Just before dawn Thursday, at Tokyo's historic Tsukiji market, a familiar face walked away with the biggest fish in town. Kiyoshi Kimura won the first auction of the year at the market, just as he has for six years running.

And to the winner go the spoils: a 466-pound Pacific bluefin tuna, which ultimately cost Kimura 74.2 million yen — or about $632,000. That comes out to more than $1,300 a pound for Kimura, whose Kimura Corp. owns a restaurant chain called Sushi Zanmai.

Still, it's not the record for the seafood market's annual first bluefin auction. That distinction also belongs to Kimura, who in 2013 bid a staggering 155.4 million yen — which at that time came out to $1.76 million.

Every year, worldwide media hype attends the year's opening auction at Tsukiji, which "handled more than $4 billion in fish and produce in 2014" alone, according to The Wall Street Journal. NBC reports that it is the world's biggest fish market.

But conservation groups protest that attention should be paid to a different, and much darker, reality confronting Pacific bluefin tuna: the species' dwindling population.

"People should be thinking about that when they see news about the auction," Jamie Gibbon, officer for global tuna conservation at the Pew Charitable Trusts, tells the Guardian.

In July, Pew called for a two-year moratorium on commercial fishing of Pacific bluefin tuna, citing a more than 97 percent drop in population from historic levels. The month before, about a dozen environmental groups petitioned the U.S. National Marine Fisheries Service to list the species as endangered under the Endangered Species Act.

Conservationists argue part of the problem is that when fisheries catch Pacific bluefin tuna, they're mostly catching juveniles who have not yet reached the age of reproduction. That practice has always been around, says the National Oceanic and Atmospheric Administration, or NOAA, but "more fisheries specifically targeting juveniles started in the 1990s, increasing pressure on the juvenile population."

And even if the species gets an endangered listing in the U.S., as conservationists would wish, it's not likely to make much of an impact on the species' population worldwide. That's because American fishermen don't comprise a large portion of Pacific bluefin fishing worldwide, as Alistair Bland reported for NPR:

"Of the 37 million pounds of Pacific bluefin caught by fishermen in 2014, American fishermen caught just 2 percent, according to data provided by Michael Milstein, a public affairs officer with NOAA Fisheries. (Japan took about half and Mexico almost 30 percent.)"

The Guardian estimates that Japan consumes 80 percent of the global bluefin catch.

For now, the only major change looming for the Tokyo market's annual New Year auction is its location: The city had planned to move the historic market to a new location to make way for a highway planned for the 2020 Tokyo Olympics — but the market was granted a reprieve when concerns were raised about soil contamination at the new site, which used to be home to a gas plant.

The Tokyo government expects to have a clearer idea on the safety of the new site this year.

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