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Describing patterns of connectivity among populations of species with widespread distributions is particularly important in understanding the ecology and evolution of marine species. In this study, we examined patterns of population differentiation, migration, and historical population dynamics using microsatellite and mitochondrial loci to test whether populations of the epinephelid fish, Gag, Mycteroperca microlepis, an important fishery species, are genetically connected across the Gulf of Mexico and if so, whether that connectivity is attributable to either contemporary or historical processes. Populations of Gag on the Campeche Bank and the West Florida Shelf show significant, but low magnitude, differentiation. Time since divergence/expansion estimates associated with historical population dynamics indicate that any population or spatial expansions indicated by population genetics would have likely occurred in the late Pleistocene. Using coalescent-based approaches, we find that the best model for explaining observed spatial patterns of contemporary genetic variation is one of asymmetric gene flow, with movement from Campeche Bank to the West Florida Shelf. Both estimated migration rates and ecological data support the hypothesis that Gag populations throughout the Gulf of Mexico are connected via present day larval dispersal. Demonstrating this greatly expanded scale of connectivity for Gag highlights the influence of “ghost” populations (sensu Beerli) on genetic patterns and presents a critical consideration for both fisheries management and conservation of this and other species with similar genetic patterns. [ABSTRACT FROM AUTHOR]

Among threats to marine species, overfishing has often been highlighted as a major contributor to population declines and yet fishing effort has increased globally over the past decade. This paper discusses the decadal reassessment of groupers (family Epinephelidae), an important and valuable group of marine fishes subjected to high market demand and intense fishing effort, based on IUCN criteria. Allowing for uncertainty in the status of species listed as Data Deficient, 19 species (11.4%) are currently assigned to a "threatened" category. This first reassessment for a large marine fish taxon permits an evaluation of changes following the original assessments, provides a profile of the current conservation condition of species, identifies the challenges of assessing conservation status, and highlights current and emerging threats. Measures needed to reduce threats and lessons learned from conservation efforts are highlighted. Present threats include intensifying fishing effort in the face of absent or insufficient fishery management or monitoring, growing pressures from international trade, and an inadequate coverage in effectively managed, sized, or located protected areas. Emerging threats involve expansion of fishing effort into deeper waters and more remote locations, shifts to previously non-targeted species, increases in the capture, marketing and use of juveniles, growing demands for domestic and international trade, and, potentially, climate change. Those species most threatened are larger-bodied, longer-lived groupers, most of which reproduce in spawning aggregations. [ABSTRACT FROM AUTHOR]