Crayfish Conservation

Written for Sarah Lee, Head of Conservation ZSEA

As the UK’s only native freshwater Crayfish, the small and bronze-coloured White-Claw Crayfish is under threat from invasive species, pollution and habitat fragmentation. We have been working with Norfolk Rivers Trust and guided by the team at Bristol Zoo Gardens to protect this invertebrate and curb the decline in their numbers.

Banham Zoological Gardens was awarded a £95,300 grant from the Government’s Green Recovery Challenge Fund in 2021 to help boost nature recovery across Norfolk. The fund is a key part of the Prime Minister’s 10 Point Plan to kick-start nature recovery and tackle climate change and has enabled us to build a crayfish hatchery on-site.

The team from ZSEA then ventured out with Ursula Juta, Catchment and Education Manager and Dr Jonah Tosney, Technical Director at Norfolk Rivers Trust to collect four “berried” or egg-carrying female crayfish from ‘ark’ site in a river in North Norfolk. These females were brought to our hatchery and the team has cared for them until the eggs have started to hatch.

Once all the eggs have hatched, the team at Banham will then begin the rearing process to ensure these young crayfish grow strong and healthy, giving them the best chance at survival. Young crayfish are small and vulnerable to predators and disease with a survival rate of only around 5% in the wild. If reared in a hatchery, their survival rate can increase up to 90%. Once they reach a sufficient size, Banham Zoo and the Norfolk Rivers Trust plan to re-release them back into the wild.

Sarah Lee, Head of Conservation at ZSEA, commented: “This project is so important for the conservation of these incredible freshwater invertebrates – their numbers are falling dramatically and we must take action. The Norfolk Rivers Trust are doing everything they can to protect and save our native crayfish, and through our vital partnership, we are committed to saving this keystone species from local extinction in Norfolk with our on-site hatchery. We are so grateful to the Green Recovery Challenge Fund grant for enabling us to build this hatchery and continue our commitment to vital conservation work.

“The crayfish are doing well and are settling into the hatchery. Once their eggs have hatched, the young crayfish will need to grow to a suitable size before release, so they stand the best chance of survival back in the wild. Once they have been health checked they will be released into safe ‘ark’ sites where new populations can be safely established.”

Ursula Juta, Education and Catchment Manager at the Norfolk Rivers Trust said: "The white-clawed crayfish is our largest freshwater invertebrate and while they are rapidly declining or extinct across the many parts of the UK, we are very fortunate to still have a few healthy populations in Norfolk. The Norfolk Rivers Trust and Norfolk Crayfish Group have been desperate to try and get a hatchery running for a few years to secure the future for the crayfish, and we are so thankful for the support of the Zoological Society of East Anglia.

“Managing the invasive signal crayfish and associated crayfish plague is our biggest challenge; the crayfish plague is highly likely to be carried on traps so stopping illegal crayfish trapping and informing and educating people is key to saving our native crayfish and the wider ecosystems."

This small invertebrate is a keystone species. This means that if centres like ours do not keep up this amazing work, and we lose this species, other parts of the ecosystem will start to crumble. The declining population numbers in the wild are due to the pressures of habitat loss, pollution, crayfish plague, and competition from invasive species such as the North American signal crayfish.