Intentional killing and extensive aggressive handling of albatrosses and petrels at sea in the southwestern Atlantic Ocean

Large Procellariiformes (albatrosses and petrels) constitute a highly threatened group of birds, for which bycatch in fisheries is the most prevalent threat. At-sea intentional killing and post-capture, handling-related injuries, remain poorly understood menaces. Here, we report fishermen off southern Brazil trying to reduce bait depredation in pole-and-line and handlining fisheries by hitting birds with a metal piece attached to a pole-and-line on four occasions. Fishermen also mutilated or killed birds caught alive on the lines (aggressive handling). In addition, we present a compilation of records of Procellariiformes with bill mutilations across the southwest Atlantic Ocean. Related to the intentional killing events, 16 birds of four species (two globally threatened) were recorded dead (n = 13) or injured (n = 3) with head trauma, broken limbs, wounds or bill mutilation. Observations spanning 1999–2019 across the waters of Brazil, Uruguay and Argentina totalize 46 Procellariiformes of eight species (four globally threatened) recorded with bill mutilations (29 alive and 17 dead). Mutilations were likely caused by aggressive handling of birds caught alive, potentially in Brazilian hook-and-line fisheries or in demersal and pelagic longline fisheries across the southwest Atlantic. Observations of deliberate killing from multiple vessels and the recurrent records of mutilated birds suggest those practices represent pervasive but largely undocumented threats to seabirds and could complicate the detection of fishery-related population effects. Coordinated actions by international bodies and national authorities are urgently needed to address this threat, including increasing at-sea observation, enforcement actions and campaigns targeting better handling practices among fishermen.