Cray Fish Plague
Anglers Asked To Look Out For Dead CrayFish
Over recent days hundreds of dead crayfish have been seen in the lower River Colne in Colchester. Crayfish plague or another disease is suspected as the cause.
Following reports from a Castle Park Ranger, Environment Agency staff confirmed the deaths and sent samples for analysis.
The CEFAS (Centre for Environment, Fisheries & Aquaculture Science) lab in Weymouth is analysing the animals to see if they are infected with the highly virulent fungal disease Aphanomyces astaci, commonly known as crayfish plague.
This outbreak follows hot on the heels of a similar outbreak on the River Waveney in October last year. Having two such outbreaks so close in time and place is very unusual. It shows more needs to be done to prevent the spread of this disease.
The animals affected in both cases are Turkish crayfish – an alien invasive species, which has died in its hundreds over the past few weeks.
However, if the disease spreads to other river systems, the rare native white-clawed crayfish could also be affected and crayfish plague has already wiped out many populations of this species.
The Environment Agency is alerting all anglers and other river users to the potential presence of this disease and asking that, as a precaution, they thoroughly clean their equipment before using it in any other waters to stop this disease from spreading once again.
Crayfish in the Colne belong to a non-native or alien species called Turkish or narrow-clawed crayfish which originates from eastern Europe and western Asia, originally imported to supply the restaurant trade. In common with other European species, this is susceptible to crayfish plague.
The population in the Colchester area has been known for a number of years. The presence of this large species can cause problems such as burrowing into banks, taking anglers bait and preying on river invertebrates and fish eggs. So a thinning or loss of this species from the Colne is not a problem in itself. However, there is great concern that the plague could spread to other river systems.
This virulent disease has wiped out many populations of our native white-clawed crayfish in England and Wales. Alien crayfish species from America, notably signal crayfish, carry the disease but are not susceptible to it. It is spread by affected crayfish or, more commonly, equipment such as fishing nets, boats etc being transferred from infected waters.
White-clawed crayfish were formerly widespread but have been wiped out from many rivers and now exist in increasingly isolated populations. There is so much concern for the future that it has been designated a Biodiversity Action Plan species as part of the UK’s response to the 1992 Rio Earth Summit and protected by EU legislation (Habitats Directive). The only remaining populations in Suffolk and Essex are in the Stour, Blackwater and Chelmer.
The Environment Agency is strongly advising that anyone using equipment in the river take recommended precautions before using the same equipment in any other river system.
Anything that comes into contact with the water – keep nets, footwear, boats, farm machinery etc – could potentially spread the disease. To stop this happening, carry out the following steps:
· Clean off any mud or vegetation and remove any standing water
Then either
· Thoroughly dry the equipment, preferably in sunlight making sure all nooks and crannies are dry.
Or
· Treat with a proprietary disinfectant capable of killing fungal spores. (Please contact the Environment Agency for further information about this option).
There is no need to carry out these precautions if equipment is being moved to another site within the Colne.
It is not known how the disease spread to the Colne or the Waveney, but it is likely that it was through contaminated equipment, possibly even an unlicensed crayfish trap. This underlines the need to carry out these precautions. If the same situation had occurred in the Chelmer, it would have lead to the eventual loss of this species from Essex.
Julia Stansfield, fisheries, recreation and biodiversity officer for the Environment Agency said: ‘This second outbreak is really worrying for the future of our native crayfish. Without a change in people’s behaviour, it seems only a matter of time before one or more populations of native crayfish is wiped out. We urge all river users to clean and dry or disinfect any equipment before taking it from one river or lake to another. A few careless acts could lead to the loss of this fascinating species from East Anglia.
‘One possible route for the spread of this disease is use of unlicenced crayfish traps. The idea of this ‘wild food’ is much in vogue. While this is safe to do in parts of the country where native crayfish have already been wiped out, in the east of England we are trying to protect one of the last strongholds.
‘If members of the public notice dead crayfish in any other rivers, please let the Environment Agency know as soon as possible.’
The number to contact is 0800 80 70 60.