PROGRESS IN BIOLOGICAL INQUIRIES, 1932 111 



The increasod take of razor clams of miniinuin legal size is believed 

 to be caused partly by the increased intensity with which operations 

 liave been prosecuted. The pack of 1932 was considerably larger 

 than that of any recent year in spite of the fact that the open season 

 -was curtailed by about 3 weeks. To prevent further expansion of 

 the industry which would result in serious depletion of the beds,, 

 regulations have been promulgated wliich prohibit tlie taking of a 

 combined total of more than 1,200,000 pounds of razor clams, includ- 

 ing shells, from these waters. This is the equivalent of 30,000 cases 

 of 48 onc-half-])ound cans or approximately 65 percent of the pack 

 prepared in 1932. 



CONSERVING FISH LIFE BY USE OF SCREENS AND LADDERS 



An investigation of means of improving screens at the mouths of 

 irrigation ditches and fish ladders over power and irrigation dams 

 was begun by the Bureau of Fisheries in 1928 and has been continued 

 to date by U. B. Gilroy, engineer, with the advice of Shirley Baker, con- 

 sultajit. The principal activities in 1932 included: (1) Completion! 

 of construction of revolving mechanical screen on Jocko Canal in 

 Montfina; (2) continued operation of mechanical and electrical fish 

 screens and fish ladders on Government projects in the States of 

 Washington, Oregon, and Montana; (3) field inspection of sites and 

 production of detailed designs and cost estimates on 13 mechanical 

 screens for diversions ranging in size from 5 second-feet to 1,100 

 second-feet in Washington, Oregon, Idaho, Utah, and Nevada; (4) 

 detailed design for fish ladder for upper Salmon Falls development 

 of Idaho Power Co. on the Snake River; (5) consulting service ren- 

 dered State commissions of Oregon, Nevada, Utah, Idaho, and 

 Montana, and to the Government of New Zealand on fish screen 

 and ladder problems; and (6) special engineering service in connec- 

 tion with activities of United States Bureau of Fisheries in the 

 construction of water supplies and hatchery buildings. 



MECHANICAL FISH SCREENS 



The revolving mechanical fish screen developed by the Oregon 

 Game Commission in 1921 and adopted and in use by this Bureau 

 since 1928 continues to be the best mechanical screen which has come 

 to the attention of the investigators. This device, fully described in 

 previous reports, is economical in operation, requires but httle atten- 

 tion, and when properly installed can be relied upon to give positive 

 fish protection. Under this investigation there have been prepared 

 detailed designs covering recommended installations of this type of 

 screen for ditch capacities ranging from 5 second-feet to 1,435 second- 

 feet. Such screens have been installed at Jocko Canal and the 

 Yakima Indian project, and plans were drawn up for 13 additional 

 locations. 



ELECTRIC FISH SCREENS 



The history and development of the electric fish screen has been 

 set forth in detail in the previous reports of this division. During 

 1932 the Bureau operated electric screens on the Government projects 

 in the Yakima country and on the Kvichak River, Alaska. However, 

 as set forth in the report for 1931, owing to public antagonism which 



