The Suitability of Fringing Salt Marshes as Nesting Habitats for the American Horseshoe Crab, Limulus polyphemus, in Long Island Sound.

The American horseshoe crab (Limulus polyphemus) is an important natural resource worth millions of dollars on the world market. Products harvested from Limulus hemolymph are used to test vaccines for the presence of harmful bacterial toxins saving billions of people from becoming ill. Horseshoe crabs are a dominant abundant species within estuaries particularly during spawning season and increase local biodiversity where their eggs are consumed by fish, shorebirds and numerous invertebrates. Better management is needed as the population is in decline in Connecticut. They are known to spawn on sandy beaches and records of spawning crabs in marshes was considered sub-optimal habitat and ignored. We investigated if horseshoe crabs spawn in alternative habitats rarely or with similar frequency to numbers spawning on traditional sandy beaches. We counted spawning horseshoe crabs on three traditional sandy and three alternative (salt-marsh) spawning areas during new and full moons of May-June, 2021. We also took 40 core samples from these six different locations, eggs were enumerated. Although adult spawning counts were higher in sandy nesting sites, the density of eggs in sandy vs. salt-marsh were not significantly different. For improved management of horseshoe crabs, better methods for spawning counts in alternative habitats need to be developed