What’s the Deal with that Weird Big Blue Crab on the Beach?

A new species of crab has arrived in North Carolina — and you might even find one in your garage. 

There have been a flurry of recent reports of blue land crabs in the Carolinas, which is north of the species’ expected range. North Carolina Division of Marine Fisheries (NCDMF) biologists are requesting public assistance to help them learn more about where the species is spreading.  

Research Need

The blue land crab lives along the Atlantic coast from Brazil to South Florida, but increasingly has appeared in the Carolinas. Researchers do not yet know the extent of the crab’s presence in the region nor its impact on the environment and other wildlife. Whether the species arrived through natural expansion of its range or human-mediated sources also is not clear.

What did they study?

In September 2022, the South Carolina Department of Natural Resources (SCDNR) created a public hotline to report sightings of the crab. This year, NCDMF has followed suit.

What did they find?

From September to November 2022, the SCDNR received 100 reports and confirmed 66 sightings of the blue land crabs from Savannah to Myrtle Beach, but mostly in the Charleston area. Reported sightings came from a range of habitats: estuaries, forests, beaches, roads, ditches, lawns — even home garages. 

Although occasional sightings of the crab began in South Carolina in 2008, the first confirmed blue land crab sighting in North Carolina occurred just this summer. In July, a blue land crab was confirmed in Bogue Sound near Emerald Isle. Since then, sightings also have occurred in nearby Morehead City and areas in Carteret County.

So what?

SCDNR and NCDMF are working together to figure out if these foreign crabs are displacing other species of crab or damaging natural habitats. Blue land crabs can create up to 6-foot-deep burrows, which can destabilize sediment, destroying crops, gardens, lawns, parks, golf courses, and more. With recent heavy rain, the crabs are now more likely to leave their underground burrows. 

Officials warn that blue land crabs are difficult to catch. In addition to their speed at retreating into their burrows, the crabs have a large claw, similar to a fiddler crab’s, that they can use to defend themselves. 

Biologists encourage you to take photos and report any sightings.

Reading

Scott, E., Sasson, D., Kendrick, M., and Kingsley-Smith, P. “Determining the Distribution of the Non-native Blue Land Crab, Cardisoma guanhumi, in South Carolina Using a Public Sightings Database.” Presentation, Gulf and South Atlantic Regional Panel on Aquatic Invasive Species Fall 2022 Meeting, New Orleans, LA, November 30, 2022.

By Sara Mirabilio, adapted from a news release from NCDEQ.

The text from Hook, Line & Science is available to reprint and republish at no cost, but only in its entirety and with this attribution: Hook, Line & Science, courtesy of Scott Baker and Sara Mirabilio, North Carolina Sea Grant.