Background to the initiative
One of the most ambitious restoration projects in the Nordic Taiga has been reconstructing rivers once devastated by timber floating. Almost all of the area’s waterways were channelised and devoid of their natural character and ecological function, and aquatic ecosystems have suffered as a result. Rivers are being reconstructed – rock by rock – with excavators moving boulders, helicopters dropping gravel, and dams being torn down to restore flow. The result? A chance for nature to heal. But one key player is still missing.
Freshwater pearl mussel (Margaritifera margaritifera) previously thrived here. 50 litres of water are cleansed by each mussel each day, keeping water clean and allowing other aquatic species to thrive. Previous mussel beds in dense clusters supported vigorous salmon and trout. Their populations since collapsed. Why? The species is sensitive to siltation from ditches and forestry, and is entirely dependent on juvenile salmonid fish, whose gills the mussel larvae must parasitize for a year before settling on the riverbed. But with damaged rivers and fragmented populations, this essential life stage virtually never succeeds. Even in restored rivers, recruitment is low – often because mussels and salmonids are too scattered or isolated to find one another. Co-evolved mussel-fish populations from the same river are most likely to succeed. Previous lab-based pairing attempts have been marred by long-distance transport and artificial conditions.
To address this, Rewilding Sweden, in partnership with the Swedish Anglers Association, is creating a mobile mussel laboratory. The field-based, fully equipped lab will travel between rewilded rivers, enabling native salmonids to be inoculated with mussel larvae in the field. An indoor stream built into the lab will circulate water from each river, providing naturalistic conditions for reintroductions to take place.
Collaborating organisations: The Swedish Anglers Association Region West, Vindel River Fishery Council, County Administrative Boards of Västerbotten and Norrbotten
