Horseshoe crabs, living fossils of the sea, draw endangered species petition

These spine-tailed sea creatures named for the shape of their body shells have been crawling ashore long before the age of dinosaurs, and in modern times were a familiar sight to summer beachgoers along the US mid-Atlantic and Gulf Coasts.

Environmental groups on Monday petitioned the US government seeking endangered species protection for the American horseshoe crab, a "living fossil" under threat from commercial harvests for bait and biomedical use as well as from habitat loss and climate change.

These spine-tailed sea creatures named for the shape of their body shells have been crawling ashore since long before the age of dinosaurs, and in modern times were a familiar sight to summer beachgoers along the US mid-Atlantic and Gulf Coasts.

But horseshoe crab populations have crashed in recent decades, with spawning numbers down two-thirds from 1990 in the Delaware Bay estuary that was once their biggest stronghold, according to conservation groups. Research also shows their egg densities falling more than 80 per cent in the past four decades.

Those trends are tied to stress on other marine species that feed on their larvae and eggs, including the rufa red knot, a migratory shorebird whose own 2014 threatened-species listing cited horseshoe crab harvests as a contributing factor.

Classified not as true crabs but as marine arthropods most closely related to spiders and scorpions, horseshoe crabs are among the oldest living creatures on Earth, with fossils of their ancestors dating back some 450 million years.

Despite their primitive appearance, horseshoe crabs are harmless to people, for whom encounters were once common along shorelines where the animals congregated each spring to lay million eggs.

Now, after surviving several mass-extinction events through the ages, including an asteroid impact 66 million years ago that killed off dinosaurs, the lowly horseshoe crab is facing its own demise from a combination of human activities.

"We're wiping out one of the world's oldest and toughest creatures," said Will Harlan, a senior scientist at the Center for Biological Diversity, one of 23 groups petitioning the National Oceanic and Atmospheric Administration (NOAA) for the endangered species declaration.

Such a listing would generally make it unlawful to harm or kill a horseshoe crab without a special permit. The petition also seeks designation of "critical habitat" to be protected, especially during spawning season.

NOAA Fisheries spokesperson said the agency would review the petition, but declined further comment.

The petition cites numerous threats to the American horseshoe crab, one of four living species of the animal, stemming from human activities.

Pharmaceutical companies reap horseshoe crabs in large numbers - nearly 1 million in 2022 - for their blue-colored blood, which contains a clotting agent used to test drugs and medical devices for bacterial endotoxins, the petition said.

Regulations allow the biomedical industry to extract only a portion of a horseshoe crab's blood and then release it alive in the area it was collected, though 10-15 per cent of harvested animals die during this process, NOAA says on its website.

Harlan said non-industry research shows about 30 per cent of horseshoe crabs collected for blood extraction die in the process. He added that synthetic alternatives are widely used in Europe, but US companies have been slow to adopt them.

Over-harvesting of horseshoe crabs as bait for commercial whelk and eel fisheries has further decimated their numbers, with no sign of recovery even after quotas were imposed, according to the petition.

The creatures also face growing habitat loss from oceanfront development, dredging, pollution, coastal erosion and sea-level rise linked to global warming from increased greenhouse gas emissions.

Mass die-offs have been observed in the past three years, with NOAA in 2023 ranking the horseshoe crab's overall vulnerability to climate change as "very high," the petition said.