<p>Understanding population structure is fundamental to the sustainable management of marine fish. Blue whiting (<i>Micromesistius poutassou</i>) plays a key ecological role in the Northeast Atlantic as a mid-trophic species linking zooplankton to top predators, while also supporting major commercial fisheries. This review synthesises available evidence on its population structure, revealing a complex metapopulation composed of resident and migratory subpopulations. Although currently assessed as a single stock, this management unit does not account for underlying biological structure, potentially limiting the effectiveness of assessment and management strategies. Our synthesis supports the presence of partial migration, with both migratory and resident contingents contributing to spatial complexity in population structure. Genetic, otolith, parasite, and life-history data indicate the existence of relatively discrete northern and southern subpopulations, mixing zones, and resident groups. We highlight the importance of adaptive, spatially explicit management approaches that account for temporal variability, support stakeholder engagement, and foster regional cooperation. Key knowledge gaps remain in fine-scale population structuring, life-history stage characterisation, and connectivity mechanisms. Addressing these will require integrative approaches using genomics, otolith chemistry, and biophysical modelling. While current stock boundaries encompass the species' range, integrating internal biological structure into assessments and management strategies will enhance their effectiveness and contribute to sustainable exploitation.</p> Graphical abstract <p></p>