Bluefin tuna are among the most metabolically extreme fish on Earth, and farming them has forced aquaculture engineers to rethink something as basic as how to deliver a meal. Most bluefin “farming” is actually ranching. Wild juveniles are captured, towed in net pens to coastal sites, and fattened for months before harvest. Australia pioneered this with southern bluefin at Port Lincoln in the early 1990s, and the Mediterranean and Japan followed at scale. Why fire the food through the air? - Bluefin are regionally endothermic. A counter-current heat exchanger, the rete mirabile, holds their swimming muscle well above water temperature, which demands an enormous and continuous caloric intake - They are obligate ram ventilators and must keep swimming to push water over their gills, so they circle the pen at speed rather than waiting at a feeding point - Pens can exceed 50 metres in diameter. Dropping baitfish over one spot lets dominant fish monopolise the meal while smaller fish go hu...