I I I I I I I I I I 



J I I I I I I I I I I I I 



S 10 IS 20 25 5 10 IS 20 25 5 10 IS 20 25 5 10 IS 20 25 5 10 IS 20 25 S 10 IS 20 2S 



HAY JUNE JULY AUGUST SEPTEMBER OCTOBER 



Figure 2.--Tailwater elevations. Rock Island Dam, May 1 to October 27, 1961. 



As in past years of counting at Rock Island 

 Dam, some fish were observed with cuts or 

 abrasions on the body. Of 40, 764 fish examined 

 as they passed over the counting boards, ap- 

 proximately 1.06 percent had injuries of some 

 type either on the body or about the head. Since 

 the counters could see only the top and one side 

 of the fish, the incidenceof injury was probably 

 greater than indicated. In period May 1 to July 

 5 all fish were quite free of injuries. Greatest 

 numbers of injuries were observed during July 

 and August and were most numerous on large 

 Chinook and sockeye salmon (table 21). In period 

 July 20 to August 12 counters reported a number 

 of fish with similar injuries. The injury most 

 commonly observed was a circular cut or 

 abrasion about 1 inch in diameter, usually along 

 the side of the fish. Some of these injuries 



were newly made as evidenced by the presence 

 of bloody tissue. Others appeared to have been 

 made much earlier as scar tissue was 

 forming. 



During extreme highwater period June 10-13 

 a considerable quantity of gravel, silt, and 

 debris was deposited in the right bank fish 

 ladder. 



On July 19 counting facilities at left fish 

 ladder were operated from 9:30 p.m. to 11:45 

 p.m. Between 9:30 p.m. and 9:45 p.m. two 

 Chinook and two sockeye salmon passed over 

 the counting board. From 9:45 p.m. to 11:45 

 p.m. there was no movement of fish ob- 

 served. 



