Background The freshwater pearl mussel (Margaritifera margaritifera) is a mollusc listed in Annexes II and V of the Habitats Directive. It is protected by French law and listed as an "endangered" species in the IUCN’s Red List. The worldwide population has decreased by at least 50% over the last decade. It is estimated that during the 20th Century, 90% of the pearl mussel population in central European and 60% of the population in French rivers has vanished. During its lifecycle, the pearl mussel has planktonic stages as well as a parasitic one – it lives in the gills of host fish such as salmon. Populations, and particularly the young mussels living in river beds, are vulnerable to increases in temperature and pollutants, as well as to eutrophication and sediment extraction. The pearl mussel represents a key indicator species of the river ecosystem quality and is also an umbrella species – i.e. protecting the pearl mussel has a positive impact on the entire river ecosystem. Objectives The MULETTE LIFE project aims to restore the freshwater pearl mussel populations of the “Massif armoricain” (French Brittany). The project will target six Natura 2000 sites (SACs) that are known to be important refuges for freshwater pearl mussel populations in western France. Expected results: Establishment of a breeding centre and the development and implementation of a methodology for the captive breeding of pearl mussels; The production of 4 000 individuals for each river area targeted; The re-introduction of pearl mussel of different ages into suitable natural sites by putting them into contact with the gills of local host fish or into the substrate; The protection of wildlife sites by creating three Biotope Protection Orders and revising a further three; The involvement of river managers and stakeholders in the implementation of actions for improving the quality of rivers; The production of maps of the distribution and the ecological status of mussel populations; The monitoring of the selected sites.