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NICK ALLEN: They are much
bigger, they outcompete them for

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food, habitat.

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They spread a disease called
crayfish plague, which if it

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gets upstream of a white-clawed
crayfish population, it can work

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its way through a stream or a
burn in two weeks and wipe out

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every single white-clawed
crayfish in there.

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ROSIE HOLDSWORTH: There's a
battle going on in Britain's

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rivers and streams. Our only
native freshwater crayfish, the

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white-clawed crayfish, is under
threat from an invasive species.

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The American signal crayfish
arrived in our waterways thanks

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to a restaurant craze in the
1970s. But the white-clawed

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crayfish is fighting back. I'm
Ranger Rosie Holdsworth. Welcome

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to Wild Tales and the Crayfish
Gladiator Battle.

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NICK ALLEN: They're just chock
full of personality. They're not

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the prettiest things but they're
full of character and that's why

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they're cool. I love them. I
absolutely love them. I think

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that doing the crayfish work
here at Wallington is some of

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the most fulfilling, exciting,
sometimes coldest spending all

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day in the river work that we do
and I just love everything to do

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with crayfish.

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ROSIE HOLDSWORTH: This is Nick
Allen, a National Trust Ranger

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at Wallington in North East
England.

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NICK ALLEN: So for anyone that
hasn't seen a white-clawed

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crayfish or any kind of
crayfish, they're basically, if

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you just picture a mini lobster,
they are a freshwater

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invertebrate. They forage along
rivers, burns and streams.

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ROSIE HOLDSWORTH: White-clawed
crayfish are ecosystem

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engineers, keeping streams and
rivers clean. They're important

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for showing the health of
Britain's waterways.

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But because of a dining craze in
the 1970s... They're currently

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under threat, as well as flared
trousers and platform shoes.

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This decade also brought the
introduction of the American

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signal crayfish by commercial
fish farms, encouraged by the

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government.

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NICK ALLEN: So crayfish are
under threat at the moment for

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multiple reasons. The main
reason is the invasive signal

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crayfish. This was brought over
from America because crayfish at

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the time were very popular in
restaurants. It was thought that

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if they were brought over.
There's a lot more meat on a

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signal crayfish, they're a lot
bigger, then they could be sold

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to restaurants.

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That craze and that fad in the
restaurants sort of phased out

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and so the crayfish that were
being held for food were

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released into rivers, ponds,
streams, up and down the country

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over the years and eventually
they took a hold of the rivers

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and streams that the
white-clawed crayfish call home.

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ROSIE HOLDSWORTH: The signal
crayfish are a bit like

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terminators.

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They've made it into our
waterways by crossing land and

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breaking through any barriers.
The signal crayfish are locked

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in a fierce battle with the
white clawed crayfish, out

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competing them for food and
habitat and even preying on

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their young. And on top of all
this, the signal crayfish are

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also spreading a killer plague.

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NICK ALLEN: They spread a
disease called crayfish plague,

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which is actually a fungal
infection. If it gets upstream

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of a white-clawed crayfish
population, it can work its way

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through a stream or a burn in
two weeks and wipe out every

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single white-clawed crayfish in
there.

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Signal crayfish are carriers but
don't show any symptoms and can

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live with the disease, but our
white-claws can't. So in this

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country, there aren't many
rivers and... Streams and

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catchments with white-clawed
crayfish left.

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Particularly in southern areas,
the situation with the invasive

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signal crayfish is a lot worse.
In the North East, we're quite

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lucky. We've got one or two
areas with white-clawed crayfish

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left, and the Wansbeck catchment
is one of the best for

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white-clawed crayfish. But
nationally, they're incredibly

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endangered.

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ROSIE HOLDSWORTH: In a bid to
save the white-clawed crayfish,

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Nick... And the team of rangers
at Wallington have implemented

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habitats at the property with a
little inspiration taken from

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the Bible.

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NICK ALLEN: Ark sites are one
main way that we combat the

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signal crayfish invasion. It's a
reference to Noah's Ark. It

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means that you are taking our
native population out of a

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potentially dangerous situation
and plopping them somewhere

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where they can't be touched by
the invasives.

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ROSIE HOLDSWORTH: So, how many
ark sites are there at

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Wallington?

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NICK ALLEN: We have... Two ark
sites on our estate. So we've

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got one down here on the hub of
the estate and we've got one a

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couple of miles out in the
middle of the estate on one of

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our farms, which is on a
spring-fed pond in the middle of

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a field.

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What you do is you find a place
that is a potentially good

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crayfish habitat or can be made
into good crayfish habitat that

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isn't connected to any other
streams or burns in the

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catchment that could easily be
accessed by potential signal

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crayfish invasions. So this one
here that we've created is in a

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historic cattle drink what we
did is we created a nice long

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dry stone retaining wall.

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Which is going to give loads of
great habitat for the crayfish,

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loads of nooks and crannies for
them to squeeze in. We filled it

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full of nice stones and rocks,
which again creates lots of

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habitats and refuges. That's
what you call the little homes

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that they live in.

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We planted lots of willow to
shore up the river bank. We

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dammed it off at the end, let it
pool up, and we translocated a

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population of crayfish from the
Wansbeck River, which is the

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river that runs through
Wallington, to create a

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self-sustaining population of
crayfish. That is isolated from

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any potential invasive species.

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ROSIE HOLDSWORTH: White-clawed
crayfish are active at night,

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which is a good time for Nick
and his colleagues to survey

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them.

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NICK ALLEN: They're nocturnal
mostly, so they forage at night,

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which means that a lot of the
surveying that we do if we're

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not in the river, stone-turning
or looking at our traps for the

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crayfish, we go out at night
torching, so shining torches

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into the water and seeing how
many crayfish are active in that

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one spot at that time.

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So we survey through the summer,
and we're just surveying for

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general health conditions,
seeing what streams have them,

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what streams don't, maybe
identifying other areas for ark

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sites and just keeping an eye on
the population, and most

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importantly, keeping an eye out
for those signal crayfish. If we

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don't find them, it's good news.

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ROSIE HOLDSWORTH: Crayfish fan
Nick admits there are challenges

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telling people about crayfish.
They're not exactly known for

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their charisma, until, of
course, you get to know them. So

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how do Nick and the team get
people as excited about

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white-clawed crayfish as they
are?

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NICK ALLEN: We've got one or two
captive bred white-clawed

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crayfish that we keep for
visitor engagement. It's really

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important that you've actually
got crayfish that people can

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see. It really helps to get
people engaged with the

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conservation work we do when
we've got these captive bred

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ones that we can get people and
show them. So that's what we're

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going to go and see now.

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ROSIE HOLDSWORTH: The busy
visitor centre at Wallington

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allows people to get up close to
the white clawed crayfish.

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NICK ALLEN: We are by our
captive bred crayfish tank. I

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think they must have known we
were coming because one of our

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females in here is sitting right
on top of a brick having a good

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show off.

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ROSIE HOLDSWORTH: Nick gets the
crayfish out of the tank to have

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a closer look and explains the
handy superpowers the crayfish

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have when they lose a limb in a
fight.

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NICK ALLEN: So they have the two
big claws at the front. Which

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are mainly used for defense. If
you look down here one of the

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crayfish in here is actually
missing one of them because

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they've been scrapping. One of
the most amazing things about

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them is if they lose a leg or
they lose a claw they're

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fantastic at growing back their
limbs.

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And they've got eight legs as
well, and then you've got these

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mini legs at the base of their
tail which are called

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swimmerets. Their main form of
defense is usually just to swim

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away from threats so what they
do is this really powerful tail

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at the back of their tail just
flap that.

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And they swim away backwards
really quick which makes stone

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turning and surveying really
hard because you've got to be

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really quick to get them or they
can just blast away and they're

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just gone so yeah they've got
that powerful tail there as

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well.

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ROSIE HOLDSWORTH: As well as
their powerful tail what they

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can do with their shell is also
pretty amazing

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NICK ALLEN: Yeah they've got
that hard outer shell as well

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which they molt when they grow
out of it so they'll crack out

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of this section here between the
main carapace and the tail and

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they'll sort of reverse out of
that and they'll be in that sort

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of jelly-like state and then
they'll go in a period of

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resting while that shell hardens
up again.

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So you've got to be careful as
well when you're surveying. If

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you're surveying and you find
one and it feels like it's in

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that jelly state, we don't take
it out and measure it and look

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at it, we just leave it to do
its thing. We always leave the

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old shell. In the tank because
they'll go back and nibble at it

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and build up their calcium
levels again to help re-hard so

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they eat it.

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ROSIE HOLDSWORTH: So these
animals are really cool but they

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need protecting. What can we do
to help?

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NICK ALLEN: So white-clawed
crayfish are really important

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for our rivers.

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They're our only native crayfish
and they're under serious threat

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at the moment and I think the
best thing that day-to-day

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people can do is just follow the
check, clean, dry procedure

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which is anything that's been in
the water, be that boots, dogs,

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fishing equipment, car tyres,
anything that's passed through,

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any water, any streams, any
burns, check it for mud, clean

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it completely and dry it
completely.

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Because those invasive signal
crayfish carry spores of

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crayfish plague.

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And crayfish plague can survive
on damp muddy surfaces for up to

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two weeks if you're moving to
and from different catchments

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you could be spreading crayfish
plague into native white-clawed

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populations so it's really
really important to check clean

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dry. I think white-clawed
crayfish really get left behind

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because they're not the most
glamorous conservation effort

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they're not the most amazing
cutesy species like a squirrel

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but they are really really
important and it's really

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important that they don't get
left behind.

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ROSIE HOLDSWORTH: With the
impact of crayfish plague and

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00:10:30,097 --> 00:10:33,059
many of Britain's rivers and
streams taken over by American

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00:10:33,159 --> 00:10:35,821
signal crayfish, the
white-clawed crayfish is a

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nationally endangered species.
But there is hope for these

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plucky little characters, thanks
to conservation work being done

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like at Wallington by Nick and
the team.

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Next time you're on a riverbank,
spare a thought for the

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00:10:50,172 --> 00:10:53,814
white-clawed crayfish. These
ecosystem engineers with their

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00:10:53,894 --> 00:10:57,244
amazing limb regrowing
superpowers keep Britain's

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rivers and streams clean. So
let's do our bit to help them in

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their crayfish gladiator battle.

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Thanks for joining me on this
wild tale. To hear more

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00:11:11,275 --> 00:11:13,977
episodes, follow us on your
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00:11:16,459 --> 00:11:20,922
And you can also find us on
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00:11:20,942 --> 00:11:21,483
next time.