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



Rock Island Dam, 1964 



\j Middle ladder closed from Oct. 14-24 in order to make repairs. 



51,603 (table 1) and surpassed the 1963 run by 

 about 4,600 fish. Peak of the run was reached 

 on July 27, when 6,247 fish were counted through 

 the fishways. Peak daily count in 1963 occurred 

 on July 15 when 4,601 fish were recorded. 



Table 6 shows semimonthly totals of the 

 number and percentage of sockeye counted over 

 each fish ladder. Of the sockeye salmon 

 passing Rock Island Dam in 1964, 66 percent 

 ascended the left ladder, while 15 and 19 

 percent ascended the middle and right ladders, 

 respectively. Percentage distribution of 

 sockeye through the left, middle, and right 

 fishways in 1963 was 66, 20, and 14, respec- 

 tively. 



Data pertaining to sockeye salmon daily 

 counts are in tables 9-14. Monthly totals 

 of sockeye counted in 1964, table 2, show 

 79 percent of the total run passed through 

 the fishways in July, as compared to 

 about 90 percent during the same month in 

 1963. 



Coho Salmon, Oncorhynchus kisutch 

 (Silver) 



The 1964 coho salmon count of 61 was about 

 75 percent of the 31 -year mean of 81, and 

 slightly more than 8 percent of the peak year 



of 737 in 1962 (table 1). The first coho was 

 observed on September 11, 1964, as compared 

 to September 2, 1963. Maximum day's count 

 of 5 occurred on October 9 and 22. Of the 

 coho salmon passing the dam in 1964, 80 

 percent used the left ladder, while 2 and 18 

 percent used the middle and right ladders, 

 respectively (table 7). In 1963, percentages 

 of coho were left, 40 percent; middle, 

 40 percent; and right, 20 percent. Addi- 

 tional data are shown in tables 2, 13, and 

 14. 



Steelhead Trout, Salmo gairdneri 



The 1964 steelhead trout count of 5,016 

 was 45 percent greater than the 31 -year 

 mean of 3,457 (table 1). In 1964, the greatest 

 number of steelhead passed through the fish- 

 ways in September when 1,688 were recorded 

 (table 2). Peak monthly movement of these 

 fish in 1963 also occurred in September 

 when 2,634 were counted. 



Of the steelhead passing Rock Island Dam 

 in 1964, 76 percent used the left ladder, 

 while 10 and 14 percent ascended the middle 

 and right ladders, respectively (table 8). 

 In 1963, percent utilization by ladder was: 

 left, 76; middle, 8; and right, 16. 



