SUMMARY AND CONCLUSIONS 



Estimates of emigration of juvenile salmon and 

 trout from Brownlee Reservoir from July 1963 

 through August 1965 were based on catches in 

 floating scoop traps below Brownlee Dam and on 

 estimates of efficiency of the traps. 



Emigration of native fall chinook salmon of the 

 Snake River was estimated at 15 percent of im- 

 migration into the Reservoir in 1963 (1963 year 

 class). Hatchery-reared fall chinook salmon (age- 

 group 0) were planted in the Snake River in 1964 

 and 1965. Estimates of emigration were 85 percent 

 of immigration in 1964 and 100 percent in 1965. 



Emigration of native spring chinook salmon 

 (Eagle Creek and the Weiser River) was estimated 

 at 16 percent of immigration in 1964 and at 51 

 percent in 1965. 



Emigration of native kokanee of the Snake River 

 system was estimated at 38 percent of immigration 

 in 1964 and at 10 percent in 1965. 



Hatchery-reared coho and sockeye salmon were 

 planted in the Snake River in 1964 and 1965, re- 

 spectively. An estimated 75 percent of the coho 

 salmon (1963 year class) that entered the reservoir 

 in 1964 passed through. Emigration of sockeye 

 salmon (1964 year class) in 1965 was estimated at 

 100 percent of immigration. 



Because anadromous rainbow trout (steelhead) 

 could not be separated from populations of native 

 and hatchery-reared resident rainbow trout, I did 

 not compare emigrations and immigrations. About 

 24,800 rainbow trout left the reservoir from August 

 1963 through December 1964. Emigration was 

 estimated at 73,600 fish in 1965. 



The environment in the reservoir during the 

 time of outmigration clearly affected success of 

 passage. In general, fish that entered the reservoir 

 early in the spring, when the reservoir was drawn 

 down and water temperature and oxygen concen- 

 trations were favorable, passed through more suc- 

 cessfully than did those that entered during the 

 summer, when water temperatures were high, cur- 

 rents were weak, and concentrations of oxygen 

 were low. 



The fish of the various stocks that emigrated 

 from Brownlee Reservoir showed a general increase" \ 

 in length as the season progressed. 



The following general conclusions were reached : 



1. Downstream migrants that entered the 

 reservoir early in the season passed through 

 more successfully than those that entered 

 later. 



2. Emigration was more successful when the 

 reservoir level was low during the time of 

 migration than when the reservoir was 

 filled before completion of the migration. 



3. Because of time of emigration, size of the 

 fish at time of entry into the reservoir, and 

 the shorter distance traveled by the fish, 

 one would expect what happened : Progeny 

 of native spring chinook salmon migrated 

 through the reservoir more successfully 

 than native fall chinook salmon. 



LITERATURE CITED 



Chapman, D. G. 



1948. Problems in enumeration of populations of 

 spawning sockeye salmon. 2. A mathematical 

 study of confidence limits of salmon populations 

 calculated from sample tag ratios. Int. Pac. Salmon 

 Fish. Comm., Bull. 2: 67-85. 

 DiTRKiN, Joseph T., Donn L. Park, and Robert F. 

 Raleioh. 



1970. Distribution and movement of juvenile salmon 

 in Brownlee Reservoir, 1962-65. U.S. Fish WUdl. 

 Serv., Fish. BuU. 68: 219-243. 

 Ebel, Weslet J., and Charles H. Koski. 



1968. Physical and chemical limnology of Brownlee 

 Reservoir, 1962-64. U.S. Fish Wildl. Serv., Fish. 

 BuU. 67: 295-335. 

 Krcma, Richard F., and Robert F. Raleigh. 



1970. Migration of juvenile salmon and trout into 

 Brownlee Reservoir, 1962-65. U.S. Fish Wildl. 

 Serv., Fish. BuU. 68: 203-217. 

 SouLE, G. B., T. R. Heiees, W. B. Mitchell, and 

 O. F. Schaufelberqer. 



1959. Design, construction, and operation of Brown- 

 lee Hydroelectric Development. Trans. Amer. 

 Inst. Elec. Eng., Pap. 59-921: 1-18. 

 Trefethen, Parker S., and Dotle F. Sutherland. 



1968. Passage of adult chinook salmon through 

 Brownlee Reservoir, 1960-62. U.S. Fish WUdl. 

 Serv., Fish. BuU. 67: 35-45. 

 Wilkes, S. S. 



7^^j^48. Elementary statistical analysis. I*rinceton 

 ^s^'OUniversity Press, Princeton, N.J., 284 pp. 



JUVBINILE SALMON AND TROUT EMIGRATION FROM BROWNLEE RESERVOIR 



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