MULTIPLE Scottish salmon farming companies are under investigation by regulators for possible misuse of chemicals, the BBC Panorama programme revealed last night.

The world’s biggest salmon farming company Mowi – formerly known as Marine Harvest – is one of a number of firms under investigation by the Scottish Environment Protection Agency (Sepa).

Farmed salmon are treated with chemicals to ward off disease and infestations but there are limits on how much firms can use.

Norwegian-owned Mowi has denied any wrongdoing and said it used medications sparingly.

The chemicals that are widely used in the fish farm industry include hydrogen peroxide baths and emamectin benzoate, which is put in the salmon’s feed.

There are concerns that the chemicals, as well as faeces and food waste coming from the thousands of salmon in the fish farm nets, could be damaging the environment in some of Scotland’s lochs.

Ian Roberts, head of communications at Mowi, said: “We have confidence in what we’re reporting for medications, it is used sparingly, we of course vaccinate our fish to protect them from health, fish health challenges.

“And we have confidence in the numbers we’re providing so of course we’re supporting Sepa in its audit which has been ongoing for six months and involving the industry.”

Sepa’s enforcement team removed documents during an unannounced inspection of Mowi’s UK head office in Fort William earlier this month, according to the BBC.

The company says the visit was part of an audit and was not unannounced.

Sepa is taking a tougher approach following criticism of the way salmon farming is regulated, and is due to publish new guidelines in the next two weeks.

Terry A’Hearn, chief executive of Sepa, said: “If companies do the right thing, then they have nothing to worry about.

“If companies do the wrong thing, we’re there to find that out and make sure they improve their game. If that’s going to take tough action, you can be assured we’ll take it.”

The industry says salmon farming is a sustainable way to produce food and provide jobs in remote areas.

Roberts said: “I wouldn’t be doing this if I thought that we had a strong negative impact on the environment. It is farming at the end of the day, so, no matter what you’re farming, you have some level of impact. We also need to manage these local impacts around the farms.”

Julie Hesketh-Laird of the Scottish Salmon Producers Organisation said “sustainable growth is in everybody’s interests”.

She continued: “We want consumers, we want the public and anybody with an interest in Scottish salmon to be confident that the salmon farming sector is doing absolutely everything that it can to grow sustainably.”