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Passive acoustic monitoring of the distribution patterns of Irrawaddy dolphins ( Orcaella brevirostris ) in the middle reaches of the Ayeyarwady River, Myanmar
Author(s) -
Wang ZhiTao,
Duan PengXiang,
Akamatsu Tomonari,
Wang KeXiong,
Wang Ding
Publication year - 2020
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/mms.12713
Subject(s) - human echolocation , geography , abundance (ecology) , endangered species , fishery , habitat , ecology , biology , neuroscience
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.