Horseshoe Crab Survey.pdf

Horseshoe crabs have been surveyed on Martha's Vineyard to monitor their population. The crabs spawn on the beach during full and new moons, with females laying up to 80,000 eggs. The eggs hatch into miniature crabs after a few weeks, which become food for shore birds like the red knot.

The adult crabs are harvested for two purposes: as bait for eel and conch fisheries, and for their blue blood, which contains a valuable compound used to test for bacterial endotoxins in pharmaceuticals. The blood is drawn from the crabs, which are then returned to the ocean, but a significant percentage do not survive.

To monitor the horseshoe crab population, volunteers conduct surveys on moonlit nights during the spawning season, counting the number of crabs on the beach. The data is submitted to the Massachusetts Division of Marine Fisheries, which regulates the commercial fishery and prohibits the harvest of horseshoe crabs during the peak spawning season.

The surveys are coordinated by Susie Bowman, a Mass Audubon teacher/naturalist, and are conducted according to the Division of Marine Fisheries protocol. More volunteers are needed for this project, and those interested can contact 508-627-4850. The goal is to gain a reliable estimate of the current population and help conserve the horseshoe crab species.