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to the rescue! |
The white-clawed crayfish is Britain’s
only native crayfish species and is our largest freshwater
invertebrate, growing up to 12cm in length. It is found
in rivers and streams throughout Europe, but has declined
dramatically over recent decades and the species could
be extinct in Britain within 30 years unless action is
taken. The white-clawed crayfish is a Priority Species
under The UK Biodiversity Action Plan (BAP). The Trust,
together with key partners, is about to embark on an
ambitious project to safeguard its future in the south
west.
Why has there been such a dramatic
decline?
Threats to the white-clawed crayfish
include changes to habitat and water quality, pollution
and most devastatingly at present, the introduction of
non-native crayfish species. These have had a severe
effect on native populations since the 1970s by introducing
a fungal disease or ‘crayfish plague’, against which
white-clawed crayfish have no immune defence. Outbreaks
cause mass mortalities and unfortunately plague can be
easily spread between watercourses by activities like
angling, as the fungus survives on damp, non-disinfected
equipment for several weeks.
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Out
of the frying pan…
…into the fire! Whatever you do, don’t believe the
myths propagated by some TV chefs that catching and
cooking non-native crayfish is of conservation benefit.
It isn’t! And it could well increase the possibility
of transmitting crayfish plague. Unfortunately, once
non-native crayfish are in a river system there is
currently no recognised way of fully eradicating
them, even through intensive trapping. |
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The most notorious of these
non-native species is the American signal crayfish, which
was originally farmed for food in the UK. It was subsequently
either illegally released into the wild or escaped and
the first British record of signal crayfish in the wild
was recorded in the south west. Much bigger and more
aggressive than its British cousins, the signal crayfish
not only carries the risk of introducing plague,
but even where American crayfish don’t carry the
disease and occur with white-clawed crayfish, it
easily out-competes for space and resources through
aggressive behaviour. Studies show that it takes
only five to seven years to wipe out a population
in
this way.
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white-clawed
crayfish |
How can we conserve our crayfish?
The future survival of the white-clawed
crayfish may well depend on identifying refuge or ‘Ark’
sites, where populations can be established which are
isolated and not vulnerable to the colonisation of non-native
crayfish or the spread of crayfish plague.
For the past
ten years, the Trust has been working to conserve crayfish
with partners like the Environment Agency in Avon, and
we have carried out over 350 miles of surveys to find
new populations, monitor existing populations and discover
records of non-native crayfish. These results inform
strategic conservation, including the first known translocation
in England of a vulnerable population to a flowing water
Ark site in 2006.
What happens next?
The good news is
that in October 2008, Natural England awarded funding
to a project bid by Bristol Zoo Gardens (lead partner),
the Environment Agency and the Trust to conserve white-clawed
crayfish at landscape scale throughout the South West.
The aim is to actively mitigate the threat of non-native
species by finding suitable Ark sites to safeguard the
future of the species in our region. Bristol Zoo will
also trial captive breeding, which could be vital for
future conservation. Other important partners include
Bristol Water and the national invertebrate charity,
Buglife. It is hoped that through the quick action and
intervention of the project, white-clawed crayfish will
remain part of our wildlife heritage.
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signal
crayfish |
“It is a great opportunity
to be able to step up our work to a regional scale, as
this is the only way we can plan an effective recovery
for the species and prioritise the most threatened populations
for translocation,” said Lydia Robbins, Trust Ecologist.
“Having worked in this area for a number of years, we’re
delighted to be joining forces with a host of other partners
through the funding awarded, to implement strategic and
sustainable action which we hope sees a long-term benefit
for this important species and our freshwater ecosystems.”
Please
note: white-clawed crayfish are protected by law and
a licence is required for surveys and ‘taking’ the animal,
to ensure disease is not transmitted between sites. A
licence from the Environment Agency is required to trap
any species of crayfish.
For advice contact the Environment
Agency www.environment-agency.gov.uk or
Natural England www.naturalengland.org.uk
Further information
For information on this
project email the Freshwater
Projects Officer
For information about our partners
go to www.buglife.org.uk
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