Search

We used the bycatch of Caspian sturgeon to quantify the species composition, length structure, spatial and temporal distribution, temporal dynamics of relative abundance (indexed as catch‐per‐unit‐effort, CPUE), effects of fingerlings released, and to forecast future sturgeon stock status. Dynamic factor analysis of temporal changes in species CPUE was used to quantify relationships to environmental variables (sea surface temperature, chlorophyll‐a, sea surface level, and river discharge) during 2006–2022. We found that the Guilan subarea had the lowest relative abundance and differed from all other subareas. Fish abundance was highest in October and November, particularly in Mazandaran and Golestan coastal waters. Relative fish abundance declined significantly over time. Acipenser persicus was the most abundant species, followed by Aciperser gueldenstaedtii, Aciperser stellatus, Aciperser nudiventris, and Huso huso. The annual number of fingerlings released decreased during 2000–2021. Over the years, environmental variables such as sea surface level, sea surface temperature, and chlorophyll‐a showed different trends, with sea surface temperature generally increasing, chlorophyll‐a generally decreasing, sea surface level decreasing nearly linearly, and river discharge varying erratically without a trend in the southern Caspian Sea during 2006–2022. The relative abundance of all species decreased and was significantly related to sea surface level. Fish abundance was forecasted to decline by 2025, as sea surface temperature increases and sea surface level decreases. Illegal, unreported, and unregulated (IUU) harvest of sturgeon must be effectively regulated to ensure the survival and recovery of sturgeon populations in the Caspian Sea. [ABSTRACT FROM AUTHOR]

Keywords: commercial fish species; catch assemblage; temporal patterns; community structure; environmental parameters; Caspian Sea EN commercial fish species catch assemblage temporal patterns community structure environmental parameters Caspian Sea 90 99 10 04/28/22 20220301 NES 220301 1 Introduction The Caspian Sea (CS), the largest lake in the world, is a unique ecosystem known for its rich and diverse aquatic fauna (Karpinsky et al. 2005). Despite the commercial importance of bony fish, no study has been carried out on the species composition of these fish assemblages in relation to environmental parameters in the CS. 2.2 Environmental data Global variables with large-scale influence - the global temperature anomaly (GTA), the East Atlantic-West Russian pattern (EAWR), the North Atlantic Oscillation (NAO), and two regional environmental variables - sea surface temperature (SST) and sea surface level (SSL) were investigated to assess the potential effects on fish species assemblages between 1996 and 2017 (Table 1). Table 4 Relationship between environmental variables and diversity index, most abundant fish species (species with a percentage value higher than 1%) in the Caspian Sea. [Extracted from the article]