MIGRATION RATE 



1.8 KM. PER OAY- 



-0.9 KM. PER DAY- 



WATER LEVEL V 



OUTFLOW 



20 

 MAY 



20 

 JUNE 



1,500 



i 

 c 



 1,000 1 

 i 



500 



30 



FiouBE 18. — Rate of downstream movemenit of tagged hatchery-reared echo salmon in 

 relation to water level and outflow in Brownlee Reservoir, April 1 to June 30, 1964. 



These fish moved rapidly downstream after re- 

 lease. The first sockeye salmon were captured in 

 the reservoir on March 17^ — 2 days after the initial 

 release. Catches above the reservoir reached a peak 

 during the first week of April and below the reser- 

 voir the following week. During the ensuing 2 

 months, 44 sockeye salmon were recaptured at Ice 

 Harbor Dam and two at Bonneville Dam. The 

 capture of fish in gill nets in the reservoir indi- 

 cated that the fish moved consistently downreser- 

 voir. No sockeye salmon were observed in the 

 Powder River Arm, and no delay within the reser- 

 voir was evident. 



The average daily rate of movement for 117 

 tagged sockeye salmon that moved toward the out- 

 let was 5.2 km./day. On the basis of this rate and 

 the length of the reservoir (45-50 km.) in late 

 March and early April, sockeye salmon required 

 an average of about 8 or 9 days to move through 

 the reservoir. 



Most sockeye salmon were captured within 4.5 m. 

 of the surface, some were between 4.5 and 13.5 m., 

 and a few were taken as deep as 22.5 m. (table 5). 



Data on catch per unit of effort at three gill net 

 stations indicated that the vertical distribution 

 was similar throughout the reservoir. 



Sockeye salmon were captured near shore and 

 offshore in the upper reservoir. In the lower reser- 

 voir they were captured almost exclusively off- 

 shore. The recovery of tagged sockeye salmon 

 indicated that fish tagged near the shore even- 

 tually moved to the open water, whereas those 

 tagged offshore remained offshore. 



During the migration period from March 

 through mid-May 1965, the environment was 

 favorable for fish passage. Dissolved oxygen con- 

 centrations were 6 to 11 p.p.m. until early May, 

 and temperatures ranged from about 5° C. in late 

 March to 15° C. in late April. The reservoir level 

 was 24 to 30 m. below full pool through mid-May, 

 and its length was reduced to about 45 km. Spill 

 discharge at Brownlee Dam was continuous, rang- 

 ing from a weekly average of 424.5 to 1,440.3 c.m.s. 

 Current monitors, operated by persomiel studying 

 the limnology of the reservoir, revealed that sur- 

 face currents were oriented toward the outlet. Ac- 



Table 5. — Depth distribution of sockeye salmon yearlings as indicated by the catch per gill net day at different depths in Brownlee 



Reservoir, March 17 to April 26, 1965 • 



Depth 



MUel 



MUe24 



M 



.<1.4 



1.6- 4.1 



4.2-13.7 



13.8-18.3 



18.4-22.9 - 



23.0-27.6 



'Mesh sizes used were 1.9, 2.6, 3.1, and 3.8 cm. stretched mesh. 

 JUVENILE SALMON DISTRIBUTION AND MOVEMENT IN BROWI>rLEE RESERVOIR 



241 



