AT THE SMITHSONIAN

Wanted: Mitten Crab—Dead or Alive

Senior Editor

September 5, 2007

An intruder is among us. A hairy-clawed invertebrate is trying to invade the Chesapeake Bay and Smithsonian officials want help rounding up the villain.

The critter, which the U.S. Feds call "injurous wildlife," is the Chinese Mitten Crab, or Eriocheir sinensis. It is a harmful invasive species that burrows into embankments and causes erosion and threatens levies. An established population can be so overwhelming in sheer numbers that the critters clog fishing equipment and the cooling systems of power plants. Since 1927, the crab has been spreading throughout Europe and reached California’s San Francisco Bay in 1992.

Smithsonian officials confirm ten captures of the crab, which measures about four inches across its back and varies in shades from light brown to olive green, in the Chesapeake Bay, the nation’s largest estuary. The crab likely made its way here from Asian ports in the ballast tank of an ocean-going vessel, says Gregory Ruiz, a senior scientist at the Smithsonian Environmental Research Center (SERC), with headquarters on the Rhode River in Edgewater, Maryland.

Unlike Maryland’s native blue crab, young mitten crabs prefer fresh water, and so experts say the animals could be lurking in places up to 50 miles inland from Bay waters.

The crab is easily recognized by its so-called "mittens," a fur-like coating on its oval-shaped claws. It looks nothing like a native blue crab, however young mitten crabs may be confused with the Harris mud crab, which burrows into the same areas. To make a positive ID of the culprit, check for the furry claws.

SERC officials warn, however, that if you catch a mitten crab, you should not throw it back alive. They want you to note the exact location of where the animal was found, take its picture if possible, then freeze the animal on ice, or preserve it in rubbing alcohol. The Mitten Crab Hotline is 443-482-2222.

(Courtesy of SERC)