Marine scientists spent a year listening to the “vast soundscape” created by whales and dolphins off the Scottish coast.
Researchers recorded the iconic underwater calls and clicks of ocean mammals using sophisticated underwater microphones to better understand when migratory species arrive, how long they stay and when they leave.
The project will help inform the safe development of the underwater environment, such as positioning and mitigation strategies for renewable energy and other human activities at sea.
It will also provide insight into the habits of migratory cetaceans as their behavior changes in response to warming sea temperatures and allow for an assessment of how populations are recovering since the end of whaling in the 1950s.
Scientists have already been amazed by the number of sie and humpback whales recorded in Scottish waters.
Common dolphins – photo: Nienke van Geel
Dr Nienke van Geel, a marine mammal expert at SAMS and lead author of the research, said: “At present, most of our predictive models of species distribution and population size are based on occasional sightings at sea. Visual surveys typically take place on the coast and during daylight hours in the summer months, so it is not possible to provide a complete picture.
“We therefore have large seasonal and nocturnal data gaps for marine mammals in Scottish waters and particularly in the offshore area from the Hebrides to the edge of the continental shelf.
“This year-round collection of acoustic data on what is happening and when is extremely exciting and provides the best indication of which species we have in our waters.
“For example, we detected a lot of dolphin activity – their sounds were detected almost every day throughout the year at some sites. There were even more songs of six and humpback whales than we expected.
The data collection, funded by the European Marine Fisheries Fund (EMFF) through the Scottish Government Directorate of Marine Scotland, was carried out using microphones between the Hebrides and the edge of the continental shelf between September 2020 and August 2021.
Overall, the covered area stretched from Lewis and Barra to the west of St Kilda.
Dr Denise Risch, marine mammal ecologist and author of SAMS research, said ongoing funding would be needed for such noise monitoring to provide crucial long-term data to help measure changes in the environment.
He said: “As the ocean warms, more species that have adapted to warmer waters come north. For example, in recent years we have seen more common dolphins following their prey as they migrate north. It will only take another couple of decades before there is a different species composition in Scottish waters.
“This kind of data is valuable in explaining how ocean warming is affecting the movement of cetaceans and their prey, but it is also the best way to find out if some species are recovering from the devastating effects of whaling and how we can protect them. from current threats, such as entrapment in fishing gear and ocean noise. “