Signal Crayfish in the Itchen

The invasive, non-native American signal crayfish, Pacifastacus leniusculus, has been confirmed as present in the River Itchen below Winchester. The photo shows one Itchen specimen. Little is known about the population though river keepers have found mature individuals that look to be in poor health; this aspect is being investigated by Cefas.

It is crucial for anglers (and others) to remember the risks of spreading signal crayfish and the crayfish plague disease that they can transfer to our native crayfish, a population of which exists in the Upper Itchen. Disinfection and/​or cleaning and drying of fishing gear and boots is vital. More info is available on the WTT website on biosecurity at http://​www​.wildtrout​.org/​c​o​n​t​e​n​t​/​b​i​o​s​e​c​urity and on signal crayfish under Invasive Non-Native Species at http://​www​.wildtrout​.org/​c​o​n​t​e​n​t​/​index.

There is also some excellent information on signal crayfish (and other invasive, non-native species) at the GB Non-Native Species Secretariat website http://​www​.non​na​tivespecies​.org/​i​n​d​e​x​.​c​f​m​?​s​e​c​t​i​o​n​id=47

Also noteworthy is that crayfish trapping needs to be licensed by the EA and that on the Test & Itchen, no licences other than for science and conservation are issued. Trapping for personal consumption has no conservation benefit and can potentially make things worse. There have been some recent, fairly high profile issues in Hampshire around crayfish trapping:



Anyone encountering signal crayfish in Hampshire should inform Ben Rushbrook at the Hants & IoW Wildlife Trust (Ben.​Rushbrook@​hiwwt.​org.​uk) and Tim Sykes at the Environment Agency (tim.​sykes@​environment-​agency.​gov.​uk).

invasive crayfish