A non-native species of fish could return to Scottish rivers in large numbers this year.
Pink salmon are native to Pacific Ocean waters but have spread to parts of northern Europe after being released into rivers in Russia in the 1960s.
Fisheries Management Scotland said 2017 saw “unprecedented numbers” of pink salmon in UK rivers.
It said due to the fishes’ two-year life cycle the salmon could be seen again this year.
There are concerns the invasive species could become established in Scottish rivers and compete with native Atlantic salmon for food.
The Ness, which flows from the northern end of Loch Ness to Inverness and the Beauly Firth, and Helmsdale in Sutherland were among the rivers pink salmon were spotted in during 2017.
The fish have already colonised some rivers in Norway.
Fisheries Management Scotland has issued advice to anglers on what to do if they should encounter the fish this year.
The national body said the fish should be humanely killed and handed over to the local district salmon fishery board for further analysis.
Anglers have also been asked to report sightings of pink salmon, including their spawning activity in August and September. The invasive species spawns at a different time of the year from Atlantic salmon.
In its new advice, Fisheries Management Scotland said the Scottish government had been involved in work looking at how to control pink salmon.
Options being considered include allowing district salmon fishery boards and trusts to capture the fish under licence in targeted efforts.
Also being looked at is the setting up of a formal framework for anglers’ reports of pink salmon they catch while fishing for native species of fish.