PASSAGE OF ADULT CHINOOK SALMON 

 THROUGH BROWNLEE RESERVOIR, 1960-62 



By Parker S. Trefethen and Doyle F. Sutherland, Fishery Biologists 

 Bureau of Commercial Fisheries Biological Laboratory 

 Seattle, Washington 98102 



ABSTRACT 



Adult chinook !-uliiion iOncorhynchus tshaujytscha) 

 were tagged and released in Brownlee Heservoir and up- 

 stream in the Snake Hivertodelerniine if adjiltscoidd pass 

 through the reservoir and reaeh spawning grounds. 

 Experiments with Petersen disk tags were performed hv 

 the Idaho Fish and Game Department in 19()()-61 and by 

 the Department and the Bureau of Coniniereial Fish- 

 eries in 1962. In a<hlition, the Bureau marked salmon 

 with sonic tags in 1961-()2 to trace orientation an<l 

 movement. Information was also obtained on the use of 

 tributary streams for spawning and success of spawn- 

 ing. 



Fish marked with Petersen disk tags and released in 

 the 92.5-km.-long reservoir reached their spawning area 

 as successfully as those transported above the impound- 



ment and released in the river. Fish released during 

 periojls of constantly high water temperature in 1961-62 

 suffered losses, which may have been caused by stress 

 during tagging. Some salmon with sonic tags were 

 inilially disoriented when released in the reservoir; 

 those released in the river above the impoundment 

 cjuickly oriented to the flow and resumed migration 

 upstream. 



Subpopulations of spring- and fall-rini chinook 

 salmon eontinue<l to use ancestral spawning areas in 

 streams tributary to the impoundment after it was 

 formed in 1958. No differences were noted between 

 percentages of totally spent fall-run fish on the spawn- 

 ing grounds in the years before and after Brownlee 

 Reservoir was filled. 



Knowledge of the effect of impoundments on 

 upstream migration is needed to plan the pas- 

 sage of adult salmon (Oncorhynchus spp.) and 

 steelhead trout {Salmo gairdneri) at high 

 dams. If mortality is high in the reservoir, or 

 if delays or other factors associated with pas- 

 sage impair the ability of survivors to spawn, 

 the fish may have to be transported around the 

 impoundment. Transportation could prove diffi- 

 cult if spawners bound for several tributaries 

 were intermingled below the dam. Subpopula- 

 tions would then have to be separated before 

 their release into respective tributaries — a dif- 

 ficult or impossible task. On the other hand, 

 if anadromous fish can migrate up through the 



Published July 1968. 



FISHERY BULLETIN: VOL. 67, NO. 1 



impoundment and spawn successfully, they can 

 be passed directly to the forebay of the dam to 

 continue their natural migration upstream. 



Neither Brownlee Dam nor Oxbow Dam, 

 which is 19.3 km. downriver from Brownlee, 

 has a fishway leading up to its impoundment. 

 Migrating adults enter a collection facility at 

 Oxbow Dam where they are trapped and trans- 

 ferred to a tank truck ; they are then trans- 

 ported 23.3 km., to a point 4.0 km. above 

 Brownlee Dam, and released into Brownlee 

 Reservoir to resume their migration. Release 

 of fish in the reservoir was discontinued 

 after these studies were completed ; all fish were 

 transported to hatcheries for artificial propa- 



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