The Chinese mitten crab, like this one pulled out of the Hudson River, were first spotted in the Chesapeake Bay in 2006.
Researchers are tracking the spread of the Chinese mitten crab, which are named for their furry claws. The crabs pose a threat because they burrow into mud and other areas and can damage stream-banks, dams, levees and water intake pipes.
They were first spotted in the Chesapeake Bay in 2006 and researchers want to know what impact they are having on native crabs and the environment.
If you come across a mitten crab, don't throw it back alive. The scientists studying the crabs are asking people to freeze the crabs or put them on ice, take a photo, and note where they were found. Then, contact the Smithsonian Environmental Research Center.