Off the scale.

The South Pacific island nations of Kiribati, Marshall Islands, Micronesia, Nauru, Palau, Papua New Guinea, and Tuvalu recently told Japan, the United States, and other commercial giants to get some of their trawlers out of the islanders' waters. Because fish have become too valuable to allow intruders to continue taking them, other countries are likely to join the South Pacific nations in restricting foreign access to their waters.

The evidence of that value can be measured in dollars and demand. Worldwide, people eat more fish than beef and chicken, combined. In some low-income countries, fish provides most of the protein people get from animal sources. But scarcity and rising prices are pushing this traditionally inexpensive source of protein out of reach of many of the world's poor.

Seafood sales are a textbook case of the law of supply and demand. With the harvest of fish and shellfish per person in decline and demand continuing to rise, prices have mounted stcadily. In the United States, seafood cost 40 percent more in the early 1990s (adjusted for inflation) than i ii 19 5 0. Meanwhile, the price of beef during the same period fell by one quarter and poultry by more than half.

Although the most reliable data for seafood price trends come from the United States, these numbers are an effective barometer of the worldwide situation. The same pressures that have meant fewer fish per person in the United States - lack of growth in fish stocks coupled with growing populations and demands - are at work in almost every region of the world.

What is unusual about the rising prices for seafood is that with the dramatic improvements in fishing technology that took place over the last 40 years, prices would ordinarily have come down as supply rose. However, a threshold was crossed during the same period in many of the world's seas: fish were harvested faster than they could reproduce, and their populations actually declined.

Overfishing and the higher prices that result are reshaping the global diet. It's becoming clear that seafood is a commodity that follows the pathways to the highest bidder. In poorer countries, the export of seafood may help balance trade deficits in the short term, but it could ultimately mean less access to this food source at home, especially in those countries where many people's diets lack protein and where traditional fishers have fed their families and supported their communities through the ages with fish.

Indeed, seafood exports from developing countries have increased in volume by 75 percent since 1981. Until 1988, the European Community countries were self-sufficient in fish and shellfish, but now they import. In Japan, imports of seafood rose from $4 billion in 1985 to $10 billion in 1990 - a level of import dependence unusual for any Japanese industry.

The new global economics of seafood is certain to touch jobs, national incomes, and natural resources. For example, the United States is bidding for fishing rights in Argentine waters that are now off-limits. Many Argentines want to open those waters and sell the rights for cash; others want only fellow Argentines to fish the waters and then sell the fish in the United States after it is processed. This, they argue, would generate jobs and value-added income for Argentina.

As the price for fish has risen, a whole new industry has flourished - fish farming. The amount of fish raised in ocean pens and inland ponds or tanks, also known as aquaculture, has grown from 9.2 million metric tons in 1984 to 14.2 million metric tons in 1990. Some aquaculture enthusiasts, who see seafood as a solution to the world's escalating food needs, promote the idea of a "blue revolution" that does for food from the water what the Green Revolution did for food from the land.

But aquaculture, like agriculture, must contend with scarce resources, pollution, and other problems. Fish farmers will be challenged in the years ahead with the need to limit the spread of disease among fish kept in tight quarters, keep diseases from infecting wild fish, prevent inbreeding and genetic weakening of wild species, reduce their waste releases, and stabilize the market for their products. From the wreckage of Thai mangrove forests cleared to make room for shrimp ponds to the infection and decimation of wild fish populations in Ireland by diseases cultivated in farmed stocks, aquacultural science has many adjustments to make before it can be called a "revolution."

Despite these problems, the strong demand for fish and rising prices will ensure a bright future for aquaculture. The explosive growth of salmon farming in Chile, which now supplies nearly 5 percent of the world's salmon harvest after just 10 years in business, and the expansion of shrimp farming throughout Central America in the late 1980s and early 1990s, are just indications of the possibilities ahead.

While the success of aquaculture will help the supply problem, its effect on global fish prices will be more ambiguous. Fish farmers compete with meat producers and grain farmers for some of the same resources - grain and soybean for feed, increasingly scarce fresh water, and valuable land. The cost of those resources will raise the price of farmed fish, as will the costs of fighting disease among close-quartered stocks and preventing concentrated fish waste from spoiling coastal areas and lakes.

Which brings us back to the more basic problem - affordable food for growing populations has not been made more plentiful by the advent of sonar, factory ships, drift nets and other innovations. The seas' food, it turns out, is a commodity that cannot be increased - at least not for long. Rising prices attest to that.