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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 2024 survey season? Register now with our free-to-use volunteer management software, Better Impact. Better Impact organizes all the information, forms, and updates you need in one easy-to-access place.

Review the Frequently Ask Questions for the Horseshoe Crab Survey

If I sign up as a volunteer, do I have to go to every survey?

No! You can attend one survey or as many as possible. However, the more you participate, the more you will be likely to have a role in the survey procedures. If you only come a couple of times, you may play more of a spectator role, assisting with counts and capturing crabs to tag, which is still a great experience!

What do I bring?

All volunteers must wear closed-toe shoes with soles. No bare feet, flip-flops, or neoprene booties will be allowed. We recommend rubber boots, waterproof shoes (with soles) or old sneakers. Bring a headlamp or flashlight. Headlamps are preferred because they free up both hands. Lastly, bring bug spray or sunscreen, wear appropriate clothes and if you are bringing a camera, some protective case for that.

Where does each team survey?

See the graphic below and pick the location closest to your home to make travel during those late nights safer. Tower Road is our most northern location off of Route 1 in Delaware Seashore State Park in the Rehoboth Bay. Camp Arrowhead is the second location that captures the crabs within the Rehoboth Bay and is located within the Camp Arrowhead Campus off of Route 24 in Lewes. Peninsula site is located within a gated community of 24 in Longneck on the north side of the Indian River Bay. Bay Colony also located in the Indian River Bay but on the south side just off Route 24, north of Clarksville. Ellis Point is also located within a gated community off of a cul-de-sac and surveys crabs on the south side of the Indian River Bay. It is right next to Holts Landing State Park. The James Farm site is in the Ocean View area within the James Farm Ecological Preserve, and crabs are captured on the south side of the Indian River Bay.

How long does the survey take?

This varies greatly on the crab activity. If there are no crabs on the beach, then you should be done within half an hour. If the entire beach is lined, it may be a couple of hours.

Can my children or grandchildren come?

Absolutely! However, anyone under 18 must be accompanied by an adult for supervision, and fill out a volunteer waiver form (scroll below to access the waiver forms).

Survey Locations Map



Tower Road

Click to see location on map

James Farm

Click to see location on map

30048 Cedar Neck Rd, Ocean View, DE 19970

Bay Colony

Click to see location on map

The Peninsula

Click to see location on map   

Ellis Point

Click to see location on map

Camp Arrowhead

Click to see location on map

35268 Homestead Wy, Lewes, DE 19958

Little Assawoman

Click to see location on map

284 Coastal Hwy, Fenwick Island, DE 19944


Let’s count some Horseshoe crabs!

Thank you for your support of the Center’s mission. Another way to support our mission is by donating HERE!


Volunteer Resources/Documents

Data and Project Reports: