Background Aquatic species are considered to be some of the most endangered species in Europe. This is certainly the case of the freshwater pearl mussel, whose population has declined by more than 90% across the continent. In France, the decline has been more dramatic and represents more than 99% of the population. Currently, the population is estimated to be around 100 000 mussels in around 80 rivers. The upper Dronne River is home to the first French population of freshwater pearl mussels with about 15 000 mussels. The conservation problems and threats are related to a deterioration of the water quality, the clogging of the river by substrates and the breakdown of river continuity (the flow of the river is obstructed by man-made obstacles such as dams and weirs). The water quality of the upper Dronne River is good but can exceed 7 mg /L of nitrate (NO3). This level is very close to the limit at which juvenile mussel can survive – 1.7 mg /L. Objectives In the short-term, the Marga Haute-Dronne project aims to establish the best conditions for maintaining the population of freshwater mussels on the Upper Dronne. The long-term goal of the project is to enable population growth to make the mussel population viable. The river continuity will be restored by removing or finding other methods to get around the main obstacles to the river course: dams, weirs and pipelines. This will enable habitat restoration in the river and some of the main tributaries within the Natura 2000 area. The actions will also include the restoration of a population of wild brown trout, ensuring a sufficient number of fish hosts. Parallel to this action, a rearing facility will be set up to produce freshwater mussel juveniles in captivity. The production of juvenile mussels will help to strengthen the small population in the natural environment of the upper Dronne and to understand the impact trace metals has on it. Expected results: Restoration of the habitats on the main stream and tributaries of the upper Dronne; Creation of a rearing facility for freshwater mussels, aiming to produce 16 000 juveniles over the five years of the project; and An awareness campaign about the protection of the freshwater pearl mussel.