Crayfish plague confirmed in River Wensum near Fakenham

Psart of the upper reaches of the River Wensum. Photo: Bill Smith

Psart of the upper reaches of the River Wensum. Photo: Bill Smith - Credit: Bill Smith - Archant

Thousands of rare native crayfish have been killed by a 'plague' spread by an alien species.

Environment Agency fisheries scientists sent the carcases of white clawed crays off for analysis, when a number of the creatures were found dead in the River Wensum near Fakenham last month.

Since then thousands more of the aquatic animals have been killed by what has now been confirmed to be an outbreak of crayfish plague.

'Since that initial report we have had a lot more,' said EA technical officer Helen Beardsley. 'It's really sad news for the Wensum. It's been confirmed by the lab at CEFAS that it's the crayfish plague. It's gone from suspected to confirmed.'

Experts believe the deadly plague is carried by an invasive alien species, the American signal crayfish.

Signals - named after their bright red claws - began colonising our river systems in the 1970s.

While they carry the plague, a type of aquatic fungus, they are immune to it. As they spread through waterways, they wipe out the indigenous white clawed crays.

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Until the most recent outbreak, scientists believed the signal crays in the Wensum were clear of the plague, because they appeared to be living side-by-side with the native species.

Now experts fear spores of the mould which causes it could be spread to other rivers by a careless angler, canoeist or farmworker.

The Environment Agency is urging river users to take extra care.