Fisheries and fish suppliers are benefiting from changes the Environment Agency is making to the way it controls harmful fish parasites.

Paul Lidgett, Fisheries Policy Advisor at the Environment Agency, said: “Over the past year our scientists have established a new process to assess the risks parasites pose to fisheries.

“This allows us to assess the risk of new parasites to fisheries and those we already control. We can establish which parasites pose little or no risk and remove controls on them to help reduce the costs on fisheries and fish suppliers. The assessment also helps us take rapid action to apply controls and prevent spread where new parasites are detected which do pose a threat.”

One project looked at the fish parasite Neoergasilus japonicus, a crustacean that infects the skin of a wide range of coarse fish and salmonids. The parasite, which first appeared in fisheries in the early 1990s, is currently classed as a Category 2 parasite. This means strict controls are placed on where infected fish can be moved to and can only be stocked into totally enclosed waters with no risk of escape.

However, as a result of research work by the Environment Agency, from 1 September 2008, Neoergasilus japonicus will be removed from the list of Category 2 controlled pathogens. This change could benefit the fish supply industry to the tune of £100,000 and free up fish for sale from many restricted waters.

Paul Lidgett continued: “Our decision was independently peer-reviewed by a panel of scientists and independent fish health experts. The group concluded that Neoergasilus japonicus does not pose a significant threat to fish stocks, either at an individual host or population level.

“The change to the parasite list enables us to focus on more significant threats and will help us strengthen the controls we have in place. By critically assessing each Category 2 parasites we are increasing credibility of the list. The project has also shown that there is a real need for other parasites to remain on the Category 2 list and be strictly controlled.”

Mike Heylin of the Fisheries and Angling Conservation Trust said: “The work now done by the Environment Agency is strengthening the control of fish parasites. The removal of those that don’t cause harm and the assessment of new threats can only help protect our fisheries by allowing the Environment Agency and fisheries managers to concentrate on those which do cause fish problems.”

In the last year, the fish health team at the Environment Agency has also:

• detected fish parasites new to England and Wales and assessed the need for controls on them;
• investigated cases of swollen vents (Red Vent) in salmon;
• investigated specific disease problems on stillwater fisheries;
• developed new guidance to prevent fish disease outbreaks;
• produced guidance for the identification of Category 2 parasites;
• expanded our work on fish deaths;
• investigated the disease potential of some non-native fish populations;
• assessed the fish disease threat climate change may bring to our fisheries;
• supported the work to improve fish movement legislation through the Marine Bill.

Further information can be found at and for more information about the Environment Agency’s fisheries work, visit

Category 2 parasites include those fish parasites and diseases that the Environment Agency considers to pose a known or potential threat to native fish stocks in England and Wales. They are all non-native parasites, and include those which have entered the country in recent decades and have become established in some waters.

Category 2 and known novel parasites (from 1 September 2008)
Parasite Hosts
Category 2 parasites Anguillicola crassus Eel
 Bothriochephalus acheilognathi Common carp/variants, grass carp, tench, crucian carp, orfe, roach, common bream.
 Ergasilus briani Large range of coarse and salmonid species
 Ergasilus sieboldi Large range of coarse and salmonid species
 Monobothrium wagneri Tench

 Neoergasilus japonicus Large range of coarse and salmonid species
 Pomphorhynchus laevis Riverine coarse fish and salmonids.

Novel parasites Lernea sp. Cyprinids

 Pellucidhaptor pricei Common bream. Potential range unknown.
 Philometroides sp.
 Crucian carp and goldfish.
 Tracheliastes sp. Range of coarse fish species, potentially salmonids.