Horseshoe crabs are recovering because Massachusetts capped harvest — and biomedicine is already 80% weaned off their blood

Horseshoe crab blood clots on contact with bacterial toxins, making it the standard test for contamination in vaccines, injectables, and medical devices for 40 years. But crabs are also a keystone food source — their eggs feed migratory shorebirds, sharks, and turtles — so bait harvesting and blood harvesting both ripple through the coastal food web, not just the crab population.

Eli Lilly began switching to a lab-made, biotech-produced version of the crab's clotting protein in 2016; it now covers 80% of the company's testing, with a stated goal of eliminating crab-blood use entirely. Lilly says the synthetic performed as well or better across thousands of samples and hundreds of products — meaning the argument for continued wild harvest is shrinking from the demand side, not just the regulatory side.