112 BULLETIN OF THE BUKEAIT OF FISHERIES 



consisting of two parallel rows of J/^-inch standard pipe spaced 18 inches apart in the 

 rows and the tv/o rows 2 feet apart. The angle of the electrode rows with the direc- 

 tion of stream flow was kept at 30 degrees, as before. The electrodes of each row 

 were connected parallel and the two rows made opposite in polarity. This arrange- 

 ment of electrodes put the Unes of current flow approximately in the direction of 

 stream flow, and consequently in the direction the fish approach the screen. With 

 some trout used in the previous test in the open channel, the electrodes were ener- 

 gized with 24.5 volts and left on from 4.30 p. m. until 8 a. m. The fish did not enter 

 the protected channel. It was observed that trout that had passed through the 

 electric field of the screen could not be driven through it again except with great 

 difliculty. For this reason a new group of 12 rainbow trout was substituted for those 

 that apparently had become screen shy. When first hberated, 5 of the 12 were 

 frightened and dashed through the screen. They were then driven out into the open 

 end of the pool and the potential left on over night. The fish did not reenter the 

 screened area during the night, and the next morning we were unable to drive any 

 of them through the screen. 



The fourth screen used was but a very slight modification of the third. One 

 electrode was added to fill a rather large opening on the by-pass charmel side of the 

 screen. The electrode voltage was adjusted to 23 volts, and approximately 2,500 

 chinook-salmon fingerUngs were put in the outside channel at 11.30 a. m. These 

 fish were allowed to move about as they pleased. Frequently the entire school 

 would swim directly toward the screen but always turned away when within from 

 18 to 24 inches of the first row of electrodes. They were continually feeding on elm 

 beetles, which were blown on the water from the elm trees above the pool, but they 

 would never venture through the screen for those in the protected area. An attempt 

 was then made to attract them through the screen by throwing a mixture of ground 

 salmon and salmon eggs between the electrodes and in the protected area. They 

 could be drawn into the screen by throwing the food outside and leading up to it, 

 but they would dash out without taking the food and never passed beyond the second 

 row of electrodes. The only way the yoimg salmon could be driven through the 

 screen was by fright. A few were driven through the screen by waiting until a school 

 was immediately in front of the screen and then making a sudden motion toward 

 them with a pole, net, or other device. 



The last two screens tried were by far the most effective. This undoubtedly 

 was due to a more eft'ective use of the electric field by arranging the fines of current 

 flow parallel with the stream flow and at right angles with that of the protected 

 opening. The tests in the concrete pool, however, were not as conclusive as they 

 might have been, because conditions were unnatural. The water velocity was 

 extremely low; in fact, it was virtually still water, hence the fish did not fine up with 

 the direction of water flow as in a stream. The pool was near the main hatchery 

 driveway, and the fish were continually frightened and disturbed by tourists and 

 therefore were unnatural in their behavior. However, those who witnessed the tests 

 with the third and fourth screens were convinced that the fish did have a directional 

 sense of the location of the source of the electric fields and a decided incHnation to 

 avoid them. These observations led to the decision to install a screen under more 

 natural and normal conditions for further observations and tests. This screen and 

 the results obt-ained will be discussed later in this report. 



