Possible outbreak of Crayfish Plague in Lough Owel under investigation

 

“Large numbers” of rhe globally-threatened white-clawed crayfish are reported to have been killed in Lough Owel, in recent days.

The cause of the kill is currently being investigated by the National Parks and Wildlife Service (NPWS) of the Department of Culture, Heritage and the Gaeltacht, Waterways Ireland and the Marine Institute. 

The death of the fish was reported to NPWS by several visitors to the lake. Samples of the crayfish have been collected by Waterways Ireland staff and these will be tested by the Fish Health Unit of the Marine Institute.

According to the NPWS, it is expected that the test results will be available in a few days.

Unexplained mortalities of crayfish have previously been reported on the lake but as Crayfish Plague is present in Ireland, this would seem the most likely explanation. Tests on dead specimens found near the lake earlier in the year proved negative for the Crayfish Plague.

Lough Owel supports a large and up to now healthy population of the endangered White-clawed Crayfish, the only freshwater crayfish species found in Ireland. 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.

All water users who have been on Lough Owel in recent days are asked to observe the Check, Clean and Dry protocol and thoroughly clean their equipment before using it again. This is especially the case if they are moving to another lake or river.

All wet gear should be checked for any silt or mud, plant material or animals. It then should be cleaned and finally dried. Disinfectant or hot water (over 40C) should be used to clean all equipment followed by a 24hr drying period should be adopted as standard practice in all freshwaters.

 

Drying is especially important, including removing of any water from inside a boat and disposing of it on grass. A drying period of at least 24 hours is needed to ensure that a boat is clear of infectious organism.

If Crayfish Plague becomes established there is a high probability that the White-clawed Crayfish will be eliminated from much of the island. Furthermore, if non-native crayfish are found to be established in Ireland, this could have a severe impact on habitats (e.g. destabilising canal and river banks by burrowing) and other freshwater species, such as salmon and trout fisheries. However there is no evidence to date that non-native freshwater crayfish have been introduced to Ireland.