Mitten crabs (Eriocheir sinensis) are native to East Asia. They migrate from freshwater to brackish/marine waters to spawn. Introduced populations exist throughout Europe and the continental U.S. along the East and West Coasts. In New York, mitten crabs occur in the Hudson River, New York Harbor, and the Long Island Sound. Although the impacts of mitten crabs in New York are currently unknown, their negative ecological and economic impacts are well document in other areas including Europe and the San Francisco Bay Delta. NYSDEC is asking the public to report observations of mitten crabs and take steps to limit their spread and potential impacts on local ecosystems.
Description
How to identify mitten crabs:
- Claws of equal size with white tips and dense patches of brown setae that look like hairy mittens (mittens present in adults and juveniles with carapace (shell) width > 1 in)
- Carapace (shell) up to 4 inches wide with four lateral spines on each side (4th spine is smaller)
- Notch between the eyes
- Light brown to olive color
- Eight sharp pointed walking legs approximately twice as long as the carapace (shell) width; no swimming legs
Habitat & Distribution
Mitten crabs are native to East Asia from northern China to the Korean Peninsula. They are catadromous, meaning they migrate from freshwater to brackish-marine waters to spawn. Non-native populations are established throughout Europe and the continental U.S. along the San Francisco Bay Delta in California and along the East Coast in the Hudson River Bay. In the U.S., there are also reports of mitten crabs from the mid-Atlantic (e.g., Chesapeake Bay, Delaware Bay), Louisiana, and Eastern Great Lakes. However, it is unknown if these are established breeding populations. The first mitten crab was reported in New York in 2007 from the Hudson River near Tappan Zee Bridge (Nyack, NY). Since 2007, mitten crabs have been reported in the Hudson River between Coxsackie, NY, and the Battery (including tributaries), Hudson River tributaries, New York Harbor, and the Long Island Sound (including tributaries).
To view mitten crab reports in NY, visit iMapInvasives.
Impacts
In New York, the impacts of mitten crabs are currently unknown; however, populations in Europe and California have had several negative economic and ecological impacts. Mitten crabs:
- Interfere with commercial and recreational fisheries, stealing bait and damaging fishing gear and catch.
- Have caused industry disruptions by blocking the cooling systems of power plants.
- Burrow in the stream bank, causing bank instability and increased erosion, which in turn increases flood risk and reduces habitat.
- Are generalist predators that can alter food webs as they forage on native fish eggs and invertebrates.
- Can compete with native species for food and habitat [e.g., blue crabs (Callinectes sapidus)].
Spread
Mitten crabs were most likely introduced to the U.S. through ballast water. Some populations may have been accidentally introduced from escaped live crabs that were imported for food.
Species Regulation
The mitten crab is a prohibited species under New York State Invasive Species Regulation 6 NYCRR Part 575. Prohibited species cannot be knowingly possessed with the intent to sell, import, purchase, transport or introduce. In addition, no person shall sell, import, purchase, transport, introduce or propagate prohibited invasive species.
Management
DEC is a partner in the Mitten Crab Network, a partnership among several state, federal and research organizations that is collecting data to determine the status, abundance and distribution of this species. DEC has agreed to collect and hold specimens for genetic testing to determine the origin of individuals caught in the Hudson River. Testing will be conducted by the Smithsonian Environmental Research Center (SERC) where scientists are tracking the distribution and spread of Chinese mitten crab throughout North America. All confirmed reports of Chinese mitten crab will be added to the National Exotic Marine and Estuarine Species Information System (NEMESIS).
How You Can Help
- Clean, drain, and dry your watercraft and equipment thoroughly before visiting other waterbodies.
- Inspect and remove debris and mud from boats, trailers, and equipment.
- Dispose of all debris and bait in trash cans or at disposal stations.
- Drain all water-holding compartments including live wells, bait wells, and bilge areas. If possible, visit a decontamination station and disinfect compartments with hot water (140°F) for at least 30 seconds.
- Dry boats, trailers, and all equipment before use in another water body. A minimum of 5-7 days of drying time in dry, warm conditions is recommended.
- Do not dump aquarium contents in any waterbodies, drainage ditches, or sewers.
- Use certified bait that is non-invasive and disease free.
- Learn how to identify mitten crabs and report any encounters.
- If you think you have caught a mitten crab:
- DO NOT RELEASE IT.
- Take several photos of it from different angles, including the underside, and freeze it, (someone may collect it for testing).
- Email the photos, noting where it was caught (coordinates preferred), to mailto: [email protected], OR
- Submit a report through iMapInvasives, OR
- Contact your local Partnership for Regional Invasive Species Management.
