ABSTRACT
The knowledge of the difference in character and density of the fish distribution is one of the main factors facilitating the species interpretation of readings of acoustic instruments. Numerous results of acoustic observations have been accumulated on fish distribution and movement in various water bodies, on fish vertical migrations, and on their reaction to light and to fishing gear. Various forms of distribution and registration of different fish species facilitate the interpretation of their readings. Species interpretation of mixed concentrations including several fish species presents considerable difficulties. The experimental conditions on the commercial concentrations at sea were controlled with the help of fish-finding echo sounders. Recordings of schools of various fish species have specific distinctions. Recordings of schools of horse mackerel, unlike those of sardine, had a more regular shape, with more distinct borders. The presence of fish readings over rocky ground provides complete certainty in determining the fish species in the areas of perch fishing of the Far East.
