128 PROBLEMS IN WILD LIFE CONSERVATION 



The Agricultural Investigations Section maintains two 

 experimental fish hatcheries and its studies go to aid the 

 work of the Division of Fish Culture. New and better 

 equipment for hatcheries, more efficient methods of propa- 

 gation, fish diseases and their cure are all contributions made 

 by Scientific Inquiries to the work of the Division of Fish 

 Culture. 



An investigation of the means of improving screens at 

 the mouths of irrigation ditches and fish ladders over power 

 and irrigation dams was begun in I928, 32 under the direc- 

 tion of the Screen and Ladder Section. Two general types 

 of screens have been developed, one mechanical, the other 

 electrical. Either when properly placed has been found to 

 operate with efficiency in preventing fish from entering irri- 

 gation ditches or in directing them to safe by-passes around 

 power projects. 33 



The Federal Power Commission has been in the habit in 

 recent years, when granting permits for the construction of 

 private power projects, of providing that in streams in which 

 fish are likely to go to spawn, fish ladders must be con- 

 structed at the dam to enable them to go around it into the 

 upper waters. Congress in 1934 wrote such a requirement 

 into law providing that no dam should be constructed, either 

 by the federal government itself or by any private agency 

 under permit, until the plans had been approved by the 

 Bureau of Fisheries. 34 The Screen Ladder Section has 

 supervision of the planning and construction of such ladders 

 and screenage. 



The western trout investigations are carried on chiefly 

 for the benefit of the National Parks and Forests in the 



32 45 Stat. L. 478. 



33 Report of the Commissioner, Bureau of Fisheries, Appendix II, 

 P. H5 (1933). 



3 * Public No. 121, 73rd Congress. 



