Published 19.03.2025

The vulnerable freshwater pearl mussel is at risk of extinction in the Lenna River in Trøndelag due to hydropower regulations. NMF is now demanding that NVE impose a minimum water flow to ensure the species' survival.

Foto of freshwater mussels By Joel Berglund. Licence: CC BY SA 3.0

The Lenna River is being drained: Threatening one of Norway's most important red-listed species.

NRK publiserte nylig en article Which highlights how the energy supplier Småkraft AS has been granted a concession to drain the Lenna River in Trøndelag. The company is not currently required to release water into the Lenna River, and such water extraction could threaten the freshwater pearl mussel living there with extinction.

The freshwater pearl mussel is a red-listed species that plays a crucial role in our ecosystems. Each mussel can filter up to 50 liters of water daily, helping to maintain water quality in the rivers it inhabits. Norway is home to over half of Europe's populations of the freshwater pearl mussel, which gives us a particular responsibility for the species' conservation.

NVE needs to take responsibility

NMF finds it concerning that NVE has not imposed a minimum water flow in the Lenna River, despite the critical situation for the freshwater pearl mussel. In the NRK article, senior advisor Brit Torill Haugen at NVE states that it is not illegal for Småkraft AS to use all the water in the river, which will directly lead to the mussel's extinction there. She further points out that the energy authorities can intervene and impose a minimum water flow when strong environmental considerations demand it, but that this must be considered if such a request is made.

NMF believes that external demands should not be necessary for NVE to act in accordance with the provisions of the Nature Diversity Act. To ensure the survival of the freshwater pearl mussel in the Lenna River, NMF demands that NVE immediately impose a minimum water flow that is sufficient to maintain viable conditions for the species in the long term. This also includes ensuring the survival of trout and salmon in the river, as the freshwater pearl mussel depends on these species as host fish in its life cycle.

NMF demands action to restore the freshwater pearl mussel.

If the freshwater pearl mussel gets driven to extinction in the Lenna River due to the water extraction, NMF believes that Småkraft AS should be held responsible for financing the restoration of a viable population in the river. This would be in line with the "polluter pays" principle and ensure that the company takes responsibility for the environmental consequences of its activities.

The freshwater pearl mussel is an indicator species that reflects the condition of our waterways. If the species disappears from an area, it indicates that the ecosystem is out of balance. The loss of the freshwater pearl mussel can therefore have ripple effects on other species and on water quality in general.

To preserve the freshwater pearl mussel and ensure healthy waterways, holistic management is necessary, as there are other factors beyond water levels and fish that must be considered. Measures that can contribute positively include:

• Reduced use of fertilizers in agriculture around rivers: This minimizes the risk of eutrophication and pollution of the waterways.

• Sanitation of sewage discharges: Ensures that wastewater does not enter the rivers untreated.

• Liming of acidified waterways: Helps maintain a pH level that is beneficial for the freshwater pearl mussel and other species.

These measures will not only benefit the freshwater pearl mussel but will also improve the overall health of our waterways and the many species that depend on them.

We Must Act Now to Protect the Freshwater Pearl Mussel with Responsible Management

NMF emphasizes that it is crucial for NVE to take its management responsibilities seriously and act proactively to protect threatened species like the freshwater pearl mussel. This includes imposing necessary environmental requirements, such as minimum water flow, without waiting for external demands. By doing so, we can ensure that our waterways remain vibrant and healthy ecosystems for future generations.

In conclusion, NMF also calls for increased awareness of the significance of the freshwater pearl mussel and the threats the species faces. Through collaboration between authorities, the business sector, and environmental organizations, we can implement effective measures to conserve this important species.

• NMFs letter to NVE