A sample of the affected animals has been sent to the Centre for Environment, Fisheries and Aquaculture Science for laboratory analysis.
It is believed they could have been killed by the so-called ‘crayfish plague’.
Crayfish plague is a non-native fungus carried by the invasive 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.
Spores of crayfish plague can be carried elsewhere and to other watercourses if equipment that has been in the water has not been thoroughly cleaned.
Helen Beardsley, the EA’s fisheries technical officer, said: “We urge everyone with an interest in this iconic river to help do as much as they can to preserve these precious remaining populations.
“We ask that all anglers, canoeists and other 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.”
The Environment Agency is strongly advising anyone using equipment to clean off any mud or vegetation and remove any standing water.
They should then either thoroughly dry the equipment, preferably in sunlight , or treat it with a disinfectant capable of killing fungal spores.
