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Crabbers Claw for Survival

Ecology: Some contend that overfishing is not the cause of the crustacean drop-off, which threatens the marsh itself.

September 29, 2002|ALLEN G. BREED | ASSOCIATED PRESS WRITER

DARIEN, Ga. — As Carl "Poppa" Poppell zooms his boat around the North River, shrimp skip in his wake like water skiers and the wind flattens his cap against his tanned forehead. "Going NASCAR," the crabber, 50, calls it.

Then something stops him cold. Tangled in the cordgrass off the starboard side is a pink-and-white buoy with the initials "C.P." marking one of his crab traps.

"See that clean cut?" he said as he ran his calloused hand across the shorn rope. "That's a knife or a machete or a hatchet.... Props don't do that."

Poppell has lost 60 crab pots to vandalism this summer, some of the 600 cut during a turf war in the marshlands south of Savannah. That's what competition and frustration have driven some of these blue crab fishermen to.

In many ways, the crabbers have become like their prey, scratching and clawing for survival in an ecosystem that is quickly becoming less hospitable to them. Last year's Georgia blue crab catch was a historically low 2.7 million pounds, less than a third of the 46-year average, and it's worse elsewhere in the Southeast.

Now, a young ecologist is saying that without the crabs, the marshes themselves might die -- the very marshes that serve not only as the crabs' nursery but as a breeding and feeding ground for shrimp, drum, oysters and other commercially important species. In some areas, the researcher suggests, overfishing of the crabs may be a major culprit.

No, no, no, Poppell says. Development, drought and other factors upstream are starving the estuaries of fresh water, raising their salinity, breeding disease. That's what got him where he is today, he says -- not overfishing. But with things as they are, he worries that he may be overfishing what's left without even meaning to.

As he motors through the creeks, Poppell wonders whether he and the crabs are racing toward the same bleak future.

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Hundreds of miles of Southern spartina, or cordgrass, marsh have died in recent years from the Chesapeake Bay to the Gulf coasts of Florida and Louisiana. Ecologist Brian Silliman says some are dying at a snail's pace -- and that's what scares him.

For the last half a century, a basic assumption of salt marsh ecology was that the forces regulating spartina grass growth and health were generally "bottom-up" -- nutrient levels, water salinity, oxygen conditions. But Silliman surveyed several of those dead and dying marshes and found very high densities of periwinkle snails.

Blue crabs are one of the snail's most important predators, and crab populations have been in rapid decline. In the Chesapeake, researchers have documented an 81% decline in spawning stock since 1992.

Silliman set out to see if the two phenomena were connected.

Researchers have long known that the periwinkle feed off dead or dying spartina. But the 29-year-old Brown University doctoral student noticed something -- without blue crabs, the snails were going after the healthy, live grass.

Testing his theory on Georgia's Sapelo Island, Silliman found that the inch-long snails graze the grass to cause scars that then become infected by fungi. That's what the snails are really after, and they're literally farming the grass to get it.

Slogging through black mud that sucks the boots off their feet with every step, Silliman and Mark Bertness, his professor, peppered Sapelo with meter-square wire cages, excluding blue crabs from test plots to see what the snails would do.

The result: Within eight months, the snails had changed one of the world's most productive grasslands into a barren mud flat.

"They just mow it down," Silliman said, standing between two cages -- one with tall, healthy green grass, the other a dead zone.

What Silliman found were signs of a classic "trophic cascade," a process in which the removal or compromise of one key species starts a chain reaction that results in a total system collapse. Bertness compares it to the destruction of California's kelp beds around the beginning of the 20th century, when otter overharvesting led to rampant sea urchin overgrazing.

Rom Lipcius, a crab specialist at the Virginia Institute of Marine Science, says Silliman's research is both fascinating and timely as scientists and regulators grapple with man's influence on nature -- and his attempts to set things right.

In the Chesapeake, for instance, much effort has been put into restoring the oyster beds that are as synonymous with the bay as lobster is to Maine. Now researchers are considering whether increasing stocks of blue crabs, the oysters' main predator, will preclude that restoration.

Crabbers, in turn, are worried that the success of efforts to restore the bay's striped bass fishery have cut into their business. Lipcius has heard reports of bass being caught with 100 juvenile blue crabs in their stomachs.

"You sort of get into all these vicious cycles," he said. "We might not be able to fix it because we've changed so many other parts of the system as well that it's just not able to adjust."

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