Milton Horseshoe Crab Festival

by Dave on May 28, 2010

photo courtesy Delaware Sea Grant

story by Michael Short

It’s time for the fossils to gather.

Every spring, horseshoe crabs mate and lay their eggs on Delaware Bay beaches. These ancient mariners have spawned here almost since time began, but only recently have we realized their importance.

Until recently, crabs have largely been considered a smelly nuisance as the heat rises along Delaware Bay beaches. Many of the crabs do not survive the annual spawning season and they litter bay beaches in the early summer.

But the once-lowly horseshoe crab has had a public relations makeover. Now, it’s considered of such medical and ecological importance that it even has its’ own festival. On May 29, Milton and Prime Hook Wildlife Refuge celebrate the annual Horseshoe Crab and Shorebird Festival, sponsored by the Refuge and the Milton Chamber of Commerce.

The name comes from the link between horseshoe crabs and shorebirds, a link that makes flights of thousands of miles possible for often rare migrating shorebirds.

The crabs, however, are also important to your health and mine. Horseshoe crab blood is considered very important to the pharmaceutical industry because it contains an agent that allows drugs to be tested for purity. The crab’s light blue-colored blood will clot quickly in the presence of bacteria, thus allowing drugs to be tested quickly and safely.
We owe much of our knowledge of human eyes to the study of the horseshoe crab’s eyes. In 1967, Dr. H. Keffer Hartline received the Nobel Peace Prize for his research on horseshoe crab vision.

His research shows how the retina helps the brain to interpret visual clues. For horseshoe crabs, this allows them to to find a mate in murky water. For people, it helps scientists understand diseases like retinitis pigmentosa that can cause tunnel vision and rob a person of their sight.

But crabs, once fed by farmers to pigs, are best known for being linked to shorebird populations. Migrating shorebirds, many of them very rare, migrate thousands of miles each spring to Arctic areas.

On their trip north, they stop to feast on the tiny greenish eggs of the horseshoe crabs. Female crabs can lay as many as 20,000 of the birdshot-size eggs. Shorebirds linger for days, feasting and gorging on eggs. Without this stop, the birds will not be able to complete their migration.

Red knots can travel up to 5,000 miles on that journey to the Arctic and red knots, ruddy turnstones, dunlins and semipalmated sandpipers are some of the many species that visit Delaware Bay each spring.

“The Delaware Bay hosts the world’s largest spawning concentration of horseshoe crabs. Each May and June, crabs spawn and lay eggs around the new and full moons that’s timed perfectly to coincide with the arrival of migrating shorebirds,” said Dawn Webb, manager of the Dupont Nature Center at Mispillion Harbor Reserve, which just hosted a festival on May 22, called “Peace, Love and Horseshoe Crabs.”

Volunteers conduct surveys of the spawning crabs along Delaware Bay beaches each spring to count the numbers of horseshoe crabs. One bit of good news for the horseshoe crab is that for the third year, surveys have also been done along inland bays beaches such as the James Farm.

What volunteers have found is that the horseshoe crabs also spawn in large numbers on those inland bays beaches. In some areas, the spawning numbers are comparable to the much more widely known bay beaches.

Tower Road near Dewey Beach produced good survey numbers last year and initial counts from Little Assawoman Bay appear to be up dramatically this season over last year.

Horseshoe crabs, however, are in trouble and efforts are being taken to protect theirwindling numbers. Declining populations are blamed on loss of habitat and overfishing. Jetties and other structures to prevent beach erosion are one example of efforts that may prevent crabs from reaching some spawning areas. The decline is also linked to the crab’s use by eel and conch fishermen, who use the crab for bait.

While crabs are also “bled” to gather their blood, the crabs are released alive afterwards after the “donation” and usually survive the process.

With the horseshoe crabs in trouble, some of the shorebirds that depend so heavily upon them are also in trouble.

This weekend’s joint festival will include a canoe trip, trail walks, bluebird house building, hay rides and other activities at Prime Hook Wildlife Refuge on Saturday, May 29. Please call ahead at 684-8419 to register for the canoe trip because of limited space. In Milton, there will be exhibits, vendors, food, boat rides, an art tent, music and more on May 29.

Milton also hosts additional activities on May 28 and 30. For more information about the Shorebird and Horseshoe Crab Festival this weekend, contact

For more information about Delaware Bay spawning surveys, contact Kimberly Cole at 739-3436 or For more information about inland bays spawning surveys, contact Sally Boswell with the Center for the Inland Bays at 226-8105 or at For more information about the DuPont Nature Center and its programs, please call 422-1329, or visit

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