decline in survival rate for summer and fall, 

 partially offset by an increase in spring survival 

 rate. 



Close observation of the annual abun- 

 dance curve, figure 4, reveals a decline no 

 more rapid after Bonneville Dam than before. 

 The decline appears to be fairly constant through- 

 out the 27 years. Observing the seasonal 

 abundance curves: the spring season has im- 

 proved since 1938; the summer abundance curve 

 fell previous to Bonneville Dam and continued 

 at a low level for a few years, then recovered 

 noticeably; the fall abundance curve looked 

 promising up to 1948, 10 years after Bonneville 

 Dam, and then declined rapidly. 



Briefly, the conclusions found in this 

 study are the following: 



(1) A 14 percent increase in spring 

 returns averaging one -half million pounds 

 per year after Bonneville Dam . 



(2) A 70 percent drop in summer re- 

 turns averaging 3-1/2 million pounds 

 per year. 



(3) The 1949 to 1954 fall run failures 

 balancing the previously upswinging fall 

 returns at 14 million pounds per year 

 before and after Bonneville Dam . 



(4) Average decline in total run of 13 

 percent or 3 million pounds after Bonne- 

 ville Dam . 



(5) Return-to-escapemement ratios 

 for spring, summer, fall, and annual 

 being2.3, 4.4, 4.3, and 3.8:1 before 

 Bonneville Dam and 2.6, 2.7, 3.2, and 

 3.0:1 after in that order. 



(6) An improved spring return -escape- 

 ment ratio and declining summer and fall 

 return -escapement ratios after Bonneville 

 Dam presented evidence that success cor- 

 responded with larger proportion of 

 spawning occurring below the dam . 



(7) The abundance curves represent- 

 ing 27 years of Columbia River chinook 

 salmon returns (figure 4) reveal no special 

 decline in trend after the construction date 

 of Bonneville Dam . 



21 



LITERATURE CITED 



Baranov, F. I. 

 1918. 



On the question of the biological 

 basis of fisheries. U.S.S.R. 

 Bui. Dept. Fish and Sci. Indust. 

 Inv., Vol. 1, pp. 81-128, 12 

 figs. 



Craig, J. A., and R. S. Hacker 



1940. The history and development of 



the fisheries of the Columbia 

 River. U.S. Bur. Fish. Bull. 

 No. 32 (Vol. 49), pp. 133-216. 

 27 tables, 15 figs. 



Johnson, D.R., W.M. Chapman and 

 R. W. Schoning 

 1948. The effects on salmon popula- 



tions of the partial elimination 

 of fixed fishing gear on the 

 Columbia River in 1935. Oregon 

 Fish. Comm. ContributionNo.il, 

 32 pp., 18 tables, 8 figs. 



Pacific Fisherman Yearbooks, Consolidated 

 Publishing Co., 71 Columbia Street, 

 Seattle, Washington 

 1929-1955 Columbia River salmon reports. 



Ricker, W. 

 1940. 



1944. 



Silliman, R. 

 1950. 



Relationship of "catch per unit 

 of effort" to abundance and rate 

 of exploitation . Jour. Fish. Res. 

 Bd. Canada, Vol. 1, pp. 43-70, 

 4 tables, 3 figs. 



Further notes on fishing mortality 

 and effort. COPEIA, 1944, No. 1, 

 pp. 23-44, 2 tables, 1 fig. 



Fluctuations in abundance of 

 Columbia River chinook salmon 

 ( Oncorhynchus tschawytscha ) 

 1935-1945. U. S. Fish and 

 Wildlife Service Fishery Bulletin 

 No. 51, 19 pp., 16 tables, 

 11 figs. 



IWT.-DUP. SEC, WASH.. D.C. 



20878 



