Andrew David Thaler, who writes about the ocean on his blog Southern Fried Science, had this to say about the many factors at play in the Tsukiji auction last January:

I’m certain that we’ll see this number presented as an argument against bluefin tuna fishing, as an example of an industry out-of-control, and as a symbol of how ruthlessly we'll hunt the last few members of a species to put on our dinner plates. These issues are reflected in the tuna market, but I want to urge caution in drawing too many conclusions from this record breaking number. There are several issues in play at the first tuna auction of the year, and only some of them relate to the tuna fishery. Among the patrons of the Tsukiji fish auction, it is considered an honor to buy the first bluefin of the new years, and bidding wars reflect this fight for status. The massive international headlines that follow the purchase of such a fish is free advertising for the winner. As many auction-goers know, landing a high, early win is a way of marking your territory and letting your competitors know that you have the bankroll to push them out of a bidding war. If $1.8 million is actually what this fish is worth to the consumer, it would sell for a hefty $345 at the dinner table, minimum. The owner, Kiyoshi Kimura, reports that the tuna will be sold at a huge loss–about $4.60 per serving. All three species of bluefin tuna are currently overfished, and over the last few years attempts to protect bluefin tuna have been thwarted by fishing interests in Japan, New Zealand, the United States, and Mediterranean countries, among others. While this record breaking sale should serve a clarion call for increased scrutiny of the global tuna trade, it does not accurately reflect the market value of the fish.

What should we make of the dramatic nosedive in bluefin bidding at this year's auction? To answer that, we need to understand how this species rose to such prestige in the first place.

Issei Kato/Reuters

In the 1960s, no one wanted bluefin. In the United States, the fish sold for pennies per pound, and it was usually ground up for cat food. Japan fished for it, but few people there liked the bluefin's bloody, fatty meat. Then sushi bars started cropping up in America, and Americans developed a taste for toro—the prime meat of the bluefin's belly. By the 1970s, the Japanese had also developed a taste for bluefin.

All of a sudden, bluefin was one of the most sought-after fish not only by Japanese fishermen but also by American and Canadian ones. According to the International Union for Conservation of Nature, between 1970 and 1990 fishing for bluefin in the Western Atlantic increased by more than 2,000 percent. The average price paid to Atlantic fishermen for bluefin exported to Japan rose by 10,000 percent. And it was mostly all being exported to Japan. Even today, a bluefin caught off the coast of New Hampshire will be shipped off to Tokyo before ending up on sushi plates somewhere else.

The graph above was published in a 2013 stock assessment by the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean. It was this stock assessment that prompted The Pew Charitable Trusts to announce, just days after Kimura bought his tuna for $1.76 million, that global bluefin tuna stock has declined by 96.4 percent from pre-1950 levels.