Charles, known as the Duke of Rothesay in Scotland, visited Amity Fish Company Ltd in Peterhead on Tuesday.
The company is headed by renowned skipper Jimmy Buchan, who starred in the Bafta award-winning series.
Mr Buchan said: “We were proud to host a walk-through of our supply chain operations where we explained our desire to improve on our sustainability footprint and how we are working to improve the integrity of our products during transit to customers.”
Charles also learned about the challenges to the business from Covid-19 and lockdown.
On Tuesday, Charles also visited Rora dairy which produces a range of Scottish yogurts on an organic family-run farm near Peterhead.
Bruce and Jane Mackie welcomed him to their farm, which has been selected to supply November’s Cop26 climate change conference in Glasgow.
Mrs Mackie said: “This year has been tremendously exciting for us all at Rora and we were delighted to welcome Prince Charles to the farm to show him the results of our work to improve biodiversity and sustainability here.
“Our organic certification and selection for Cop26 is recognition of our efforts and, like so many of our customers, we really feel that the prince, who is a farmer himself, understood and appreciated this.”
Glen Garioch in Oldmeldrum, one of the country’s oldest distilleries, is also welcoming Charles during his royal tour in the North East.
It is being renovated and upgraded following a £6 million investment from American drinks company Beam Suntory to reinstate more traditional production processes and reduce the distillery’s carbon footprint.
The Duke of Rothesay’s tour also includes a visit to Inverurie where he will meet with traders at the town’s farmers’ market and visit the Garioch Heritage Centre, home to collections highlighting the history of the area.
Charles will also meet with the Inverurie Community Allotment and representatives from Grampian Opportunities, an organisation which promotes learning, volunteering and employment opportunities, and offers support for disabled people and people with mental health problems.