Email Writing Campaign to Better Protect Horseshoe Crabs in MA Waters.

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Watercolor by Kathy Miller

Horseshoe Crabs (Limulus polyphemus)

Horseshoe Crabs are a marine crustacean that has lived on planet earth for over 445 million years. This living fossil plays an important role in marine ecosystems and in human health. However, Horseshoe Crab populations are decreasing across the state of MA and more needs to be done to protect them. Learn about this amazing and ancient species and see how you can help protect the Horseshoe Crab in Massachusetts' waters.



Overview:

Horseshoe Crabs are bioturbators that dig-up bottom sediments in search of prey or when nesting in shallow water. The shell of the Horseshoe Crab is often covered in algae, slipper shells, and barnacles that hitch a ride on this slow-moving, tank-shaped animal. Horseshoe Crabs help control populations of various benthic invertebrates targeted as prey and they themselves are a food source for other marine animals. The fertilized eggs of Horseshoe Crabs are an important source of energy for many animals, including arctic nesting shorebirds like Red Knots and Ruddy Turnstones.

Spawning Season Brings Horseshoe Crabs into Shallow Water:

The Horseshoe Crab spawning season starts in April and continues through June. Adults move from deep offshore waters to shallow inshore waters where nesting occurs. Males follow females inshore and will try to attach to her back shell so they can be present when she spawns. Males are smaller in size than females and only 1 male can attach directly to her back. However, other males, called satellite males, crowd around this love-pair hoping to also provide sperm for egg fertilization.


Why are they in Trouble? 

Horseshoe crab populations are in decline in the coastal waters of Massachusetts due to a number of factors:

  • over harvesting by the commerical bait industry (eel, conch and whelk)
  • loss of spawning habitat due to sea level rise and armoring of our shorelines
  • use the biomedical industry for an essential medical safety resource (LAL)

The Bait Industry:

The bait industry is composed of local hand harvesters and offshore trawlers. Hand harvesters collect Horseshoe Crabs along shorelines during the spring spawning season, whereas trawlers catch crabs when participating in the mixed species trawl fishery in late spring through the fall in Nantucket and Vineyard Sounds. The bait industry is allowed to harvest thousands of Horseshoe Crabs for use in the commercial eel, whelk, and conch fisheries and can currently take up to 165,000 crabs each season. Although DMF has placed closures around the Full and New Moons during the spring spawning events, Horseshoe Crabs, including spawning females, can be taken at other times over the course of the season. 


The Biomedical Industry:

The biomedical industry harvest collects thousands of Horseshoe Crabs and bleeds them to extract a natural source of Limulus Amebocyte Lysate (LAL) from their blue blood. Since the 1970's, products in Horseshoe Crab blood has been used to ensure the sterility of medical equipment and other tools, including all injectable drugs (such as vaccines), medical equipment, and surgical implants. LAL is a protein coagulation system that detects contamination by dangerous bacterial toxins called endotoxins. There is an alternative or man-made derivative to Horseshoe Crab blood called recombinant Factor C or rFC for short. Studies have shown rFC to be just as effective as Horseshoe Crab LAL. This synthetic material, rFC, has been approved in over 60 countries, including the EU and China, but the US has not move forward with final approval.  

 

As a side note, lunar closures by DMF for bait harvesting and biomedical bleeding has not shown to be effective in managing this species. Research indicates that water temperature is a key environmental factor in spawning not lunar cycles. Therefore, DMF's current management scheme is outdated and in great need of revision. To read a 2016 study on this topic from the University of New Hampshire, click HERE.



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