Scientists fear 'distinct species' of brown trout never seen before is at risk in Scotland's 'Galapagos lochs'

Ron Greer on Loch Laidon in Perthshire - Ron Greer
Ron Greer on Loch Laidon in Perthshire - Ron Greer

Scientists fear the survival of a distinct species of brown trout, which has never been seen before and was only discovered in recent years, is under threat from non-native fish being introduced to pristine Scottish waters.

The rare trout, which could be a new vertebrate species for the UK, is one of four forms found in Loch Laidon in Highland Perthshire.

The same team of experts also detected three forms of Arctic charr in nearby Loch Rannoch, and similar diversity in Lochs Tummel and Ericht.

The freshwater fish are examples of evolution in action in Scotland since the last Ice Age 10,000 years ago, and reveal far greater diversity than previously suspected in some of the country’s most picturesque lochs.

Ron Greer, an independent fisheries ecologist, who was the first person to see the new deep water species in Loch Laidon, describes the Perthshire lochs as an “archipelago of biological islands”. He said the different forms also debunk the common view that all brown trout are the same.

He claims the discoveries are as “gobsmacking” as the diversity in finches that Charles Darwin found on the Galapagos.

laidon - Credit: Ron Greer
Ron Greer (left) and a colleague fishing for ferox trout on Loch Laidon Credit: Ron Greer

But he also fears that exotic fish - pike, roach and rudd - introduced by anglers in the catchment areas of Loch Laidon and Loch Rannoch, could destory the potentially unique ecosystem, almost as soon as it has been discovered.

The new species, a benthic, or bottom living, brown trout was pulled up in nets from the depths of Loch Laidon in 2012, during a search for new forms of charr.

Mr Greer told the Telegraph: “I’ll never forget it. Even as I peered down into the water before lifting them over the gunwale, I was struck by their strange appearance; large blunt head, pale colouration and ‘goggle’ eyes, which were all analogous features to the specialist deep water Arctic charr caught in the same nets in Rannoch some 28 years previously.”

DNA testing has confirmed it is a distinct species and the science has been peer reviewed, with a paper appearing late last year in the Freshwater Biology journal.

Mr Greer said he had told the Scottish Government and Scottish Natural Heritage, which is responsible for Scotland’s “natural, genetic and scenic diversity”, that the fish are in danger.

He would like to see pike removed from the catchment area, and says it may be necessary to relocate unique charr populations to “refuge” lochs.

He added: “We have found an endemic species in our own back yard and if we’re not protecting it, what chance have we got of saving the wildcat?”

“If we had found a new bird or a new dormouse on a Scottish island, they would put up machine gun posts to protect it. There is one new species and three other forms in Laidon. It is so special, it is a unique assemblage.”

He would like to see an agreement with landowners to prevent non-native fish being stocked in the area and called for a “paragraph” to be inserted into existing conservation designations to protect the discoveries.

Dr Eric Verspoor, director of The Rivers and Lochs Institute at the University of the Highlands and Islands, who led the study, said the Loch Laidon trout could in due course be recognised as a new species by the International Union for Conservation and Nature.

He added: “It is a distinct species of trout. From a purely biological point of view it is a distinct evolutionary unit and distinct evolutionary units, which are isolated from other things, are from an evolutionary perspective what we think of as a species.

“We do not know whether this form has evolved somewhere else. Something so marvellous does deserve special protection and concern. This biodiversity really needs to be protected and treasured.

“The important message that comes is that there is a lot of diversity out there that we are not even aware of. We drop a net into Loch Laidon and we discovered no charr, but a new form of trout.

“As soon as you bring in these non-native species you are going to change the whole ecology.

This is serious if we are concerned with the conservation of native biodiversity.”

He suggested that if actions were being taken to eradicate exotic plant species in the UK, there was no reason not to control invasive species to protect freshwater lochs.

A spokesman for the Scottish Government said it was aware of Dr Verspoor’s study and was committed to doing everything it could to protect Scotland’s rivers and lochs. SNH claimed that existing legislation provided “significant protection for these locally unique and adaptable trout” and that 2008 legislation made it illegal to release non-native species without a licence