Research Article: Population dynamics of stellate sturgeon Acipenser stellatus Pallas, ۱۷۷۱ in the southern Caspian Sea

In the last three decades, several ecological factors were changed and affected the most important commercial fish stocks in the Caspian Sea. This paper aims to assess the effects of these pressures on the population structure, stock status and the vulnerability risk of stock extinction of the stellate sturgeon (Acipenser stellatus Pallas, ۱۷۷۱) in the Southern Caspian Sea, in the years ۱۹۹۰-۲۰۱۱. For this period, we estimated growth parameters, the age structure of catch, sexual maturity, age at first capture, natural and fishing mortality, biomass and risk of stock extinction of stellate sturgeon by IUCN Red List categories. Fork lengths of individuals ranged from ۸۲ to ۲۰۶ cm and ages from ۴ to ۲۹ years. The growth parameters were L∞=۲۱۵.۰ cm, K= ۰.۰۶۴ year−۱, t۰=−۳.۲ years. The majority of the catch (۶۷.۴-۹۰.۱%, averaged ۸۰.۰%) belonged to ۹-۱۳ years old. The biomass had a descending trend from ۴۹۸۳.۵ mt in ۱۹۹۰-۹۱ declined to ۱۰.۶ mt in ۲۰۱۱-۱۲. The generation length was ۱۶ years. Stock status indicators showed that ۸۹% of catch were mature individuals, mature and optimum fish length comprised ۷۴% and ۱۰% of the fish captured comprise mega-spawners. This study revealed that the stock of the stellate sturgeon is being overfished for the whole years and critically endangered.

Keywords:

Growth parameters , Biomass , Stock extinction , Acipenser stellatus , Caspian Sea