Catchment News

Outbreak of Crayfish Plague on a stretch of the River Suir downstream of Clonmel to Carrick-on-Suir

All water users are being urged to take precautions after confirmation of an outbreak of Crayfish Plague on a stretch of the River Suir downstream of Clonmel to Carrick-on-Suir.

It comes after large numbers of dead freshwater crayfish were reported on the river earlier this month. DNA analysis has now confirmed that the cause of death was crayfish plague.

What can you do to help?

Clean, Check and Dry

Anyone using the river is being urged to observe the ‘Check, Clean and Dry’ protocol once they leave the river and before using it again.

This means that all wet gear (boats, clothing and equipment) should be checked for any silt or mud, plant material or animals before being cleaned and finally dried. Disinfectant or hot water (over 40 degrees Celsius) should be used to clean all equipment and this should be followed by a 24 hour drying period.

The drying period is especially important in ensuring that all equipment is clear of infectious organism, including the removal of any water inside the boat. The crayfish plague organism can be carried on wet equipment to new sites and containment of the outbreak is essential to prevent spread to other unaffected populations in Ireland.

Can you print this sign?

You can also print this sign (PDF) and put it up at any point where people access the river near you. Thanks.

Can you share this on social media?

We’d would also like you to share this image or this post from the Waters and Communities office on your social media channels. Thanks.

Report Crayfish sightings

As well as following the ‘Check, Clean and Dry’ protocol when using the river and to alert the authorities of any mass mortality of crayfish as well as sightings of unusual crayfish (e.g. red claws, large size). by emailing Colette O’Flynn (coflynn@biodiversityireland.ie) at the National Biodiversity Data Centre, Waterford.

The kill has only impacted White-clawed Crayfish and other freshwater animals are not affected. This is a characteristic feature of the disease which only infects species of crayfish but causes 100% mortality. All agencies including the National Parks and Wildlife Service, Inland Fisheries Ireland and Tipperary County Council will be working to contain the outbreak to this stretch of the River Suir. Given the experience of outbreaks elsewhere, a total kill of the population is expected which will have major consequences for the ecology of the river. Crayfish are very common in the Suir and are important in maintaining its ecology.

This is the second confirmed outbreak of the disease in Ireland following one in County Cavan in 2015. There is no indication of how the disease reached the Suir although a link to the Cavan outbreak is considered unlikely as the disease there appears to have run its course. This outbreak on the River Suir is of great concern as the stretch of river affected is popular with anglers and canoeists.

The White-clawed Crayfish is a globally threatened species and Ireland holds one of the largest surviving population. It is the only freshwater crayfish species found in Ireland and is present in lakes, rivers and streams over much of the island. Throughout its European range, this species has been decimated by the impact of Crayfish Plague which spread to Europe with the introduction of North American species of crayfish. Until 2015, Ireland was considered free of the disease and it remains the only European country without any established non-native crayfish species.

If Crayfish Plague becomes established there is a high probability that the White-clawed Crayfish, which is currently protected under Irish Law and the EU Habitats Directive, will be eliminated from much of Ireland. If non-native crayfish are found to be established in Ireland, this could have a severe impact on habitats as they can destabilise canal and river banks by burrowing. It could also impact other freshwater species, such as salmon and trout fisheries. At this time however, there is no evidence that non-native freshwater crayfish have been introduced in this country.
Notes

Anyone who sees any dead or dying crayfish should report this to National Parks and Wildlife Service, Inland Fisheries Ireland, Tipperary County Council or Colette O’Flynn at the National Biodiversity Data Centre, Waterford (email: coflynn@biodiversityireland.ie)

Members of the public who suspect they have seen a non-native species of crayfish are asked to take a picture of it showing the underside of the claws and submit this through this web page http://records.biodiversityireland.ie/record/invasivesor direct to Colette O’Flynn (email: coflynn@biodiversityireland.ie) Phone: 051 30624

White-clawed Crayfish Austropotamobius pallipes: This occurs throughout Ireland mainly but not exclusively in areas of limestone geology. It lives in a very broad range of freshwater from tiny streams and ditches to many small, medium and large lakes. The species is a generalist feeder and it in turn is a significant prey item of the Otter.

Crayfish Plague is caused by a fungus-like organism Aphanomyces astaci which is of North American origin but now occurs throughout Europe. The Crayfish Plague organism (technically an Oomycete and often called water moulds) normally grows on the outer shell of crayfish and as North American crayfish are generally immune to it, as they can prevent any infection reaching their body tissues. However, when the water mould infects White-clawed and other European crayfish, it rapidly, and fatally, spreads into the body tissues. Infected animals become distressed and behave abnormally and may survive several weeks before dying.

Non-indigenous Crayfish: These are any species which are not native to the country. Many crayfish species have been moved within Europe and into Europe from North America and Australia. The most significant of these is the North American Signal Crayfish Pacifastacus leniusculus which is one of the main carriers of Crayfish Plague. This species is much larger than the White-clawed Crayfish and with distinctive red coloration on the underside of the claws.

Background information on the native and non-native crayfish and the crayfish plague is available to view and print from these web pages: http://www.biodiversityireland.ie/crayfish-plaque-2017and http://www.npws.ie/sites/default/files/publications/pdf/Crayfish_leaflet.pdf

Information on the Check, Clean, Dry protocol is available from the GB Non-native Species Secretariat web site http://www.nonnativespecies.org/checkcleandry/