The wild bluefin tuna is being eaten to extinction, but this hasn’t curbed the global appetite for this valuable fish in Japan and across the globe.In the last 70 years the fish has become a staple of high-end sushi restaurants and celebratory meals. It sells for up to hundreds of thousands of dollars–as to eat bluefin caught in the wild signifies quality. It is the apex of the sushi platter across Japan, which eats about 80% of all the wild bluefin consumed. But the tuna’s popularity is actually a relatively new phenomenon, as tuna was once regarded as a waste product until the middle of the 20th century, and even used for cat food. But recently, the appetite for the huge ocean-going fish has led to an ecological crisis, with projections that wild bluefin will no longer exist in the coming decades. The BBC’s Edwin Lane visits the iconic Tsukiji fish market, the hub of the global tuna trade, and speaks to a sushi chef who can’t bring herself to stop preparing the fish despite the extinction warning, and visits one of the world’s only functioning bluefin farms to talk about why it’s so difficult to raise bluefin tuna in captivity.