Data from: Avoidance of windfarms by harbour seals is limited to pile driving activities

As part of global efforts to reduce dependence on carbon-based energy
sources there has been a rapid increase in the installation of renewable
energy devices. The installation and operation of these devices can result
in conflicts with wildlife. In the marine environment, mammals may avoid
wind farms that are under construction or operating. Such avoidance may
lead to more time spent travelling or displacement from key habitats. A
paucity of data on at-sea movements of marine mammals around wind farms
limits our understanding of the nature of their potential impacts. Here,
we present the results of a telemetry study on harbour seals Phoca
vitulina in The Wash, south-east England, an area where wind farms are
being constructed using impact pile driving. We investigated whether seals
avoid wind farms during operation, construction in its entirety, or during
piling activity. The study was carried out using historical telemetry data
collected prior to any wind farm development and telemetry data collected
in 2012 during the construction of one wind farm and the operation of
another. Within an operational wind farm, there was a close-to-significant
increase in seal usage compared to prior to wind farm development.
However, the wind farm was at the edge of a large area of increased usage,
so the presence of the wind farm was unlikely to be the cause. There was
no significant displacement during construction as a whole. However,
during piling, seal usage (abundance) was significantly reduced up to 25
km from the piling activity; within 25 km of the centre of the wind farm,
there was a 19 to 83% (95% confidence intervals) decrease in usage
compared to during breaks in piling, equating to a mean estimated
displacement of 440 individuals. This amounts to significant displacement
starting from predicted received levels of between 166 and 178 dB re 1
μPa(p-p). Displacement was limited to piling activity; within 2 h of
cessation of pile driving, seals were distributed as per the non-piling
scenario. Synthesis and applications. Our spatial and temporal
quantification of avoidance of wind farms by harbour seals is critical to
reduce uncertainty and increase robustness in environmental impact
assessments of future developments. Specifically, the results will allow
policymakers to produce industry guidance on the likelihood of
displacement of seals in response to pile driving; the relationship
between sound levels and avoidance rates; and the duration of any
avoidance, thus allowing far more accurate environmental assessments to be
carried out during the consenting process. Further, our results can be
used to inform mitigation strategies in terms of both the sound levels
likely to cause displacement and what temporal patterns of piling would
minimize the magnitude of the energetic impacts of displacement.