Temporal and spatial characterization of acoustic activity patterns of Indo-Pacific humpback dolphins (Sousa chinensis chinensis) in Hong Kong waters

Abstract

Indo-Pacific humpback dolphins face a number of serious anthropogenic pressures in Hong Kong waters. Since the late 1990’s, data has shown both a decline in their abundance and shift in their distribution, therefore obtaining a better understanding of their habitat use through passive acoustic monitoring is important. Twelve C-PODs deployed throughout their habitat from June 2018-July 2019 were able to provide data on diel, seasonal and geographical patterns in their acoustic activity; and location had the largest effect on the probability of detections. When acoustic and visual data were compared to characterize the ability of the C-PODs to detect dolphins and assess the relative efficacy of each detection method, little overlap was found between methods. Despite these limitations, the C-PODs are able to survey continuously and simultaneously over many areas and represent a valuable tool for long-term monitoring.