A Multi-species modeling approach to consider the effects of environmental parameters on Caspian sturgeon fishes stock status

Abstract

In the three last decades, a drastic decrease has been observed in the catch and stocks of sturgeons in the Caspian Sea. All the sturgeon species are now classified as “critically endangered” by the International Union for Conservation of Nature (IUCN). Here, we investigated whether global (Atlantic-West Russian pattern EAWR), regional (sea surface level SSL and sea surface temperature SST), and local (Volga discharge VD) environmental changes might have caused such a situation. For this, we fitted dynamic factor analysis (DFA) on three biological indices (relative condition factor Kn, gonadosomatic index GSI, and catch per unit effort CPUE) of sturgeons datasets spanning from 1990 to 2014 (25 years) to consider the environmental variables that can better describe variability in bioindicators of these species over the last decades. Among 180 different models, the model that includes with “diagonal and unequal” R matrix, 2 common trends, with explanatory covariates of SST and without explanatory covariates identified as the best model with the lowest AICc value for GSI and CPUE, respectively. The best model is characterized by 1 common trend and “diagonal and unequal” with covariates of SSL and EAWR for Kn. There was good agreement between observed and predicted indices for five sturgeon species. The application of DFA to three biological indicators of the temporal structure of five sturgeon is essential because the patterns are not evident in other analyses in the Caspian basin.