Horseshoe crabs begin their migration to the Atlantic coast

The annual spawning migration of horseshoe crabs – Limulus polyphemus – now returns to the beaches of Maryland. Peak horseshoe crab spawning is dependent on high tides in late spring and early summer, peaking at or around each full and new moon in June. Dating back around 350 million years, this annual event along the Atlantic coast is considered the oldest and largest migration of wild animals in the world.

Credit: Maryland DNR

Biologists from Maryland Department of Natural Resources (MRN) monitor the population of returning horseshoe crabs to ecological and scientific research purposes. The ministry encourages the public to report any spawning activity and sightings of horseshoe crabs to MNR. Survey of Volunteer Horseshoe Crab Fishermen.

On average, a female horseshoe crab will lay 20,000 eggs in the sand.

Horseshoe crab eggs are a natural part of the diet of migrating shorebirds as they prepare to return to their summer nesting grounds in northern Canada. Horseshoe crab larvae are also an important staple food for juvenile Atlantic loggerhead sea turtles, as well as striped bass, American eel, and plaice.

The copper-based blue blood of the horseshoe crab is essential for biomedical research – the animals are collected by specially authorized fishing operations, their blood is drawn at a biomedical facility, and then they are released back into the water.

Despite their menacing armor and tail, horseshoe crabs are gentle creatures that neither bite nor sting. The tail is not a weapon but is used to plow the crab through sand and mud, to act as a rudder in the water, and to straighten the crab when it accidentally rolls over. They can only survive out of water for a short time.


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