A distinct “species” of brown trout that has never been reported before has been discovered in a Perthshire loch.

The specimen was one of four species of the fish found in Loch Laidon, suggesting biodiversity in freshwater habitats is greater than first thought.

The new species differs from the common form in having lighter skin, and a larger mouth and eyes.

It was discovered by a team from Inverness College, which is part of the University of the Highlands & Islands.

The study, led by Prof Eric Verspoor, found four genetically, ecologically and visually distinctive species that have evolved in the loch over the last 10,000 years.