The largest mass stranding of dolphins in the UK has been blamed on sonar from navy exercises, "most probably".

Royal Navy exercises have been cited as the “most probable” cause for the mass stranding of 26 dolphins found dead or dying in and around the Percuil River at St Mawes almost five years ago, according to a report released by scientists.

The study has been called a 'game changer' by charity Whale and Dolphin Conservation who said it was compelling that all other causes of death were ruled out.

Read the story from 2008 here:

Dolphins die after mass stranding.

Battle to save stranded dolphins

On June 9, 2008, the UK’s largest mass stranding event (MSE) of common dolphins occurred in Falmouth Bay when at least 26 animals died and a similar number were refloated or herded back to sea.

At the time, exercises involving up to 20 Royal Navy surface and submarine vessels and 11 ships from seven other countries were being conducted off the south coast of Cornwall, Devon and Dorset.

A group of scientists carried out a four year investigation into the incident with their report, published in the journal PLOS One, ruling out all other causes for the strandings.

The report states: “It is possible that the MSE was a ‘two-stage process’ where a large group of dolphins initially entered a coast bay, possibly to avoid a perceived acoustic threat, and then after three to four days in/around Falmouth Bay, a second acoustic or other type of disturbance event occurred, causing them to strand en masse.

"The international naval activities that took place in very close proximity to this MSE are the only established cause of cetacean MSEs which cannot be eliminated and is ultimately considered the most probable, but not definitive, cause.

“All dolphins in this MSE appeared to be in good nutritional condition and showed little evidence of acute physical injury or disease that might have precipitated the MSE.”

The Royal Navy has said it does not agree with the findings. In a statement a spokesman said: “Even its own extensive investigation has found no evidence to show naval activity was responsible.

“Naval training has taken place in the area for over 60 years and active sonar has been in use throughout that time without any similar reported mass strandings. The Royal Navy is committed to taking all reasonable and practical measures to mitigate effects on marine animals.”

The report and its findings, though, have been welcomed by Whale and Dolphin Conservation which refers to them as a “game changer.”

Sarah Dolman, policy lead at the organisation, said: “This stranding followed a major military exercise in one of the UK’s two offshore exercise areas and it is compelling that all other causes of death were ruled out.

“Common dolphins are not a deep diving species and so are not considered particularly vulnerable to noise pollution. As a result, this stranding is a game changer.”