Table 3. --Maximum daily counts, salmon and 

 steelhead, Rock Island Dam, 1963 



Species 



Chinook (except jacks) 



Chinook ( jacks ) 



Steelhead 



Sockeye 



Coho 



Date 



Aug . 5 . . . 

 Sept. 15. 

 Sept. 15. 

 July 15.. 

 Sept. 18. 



Number 

 of fish 



430 



568 



201 



4,601 



3 



5 show semimonthly totals of the number and 

 percentage of chinook salmon counted over 

 each ladder. Of the chinook salmon (jacks 

 excluded) that passed Rock Island Dam in 

 1963, 72.8 percent ascended the left ladder, 

 while 13.7 and 13.5 percent ascended the middle 

 and right ladders, respectively. In 1962, per- 

 centages of chinook salmon (jacks excluded) 



that used the left, middle and right ladders 

 were 65.6, 13.5, and 20.9, respectively. 



Chinook Salmon Jacks 



Some chinook salmon return from the ocean 

 as mature fish the year following their seaward 

 migration and are referred to as "jacks." 

 These fish are small, and males predominate. 

 At Rock Island Dam in 1963, all chinook salmon 

 24 inches or less were counted as jacks. Each 

 counting board has a marked section, 24 inches 

 long, for gauging the length of small chinook 

 salmon. The maximum daily count of 568 fish 

 occurred on September 15 (table 3), about 5 

 weeks later than in 1962. The 19,409 fish 

 recorded as jacks constituted 56.0 percent of 

 the total chinook salmon run as compared to 

 20.8 percent in 1962. 



Table 5 shows the number and percentage 

 of chinook salmon jacks counted over each 

 fish ladder. In 1963, 72.2, 11.1, and 16.7 

 percent of the jacks used the left, middle, 

 and right ladders, respectively, compared to 

 68.1, 13.1, and 18.8 percent in 1962. Monthly 

 totals are in table 2. 



Table 4. — Semimonthly number and percent of chinook salmon counted over each fish ladder, Rock 



Island Dam, 1963 



(Jacks not included) 



1 Middle ladder inoperative from May 1-20. 



2 Right ladder inoperative for several hours on Sept. 1. Closure was made in order to permit 

 removal of debris. 



