RESEARCH – Marine Science

The Green Crab

The European green crab (Carcinus maenas) is an invasive species that threatens Nantucket’s native species and eelgrass habitats. Their diverse diet, tolerance of a large range of ocean temperatures, and long larval period makes them excellent at conquering new environments. Green crabs are generally regarded as one of the top five most invasive species in the marine environment.


European green crabs were first introduced to North America in the 1800s, likely traveling in ballast water of merchant ships from Europe. This species has since drastically increased in number and spread to all of New England and as far north as Newfoundland, Canada. Subsequent introductions in South America, Asia, Africa, Australia, and the west coast of North America have caused concern globally.


Here in New England, green crabs have few predators. They are faster, more aggressive hunters than most local crabs, allowing them to successfully multiply and outcompete local species for food and shelter. These invaders are extremely efficient predators of clams and scallops and destroy seagrasses while hunting and burrowing. Green crab populations in New England have been associated with crashes in shellfish populations, reduced biodiversity, destruction of eelgrass beds, and declines in native crab species.

The green crab is now abundant on Nantucket and specifically threaten three important marine resources:


  • Nantucket’s biodiverse eelgrass beds, that protect our shoreline from erosion, are destroyed when green crabs cut them down to hunt and burrow near their roots.
  • Nantucket’s shellfish populations including quahogs, soft-shelled clams, and bay scallops could see large declines due to predation from green crabs.
  • Native crabs species, such as the common spider crab and black-fingered mud crab are threatened by direct predation and competition from green crabs

Hear more about the history and impact of the green crabs with our video on The Green Crab Problem

Our Research

For more information on our survey, watch our Youtube video.

We are monitoring the green crab population in Nantucket using a Citizen Science survey, which means you can participate in our research! The goals of the Nantucket Beach Green Crab Survey are to assess where green crabs are most abundant on Nantucket and to remove the invasive species from the environment. While we suspect that European green crabs are present in all of Nantucket’s marine environments, we are particularly interested in how the crabs are using Nantucket’s eelgrass beds.


Please check out the survey to find out how to participate and help us monitor the green crab population.

Nantucket Green Crab Week

In 2020, we launched our first ever Nantucket Green Crab week to raise awareness about the invasive species and share the opportunity to participate in our research. For more information on the event, please visit our Nantucket Green Crab Week page.


Contact:

You can send green crab inquiries to MMA Aquarium Director and Research Center Coordinator, Jack Dubinsky, at jdubinsky@mariamitchell.org!


Learn More About Green Crabs:

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