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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.
Signal crayfish are now present in the upper
Earn and possibly other locations in Tayside.
As yet they are not yet known to be present in
the Tay, but they are present in a pond from which
they could potentially escape into a tributary
of the Tay.
The Tay Foundation is contributing to a project
to eradicate these crayfish before they can spread
to the river, from which it would be impossible
to remove them. The procedure used to eradicate
them is novel and has only once been used previously
in Britain, in some ponds near Edzell in 2004.
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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 from Fisheries Research Services
click
here. |
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Project Completed 2006
Photos courtesy of Stephanie Peay
Project supported by:
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| 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. |
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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. |
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Spraying a pond
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Building dams
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Spraying margins and banks
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Dams pumps and pipe work manned 24hours a day
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Test crayfish used to ensure 100% effectiveness
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Dead crayfish found in pond and stream
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Backup systems for backup systems
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More dams and more spraying
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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. |
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