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How the fate of a shorebird is connected to the fate of the horseshoe crab

Red knots feed on the eggs of horseshoe crabs that come ashore in May on Delaware Bay.
Gregory Breese/USFWS
Red knots feed on the eggs of horseshoe crabs that come ashore in May on Delaware Bay.

The lowly horseshoe crab – due to laziness or extreme stubbornness, somehow it hasn’t managed to evolve perceptibly in over 400 million years. And yet, somehow, people love them. I’m kidding, of course, about the lazy and stubborn part – the fact that they have remained unchanged for so long is part of the mystique of this beloved ancient mariner. They are the OG of OG’s. You may also know that horseshoe crabs are of outsized importance to hemisphere-wide populations of certain shorebirds, which is how they made their way into the weekly bird report.

Each spring, horseshoe crabs have a standing date with Red Knots, Ruddy Turnstone, and other Arctic nesting shorebirds. The crabs come ashore to spawn in May, and when numbers of them are big enough, they dig up each other’s eggs, leaving windrows of them along the shoreline to be eaten by the shorebirds. The federally Threatened Red Knot is especially dependent on these eggs at stopovers from South Carolina to New Jersey, where they refuel and gain weight lost during the 6000-mile flight from their wintering areas at the southern tip of South America. They need to gain enough weight to then fly straight to the high Arctic, another 2000 miles, in good enough condition to breed. No horseshoe crab eggs, no breeding.

Here in Massachusetts, there’s only one place left where horseshoe crabs are protected enough to retain some vestige of this old connection with shorebirds. On the Cape’s wild elbow, at Monomoy National Wildlife Refuge, the crabs are protected from all forms of harvest, and spawning and nursery habitat abounds. As a result, you might see shorebirds clamoring around spawning crabs, frantically hoovering up any loose eggs, in a microcosm of what plays out further south.

Elsewhere in Massachusetts, horseshoe crabs have endured many slings and arrows, and populations are merely sputtering along. The ravages of the bounty era, when horseshoe crabs were considered pests and had to be killed under the old shellfish regulations, reduced their numbers to an extent we’ll never know. Currently, horseshoe crabs are taken from spawning beaches to be used as an optional bait in the whelk fishery, a declining fishery formally classified as overfished by state regulators. Hand harvesters target spawning females, who end up stockpiled in a freezer in New Bedford instead of laying eggs on a beach. It is illegal to take females with eggs in the lobster and crab fisheries, but lowly horseshoe crabs are not afforded the same respect.

There is also a biomedical fishery, where horseshoe crabs are bled and returned to the water. Components of their ancient immune system are used to make the only fully FDA approved test for bacterial contamination of drugs and medical equipment. Some 15- 30% of the crabs don’t survive the bleeding, and others miss their chance to spawn in years when they’re caught. Only one company did this biomedical bleeding here in Mass until last year, when the world’s largest such company, Charles River Labs, set up shop in Harwich, causing an exponential spike in the biomedical harvest. This alarmed the regulators and conservationists alike.

The Massachusetts Division of Marine Fisheries manages horseshoe crab harvests here, and they have recently proposed some regulations that would afford some modest new protections to spawning horseshoe crabs. Until May 1, anyone can comment on these proposed changes, which would protect crabs from all forms of harvest from January 1 to May 31 each year, thus protecting at least 80% of spawning. This is still substantially less than protections other states have in place, like New Jersey and South Carolina, both of which prohibit bait harvest, but it’s an important start. Check the website for information on the proposed regulations, public hearing dates, and how to submit a comment (marine.fish@mass.gov) .

Whether you love them for their ecological value to shorebirds, their intrinsic value and contribution to our cultural heritage, their dollar value as a side hustle, or just their general coolness, this is your chance to weigh in on how the state manages horseshoe crabs. Wherever you stand on the issue, hopefully we all have the same goal, which is to give the crabs what they need to keep stubbornly refusing to evolve for another 400 million years.

Mark Faherty writes the Weekly Bird Report.