A substantial increase in common dolphin numbers around the Hebrides is to be studied in a new season of marine research expeditions beginning next month.
The Hebridean Whale and Dolphin Trust say the number of sightings has risen by 68% over the last 12 years.
The causes – and broader effects on the marine environment and other species – are still unclear.
Hebridean Whale and Dolphin Trust is now recruiting volunteers to work alongside marine scientists in its annual summer surveys, which it hopes will shed further light on the dramatic changes.
Dr Conor Ryan, sightings officer at the trust, said: “An increase in common dolphins means that those wishing to encounter dolphins in the wild are in luck – but further research is needed to explain why this is happening, the extent to which this has been caused by human activity, and the implications for other cetacean species.”
Common dolphins come to the Hebrides each spring to take advantage of seasonal food
stocks. They are gregarious, often approaching boats to bow-
Despite their name, common dolphins were once only occasionally seen in the Hebrides, preferring more southern waters generally warmer than 10°C.
With climate change causing sea surface temperatures in the Hebrides to rise at a rate of 0.5°C per decade, it appears that such warmer water species are starting to colonise new areas in the north or closer to shore.
As this shift potentially creates new opportunities for common dolphins, it may be generating competition for food with other dolphin species or seabirds.
Volunteers will live, work and sleep on the trust’s survey vessel, Silurian, for up to 12 days.
They will receive training and work with scientists – conducting visual surveys, acoustic monitoring using specialist equipment, and cetacean identification through dorsal fin photography.
Areas covered depend on the weather but will range from Mull of Kintyre in the south, Cape Wrath in the north and St Kilda in the west.
Rise in dolphin numbers around Hebrides
19 April 2015