Every autumn, salmon push hard against the current of Sweden’s northern rivers, following a biological script written over thousands of years. For much of the 20th century, that journey ended at a concrete wall.
Hydropower dams transformed Scandinavia into a clean energy powerhouse — but at a cost to river ecosystems that researchers are still measuring. Across Sweden and Finland, barriers fragment the migration routes that salmon and sea trout depend on to reach their spawning grounds. Now, one of the region’s largest energy producers is working to reconnect what was cut apart.
When clean energy blocks a natural highway
Rivers aren’t simply channels of water. For migratory fish, they’re highways — precisely mapped routes connecting ocean feeding grounds to inland spawning beds. Hydropower infrastructure, by its nature, interrupts those routes. Dams and diversions create physical walls that salmon and sea trout can’t pass, severing the connection between where fish live and where they must go to reproduce.
The consequences are direct. Salmon and sea trout that can’t reach upstream spawning grounds can’t sustain their populations. Over generations, blocked migration routes translate into declining numbers — and in some rivers, near-disappearance of species that were once abundant.
This tension between renewable energy and river ecology isn’t unique to any single company or country. It’s a recognized challenge across Sweden and Finland, where hydropower has long been central to the electricity supply. Vattenfall, one of the region’s largest energy producers, operates hydropower stations on rivers where migratory fish populations have historically been significant — making the conflict both concrete and consequential.
A 300-meter ladder through a Swedish river
At Stornorrfors on the Ume River in northern Sweden, Vattenfall’s most prominent fish passage solution has been operating for over a decade. The fish ladder there stretches 300 meters and was put into operation in 2010, giving salmon and sea trout a navigable route around the hydropower station and toward the spawning grounds of the river Vindelälven.
The numbers from 2025 offer a tangible measure of what that infrastructure can achieve. Over 10,000 salmon and more than 400 sea trout passed through the Stornorrfors ladder on their way upstream to spawn — figures that represent a meaningful restoration of a migration route that had been effectively closed for decades.
Upstream passage is only part of the challenge. Fish that have spawned — known as kelts — also need to travel back downstream, and that return journey through hydropower infrastructure carries its own risks. Vattenfall has taken additional measures to facilitate fish movement in the old riverbed downstream of the plant and is working with the Swedish University of Agricultural Sciences (SLU) to study how salmon and trout kelts pass through Stornorrfors on their way back out. That scientific partnership brings monitoring to bear on a problem engineering alone can’t fully solve.
Expanding the network: Finland joins the effort
The work at Stornorrfors isn’t an isolated project. Fish ladders have been constructed at Hietamankoski and Leuhunkoski on the Kymmene River in Finland as well, extending the geographic scope of Vattenfall’s fish passage efforts beyond Sweden’s borders.
A further project is now in development. Vattenfall is planning to build a new fishway together with the Finnish state at a jointly owned and operated dam. The site divides flow between the artificial Lake Hirvijärvi — where Vattenfall owns a hydropower plant — and the original stream that bypasses the lake. A constant flow is already maintained in that original stream, but the planned fishway would go further, enabling migration of local fish populations that currently can’t move freely through the area.
That project remains in its early stages, still in the design phase and without a permit. Regulatory processes take time. But the planning itself signals that restoring fish migration is being treated as ongoing work rather than a completed chapter.
Biodiversity as a core part of energy operations
For energy companies, environmental commitments can sometimes read as peripheral — a communications layer applied over core industrial operations. What distinguishes the fish ladder program is that it involves durable physical infrastructure and measurable ecological outcomes, not stated intentions alone.
Vattenfall identifies biodiversity and nature protection as a formal priority within its environmental policy, describing it as a central part of its environmental work. Fish passage infrastructure is one of the more concrete expressions of that policy. It either works or it doesn’t, and the passage counts at Stornorrfors provide a direct indicator of whether it’s working.
The combination of engineering solutions and scientific partnership with SLU reflects an approach that treats ecological stewardship as a technical problem requiring ongoing study. Monitoring downstream passage, analyzing kelt survival, and adapting based on findings are the kinds of activities that distinguish a long-term commitment from a one-time mitigation measure — and that distinction matters when the goal is species recovery rather than regulatory compliance.
What comes next for fish and rivers
The picture that emerges from Vattenfall’s fish ladder program is one of gradual, expanding effort. A single ladder at Stornorrfors in 2010 has grown into a multi-site program spanning two countries, with new projects still entering the design phase.
Whether that trajectory continues will depend on permitting outcomes in Finland, the findings from ongoing SLU research, and how Vattenfall weighs ecological investment against the operational demands of its hydropower portfolio. The 2025 passage counts at Stornorrfors suggest the approach can produce real results. The question is how far the network of reconnected rivers will eventually extend — and how many salmon will find their way back to spawning grounds that have been waiting for them.
