Pilot whale stranding: acoustic analysis report

3. Aims

Scientists within the Scottish Government’s Marine Directorate – Science, Evidence, Data and Digital (MD-SEDD) have undertaken an analysis of acoustic data collected by the Scottish Passive Acoustic Network (SPAN) project which has underwater sound recorders distributed throughout Scottish waters. This report has focused on passive acoustic data collected with broadband devices and echolocation click detectors at the site closest to the strandings (Tolsta site, see Figure 1), with the aims of:

• identifying any anomalous sounds which may have the potential to elicit a response or potentially harm the pilot whales involved in the stranding event; and
• determine whether any cetaceans were recorded by the acoustic recorders during the hours and days leading up to the mass stranding event.

Additionally, broadband data from a site off the west coast of Lewis (Garenin site, see Figure 1) were also analysed as part of a separate analysis conducted by the Sea Mammal Research Unit (SMRU), University of St Andrews, with the aim of summarising the underwater noise landscape at that site around the time and the days leading up to the stranding, and for presence of cetacean vocalisations. These results are summarised here alongside the analysis of the Tolsta site recordings.

MD-SEDD reviewed potential sources of underwater noise from activities undertaken within the region in the days preceding the stranding event.