Invasive crabs may threaten blues

EDGEWATER, Md. (AP) — Scientists tracking progress of an invasive crab in the Chesapeake Bay say a third Chinese mitten crab was caught Friday.

Two watermen checking crab pots in Southern Maryland discovered one of the crabs, which burrow in tributary banks and may compete with native blue crabs for food.

Gregory M. Ruiz, senior scientist at the Smithsonian Environmental Research Center in Edgewater, told the Baltimore Sun the mitten crabs are either reproducing in the Chesapeake Bay or repeatedly being released in the ballast water of ships.

Biologists fear the mitten crab, which has furry claws and long legs, could swarm over riverbanks, dig burrows that cause erosion and rip up fishing nets. The crabs are believed to have hitchhiked to the Chesapeake aboard ships from Asia. The crab also has been found in California, Germany and England.

“It’s a concern, because there is a lot of evidence that this crab could establish itself here,” said Mr. Ruiz, a marine ecologist. “In other places where it has been established, it goes through years where there are outbreaks, and they are incredibly abundant.”

Mr. Ruiz said that mitten crabs aren’t likely to directly hurt blue crabs, but they could compete for valuable food sources such as submerged aquatic vegetation and young blue crabs and mussels.

“I don’t want to be alarmist about it, but there are a lot of potential dynamics that we don’t understand,” Mr. Ruiz said. “Like a lot of invasive species and nonnative species, this is not one that we want. We don’t want to take that risk.”

The first mitten crab identified in the Chesapeake was caught by a waterman last June at the mouth of the Patapsco River.

Then, a few days later, scientists concluded that a second crab, also caught in the Patapsco River more than a year earlier and frozen, was of the Chinese species.

“I don’t know if these numbers are cause for great alarm, but periodically having them turn up like this is cause for some concern,” said Eric Schwaab, deputy state natural resources secretary.

Mr. Schwaab says it’s still not clear whether the mitten crabs are reproducing in the Bay.

“I don’t think this suggests there is a significant population, let alone a growing population,” Mr. Schwaab said.

Vince Meyer, owner of Vince’s Crabhouse in Essex, caught the most-recently reported mitten crab off Chesapeake Beach Friday in his boat, the Brittany Lynn.

“It looked different,” Mr. Meyer told the newspaper. “The legs had like long hairs on them, and the hair had an almost purple color. It was freaky-looking for the Bay.”