584 



562 



580 



578 



578 



574 



572 



570 



568 



566 



I I I — \ — r 



-T-\ — rr- 



I I I r 



1—1 — I I I I I I I 



564 - 



ui 562 



560 



558 



556 



554 



I I I l_l I L 



I I I I I I I I I I I I I I I I I I I 



5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 



MAY JUNE JULY AUGUST SEPTEMBER 



Figure 2.- -Tailwater elevations. Rock Island Darn, 

 May 10-September 30, 1959 



year were recorded on May 18, approx- 

 imately 17 days later than the average 

 arrival date for the past 15 years. 



General physical condition of salmon 

 and steelhead passing over the Rock 

 Island Dam fish facilities throughout 

 the 1959 season appeared to be con- 

 siderably below normal. Fish counters 



observed many fish bearing /isible in- 

 juries about the head and sides. In- 

 juries appeared to be more preva- 

 lent among large chinook and blue- 

 back. 



Upstream migration of blueback sal- 

 mon during 1959 showed a peculiar 

 deviation from the nornnal. Usually, 



U 



