Are Horseshoe Crabs, Limulus polyphemus, Functionally Extinct in Long Island Sound?

The American horseshoe crab (Limulus polyphemus), is an economically and ecologically important species that lives throughout Long Island Sound. They are used as bait, and pharmaceutical companies produce medical products from their blood. Two no-harvest zones were established in 2006 by the State of CT in hopes of preventing population decline. An annual census of the spawning adult population by SHU students and citizen scientist volunteers since then was conducted May-June during high tides of full and new moons. Additional population dynamic information was collected including mating patterns and age structure. The spawning population is declining and varies by year and by beach. The population is aging, less than 6% of adults observed were newly molted (2016-2021). The main causes include overharvest, pollution, climate change, and habitat loss. New management regulations are warranted in order to bring population numbers back up. This species low spawning numbers has removed it from the food web of Long Island Sound with little to no eggs available to fish shorebirds, and marine invertebrates. This is known as a functional extinction event