Seabird bycatch in longline fisheries causes an estimated 160,000-320,000 seabird deaths annually, including 100,000 albatrosses - contributing to population declines in 15 of 22 albatross species. Birds dive for baited hooks as longlines are set, becoming hooked and drowned. Welfare impacts include drowning, hook injury, and stress before death. Mitigation measures are highly effective when deployed: night setting (reduces visibility), weighted branch lines (sink baits faster), bird-scaring lines (tori lines), and underwater setting devices reduce bycatch by 80-98%. The Agreement on the Conservation of Albatrosses and Petrels (ACAP) coordinates international mitigation implementation. FAO International Plan of Action for Seabirds requires national bycatch reduction plans. Observer coverage remains inadequate in many high-seas fisheries, hindering accurate bycatch quantification. Consumer certification (MSC) increasingly requires bycatch mitigation as a fishery standard.