The holy grail of fish breeding

The farming of bluefin tuna, a delicacy at sushi restaurants, may have been developed in the nick of time as wild stocks come under increasing pressure


Sat, Sep 30, 2006 - Page 9

In the dark green waters off the coast of western Japan, scores of 68kg bluefin tuna glided counterclockwise inside a pen 46m in diameter, the telltale blue streaks on their bodies shimmering just below the surface.


They were also the lifework of the man shoveling mackerel into the pen from the edge of a boat one recent afternoon, Hidemi Kumai, 71, the head of Kinki University's Fisheries Laboratory. Kumai had spent more than three decades trying to farm the bluefin tuna -- an unusually delicate fish, both physically and psychologically, prone to everything from restlessness to cannibalism -- before succeeding in 2002. Two years later, he began sending it off to sushi counters in Osaka and Tokyo.

"I felt as if I were giving away my daughters in marriage," Kumai said.


The competition has become fiercest over the bluefin tuna, which fetches about US$110 a pound at the Tsukiji fish market in Tokyo, the world's biggest. Of the five kinds of tuna eaten in Japan, bluefin accounts for less than 2 percent. But fishermen from New Zealand to Libya comb seas for it; in Croatia, Spain and elsewhere, young bluefin tuna are caught and fattened inside giant underwater cages before being shipped to Japan.



There is a "high possibility," Kumai said, that in a decade or two, as China keeps getting richer, Japan may simply be priced out of a shrinking bluefin market.

"Now only Chinese in the coastal areas are eating sushi or can afford to," Kumai said. "What happens when the Chinese in the vast hinterland start eating sushi?"

As part of Japan's national interest, and also because the Japanese have been exhausting the world's tuna stocks, Kumai advocated the large-scale farming of bluefin tuna, led by the government.

"This has to be a national project," he said. "Now Americans and Chinese are eating sushi, so we can't just sit back."

The outside threat has added urgency to Kumai's work, one that he had never imagined when he began fish farming in the late 1950s. As a boy growing up in the landlocked prefecture of Nagano, he had longed to see the ocean, but World War II restricted travel. When he finally caught a glimpse of the sea during a junior high school trip, he was hooked.

Over the years, the university's Fisheries Laboratory was first in the captive breeding of about 20 fish species, including halibut, flat bream and Japanese amberjack. Much of the work went on in the placid Pacific waters between the town of Kushimoto and the small island of Oshima, where various fish are farmed inside pens.




"Other fish, the sea bream or flatfish, do that, too," Kumai said. "But tuna are very aggressive. The population could shrink to a third overnight."


"They kept crashing into nets and dying," Kumai said with a grave face. "We took X-rays and found their necks were broken."

For fish that can grow to be as large as 800kg, they are also unusually sensitive. Fireworks, even the headlight of a car, can cause them to panic, crash into nets and break their necks.


"I've never met anyone who told me it tastes bad, though I know it's hard to say that to my face," said Kumai, who said he had never eaten wild bluefin.

Some sushi chefs in Kushimoto sniff at the ranched bluefin, saying it yields a fatty meat that does not taste as good as the wild variety. Wild bluefin, migrating across oceans, tend to be lean. But Kumai's couch potatoes are 10 percent lean and 90 percent fatty.

Because of decreasing stocks, Kumai's bluefin is now sold only once a month at a Mitsukoshi department store in Tokyo -- for a third less than the wild kind. That fact annoyed Kumai.

"Just because it's farmed, the prices are automatically lower," he said. "If it's good, it's good. There shouldn't be a difference."