Habitat inventory trend analysis of Limulus polyphemus populations on long Island, U.S.A.: From the tip of Brooklyn to the tip of Montauk, 2003–2014

Abstract

Considerable concern regarding the abundance of the American horseshoe crab (HSC) Limulus polyphemus, along the east coasts of New Jersey and Delaware prompted past moratoriums on collecting HSC for bait in New Jersey. The parallel population decline in migratory shorebirds such as Red knots Calidris canatus, Ruddy turnstones Arenaria interpres and others that seasonally feed on the copious quantities of HSC eggs laid along this shoreline resulted in reduced HSC collection permits to numbers considered sustainable. In New York State's Marine District, which is mostly comprised of the Long Island coastline, there is no reliable or routine habitat inventory network existing for determining HSC populations or habitat. Shorebird data, which have been collected by Audubon Chapters, the National Park Service and the US Fish and Wildlife Service, as well as academia, have hinted at declining HSC populations. However, due to the lack of a formal and extensive or reliable inventory network, assessing changing trends in HSC population levels is unattainable or mostly inaccurate. Molloy College's Long Island HSC Network provides survey forms and a website to (1) collect data on Long Island sites which support HSC; (2) count HSC for as reliable an estimate of the HSC population as practical; (3) sex and age individual HSC at each site; and most importantly (4) establish a network that can be repeated annually to detect precipitous changes in HSC population numbers, distributions, and habitat. Data collection for HSC will aid in protecting the HSC population as well as bird species number which require HSC eggs as food during significant migratory periods. Results for the last 11 years for 68 sites monitored annually reveal (1) considerably reduced numbers of HSC than “remembered in the past”; (2) sites along the Long Island coastline now believed to support HSC have been found to have few to modest numbers of HSC; (3) a preliminary number projection of Limulus on Long Island at approximately 15,000 adult breeding individuals on beaches surveyed; (4) of the 68 beaches monitored since 2003, an increase of 8.2 #x0025; had been observed for the number of beaches exhibiting “no breeding activity”; and (5) there has been observed an average of 1 #x0025; per yr decline in the total number of HSC observed.