Horseshoe Crab Spawning Survey at Big Stone Beach
Each spring, horseshoe crab (Limulus polyphemus) spawning surveys are conducted at over 20 Delaware Bayshore beaches across the region, often with the help of community scientists.
These surveys take place during the evening high tide on 12 distinct nights that coincide with May and June’s full and new moons, when peak horseshoe crab spawning takes place. The goal of this annual count is to document the number of males compared to the number of females spawning on Delaware Bayshore beaches. This is one of several pieces of information that are used by managers to make decisions about this important marine resource.
Delaware Sea Grant administers a horseshoe crab spawning survey at Big Stone Beach, with support from university students and community scientists. Check out this Storymap to learn more about horseshoe crab spawning surveys.
For information about horseshoe crab spawning surveys across the region, visit Delaware Bay Horseshoe Crab Survey
Delaware Bay supports the largest spawning population of Horseshoe Crabs in the world and are closely managed because:
Proteins in horseshoe crab blood are used to concoct the Limulus amoebocyte lysate (LAL) test, which is capable of detecting bacterial endotoxins in medical resources like injectable medications, tools, vaccines or implantable medical devices.
Horseshoe crabs are used as bait in whelk and American eel fisheries.
Horseshoe crab eggs released during spawning are an essential food source for many migratory shorebirds, including the federally threatened Red Knot.
Stranded Horseshoe Crabs
Throughout the spawning season it is not uncommon to find horseshoe crabs stranded upside-down on shore, unable to right themselves. Beach-goers can help this species by turning them back over and orienting them towards the water.How does one safely help a stranded horseshoe crab? Horseshoe crabs may look a little scary but they are harmless. To right a stranded horseshoe crab, grasp both sides of the shell above the hinge, away from the tail – this portion of the shell is called the prosoma. Put it back down with its legs facing the sand. Although a horseshoe crab can sometimes use its tail, or telson, to flip itself over, you should not. Horseshoe crab tails are fragile and touching it can harm the animal.
Educational resources
To learn more about horseshoe crabs and other marine science topics, including coloring images, crosswords, and word searches, visit our educational resources page. You can also check out this Storymap, or take a 360° tour of Big Stone Beach.