On Saturday, a bluefin tuna was sold at Tokyo’s Tsukiji fish market tuna auction for $1.76 million. Which is a little crazy. (Also crazy, the size of the fish in question.) But the amount paid for this specimen of a chronically overfished species doesn’t really represent simple supply and demand, explains marine biologist Andrew David Thaler. It shouldn’t be read as a measurement of tuna scarcity, he says, but rather as an artifact of culture (and marketing).