An outbreak of crayfish plague caused by a water mould (a fungal-like organism) has been confirmed by the Marine Institute in the Annies River at Lough Carra, Co Mayo.

The Department of Housing, Local Government and Heritage is urging anyone using rivers and lakes to follow the Check, Clean, Dry approach for all boats, fishing equipment, clothing and other items that come into contact with water, both when leaving an affected site and before entering any other water body.

Minister for Nature, Heritage and Biodiversity, Christopher O'Sullivan TD, said: "Ireland hosts some of the largest surviving populations of the rare, white-clawed crayfish in Europe. This vulnerable species plays an important role in keeping our waterways clean and provides food for wildlife around our rivers and freshwater habitats.

"This disease outbreak is a real threat to Ireland's only native crayfish species as it can spread extremely easily to other waters.

"The National Parks and Wildlife Service is leading efforts and working with stakeholders around Lough Carra to understand the impact of this disease and engage with people using the river. So I'm asking all water users to implement the Check Clean Dry principles to help stop it from spreading. Please check, clean and thoroughly dry all equipment and clothing that comes in contact with the water before entering water again." White-clawed crayfish are globally threatened, protected under the Wildlife Act and listed on Annex II and Annex IV of the Habitats Directive. They occur in rivers, streams and lakes nationwide, and Ireland supports some of the largest remaining European populations. Since 2015, outbreaks have led to the complete loss of white-clawed crayfish in affected waters. While the disease poses no risk to humans, pets or livestock, it is difficult to manage once established.

It is unclear how the pathogen reached Lough Carra, but contaminated wet equipment is the most likely route. Spores can persist in open water and in damp conditions for up to 21 days, making effective decontamination essential. The implications for the wider Lough Carra–Lough Mask–Lough Corrib catchment are considered very serious.

The National Parks and Wildlife Service, the National Biodiversity Data Centre (NBDC), the Lough Carra Association, Inland Fisheries Ireland (IFI), the River Basin Management Service, Mayo County Council and the Marine Institute are coordinating efforts to understand and contain the outbreak.

Water users are reminded to:

- Check equipment and clothing for mud, plants or animal material picked up in the water or on banks. Remove and dispose of debris safely.

- Clean everything thoroughly, ideally with hot water, paying special attention to damp or hard-to-reach areas.

- Dry for as long as possible; if drying isn't feasible, use an appropriate disinfectant. Spores can remain active for up to three weeks.

- Wash dogs after swimming in one river or lake before they enter another system.

- Review guidance at www.invasives.ie/crayfish for further information.

Members of the public who see dead crayfish in the area should inform the NPWS by emailing [email protected] or by logging records at www.invasives.ie.