Bridge over the River Blackwater. Credit Terry Stewart
The Department of Agriculture, Environment and Rural Affairs today urged water users, both recreational and commercial to take precautions when visiting the River Blackwater in Co Tyrone.
The warning comes after dead native white-clawed crayfish (Austropotamobius pallipes) were discovered during routine field surveys at the headwater of the River Blackwater near Aughentaine.
The crayfish were subsequently laboratory tested for the presence of crayfish plague (Aphanomyces astaci) and the preliminary test results confirmed that all three samples tested positive.
Crayfish plague (Aphanomyces astaci) is a type of water mould and outbreaks are characterised by mass mortalities of native crayfish without any apparent effect on other aquatic organisms.
All relevant organisations will be working to prevent the spread of this outbreak to other catchments in the area.
A spokesperson for DAERA said: “If you think you may have found some infected crayfish please enter the location, images and any other details here.
“Crayfish plague tends to move upstream, but at this location it is already high up the catchment, so there may be mortalities further downstream. All field staff will be asked to check the area for any further dead crayfish and will be instructed to collect them if they do and send for further testing until we establish the extent of the outbreak.”
This organism, based on previous incidences across the island of Ireland, has the potential to severely damage the crayfish population, thereby causing an ecological imbalance in the river.
Anyone using this river or any others in the catchment are being urged to observe the "Check, Clean, Dry” and “Stop the spread” biosecurity protocols after leaving the river or before returning to it again.
The department's advice is to:
More details about biosecurity for water users and identifying crayfish plague can be found here