Historic garden may be last refuge for threatened crayfish

Non-native red signal crayfish SUS-170302-151629001
Non-native red signal crayfish SUS-170302-151629001

An historic garden in Handcross may be the last refuge in Sussex for embattled native crayfish.

Staff at the National Trust-owned Nymans estate are now battling to protect the species - Britain’s only native crayfish - and hope that the estate garden may provide valuable niches for it.

Native white-clawed crayfish SUS-170302-151612001

Native white-clawed crayfish SUS-170302-151612001

Native White–clawed crayfish were once widespread in the UK, but numbers have been decimated by the invasive non-native Signal crayfish from North America. Many have been hit by a form of crayfish plague.

The White-clawed crayfish is now classed as ‘endangered’ internationally, with an estimated decline of over 70 per cent in the UK since the 1970s.

As well as being bigger and more aggressive than the native crayfish, the foreign Signal crayfish often carries crayfish plague, a fungal disease which affects the smaller native species but not the invader.

It was while trying to control the Signal crayfish that Nymans lead ranger Chloe Bradbrooke discovered a few of the native species.

She said: “We have been trying to control Signal crayfish in waterbodies at Nymans since they were discovered last summer.

“One day, after months of trapping the American signal crayfish, I noticed a few that looked a little different and, it may sound strange, they acted differently too.

“Despite some initial scepticism I thought perhaps they could be our native crayfish. I am glad I followed my instincts and had them expertly verified, as we now have this very exciting discovery of a remnant native population.”

The Trust is currently working with the Environment Agency, Natural England and other conservation bodies to try and protect the native crayfish which is threatened across Europe.

Work planned at Nymans for the coming year is likely to include identifying key areas where the two species are present on the estate, assessing numbers of the two species and identifying whether the Signal crayfish are diseased.

Bio-security measures will also be taken to try to ensure the native crayfish remain disease free and controls put in place to limit the numbers of the invaders.

Meanwhile, plans will be drawn up to maximise the White-clawed’s chance of long-term survival.