Crayfish plague alert – 2017

Species Alert for: Crayfish plague (Aphanomyces astaci). Issued by: National Parks and Wildlife Service.

View latest information on Crayfish Plague outbreaksUpdate December 2017

View Emergency Containment Measures. Further guidance in Waterways Ireland notice.

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Click to access Anglers Biosecurity guidance
Click to access Boating Biosecurity Guidance









National map showing infected catchments –View map
River Suir – Counties Waterford and Tipperary. View map

River Deel – Co. Limerick. View map (Best viewed if saved first then open and zoom in to see detail)

Lorrha River – North Co. Tipperary. View map

River Barrow. Counties Kilkenny and Carlow. View map

River Bruskey. Counties Cavan and Longford. View map

As the plague can spread throughout the water bodies connected to these infected rivers, all connecting streams, rivers and lakes should be treated as infected and emergency containment measures also applied to them.

Report sightings of many dead/dying crayfish or sightings of unusual crayfish that might be non-native species (e.g. crayfish with red claws, large size):

Reason for issue: Confirmation of Crayfish plague as present in the River Suir between Clonmel and Carrick-on-Suir. This has caused mass mortality of the native and protected White clawed crayfish (Austropotamobius pallipes). Subsequently confirmed on 01/06/2017 as present in the River Deel, Rathkeale, Co. Limerick; confirmed on 21/08/2017 in the Lorrha river, in north Co. Tipperary and confirmed in the River Barrow, at Royal Oak Bridge on 01/09/2017.

Protected White-clawed crayfish (D. Gerke)
Dead White-clawed crayfish in the River Suir (B. Nelson)









Summary of Potential impacts: Establishment of the crayfish plague could result in 100% mortality of the protected native White-clawed Crayfish (Austropotamobius pallipes).  Throughout its European range, this species has been decimated by the impact of Crayfish plague disease which spread to Europe with the introduction of the plague carrier North American species of crayfish.

The implications of this disease occurrence are extremely concerning. If crayfish plague continues to spread and become established there is a high probability that the native White-clawed Crayfish will be eliminated from much of the island.  Worryingly would be the establishment of non-native crayfish as the experience in Britain and Europe has been that these species have very severe impacts on habitats and other species. Could also be potential impact on salmon and trout fisheries with the loss of  tourism revenue from these fisheries.

What can you do?

  • The Crayfish plague disease can be carried on wet equipment so ALL water users are asked to operate a temporary ban on moving water sports and angling equipment etc out of the infected catchments – commencing immediately. This will avoid the accidental spread of the disease to other areas.
  • Check, Clean and allow all equipment to thoroughly DRY-out then dry for further 48 hours.
  • If drying out equipment is not feasible equipment should be:
    o Power Steam washed at a suitably high temperature (at least above 65 degrees)– use of mobile steam power washers or use of nearby power washers at Service stations as an alternative.
    o Disinfect everything using an approved disinfectant such as Milton (follow product label), Virkon Aquatic (3mg/L), Proxitane (30mg/L) or an iodine-based product for 15 minutes. Items difficult to soak can be sprayed or wiped down with disinfectant. Engine coolant water or residual water in boats/kayaks should be drained and where possible flushed out with disinfectant.
  • Become familiar with the identification of the native and non-native crayfish: view crayfish identification tips.
  • Immediately report all suspected sightings of non-native crayfish or dead native White-clawed Crayfish to or through the online form. Please supply the date of sighting, location name, location coordinates and your contact details. If possible, please supply a photo of the crayfish showing the underside of the claws to aid in verifying the sighting.
  • Do not release any non-native crayfish into Ireland’s waters, it is illegal to do so.
  • Please circulate this species alert as widely as possible.

Invasive status: Crayfish plague is listed as one of Ireland’s most invasive species by Invasive Species Ireland. This species is listed by DAISIE as among 100 of the worst invasive species in Europe. All non-native crayfish, which may be carriers of the crayfish plague, are listed on the Third Schedule Part 2 of the European Communities (Birds and Natural Habitats) Regulations 2011 in Ireland. Five non-native crayfish that have gone through a detailed risk assessment process are each assessed at MAJOR risk of impact to Ireland see:

Introduction status: Established and spreading. The plague is confirmed from 5 different river catchments.

Is there a reference specimen?: Yes. Specimens taken and tested for the DNA plague from all confirmed sites.

Pathway of introduction: Either the disease was introduced accidentally on contaminated equipment (e.g. wet fishing gear, canoes/kayaks, boats etc used recently in affected waters in the UK or elsewhere) or else non-native species have been illegally introduced to the area and have now passed the disease to the native White-clawed crayfish.

If the disease outbreak was accidentally introduced on contaminated equipment then containment may be possible, but if non-native crayfish have been introduced then the disease is likely to become established with severe and probably irreversible ecological impact on Ireland’s freshwater fauna and flora if not acted on immediately.

How the disease got to the Rivers and extent of spread from initial sites of infection infection is under investigation. There is no indication at this stage of how the disease reached the Lorrha River. It is however known that the outbreak on the Suir involved a different strain of the disease to that in the Cavan (2015) outbreak. Samples from the Lorrha River and the RIver Barrow are being tested to determine which strain has caused the outbreak of the disease.

Management actions taken to date: The following actions have been taken to date:

  • Site inspections to assess extent of native White-clawed Crayfish mortalities and to collect specimens for analysis.
  • DNA analysis of the collected dead White-clawed crayfish specimens shows diagnosis of the Crayfish plague.
  • Additional site inspection surveys ongoing.
  • Initial press release and Species Alert issued to key stakeholders and the wider public on 17/05/2017 with up-dates issued as more sites are confirmed for presence of the crayfish plague.
  • Inter-agency Emergency Containment Measures issued first 25th May, 2017 and up-dated as more sites are confirmed.
  • National Biodiversity Data Centre maintains an online reporting function:

Additional Resources:

More information on the White-clawed crayfish (source NPWS)

Crayfish are freshwater relatives of the marine lobsters which they resemble closely. Species of crayfish can be found in many parts of the world with most species occur in North America (330 species) and Australia (100 species). There are seven European species including the White-clawed Crayfish which is the only species naturally occurring in Ireland. The populations of European crayfish have been affected by the impact of introduced mainly American species and disease (crayfish plague). The White-clawed Crayfish was listed on Annex II and Annex V of the Habitats Directive and the species is protected in Ireland under the Wildlife Acts. Ireland has international responsibility for the White-clawed Crayfish as it remains the only part of the EU with no introduced species of crayfish and no proven incidence of crayfish plague. The animal remains common in many lakes, rivers and streams in limestone districts. It is an important species ecologically both as a grazer of plants and as a favoured food item of the Otter.

NPWS has funded research on this species to look at monitoring methods for the species in lakes. Distribution data is also gathered to inform the Article 17 assessment.

Anyone intending to work on this species is required to obtain a licence from NPWS under Sections 22, 23 and 34 of the Wildlife Acts.

Below is the known distribution for White-clawed crayfish in Ireland including historical records (red dots) . Map also shows confirmed records of crayfish plague (white x) and the infected catchments (shaded in orange). Click map download a full resolution with map legend (Pdf 2.89MB).