HORIZONTAL AND VERTICAL 



DISTRIBUTION OF JUVENILE 



SALMONIDS 



The following analysis is based on 11,467 

 fish consisting of 60.5 percent coho salmon, 

 29.7 percent chinook salmon, and 9.8 percent 

 rainbow trout. Although 236 cutthroat trout 

 were captured, they are not included because 

 of the small sample size. Squawfish was the 

 only other common species; over 1,000 were 

 netted. 



The mesh size generally affected the size of 

 fish captured. Fish between 85 and 125 mm. 

 long were caught most effectively with 2. 2-cm. 



mesh, fish between 110 and 140 mm. by 2.9- 

 cm. mesh, and those between 140 and 210 mm. 

 by 3.5-cm. mesh. Fish longer than 210 mm. 

 were captured by all mesh sizes but were 

 generally entangled only by their teeth. 



Salmonids in age- group I were taken at all 

 depths, but by far the greatest catch was made 

 in the top 3.7 m. (table 2). Catches at individual 

 stations generally declined as the depth in- 

 creased. Migrants in the upper 3.7 m. were 

 distributed completely across the experimental 

 area but were slightly more concentrated 

 adjacent to each shore. In terms of total area 

 sampled, about 87 percent of the fish were 

 captured in the top 7.3 m., which made up 

 52.8 percent of the total a: ea sampled (table 3). 



Table 2. — Horizontal and vertical distribution (percentage based on catch per unit of effort) of 

 3,378 chinook salmon, 6,553 coho salmon, and 1,098 rainbow trout captured by gill netting in 

 upper Mayfield Reservoir (Cowlitz River) from April 1964- to June 1965 



[Dashes indicate stations not sampled because of insufficient depth] 



