ENUMERATION OF FISH 



Chinook Salmon, Oncorhynchus tshawytscha 



The chinook salmon count in 1960 of 26,550 

 is well above the mean of 15,153 for the 

 27-year period, 1933-59. The count increased 

 from that of 1959 (Zimmer, Davidson, and 

 Anders 1 ), and was slightly more than half 

 the annual fish count of 50,713 in 1957 (table 

 1). Monthly totals of chinook salmon counted 

 are given in table 2. Maximum day's count 

 in 1960 was 401 fish on August 3 (table 3). 

 In 1960 peak movement of chinook salmon 

 (jacks included) occurred on August 3, when 

 516 fish were counted through the fishways. 



Tables 4 and 5 show semimonthly totals 

 of number and percentage of chinook salmon 

 counted through each fish ladder in 1960. 



Data pertaining to chinook salmon daily 

 counts are contained in tables 6-11. 



Chinook Salmon Jacks 



Some chinook salmon return from the ocean 

 during the year following their seaward mi- 

 gration and are referred to as "jacks." These 

 fish are predominantly males and are smaller 

 than the average. It has been determined at 

 Rock Island Dam that up to June 30 of each 

 year jacks rarely, if ever, exceed 18 inches 

 in length, while the balance of the fish ap- 

 preciably exceed that length. Likewise, from 

 July 1 to the end of the season jacks rarely, 

 if ever, exceed 22 inches in length. Conse- 

 quently, jacks at Rock Island Dam are identi- 

 fied by considering all chinook salmon 18 

 inches or less in length prior to July 1 as 

 jacks, and all chinook salmon 22 inches or 

 less in length subsequent to June 30 as jacks. 

 Monthly totals of jacks counted in 1960 are 

 given in table 2. In 1960, the maximum day's 

 count of chinook salmon jacks, 128, occurred 

 on August 10 (table 3). The 5, 08 2 fish recorded 

 as jacks constitute 19.1 percent of the total 

 1960 chinook salmon run. 



iZimmer. Paul D„ Clifton C. Davidson, and Floyd S. 

 Anders. 1961. Annual fish passage report. Rock 

 Island Dam, 1959. UJS. Fish and Wildlife Service. 

 Special Scientific Report --Fisheries No. 394, p. 1-14. 



Data pertaining to semimonthly counts of 

 chinook salmon jacks utilizing each fish ladder 

 at Rock Island Dam in 1960 are given in 

 table 5. 



Sockeye Salmon, Oncorhynchus nerka (blue- 

 back or red) 



The sockeye salmon count of 60,341 for 

 1960 was greater than the 27-year mean of 

 53,092 (table 1). In 1960, peak of the run 

 was reached on July 19, when 3,524 fish 

 were counted through the fishway at Rock 

 Island Dam. 



In recent years attention has been drawn 

 to the many small sockeye salmon at Rock 

 Island Dam. During the 1960 counting period 

 sockeye salmon under 16 inches in length 

 were enumerated as small fish. Number of 

 sockeye salmon recorded as "small" was 

 6,335 (10.5 percent). 



Monthly totals of sockeye salmon counted 

 in 1960 are given in table 2. 



Data pertaining to sockeye salmon daily 

 counts are contained in tables 8-11. 



Tables 12 and 13 show semimonthly totals 

 of number and percentage of sockeye salmon 

 ascending each fishway. Of the sockeye salmon 

 passing Rock Island Dam in 1960, 61.52 per- 

 cent ascended the left ladder, while 22.36 

 and 16.11 percent ascended the middle and 

 right ladders, respectively. 



Coho Salmon, Oncorhynchus kisutch (silver) 



The coho salmon count of 94 in 1960 was 

 greater than the 27-year mean of 63 and is 

 the sixth highest count recorded at Rock Island 

 Dam for this species (table 1). Monthly totals 

 of coho salmon counted in 1960 are given in 

 table 2. Maximum day's count in 1960 of 11 

 fish occurred on September 24. Daily counts 

 of coho salmon passing the dam are given in 

 tables 10 and 11. 



Steelhead Trout, Salmo gairdneri 



The steelhead trout count of 6,226 in 1960 

 was higher than those of the preceding 4 years 



