EBEL, PARK, and JOHNSEN: EFFECTS OF TRANSPORTATION 



throughout the recapture period at The Dalles 

 Dam. The overall average recovery of chinook 

 salmon indicates that transportation increased 

 survival by about 90% , or a ratio of about 

 1.9:1. Recapture data from steelhead trout 

 indicated a 245% increased with a ratio of 

 about 3.5:1. No downstream survival data were 

 obtained in 1970. 



Returns of Adult Spring and 



Summer Chinook Salmon to 



Ice Harbor Dam 



Table 4 lists the number of adult salmon 

 successfully detected, separated, and identified 

 at the automatic separator in the south ladder 

 at Ice Harbor Dam. It should be stressed that 

 the observed return represents only a fraction 

 of the total return of marked fish to Ice Harbor 



Dam. The observed tally is low for the following 

 reasons: 1) Approximately 20% of the run at 

 Ice Harbor passes up the right bank (North) 

 fishway which did not have a tag detection 

 device; 2) the tag detection system in the left 

 bank (South) fishway was less than 100% 

 efficient; 3) the system was operated less than 

 full time during salmon runs; and 4) some 

 tag losses had occurred between tagging and 

 recovery. 



The combined adult returns of spring and 

 summer chinook salmon at Ice Harbor Dam 

 to 31 July 1971 from juveniles marked in 

 1968 (Table 4) indicate that survival from 

 releases at Bonneville Dam were significantly 

 (X- = 33.184; d.f. = 1) greater (2.0:1) than 

 those from control releases at Ice Harbor. 

 When these returns at Ice Harbor are divided 

 into spring and summer seasonal races and 



Table 3. — Releases and recaptures of transported and nontransported juvenile chinook salmon and steelhead trout 

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

 that were recaptured at The Dalles Dam, 1969 (figures not adjusted for tag loss). 



' Recovery efficiency based on overage 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)/(°o recapture of control)] - 100. 



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