LONG-TERM DYNAMICS OF THE BREAM STOCKS IN THE AZOV SEA (RUSSIAN WATERS) BASED ON THE RESULTS OF CMSY MODELING UNDER THE CONDITIONS OF LIMITED DATA AVAILABILITY (2002-2020)

Abstract

. Analytical assessment of the Azov Sea stock of the common bream Abramis brama (Linnaeus, 1758) for the time range 2002–2020 has been performed using CMSY trend model in R that is suitable for application in the context of limited data availability. Current state of the stock is at the level of the reference point based on stock biomass, and shows evidence of substantial overexploitation (B 2020 /B MSY =0.989; F 2020 /F MSY =1.82). Accounting for the volumes of IUU-fishing using indirect estimates increases comprehensiveness of the results and ensures adequate stock assessment and evaluation of fishing mortality. Pooled estimates of bream stock biomass for the investigated period indicate a collapse of population abundance that fell upon 2005–2013 and, presumably, stemmed from climatic and hydrochemical changes in the Azov Sea environment, not being associated with overexploitation of the population in those years. At present, the bream population still remains in depressed state, with prerequisites for stock recovery. Following the results of modeling and after a consideration of forecast scenarios, the size of recommended legal catch for 2022–2023 could be set within the range between 40 and 110 t, depending on the efficiency of control, accounting, prevention and suppression of IUU-fishing. So long as the population is exploited within these limits, stock biomass will remain at a safe level and has the possibility of reaching 950 t. The results of this investigation highlight the necessity of control and prevention of bream IUU-fishing in the Azov Sea and Don River Basins; this is a crucial factor influencing bream population in the recent years.