Habitat preference of two sympatric coastal cetaceans in Langkawi, Malaysia, as determined by passive acoustic monitoring

Abstract

Little is known about the ecology of the Indo-Pacific finless porpoise Neophocaena phocaenoides or the Indo-Pacific humpback dolphin Sousa chinensis in Southeast Asia. The present study describes the distribution and habitat preferences of these species around the Langkawi Archipelago of Malaysia. Vessel-based passive acoustic monitoring surveys were conducted 5 times between 2012 and 2013. Both species mainly preferred relatively shallow waters, especially on the east sides of the islands at <15 m depth. However, the species differed in number of detections and spatial distribution, preferred distance from shore, chlorophyll a concentration in the water where they resided, and season in which they were detected, indicating that they have different habitat preferences. The best spatial habitat model for the prediction of finless porpoise distribution included bathymetric depth and longitude. The distribution of finless porpoises was relatively stable around the islands and especially in the eastern waters, whereas humpback dolphins may only seasonally visit specific regions of the waters around the islands. Their detection sites were too patchy to enable distribution modeling. The results of this study provide baseline information that can facilitate conservation planning for these species according to their habitat preferences and core areas.