Seafood on the skids.

The last tuna. The last swordfish.

The idea sounds absurd. Yet the world's growing appetite for fish and shellfish could spell disaster for seafood around the globe.

"The sea is in serious trouble and we need to take action now," warns Elliott Norse, president of the non-profit Marine Conservation Biology Institute (MCBI) in Redmond, Washington.

Last September, the National Marine Fisheries Service (NMFS) said that 86 of the species caught in U.S. waters are "overfished." In most cases, that means they're being caught faster than they can reproduce.

"We are squandering the greatest remaining natural resource on earth," says Norse. "If we don't do something immediately, we will live to regret it."

How did we get ourselves into this mess? Can fish-lovers eat any seafood with a clear conscience?

Deplete the oceans' wealth of fish and shellfish? A generation ago it would have been unthinkable. No longer.

"Roughly 70 percent of the world's commercially important marine fish populations are now fully fished, overexploited, depleted, or slowly recovering," says Lisa Speer of the Natural Resources Defense Council (NRDC), a non-profit environmental advocacy group based in New York.

The major problem: Too much fishing firepower is hunting down a limited number of fish. According to the United Nations, the world's fishing capacity would have to be reduced by 30 percent to allow overfished resources to recover.

That's unlikely to happen. Governments around the world invest more than $50 billion a year in ships and fishing technology. As a result, fish don't have a fighting chance:

* Fishing fleets now use sonar to probe the ocean depths and detect schools of fish.

* Boars equipped with satellite guidance systems can return to the same spot year after year.

* Ships that hunt tuna and swordfish slowly release high-strength fishing line up to 80 miles long that's baited with thousands of hooks. Thanks to the killing efficiency of these "longlines," supplies of Atlantic tuna and swordfish are dwindling.

* "Bottom trawlers" drag heavily weighted nets across the seabed to SCOOP Up shrimp, scallops, and fish like cod, which swim near the ocean floor. In the process, the nets "crush or bury lobsters, clams, corals, sponges, and other creatures that live on or in the sea bed," says the Marine Conservation Biology Institute (MCBI). Trawling accounts for more of the world's fish catch than any other method.

"Its effects are similar to clearcutting forests, but are more extensive," says the MCBI's Elliott Norse. "The area of seabed trawled worldwide is at least 15 times greater than the area of forests that is clearcut each year."

The biggest factory trawler, the American Monarch, reportedly can scoop tip a million pounds of fish a day. Earlier this year, Chile and Peru refused to let the ship anchor off their coasts. They were afraid that it would deplete local fish stocks.

The Toll

These indiscriminate fishing methods take a grisly toll. "Bycatch" is the bloodless-sounding term for the slaughter of sea turtles, dolphins, white whales, and other animals that are inadvertently caught tip in nets and lines. The United Nations estimates that 27 million tons of unwanted fish are tossed--usually dead or dying--back into the oceans each year. That's more than a quarter of the total annual marine catch.

"We are no longer living off the income of our fisheries," warns the NRDC. "We're eating deeply into the capital."

As the big predators like cod, tuna, and swordfish are depleted, commercial fishermen are "fishing down the food chain." As a result, fish that used to be eaten by other fish are now eaten by humans.

Another trend that worries marine ecologists is deep sea fishing. As species that live just below the surface are overfished, commercial fleets are forced to go deeper. And that can have unforeseen consequences.

Orange roughy are found in deep pockets in the Atlantic and off the coast of New Zealand. They might live for 100 years or more, and don't even reach sexual maturity until they're 25 or 30. By the time scientists realized that, fishing fleets had taken all they could find ... including enormous numbers of sexually immature fish.

As a result, orange roughy have become rare. In the Pacific, the species may not recover for 100 years or more.

Growing Fish

Did you know that your salmon steak may have come from a fish reared in a pen off the coast of Chile or Norway? Or that the shrimp in your Hunan Shrimp may have been grown in a pond along the coast of Thailand?

About half our shrimp, a third of our salmon, and most of our catfish and trout have never swum freely in a lake or the ocean, says Rebecca Goldburg of the non-profit Environmental Defense Fund (EDF) in New York.

What do we gain (or lose) by growing instead of catching our seafood?

* Nutritional Value. Farmed fish is fattier than wild fish. But most of the extra fat is monounsaturated, so it doesn't raise LDL ("bad") cholesterol and may help raise HDL ("good") cholesterol. And in most cases, farmed and wild fish have about the same amount of omega-3 fatty acids, which give fish their healthy reputation (see "Fishing for Omegas," p.8).

* Pesticides. Farm-raised fish are more likely than wild fish to contain small amounts of pesticides, according to data from the Food and Drug Administration. Some of it leeches into the fish ponds from the surrounding soil--often decades after it was applied. Some comes from the feed or the water that's added to the ponds.

In 1994, the FDA collected 1.60 samples of fish and shellfish raised in the U.S. A little more than half contained traces of DDT, a pesticide that was banned in 1972. But all of the samples had far less than the maximum allowable amount.

"That's not surprising," says Ellen Silbergeld, a toxicologist at the University of Maryland Medical School in Baltimore who has worked for the Environmental Defense Fund. "Those levels don't appear to represent anything above the unfortunate general widespread contamination of the planet by DDT."

Others agree.

"For a typical consumer those pesticide levels should not be a concern, even for high-risk groups like pregnant or nursing women," says Henry Anderson, Chief Medical Officer for Occupational and Environmental Health in the Wisconsin Division of Health.

In 1995, the FDA decided that pesficide levels in farm-raised seafood did not pose a health hazard and stopped tracking them separately.

* Antibiotics. Antibiotics are used to treat bacterial infections and prevent them from spreading throughout the stock. "We've looked and haven't found residues of any antibiotics in domestic or imported farm-raised seafood since 1994," says Kim Young of the FDA's Office of Seafood.

Still, the FDA has only a limited inspection program, says the Environmental Defense Fund, so it could be missing some residues.

* Environmental Pollution. "Some aquaculture systems are environmentally more responsible than others," says the EDF's Rebecca Goldburg. Oyster, clam, scallop, mussel, and catfish farms tend to be among the responsible ones, she says, though some catfish farmers shoot fish-eating birds.

Salmon farms may not be responsible. "The he uneaten food and the excrement that's created can pollute the local marine waters just like raw sewage," says Goldburg.

She and other environmentalists also worry that domesticated Atlantic salmon--which are often grown on the West Coast--will escape captivity and settle in the local waters, displacing Pacific salmon. "Anything that cuts down on the diversity of species carries a risk," she says.

The worst aquaculture? "Shrimp farming is a rapacious and primitive way of producing seafood," says Goldburg. Huge tracts of mangrove forests have been cut down in Southeast Asia, Central America, and South America to make room for shrimp ponds to feed North America's and Europe's voracious appetite for shrimp.

"The industry is learning from mistakes that were made in the early stages of its development," says Ken Gall of New York Sea Grant, a federally funded program that does research and education on seafood and other marine issues.

"There now appears to be less clearing of mangrove forests for shrimp ponds than there used to be," agrees Goldburg. But there are still plenty of other problems. For example: To seed their ponds, shrimp farmers need huge numbers of shrimp. "For every one stalked, up to a hundred other marine creatures may be killed."

Another reason to think twice about that shrimp-lover's feast: "For every pound of wild shrimp sold in markets Or restaurants, five pounds of other sea creatures are caught and killed," says Goldburg.

What to Do

What can you do to stop the high-tech, increasingly effective worldwide fish hunt? Avoiding overfished species like Atlantic sea scallops, flounder, and red snapper isn't the answer, say most environmentalists.

"We're not recommending that people avoid eating seafood that's being overfished--with the one exception of North Atlantic swordfish during 1998," says the NRDC's Lisa Speer.

"With swordfish, our traditional methods of advocacy haven't worked. So we're trying to enlist consumers to help us get the federal government to act more effectively to secure their recovery. Everybody's heard of swordfish and giving it up for awhile is not going to hurt anyone nutritionally. The good news is that swordfish can come back because this is a really prolific species. We can bring them back in ten years without shutting down the fishery or taking really drastic measures."

The government agency responsible for managing marine resources, the National Marine Fisheries Service (NMFS), opposes boycotts.

"For each species we've declared overfished, there's now a plan in place or being prepared to fix that," says Gary Matlock, director of the NMFS's Office of Sustainable Fisheries. "Thanks to a 1996 law, the NMF's must restore any overfished species back to sustainable levels as soon as possible, or within ten years, unless the biology of the fish, an international agreement, or other environmental conditions dictate otherwise."

The NRDC has its doubts about some of the NMFS's plans. "We think the international community and the government are allowing too many Atlantic swordfish and some other fish like Ted snapper to be caught," says the NRDC's Karen Garrison.

But North Atlantic swordfish is the NRDC's only "don't buy," and only during 1998. The "don't eat" list of the Marine Conservation Biology Institute's Elliott Norse is longer.

* Shark. "We should not be eating sharks. That means no shark fin soup, no blacktip steak, no mako shark steak. Sharks are too vulnerable to overexploitation. They're like people. They live a long time, they have small numbers of young, and it takes many sharks 15 years or more to reach reproductive age."

* Atlantic Swordfish & Marlin. "We've hit their populations so hard that they're in real trouble, especially in the Atlantic. When you see them for sale, just say `no."'

* Bluefin Tuna. "They're prized by people in Japan in particular. The big fatty bluefin make the most expensive sashimi. The rarer they get, the more pressure there is to fish them. I don't discourage people from eating canned tuna because most of it is caught in a less-harmful method than in years past."

* Orange Roughy. "They're inherently difficult to fish sustainably because they take such a long time to grow and reach sexual maturity."

* Chilean Sea Bass. "It's a great fish. It's delicious. It broils, it stews, you can do almost anything with it. But you're only going to get one chance ... because they are deep-sea, long-lived fish and nobody is fishing them sustainably. Unless we act right now, we're not going to have Chilean sea bass on the menu in the future."

* Shrimp. "Everyone in the Red Lobsters and the Ruth's Chris Steak Houses of this world wants shrimp. And that makes it worthwhile economically to catch them, even if they make up only five percent of the catch and if the other 95 percent consists of other living things that are killed in the process. As for farmed shrimp, we destroy coastal ecosystems like mangrove forests from Ecuador and Panama to Thailand and India and turn them into shrimp farms, which produce for a few years and then are abandoned, as people move on and cut more forest. The only shrimp I'll eat are cool-water species that are caught in shrimp pots."

"Whatever generated us generated all other living things," says Norse. "It's our moral responsibility not to destroy the sea.

"Nature works slowly, but our economies work quickly. And our regulatory systems, unfortunately, are much slower to respond than our economic systems. If we want to eat seafood in the future, we're going to have to do a better job than we're doing today."

RELATED ARTICLE: MERCURY RISING

Mercury is a toxic metal that accumulates in brain tissue. It can cause birth defects and behavior problems in children and nerve damage in adults.

While "human exposure to mercury occurs primarily through eating contaminated fish," says the Environmental Protection Agency (EPA), "the levels of mercury encountered in commercial fish are generally low." According to both the EPA and the Food and Drug Administration (FDA), "it is safe to eat fish and other seafood from grocery stores and restaurants."

The people who are at greatest risk, says the EPA, are recreational fishers and others who eat large amounts of locally caught fish from mercury-polluted waters.

To play it safe, the FDA recommends that women of chilbearing age at shark or swordfish (which accumulate mercury from their prey) no more than once a month. Everyone else should limit those fish to seven ounces a week.

The FDA also recommends that everyone limit grouper, marlin, and orange roughy to 14 ounces a week and all other seafood (including canned tuna) to about two pounds a week.

RELATED ARTICLE: FIND YOUR FISH

Every year the National Marine Fisheries Service must tell Congress which ocean fish and shellfish in U.S. waters are already--or are at risk of becoming--overfished. We've listed the most commonly eaten fish from the NMFS's latest report, which was issued in September 1997. We've also added a few popular fish like cat-fish and trout.

Use this list to check on the status of your favorite species, but keep in mind that environmentalists don't recommend boycotting all the fish in the "overfished" column.

Not Overfished

Catfish, all Clams Mackerel, jack (canned) Oysters Perch Pollock Salmon, farm-raised Salmon, pink and sockeye, wild Scallops, Alaskan Shrimp Swordfish, Pacific Trout, farm-raised or wild Tuna, except West Atlantic bluefin Whiting

Overfished

Flounder, most varieties Halibut, Atlantic Lobster, American Red Snapper Salmon, Atlantic, wild Sea bass, Chilean Sea Scallops, Atlantic Swordfish, North Atlantic Tuna, West Atlantic bluefin

Unknown or Depends on Location

Cod Crabs, most varieties Haddock Rockfish Salmon, wild (except Atlantic, pink, and sockeye

Source: Adapted from Status of Fisheries of the United States, National Marine Fisheries Service, September 1997.