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How to Stop the Spread of Gyrodactylus Salaris

06 August 2012

G. salaris is a tiny creature measuring less than half a millimetre in length. It uses its tiny claws to attach itself to the skin of young salmon, which it then eats. G. salaris breeds prolifically and a young salmon may be host to up to 10,000 individual specimens before it dies. The parasite is often referred to as the salmon killer or simply, Gyro.

Why Should this Concern Me?

The effects of this illness are so serious for the salmon that it can disappear completely from the infected rivers . If we don’t do something, fishing for wild salmon in Norway could be consigned to the history books. For this reason it is very important that everyone who is out and about around rivers and fresh water knows what to do. We all have to do our bit to ensure that this parasite does not spread to other rivers.

Where does G. Salaris Come from?

It is believed that G. salaris is widespread in rivers which flow into the Baltic Sea from Finland and Russia and possibly also Eastern Sweden. It seems that the Baltic salmon can withstand the parasite better than our own. In Norway, the parasite was first discovered in 1975 after grower stock was imported from Sweden. This underlines how careful we must be in moving and setting out fish.

Can Salmon Become Resistant?

The Norwegian salmon has very little resistance to the parasite. It is uncertain how long it will take to develop resistance which is high enough that the parasite does not threaten our salmon stocks. Experience from Norwegian watercourses which are infected by «Gyro» is that the parasite leads to almost total extinction of salmon.

How does the Parasite Spread?

The parasite can be spread by fish, tackle, nets and water from infected watercourses and water systems. In most spreading where the parasite has been introduced into new parts of Norway this has been the result of infected fish being moved and then released, but it can also be spread through tackle which is used on several watercourses. G. salaris can survive for several days in damp surroundings, for example in plastic bags, on dead fish, in other packaging and equipment, such as waders, nets, lines and landing nets. It is not just fishing tackle which can cause infection, but everything we use in and near fresh water: rubber dinghies, lilos, canoes and kayaks. It isn’t difficult to get rid of G. salaris, provided the correct procedure is followed.

Do Not:

  • Release live fish into the wild unless you have cleared this with the District Governor
  • Wash and gut fish anywhere other than where you caught them.
  • Take tackle from one watercourse to another without disinfecting it.
  • Throw water out into another watercourse than the one it was fetched from.

August 2012

Further Reading

- Find out more information on Gyrodactylus Salaris by clicking here.

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