Anglers have been issued with a "kill on sight" message to combat the spread of American signal crayfish.
Environment Minister Mike Russell made the call ahead of the launch of a new leaflet on the issue at the Galloway Country Fair.
The species has become an increasingly common sight in Scotland, particularly at Loch Ken in Dumfries and Galloway.
The signal crayfish has been blamed for eating young fish and destroying their natural habitat.
Mr Russell branded it one of the most problematic, invasive species in the country alongside the grey squirrel, Japanese knotweed and American mink.
'Particular problem'
"As well as competing with valuable native fish such as trout and salmon, the holes they bore into river banks for their nests can leave the land weak and lead to a greater risk of flooding," he said.
"Any angler who catches one is urged to kill it on sight, not to throw it back into the water or take it away alive and contact the Scottish Government, Fisheries Research Services, Scottish Natural Heritage or the Scottish Environment Protection Agency."
The signal crayfish was introduced to waters in England and Wales through fish farms about 20 years ago.
In Scotland, they were first recorded in the catchment of the River Dee in Kirkcudbrightshire in 1995.
Since then, specimens have been found in Scottish ponds, rivers and lochs as far north as Inverness-shire.
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