Almost 75,000 farmed salmon have escaped into open water in Loch Linnhe in the Highlands after a fish farm was damaged by Storm Amy.
Operator Mowi said a net on a pen at its Gorsten farm was torn during the severe weather.
The fish farm company said it was investigating the incident.
Scottish Greens MSP Ariane Burgess and charity WildFish Scotland said the escaped fish could pose a risk to wild salmon.
High winds during last weekend’s storm caused power cuts and also damaged sub-sea cables that bring internet services to Shetland and Tiree.
Mowi said it regretted the escape of fish into Loch Linnhe, a sea loch in Lochaber.
A spokesperson said: “Initial investigations indicate that the intense weather conditions caused mooring anchors to drag, and this brought the pen net into contact with a flotation pipe subsequently causing a tear.
“Despite challenging conditions, Mowi swiftly informed the relevant authorities, including local fisheries stakeholders and is now undertaking a full investigation.”
Ms Burgess said: “The escaped fish pose a serious threat to Scotland’s wild salmon.
“When farmed salmon breed with wild fish, it weakens the wild population and reduces their chances of survival.
“Every escape adds to the pressure on our already depleted wild salmon populations.”
WildFish Scotland has also raised concerns around farmed and wild salmon breeding.
It described the incident as one of the biggest in recent years.
The Scottish government said it was committed to working with industry, conservation groups and communities to ensure fish farming had a “sustainable and prosperous” future.