Analysis of materials from long-term studies characterizing the current state of sturgeon stocks in the Volga-Caspian fisheries basin, and the dynamics of commercial catches of beluga, sturgeon and stellate sturgeon in the XX - XXI centuries indicates that the Northern Caspian occupies the leading value in catch volumes, where more than 70 % of sturgeon fish are annually harvested. In the first half of the twentieth century sturgeon stocks were determined by the scale of natural reproduction in rivers and fishing volumes; in the second half, natural and anthropogenic factors began to intensively influence the formation of sturgeon stocks. The development of hydraulic construction on rivers, an increase in the withdrawal of freshwater runoff, a decrease in sea level to -29.0 mBS, pollution by industrial and agricultural runoff have necessitated the development of a set of measures for the reproduction, conservation and rational use of the Caspian’s aquatic biological resources. As a result of the studies, the response of the sturgeons to the changed conditions of reproduction has been determined in order to restore and increase their commercial stocks; high ecological adaptability of sturgeons to various living conditions within their range, their exceptional plasticity and pronounced intraspecific differentiation have been established. These indicators point to the possibility of creating conditions that meet the requirements for water quality for the life of sturgeons during migration and reproduction. In the course of the analysis of the obtained data, the influence of regulation of the Volga River flow on the efficiency of natural reproduction of sturgeons has been evaluated; the role of industrial sturgeon breeding in sturgeon stock formation has been shown; the abundance of juveniles in the North Caspian and adult individuals on feeding pastures of the sea has been estimated; trends in the number of sturgeon producers migrating in the Volga to spawning sites have been identified; the prospects for the restoration and rational use of sturgeons in the Volga-Caspian basin have been determined.

No abstract

The aim of the paper is a qualitative assessment of the stock of long - clawed crayfish on the basis of the indicator approach.Methods used: indicator approach of qualitative stock assessment, methods of descriptive statistics, regression analysis.Novelty: a qualitative assessment of the stocks of long - clawed crayfish in the Astrakhan region by the indicator approach has not been previously carried out.Result: Qualitative assessments of the state of the stock of long- clawed crayfish in the Astrakhan region in 2016-2020 were obtained. The results of the assessments showed that in 2016, 2019 and 2020 its stock in the Astrakhan region was in an uncertain state (an integral assessment showed no dynamics in the state of the stock for the worse or better), and in 2017 and 2018 - in the alarming state (the integral assessment showed a negative trend in the state of the stock). The final integral assessment made it possible to formulate recommendations for the further exploitation of the stock of this species of hydrobiont.Practical significance: this study represents the application of the indicator approach in the biological sub -stantiation of the assessment of the total allowable catch of long - clawed crayfish in the Astrakhan region.