This is how they make a 535-pound bluefin tuna that sells for $3.24 million.Each fish eats 10 kg of fresh sardines per day for roughly two years to get there. Bluefin biology dictates the ratio.A bluefin runs its red swimming muscle, brain, and viscera 10 to 21°C above the surrounding water using a countercurrent heat exchanger called the rete mirabile, which traps metabolic heat that would otherwise vent through the gills. The heat is what lets the fish cruise at 7 mph and burst at 40. It is al