a method of obtaining fish without using net devices. It is based on a thorough study of the biological characteristics of a species offish and the characteristics of its reaction to various stimuli; it is also based on the use of modern technological means for concentrating the fish scattered in the depths. Electrical currents and light are used in netless fishing, and the possibility of using sound and chemical agents is under study.
Fishing with the aid of electrical currents initially came into practice in fresh water. Electrodes are joined to a direct-current source and placed in the water. Under the influence of the electric field, fish orient themselves between the electrodes and move in the direction of the anode. When the distance to the anode is sufficiently small, fish fall into a state of electronarcosis and can easily be gathered up with hand nets or other devices. When the current is shut off, fish come out of the electronarcotic state comparatively quickly. The effect of the current depends on the species and size of the fish. The effect on large species is stronger than that on small species, and this is the basis for selective fishing, making it possible to gather fish of a given size. The apparatus for catching fish in fresh water operates with diesel generators that put out a direct current of 5–10 amps and 200–300 volts. In seawater, this current proved insufficient, so that it had to be increased to 10 kiloamperes. This required larger systems, which were economically inexpedient. The problem was resolved by the use of impulse current.
Very successful dense accumulations of fish, suitable for mass fishing, have been created through the use of electric lights. At certain periods in their lives, different species of fish react differently to light. Some (sardines, herring, saira, sprats) are attracted by light. For example, to catch Caspian sprat with lights during darkness, a fishing vessel—after locating the fish—switches on the lamps it has put over the side, and the sprats head for the light in such a dense shoal that they may be easily pumped up. Further development of netless fishing is opening broad vistas for industrial fishing.
REFERENCESNikonorov, I. V. Lov ryby na svet. Moscow, 1963.
Shishkova, E. V. Fizicheskie osnovy rybolokatsii. Moscow, 1963.
Protasov, V. R. Bioakustika ryb. Moscow, 1965.
A. V. ZASOSOV