Bluefin tuna ranching involves capturing wild fish and fattening them in sea cages before slaughter. The welfare implications of this practice at each stage deserve careful examination.
Bluefin tuna are highly active, migratory fish that in the wild swim thousands of kilometres annually. Confinement in sea cages represents a radical curtailment of natural behaviour that evidence suggests causes chronic stress. Capture, towing, and the transition to captivity involve acute suffering including physical injury and extreme metabolic stress. Slaughter without stunning, common in many operations, involves prolonged suffering in large, sentient fish. Improving welfare standards in tuna ranching requires both regulatory action and consumer pressure on certification schemes.