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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 HSC_Survey_Pics-01in 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’s it 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 Power Point: The Importance of the Inland Bays Beaches as Horseshoe Crab Nesting Sites — Kat McCole and Doug Miller, UDCMES

Survey Locations - click to enlarge

Survey Locations – Click to enlarge

Data and Project Reports:


Volunteers Needed for this Survey!

If you would like to participate in the survey, contact vspice@inlandbays.org by calling 302-226-8105 ext. 116. Even if the survey is not currently underway, you will be added to the mailing list and receive information prior to the next survey season. The season kicks off in April of each year, then runs from May to June.  

*You will need to fill out a Liability Waiver for each individual or family member participating and give it to the Team Leader prior to your survey. Individuals under the age of 18 must have an adult chaperone on-hand at all times.

Volunteer Resources/Documents: