Research
| Title： | Passive acoustic monitoring of the distribution patterns of Irrawaddy dolphins (Orcaella brevirostris) in the middle reaches of the Ayeyarwady River, Myanmar |
|---|---|
| First author： | Wang, Zhi-Tao; Duan, Peng-Xiang; Akamatsu, Tomonari; Wang, Ke-Xiong; Wang, Ding |
| Journal： | MARINE MAMMAL SCIENCE |
| Years： | 2020 |
| DOI： | 10.1111/mms.12713 |
| Abstract： | The Irrawaddy dolphins (Orcaella brevirostris) are an endangered species. Thus, up-to-date information on the distribution pattern of dolphins is critical for its proper management and conservation. Using a towed passive acoustic monitoring device, the distribution pattern of the Irrawaddy dolphins in the middle reaches of the Ayeyarwady River, Myanmar, was investigated during a vessel-based survey between Mingun and Katha. This region was successively divided into segments 1-4 from upstream to downstream. Sixteen echolocation encounters, with a series of click trains separated by <8 min and 26 dolphin acoustic trajectories were recorded. The mean dolphin detection rate (animals/kilometer) across the four segments progressively increased from upstream to downstream. High relative abundance was observed in segment 4 (46%) and segment 1 (23%) which was consistent with findings from historical boat-based visual surveys. The averaged interclick intervals of each click train in segment 2 and 4 was significantly shorter than that in segment 3, indicating that the dolphins in these segments frequently use shorter-ranged biosonar. More frequent and consistent surveys with a systematic sampling track design that incorporates other factors and covering the whole distribution range along the Ayeyarwady River and at varied water levels are needed in the future. |
