Horizontal and Vertical Distribution of Juvenile Salmonids in Upper Mayfield Reservoir, Washington
horizontal, horizontal distribution, juvenile, reservoirs, salmon, salmonids, upstream, vertical distribution
Fisheries No. 566
United States Fish and Wildlife Service
Special Scientific Report
The proposed installation of a fish collecting device in the upper end of Mossyrock Reservoir, soon to be created on the Cowlitz River in southwestern Washington, prompted this study to determine the horizontal and vertical distribution of juvenile salmonids in such an environment. A section of the upper end of Mayfield Reservoir, an existing body of water on the Cowlitz River, was systematically sampled with gill nets and a trawl from April 1964 to June 1965. Eighty-seven percent of the 11,467 salmonids captured were taken in the upper 7.3 m. of water, which constituted 52.8 percent of the total sampling area. If the distribution of fish in upper Mossyrock Reservoir is similar to the distribution in Mayfield Reservoir, a collecting device running from shore to shore, extending to a depth of 7.3 m., and designed to collect fish approaching from both upstream and the downstream sides should collect over 80 percent of all migrating salmonids.