American Oceans

Are Horseshoe Crabs Endangered?

The horseshoe crab has a unique, iconic look with its rounded body and long tail. It doesn’t look like your typical crab, with pincers and spider-like legs, but it’s one of the most successful organisms in the history of the world.

Horseshoe crabs were horseshoe crabbing 200 million years before the dinosaurs ruled the world, and they’re still around. However, human activity, overfishing, and disappearing habitats currently threaten their continued existence. But, are horseshoe crabs considered endangered?

Depending on the list you consult, they are either endangered or vulnerable. No matter what name you attach to it, the horseshoe crab’s habitats and existence are being directly impacted due to the onset of the Anthropocene era.

Horseshoe Crabs Conservation Status

While the World Wildlife Fund doesn’t list the horseshoe crab on its list of endangered species, that list isn’t the end-all, be-all. However, the International Union for Conservation of Nature (IUCN) does, and the IUCN takes the horseshoe crab’s plight pretty seriously.

The IUCN has mounted a global effort to educate the public on the importance of the horseshoe crab to biodiversity, local habitats, and humanity. Education as to the significance of the horseshoe crab forms a large part of this effort, as well.

We live in a world where we have only four species of horseshoe crabs left, one of which is the American horseshoe crab (Limulus polyphemus), which lives in the Atlantic near the east coast of the US and also maintains a significant presence in the Gulf of Mexico. 

The Wetlands Institute, based in New Jersey, goes past horseshoe crabs in spelling out the need for conservation efforts. Birds like the red knot (Calidris canutus) and the sanderling (Calidris alba), among others, enjoy a kind of symbiotic relationship with the horseshoe crab, feeding on their eggs and otherwise interacting with the arthropods- enough that the decrease in the population of horseshoe crabs affects the population of those shorebirds proportionally. 

Conservation programs include efforts to harvest fertilized eggs to hatch them without the risk of the hatchlings getting eaten in their infancy.

Another effort by the Horseshoe Crab Recovery Coalition (HCRC) includes pushes for legislation and other awareness programs to help push the idea of the horseshoe crab’s importance to the environment, local biospheres, and the medical industry— that last one a bit of a double-edged sword.

Why Are Horseshoe Crabs Endangered?

The no-brainer answer to this question is the same as for why anything is endangered— habitat destruction figures mainly in almost every species and the reason behind their endangerment. However, the horseshoe crab is also something of a victim of its own utility.

Their blood is bright blue. Past that neat-o factor, the blood has clotting properties that make it ideal for testing vaccines. In fact, the development of the COVID-19 vaccines included testing with horseshoe crab blood.

Immune cells specific to the horseshoe crab live in that blood, and these particular cells are susceptible to harmful bacteria. For this reason, the blood is perfect for testing vaccines. That’s great for people. We eliminated smallpox, saved millions from polio, and came up (in record time) with a vaccine that would fight a global pandemic if everyone would take it.

Horseshoe crabs being bled
Photo Credit: Jacqui Frank and Abby Tang from Business Insider

However, since the development of all those vaccines takes horseshoe crab blood, and since horseshoe crabs need their blood for their own purposes, the utility of their blood has helped thin their numbers. 

Some people might also think that since it’s a crab, it must be getting eaten, too. This idea isn’t entirely accurate, but it’s not far off the mark. A delicacy in many Asian countries, horseshoe crab dishes actually consist of the crab’s eggs, known as roe. There’s not much meat on the crab itself, but many cultures love the eggs.

When you eat a fish, you remove that one fish from the river or ocean. When you eat a horseshoe crab’s eggs, you’re preventing hundreds of horseshoe crabs from being born in the first place. Since the birds mentioned earlier feed on many of those eggs, you’re taking food out of their beaks, as well.

How Can We Help Horseshoe Crab Populations?

Sometimes, horseshoe crabs get washed up on shore and end up turned over on their backs. While it may seem scary (with it’s long tail and spiked shell), you can help that one horseshoe crab by gripping the sides of its shell and turning it back over since they can’t always right themselves of their own accord. You won’t save the species by doing this, but you’ll save that one, and that’s something.

horseshoe crabs flipped on their backs

Larger-scale efforts include throwing in with conservation efforts and organizations like the HCRC, which works with state governments along the Atlantic coast to develop fishery management plans. These plans intend to regulate fishing techniques and methods to cut down on collateral damage to the horseshoe crabs and to prevent the crabs themselves from being overfished.

Several governments have enacted laws to help protect the horseshoe crab populations in Asia, but there is some question about the efficacy of those laws’ enforcement. Calling on governmental officials to exert diplomatic pressure on these countries’ governments is one way to help conserve these living fossils in other parts of the world.

While Americans can work hard to make a difference in their neck of the woods, remember that three of the four horseshoe crab species live in Asian waters. 

Final Thoughts

Like just about any extinction, the extinction of the horseshoe crab would create a ripple effect. Shorebirds who depend on the horseshoe crab would be adversely affected, some facing extinction themselves in the event of the disappearance of the horseshoe crab.

Human activity negatively affects the planet and its environment, adversely impacting biospheres worldwide. As our presence on the earth continues to harm it, efforts to save disappearing species like the horseshoe crab become more and more critical. 

Even if we don’t care about the environment and biodiversity, when the horseshoe crab is gone, its blood will be gone, and medical testing will get more difficult as a direct result.

Want to learn more about Horseshoe Crabs? Click here for out Fact & Information Guide on this species.

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