Biologists working to prevent spread of invasive crab into Gulf of Maine

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An invasive crab species known for its devastating impacts on west coast marshes and commercial fisheries has not yet made its way into N.H. waters, and New England biologists are working to keep it that way. Specialists from three Sea Grant Programs — MIT, N.H. and Maine — have finalized a comprehensive protocol that encourages a rapid management response to any sightings of the Chinese mitten crab in the marine, brackish and fresh waters of New England and the Canadian Maritimes.

The mitten crab — so-named for its fuzzy claws — made its way to New York’s Hudson River about a decade ago either by way of ship ballast water or live introduction. So far, the East Coast has largely been spared from the crab’s population explosions experienced in California that have caused millions of dollars in damage to the fishing industry, where they clog and destroy fishing nets and eat the fish captured alongside them. The mitten crabs also have a habit of burrowing in — and thus destabilizing — streambanks, leaving the mud susceptible to collapse. Although it is unclear just how much of an impact this species could have in New England and Canada, biologists don’t want to take any chances.

close-up of mitten crab

The publication, “Rapid response plan for management and control of the Chinese mitten crab,” provides a thorough overview of the species, its impacts in other states and countries, habitat suitability and a comparison of eradication methods and their relative success. Canadian provincial regulatory agencies and U.S. state and federal regulatory agencies that deal with invasive species — as well as the  members of the Northeast Aquatic Nuisance Species (NEANS) Panel — are those most likely to use this guide in response to a mitten crab sighting, said Alyson Eberhardt, N.H. Sea Grant/UNH Cooperative Extension coastal ecosystems specialist. Eberhardt worked closely with Maine Sea Grant associate director Beth Bisson and MIT Sea Grant research affiliate Judith Pederson to develop the publication.

“We wanted to get all this information organized into one document before a possible crab invasion takes place in the Gulf of Maine,” Eberhardt said.

The publication indicates that the likelihood of Chinese mitten crabs becoming established in N.H. estuaries is relatively low based on a variety of factors, including tidal flushing, water temperature and the size of the water bodies. However, other states’ waterways are potentially at risk, including Maine’s Penobscot Bay that has a higher likelihood of offering suitable habitat for the invasive crab.

When it comes to dealing with aquatic invasive species, the best approach is prevention coupled with early detection, Eberhardt said. Eberhardt, Bisson and Pederson have already alerted many of the individuals considered part of the informal “early detection network,” including habormasters, recreational boaters, volunteers and others who may come into contact with the Chinese mitten crab, asking them to be on the lookout for this invader. The pocket-sized watch card, created as part of this project, also provides a quick reference guide with phone numbers of the appropriate agencies to call if a crab is spotted.

Eberhardt, Bisson and Pederson collaborated with the NEANS Panel to ensure the rapid response publication contained the appropriate amount of information needed to help address any potential sightings as quickly as possible.

"The rapid response plan for the Chinese mitten crab is a significant contribution to invasive species management in the northeastern United States and Canada," said Michele L. Tremblay, a representative of the NEANS Panel. "The Panel's focus is on coordination with the states, provinces, federal agencies, academia, nonprofits, and other organizations who are affected by invasive species. We look forward to continuing this role with the plan as a new tool and model for other invasive species efforts," she added.

For more information, please visit our webpage on the Chinese mitten crab or contact Alyson Eberhardt at

N.H. Sea Grant promotes the wise use, conservation and sustainable development of marine and coastal resources in the state, the region and beyond. Located at the University of New Hampshire, NHSG is part of a national network of programs located in our coastal and Great Lakes states as well as in Puerto Rico and Guam.  






Rebecca Zeiber, N.H. Sea Grant Science Writer