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Investigating the Impact of Climate Parameter Changes on the Distribution and Catch Rate of Caspian Carp in the Southeastern Part of the Caspian Sea
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Abdolazim Fazel *   , Fatemeh Abbasi , Salman Malekpour Kolbadinajad , Parviz Zare , Arezu Vahabnejad , Maryam Forouzad , Mohsen Yahyaei , Yaser Abdullah Tobar |
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Abstract: (24 Views) |
Time series analysis of CPUE in the eastern and southern fishing grounds of Golestan Province from 2006 to 2024 reveals a regional and integrated regime shift in the carp (Cyprinus carpio) stock. This transformation occurred from a state of high abundance with a clear seasonal pattern (peak catch in winter months) to a persistent low-abundance condition lacking a significant seasonal pattern, beginning between 2008 and 2012 and continuing through 2024. This finding aligns with previous reports and indicates that the decline in carp populations is not merely a local phenomenon, but rather a structural change at the regional scale, likely driven by a combination of high fishing pressure, environmental changes, and their interactions. GAM modeling with 2- and 3-month lags enabled the examination of complex, non-linear relationships between CPUE and environmental variables. Results identified wind speed (Lag-2 and Lag 3), sea surface temperature (SST, Lag-3 and mean sea level (MSL, Lag-3) as the most significant predictors of CPUE. Partial dependence plots revealed non-linear responses, such as increased CPUE under extremely calm or strong winds and at both very cold and very warm temperatures, indicating species-specific threshold and synergistic responses. These patterns are consistent with ecological mechanisms like water mixing, primary production, and prey distribution, highlighting the importance of temporal lags in ecosystem responses. Climate anomaly analysis further revealed two prominent trends over the past two decades: gradual warming of sea surface temperature (SST) and declining mean sea level (MSL), both of which are consistent with global climate change. The reduction in water level, in particular, may lead to the loss of shallow feeding and spawning habitats, exacerbating population decline. These findings are in agreement with prior studies documenting reduced river discharge, habitat degradation, and declining biodiversity, underscoring the need for integrated, climate-informed fisheries management. In conclusion, this study provides a robust scientific framework by combining climate data with temporal lags, non-linear modeling, and predictive analysis, emphasizing the necessity for policy reform, stricter fishing pressure controls, protection of critical habitats, and the integration of climate projections into fisheries planning.
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| Keywords: Caspian Sea, Climate Change, and Time Lag |
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Type of Study: Research |
Subject:
Special
Received: 2026/04/12 | Accepted: 2026/04/15 | Published: 2026/04/18
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