Maryland Limits Horseshoe Crab Harvest to Feed Red Knots

This action will immediately increase the availability of horseshoe crab eggs to migratory shorebirds in Delaware Bay this May and June.

"The Department is responsible for the conservation and management of our natural resources," said Tom O'Connell, director of the DNR Fisheries Service. "We also recognize the increasing dependency of horseshoe crabs to Ocean City watermen and seafood processors, and believe this is a prudent action that balances these needs while ensuring future generations have the opportunity to experience the Delaware Bay phenomenon between horseshoe crabs and shorebirds."

The DNR conducted a technical analysis and reviewed public input on a range of management options, including closure of the female horseshoe crab fishery, before imposing this limit.

Maryland watermen, both horseshoe crab harvesters and conch and eel fishermen who use horseshoe crabs as bait, will be affected by this action but will retain their current harvest quota.

"This is a strong step in the right direction in ensuring more critically important horseshoe crab eggs will be on the beach when Red Knots stop to refuel on their long migration northward," said Darin Schroeder, vice president of conservation advocacy for American Bird Conservancy.

Red knots at Delaware Bay (Photo by Douglas Norton)

But scientific studies have shown that the number of available horseshoe crab eggs has dropped, leading the U.S. Fish and Wildlife Service to conclude that, "The primary factor threatening the red knot is destruction and modification of its habitat, particularly the reduction in key food resources resulting from reductions in horseshoe crabs."

Due to a 15 percent decline in red knot numbers at the species' wintering grounds in the past year, and a 75 percent decline from 1985 to 2007, the Fish and Wildlife Service has increased the listing priority for the species. Only 14,800 red knots were counted in 2007 at the species' primary wintering areas.

"Both the U.S. Fish and Wildlife Service and the U.S. Geological Survey have concluded that without greater conservation of horseshoe crabs, the eastern red knot rufa subspecies could be extinct within a decade," said Schroeder.

"Governor [Martin] O'Malley and the Maryland Department of Natural Resources are to be commended for taking this action, which we hope will ensure future generations of Americans will be able to see this magnificent bird like past generations have," he said.

In 1999, the red knot was listed as a threatened species in New Jersey under state law. As a result of the Red Knot Status Assessment in fall 2006, the U.S. Fish and Wildlife Service announced the red knot as a candidate for federal listing and the Committee on the Status of Endangered Wildlife in Canada recommended listing the red knot as endangered in April 2007.

In March 2008, New Jersey Governor Jon Corzine imposed a moratorium on harvesting horseshoe crabs in that state. "This moratorium will be held in place until the populations of both horseshoe crabs and red knots have returned to a level where they will be self sustaining as determined by the U.S. Fish and Wildlife service," the governor at that time.

Horseshoe crabs on a Delaware beach (Photo courtesy NOAA)

Although called a "crab," the horseshoe crab is actually closely related to spiders and scorpions. It is also one of the Earth's oldest creatures, having appeared 100 million years before the dinosaurs, according to the University of Delaware Sea Grant College Program. The largest population of horseshoe crabs in the world lives in Delaware Bay.

Along with the horseshoe crab's role as part of the coastal ecosystem, the blood of these crabs provides a valuable medical product. An extract of the horseshoe crab's blood called limulus amebocyte lysate, LAL, is used by the pharmaceutical and medical device industries to ensure that their products, such as intravenous drugs, vaccines, and medical devices, are free of bacterial contamination. No other test works as easily or reliably for this purpose.

The DNR's new horseshoe crab harvest action does not impact the biomedical industry as blood to produce the LAL test is removed from the horseshoe crabs, which are returned to the water to recover.

In shallow water, horseshoe crabs are collected by hand from a boat using a clam rake, and the animals are not injured during this process, according to the nonprofit Ecological Research and Development Group, a wildlife conservation organization whose primary focus is the conservation of the world's four remaining horseshoe crab species.

In deeper water, a dredge is used, and in this case, some horseshoe crabs do get injured, says the ERDG. "Injured crabs are released immediately and most will survive. It is quite common to find crabs with scars of old injuries that have healed," the group says.

Captured crabs are transported to the laboratory from the fishing pier by truck. During the bleeding process, up to 30 percent of a crab's blood can be removed. Research has shown that once returned to the water, the horseshoe crab's blood volume rebounds in about a week, ERDG says.

Besides LAL, a number of reagents and medically useful compounds have been discovered in the blood of the horseshoe crab, including a number of other proteins that show anti-viral and anti-cancer activity.

A new test for fungal infections, the G-Test, has been developed from horseshoe crab blood. This test is already in use in Japan and is expected to be licensed in the United States next year.

An endotoxin-neutralizing protein which has potential as an antibiotic and as an alternative endotoxin assay has been identified. This protein can be made synthetically, which might eliminate the use of live horseshoe crabs to produce the LAL reagent.

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