Glen Martin, Chronicle Staff Writer

Monday, January 24, 0

Dungeness crabs may not be lovely, but they are by no means unloved. These big, brown crustaceans are as much a symbol of San Francisco as cable cars and the Golden Gate, a gastronomic emblem as enduring for Northern California as lobsters for Maine.

Unhappily, their populations may not be as enduring as their image.

Commercial Dungeness landings at San Francisco have recovered modestly from their nadir during the early 1970s, thanks to steadily tightening regulations. Now, only males may be commercially taken, and their carapaces must measure at least 6 1/4 inches across.

But today's annual catches of 2 million to 3 million pounds still don't approach the glory years of the 1950s, when crab boats hauled 9 million pounds one year from the waters off the Bay Area.

Why? Several factors may be at work, including long-term ocean temperature cycles and loss of habitat. But many fishermen, at least, think overfishing is still a problem.

Larry Collins, a San Francisco fisherman who has crabbed for 13 years, said things started getting particularly bad about four years ago when tough quotas were put on groundfish, such as rock fish. Last week, the U.S. Department of Commerce declared a federal disaster for West Coast groundfish.

``After groundfish tanked,'' Collins said, the large groundfish trawlers rigged for crab. ``You're talking 125-foot boats that are setting out one to two thousand pots. They can fish all day and night in any weather. Little guys like me running 50-foot boats and 200 pots can't compete. And the crabs can't handle it.''

Collins said new recreational fisheries also are hurting Bay Area Dungeness.

``A few years ago, the party boats started setting out crab pots and then hauling them up after everyone got their limit of rockfish,'' he said. ``They're taking crates and crates of crabs out there now, including females and small ones.''

Dave Hankin, a professor of fisheries at Humboldt State University who has studied Dungeness for 20 years, said he is also concerned about overfishing.

``Dungeness have risen in commercial importance as other California coastal fisheries have fallen apart,'' Hankin said. ``We need to make sure they aren't overexploited. People always underestimate the impact recreational fisheries have on local stocks.''

Human appetites aren't the only problem facing Dungeness. Their numbers also fluctuate in response to habitat conditions. Because Dungeness like estuaries, most scientists agree that local populations are highly dependent on the biological integrity of San Francisco Bay. State researchers estimate 85 percent of the Dungeness caught in the Gulf of the Farallones are reared in the bay.

Dungeness begin life as minute, free-swimming larvae that form part of the vast shoals of zooplankton that periodically bloom in coastal waters. Eventually, they ``settle out,'' transforming into bottom-dwelling crustaceans. Through a series of molts, they ultimately reach edible size within three to six years.

State studies have demonstrated that crabs lucky enough to settle out in San Francisco Bay grow about twice as fast as crabs that settle out in the open waters of the Gulf of the Farallones.

Once they go through a few molts, bay-reared Dungeness migrate to the open sea to mature.

``Estuarine marshes are far richer than the open sea in the particulate food young crabs need,'' said William Kier, a Sausalito-based fisheries consultant. ``The marshes also provide abundant shelter. Part of the problem facing the crabs is that we've lost so much salt marsh in the Napa-Suisun area, where many of the young mature.''

Zeke Grader, executive director of the Pacific Coast Federation of Fishermen's Associations, said Dungeness populations are highest near areas of freshwater outflows.

``You have a sizable population in the Gulf of the Farallones near San Francisco Bay; there's one off the Eel River and one off the Klamath River,'' Grader said. ``It continues like that all the way up through Canada. That's why we have to do everything possible to preserve and enhance the biological health of our estuaries.''

Hankin agrees that the density of young Dungeness is particularly high in estuaries, but he believes the open ocean is also important nursery habitat. ``It constitutes such a vast area that it ultimately produces many more crabs than the estuaries,'' he said.

Another factor can affect Dungeness: water temperature. They like it cold. That means El Nino years aren't particularly healthy for them, observed Kathy Hieb, an associate biologist with the California Department of Fish and Game who conducts crab and shrimp surveys in San Francisco Bay.

``The warm water is especially hard on the embryos and larvae,'' Hieb said. ``Also, El Nino usually brings heavy storms. That means heavy south winds, which set up a near-shore surface current in this area called the Davidson Current. That can sweep young crabs out the bay and north of Point Reyes, far enough so they can't get back.''

Hieb said the rash of major El Ninos during the past decade probably is negatively affecting Dungeness populations. But that may be normal in the context of oceanographic history, she added.

``San Francisco is at the extreme southern end of Dungeness range, and during El Nino years, crab larvae production seems to be significantly curtailed here,'' she said. ``But this doesn't appear to be exceptional. We have sediment cores that show fluctuations in sardine and anchovy scale depositions. Sardines like warm water, anchovies like cold water, and the deposits go back and forth. This has all happened before.''

Hankin also feels it is important to take a long-range perspective on temperature fluxes and Dungeness densities.

``There is some compelling evidence to suggest that the warm water temperature changes (affecting Dungeness) are measured in decades, not in the months or years that individual El Ninos are measured,'' he said. ``The argument has been made that we need to see a major shift to a cold-water regime before Dungeness can thrive again around San Francisco, and I think there's some merit to that.''

Last week, scientists from NASA's Jet Propulsion Laboratory said new satellite images suggest a ``giant horseshoe'' of warm water may dominate the Pacific Ocean for the next 20 years.

Hankin isn't necessarily pessimistic. With reasonable regulations and adequate research funds, he feels Dungeness populations can be maintained.

``I am alarmed by the lack of research, however,'' he said. ``It's basically nil at this point. As other fisheries are depleted, the pressure on Dungeness will inevitably increase. Typically, management agencies ignore a natural resource until it collapses, then they look into it. But by then, it's too late.''
The Lowdown on Dungeness Crab. Chronicle Graphic by Todd ...

THE LOWDOWN ON DUNGENESS CRAB

Unique to the West Coast of North America, Dungeness crabs are the pride of the bay's fishing industry. But commercial landings of the crabs have been in decline in San Francisco since the 1950s. Some facts about Dungeness crabs and their habitat:

-- Life cycle Mating occurs near the coast but outside of estuaries. Once developed, eggs hatch into tiny larvae called zoea. Molting several times before adult-hood, the crabs settle in shallow coastal waters and estuaries.

-- Range

Dungeness crab, are found along the continental shelf from Amchitka Island in the Aleutians to Point Conception in southern California. The region from San Francisco to Monterey Bay, however, is generally considered the southern limits of their range.

-- At home in San Francisco Bay Dungeness spawn offshore, but large quantities of fertilized eggs are swept into estuaries by tidal action. The young crabs that ``settle out'' in estuaries grow at about twice the rate of crabs raised in the open ocean. It's estimated that 85 percent of Dungeness caught in the Gulf of the Farallones were reared in San Francisco Bay.

Dungeness like cold water, and are adversely affected by El Nino events. The large storms associated with El Ni\226o pose danger to crabs by flushing them from their brood areas in bays and estuaries.

-- Decline in landings

Population crash was attributed to overfishing in the 1950s. Population has remained low due in part to long-term warm water conditions and the loss of salt marsh habitats.

Sources: Alaska Department of Fish and Game, the Crustacea Laboratory at Museum Victoria, Pacific States Marine Fisheries Commission.

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This article appeared on page A - 4 of the San Francisco Chronicle