Tuna Fishing Welfare: Bycatch, Capture Stress, and Slaughter Practices

Commercial tuna fisheries cause significant welfare harm through bycatch of dolphins, sea turtles, and sharks, as well as through stressful capture methods and inhumane slaughter practices for tuna themselves.

Key Facts

Purse seine fisheries using fish aggregating devices (FADs) generate substantial bycatch including juvenile tuna of non-target species, sharks, rays, sea turtles, and marine mammals
Dolphin-set purse seine fishing in the Eastern Tropical Pacific deliberately encircles dolphin pods to capture associated yellowfin tuna — a practice causing ongoing controversy about dolphin welfare despite reduced direct mortality
Tuna caught by longline experience prolonged suffering: fish may be hooked and struggle for hours to days before the line is retrieved, causing exhaustion, injury, and drowning in air-breathing bycatch species
Evidence increasingly supports that tuna are sentient and can experience pain and fear — physiological stress responses during capture include elevated cortisol, lactic acid, and tissue damage
Commercial bluefin tuna are often transferred live to ranching pens and fattened before slaughter — slaughter methods vary from spiking (ike jime) which is rapid and welfare-positive, to CO2 stunning or live chilling which is slower
Skip jack and yellowfin tuna caught by pole-and-line methods have significantly lower bycatch rates than FAD-associated purse seine fishing, and the fish are killed immediately on capture
MSC certification has been criticized for certifying some tuna fisheries with documented high bycatch rates — consumer guidance on tuna welfare and sustainability requires careful label reading

Welfare Considerations

Tuna welfare encompasses both the fish themselves and the large number of non-target species caught as bycatch. For tuna, the key welfare concern is the duration and intensity of capture stress: longline-caught tuna may suffer for many hours before retrieval, and slaughter practices vary widely in how quickly they induce unconsciousness. For bycatch species including dolphins, sharks, sea turtles, and manta rays, entanglement causes panic, injury, and drowning. The sheer scale of global tuna capture — millions of tonnes annually — means that even small improvements in fishing methods and slaughter practices translate into enormous reductions in total suffering across the ocean ecosystem.

What You Can Do

Choose pole-and-line caught tuna over FAD-associated purse seine as a significantly lower-bycatch option
Look for the Friend of the Sea or Dolphin Safe labels as indicators of lower dolphin bycatch, understanding their limitations
Support advocacy by World Animal Protection and Aquatic Life Institute for welfare-positive tuna slaughter standards
Reduce tuna consumption or shift to sustainably certified options that include bycatch monitoring requirements
Advocate for improved MSC certification standards that explicitly include bycatch welfare criteria
Support observer programme funding on commercial tuna vessels to accurately document and reduce bycatch
Learn to distinguish between pole-and-line, FAD, and non-FAD tuna labels when making purchasing decisions