Protection of Spawning Habitat
Horseshoe crabs are a species that can live in a wide range of marine habitats. They are found in habitats ranging from the beach to the continental shelf and in varying temperatures and salinities. However, some specific habitats are considered essential to maintaining stable horseshoe crab populations. Adult horseshoe crabs prefer beach habitats that are protected from wave energy and have well oxygenated sediments to spawn. Shallow water areas are important nursery areas for juvenile crabs. Juvenile crabs prefer intertidal sand flats during their first few years of growth. Older juvenile or adult crabs prefer subtidal sand and mud flats for feeding and overwintering.
Although the Delaware Bay is the epicenter for horseshoe crabs, Maryland has prime horseshoe crab spawning and nursery habitat throughout the Chesapeake and Coastal Bays. Spawning has been observed on numerous beaches from the Chester River southward in the Chesapeake and throughout the beaches and intertidal flats of the Coastal Bays. Prime nursery habitat can be found on intertidal sand and mud flats in the Bays and tributaries of the region where the salinity is higher than 5 parts per thousand.
Recognizing the importance of horseshoe crab spawning habitat in Chesapeake Bay, Maryland DNR’s Fisheries Service started a volunteer spawning beach survey in 1994. Its primary goal was to document horseshoe crab spawning areas in Maryland. A secondary goal was to provide information about their abundance and determine whether or not this survey could be utilized to monitor the spawning population. The survey was completed in 2001.
The survey succeeded in identifying several spawning areas and providing fisheries biologists with a better understanding about the spawning behavior of horseshoe crabs. Reports from the survey indicate that horseshoe crabs are widely distributed throughout Maryland, but are restricted from parts of the upper Bay and its tributaries due to low water salinity. We have also learned that the duration and peak of spawning activity fluctuates annually and appears to be related to water temperature.
Maryland also encourages waterfront property owners to use non-structural shoreline erosion control methods. Examples include using shoreline plants (i.e., salt marsh cord grass) and offshore groins to reduce wave energy striking the shore and to preserve beach habitat.
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Raising Horseshoe Crabs in the Classroom
- Stacy Epperson
Aquatic Resource Education Dept
Department of Natural Resources
580 Taylor Ave., E-2
Annapolis, MD 21401