16/05/2022

Rare UK crayfish released at a secret site to boost dwindling wild populations

A smiling woman with long blonde hair and wearing waterproofs is crouching in a river holding a white tub. A smiling woman with long blonde hair and wearing waterproofs is crouching in a river holding a white tub.

Endangered crayfish bred by conservationists from Bristol Zoological Society have been released into rivers to help safeguard the future of the species.

More than 200 white-clawed crayfish were released into safe river sites in Somerset and Hampshire as part of a coordinated effort to boost the dwindling number of this Endangered crustacean.

White clawed crayfish release in the River Itchin, Hampshire, by conservationists at Bristol Zoological Society 23.03.22 5


This species is the only native freshwater crayfish in the United Kingdom but is at risk from non-native, invasive crayfish such as the American signal crayfish.

The American signal crayfish not only out-competes the white-clawed crayfish, but carries a fungal disease, called crayfish plague, which is deadly to our native species. 

Invasive signal crayfish species also have serious economic implications. Their extensive burrows destabilise banks and increase the chance of flooding, causing erosion and collapse. And they have decimated invertebrate and fish populations within our rivers.

As a result, the native white-clawed crayfish are listed as Endangered on the International Union for the Conservation of Nature’s Red List.

Bristol Zoo Gardens is home to a hatchery where hundreds of crayfish are bred and reared to adulthood each year, before being released into safe rivers and lakes, free from signal crayfish predators, to boost wild populations.

Dr Jen Nightingale, UK Conservation Manager with Bristol Zoological Society, leads the South West Crayfish Partnership. 

She said: “We are building up populations using captive-born crayfish in the hope that we will prevent them becoming extinct.

“Numbers are in decline and, without projects like this, white-clawed crayfish could disappear from south west England in the next 10 years.”

The crayfish have been released ready for the start of the breeding season.

Bristol Zoological Society’s crayfish hatcheries are the only ones in England from where thousands of white-clawed crayfish have been taken to ark sites all over the country.

Dr Nightingale said: “Signal crayfish are so pervasive and controlling them is a long-term job but ark sites give our native crayfish a safe environment.

Dr Nightingale said research was taking place across Europe on invasive crayfish control methods, including investigations into curbing the reproduction of signal crayfish, to help ensure the survival of the white-clawed crayfish and other native European crayfish species.

Bristol Zoological Society has been a permanent member of the South West Crayfish Partnership. Other organisations in the South West Crayfish Partnership are the Environment Agency, the Centre for Environment, Fisheries, and Aquaculture  Science, Hampshire & Isle of Wight Wildlife Trust, Bristol Water, Buglife, South West Water, the charity Wild Planet Trust and, Nicky Green Associates. 

Now’s your last chance to visit before the Zoo’s last day 03.09.22

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Now’s your last chance to visit before the Zoo’s last day 03.09.22