At the end of 2014, I moved to China to start a post-doctoral fellowship on noise impacts on China's marine mammals. The fellowship was based at the Chinese Academy of Science's Institute of Hydrobiology and focused on the Yangtze finless porpoise (in Hubei Province), Indo-Pacific finless porpoises (in Guangdong Province and Hong Kong SAR) and Chinese White Dolphins (in Guangdong Province and Hong Kong SAR).
Since the completion of my Chinese postdoc in early 2017, I have been working with WWF-Hong Kong to undertake passive acoustic monitoring of Chinese white dolphins and Indo-Pacific finless porpoises around Southern Lantau Island and the Soko Islands. The project utilises seven PAM listening stations, and in 2018 was extended to nine stations extending from Tai O on western Lantau Island to the Soko Islands. |
Investigating the marine soundscapes of the Pearl River Estuary
Characterising marine soundscapes from as many different environments and habitats as possible is becoming increasingly important. So much on the impacts of underwater noise pollution from shipping and marine-based developments on marine life depends on what sound levels a receiving animal is already exposed to. Thus, since 2015 we have been building an underwater soundscape dataset at the Institute of Hydrobiology (Chinese Academy of Sciences) to investigate what underwater anthropogenic noise sources are likely to have the highest impact on marine mammals.
Well over 500,000 recordings from multiple listening stations around the Pearl River Estuary, both in Hong Kong SAR and mainland Chinese waters, have been made - revealing a spectacularly complex soundscape. Remarkable seasonal and spatial variations between different habitats within the estuary have been seen and the impact of bottom trawling on the soundscape can also be seen. |
Using passive acoustics to map the spatio-temporal distributions of soniferous fishes
Indo-Pacific humpback dolphins and Indo-Pacific finless porpoises survive almost exclusively on a fish diet. In an area like the Pearl River Estuary where intense development is occurring, a long established fishery with millions of tonnes of fish harvested annually and a decreasing dolphin and porpoise population, there is an urgent need to understand where the fish are and where they go at different times of the year. Necropsies performed on stranded dolphins in Hong Kong have showed soniferous fishes to be the most important prey numerically (over two thirds of the stomach contents were these kind of fish). Therefore, this presented a unique opportunity to use passive acoustics to eavesdrop on the Pearl River Estuary and start mapping the distributions of these fish throughout the year.
The dataset collected so far has shown at least five clear chorus-types, that we believe are from five different species of soniferous fishes. This is because the fish chorus-types show distinct and consistent temporal partitioning (i.e. they occur at different times of the morning or night) and our statistical tests show the spectral characteristics of each chorus-type to be significantly different. See - Pine, M.K., Wang, D., Porter, L., Wang, K. (2018). 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, doi:10.1093/icesjms/fsx197. |
Looking at the presence of Indo-Pacific humpback dolphins around the Pearl River Estuary using passive acoustics
Shifts in habitat use and distribution patterns in dolphins are often concerns that can result from habitat degradation. With Professor Ding Wang and Kexiong Wang at IHB, we investigated how potential changes to a habitat from human activity may alter dolphin distributions within Lingding Bay in the Pearl River Estuary by studying the relationships between fish, dolphins and vessels.
What we are seeing in the Pearl River Estuary is that the dolphins are returning to a specific area to forage, irrespective of the vessel pressure during that time. Several questions arise from this - are the dolphins demonstrating a particular level of tolerance to vessel noise (there's not enough data to show this), are they following the fish to because the fish are so limited in their distributions and what can we expect if the the fish populations were to drop off from over-fishing and/or habitat degradation? |
Movements of Indo-Pacific humpback dolphins and Indo-Pacific finless porpoises within high speed ferry lanes
In collaboration with the World Wild Fund - Hong Kong (WWF-HK) and The Oceanway Corporation, and generous funding from WWF-HK, we are continuously collecting data from several listening stations systematically deployed near the Soko Islands to monitor dolphin movements, habitat use and their responses to the high speed Hong Kong-Macau ferries. These data are urgently needed as the HSFs' come close to important feeding grounds for Indo-Pacific humpback dolphins and Indo-Pacific finless porpoises. The data from this project will be used to help the government in ensuring the conservation of these marine mammals.
Between October 2016 and August 2017, over 4300 marine mammal detections have been made. This monitoring is still underway, set for completion mid 2019. |
Studying cetacean vocalisations
-Collaborating with scientists at the Institute of Hydrobiology, Chinese Academy of Sciences to better understand the sounds of the Yangtze finless porpoise, East Asian finless porpoises, Indo-Pacific finless porpoise and Indo-Pacific humpback dolphins. The data from those collaborative studies feed into our soundscape models and used for the detection of marine mammals in Chinese and Hong Kong SAR waters.
See - Cheng, Z., Pine, M.K., Huang, S., Wang, D., Wu, H. Wang, K. (2018). A case of epimeletic behavior and associated acoustic records of Indo-Pacific humpback dolphins (Sousa chinensis). Journal of Mammalogy 99(5): 1112-1119. - Cheng, Z. Wang, D., Wu, H., Huang, S., Pine, M.K., Peng, C., Wang, K. (2017). Evidence suggests signature whistle production in an injured free-ranging adult Indo-Pacific humpback dolphin (Sousa chinensis). Aquatic Mammals 43(2):185-192. - Fang, L., Wu, Y., Wang, K., Pine, M.K., Wang, D., Li, S. (2017). The echolocation transmission beam of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis). Journal of the Acoustical Society of America 142(2):771-779. - Fang, L., Wang, D. Li, Y., Cheng, Z., Pine, M.K., Wang, K., Li, S. (2015). The source parameters of echolocation clicks from captive and free-ranging Yangtze finless porpoises (Neocphocaena asiaorientalis asiaeorientalis). PLoS One 10(6): e0129143. |