MAJOR and PAULIK: ENCROACHMENT OF WANAPUM DAM RESERVOIR 



TAG OBSERVATIONS AT ROCK ISLAND 

 DAM, 1964 AND 1965 



The 1964 and 1965 data are treated by spe- 

 cies — spring Chinook salmon first, followed by 

 sockeye salmon. In a later section these data 

 will be compared to the 1954 and 1955 results 

 to determine the effects of encroachment of 

 Wanapum Reservoir on fish passage at Rock 

 Island Dam. 



SPRING CHINOOK SALMON 



The tag release and tag observation data for 

 1964 and 1965 are presented in Table 2. In- 

 cluded are the date and location of release, the 

 number of fish tagged, the release area, and the 

 number and mean travel time of tagged fish sub- 

 sequently observed passing Rock Island Dam. 

 Logarithmically transformed data are used 

 throughout this paper for analysis of travel time; 

 means are geometric means. 



Three times as many chinook (311) were 

 tagged in 1965 as in 1964 (103). The small 

 number released and the short duration of the 

 tagging period in 1964 (May 19-27) can be at- 

 tributed to difficulties in completing the access 

 roads, difficulties with the trapping and trans- 

 portation systems, and a shortage of fish in the 

 left-bank ladder — the ladder where the trap was 

 located. Tagging was from May 16 to June 9, 

 1965. The 1965 data are grouped, somewhat 

 arbitrarily, into five time periods. 



Percentage Observed 



The overall percentages of tagged chinook 

 salmon subsequently observed passing over Rock 

 Island Dam were 90.3 in 1964 and 91.6 in 1965. 

 Variability among the release groups was high, 

 ranging from 67 to 129^; in 1964 and 60 to 115% 

 in 1965. It is noteworthy that the number ob- 

 served exceeded the number released for 6 of 

 the 24 releases over the two tagging seasons. 



Table 2. — Numbers of chinook salmon that were tagged, released below Rock Island Dam and the numbers and mean 

 travel times of tagged fish that were later observed passing over the dam's fish ladders, 1064 and 1965. 



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