Tuna Welfare in Purse Seine and Longline Fisheries

Tuna are highly migratory, warm-blooded fish with complex behaviour and high cognitive ability. The methods used to catch billions of tuna annually cause significant welfare harms that are only beginning to be addressed.

Key Facts

Global tuna catch exceeds 7 million tonnes annually, making them among the most heavily fished fish groups
Skipjack, yellowfin, and bigeye tuna are the three most commercially important species
Purse seine nets capture thousands of tuna simultaneously; the net closing process crushes animals at the bottom
Fish aggregating devices (FADs) attract tuna by the thousands and result in large bycatch of juveniles and non-target species
Atlantic bluefin tuna are ranched in Mediterranean pens before slaughter, often via live capture of wild fish
Longline fisheries use lines up to 100 kilometres long with thousands of hooks, causing bycatch of sharks, turtles, and seabirds
Tuna are among the few fish that maintain body temperature above ambient seawater through specialised heat-exchange systems
Bluefin tuna can swim at speeds exceeding 70 kilometres per hour and range across entire ocean basins

Welfare Considerations

Tuna welfare in commercial fisheries is largely unaddressed in policy and practice. Purse seine hauls bring thousands of fish into nets where crushing, oxygen depletion, and extreme crowding cause intense stress before slaughter. Longline-caught tuna may spend many hours on hooks before retrieval, experiencing sustained pain and exhaustion. Research on tuna cognition and thermoregulation suggests a higher welfare sensitivity than cold-water fish — their ability to regulate body temperature is associated with increased neural activity rates. Ranching operations that hold wild-caught fish in net pens cause stress through confinement, handling, and exposure to pathogens. Consumer pressure for certified, low-bycatch tuna and improved on-board slaughter standards are the most direct welfare interventions available.

What You Can Do

Choose tuna certified by the Marine Stewardship Council with a low-bycatch fishing method preference
Prefer pole-and-line caught tuna, which kills fish one at a time with less suffering than net fishing
Reduce overall tuna consumption given the difficulty of verifying welfare claims
Support Fish Welfare Initiative research into tuna welfare and slaughter standards
Advocate for on-board humane slaughter requirements to be included in fisheries management plans
Support ISSF (International Seafood Sustainability Foundation) tuna welfare guidelines
Ask supermarkets and food brands for disclosure of tuna fishing methods and bycatch rates