Warning after signal crayfish found in River Nar

PUBLISHED: 15:03 30 October 2013 | UPDATED: 15:03 30 October 2013

Signal crayfish

Signal crayfish


A warning has gone out for people not to try and catch a potentially dangerous form of crayfish which has been found in a West Norfolk river.

The signal crayfish has been spotted in the River Nar, with the furthest upstream sighting at High Bridge, near Blackborough.

The Environment Agency (EA) has warned people not to try to trap or kill the species, which spreads deadly disease to other crayfish.

It has reminded members of the public that they must have written authorisation if they do want to catch the species and that they should report any sightings.

“This unwanted visitor preys on native wildlife and spreads crayfish plague, a disease deadly to native white-clawed crayfish,” a spokesman for the EA said.

“Once a non-native species is established it is incredibly difficult to remove them.

“Although signal crayfish are not a native species, they cannot be removed by the public unless they have our written authorisation to trap them.”

One of the reasons for that, the spokesman said, is that it is important to make sure the methods and equipment used are safe for other aquatic animals, like otters and water voles.

“People should not simply try to trap or kill the invasive species,” the spokesman said.

“However, if an angler happens to unintentionally catch a signal crayfish, they should be humanely destroyed and not returned to the water.

“If you want to catch non-native crayfish it is vital that you follow the rules to avoid breaking the law.”

Anyone who wants to fish for crayfish by any means, including hand-picking, must ask for permission from the EA to do so. The EA has strict rules in place to protect native white-clawed crayfish, as well as control the spread of invasive non-native crayfish.

Catching non-native crayfish is only allowed in certain areas, due to the risks to native crayfish, and those with written authorisation must attach EA identity tags to their traps and fishing instruments.

They must also have permission from the relevant land-owner.

Anyone who spots a signal crayfish is asked to report it to the Centre for Ecology and Hydrology, which tracks the species’ movement, by visiting the website

Alternatively, people can download the ‘Aquatic Invaders’ mobile phone app.

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