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a commercial method of catching fish based on their characteristic responses to an electric current passing through the body.
Depending on the intensity of the current (direct or pulsating), three stages are distinguished: (1) frightened repulsion, (2) direct movement toward the anode, and (3) electronarcosis. Any of the three stages may be used in electrofishing; the boundaries of the stages depend on the species, size, and physiological state of the fish. Moreover, the reactions of fish of various species depend on the duration and frequency of the pulses. In electrofishing the current passes through the fish when they enter an electrical field between electrodes located in the water and connected to the source of the current. Direct currents are used in freshwater; they are produced by a relatively weak electric generator. Electrofishing with a pulsating current is more suitable in saltwaters, since less electricity is required.
The main types of electrofishing are electrified trawling and netless fishing. To catch benthic fish the electrodes are placed in the mouth of the trawl; the parameters of the electric pulses are selected so as to cause an anode reaction in the fish and not let them escape under the lower edge of the trawl. To catch fish inhabiting deep waters the electronarcosis effect is produced. The electrodes are placed in the front of the bag section of the trawl; fish entering the space between the electrodes are narcotized and washed to the back, accelerating formation of the catch and reducing loss of fish from the trawl. Netless electrofishing is used to catch fish having a pronounced anode reaction; under the influence of the current the fish head for the pump area. Electrofishing with pulsating currents is often used in combination with light fishing.
To increase the efficiency of electrofishing, research is being conducted on selecting the parameters and configuration of the electric field, the intensity of the current, and the repetition frequency of the pulses.
REFERENCESternin, V. G., I. V. Nikonorov, and Iu. K. Bumeister. Elektrolov ryby. Moscow, 1972.
S. K. MAL’KIAVICHIUS