The symptoms do not appear to be fatal to the entire population and it appears some, particularly younger crayfish, can recover via the normal moulting process.
There have been no further reports of native crayfish deaths in any North East catchment since autumn 2024.
Healthy crayfish were rescued from the River Wansbeck after the incident by the EA, the NT and Northumberland Zoo.
Females carrying eggs were kept in tanks at the zoo where there were facilities to rear the young.
The offspring will be released into “ark” sites, bodies of water that are isolated from the risks commonly affecting white-clawed crayfish, later this year.