Two Iconic Delaware Bay Species are in Trouble
The rufa red knot — a shorebird and spring visitor to Delaware Bay shores during migration — is listed as “threatened” under the Endangered Species Act. Some sources report that red knot numbers have declined by 94% over the past 40 years. One reason cited for the listing is the continuing overharvesting of horseshoe crabs for bait and biomedical tests.
Horseshoe crab eggs are critical food for red knots as they undertake one of the longest annual migrations in the avian world. The red knots’ journey of 9,000-plus miles begins in mid-February at the southern tip of South America. By mid-April they reach Brazil, and by the middle of May they arrive at the Delaware Bay, where horseshoe crabs have laid their eggs for eons. The red knots’ survival depends on the abundance of horseshoe crab eggs in the Delaware Bay; this migration stopover is the bird’s last chance to gain sufficient energy reserves to reach the Arctic for its breeding season.
As living fossils, horseshoe crabs have existed unchanged for an estimated 445 million years, from well before the dinosaurs. They may be resilient, but it often takes human intervention to turn them over when they’re belly up on the beach with 10 legs grasping for the sky.
The Common Sense article, “Horseshoe Crabs and Red Knots are in Peril,” described the importance of the horseshoe crab as a critical biodiversity link in the Delaware Bay. Their hard shells serve as microhabitats for other species, such as sponges, mud crabs, mussels, and snails. Their nutritious eggs are needed for migratory red knots and other shorebirds, fish, and wildlife.
The world’s largest springtime spawning population of horseshoe crabs is found in the Delaware Bay. Concerned about overharvesting, 23 organizations are petitioning the federal government to list the horseshoe crab as an endangered species under the Endangered Species Act.
Threats: Harvesting, Environment, and Counting
Horseshoe crab blood contains a rare clotting agent, limulus amebocyte lysate (LAL), that is critical for the safe development of biomedical devices and injectable drugs through bacterial endotoxin testing. About 500,000 horseshoe crabs are collected from marine populations in the United States annually. They are bled in biomedical labs and returned to the water. The mortality rate for bled and released crabs is 8-20%.
Environmental threats to the horseshoe crab include oil spills and other pollution, habitat loss from coastal development or shoreline alterations to prevent erosion, other human disturbances, and sea level rise due to climate change. Coastal development and climate change have encroached on areas where horseshoe crabs lay their eggs and mature horseshoe crabs have to spawn further and further above the tide line.
The Atlantic States Marine Fisheries Commission (ASMFC) recently made a controversial change to how to measure the horseshoe crab population and determine annual harvest limits. A U.S. Fish and Wildlife Services analysis and an independent peer review by experts claim that the changes reflect “the best available science.”
Conservation groups disagree and contend the revisions “will generate significantly higher horseshoe crab population estimates” and thus permit the harvesting of females, that hasn’t been done in a decade. “With the red knot on the very edge of extinction, now is the time to double down, not diminish, horseshoe protections,” said Defenders of Wildlife’s Christian Hunt.
Other conservation organizations — Earthjustice, New Jersey Audubon, Delaware Audubon, and the Delaware Center for the Inland Bays — have also spoken out against revising how to measure to the Bay’s horseshoe crab population.
In a News Journal article, the conservationists wrote, “The commission claims sophisticated computer modeling supports the counterintuitive conclusion that harvesting more crabs, including females, would not harm the horseshoe crab population or the red knots that depend upon the crabs’ eggs. But it would be risky to reopen a female bait harvest and add further mortality to the population.”
Some Progress
A South Carolina lawsuit brought by several environmental groups against the South Carolina Department of Natural Resources and Charles River Laboratories — a multinational biomedical company that provides the pharmaceutical industry with more than half its supply of LAL — was settled in 2023. For the next five years, horseshoe crab harvesters will be banned from 30 island beaches, prohibited from keeping female crabs in ponds away from the shore, and required to report their harvest locations. An independent company will oversee compliance with these rules.
U.S. Pharmacopeia, the regulatory body charged with setting national medication safety standards, announced a proposal to make it easier for companies to use non-animal-derived reagent tests, i.e., synthetic alternatives to LAL. This is expected to take effect early this year. Most of the East Coast bleeding companies now sell non-animal-derived reagent tests, synthetic alternatives to LAL.
The Recovering America’s Wildlife Act would provide federal funding for the conservation or restoration of wildlife and plant species. The bill was introduced in 2021 and passed the House of Representatives in 2022, but needs to restart the legislative process with the new Congress. If passed, the bill would provide up to $1.4 billion annually to states and territories to implement their wildlife action plans to include helping recover endangered species and prevent at-risk wildlife from becoming endangered.
Delaware’s senior U.S. senator, Tom Carper, signed onto the act and expects $11.5 million will go to Delaware’s Department of Natural Resources and Environmental Control, which has listed the red knot among the 692 species it will prioritize aiding.
Jessica Clark is a graduate of the University of Maryland School of Journalism. After a 30-year career as a Public Information Specialist and photojournalist for several federal agencies, she retired to Georgetown, Del. She restored former Governor John Collins’ 1790s home on Collins Pond and is a Sussex County Master Gardener.
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