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Disease Control

Gyrodactylus Salaris

It is the policy of the Western Isles District Salmon Fisheries Board that no fishing is to take place until a GS declaration has been signed.

A declaration is available from the Clerk to the Board, on our Publications page as a word document to download and edit accordingly or HERE. Further advice is also available from the Outer Hebrides Fisheries Trust Biologist


Gyrodactylus salaris (GS), commonly known as salmon fluke, is an extremely dangerous parasite responsible for the destruction of salmon stocks in over 20 rivers in Norway. Gyrodactylus is present in Russia, Finland, Sweden, Germany, France, Spain and Portugal. The parasite infects the skin, gills and fins of fish and is capable of rapid multiplication causing serious physical damage to Atlantic salmon parr.


Gs is a listed disease that must be reported under Schedule 1 of the Aquatic Health (Scotland) Regulations 2009. The U.K is currently recognised as being free from Gs although evidence exists to suggest that our Atlantic salmon populations are highly susceptible to both infection and mortality.

Once introduced it may be impossible to eradicate Gs. The only method is the complete sterilisation of the system and allowing the system to remain fallow. The parasite is carried in fresh water and will survive away from a fish host for some time. Damp fishing tackle such as landing nets, fly boxes and waders all provide suitable conditions for the transfer of this parasite. 

It is vital that we take the appropriate bio security precautions to ensure that Gyrodactylus does not enter our rivers. If travelling from a region where Gs is present or its status is undetermined, all equipment associated with angling and water sports should be thoroughly cleaned and treated to kill the parasite. 

  • Drying at a minimum temperature of at least 20 °C for at least 2 days

  • Heating for at least 1 hour at temperatures of above 60 °C

  • Deep freezing for at least 1 day

  • Immersion in a solution* suitable for killing the parasite for a minimum of 10 minutes - *Virkon ® Aquatic (1%), Wescodyne (1%), sodium chloride (3%), and sodium hydroxide (0.2%).




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