TRANSPORTATION OF CHINOOK SALMON, ONCORHYNCHUS 

 TSHAWYTSCHA, AND STEELHEAD, SALMO GAIRDNERI, SMOLTS IN 

 THE COLUMBIA RIVER AND EFFECTS ON ADULT RETURNS 



Wesley J. Ebel^ 



ABSTRACT 



Chinook salmon, Oncorhynchus tshawytscha , and steelhead, Salmo gairdneri, were captured at Little 

 Goose Dam in the Snake River during their seaward migration and transported 400 km downstream to 

 the lower Columbia River below Bonneville Dam. Their survival was increased from 1.1 to 15 times as 

 compared with control fish which passed by seven mainstem low-level dams and reservoirs. Variations in 

 survival were mainly dependent on species and environmental conditions in the river during the period 

 fish were transported. 



The homing ability of the adult fish was not significantly diminished; less than 0.2% of strays occurred 

 among adult returns from groups transported. Transportation did not affect ocean age or size of returning 

 adult steelhead, but ocean age of returning adult chinook salmon may have been affected. Steelhead 

 returned to Little Goose Dam at a substantially higher rate (1.4-2. 7% I than chinook salmon (0.1-0.8%) 

 from groups transported. The timing of adult returns of both species to Little Goose Dam was not related 

 to the time of capture and downstream release of smolts. 



Salmonid populations of the Snake River and its 

 Idaho tributaries have declined rapidly in recent 

 years to the point that the very survival of some 

 stocks is threatened. The total run (i.e., catch plus 

 escapement) of chinook salmon, Oncorhynchus 

 tshawytscha, attributable to the Snake River 

 dropped from 120,000 adults in 1972 to 50,000 in 

 1974 (Raymond 1979). Similarly, the total run of 

 steelhead, Salmo gairdneri, an anadromous form 

 of rainbow trout, declined from 100,000 adults in 

 1972 to below 20,000 in 1974. The downward trend 

 of the anadromous salmonid populations has been 

 ascribed to losses of juvenile migrants at the series 

 of eight dams (Figure 1) and associated reservoirs 

 in the Snake and Columbia Rivers through which 

 the smolts must pass on their way to the sea 

 (Raymond 1979). 



With the goal of protecting the migrants from 

 the hazards of dams, a system for transporting 

 smolts around the dams was investigated by the 

 National Marine Fisheries Service. The juvenile 

 migrants were collected from the Snake River at 

 Little Goose Dam (the uppermost dam — Figure 

 1), transported around the entire series of dams, 

 and released below Bonneville Dam (the lower- 



'Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service, NOAA, 2725 Montlake Blvd. E., Seattle, WA 

 98112. 



most dam) on the Columbia River. The effects of 

 such transportation on the survival and catch of 

 the fish and on the ability of the adults to "home" 

 to their natal streams must be known if fishery 

 agencies are to evaluate the transportation sys- 

 tem as a practical means of protecting Snake River 

 salmonid runs. The main objectives of the research 

 at Little Goose Dam were: to determine the effect 

 of transportation on homing and survival of 

 juvenile chinook salmon and steelhead collected at 

 Little Goose Dam and released at two locations 

 downstream from Bonneville Dam and to compare 

 these results with an earlier study done at Ice 

 Harbor Dam (Ebel et al. 1973) where fish were 



Little Goose 

 Lower n, _ 



Monumental ^\L*-Central 



Manuscript accepted December 1979. 

 FISHERY BULLETIN: VOL. 78, NO. 2. 



Figure l.— Transportation routes and release location of exper- 

 imental chinook salmon and steelhead collected and marked at 

 Little Goose Dam, 1971-73. 



491 



1980. 



