Threatened species bycatch hotspots in the tropical Atlantic Ocean

Abstract

Predicting bycatch patterns in tropical tuna purse seine fisheries remain challenging due to low variance explained by existing models, limiting their use for management purposes. To address this limitation, we combined ecological network analyses and community detection methods to characterize recurring bycatch assemblages in tropical tuna purse seine fisheries. Ecological network analyses consistently revealed two key bycatch communities: one dominated by bony fishes with low conservation concern, and another by IUCN-listed threatened species (NT-CR; sharks, rays, sea turtles). By focusing on sets with high numbers of threatened species, we identified bycatch hotspots near Mauritania, Gabon and Angola. These hotspots result from seasonal fishing patterns and specific bycatch compositions, with specific composition in terms of sex and age, compared to the rest of the Atlantic. We suggest that the Mauritanian region is a potential candidate for shark nursery and sea turtle foraging grounds. These insights can guide the development of bycatch reduction strategies based on predictable spatio-temporal or community-specific features and provide a basis for targeted management actions.