A ban has been imposed on hunting trout in Scotland’s longest freshwater loch as a heatwave is causing fish to die a painful death before they can be safely released.

Loch Awe in Argyll near Oban is 25 miles long and is a world-famous fishing destination. Anglers come in search of the legendary Ferox Brown Trout, as well as pike and sea trout. The sports fishermen often take great care to return their catch to the water alive.

But at the weekend, a number of large trout suffered unintended painful deaths, due to what scientists believe to be the high water temperature in the loch, caused by a current heatwave. Alan Kettle-White is a biologist for the Argyll Fisheries Trust and a member of Loch Awe Improvement Association.

He said: “We have had very high water temperatures, much more than usual. Obviously fish like trout are cold water fish. They are at the upper levels that they can tolerate at the moment.