Where's the Horseshoe?

 

General Habitat and Distribution

The Limulus polyphemus populations are distributed alongside the northern coast of the Atlantic Ocean between Georgia and New York.  There are also smaller populations along the Gulf of Mexico. The green sea turtle also lives in the Gulf of Mexico!  To learn more click here! The most popular area for the horseshoe crabs is in the Delaware Bay. They are mainly found in shallow waters with soft ocean floors.  The habitat for horseshoe crabs depends on what stage it is in, whether the horseshoe crab is spawning, breeding, or just growing to maturity.  At each point in its life, the waters and substrates are important factors.  Multiple organisms live in its habitat including numerous species of shorebirds, fish including striped bass, white perch American eel, weakfish, silversides, summer and winter flounders, sea turtles, many gastropods, sponges, mud crabs and sand shrimp, bivalves, flatworms, snails and many more!

This is a map that illustrates the distribution of not only the Limulus polyphemus but the three other species of horseshoe crabs.  Our focus is along the Atlantic coast as well as within the Gulf of Mexico.

 

 Spawning Habitat

Sandy beaches of bays and coves are the preferred habitat for spawning horseshoe crabs.  The environment for the egg needs to have porous, well-oxygenated sediments.  They lay their eggs in the sand and the survival of the eggs is dependant upon the beach.  This is also where their offspring will grow and develop. These areas are favored because they are sheltered from the wave energy and the habitat is generally near places of large intertidal sandy flat areas. 

Delaware Seashore State Park.

Photographer: Mr. William Folsom, NOAA, NMFS

 

Nursery Habitat

Within bays and coves, next to the sandy beaches, are intertidal sand flats.  The young horseshoe crab generally spends the first two years of its life here. The water is shallow, food is sufficient, and has their preferred salinity of the water around 5 ppt (parts per thousand).  As the horseshoe crabs age, they maneuver out of the shallow areas to deeper parts of the bay.  They will not come back to the beaches until they are fully grown into an adult.

 

Adult Habitat

The adult habitat varies.  Their preferred habitat has not been determined. They have been found below 200 meters of water as well as shallower depths of 30 meters.  Through the duration of spawning season, the adults who are not spawning move to adjacent beaches. 

 

Winter Habitat

During the winter season the horseshoe crabs will move into the ocean or stay located in the bay.

 

Horseshoe Crabs spawning on a Delaware beach.
Photo by Greg Breese, USFWS.

 

Horseshoe crabs have been part of this planet for an estimated 500 million years!  To learn about how it adapts to its environment click here!

To go back to the classification page click here!