f:.a3- 





FiGTTRE 3. — Stationary louver used to estimate the number of juvenile salmon and rainbow trout migrating 



into Brownlee Reservoir from Eagle Creek. 



pling site to determine trapping efficiencies of the 

 louver. Fish to be stained could be held in the 

 cooler waters of Eagle Creek with little difficulty, 

 whereas they could not be kept alive for sufficient 

 time to stain them in the warmer waters of the 

 Snake River. We obtained test fish mainly from 

 irrigation bypass traps and fyke nets located sev- 

 eral kilometers ui>stream. "Wlien sufficient numbers 

 of migrating fish were not availalble from these 

 sources, we used fingerlings captured at the louver. 

 Periodically, groups of migrants from Eagle 

 Creek were marked by fin-clipping, jaw tags, or 

 plastic thread tags - for identification in the 

 reservoir. 



DOWNSTREAM MOVEMENT, AGE, 

 LENGTH, AND TIME OF ENTRY INTO 

 THE RESERVOIR OF JUVENILE SALM- 

 ON AND TROUT 



The characteristics of the migrations into 

 Brownlee Reservoir were determined from catches 



= Developed by the Fish Commission of Oregon. 



at the sampling sites. Timing and peaks of runs 

 are expressed as weekly percentages of the esti- 

 mated numbers of fish in the migrations. About 10 

 percent of each daily catch was examined for data 

 on length and age. 



MIGRATIONS OF WILD SALMON AND TROUT 



Migrations of wild chinook salmon and steel- 

 head trout juveniles entered tlie reservoir from 

 three tributaries. Fall chinook entered from the 

 Snake River, whereas spring chinook and steelhead 

 entered from Eagle Creek and Weiser River. 



Fall Chinook Salmon 



The movement of juvenile fall chinook salmon 

 fi-oni the Snake River to Brownlee Reservoir be- 

 gan about mid-Ai^ril and peaked in mid-May in 

 1962 and 1963 (fig. 4). About 75 i^ercent of the 

 migration took place during a 2-week period, and 

 nearly all of the fish liad migrated by mid-June. 

 Principal movement was between sunrise and 

 10 a.m. and from 3 to 7 p.m. 



206 



U.S. FISH AND WILDLIFE SERVICE 



