PROGRESS IN BIOLOGICAL INQUIRIES, 19 30 595 



tracting downstream migrating fish into a by-pass. This installation 

 was 100 per cent effective in screening out the fish. 



At the present time the bureau has under consideration the instal- 

 lation of such a mechanical screen in one of the Government diver- 

 sions in Montana and is assisting the State of Michigan authorities by 

 examination and reports covering the screening problems in various 

 sections of that State. 



ELECTRIC FISH SCREENS 



In the work of this investigation the electric fish screen has been 

 applied to three major problems confronting fish conservation, the 

 device being employed: (1) As a stop or diverter to prevent the 

 small, downstream migrating fish from entering irrigation and power 

 diversions; (2) to stop or divert the mature, upstream migrating 

 fish from entering tailrace waters at power houses; and (3) as a 

 guide to lead upstream migrating fish to some particular location in 

 the channel such as a counting weir or hatchery trap. 



Patents on electric fish screens have been granted to H. T. Burkey, 

 whose activities in the early development of the electric fish screen are 

 related in the two previous reports. The type of screen now in use 

 by the Bureau of Fisheries has departed widely from Mr. Burkey's 

 original design and now conforms to the design developed and advo- 

 cated by Professor McMillan.^ The use of the old style grounded 

 type of electric screen consisting of a row of suspended chain elec- 

 trodes and a pipe, or similar ground element, laid in contact with the 

 bed of the channel, has now been definitely abandoned in favor of the 

 insulated type of screen consisting of a double row of large diameter 

 jiipe electrodes suspended into the water and entirely insulated from 

 contact with the channel. Such a screen, due to the large diameter 

 of the electrodes, eliminates the undesirably high voltage gradients 

 which existed around the chain electrodes previously used, and the 

 whole installation, being insulated from ground, is independent of 

 the effects due to the conductivity of the channel material. Thus, the 

 new screen is free from those defects due to the distorted and badly 

 distributed electric field which, at certain locations, were unavoidable 

 with screens of the grounded t3rpe. 



Sunwyside electric screen. — The Sunnyside Canal, main diversion 

 of the Yakima project. United States Keclamation Service, diverts 

 water from the Yakima Kiver, near Yakima, Wash. 



The electric screen employed in this canal was of the grounded 

 type, the spacing between chain electrodes being 24 inches and the 

 ground element being a 2^2 -inch diameter galvanized pipe, laid flat 

 on the bottom of the canal, parallel with the curtain of chain elec- 

 trodes and 9 feet upstream from it. Electrification of the screen was 

 effected with 60-cycle alternating current passed through the sign- 

 flasher interrupter (2 to 20 interruptions per second) applied to the 

 screen at voltages varying from GO to 80 volts. 



As commented on in the 1929 report operating conditions at this 

 site were especially severe when high water caused increased veloci- 

 ties and the accumulation of debris at the screen, but results of the 



3 Electric Fish Screen, by F. O. McMillan. Bulletin, U. S. Bureau of Fisheries, Vol 

 XLIV, 1928 (1929). Document No. 1042. Washington. 



