Directional hydrophone clusters reveal evasive responses of small cetaceans to disturbance during construction at offshore windfarms

Isla Graham* (Corresponding Author), D Gillespie, K. C. Gkikopoulou, G D Hastie, Paul Thompson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
2 Downloads (Pure)


Mitigation measures to disperse marine mammals prior to pile-driving include acoustic deterrent devices and piling soft starts, but their efficacy remains uncertain. We developed a self-contained portable hydrophone cluster to detect small cetacean movements from the distributions of bearings to detections. Using an array of clusters within 10 km of foundation pile installations, we tested the hypothesis that harbour porpoises (Phocoena phocoena) respond to mitigation measures at offshore windfarm sites by moving away. During baseline periods, porpoise movements were evenly distributed in all directions. By contrast, animals showed significant directional movement away from sound sources during acoustic deterrent device use and piling soft starts. We demonstrate that porpoises respond to measures aimed to mitigate the most severe impacts of construction at offshore windfarms by swimming directly away from these sound sources. Portable directional hydrophone clusters now provide opportunities to characterize responses to disturbance sources across a broad suite of habitats and contexts.
Original languageEnglish
Article number20220101
Number of pages6
JournalBiology Letters
Issue number1
Early online date18 Jan 2023
Publication statusPublished - Jan 2023

Bibliographical note

Open Access via the Royal Society Agreement
This study was funded by Moray Offshore Wind Farm (East) Ltd.

We thank Tim Barton, Michael Oswald, Bill Ruck and colleagues at the Lighthouse Field Station for their assistance with data collection, and the team at Moray East for facilitating data collection fieldwork. Finally, we thank the members of MFRAG for their advice.

Data Availability Statement

Data accessibility. The data and R code for this study are available
through the Dryad Digital Repository:
dryad.7h44j0zvq [36].
Additional data are provided in electronic supplementary
material [37].


  • evasive response
  • mitigation measures
  • acoustic deterrent device
  • offshore windfarm
  • passive acoustic monitoring
  • phonotaxis


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