SALMON farmers have insisted a highly-critical report which claimed the industry’s expansion could cause “irrecoverable damage” to the environment is not fully backed up by the facts.

A Holyrood committee previously said it was "deeply concerned" about the environmental impact of salmon farming, and concluded the status quo was “not an option" following an inquiry.

It comes amid rising fears over sea lice, the spread of disease and the high mortality rate of farmed fish – as well as the impact of the industry on wild salmon.

But Ben Hadfield, managing director of Marine Harvest Scotland – one of Scotland's largest fish farm operators – said he was “slightly concerned” over some of the findings of the report by Holyrood’s environment committee.

He said: “There are elements of the report which I believe go beyond evidence-based criticism.

“We have to accept that mortality levels have been too high. I can assure you that all the companies have put vast resources – figuratively thrown the kitchen sink at dealing with this issue.

“The sea lice issue and the hazard that uncontrolled, or badly controlled lice present to wild fish is serious, and we take it very seriously. We need more research in that, and we need to work collaboratively with the wild fish.

“But what we mustn’t do is over-exaggerate it to the point of making salmon farming a single issue in certain areas. And I can assure you that that does happen.

“So yes, we think the report is thorough, and very good. It’s obviously setting a clear challenge of improvement to the industry.

“But also as a scientist I can assure you that there are areas where it goes beyond the evidence available, and I’m slightly concerned by that.”

Speaking to MSPs on the rural economy committee, he said other farming industries had higher mortality rates but were “not singled out for such criticism”. But he said he recognised the environmental concerns raised.

Mr Hadfield also accused the National Trust for Scotland of “sensational” comparisons between fish farm waste and human sewage.

Craig Anderson, chief executive of the Scottish Salmon Company, said it was investing in training and new ships – including two vessels specifically for tackling sea lice.

The Global Alliance Against Industrial Aquaculture previously said 2.3million salmon died in the first nine months of 2017 at Marine Harvest farms.

Production in the aquaculture industry is expected to increase from 163,000 tonnes in 2016 to between 300,000 and 400,000 tonnes by 2030.

But the environment committee’s report raised serious concerns about this expansion, and found the salmon farming industry is failing across a range of key areas.

Salmon is Scotland’s single biggest food export, and is estimated to be worth £600million a year.