Farm-raised tuna in your sushi

One of the most popular sushi fish, the Bluefin tuna, is facing extinction. In Japan, where 70 per cent of the global catch is consumed, a project is underway to commercialise the first ever fully sustainable tuna fish farm. Susanne Steffen reports from Tokyo.

Photo credit: The world’s first sustainable commercial tuna fish farm will go into operation in Japan next summer. (InvernoDreaming, flickr)

Photo credit: The world’s first sustainable commercial tuna fish farm will go into operation in Japan next summer. (InvernoDreaming, flickr)

The world’s priciest Bluefin tuna to date fetched a whopping 150 million yen. That’s 1 million euro. The 220-kg fish was bought by a sushi chain at the Tokyo fish market’s New Year’s auction. “I want to offer my customers the best fish,” replied the owner of the restaurant chain when asked why he was willing to pay the record-breaking price without even batting an eyelid.

While the first auctions of the year in Japan often see dizzyingly high prices, the world’s rapidly shrinking tuna fish stocks are making Japanese consumers anxious that the coveted delicacy will soon be unaffordable to the average palate. Last month, the International Union for Conservation of Nature (IUCN) put the north Pacific Bluefin tuna population on its red list of threatened species after stocks shrunk by nearly one third – from 33 per cent to 19 per cent – in the past 22 years.

Reproduction is jeopardised

One of the main reasons behind the dramatic decline in fish stocks is that catching the fish when they’re young to raise on giant fish farms robs the Pacific Bluefin tuna of the chance to reproduce, warns the IUCN. Until now, fish farms around the world use wild-caught young fish and then fatten them in breeding ponds. Researchers have spent years desperately looking for an alternative to more restrictive fishing quotas as the latter would inevitably result in skyrocketing consumer prices.

After 30 years of research, Japan’s Kinki University succeeded 12 years ago for the first time anywhere in the world in bringing tuna into captivity to spawn, raising the young fish and then bringing them back to reproduce. Next summer, the first commercial tuna fish farm in the world, which doesn’t use any wild catches whatsoever, will go into operation in Japan.

Trading company Toyota Tsusho, which belongs to the Toyota Group, wants to invest 15 billion yen to work together with Kinki University to produce one-tenth of Bluefin tuna consumed in Japan in a completely sustainable manner by 2019. 100,000 hatchlings will then be delivered to conventional fish farms so they no longer have to rely on wild stocks.

Breeding both difficult and expensive

The challenge is that it’s difficult to breed these extremely sensitive large fish. Only about three per cent of the hatched animals survive to the juvenile age. The first breeding attempts at Kinki University didn’t even reach 0.1 per cent. Given the high rate of loss, CEO Jun Karube doesn’t expect quick profits in the beginning. “But the societal value of our fish farming is immense. We are perseverant and firmly believe that we will see profits in five to ten years,” he said at a press conference last month. If successful, Karube plans to expand production and is already thinking about how to export this sustainable farming method.

Not too fat, please!

Tuna fish bred fully in captivity are just as delicious as their wild cousins, and the researchers have even managed to develop ways to prevent the animals from gaining too much fat in the breeding ponds. When Kinki University opened its first “Eco Sushi” store last year, the crowd was so large that the farmed tuna fish sold out after only 15 minutes. The store has since become a local tourist attraction with customers lining up for the sustainably raised fish to this day.


Photo credit: InvernoDreaming, flickr/Creative Commons

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