Dave Gershman at the Pew Charitable Trusts' international fisheries team used news of the auction to highlight that stocks of Pacific bluefin tuna were improving after being "near collapse".

Self-styled "Tuna King" Kiyoshi Kimura's sushi restaurant chain paid the top price for the 243-kilogramme (536-pound) fish that was caught off Japan's northern coast.

"I'd thought we would be able to buy a little cheaper, but the price soared before you knew it," Kimura said after the pre-dawn auction at Tokyo's main fish market.

"I was surprised at the price...I hope that by eating auspicious tuna, as many people as possible will feel energised," he told reporters.

The 510.3 million yen price at the new year's auction was the highest since comparable data started being collected in 1999.

The previous high was 333.6 million yen for a 278 kilogramme bluefin in 2019, after the fish market moved from its traditional Tsukiji area in central Tokyo to a more modern facility.

The top bidder last year paid 207 million yen for a 276-kilogramme bluefin.

Shortly after this year's auction, the tuna was butchered and turned into sushi, selling for around 500 yen ($3) per roll.

"I feel like I've begun the year in a good way after eating something so auspicious as the year starts," 19-year-old Minami Sugiyama told AFP from a table in one of Kimura's restaurants in Tsukiji.

Fellow customer Kiyoshi Nishimura agreed.

"Even without dipping it in soy sauce, there's sweetness. And the richness, the texture... it just makes you feel happy," the 40-year-old Shinto priest said.

During the Covid-19 pandemic the new year tunas commanded only a fraction of their usual top prices as restaurants scaled back operations.

Gershman said in an emailed statement that a 2017 recovery plan "is working, and if decision makers take further action in 2026, the future for Pacific bluefin will be bright".

"This year, fisheries managers from Japan, the United States, Korea, and other countries from across the Pacific who target bluefin should agree on a long-term, sustainable management plan that would lock in a healthy population and ensure that the species never again faces the overfishing of the past," he added.