Status of Crayfish Populations (<i>Astacidae</i>) on the Eastern Coast of the Caspian Sea

Abstract

Aim. This work aims to study the distribution and stocks of crayfish on the eastern shelf of the Caspian Sea at places where they mostly habitat.Material and Methods. The studies were implemented in the spring and summer of 2019. The material was collected by scuba divers surveying routes of transects 100 m2 in area. Collected crayfish were identified at species level, measured, weighed and their fertility was evaluated. Their abundance was calculated by estimating the aggregation density along the routes (ind./m2), with subsequent recalculation for the biotope areas, which were identified using data from the Caspian Sea satellite monitoring. The stocks were estimated according to the size and weight characteristics of collected individuals.Results. Two astacid species inhabit the surveyed area: Pontastacus eichwald Bott – long‐clawed crayfish and Caspiastacus pachypus Rathke – thick‐clawed crayfish. Certain changes have occurred compared with archival data of the 1970s‐1990s. The range area has expanded and the abundance of C. pachypus has increased. The fertility of both C. pachypus and P. eichwald has reduced.Conclusion. The crayfish stocks in the surveyed area are of commercial importance. The application of satellite survey data greatly increases the objectivity of research.

Keywords

• caspian sea
• eastern coast
• crayfish
• distribution
• species composition of populations
• features of species biology
• commercial and economic value of stocks
• total allowable catch