The assignment consists of monitoring river mussels (Margaritifora) in Norway. The species is listed under the vulnerable category in the Norwegian Red list for species (2015) and it, thus, to be seen as threatened. On the international red list (IUCN), the species is listed as very threatened and many stocks in Europe are rapidly declining. Norway has 1/3 of the known populations in Europe and >50 % of the number of mussels in Europe live in Norwegian river systems. Norway is thus responsible for the species.