Horseshoe crabs are harvested for their medically invaluable blood and as bait fish, with significant welfare implications for millions of individuals annually.
Horseshoe crabs during bleeding harvest experience capture stress from trawling or collection, transport out of water, immobilization for bleeding, and the physiological stress of losing 30% of their blood volume. Mortality from harvest stress reflects the cumulative physiological burden of these procedures on animals with limited physiological reserves. The welfare status of horseshoe crabs is uncertain given their ancient physiology, but their stress responses and mortality rates indicate genuine harm. The availability of a validated synthetic alternative - recombinant factor C - makes continued large-scale animal harvest an unnecessary welfare burden that can be eliminated with appropriate regulatory and industry transition.