Pearl mussel conservation in Sweden

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Europe/Middle-East > -Regions- > Baltic Sea

Europe/Middle-East > Northern Europe > Sweden

Freshwater pearl mussels. Sweden.
© WWF Sweden / Lennart Henrikson


The freshwater pearl mussel, a protected species in Sweden, has disappeared from almost 40% of the country’s rivers as a result of pollution and decline in water quality. As the species is capable of making fine quality pearls, it has historically been exploited.

WWF and its partners are working to improve the health of 21 rivers and streams in southern Sweden in order to conserve the species.


The freshwater pearl mussel (FPM) is a fascinating species that has interested people for centuries. What caught the interest of people at the beginning was its valuable pearls, which led to widespread mussel fishing throughout the country. Today, however, the freshwater pearl mussel is red-listed in Sweden and protected from fishing. The mussel has an exciting biology, with its parasitic stage on brown trout or salmon before it develops into a recognizable mussel. The FPM lives in fresh, running water with clean bottoms, lots of host fish, and protected edge zones of forest along the water. It is a good indicator of clean, living forest water. The biggest reasons behind the mussel’s decrease in numbers today include acidification, pollution, inadequate regulation of water flow, and forestry.

Today the FPM is threatened in several regions of the country, and large parts of Europe. Still, Sweden is a core zone for the mussel, which means that we have an international responsibility for the species’ long-term survival.

The FPM was selected as a target species as (1) it is a fascinating species (has a parasitic life stage on fish, can live to be 200 years old, can form pearls, can be used as an environmental indicator), (2) the knowledge of the species is good, (3) it has a large distribution within EU and Sweden is a core area for its occurrence within EU, (4) it is an indicator for healthy ecosystems, measures favouring FPM will also favour other species and even terrestrial habitats, (5) it is listed in the Habitat Directive.


Develop and test methods to achieve favourable conservation status for the freshwater pearl mussel (FPM), Margaritifera margaritifera, in Sweden by:

1. Developing planning methods.
2. Taking measures to improve the aquatic and riparian biotopes to improve the conditions for FPM as well as the host fish species.
3. Informing the landowners and other actors within the drainage area.
4. Re-introducing FPM.
5. Summarising the experiences in a manual for conservation of Natura 2000 sites.


WWF, together with 9 partners, will improve the conditions for the freshwater pearl mussel in 21 rivers and streams in southern Sweden. The project is financed to 50% by the EU’s LIFE fund. The Swedish Environmental Protection Agency is co-financier. The 9 partners are the County Administrative Boards in the counties of Västmanland, Örebro, Västra Götaland and Kalmar, the National Forestry Board offices in Värmland-Örebro, Västra Götaland and Östra Götaland, the City of Göteborg, and Karlstad University.

21 Natura 2000 sites were selected by the following criteria: (1) populations of different viability, (2) populations of different sizes, (3) geographical distribution, (4) possibilities for success.

The project includes approx. 500,000 mussels, corresponding to approximately 5% of the Swedish and 3% of the population within EU.

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