The salmon fish rainbow is not a fish that occurs naturally in Sweden, but originally comes from North America.

In the places where rainbows are found, they have either been planted out or escaped from a fish farm, which is the case in Storsjön.

Anders Rydeborg and Erica Roos from the county administrative board have now, with the help of electric fishing, made an inventory of the possible presence of rainbows in the streams and rivers around Storsjön where grayling are currently playing.

Scares the grayling

The common image has been that the rainbow does not affect the natural fish stocks so much.

Since it is raised in captivity, it must lack the natural drive to seek out streams and rivers in the spring to play.

- There are no huge amounts, but we have caught rainbows that are both rum and milkweed so they are there to play.

The largest was seven kilos, so it was very playful, but we have also seen them under one kilo, says Anders Rydeborg.

The species both disturbs and destroys.

On the one hand, it scares away the grayling, and if it scurries around on the bottom, there is no doubt that it whips away the grayling's rum.

One way to minimize the disturbance of the rainbow is to place obstacles with cages in the play streams, where you gather and just lift over grayling.

However, it is a time-consuming and labor-intensive method, as there are many streams around Storsjön and each cage must be whitewashed several times every day.

In Billstaån outside Hackås, an obstacle with a cage is placed.

Twice a day you lift over the fish you want to be able to continue up the river.

Photo: Fredrik Lundmark

"Fish as much as possible"

There are some known cases in southern Sweden where rainbows have managed to rejuvenate, but so far there are no signs that they have succeeded in Storsjön.

- The risk that it happens here too may not be so great, but considering that there is a lot of rainbow in Storsjön right now, it could happen, says Anders Rydeborg.

He says it is good if people continue to fish and catch as much rainbow as possible.

- If you catch one, you should not release it - but kill it.

It is also an excellent food fish.

See more in the clip above.

Erika Roos from the county administrative board shows the 7 kilo rainbow that has hiked up in one of Storsjön's rivers where the grayling is currently playing.

Photo: Anders Rydeborg / County Administrative Board of Jämtland County