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Number 6 (2011)

Sound Radiation of Seafloor-Mapping Echosounders in the Water Column, In Relation to the Risks Posed to Marine Mammals

August 13, 2013


Currently, more and more attention is focusing on the impact of anthropogenic sound sources on marine life, particularly marine mammals. Indeed, several unusual cetacean strandings linked to the use of high-power sonar have been observed over the past years. Hydrography and seafloor-mapping make extensive use of acoustic sources; this paper aims to present the order of magnitude of sound radiated by such echosounders, and hence estimate their potential impact on marine mammals. The paper begins with a presentation of the main issues related to sound-mediated risks to marine life and a reminder of echosounder characteristics and geometry. Next, the numerical results from several case studies are compared with currently accepted threshold values for marine mammal sound exposure. This comparison makes clear that, while echosounders may transmit at high sound pressure levels, the very short duration of their pulses and their high spatial selectivity make them unlikely to cause damage to marine mammal auditory systems, according to current knowledge. There remains a possibility that echosounders may affect marine mammal behaviour at ranges on the order of kilometres; however, the likelihood and biological effects of such behavioural responses to sound remain poorly understood at present.