Atlantic and Pacific bluefin tuna are being farmed in sea cages, primarily for the high-value sashimi market. These powerful, fast-swimming oceanic fish have welfare needs that are extremely difficult to meet.
Bluefin tuna welfare in sea cage systems is severely compromised by the fundamental mismatch between these animals' biological needs and captive conditions. Bluefin tuna are built for high-speed, long-distance oceanic movement — their circulatory and respiratory systems are adapted for continuous high-exertion swimming. Confinement in sea cages causes disorientation, collision injuries from net strikes, and the chronic stress of restricted movement. Oxygen requirements are extremely high and difficult to maintain in densely stocked cages, causing respiratory distress. Wild capture for fattening operations compounds welfare harm through the intense stress of purse-seine netting and transport. Full-cycle farming — achieving reproduction and larval rearing in captivity — eliminates wild capture welfare harms but still faces the fundamental challenge of meeting tuna welfare needs in any confined system.