*The Namsblanken never goes to sea. Photo: Per Harald Olsen, NTNU*

There are always people who have to do things their own way. This is also the case in the world of salmon. Two strains of salmon in Norway live their entire lives in freshwater.

Wild salmon start life in a river. It then swims out into the nutrient-rich sea and grows up there. When it's time to spawn, it returns to the river it was born in. This is the normal life cycle of wild salmon.

But there are two salmon strains in Norway that live very different lives. One is from southern Norway and is called byglandsbleke. The other is from Trøndelag and is called namsblank or småblank. Neither of them go to sea. Instead, they live their entire lives in freshwater. We call them relict salmon, and they are very rare. Relict means "something that has been left behind", and we have to go all the way back to the last ice age to explain what relict salmon means.

Ice age, land uplift and wild salmon

There have been several ice ages. The last one was between 110,000 and 10,000 years ago. At that time, large parts of Europe were covered in ice. At most, the ice was up to three kilometers thick. When the ice melted, rivers formed. The salmon in the sea quickly found their way to our rivers and made use of them. When the heavy ice disappeared, the land began to rise. In some places, the land rose even more, and small and large waterfalls formed in the rivers. Some of the waterfalls became too high for the salmon, which therefore had to make do with spawning grounds below the large waterfalls.

Over four large waterfalls, something strange happened

Since the salmon no longer returned to spawn in the areas above the large waterfalls, they died out there. But above four large waterfalls in Norway, something strange happened. Although no new salmon returned from the sea, there were still salmon there. The conditions must therefore have been such that both the female and male salmon that remained became sexually mature without going to the sea. Spawning continued, and the salmon lived on over the four large waterfalls. Salmon still live in two of these places: In the Otravassdraget in southern Norway, the byglandsbleka lives, and above Fiskumfoss in the Namsenvassdraget in Trøndelag, the namsblanken or småblanken lives.

Relict salmon

Both byglandsbleka and namsblanken have lived in isolation from the sea-going salmon for about 10,000 years. They never get to eat nutritious food from the sea and therefore do not grow very large. Since they remained in the old areas of the wild salmon, we call them relict salmon. They are something that has remained above the waterfalls. Relict salmon are the same species as anadromous salmon (sea migrating).

The salmon that never goes to sea

There are always people who have to do things their own way. This is also the case in the world of salmon. Two strains of salmon in Norway live their entire lives in freshwater.