Trap and transport of salmonids in Finland and Sweden

A long-term co-operation and a number of measures are needed when restoring the natural life cycle of salmonids in rivers harnessed with hydropower. Depending on the waterway, measures may e.g. include regulation of fishing, fishways, habitat restoration, supporting fish stockings, transporting of fish, or their various combinations.

Montta hydropower plant


Trap and transport systems enable efficient and safe transporting of the salmonids to the spawning areas behind the hydropower dams. The fish born in the upstream areas of the river are likely to return to the same river for spawning and sustain the natural life cycle of migrating fish.

Trap and transport in Sweden

In river Klarälven in Sweden, salmon have to pass eight hydropower plants before reaching the spawning areas, and cumulative losses and delays for salmon passing the hydropower plants by fishways would not result in a large enough number of fish reaching the spawning grounds to sustain the wild salmon population. This is why the natural smolt production in the Klarälven river has been sustained via an active trap and transport of spawning fish since the 1930s. Fish are collected in a fish trap at the lowermost dam (Forshaga) and transported by truck to the spawning areas some 100 kilometers upstream past the hydropower plants.

Trap and transport in Finland

The river Oulujoki has similar trap and transport facilities. The trapped fish are used to increase the genetic biodiversity of the hatchery-reared fish population and this process also helps us study fish behavior and gain knowledge that can be used in future fish migration projects.

Our approach

Fortum believes in a natural life cycle of migrating fish in heavily regulated rivers like the Klarälven and the Oulujoki, however the enhancement of the salmon populations calls for a combination of several supporting measures and step-by-step progress with the best available knowledge and technology in fish migration.