CALIFORNIA ALBUM : Coming Out of Their Shells : After nearly vanishing, the famed giant pismo clam has rebounded--only to be threatened again by mollusk lovers and voracious sea otters.

Chuck Bray was in the surf above his knees, digging with a pitchfork for one last pismo clam before the tide rose too high.

Just a few yards away, his fiercest competitor, a four-legged fur ball, happily banged two clamshells together until one broke. The 50-pound sea otter, once threatened with extinction, gobbled up the clam and dived down for another.

“At one point, the otter was just 15 feet from us,” said the cold and soggy Bray, who drove all the way from Salinas to go clamming. “He was eating clams, flat on his back. It was pretty exciting.”

The famed pismo clam, which virtually vanished from Pismo Beach in the 1980s, has returned, at least for the time being. But along the Central Coast, the days of being as happy as a clam may be numbered.

When the tide is low, hundreds of people a day go clamming; when the tide is high, the otters go clamming. Sometimes, when the tide is in between, they both go clamming.

Between the voracious otters and the crowds of people, the clams hardly stand a chance.

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Drew Brandy, a warden with the Department of Fish and Game, sat in his truck and peered through a telescope at the human clam diggers. Most appeared to be obeying the law, but one couple seemed suspicious, digging up the bivalves with their feet and stuffing them into their pockets.

After watching them take two trips to their car parked on the beach, Brandy moved in. He asked to see their clams and found what distresses him most: “a lackadaisical attitude toward wildlife.”

Of 43 clams the pair had dug up, all but two were smaller than the legal harvesting size of 4 1/2 inches. Plus, they had exceeded the limit of 10 clams per person each day. Their only saving grace was that they had purchased the required fishing licenses that morning.

Brandy wrote them a ticket that could cost as much as 300 clams, er, dollars. He gave them back the two legal-sized mollusks and buried the rest of the loot in the wet sand.

Among California beaches, Pismo State Beach is an oddity--the only beach where it is legal to drive up on the sand. On weekends, the shoreline looks like a disorderly highway as cars cruise up and down six miles of beach without the benefit of lane lines or Botts Dots.

For the clams, the cars are just one more agent of death.

Most clams that people dig up are under the legal size and, by law, must be promptly reburied. But some clammers do not bury them well; others just toss them in the surf. And when the clammers are at work, hundreds, if not thousands, of clams wash up along the high water line.

“It’s like a ribbon of clams all the way down,” Brandy said.

Many mollusks are crushed by the traffic. Others get overheated and die in the sun, or they become food for the sea gulls, who drop them repeatedly from on high until they break open.

Game wardens try to crack down on clammers who fail to bury the petite clams properly (with the shell entirely covered by sand and the hinge facing the ocean, thank you). But it is often hard to prove who is responsible for a clam washing up on the beach.

“I just wish they’d take a little effort and rebury their clams,” Brandy said, as he quickly poked two dozen stranded clams back into the sand. “I don’t really have time to walk the beach and rebury their mess. I’m trying to catch the poachers.”

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The pismo clam takes its name from Pismo Beach, an eight-mile stretch of sand where the clams historically have been plentiful and the conditions for clamming ideal. But the species is found as far north as Monterey Bay and as far south as Baja California.

The name comes from pismu, the American Indian word for globs of tar that sometimes wash up on the sand, said Paul Scott, an expert with the Santa Barbara Museum of Natural History who is penning a book on clams of North America.

Before the arrival of Europeans in California, the pismo clam and the otter lived in a state of natural balance. But in the 1800s, trappers hunted the otter to the verge of extinction.

Without the ravenous mammal as a predator, the pismo clams flourished. Early settlers turned up thousands of clams to feed their hogs. Until the 1970s, people came from miles around to dig for the mollusks, which can grow to six inches.

Then the slowly growing population of Central Coast otters took up residence at Pismo Beach in 1979, and the clam numbers collapsed. The otters, which can consume more than 12 pounds of clam meat a day--a fourth of their body weight--devour any clam larger than two inches long.

The remaining small clams were mature enough to reproduce, but clamming by humans along the beach came to an end. Biologists figured that the days of the giant pismo clams were gone forever from the beach that gave them their name.

“Everybody was resigned to the fact that we were no longer going to have clamming at Pismo Beach,” said Bob Hardy, a marine biologist with the Department of Fish and Game.

And so the experts were surprised in the late 1980s when the mollusk began to make a comeback.

Through a fluke of nature that had never been observed since scientists began keeping records in the 1920s, the clam had three consecutive years of hugely successful breeding, producing as many as 50 times the usual number of offspring. Since 1990, many clams have been reaching full size and providing a large enough harvest for people and otters.

But biologists say the recovery will be short-lived: There is no baby-boom generation of clams following.

“We saw the population reduced to where there were no more legal-sized clams and we anticipate that will happen again,” Hardy said. “We just can’t say when that will be. It might be a year, it might be longer.”

Already, clammers have to work hard to get their limit of 10 full-grown clams a day.

After several hours of effort, George Kraul came up with three full-sized clams to go along with the seven uncovered by Bray. In perhaps a bit of an overstatement, the waterlogged Kraul said: “We dug 10,000 clams and ended up with only a limit between us.”