In the end, the price was a little underwhelming. The prized fish, weighing in at 180kg, was worth just 4.51m yen (£24,500), and its new owner was left puzzled.

Kiyoshi Kimura, who runs a chain of sushi restaurants, said he was surprised after securing the giant Pacific bluefin tuna for such a low price at the first auction of the year at Tsukiji fish market in Tokyo. Two years ago, he paid a record 155.4m yen for a slightly bigger bluefin after entering into a bidding war with a Hong Kong restaurateur.

“But it’s the best quality,” Kimura added. “I’m satisfied with buying the best one – it has a good shape and great fat.”

On a day when Tsukiji, the world’s biggest fish market, was bursting with energy after the New Year break, Kimura’s willingness to part with such large sums for a single fish says much about Japan’s obsession with bluefin tuna.

Bluefin tuna. Photograph: Alamy

Over the holidays, TV networks devoted hours to profiling the fishermen whose heroics on the high seas bring the prized delicacy to millions of dinner tables; the “Ferraris of the ocean” even get a mention in Man’yōshū, a collection of Japanese poetry compiled in the 8th century.

This year’s “big fish sale” price was lower than expected due to a lack of rival bids and a higher number of bluefins in the waters off Japan’s northern coast, according to AFP, but Japan’s appetite for bluefin tuna now risks plunging the fish into commercial extinction.

The country’s diners eat their way through about 80% of the global bluefin catch, while soaring demand in China and other parts of Asia is hastening its demise.

The threat from overfishing made headlines at the end of last year, when the International Union for Conservation of Nature moved the Pacific bluefin from the “least concern” to the “vulnerable” category on its red list of threatened species.

The IUCN estimates the Pacific bluefin population has declined by 19-33% over the past 22 years, mainly to satisfy demand for sushi and sashimi in Asia. Most of the fish caught are juveniles, making it impossible for them to reproduce.

Faced with the imminent collapse of bluefin stocks, Pacific fishing nations last year agreed to cut their catch of juvenile bluefin to half the average for 2002-04, although environmental groups had called for a moratorium to give stocks time to recover.

To ensure that tuna retains its place in Japanese culinary affections, Kinki University has spent more than 40 years developing a method of raising bluefin tuna from larvae to maturity at its two research farms in western Japan. It recently said it would triple shipments of adult Bluefin tuna to 6,000 fish by 2020.

Facebook Twitter Pinterest 100% farmed tuna, reared at Kinki University’s site in western Japan. Photograph: Justin McCurry for the Guardian

Most tuna farming in Japan involves catching young tuna in the wild and cultivating them in coastal reserves – a practice that experts believe has contributed to plummeting populations of small fish.

Kinki University, however, prides itself on a method it calls “complete cultivation”, in which the fish are artificially raised from egg to adulthood before the larvae are then used to start a new cycle.

Experts involved in the project say they still have a long way to go before they can farm enough tuna to meet demand. The survival rate for newly hatched fry is low, and rearing tuna in captivity requires vast areas of coastal water.

Shigeru Miyashita, of the university’s fisheries laboratory, said the rate at which researchers had successfully raised bluefin from egg to adult – without using any fish caught in the wild – had improved over the years. But he added that many challenges remained.

“Through the complete aqua-farming of bluefin tuna, we hope to help ensure the stability of the world’s marine resources,” Miyashita said. “But to make 10,000 tonnes of farmed adult tuna you need 1.6m fry. The other problem is space. Wild Pacific bluefin have the whole ocean to swim in, but we have to raise them in a confined area.

“We started this project because we were concerned about the future of the bluefin tuna. Japanese people love tuna – we now want to encourage them to eat ours instead of the wild variety.”

The university’s project received a boost at the end of last year when it joined forces with Toyota Tsusho, the trading arm of the Japanese carmaker, to begin the mass farming of bluefin tuna hatchlings at a site in Goto, south-western Japan.

The world’s most famous sushi chef recently added his voice to warnings that overfishing threatened to make his menu unrecognisable within a few years.

Facebook Twitter Pinterest A selection of sashimi, including slices of 100% farmed tuna, from Kinki University. Photograph: Justin McCurry for the Guardian

“I can’t imagine at all that sushi in the future will be made of the same materials we use today,” said Jiro Ono, the 89-year-old owner of the three Michelin-starred Sukiyabashi Jiro restaurant in Tokyo, whose VIP customers have included the Japanese prime minister, Shinzo Abe, and the US president, Barack Obama.

“Three years ago I told the young men who work for me that sushi ingredients will totally change in five years,” added Ono, who charges 30,000 yen (£162) for a 20-piece sushi set. “And now, little by little, that trend is becoming a reality.”

To give aficionados the opportunity to sample the fruits of its research, the university has opened restaurants in Osaka and Tokyo that serve 100% farmed tuna.

Fukako Saito, from Saitama, near Tokyo, finished every last morsel of a seafood donburi – a selection of raw fish, including bluefin, served on rice – during a packed lunchtime service.

“It was delicious, and I couldn’t tell the difference between this and wild tuna,” she said. “I haven’t really thought about the red list and what we’d do if bluefin became extinct. I guess we’d have to eat the farmed version all the time.”

Eiichi Uesugi, a businessman visiting from Osaka, said his tuna belly sashimi contained “just the right amount” of fat. “I’m no expert, but I think it tastes just as good as wild tuna,” he said.

The restaurant’s head chef, Takuya Sugimura, said there was no compromise on taste or texture. “One of the advantages of using farmed tuna is that the quality is the same all year round. And if we want to cater to customers who prefer the fatty cuts, we change the feed accordingly.”