A KEY wild salmon run has been “decimated” by parasites as concern over the future of one of Scotland’s most iconic species continues to grow.

Shocking images from Loch Roag on the Isle of Lewis show fish covered in hundreds of deadly sea lice, which campaigners claim are being spread by salmon farms.

Fishing groups claim the farm parasites are having “devastating consequences” on Scotland’s wild salmon and have called for legislation to be introduced to protect the species.

The issue is currently the subject of an inquiry at the Scottish Parliament, with a report due later this month.

Andrew Graham-Stewart, director of Salmon and Trout Conservation Scotland (STCS), said: “We believe that the explosion in lice numbers on the Loch Roag farms, spreading out into the wider sea loch environment, has had deadly implications for wild fish.

“These fish were literally eaten alive and a large number of adults, that would have bred in the river, have been killed by the lice.

“Laboratory tests have failed to find any other possibility. Adult salmon are well adapted to coping with a few lice but, when plastered with hundreds, they simply do not have a chance.”

Farmed salmon is Scotland’s single biggest food export - worth £600million - and is estimated to provide nearly 2,500 jobs with thousands more supported by the aquaculture sector, often in rural communities.

There are seven salmon farms on Loch Roag, all owned by The Scottish Salmon Company.

STCS claim there is strong evidence that lice levels at the farms have been far too high over the summer, with “numerous” special waste skips full of dead fish leaving the loch over the last two months.

The group believe the lice in the farms will have released “unimaginable numbers” of juvenile lice into the water to infest wild fish.

Mr Graham-Stewart added: “This episode represents exceptionally strong evidence of how lice on fish farms, where many hundreds of thousands of fish are packed close together in cages, can increase rapidly in number and release vast numbers of juvenile lice into the surrounding waters.

“This can have absolutely devastating consequences for wild fish populations.

“The loss of a very substantial proportion of the Blackwater River adult salmon run this year has severe implications for spawning and thus future salmon numbers.

“Furthermore, if sea lice numbers were high during May and June, then migrating wild juvenile salmon are likely to have been badly infested, compromising their survival chances.”

Currently, legislation only offers protection to farmed salmon but SCTS is calling for a statutory obligation which also protects wild salmon.

Some of the measures the fishing group want to see introduced include enforced culls or early harvesting in areas where lice infestations are a problem, and closed containment of farmed salmon which would see it separated completely from the wild fish.

Guy Linley-Adams, solicitor for STCS, said: “As the Scottish Parliament’s Environment and Rural Economy Committees have both heard this year, the law is insufficient to protect wild fish from this sort of event.

“We desperately need MSPs to act quickly to plug this gap in Scottish law.

“Currently, there is no regulatory body that is responsible for protecting wild salmon from the impacts of salmon farming and so one of Scotland’s most iconic species is under serious threat.

“The Fish Health Inspectorate has been to the Roag farms, but the law means it is only able to involve itself in the health and welfare of the farmed fish, though the truckloads of mortalities that have been seen suggest that it has not been very successful.”

A report published earlier this year by the Environment committee warned that Scotland’s marine ecosystem faces “irrecoverable damage” from salmon farming if environmental concerns are not addressed.

The issue is now being looked at by the Rural Economy Committee, which will publish a report within the next few weeks.

A spokesman for The Scottish Salmon Company said: “Fish health and welfare is central to responsible salmon farming and we take this very seriously.

"However, as with any farmed stock, mortalities can occur and this has been exacerbated by the warm weather this summer.

“Following receipt last week of video footage and photographs, the SSPCA visited at random a number of sites.

“The Scottish Salmon Company have not had an opportunity to examine or authenticate this information, but openly facilitated the SSPCA visits and look forward to receiving their feedback.”