Yellowfin Tuna Welfare in Ranching and Aquaculture Operations

Yellowfin tuna are captured from the wild and held in sea pens for fattening, with severe welfare problems during capture, confinement, and slaughter for this highly active, wide-ranging species.

Key Facts

Yellowfin tuna are highly migratory, naturally swimming hundreds of kilometres daily
Tuna ranching involves purse-seine capture of juvenile or sub-adult fish and transfer to sea pens
Confinement causes severe stress, with cortisol and injury rates far higher than in wild fish
Tuna cannot be fully closed-cycle farmed due to difficulties replicating feeding behaviour and water quality needs

Welfare Considerations

Purse-seine capture involves crowding, exhaustion, and physical injury during transfer to sea pens. Tuna in pens frequently collide with net walls at high speed, causing rostrum damage, scale loss, and eye injury. The extreme muscular metabolism of tuna means oxygen depletion in crowded pens is rapid and life-threatening. Slaughter by live bleeding without prior stunning is standard practice and causes prolonged pain. Full aquaculture of tuna remains welfare-problematic due to the species' biological requirements.

What You Can Do

Avoid purchasing farmed or ranched tuna where welfare standards cannot be verified
Choose pole-and-line or MSC-certified tuna fishery products with lower bycatch
Support organisations advocating for stunning requirements in tuna slaughter
Raise awareness that tuna ranching involves significant welfare costs often hidden from consumers