Outbreak of crayfish plague of great concern
Large numbers of dead crayfish were reported earlier this month in the River Suir along the stretch from downstream of Clonmel to Carrick-on-Suir. DNA analysis has now confirmed that the cause of death was crayfish plague.
The outbreak is of great concern as the stretch of river affected is popular with anglers and canoeists, posing a risk that the disease may be inadvertently carried by them to other watercourses around the country.
The White-clawed Crayfish is the only species of freshwater lobster that we have in Ireland. It is a native and is abundant in lakes, rivers and streams over much of the island especially in the Midlands and in limestone areas where it is an important food source for Otters.
Crayfish plague is caused by a fungus, is spread by spores and is incurable and fatal. It originated in North American and spread to Europe when American crayfish species were introduced that are resistant to the infection but are carriers of the disease. The plague decimated crayfish stocks throughout mainland Europe and Britain leaving Ireland as the last stronghold of White-clawed Crayfishes.
Ireland was free of the disease until recently and is the only European country without alien crayfish. How the disease got to Ireland is unknown; possible pathways are either spores on gear used by anglers or other waters users, or someone is illegally introducing infected foreign crayfish.
The disease is confined to crayfish. People and other wildlife do not contact it. While there is no public health issue, the challenge at present is to try to stop the spread of the plague from the River Suir to other waterbodies.
Anglers and other water users are urged to report sightings of dead crayfish and to ensure that all equipment, clothing and gear that has been in freshwater is disinfected or washed in either hot (over 40°C) water or a strong salt solution and then dried for at least 24 hours before using it in another waterbody. One person could theoretically carry the disease from one river to another via muddy wellington boots.
Ireland supports the greatest population density of Whiteclawed Crayfish in Europe but that population is under threat from any spread of the present outbreak of plague. Anyone with an information is urged to contact the authorities at the earliest possible stage. First point of contact for sightings, reports and/ or further information is Colette O’Flynn, e-mail coflynn@biodiversityireland.ie, ‘phone (051) 306 248.