Long Island Sound is home to a living fossil: the horseshoe crab. They have been around for nearly half a billion years, but today this hardy and helmeted species faces new challenges. So, how are they faring in Connecticut?
At the mouth of the Connecticut River is Old Lyme’s Griswold Point, a gorgeous rocky beach that’s crowded with visitors today. But it hasn’t seen much horseshoe crab activity this summer, according to researchers with the Connecticut Audubon Society.
“They’re an indicator of how our waters are doing," said Emily Watling, conservation coordinator with the Audubon Society. "The more we see of our horseshoe crabs, the more we can see about the surrounding ecosystem.”
We are also out here with interns Pearl Lasser and Sadie Garfinkel.
“Most of the time when people think about one species, like horseshoe crabs or fish, they think about the individual. But they’re really interconnected," Lasser said. "And we need the change to continue and to exist because we need each other!"
“Plus, charismatic megafauna! People want to be connected to these things," Watling chimes in. "People can’t hang out with a whale, but you can hang out with a cute little horseshoe crab!"
Emily’s right! These guys certainly have a "charismatic" look -- a dome shell with their legs and claws underneath. They have ten eyes on their body, with two distinct ones on top of their shell. And they are actually not even crabs, but more closely related to spiders. The name comes from their crustacean-like look.
The population in Long Island Sound has been in “severe decline” over the last two decades, averaging between a two and nine percent loss each year. That is based on counts done at Maritime Aquarium in Norwalk, Millstone Environmental Laboratory in Niantic, and elsewhere. Garfinkel says it’s important to get the community involved to raise awareness.
"It's about feeling that connection to the environment — that's a big part of it! Helping people get out there and be involved, know that they can participate in science is really important," she said. "It's important to understand our past, what's worked for species in the past to understand how things could evolve in the future."
The Audubon Society trains the public how to tag horseshoe crabs to track their numbers and fill out a fact sheet. It is part of the Project Limulus program out of Sacred Heart University. Data goes back to the U.S. Fish and Wildlife Service. Watling shows me how to tag on a molted shell.
“First thing you do, you check their feet to see if there’s injuries, check the top of their shell. We record if they are injured first, then record the size of their shell. The largest part of their shell is here; this guy looks roughly five inches…”
You write down where you found the crab, their sex -- females have a flatter, rounder front of their shells. A few more notes and then it is time to tag! Watling uses a little screwdriver to make a hole in the shell.
“It’s basically like a little earring. You go in slightly... but you impale and twist really hard. And these lock in place, so when you push it in, you’ll feel it lock, and it opens in the back, which is super cool!”
Horseshoe crabs need to mate in shallow water and sand, but like a lot of Connecticut's coastline, this beach is rocky and built out. That's probably why the team has not seen any this summer at this location, and why we end up not seeing any live ones today.
But zero is still data. Connecticut banned the harvest of horseshoe crabs in 2023, and New York just this year, so it will take time to see a change.
“We can say okay -- we didn’t see anything in 2026, but let’s go back in 2027, 2028," Watling said. “We’re hoping that if we monitor these areas every couple of years, eventually we’ll start to see more as they’re about to come back, and the ban has an impact.”
So, no luck on the horseshoe crabs today, but our day out here is not over yet. Now we are going to look for other species in the water.
"This is a huge part of biodiversity sampling around here. We do it every week to see what species we see before and after," Watling said.
To do that, we are going to use a seine net. It kind of looks like a volleyball net; long and rectangular with posts on either side. Garfinkel and I walk it out to about waist deep.
“We’re going to hold this nice and tight," she explains. "So, I’ll let you know when we can start walking together once I wrap around you."
Holding either post, we pull the net tight, so it is perpendicular to the floor. Then we walk it back slowly to shore. The tide is high today, so Garfinkel said she is hopeful for a good pull.
"A little arm work for the day! Usually we sample at low tide, where the net will only be about a quarter submerged," Garfinkel said.
We haul the net up on the sand, laying it down flat. There are a bunch of little fish jumping around. We grab what we got and put everything in a bucket of water to take a closer look. Aside from the fish, we also grab a few crabs and some native sea grasses — a welcome sight!
If you would like to get in on the fun and be a part of this community science effort, visit ctaudubon.org.
