Horseshoe Crab Count Under Way on East Coast

Anyone can participate in the annual counting and tagging of horseshoe crabs during their spawning season.

For some, the coming of summer means wearing white, but for citizen scientists like Gina Mulhearn and Mark Cappiello, it means donning wellies and waders, then heading to the beach to count and tag horseshoe crabs as they spawn up and down the eastern seaboard, a phenomenon that peaks around the full moons in May and June.

During their 450-million-year span on the planet, horseshoe crabs—which resemble aquatic steam shovels and are more closely related to spiders than crabs—have survived mass extinctions, ice ages, and asteroids. As such, they hold a slot on evolution's time line that makes humans look like a vulnerable speck.

For decades, these animals have been invaluable to human health. If you've ever had an inoculation and not gotten an infection, you can thank horseshoe crabs: A clotting element in their blood is used in drugs and intravenous devices.

Scientists have even found antiviral and anti-cancer components in horseshoe crab blood, which is worth $15,000 a pint—the maximum amount a female crab can yield and stay alive; males are smaller and yield less. According to the Atlantic States Marine Fisheries Commission (ASMFC), in 2012 the biomedical industry reported that more than 611,000 crabs were collected and bled.

Horseshoe crabs have also long been used as bait for catching conchs and eels, which are attracted to their smell. Synthetic baits have been developed, but the commercial bait industry still gathers hundreds of thousands of crabs every year. (See: "Horseshoe Crabs Need Compassion and Help to Survive.")

Irresistible Creatures

Fascination with and concern for horseshoe crabs is why I joined Mulhearn and Cappiello, volunteer site coordinators for the Cornell Cooperative Extension, on one of Long Island's barrier islands to count and tag crabs.

Seven years ago, after Mulhearn and Cappiello retired, they decided to get involved by overseeing the survey here. "It's not a competition," Mulhearn said, laughing, "but we count more than anyone else, every year!"

Every state up and down the eastern seaboard has similar volunteer programs—which have taken place every year since 2004 and will continue through the end of June.

The data from these counts directly influence the harvest quotas set by ASMFC and implemented individually by states.

Last year about 30 kids from area schools on Long Island participated in tagging the crabs. "Some kids are scared," Cappiello said. "But when I pick [a crab] up and put it on my head like a helmet, they laugh. By the end of the night, they'll be begging to tag crabs."

But the first night of this year's survey, May 12 (two days before the full moon) fell on a weeknight, too late for schoolchildren to join in.

Counting Crabs

To conduct our count, we used the so-called Quadrat Protocol. It sounds fancier than it is—you take PVC pipe in the shape of one square meter (11 square feet), place it over the shallows where the crabs are burying their eggs, and count the crabs inside the square.

We counted along a one-kilometer (about half a mile) area of the beach, using a random sequence suggested by the cooperative extension.

Foraging horseshoe crabs move slowly through the water. Spawning crabs dance. They swirl and pivot on their spindle legs, so it's sometimes hard to judge if they're in or out of your quadrat as they dash around.

A female crab, tiptoeing en pointe toward the shore, buries herself in sand, where she lays thousands of eggs as males form a conga line behind her. The sight is at once prehistoric, mysterious, and delightful.

We finished our count in less than an hour: 39 males, 27 females. (A low number, possibly because of the colder-than-usual water this year, after the hard winter.)

Tag Time

To tag a crab, you use a battery-powered drill with a rubber guard on it to stop the bit from going too far through the shell. You then fasten the plastic, disk-shaped tag to the shell.

As I tagged my first crab, a female, she was so laden with eggs that they bubbled out of the hole in her shell.

Tagging crabs serves two purposes—to discover how far males and females travel and to help record their growth. They also carry a message that if the crab is found or harvested, its location should be reported.

How many crabs actually get reported is hard to know because there's minimal regulatory oversight in the bait and biomedical harvesting industries.

Bird Feast

The next morning, our beach was devoid of crabs but crowded with tiny birds called red knots, relatives of the eastern sandpiper, making a pit stop on their flight from Tierra del Fuego to summer nesting grounds in the Arctic. They were digging into a smorgasbord of crab caviar.

Red knots need the nutrients in horseshoe crab eggs. About ten years ago the birds' numbers fell by 80 percent, and that, the Audubon Society of New Jersey asserted, was because horseshoe crab numbers were dropping owing to overharvesting.

Since then, crab harvests have been regulated to some degree, and along with the red knots, crabs in some states have been doing better. Southern states, the ASMFC reports, are seeing an increase in crab populations, while the mid-Atlantic states are holding stable. New York and Massachusetts are still declining.

William Hall, who helped introduce conservation efforts in Delaware Bay two and a half decades ago, believes the biomedical industry is responsible for the decline. (His concern is buttressed by a study released in December 2013 revealing that female crabs that have been bled and released don't spawn again for a year or two.)

Ten years ago, biomedical companies were required by law to return the tens of thousands of female crabs whose blood they'd collected to the bays they were harvested from. This was supposed to help prevent populations from being decimated. In some states, the law has now changed, so biomedical companies can now sell bled crabs for bait instead.

"The biomedical industry now has no obligation to report numbers landed or bled or to mark all bled individuals with tags," according to Eric Hallerman, professor of fisheries and wildlife at Virginia Tech.

The ASMFC 2012 report on Massachusetts, for instance, reveals only the percentage of crabs harvested by the biomedical industry, stating that "confidentiality prohibits use of numbers."

Full Moon: Bait Collectors' Delight

Wednesday was a full moon, and I anticipated seeing many more crabs. Crabs can perceive light, but whether it's the moon, the tide, or both calling them to spawn is not clear. (They spawn on the new moon as well.)

High tide was about ten o'clock, and the beach wasn't empty. Baymen were busy harvesting crabs for bait, and Cappiello didn't even need to place the quadrat in the water. "Zero," he called out again and again.

Bobby Makis had a broad grin, teeth the color of tobacco, and few days' beard growth. Using his clamming rake, he was hauling crabs out of the water and tossing them into a crate he'd rolled down the beach. "I got a hundert already," he said in the local vernacular, "but last night was better."

He planned to drive his haul to the bait wholesalers on Long Island in the morning and was expecting to get up to a $1.50 a crab. The Chinese, he says, come all the way from the city. "They want 'em real bad. They claim they have conch in China but no horseshoe crabs, and they can't catch the conch without the crabs, so they freeze 'em and ship 'em over. Buy a thousand at a time."

Last year, he said, the Chinese paid up to four dollars a crab, but that, he said sheepishly and with a shrug, "was after the season ended."

Makis has harvested crabs for 25 years, before the ASMFC began setting harvesting regulations for states, before anyone was interested in the crabs for anything but bait.

"Back in the day," he said, "you could find hunderts in Peconic Bay. Big 'uns too. You don't see hardly none there now, and none that size."

He blames the red knots. "Those birds eat a lot of eggs—they're so fat when they leave here, they can barely fly. You know what we gotta do?" He smiled. "Gotta get rid of them damn little birds."

We had a dismally low count for a full moon: just two females and four males. But Mulhearn remained positive. "When the state sees numbers this low on a beach like ours," she said, "they close the harvest."

Next week I'll join Mulhearn and Cappiello as they hope to tag a thousand crabs in three days, and I'm gathering everyone I know to join the effort. Maybe I can get Bobby Makis to join us.

Heather Dune Macadam is the author of the upcoming novel The Sag Harbor Mermaid Club. You can join the club by visiting her website and following her on Twitter.

For more information, contact a coastal conservation agency and marine fisheries department to volunteer as a citizen scientist and count the horseshoe crabs from now through July.


Crab Wars: A Tale of Horseshoe Crabs, Bioterrorism, and Human Health By William Sargent

Children's Books:

Crab Moon, by Ruth Horowitz

Horseshoe Crabs and Shorebirds—The Story of a Food Web, by Victoria Crenson

Moonbird: A Year on the Wind With the Great Survivor B95 (Robert F. Sibert Informational Book Honor (Awards), by Phillip Hoose

Harry Horseshoe Crab: A Tale of Crawly Creatures, by Suzanne Tate; illustrated by James Melvin

Read This Next

An ambitious new Florida trail links two U.S. national parks
How reading the night sky helped Black Americans survive
Does a woman’s fertility really plummet at age 35?

Go Further

Subscriber Exclusive Content

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet