Building a Case for Horseshoe Crab Conservation

As I search for horseshoe crabs in the tall seagrass of the incoming tide at the sanctuary beach, it’s easy to imagine I’m in the warm waters of an ancient sea. I’m transported to the pages of the dinosaur-themed coloring books I filled in as a kid, even though 450 million years ago, when horseshoe crabs first made their debut, plants were just starting to make their way onto land, and dinosaurs were as futuristic as flying cars are now.

I continue my search, find two stray males, and wonder if our current era —the Anthropocene—could be the horseshoe crab’s last. How incredulous their ancestors would be to hear that the largest threat to their species is not an ice age or a meteor, but an upright biped unable to curb its consumption.

I squint up at a familiar silhouette on the horizon. It’s the harvester, scooping up horseshoe crabs with a long-handled net. It feels like he’s stealing from me. Every crab he gets is one that will not come to the beach next week to spawn, to pass on its DNA and get counted by survey volunteers. Instead, its destiny is to become bait for the whelk and eel fisheries. 

The harvester is acting perfectly within his rights. According to Mass Reg section 6.34, it is legal for permitted harvesters to collect up to 400 crabs for bait a day in Wellfleet Bay—as long as they are not taken during the week of the new and full moons when horseshoe crabs are supposed to be spawning in the highest numbers. For years the sanctuary and local shellfishermen have urged the state to impose a harvest moratorium to try to give the minuscule local horseshoe crab population a chance to recover. But despite our years of monitoring and data collection, the state so far has declined.

Spawning horseshoe crabs at Nauset Beach. The population here is recovering due to the Cape Cod National Seashore’s ban on harvests.

Down the road toward Orleans, in Pleasant Bay, it’s easier to find horseshoe crabs spawning. They appear in desperate, male-dominated hordes. It’s not an elegant affair—the males scuttle over each other, latch onto my boots or transect poles in a frenzied search for females laden with eggs. It looks like a large amount of horseshoe crabs, but I inherited a world missing 90% of its wildlife and I don’t really know what a lot of anything is.

In Pleasant Bay, horseshoe crabs are targeted for blood rather than bait. Unlike the bait harvesters, biomedical harvesters can take up to 1,000 horseshoe crabs a day. While the extraction of blood is designed to be non-lethal, it is estimated that up to 30% of horseshoe crabs don’t survive the process. Further, since females are bigger, they are more likely to be targeted, likely explaining the highly male-skewed sex ratio in this embayment. 

Their goal is to obtain Limulus amebocyte lysate, (LAL) extracted from horseshoe crab blood. Amebocytes (the A in LAL) are the invertebrate equivalent to white blood cells and are extremely adept at clotting around pathogens to provide defense. Health professionals use LAL to ensure the cleanliness of medical devices that come into contact with blood and injectables, including vaccines. Clearly, this stuff is useful but does the fate of modern endotoxin testing have to rest solely on a prehistoric and declining species?

Before horseshoe crabs were used for endotoxin testing, rabbits were the test subject of choice. Now, there are synthetic alternatives, the best known being recombinant factor C assay (rFC). This substitute has been approved in China, Europe and Japan, but not in the US. With more research and higher demand, synthetic options could eliminate the need for a biomedical harvest.

While horseshoe crabs are up against major hurdles, they are not without allies. Drive around the Cape long enough and you’ll see lawn ornaments in their likeness, statues of horseshoe crabs clinging to buildings, jewelry shaped like them, postcards with their image stamped on the front. Here at Wellfleet Bay, there are dozens of volunteers ready to dedicate their time to check the beach for them at high tide, willing to go out into dense marsh, down beat-up staircases, sometimes in the middle of the night, just to contribute to the study and conservation of this species.

Volunteers at Pleasant Bay preparing to survey for horseshoe crabs. A female is trailed by two males. (Photo courtesy of New England Coastal Wildlife Alliance).

There are many reasons to protect horseshoe crabs. One is so we can continue to benefit from their blood, and harvest them for commercial fisheries. Another is so we can marvel at the flocks of shorebirds in Delaware Bay who depend on their eggs to fuel their flights to the Arctic breeding grounds. Some find them worthy of saving for the chance to meet a living fossil. These reasons are all compelling, but my favorite reason to protect horseshoe crabs is also the simplest: because they were here first and we can.

The author, Abigail Costigan, holds a horseshoe crab with a broken tail or telson. Horseshoe crabs should never be picked up by the telson, which they use to navigate and to right themselves.

This post was contributed by Abigail Costigan, Wellfleet Bay’s horseshoe crab field coordinator.

8 thoughts on “Building a Case for Horseshoe Crab Conservation

  1. Barbara Bruell

    I have fond memories as a child at the beach on cape cod seeing the horseshoe crabs. It was always with a bit of fear based on less knowledge we would pick them up.

    As an adult on a visit back to the Cape I found a tagged horseshoe crab. I logged it into a database and found out that this crab had covered several hundreds of miles from where it had been tagged initially. It was an exciting bit of knowledge and it made for a memorable visit.

    1. Wellfleet Bay Post author

      Hi, Barbara, Thanks so much for your horseshoe crab memories. I think all of us as kids were a bit unnerved by horseshoe crabs and those “tails”! Isn’t it cool to find a tagged one? It’s great that you can find out so much about where the animal’s been and for how long.

  2. Kathleen Miller

    I was so encouraged by your commitment to these amazing animals. I heard the show as well and hoped many did. I often share my meager knowledge(and your piece here helped me learn more) about them with folks that are afraid of or mishandling them. I have been a member of ERDG Horseshoe Crab Conservation for many years, I am disappointed there is such pushback here on the Cape. I used to teach art to children and often did lessons about them for more people to understand and appreciate them. I share your passion.

  3. Carol Amato

    Hi Abigail!
    I was so happy to see your post today about horseshoe crabs! I was recently wondering if WB was still involved with conservation efforts since I hadn’t seen anything posted for awhile. I’m a member and for years (since the early 1990’s!) I’ve been involved with conservation efforts concerning the HSC in a number of ways: I volunteered with tagging and other activities at WB and presented HSC programs at the HSC Festivals (sadly, no longer a program…local citizens were so vitally concerned and vocal about this conservation and turned out in large numbers); was a member of the HSC Conservation Association for years (left for reasons of dismay discovering how political the HSC issue was . …along with the state and federal fisheries); wrote many articles in the Cape Codder and other media (under a pseudonym when fishermen made threatening calls to me since I advocated for HSC quotas!; had a decades correspondence with Dr. Carl Shuster who was my mentor for all things HSC…in later years he sadly did not support conservation efforts well; raised a HSC from it’s 2nd molt to 9 years…Shuster helped me with specifics such as sexing (a male, that may have died while molting male legs, and I helped him with raising horseshoe crabs!; corresponded often with Dr. Ruth Carmichael about her enlightening studies; joined the HSC Recovery Coalition a few years ago, and on and on.

    Unlike the other more southern States like New Jersey and Delaware, from what I can see, Cape Cod’s efforts in conservation of this threatened species seem meager at best. I may be missing something, but I think 2019 was the last effort Wellfleet Bay organized. The pandemic may have brought much to a halt, but not for the crabs that were being harvested by the fishermen and the the biomeds in Falmouth all along. I have read recently (April) that Cape Cod Associates has developed PyroSmart recombinant LAL Reagent for bacterial endotoxin testing although another synthetic C(rFC) that was not approved by the FDA awhile ago but accepted and used in other countries. You mentioned this in your excellent article. Any further developments?

    Is Wellfleet Bay intending to offer further public programs, continue research about sustainability and population status, follow-up with Cape Cod Associates about their role in conservation and track closely their take and treatment of the crabs and if and when the synthetic use will begin, if so. If only passion were enough to insure the sustainability of these amazing prehistoric creatures! And you have that passions, so WB is so lucky to have you! If you’d like, I would be happy to send you a couple of photos of my Horseshoe crab (the collection of molts and a photo of it molting as an adult. I also did many programs about this on and off Cape. Thanks you so much Abigail and sorry for giving you eyesore! I know Melissa well and if you mention my name, she will agree that if nothing else, I share your passion! So glad she is heading the helm.
    Carol Amato

    1. Wellfleet Bay Post author

      Hi, Carol! Yes, our spawning surveys continue every spring and we continue to make a case for at least a local moratorium on crab harvests. We’re also part of a larger group of conservation organizations working on behalf of promoting the approval and use of synthetic LAL. Just this week, WCAI Radio did a program on horseshoe crabs with author and horseshoe crab advocate Deborah Cramer and others to update the status of winning approval for greater use of synthetic LAL and other efforts to protect horseshoe crabs. Here’s a link to it:

      Thanks for your comments and Wellfleet Bay remains committed to protecting horseshoe crabs!


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