48 



REPORT OF THE FISH AND GAME COMMISSIOX. 



reduced to a minimum. Large revolving screens which work in sections 

 can be quickly cleaned by turning a crank, thus saving the labor 

 attached to the cleaning of a parallel-bar screen. The cost of a 50-foot 

 screen of this type is approximately $2,200. With the exception of the 



Fig. 33. Screen installed in an irrigating ditch near Edgewood, 

 Siskiyou County. Fish are prevented from entering 

 this ditch, but the flow of water is unhampered. 

 Photograph by A. E. Culver. 



San Joaquin Valley, where some of the large canal owners are resisting 

 the order to install screens, w^e have met with willing cooperation. 

 Nearly 600 surveys have been made and 377 screens have been installed. 



Commercial Fisheries. 

 The rapid groAvth of our fisheries has necessitated more detailed and 

 accurate knowledge in order that our fishery resources may be intelli- 

 gently conserved. The Department of Commercial Fisheries, established 



