A bluefin tuna can grow to the size of a car, weigh twice as much as a grand piano, swim as fast as a running lion, and keep its muscles at human body temperature even in the ocean's coldest depths. It's also wildly delicious, with a sweet, briny, but meaty taste and a melt-in-your mouth texture that has made it the most expensive fish in the world, with a single bluefin selling for a record-breaking $3 million in 2019. Not bad for a fish that, until recently, New England fishermen used to have to pay to dispose of. This episode, we've got the story of how the king of fish went from the coin of the realm in ancient Byzantium to cat food before bouncing back, in a tale that involves Alexander the Great, Ernest Hemingway, and a couple of Canadian coffin-makers. But popularity has proven a double-edged sword for the bluefin: in the past few decades, it's been fished almost to extinction, while also becoming the poster child for saving the oceans. These days there's big news in tuna world, and, for the first time in years, environmentalists and scientists have hope for the bluefin's future. So is it time to start ordering maguro again at the sushi bar?