Horseshoe Crab Survey
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
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?
What do I bring?
Where does each team survey?
How long does the survey take?
Can my children or grandchildren come?
Survey Locations Map
30048 Cedar Neck Rd, Ocean View, DE 19970
35268 Homestead Wy, Lewes, DE 19958
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!
- Survey Protocol (PDF)
- Random Quadrat Tally Sheet (PDF)
- Total Quadrat Tally Sheet (PDF)
- Tagging Protocol (PDF)
- Beach Site Data Sheet (PDF)
- Tagging Fact Sheet
Data and Project Reports:
- 2023 Horseshoe Crab Survey Factsheet
- 2022 Horseshoe Crab Survey Project Report
- 2020 Horseshoe Crab Survey Project Report
- 2020 Horseshoe Crab Annual Report
- 2019 Horseshoe Crab Survey: Five-Year Trend Report
- 2018 Horseshoe Crab Survey Project Report
- 2017 Horseshoe Crab Survey Project Report
- 2016 Horseshoe Crab Survey Project Report
- 2015 Horseshoe Crab Survey Annual Report
- 2014 Horseshoe Crab Survey Annual Report
- 2013 Horseshoe Crab Survey Annual Report
- 2011 Horseshoe Crab Survey Results
- 2010 Horseshoe Crab Survey Results
- 2009 Horseshoe Crab Survey Results
- 2008 Horseshoe Crab Survey Results
- 2008-2010 Chart of Spawning Horseshoe Crabs
- 2008-2010 Chart of Adult Female Horseshoe Crabs