Chester Zoo begin rescue mission for species thought to have gone extinct nearly thirty years ago

Chester Zoo has begun a rescue mission after rediscovering a critically endangered species 28 years after it was declared extinct.  

Conservationists at the zoo have become the first in Europe to successfully breed a critically endangered insect, following its rediscovery in the River Dee.

Called in by fellow charity Buglife Cymru, the conservationists began an emergency breeding effort for the scarce yellow sally stonefly - which had not been recorded since 1995.

Two small populations were found in the river, believed to be the only remaining location for the stonefly in the UK.

Rescue mission

In 2022, conservationists from Buglife Cymru, Chester Zoo, the Welsh Dee Trust and freshwater invertebrate specialist John Davy-Bowker set about sampling and carefully collecting a small number of the stoneflies from the areas where they were rediscovered.

Thirty of the animals were then carefully transferred to a special behind-the-scenes facility at Chester Zoo where a dedicated team of specialists set about studying the insect during its lifecycle.

Experts believe it to be the first time ever that the species has been successfully bred and reared through its complete lifecycle in a zoo setting.

After receiving National Lottery Heritage funding, conservationists now plan to carry out further surveys for the species along the Dee, helping to inform future conservation efforts over the next four years, which may include re-introductions to areas where it has historically been recorded.

Joe Chattell, an Aquarist at the zoo, said: “We’re enormously proud to be the first zoo to successfully breed this special stonefly, adding valuable scientific insight into the project with our partners, Buglife Cymru, who are safeguarding the species and its future here in the UK.”

Scarce Yellow Sally Stonefly fact file

• The scarce yellow sally is a critically endangered stonefly which is found along a 20km stretch of the River Dee in Wrexham County Borough.
• The species is highly vulnerable to habitat loss, pollution incidents from sewage and litter, as well as climate change.
• The scarce yellow sally stonefly is a critically endangered species that was first identified in the River Dee in 1959 and was regularly recorded up until 1995 when subsequent surveys failed to locate any living populations in the UK. The species was presumed to have gone extinct in the British Isles.
• Surviving European populations are likely to be few in number and occur mainly in eastern Europe in the Lafnitz and Rába rivers in south-eastern Austria and western Hungary, the River Tisza in Hungary, the River Jelesna in Slovakia where a single nymph was found in 1998, Northrhine-Westfalia in Germany and in central Sweden. The scarce yellow sally may potentially also occur in Finland, Estonia, Latvia and Lithuania.