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American Crayfish

An invasive species of crayfish is threatening to take over in Worcestershire streams and watercourses including the Leigh Brook. A local group has formed to tackle the problem and is looking for volunteers. Keith Falconer, the group’s leader, tells us more.

Since 2016, an increasing number of crayfish identified as the North American signal crayfish (Leniusculus pacificastacus) have been found in the streams around Cradley and Suckley. 

This species is well known to affect fisheries and most other freshwater life badly. Deliberately introduced under advice from MAFF in the late 1970s to be farmed as a luxury food, this large crustacean soon escaped from its breeding ponds into British waterways and is now established widely in the UK.
Having been discovered in the Suckley area a few years ago, a citizen's science project was set up to examine the situation and research a new method aimed at controlling the rapidly breeding animals. 

Every female crayfish over three years old can carry up to 250 eggs, which are released in the spring as highly mobile juvenile crayfish. Crayfish can live for over ten years and have been found to have spread down the Cradley and Suckley Brooks into the Leigh Brook. The species is a pest in fisheries and is well advanced on its way to the River Teme and thence to the Severn with its important populations of migratory fish such as Atlantic Salmon and Sea Lamprey.

The experimental release of sterilised male crayfish has failed to slow the breeding of the population where it has been tried by the group and so a new method is now being sought, perhaps introducing a native fish that likes to eat small crayfish. Eels are particularly adept at pursuing the invading crayfish into their homes but it is impossible under current fisheries regulations to relocate adult eels which can carry disease and parasites, but also being an endangered species themselves. Fish such as Perch or possibly Chub may be an option.

The group is also looking for any surviving populations of our small native whiteclawed crayfish - a species that has now been almost wiped out in the West Midlands by the larger and more aggressive American invader. The signal crayfish also carry a fungal disease that doesn’t harm them but has proved deadly to our native crayfish.

It is hoped that a sanctuary isolated from the alien crayfish can be established somewhere in the Malvern Hills, where our native crayfish can survive the imminent danger of extinction in our part of the Midlands, whilst the menace of the signal crayfish invaders is tackled.

The work of the group is supported by the Malvern Hills AONB Partnership and Severn Rivers Trust and they are happy to share their data. In particular the group would welcome new members unafraid to handle creatures that can nip.     

CITIZEN SCIENCE PROJECT
Please contact group leader Keith Falconer (07917 003470) for further information and to volunteer your help. They are happy to deliver a presentation on the crayfish issue to interested groups.