Discovery of dead crayfish in Norfolk river raises concerns about survival of iconic species

White-clawed crayfish. Picture: Environment Agency

White-clawed crayfish. Picture: Environment Agency - Credit: Archant

The discovery of dead crayfish in a Norfolk river has raised concerns about the survival of an iconic species.

Signal crayfish. Picture: Trevor Renals

Signal crayfish. Picture: Trevor Renals - Credit: Archant

Dead and dying native white-clawed crayfish were found in the River Glaven by members of the Glaven Conservation Group and the Norfolk Rivers Trust upstream of Letheringsett Mill, near Holt.

This section of the river holds a native population as the mill acts as a barrier to the spread of invasive American signal crayfish, which are present below the mill.

After consultation with the Environment Agency, samples of the affected white-clawed crayfish were sent to the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) for analysis and the results are expected in the next few days.

It is suspected the cause could be an outbreak of crayfish plague.

Crayfish plague is a non-native water mould (fungus) that is carried by American signal crayfish. This virulent disease has wiped out many populations of our endangered native white-clawed crayfish in England and Wales. Although signal crayfish carry the disease, they are not susceptible to it.

For many years populations of native and signal crayfish co-existed in a number of watercourses within Norfolk.

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Spores of crayfish plague can be carried elsewhere and to other watercourses if equipment that has been contaminated has not been thoroughly checked, cleaned and dried or vigorously treated with suitable disinfectant.

Jeff Compton, monitoring Officer with the Environment Agency, said: 'It is very upsetting to witness the death of historic native crayfish within Norfolk.

'We urge all water users to do as much as they can to preserve the precious remaining populations. A number of native crayfish populations exist within Norfolk rivers. The continued survival of this iconic species is important at local, national and European levels.

'We ask that all river users follow the Check, Clean Dry guidance and thoroughly clean their equipment before using it anywhere else to stop this disease from spreading.

'We would like to thank those involved for reporting this information and encourage members of the public who spot any dead crayfish to please let us know as soon as possible through our incident hotline on 0800 807060.'