y known block periods t h a t were revealed by tagging i n 1942j 1944 and 1945. Frontpiece General view of the lower and upper f a l l s at the Bridge R i v e r Rapids l o o k i n g upstream. September 6, 1944. .Vater l e v e l RI gauge - 655 f e e t . CONTENTS I INTRODUCTION 1 I I REVIEW OF LITERATURE ......................... v.. 3 Reports of J . P. Babcock ............................ 3 (1) Condition of sockeye salmon i n Seton Creek i n 1912. ........ 3 (2) Observations at the Rapids 1912 and 1925 ...... 4 Dominion F i s h e r i e s r e p o r t .............. i . 5 (1) No cohoe salmon present i n the Upper Fraser watershed .......... 5 (2) F l u c t u a t i o n s i n the Seton Creek populations ... 5 I n v e s t i g a t i o n s - o f 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 7 (1) Reports of H. S. Tremper . *................... 7 (2) B u l l e t i n #1 - W. F. Thompson ................... 8 I I I METHODS 10 Method and l o c a t i o n of tagging ...................... 10 Water l e v e l s ....•* 11 Theory of conducting a tagging experiment to. evaluate blockades ................ » 11 IV RESULTS ........................... • 13 Number of Sockeye tagged 1942 - 1946 13 Section'A - Evidence of o b s t r u c t i o n from the a n a l y s i s of tagging 1942 - 1945 14 (a) F i s h i n g i n t e n s i t y and races of sockeye ........ 14 CI) 1942 . . . . * . . . . . . . . . i . . . . . . . . . 16 (2) 1944 .... ; . 18 " (3) 1945 18 (b) Percentage recovery of tags below and above the Rapids 20 (1) 1942 ....... r . 2 1 (2) 1944 23 (3) 1945 25 (c) Time out before recovery of tags below ........ 27 (1) 1942 .................. ............... 28 (2) 1944 30 (3) 1945 .. 30 (d) i n f l u e n c e of water l e v e l s on percentage recovery below.......................................... 33 (1) 1942 . . . . . . . . . . . . 3 5 (2) 1944 . 35 (3) 1945 i . 37 The e f f e c t of H e l l ' s Gate 39 Summation of the evidence of d i f f i c u l t and block c o n d i t i o n s 45 Recommendations f o r f1shways 47 Sec t i o n B - The. a n a l y s i s of the 1946 tagging e x p e r i -ment to t e s t the e f f i c i e n c y of the fishways. 48 (a) F i s h i n g i n t e n s i t y and the races of sockeye.48 (b) Percentage recovery of tags below ahdabove.52 (c) P e r i o d of delay of tags below the Rapids .... 52 (d) Cummulative percentage of tags recovered below the Rapi ds........................... . 54 V SUMMARY AND' CONCLUSIONS 56 Before the fishways were constructed 57 Af t e r the fishways were constructed ................. 59 VI ACKNO'ffLSDG'EMENTS ................................ ... 60 VII LITERATURE CITED 61 % B i o l o g i c a l Study of the I n f l u e n c e of the  Bridge R i v e r Raplda on the Sockeye Runs of the Upper  Fraser 'Watershed. 1 by Stanley R e g i n a l d 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 Rapids, and subsequent remedial measures taken by the I n t e r n a t i o n a l P a c i f i c Salmon Commission represents the sec-ond major program for the removal of 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 of sockeye salmon w i t h i n the Fraser R i v e r water-shed. The f i r s t task was the d i s c o v e r y and d e f i n i t i o n of the block at H e l l ' s Gate and the c o n s t r u c t i o n of fishways designed to pass salmon through a wide range of water l e v e l s . The s i g n i f i c a n c e of obstructed passage of sockeye up the Fraser 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 very d i s -asterous e f f e c t s of H e l l ' s Gate were r e v e a l e d i n 1941. I n t h a t year i t became apparent t h a t water l e v e l s acted as a major c o n t r o l of the numbers of salmon reaching the v a r i o u s spawning grounds. A f t e r the importance of the H e l l ' s Gate bl o c k was e s t a b l i s h e d , evidence on the c o n d i t i o n s at Bridge R i v e r Rapids was reviewed more thoroughly and i t became ev l d r ent that a study should be a t a r t e d at t h i s p o i n t immediately. In the summer of 1943, the w r i t e r was s t a t i o n e d at the Rapids, and an extensive tagging program was commenced below and,above the Rapids. This study was designed to 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 of the problem: (1) Dates of the a r r i v a l , peak, and end of the var i o u s runs through the Rapids. (2) Evidence as to whether sockeye dropped downstream and entered Seton Creek upon being blocked at the Rapids. (3) Dates and.durations of blockades. (4) P r e c i s e water l e v e l s causing blocks.; ; (5) I n f l u e n c e of H e l l ' s Gate on the movements of sock-eye and i t s r e l a t i o n s h i p to the Bridg e R i v e r Rapids. The problem as defined by the Commission was to det-ermine the d i r e c t i n f l u e n c e of the Rapids on the cu r r e n t sock-eye populations and to make such adjustments i n the contour of the Rapids as to allow unobstructed passage of salmon to the Upper F r a s e r , should blockade c o n d i t i o n s be revealed as a r e -s u l t of t h e i r study. I t i s the purpose of t h i s paper to pre-sent accumulated'evidence of blockade c o n d i t i o n s at the Bridge R i v e r Rapids 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 fishways i n 1946. R e f e r r i n g to the map, the c r i t i c a l p o s i t i o n of the Bridge R i v e r Rapids i s r e a d i l y noted w i t h respect to a l l the Fraser R i v e r runs that, spawn above the confluence of the Thom-pson R i v e r at L y t t o n . Apart from the three runs i n t o the Thompson R i v e r watershed (Adams-Little R i v e r , R a f t and Seymour) a l l the sockeye populations of the Fraser above H e l l ' s Gate must pass through the Bridge R i v e r Rapids except f o r the s m a l l 3 Seton-Anders on run. To ssvoid confusion-, i t must be noted that the Rapids are not on Bridge R i v e r despite the name but are on the Fraser proper, one-half m i l e upstream from the mouth of Bridge R i v e r and s i x m i l e s n o r t h of the town of L i l l o o e t . The Rapids c o n s i s t of two separate f a l l s approximately 900 f e e t a p a r t . These have been designated as the "lower" and "upper" f a l l s , both of which appear to become d i f f i c u l t or impossible f o r salmon to ascend during c e r t a i n years when the water l e v e l of the Fraser R i v e r becomes low i n . September and October. D e t a i l s on the height of the drop through the two f a l l s and -a3L other r e q u i r e d data p e r t a i n i n g to p r o f i l e s and r i s e and f a l l , of water l e v e l s have been s t u d i e d by the engineering d i v i s i o n of the Commission and are Included In an unpublished manuscri-pt by M i l o B e l l (1945). P l a t e s I and I I i l l u s t r a t e the t urb-ulence and drop through the lower and upper f a l l s . REVIEW OF LITERATURE A review of 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 Bridge R i v e r Rapids has aided m a t e r i a l l y i n determining the method of study and d e f i n i n g the o b j e c t i v e s to 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 Rapids had been under-taken p r i o r to the work of the Commission but the sum of the accumulated evidence 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 the passage of salmon at t h i s l o c a t i o n f o r many years. Reports of J . P. Baboock (1) Condition of sockeye salmon i n Seton Creek i n 1912. 4 I n the r e p o r t of the 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, Babcock made the f o l l o w i n g s t a t e -ments : "The f i r s t sockeye entered our hatchery weirs at the o u t l e t of Seton Lake on J u l y 35. Between that date and August 17, when t h i s run ended, 3,000 unus u a l l y l a r g e prime f i s h had entered the w e i r s . On September 1 the sockeye again began, ent e r i n g the hatchery w e i r s , and by the 17th of the month up-wards of 10,000 were impounded i n the s e i n i n g p o o l . The run continued u n t i l October 8. The f i s h which passed'through the weirs a f t e r September 10 were i n poor c o n d i t i o n , being badly s c a r r e d about the head and many showed hook and spear wounds. I t was estimated that more than h a l f of the 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 spear. Many were so badly waunded that they died. During 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 of sockeye eggs at the Seton Lake hatchery t h i s year, and the battered and wounded c o n d i t i o n of the f-ish that came to the s t a t i o n a f t e r September 10th, to the low stage of water i n the Fraser R i v e r , which prevented t h e i r passing through the canyon h a l f a m i l e above the mouth of the Bridge R i v e r " . I n 1937 and 1940 considerable numbers of sockeye were again found dead and unspawned i n Seton Creek, This f i n d i n g agreed w i t h observations made i n the strBams below H e l l ' s Gate where many salmon were examined during block years and found dead and unspawned, (3) Observations at the Rapids 1913 and 1935. I n conduction of Mr. Babcock's r e p o r t on the:jpopulations i n Seton Creek (Cayoosh C r . ) , he made a few actualyobservations on the Bridge R i v e r Rapids themselves. A f t e r a v i s i t to the Rapids i n 1913, Mr. Babcock re p o r t e d t h a t : "The r i v e r bed of the Fraser where the blockade occur-red 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 , that even during o r d i n a r y stages the water rushed through w i t h such v e l o c i t y as to give the sockeye considerable d i f f i c u l t y i n passing. The water was so low that the sockeye found t h e i r passage completely blocked by September 10. The waters of the Fraser were too d i s c o l o u r e d to trace the movements of these salmon from the canyon back to Cayoosh Creek, but the f i s h 5 th a t reached the hatchery the l a s t of September and the f i r s t of October were so s c a r r e d about the head as t o convince any-one who had seen the bruised f i s h i n the pools below the canyon (Rapids) that they r e c e i v e d t h e i r i n j u r i e s there, and being unable t o pass up the Fraser had turned back to enter 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 to the Rapids i n 1925 Babcock s t a t -es ' ed; "At such low stages of water as e x i s t e d there t h i s year the f i s h encountered as much d i f f i c u l t y as they did at H e l l * s Gate. They (sockeye) were blocked f o r two weeks and during that time most of them that escaped capture by Indians dropped down-stream and entered Cayoosh Creek. F i v e hundred" sockeye entered Seton. 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 to be a l l blocked sockeye." Dominion F i s h e r i e s Reports. (1) No Cohoe salmon present i n the Upper Fraser watershed. In reviewing some of the p e r t i n e n t l i t e r a t u r e i n the Dominion F i s h e r i e s r e p o r t I t was found that ishoro. aro no Cohoe salmon (Oncorhychus k i s u t c h ) have ever been reported i n the upper Fraser r i v e r d i s t r i c t ; however, they are present i n the South Thompson watershed which i s a c c e s s i b l e without pas-s i n g through the Bridge R i v e r Rapids. 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 at the Rapids In l a t e Oct-ober and November i f they passed the Thompson R i v e r j u n c t i o n . (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 blockade at the Rapids i s found i n a review of the s i z e s of the Seton Creek populat-i o n s . One important c o n s i d e r a t i o n , to be described i n the subsequent a n a l y s i s of the tagging data, was the t r a c i n g , o f blocked sockeye from below Bridge R i v e r Rapids down the Fraser and i n t o the Seton-Anders'on watershed. I n 1942,this behaviour-was a c t u a l l y proved, by the r e c o v e r y , i n Seton and Portage creek, of tagged sockeye t h a t were h e l d up by. low water at the Rapid during September and October. This phenomenon was s t r o n g l y suspected i n 1912, 1925, 1937 and 1940 by v a r i o u s observers but lacked proof u n t i l tags could be t r a c e d from the Rapids to Seton creek. With, the knowledge of 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 years i n the past i n which block co n d i t i o n s must have e x i s t e d at the Rapids. The estimated sockeye populations of Seton Creek have been tabulated from the records of the Dominion Department of F i s h e r i e s f o r a l l years from 1901 to 1946 (Table I ) . I n those years i n wMch Seton creek had an unusually l a r g e run, the presence of blocked sockeye was i n d i c a t e d by the f a c t that the brood year was too small to warrant the great i n c r e a s e . Furthermore,the run four years l a t e r showed no improvement as a r e s u l t of the i n f l u x of blocked f i s h . Those years i n which the populations of Seton Creek were thus incr e a s e d are marked wit h a double a s t e r i s k For example, the year 1937 showed a population of approximately 50,000 sockeye, yet the brood year of 1933, showed only a run of 100. S t i l l more evident was the f a c t that the 1941 populations which should be the progeny o f the 50,000 sockeye In 1937 c o n s i s t e d of only 50 salmon. The block at Bridge R i v e r Rapids must have been s e r -ious i n 1937 as i n d i c a t e d by the Seton p o p u l a t i o n . In 1942, when the Rapids were under d a i l y o b s e r v a t i o n , tagged sockeye were.traced back to Seton but the f i s h were not as abundant i n that year as they were i n 1937. TABLE I ESTIMATED SOCKEYE POPULATIONS OF SETON CREEK Year P o p u l a t i o n Year P o p u l a t i o n -1901 1,000,000- " 1924 -• 50 1902 0 1925 66,000*-*-1903 971 1926 40G 1904 1,000 1927 200 1905 200,000 1928 700 1906 15,000** 1929 200 1907 — •' 1930 100 1908 - 1931 100 1909 1,000,000 1932 100 1910 - 1933 100 1911 90 1934 400 1912 10,000 1935 200 1913 30,000 1936 15,000** 1914 300 1937 50,000** 1915 200 1938 500 1916 100 1939 20 1917 - 200 1940 2,000** 1918 100 1941 50 1919 200 1942 1,000** 1920 0 1943 800 1921 0 1944 100 1922 0 1945 20 1923 0 1946 75 ** Block at Bridge R i v e r Rapids i n d i c a t e d . 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) Reports of H. S; Tremper. • The f o l l o w i n g observations were made by the Commiss-ions observer s t a t i o n e d at the Rapids i n 1940; "A s l i g h t blockade t o the mi g r a t i n g salmon at Bridge R i v e r Rapids was evident on September 26. This p a r t i a l block-l a s t e d two days. From then (September 28) u n t i l October 4 the 8 Rapids were a very serio u s o b s t a c l e to the migrating sockeye. There were l a r g e numbers of sockeye which were weakened to such a s t a t e that i t d i d not seem p o s s i b l e that they could ascend the R a p i d s i I t then seems obvious t h a t the Rapids had a deter-ant e f f e c t on l a r g e numbers of sockeye at c e r t a i n water l e v e l s . Weak, battered sockeye were observed attempting the Rapids and two days l a t e r , c leaner, f r e s h e r sockeye appeared i n the eddies;" The observer s t a t e s i n conclusion: " I t i s evident that the Bridge R i v e r Rapids represents a problem of near equal magnitude as H e l l ' s Gate. I t should be s t u d i e d i n ' a s i m i l a r manner and w i t h equal 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 review 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 to demonstrate that d i f f i c u l t passage at Bridge R i v e r Rapids has been e f f e c t -i v e f o r many years. I n v e s t i g a t i o n conducted by the I n t e r n a t i o -af H e l l ' s Gate 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 that 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 of the, sockeye races i n t h e Fraser River system. Thompson (1945) described the f l u c t u a t i n g populations of the Seton-Anderson watershed and a l s o showed the major d i v i s i o n of the sockeye races i n t o the Upper Fraser and the Thompson area by the recov-ery of H e l l ' s Gate tags on the spawning grounds. The p a t t e r n of race segregation Into the two systems noted above Is an important f a c t o r i n the a p p r e c i a t i o n of the seriousness of the Bridge R i v e r Rapids. Reference may be made to f i g u r e 21 i n Thompson's r e -port where the r e c o v e r i e s of H e l l ' s Gate tags on the various-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 that at present there are two main d i v i s i o n s of the sockeye runs w i t h i n the Fraser R i v e r system. The f i r s t d i v i s -9 i o n passing H e l l ' s Gate before September 18 i s comprised of sockeye going to the Upper Fraser watershed. 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 destined f o r the South Thompson d i s t r i c t . With onl y minor exceptions t h i s p a t t e r n of d i v i s i o n holds true f o r every c y c l e of t»he present day runs. However, the h i s t o r y of the Thompson r i v e r runs has shown t h a t sockeye formerly migrated during the p e r i o d before September 18 and Thompson'(1945) presents various reasons f o r t h e i r d e c l i n e almost to the p o i n t . o f complete e x t i n c t i o n . I t then remains to be shown what f a c t o r or f a c t o r s could r e s t r i c t the passage of sockeye a f t e r September 18 to the Upper F r a s e r , A strong clue as t o the f a t e of some of these l a t e runs to the Upper Fraser i s found i n the sudden appearance of . l a r g e , unexpected runs i n t o the Seton-Anderson watershed* Further evidence of the o b s t r u c t i o n of 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 tagging i n the f o l l o w i n g s e c t i o n s of 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 that d i f f i c u l t passage and often s e r i o u s block c o n d i t i o n s to the salmon migra t i n g to the Upper Fraser have been i n e f f e c t f o r many years. However, only the dates of d i f f i c u l t passage were given and no d e f i n i t e water l e v e l s were assigned to the periods of s l i g h t delay and periods of s e r i o u s o b s t r u c t i o n . Thus, the apparent need f o r adequate data on accumulations of f i s h j dates of blockade and accurate water l e v e l s became evident. The determination o f the seriousness of any suspected 10 o b s t r u c t i o n to the m i g r a t i o n of salmon presents a d i f f i c u l t problem that r e q u i r e s study from every p o s s i b l e approach. To date, only l i m i t e d means are a v a i l a b l e to 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 other watershed than the Fraser r i v e r . Thus, the method of tagging as employed by the Salmon Commission at H e l l ' s Gate was used again at the Bridge R i v e r Rapids as the best 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 type of problem. C e r t a i n m odifications"and adjustments have been made t o s u i t the 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 evidence of blockade i s I n t e r p r e t e d by the p a t t e r n 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 of Tagging The method of a f f i x i n g the tags to the sockeye at the Rapids was the same as that'uaed In a l l the tagging program conducted by the Commission and may be r e f e r r e d . t o i n the re p o r t of MacKay, Howard and K i l l i c k (1944). The sockeye were captured f o r tagging i n In d i a n dip ne t s . A l l f i s h tagged were kept out of the water f o r as short a time as p o s s i b l e and s e l -dom more than 45 seconds was r e q u i r e d f o r the whole op e r a t i o n . D e t a i l s on the c o n d i t i o n , t o t a l l ength and scars were recorded and ;a':.scale sample taken from each f i s h ; F i s h i n g s t a t i o n s were lo c a t e d below and above the Rapids so that comparisons of the f i s h i n g i n t e n s i t i e s and r e -covery of tags could be made* In 1944, tagging was l i m i t e d to the s t a t i o n s below the Rapids on l y , because of a reduced crew. Sockeye were tagged at both the 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 of the tag r e c o v e r i e s i t was found that there 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 of r e c o v e r i e s from the two banks; t h e r e f o r e , a combin-a t i o n of both groups of tags was used. Water Leve l s Consistent water l e v e l readings were recorded s i n c e 1942^ from a s i n g l e gauge below the Rapids^ during the salmon mi g r a t i o n s . These re a d i n g s j taken d a l l y except on Sundays, f o r the months of J u l y A u g u s t , September and October w i l l be found at the appendix of t h i s paper. During the 1944 season, more extensive water l e v e l readings were taken by the Commiss-ion engineers at ten separate l o c a t i o n s below and above the Rapids on both r i g h t and l e f t banks-'! The gauge ;used i n the i n t e r p r e t a t i o n of the b i o l o g i c a l data^ i s l o c a t e d on the r i g h t bank of the r i v e r below the lower f a l l s . (Gauge Rl) As i t was d e s i r a b l e to have water l e v e l readings f o r years previous to 1942, the r a t e of flow 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 readings at the Rapids as f a r backa as 1935. Jesmond i s l o c a t e d approximately 30 miles n o r t h of L l l l o b e t . For the purposes of the block-ade a n a l y s i s , the water l e v e l readings at the Rapids 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 of conducting a Tagging Experiment to evaluate  blockades. As i t i s impossible to a c t u a l l y observe the salmon 12 w i t h i n the Fraser r i v e r , some mark or i d e n t i f i c a t i o n must be attached to the f i s h i n order that t h e i r movements may be traced, . i n t h i s case, numbered c e l l u l o i d tags were attached to as many salmon as p o s s i b l e both 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 returned to the r i v e r , represent the best known means of demonstrating what i s happening to the population as a whole. In conjunction w i t h the tagging o p e r a t i o n , accurate water l e v e l readings were taken each day and the developement of any f a l l s or t u r b u l e n t waters recorded. I t then remains to be seen where and when these tags w i l l be recovered and i n what numbers they w i l l be taken above and below the tagging s i t e * The place of recovery of the tags put on below w i l l be considered f i r s t . I n t h i s regard i t i s q u i t e l o g i c a l to assume that i f some tags are recovered above and h£ tags are recaptu-red at the place of tagging or at any downstream poi n t then these tagged f i s h have proceeded upstream without 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 to reason that I f these tags were recov-ered In s i g n i f i c a n t numbers at the place of tagging below or at any downstream poi n t then some f a c t o r has impeded t h e i r pro gress passed-the s i t e under study. Concurrent w i t h the abun-dance of tags recovered below, there may be a corresponding s c a r c i t y i n the numbers of 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 , the p a t t e r n of u p r i v e r r e t u r n s from the tagging below and above should be the same. I f on the othec hand an o b s t r u c t i o n 13 occurs, i t has been found that the sockeye tagged.above during block periods were recovered i n reduced numbers on the spawn-i n g as were those sockeye tagged below during the same p e r i o d . I t would appear t h a t an extended delay, caused by the obstruc-t i o n , reduced the v i t a l i t y of the f i s h to such an extent t h a t , even though some sockeye were able to surmount the Rapids and be tagged above, they were unable t o reach the spawning grounds. I f a d i f f e r e n t i a l recovery of tags occurred w i t h i n the season then an e x p l a i n a t i o n should 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 to look f o r i s undoubtably the i n f l u e n c e of the r i v e r through which the salm-on must swim* ThuSj the water l e v e l s have been gauged and p l o t t e d against the p a t t e r n of tag r e c o v e r i e s . This process was repeated over a p e r i o d of years to 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 success o f pass-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 of 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 No. i n crew 3 2 4 4 1942 1173 469 1944 3341 0 1945 1980 931 1946 1808 651 Totals 7301 2041 14 A Each year the maximum numbers of sockeye were taeyeu tagged and every e f f o r t wiss made "to secure at l e a s t 10 sockeye on each day of tagging. D e t a i l s on the r e l a t i v e abundance of tags a p p l i e d throughout the season are given i n the sections on the f i s h i n g i n t e n s i t y . S e c t ion A Evidence of o b s t r u c t i o n from the a n a l y s i s of tagg- ing 1942-1945. I n t h i s s e c t i o n of the paper the r e s u l t s of the t a g g i -ng experiments f o r the years 1942, 1944 and 1945 w i l l be pres-ented to show how the Rapids 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 various means of i l l u s t r a t i n g the d i s t r i b u t i o n of tags and the numbers of r e c o v e r i e s below and above the Rapids are included for each year of tagging. The r e s u l t s w i l l then be summarized and a general statement given as to the seriousness of the Rapids and the recommend-a t i o n for. remedial 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 that the sockeye populations a r r i v i n g at the Bridge R i v e r Rapids are comprised of a number of d i s t i n c t and separate races. The segregation of these races 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 confirmed by the r e s u l t s of the present Bridge R i v e r Rapids tagging experiment. The f i g u r e s i n d i c a t e which runs might be e f f e c t e d by a block at the Rapids. They a l s o I l l u s t r a t e the var y i n g abundance of sockeye of the Rapids throughout the f season and the p e r i o d o f passage or range of the v a r i o u s races 15 Figure 1 D a i l y catches of sockeye above and below Bridge R i v e r Rapids p l o t t e d against the water l e v e l s and ranges of the runs of the Upper Fraser sockeye population i n 1943. 1942 30 10 20 30 10 H STELLAKO GHILKO 4 BOWRON H STUART 120 DAILY CATCHES Below Above 10 20 30 10 20 30 10 20 30 10 JULY. AUGUST • SEPTEMBER OCTOBER 16 destined for the spawning ground of the Upper Fraser r i v e r . (1) 1942 With reference to f i g u r e 1 i t w i l l be noted that tag-ging commenced on J u l y 10 and ended on October 16. The catches of the tagging crews i n d i c a t e that these 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 Fraser r i v e r spawning grounds passed the Bridge R i v e r Rapids during 1942. F i s h i n g was continued to October 28 but no sockeye were caught a f t e r October 16. I t i s shown that the catches were e r r a t i c through J u l y and August and a t no time except J u l y 31 were the sockeye abundant. However, on September -2 and 3 a sudden, heavy i n f l u x of sockeye occurred and l a r g e catches were made u n t i l September 21. This abundance of f i s h c o n s i s t e d of a wave of blocked salmon that were r e l e a s e d from a b l o c k at H e l l ' s Gate when the water l e v e l dropped below 28 f e e t on August 31st. These f i s h then ran i n t o low water at Bridge River: Rapids and l a r g e num-bers were seen accumulating i n the eddy below the lower and-upper f a l l s and accounted for the heavy catches occurlng i n September; I t i s i n t e r e s t i n g to note a sudden increase i n the catches about the Rapids on September 19 which 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 to 652.8 fe e t on t h i s date. Comparing the catches of f i s h below and above the Rapids 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 taken at the upper s t a t i o n a f t e r September 22, yet sock-eye were s t i l l being caught i n some numbers below. I t was at t h i s time t h a t the water l e v e l had dropped below a gauge 17 Figure 3 D a i l y catches of sockeye below the Bridge R i v e r Rapids p l o t t e d against the water l e v e l s and ranges of the runs of the Upper Fraser sockeye populations In 1944. 1944 20 30 STELLAKO H CHILKO BOWRON 200 80 60 40 20 100 80 60 40 20 0 DAILY CATCHES Below 10 20 30 10 .20 30 JULY AUGUST 10 20 30 SEPTEMBER 10 18 reading of 650 f e e t and remained low f o r the remainder of the season. I t should a l s o he r e a l i z e d that no sockeye tagged a t the Rapids a f t e r September 27 were recovered on the spawning grounds despite 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 In 1944, the tagging was confined to the s t a t i o n s b e l -ow the f a l l s . The f i r s t sockeye were caught and tagged on J u l y 12 and operations were terminated on September 24. The d a i l y catches i n 1944 present a markedly d i f f e r e n t p i c t u r e from those o f 1942, but again the i n f l u e n c e o f H e l l a s Gate was r e f -l e c t e d . With reference to unpublished data complied by G. B. Talbot(1948)on the e f f e c t of blockade, at H e l l ' s Gate, I t was reported that salmon were delayed u n t i l August 14 a f t e r which the water rose suddenly and good passage was permitted u n t i l August 25. This opening at the Gate between August 14 - .25 was r e f l e c t e d i n the l a r g e catches at the Rapids from August 18 to September 3. None of the sockeye tagged a f t e r September 17 was recovered on the spawning grounds even though tagging continued u n t i l September 24. I t should be #oted t h a t the 1944 water l e v e l s were high throughout the sockeye m i g r a t i o n p e r i o d and no l a r g e accummulation of f i s h was observed below the Rapids. (3) 1945 A crew of four men commenced f i s h i n g at the Rapids on J u l y 5* The f i r s t catch of sockeye occurred 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 to determine, 19 Figure 5 D a i l y catches of sockeye above and below the Bridge R i v e r Rapids p l o t t e d against the water l e v e l s and ranges of the runs of the Upper Fraser sockeye populations i n .1945. 1945 WATER LEVELS BRR 30 \ STELLAKO ^ CHILKO H MIDDLE RIVER H HORSEFLY -I BOWRON -I EARLY STUART 120 DAILY CATCHES Below Above JULY AUGUST SEPTEMBER so no sockeye were taken a t the Rapids before J u l y 7. On J u l y 8 the sockeye run increased and 25 sockeye were tagged on that day* Consistent tagging continued from J u l y 8 to the end of the salmon m i g r a t i o n on October 24. The catches made by the tagging crews below and above the Rapids have been p l o t t e d s e p a r a t e l y to i l l u s t r a t e the e f f e c t s of p o s s i b l e blocks of salmon below the f a l l s ; Obser-i n g the d a i l y oatches above and below the Rapids i t i s seen th a t the bulk o f the sockeye were caught during J u l y and Aug-us t . The good catches made during J u l y were a t t r i b u t e d to the Stua r t Lake run and to a l e s s e r extent the Bowron sockeye; The l a r g e s t catches were made between August 10 and August 16 when the peak of the C h i l k o run was passing through. From August 20 to 30, the catches were poor and no l a r g e run of f i s h appeared a f t e r that date. One p o i n t of major importance was the f a c t that no lengthy breaks occurred i n the catches at the Rapids t h i s year as of t e n happened i n the past. This steady passage of sockeye was c r e d i t e d to the improved passage at H e l l ' s Gate. The most important c o n c l u s i o n drawn from f i g u r e 3 i s that no sockeye tagged at the Rapids a f t e r September 12 were recovered from the spawning grounds of the Upper F r a s e r , despite the f a c t t h a t sockeye were s t i l l being tagged at the Rapids u n t i l October 5. I t would therefore appear t h a t the Rapids were blocked a f t e r September 12. (Water l e v e l on Sept-ember 12 - 651 f e e t ) . (b) Percentage Recovery o f Tags Below and Above the K a p l d 3 t 21 The recovery of the 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 the Rapids. The r e c o v e r i e s below the Rapids were tags recovered immediately below the Rapids or at any downstream p o i n t ; The r e c o v e r i e s above were made mostly on the northern spawning ground but 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 Indian f i s h i n g s t a t i o n s l o c a t e d along the route o f the salmon migra-t i o n . The t o t a l recovery of tags was broken down i n t o the number of each day fs tagged sockeye t h a t were recovered e i t h e r below or above and are presented as percentages i n f i g u r e s 4 - 6 . , In the e a r l i e r s e c t i o n of t h i s paper d e a l i n g w i t h the theory of tagging i t was s t a t e d t h a t i f no tags were recovered below the tagging l o c a t i o n then the passage of salmon could be regarded as being unobstructed; However, i f tags were r e -captured below, then they should be s t u d i e d as to abundance, time out and t h e i r r e l a t i o n s h i p to the w a t e r - l e v e l s . The f i g u r e s on the percentage recovery of tags below and above the 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 the season, but the extent of the delay o c c u r r i n g before the tags were a c t u a l l y recovered is. not shown. This f a c t o r of time w i l l be dealt w i t h l a t e r , (see pages 27.-33} (1) 1942 The f l u c t u a t i n g p a t t e r n of the recovery of the 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 4i ) . I t i s seen that ~ some sockeye were recaptured below the Rapids throughout the whole season. I t i s al s o noted that the percentage o f recov-22 F i g u r e 4 Percentage r e c o v e r i e s of tags from each day of tagging as recovered above and below the Bridge R i v e r Rapids 194S. Blank columns represent days when l e s s than 10 sockeye were tagged. 1942 640' • ' 1 1 r 10 20 30 10 20 30 10 20 30 10 JULY AUGUST SEPTEMBER OCTOBER 0 10 2 0 . 30 10 20 30 10 20 30 10 Date of Tagging at Right Bank Above 10 20 • 30 10 20 30 10 20 30 10 JULY AUGUST SEPTEMBER OCTOBER Date of Tagging at Right Bank Below 23 ery below, fluctuates,, widely'from 0 to 68% f o r any one day of tagging. Through J u l y and August the number of r e c o v e r i e s was f a i r l y uniform except f o r s l i g h t increases i n recovery on J u l y 26 and 29 and August 17* On August 24 and 31 the number of r e -coveries increased; but the samples were too s m a l l to warrent c o n s i d e r a t i o n . However, commencing on September 2, wide f l u c t -uations became apparent* i t appears that the number of recov-e r i e s increased as the water dropped below the 650 fo o t water l e v e l on September 2,4 and 7* With the sudden r i s e i n water l e v e l to 652.8 f e e t between September 17-19 the recaptures b e l -ow decreased* By September 20 the water again dropped below the 650 fo o t mark and remained low f o r the remainder of the season. With the onset of low water the number of r e c o v e r i e s below the Rapids increased r a p i d l y and the presence of a b l o c k became apparent. The i n f l u e n c e of the c r i t i c a l water l e v e l s around the 650 foot l e v e l was a l s o r e f l e c t e d i n the p a t t e r on the recover-ies above the Rapids* Corresponding to the r i s e i n water l e v e l above 650 f e e t there was a r i s e i n the percentage recovery of 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 these three f a c t o r s t h a t provides some of the b a s i c evidence i n the d e f i n i t i o n of the presence of a blockade at the Rapids* This alone,, however, i s not s u f f i c i e n t evidence as i t must be known how long the f i s h were out before being recaptured below the place of 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 during 1944 are p l o t t e d & n f i g u r e 5* Again the percentages f l u c t u a t e widely throughout the sea-son e s p e c i a l l y through J u l y to the middle of August; No assoc-i a t i o n s jvarsi noted between the r e c o v e r i e s below and above 24 Figure 5 Percentage r e c o v e r i e s o f tags from each day of tagging as recovered above and below the Bridge R i v e r Rapids 1944. Blank columns represent days when l e s s than 10 sockeye were tagged. 1944 670 660 650 WATER LEVEL 10 20 30 1( 10 20 30 % 60 40 -20 -0 RECOVERED ABOVE 6*0 60 40 20 0 I L T— r 10 20 30 10 20 30 10 20 30 RECOVERED BELOW 10 . 20 30 10 20 30 10 20 30 JULY AUGUST SEPTEMBER Date of Tagging Below Rapids 85 the Rapids u n t i l . t h e end of August and during September; Com-mencing on August 18, i t i s shown that a steady increase occur-r e d i n the r e c o v e r i e s below and a corresponding d e c l i n e i n the re 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 that some sockeye tagged a f t e r August 30 were delayed long enough to have prevented them from reaching the spawning grounds. A f t e r Sept-ember 5 the s m a l l percentage recovered above became evident*, however,the bulk of the sockeye passed through the Rapids from August 18 to September 3. During this, p e r i o d a high percentage of r e c o v e r i e s was made above; t h e r e f o r e , only a s m a l l propor-t i o n of the runs was e f f e c t e d by the Rapids at the end of the season. As w i l l be shown l a t e r i n the a n a l y s i s of the data on the days-out before recapture of the f i s h below the Rapids, the salmon were not s e r i o u s l y delayed during the 1944 season despite the volume of r e c o v e r i e s below; (3) 1945 R e f e r r i n g to f i g u r e 6 i t i s seen t h a t a r a d i c a l cha-nge occurred i n the p a t t e d of tag r e c o v e r i e s taken above and below the Rapids i n 1945; I t was found that there 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 percentage recovery of tags above the Rapids. However, t h i s v a r i a t i o n was not caused by the block co n d i t i o n s alone, but also depends on t h e extent and e f f i c i e n c y of the recovery operations on the v a r i o u s spawning grounds. This i s best i l l u s t r a t e d by the high percentage r e c o v e r i e s made above the Rapids i n J u l y on the sockeye run to Stuart l a k e where approximately 80$ of the dead f i s h were r F i g u r e 6 Percentage r e c o v e r i e s of tags from each day of tagging as recovered above and below the Bridge R i v e r Rapids 1945. Blank columns represent 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 of Tagging Below Lower Rapids 27 examined. I n con t r a s t only about 25$ o f the C h i l k o sockeye -which pass /through the Rapids In August were examined on the spawning grounds* Were the s m a l l sample of dead f i s h at C h i l k o not taken i n t o account i t would be suspected that the August run of salmon were subject to a heavy m o r t a l i t y . Low percentage recovery of tags below during both J u l y and August i n d i c a t e s good passage; th e r e f o r e the varying percentage recovery above i s i n f l u e n c e d mostly by the v a r i a t i o n i n a b i l i t y t o recover _ tagged f i s h on the spawning grounds. Having accounted f o r the v a r i a t i o n s i n tag recovery during J u l y and August, we f i n d g r e a t l y reduced r e c o v e r i e s i n September f a r below what could have been recovered on the spawning grounds had the tagged f i s h passed the Rapids. D i r e c t -l y corresponding to the d e c l i n i n g r e c o v e r i e s above, were the r a p i d l y i n c r e a s i n g percentages r e c o v e r i e s of tags below. At t h i s same time the water l e v e l had dropped below the 650 foo t mark. In c o ntrast to the r e c o v e r i e s above, t he percentage of recaptures below was low during J u l y and August* i n d i c a t i n g a good ascent of the Salmon through the Rapids. Recaptures were few below the Rapids during the passing of the main part of the C h i l k o r u n . I t was not u n t i l September 5 tha t the higher percentages of tags were recovered. From September 5 to the end of the season, the d a i l y percentage of recaptures below the Rapids was high and block c o n d i t i o n s were In e f f e c t * (c) Time out before recovery of tags below. 28 The v a r y i n g abundance of tagged sockeye recovered below the Rapids and the l e n g t h o f the delay p e r i o d before the tags were recovered i s shown on f i g u r e s 7-9.' Each recovered tag i s represented by a s t r a i g h t l i n e drawn from the date of recovery on the r i g h t to the date of tagging on the l e f t . The numbers of recaptures below the f a l l s were few during open periods at the Rapids^ a l s o , the tags that were recovered had only been out a few days; When periods of d i f f i c u l t y and block occur, the number of recaptures w i l l be l a r g e and the number of days out before recapture w i l l be extended. The recaptures are p l o t t e d against the water l e v e l s to show when the open and c l o s e d periods o c c u r i (1) 1942 Upon a n a l y s i s of Figure 7, i t i s evident that the vc recaptures during August were few, i n d i c a t i n g good passage of salmon through the Rapids. F o l l o w i n g the drop i n water l e v e l s at the end of August, H e l l * s Gate opened and a l a r g e run of sockeye a r r i v e d at the Rapids on September 3. By t h i s date the water at the Rapids had dropped below the 650 f o o t l e v e l and the sockeye found passage up-stream d i f f i c u l t . Between September 3 and September 17 the numbers of recaptured salmon g r e a t l y increased and the sockeye were subjected t o a delay of 1 to 6 days or an average of approximately 3 days. Two tagged sockeye dropped downstream and entered Seton Creek during t h i s p e r i o d . Water l e v e l s below 648 f e e t were most se r i o u s and the p e r i o d of delay became much greater when t h i s l e v e l was reached 29 Figure 7 Periods of delay as shown by tagged f i s h recaptured below the Rapids. The l i n e s are plotted.from the date of recovery on the r i g h t to date of tagging on the l e f t . Broken l i n e s represent tags recovered from Seton and Portage Creeks, 1942. 1942 TAG RECOVERIES AT POINT OF TAGGING BELOW BRIDGE RIVER RAPIDS 10 20 30 10 20 30 10 20 3Q 10, 20 30 JULY ' AUGUST SEPTEMBER OCTOBER . 30 The block remained i n t o October and an a d d i t i o n a l 9 sockeye dropped downstream and were recovered i n Seton Creek during the month* (see -f-igure 7) The r i s e i n water l e v e l during October would have r e l i e v e d the block c o n d i t i o n s somewhat had i t occurred e a r l i e r i n the season* By t h i s date the sock-eye were so weakened that f u r t h e r m i g r a t i o n was u n l i k e l y . (2) 1944 I t has already been demonstrated i n f i g u r e 5j t h a t a considerable number of tagged sockeye were recovered below the Rapids; however, the lapse of time from the date of tagging to date of recovery was short i n most cases as shown i n f i g u r e 8. Only a few of the f i s h recaptured below the Rapids had been out for more than 2 or 3 days. The f i r s t s i g n of any delay occurred on August 6 at which time the lower east 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 permitted a l l d delayed sockeye to pass upstream. A short delay commenced on September 1 and l a s t e d u n t i l September 8; however, these sock-eye disappeared without a r i s e i n water l e v e l * I n g e n e r a l , a s l i g h t ' d i f f i c u l t y to migrating sockeye occurred a t a water l e v e l of approximately 658 f e e t i n 1944. (3) 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 that a r e l a t i v e l y good passage of salmon occ-urred during J u l y and August. Some evidence of delay and accumulation was i n d i c a t e d which may have been caused by d i f f -i c u l t passage on the east bank, e.g. August 10 and August 26. 31 F i g u r e 8 Periods of delay as shown by tagged f i s h recaptured below the Rapids. The l i n e s are p l o t t e d from, the date of recovery on the r i g h t to date of tagging on the l e f t . 1944. 1944 TAG RECOVERIES AT POINT OF TAGGING BELOW BRIDGE RIVER RAPIDS T 1 I 1 1 1 I I 1 1 1 I 10 20 30 10 20 30 10 20 30 10 20 30 JULY AUGUST SEPTEMBER OCTOBER 32 Figure 9 Periods of delay as shown by tagged f i s h recaptured below the Rapids. The l i n e s are p l o t t e d from the date of recovery on the r i g h t to date of tagging on the l e f t . 1945. 1945 TAG RECOVERIES AT POINT OF.TAGGING BELOW BRIDGE RIVER RAPIDS 10 20 30 10 20 30 10 20 30 10 20 30 JULY AUGUST SEPTEMBER OCTOBER 33 The most important c o n c l u s i o n to be drawn from f i g u r e 9 i s the e f f e c t of the o b s t r u c t i o n on the salmon during September* Commencing September 5 and even more apparent on September 8 a block 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 numb-ers of recaptures and the extended p e r i o d of delay. The water dropped below the 650 fo 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 to l e s s than 651 f e e t between September 11 and September 15 the water continued to drop through the remainder of the season* (d) i n f l u e n c e of Water Levels on Percentage Recovery Below I t may be r e a l i z e d from the tagging a n a l y s i s pres-ented so f a r that one method alone can not be r e l i e d upon to i l l u s t r a t e the t o t a l e f f e c t of a b l o c k . The method used to show the v a r y i n g percentage r e c o v e r i e s below the Rapids was u s e f u l but d i d not e s t a b l i s h the d u r a t i o n of the delay before the tagged sockeye were recovered. The second method used to demonstrate the time of the b l o c k , by means of the l i n e graph, provided i n f o r m a t i o n on the d u r a t i o n of t h e delay but d i d not allow 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 necessary to combine the two types of a n a l y s i s to show c l e a r l y how the various water l e v e l s i n f l u e n c e the passage of sockeye through the Rapids. 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 foot i n t e r v a l s so that the samples w i l l be s u f f i c i e n -t l y l a r g e to demonstrate what occurs as the water l e v e l drops* The l i n e between the p o i n t s i s a c t u a l l y a reversed cumulative curve 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 recovery of 34 Figure 10 Percentage recovery of a l l tags put on below and recovered below the Rapids at d i f f e r e n t water l e v e l s . The percentage recovery of tags out f o r varying number of days i s a l s o shown. 194E. 1942 DAYS OUT 1 2 3 4 5 6 7 B 9 1 0 - 1 5 - 2 0 20 r 1 2 3 4 5 6 7 8 9 1 0 - 1 5 - 2 0 20 ! 1 35 tags from the accumulation of a l l those taken i n c l u d i n g the day to be subtracted.- For example, i n 1942 at the 650-646 foot water l e v e l , 23.2$ of a l l the tags put on were e v e n t u a l l y recovered below the Rapids. The.number of tags that were only 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 tags out g.t l e a s t 2 days. This procedure was continued u n t i l i t was seen that 2.6$ of the tags were out f o r more than 20 days. The s i g n i f i c a n c e of t h i s type of f i g u r e i s that the percentage of the recovery i s r e a d i l y noted f o r a l l tags and als o the percentage of recovery f o r a l l periods of delay can beoaeen. This i s important because a block was o n l y s e r i o u s when a delay of c o n s i d e r a b l e l e n g t h was caused. Thus i f the l i n e dropped to a low percentage a f t e r a delay of only one or two days then no s e r i o u s damage w i l l be l i k e l y to, occur* (1) 1942 • Observing the f i g u r e 10 i t appears that there was  no delay 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 of sockeye occurred during w a t e r - l e v e l s 665-651, and serious delay i n s i g n i f i c a n t numbers occurred i n the 650-646 l e v e l s . The hig h percentage o f r e c o v e r i e s and the extent of delay below 650 f e e t appeared to be the c r i t i c a l stage i n the passage of sockeye i n 1942. This confirmed the conclusions reached by the other methods of a n a l y s i s . (2) 1944 The average water l e v e l s were high i n 1944 and no se r i o u s . d e l a y was noted at the Rapids; y e t , a considerable number of tags were recaptured below the Rapids. The p a t t e r n 36 Figure 11 Percentage recovery of a l l tags put on below and recovered below the Rapids at d i f f e r e n t water l e v e l s . 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. 1944. 1944 DAYS OUT 1 2 3 4 5 6 7 8 9 10-15-20 20 + -* °—-o . 665-66 1 66O-65 6 655-65 1 i t i i i i r 7 I 1 1 I i ' 1 2 3 4 5 6 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 range of water l e v e l s through the season was small and at no time during the sockeye mig r a t i o n d i d the water l e v e l drop below 650 f e e t . Some delay was evident between water l e v e l s 660-651 f e e t but only up to a p e r i o d of 4 days. I t i s considered that although i t would be i d e a l to have a b s o l u t e l y no delay, the co n d i t i o n s i n 1944 would not cause s e r i o u s harm. (3) 1945 The extreme range of w a t e r - l e v e l s were found i n 1945. Above the water l e v e l of 655 only a few tagged sockeye were recovered below the Rapids. With few exceptions, these socke-ye were recovered w i t h i n 3 days. Between 655-650 some d i f f i c -u l t y was shown; however, only a s m a l l percentage of the sockeye were delayed longer than 5 days. The most s i g n i g l c a n t i n f l u e -nce of seriou s o b s t r u c t i o n was evident I n the water l e v e l s of 650-646 and 645-641. During these p e r i o d s , s l i g h t l y over 34$ of a l l tags put on were recovered below the Rapids. E q u a l l y important was the entent of the delay of these obstructed sockeye* The curves do not drop to the base l i n e r a p i d l y , i l l u s t r a t i n g that a considerable number of sockeye were delayed f o r a long p e r i o d o£ time, (see f i g u r e 12) On the b a s i s of these i l l u s t r a t i o n s i t was evident that some f a c t o r was i n f l u e n c i n g the success of passage of sockeye through the Rapids. Further, i t was evident that there was a d i f f e r e n t i a l e f f e c t on the degree of passage during 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 delays of 3 to 5 days were 38 Figure 12 Percentage recovery of a l l tags put on below and recovered below the Rapids at d i f f e r e n t water l e v e l s . The percentage recovery of tags out fo r v a r y i n g number of days i s a l s o shown. 1945. DAYS OUT 1945 g 1 2 3 4 5 6 7 $ ? 1 0 - 1 5 - 2 0 , 2 0 * 3 0 3 0 5 h 0 30 25 20 15 h 10 5 0 30 25 20 15 10 5 0 665-66I 66O-656 645-641 —1 1 r - 1 1 r 1 r 1 — 1 1 r~—S— 1 2 3 4 5 6 7 J 9 10-15-20 20 39 found; howeverj the major periods of o b s t r u c t i o n occurred below the 650 foot water l e v e l and were apparent i n each of the methods of a n a l y s i s * I t then remained to be shown what would happen a f t e r the fishways were i n s t a l l e d for the passage of the 1946 run of sockeye salmon* The E f f e c t of 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 that there was the p o s s i b i l i t y t h a t a delay of sockeye at H e l l ' s Gate may have weakened the salmon to. such an extent that they would be unable to pass the turbulent waters of the Rapids l o c a t e d 76 miles 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 of the'Hell's'Gate fishways^ the unobstructed sockeye would be s u f f i c i e n t l y s t r o n g to over-come the d i f f i c u l t waters of the Rapids 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 seriousness of the Rapids could not be made on the bas i s of the 1942 and 1944 data* I t remained t o be seen what the circumstances would be during the season of 1945 at which time the H e l l ' s Gate fishways would be n e a r l y complete. The a n a l y s i s of each tag-ging experiment at the Rapids has been presented and i t was evident that d i f f i c u l t and blockade c o n d i t i o n s p e r s i s t e d at the Rapids during the 1945 season t o the same or greater extent than those o c c u r r i n g i n 1942 and 1944. Thus i t was concluded that even w i t h improved passage of sockeye through H e l l ' s Gate, the b l o ck stages at the Rapids remained as serio u s as they had i n previous years. Upon the completion of the analysis, of the 1945 data, recommendations f o r fishways at the Rapids were 40 f i r s t submitted. This 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 at any p o i n t above a previous 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 important to warrant b r i e f d i s c u s s i o n and the i n c l u s i o n of f i g u r e s 13 and 14. I f i t i s reasoned that the salmon were weakened at 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 to a c t as t h e i r only cause of delay at a second b a r r i e r , then i t must be demonstrated what weakening has occurred and which group or groups of salmon were thus e f f e c t e d . I f i t can be shown that 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 and strpng f i s h were never delayed, then i t i s probable that the second l o c a t i o n would not be a s e r i o u s f a c t o r when the f i r s t l o c a t i o n had been c l e a r e d . I t i s e q u a l l y 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 at c e r t a i n times and that both weakened and strong f i s h were delayed at other times then each b a r r i e r represents an independent f a c t o r . To demonstrate the circumstances between b a r r i e r #1 at 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 of p o s s i b l e weakness of the salmon have been i n v e s t i g a t e d . I n an e a r l i e r unpublished 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, recorded by the taggers as "green", "pink" and "red'% was analysed. I t was found that that there were few salmon i n "red" c o n d i t i o n and that the f i s h noted as "green" and."pink" were e q u a l l y delayed during water l e v e l s below 650 f e e t . I t was a l s o noted that the maj-o r i t y of the tagged sockeye that dropped downstream from the Rapids during blocked stages and entered Seton and Portage t 41 creeks were i n "green" c o n d i t i o n when tagged. However, t h i s measure of the weakness or s t r e n g t h of the salmon i s open t o c r i t i c i s i m , inasmuch as the appearance of "green" and "pink" sockeye may not a c t u a l l y represent t h e i r true 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 of the c o n d i t i o n of the sockeye when they a r r i v e a t the Rapids i s the number of days i t takes f o r the salmon to t r a v e l between H e l l ' s Gate and the Rapids. Weakened f i s h w i l l be those f i s h t a k i n g the long-est time to a r r i v e at the Rapids. 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 for sockeye t o pass from H e l l ' s Gate t o the Highway' bridge l o c a t e d s i x miles below the Rapids. H e l l ' s Gate tags recovered at the Rapids themselves have been p l o t t e d m a sep-arate manuscript but are not used here as i t i s i m p o s s i b l e to d i s t i n g u i s h between the time enroute and the time of delay be-low the Rapids. As there i s no reason to suspect d e l a y s , dur-in g any water l e v e l s , between the Highway bridge and theiRapids i t was concluded that the days - out presented on the f i g u r e s represent j w i t h i n a few hours, m i g r a t i o n r a t e to the Rapids; Observing f i g u r e 13 f o r the year 1942, i t i s apparent that a wide range i n the speed of m i g r a t i o n from 3 to 49 days was r e q u i r e d for sockeye to t r a v e l from H e l l ' s Gate to the H i -ghway bridge* F i s h a r r i v i n g at the bridge up to August 10 were out 12 days or l e s s and were considered to be i n good p h y s i c a l c o n d i t i o n ; A f t e r August 10 and during September, a consider-; able number of sockeye were out a long time before reaching the Highway Bridge and these salmon were p o s s i b l y weakened by a delay below H e l l ' s Gate; However, sockeye were 42 Figure 15 The mig r a t i o n r a t e of sockeye tagged at H e l l ' s Gate and recovered at the Highway bridge at L i l l o o e t , 1942 and 1944. M-0 £> 30 o %20 10 19^2 T r • « ... _ - - - V. o _ _ o _ * o * 10 20 30 10 20 30 10 20 30 JULY AUGUST SEPTEMBER DATES OF RECOVERY 12.22 ho EH 30 O CO _ 10 i r -> : r f —.—— ......... , 4 10 20 30 10 20 30 10 26 30~ JULY AUGUST SEPTEMBER DATES OF RECOVERY 13.5lJ-43 not obstructed at the Rapids i n August as they should have been i f weak f i s h are suspected of being delayed at the second b a r r i e r . Further, there was a block at the Rapids during 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 delayed or not. By the p a t t e r n of the days out of 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 that the block a t the Rapids was the r e s u l t of only the presence of weakened sockeye as these were present during the f u l l month of August when no evidence of a block was occurred at the Rapids. In 1944-, the data were not co n c l u s i v e as the numb-ers of 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 delayed s u f -f i c i e n t l y to cause some weakening. Low block l e v e l s were not encountered at the Rapids i n th a t year. The season of 1945 was of major importance i n the f i n a l d e f i n i t i o n of the Bridge R i v e r Rapids o b s t r u c t i o n as the fishways at H e l l ' s Gate were i n operation during that year* 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 of sockeye through the Gate,^ the Rapids would no longer act as an ob s t a c l e to the salmon* The f a c t t h a t the passage through H e l l ' s Gate i n 1945 was improved has been c l e a r l y demonstrated by data on f i l e i n the l a b o r a t o r y of the I n t e r n a t i o n a l P a c i f i c Salmon Commission. This improvement passage was r e f l e c t e d def-i n i t e l y i n the more concentrated p a t t e r n of quick r e c o v e r i e s of H e l l ' s Gate tags at the Highway Bridge as shown i n f i g u r e 14. Despite the improved passage and c o n d i t i o n of sockeye a f t e r H e l l ' s Gate was remedied, i t was found t h a t block con-44 Figure 14 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 recovered at the Highway bridge at L i l l o o e t . 1945 and 1946. 19^5 -o CQ * • • • • « •* • • 10 - • • • 8.59 •1 ••• • • •• 0 • • • • 1 .0 20 30 10 20 30 10 20 30 JULY AUGUST SEPTEMBER DATES OF RECOVERY 19^6 • i 1 1 1 1 1 1 r -• • S 30 o • CQ • g 20 • • • • -• • • 10 • • * • • jo." ~.V •• — • A - • - g.55 * * • L0 20 30 10 20 30 10 20 30 JULY AUGUST SEPTEMBER DATES OF RECOVERY 45 d i t i o n a s t i l l p e r s i s t e d at the Rapids i n 1945; I t was then evident t h a t even when no previous delay has been encountered by the sockeye at a downstream p o i n t they s t i l l were unable to pass the Rapids during c e r t a i n low water l e v e l s stages occur-r i n g i n September and October 4 The means of the number of days-out throughout the 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 of 12.22 and 13.54 days f o r sockeye tagged at H e l l ' s Gate to reach the Highway Bridge, i t r e q u i r e d only 8.59 and 8.55 days to cover t h i s same distance i n 1945 and 1946* llhe p a t t e r n of the r a t e of migratlonfrom H e l l ' s Gate to t;he Highway Bridge 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 fishways* F i g u r e 14 I l l u s t r a t e s that the bulk of thesrockeye passed undelayed between the two p o i n t s the same as they had i n 1945. The num-ber of days r e q u i r e d f o r the m i g r a t i o n during 1945 and 1946 show a remarkable s i m i l a r i t y ; thus i t was p o s s i b l e to compare the Bridge R i v e r tagging r e s u l t s f o r these two years without question as to the c o n d i t i o n of the salmon. Summation of the evidence of d i f f i c u l t and block c o n d i t i o n s . In reviewing the evidence of d i f f i c u l t and block c o n d i t i o n s at the Bridge R i v e r Rapidsj i t must be r e a l i z e d t h a t , as ye t , there 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 accurate to produce the r e q u i r e d answers to the problem. Information from every p o s s i b l e source must be considered. Thus, the review of the l i t e r a t u r e was presented t o express the opinions of e a r l i e r i n v e s t i g a t o r s . The a n a l y s i s of the tagging programs " 46 of 1942, 1944 and 1945 f o l l o w s and represents the more exten-s i v e study, the r e s u l t s of which form the b a s i s f o r p r e c i s e conclusions and the recommendation of a s o l u t i o n to the problem. Three years of tagging were r e q u i r e d before a de-f i n i t e statement could be made regarding the success of passage of sockeye salmon through the Rapids. In 1942, d i r e c t 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 pointed s t r o n g l y to 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 high d u r i n g the sockeye m i g r a t i o n making i t impossible to t e s t the r e s u l t s obtained i n 1942 during low water stages; The tagging conducted during 1945 s u p p l i e d the f i n a l answers by confirming e a r l i e r s u s p i c i o n s and a v o i d i n g 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 d e f i n i t i o n of a block a t the Rapids. Various methods of a n a l y s i n g the tagging data have been employed to t e s t the presence of obstructed passage; and i n each case the p e r i o d s of delay and block occur a t the same water l e v e l s i n each year. Upon summarizing each method o f a n a l y s i s i t was found that above water l e v e l s of 665 f e e t l e s s than 1% of the sockeye were delayed longer 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 delayed at l e a s t 1 day; however, only 5$ of the f i s h were delayed from 2 to 4 days. Delays o f over 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 during water l e v e l s between 665 - 650 but not i n s u f f i c i e n t numbers to be important. These water 47 l e v e l s were cl a s s e d as d i f f i c u l t and were considered i n the recommendations f o r the i n s t a l l a t i o n of fishways. Water l e v e l s below 650 f e e t were then considered and a remarkable change i n the pa t t e r n o f tag r e t u r n s was noted.' The recovery of tags below the Rapids increased t o as high as 34% of a l l tags a p p l i e d . Recoveries above the Rapids showed a corresponding d e c l i n e and i t was apparent fchat block 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 of delay was extended and sockeye were traced from below the Rapids down i n t o Seton and Portage creeks. The numbers of sockeye reaching the spawning-grounds dropped to n e a r l y zero during the extended block periods i n 1942 and 1945. Every method of a n a l y s i s showed the 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 that water l e v e l s below 650 feet at the Rapids were c r i t i c a l and acted as a se r i o u s b a r r i e r to the sockeye salmon m i g r a t i n g to the spawning grounds of the Upper Fraser watershed. Recommendations f o r fjshways. A summary r e p o r t on the tagging experiments f o r the years 1942, 1944 and 1945 was submitted f o r the c o n s i d e r a t i o n of the Commission i n the f a l l o f 1945. Included i n t h i s r e p o r t , was a recommendation that fishways be constructed at the Rapids, to pass salmon during periods of d i f f i c u l t and block water l e v e l s . I t was proposed that fishways be b u i l t at both the lower and upper Rapids and that they should f u n c t i o n from a top l e v e l of 665 f e e t to a bottom l e v e l of 642 f e e t . A f t e r c a r e f u l c o n s i d e r a t i o n of the b i o l o g i c a l evidence and the r e s u l t s of an extensive engineering survey the proposed f i s h -48 ways were approved* Constuction of the flshways was s t a r t e d i n the s p r i n g of 1946 and completed for the salmon runs of that year. Se c t i o n B-- The a n a l y s i s of the 1946 tagging experiment. to test, the e f f i c i e n c y of the fjshwaya. The fishways, shown i n p l a t e s I I I and 17, were constructed e a r l y i n the s p r i n g of 1946; They were designed to permit unobstructed passage of sockeye salmon to the Upper Fraser spawning grounds.through the e n t i r e p e r i o d of the sock-eye 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-essary to repeat the e a r l i e r tagging experiments and r e c o r d any changes i n the p a t t e r n of tag r e t u r n s . The r e s u l t s of the 1946 tagging at the Rapids are presented and i n c l u d e each method of study 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 races of sockeye The v a r y i n g abundance of sockeye as caught at the Rapids i s shown i n f i g u r e 15. The catches made by the tagging crews below and above the Rapids have been p l o t t e d s e p a r a t e l y . I t was noted that the peaks of abundance of sockeye correspond c l o s e l y to mid-points.of the passage of the d l f f e r -en#£r*uns. The peaks of the runs as they occurred at the Rapids were as f o l l o w s : S t u a r t - J u l y 27 j Bowron-August 3, Chilko-August 17, S t e l l a k o - September 3. The time of passage of the various runs was determ-ined from the Bridge R i v e r tags that were a c t u a l l y recovered on the spawning grounds and traced back to the date of tagging at the Rapids. Observing the ranges of the runs and the d a i l y 49 Figure 15 D a l l y catches of sockeye above and below the Bridge R i v e r Rapids p l o t t e d agains the water l e v e l s and ranges of the Upper F r a s e r sockeye runs i n 1946 1946 H STELLAKO H GHILKO BOWRON H STUART 120 100 80 60 40 20 0 — i r 10 20 30 ! JULY DAILY CATCHES Below — — Above 10 20 30 AUGUST 10 20 30 SEPTEMBER 50 catches, i t was noted that there were no extended periods of poor catches f o l l o w e d by a mass of f i s h as has occurred i n the past when H e l l ' s Gate delayed passage. Catches above the Rapids, dropped almost to zero during September, yet sockeye were s t i l l being caught below i n s m all numbers. I t would appear t h a t the dec l i n e i n the catches above i n d i c a t e d a block at the Rapids, however i t was found that sockeye tagged a t the Rapids during September below the 650 foot water l e v e l succeeded i n reaching the n o r t h e r n spawning ground. I t was then r e a l i z e d that a comparison of the abundances i n the catches above and below the Rapids cannot be r e l i e d up to measure the success of passage. Sockeye tagged on the l a s t day of tagging, September 28, were recovered on the S t e l l a k o r i v e r d i s t r i c t , (see f i g u r e 15) This f i n d i n g was i n d i r e c t c o n t r a s t to the p a t t e r n of rec o v e r i e s i n 1945 when not a s i n g l e tagged sockeye was recov-ered from the spawning grounds of the Upper Fraser r i v e r a f t e r September 12 (water level-650 f e e t ) , although sockeye were tagged at the Rapids u n t i l October 5. I t would t h e r e f o r e i n 1946 -appear that the sockeye were not blocked below the Rapids/de-s p i t e the f a c t that the water l e v e l dropped below the block l e v e l of 650 feet on September 1 1 , and continued to remain low throughout the remainder of the season. This was the 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 at the Rapids that tagged sockeye from below the f a l l s were recovered on the northern ground a f t e r continuous block co n d i t i o n s were i n e f f e c t . 51 Figure 16 Percentage r e c o v e r i e s of tags from each day of tagging as recovered above and below the Bridge Klver Kapids 1946. Blank columns represent days when l e s s than 10 sockeye were tagged. 1 9 4 6 53 (b) Percentage recovery of taga below and above the  Rapids. A comparison of the water l e v e l s and tags r e c o v e r i e s f o r 1945 and 1946 provides a s t r i k i n g i l l u s t r a t i o n as to what occurred a f t e r the fishways were i n s t a l l e d . The water l e v e l s were s i m i l a r f o r the two years; th e r e f o r e the periods of block, i as r e f l e c t e d by the recovery of tags above and below the Rapids, should have been approximately the same; such was not the case. I n 1945, the recovery of tagged sockeye below the Rapids i n c r e -ased n o t i c e a b l y w i t h the advent of low water below 650; whereas i n 1946j p r a c t i c a l l y no tagged sockeye were recovered below during s i m i l a r low water l e v e l c o n d i t i o n s . (Figure 16). i n a l l years previous to the c o n s t r u c t i o n of the fishways, there had been a d i s t i n c t increase i n the percentage recovery of tags below the Rapids and a corresponding decrease i n the percentage r e c o v e r i e s above when the water l e v e l dropped below 650 f e e t . Such was not the case a f t e r the fishways were put i n and high r e c o v e r i e s above p e r s i s t e d despite 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 that the p a t t e r n of r e c o v e r i e s of tags above and below the Rapids had d i s t i n c t l y changed and sockeye were able to pass undelaye:d through the Rapids at water l e v e l s below the 650 foot water l e v e l . Good ascent was recorded during 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 delay of tags below the Rapids. In studying the tag r e t u r n s f o r 1946 on f i g u r e 17, i t was found that few tagged sockeye were retaken below the 53 F i g u r e 17. Periods of delay as shown by tagged f i s h recaptured below the Rapids. The l i n e s are p l o t t e d from the date of recovery on the r i g h t t o date of tagging on the l e f t , 1946. WATER LEVELS 1946 i r TAG RECOVERIES AT PLACE OF TAGGING BELOW BRIDGE RIVER RAPIDS 10 20 . 30 10 20 30 10 20 30 JULY ; AUGUST SEPTEMBER 54 f a l l s which i n d i c a t e d unobstructed passage w i t h only chance recaptures being made on the same day as they were tagged; Passage i n August appears to be free from d e f i n i t e block p e r i o d s . However, some delay was caused the sockeye-about. August IE* Tt was on t h i s date that the east bank of the lower f a l l s appear-ed to become d i f f i c u l t to ascend and the delay i n d i c a t e d , pro-bably represents the time i t took f o r the sockeye t o overcome the east bank f a l l s or to cross over the west bank where the fishway 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 recaptures o c c u r r i n g i n September when the water l e v e l dropped to below 650 f e e t on September 11* Sockeye were being tagged a l l through September below the Rapids and had the f i s h -ways not been i n operation, recaptures would have probably reached a maximum during t h i s month* (see f i g u r e s 7 and 9) ( d) Cumulative percentage of tags recovered below the  Rapids at d i f f e r e n t water l e v e l s . -Figure 18 The r e c o v e r i e s below the Rapids i n 1946 have been p l o t t e d e x a c t l y the same as those for previous years. When observing a l l r e c o v e r i e s i t appears t h a t there was some delay between 665 - 656; however, when only those r e c o v e r i e s out 3 days or more were considered, there were no s i g n i f i c a n t num-bers of sockeye recaptured 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 the d r a s t i c change i n the p a t t e r n of r e c o v e r i e s below 650. f e e t * I n 1943 and 1945 the r e c o v e r i e s 55 Fi g u r e 18, Percentage recovery of a l l tags put on below and recovered below the Rapids at d i f f e r e n t water l e v e l s . The percentage recovery of tags out f o r var y i n g number of days i s also shown. 1946 1946 DAYS OUT 1 2 3 4 5 6 7 8 9 10-15-20 20 + 5 0 5 0 5 0 5 0 5 0 5" 670-6 66 \ > O 0 C 665-6 61 -660-6 56 -655-6 51 o 65O-6 46 645-6 1 1 41 1 2 3 4 5 6 7 8 9 10-15-20 20 56 below 650 fee t were numerous and periods of extended delay were recorded; however, i n 1946 there were no tags recovered from tagging i n the l e v e l s 650 - 646 and p r a c t i c a l l y none recovered between 645-641. I t was evident that whereas a bl o c k previous-l y occurred below 650 fee t before the fishways were i n s t a l l e d , the passage was almost completely c l e a r e d a f t e r the fishways were constructed. SUMMARY AND CONCLUSIONS Disc u s s i o n and i n v e s t i g a t i o n on the success of the upstream mig r a t i o n of ad u l t sockeye salmon w i t h i n the Fraser f i v e r watershed has been of v i t a l i n t e r e s t f o r at l e a s t the 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 years 1913 to 1915 but the extent t o which water l e v e l s acted as a major contfiol of the numbers of salmon reach-ing the various northern spawning grounds was not r e a l i z e d u n t i l 1941. As soon as the I n t e r n a t i o n a l P a c i f i c Salmon Com-mission became aware of the great l o s s e s of salmon at H e l l ' s Gate then a l l the evidence on the conditions at the Bridge R i v e r Rapids were reviewed ^thoroughly and a b i o l o g i c a l study was commenced at the Rapids i n 1942. The purpose^ of t h i s study was to determine the d i r e c t i n f l u e n c e of the Rapids on the current sockeye populations and to recommend such measures as to provide unobstructed passage.for salmon should blockade con-d i t i o n s be re v e a l e d . A program of tagging 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 repeated i n 1944 and the r e s u l t s reported f o r each of these years. I t was then thought t h a t 57 the delayed passage of salmon at H e l l ' s Gate might have been a f a c t o r m the c o n d i t i o n s at the Rapids; t h e r e f o r e , a t h i r d tagging program was conducted at the Rapids a f t e r the fishways at H e l l ' s Gate has been constructed. At the conclusion of the 1945 study, i t was apparent that d i f f i c u l t passage and block 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 at the Rapids and two fishways were recommended. A f t e r c a r e f u l c o n s i d e r a t i o n of the b i o l o g i -c a l and engineering r e p o r t s on the Rapids, the recommendations were approved^, and the two fishways constructed i n the s p r i n g " of 1946. A f o u r t h tagging experiment was conducted i n the summer of 1946, to t e s t the e f f e c l e n c y of the fishways. This paper presents the most p e r t i n e n t facfis r e v ealed by the analy-s i s of each of the four tagging experiments. The most important conclusions are o u t l i n e d below: A..-Before the fishways were constructed. (1) A review of the re p o r t s of J . P. Babcock i n d i c a t e d o that serious block c o n d i t i o n s e x i s t e d a t the Rapids as e a r l y as 1912. He s t a t e d that the sockeye e n t e r i n g Seton Creek l a t e i n the season were ba t t e r e d and wounded a f t e r being blocked at the Rapids. (2) The f a c t that no cohoe have yet been found i n the upper Fraser may be a t t r i b u t e d to block c o n d i t i o n s at the 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 the Seton Creek sock-eye population s t r o n g l y i n d i c a t e that block c o n d i t i o n s at the Rapids have been e f f e c t i v e f o r many years. (4) Figure 21 i n B u l l e t i n No.l of 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 that there are two main d i v -i s i o n s of sockeye runs w i t h i n the upper Fraser 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 before September 18 and goes to the Upper Fraser while the second d i v i s i o n passes the Gate a f t e r September 18 and goes to the Thompson d i s t r i c t * Thompson suggests that blocks during September and October, at the Bridge River, Rapids may have prevented the occurance of a f a l l run of sockeye i n the upper F r a s e r . (5) Block 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 the d a i l y catches above the Rapids became poor w h i l e f a i r catches, were s t i l l being made below. (6) A l o s s of sockeye f.r,omthe S t e l l a k o and C h l l k o runs was i n d i c a t e d i n 1942 and 1945. A f t e r the water l e v e l dropped below 650 f e e t , sockeye were s t i l l being tagged a t the Rapids u n t i l October 12 i n 1942 and October 5 i n 1945; y e t , none of the sockeye tagged a f t e r September 27 i n 1942 and September 12 i n 1945 were recovered from the spawning grounds.' A l o s s of the l a s t part of the C h l l k o run was i n d i c a t e d i n 1944; however only a small p o r t i o n of the run was e f f e c t e d . (7) . The percentage recovery of tags below the Rapids increased r a p i d l y i n 1942 and 1945 during water l e v e l s below 650 f e e t . Recoveries of tags above-.the Rapids showed a c o r r e s -ponding d e c l i n e during these same water l e v e l s ; , . (8) Less than 1% of the sockeye were delayed longer than 1 day when the water l e v e l s at the Rapids 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 delayed at l e a s t 1 day; however, only 5% of the f i s h were delayed from 2 to 4 days* (10) When the water l e v e l dropped below 650 f e e t , the recovery of tags below the Rapids increased to as h i g h as 34$ of a l l f i s h tagged. (11) During extended periods of block, sockeye tagged at the Rapids were recovered i n Seton arid Portage Greeks. ' (12) The numbers of tagged sockeye reaching the spawn-in g ground dropped to n e a r l y zero during the b l o c k periods of 1942 and 1945. (13) Fishvmys were recommended to provide passage f o r salmon during the low water p e r i o d . These were constructed by the Commission i n 1946. (14) A f t e r studying the m i g r a t i o n times from Hell*!s Gate to the Highway Bridge l o c a t e d 6 m i l e s below the Rapids, I t was concluded that the Rapids would act as a b a r r i e r to s a l -mon i r r e s p e c t i v e of a previous block at H e l l ' s Gate* B - A f t e r the Fjshways were constructed. (1) A f t e r the flshways at ths; Rapids were b u i l t f o r the salmon runs of 1946 i t was found that sockeye tagged dur i n g water l e v e l s below 650 f e e t were not recovered below* (2) Up to the l a s t day of tagging, sockeye were recover-ed on the northern spawning grounds* (3) Sockeye were known to have passed through the Rapids 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 665 - 656 f e e t a s l i g h t delay s t i l l remained; however, when only tags out more than 3 days were considered the number of 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 recovered below the Rapids from tagg-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 recovered be-tween 645-641* (6) From the sum of the 1946 a n a l y s i s i t was concluded that d i f f i c u l t passage above 650 feet was r e l i e v e d and previous block c o n d i t i o n s below 650 feet' were completely remedied a f t e r the fishways were constructed. i ACKNO WLEDGEMBNT3 The w r i t e r wishes to express h i s a p p r e c i a t i o n to Mr'. B. M. Brennan, D i r e c t o r of 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, f o r permission to use the m a t e r i a l con-t a i n e d i n t h i s paper and to Dr. R. Yan Cleve f o r h i s c r i t l s i m of the manuscript. I n a d d i t i o n , the author i s indebted to Dr. Wi A. Clemens f o r h i s encouragement and advice during the a n a l y s i s of the data* Sincere thanks are extended to Mr. R. I. Jackson f o r the development of the p l a t e s . LITERATURE CITED Babcock, J . P. 1913• The spawning beds of the Fr a s e r . Report of Commissioner of F i s h e r i e s f o r B r i t i s h Columbia. 1912, p.28. 1926. The spawning beds of the Fr a s e r . Report of Commissioner of F i s h e r i e s f o r B r i t i s h Columbia. 1925. p. 4 1 . B e l l , M. I945• P r e l i m i n a r y report on Bridge R i v e r Rapids remedial work, Fraser 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.. Manuscript. Canada. Department of F i s h e r i e s . • 1901 - 1946.. Various f i e l d r e p o r t s on f i l e at the Dominion F i s h e r i e s O f f i c e , New Westminster, B. C K i l l i c k , S. R. 1945* The o b s t r u c t i o n at the Bridge R i v e r Rapids. 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 tagging at 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 Report, 1943» p. 21-22. New Westminster, B.C., Talbot, G. B. 1948. A b i o l o g i c a l study of the e f f e c t i v e n e s s of the Hell's Gate fishways. 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. Thompson, W. F. 1945. E f f e c t of the o b s t r u c t i o n at H e l l ' s Gate on the sockeye salmon of the Fraser 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. . B u l l e t i n 1, 1945* P. 101-113. New Westminster, B.. C. 2. Tremper, H. S. 1940. Season's report for the Seton-Anderson watershed. , International Pacific Salmon Fisheries Commission. Manuscript. Water Levels at Bridge R i v e r Rapids - 1942 C a l c u l a t e d from. Jesmond Day J u l y August September October 1 666.6 661.5 649.5 646.2 2 667.0 660.9 649.3 646 ;0 3 667.3 660.5 649.2 645.8 4 668.0 659.8 648.8 645.6 5 669.1 659.4 648.5 646.0 6 670.0 658.9 648.1 647.4 7 670.1 658.7 648.1 647.1 8 670.1 658.9 647.9 646*9 9 669,7 658.9 649.0 647*4 10 670.0 658.7 649.3 648*3 11 668.0 658.7 649*8 649.2 12 667.3 658.7 649.8 650*1 13 666.8 658.4 649.5 650;0 14 666.4 658; 2 649.3 650 ;0 15 666.1 657.9 649.2 650.0 16 665.5 656;7 649.0 649.0 17 665.5 655.8 649; 5 648.1 18 667.0 655; 4 651.5 647.4 19 667.5 655.6 652.8 646.6 20 667.7 656.5 650*8 645.6 21 667.0 657.4 649*6 644.9 22 666.1 657.9 649.2 644.7 23 665.5 658.4 649.0 644.5 24 665.2 657.9 649*0 646 ;0 25 665 ;0 656.9 649.0 647.4 26 664.7 655.6 648; 7 647; 6 27 664.1 654.4 648.1 646*3 28 663.1 653;9 647.7 645*6 29 662.5 652.8 647.1 645.6 30 662.0 651.1 646.9 645.6 31 661.7 650.0 645*8 Water Levels at Bridge R i v e r Rapids -C a l c u l a t e d from Jesmond 1944 Day " J u l y August September October 1 661.-0 658.4 656,9 3 663.5 660.0 657*9 656.6 3 663.3 658;-8 656*8 655.4 4 663.0 657.3 656.6 655*3 5 662.6 656.7 655 *• 7 661.7 6 661.6 656.5 654*• 9 663*9 7 661.0 656*5 653*8 665.4 8 660.8 656*6 653*3 662*5 9 660*7 656.5 653.0 659*3 10 660*5 656.1 652.9 656.3 11 659.7 655*5 653 .-1 655*3 12 659*4 658.2 653.1 653.6 13 659*1 664.6 653.0 653.4 14 659.7 670.2 653.7 650*7 15 660*4 652;-7 649.9 16 660.7 670.1 653*1 649*7 17 660 i 5 667.6 654*0 648*9 18 661.4 664.9 655*1 648; 6 19 663;6 663,"7 655*3 648.3 20 662.1 663*8 654*3 647.8 21 661 il 662.6 654*1 647*3 22 660*8 663.4 653*8 647*0 23 660.8 661.-6 654*- 5 646*8 24 661*0 659.-7 653*1 646.8 25 661.0 658 .-4 653 s 7 647.3 26 663.3 657*0 653 i 2 647*4 27 665*4 656*'6 653 i 3 647*3 28 664.6 655; 9 659i6 647.0 29 663.2 657.0 659 .-7 646.5 30 661.9 657.-6 657 i8 646.0 31 661.4 657i6 645*5 Water L e v e l s at Bridge R i v e r Rapids 1945 C a l c u l a t e d from Jesmond Day J u l y August September October 1 . 658.0 652.6 642.3 2 668.4 657.8 642.2 3 667.3 656,4 651.1 642.5 4 666 07 655.2 650.2 642.7 5 667.0 649.7 642.9 6 666<j>2 651.1 649.1 7 665.2 655,2 648.6 642.7 8 655.0 649.1 642.8 9 663.6 655.6 647.1 10 663.3 656.0 649.4 11 663.2 656.1 650.5 648.2 12 663.1 650.4 649.4 13 663.2 656 j 7 650.9 14 663.8 656.3 650.4 15 655.9 650.4 647.0 16 663.8 655.5 646.8 17 663.9 655,4 649.0 646.5 18 663 „ 2 655.4 648.4 646.3 19 662.0 648.0 646,0 20 660 o8 654,6 647.4 646.1 21 659*8 653.8 647.8 22 653*8 646.6 645.4 23 659.4 653.3 644.3 24 658.2 652.0 645.6 644.1 25 658.5 651.1 645.3 643.6 26 659.1 651.3 644.5 642.4 27 658.8 651.4 643.6 642.3 28 658.1 651.6 643.3 641.9 29 652.6 643.0 641.7 30 658.2 653,2 641.4 1946 Water Levels - Gauge R, I Bridge R i v e r Rapids Day J u l y August September October 1 664.3 653.5 . 643.5 2 670.5 664.3 643.7 3 670* 1 652.5 642*4 4 669; 7 652.1 642.8 5 669.9 664*,5 651.9 642; 5 6 663.2 651.8 643.0 7 661.4 651.6 641.8 8 669.5 660 * . l 651.3 641.5 9 669.3 660*3 641.1 10 669.0 650.5 640*7 11 668.6 648.8 . 640,* 4 12 668.0 659.4 648,. 3 640; 2 13 ' 658.4 648.5 639; 9 14 658.9 639,. 8 15 668.0 658*9 640.1 16 668.7 658; 8 647.9 640.3 17 668.8 658.3 647.7 640.2 18 668.8 647.6 639*9 19 671*4 658.0 647.5 639*5 20 657 i'O 646*9 639.2 21 655.7 645.7 639.4 22 668.7 655*0 645.1 639.1 23 667.9 655*0 639.4 24 667.4 655.2 644^. 1 639.8 25 666.9 655.1 644.2 640.2 26 666.2 644.0 640.4 27 655.4 643.7 640.4 28 V--' <, '.. * vj 655.0 643.4 640-.8 29 664;2 654.6 643.4 640.4 30 664.1 654*2 640*0 31 664.3 653.6 640.7 P l a t e I I The upper f a l l s a t the Bridge R i v e r Rapids and the lower s e c t i o n of the upper fishway 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 at the Bridge R i v e r Rapids and the completed upper fishway. A p r i l 2 5 , 1946. v/ater l e v e l RI gauge - 647 f e e t . Plate IV General view of the lower and upper f a l l s at the Bridge R i v e r Rapids and the completed flshways. A p r i l 25, 1946. Water l e v e l RI gauge - 647 f e e t . 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0106970/manifest

Comment

Related Items