Restoring migratory fish populations requires long-term commitment

The goal of Finland’s National Fishway Strategy is to strengthen the vitality of our endangered and threatened migratory fish populations. We have implemented the strategy through multiple project entities in collaboration with hydropower companies, authorities, and ministries.

Restoring migratory fish populations is a long-term effort. Scientific knowledge can accelerate the identification of effective solutions. The natural life cycle of migratory fish is being supported by building upstream and downstream fish passages in dammed rivers, restoring habitats, and improving the effectiveness of fish stocking practices. In 2024, we ublished results from the Sateenvarjo III project, which examined the functionality of existing fishway solutions in Finland and developed current smolt monitoring practices.

New research findings were gained on efforts to restore populations of salmon, brown trout, landlocked salmon, and migratory whitefish. For example, in Haapakoski on the Iijoki River, a floating guidance fence was tested for the first time in Finland to direct downstream-migrating salmon smolts. The fence performed well on average and successfully guided the smolts to a newly completed downstream passage through the dam.

Landlocked salmon and brown trout spawners have found their way to Laurinvirta in the Pielisjoki River and accepted the restored spawning grounds. However, juvenile production in the area has remained low, likely due to strong spillway releases.

The natural reproduction of migratory whitefish in the Oulujoki River was estimated to produce an average of about 2.1 million juveniles in 2020—the highest estimated natural yield among Finland’s regulated rivers. Both the Oulujoki and Iijoki Rivers show potential for natural reproduction of migratory whitefish, but in the Iijoki, only a small portion of spawning adults are able to return to the sea after reproduction.

The results indicate that restoring migratory fish populations in regulated waters typically requires several parallel support measures. These findings can be used when planning fishway solutions at new sites.