Gyrodactylus Salaris

Gyrodactylus salaris (GS) is the greatest threat to wild salmon in the UK, as such all members will be required to complete a GS declaration form prior to membership being granted.

It is a parasitic freshwater fluke which is indigenous to rivers in parts of Russia, Norway and Sweden, where salmon have evolved resistance to it. However, GS has spread to rivers in Norway, Denmark, Germany, France, Spain and Portugal where native salmon have no resistance, resulting in mass mortality of juvenile fish.

In Norway infected rivers lost 98% of their salmon within 5 years. Infected rivers must be poisoned to remove all fish hosts, and barriers erected to stop salmon entering the river to spawn and generate more hosts. GS can survive for 5 to 7 days without a host in damp con-ditions (e.g. angling clothing, waders, wet reels, lines or landing nets).

Currently the UK is GS-free

The economic and ecological consequences of GS entering the country would be cata-strophic. All fishing proprietors, fishery managers, ghillies, angling associations, hotels, rainbow trout fisheries and farms are urged to prevent infection from visiting anglers by using the GS Angler Declaration Form. Please download this and give it to all fishermen be-fore they start fishing, whether they are salmon, sea trout brown trout, rainbow trout or pike anglers.

The parasite can be seen under low power magnification, for example, with a good hand lens. Without magnification, heavily infected parr appear greyish, with excess mucus, and possibly concurrent fungal infections. They attach to the host by the attachment organ, or opisthaptor at one end of the body and feed using glands at the other end. Attachment can cause large wounds and feeding can damage the epidermis, allowing secondary infection. G. salaris can build up to very high infection intensity of several thousand parasites on a single salmon parr. Particular attention should be paid to anglers who have recently come from, or visited, the following ‘red list’ countries: Norway Sweden Russia Finland Denmark France Germany Spain Portugal.

Fill out or download GS declaration form here.