I I I I I I I I I I I I I I I I I I I I I I I I I I I II I I I I II I 



5 10 15 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 5 10 IS 20 25 



SEPTEMBER OCTOBER 



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

 October 27. 1962. 



both years of observation the counters could 

 see only the top and one side of the fish, the 

 incidence of injury was probably greater than 

 indicated. Percentages of in jured fish observed 

 in the left, middle, and right ladders in 1962 

 were 68, 10, and 22 percent, respectively. 



In 1962, injuries were most numerous on 

 large chinook and sockeye salmon (table 21). 

 Of the 7,591 steelhead observed, only 16 fish 

 showed evidence of injuries. Very few chinook 

 salmon jacks displayed visible external in- 

 juries. It is of interest to note that of 737 coho 

 salmon examined, only 3 fish showed evidence 

 of visible injuries. 



As in 1961, circular cuts or abrasions about 

 1 inch in diameter were more prevalent among 

 the sockeye salmon. The most prevalent in- 

 jury among the large chinook salmon was a 

 deep cut along the side of the body or on the 

 head. Some of these cuts or gashes were 

 estimated to be as long as 6 inches and from 



one-quarter to one-half inch deep. Some of 

 the injuries were newly made, as evidenced 

 by the presence of bloody tissue. Others 

 appeared to have been made earlier, as scar 

 tissue had formed. In some instances, large 

 injuries or abrasions were covered with fungus 

 growth. The greatest number of injuries oc- 

 curred in July and August. 



In the period July 17 to July 26, 1,024 sock- 

 eye salmon were trapped in the left bank fish- 

 way. These fish were tagged as part of a 

 study to measure the effectiveness of the fish- 

 ways at Rocky Reach Dam, located approxi- 

 mately 20 miles upstream from Rock Island 

 Dam. All tagged fish were released into the 

 forebay of Rock Island Dam. In the period 

 July 21 to July 26, 16 of these tagged fish 

 were again counted through the fishways at 

 Rock Island Dam, indicating that some of the 

 fish proceeded downstream after release and 

 came up through the fishways a second time. 



