Table 10. — Estimates of juvenile salmon that entered 

 Brownlee Reservoir from the Snake River system, 1962-65 



the reservoir, and coho salmon the lowest. Sur- 

 vivals from release point to reservoir were in- 

 versely coiTelated with time spent in the river but 

 not to distance traveled (table 11) . 



Table 11. — Time in river and survival of hatchery fish from 

 release site to Brownlee Reservoir, 1964 and 1965 



Weeks Number Number 



1961 (Coho 



120 km. (Chinook. 



1965 (Chinook. 

 88 km.. (Sockeye.. 



Mar. 

 Apr. 

 Mar. 

 Mar. 



Mid-May.. 



Mid-May.. 

 Mid-May.. 

 Early 

 AprU. 



375,000 

 250,000 

 592,000 

 473,000 



69,000 

 111,500 

 162, 800 

 360,000 



Per- 

 cent 

 18.4 

 44.6 

 27.5 

 76.1 



EAGLE CREEK 



Estimates of migi-ation from Eagle Creek were 

 based on average efficiencies of the louver facility 

 throughout the year (table 12). In 1962, the aver- 

 age efficiency was 10.2 percent but the louver was 

 selective for larger fish. Alteration of the structure 

 in 1963 increased the efficiency to 57.5 percent and 

 eliminated selectivity. Straightening of the river 

 channel above the louver in 1964 pro\-ided a 

 straighter angle of approach for the current and 

 further increased the efficiency of the louvers to 

 91.3 percent during the fall migration. In the 

 spring of 1965, efficiency was less (85.2 percent) 

 as a result of ice and high flows, which created 

 currents that varied in velocity and direction of 

 approach across the face of the louver. 



Juvenile fish that entered the reservoir from 

 Eagle Creek in 1962-63 (table 13) were progeny 

 of native adults that were transported around 



Brownlee Dam in 1960-62. Thereafter natural 

 production in the creek declined markedly because 

 the policy of passing fish changed. Juvenile mi- 

 grants in 1964-65 were primarily from adults that 

 were surplus to hatchery needs and werB trans- 

 ported from a collection facility at Oxbow Dam 

 ( 19 km. downstream from Bro%vnlee Dam) tx> 

 liolding ponds near the spawning area. Prespawn- 

 ing fish were held in these ponds imtil nearly 

 mature and then released into Eagle Creek. 



T.4.BLE 12. — Collection efficiencies of the louver system at 

 Eagle Creek, 1962-65 



Efficiency of collection 

 by period of migration 



Year 



Spring Fall 



Percent Percent 



1962 10.2 



1963 14.7 57.5 



1964 42.0 91.3 



1965 85.2 (1) 



' Not in operation. 



Table 13. — Estimates of juvenile spring chinook salmon 

 that entered Brownlee Reservoir from Eagle Creek, 1962-65 



Estimated recruitment by season 

 and age-group 



Year of migration Total 



Spring migration Fall migration 



I II I 



1962 (1) (I) (1) 116,000 1,200 117,200 



1963 600 13,600 (?) 7,500 (!) 22,300 



1964.. (2) 6,700 (!) (2) (2) 7,200 



1966 (!) (!) (!) (I) (I) 



' Not in operation. ! Negligible numbers. 



SUMMARY AND CONCLUSIONS 



Movements of juvenile salmon and rainbow 

 trout from tributary streams into Brownlee Reser- 

 voir were examined in 1962-65 as part of a study 

 on the effect of a large impoundment on the mi- 

 gration and survival of anadromous fish. Esti- 

 mated numbers of migrant juvenile salmon were 

 determined by sampling of juvenile fish popula- 

 tions that were en route to the reservoir from the 

 Snake and Wei.ser Rivers and Eagle Creek, the 

 three tributaries supporting indigenous popula- 

 tions of salmon and anadromous rainbow trout. 

 Juvenile fall and spring chinook salmon, kokanee 

 salmon, and rainbow trout entered the upper reser- 

 \'oir ^-ia the Snake River. Hatchery-reared fall 



JUVENILE SALMON AND TROUT MIGRATION INTO BROWNLEE RESERVOIR 



215 



