Dynamics of indices of the state of the blue king crab stock in the western part of the Bering Sea in 2005–2021

Abstract

The aim of the research is a retrospective analysis of the stock of the blue king crab Paralithodes platypus inhabiting the western part of the Bering Sea, to show the prospects of using the relative abundance index (I%N) as an assessment characterizing the state of the stock of this species. Material and methods. It is based on the data of direct accounting of P. platypus during trawl and trap surveys in 2005–2021. For each year, an index of relative abundance was established, expressed as a percentage of the maximum number of crabs noted in the retrospective period. The I%N index was determined for different functional groups of the crab separately and for combined size and age groups. New data. The use of the relative abundance index I%N in quartiles makes it possible to apply a four-zonal evaluation characteristic of the stock status of P. platypus: the stock condition is good, satisfactory, uncertain and depressive. This indicative method displays the dynamics of the state of the stock in the studied period and visualizes its variability in the historical period. In the West Bering Sea population of P. platypus, there has recently been a decrease in the number, which is less than 40 % of the maximum number observed during the study period. In all functional groups of P. platypus, the estimate of abundance (stock) is currently characterized as uncertain. Practical significance. The retrospective dynamics of the relative abundance index I%N is an additional operational indicator in making a management decision when developing P. platypus as a commercial reserve unit in the western part of the Bering Sea.