Résumé
The Mediterranean Sea is a significant habitat for seabirds, including endemic and endangered species. However, French pelagic longline fisheries overlap with foraging zones of seabirds, posing risks of bycatch. Insufficient monitoring and reporting hinder efforts to understand and mitigate these interactions. To identify effective fisheries bycatch mitigation measures, documenting species-fishing gear interactions and foraging strategies for each species are needed. Seabird underwater interaction processes were investigated in situ on pelagic longline gears. Cameras affixed on branchlines 1–2 m above the hook were deployed between May 2022 and June 2024 to enable a precise description of interactions of various species with baited hooks, including the Yelkouan Shearwater (Puffinus yelkouan) and the Atlantic Puffin (Fratercula arctica). Foraging strategies are documented for the two pursuit-diving seabirds. The Yelkouan Shearwater foraged in association with conspecifics and competitive events were observed. Videos revealed cryptic events of successful and unsuccessful attempts in consuming the bait during the gear soak at depths to ca 10 m. Underwater interactions occurred during the gear soak on unattended gear, while the vessel was away from the site. The Yelkouan Shearwater and the Atlantic Puffin may have developed strategies to feed on pelagic longline bait. These observations suggest that bycatch mitigation approaches are needed during multiple phases of fishing operations, and not just during setting and hauling as is the prevailing paradigm. Technical seabird bycatch management measures tailored to regional fishing practices are proposed and discussed.