A Colony of rare white-clawed crayfish in a Derbyshire river has been wiped out.
The Environment Agency has confirmed that hundreds were killed by crayfish plague in the River Manifold.
The disease can be spread by the introduction of infected crayfish into water previously free of the disease, or on people's wet footwear or equipment.
Plague spores can survive for up to two weeks in water, but can be killed by drying or disinfect-ing.
The agency said any remaining crayfish downstream of the outbreak were likely to suffer the same fate.
Fisheries and recreation team leader Phil Wormald said: "This is a tragedy for one of our rare native species. It highlights the importance of protecting native crayfish populations and preventing the spread of diseases between river catchments."
To help protect the local crayfish, non-native species of fish or crayfish must not be introduced into waterways except under licence from the Environment Agency.
Also, if any native crayfish is caught inadvertently, it must be returned immediately to the water it came from.
Further advice on how to help protect crayfish is available by calling 08708 506 506 or by visiting www.environment-agency.gov.uk/ fish.