And so it has come to this: The rapacious appetite of humankind has pushed a lowly sea snail to the point where federal regulators are considering adding it to that sad ledger known as the Endangered Species List.

In other words, this may be the first time that we as a species literally have eaten a marine invertebrate to near-extinction.

Until now, scientists and resource managers thought this would be impossible. But we have done it.

"It's pretty amazing when you think about," said Peter Haaker, a biologist with the California Department of Fish and Game, standing on the swaying deck of the research vessel Velero IV off Santa Cruz Island in the Channel Islands National Park. "Scientists never thought you could drive an animal that produces millions of eggs and make it extinct through fishing. But that's what happened."

The woeful tale of the white abalone shows clearly that the sea is not endlessly bountiful, Haaker and his colleagues say, and that more science, more monitoring and more regulation are often necessary. But many Republicans in Congress have argued the Endangered Species Act already is overreaching.

Overfishing often can severely deplete marine populations, as has happened to wild salmon populations. But the abalone are not merely depleted. They have become among the rarest of the rare. This after a decade of being able to order them in restaurants.

From gourmet to gone. In a generation.

And once things get this desperate, it may be impossible to reverse the trend. In recent years, scientists increasingly have been called upon to restore animal populations and rebuild damaged habitats. Some efforts, such as the rebound of bald eagles and American alligators, have been impressive successes. But other attempts are far more challenging.

The California condor, for one, has been returned to the wild. But scientists must continue to feed the birds. The Florida panther barely is holding on in the Everglades, but researchers have taken the controversial step of bringing cougars from Texas to mate with their Florida kin to bolster their gene pool. In both cases the wild populations of condors and panthers number in the mere dozens.

The proposed plans for saving the white abalone have a similar sense of desperation. One idea is to farm-raise abalone on shore and then "outplant" them back in their habitat. Perhaps by the millions. Another idea is literally to pick up individual wild abalone (which must be within three feet of another to reproduce) and move them around in an elaborate dating game.

All of this will take years, millions of dollars and hundreds of hours of dive time, some of it quite dangerous because of the depths.

At present, the scientists with the Abalone Restoration Consortium just want to know how endangered the creature is. The National Marine Fisheries Service already has been petitioned by environmentalists to list the animal as endangered.

The white abalone is one of eight related species that live along the California coast. Unlike the other consumable species--the greens, blacks and reds--the white abalone does not live in tidal pools or in more shallow waters. Its home is the deep rocky slopes around the islands or far offshore on isolated reefs and banks.

To the uninitiated, an abalone looks like a clam with one shell. But it is a gastropod, related to snails and sea slugs. It has a single spiral shell (ugly and covered with growth on the outside but pearly iridescent white on the inside) and a large muscular "foot" underneath that allows it to grasp onto rocks and to walk--albeit very slowly--along the sea bottom.

Its foot is what got the abalone into trouble. It is a big meaty thing (an abalone can grow to 10 inches and live for 15 or 20 years) that can be beaten with a mallet into flattened steaks. The whites are better than the reds, greens and blacks. Their foot meat is so tender it can just be sliced and eaten, either sauteed with a pat of butter and lemon, or raw as sashimi or sushi.

However, so well hidden was the white abalone, that it was not scientifically discovered and described until 1940, when it was given the name Haliotis sorenseni. Until Jacques Cousteau invented the Aqualung and scuba technology developed, no one would ever think of hunting them.

But in the 1970s, there was a booming abalone fishery. Commercial landings peaked in 1972 at 144,000 pounds. By 1978, the fishery had collapsed. A few years ago, it became illegal to take white abalone anywhere, and all abalone species now are protected in Southern California from sport and commercial divers, though poaching still occurs.

Konstantin Karpov, another Fish and Game researcher aboard the Velero, sat in the galley after a dive and pulled up a graph on one of the dozens of computers and pointed. What the data clearly showed was that as the easier-to-catch abalone species were depleted, divers moved on to the harder species, until they were literally risking their lives to get the whites to market. And then, as the whites became harder and harder to find, the pressure on the resource continued because the prices climbed for this gourmet snack, until a single large individual would sell for as much as $100.

In the 1970s, divers reported seeing as many as 5,000 white abalone clustered together in a single acre. In research dives in 1992 and 1993, divers found three live abalones.

And so the mysterious gastropod, which wants nothing more than to consume floating kelp and occasionally reproduce with its neighbors, is now so rare that last Monday, a team of dedicated abalone researchers spent the day off the Channel Islands, making repeated dives in a little yellow submarine, and found exactly one living specimen.

What was the abalone doing?

"He was just sitting there," said Kevin Lafferty, a marine ecologist with the U.S. Geological Survey, as he emerged from the two-person Delta submarine and onto the Velero IV. "He was just sitting there all alone."

That is the problem--or one of many problems.

In three weeks of making almost 70 dives in the submarine, giving researchers unprecedented time of 100 hours on the bottom, the scientists found 157 live abalone. Most were isolated mature individuals.

What disturbed the researchers was that the abalone were so alone, and getting older. To successfully reproduce, a male and female abalone must be within a few feet of each other when they spawn their sperm and eggs.

Moreover, the researcher could find no juveniles, making them suspect that the last big successful breeding occurred in the 1970s when the species was plentiful.

When abalone populations began to crash, many blamed the sea otter, which also had been threatened, but was rebounding along the coast. But the sea otter cannot explain the plummeting white abalone populations in Southern California, because sea otters by law are not allowed to live in the southern waters. When they stray from Central California below Point Conception into Southern California, they are removed.

Disease also could play a role in the white abalone demise. Some other species suffer from an infection that causes "withering syndrome." It is unknown if such an infection could be making the white abalone sick, but the researchers doubt it. Pollution is also suspect, but the waters surrounding the Channel Islands of Southern California are some of the most pristine in the United States.

On the research trip that ended on Monday evening, the scientists took no living abalone, only a handful of dead shells. But there is something waiting. In a tank at the University of California at Santa Barbara, there is the only known white abalone in captivity, a female they have named Abagail. She, too, lives alone. In the coming months, the scientists plan on bringing her some company and seeing if the males will spawn with her, perhaps providing the knowledge and first individuals to replenish the once vast herds of abalone living on the sea floor.

CAPTION: A diver measures an abalone found in waters off California. In the 1970s, divers reported seeing as many as 5,000 white abalone clustered in a single acre. A recent underwater search by researchers found one living specimen.