Bioregionalization of the southwest Atlantic Ocean based on fish life-history traits: perspectives on fisheries impacts

Large-scale environmental gradients influence the distribution of species and their ecological strategies, shaping the functional organization of marine ecosystems. In marine fishes, life-history traits such as growth rate, longevity, and reproductive investment regulate population turnover and biomass production, linking macroecological processes to ecosystem functioning and fisheries dynamics. We investigated how environmental gradient’s structure life-history strategies across the Southwestern Atlantic (SWA) and evaluated how fishing pressure affects the functional diversity of regional assemblages. We compiled a comprehensive database of marine fish species and associated life-history traits, using multivariate analyses to describe functional gradients and redundancy analysis to assess the role of environmental variables in structuring these patterns. Functional bioregions were identified using generalized additive models applied to smoothed latitudinal trends in trait space, while potential fishing impacts were evaluated through simulations of progressive species removal based on commercial importance. Results revealed that tropical assemblages were characterized by a high diversity of life-history strategies and faster demographic turnover, whereas temperate assemblages were dominated by larger-bodied species with slower life histories. Simulated species loss showed region-specific impacts; temperate assemblages exhibited stronger declines in functional diversity following the removal of highly commercial species, while tropical assemblages were more sensitive to the loss of species with lower commercial importance. These findings demonstrate that environmental gradients shape the functional organization of marine fish assemblages across the SWA and that fishing acts as a directional filter altering this structure. Integrating trait-based macroecology with fisheries dynamics provides valuable insights for understanding ecosystem resilience and supporting spatially explicit management strategies.