Crabs at the crossroads of science and survival

Horseshoe Crabs – George Williams

Once there was a superabundance of horseshoe crabs; armadas of females blanketed the beaches of the Delaware Bayshore.

Through the 1990s, New Jersey’s horseshoe crab breeding and coinciding red knot shorebird migration was a spectacular natural phenomenon. “On the sand, there were around 50,000 horseshoe crab eggs per square meter,” says Larry Niles, biologist and co-creator of the Horseshoe Crab Recovery Coalition. “And the Delaware Bay shorebird stopover was one of the biggest in the world.” Today, horseshoe crab egg densities are down to 10,000 per square meter, a 90 percent decline over just three decades.

The phenomenon has become a whisper.

In the early 2000’s, the Atlantic States Marine Fisheries Commission and the State’s Marine Fish Agency allowed an overharvest of horseshoe crabs for use as bait. In the years that followed, regulatory agencies allowed anywhere from 1-to-2 million crabs to be harvested per season.

Conservationists across the eastern seaboard gathered in protest. But the agencies responded by implementing regulations that had no real impact. Despite an eventual New Jersey ban on harvesting crabs for bait, “the populations have never recovered,” says Niles.

The unfathomable losses led Niles and others to band together to protect the ancient creatures that hold the key to reversing the dramatic decline in shorebird populations. He pulled together the state’s leading scientists, and in 2018, the Horseshoe Crab Recovery Coalition was formed.

The importance of horseshoe crabs cannot be overstated. The crabs have remained largely unchanged over the past 450 million years! These living fossils hold together a complex web of relationships in the ecosystem – a critical link in coastal biodiversity. Every spring, horseshoe crabs lay millions of eggs. When females are abundant, they lay more eggs than can fit deep in the sand, resulting in floating eggs that will never hatch but instead feed shorebirds, fish, turtles, and other wildlife. Without the excess eggs, New Jersey’s migratory shorebird population is in peril.

The relationship between horseshoe crabs and red knots goes back 60 million years; the birds rely heavily on crab eggs as migratory fuel. Red knots are federally protected under the Migratory Bird Treaty Act and are listed as Endangered or “Near Threatened,” depending on the state. Threats to red knots include direct effects from climate change, coastal development, reduced food availability at stopover points, and disturbance by vehicles, dogs, drones, planes, and boats. A staggering 94 percent have disappeared.

In the 1960s, scientists discovered that horseshoe crabs’ blue blood clotted in the presence of bacterial toxins. Since vaccines, drugs, and medical devices have to be sterile, a better toxin-detection system means less contamination risk for patients. Fishermen soon started collecting and selling the prehistoric animals to be bled for medical purposes.

According to Niles, the bleeding industry is completely unregulated. The numbers of crabs being impacted is startling. Throughout the region, some 1.1 million horseshoe crabs were caught for the biomedical industry in 2023.

For decades, horseshoe crabs have been taken from their natural habitats, loaded into trucks and delivered to bleeding facilities. Up to 50 percent of their blood is drained and there is no enforcement around how the crabs are handled or regulations about when or how they are released in their diminished state.

But the Horseshoe Crab Recovery Coalition is pushing pharmaceutical companies in a new direction. A synthetic version of the blood was created, and for two years the Coalition has been working to shift the industry towards the synthetic alternative. This is encouraging news in the fight to bring back the crabs and their bird brethren.

Unfortunately, companies are not required to switch to the safer – and more cost-effective – synthetic and change in the industry is very slow. “We now have 10 companies in various stages of switching,” says Niles, noting that they approached over 50. “It’s going to be a gradual transition.”

“We are trying to gain power by bringing everyone together,” he says. The Coalition isn’t focused on keeping a few token horseshoe crabs and red knots from going extinct, it wants to help nature rebuild the once-incredible Delaware Bay phenomenon. If they succeed, they will have brought back one of the most amazing and enduring displays of nature in New Jersey.

To join and support the Horseshoe Crab Recovery Coalition, please visit hscrabrecovery.org/.

To learn more about how you can help preserve New Jersey’s natural resources, visit the New Jersey Conservation Foundation at www.njconservation.org or reach out to us at info@njconservation.org.