MCBP completes study of horseshoe crab in coastal bays


By Jack Chavez, Editor-in-Chief

In late spring and early summer, horseshoe crabs spawn on the shores of Assateague Island and other coastal bays. The spawning season is important not only for the survival of the species, but also for the survival of dozens of other species that rely on eggs as a vital food source. PHOTO COURTESY MCBP

They’re large, sturdy-looking, spiny, and an ominous shade of brownish-green, but a beachgoer would be just as quickly injured in an attack by a rogue beach ball as in an encounter with a rock crab. Horseshoe.

Around the Coastal Bays region, their protection is a top priority for environmental organizations such as the Maryland Coastal Bays Program, which just completed a collaborative survey with the Maryland Department of Natural Resources of these brackish water arthropods during their spawning season.

“We go to different sites on Assateague and Skimmer Islands and walk along hundred-meter transects,” said Carly Toulan, environmental scientist at MCBP. “Along them we go one meter into the water from the high tide line and count each horseshoe crab by gender. We do this until we reach the end of the 100 meter transect.

Toulan added that the survey usually involves counting two volunteers and will use the average if there is a slight disparity between the two counts, but recount if the difference is large.

“In addition to counting and sexing horseshoe crabs, we count all dead horseshoe crabs along this beach, whether in the transect or not, just to understand the number of dead horses in this area,” he said. she declared.

Typically around six volunteers help and Toulan said the half-dozen on tap have been helping MCBP for years and therefore know where and how to investigate.

“For this particular program, the importance (of these volunteers) is to be able to cover more ground and survey more areas,” Toulan said. “We wouldn’t be able to get as many survey sites and conduct as many surveys as we do without the volunteers.”

Data from the 2022 survey won’t be available until the fall, but Toulan said so far there won’t be much of a deviation from the 2021 survey.

“The population has been stable, which is really good,” she said. “We haven’t seen any major declines, but we haven’t seen any drastic increases either. Which is good. We want stable and steady. We’ve been doing this survey since 2002 in the coastal bays and the populations are stable since. it’s really great and it seems to be constant this year too.

The survey didn’t extend until the very end of the spawning season, which could prompt MCBP to take the waves again in July to see how long the spawning season lasts, Toulan said.

There has also been an addition to MCBP’s focus on horseshoe crabs this year with the Stranded Horseshoe Crab Recovery Team, a group of nearly three dozen volunteers who monitor four different locations. for stranded horseshoe crabs that they can safely remove and release.

Although the investigation doesn’t need more volunteers, Toulan said the recovery team is still looking for help.

Protecting horseshoe crabs is vital for three main reasons, Toulan said. The first is the human health of the horseshoe crab. Their blue blood can be harvested to create Limulus Amebocyte Lysate, which is used to test injectable drugs to ensure they are safe and that no endotoxins are present.

“Any injectable medicine or vaccine you’ve had will have been tested with horseshoe crab blood to make sure it’s safe,” Toulan said. “There’s a whole biomedical industry that revolves around the horseshoe crab.”

Second, ecologically speaking, horseshoe crabs are vitally important at this time of year as their eggs are the primary food source for dozens of different fish, birds, mammals and reptiles. For example, the endangered red knot stops in this region on its great migration from South America to the Arctic Circle and depends on the eggs to swell and store the energy needed to complete their flight, said Toulan.

Third, she added that they are used as bait for whelks and eels, which gives them importance for local fishing.

And, again, as Toulan points out, horseshoe crabs are not dangerous.

“It’s really important that people know that,” she says. “They can’t hurt you. They do not pinch, sting or bite. (If you’re helping a stranded horseshoe crab), the correct way to hold it is by the sides of its shell. Never pick it up by the tail, which is very sensitive and fragile. If this tail breaks, it will hamper the horseshoe crab’s ability to move around and turn around if it gets stuck on its back.

Anyone who would like more information about the Stranded Horseshoe Crab Recovery Team or to volunteer can contact Toulan at or find more information online at

This story appears in the print version of the Bayside Gazette on July 7, 2022.


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