600 U. S. BUREAU OF FISHEKIES 



open section of the river in ^Yllich the electric screen was installed. 

 Over the major portion of the screen section the channel depth was 

 about 15 feet and water currents w^ere quite swift. 



ExperhneniaJ electric screen at Green River. — Seeking to develop 

 the electric screen for use in guiding fish to some particular point 

 in the channel the bureau in cooperation Avith the NortliAvestern 

 Electric Light & Power Association installed an experimental elec- 

 tric screen at the Green River hatchery of the AVashington Division 

 of Fisheries this sunmier. The facilities and services of the liatchery 

 staff were kindly ottered by tliat body. The location art'or(kMl fine 

 visibility and opjjortunity to exi)eriment on large runs of fish. 



The site chosen was favorably located for obtaining a check on 

 the efficiency of the screens inasmuch as the installation was made 

 directly downstream from the wooden rack and trap structure built 

 across the river to obtain fish for spawning purposes. Thus, fish 

 that might i^enetrate the electric screen were caught against the 

 wooden rack; many thousand Chinook, silver, and dog salmon en- 

 countered the screen during the season of its operation. The insu- 

 lated type of screen was employed, consisting of a double row of 

 6-inch diameter pipe electrodes suspended in the Avater from sup- 

 porting cables. Best results Avere found to be obtained Avhen the 

 spacing Avas 4 feet center to center betAveen electrodes in roAvs, and 

 Avith the rows 6 feet apart. 



The screen Avas electrified Avith 60-cycle alternating current sup- 

 plied from a transformer. For the purpose of studying the guide 

 features of the screen a pool of timber construction resembling the 

 entrance pool to a fish ladder Avas built at the end of the electric 

 screen on the east bank and Avater Avas supplied to this pool to produce 

 an overfall for attracting fish. In addition to this a small creek 

 joins the river from the east about 50 feet doAvnstream from the 

 electric screen. Some salmon haA-e ahvays run this creek and the 

 Green River hatchery maintains a rack in this creek about one- 

 quarter mile above its mouth. It Avas thought that fish running in 

 Green River, upon encountering the electric screen, might be di- 

 verted up the creek. 



When electrified at 80 volts the screen effectiA'ely stopped the up- 

 stream migrating salmon, but Avas found to be killing a number of 

 doAvnstream migrating fish. When the potential Avas loAvered to 

 60 or 65 volts the screen Avas still found to be effectiA'e against the 

 upstream migrants and at the same time doAvnstream migrants Avere 

 no longer affected. The effectiveness of the screen in holding up- 

 stream migrating salmon Avithout injury Avas at once evident; in 

 fact, in order to get fish for spaAvning purposes it Avas necessary to 

 deenergize the screen, as practically no fish Avere able to penetrate 

 the electrified Avater. 



Results obtained, considering the screen as a guide, Avere held to be 

 very encouraging despite the fact that the presence of the electric 

 screen in the riA'er did not cause any material increase in the number 

 of fish being taken at the creek rack. Reasons for lack of increase 

 in the creek run over previous years are believed to be due to the 

 instinct of the fish to remain in the Green River Avater rathei- than to 

 pass into the creek, and physical conditions at the mouth of the creek 

 Avhere the Avater was deep and there was almost no current. On the 



