The habitats of South East Asian horseshoe crabs span across the shallow waters of many countries and biogeographic regions in the Indo-Pacific. Such ubiquitous presence makes it difficult to obtain an up-to-date and overall picture of the current distribution, density and wealth of horseshoe crab populations with obvious implications for the conservation efforts of the three Asian species. Historical records show that Tachypleus gigas (Müller, 1785) and Carcinoscorpius rotundicauda (Latreille, 1802) have a largely overlapping distribution ranging from the Bay of Bengal to the South China Sea where T. gigas lives in sandy and shallow near-coast habitats, while C. rotundicauda mostly inhabits estuaries and mangroves. The third species T. tridentatus is living in shallow coastal zones from Malaysia to Japan. In order to improve our knowledge on current and future distribution of horseshoe crab populations, we developed and tested a series of ecological niche models for these species using occurrence data from our fieldwork and recent literature. These data were correlated with environmental information using the openModeller webservices. Results were used to identify the most decisive environmental factors for the species distribution, quantify range shifts of the species in response to predicted climatic change, and obtain spatial predictions of suitable habitats under present and future climate scenarios. Suitable habitat was projected into marine protected areas in the region to better understand the potential of existing horseshoe crabs’ sanctuaries to accommodate the species in a changing climate.
The Third International Workshop on the Science and Conservation of Horseshoe Crabs, 2015