40 



X 



u 

 ^ 30 



UJ 



o 20 



t- 

 z 



UJ 



o 

 q: 



10 



1962 CATCH 



D CATCHES ABOVE THE RESERVOIR 



 CATCHES IN UPPER RESERVOIR TRAPS 



Q CATCHES IN FOREBAY BY SKIMMER NET TRAPS 



Jl 



I 



1963 CATCH 



(56) 



40 



I 

 o 



o 



Ul 



30 



o 20 



IT 

 UJ 

 Q. 



10 



I 



I 



2 3 

 APRIL 



PlOUBE 



512 34 123 412345 

 MAY JUNE JULY 



12. — Oatehes of naibLve juvenile fall chinook salmon in the upper reservoir and at Brownlee Dam, 1962-63. 



Trap and surface trawl catches in 1963 indicated 

 tliat most of the migrants were remaining in the 

 upper reservoir. They were in the Snake River 

 water mass upstreajn from the point where the 

 colder river water sank below the reservoir surface 

 (Ebel and Koski, 1968; Raleigh and Ebel, 1967). 

 Gill net sampling showed the fish were near the 

 surface of the reservoir through mid-June. By late 

 June, however, they were captured at all depths. 

 At this time the river water began to warm and 

 mix with the reservoir water mass; the convergence 

 line disintegrated, and the juvenile fish began to 

 move through the reservoir. Peak catches by traps 



in the upper reservoir and at Brownlee Dam 

 showed that after the initial 5-week delay the fiSh 

 migrated through the reservoir in about 2 weeks 

 (fig. 12). 



In 1963, the capture of a number of large finger- 

 lings in the Snake River above the impoundment 

 indicated a pronounced upreservoir movement of 

 young fall chinook salmon (Krcma and Raleigh, 

 1970). Growth patterns on the scales ^owed that 

 these fish had lived in the reservoir. The identifica- 

 tion of marked fish indicated that most of the fish 

 that moved upstream had migrated from Eagle 

 Creek and the Snake River in the spring of 1963. 



JUVENILE SALMON DISTRIBUTION AND MOVEMENT IN BEOWNLEB RESERVOIR 



233 



