Collaborative research conducted by the SMRU Asia Pacific team was recently published as the Editors Choice in the ICES Journal of Marine Science (IJMS). The research described how the noises made by chorusing fish can help identify the foraging habitat of the Indo-Pacific humpback dolphin (Sousa chinensis) in the Pearl River Estuary, southern China.

As the economy of Asia continues to boom, large-scale coastal infra-structure developments are proposed, commissioned and completed in very short time frames. Often, there is little information on the marine life that inhabit these coastal areas and little time allocated to gather sufficient information to inform of long-term or cumulative impacts. Marine mammals make up an important component of a region’s ecological system, and the acoustic overlap between coastal construction activities and the habitat of such animals is of international concern, indeed the International Whaling Commission scientific committee focused on the small cetaceans of Asia as a priority topic in 2017.

A mounting body of evidence shows changes in marine mammal habitat use only becomes apparent during or after construction or development activities, e.g., habitat exclusions from important foraging grounds. Understanding where important foraging habitats may be before or during the environmental impact assessment phase of future developments is thus fundamental for the conservation of marine mammals.

This study focuses on the Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary (PRE) in China. The study utilises passive acoustic monitoring to eavesdrop on chorusing fish, a key prey item of the dolphins. Five listening stations consisting of autonomous acoustic recorders were set up within the estuary, continuously recording the underwater soundscape. Doing so revealed several different fish chorus-types that show associations of co-existing fish species (assemblages) are not consistent around the estuary. This new data provides the first baseline record for noisy fish, as a main prey item for the dolphins, in the PRE. It therefore forms a basis for identifying potentially important foraging habitats which, after being overlaid with acoustic detections of foraging dolphins, should be afforded the highest priority for protection.

You can read the full study here: Pine, M. K., Wang, D., Porter, L., & Wang, K. (2017). Investigating the spatiotemporal variation of fish choruses to help identify important foraging habitat for Indo-Pacific humpback dolphins, Sousa chinensis. ICES Journal of Marine Science.

Following this paper’s publication, a series of workshops and public seminars will take place in Hong Kong highlighting the importance of acoustics studies in revealing the requirements and activities of dolphins in the waters of the PRE. Keep an eye out for updates on this here, on twitter and facebook.