Tallying seaside trysts in the interest of science

Conservation: Flashlights in hand, volunteers in the twilight count mating horseshoe crabs on Maryland beaches to provide data that will help officials manage the population.

June 20, 2000|By Joel McCord | Joel McCord,SUN STAFF

ASSATEAGUE ISLAND - John Henglein, a volunteer for the Maryland Coastal Bays Program, splashed through the water behind a stone jetty at the northern tip of this barrier island one evening last week, counting horseshoe crabs in their spring mating frenzy.

He is among about 70 volunteers who annually record the number of clasping pairs - burrowed and swimming - as well as satellite males trying to get in on the mating, and solitary males.

The information, gathered for the state Department of Natural Resources from 14 beaches around Assawoman, Isle of Wight, Sinepuxent and Chincoteague bays near Maryland's beach resorts and three on Chesapeake Bay, will be shared as part of a larger East Coast effort to develop a plan to manage the horseshoe crab fishery.

Horseshoe crabs, which were on Earth 100 million years before dinosaurs, are at the center of a multi-state battle over conservation measures.

The Atlantic States Marine Fisheries Commission, which regulates East Coast commercial fishing, has moved to close Virginia's lucrative horseshoe crab industry because the commonwealth has defied a plan to cut harvests by 25 percent.

Fisheries managers in Virginia argue that the plan, which documents record harvests and declining spawning surveys, is based on flimsy science. Because of that, they say, they don't have the authority to order the harvest cuts without an act of the Virginia General Assembly, which won't meet until January. Advocates of the cuts say the survey results are compelling, even if they don't meet rigorously scientific standards.

The helmet-shaped creatures, which provide bait for a multimillion-dollar conch and eel fishery, food for migrating shorebirds and blood for pharmaceutical tests, swarm to beaches along the Atlantic Coast in May and June to mate, leaving millions of fertilized eggs buried in the sand.

At this bayside beach within sight of the rides of Ocean City's boardwalk, amorous males patrol in less than a foot of water, ready to latch onto the first female they catch swimming for the beach on high tide of the full moon. Often, four or five males pursue the same female, forming a rocky mass of shells at the water's edge.

Henglein, a retired facilities administrator for New York City's public schools who lives in Ocean Pines, has been participating in spawning surveys for three years, and says he has seen little difference in the mating frenzy, although scientists say the horseshoe crab population is dropping.

Maryland's count, taken during three weeks from May to July, does more than document a decline in horseshoe crabs. The numbers also will help state officials identify the best spawning habitat and "get that information to local land-use planners" who make decisions about where development is allowed, says Thomas J. O'Connell, who organizes the volunteers for the state Department of Natural Resources.

Maryland has cut its horseshoe crab harvest by 75 percent, "so the best thing we can do is protect those beaches where they spawn," O'Connell says. One of the Coastal Bay spawning areas, Stinky Beach, was lost to development last year.

Horseshoe crabs spend most of their lives on the continental shelf from Maine to the Gulf of Mexico. But sometime around the winter solstice, they begin their migration to the beaches, with the largest concentrations between New Jersey and Maryland.

Males start showing up in late April, followed within a few weeks by females, which give off a scent to attract mates. With front claws shaped like boxing gloves, the male latches onto the female from behind, then rides up over her shell. He fertilizes the eggs as she deposits them in the sand.

One female can lay about 90,000 eggs, a University of Delaware study shows, and only two of them will survive the 10 years required to reach sexual maturity. The eggs provide food for migrating shorebirds that reach Delaware Bay, the greatest spawning ground, at the height of the mating season. The hatchlings are a target for other predators as they head back to sea.

With flashlight in hand, Henglein wades into the water to spot the crabs and record the details. "There's a burrowed pair," he says, pointing to two barely distinguishable lumps in the sand. "Another burrowed pair with one, two, three, four, five satellites. No, six."

One male had attached himself from behind to fertilize the egg mass the female was dropping, and more males had swarmed around her. Henglein recorded nearly 100 crabs, mating in the crepuscular light, from the stone jetty at the northern tip of this barrier island to a spot about 300 yards south that marks the ending of his territory.

He says he counted 120 in one night last year. And Dave Wilson, outreach director of the Coastal Bays Program, recalls a night on Skinner Island last summer when he saw so many crabs, "you couldn't count them all."

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.