SALMON RUNS OF THE COLUMBIA RIVER IN 1938 



135 



Data on the blueback run are presented in modified form in tables 20 and 21. 

 As previously stated (p. 114), two methods have been applied in changing the poundage 

 records to numbers of fish; (1) assuming an average weight of 3 pounds throughout 

 the season in all zones, and (2) assuming an average of 3 pounds throughout the 



THOUSANDS 



5 S 



APRIL 30 



Figure 6.— Dominant elements in the 1938 blueback salmon run, by weeks. 



season below Bonneville and of 2% pounds throughout the season above Bonneville. 

 The first method gives the figures of table 20 and the second those of table 21. It is 

 known that the fish caught above Bonneville are smaller than those caught below on 

 account of the selective effect of the gill nets which provide a large portion of the catch 

 below Bonneville, while the catch above Bonneville is made largely by means of dip 

 nets which are not selective. These conversion figures are based on data secured from 

 Harlan B. Hohnes, of the Fish and Wildlife Service. 



