TY - JOUR

T1 - Harbour porpoises respond to chronic acoustic deterrent device noise from aquaculture

AU - Findlay, Charlotte

AU - Coomber, Frazer

AU - Dudley, Rebecca

AU - Bland, Lynsey

AU - Calderan, Susannah

AU - Hartny-Mills, Lauren

AU - Leaper, Russel

AU - Tougaard, Jakob

AU - Merchant, Nathan

AU - Risch, Denise

AU - Wilson, Ben

PY - 2024/5/1

Y1 - 2024/5/1

N2 - Acoustic deterrent devices (ADDs) are used globally by the aquaculture industry to attempt to reduce pinniped depredation. However, noise from ADDs sited in areas used by cetaceans may lead to changes in cetacean behaviour and displacement from habitats impacting conservation status. Here, we investigate whether ADD noise from aquaculture within a habitat reduces acoustic detections of harbour porpoises, indicating either displacement or changes in echolocation activity. Nine years (2011–2019) of boat-based acoustic line-transect data for harbour porpoises were collected across the west coast of Scotland together with ADD presence and perceived loudness recorded by volunteers at regular listening stations along each transect. The most intense ADD noise coincided with significantly fewer harbour porpoise detections than in areas with no ADD noise. This corresponded with an estimated displacement of 34 % of the total undisturbed population, assuming that there was no change in echolocation behaviour. Furthermore, significant responses occurred at estimated received sound levels from ADDs >108 dB re 1 μPa RMS (frequency weighted for harbour porpoises). These findings suggest porpoises are either displaced from habitats degraded by intense ADD noise and/or echolocate less. In Scotland, ADD use in aquaculture has required a license since 2021. Limiting licensing, and monitoring ADD use by aquaculture should be considered by conservation managers globally, particularly in areas used by acoustically sensitive protected species. Non-acoustic (and non-lethal) measures to mitigate pinniped depredation on aquaculture sites are available and should be encouraged.

AB - Acoustic deterrent devices (ADDs) are used globally by the aquaculture industry to attempt to reduce pinniped depredation. However, noise from ADDs sited in areas used by cetaceans may lead to changes in cetacean behaviour and displacement from habitats impacting conservation status. Here, we investigate whether ADD noise from aquaculture within a habitat reduces acoustic detections of harbour porpoises, indicating either displacement or changes in echolocation activity. Nine years (2011–2019) of boat-based acoustic line-transect data for harbour porpoises were collected across the west coast of Scotland together with ADD presence and perceived loudness recorded by volunteers at regular listening stations along each transect. The most intense ADD noise coincided with significantly fewer harbour porpoise detections than in areas with no ADD noise. This corresponded with an estimated displacement of 34 % of the total undisturbed population, assuming that there was no change in echolocation behaviour. Furthermore, significant responses occurred at estimated received sound levels from ADDs >108 dB re 1 μPa RMS (frequency weighted for harbour porpoises). These findings suggest porpoises are either displaced from habitats degraded by intense ADD noise and/or echolocate less. In Scotland, ADD use in aquaculture has required a license since 2021. Limiting licensing, and monitoring ADD use by aquaculture should be considered by conservation managers globally, particularly in areas used by acoustically sensitive protected species. Non-acoustic (and non-lethal) measures to mitigate pinniped depredation on aquaculture sites are available and should be encouraged.

KW - Acoustic Harassment Devices

KW - Aquaculture

KW - Displacement

KW - Habitat Degradation

KW - Marine mammals

KW - Seal scarer

KW - Underwater noise

U2 - 10.1016/j.biocon.2024.110569

DO - 10.1016/j.biocon.2024.110569

M3 - Article

VL - 293

JO - Biological Conservation

JF - Biological Conservation

SN - 0006-3207

M1 - 110569

ER -