ONE OF Scotland's finest salmon rivers is facing "absolute ruin" following the escape of thousands of farmed "Norwegian" fish from their cages in a Highland loch.
The escape - involving at least 15,000 fish - took place two weeks ago in Loch Shiel, on the west coast, south of Glenfinnan, according to documents lodged with the Scottish Government.
Fisheries managers and environmentalists, who claim the numb
er of escapees could be much higher, now fear that native wild salmon in the nearby River Shiel will be wiped out as the two species interbreed.
Marine Harvest, the Norwegian-owned company that runs the Loch Shiel salmon hatchery, uses salmon eggs from Norway or Ireland - significantly different genetic strains - to produce its stock.
Scientific studies have shown that the hybrid fish created by interbreeding will have a low life expectancy.
Roger Brook, chairman of the Rivers and Fisheries Trust of Scotland, is even warning that the Loch Shiel escape could end salmon fishing on the River Shiel, once one of the finest salmon rivers on the west coast.
"The apparent sheer scale of this escape is very worrying and has the potential to do enormous damage," he said.
"These fish will go to sea carrying the imprint of the Shiel. If significant numbers return and cross-breed with the Shiel's wild stock then the genetic integrity of the wild fish will be absolutely ruined."
Every year Marine Harvest uses the freshwater Loch Shiel to grow hundreds of thousands of young salmon from the fry stage to the smolt stage, after which they are mature enough to be released into sea cages.
The company confirmed the escape yesterday, saying its Loch Shiel enclosures at Glenfinnan were attacked by predators at the end of September.
Steve Bracken, the company's technical development manager, said: "We suspected a fish escape on September 26 and September 27 at Glenfinnan as a result of a predator, probably a mink or cormorant eating holes below the waterline in two of our nets.
"The number may be as high as 15,000 but we will not be able to confirm this until we recount the fish during the November transports to sea. We greatly regret the loss of any of our stock as it is both embarrassing and expensive."
Bracken said the condition of the Loch Shiel nets were "checked regularly to ensure their integrity throughout their lifespan. As a business we continue to invest in more robust farming equipment, particularly in our pens and moorings."
But one west coast fisheries insider claimed: "The truth is that neither we nor Marine Harvest know the exact number. We believe that from the number of holes there were many times more escaped fish than their estimate, up to 10 times as many."
He claimed mink or cormorant should not be able to breach nets that are "fit for purpose".
The escape is expected to damage recreational angling for wild salmon along the River Shiel, which connects the southern end of the loch to the Atlantic.
Jon Gibb, director of Lochaber fishery board, which has a statutory role for the protection and enhancement of salmon fishing in Lochaber, which includes Loch Shiel, said: "News of this latest escape is particularly disappointing, especially as the fishing prospects on the Shiel have shown some faint signs of recovery, with a return of fishermen to the once thriving river after significant investment in the hatchery and improved fish farm practices at sea.
"This escape will undermine all of the progress which has been made.
"I think this is surely the final proof that salmon farming has no place on Highland lochs with runs of migratory fish. It has to go on shore."
One concern about the escape relates to Marine Harvest's decision to use Norwegian eggs, which has been fiercely resisted by wild fish groups.
They argue that the high likelihood of escapes would result in alien fish being let loose into Scotland's fragile eco-system.
Norwegian salmon have evolved for life in deep fjords, and have a far more muscular build than the lithe Scottish salmon, which have adapted to navigate the shallow, fast-flowing rivers and waterfalls which lie between the sea and their spawning grounds.
