Prince Charles has visited one of Scotland's leading salmon farms in Kinlochleven to observe work on its "cleaner fish" project.

The Duke of Rothesay, who has long championed sustainable fish farming, visited the Marine Harvest site to see how the sustainable fish farm operates.

Steve Bracken, business support manager for Marine Harvest Scotland, explained the cleaner fish project.

He said: "We use commonly-found fish, such as wrasse and lumpfish, which nibble the lice from the salmon as sea lice is a huge problem for the industry.

"We want to move away from medicinal methods of removing sea lice, and we have also been working with new technology to get rid of the sea lice using high pressure water jets or warm water.

"We are delighted that His Royal Highness has come to look at our cleaner fish project because we have had such success in using these smaller fish to get rid of sea lice."

Charles took a boat ride out to tour the fish pens, where he spoke with Marine Harvest veterinarian David Cockerill and Ronnie Hawkins, the cleaner fish manager.

Mr Cockerill said: "We have 40,000 to 60,000 salmon in each cage here. We try to make all our sites sustainable in terms of feed and getting rid of parasites.

"This non-medicinal way of managing sea lice is a natural solution to problems facing the salmon industry."

The Loch Leven site started using wrasse and lumpfish in 2012, and is the first place in the UK to be approved by the international Aquaculture Stewardship Council (ASC), which certifies and labels responsibly-farmed seafood for consumers.

Mr Cockerill added: "We feel that we understand the spawning process of the wrasse and lumpfish, and now the goal is to be able to use cleaner fish on all our farms.

"About three-quarters of our cleaner fish are farmed at several hatcheries across the UK. We think by 2018 we will have sprouted enough for our farms, and by 2020, 100% of our cleaner fish will be farmed as opposed to caught wild.

"I have worked as the vet here for 10 years and non-medicinal methods of getting rid of sea lice is the way forward."

The Prince went on to attend a meeting hosted by his International Sustainability Unit in the nearby Ballachulish Hotel.