METHOD OF SEARCHING FOR CORRELATION BETWE EN HYDROBIOLOGICAL INDEXES AND ABIOTIC FACTORS (USING COMMERCIAL FISH CATCHES AND PRODUCTIVITY ASEXAMPLES)

A system of determining ecologically tolerable levels of abiotic facto rs related to variations in fish abundance is proposed. Factors relate d to decreases in commercial catches of bream, sabrefish, pike-perch, and Volga zander in the Don water reservoirs and to the productivity o f bream and sturgeon in the Lower Don basin were identified. We determ ined the importance of these factors based on a ''stepwise'' analysis for arranging environmental protection measures in order of their prio rity. The basic principles of the concept of ecologically tolerable le vels are outlined. This concept is more successful and promising than the usual concept of threshold limits of pollutant concentrations.