Observations and tracking of killer whales (Orcinus orca) with shore-based X-band marine radar at a marine energy test site

The Atlantic killer whale (Orcinus orca) is a top-level marine predator with a global range, being found in all of Earth’s oceans. The potential interaction between killer whales and marine renewable energy projects requires surveillance and monitoring efforts that call for new technologies, with marine radar showing promise in the field. Marine radar images recorded at the European Marine Energy Centre (EMEC) were used to track a pair of male killer whales undertaking Surface Active Behavior (SAB) with visual observations used as validation. Using a tidal prediction model, the tide-adjusted, radar-derived target speeds between SAB events provide estimates of swim speeds averaging 4 ms-1 and time between SAB events of 30 s. The similarities between the radar signatures of the animals and sea clutter, combined with their low occurrence compared to other imaged phenomena renders automatic detection with this system difficult. However, the combination of opportunistic radar imagery and independent visual observation has allowed the radar signature of one form of killer whale SAB to be documented. It is hoped that with a greater number of validated observations such as these that automated, radar-based identification and the benefits it will bring to long-term observations at MRE sites will be possible.