Anglers are being warned to kill any crayfish they come into contact with. It comes after the non-native American Signal Crayfish was found for the first time in the River Nith in Dumfries.
The invasive species kills young fish and destroys natural habitats. Fishermen are now being asked to kill the crayfish if found and to take extra care when cleaning their fishing equipment and clothing to prevent eggs being spread.
A local fisherman has raised concerns about the future of sea life in the Solway firth after he claims he caught the first American Signal crayfish to be found in saltwater in Britain.
Roy Kerr, from Kingholm Quay in Dumfries, said the species has already wiped out most of the fish in nearby Loch Ken.
The Nith Catchment Fishery Trust say that the presence of crayfish would be detrimental to the health of the Nith catchment as they cause bank instability from the act of burrowing, increasing the erosion of the river banks and sediment input to the river.