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Sci Rep. 2019 Oct 28;9(1):15426. doi: 10.1038/s41598-019-51664-1.

Interacting effects of vessel noise and shallow river depth elevate metabolic stress in Ganges river dolphins.

Author information

1
P.G. Program in Wildlife Biology and Conservation, National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore, 560065, Karnataka, India. mayukh.d27@gmail.com.
2
Ashoka Trust for Research in Ecology and the Environment (ATREE), Royal Enclave Srirampura, Jakkur PO, Bangalore, 560064, Karnataka, India.
3
Mie University, 1577 Kurimamachiya-cho, Mie, 514-8507, Japan.

Abstract

In riverine 'soundscapes', complex interactions between sound, substrate type, and depth create difficulties in assessing impacts of anthropogenic noise pollution on freshwater fauna. Underwater noise from vessels can negatively affect endangered Ganges river dolphins (Platanista gangetica), which are 'almost blind' and rely entirely on high-frequency echolocation clicks to sense their environment. We conducted field-based acoustic recordings and modelling to assess acoustic responses of Platanista to underwater noise exposure from vessels in the Ganga River (India), which is now being transformed into a major waterway. Dolphins showed enhanced activity during acute noise exposure and suppressed activity during chronic exposure. Increase in ambient noise levels altered dolphin acoustic responses, strongly masked echolocation clicks, and more than doubled metabolic stress. Noise impacts were further aggravated during dry-season river depth reduction. Maintaining ecological flows, downscaling of vessel traffic, and propeller modifications to reduce cavitation noise, could help mitigate noise impacts on Ganges river dolphins.

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