Winter circumnavigation around Mull

We recently welcomed six local Mull and Ardnamurchan residents aboard Silurian for a winter research expedition. Our aim was to collect much-needed data at a time of year when historically, far lower survey effort has been carried out than the summer season. Over five days, we circumnavigated the Isle of Mull, gathering continuous visual and acoustic data to help deepen our understanding of cetaceans around the Hebrides during the colder, darker months.

Although November is known for challenging conditions, we were fortunate with mostly manageable seas, even if occasionally damp. Within hours of leaving Tobermory, the group had settled into data-collection routines and were rewarded with early encounters with harbour porpoises, common dolphins, and busy flocks of auks.

We travelled south past the Garvellachs and toward Colonsay, then on to the dramatic west coast of Jura, where red deer grazed along the tideline. A white-tailed eagle greeted us in Loch Tarbert, and sightings of great northern diver, long-tailed duck, and shifting rafts of seabirds reminded us how rich these waters remain through winter.

One of the most memorable moments came in Loch Scridain, where a group of common dolphins rode our bow for more than 40 minutes. On the hydrophone, we could hear their echolocation clicks as they foraged for food, followed by lively and loud sociable whistles.

Conditions briefly turned lively, instigating the challenge of the day: how to eat a jacket potato on Silurian’s simulation of a roller coaster. Rolly seas make for challenging baking conditions in the galley, but undeterred, we managed to rustle up chocolate cake and marine-themed gingerbread biscuits.

Sunshine broke through for our final hours at sea, accompanied by more dolphins and a few harbour porpoises. We arrived into Tobermory in the golden hour afternoon light, bringing home a valuable winter dataset that will help improve our understanding of cetacean distribution around Mull.

This expedition was made possible through NatureScot’s support for community-based marine monitoring, enabling local people to take part in data collection that directly contributes to understanding and protecting the waters that shape life on Mull. Each participant brought unique knowledge, curiosity, and fantastic humour, and we’re grateful for their commitment to winter surveying, a task that is often as challenging as it is important.

Thank you Jacqui, Ewan, Alexa, Rachel, Nicola and Lynne – together we surveyed 636 km and collected 55 hours of acoustic recordings. We had 68 marine mammal sightings – common dolphins, harbour porpoise, grey seal and common seal, as well as a possible minke whale!