Non-model method for the stock status assessing and catch forecasting of the Flounder 26+28 subdivisions ICES in the Baltic Sea

Abstract

The aim of this article: to assess the flounder stock state in the 26+28 ICES subdivisions of the Baltic Sea and forecast its catch in the Russian part of the 26th ICES subdivision using non-model methods.Methods used: The qualitative condition of the stock was assessed by length (LBI method — Length Based Indicators). To develop catch recommendations for flounder stock in 26+28 ICES subdivision, as well as in the Russian sea area, was used an approach for a stock category 3 (ICES classification), based on a combined biomass index for fish from bottom trawl surveys. The assessment was based on the ratio of the average values of population indices of the last two years to the previous values for three years. All methods have been successfully tested at the international level within the framework of seminars and Working Groups of the International Council for the Exploration of the Seas (ICES), in which Russian specialists took part.Novelty: In conditions of insufficient completeness and quality of available information to justification the flounder catch, using models of the exploited stock, for the Russian water area of the 26th ICES subdivision of the Baltic Sea, non-model methods for assessing the state and predicting its catch were used for the first time. Result: to solve problems of rational management and conservation of fish stocks, the LBI method, as a non-model assessment tool, allows timely identification of qualitative changes occurring in the stock. The flounder stock is within biologically safe limits. The fishery is aimed at preserving small and large fish (conservation option), the stock is exploited optimally. It is possible to maintain the species’ production level at least at the current level.Practical significance: In modern conditions the current level of information support for forecasting the flounder stock state and catch in the Baltic Sea will make it possible to solve problems related to the management of this resource in the near future.