Horseshoe Crabs Stock Status: Sustainable, Flourishing in Southeast
The biomedical industry and ongoing conservation efforts continue to be a positive attributing factor to horseshoe crab sustainability
The recently published 2019 Atlantic States Marine Fisheries Commission (ASMFC) reports that the Atlantic horseshoe crab (HSC) is either stable or flourishing in most Atlantic state coastal waters. The Assessment is based on harvest data, trawls in known HSC habitats, surveys on spawning beaches, and other conducted scientific marine studies.
The 2019 Horseshoe Crab Benchmark Stock Assessment and Peer Review Report found that HSCs in the Southeast and Delaware Bay region are thriving and abundant. Importantly, the Assessment found no evidence of adverse effects upon either HSC, or migratory birds that feed on HSC eggs, from Limulus amoebocyte lysate (LAL) production, which the Commission refers to as biomedical use.
This is good news for both biomedical manufacturers and fisherman who have worked hand in hand to conserve these ancient creatures. LAL firms have a responsibility to produce >70 million test units annually for assuring the safety of parenteral products. Biomedical firms should use all possible conservation measures to ensure the continued availability of healthy crab populations. The net effect of the biomedical industry for horseshoe crab sustainability is positive because of nearly 50 years of consistent and unique conservation efforts. It also contradicts the unproven claims circulating that LAL production threatens, kills, or harms the horseshoe crab.
Additionally, the Assessment and Peer Review Report’s findings found that the bait fishery and discards are the major threats to the horseshoe crab from commercial ventures. Although mentioned superficially in the previous Stock Assessment of 2013, the current assessment now states that the magnitude of horseshoe crab discards in the various marine fisheries is potentially the most important uncertainty and highest priority for research. In fact, discard mortality may be comparable to or greater than mortality from all other sources.
Discards include loss as bycatch, when HSCs are inadvertently harvested during trawls for another species. For decades, horseshoe crabs were held in low esteem by commercial fishermen because the HSCs would tangle nets during trawling operations and could crush the shell of a modest-size clam. HSC use for eel, whelk, and conch bait was therefore considered the "perfect solution" for ridding Northern Atlantic waters of this "pest."
For a short period, the Commonwealth of Massachusetts actually paid a bounty for dead crabs.1 It was also past common practice among fishermen in South Carolina waters to destroy HSCs brought up in shrimp nets in order to minimize this nuisance. These destructive practices were abandoned in South Carolina when fishermen became informed of their value to man and animal kind and as a source of safe parenteral and medical device manufacturing.
The important message from the ASMFC’s most recent assessment is that the loss of HSCs due to LAL production (biomedical) is insignificant when compared to the major threats of commercial fisheries and loss of habitat. The LAL industry observes that >90% of collected crabs survive when good management practices are followed, and HSCs are returned promptly to the sea. Mortality does not occur during the LAL-related bleeding process of donor crabs, which is analogous to human blood donation. Rudloe studied the impact of bleeding on a large number of crabs in a Florida bay and estimated that bleeding increased the risk of loss by about 10%.2 The Stock Assessment considers this number trivial in comparison to other HSC threats.
The LAL industry, as well as ASFMC conservation efforts, have played a major role in sustaining the horseshoe crab in addition to educating the public on the value of the crab’s blood to our healthcare industry. Bang and Levin3 used catch and release from the beginning of LAL production. Cooper established LAL capability at the FDA's Biologics group in 1971, and led them to require all LAL producers to return bled crabs to the sea as a condition for licensing.4 South Carolina passed legislation in 1991 to protect horseshoe crabs by banning commercial bait fishery.5 ASMFC created a Fisheries Management Plan (FMP) in 1998 that set state-specific limits for harvesting HSCs.
The biomedical industry was exempted from ASMFC harvest limits for horseshoe crab because of low mortality and the critical need to assure the safety of injectable medications and implanted medical devices. States near the Delaware Bay have also enacted regulations to limit harvesting of female HSC. The ASMFC sponsored a meeting of state marine resource leaders and scientists from biomedical firms to write Biomedical Best Management Practices (BMPs) for LAL firms.6
Horseshoe crabs thrive where LAL is produced and baiting is banned. This positive sustainability can and will continue through partnered efforts of industry scientists, commissions, and ongoing education of the public.
- Novitsky T. 1984 Discovery to commercialization: the blood of the horseshoe crab. Oceanus. 27:13-18.
- Rudloe A. 1983. The effect of heavy bleeding on mortality of the horseshoe crab, Limulus polyphemus, in the natural environment. Invert Pathol. 42:167-76.
- Levin J and FB Bang. 1964. The role of endotoxin in the extracellular coagulation of Limulus blood. Johns Hopkins Hosp. 115(3): 265-274.
- Cooper JF, DH Hochstein, EB Seligmann. The limulus test for endotoxin (pyrogen) in radiopharmaceuticals and biologicals. Bull. Parent. Drug Assoc. 26:153-162.
- South Carolina Department of Natural Resources. 2012. South Carolina Horseshoe Crab Fishery and Management Program Compliance Report for the Year 2011. http://www.dnr.sc.gov/marine/mrri/pubs/SCComplianceHSC2011.pdf.
- 2011. Horseshoe crab biomedical ad-hoc working group report. www.asmfc.org/uploads/file/biomedAdHocWGReport_Oct2011.pdf. Accessed May 2018.