Natural History

Horseshoe Crab Research at Wellfleet Bay

The Atlantic Horseshoe Crab (Limulus polyphemus) has been crawling ashore to mate on full moon nights for about 350 million years, and Mass Audubon is looking to ensure this ancient rite of spring continues.

In Massachusetts , horseshoe crabs are harvested to be used as bait for the eel and conch fisheries, and their blood is the source of a chemical used to test medical devices and injectable drugs for toxins. For this crabs are caught, bled, and then returned to the water.

Recent closures of the horseshoe crab fisheries in New Jersey, New York, and other neighboring states is expected to increase harvest pressure on already apparently dwindling populations in Massachusetts embayments. Given this, it is critical that state managers have a robust estimate of the number of crabs in Massachusetts before they can set appropriate harvest quotas to ensure a sustainable fishery. As a first response, the state has reduced the annual quota to reflect recent highest harvests, ensuring that at least the annual harvest will not get any higher.

In collaboration with the University of Rhode Island, the National Park Service, the Massachusetts Division of Marine Fisheries, and others, Mass Audubon is beginning a three year survey of spawning horseshoe crabs. At a number of sites around the Cape and Southeastern Massachusetts, scientists and volunteers will be counting the number of adult spawning horseshoe crabs on and around the new and full moons at high tide.

We need your help! Please volunteer today to help preserve these very special creatures. To sign up to volunteer for the surveys, please email Cynthia Franklin or call her at 508-349-2615 or

If you are already doing surveys, then please visit Mary-Jane James-Pirri's website where you can download protocols, data sheets, and survey schedules.

Survey Sites: Wellfleet, Barnstable, Chatham, Buzzards Bay, Pleasant Bay, Provincetown/Truro, Waquoit Bay, Duxbury, Westport Harbor and many more.

Collaborators: National Park Service, University of Rhode Island, University of Massahusetts/Boston, Massachusetts Division of Marine Fisheries, Worcester Polytechnical Institute, The Center for the Conservation of Horseshoe Crabs, Mass Bays Program, Provincetown Center for Coastal Studies, Westport River Watershed Alliance, Monomoy-National Wildlife Refuge, U.S. Fish and Wildlife Service and many more.