The American horseshoe crab obtains food resources, spawns and has nursery habitats in our urban coastal seas. The east coast of the US and particularly Long Island Sound (LIS) is dominated by human activity and characterized by armored shorelines, high nutrient loads, large fluctuations in algal and bacteria populations, increased levels of pollutants (e.g. heavy metals and pesticides), hypoxia and relatively low pH. The LIS watershed harbors more than 9 million people and this urban sea has been significantly modified by human use. We have found that the horseshoe crab population in LIS is reproducing well below its maximum rate with the recruitment of newly molted adults ranging from 5.6 to 12% of the spawning population on sampled beaches. One- to three- year-old juvenile horseshoe crabs have low population densities, with a patchy distribution and are absent from more than half of estuarine habitats surveyed (n = 10). The probable causes are due to legal and illegal overharvest of adults and poor quality nursery habitat (polluted and hypoxic estuaries). Possible solutions include multi-habitat restoration using the living shoreline concept (e.g. beach stabilization, marsh grass planting, and artificial reef installation) for wave abatement, sediment deposition, capping of heavy metals and increased biodiversity. Also, establishing marine protected areas in LIS is imperative to increase recruitment of juvenile horseshoe crabs as well as other ecologically and economically important marine species
