Fish and aquatic environment

Hydropower production alters the aquatic environment. We therefore work persistently in co-operation projects to develop aquatic environment. We are committed to furthering the restoration of the natural migration patterns of migratory fish with extensive co-operation, step by step. We believe that restoring the migratory fish and hydropower production can co-exist.

We are committed to restoring natural migration patterns in cooperation with other operators. The task is enormous, and requires extensive expertise and commitment from the parties involved, as well as versatile methods. Channels for upstream and downstream fish migration are important, but it is just as important to plant fish and spawn, transfer fish, and restrict and ban fishing.

We strongly believe that the best outcome will be achieved step by step with extensive cooperation.

Years of good cooperation in the Iijoki river has a clear aim: to build fishways at each of the power plants. In the first phase, the aim is to build a fishway and equipment for catching the fish for research and transfer at the Raasakka power plant. Additionally, a downstream migration solution with catching equipment has already been built at the upstream power plant in Haapakoski. It is the first downstream migration solution in Finland. These solutions provide a valuable insight, based on which we can then plan for the future.

In 2022–2024 the Lohi Iijokeen (Salmon to Iijoki) project continues the extensive cooperation in migratory fish restoration. The project will produce, among other things, information on the functionality of the Haapakoski downstream migration route.

We are active in the extensive  Iijoki river migratory fish project in 2020–2022. The project includes e.g. building a downstream migration fishway for smolt, as well as catching equipment, in Haapakoski. The project also promotes the launch of fishway constructions at Raasakka.  

We take part in the Iijoki Agreement for the years 2019–2023 which implements the Iijoki waterway vision and action plan. The joint project includes e.g. restoring drained swamps and undertaking other water management tasks in drainage basins.

We are also participating in joint projects in the Kemi-Ounasjoki river basin to restore migratory fish.

We have been actively involved in and have provided co-financing for studies and joint projects that have examined the prerequisites of the natural migration patterns of migratory fish since 2008.


The hydraulic fishway Fishheart will be in use at the lowermost power plant on the Iijoki river, PVO-Vesivoima Oy’s Raasakka power plant, from 2023 to 2025. The system will be used not only as a migration solution for fish to bypass the Raasakka power plant, but also to improve the efficiency of the transport of fish. Fishheart in Raasakka is the first ready-to-use solution at the lowermost power plant on a harnessed river flowing into the sea. Its operation will provide valuable additional information on the efficiency of the system as part of a solution to migratory fish issues in harnessed rivers.

A fishway has been planned at the Raasakka power plant in the Iijoki river. The fishway is part of the Iijoki river migratory fish project in 2020 – 2022. The authority granted permissions to build fishways in Raasakka in December 2020. With Metsähallitus, we applied for a permit in 2017.

Finland’s best experts have been planning the Raasakka fishway. The fishway utilises smart solutions. It is extremely advanced in its monitoring equipment, structure and dimensions. The results from the fishway can later be used as a basis for other fishways constructed in Finland. According to experts, a technical fishway will function better at Raasakka than a natural one.

There has been one fishway at Pohjolan Voima’s power plant Isohaara in the Kemijoki river since 1993. Isohaara is the lowermost power plant along the Kemijoki. There is also another fishway in Isohaara, the Vallitunsaari fishway, which was completed in 2012. Another fishway is located in the Iijoki headwaters, at the dam of the Kostonjärvi regulation lake.

The planned fishway at the Raasakka power plant.

Our affiliate company Tornionlaakson Voima, together with the municipalities of Pello and Ylitornio, has received permission to build two natural fishways at Portimokoski rapids on the Tengeliönjoki river. The fishways will open up a migration route for migratory fish and over a 1,000 km of waterways suitable for spawning above the Lake Portimojärvi.

Downstream migration

At the Haapakoski power plant in the Iijoki river, the downstream migration of smolt, migratory salmon fry, is being studied. Finland’s first downstream migration fishway was completed at Haapakoski in 2021.

In the summer of 2019, a guide fence for smolt was installed at Haapakoski. It helps to guide young fish migrating to the downstream migration fishway.

The guide fence and the downstream migration fishway at Haapakoski form Finland’s first downstream migration route.

The Natural Resources Institute Finland is studying the functionality of the constructions.

The guide fence that guides the smolt downstream at the Haapakoski power plant.

The old Iijoki riverbed in Raasakka

Measures to return migratory fish to the old natural riverbed of the Iijoki river at Raasakka continue with a cooperation project in 2022 and 2023. The project continues the efforts to restore the natural cycle of migratory fish and river lampreys and to improve the recreational value of the area.

The joint development project for the old Iijoki riverbed in Raasakka (from 2017 to 2021) aimed to facilitate the upstream migration of fish and their reproduction, as well as to improve the area’s recreational use. The project included studies of water quality, the construction of swimming places and other recreational areas, the cutting of horsetail, and the improvement of boating routes.

The project has generated promising results on the natural reproduction of migratory fish in the old Iijoki riverbed in Raasakka.

Fish stock management and transferring fish

Annually, we stock more than three million young fish, transfer breeding fish and river lampreys, and support fishing associations in fish stock management.

In the Iijoki and Kemijoki rivers, our obligations for fish stock management are the most extensive in Finland. In the Iijoki river, we are responsible for stocking fish in the river and ocean areas, as well as in two lake regions. In addition, we handle 17 % of the fish stock management in the main channel of the Kemijoki river and the ocean area, as well as in one lake region. Annual fishery fees are also paid in the Iijoki headwaters and in the areas of Irnijärvi and Kostonjärvi regulation lakes. 

Voimalohi Oy, which we own with Kemijoki Oy, grows the fish we need for our statutory stocking and takes care of the stock management with local operators across our operating area. Monitoring provides information about the effects of fish stock management efforts.

Stocking young fish to the Irni waterway. Mika Pylväs of Voimalohi Oy at Polojärvi lake.

Ecological flow

Annual ecological flows to the Kostonjoki and Irninjoki rivers have been agreed with the municipality of Taivalkoski and the authorities. In the Irninjoki river, we have restored appropriate spawning beds for trout and grayling.

Based on the monitoring results, the ecological flow in the Irninjoki river was further increased in 2020.

Spawning bed for trout and grayling at he Irninjoki river.

Regulation of waterways

In regulating waterways, the aim is to generate hydropower, prevent flooding and promote waterway traffic, the recreational use of the waterways and water supply. The regulation of waterways always requires a permit in compliance with the Water Act. The permit is granted by the Regional State Administrative Agency. Various Centres for Economic Development, Transport and the Environment monitor compliance with the permit conditions.

Regulation is constantly being developed with the authorities and local residents to mitigate environmental impacts.

Environmental management and protection of shorelines

Flooding and regulation cause erosion of shorelines. The shorelines of regulated lakes and rivers are protected against erosion with supportive structures. Environmental management also includes the clearing of shorelines, as well as earth dams and submerged dams.

By the end of 2022, about 364 kilometres of shoreline had been protected against erosion, while almost 1,000 kilometres of shoreline had been cleared for landscaping purposes.

Clearing earth dams at the Isohaara power plant area in Kemijoki river.