NICK ALLEN: They are much bigger, they outcompete them for
food, habitat.
They spread a disease called crayfish plague, which if it
gets upstream of a white-clawed crayfish population, it can work
its way through a stream or a burn in two weeks and wipe out
every single white-clawed crayfish in there.
ROSIE HOLDSWORTH: There's a battle going on in Britain's
rivers and streams. Our only native freshwater crayfish, the
white-clawed crayfish, is under threat from an invasive species.
The American signal crayfish arrived in our waterways thanks
to a restaurant craze in the 1970s. But the white-clawed
crayfish is fighting back. I'm Ranger Rosie Holdsworth. Welcome
to Wild Tales and the Crayfish Gladiator Battle.
NICK ALLEN: They're just chock full of personality. They're not
the prettiest things but they're full of character and that's why
they're cool. I love them. I absolutely love them. I think
that doing the crayfish work here at Wallington is some of
the most fulfilling, exciting, sometimes coldest spending all
day in the river work that we do and I just love everything to do
with crayfish.
ROSIE HOLDSWORTH: This is Nick Allen, a National Trust Ranger
at Wallington in North East England.
NICK ALLEN: So for anyone that hasn't seen a white-clawed
crayfish or any kind of crayfish, they're basically, if
you just picture a mini lobster, they are a freshwater
invertebrate. They forage along rivers, burns and streams.
ROSIE HOLDSWORTH: White-clawed crayfish are ecosystem
engineers, keeping streams and rivers clean. They're important
for showing the health of Britain's waterways.
But because of a dining craze in the 1970s... They're currently
under threat, as well as flared trousers and platform shoes.
This decade also brought the introduction of the American
signal crayfish by commercial fish farms, encouraged by the
government.
NICK ALLEN: So crayfish are under threat at the moment for
multiple reasons. The main reason is the invasive signal
crayfish. This was brought over from America because crayfish at
the time were very popular in restaurants. It was thought that
if they were brought over. There's a lot more meat on a
signal crayfish, they're a lot bigger, then they could be sold
to restaurants.
That craze and that fad in the restaurants sort of phased out
and so the crayfish that were being held for food were
released into rivers, ponds, streams, up and down the country
over the years and eventually they took a hold of the rivers
and streams that the white-clawed crayfish call home.
ROSIE HOLDSWORTH: The signal crayfish are a bit like
terminators.
They've made it into our waterways by crossing land and
breaking through any barriers. The signal crayfish are locked
in a fierce battle with the white clawed crayfish, out
competing them for food and habitat and even preying on
their young. And on top of all this, the signal crayfish are
also spreading a killer plague.
NICK ALLEN: They spread a disease called crayfish plague,
which is actually a fungal infection. If it gets upstream
of a white-clawed crayfish population, it can work its way
through a stream or a burn in two weeks and wipe out every
single white-clawed crayfish in there.
Signal crayfish are carriers but don't show any symptoms and can
live with the disease, but our white-claws can't. So in this
country, there aren't many rivers and... Streams and
catchments with white-clawed crayfish left.
Particularly in southern areas, the situation with the invasive
signal crayfish is a lot worse. In the North East, we're quite
lucky. We've got one or two areas with white-clawed crayfish
left, and the Wansbeck catchment is one of the best for
white-clawed crayfish. But nationally, they're incredibly
endangered.
ROSIE HOLDSWORTH: In a bid to save the white-clawed crayfish,
Nick... And the team of rangers at Wallington have implemented
habitats at the property with a little inspiration taken from
the Bible.
NICK ALLEN: Ark sites are one main way that we combat the
signal crayfish invasion. It's a reference to Noah's Ark. It
means that you are taking our native population out of a
potentially dangerous situation and plopping them somewhere
where they can't be touched by the invasives.
ROSIE HOLDSWORTH: So, how many ark sites are there at
Wallington?
NICK ALLEN: We have... Two ark sites on our estate. So we've
got one down here on the hub of the estate and we've got one a
couple of miles out in the middle of the estate on one of
our farms, which is on a spring-fed pond in the middle of
a field.
What you do is you find a place that is a potentially good
crayfish habitat or can be made into good crayfish habitat that
isn't connected to any other streams or burns in the
catchment that could easily be accessed by potential signal
crayfish invasions. So this one here that we've created is in a
historic cattle drink what we did is we created a nice long
dry stone retaining wall.
Which is going to give loads of great habitat for the crayfish,
loads of nooks and crannies for them to squeeze in. We filled it
full of nice stones and rocks, which again creates lots of
habitats and refuges. That's what you call the little homes
that they live in.
We planted lots of willow to shore up the river bank. We
dammed it off at the end, let it pool up, and we translocated a
population of crayfish from the Wansbeck River, which is the
river that runs through Wallington, to create a
self-sustaining population of crayfish. That is isolated from
any potential invasive species.
ROSIE HOLDSWORTH: White-clawed crayfish are active at night,
which is a good time for Nick and his colleagues to survey
them.
NICK ALLEN: They're nocturnal mostly, so they forage at night,
which means that a lot of the surveying that we do if we're
not in the river, stone-turning or looking at our traps for the
crayfish, we go out at night torching, so shining torches
into the water and seeing how many crayfish are active in that
one spot at that time.
So we survey through the summer, and we're just surveying for
general health conditions, seeing what streams have them,
what streams don't, maybe identifying other areas for ark
sites and just keeping an eye on the population, and most
importantly, keeping an eye out for those signal crayfish. If we
don't find them, it's good news.
ROSIE HOLDSWORTH: Crayfish fan Nick admits there are challenges
telling people about crayfish. They're not exactly known for
their charisma, until, of course, you get to know them. So
how do Nick and the team get people as excited about
white-clawed crayfish as they are?
NICK ALLEN: We've got one or two captive bred white-clawed
crayfish that we keep for visitor engagement. It's really
important that you've actually got crayfish that people can
see. It really helps to get people engaged with the
conservation work we do when we've got these captive bred
ones that we can get people and show them. So that's what we're
going to go and see now.
ROSIE HOLDSWORTH: The busy visitor centre at Wallington
allows people to get up close to the white clawed crayfish.
NICK ALLEN: We are by our captive bred crayfish tank. I
think they must have known we were coming because one of our
females in here is sitting right on top of a brick having a good
show off.
ROSIE HOLDSWORTH: Nick gets the crayfish out of the tank to have
a closer look and explains the handy superpowers the crayfish
have when they lose a limb in a fight.
NICK ALLEN: So they have the two big claws at the front. Which
are mainly used for defense. If you look down here one of the
crayfish in here is actually missing one of them because
they've been scrapping. One of the most amazing things about
them is if they lose a leg or they lose a claw they're
fantastic at growing back their limbs.
And they've got eight legs as well, and then you've got these
mini legs at the base of their tail which are called
swimmerets. Their main form of defense is usually just to swim
away from threats so what they do is this really powerful tail
at the back of their tail just flap that.
And they swim away backwards really quick which makes stone
turning and surveying really hard because you've got to be
really quick to get them or they can just blast away and they're
just gone so yeah they've got that powerful tail there as
well.
ROSIE HOLDSWORTH: As well as their powerful tail what they
can do with their shell is also pretty amazing
NICK ALLEN: Yeah they've got that hard outer shell as well
which they molt when they grow out of it so they'll crack out
of this section here between the main carapace and the tail and
they'll sort of reverse out of that and they'll be in that sort
of jelly-like state and then they'll go in a period of
resting while that shell hardens up again.
So you've got to be careful as well when you're surveying. If
you're surveying and you find one and it feels like it's in
that jelly state, we don't take it out and measure it and look
at it, we just leave it to do its thing. We always leave the
old shell. In the tank because they'll go back and nibble at it
and build up their calcium levels again to help re-hard so
they eat it.
ROSIE HOLDSWORTH: So these animals are really cool but they
need protecting. What can we do to help?
NICK ALLEN: So white-clawed crayfish are really important
for our rivers.
They're our only native crayfish and they're under serious threat
at the moment and I think the best thing that day-to-day
people can do is just follow the check, clean, dry procedure
which is anything that's been in the water, be that boots, dogs,
fishing equipment, car tyres, anything that's passed through,
any water, any streams, any burns, check it for mud, clean
it completely and dry it completely.
Because those invasive signal crayfish carry spores of
crayfish plague.
And crayfish plague can survive on damp muddy surfaces for up to
two weeks if you're moving to and from different catchments
you could be spreading crayfish plague into native white-clawed
populations so it's really really important to check clean
dry. I think white-clawed crayfish really get left behind
because they're not the most glamorous conservation effort
they're not the most amazing cutesy species like a squirrel
but they are really really important and it's really
important that they don't get left behind.
ROSIE HOLDSWORTH: With the impact of crayfish plague and
many of Britain's rivers and streams taken over by American
signal crayfish, the white-clawed crayfish is a
nationally endangered species. But there is hope for these
plucky little characters, thanks to conservation work being done
like at Wallington by Nick and the team.
Next time you're on a riverbank, spare a thought for the
white-clawed crayfish. These ecosystem engineers with their
amazing limb regrowing superpowers keep Britain's
rivers and streams clean. So let's do our bit to help them in
their crayfish gladiator battle.
Thanks for joining me on this wild tale. To hear more
episodes, follow us on your favourite podcast app.
And you can also find us on Instagram, @wildtalesnt. See you
next time.