- The Washington Times - Thursday, August 10, 2006

Forget the Frankenfish. Local marine biologists are warning of a new threat to Maryland waterways.

It’s a crab from China with furry “mittens” on its claws.

Watermen have caught two Chinese mitten crabs near the opening of the Patapsco River, and biologists fear that the invasive species could damage the Chesapeake Bay if they establish a significant population.

Rom Lipcius, a researcher at the Virginia Institute for Marine Science, said that there is a slim chance that the crabs will make a home in the Bay, but if they do, other species in the Bay could be in a pinch.

“The idea of one more introduction [of an invasive species] might just be the last nail in the coffin for [native] species that are near collapse or decline,” he said. “It could be a serious matter for the food web.”

Mollusks such as shell clams and oysters, which are the primary food for mitten crabs, have been on the decline in the Bay for years.

Mitten crabs, which can live in both saltwater and freshwater, not only would threaten the Bay’s various shellfish populations but also would compete with native blue crabs for food.

This could be bad news for the home crabs because blue crab spawning has declined by more than 80 percent since the early 1990s, Mr. Lipcius said.

Lynn Fegley, a state biologist for the Maryland Department of Natural Resources, said that mitten crabs most likely would not become ferocious predators.

Mitten crabs would be very tame in comparison to the Frankenfish, the nickname of the northern Chinese snakehead — a voracious, eel-like fish.

The snakehead can breathe and “walk” on land, gorges itself on other species and breeds quickly. Hundreds of snakeheads have been found in local waterways since the first was found in a Maryland pond a few years ago.

“Snakeheads were blown up fairly rapidly by the media. The snakehead was a top predator,” Mrs. Fegley said. “The mitten crab is not a top predator, but it is nevertheless a member of the ecosystem that we need to [monitor].”

Mrs. Fegley said that it is not clear whether mitten crabs are breeding in the Patapsco. Both of the crabs that have been caught were male and could have been swept up in a ship’s ballast overseas and then expelled near the Port of Baltimore, she said.

Biologists’ top concern about the mitten crab is that it digs tunnels in river and lake beds, which can destroy marsh fringes and increase erosion.

In the San Francisco Bay and northern Europe, where mitten crabs have set up large populations, mitten crabs have played a large role in erosion, said Greg Ruiz, a marine ecologist for the Smithsonian Environmental Research Center.

As for the Chesapeake, biologists are unsure about the effects the crab could have.

“I wouldn’t expect such a striking effect, but at this point it’s difficult to predict anything,” Mr. Ruiz said.

Chinese mitten crabs are distinguishable by their large size and black hair on their claws that make it look like they are wearing mittens.

Anyone who finds a mitten crab is asked to call the Maryland Department of Natural Resources at 410/260-8285 or the Smithsonian Environmental Research Center at 443/482-2227.

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