Invasive, 'Furry'-Clawed Mitten Crabs Seen In LI Sound, Hudson River

NEW YORK — An invasive species has started an assault on New York estuaries and we are the last line of defense — luckily, the alien invaders are easy to spot.

The mitten crab (Eriocheir sinensis), an invasive shellfish species native to East Asia, has been spotted in the Long Island Sound, the Hudson River and the Nissequogue River, according to the New York State Department of Environmental Conservation (NYSDEC). It has also been introduced to other parts of the east coast, the west coast, and Europe.

Mitten crabs most likely arrived in the U.S. in ballast water from ships. Some populations may have also been accidentally introduced from escaped live crabs that were imported for food.

The mitten crabs move between freshwater and brackish/marine waters to spawn and have the potential to disrupt local ecosystems by out-competing native marine life. While the effects of mitten crabs in New York are still unknown, the negative ecological and economic impacts have been documented in Europe and the San Francisco Bay Delta.

Mitten crabs have interfered with commercial and recreation fisheries, by stealing bait and damaging fishing gear and catch. They have caused industry disruptions by blocking the cooling systems of power plants. The species burrows in stream banks, causing bank instability and increased erosion, which can increase flood risk and reduce habitat. The crabs are known as "generalist predators" that can change food webs as they eat native fish eggs and invertebrates. Mitten crabs also compete with native species, such as blue crabs (Callinectes sapidus), for food and habitat.

The mitten crab is therefore a prohibited species under NYS Invasive Species Regulation 6 NYCRR Part 575.

Adult mitten crabs can be recognized by their "furry" claws of equal size with white tips and dense patches of brown setae, resembling hairy mittens, in adults and juveniles with a shell width greater than 1 inch. The crabs are light brown to olive in color, with shells up to 4 inches wide with four lateral spines on each side, with the fourth spine being smaller. They also have a notch on the shell between the eyes and eight sharp pointed walking legs about twice as long as the shell width.

The DEC is part of the the Mitten Crab Network, a partnership among state, federal and research organizations that is collecting data to learn about the status, abundance and distribution of the species. The DEC is collecting and storing specimens for genetic testing to determine the origin of those 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 the mitten crab throughout North America. All confirmed reports of the species will be added to the National Exotic Marine and Estuarine Species Information System (NEMESIS).

If you come across a mitten crab, the agency asks that you remove it from the environment and freeze it. Be sure to also take identifying photos and make a note of your precise location. You can then report your sighting to the Bureau of Invasive Species and Ecosystem Health by sending an email to this address.

Mitten crab reports in NY can be viewed here.

DEC's List Of Other Ways To Help:

• Clean, drain, and dry watercraft/equipment thoroughly before visiting other bodies of water. 
  • Inspect & remove debris and mud from boats, trailers, & equipment. 
  • Dispose of all debris and bait in trash cans or at disposal stations. 
  • Drain all water-holding compartments, including live wells, bait wells, & bilge areas. If possible, visit a decontamination station and disinfect compartments with hot water (140°F) for at least 30 seconds. 
  • Dry boats, trailers, & 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 bodies of water, drainage ditches, or sewers. 
• Use certified bait that is non-invasive & disease free.