Horseshoe crabs are “living fossils”, the last survivors of a group of organisms that first appeared in the fossil record some 350 million years ago.  Delaware Bay has the largest population of horseshoe crabs (Limulus polyphemus) in the world.

Besides their extraordinary antiquity, horseshoe crabs are also of paramount importance to human health.  Their blood contains a clotting agent, LAL (Limulus Amoebocyte Lysate), which provides a fast, reliable test for the presence of infectious bacteria in drugs, as well as prosthetic devices such as heart valves and hip replacements.

Since 1991, the Wetlands Institute has brought scientists and volunteer citizens together to conduct censuses of the ecologically vital horseshoe crab population on the New Jersey side of the Delaware Bay.  These censuses take place during May and June and are central to our understanding and responsible management of this ancient marine creature.

Watch our new video and learn how we are working with partners and volunteers to save horseshoe crabs through our research and conservation efforts.



Horseshoe Crab Conservation

The Horseshoe Crab, an important keystone species of the Delaware Bay, is an animal that is very much depended upon by many other species participating in the ecosystem. Shorebirds such as the Red Knot (Calidris canutus), Ruddy Turnstone (Arenaria interpres), and the Sanderling (Calidris alba) depend upon Horseshoe Crab eggs deposited along the banks of the Delaware Bay for their own nutritional welfare.

Horseshoe Crab Eggs
Some of these shorebirds make a 9,000 mile migration from their wintering grounds along the southern tip of South America to their breeding grounds in the Arctic tundra. Their journey is timed so they can take a rest along the shore of the Delaware Bay in order to feast upon this large concentration of Horseshoe Crab eggs. Shorebirds will spend approximately 2 weeks dining on the eggs in order to double their body weight and replenish the fuel reserves needed to continue with their long journey to the Arctic.

Unfortunately this natural phenomenon is in peril as the number of Horseshoe Crabs in the Delaware Bay has dramatically decreased over time.

Horseshoe Crab Hatchlings

In fact, the Delaware Bay’s Horseshoe Crab population has declined significantly, mostly due to overharvesting and habitat degredation. As the number of Horseshoe Crabs have decreased, so have the number of eggs available for consumption by migrating shorebirds. Shorebird population numbers are therefore plummeting as well, as many cannot gain the amount of energy needed to complete their migrations. The Red Knot has been placed on New Jersey’s Endangered Species list and many other shorebirds are in danger of being placed on that list if horseshoe crab populations are unable to rebound.

Horseshoe Crab Adults

In an effort to address the Delaware Bay Horseshoe Crab situation, The Wetlands Institute has embarked on a statewide partnership project to support the stewardship and conservation of Horseshoe Crab populations in New Jersey. As part of this partnership, The Wetlands Institute collects fertilized Horseshoe Crab eggs with the proper permits from spawning beaches along the Delaware Bay and rears the eggs under controlled conditions in our aquarium. After about a month, eggs hatch and newly born Horseshoe Crabs are maintained in their culture tanks. Enclosed in this cultured environment and free of predation, aquaculture dramatically increases Horseshoe Crab survival both before and after the first molts. These small crabs are kept in culture tanks until they are ready to begin feeding, and then are released at their respective egg collection locations.


Click here to read an article published in the New York Times discussing the relationship between shorebirds and horseshoe crabs.

The Wetlands Institute is a leading partner in the multi-partner reTURN the Favor program. This program works to rescue overturned or impinged Horseshoe Crabs stranded on New Jersey’s Delaware Bay beaches. Though this program works to rescue Horseshoe Crabs on beaches open to the public, it primarily concentrates on rescuing crabs stranded on beach areas seasonally closed during shorebird migration and the Horseshoe Crab spawning season occurring in May and June.

Ørsted is a proud supporter of our reTURN the Favor initiative.
Thank you!

A Model Citizen Science and Volunteer Project Turns 5

Every spring, Delaware Bay host the largest concentration of spawning horseshoe crabs on the Atlantic Coast. Surveys estimate 300,000-1,300,000 horseshoe crabs annually come ashore onto NJ Bayshore beaches and are in greatest numbers during spring tides in May and...

Learning with Living Fossils

by Shelby Schmeltzle Continuing efforts to conserve and restore the local Atlantic Horseshoe Crab population, The Wetlands Institute (TWI) has partnered with the NJ Division of Fish and Wildlife’s Aquatic Education Program to launch the Horseshoe Crabs in the...

Volunteers Rescue Thousands of Stranded Horseshoe Crabs

by Allison Anholt, Research Scientist Extra high tides during the new moon in May, combined with warm water temperatures and high sustained winds caused mass strandings of spawning horseshoe crabs on the Delaware Bay over Memorial Day weekend. The water overflowed the...

Horseshoe Crab Connection

by Sue Slotterback An annual ritual is about to commence along our shoreline. It’s time for the migration and spawning of horseshoe crabs. Known as a “living fossil”, horseshoe crabs date back more than 450 million years! They are closely related to spiders, ticks,...

reTURNing the Favor for Horseshoe Crabs

The reTURN the Favor program works to make the beaches of New Jersey safer for the thousands of horseshoe crabs that spawn annually between May and July on the Delaware Bayshore. Many of these crabs die by becoming overturned by wave action, or upon being caught in...

Wetlands Institute Celebrates 3rd Annual Spring Shorebird and Horseshoe Crab Festival

Stone Harbor, NJ – The Wetlands Institute is pleased to announce our 3rd annual Spring Shorebird and Horseshoe Crab Festival. Located on the Cape May Peninsula between the Delaware Bay and Atlantic beaches, The Wetlands Institute is situated in an area considered to...

Beating the Clock to Restore Horseshoe Crab Beaches Following Sandy’s Impacts

In a race against the clock, the Wetlands Institute, American Littoral Society and Middle Township, along with a committed group of conservation partners, will restore prime horseshoe crab and shorebird habitat destroyed by Superstorm Sandy on the Delaware Bayshore in...

ASMFC Horseshoe Crab Board Approves Addendum VII

The Commission’s Horseshoe Crab Management Board has approved Addendum VII. The Addendum implements the Adaptive Resource Management Framework, which incorporates both shorebird and horseshoe crab abundance levels to set optimized horseshoe crab harvest levels for the Delaware Bay area.

Wetlands Institute Releases Comment on Atlantic States Marine Fisheries Commission’s Draft Addendum VII – Interstate Fishery Management Plan for Horseshoe Crabs

The Wetlands Institute posts their public comment on the Atlantic States Marine Fisheries Commission’s “Draft Addendum VII” to the Interstate Fishery Management Plan for Horseshoe Crabs: Adaptive Resource Management Framework.”