Longline fisheries targeting tuna catch enormous quantities of non-target species including sea turtles, seabirds, sharks, and billfish — causing massive welfare harms alongside population-level conservation damage.
Sea turtles caught on longline hooks drown over minutes to hours. Seabirds hooked at the surface during line setting die from hook injuries or drowning. Sharks caught as bycatch may be finned and returned alive. The welfare scale of longline bycatch is enormous — hundreds of thousands of sentient vertebrates dying unnecessarily each year in fisheries where mitigation measures are available.