Table 5. — Semimonthly number and percent of Chinook salmon jacks counted over each fish ladder, 



Rock Island Dam, 1963 



Middle ladder inoperative from May 1-20. 

 2 Right ladder inoperative for several hours on Sept. 

 removal of debris. 



1. Closure was made in order to permit 



Sockeye Salmon, Oncorhynchus nerka 

 (Blueback or red) 



The sockeye salmon count of 64,768 was 

 greater than the 30-year mean of 51,164 

 (table 1). In 1963, peak of the run was reached 

 on July 15 when 4,601 fish were counted through 

 the fishways at Rock Island Dam. In 1962, 

 peak count of 2,541 occurred on July 21. Table 

 6 shows semimonthly totals of the number and 

 percentage of sockeye salmon counted over 

 each ladder. 



Of the sockeye salmon passing Rock Island 

 Dam in 1963, 65.6 percent ascended the left 

 ladder, while 20.4 and 14.0 percent ascended 

 the middle and right ladders, respectively. 

 Distribution of sockeye to the three ladders 

 in 1963 varies considerably from the 48.3 

 percent using the left, 21.7 percent the middle, 

 and 30.0 percent the right ladders in 1962. 

 Other data pertaining to the sockeye salmon 

 daily counts are in tables 9-14. Monthly totals 

 of sockeye salmon counted in 1963 are given 

 in table 2. In 1963, about 92 percent of the 

 total run of sockeye salmon passed through 

 the ladders in July, compared to about 75 

 percent in 1962. 



Coho Salmon, Oncorhynchus kisutch 

 (Silver) 



The coho salmon count of 20 fish in 1963 

 was about 25 percent of the 30-year mean of 

 83 fish and less than 3 percent of the 1962 

 peak count of 737 fish (table 1). Additional 

 data are shown in tables 2, 7, and 9-14. 

 Maximum day's count of three fish occurred 

 on September 18 (table 3). In 1962, maximum 

 day's count of 70 fish occurred on September 

 27. The first coho salmon was counted at Rock 

 Island Dam on September 2, 1963, compared 

 to August 27 in 1962. Of the coho salmon 

 passing the dam in 1963, 40 percent used the 

 left ladder, 40 percent the middle, and 20 

 percent the right (table 7). In 1962, percent- 

 ages of coho were 77.3 percent, left ladder; 

 3.9 percent, middle; and 18.8 percent, right. 

 Sizeable returns of coho salmon were expected 

 in 1962 as a result of liberations from 

 Winthrop National Fish Hatchery located on 

 the Methow River upstream from Rock Island 

 Dam. The low count of coho salmon at Rock 

 Island Dam in 1963 was anticipated since there 

 were no hatchery fish expected to return that 

 year. 



