– The health report of the Skibotnelva, Signaldalelva and Kitdalselva in Troms and Finnmark is an important victory in the fight to preserve wild salmon in Norwegian rivers. Gyrodactylus salaris is an introduced alien species that can eradicate entire populations of wild salmon in infected rivers, says Ellen Hambro, director of the Norwegian Environment Agency.
The Norwegian Food Safety Authority on Wednesday declared the Skibotn region in Troms and Finnmark healthy for Gyrodactylus salaris, after the latest tests show that the salmon fry in the rivers are free of the salmon parasite.
Work against the parasite has been going on for a number of years, and it has taken a total of 43 years to get rid of it.
Gyrodactylus salaris was first detected in Skibotnelva in 1979, and later spread to Signaldalelva and Kitdalselva. In the period 1988 to 2016, three treatments were carried out with rotenone in the Skibotn region.
Saved the salmon with gene banking
Thanks to the fact that the original populations of wild salmon and char have been taken care of in the Norwegian Environment Agency’s gene banks, it has been possible to release them back into the rivers in the years following the rotenone treatments.
– The salmon populations in the rivers were virtually extinct in the wild. The waterways have now regained salmon and char, which are the offspring of fish from the original stocks, and which are therefore adapted to the local conditions, says Hambro.
The health report is the result of extensive work to combat the parasite, and bring original salmon stocks back to the rivers.
The state administrator in Troms and Finnmark, the Norwegian Food Safety Authority and the Veterinary Institute have collaborated on the eradication.
Thanks local people
– The waterways in the Skibotn region have been challenging to treat. These have long and difficult-to-access stretches of river, and groundwater seepage that diluted the rotenone and made treatment difficult. Especially in the first years before new methods were put into use, says Pål Adolfsen at the Veterinary Institute, who has been the project manager for the work.
– In addition, there was a widespread occurrence of char, which carries the parasite, and which made it more likely that one infected fish could sneak away. The joy of being successful is therefore extra great, he says.
Adolfsen believes that extensive mapping of the spread of infection and the treatment area, combined with adapted treatment strategies and local efforts, are important success factors.
‒ The healthy declaration of the Skibotnelva, Signaldalelva and Kitdalselva is a milestone for the wild salmon, the local population and all of us. We would like to thank everyone who has helped fight the parasite in these waterways, and especially the local voluntary actors, says environmental director Lisa Bjørnsdatter Helgason at the State Administrator in Troms and Finnmark.
– Must disinfect fishing rods
The Norwegian Food Safety Authority remains concerned about contamination from waterways in Norway’s neighboring countries.
The parasite can survive for several days in moist environments and is spread by fish, fishing equipment, canoes and water from infected waterways and facilities. It is also prohibited to move fish between all rivers and bodies of water, and between different parts of the same watercourse.
– It is important that everyone who travels in the area helps, so that we avoid new infections in the watercourse. Fishing and other water sports equipment used in different waterways must either be dried or disinfected, says Geir Arne Ystmark, regional director of the Norwegian Food Safety Authority.
The Signaldale river and the Skibot river have traditionally been good salmon rivers. Many are excited about when they will be opened for normal fishing again.
– We know that the re-establishment of the stocks is well on track, but we cannot say anything for sure about the fishing until we know whether there is a harvestable surplus. We will make a professional assessment when we receive the results from monitoring and spawning fish counts next year, says Hambro in the Norwegian Environment Agency.
And soon the parasite may be completely eradicated in Norway.
– Out of a total of 51 infected waterways in Norway, 43 have now been fully treated, says Hambro’s colleague Jarle Steinkjer in the Norwegian Environment Agency.
He leads the national fight against the deadly salmon parasite.
– Only two regions remain. The Driva region and the Drammen region. The chance of spreading the parasite has therefore become significantly less. Eventually it will be equal to zero in Norway. Then the challenge is that we don’t get the parasite in from Sweden, as we did when we first got it into Norway.