Present and Potential Future Distributions of Asian Horseshoe Crabs Determine Areas for Conservation

Francisco J Quevedo Fernandez,Stine Vestbo,Itsara Intanai,Matthias Obst,Peter Funch

doi:10.3389/fmars.2018.00164

Francisco J Quevedo Fernandez, Stine Vestbo + Show 3 more

Open Access

https://doi.org/10.3389/fmars.2018.00164

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Abstract

Conservation of horseshoe crabs has recently received increasing attention as several populations are in decline. However, scarce information on their distributions in Southeast Asia is impairing conservation efforts. In this study, we sought to improve our understanding of the geographical range and distinct populations of the three Asian horseshoe crabs species in order to identify optimal conservation areas. We mapped the geographic range of Carcinoscorpius rotundicauda, Tachypleus gigas, and T. tridentatus using recent data from field work, literature, Global Biodiversity Information Facility (GBIF), and unpublished data from our scientific network. The data were correlated with 23 different environmental variables of potential ecological importance for horseshoe crabs using the openModeller webservices, including new tidal variables. Ecological niche models were generated using two algorithms, Maximum Entropy and support vector machine, for the three species under present conditions, and projected into a climate change scenario of 2050. The niches of the Asian horseshoe crabs were mostly determined by tidal regime, chlorophyll A concentrations, depth, distance to land, and sea surface temperature. According to our predictions, horseshoe crabs in Southeast Asia are not expected to experience any severe change in extent and distribution of suitable habitat in the future. In order to conserve Asian horseshoe crabs, we suggest establishing Marine Protected Areas at locations where distinct populations and several species occur, such as northern Vietnam, China, Borneo, and southern Japan.

Highlights

Coastal and intertidal areas are currently under threat globally due to a range of anthropogenic activities, including infrastructure development and coastal protection, as well as effects of climate change, such as rising sea levels pushing coastal areas closer to anthropogenic structures, resulting in “coastal squeeze” (Defeo et al, 2009)
The principal component analysis (PCA) showed that C. rotundicauda and T. gigas largely share the same ecological niche, and that the niche of T. tridentatus to some extent overlaps with the niches of the other two species (Figure 1)
The mean minimum sea surface temperature found for T. tridentatus was 17.0◦C and 10 degrees lower than those for T. gigas and C. rotundicauda (Figure 2D)

Summary

Introduction

Coastal and intertidal areas are currently under threat globally due to a range of anthropogenic activities, including infrastructure development and coastal protection, as well as effects of climate change, such as rising sea levels pushing coastal areas closer to anthropogenic structures, resulting in “coastal squeeze” (Defeo et al, 2009). Populations of horseshoe crabs world-wide are currently in decline (e.g., Cartwright-Taylor et al, 2011; Kwan et al, 2016; Smith et al, 2017), and the IUCN Red List of Threatened Species describes L. polyphemus as vulnerable (Smith et al, 2016). The Asian horseshoe crab species are thought to be in greater decline than L. polyphemus, these species are currently listed as data deficient (World Conservation Monitoring Centre, 1996a,b,c). While the geographic range of L. polyphemus is known (Sekiguchi, 1988; Anderson and Shuster, 2003; Sekiguchi and Shuster, 2009; Faurby et al, 2011), the precise distribution of the three Asian species remains less clear (World Conservation Monitoring Centre, 1996a,b,c), impairing conservation efforts

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