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Horseshoe Crab Survey

Project Status: Current / Annual


Each year, horseshoe crabs come ashore by the thousands to spawn on the sandy beaches of our Bays around the full moon and new moons in May and June. Researchers from all over the world travel to Delaware to observe this annual phenomenon on the beaches of Delaware Bay, but much less was known about the horseshoe crab spawning population on the Inland Bays.

In 2008, the Center for the Inland Bays partnered with Dr. Doug Miller at the University of Delaware, School of Earth, Ocean and the Environment in Lewes to begin to answer questions about horseshoe crab spawning in the Inland Bays. Our data has shown that the Inland Bays are host to a significant horseshoe crab spawning population and that spawning density at surveyed Inland Bays sites approach those found in Delaware Bay surveys.

What it’s like to do a Survey

In the spring, on the first full or new moon in May at high tide, volunteers will meet on six beaches around the Inland Bays. With flashlights in hand, bug repellent in their pockets and old sneakers on their feet, they’ll carry equipment down to the water’s edge.

Each site has a volunteer leader and a team of volunteers to assist. Working teams of three or more; two handling the equipment and counting, and one keeping dry to record the data, work their way down the beach. The teams count horseshoe crabs in a 1-meter quadrat (measuring square), ‘leap-frogging’ along the length of the beach. These random samples are used to estimate the number of horseshoe crabs per width of beach, the total number of females nesting on that beach, and the male: female sex ratio.

Click here to view a PowerPoint: The Importance of the Inland Bays Beaches as Horseshoe Crab Nesting Sites — Kat McCole and Doug Miller, UDCMES

Get Involved

Interested in helping out with the 2021 survey season? Contact the Center’s Project Manager, Nivette Pérez-Pérez, at nperezperez@inlandbays.org and join the Inland Bays Horseshoe Crab Survey mailing list.

As the 2021 season approaches, additional information will be sent to all potential volunteers regarding team assignments, scheduling, and other important details. Then, you will be able to participate in the survey training, sign up for a team, and start counting horseshoe crabs!

On April 14, 2021, we will host a virtual survey training to prepare for the upcoming season. You can register for the training HERE! After registering, you will receive a confirmation email containing information about joining the meeting.

If you would like more information about other volunteer opportunities, fill out the Center’s 2021 Volunteer Application. Another way to support our mission is by donating HERE!

Volunteer Resources/Documents

Data and Project Reports: