Threatened tuna bred in captivity

Top-quality tuna meat can cost as much as $50,000 in Japan

TOKYO, Japan -- Pacific Bluefin tuna, a fish threatened with extinction, has been successfully bred in captivity for the first time, Japanese researchers say.

Researcher Yoshifumi Sawada, of Kinki University, told Reuters: "This is the first time the fish has been taken from egg to egg at the hands of man.

"This has enormous potential for not only does this mean we may be able to get Bluefin without depleting limited wild resources, we also may someday be able to restock the seas by releasing the fish we raise."

Falling numbers of Bluefin around the world have alarmed scientists and environmentalists. The southern Bluefin is endangered, and while the Pacific Bluefin is in slightly better shape, its future is uncertain.

Bluefin, which can measure up to three metres (10 ft) long and weigh up to 550 kg (1,200 lb), is popular around the world and especially in Japan, where it is eaten raw and in sushi.

GLOBAL BALANCE Businesses and countries move to help environment

Top-quality meat from the fish commands dear prices at Japanese fish markets, going for as much as $50,000 (£32,960).

Although wild Bluefins captured when young are being raised in captivity in a number of countries, no eggs from fish bred and raised entirely in captivity have been successfully hatched before, Sawada said.

Some 240,000 fry have successfully hatched at the Kinki University experiment station in Kushimoto, some 450 km (280 miles) west of Tokyo, and Sawada is optimistic a good number will live to maturity.

While other fish species are routinely raised in hatcheries, little is known about the behaviour and habitat of the Bluefin tuna, making artificial breeding extremely difficult.

"We don't know what life it lives and so we didn't know how to raise it in the lab," Sawada said. "We had to figure everything out as we went along."

The saga began in 1970 with the capture of young wild fish to raise to sexual maturity, which comes at five years. The first successful spawning took place until 1979, and then all the young fish died within several months.

Bluefin tuna is eaten raw and in sushi worldwide

Between 1982 and 1994 there was not a single spawning, probably due to a lack of experience and skills, plus various fluctuations in the temperature of the water, crucial to spawning, Sawada said.

A lack of funds also posed problems, so researchers raised and sold fish such as sea bream, another gourmet treat, to finance the project.

But some 20 Bluefin fry hatched in 1995 and 1996 and lived to maturity. It was several of these fish that spawned from late June until earlier this week.

In a reflection of their increasing success, the Japanese government this April granted the university funding of some 100 million yen ($832,100) over the next five years.

The task now is to raise these fish to lay eggs of their own. This is likely to become easier with each succeeding generation, in a process Sawada likened to the domestication of horses and dogs.