Movement of fish through the fishways at 

 Rock Island Dam in 1963 also was affected by 

 fluctuations of the Rock Island pool. On many 

 occasions during September and October, the 

 pool level was so low that insufficient water 

 was available for proper operation of the 

 fishways. This affected movement of fish to 

 and through the ladders and required daily 

 changes in fishway weir operations. 



In comparing data on movement of fish 

 through each of the fish ladders in 1963 (tables 

 4-8) with similar data for 1962, many differ- 

 ences are noted in the percent utilization by 

 species in each of the three ladders. 



During 1963, fish were observed with cuts or 

 abrasions on their bodies. Of 106,554 salmon 

 and steelhead observed as they passed over 

 the counting boards, 2,209 fish, about 



Table 21. 



—Injured fish observed at Rock Island Dam, May 1 to October 30, 



1963 



(Number of fish) 



21 



