The 25MW Leppikoski hydropower plant was completed in 1963. It is located along the Emäjoki River, in the Oulujoki river shed in Finland. The scheme has two Kaplan turbines, two embankment dams (40m and 450m long) and a 57m long concrete dam. The concrete dam comprises a spillway with two gated openings, and a bottom outlet spillway located below a decommissioned log floating basin.

The Finnish National Fishway Strategy prioritises sites according to their potential for restoring river connectivity for migratory fish. Leppikoski is one of these key national sites assessed by authorities since there are potential spawning grounds and habitats above the hydropower plant. Access to  sufficient spawning grounds and habitats is a prerequisite for the natural life cycle of migrating fish. 

To enable strengthening of the natural life cycle of migratory fish, a variety of different tools and measures are needed. Each river and hydropower plant are unique, and thus solutions vary by river and hydropower plant. Fishheart is a good alternative for enabling fish migration at hydropower plants such as Leppikoski with tightly built surroundings around the power plant. The Fishheart installation is a floating solution that does not require a lot of space on the ground. 

Floating fishway

The floating hydraulic Fishheart fishway unit is designed to be installed on the downstream side of a dam close to turbine outlets where fish naturally gather. The floating solution enables positioning and repositioning of Fishheart to the best fish migration route. The Fishheart unit connects to tubes passing over the dam with inlet and outlet lines. Water from the upstream side of the dam is fed into the tubing through the inlet line utilising the siphoning effect. An attraction flow tubing atop Fishheart also runs on siphoned water. In addition, there is an underwater attraction flow guiding the fish into the system. 

The Fishheart control unit is inside a separate container, containing electrical system hardware, monitors, meters, and controller unit. The system is operated remotely and runs 24/7. Once AI has identified a desired fish in the camera system the logic automatically operates tube pumps and valves to provide that fish an opportunity to pass over the dam. A pump helps the elevation process. 

Fishheart is not selective about fish species and thus fish in all sizes and with different swimming capacities can use the system, including salmon, trout, whitefish, lamprey, herring, and eel.  It can also be used to separate invasive species.

Water usage is around 10% compared with traditional fish passages. The unit can be placed where fish naturally gather and has a passing rate comparable with many other solutions. During transfer upstream the fish are also constantly within water, protecting them from mechanical damage which can cause bruising and infection risk.


The Fishheart fishway at the Leppikoski hydropower plant was inaugurated on 1 October 2021. Since the start of testing in August it has successfully transferred several mature lake trout (over 60cm) above the dam. So far, the ishway has transferred about 2500 fish this fall.  In addition to trout, Fishheart has registered other fish species, including perch, lamprey, bream, vendace, whitefish, and pike perch. The system at Leppikoski will be tested until mid-October, and its use will continue next summer.

Fish population

Fishheart is part of a set of measures being implemented to strengthen the natural cycle of the threatened trout in lake Oulujärvi in the vicinity of the Leppikoski hydropower plant. The tributaries upstream of the Leppikoski power plant provide potential habitats and breeding grounds essential for the life cycle of the trout population; this year there have been habitat restorations in the tributaries. Moreover, Fortum is annually stocking lake trout fry upstream in an effort to strengthen the fish population that imprints to the river.

Fortum has been working on biodiversity for a long time and is committed to several climate and environmental targets, which include the goal to implement at group level significant voluntary measures to improve biodiversity. Leppikoski Fishheart is one of these voluntary measures advancing biodiversity. Local cooperation is the key to sustainable development for people, nature and the energy future.