Bluefin tuna are caught wild and fattened in sea cages before slaughter. Their welfare during capture, transport, and holding is a growing concern for aquaculture scientists.
Bluefin tuna are highly mobile, socially complex fish that in the wild migrate thousands of kilometres. Capture involves violent crowding and air exposure; tuna frequently die from capture stress or injure themselves on nets. Sea cage conditions impose severe restrictions on fish that evolved to swim at speed across open ocean. The welfare science of large pelagic fish is relatively underdeveloped, but the precautionary principle suggests that the distress experienced during capture and confinement is substantial. Welfare-conscious slaughter methods (ike jime) are practised by higher-welfare producers.