,— *-*™lrdWW^^^ 



PiGUKE 5. — One leg of electrode array. 



delivered, the cycle was complete and the sequen- 

 tial pulsing equipment switched automatically to 

 start the second cycle. During the second and each 

 succeeding cycle, the electrodes were energized in 

 exactly the same manner as they were during the 

 first cycle. 



Although the polarity of the electrodes was not 

 alternated, we experienced very little electrolysis. 

 Once the desired electrical conditions had been set 

 into the sequential switching equipment, the gear 



functioned automatically and dependably for the 

 duration of the experiment. 



The purpose of a sequentially pulsed field, 

 sweeping in the direction of the array trap, was to 

 take advantage of any electrotactic effect that the 

 electrical energy might produce. Although the 

 electrode array and electrical conditions in this 

 experiment were designed to divert the fish by 

 stimulating an avoidance response at the periph- 

 ery of the electrical field, it is known that when 

 fish penetrate a pulsed d.c. electrical field of 

 sufficient intensity they are stimulated to propel 

 themselves in the direction of the positive pole or 

 anode (Haskell, MacDougal, and Geduldig, 1954). 



ARRAY TRAP 



The array trap was at the downstream end of 

 the electrode array. It was constructed with a 6.4 

 m.-wide entrance so that the effective electrical 

 fields created by the converging legs of the elec- 



312 



U.S. FISH AND WILDLIFE SERVICE 



