University of Veterinary Medicine Vienna Seascape genomics and mitogenomic phylogeography of the sailfish (Istiophorus platypterus) Permeable phylogeographic barriers characterize the vast open ocean, boosting gene flow and counteracting population differentiation and speciation of widely distributed and migratory species. However, many widely distributed species consists of distinct populations throughout their distribution, evidencing that our understanding of how the marine environment triggers population and species divergence are insufficient. The sailfish is a circumtropical and highly migratory billfish that inhabits warm and productive areas. Despite its ecological and socioeconomic importance as a predator and fishery resource, the species is threatened by overfishing, requiring innovative approaches to improve their management and conservation status. Thus, we presented a novel high-quality reference genome for the species and applied a seascape genomics approach to understand how marine environmental features may promote local adaptation and how it affects gene flow between populations. We delimit two populations between the Atlantic and Indo-Western Pacific oceans and detect outlier loci correlated with sea surface temperature, salinity, oxygen, and chlorophyll concentrations. However, the most significant explanatory factor that explains the differences between populations was isolation by distance. Despite recent population drops, the sailfish populations are not inbred. For billfishes in general, genome-wide heterozygosity was found to be relatively low compared to other marine fishes, evidencing the need to counteract overfishing effects. In addition, in a climate change scenario, management agencies must implement state-of-the-art sequencing methods, consider our findings in their management plans, and monitor genome-wide heterozygosity over time to improve sustainable fisheries and the long-term viability of its populations. en TEXT article Population-Structure; Genetic Diversity; Marine Fish; Fisheries; Evolution; Accurate; Speciation; Discovery; Framework; Inference 2023 2023 Ferrette, Bruno Lopes da Silva (Senckenberg Biodiversity and Climate Research Centre / LOEWE Centre for Translational Biodiversity Genomics / Santa Cecília University ) Janke, Axel (Senckenberg Biodiversity and Climate Research Centre / LOEWE Centre for Translational Biodiversity Genomics / Goethe University) Winter, Sven (Senckenberg Biodiversity and Climate Research Centre / University of Veterinary Medicine Vienna) Coimbra, Raphael T. F. (Senckenberg Biodiversity and Climate Research Centre / Goethe University) Mendonça, Fernando Fernandes (Universidade Federal de São Paulo) Mourato, Bruno Leite ( Universidade Federal de São Paulo) Arocha, Freddy (Universidad de Oriente) Rotundo, Matheus Marcos (Universidade Santa Cecília) Rosa, Daniela (Instituto Português do Mar e da Atmosfera / Universidade do Algarve) Coelho, Rui (Instituto Português do Mar e da Atmosfera / Universidade do Algarve) Williams, Samuel Mackey (The University of Queensland) De Jong, Menno J. (Senckenberg Biodiversity and Climate Research Centre) Oxford University Press