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New York beaches are dating hot spots for horseshoe crabs
By
Rosemary Misdary
Published Jun 6, 2025
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Andrew Lichtenstein/Corbis via Getty Images
By
Rosemary Misdary
Published Jun 6, 2025
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Beneath a full moon in Jamaica Bay, horseshoe crab love was in the air.
Female crabs skirted along the shore, each with two or three smaller male crabs attached to their backs and sides, fertilizing thousands of eggs in the sand. Hundreds of casual encounters like this were taking place during a visit by Gothamist last week to Plumb Beach in Brooklyn. A similar episode occurs every May and June during high tides around full and new moons.
“ It's a bar scene,” said Matthew Sclafani, marine educator at the Cornell Cooperative Extension. “It's typically 3-to-1 males to females in this area. So, sperm is cheap.”
Plumb Beach, a narrow strip just off the Belt Parkway, is one of the hottest spots for thousands of horseshoe crabs to find mates. A female crab will have as many as three male crabs attached to her for two months. Scientists conducting an annual spawning census at the beach have noticed a heartening trend: Horseshoe crabs in New York City waters are experiencing a population bump, bucking the overall trend in the Atlantic Ocean.
Horseshoe crabs spawn at Plumb Beach in May and June every year.
Parks Department
“ We're starting to see some positive trends the last five to 10 years in almost all of the areas that we're monitoring,” Sclafani said. “Jamaica Bay has been showing a slow and steady increase over the last five years, the last 10 years for sure.”
The 2023 Jamaica Bay survey — the most recent that’s been analyzed by scientists — counted nearly 40% more crabs than the previous year. Compare that to their population stronghold in the Delaware Bay, where horseshoe crabs have declined by two-thirds since the 1990s, according to the Center for Biological Diversity. Last year, the group petitioned the federal government to list the 10-eyed creatures as endangered. The request is still pending.
Habitat loss and overharvesting by the pharmaceutical industry — which uses horseshoe crab blood to test certain medical products — are the primary reasons for the dwindling numbers. Sea level rise and extreme weather also threaten the species, which is twice as old as the dinosaurs. Last year, Gov. Kathy Hochul vetoed a bill that would have banned all commercial take of the crabs, saying oversight of the creatures was best left to the state’s environmental agency.
“ It's amazing that we are handling animals that have been on the planet for a very, very, very, very long time,” Ann Seligman, the site coordinator, said at Plumb Beach. “A lot of people when they think about New York City, they do not think about our seashore and our natural life, but to be here on a beautiful night with the moon and the horseshoe crabs and each other is a really beautiful experience.”
Katherine Chen, a senior manager at the NYC Bird Alliance, said the annual horseshoe crab counts in the city were influential in the New York State Department of Environmental Conservation’s 2020 decision to tighten restrictions on commercial harvests during spawning season.
“Because of data that we are collecting here and elsewhere, there are horseshoe crab limits that get put in place to help prevent overharvesting,” Chen said.
Scientists call horseshoe crabs “living fossils.” The prehistoric invertebrates have not changed much in their 445 million-year history, and play a key role in the ecosystem.
”Some birds can even double or triple their body mass when they're gorging themselves on these horseshoe crab eggs, and it's a really important fuel source for them to be able to make it for the rest of their migratory journey,” Chen said.
Scientists and volunteers document the health of horseshoe crabs during spawning season every year.
Rosemary Misdary / Gothamist
Over 12 spring evenings, volunteers and ecologists survey two sites in New York City: Plumb Beach and Big Egg Marsh in Jamaica Bay. They count the number of horseshoe crabs coming ashore at high tide, then take measurements noting age, gender and shell condition.
They also tag the horseshoe crabs — and find many return visitors.
“ The majority of horseshoe crabs that we tagged, and recaptured in New York state tend to come back to New York state. They stay local,” Sclafani said.
The scientists said they need at least another three years to make a confident assessment about the local rebound.
”It takes a long time to see any changes that result from any management changes because they're a long-lived species and it takes about 10 years for them to reach sexual maturity,” Sclafani said.
A female horseshoe crab lays up to 4,000 eggs at a time by burrowing a few inches in the sand. During the entire mating season, a single female will produce more than 100,000 eggs. While the male attached directly behind her has the best chances of fertilization, the other two attached to her sides also contribute to a lesser degree. Only about 1% of the eggs survive. Most are eaten by birds.
“ There's no parental care. They just release lots of eggs and they say 'good luck,'” Sclafani said. “If you get 1% through, you're doing a really great job.”
Seligman hoped New Yorkers supported protecting the natural marvel in their backyard.
”You have to really appreciate what is here,” Seligman said. “If people do not have a connection to the natural world, they don't care about it and they won't protect it.”
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Rosemary Misdary
Rosemary is health & science reporter. Got a tip? Email [email protected] or Signal 646-544-9524.
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Gothamist is funded by sponsors and member donations
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