The Tay Foundation is a Charitable Trust helping the River Tay and its tributaries, fish and environment

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Eradication of North American Cray Fish - Pacifasticus Leniusculus

North American signal crayfish which have been introduced to Britain represent a major threat to the natural ecology of our rivers.

These animals have spread rapidly in many rivers, especially in England. Their numbers are prolific and they can dominate those environments they invade. They eat almost anything, vegetable matter, carrion or fish if they can get them. They threaten fish because they can hide in crevices below stones or under banks, which fish like young salmon and trout also use during the winter or during spates.

By 2006 signal crayfish were present in the upper Earn and several other locations in Tayside but were not known to be present in the Tay, but they were present in a pond from which they could potentially escape into a tributary of the Tay.

As that population of crayfish represented a direct threat which might still be prevented, the Tay Foundation contributed to a project to eradicate it before the crayfish spread to the river, from which it would be impossible to remove them. The procedure used to eradicate them was novel and had only once been used previously in Britain, in some ponds near Edzell in 2004.

The project was very challening but considered successful. However, since that time another population of signal crayfish has been found and in the autumn of 2010 it was confirmed that crayfish from this other population have in fact become established in a tributary of the Tay from which eradication may now be impossible.

A report on the 2006 eradication project is provided below.

signal Crayfish s
North American signal crayfish pose a real threat to the ecology of Scottish rivers even to fish like trout and salmon. Their spread must be prevented. For more information visit Marine Scotland Science.

Project Completed 2006

Crayfish have been poisoned in ponds before, but this was the first attempt anywhere to treat moving water.

The project involved dozens of staff from agencies across the UK and took over 3 weeks to complete.

Two ponds were treated as well as 700m of stream. At all times 100m sections were divided off by double sandbag dams so that no poison could escape and a complex system of pumps and pipes re circled the water, isolated the section under treatment and provided for de-watering.

Thanks are due to a great number of people and organisations for the successful conclusion of the Project, especially to Stephanie Peay the lead consultant, to the staff of the Tay District Salmon Fisheries Board, the Tay Foundation, Scottish Natural Heritage, Scottish Executive Environment and Rural Affairs Department, Fisheries Research Services and to the staff from The Environment Agency who traveled north of the border to lend a hand.

Project supported by:

scottish national heritage

tay foundation

scottish exec

 Photography by Stephanie Peay

Spraying a pond
Spraying margins and banks
Building dams
More dams and more spraying
Dams pumps and pipe work manned 24hours a day
Test crayfish used to ensure 100% effectiveness
Backup systems for backup systems
More dams and more spraying