Two kids running in the snow. We all need nature—and nature needs you. Together, we can protect the wildlife and wild lands of Massachusetts for generations to come. Make a tax-deductible donation today.
Two kids running in the snow. We all need nature—and nature needs you. Together, we can protect the wildlife and wild lands of Massachusetts for generations to come. Make a tax-deductible donation today.
boardwalk trail through a grassy meadow
Wellfleet Bay Wildlife Sanctuary, Wellfleet

Horsehoe Crabs Research at Wellfleet Bay

Horseshoe crabs (HSC) have been crawling ashore on Cape Cod to mate on full moon nights for about 350 million years, and Mass Audubon seeks to ensure this ancient rite of spring continues for the Atlantic horseshoe crab (Limulus polyphemus). However, increased harvesting of these fascinating animals threatens their population.

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

Closures of the horseshoe crab fisheries in New Jersey, New York, and other neighboring states are expected to increase harvest pressure on dwindling populations of Massachusetts horseshoe crabs.

It is crucial 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 and prohibited harvests around the full moons from late April through June.

Research & Findings

Horseshoe crab on beach
Horseshoe Crab

Data collected by the Wellfleet Bay Wildlife Sanctuary and other collaborators indicate that these closures are not working and the horseshoe crab population continues to dwindle.

An analysis of Wellfleet Bay’s data indicates low and likely declining numbers of spawning crabs in Wellfleet Harbor. This report was presented to the Massachusetts Marine Fisheries Commission in support of a petition by Wellfleet’s shell fishing community to ban horseshoe crab harvest in Wellfleet.

In collaboration with the University of Rhode Island, the National Park Service, the Massachusetts Division of Marine Fisheries, and others, Mass Audubon also surveys spawning horseshoe crabs on the Outer Cape.

Throughout the Cape and Southeastern Massachusetts, scientists and volunteers count the number of adult spawning horseshoe crabs on and around the new and full moons at high tide.


National Park Service, University of Rhode Island, UMass Amherst, Massachusetts Division of Marine Fisheries, Worcester Polytechnical Institute, The Horseshoe Crab Conservation Association, Mass Bays Program, Provincetown Center for Coastal Studies, U.S. Fish and Wildlife Service and many more.

Get Involved

Horseshoe Crab survey volunteers at work © Gabrielle Mannino
Horseshoe Crab volunteers © Gabrielle Mannino

We need your help! You can make a difference in the effort to preserve these very special creatures.

To sign up as a survey volunteer, please email us. Wellfleet Bay survey sites include Wellfleet Harbor, Nauset Estuary, and Pleasant Bay.

Rapid Assessment Surveys

download Rapid Assessment - Protocol (670.1 kB)
download Rapid Assessment - Data Sheet (371.5 kB)

A New Campaign to Protect Horseshoe Crabs

In recognition of sound science and overwhelming public support, DMF recently announced plans to revisit Horseshoe Crab fishery management. They’re proposing to ban harvest during spawning and this critical action needs your support. And this should be only a first step—DMF should establish goals to restore breeding populations on beaches across the state and phase out the harvest of horseshoe crabs for bait. 

That’s why we’ve launched a full-fledged campaign to put pressure on DMF and the MFAC to implement these stronger Horseshoe Crab protections in the spring of 2024. 

Take Action

The Division of Marine Fisheries has opened a public comment period until March 8, 2024, and will be passing on all comments to the MFAC. We need you to weigh in today