New paper: Far-Field Effects of Impulsive Noise on Coastal Bottlenose Dolphins
Dear MARMAM colleagues, On behalf of my co-authors I would like to share our recent publication in Frontiers in Marine Science (open access): Fernandez-Betelu O, Graham IM, Brookes KL, Cheney BJ, Barton TR and Thompson PM (2021) Far-Field Effects of Impulsive Noise on Coastal Bottlenose Dolphins. Front. Mar. Sci. 8:664230. doi: 10.3389/fmars.2021.664230 The paper was published as part of the Frontiers research topic "Before-After Control-Impact (BACI) Studies in the Ocean" and can be downloaded freely from: https://www.frontiersin.org/articles/10.3389/fmars.2021.664230/full Abstract Increasing levels of anthropogenic underwater noise have caused concern over their potential impacts on marine life. Offshore renewable energy developments and seismic exploration can produce impulsive noise which is especially hazardous for marine mammals because it can induce auditory damage at shorter distances and behavioral disturbance at longer distances. However, far-field effects of impulsive noise remain poorly understood, causing a high level of uncertainty when predicting the impacts of offshore energy developments on marine mammal populations. Here we used a 10-year dataset on the occurrence of coastal bottlenose dolphins over the period 2009-2019 to investigate far-field effects of impulsive noise from offshore activities undertaken in three different years. Activities included a 2D seismic survey and the pile installation at two offshore wind farms, 20-75 km from coastal waters known to be frequented by dolphins. We collected passive acoustic data in key coastal areas and used a Before-After Control-Impact design to investigate variation in dolphin detections in areas exposed to different levels of impulsive noise from these offshore activities. We compared dolphin detections at two temporal scales, comparing years and days with and without impulsive noise. Passive acoustic data confirmed that dolphins continued to use the impact area throughout each offshore activity period, but also provided evidence of short-term behavioral responses in this area. Unexpectedly, and only at the smallest temporal scale, a consistent increase in dolphin detections was observed at the impact sites during activities generating impulsive noise. We suggest that this increase in dolphin detections could be explained by changes in vocalization behavior. Marine mammal protection policies focus on the near-field effects of impulsive noise; however, our results emphasize the importance of investigating the far-field effects of anthropogenic disturbances to better understand the impacts of human activities on marine mammal populations. Please, do not hesitate to contact me should you have any questions regarding our work (oihane.fernandez@abdn.ac.uk). Kind regards, Dr Oihane Fernandez-Betelu Research Fellow Lighthouse Field Station, Institute of Biological & Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL. Tel: 01381600548 [Aberdeen_Uni_logo_big low res]<http://www.abdn.ac.uk/lighthouse/> [FB_FindUsOnFacebook-320] <https://www.facebook.com/lighthousefieldstation> [follow us on twitter logo] <https://twitter.com/cromartylh> The University of Aberdeen is a charity registered in Scotland, No SC013683. Tha Oilthigh Obar Dheathain na charthannas cl?raichte ann an Alba, ?ir. SC013683.
Dear MARMAM colleagues, On behalf of my co-authors I would like to share our recent publication in Royal Society Open Science (open access): Oihane Fernandez-Betelu, Virginia Iorio-Merlo, Isla M. Graham, Barbara J. Cheney, Simone M. Prentice, Rachael Xi Cheng and Paul M. Thompson (2023) Variation in foraging activity influences area-restricted search behaviour by bottlenose dolphins. Royal Society Open Science. https://doi.org/10.1098/rsos.221613 Abstract Area-restricted search (ARS) behaviour is commonly used to characterize spatio-temporal variation in foraging activity of predators, but evidence of the drivers underlying this behaviour in marine systems is sparse. Advances in underwater sound recording techniques and automated processing of acoustic data now provide opportunities to investigate these questions where species use different vocalizations when encountering prey. Here, we used passive acoustics to investigate drivers of ARS behaviour in a population of dolphins and determined if residency in key foraging areas increased following encounters with prey. Analyses were based on two independent proxies of foraging: echolocation buzzes (widely used as foraging proxies) and bray calls (vocalizations linked to salmon predation attempts). Echolocation buzzes were extracted from echolocation data loggers and bray calls from broadband recordings by a convolutional neural network. We found a strong positive relationship between the duration of encounters and the frequency of both foraging proxies, supporting the theory that bottlenose dolphins engage in ARS behaviour in response to higher prey encounter rates. This study provides empirical evidence for one driver of ARS behaviour and demonstrates the potential for applying passive acoustic monitoring in combination with deep learning-based techniques to investigate the behaviour of vocal animals. Please, do not hesitate to contact me should you have any questions regarding our work (oihane.fernandez@abdn.ac.uk<mailto:oihane.fernandez@abdn.ac.uk>). Kind regards, Dr Oihane Fernandez-Betelu Research Fellow Lighthouse Field Station, Institute of Biological & Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL. Tel: 01381600548 [Aberdeen_Uni_logo_big low res]<http://www.abdn.ac.uk/lighthouse/> [FB_FindUsOnFacebook-320] <https://www.facebook.com/lighthousefieldstation> [follow us on twitter logo] <https://twitter.com/cromartylh> The University of Aberdeen is a charity registered in Scotland, No SC013683. Tha Oilthigh Obar Dheathain na charthannas cl?raichte ann an Alba, ?ir. SC013683.
participants (1)
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Fernandez, Oihane