Ecosystem Targets and Supporting Indicators
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The horseshoe crab (Limulus polyphemus) is an arthropod more closely related to spiders than other crabs and has a body form that evolved more than 200 million years ago. They are found from Nova Scotia to Mexico and live year-round in Long Island Sound. They are harvested as bait for other fisheries, but are not typically eaten for meat. They come onshore to spawn in May and June, with spawning tending to peak at night around the new and full moons.
Since horseshoe crabs rely on beaches and the shallow intertidal environment to produce their young, their abundance is an indicator of the health and productivity of this transitional environment. Horseshoe crab eggs are an essential food source for migrating shorebirds, and their larvae and juveniles are consumed by many fish. They are most valuable to humans for their blood proteins which are extremely sensitive to bacteria. The extracted compound, known as LAL, is used to screen injected drugs and implanted biomedical devices for contamination.
CT DEEP’s Long Island Sound Trawl Survey samples throughout the Sound in both Connecticut and New York waters during the spring (April, May, and June) and Fall (September, November, October). The Millstone Environmental Laboratory dataset in Niantic Bay reflects the abundance in the eastern Sound near the Connecticut shoreline. The Manhasset and Little Neck Bays NYSDEC seine survey reflects conditions in western Long Island Sound along the New York shoreline, while the trawl survey in Peconic Bay, which borders Long Island Sound, is indicative of conditions in eastern Long Island Sound near the New York shoreline.
Both the CT and NY indices show a decreasing abundance in Long Island Sound from the early ‘00s. Although American horseshoe crab populations increased in the 1990s, recent years show a declining trend due to various stressors (e.g., loss of habitat and illegal harvesting). To stabilize and restore the horseshoe crab populations, regulations have been implemented such as limiting harvesting permits, closed areas, seasonal closures, commercial quotas, and restricting the timing (lunar closures) and daily number of crabs a harvester can possess.