Horseshoe Crabs Wash into O.C. Canal - WBOC-TV 16, Delmarvas News Leader, FOX 21 -

Horseshoe Crabs Wash into O.C. Canal

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(Photo: Michael Baier) (Photo: Michael Baier)
(Photo credit: MCBP) (Photo credit: MCBP)

OCEAN CITY, Md.-  Dead horseshoe crabs washed into a canal at 94th Street in Ocean City last week, causing concern and inconvenience to people living near the area, according to the Maryland Coastal Bays Program.

The MCBP reports the episode happened shortly after a spawning event, which experts say may indicate it's tied to a natural occurrence since up to ten percent of horseshoe crabs can die during spawning. The group reports that spawning is particularly stressful to older horseshoe crabs. As spawning occurs during full and new moon cycles, often they can get also caught in rip-rap and sand bars, which can cause death as well.  Most of the dead crabs washed into a dead end canal, according to the MCBP.

According to Natural Resource Biologist Steve Doctor, there may have been additional stress on the horseshoe crabs from large deficits of dissolved oxygen (DO) attributed to a huge bloom of macroalgae in the Assawoman Bay earlier in the year.  Low DO is when oxygen levels in the water are too low to support life. The low DO may be attributed to a huge bloom of macroalgae that recently died and decayed in Assawoman Bay, Doctor says. He adds that factors leading to this possible conclusion were carapaces (molts) of horseshoe crabs too young to spawn along with the adults, as well as carapaces of blue crabs. 

The MCBP says people can help improve water quality throughout the canals and bays by following guidelines for chemicals and lawn fertilizers used around homes.

Currently, there is not an agency responsible for response and clean-up for these events. Local resident Michael Baier, is credited with coordinating neighborhood volunteers to pick up hundreds of horseshoe crabs and Ocean City’s Environmental Engineer Gail Blazer who made arrangements through Ocean City’s Director of Public Works Hal Atkins to provide the necessary means to dispose of the carcasses.

The MCBP says horseshoe crabs are not true crabs at all.  They are more closely related to arachnids, a group that includes spiders and scorpions, than to crustaceans which includes true crabs, lobsters, and shrimp. 

During the nesting season, especially in the Mid-Atlantic States, horseshoe crab eggs become the major food source for migrating birds. More than 50 percent of the diet of many shorebird species consists of horseshoe crab eggs, experts say.

Horseshoe crabs are extremely important to the biomedical industry because their unique, copper-based blue blood contains a substance called Limulus amebocyte lysate, the MCBP notes. The substance, which coagulates in the presence of small amounts of bacterial toxins, is used to test for sterility of medical equipment and virtually all intravenous drugs. Research on the compound eyes of horseshoe crabs has led to a better understanding of human vision, officials say.

Maryland Coastal Bays Program is working on a program to determine areas where horseshoe crabs are getting stranded to begin a volunteer program to help prevent unnecessary horseshoe crab deaths. If you know of an area where these animals are getting caught during low tides, contact Amanda Poskaitas at or by calling her at (410) 213-2297, ext. 103.

For more information on this horseshoe crab kill event, contact Sandi Smith at or by calling (410) 213-2297, ext 106.

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