Transmission loss patterns from acoustic harassment and deterrent devices do not always follow geometrical spreading predictions

Acoustic harassment and deterrent devices have become increasingly popular mitigation tools for negotiating the impacts of marine mammals on fisheries. The rationale for their variable effectiveness remains unexplained, but high variability in the surrounding acoustic field may be relevant. In the p...

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Bibliographic Details
Published in:Marine Mammal Science
Main Authors: Shapiro, Ari D., Tougaard, Jakob, Jorgensen, Poul Boel, Kyhn, Line A., Balle, Jeppe Dalgaard, Bernardez, Cristina, Fjalling, Arne, Karlsen, Junita, Wahlberg, Magnus
Format: Article in Journal/Newspaper
Language:English
Published: 2009
Subjects:
acoustic harassment device (AHD)
acoustic deterrent device (ADD)
non-geometrical acoustic spreading
sound exposure level
multipath interference
marine mammal-fisheries
interactions
bycatch
TEMPORARY THRESHOLD SHIFT
WHALES PHYSETER-MACROCEPHALUS
PORPOISES PHOCOENA-PHOCOENA
BOTTLE-NOSED DOLPHINS
TURSIOPS-TRUNCATUS
BRITISH-COLUMBIA
FISHING NETS
HARBOR SEALS
UNDERWATER
SOUND
Phocoena phocoena
Physeter macrocephalus
Online Access:https://risweb.st-andrews.ac.uk/portal/en/researchoutput/transmission-loss-patterns-from-acoustic-harassment-and-deterrent-devices-do-not-always-follow-geometrical-spreading-predictions(cdd48178-c629-46d5-a02a-8165e03e2976).html
https://doi.org/10.1111/j.1748-7692.2008.00243.x
Description
Summary:Acoustic harassment and deterrent devices have become increasingly popular mitigation tools for negotiating the impacts of marine mammals on fisheries. The rationale for their variable effectiveness remains unexplained, but high variability in the surrounding acoustic field may be relevant. In the present study, the sound fields of one acoustic harassment device and three acoustic deterrent devices were measured at three study sites along the Scandinavian coast. Superimposed onto an overall trend of decreasing sound exposure levels with increasing range were large local variations in the sound level for all sources in each of the environments. This variability was likely caused by source directionality, inter-ping source level variation and multipath interference. Rapid and unpredictable variations in the sound level as a function of range deviated from expectations derived from spherical and cylindrical spreading models and conflicted with the classic concept of concentric zones of increasing disturbance with decreasing range. Under such conditions, animals may encounter difficulties when trying to determine the direction to and location of a sound source, which may complicate or jeopardize avoidance responses.

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