8-Aug-2006
- The native white-clawed crayfish is to be given
a helping hand by the Environment Agency in a
bid to halt its dramatic decline.
Several hundred of the protected
species, increasingly under threat from the more
aggressive alien species, the American signal
crayfish, are to be moved to a safe haven where
it is hoped it will flourish.
The Environment Agency in the
south-west, assisted by crayfish experts at Avon
Wildlife Trust, is to undertake this unique rescue
by transporting crayfish from the Bristol Avon
and moving them to specially identified streams
in the Mendips.
It is hoped that by re-establishing
the native species in a particular area, free
of the American crayfish, will help it to re-establish
itself and increase in number. They will be caught
from a threatened tributary of the Bristol Avon,
in the Bt Brook catchment area near Chippenham
and transported in prepared, cooled tanks to their
new habitat in the Mendips.
The alien invaders were originally
imported for food, but escaped into the wild where
they now out-compete the smaller and less aggressive
native white-clawed species. Signal crayfish also
carry the fungal disease ‘crayfish plague’ to
which native species have no immunity.
‘Non-native crayfish are bad
news, not only do they push out our native crayfish
they can carry the deadly crayfish plague which
is responsible for wiping out these populations
in large parts of the country,’ said Peter Sibley
from the Environment Agency.
‘Moving the native crayfish
to this new habitat should mean it will be able
to flourish without being threatened by the American
crayfish or wiped out by disease. The creation
of a refuge population in this way has never been
done before but we hope this rescue bid pays off.’
Craig Stenson, from Avon Wildlife
Trust, says: ’This is the first time a translocation
has been attempted – rather than a re-introduction.
Other populations of native crayfish are under
threat – like those in the River Frome and Wellow
Brook, south of Bath – but in the By and Broadmead
Brooks the situation is perilous.
‘The American crayfish are literally
advancing downstream and if we do not take urgent
action, will soon be munching their way through
our crayfish. This rescue is in the nick of time.’
‘We’ve surveyed as many water
courses as possible and found a catchment in North
Somerset with a suitable habitat and water quality
and one where there are no crayfish currently.
We will move all our rescued crayfish to this
first ark site and then, in a second move, take
smaller numbers to new locations next year.’
Detailed investigations into
interactions between crayfish and other species
in the wild, and investigations into methods of
controlling the non-native species has shown that
unless action is taken, the native crayfish could
be wiped out.
A plague on the Sherston Avon
in the early 1980’s wiped out a large number of
native crayfish and resulted in a major re-stocking
programme. The disease again hit this part of
the river in early 2006.
Peter Sibley said it was important
not to harm the resident ecology when transferring
the crayfish to new sites and exhaustive tests
had been undertaken to assess the new habitat
and ensure that there was a high water quality,
tree cover with leaf litter, and rocks and boulders
for refuge.
Notes to Editors:
To protect native species:
non-native species of fish or crayfish must not
be introduced into waters in England and Wales
except under licence
all removals, transfers and
introductions of fish and crayfish to waters in
England and Wales must be licensed by the Environment
Agency
you must have an English Nature licence before
handling white-clawed crayfish
If any native crayfish is caught inadvertently,
it must be returned immediately to the water it
came from
Briefing notes:
Avon Wildlife Trust owns and
manages 37 local nature reserves and fosters a
vision of local landscapes richer in wildlife,
delivering a better quality of life for all. www.avonwildlifetrust.org.uk
The Environment Agency plays
a key role in protecting the white-clawed crayfish,
in fulfilment of its role as ‘Contact Point’ for
the species UK
Biodiversity Action Plan. A
new national crayfish bye-law will enable the
Environment Agency to authorise the use of crayfish
traps throughout England & Wales. Authorisations
will be subject to criteria and conditions depending
on geographical location and purpose of trapping.
The primary reason for trapping
native crayfish can only be for scientific or
conservation purposes. In some circumstances,
trapping of signal crayfish for fisheries management
may be licensed. The native white clawed crayfish
is a protected species by law.
Never use any crayfish as bait
– it is illegal to take native crayfish from the
wild or use them as bait. If non-native crayfish
are used as bait this could spread crayfish plague
and it is illegal.
Under both the Wildlife and
Countryside Act and the Import of Live Fish Act,
it is illegal to introduce non-native crayfish
in England and Wales without a licence.
The Native British crayfish
breeds from the age of three-four
years
females produce up to 200 eggs
young hatch from May to June
adults smaller than signal crayfish
can be identified by white or peach colouring
under the claws
Invasive American Signal crayfish
breeds from the age of two (one
in exceptional circumstances)
females produce up to 500 eggs
young hatch April to May
more aggressive than native crayfish
can be identified by bright red colouring under
the claws and white patches on claw joints.
Paul Gainey
