1100 U. S. BUEEAU OF FISHERIES 



As a means of alleviating this condition of high-voltage gradients 

 and following vei;v encouraging results at an experimental electric 

 screen erected for this purpose in the Gold Ray sluiceway, the use 

 of the grounded type of screen was abandoned and a screen insulated 

 from ground and employing a double row of large diameter pipe 

 electrodes was installed. Operation of this screen was continued un- 

 til late in November, but no real check on its efficiency was possible 

 because the season for downstream migration of fish had almost 

 wholly passed. The operation of the grounded screen throughout 

 the migration season without question diverted some fish from the 

 intake channel, but it is doubtful if the number so diverted was 

 more than 25 per cent of the total number of such fish encountering 

 the screen. It is felt that greatly improved results will be obtained 

 with the new scieen the coming season. 



Gold Ray sluiceway experimental screen. — During the late sum- 

 mer considerable experimenting was done with a view to determining 

 the best type of electric screen for operation against downstream 

 migrants. The first experiments were made with the grounded type 

 of screen as employed at all previous installations. The action of 

 the fish was noted under a variety of conditions. Various arrange- 

 ments of spacing electrodes and ground element with voltages rang- 

 ing from 45 to 110 volts were tried. The action of the fish in the 

 electrified zone was erratic. Resort was then had to a screen insu- 

 lated from the ground, and highly satisfactory results were obtained. 



Gold Ray ta'ilrace screen. — Three heavy runs of salmon and steel- 

 head pass up the Rogue River each season on their way to the spawn- 

 ing beds. For the accommodation of these upstream migrants two 

 fish ladders are maintained at Gold Ray Dam, one being at each 

 abutment of the dam. The discharge from the power-house tailrace 

 returns to the river about 500 feet downstream from the dam. Dur- 

 ing periods of large overflow the volume of water in the main 

 channel is sufficient to keep most of the fish safely headed up past 

 the tailrace to the fish ladders. When, however, the overflow at the 

 dam is diminished and a considerable part of the river flow is being 

 taken through the power house, these fish are attracted into the tail- 

 race. Trapped in this channel they wear themselves out fighting 

 the strong flow from the turbines and are thus prevented from reach- 

 ing their goal up river. In the spring of 1928 the California-Oregon 

 Power Co. installed and, for a time, operated an electric fish screen 

 in this tailrace. The results obtained encouraged further investiga- 

 tion, and to this end the power company has cooperated with the 

 Bureau of Fisheries in bearing one-half the expense of all work done 

 on the Gold Ray electric screens this season. 



The object of the experimental electric screen installed by the 

 bureau in the tailrace was twofold. Primarily the purpose was to 

 screen this waterway against the entrance of upstream migrating 

 fish and thus divert them upstream to the fish ladders. It was also 

 desired to study the possibility of directing fish to some definite point 

 in a channel by means of an electric field. With this latter purpose 

 in view the screen was installed well up in the tailrace and diagonally 

 across it. At the upstream end of the screen a fish trap or box 

 of timber construction was placed ; the object being to see if the fish 

 upon coming in contact with the electrified-zone of water would con- 



