COHO SALMON OF AGE-GROUP I 



Of 375,000 juvenile coho salmon released in the 

 Snake River 120 kin. above the reservoir from 

 March 15 to 30, 1964, an estimated 69,000 entered 

 the reservoir (Krcma and Raleigli, 1970). Early 

 in the migration these fish averaged 112 mm. long; 

 by the end they averaged 131 mm. 



On the basis of peak catches at the Snake River 

 trapping site above the reservoir and at the dam, 

 passage time through the reservoir was 2 weeks 

 (fig. 17). The reservoir was only 64 km. long at 

 the beginning of the migration as a result of a 

 13.5-m. drawdown ; the distance between the reser- 

 voir and the trapping site in the river was about 

 35 km. 



Recapture data from 26 tagged fish indicated 

 that the rate of movement changed during the 

 migration (fig. 18). Before May 20 when the res- 

 ervoir was drawn down about 13 m. and the out- 

 flow volume was large (about 850 c.m.s.), 17 

 tagged migrants averaged 1.8 km./day. As the 

 outflow was curtailed and the reservoir began to 

 fill, the migration i-ate of nine tagged fish then 

 dropped to 0.9 km./day. At this time the propor- 



tion of fish moving upreservoir also appeared to 

 increase. 



In early May most coho salmon were near the 

 surface in the upper reservoir, but by the end of 

 the month most had shifted to the vicinity of the 

 dam at greater depths. As the migration rate 

 slowed in late May and recruitment from the 

 Snake River continued, catches were again good 

 in the upper reservoir. In July the greatest con- 

 centration appeared to be in midreservoir at 

 depths of 18 to 31 m. Catches declined through 

 July, and only a few fish were captured thereafter. 



SOCKEYE SALMON OF AGE-GROUP I 



In 1965, 473,000 yearling sockeye salmon were 

 released in the Snake River, 88 km. aJbove Brown- 

 lee Resei-voir. Krcma and Raleigh (1970) esti- 

 mated that 360,000 had entered the reservoir. The 

 salmon were from Babine Lake, British Ck}liunbia 

 and reared to yeai"ling stage at the Leavenworth 

 National Hatchery, Wash. The left ventral fin 

 was clipped on all fish. Migrants in March aver- 

 aged 121 mm. ; later migrants averaged 130 mm. 

 by mid-May. 



35 

 30 

 25 

 20 

 15 

 10 

 5 5 



S 



fe45 

 ^40 

 z 35 



UJ 



o 

 a: 30 



UJ 



■^25 



20 



15 



10 



5 







MIGRANT DIPPER TRAP CATCHES IN THE 

 SNAKE RIVER ABOVE THE RESERVOIR 



SCOOP TRAP CATCHES BELOW THE DAM 



-18 19-25 26-2 3-9 10-16 17-23 24-30 31-6 7-13 14-20 21-27 28-4 5-11 12-18 19-25 26-1 2-8 9-15 16-22 

 APRIL MAY JUNE JULY AUGUST 



FiouBE 17.— Weekly cafjches of juvenile hateheiy-reared coho salmaa above Brownlee Reservoir and below Brownlee 



Dam, 1964. 



240 



U.S. FISH AND WILDLIFE SEBVICK 



