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’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 PowerPoint: The Importance of the Inland Bays Beaches as Horseshoe Crab Nesting Sites — Kat McCole and Doug Miller, UDCMES
This year because of the recent development of the COVID 19, the Center is launching a virtual Horseshoe Crab Survey Training to start our preparation for the survey season*. If you would like to participate in this year’s survey, it is as easy as following the steps below. We invite you to start watching the Horseshoe Crab Survey Training. After watching the video you can complete all the required information to sign-up using the resources below. Thank you for your interest and support. We hope to see you soon!
*All Center survey activities are postponed until at least June 1st or until health and safety risks related to COVID-19 are resolved.
STEP 1: Watch the Virtual Horseshoe Crab Survey Training (Part 1 & 2)
STEP 2: 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?
Can I bring my kids or grandkids? Is anyone allowed to participate?
What do I bring?
Where does each team survey?
How long does the survey take?
STEP 3: Determine which team works best for you using the 2020 Horseshoe Crab Survey Schedule and Survey Locations Map
STEP 4: Fill the sign-up form
STEP 5: Fill the 2020 Volunteer Liability Waiver*
*It is needed for each individual or family member participating and it should be completed prior to your survey date. Please note: Individuals under the age of 18 must have an adult chaperone on-hand at all times.
STEP 6: Let’s count some Horseshoe crabs!
Thank you for your support of the Center’s mission. If you would like more information about other volunteer opportunities with the Center filled our Volunteer Application. Another way to support our mission is by donating HERE!
Complete the information above, 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.
- Survey Protocol (PDF)
- Random Quadrat Tally Sheet (PDF)
- Total Quadrat Tally Sheet (PDF)
- Tagging Procedure Beach Site Data Sheet (PDF)
Data and Project Reports:
- 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