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<p>Connectivity between critical habitats shapes the population dynamics of migratory fishes, yet direct movement data remain scarce for many estuarine species. We combined fishery-independent bottom-trawl surveys (2024–2025; 330 hauls), a spatial Tweedie generalised additive model (deviance explained: 73.4%) and circuit theory analysis of predicted density surfaces to infer seasonal connectivity hypotheses and candidate bottlenecks for post-young-of-the-year (post-YOY) <i>Coilia nasus</i> in the Yangtze Estuary. Predicted density showed strong seasonality: spring densities were highest and concentrated in the inner-to-mid-estuary (mid-estuary mean predicted density: 2883 ind km⁻<sup>2</sup>), consistent with a spring inward-migration scenario, whereas summer and autumn densities declined and shifted seaward, consistent with post-spawning redistribution. Circuit theory current maps indicated a narrow spring corridor of inferred high permeability broadly aligned with the South Channel, and broader, northward-displaced corridors in summer and autumn. Five candidate bottlenecks clustered in three geomorphically distinct zones: the inner-estuary/South Channel transition (~ 122.1–122.3°E), a northern inner-estuary gateway (~ 122.1°E), and a recurrent mid-to-outer estuary constriction (~ 122.6–122.7°E) near the reported summer Changjiang Diluted Water plume-front region. These density-derived connectivity hypotheses identify priority locations for monitoring and movement validation under China's 10-year fishing ban. More broadly, the density–resistance–circuit workflow provides a reproducible framework for generating testable connectivity hypotheses for estuarine diadromous fishes where direct movement data are scarce.</p>

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Density-derived circuit theory identifies seasonal connectivity hypotheses and candidate bottlenecks for Coilia nasus in the Yangtze Estuary

  • 期刊论文

  • 发表日期：

    2026年6月25日

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  • Hongyi Guo,
  • Xuguang Zhang,
  • Wenqiao Tang,
  • Kai Liu

摘要

Connectivity between critical habitats shapes the population dynamics of migratory fishes, yet direct movement data remain scarce for many estuarine species. We combined fishery-independent bottom-trawl surveys (2024–2025; 330 hauls), a spatial Tweedie generalised additive model (deviance explained: 73.4%) and circuit theory analysis of predicted density surfaces to infer seasonal connectivity hypotheses and candidate bottlenecks for post-young-of-the-year (post-YOY) Coilia nasus in the Yangtze Estuary. Predicted density showed strong seasonality: spring densities were highest and concentrated in the inner-to-mid-estuary (mid-estuary mean predicted density: 2883 ind km⁻2), consistent with a spring inward-migration scenario, whereas summer and autumn densities declined and shifted seaward, consistent with post-spawning redistribution. Circuit theory current maps indicated a narrow spring corridor of inferred high permeability broadly aligned with the South Channel, and broader, northward-displaced corridors in summer and autumn. Five candidate bottlenecks clustered in three geomorphically distinct zones: the inner-estuary/South Channel transition (~ 122.1–122.3°E), a northern inner-estuary gateway (~ 122.1°E), and a recurrent mid-to-outer estuary constriction (~ 122.6–122.7°E) near the reported summer Changjiang Diluted Water plume-front region. These density-derived connectivity hypotheses identify priority locations for monitoring and movement validation under China's 10-year fishing ban. More broadly, the density–resistance–circuit workflow provides a reproducible framework for generating testable connectivity hypotheses for estuarine diadromous fishes where direct movement data are scarce.