First ever seen in state – Chinese mitten crab found in local waters

For the first time in state history, a Chinese mitten crab was spotted in Connecticut waters, prompting concern from a number of local environmental officials.

The creature was collected from the Mianus Pond fishway on the Mianus River by Conservation Assistant for the Greenwich Conservation Commission Joe Cassone in late June. Following an examination by the Department of Energy and Environmental Protection (DEEP) and Connecticut Sea Grant, the identification of the freshwater crab was confirmed earlier this month.

The species is native to eastern Asia, but has spread to both Europe and North America, making its first appearance on the Atlantic Coast in 2005. According to Mr. Cassone, the crabs have been found as close by as the Hudson River, but continue to be a fairly rare siting in this part of the country.

Although it was a single Chinese mitten crab that was found in June, high densities of the animals have the potential to be problematic, Mr. Cassone said.

Since the species live part of their lives in fresh water and part in marine water, they can clog pumps and intake pipes, which is not as great a problem in Connecticut as it is in more agricultural areas, but remains a risk regardless, he explained.

The crabs are also known for creating burrows as large as two-liter soda bottles, which can cause extreme riverbank erosion when they are found in larger groups, Mr. Cassone said.

Another risk, he added, is that the invasive creatures are not native to this area and could compete with native species such as crayfish or other crabs for food and habitat.

Although it is of very little concern at this time, Mr. Cassone said Chinese mitten crabs additionally have the potential to carry a type of Asian liver flu parasite, which is the only known health risk they pose to humans.

Interestingly, the creature is an expensive delicacy in its native China, where vending machines that dispense the animal have been introduced around the country to cut costs, Mr. Cassone explained.

According to a DEEP press release, the two most likely means of the animal’s introduction to Connecticut appear to be transport of larvae and small crabs in ship ballast water and their deliberate release to establish a local food source. Under the federal Lacey Act, however, importation and interstate transport of the species is prohibited.

Though it is unclear what the effects of the crabs will be, the DEEP strongly urges any individual who finds a Chinese mitten crab to contact the proper authorities. Since there are no freshwater crabs in New England, any crab found in fresh water should be investigated.

The creatures appear to have dark, fuzzy growth on the claws with white tips, with four spines on each side and a notch between the eyes. Their total size, including legs, can be up to 12 inches.

Anyone who finds a crab that they suspect to be a Chinese mitten crab should keep the crab on ice or freeze it, note the exact location it was found and contact DEEP Marine Fisheries at 860-434-6043, DEEP Inland Fisheries at 860-424-3474 or Nancy Balcom of CT Sea Grant at 860-407-9107.


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