Table 1.— Number of transported and non transported (control) 

 juvenile chinook salmon and steelhead trout that were marked 

 and released, 1969-70 (figures adjusted for tag loss)'. 



'Initial tag loss was determined for the control releases by ex- 

 amination of juveniles after recovery at Ice Harbor Dam, 1969- 

 70; tag loss for the test groups were determined by fish held at 

 release sites after transport. 



migration. These included returns to the sport, 

 commercial, and Indian fisheries in the Lower 

 Columbia River; to Ice Harbor and Little Goose 

 dams on the Lower Snake River; to Rapid River 

 and Dworshak hatcheries in Idaho; and to the 

 spawning grounds. 



Most of the tagged adults were captured at Ice 

 Harbor Dam or Little Goose Dam. At Ice Harbor 

 Dam about 809c of the run of adult fish ascend the 

 south ladder enroute to the spawning grounds. At 

 Little Goose Dam all fish must ascend the single 

 ladder installed there. Adults were recovered at 

 Ice Hai'bor Dam by a detector-separator device 

 that intercepted tagged salmon and trout (Durkin 

 et al. 1969). At Little Goose Dam, recoveries were 

 made by an improved but similar detector ap- 



paratus. A major modification of the system 

 included a Denil-type fishway instead of the pool- 

 and-overfall ladder used at Ice Harbor Dam.- 

 Improvements incorporated in the facility at Lit- 

 tle Goose Dam increased detection efficiency 

 markedly in 1970. 



Results 



Returns of Adult Spring and Summer Chinook 

 to Ice Harbor and Little Goose Dams 



Numbers of returning adult salmon successfully 

 detected, separated, and identified at the adult 

 separator are listed in Table 2. It should be 

 stressed that the observed return of adults 

 represents only a fraction of the total return of 

 marked fish to Ice Harbor and Little Goose dams. 

 The observed tally is low for the following reasons: 

 1) approximately 20'^i of the adult run at Ice Har- 

 bor Dam passed up the right bank (north) fishway 

 which did not have a tag detection device; 2) at 

 Little Goose Dam, the barrier gates at the en- 

 trance to the automatic separator were open at 

 night (2100-0500) allowing some adults to pass 

 undetected; 3) some tag loss had occurred between 

 tagging and recovery as adults; 4) the tag detec- 

 tion system was less than W07c eflScient; 5) 



-Slatick E. 1974. Laboratory evaluation of a Denil-type steep- 

 pass fishway with various entrance and e.xit conditions for pas- 

 sage of adult salmonids and American shad. Unpubl. manuscr. 

 Natl. Mar. Fish. Serv., NOAA, Pasco, Wash. 



Table 2.— Percentage of transported and nontransported (control) juvenile 

 chinook salmon (released in 1969 and 1970) that were recaptured as adults at 

 Ice Harbor and Little Goose dams, 1 April through 18 August 1971-73. 



'Adjusted for initial tag loss. 



'Based on a comparison of the known recovery of fish with magnetized 

 wire tags at Ice Harbor and Little Goose dams and the subsequent recovery 

 of these and other marked fish at a hatchery upstream. Returning fish iden- 

 tified at the dam were marked with dart tags and released to continue their 

 migration upstream. Numbers of dart-tagged fish arriving at Rapid River 

 Hatchery were compared with the recovery of other wire-tagged fish not 

 previously detected and identified at Ice Harbor and Little Goose dams. 



926 



