Table 1. — A summay of threshold voltages. 



widths greater than 2,000 a'S were similar be- 

 tween species. 



Atlantic croaker were used to test the 

 hypothesis that fish require more voltage to show 

 a threshold reaction when facing the positive elec- 

 trode. Analysis of the average threshold voltages 

 of croakers facing the positive and negative elec- 

 trode by Student's ^-test shows a significant differ- 

 ence between the values 



it = 3.60 and t 



0.975 (18) 



2.101). 



Scaled sardines showed a similar response (Table 

 1). These results confirm those of Bary (1956) 

 where he showed that mullet required more vol- 

 tage to respond when facing the anode than the 

 cathode. 



The cost of producing a useful electrical field in 

 seawater is dependent upon the power required to 

 elicit specific responses in the desired species. 

 Pulse width obviously is a major factor which af- 

 fects the power requirements along with voltage 

 and pulse rate (Klima, 1972). Narrow pulse 

 widths require proportionately less power than 

 wider ones. Engineering design criteria for pulse 

 generators are usually based on the minimum 

 pulse width electronically possible. These results, 

 however, indicate that pulse width should not be 

 less than 250 jUS and probably should range be- 

 tween 250 and 1,000 ms. 



Literature Cited 



Bary, B. M. 



1956. The effect of electric fields on marine fishes. Scotl. 

 Home Dep, 1, 32 p. 



Kessler, D. W. 



1965. Electrical threshold responses of pink shrimp 

 Penaeus duorarum, Burkenroad. Bull. Mar. Sci. 

 15:885-895. 

 Klima, E. F. 



1968. Shrimp-behavior studies underlying the develop- 

 ment of the electric shrimp-trawl system. U.S. Fish Wildl. 

 Serv., Fish. Ind. Res. 4:165-181. 

 1972. Voltage and pulse rates for inducing electrotaxis in 

 twelve coastal pelagic and bottom fishes. J. Fish. Res. 

 Board Can. 29:1605-1614. 

 Taylor, G. N., L. S. Cole, and W. F. Sigler. 



1957. Galvanotoxic response offish to pulsating direct cur- 

 rent. J. Wildl. Manag. 21:201-213 



ViBERT, R. 



1967. Part I — General report of the working party on the 

 applications of electricity to inland fishery biology and 

 management. /^ R. Vibert (editor). Fishing with electric- 

 ity — Its applications to biology and management, p. 

 31-73. Fishing News (Books) Ltd., Lond. 

 Wickham, D. a. 



1970. Collecting coastal pelagic fishes with artificial light 

 and a 5-meter lift net. Commer. Fish. Rev. 32( 12):52-57. 



Edward F. Klima 



Southeast Fisheries Center 



National Marine Fisheries Service, NOAA 



Pascagoula, MS 39567 



Present address: 



Office of Living Resources, NOAA 



6010 Executive Boulevard 



Rockville, MD 20852 



853 



