As the weather warms each year on Cape Cod, an ancient species older than dinosaurs crawls up just below the sandy shores to spawn. Then in the midst of their mass mating event, the unlucky ones are plucked up by fishermen and pharmaceutical companies alike: Horseshoe crabs as good for bait as they are for testing new vaccines using their bright blue blood.
But this year, horseshoe crabs in Massachusetts will return to uninhibited procreation. For the first time, the state will ban collecting the crabs during the animal’s spawning season.
Massachusetts’ protections for the crabs have long lagged behind other states with biomedical fisheries. The new ban will put Massachusetts on the other side of the spectrum with among the strictest regulations on horseshoe crab harvesting in the country. The controversial ban was approved Tuesday after a commission that represents the fishing industry gave its blessing; the regulation still awaits final approval by the governor, which is expected this spring.
The blood of horseshoe crabs, which are more similar to scorpions or spiders than crabs, is the main ingredient in an important pharmaceutical test to determine whether vaccines are safe to administer to humans. Their blood has been used to test vaccines for contamination since the 1970s because it naturally clots around harmful bacteria. An alternative synthetic test has been developed but has not yet been approved by US drug regulators for widespread use.
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Though the species, whose range extends from the Gulf of Maine to Florida, is not listed by US regulators as an endangered or threatened species, conservation groups warn that horseshoe crab populations are at risk both from the impacts of climate change and overfishing.
As glaciers melt and ocean water expands due to climate change, sea levels along the east coast are rising. For the more than 400 million years old species, often called “living fossils” due to the age of their existence, that means horseshoe crab habitat — salt marshes and intertidal sandbars — is shrinking.
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“They’re getting squeezed, now, by sea level rise,” said Mark Faherty, Cape Cod science coordinator for Mass Audubon, a conservation group. Faherty has studied the horseshoe crab for more than a decade. “There aren’t as many places to spawn.”
Recent survey data show the horseshoe crabs’ populations in 2023 declined on several beaches in Cape Code Bay, according to the Division of Marine Fisheries.
Biomedical fisheries have existed in Massachusetts since the 1970s, and the state produced a fifth of the Atlantic coast’s biomedical harvest in 2022, according to the Massachusetts Division of Marine Fisheries. Although the horseshoe crabs are released back into the wild after being drained of their blood, many die after being returned. The mortality rate is debated, but most researchers estimate that about 15 percent of bled horseshoe crabs ultimately perish.
Horseshoe crabs are also captured by fishermen who use them as bait to attract edible snails.
About 1.5 million horseshoe crabs were captured along the Atlantic coast in 2022, the most recent year for which data are available; just under half of those died, the Atlantic Marine Fisheries Commission estimates. More than 900,000 were captured for the biomedical industry and about 571,000 for bait, which, despite the smaller numbers captured, results in a higher number of crab mortalities. About 311,000 of the harvested horseshoe crabs came from Massachusetts.
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The Marine Fisheries Advisory Commission, which represents the commercial and recreational fishing industry, voted 6-1 on Tuesday morning, with one member abstaining, in favor of the ban on horseshoe crab harvesting from April 15 to June 7. State law requires that the advisory group of industry representatives approve any regulations on marine fisheries.
Last year, the advisory commission voted down a similar proposal after commission members voiced concern that the ban would financially hurt the biomedical industry and the sea snail, or whelk, fishing industry. Since then, one of the commission members who voted against the ban was replaced by Christopher McGuire, who works for the Nature Conservancy and voted in favor of the new restrictions. The commission members are appointed by the governor for terms of up to three years.
Biomedical industry groups asked regulators to exempt their harvest from the ban, but Division of Marine Fisheries director Daniel McKiernan decided against an exemption because capturing horseshoe crabs during their spawning season hurts their ability to procreate and he thought it unlikely that the industry’s annual harvest would be impacted by the ban.
The biomedical industry is allowed to capture up to 200,000 horseshoe crabs per year in Massachusetts.
Many bait fishers, some of whom capture the creatures by hand, have complained that the ban would financially impact their businesses and way of life.
“These impacts are inescapable when expanding spawning protections,” McKiernan wrote in his memo to the commission.
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He added, however, that the agency must balance current economic concerns with future ecological problems. He said during the Tuesday meeting that he supports using other species, such as the green crab, an invasive species to Massachusetts, to replace the horseshoe crab as bait.
Faherty, of Mass Audubon, wants Massachusetts to go further in its protection for the crab. The horseshoe crab is ecologically important for shore birds, which feed on its eggs, including the rufa red knot, a threatened species under the Endangered Species Act.
“Maybe [horseshoe crabs] aren’t going to go extinct tomorrow in Massachusetts,” Faherty said, but their numbers are well below where they are able to “play out their role in the ecosystem.”
Erin Douglas can be reached at erin.douglas@globe.com. Follow her @erinmdouglas23.