The Chinese mitten crab is a medium-sized burrowing crab from East Asia. It made its way to the United States in parts of San Francisco, the Great Lakes region, and the Mid-Atlantic region. It can tolerate both fresh and salt water, and its aggressive nature has allowed it to become a costly and environmentally damaging invader in these areas.

Identification

Size of the Chinese mitten crab ranges from 30-100 mm (1.2-4 in), with legs about double the length of the torso. It gets the name “mitten crab” from the dense patches of hairs covering the claws, resembling mittens. These hairs are more common in males than females, and juveniles may not have any hair. The tips of the claws are typically white. Four pairs of spines are located on the side edges of the carapace. Color ranges from a light brownish-orange to a greenish-brown. There is also a small notch present between the eyes.

Similar Species

None.

Habitat

While the mitten crab is the only crab found in the fresh waters of the United States, it can also tolerate saltwater. These crabs are very skillful at walking on land, especially during upstream migration, allowing them to bypass dams and other natural obstructions.

Spread

The Chinese mitten crab has most likely spread in the ballast water of ships and as it clings to the hulls of barges during transport. It is becoming popular in the seafood market, especially in New York, and may have been released by purchasers into new areas.

Distribution

This species was first identified in eastern Asia and subsequently spread throughout Europe. It was discovered in the United States in 1962 in the Great Lakes and has since been reported along the Gulf Coast, San Francisco Bay, Chesapeake Bay, the Hudson River, and other East Coast areas.

Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.