Distinct 'species' of brown trout discovered by university researchers, suggesting biodiversity underestimated

A DISTINCT ‘species’ of brown trout has been discovered by researchers at the University of the Highlands and Islands, suggesting biodiversity in Scotland’s lochs is much greater than originally thought.

The Rivers and Lochs Institute at Inverness College UHI found four different ‘species’ of brown trout in Loch Laidon, Perthshire, including one which has never been reported before.

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

The researchers used a methodology designed to detect the presence of distinct population types within the brown trout. This involved systematic sampling of the loch and the use of DNA analyses specifically designed to identify different genetic populations of trout.

One of the trout ‘species’, a ‘Profundal Benthivore’, has not as yet been reported to occur in any other loch in the brown trout’s native range.  This type of trout differs from the common form in having lighter skin, and a larger mouth and eyes. It inhabits the deep, dark waters of the loch where little light penetrates and feeds on organisms on the loch bottom.

Professor Eric Verspoor, Director of the Rivers and Lochs Institute said: “This is essentially a distinct species of brown trout, never before reported, and the total number of forms found in Loch Laidon is the highest number so far found in a single lake.  While that in itself is exciting, what’s more significant is that the study strongly suggests that the amount of biodiversity in Scotland’s lochs, and indeed many of the freshwater lakes in the northern hemisphere, has been massively underestimated.  This is because, unfortunately, few of our lochs have so far been studied with methods such as those we employed that are better able to resolve such diversity when it exists.  Thus findings such as those for Loch Laidon may well be the tip of a biodiversity iceberg in Scottish and other northern lakes; the true size of this iceberg will only become clear once we study more lakes using methods such as those we employed.”

The research on the Laidon trout by Professor Verspoor and Dr Mark Coulson, of the Rivers and Lochs Institute, and co-workers was published in September in the journal of Freshwater Biology, with a sister paper published earlier in the year in the Biological Journal of the Linnaean Society.