Horseshoe crabs crawl back
Spawning surge in Chesapeake, Delaware bays could signal payoff from coastwide harvest restrictions
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Every spring, John Rodenhausen looks forward to seeing a few horseshoe crabs on the beach at the Chesapeake Bay Foundation’s headquarters outside Annapolis.
This year, Rodenhausen said, thousands of the prehistoric-looking creatures, which resemble spiders more than crabs, were mating on the Annapolis beach in late May. As is their wont, the smaller males attached to the larger female, sometimes four to five at a time — one large carapace surrounded by smaller ones, like points on a star.
“It blew us all away,” said Rodenhausen, the foundation’s Maryland development director. “You’ll always see a few, and you might see a dozen, but we saw thousands. And it wasn’t even a full moon.”
Citizens and scientists are documenting large numbers of the spike-tailed, helmet-shelled creatures on Chesapeake Bay and Delaware Bay beaches. The uptick could be a sign that once-unpopular management restrictions are working and could help secure a future for the Atlantic Limulus polyphemus, long prized for what it could do for other species instead of for its own virtues.
The eggs that female horseshoe crabs lay on beaches feed large quantities of shorebirds, which can double their weight in two weeks of feasting, helping them to fly halfway around the world. Their copper-rich, blue blood can save human lives; scientists use a chemical found only in the species’ blood to test for bacteria and identify potentially lethal contaminations in intravenous medications. For decades, companies took the animals to grind into fertilizer and raise food. Fishermen backed their trucks up to crab-rich beaches and took what they wanted to use as bait in the conch and eel fisheries.
But now, wildlife officials say, protections put in place in the last two decades could finally be stabilizing and even helping to rebuild the 450 million-year-old species. And the long unloved creature is finally getting some love — especially from those interested in watching some sex on the beach.
“They’re definitely not cute and cuddly, but they’re nerdy cool,” said Stewart Michels, program manager for the fisheries section with the Delaware Department of Natural Resources and Environmental Control. “Nowadays, we are seeing a lot of kids, school groups, individuals. They’re coming just to see the horseshoe crabs.”
For years, it was mostly bird enthusiasts who flocked to the Delaware shores to see an ancient ritual that shows the interplay between species better than almost anything else in nature. Every year in May and June, millions of horseshoe crabs crawl out of the gentle Delaware Bay surf at high tide under the full moon, searching out the opposite sex. The females lay their pearly green eggs, and the males release sperm to fertilize them.
When day breaks, thousands of shorebirds arrive from South America, emaciated and exhausted. They feast on the protein-rich eggs, double their weight, and then take off for the next leg to the Canadian arctic. Delaware Bay is the epicenter of horseshoe crab activity.
The birds include American oystercatchers, skimmers, sanderlings and ruddy turnstones. But the most famous is the rufa red knot, a 5-ounce stunner that flies 9,300 miles from Tierra Del Fuego at the southernmost tip of Chile to the Canadian Arctic. Their numbers have plummeted in Delaware mainly because of a lack of food, but also because rising sea levels are swallowing their beach habitat. In late 2014, the red knot was listed as threatened, principally because of long-term declines in horseshoe crab eggs, its primary migratory food supply.
To save the red knot, wildlife officials in New Jersey, Delaware, Virginia and Maryland implemented some conservation measures and have been tweaking them ever since. New Jersey has gone the furthest, with a moratorium on any harvest of horseshoe crabs since 2006.
Maryland’s harvest is regulated by the Atlantic States Marine Fisheries Commission and managed for “ecosystem benefits,” meaning shorebirds are part of conservation considerations. It had a limited harvest for females until about three years ago. It now has no harvest for females, making its harvest virtually nothing, according to Carrie Kennedy, who used to manage the horseshoe crab fishery for the Maryland Department of Natural Resources and now is a data and quota monitoring manager. Even at its height, only about 10 watermen harvested the crabs, and most of them worked out of the coastal bays near Ocean City, she said.
Delaware, after a long court fight with a horseshoe crab harvester, put in a harvest limit of about 160,000 horseshoe crabs a year.
Virginia cut its horseshoe crab fishery, but only when the federal government forced its hand. As recently as 1998, harvesters took one million crabs for the state’s conch, eel and whelk fisheries. The Virginia Marine Resources Commission has been cutting the quota ever since, under pressure from federal fisheries officials and the ASMFC. It is now about the same as Delaware’s, with the added restrictions that harvesters can take only five per day and cannot trawl for the animals in state waters and within 3 miles of the coast.
Maryland, Delaware and Virginia also have a limited biomedical harvest, which allows pharmaceutical companies to take horseshoe crabs, extract their blood and return them. The blood-letting can lead to difficulty in mating and occasionally death; when they die, they are counted as bycatch for the bait fishery.
Horseshoe crabs span the Atlantic Coast, with populations from Maine to Mexico. They are also in the Gulf of Mexico. The most recent stock assessment, now 3-years-old, showed increased populations in the Southeast United States; a stable population of females and an increase in males in the Delaware-Maryland-Virginia region, and a decrease in the Northeast, possibly because harvesters have moved to states with fewer restrictions.
The harvest limits reduced the horseshoe crab catch for bait by about 75 percent coast-wide, Michels said. They were gradual; Delaware completed its management plan in 1998, and began phasing in the cuts over the next five or six years. But Michels said she believes they are making a difference. Eel fishermen once used a half or a whole crab to bait a pot; conch fishermen sometimes used more.
“It took about zero infrastructure to get into the fishery,” Michels said. “Everyone with a pickup truck and a pair of gloves was harvesting horseshoe crabs.”
Horseshoe crabs live about 20 years and begin to mature at about 10, so many management actions will take at least a decade to bear fruit. The last species-wide stock assessment, in 2013, showed a modest increase in the populations in Delaware and Maryland. Delaware Bay surveyors are counting 50 males and 10 females in one square meter of beach, as opposed to maybe 10 or 15 total a decade ago. It was so crowded, Michels said, that females were upending other females who were trying to spawn.
Maryland has never had as many horseshoe crabs as Delaware, in part because it doesn’t have the large, protected beaches. But in addition to the Bay Foundation’s beach, increased numbers of horseshoe crabs are turning up at Sandy Point State Park and at Terrapin Park in Kent Island. In Virginia, they have been spotted off Tunnels Island near Saxis.
Shawn Kimbro, a Kent Island fisherman, was shocked to find hundreds of them on a late-night bike ride to his local beach, Terrapin Park.
“I have seen them before, but never in the numbers that they are now,” he said. “There are so many this year, I’m even seeing them on the Matapeake boat ramp.”
Rodenhausen wondered if the recent efforts to clean up the waterways had spurred the horseshoe crab increase. Watermen, biologists and recreational boaters are reporting that parts of the Bay are clearer than they have been in recent memory.
It can’t hurt, but it’s more likely due to harvest restrictions, scientists say.
“We all agree that certainly implementing this harvest model, taking these reductions, all of this work that we do, it has to have been worth something,” Kennedy said.
Horseshoe crab mating season won’t be over until the end of June. But Michels, who was preparing for another weekend of surveys on the Delaware beaches approaching a full moon, said the results so far have been encouraging.
“It’s a great story,” he said, “and I’m so hopeful that here, very shortly, that we’ll be able to talk about a happy ending.”
IF YOU GO ….
Horseshoe crabs should be spawning on the beaches until about June 21, the last full moon of the month. The best place to see them are the beaches on Delaware Bay, which has more spawning horseshoe crabs than anywhere else in the world.
For an overview of the species and a great view of the beach, start at the DuPont Nature Center, run by the state, at 2992 Lighthouse Rd., Milford, DE 19963. It is open 10 a.m. to 4 p.m. Tuesday through Sunday. Nearby Slaughter Beach offers great viewing opportunities and is open to the public. Bowers Beach and Pickering Beach are also good observation points, according to Delaware officials.
- Category: Fisheries
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