1965 to determine the distribution of salmonids 

 not vulnerable to gill netting. 



Eighty-seven percent of the salmonids cap- 

 tured by the gill nets and the trawl were netted 

 in the upper 7.3 m. of water, which constituted 

 52.8 percent of the area sampled. Migrants 

 in the upper 3.7 m. of the reservoir were 

 distributed completely across the experimental 

 area, but slightly higher numbers were caught 

 adjacent to each shore. 



Trawling indicated that salmonids of age- 

 group were distributed throughout the upper 

 end of the reservoir. Their horizontal and 

 vertical distribution was similar to that of 

 salmonids of age- group I, sampled during the 

 same period by gill nets along a cross section 

 just upstream from the trawling area. Over 

 90 percent of all the juvenile salmonids cap- 

 tured by trawling were taken in the upper 

 3.7 m. of water. 



Movement in the experimental area was not 

 strongly downstream; 57 percent of the sal- 

 monids entered the nets from the upstream 

 side and 43 percent from the downstream side. 



Juvenile coho salmon and rainbow trout were 

 most abundant during maximum water flow in 

 June, whereas juvenile chinook salmon were 

 predominant during the period of minimum 

 flow in September. The gill nets and trawl 



captured fish more effectively when the water 

 was very turbid. 



If the distribution of fish in upper Mossyrock 

 Reservoir is similar to that in Mayfield Reser- 

 voir, a collecting device running from shore 

 to shore, extending to a depth of 7.3 m., and 

 designed to collect fish approaching from both 

 the upstream and downstream sides should col- 

 lect over 80 percent of all migrating salmonids. 



ACKNOWLEDGMENTS 



A. Westrope, Superintendent of the Mossy- 

 rock Trout Hatchery (Washington Department 

 of Game) and his staff assisted us. The Water 

 Resources Division of the U.S. Geological 

 Survey provided us with unpublished hydro- 

 logical data. 



LITERATURE CITED 



REES, WILLIAM H. 



1957. The vertical and horizontal distribu- 

 tion of seaward migrant salmon in the 

 forebay of Baker Dam. Fish. Res. Pap., 

 Wash. Dep. Fish., 2(1): 5-17. 



MS. #1700 



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GPO 935-765 



