Establishing a white-clawed crayfish hatchery to bolster the population of this endangered native species in Norfolk.
White-clawed crayfish, a native species protected under UK law, once thrived in our rivers. Nowadays, the species is at a high risk of extinction, threatened by pollution, habitat loss, crayfish plague and competition from invasive species such as the American signal crayfish.
Existing largely in its own nocturnal, underwater world, white-clawed crayfish play an important role in the functioning of the wider riverine ecosystem, and we are very fortunate to still have a few healthy populations in Norfolk.
Working in partnership with the Zoological Society of East Anglia (ZSEA), we established a dedicated hatchery at Banham Zoo to breed and rear white-clawed crayfish.
Four females carrying eggs (known as berried females) were caught in North Norfolk and carefully transported to Banham Zoo to be slowly acclimatised to the hatchery. Once the eggs hatched, the ZSEA team began the rearing process to ensure the young crayfish reach a suitable size before their wild release; 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%.
The aim of this process is to release the young crayfish to safe ‘ark sites’ (isolated refuge areas away from threats) where new populations can establish and have the best chance of survival. Alongside these efforts, we have been working to enhance the habitat where white-clawed crayfish will be released by using materials such as brash bundles to create in-water refuges.
In 2024, 83 white-clawed crayfish were released at an ark site in North Norfolk. While it will take several years to assess the outcome, further release sites have been earmarked, and the number of egg-carrying females to be translocated will also increase.
While we hope this effort will bolster populations, the ongoing pressure of non-native crayfish remains, and no effective management technique has been found. Furthermore, stopping the spread of crayfish plague continues to be vitally important.
We are a member of The Norfolk Crayfish Group – along with the Environment Agency, Water Management Alliance, Norfolk Non-Native Species Initiative, Zoological Society of East Anglia (ZSEA) and several other individuals and independent organisations. Collaboration is crucial in conserving native species populations.
With thanks to the Green Recovery Challenge Fund for supporting the hatchery with a £95,300 grant.
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Norfolk is one of the last known strongholds for white-clawed crayfish. Join the battle to safeguard this species:
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