02/05/2018

Endangered UK crayfish released into the wild by Bristol Zoo conservationists

​Conservationists from Bristol Zoological Society have released a healthy population of native crayfish into the wild to help bolster dwindling numbers in UK waterways.

A team of native wildlife experts from Bristol Zoo have collaborated with Hampshire & Isle of Wight Wildlife Trust on the project, which aims to turnaround the plight of the UK’s endangered native white-clawed crayfish.

117 adult crayfish were released into the River Itchen in Hampshire after being reared from eggs at Bristol Zoo for between three and five years to ensure they had a good chance of survival when introduced into their new home.

Jen Nightingale, Bristol Zoo’s UK conservation manager said; “We have worked so hard at the Zoo to successfully breed this endangered species, and we are thrilled to see them return to their natural habitat.”

The River Itchen has one of the last remaining white-clawed crayfish populations in Hampshire and this captive-bred release is a river supplementation upstream of the resident crayfish population. White-clawed crayfish are the only species of crayfish native to the UK and are protected by law.

They are under threat of extinction due to the spread of invasive North American signal crayfish, which compete for food and habitat and carry crayfish plague - a disease which is deadly to white-clawed crayfish.  This disease can be easily spread by people on damp wellies, walking boots, fishing tackle and nets.

As a result, there has been a 70 per cent decline in numbers of the UK’s only native crayfish species in south west England. This species is at risk of becoming extinct from Great Britain in the next 20 years.

As well as releasing captive-born crayfish into the river, conservationists caught ‘berried’’ (egg-carrying) female crayfish to bring back to the Zoo, as Jen explains: “The plight of juvenile crayfish in the wild is fraught with danger and only around five per cent survive. So, as well as supplementing wild populations, we bring berried females into the safety of the Zoo to rear their young. At the Zoo we can offer safe, stable conditions and we have a 90 per cent success rate with hatching and rearing crayfish from eggs.”

She added: knowing that we can keep them and their hatchlings safe and raise them to adulthood is a fantastic feeling. Captive populations are paramount in the effort to halt the threat of extinction of this species.”

Dr Ben Rushbrook of Hampshire & Isle of Wight Wildlife Trust, leads white-clawed crayfish conservation work in Hampshire through the Trust’s Southern Chalkstream project, which aims to protect precious and rare chalkstream habitats.

Ben emphasised the importance of this work from their perspective: “since working with Jen and her team at Bristol Zoological Society, we have been able to take significant steps in the conservation of this species in Hampshire that simply weren’t possible before this collaborative work,” he explained. “These steps are likely to be critical in ensuring the long-term survival of this species in Hampshire.”

Bristol Zoological Society’s crayfish breeding project has been underway for 10 years, with more than 5,000 white-clawed crayfish hatched and reared at the Zoo over that time. In 2017 alone, 1,005 crayfish hatched, with a captive reproductive success rate of 80 per cent.

Invasive, non-native species can have a damaging impact on British plants, animals and ecosystems by spreading disease, competing for food and habitat and through predation.

To help stop the spread of invasive plants and animals, from one water body to another, conservationists are urging the public to ensure they check, clean and dry all equipment, shoes and clothing that have been used in or around waterways.

Bristol Zoological Society’s white-clawed crayfish conservation project is sponsored by IOP Publishing, which has its UK headquarters in Bristol.

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