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 worlds 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. 0rdinarly 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.
At the University of Washington, researchers have succeeded in breeding a so-called "supertrout," which outstrips its punier kin by gaining as much as two pounds a year and thriving in salt water. By cultivating the supertrout, as well as oysters and algae, Washington State's impoverished Lummi Indians are establishing one of the more promising U.S. aquafarms. The Oceanic Institute's founder, Taylor A. Pryor, whose researchers advise the Lummis, thinks similarly lucrative aquafarms can be set up all along the tidal areas of the U.S. Northwest, British Columbia and southern Alaska.
One of the more ingenious experiments in aquaculture has just begun on the Caribbean island of St. Croix. Conceived by scientists of Columbia University's Lamont-Doherty Geological Observatory, it is based on a natural sea phenomenon. In areas of the world where the right combination of wind, current and slope of the continental shelf occurs, cold water from the ocean depths sometimes churns up to the surface. Laden with nutrients from decomposed sea life that has settled to the ocean deeps, these rising currents possess extraordinary fertilizing power. Once they reach the upper level of the ocean, where sunlight penetrates, they turn it into a garden of phytoplankton--the tiny floating plants that are the bottom link in the sea's food chain. Actually the "upwelling" occurs only in a few areas like the extremely rich fishery off Peru. Much of the rest of the ocean is what one scientist recently called a "biological desert."
To make such a desert bloom, the Columbia scientists are creating some upwelling of their own-in miniature. Dropping a 31-in.-wide plastic pipe off the northern coast of St. Croix, where the Caribbean slopes off very steeply, they are siphoning up nutrient-rich, cold (41 ' F.) seawater from a depth of half a mile and feeding it into small pools, each with a capacity of 16,000 gallons. Within ten days the pools teem with phytoplankton and become ideal breeding grounds for aquatic life. Last week the Columbia scientists "set" their first batch of young Chesapeake Bay and Long Island oysters in the ponds, where they should thrive on the bountiful food supply. Eventually the scientists hope to raise snails, shrimps and anchovies in the pools.
Some recent aquaculture projects actually make use of pollution. In southern Germany near Munich, the Bavarian Hydropower Co. is already reaping a profit by using sewage (rich in minerals) as a fertilizer in carp ponds. The idea is not entirely new; natives of West Java have long known that carp raised in streams filled with wastes grow unusually robust. There is only one caveat: the fish must be well cooked before they are eaten.
Thermal pollution can be equally useful. Not only trout, but oysters and other shellfish have been grown more rapidly in the hot effluent from power plants. Indeed, one New York producer, who raises his oysters in the Long Island Lighting Co.'s cooling ponds, says that they reach full size in less than three years (vs. four to five years normally). Even more spectacular results have been reported by the Scots. By placing sole and plaice in water discharged from an atomic generator, they have raised the fish in six to eight months (vs. three to four years). The explanation: warm water increases both the metabolism rate and appetite of fish.
In the future, experiments in aquaculture will become even more dramatic. Japanese scientists have already proposed raising tuna-a fish that can reach a weight of several hundred' pounds-- in closed off atolls and lagoons in the Pacific. Indeed, the open sea itself may be \93ranched.\94 Columbia University Marine Biologist Oswald Roels is now exploring a \93fertilizing\94 scheme in which a seagoing dredge would bring up nutrients from the depths, distribute them near the surface to encourage the growth of plankton, and harvest the fish that might then thrive in the area.