Aquaculture Magazine

February/March 2015

Taming the Wild Tuna

Japan Breeds Bluefin Tuna in Captivity, Following Path of Salmon, Shrimp.

By Yuka Hayashi*

Not long ago, full farming of tuna was considered impossible. Now the business is beginning to take off, as part of a broader revolution in aquaculture that is radically changing the world’s food supply.

“We get so many orders these days that we have been catching them before we can give them enough time to grow (at 130 pounds, or 58 kg),” said Tokihiko Okada, a researcher at Osaka’s Kinki University, who is also an entrepreneur.

With a decade-long global consumption boom depleting natural fish populations of all kinds, demand is increasingly being met by farm-grown seafood. In 2012, farmed fish accounted for a record 42.2% of global output, compared with 13.4% in 1990 and 25.7% in 2000.


The moody tuna

Until recently, the Pacific bluefin tuna defied any sort of domestication. The bluefin can weigh as much as 900 pounds (405 kg) and barrels through the seas at up to 30 miles/hour (48 km/hour). The fish is also moody, easily disturbed by light, noise or subtle changes in the water temperature. It hurtles through the water in a straight line, making it prone to fatal collisions in captivity. However, the Japanese treasure the fish’s rich red meat. All this has put the wild Pacific bluefin tuna in a perilous state. Stocks today are less than one-fifth of their peak in the early 1960s. The wild population is now estimated at 44,848 tons, or roughly nine million fish, down nearly 50% in the past decade. The decline has been exacerbated by earlier efforts to cultivate tuna. Fishermen often catch juvenile fish in the wild that are then raised to adulthood in pens. The practice cuts short the breeding cycle by removing much of the next generation from the seas.

Scientists at Kinki University decided to take a different approach. In 1969, they embarked on a quest to tame the bluefin. It sought to complete the reproduction cycle, with Pacific bluefin tuna eggs, babies, juveniles and adults all in the farming system. Two scientists from Kinki went out to sea with local fishermen, seeking to capture juvenile tuna for raising in captivity. It has proved to be more than a challenge. The moment the researchers grabbed a few juvenile fish out of a net, the skin started to disintegrate, killing them. It took four years just to perfect delicate fast-releasing hooks for capturing juveniles and moving them into pens.

It took nearly 10 years for fish caught in the wild to lay eggs at Kinki’s research pens. Then, in 1983, they stopped laying, and for 11 years, researchers couldn’t figure out the problem. The Kinki scientists now attribute the hiatus to intraday drops in water temperature, a lesson learned only after successful breeding at a separate facility in southern Japan.

In the summer of 1994, the fish finally produced eggs again. The researchers celebrated and put nearly 2,000 baby fish in an offshore pen. The next morning, most of them were dead with their neck bones broken. The cause was a mystery until a clue came weeks later. Some of the babies in the lab panicked when the lights came on after a temporary blackout and killed themselves. The researchers realized that sudden bright light from a car, fireworks or lightning caused the fish to panic and bump into each other or into the walls. The solution was to keep the lights on at all times.

At last, in 2002, the Kinki team became the first in the world to breed captive bluefin from parents that were themselves born in captivity. The circle was complete. But the survival rate remained low. Troubles didn’t end there. In 2011, Kinki lost more than 300 grown fish out of its stock of 2,600 after an earthquake-triggered tsunami hit a coastline 400 miles away. The tsunami triggered a quick shift in tide and clouded the water, causing the fish to panic and smash into nets. In 2013, a typhoon decimated its stock. Again in the summer of 2014, frequent typhoons kept the researchers on their toes as they waited for the breeding season to start. It seemed doubtful for years that the tuna undertaking could be commercially viable.


Commercial partners

Kinki University had funded its project with proceeds from the sale of more common fish raised at its research facilities. That kept the tuna farming alive even after other academic and commercial organizations gave up. Now the university needed help from someone with deeper pockets, and by the latter half of the last decade the timing was right. The world’s voracious appetite for sushi and gourmet fish was eroding stocks of bluefin tuna and governments were beginning to clamp down on overfishing. The country most at risk of a tuna shortage was Japan, which consumes 80% of the world’s overall catch, or some 40,000 tons annually.

One early supporter was an employee of Toyota Tsusho Corp., a trading company affiliated with the auto maker. Taizou Fukuta was working in the company’s finance department in Nagoya when he saw a documentary about the tuna project. He was inspired to propose a tuna farming business in a Toyota in-house venture contest and won. With USD$1 million in seed money, Fukuta visited Okada, the university’s head of tuna research, many times until the academic agreed to team up with Toyota in 2009. Toyota footed the bill for larger facilities where baby fish hatched at the university’s labs could be raised in large numbers for about four months. At that point, the juvenile fish are stable enough to be sold to commercial tuna ranches, where they are fattened in round pens around 100 feet (30 m) in diameter and 30 feet (9 m) deep for three to four years before being sold for slaughter.

Fukuta moved to a small island off the southern island of Kyushu that offered a warm climate ideal for raising baby tuna. He persuaded local fishermen to lease his company the rights to set up dozens of fish pens. The first shipment of fry from Kinki came in a tank carried on a truck and ended with a 90% loss. The following shipments arrived by boat. More fish died when the winter’s chill arrived, sending the businessman to work with a feed company to develop artificial feed that kept the fish warm. Yet more fish were lost as they were prepared for shipment to buyers; they couldn’t be transferred into the hold of a boat for their journey without smashing into the body of the vessel. A giant funnel made of smooth material was invented to guide the fish into the ship.

After shipping an average of 20,000 juvenile fish a year over the past three years, Toyota’s production is expected to rise to 40,000 by next year. That complements Kinki’s own capacity for about the same number of fish. Together, they could supply nearly 20% of the demand for juvenile fish at Japanese tuna farms, taking pressure off the wild stock. This year, the venture is likely to break even for the first time.

Today around one or two in 100 of the baby tuna hatching from eggs at Kinki survive to adulthood, up from one in several hundred a few years ago. By contrast, only about one in 30 million babies hatched from eggs in the wild survive to adulthood.

Other companies are also expanding their tuna business. Using Kinki-bred juvenile fish, a Mitsubishi Corp. unit has opened a commercial tuna ranch in southern Japan. It hopes to ship 300 tons of farm-bred tuna this year, up from 40 tons last year. Demand is rising for the farmed tuna from gourmet stores and sushi restaurants in Japan. The university itself runs two restaurants in Tokyo’s Ginza district and Osaka. In Nagasaki prefecture, one of the main areas for domestic tuna farming, shipments of farmed bluefin rose to 3,000 tons in 2013, nearly five times the amount five years earlier.



Environmental concerns remain. Bluefin tuna require 15 pounds (6.75 kg) of feed fish to produce 1 pound (0.45 kg) of meat, prompting the Kinki team and others to look for artificial feed. Benefits of artificial feed include less pollution. With real fish, a large part is left uneaten and sinks to the bottom of the ocean, polluting the water. Artificial pellets are easier to eat so there are fewer leftovers. The team has been able to replace up to 30% of the ingredients with vegetable protein but going further stunts the fish’s growth.

There is also the question of whether farmed tuna taste as good as wild-caught. Some customers complained the early generation of Kinki’s tuna were too fatty even in a market where fatty tuna is treasured. The problem has been solved by changing the composition of feed. Besides, farm-grown fish currently fetch only about half the price of premium wild-caught tuna. Still, the biggest problem is the high attrition rate of juvenile farmed tuna. While captive-bred bluefin are visually indistinguishable from their wild counterparts, their behaviors are different. The farmed fish are delicate and moody, favoring one type of feed one day and another the next day. They are also less capable in avoiding sudden danger, making them more prone to fatal collisions.

Researchers also worry about the possibility of an outbreak of abnormalities as the fish all come from a single genetic linage, descended from the successful breeding in 2002. They have experimented with bringing in wild-caught fish to mate with the captive-bred fish to diversify the gene pool, but without success so far.

Although it still faces constant challenges, there’s no doubt that the future of bluefin tuna aquaculture looks bright. There is still a lot to research, but today tuna aquaculture is a reality.




*Original article: Hayashi, Yuka. Taming the Wild Tuna: Why farmed fish are taking over our dinner plates. The Wall Street Journal.

November 14th, 2014.


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