32 



FISH AND GAME COMMISSION 



Studies of Young Salmon: Fyke-netting studies of downstream 

 migrants have included studies of the time of migration in the Feather, 

 American, Cosumnes, Mokelumne, and San Joaquin Rivers, and studies 

 of the damage done by various large unscreened and inadequately 

 screened irrigation diversions. The diversions are all taking salmon, but 

 the ones in the Mendota area are the worst. 



Figure 10. Fyke net being used to estimate the loss of baby salmon into 

 a canal. The canal was taking very little water when this photograph was 

 made and practically the entire flow was going into the fyke net. Photograph 

 by Donald H. Fry, Jr. 



Electric Screen Testing: Since the cost of screening irrigation 

 canals, particularly the largest ones, by fine mesh screens (rotary drum 

 or similar) would be almost prohibitive, the Fish and Game Commission 

 decided to investigate the possibilities of electrical screening. Two screens 

 were installed at Mendota and one at Dos Palos. Intensive tests carried 

 out when small salmon were migrating in the early part of 1946 showed 

 that the screens as purchased would not keep small salmon out of the 

 canals, but frequent changes made by the manufacturer and the division 

 have resulted in improved performance, and give hope that eventually 

 such methods may prove adequate. It should be kept in mind that small 

 fish are much harder to deflect electrically than large ones, and that fish 

 which are actively migrating are much harder to turn than ones which 

 are merelj'' wandering. Thus it will be seen that screening of small salmon 

 electrically is a very difficult problem which must be approached with 

 caution. 



