What is a Horseshoe Crab Worth?

Zack Royle, ​Habitat Restoration Manager

In 1588, Thomas Harriot published his Briefe and true report of the new found land of Virginia (as North Carolina was known at the time). It became a huge hit in Europe and largely shaped the European ideal of Native Americans for hundreds of years. Even today, it serves as one of our best accounts of how coastal Algonquians lived just after contact with Europeans. In a section on foods eaten by local tribes, Harriot provides the first European account of Atlantic horseshoe crabs (Limulus polyphemus) or Seekanauk: “ a kinde of cruftie shell fishe which is good meate, about a foote in breadth, hauing a cruftie tayle, many legges like a crab; and her eyes in her backe. They are founde in shallowes of falt waters; and fometime on the shore.” Later, in describing how coastal Algonquians fished, he notes that because they lack iron and steel, they make their fishing spears with "the hollowe tayle of a certaine fishe like to a fea crab” The image of a horseshoe crab can be seen in the accompanying drawing of the 1590 edition (Figure 1). 

Figure 1. John White watercolor of Coastal Algonquians fishing. This image would be translated to engravings by Theodor de Bry and included in the 1590 edition of Harriot’s book. Note the horseshoe crab in the lower right.

Based on Harriot’s account, it is likely that pre- and early contact Algonquians in Coastal Carolina were eating horseshoe crabs for meat (at least occasionally) and using their telsons to fashion points on their fishing spears. In conservation biology, we refer to this as direct use – tangible foods or services that we use directly – and the value they provide as direct benefits. In the 1600s, Samuel de Champlain noted that Native Americans along the Maine coast were using dead horseshoe crabs to fertilize their corn fields – another direct use – and this practice was likely adopted by farmers in the Delaware Bay region in the 1800s, who also fed horseshoe crabs and horseshoe crab eggs to their hogs and chickens. In the latter 1800s and early 1900s, this process became more industrialized with factories springing up around Delaware Bay processing millions of crabs each year into fertilizer. Dwindling numbers of horseshoe crabs and the advent of synthetic fertilizer in the 1960s led to the cessation of these activities in the 1970s (Kreamer & Michels, 2009).
 
There have been other direct uses of horseshoe crabs in recent history. By the late 1800s, horseshoe crabs were being harvested as bait for American eels (Anguilla rostrata) and, later, for whelk (Busycon spp.) (Kreamer & Michels, 2009). Beginning in the early 1900s, the horseshoe crab was used as a model for studying how the eye and brain process visual information, research that contributed to Nobel Prize-winning discoveries on visual physiology in the 1960s (Barlow, 2009). An even more consequential discovery came in the 1950s, when scientists found that horseshoe crab blood clots in the presence of bacterial endotoxins. This observation led to the development of the Limulus Amebocyte Lysate (LAL) assay, which since the late 1970s has become the standard test for detecting bacterial contamination in injectable drugs, vaccines, intravenous fluids, surgical implants, and many other sterile medical products (Levin, 1985). As a result, virtually everyone who has received an injection, infusion, or implant over the past half century has benefited from horseshoe crabs.
 
For nearly four centuries, people valued horseshoe crabs primarily for what could be taken from them. Today, scientists increasingly recognize that their greatest value may lie in the ecological processes they support while alive. Spawning horseshoe crabs in Delaware Bay fuel one of the world's largest shorebird migrations, and their eggs also feed numerous fishes, crustaceans, worms, and other invertebrates, creating a massive seasonal pulse of energy in the Delaware Bay ecosystem. This directly supports ecotourism and recreational and commercial fisheries that can generate substantial monetary value (Edwards et al., 2011). Because this value comes from supporting ecological processes rather than through the direct use of horseshoe crabs, we refer to them as indirect benefits. Additional benefits are derived, for some, by just knowing horseshoe crabs (and the species that depend on them) exist. This is referred to as existence value.
 
Recognizing indirect and existence values has fundamentally changed how people approach conservation and management. Horseshoe crabs are no longer thought of as simply a harvestable resource, but a keystone species that supports the functioning of a healthy Delaware Bay ecosystem that, in turn, supports Delaware Bay communities. We’ve gone from creating value by extracting horseshoe crabs, to generating value by protecting them. To this end, for more than a decade, the American Littoral Society (Society) has been restoring spawning beach habitat for horseshoe crabs, with an upcoming restoration project at Kimbles beach scheduled for 2027. In addition, the Society has supported continued restrictions on horseshoe crab harvest and promoted the use of a synthetic LAL alleviating the need to catch and bleed crabs.

​What is a horseshoe crab worth? The answer depends on who you ask, and when. Over the last four centuries humans have valued horseshoe crabs as food, tools, fertilizer, bait, biomedical resources, and more recently, the foundation of an incredible coastal ecosystem. As we move further into the 21st century, our challenge is not only to continue to protect horseshoe crabs, but to continue discovering and communicating the many ways they benefit coastal ecosystems and communities.

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 (For those interested, Thomas Harriot originally traveled to North Carolina in the summer of 1585 as part of a contingent of men sent by Sir Walter Raleigh of England to colonize Roanoke Island on behalf of Queen Elizabeth I. This new colony would serve as a staging point from which to search for gold on the mainland, raid Spanish ships along the coast, and establish a potential trade route to the Pacific – years earlier, Verrazzano had mistakenly described Costal Carolina as an isthmus like Panama. Harriot, an English scientist and polymath – he made huge advances in navigation, pioneered binary notation, and may have invented the < and > signs – was one of the men on the trip. While he was there, he visited multiple Coastal Algonquian tribes and recorded their way of life. John White, an artist, was also on the trip and painted the watercolors that were incorporated into the second printing of Harriot’s book (Lawler, 2018)
 
Raleigh’s colonization attempt failed. Fraying relations with local tribes led to dwindling food supplies – the colonists were almost entirely dependent on trade with the native tribes for food – and outright hostilities, and in 1586, the colonists were rescued by Sir Frances Drake, who had been raiding Spanish ports in the Caribbean. A second colonization effort was attempted in 1587, this time with men, women, and children, and a larger focus on agriculture. It also failed; however, there's some mystery about what happened to it. It is famously known as The Lost Colony.

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References:
 
Barlow, R. (2009). Vision in Horseshoe Crabs. 10.1007/978-0-387-89959-6_13.
 
Edwards, P. E. T., Parsons, G. R., & Myers, K. H. (2011). The economic value of viewing migratory shorebirds on the Delaware Bay: An application of the single-site travel cost model using on-site data. Human Dimensions of Wildlife, 16(6), 435–444. https://doi.org/10.1080/10871209.2011.608180
 
Kreamer, G., & Michels, S. (2009). History of horseshoe crab harvest on Delaware Bay. In T. J. Tanacredi, M. L. Botton, & D. R. Smith (Eds.), Biology and conservation of horseshoe crabs (pp. 299–313). Springer. https://doi.org/10.1007/978-0-387-89959-6_19
 
Lawler, A. (2018). The secret token: Myth, obsession, and the search for the Lost Colony of Roanoke. Doubleday.
 
Levin, J. (1985). The history of the development of the Limulus amebocyte lysate test. Progress in Clinical and Biological Research, 189, 3–30.