A rare shot of a white beaked dolphin, spotted by a Silurian volunteer. Photo: HWDT
Sightings of common dolphins across the Hebrides have reached a new record high according to research by marine conservation charity Hebridean Whale and Dolphin Trust.
Evidence collected during 2017 marine research expeditions has revealed a dramatic 24% increase from the previous year’s already record-breaking figures, said the charity.
“We have never documented so many sightings of common dolphins off Scotland’s west coast before,” said Science and Policy Officer Dr Lauren Hartny-Mills.
“Our findings highlight the importance of on-going monitoring and research to strengthen our understanding of what is taking place in Hebridean waters. It is hard to say what is causing this increase, but a rise in sea surface temperatures linked to climate change could be playing a role.”
The Hebridean Whale and Dolphin Trust research was undertaken from the charity’s specialised research yacht ‘Silurain’ during the research season running from April to October last year.
In that time, the Trust recorded 93 sightings of common dolphins – its highest total ever, up from 75 sightings in 2016.
The encounters included a total of 1,340 individual animals, down from last year’s high of 2,303, due to smaller group sizes and fewer super pods.
Over the past two years, the charity has also recorded higher than average number of sightings of white-beaked dolphins – with 14 sightings of 74 individuals in 2017.
Generally preferring colder, deeper waters in the North Atlantic, white-beaked dolphins have distinct white noses; and these fast, acrobatic swimmers are usually spotted further away from the coast – favouring sites around the Outer Hebrides and usually seen in groups of five to 20 individuals.
Dr Hartny-Mills continued: “Silurian is more frequently travelling further north in her surveys, with trips now departing from Ullapool. This could explain why more white-beaked dolphins are being spotted each year.
“It also highlights the need for further research in the far north of our survey area, where white-beaks reside.”
Other findings from the 2017 Hebridean Whale and Dolphin Trust survey season – which recorded nearly 3,00 whales, dolphins, seals and sharks during more than 1,100 sightings – included large numbers of Minkie whales (62 sightings, 80 individuals), and Risso’s dolphins (eight sightings, 58 individuals).
And the harbour porpoise was again the most commonly seen species, with 363 sightings of 621 individuals.
The Trust is the only organisation collecting long-term data on such a large scale on Scotland’s west coast, and relies on volunteers working alongside marine scientist to conduct visual surveys and acoustic monitoring underwater.
Its volunteers and scientists have now recorded more than 30,000 marine mammals and sharks; and the Hebridean Whale and Dolphin Trust is currently recruiting volunteers to work as citizen scientists on board Silurian for periods of one to two weeks from April to September this year.