Aquaculture Welfare

Tuna Ranching and Welfare in Open-Net Pens

Southern bluefin and Atlantic bluefin tuna are raised in open-net ocean pens under conditions that cause chronic stress and injury.

Key Facts

Bluefin tuna are highly migratory fish that naturally travel thousands of kilometers annually
Pen densities in tuna ranching are a fraction of wild space requirements
Tuna frequently collide with net walls, causing scale loss, fin injury, and eye damage
Capture from the wild for ranching causes acute stress; mortality during capture can reach 20%
Bluefin tuna are thermally regulated and require cooler, well-oxygenated water than pens often provide

Welfare Considerations

Tuna ranching combines the welfare harms of capture from the wild with chronic confinement in conditions incompatible with their highly mobile nature. Behavioral evidence shows persistent wall-following and repetitive circling — hallmarks of stress and frustration in mobile species. Market premiums for bluefin create economic incentives that override welfare concerns.

What You Can Do

Avoid bluefin tuna consumption or choose sustainably farmed alternatives with welfare certifications
Support international fishing agreements that restrict wild capture for tuna ranching
Advocate for aquaculture welfare standards that include space and behavioral requirements for highly mobile species