Fleet herds bottlenose whales from Scottish loch ahead of naval exercise

Their usual mission is a spot of fishing, or a leisurely voyage taking in the picturesque scenes of the Scottish west coast.

But a small army of local boat owners were on Thursday tasked with saving a huge military exercise involving the UK's nuclear submarines and navies from 13 other nations when Nato-backed war games were threatened by a pod of lost northern bottlenose whales.

Exercise Joint Warrior, a bi-annual multinational operation also involving the British Army, the RAF and forces from the US, Canada and Japan, is due to begin on Friday.

However, the two-week operation – which involves live fire exercises, amphibious landings and anti-piracy drills – was cast into doubt when five bottlenose whales were spotted in the Gare Loch in Argyll, blocking the Faslane naval base, the home to the UK's Trident nuclear deterrent.

There were fears that the whales, hundreds of miles from their normal location, could become more distressed due to the sonar used by the military vessels because of their high sensitivity to underwater sound.

The Ministry of Defence admitted its plans for the operation could have to be overhauled due to environmental concerns and in order to comply with animal protection legislation.

On Thursday, the British Divers Marine Life Rescue group was asked to try to shepherd the mammals on a 26-mile journey to open water – but as the charity organisation does not have its own boats, an appeal was made for locals to help out.

Vari Edwards, a marine mammal medic with the charity, said there had been an "amazing" response from amateur seafarers desperate to volunteer.

"We put an appeal out through our contacts, and it was 'we'll lend you this, we'll lend you that, we're available to help in any way at all'," she said.

"Private boats have come from all around the region. Some of them have no toilets and they're on the boats all day, so it's a long, hard slog for them.

"We've had a lot of experience, but I've never been involved in anything like this before. We never want to step in, but we've noticed one of the whales looked extremely thin, so we had to do something to help them."

There were around 20 boats taking part in the mission, with police and MoD vessels supplemented by the volunteers. Between six to 10 were on the water at any one time.

Ms Edwards said the rescue mission was looking promising on Thursday night, although she admitted the charity and MoD would have to go "back to the drawing board" if it failed.

David Devoy, the area coordinator at the charity, said noise emitted from the boats could steer the whales out to sea, with the operation assisted by "spotters" on the land.

It got under way at around noon on Thursday. Boats' positions were co-ordinated by radio in an effort to create a barrier that would prevent the whales from turning in the wrong direction.

At around 6.30pm the operation was stood down due to the loss of daylight after two unsuccessful attempts to shepherd them out of the loch.

Northern bottlenose whales are a deep-diving species normally found off the edge of the continental shelf to the west of the UK and Ireland.

"It is very unusual for them to be in coastal waters," a charity spokesman said. "However, we have had similar incidents in recent years where animals of the same species have entered lochs, including Loch Long, that have left of their own accord without intervention.

"We recently became aware that a significant military exercise is due to begin next week and, as whales are particularly sensitive to underwater sound, have been concerned about the effect it may have on the animals."

The whales have been monitored for around a month, although the military exercise, as well as the concerns at signs of distress from the mammals, led to Thursday's rescue mission.

An MoD spokesman said: "The Royal Navy takes its environmental responsibilities very seriously and continues to work with the relevant UK authorities to ensure all practical measures required to reduce environmental risk and comply with legislation are taken."