August 10, 2018
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Wanted: Mitten Crabs Found In Local Waterways

Maya Pottiger
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July 10, 2018

After Anne Arundel County’s Facebook page posted a wanted flyer for mitten crabs, the post quickly racked up shares and garnered a lot of attention.

However, the message wasn’t entirely clear: There is nothing to be afraid of, and you may never find any mitten crabs.

This summer, the Smithsonian decided to revitalize its search for the species after a lack of reports in recent years.

“We stopped getting reports,” said Darrick Sparks, the marine crab coordinator at the Marine Invasion Research Laboratory. “What we’re trying to do now is put out reports and say, ‘Hey, is it just the ones that were being found were just one-offs? Or is there a population?’ We don’t know.”

The first mitten crab sighting in Maryland was in 2005, but the sightings weren’t regular until 2007. From 2005 to 2007, there were five mitten crab sightings in Maryland, according to the Smithsonian’s official log.

The last mitten crab sighting in the Chesapeake Bay was in Baltimore in 2011, Sparks said. That sighting wasn’t recorded in the online log.

The crabs are native to northern China, so there are two working theories as to how they got to the mid-Atlantic: commercial vessels or commercial sales, Sparks said.

“Those are the two working [theories], but there’s no way to really say which is the most probable answer,” Sparks said.

Mitten crabs are an invasive species, and if a population were found in the Chesapeake Bay, they would completely alter the bay’s ecosystem.

“The reason we’re looking at them is it adds another top predator to the area. Not only does it add a top predator to salt water, but it also adds a top predator to fresh water,” Sparks said. “These guys have the ability to go all the way to the fresh water, and that can change an ecosystem when a new predator moves in: could unbalance it, could create other problems.”

The Smithsonian is asking locals who spend time on the water to keep an eye out for mitten crabs, as they are in salt water from May to October.

A mitten crab can be identified by three main characteristics: they are a walking crab, so they don’t have a swimmer fin in the back like a blue crab; the adults have hairs on their claws; and there is a distinct notch on the carapace between its eyes.

If you see what you think is a mitten crab, don’t throw it back. Take a picture of it, and find a way to preserve it: freeze it, put it on ice or, as a last resort, put it in rubbing alcohol. Then, upload your picture and the location to the Mitten Crab Watch website, and wait for someone from the Smithsonian to contact you.

Right now, researchers are working to see if the species is still in the United States. They will potentially revisit some of the locations the crabs were found as a follow-up from previous years.

“We don’t know if they’re reliably here or not, and until we do, there’s not much else we can do until we figure that part out,” Sparks said. “That’s why we’re asking people to help us look for them.”

For more information or to report a mitten crab sighting, visit

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