PRINCETON-BY-THE-SEA

THE LONE MAN strolling on top of the stone breakwater at Pillar Point harbor here last week had no idea he was witnessing natural history in the making.

Below him, in waters reflecting the gray of an overcast afternoon sky, a California sea otter floated on its back, its head and tail above the water. The man strolled past the gently bobbing animal.

But from a slender aluminum motor boat a hundred yards a way, Jack Ames, a marine biologist with the California Department of Fish and Game who has studied sea otters for more than three decades, knew the animal was worth his heed.

"It's going to go under," Ames said as the otter rose up slightly. Seconds later, the lively animal did just that, disappearing beneath the water's surface, leaving a circle of turbulence.

Minutes before, where the harbor opens to the Pacific Ocean, Ames and two other marine biologists on board saw five other otters, floating on their backs in a rough circle. Upon seeing them, Ames shouted, "There are sea otters!," and the other two spun around to see them.

The otters at Pillar Point keep hopes alive that the imperiled population, listed as threatened under thefederal Endangered Species Act, may resume its stalled recovery.

Ames spotted them as he piloted the boat back from Pacifica last Monday, after laying out otter decoys off the coast of Pacifica for an otter-counting exercise for scientists flying overhead in planes. The decoys let scientists practice spotting the animals in the ocean. But Ames had to move the operation north to Pacifica, as several real otters were interfering with the exercise in January off Pillar Point.

The playful animals once ranged along inland coastal waters from Baja to Washington, in numbers approaching 20,000, researchers estimate.

But Russian hunters in the 18th century discovered the otters' luxurious brown pelt. Sea otter fur, the animal's sole defense against frigid ocean waters, is the densest fur known, said Andy Johnson, manager of the sea otter research and conservation program at the Monterey Bay Aquarium.

Less than 200 years later, California sea otters were considered extinct.

With the opening of Highway 1 on the Central Coast in 1938, however, Johnson said a remnant group of a few dozen sea otters was discovered living near the mouth of Bixby Creek, where it spills into the Pacific in Big Sur.

Over the next decades, the California sea otter population rebounded, growing by roughly 5 percent a year, said David Jessup, senior wildlife veterinarian with the California Department of Fish and Game.

But the expansion ceased about 1994, with the population remaining at roughly 2,800, Jessup said.

The otters spread north and south during their expansion, with a particularly robust population settling in Monterey Bay. The animals are beloved by tourists for their playful antics, endearing furry expressions and practice of using rocks to pound open shellfish resting on their breasts.

In the late 1980s, a permanent population also established itself at Ano Nuevo, thriving in a large kelp forest half a mile from shore.

"Last year I saw three pups," said Gary Strachan, supervising ranger at Ano Nuevo State Reserve. When they first arrived "we'd be really excited to see two or three."

"I'm still excited to see them," he added. "They are charmers." One recently made Pescadero Creek a temporary home, where it played with children, Strachan said, but not adults.

Otters and kelp forests like the one at Ano Nuevo are inextricably linked, marine biologists point out.

When otters return to their historic habitat, "we see a re-emergence of kelp beds," said Johnson, with the Monterey Bay Aquarium.

"The marine life that thrives in kelp beds re-emerge as well," he added, such as kelp crab, snails and rock fish. These species, in turn, provide food for the otters. The kelp forest also provides a place of rest and shelter.

Otters are voracious, consuming one-quarter of their body weight each day. Females weigh around 40 pounds, and males about 70. Among their prized prey are sea urchins and other kelp-eating herbivores. When their populations are unchecked by otters, these herbivores can damage the kelp forest with overgrazing.

Otters' appetite for urchin and abalone, valuable commercial species, also make them intensely unpopular with those in the fishing industry.

Marine biologists concede that otters do ruin some segments of the fishing industry when they repopulate an area, primarily species that are captured in inland waters. Deep-sea species like salmon and halibut, or crab pots placed far off shore, are not affected, they point out.

Calls to the Pacific Coast Federation of Fishermen's Associations, an industry group, seeking comment on the effect of sea otters on the fishing industry were not returned.

Johnson, with the aquarium, echoed the view of many in his enthusiasm to see sea otters repopulate their former territory.

"It's not just that otters were here first," he said. "It's that there wouldn't be a commercial industry (for certain species) if otters hadn't been hunted.

"I think the majority of people feel that otters deserve to be here, and that anything that helps them persist is a good thing," Johnson added.

But something in the waters off the San Mateo County coastline is holding the otters in check at Ano Nuevo, aside from the occasional glimpses of a few wandering animals, invariably males exploring new territory, farther north along the Peninsula coast and in San Francisco Bay

And throughout the otters' 375-mile range, from Ano Nuevo to Pt. Conception in Santa Barbara County, an unusual number in their prime years are dying.

Brian Hatfield, an otter expert with the U.S. Geological Survey, said great white sharks are one reason for the halted northward expansion of California sea otters. The USGS conducts research for other federal agencies, including the Fish and Wildlife Service, which has funded sea otter research.

"It's not really known what's limiting expansion to the north," Hatfield said. "But great white shark predation is believed to be a key part."

Otters at Ano Nuevo can shield themselves from shark attack in the kelp forest. But otters in the open ocean are vulnerable, and about half of otter deaths off the San Mateo County coast are caused by shark attacks, compared with about

12 percent throughout its range, according to Jessup, with the Department of Fish and Game.

The sharks, however, don't eat the otters, probably because they contain little fat.

"They bite them and spit them out," Jessup said. "There's a sea otter that looks an awful lot like a seal, and then there's a dead otter."

Elephant seals pack on generous amounts of blubber for insulation. The layer of fat makes them favorite targets of great white sharks, which need the high-energy sustenance to survive in the cold waters of the Pacific.

Shark predation, however, is only one piece of the puzzle over the malaise that's threatening the California sea otter population.

Pollution pouring into the ocean from creeks and sewage and drainage systems is the likely cause of the unusual pattern of diseases in otters, researchers believe.

About half of otter deaths throughout its range are due to infectious diseases, Jessup said, caused by bacterial contamination, harmful algal blooms and parasites.

The disease most threatening to the otters is caused by a parasite called Toxoplasma gondii, although it's only one of several plaguing the species. The only known hosts for Toxoplasma gondii are cats, Jessup said. It leads to neurological impairment in otters.

In September, Gov. Arnold Schwarzenegger signed legislation to address the stalled California sea otter expansion.

Among its provisions, the bill prohibits the dumping of material into the ocean that's harmful to sea otters and requires a label, as of this year, on cat litter sold in the state, encouraging cat owners to landfill the litter instead of flushing it. Cat litter is one source of Toxoplasma gondii, which survives the sewage treatment process and ends up in the ocean.

Otters pick up Toxoplasma gondii by eating filter feeders, such as clams or mussels, which capture the parasite.

The bill, AB 2485, increases the penalty for killing sea otters to $25,000. It also adds a contribution line to the state tax form, allowing taxpayers to donate money from their tax return to a sea otter fund.

However, if during the next two years less than $250,000 is donated each year, the Franchise Tax Board will eliminate the option from the tax form.

The funding, said Jessup, may prove essential to the continued operation of the state's otter recovery program. Federal funding declined by 50 percent last year and may be eliminated by 2008, he said.

A windfall from state taxpayers, he said, would keep the program robust. "It may keep us from having to contract violently," Jessup said. "I'm hoping and praying for that funding."

• InsideBayArea.com