Tens of thousands of horseshoe crabs from all over the East Coast climb like small army tanks from the Delaware Bay and onto soft, sandy beaches each spring, ready to spawn with females capable of laying 90,000 eggs a season.

They also carry within them a highly prized, copper-based, blue-colored blood that’s used worldwide for testing vaccines and medical devices for toxins. In fact, up to 750,000 horseshoe crabs were taken from waterbodies last year, and transported to labs. There, up to 40% of their blood was drawn by needles before they were released back into the wild.

Research has shown that up to 30% of horseshoe crabs tested can die as a result of the blood extraction process, say the Horseshoe Crab Recovery Coalition, though specific numbers are hard to track. The need for a worldwide vaccine for COVID-19 has stoked fresh worries about the steady decline of horseshoe crabs as more of their blood might be needed for testing, leading to more deaths and an impact on spawning. Horseshoe crabs that have had blood taken have showed less movement, a necessity for breeding and spawning to keep populations thriving.

“In a technologically advanced society, there has to be a better way,” said Eric Stiles, president and CEO of New Jersey Audubon.

Stiles has taken a lead role in the Horseshoe Crab Recovery Coalition, a group of 30 organizations that recently briefed congressional staff members on the issue. The coalition is urging that a synthetic alternative to blood be used instead.

"Fortunately a synthetic alternative exists that would conserve this iconic species without compromising human health,” Stiles said.

Though horseshoe crabs are native to the Mid-Atlantic, they are closely identified with the Delaware Bay, the part of the Delaware River estuary that borders New Jersey and Delaware before emptying into the Atlantic Ocean. Their eggs provide food for 11 migrating bird species such as the red knot, a federally threatened species.

They are not considered endangered, but the number of Atlantic horseshoe crabs has been declining since at least the 1990s, according to the National Oceanic and Atmospheric Administration, citing habitat loss and demand as commercial bait.

Horseshoe crabs are not really crabs but more distant cousins to spiders. They are not venomous or dangerous, and their ancestors date back 450 million years. Their blood contains Limulus Amoebocyte Lysate (LAL), which clots in the presence of bacteria and is used by researchers to detect toxins that could find their way into vaccines, needles, and medical equipment that go into human bodies.

That blood is valued at $15,000 a quart.

The coalition is in favor of greater adoption of recombinant Factor C (rFC), a synthetic alternative to the blood. It is already being used in the manufacturing of two marketed medicines, according to the coalition, and is recognized as an alternative by the European Pharmacopoeia, which helps to establish standards and protocols in the European Union.

The U.S. Pharmacopeia has yet to adopt a similar measure, and said in a statement that it supports investigating the use of rFC as part of an overall goal to move towards animal-free testing, but its mission is “first and foremost to protect patients and improve public health.”

“At this point in time, however, endotoxin tests using rFC do not benefit from the same level of real-world evidence as LAL” the statement said, adding that, “a lot is at stake. One adverse incident … could damage overall trust in vaccines or other injectables, already plagued by misinformation.”

The USP has a proposal that could lead to a pathway for use of rFC as an alternative, if it can be shown as comparable to LAL. The proposal is now in a public comment period.

The Horseshoe Crab Coalition calls the USP’s proposal "a lengthy and burdensome pathway.”

“The COVID-19 pandemic is likely to lead to major increases in the use of horseshoe crab blood, as the nearly 200 vaccines and over 60 injectable therapies in development for COVID-19 will all need to be tested multiple times for fever-inducing contaminants,” Elizabeth Baker, pharmaceutical policy program director of the Physicians Committee for Responsible Medicine, said in a statement. “As is often the case, policy is lagging behind the science. We must act now to remove unnecessary barriers to industry use of rFC.”

The coalition is asking members of Congress to urge the U.S. Pharmacopeia to acknowledge that rFC is equivalent to the product derived from horseshoe crab blood. It is also urging the FDA to review existing regulations and guidance.

The coalition also wants to see better regulation of the use of horseshoe crabs for bait, and the bleeding process.

New Jersey implemented a moratorium in 2008 of harvesting horseshoe crabs from May 1 through June 7 each year, and only one person carries a special permit to bleed crabs in the state. In addition, South Carolina limits the harvest of horseshoe crabs to biomedical bleeding.

Other states have no such protections. Yet, the horseshoe crabs are found from Maine to Florida. The Delaware Bay is the biggest spawning ground in the world for the horseshoe crab, so practices in other states influence spawning.

Stiles said horseshoe crabs are vital to the New Jersey economy. Tens of thousands of birders flock to Cape May starting in the spring to catch glimpses of migrating birds such as the red knots and ruddy terns that feast on the bay on their long journeys to the Antarctic.

“When you look at birding in Cape May,” Stiles said. “It is a multi hundred million dollar industry … if you go to the Delaware Bay to watch these horseshoe crabs and shorebirds, and part of your soul doesn’t melt, you’re not human.”