the largest fish represented in the figure. 

 Scale readings of the fish taken from July 

 through October revealed no first year 

 annulus had been formed. 



Steelhead trout . — Figure 24 gives the 

 length-frequencies by month of the young 

 steelhead measured during 1955 and 1956. 

 No fry steelhead were taken in the Tumwater 

 bypass trap during the spring of 1955; only 

 fish in their second year made up the catch. 

 The few fry shown for May and June of 1956 

 were taken in fyke nets used to augment the 



APRIL ond MAY 

 X = 94.9 



bypass trap catches this season. Summer 

 and fall catches were made up almost entire- 

 ly of the fry or young of the year group. 

 A few larger fish, 5 to 7 inches in length 

 (130- 170 mm., not shown) were taken in the 

 trap. It is not known if these were resi- 

 dent trout or migrating steelhead. 



Young of the year steelhead, the fry 

 group, comprised 86 percent of 1,962 steel- 

 head taken at Tumwater during 1955. Thir- 

 teen percent of the steelhead were in their 

 second year and migrated mostly during the 

 spring. Twenty-four larger fish (5-7 

 inches) constituting one percent of the 

 total were taken mostly in April Bind May. 



Scale readings from the August and 

 September seimples revealed no annulus pre- 

 sent. In particular, scales from the lar- 

 gest fish sampled (80 mm.) gave no indica- 

 tions of an annulus. 



20 



10 



35 45 55 65 75 85 95 105 115 125 135 

 LENGTH IN MILLIMETERS 



1955 N = I4 li =62.6 



1955 N = 4 8 =66.3 

 • 1956 N =4 ! =48.6 



1955 N = I 

 ■1956 N =4 5=29.8 



1955 N =6 S=70.7 

 ■ 1956 N =54 S =30 



1955 N =30 5 =42 

 -1956 N =153 X =30 



SEPTEMBER 1955 N = IO0 X =49.5 



25 35 45 55 65 75 85 95 105 115 125 

 LENGTH IN MILLIMETERS 



Figure 23. — Length frequency of chlnook 

 salmon migrants. Tumwater 

 Dam, 1955. 



Figure 2k. — Length frequency of steelhead 

 trout migrants. Tumwater Dam, 

 1955 and 1956. 



16 



