The Response of a Tropical Fish to Direct Current and Its Application to the Problems of Eleetrofishing in Sea Water

METHODS OF ELECTROFISHING have been developed successfully for use in fresh-water ponds and streams, but this equipment is not effective in sea water because the high conductivity of salt water greatly changes the power requirements (Smolian, 1944). If this obstacle can be overcome, it is reasonable to assume that electrofishing can be conducted in the sea with a success which would be at least equivalent to that experienced in fresh water. Electrofishing in fresh water is now widely practiced in Germany, the United States, and Canada , where it is used mainly as a new tool to supplement the facilities for stud y of fish populations. The progress made in Germany has been described by Smolian (1944) in a comprehensive report which includes a description of the equipment and techniques used in that country. In the United States, the first efforts concerned with the reaction of fish to electrical stimulation centered around the development ofelectric fish screens and began as early as 1917 (Holmes, 1948). However, a method of actually collecting fish in fresh-water streams was first developed in 1939 (Haskell, 1940). Equipment used for electrofishing in fresh water has consisted mainly of small, portable, gas-driven generators which produced alternating current. However, Smolian (1944) reported that the greatest effect seemed to be realized from using direct current interrupted at frequent intervals . large fish were affected