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.