Horseshoe crabs face ‘ecological extinction’ in Long Island Sound, driven by harvest and habitat loss

CALF PASTURE BEACH — Drawn by the full moon rising over the Norwalk Islands on Tuesday night, a swarm 450 million years in the making lurked just below the waves lapping onto the sandy beach.

Joe Schnierlein, a former marine biologist and high school teacher, swooped into the shin-deep water and pulled up the armored shell of a female horseshoe crab, one of several hundred animals of the spider-like chose that this night to come ashore and lay their eggs to spawn the next generation in Long Island Sound.

The full moon and its associated high tide — which provides good cover for the horseshoe crabs to lay their eggs high up on the beach — also attracted about 40 human volunteers, including Schnierlein, who have come to place tags on the animals as they spawn, part of a scientific monitoring program that has attempted to track populations of these ancient crabs in the Sound for more than two decades.

Led by staff from the nearby Maritime Aquarium, volunteers like Schnierlein have been coming to this particular spot on the beach for years, where they say favorable tides and clear nights can help them find and tag upwards of a hundred crabs in about an hour. On other occasions, however, it can be a struggle to find even a few dozen crabs.

“There’s been some good years, some bad years,” Schnierlein said. “Is it because of the weather? You don’t know.”

Across Long Island Sound, researchers who monitor the results of these and other tagging efforts say that horseshoe crabs are on the decline, driven by a combination of habitat loss, pollution and commercial fishing that is threatening the role this species has played in the environment since before the time of the dinosaurs.

The Atlantic States Marine Fisheries Commission reported in 2019 that stocks of horseshoe crabs in the New York region, which includes Long Island Sound, were in “poor” condition, after a series of surveys showed their numbers declining since the late 1990s.

Jennifer Mattei, a biology professor at Sacred Heart University who has studied horseshoe crab populations for years as part of Project Limulus, said those findings were in contrast to more abundant populations farther south in places such as Delaware Bay, where millions of eggs laid by the crabs serve as a vital smörgåsbord for migrating birds such as the endangered red knot, which flock to the bay in the thousands on their way to nesting grounds in the Arctic.

While the horseshoe crabs in the Sound are not in danger of going away completely, Mattei said that their numbers are so low that they cannot support the numbers of birds and other wildlife that they do elsewhere in their range.

“We don’t have that phenomenon here because there just aren’t enough crabs for that to happen.” Mattei said. “It’s kind of what’s quoted as an ‘ecological extinction,’ where they’re just not feeding the birds, they’re not feeding the fish, because the eggs are sparse and buried and so they’re unavailable to most of the animals that use them for nutrition.”

Prompted by the concerns raised by Mattei and others, officials with the state Department of Energy and Environmental Protection began drafting new regulations last year to sharply reduce the annual harvest of crabs within the Sound.

While the crabs are harvested in some areas for biomedical research that uses their blue blood to test the purity of vaccines, the majority of those harvested off the coast of Connecticut are taken by about a dozen licensed fishermen to be cut up and used as bait in eel and whelk traps, according to DEEP.

Fishermen were incredulous at the new rules, arguing that volunteer efforts to tag and count the crabs were doing a poor job of finding them, leading researchers such as Mattei to underestimate the overall population.

“There’s more than they think,” said Bob Guzzo, a commercial fisherman based in Stonington. “I don’t think they’ve got the science all right either yet, (but) they don’t ask us much, all they do is keep restricting us more and more and more.”

This year, Guzzo said he’s given up on harvesting horseshoe crabs altogether in favor of alternative, less regulated bait species such as the Jonah crab.

For researchers, the decision of a few fisherman to find an alternative baits may represent the best opportunity for the population to rebound, after state lawmakers earlier this year ran out of time to enact a complete moratorium to cut off the harvest of tens of thousands of horseshoe crabs each summer.

“I didn’t do this work to take people’s livelihoods away, I want to manage the resources so they’re sustainable,” Mattei said. “But what we’ve found is that the horseshoe crab has continued to decline for all of these various reasons, everything from loss of habitat to pollution and harvest, and that their role in the ecosystem and the environment has declined.”

In addition to regulatory changes, advocates for horseshoe crabs say that public outreach is also vital to raising awareness for the species and efforts to monitor and preserve their populations.

Bridget Cervero, an educator for the Maritime Aquarium who led the group of volunteers to Calf Pasture Beach this past week, said the program has experienced “massive” interest this year after such outings were limited during the first two years of the COVID-19 pandemic .

As she spoke to the group of volunteers at about 11:30 pm Tuesday, nearly all of the adults and children huddled around in headlamps raised their hands to indicate that it was their first time tagging horseshoe crabs.

The aquarium, which leads two or three trips to the beach during May and June, requires that first-time volunteers attend a training session to learn about the horseshoe crabs and how to properly collect them and apply the tags.

One of the newcomers, Jeff Spahr of Norwalk, said he grew up seeing horseshoe crabs while taking trips out to the nearby islands on his boat, but said those sightings had become less frequent in recent years.

“I always felt the population was declining and I felt bad about that so I wanted to do something to help document them,” Spahr said. “When I saw this, I jumped on it, it was great.”

For others, including roommates Andrea McKenna and Johnny Fremgen of Saugerties, NY, the midnight excursions have become a regular summertime activity and a way to tap into a love of nature.

“It seemed to me a better way to contribute than your typical reduce, reuse, recycle,” McKenna said. “Even if it was squids, I’d be out here doing it.”

As a result of years of tagging data done by the volunteers, Mattei said she and her fellow researchers have been able to determine that the horseshoe crabs tagged along the Connecticut shoreline will cross the Sound, but rarely venture outside of its waters.

That finding helped prompt regulators in New York and Connecticut to work together drafting similar limits on the horseshoe crab harvest on both sides of the sound, Mattei said.

The horseshoe crabs have also found other allies in the conservation movement, most notably from the Connecticut Audubon Society, whose members have called for a complete ban on the commercial harvest to help support migratory bird populations.

“The more horseshoe crab population we have here, the more fuel these birds are going to have when they stop over here,” said Patrick Comins, executive director of the Connecticut Audubon Society. “If they don’t get the nutrition they need, they’re not able to arrive on their breeding grounds in the Arctic.”

On Tuesday night, the results from the expedition along Calf Pasture Beach were encouraging, as volunteers used up all the 180 tags brought by Cervero in about an hour-and-a-half.

As with an earlier outing in May, Cervero said volunteers reported that most of the animals they found, including breeding pairs, were healthy and free of parasites. After the animals are tagged, they are placed back in the water so that they may continue to lay their eggs.

“They’re hardy animals,” Cervero said. “They’ve been around for 450 million years and they’ve done that because they’ve figured out how to live.”

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