Connectivity of the Blue Crab Callinectes sapidus in the Southwest Atlantic Ocean: Population Genetics, Biophysical Modeling and Management Implications

Bio‐oceanographic modeling and population genomics were combined to assess connectivity of the blue crab Callinectes sapidus in the Southwestern Atlantic Ocean, with particular attention to the scale of its fishery management, and the potential role of Marine Protected Areas (MPAs) in Uruguay as larval source zones. A bio‐physical model, coupled with hydrodynamic outputs of a model experiment, incorporated larval vertical migration behavior and key species‐specific traits to simulate dispersal pathways across the region. Population structure was assessed by using SNPs variability. Both approaches revealed substantial connectivity among sampled locations. Genomic population genetic analysis supported a single, well‐mixed population across the study area, consistent with the extensive dispersal predicted by the model. These results highlight the need for management strategies tailored to the species' population structure and emphasize the importance of binational (Brazil‐Uruguay) coordination for this transboundary fishery, which is already showing clear signs of overexploitation. Model simulations further showed that Uruguayan MPAs may act as important larval sources, particularly during winter recruitment under La Niña conditions, exporting propagules to non‐protected areas in southern Brazil. By resolving the spatial and temporal scales of larval exchange, this study enhances regional understanding of connectivity patterns and supports evidence‐based conservation planning for C. sapidus .