700 



600 



500 



400 



300 



200 



100 



l~r 



1 — I 1 I 



I I I I — n — 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 I 



5 10 15 20 25 

 MAY 



10 15 20 25 

 JUNE 



10 15 20 25 

 JULY 



10 15 20 25 

 AUGUST 



5 10 15 20 25 

 SEPTEMBER 



Figure 3. --Daily river discharge. Rock Island Dam, 

 May 10-September 30, 1959 



decline in the run after peaking is very 

 rapid until the count is just a few fish 

 per day. Decline from the peak in 1959 

 was comparatively rapid until the num- 

 ber of fish was approximately 100 to 

 300 per day. Counts continued at this 

 level for an unusually long period of 

 time and many very red (near ripe) 

 fish were observed. 



The cooling-water screens at Rock 

 Island Dam were a hazard to down- 

 stream migrant salmon in previous 

 years. Several hundred dead migrants 

 were taken from these screens in a 

 24-hour period. Hoods have now been 

 installed which cover the cooling -water 

 intakes and prevent migrants from 

 entering. As a result of installation of 



12 



