Modeling potential distribution of Indo-Pacific humpback dolphins ( Sousa chinensis ) in the Beibu Gulf, China

Background: Mapping key habitats of marine mega-vertebrates with high mobility is crucial for species conservation. Due to difficulties in obtaining sound data in the field, Species Distribution Modeling (SDM) provides an effective alternative to identify habitats. As a keystone and flagship species in inshore waters in southern China, Indo-Pacific humpback dolphins ( Sousa chinensis ) play an important role in coastal ecosystems. However, our knowledge on their key habitats remained unclear in some waters including the Beibu Gulf of South China Sea. Methods: . We used a maximum entropy (Maxent) modeling approach to predict potential habitats for Sousa chinensis in the Beibu Gulf of China. Models were based on eight independent oceanographic variables derived from Google Earth Digital Elevation Model (DEM) and Landsat images, and presence-only sighting data from boat-based surveys and literatures during 2003-2013. Results: . Three variables, distance to major river mouths, to coast and to 10-m isobaths, were the strongest predictors, consistent with other studies on the dolphin habitat selection. Furthermore, we confirmed that influence of estuaries was the most important and irreplaceable. Besides two known distribution areas as well as data sources, a new area close to the boundary of China and Vietnam, Beilunhe Estuary (BE), was predicted as a potential habitat. Discussion: Influence of estuaries is likely to indicate feeding preference of the humpback dolphins. The “new” habitat BE should be a key area connecting China and Vietnam dolphins, and deserved to be examined and preserved.