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5 10 IS 20 25 

 MAY 



5 10 15 20 25 



JUNE 



5 10 15 20 25 

 JULY 



5 10 15 20 25 

 AUGUST 



5 10 15 20 25 

 SEPTEMBER 



5 10 15 20 25 

 OCTOBER 



Figure 3. --Daily river discharge. Rock Island Dam, May 1 to October 27, 1961. 



The six times that dewatering of fishways at 

 Rock Island Dam occurred in 1961 were as 

 follows: 



1. Left fish ladder, from 10 p.m. on May 3 

 to 1 p.m. on May 5, to install electronic count- 

 ing equipment. 



2. Right fish ladder, from 10 a.m. to 3p.m. 

 on June 5, to clean ladder orifices and repair 

 telescopic gate chains, 



3. Right fish ladder, from 12:45 p.m. to 

 2:40 p.m. on June 7, to complete ladder re- 

 pairs. 



4. All three fish ladders, from 1 p.m. on 

 June 9 to start of counting on June 14, were 

 inoperative due to high water. 



5. Right fish ladder, from 11 a.m. to 3:15 

 p.m. on June 29, to replace stoplogs lost during 

 high water period. 



6. Right fish ladder, from 12:50 p.m. to 

 2:40 p.m. on July 5, to repair broken gate 

 chain. 



SUMMARY 



1 . The total Rock Island Dam count of salmon 

 and steelhead in 1961 was 59,392, which was 

 slightly more than half the 1960 count of 

 93,183. 



2. Yearly total counts of salmon and steel- 

 head passing Rock Island Dam during theperiod 

 1933-61, inclusive, are given in table 1. 



3. The Chinook salmon count of 33,067 in 

 1961 was greater than in 1960 and slightly more 

 than half the peak year of 1957. In 1961, 9,260 

 jacks were recorded, representing 28.0 percent 

 of that year's total Chinook salmon counted. 



4. The sockeye count of 19,233 was slightly 

 less than one-third the 1960 count of 60,341 

 and considerably less than the 28-year mean 

 of 53,079. A greater percentage of sockeye 

 salmon utilized the left bank ladder than used 

 either the middle or right bank ladders. In 

 1961, sockeye salmon under 16 inches in length 

 comprised 18.2 percent of the count. 



