MIGRATION OF JUVENILE SALMON AND TROUT INTO BROWNLEE 



RESERVOIR, 1962-65 



BY RICHARD F. KRCMA AND ROBERT F. RALEIGH, FISHERY BIOLOGISTS 



BUREAU OF COMMERCIAL FISHERIES BIOLOGICAL LABORATORY 



SEATTLE, WASH. 98102 



ABSTRACT 



Migrations of juvenile chinook salmon (Oncorhynchus 

 tshawytscha), coho salmon (O. kisutch), sockeye and 

 kokanee salmon (O. nerka), and rainbow trout {Salmo 

 gairdneri) from the Snake and Weiser Rivers and from 

 Eagle Creek were studied. Populations of fish were 

 sampled with floating traps above the reservoir and a 



fixed louver trap in Eagle Creek near the lower end of 

 Brownlee Reservoir. Age and length of fish, timing of 

 migration, and numbers of fish of native or hatchery 

 origin were determined. This information was needed to 

 evaluate the effect of Brownlee Reservoir on migrations 

 of anadromous fish. 



Brownlee Reservoir was created when a high- 

 head hydroelectric dam was built in 1958 at the 

 upstream end of Hells Canyon on the Snake River. 

 The 92-km. long reservoir forms part of the 

 boundary between Idaho and Oregon. At full pool, 

 it is 92 m. deep and less than 1 km. wide ; the upper 

 end (22 km.) is relatively shallow and essentially 

 riverine. 



BCF (Bureau of Commercial Fisheries) chose 

 Brownlee Reservoir for an extensive research pro- 

 gram to determine how a large impoundment af- 

 fects the i:)assage of salmon and trout. The re- 

 search, begun in the spring of 1962, comprised five 

 studies: (1) limnology' of the reservoir system 

 (Ebel and Koski, 1968), (2) upstream migration 

 of adult chinook salmon {OncorhyiifiMis tshawi/fx- 

 rha) througli the reservoir (Trefethen and 

 Sutiierland, 1968), (8) migration of juvenile 

 salmon and trout into the reservoir (this report), 

 (4) distribution and movement of juvenile salmon 

 in the reservoir (Durkin, Park, and Raleigh, 

 1970), and (5) migration of juvenile salmon and 

 trout from the reservoir (Sims, 1970). 



Three major streams — the Snake, Burnt, and 

 Powder Rivers — and more than a dozen minor 

 streams, most of which have intermittent flows, 

 are tributaries to Brownlee Reservoir. Previous 

 investigations had shown that most of the streams 

 supported local populations of rainbow trout 

 {Salmo gairdneri) , but chinook salmon and stcel- 



Publlshed April 1970. 



FISHERY BULLETIN: VOL. 68, NO. 2 



head trout (the anadromous form of rainbow 

 trout) sjDaAvned in only three of the streams. 

 Spring- and fall-migrating steelhead trout and 

 spring-migrating chinook salmon spawned in 

 Eagle Creek, a tributary of the Powder Ri\"er, and 

 in the Weiser River, a tributary of the Snake 

 River (fig. 1). Fall-migrating chinook salmon 

 spawned in the Snake River about 257 km. above 

 the dam. 



Wild (native) salmon and trout fingerlings en- 

 tered the reservoir during each year of study 

 (1962-65). From 1963 on, most of the chinook 

 salmon spawners were diverted to a hatchery. In 

 1964 and 1965, therefore, hatchei-y-reared progeny 

 of fall chinook salmon from the lower Cohunbia 

 Ri\er were released in the Snake River spawning 

 area above the reservoir. Wo wislied to study the 

 etfect of a large impoundment on other species of 

 salmon, so yearling cojio (O. kisutch) from the 

 lower Columbia River and sockeye salmon {O. 

 nerka) from the Skeena River were included in 

 the hatchery releases in 1964 and 1965, respec- 

 tively. In 196.3, 1964, and 1965, migi-ations of wild 

 kokanee {0. nerka) entered the reservoir from the 

 Payette River system. 



Tliis report provides estimates of age and 

 length of fish from each population at the time of 

 entry into the reservoir, time and duration of 

 downstream migrations, and numbers of fish of 

 native and hatchery origin for 1962 through 1965. 



203 



