Spatial Dynamics in Fisheries Stock Assessment

Fisheries stock assessments have traditionally treated populations as homogeneous entities confined to single management units. In reality, many marine species exhibit spatial structure driven by habitat heterogeneity, life-history stages and environmental gradients. Spatial dynamics encompass movement of individuals among areas, localised depletion and shifts in distribution under changing oceanographic conditions. Incorporating spatial processes into assessment models enhances the realism of population estimates, supports identification of critical habitats and informs adaptive management. Spatially explicit approaches range from simple two-area frameworks to high-resolution grid-based models. They can reveal cryptic collapses in sub-regions, distinguish dynamics of subpopulations and refine estimates of biomass, recruitment and fishing mortality. Recent advances in tagging, remote sensing and geostatistics have improved parameterisation of movement and connectivity, while simulation studies have evaluated the trade-offs between model complexity and data availability. Ultimately, integrating spatial dynamics into stock assessment strengthens the scientific basis for quota setting, marine protected area design and ecosystem-based management, contributing to the sustainability and resilience of global fisheries.

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Spatial Dynamics in Fisheries Stock Assessment publication trend

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Technical terms

Spatially explicit model: An assessment framework that accounts for variation in population parameters and fishing effort across geographic areas.

Operating model: A simulation tool representing underlying population dynamics and data-collection processes to test assessment methods.

Metapopulation: A collection of spatially separated subpopulations connected by movement or larval dispersal.

Sequential spatial depletion: A pattern in which intensive fishing successively reduces biomass in adjacent areas over time.

Spawning Potential Ratio (SPR): The reproductive output of a stock under current fishing pressure relative to its unfished state.

References

1. ‘Drivin' with your eyes closed’: Results from an international, blinded simulation experiment to evaluate spatial stock assessments. Fish and Fisheries (2024).
2. Spatially explicit stock assessment uncovers sequential depletion of northern shrimp stock components in the North Sea. ICES Journal of Marine Science (2023).
3. Spatial heterogeneity of biological traits and effects on fisheries management based on the assumption of a single stock. The case of the common hake (Merluccius gayi) in Chile. Frontiers in Marine Science (2023).