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.Īmbient noise in the marine environment has increased since the 1950s due to the rise of human activities at sea ( Frisk, 2012). We suggest that this increase in dolphin detections could be explained by changes in vocalization behavior. 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. 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. We compared dolphin detections at two temporal scales, comparing years and days with and without impulsive noise.

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. 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. 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. 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. 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. Increasing levels of anthropogenic underwater noise have caused concern over their potential impacts on marine life. Lighthouse Field Station, School of Biological Sciences, University of Aberdeen, Aberdeen, United Kingdom.

Dolphin sounds dolphin sound