A major salmon farming company is one of a number of firms under investigation over possible misreporting of chemical use, the BBC has revealed.
Mowi, which was previously known as Marine Harvest, is said to be among those being looked at by regulators Scottish Environment Protection Agency (Sepa).
Mowi has denied any wrongdoing and said hundreds of audits of its activities are carried out every year.
Farmed salmon are treated with chemicals to ward off disease and infestations such as sea lice but there are limits on the volumes that can be used.
Concerns have been raised that the chemicals, as well as faeces and food waste coming from salmon in fish farm nets, could be damaging the environment in some of Scotland’s lochs.
BBC Panorama has been examining the salmon farming industry and found that Mowi is one of a number of companies under investigation by Sepa.
In a statement, Mowi Scotland said: “Our business is strictly regulated, licensed and inspected, with more than 300 third-party audits occurring every year.
“Sepa’s audit of medicine use is an industry-wide audit and continuation of a process beginning last year.
“We strive for zero-use of medicines, and our innovative use of non-medicinal health solutions has resulted in just 10 grammes of licensed and prescribed antibiotics used in 2018 to treat 1,000 kilogrammes of salmon.
“We’re very supportive of Sepa’s evidence-based industry regulation, inclusive of audits and data transparency.
“Working to exceed Scotland’s strict regulatory regime will ensure the long-term sustainability of our business, the environment where we farm, and the communities where our 1,500 employees live.”
Sepa chief executive Terry A’Hearn said: “As one of a number of organisations regulating finfish aquaculture, Sepa is clear that our job is to make sure environmental standards protect the marine environment for the people of Scotland and we make sure the industry meets those. That’s unequivocally our focus.
“Consequently, across the last 22 months we’ve done more science, more analysis and more listening than ever before. We announced enhanced environmental monitoring and the creation of a new Sepa enforcement unit to ensure compliance is non-negotiable.
“Alongside our routine inspection schedule, officers are currently engaged in a programme of unannounced visits to confirm compliance with regulatory requirements.
“As an organisation based on law and evidence, Sepa routinely reviews data from operators, from Sepa monitoring and from third parties.
“While it would be inappropriate to pre-judge potential outcomes, Sepa will fully investigate suggestions of alleged industry wrongdoing made by BBC Panorama.
“Sepa is unable to comment further on its current audit and unannounced inspection programme under way at present.”