Analysis of nowadays fisheries and the recommendations of the regulation of the main commercial fish species stocks exploitation in the Dniestrovskiy liman

Abstract

The dynamics of the catch of the main commercial fish species of the Dniesterovskiy liman are presented. The sizeage composition of the gibel carp Carassius gibelio (Bloch, 1783), common carp Cyprinus carpio (Linnaeus, 1758), common bream Abramis brama (Linnaeus, 1758), roach Rutilus heckelii (Nordmann, 1840) and common pike-perch Sander lucioperca (Linnaeus, 1758) from commercial catches in the Dniesterovskiy liman in 2012–2021 was analyzed. The obtained data were used to analyze the state of fish stocks and to obtain the recommended optimal indicators of their exploitation using modern models BSM, LBB and LB-SPR. The overexploitation of gibel carp in the Dniesterovskiy liman was observed accordingly BSM, LBB and LB-SPR results. A sharp increase in the level of exploitation of gibel carp has led to its stock decline. The level of common carp exploitation in 2018–2021 has approached the optimal value. The currently state of its population in the Dniesterovskiy liman is relatively good. Commercial exploitation of the common bream and roach remains at an excessive and at a relatively moderate level respectively. The catch and CPUE of the pike perch have been declined significantly in recent years. The stock of this species is in a very unfavorable condition. The recommendations for further use of the main commercial fish species in the Dniesterovskiy liman are given. Accordingly obtained results the value of the maximum sustainable yield (MSY) of gibel carp is 813 tons with the optimal average commercial length in the catch – 18.5–19 cm. MSY of common carp is set at 92.7 tons with the optimal length in the catch – 39.9 cm, common bream – 148 tons with an optimal length in the catch no less than 30.0 cm. MSY of roach is set at 57.7 tons. The value of pike perch biomass is significantly lower than the critical value of Bpa=0.5 BMSY – its catch should not exceed 5 tons. The strict compliance with the Rules (1998) and Regimes of commercial fishery, as well as commercial fishing regulating by limiting the use of fishing gear are the most effective methods of the abundance increasing and rational use of water biological resources of the Dniesterovskiy liman.