Start receiving our award-winning magazine today!



Horseshoe Crab Survey

Horseshoe Crab Survey

See what happens when volunteers gather each year to count these versatile creatures.

It is evident how happy crab counting makes Corinne Kee (with Joni and Todd Carpenter in the background).

Each spring, the Delaware Bay becomes the site of one of the most spectacular and ancient phenomena in the natural world: the spawning of horseshoe crabs and the flocking of ravenous shorebirds that depend on them. 

On moonlit nights in May and June, thousands of the crabs crawl ashore on Delaware Bay beaches at high tide to lay eggs, as they have for 450 million years. The crabs are sometimes so dense that the water’s edge looks like a road paved with brown shells. 

Why Count the Crabs?

Knowing how many horseshoe crabs there are helps fisheries managers develop effective policy for managing populations. You can help by volunteering to count the crabs in May and June. 

To help with the crab survey, register with the Delaware Department of Natural Resources at The site shows a schedule of survey dates and times. Volunteer training is offered April 11 and April 16. You can volunteer to count horseshoe crabs with The Nature Conservancy, Delaware. Contact us at or 302-654-4707 x424.

Crabs are Critical for Birds and People

Horseshoe crab eggs are critical in sustaining birds that migrate up to 10,000 miles each year. The threatened red knot, for example, flies from wintering grounds in South America to the Arctic each spring, stopping in Delaware along the way to fuel up on horseshoe crab eggs. Without the food, the red knot cannot complete its journey. 

Red knots often compete with humans for the crabs. Watermen harvest horseshoe crabs to use as bait for eel and whelks. The crab is also harvested for medical use. Its blood is used to make a chemical that detects bacterial toxins. 

Some evidence suggests that the crabs are overharvested in North America, which has led to a harvesting ban in New Jersey and restrictions in Delaware. Participating in a count is a wonderful way to help protect them while witnessing the ancient ritual and spending an evening under the stars. 

The Crab Count Experience

Shorebirds aren’t the only ones to descend upon the Bayshores in May and June to convene with crabs. Each year, a cadre of volunteers arrive to check in on the prehistoric creatures. Veteran counters Joni and Todd Carpenter have celebrated more than a decade of horseshoe crab surveys.

“We learned about this amazing phenomenon during a weekend trip to the Delaware beaches in the summer of 2002,” says Joni Carpenter, who lived in Ohio at the time. “We signed up for the 2003 horseshoe crab count after reading about it in Nature Conservancy magazine.”

They enjoyed the experience so much, they have made the trip back to help every year since.

Read a diary of the horseshoe crab count by a Conservancy staffer.

An Annual Ritual

“The sight of all the horseshoe crabs on the beach is awe inspiring and provides a bit of reassurance that humankind has not completely ruined the planet," says Joni Carpenter. "I don't want to see this spectacle of nature that has been happening for 350 million years come to an end because of our species.”

Corinne Kee has made the 11-hour drive from Michigan for the past five years to play her part in ensuring healthy populations for both horseshoe crabs and the shorebirds which depend on them.

“My first count occurred at midnight during a full moon,” recalls Kee, who grew up in New Jersey and has ties to the east coast. “One minute you are just hanging out on the beach and then the tide turns and you need to look where you step for all the crabs!”

In recent years, erosion removed most of the crab nesting habitat at Bennett’s Beach. Hurricane Sandy led to some erosion issues at Big Stone Beach as well, but the census continues there.

It will take much more than extreme weather to deter counters like Joni and Todd Carpenter and Corinne Kee from helping the crabs and shorebirds convening along the eastern seaboard in May and June. Now living in Maryland, the Carpenters mark the event on their annual calendar—in pen, adding, “I think we will participate in the census as long as there are beaches and horseshoe crabs—which means hopefully for a very long time.” 

We’re Accountable

The Nature Conservancy makes careful use of your support.

More Ratings

x animal

Sign up for Nature eNews!

Sign Up for Nature e-News

Learn about the places you love. Find out
how you can help.

Thank you for joining our online community!

We’ll be in touch soon with more Nature Conservancy news, updates and exciting stories.

Please leave this field empty

I'm already on the list!

Read our privacy policy.