Valvtjärnsbäcken is a forest tributary of River Ljusnan with one of Sweden's
remaining stocks of the endangered and protected species of freshwater pearl mussel.
Inventory of the creek has confirmed that the
population is aging and that the mussel stocks have declined over the past 20
years. This is probably due to loss of reproduction, which ultimately will mean
that the stock vanishes if no restoration
efforts are performed.
reason for the reduced reproduction of the mussels is most likely that trout
has had no possibility to migrate upstream in the creek because the stream has
been, for a distance of about 300 m, fully covered with large masses of blasted
stone. Trout is vital to the fresh water pearl mussels as for a few months the mussel
lives as parasite in the trout's gills and later it further develops to
Restoration of the creek
the project, the stream was cleared from the blasted stone deposited in
Valvtjärnsbäcken. The creek was designed in the best possible way for both
trout and freshwater pearl mussel in terms of depth and bottom structure.
Restoration of Valvtjärnsbäcken was conducted during the summer of 2013. The
work was done respecting the surrounding nature. After completion of the
project, information signs were put up on the site to avoid any new rock material
to be dumped to the creek and to provide information about the restoration and
the protected freshwater mussel.