ELECTRIC FISH SCREEN 



117 



and therefore were normal in their activity there. The area screened was frequented 

 by largo numbers of fish before the screen was installed. 



The screen installed for this test consisted of fourteen 2j^-inch standard-pipe elec- 

 trodes (2.875 inches outside diameter) in two rows of seven electrodes each. The elec- 

 trodes were spaced 18 inches, center to center, in the rows, and the two rows were 24 

 inches, center to center. The electrodes of the second row were staggered 9 inches with 

 respect to the first row, making them come opposite the centers of the openings be- 

 tween the electrodes of the first row. The electrodes were supported, through holes 

 in 2 by 10 inch planks, 18 inches above the water level and projected to within 2 inches 

 of the bottom of the pond. The electrodes in each row were connected by means of 

 14-gauge wire and made the same electrical polarity. The two rows of electrodes were 



of opposite polarity. The opening protected by this electric screen was 9 feet 3 inches 

 wide. 



The installation of the screen was completed at 10 a. m., August 7. The fish were 

 attracted out of the screened area by feeding on the opposite side of the pond, and 25 

 volts at 60 cycles were put on the screen from a 3-kilovolt-ampere ungrounded supply 

 transformer. A graphic recording voltmeter was connected to the potential supply 

 to check the continuity of the electrical supply to the screen. 



When the screen was first electrified the fish would drift dowm toward it in large 

 schools, and as soon as the outer fringe of the school struck the electrified area it 

 would swim out swiftly, giving warning of the danger, and the whole school would 

 move away. The school would soon drift back into the electrified area and repeat 

 the above movement. At times fish that drifted too far into the electrified area would 

 become bewildered and swim through the screen. The number swiniming through 



