Environmental and Fishery-Related Threats to Population of Rutilus kutum (Kamensky, 1901) in the Caspian Ecosystem: A Comprehensive Analysis

Context. Rutilus kutum stocks in the Caspian Sea have experienced long-term declines due to intensified fishing and environmental stressors. Despite its ecological and economic importance, no integrative assessment of population dynamics had been conducted over an extended period. Aims. To evaluate the status and productivity of R. kutum stocks over three decades, using biological indicators and environmental drivers, and to inform adaptive fisheries management strategies. Methods. Biological data were analyzed to estimate growth parameters, mortality rates, and exploitation levels. Novel application of Generalized Additive Models was applied to assess recruitment relationships with seawater temperature, sea level, marine heatwaves, and hatchery releases. Key results. Exploitation rates frequently exceeded 0.5, indicating unsustainable fishing pressure. The length at 50% capture declined below the maturity threshold, increasing juvenile vulnerability. By 2021, abundance had dropped to less than one-third of 2006 levels. GAMs explained 72.8% of recruitment variation, revealing strong non-linear associations with environmental variables and hatchery output. Stock condition was rated “good” in only one year. Conclusions. Climate variability significantly affects stock productivity, while overfishing continues to undermine population resilience. Implications. These findings support the need for ecosystem-based, adaptive management approaches that integrate environmental variability and regulate exploitation to conserve R. kutum stocks.