State and dynamics of commercial fish stock recruitment in the Dnieper-Bug mouth system

Abstract

The purpose. To determine quantitative and quality indicators of groups of young fishes as a basis for formation of source of raw materials of trade and biological diversification of Dnieper-Bug mouth system. Methods. Field ichthyologic probes, mathematical calculations. Results. Data on species composition, numerosity and allocation of groups of young fishes of Dnieper-Bug mouth system are taken and analysed. Basic trends in dynamics of catches of young fishes on force of control fishing gears, as integral characteristics of natural reproduction and basis for enforcement of source of raw materials of trade are specified. Conditions of reproduction of different ecological groups of fishes are probed. Dynamics of quality contents of commercial catches is analysed. Conclusions. Basis for commercial catches of fishes of Dnieper-Bug mouth system made Black-sea sprat (62,2 %) and Prussian carp (21,4 %). Part of a class «valuable trade sorts» made 7,3% of overall catch. Self-reconstituting populations of fishes ensured formation of 93,5% of a catch, i.e. natural reproduction remained the basic source of enforcement of source of raw materials of piscatory trade of Dnieper-Bug mouth system. According to probes of 2006–2015 period young fishes of 18 sorts were fixed on foreshore plots, the basis of numerosity (56,3–57,2%) made invaluable and minor in economic ratio sorts - Prussian carp, Black-sea sprat, atherina. Among valuable trade sorts the most numerous were roach (7,3%) and bream (3,4%). These species formed 16.4% of total catch in gill nets in 2010–2017. Interannual dynamics of numerosity of young fishes of trade sorts for the last 10 years specifies that at maintenance of optimum hydrological regime of Dnieper-Bug mouth system it is possible to forecast stability of commercial catches in immediate prospects.