Science: Aquaculture: Food from the Deep

IN the past 100 years, the amount of food taken from the sea has multiplied more than tenfold, a rate in excess of global population growth. But the annual world catch—now about 60 million metric tons—cannot continue growing indefinitely. In fact, such sea staples as California sardines, Northwest Pacific salmon and Barents Sea cod —not to mention the beleaguered whale —are already rapidly dwindling. Contrary to the myth, Fisheries Biologist William Ricker recently warned, in a National Academy of Sciences report, the sea is not "a limitless reservoir of food energy."

Urchins to Octopus. Fortunately, there is an alternative to harvesting food directly from the sea. By using artificial ponds, lakes, streams and even cordoned-off estuaries and bays to raise fish, man can give nature a helping hand. Fish farming is hardly new; as long ago as 475 B.C., a Chinese scholar-statesman named Fan Li wrote the first how-to-do-it treatise. But as marine biologists seek to exploit its full potential —especially as a way of relieving the world's chronic shortage of protein—water farming, or aquaculture, looms as an ever more important source of food.

The island-bound Japanese seem to be the most ingenious aquaculturists. Dependent on the sea for 60% of their protein intake, they have long led the world in growing oysters, shrimp and other aquatic delicacies. But lately, as their fisheries have become overtaxed and their world-traveling trawlers run into increasing opposition from foreign governments, Japanese researchers have been working overtime on breeding projects, experimenting with everything from sea urchins to octopus. To make fish more accessible to fishermen they have even taken to dumping old streetcars, buses and, most recently, concrete pipes into offshore waters in hopes of providing "aparto" (apartments), in and around which fish tend to congregate.

Other nations are not far behind. On the Chinese mainland, Fan Li's descendants have dotted the countryside with so many fishpond cooperatives that their annual production of carp and related fish (1.5 million tons) nearly equals the total U.S. catch. The Israelis, who have extensive breeding pools, learned that by injecting mullets with pituitary hormones they could cause the fish to spawn in captivity. Ordinarily the mullet —a popular tropical food fish—will spawn only in open water. Similar projects are underway on Taiwan, in India and at Hawaii's privately run Oceanic Institute, where scientists have just made an esoteric contribution to mullet cultivation. By stringing out buoyant strips of plastic just below the ocean's surface, they have created artificial sea grass on which diatoms will grow. These single-celled algae constitute the basic ingredient of a young mullet's diet.