The outbreak of crayfish plague in the River Suir at Clonmel, Co Tipperary is "extremely concerning" for the future of the species in Ireland, environmental groups have warned.
Large numbers of dead crayfish were found at riverbanks between Clonmel and Carrick-on-Suir in Co Tipperary, and recent DNA testing confirmed the cause of death was crayfish plague.
The disease only affects the crayfish species but is 100 per cent fatal if contracted by the fish.
The National Parks and Wildlife Service have warned it is “highly probable” that the entire Irish crayfish population will be wiped out if the disease spreads from the River Suir to other regions.
They have also estimated the plague will kill off all of the Irish crayfish in the River Suir.
The plague was introduced to Europe a number of years ago from the North American species of crayfish, and has decimated most of the indigenous crayfish population across European waters.
Environmental groups have warned if the Irish white-clawed crayfish population is killed off by the plague, the North American species of crayfish may take its place and establish in Ireland.
A spokeswoman from Inland Fisheries Ireland said the North American species has overtaken British and European waters, and they "have had very severe impacts on habitats and other species".
The disappearance of the native crayfish would also have an impact on many species who feed on the fish.
“Crayfish are a valuable food item for many freshwater species. Otters, herons, trout and pike all feed on crayfish where they are available” the Fisheries Ireland spokeswoman said.
Ciaran O’Keefe, scientific advisor at the National Parks and Wildlife Service said there is evidence the disease is spreading up the river and will “wipe out the entire river’s” population of crayfish.
Crayfish also feed on the vegetation in the river, keeping the level of vegetation down and controlled he said.
How to prevent the spread of the plague
Tipperary County Council and the National Parks and Wildlife Service have issued emergency instructions to any fisherman or those active in the River Suir to help prevent the spread of the plague.
Fishermen or anyone using the river have been advised that all wet gear, equipment, or clothing should be cleaned of mud, and left to dry for over twenty four hours before being used in the water again.
The crayfish plague organism can be carried on wet equipment to new sites, so disinfecting fishing equipment and clothes is essential to prevent the disease spreading to other unaffected crayfish populations in Ireland.
The last recorded outbreak of the crayfish plague among the Irish population was in Co Cavan in 2015.
That incident was successfully contained and did not spread to other Irish rivers or waterways.
The National Parks and Wildlife Service fear that the size and popularity of the River Suir among anglers and canoeists will lead to the plague spreading to other parts of Ireland.
Ireland has the largest surviving population of the white-clawed crayfish, which has become a globally threatened species.
The Irish National Biodiversity Data Centre say the cause of the plague’s introduction to the River Suir is not yet known.
“Either the disease was introduced accidentally from equipment used in contaminated UK waters, or else non-native species have been illegally introduced to the area and have now passed the disease to the native white-clawed crayfish” a spokesperson said.
