Bluefin tuna ranching in the Mediterranean raises profound welfare questions about capture stress, captive confinement, and slaughter of this large, active pelagic fish.
Bluefin tuna welfare in ranching systems is severely compromised at multiple stages. Wild capture in purse seines causes extreme physiological stress with associated cardiac and muscle damage. Confinement in sea cages prevents the continuous high-speed swimming that is natural for this species, causing chronic behavioural frustration. Slaughter by exsanguination without prior stunning causes prolonged death. The welfare costs of bluefin ranching are among the highest per fish of any aquaculture system due to the profound mismatch between this species' natural behaviour and captive conditions.