THIRTY-EIGHTH BIENNIAL REPORT 11 



Experiments on the electric fish screen were carried on by J. H. 

 Wales at Hat Creek in Shasta County where the Pacific Gas and Electric 

 Company installed one of these devices at their Hat No. 2 Power House 

 and made it available to us for this purpose. Here the discovery was 

 made that if, instead of placing the live electrodes downstream from the 

 ground as has been done in the past, they were placed upstream, there 

 would result an electric field extending upstream from the electrodes with 

 gradually diminishing strength. It is possible that this system will 

 prove better adapted to the repulsion of fish of all sizes than the previ- 

 ously used design, where the field extended with quite uniform strength 

 from the electrodes upstream to the ground and then ended rather 

 abruptly. As a result of these experiments the desirability of further 

 knowledge of the water velocities which trout of various sizes can over- 

 come became apparent and accordingly tests on their swimming speed 

 are now underway at Mt. Shasta Hatchery. 



Lake fisheries have received much attention during the biennium. 

 June and Gull Lakes in Mono County were under close observation by 

 Elden Vestal prior to his induction into the Army in DecenifeFS'-^-i942, 

 and here it was shown that planting of sized rainbow from th4j;Iay Creek 

 fall spawning stock at the opening of the fishing season would provide 

 a yield of 50 per cent to the anglers' creels. Intensive studies by J. H. 

 Wales of Castle Lake in Siskiyou County dealt with the yield obtained by 

 planting fingerling trout of various species and showed that on the aver- 

 age about 5 per cent of the number planted would reach the angler 's creel. 

 The latest step here has been the introduction of soy bean meal to see if 

 fertilization of a natural lake of this size can be a practical means of 

 improving its fishery. Clear Lake was investigated at the request of 

 the Lake County Board of Supervisors with respect to the effect on the 

 sport fishery of commercial netting of rough fish and regulations were 

 proposed under which the latter is now carried on. A preliminary 

 survey of Millerton Lake above Friant Dam was completed and one of the 

 Shasta Reservoir initiated. Creel counts of a less extensive nature were 

 carried on at Stevens Creek Reservoir in Santa Clara County and at Frog 

 Lake in Nevada County. A project for the survey of barren lakes has 

 been carried on each summer by Mr. Dill in cooperation with the Fresno 

 County Sportsmen's Club for the purpose of assuring proper manage- 

 ment of these lakes from the start. 



The control of rough fish in lakes through rotenone poisoning has 

 been difficult due to the shortage of this material, but Ballard Reservoir 

 in Modoc County has been successfully treated and brought back into 

 production, as well as two smaller lakes in this same region, Cave and Lily. 



The whole question of stream flow maintenance has received much 

 attention, from high altitude check dams for the improvement of moun- 

 tain streams to amounts of water needed for release, from dams built 

 and to be built on our large rivers, for preservation of fish and fishing. 



The Salton Sea mullet fishery was briefly investigated by Dill and 

 Woodhull and recommendations made on which the present regulation of 

 the commercial catch is based. 



At the Central Valleys Hatfchery at Elk Grove experiments were 

 initiated which have to do not only with the production of spiny rayed 

 fishes for stocking but also with desirable species combinations for use 



