FISHERY BULLETIN: VOL. 71, NO. 2 



Table 2. — Releases and recaptures of transported and nontransported juvenile chinook salmon (transported fish were 

 released below John Day Dam and nontransported fish were released above Ice Harbor Dam) that were recaptured 

 at The Dalles Dam from releases before and after spilling began, 1968 (figures not adjusted for tag loss). 



' Recovery efficiency based on average percentage recapture of transported fish at The Dalles Dam for the recovery period shown. 

 One hundred percent survival assumed between release site below John Day Dam and The Dalles Dam. 



'^ Percentage increase in survival of transported groups equal to [(recovery efficiency) (100)/(% recapture of control)] - 100. 



Dalles Dam. Recovery rates of survivors to 

 The Dalles Dam varies tremendously depending 

 on flow condition. Because the controls released 

 at Ice Harbor Dam often took several days to 

 reach The Dalles Dam, the recapture rate 

 varied and was spread out over a longer period 

 than the test groups. The recapture rate com- 

 puted for the controls was therefore based 

 on average recapture rate measured throughout 

 the recovery period of the controls. As the 

 table indicates, this rate was based on average 



percentage recovery rate of the test groups 

 released during that period. It should be stressed 

 that spilling also occurs at upstream dams 

 once steady spilling begins at The Dalles. 

 Before heavy spilling, the data indicate that 

 survival of fish transported to John Day Dam 

 was increased about 69% ; the ratio of recapture 

 of transport/control fish was 1.7:1. After 

 heavy spilling, survival was increased by about 

 250% or 3.5:1. 



In 1969 (Table 3), heavy spilling occurred 



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