Dam was estimated to be 16.8 percent of the 

 total run during the period of our 1955 experi- 

 ment (June 21 through July 10). 



6. If a substantial proportion of the fish died 

 after they were counted (by being swept back over 

 the spillway) and if a substantial number of these 

 carcasses were mutilated and rendered unrecover- 

 able, actual mortality was substantially higher 

 than our estimate. 



7. Our experiment probably included the period 

 of maximum mortality in 1955. 



8. The numbers of floating carcasses are related 

 to the amount of flow of the Columbia River. 

 The mortality of salmon is highest when flows 

 exceed 7,000 c.m.s. 



9. Fall Chinook salmon runs have never been 

 subjected to flows above 7,000 c.m.s. (killing 

 flows); spring runs were exposed to such flows in 

 some years; and summer runs nearly always en- 

 countered such flows. 



10. Water temperature, turbidity, disease, and 

 injuries from gill nets had little influence on the 

 number of carcasses in the river. 



11. The specific causes of death and the pre- 

 cise areas at Bonneville Dam where death oc- 

 curred were undetermined, but the major source 

 of chinook salmon mortality is associated with 

 the spillway during high flows. 



12. We did not consider nitrogen poisoning 

 resulting from high flow turbulence as a possible 

 cause of mortality at the time of our experiment, 

 but evidence subsequently developed by other 

 investigators indicates that this may be a major 

 specific mortality factor. 



ACKNOWLEDGMENTS 



Fred C. Cleaver, formerly Assistant Director 

 of the Oregon Fish Commission, contributed 

 greatly to the planning and analysis. Ivan J. 

 Donaldson, Resident Biologist, U.S. Army Corps 

 of Engineers, Bonneville Dam, helped release 

 tagged experimental fish and provided information 

 on mortalities of previous years. 



John A. Dudman, Associate Professor of Mathe- 

 matics at Reed College, and Richard F. Link, 

 Assistant Professor of Statistics and Mathematics 

 at Oregon State College, provided technical as- 

 sistance in the early stages of the statistical 

 analyses. 



Lee Motley, operator of Beacon Rock Moorage, 

 supplied information on the use of salmon car- 



casses by fishermen for sturgeon bait. Finally, 

 Edward M. Wood, former pathologist of the U.S. 

 Fish and Wildlife Service, performed the histo- 

 logical examinations of freshly killed salmon to 

 determine causes of death. 



LITERATURE CITED 



Ebel, Wesley J. 



1969. Supersaturation of nitrogen in the Columbia 

 River and its effect on salmon and steelhead trout. 

 U.S. Fish Wildl. Serv., Fish. Bull. 68: 1-11. 

 Hanson, Harry W., Paul D. Zimmer, and Ivan J. 

 Donaldson. 



1950. Injured and dead fish in the vicinity of Bonne- 

 ville Dam. [U.S.] Fish Wildl. Serv., Spec. Sci. Rep. 

 Fish. 29, 41 pp. 

 Jackson, R. I. 



1950. Variations in flow patterns at Hell's Gate and 

 their relationships to the migration of sockeye salmon. 

 Int. Pac. Salmon Fish. Comm., Bull. .3: 81-129. 

 JuNGE, Charles O., Jr., and Lloyd A. Phinney. 



1963. Factors influencing the return of fall chinook 

 salmon (Oncorhynchus tshawytscha) to Spring Creek 

 Hatchery. U.S. Fish Wildl. Serv., Spec. Sci. Rep. 

 Fish. 445, iv + 32 pp. 

 Paulik, G. J., and D. S. RoBSON. 



1969. Statistical calculations for change-in-ratio esti- 

 mators of population parameters. J. Wildl. Manage. 

 33: 1-27. 

 Pearson, E. S., and H. 0. Hartley (Editors). 



1966. Biometrika tables for statisticians. Vol. 1. 

 3d ed. Cambridge Univ. Press, New York, 263 pp. 

 ScHONiNG, Robert W., and Donald R. Johnson. 



1956. A measured delay in the migration of adult 

 chinook salmon at Bonneville Dam on the Columbia 

 River. Oreg. Fish Comm., Contrib. 23, 16 pp. 

 Talbot, G. B. 



1950. A biological study of the effectiveness of the 

 Hell's Gate fishways. Int. Pac. Salmon Fish. 

 Comm., Bull. 3: 1-80. 

 Thompson, William F. 



1945. Effect of the obstruction at Hell's Gate on the 

 sockeye salmon of the Eraser River. Int. Pac. 

 Salmon Fish. Comm., Bull. 1, 175 pp. 

 U.S. Army, Corps of Engineers. 



1943-56. Annual fish passage report, North Pacific 

 Division, Bonneville, The Dalles, and McNary 

 Dams, Columbia River, Oregon and Washington, 

 1943-56. Prepared by the U.S. Army Engineer 

 Districts, Portland and Walla Walla, Corps of En- 

 gineers, Portland, Oreg. [Each year published 

 separately.'! 



APPENDIX 



EXPERIMENTS ON FLOATING QUALITIES OF 

 CHINOOK SALMON CARCASSES 



This appendix describes experiments designed 

 to test two key assumptions: (1) that experi- 



CHINOOK SALMON MORTALITY IN COLUMBIA RIVER NEAR BONNEVILLE DAM 



489 



