In 2013 John Tanacredi, an environmental sciences professor at Molloy College on Long Island, N.Y., received a call from a friend who worked at nearby John F. Kennedy International Airport. “You’ve got to see this,” he told Tanacredi, and sent him a photo of a cargo container filled with 600 dead horseshoe crabs. It was mid-July, and airport officials had opened the container because of a rotting stench.

It turns out the crabs were sent by a Vietnamese exporter to some fishermen in the U.S., to be used for bait. After seeing a decline in the horseshoe crab population on the eastern seaboard, fishing authorities there had imposed restrictions on harvesting crabs for bait. Importing them was a way around the regulations.

Fishermen are not the only ones pursuing the odd and primordial helmet-shaped creatures, however. The biomedical industry harvests hundreds of thousands of them each year because their rich blue blood contains a protein that thickens when it comes in contact with impurities. The crabs are bled for this substance, known as limulus amebocyte lysate, or LAL, because it can detect bacterial endotoxins, which can cause toxic hemorrhagic shock and severe diarrhea in people. Laboratories use LAL to test medical instruments, implants and some pharmaceuticals—basically, anything that contacts human blood. “It all comes down to this animal,” Tanacredi says.

LAL is so prized that a 2011 article in Wired magazine estimated a quart of it to be worth about $15,000 dollars. It is no surprise, then, that the number of crabs harvested by the U.S. biomedical industry jumped 86 percent from 2004 to 545,973 animals in 2013. There are currently no restrictions on how many the industry can take, because after technicians draw the blood they send the crabs back out to sea, where the animals supposedly recover.

That assumption is now being scrutinized. A growing number of researchers believe the biomedical industry is having a negative impact on the horseshoe crab population—either injuring them during blood harvesting or taking too much blood, which may be condemning the creature to die after being returned to the ocean. In Changing Global Perspectives on Horseshoe Crab Biology, Conservation and Management (Springer, 2015) scientist Thomas Novitsky wrote, “Evidence is accumulating that mortality of bled horseshoe crabs is higher than originally thought [29 percent versus 15 percent]; that females may have an impaired ability to spawn following bleeding and release; and that bled crabs become disoriented and debilitated for various lengths of time following capture, handling, bleeding and release.” Novitsky was CEO of Associates of Cape Cod, an LAL company in East Falmouth, Mass.
How big an impact the LAL industry is having on horseshoe crabs is unclear, because the companies do not have to publicly reveal exactly how many they harvest, and because it is difficult to tell how many crabs may eventually die once they are returned to the water. The Atlantic States Marine Fisheries Commission’s most recent survey shows that although the number of horseshoe crabs in the Delaware Bay region has stabilized, the female population is just a third of what the bay is capable of supporting, says Larry Niles, a biologist for several nonprofit conservation groups. And the populations along the coasts of New York State and New England continue to decline. “Nobody has ever argued that the crab was going extinct. What we’re talking about is the collapse of an ecosystem, because a key species has been reduced" extensively, Niles says.*

Drained of Blood

The labs claim they are not hurting the animals. John Dubczak, director of operations at Charles River Laboratories, an LAL facility in Charleston, S.C., says his firm uses best practices to assure the crabs are not injured during their harvest and that no more than 30 percent of their blood is removed. His firm harvests by hand, for instance, and does not pay for injured crabs, which gives his suppliers an economic incentive to handle them properly. “It reduces the injury, it reduces the stress, it’s better for [sustaining] the population, and it’s better for us,” he says, noting that the mortality rate for crabs used in his operation is just 4 percent. “One of my suppliers built a water slide to put the crabs back into the water. They love it!”

But Dubczak notes that 4 percent number pertains only to the handling and transportation of crabs to and from his facility. Conservationists believe mortality rates for the industry are at least 15 to 30 percent. They say that although bleeding operations report harvest numbers to their respective state environmental authorities, when they obtain bleeding permits—data which is then shared with the Atlantic fisheries commission—they are not required to publicly release such statistics. The other four bleeding operations in the U.S. did not respond to requests to be interviewed. “There’s not very good science-based information on the mortality of the crabs. I’ve see figures range from 15 percent to 40 percent but nobody has a really good handle on that,” says Michael De Luca, senior associate director at the Institute of Marine and Coastal Sciences at Rutgers University.*

Female horseshoe crabs lay their eggs in the sand, and the males cover them with sperm. Credit: Caren Chesler

The Atlantic fisheries commission, which manages fishery resources along the east coast, already has best practices spelled out, but they have neither enforcement nor surveillance capabilities. Furthermore, Niles says, “The LAL bleeding is done so secretly, nobody knows how many they harvest.” The only claims that can be verified, he says, are mortality rates of up to 30 percent, based on independent assessments of the methods used. “And that doesn’t account for the losses that come from dredging crabs at an industrial level, and then taking them to labs for bleeding.” He adds that some companies may be selling crabs for bait instead of putting them back to sea.

Injury can also happen in various ways. Crabs being bled by the labs spend from 24 to 72 hours out of the ocean, says Chris Chabot, professor of neurobiology, physiology and behavior at Plymouth State University. He wants to know if that’s too much time. “As you might imagine, being an aquatic organism, that probably has an impact on their viability, their health, their mortality, perhaps—as well as their ability to bounce back after this bleeding,” he says. The animals are also not very active for weeks after they are bled, and they are also more susceptible to disease because certain blood factors have been taken out.

It’s not yet clear whether the process affects their reproduction, either. “I don’t know if anyone’s measured the number of eggs laid after they’ve been bled,” says Jane Brockmann, a biology professor emeritus at the University of Florida. “You’d have to find [recently bled] animals amongst the millions of them that are out there.”

Researchers at the University of New Hampshire and Plymouth State are trying to do just that. They conducted a study in 2014 that replicated the bleeding process in their lab and found the crabs exhibited behavioral and physiological deficits for two weeks after they had been bled, such as moving less frequently and with different patterns and rhythms, indicating they may have been disoriented.

In a new study launched last month the researchers will bleed about 60 crabs and observe how the animals behave when subjected to the three main stress factors they would experience under conditions in the biomedical industry: the amount of blood taken, the amount of time spent out of water and the degree of temperature fluctuations. The crabs will first be observed in lab water. They will then be put back into the ocean with tiny transmitters attached to their shells that will give off an acoustic beep every 45 seconds to let researchers know a crab’s depth and how active it has been in the prior 45 seconds. The experiment will be repeated a year later with another 60 crabs.

The group believes that adjusting stress factors will help ameliorate negative effects. For example, “The biomedical industry reports that they remove 30 percent of the crab’s blood. We’re wondering, if you bleed them less, might it impact them less?” Chabot says. He also noted that when his group bled crabs in his lab, they generally stopped well short of 30 percent because the blood flow had dropped to a trickle. “We don’t open up another hole to get more blood. Who knows how many holes [the labs] open,” he says. Under the industry’s shroud of secrecy, scientists fear the worst. For example, stories are circulating that labs use suction devices to obtain more blood and that lab technicians hold contests to see who can obtain the most blood.

In Danger of Becoming Endangered

In the meantime a group of scientists plans to ask the International Union for Conservation of Nature, which sets global standards for species extinction, to move the American horseshoe crab’s status one notch closer to extinction on its Red List of Threatened Species categories—from Near Threatened to Vulnerable. Their report will be submitted to the union’s World Congress in Hawaii in September.

They plan on writing similar reports for several Asian species, which are already disappearing in some countries where they once thrived. “I wouldn’t be surprised if they weren’t on the Red List very soon. The [Asian] populations are significantly declining,” says Dubczak of Charles River, which has an operation in China called Zhanjiang A&C Biological, Ltd. “Between pollution, loss of habitat and the animals being eaten in Asia, their populations are under a tremendous amount of stress.”

The Ecological Research & Development Group, a nonprofit conservation organization that focuses on the world’s four remaining horseshoe crab species, wrote on its Web site: “The three Asian species of horseshoe crabs are in decline. Loss of habitat and exploitation are major factors, as are the methods used and number of horseshoe crabs collected for the endotoxin-detection industry.” The crabs simply are not showing up anymore on certain beaches—and crabs tend to go back to the same site year after year. Glenn Gauvry, president of the group, wrote in an e-mail response to Scientific American, “The limited harvesting numbers available suggest a drop in availability from 600,000 [crab] pairs five to 10 years ago to less than 100,000 pairs currently.”

His group fears that if horseshoe crabs disappear in Asia, companies producing bacteria identifiers there will set their sights on horseshoe crabs from the U.S., thereby depleting the U.S. population further. And if there’s one thing the cargo container at JFK airport proved: although some species disappear from an area because of environmental pressure, others leave by plane. Conservationists would prefer U.S. horseshoe crabs were not so well-traveled.

*Editor's Note (6/13 & 6/22/16): These paragraphs were edited after posting on these dates to clarify several statements as well as correct statistical information.