River Tweed Commission

Established by Order under an Act of Parliament to protect the fish stocks in the Tweed River System


start_stop end_stop1

Gyrodactylus salaris

Gyrodactylus salaris is an extremely dangerous parasite which is not present anywhere in the British Isles. The RTC is taking the most careful steps to make sure it does not enter the Tweed fishery. As such we are encouraging rigourous biosecurity procedures which we request you support.

What are the risks?

G. salaris has been shown to survive away from a live fish host for five-seven days at ambient river temperatures and for 78 hours and 42 hours at salinities of 10 ppt (parts per thousand) and 20 ppt, respectively. Risk is associated with movement of materials (animate and inanimate) that can carry low salinity water, which have recently been in contact with infected fish, and which have been kept in cool conditions sufficient to permit the temporary survival of the parasite away from live fish. Equipment or product that has been kept cool and damp and is transferred rapidly (within one week) may present high levels of risk.

This notorious parasite has destroyed the Salmon stocks of over 20 rivers in NORWAY. It was introduced to the Atlantic coast of Norway on Baltic Sea salmon taken to fish farms there. Baltic Salmon are immune to it, Atlantic Salmon are not – and tests have shown that Scottish Atlantic Salmon are destroyed by it just as easily as Norwegian.

It is also indigenous to, or has been spread to RUSSIA, FINLAND, SWEDEN, GERMANY, FRANCE, SPAIN and PORTUGAL.

It is a minute, external parasite, less than half a millimetre long and can live off fish, in the gravel, for a considerable time, making it (as yet) impossible to eradicate from any river. Desperate methods being used in Norway involve poisoning all the fish in a river and leaving it fallow for several months at least to try and break the cycle. No successes have yet been reported.

If this parasite gets into Tweed it means the absolute end of our Salmon.

Therefore we require you to sign the declaration below before you arrive to fish. You can download the form by following one of the links below


When you visit Tweed you will see small signs on fence posts near the river alerting you to the dangers of G. salaris. Please take a moment to read these and make sure you comply with them. An example of the sign can be seen here.

If you would like to learn more about Gyrodactylus salaris please you may be interested to read “A guide to protecting freshwater fish stocks” (698k) or to follow this link to the Fisheries Research Services.

Disinfection against Gyrodactylus salaris

The Scottish Government has published a Contingency Plan for dealing with Suspicion and/or confirmation of Gyrodactylus salaris in Scottish Waters including the Tweed. Similar Plans have also been produced by DEFRA and the Welsh Government. The River Tweed Commission has appraised, assessed and updated this Plan with specific reference to Tweed’s local characteristics. It has prepared and collated all the information that would be required if such a plan were required to be put into action. Tweed’s supplementary planning preparation to the Government’s Contingency Plan in the event of a Gs outbreak addresses the risk assessment specifically appropriate to the Tweed (and Eye) District.

Download the Plan


RTC Logo

Established by order under The Scotland Act 1998 (River Tweed) Order 2006