Saltwater fish farming began in Japan in 1927, in the calm waters of the Seto Inland Sea. The project involved stringing a net across the mouth of a narrow cove, then feeding the yellowtail and sea bream that remained inside. The cove, called Adoike, is near Hiketa-cho in Kagawa Prefecture, Shikoku.

Full-scale fish farming of marine species began in the mid-1950s, using nets to make artificial "swimming pools for fish" in the sea. It was around then that aquaculture techniques became advanced enough to raise fish in pens.

"Years ago, yellowtail, sea bream and flatfish were too expensive for the average family, but when the economy expanded after the war, many more people were able to buy them. The increased demand really helped develop the aquaculture industry," says Inagaki Mitsuo, a director at the Japan Seawater Fishery Cultivation Association.

Yellowtail and sea bream farms sprang up in coves and bays in the Seto Inland Sea, a sheltered body of water relatively free from the danger of typhoons. Other areas along the coasts of Shikoku and Kyushu were also developed because they, too, had warm water, an important condition for fast fish growth.

According to Inagaki, almost half of all fish taken from Japan's coastal waters now come from fish farms. The country's total marine aquaculture harvest was about 1,220,000 tons in fiscal year 2000. Of this amount, saltwater fish from fish farms came to about 260,000 tons—the remainder was shellfish, mainly oysters and scallops, and seaweed like wakame and nori. Almost all of the saltwater fish from fish farms was yellowtail (about 150,000 tons) and sea bream (80,000 tons), with the remaining 30,000 tons being primarily flatfish, blowfish and yellow jack. These figures show that yellowtail and sea bream—two favorites in Japan—are the most important fish farm products.

From the time the fry are placed in holding tanks, about 18 months are needed for yellowtail to reach a good weight for harvest (about 4 kg), and two years for sea bream (1.2 kg).