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News Navigator: Has complete farm-raising of bluefin tuna been successful?

In this photo provided by Kindai University, a farmed tuna is pulled from the water at the Amami Station of the university's Aquaculture Research Institute.

Overfishing has depressed the number of tuna in the wild, prompting Kindai University in Higashiosaka, Osaka Prefecture, to research farm-raising the popular fish from egg to adulthood. The Mainichi answers some common questions readers may have about these ongoing efforts.

    Q: Is Kindai University actually farm-raising tuna from start to finish?

    A: In 2002, Kindai University became the first in the world to completely farm-raise bluefin tuna from eggs to adulthood, and began mass production in 2010. Normally, farming tuna means raising juvenile fish caught in the wild. However, in the Kindai University process, eggs spawned by adult fish are hatched and raised to adulthood, without the need to catch juvenile fish from the wild, lessening the impact on the environment.

    Q: Is the university continuing to farm tuna in this way?

    A: General trading companies and fisheries are also participating in production. Toyota Tsusho Corp. mainly raises the juvenile fish hatched from the eggs to a size of about 30 centimeters. These fish are called "yokowa." Companies like Mitsubishi Corp. then raise the yokowa to adulthood before shipping them.

    Q: How widely are these farmed tuna being distributed?

    A: According to Kindai University, the annual domestic distribution of yokowa is between 500,000 and 700,000 fish, and of that, some 10 to 20 percent are completely farm-raised. However, the percentage that reaches consumers is even less. So mindfulness of the limits of natural resources is still important.

    Currently, only 1.2 to 1.3 percent of the fish survive to adulthood and distribution after being hatched from farmed eggs, says the university's Aquaculture Technology and Production Center.

    Q: How do the farmed tuna compare to wild fish, in terms of both price and taste?

    A: Farm-raised fish do not taste any different from wild varieties, and there is no difference in market price. There are restaurants that are gaining popularity by serving the farm-raised fish. Kindai University says that the low survival rate and the high costs of raising the fish are still problematic, but if technology increasing the survival rate can be developed, the market price of the fish is expected to fall.

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