Crayfish plague alert – 2017

View Press Release issued 17/05/2017

View Emergency Containment Measures issued May, 2017

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Species Alert for: Crayfish plague (Aphanomyces astaci).

Issued by: National Parks and Wildlife Service





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. Znane obszary zarażone to zlewnia rzeki Suir i zlewisko rzeki Deel.

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 to NPWS and Inland Fisheries Ireland. If crayfish plague becomes established there is a high probability that the native White-clawed Crayfish will be eliminated from much of the island.  Worse still 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. One potential impact could be on salmon and trout fisheries and the loss of the tourism revenue from these fisheries.

What can you do?

  • The Crayfish plague disease can be carried on wet equipment so ALL equipment (clothing, fishing and boating gear) that has been in freshwater must be treated with a disinfectant and then completely dried before moving to another area. This will avoid the accidental spread of the disease to other areas.
  • 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 but localised. This species is currently confirmed from just one stretch of river.

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

Pathway of introduction: Either through introduction of an infected American crayfish species or through infected fishing gear.

How the disease got to the River Suir and whether it has spread from the initial area of infection is currently under investigation by NPWS and IFI. Either the disease was introduced accidentally on contaminated equipment (e.g. wet fishing gear or boots 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.

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 was undertaken in May, 2017.
  • DNA analysis of the collected dead White-clawed crayfish specimens shows diagnosis of the Crayfish plague.
  • Additional site inspection surveys ongoing.
  • Press release and Species Alert issued to key stakeholders and the wider public [17/05/2017]
  • 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.