Background The giant European pearl mussel (Margaritifera auricularia), also known as grande mulette and Spengler’s freshwater mussel, was once a common species in Western Europe, where it thrived in large, slow-flowing rivers from England, Germany and Spain, in the watersheds of the Adour, the Rhône and the Po. However, today only a few populations remain in some French rivers and the Ebro basin in Spain. The causes of this decline include the morphological degradation of rivers, habitat destruction, water pollution, overfishing, water extraction activities, fragmentation of populations and the near-extinction of its main host-fish European sturgeon (Acipenser sturio); parasitic larvae must develop on the gills or fins of host-fish until becoming free-swimming juveniles. Objectives The goal of the LIFE Giant Pearl Mussel project is the conservation of the critically endangered giant pearl mussel (Margaritifera auricularia) in France, specifically in the Charente, Vienne and Creuse rivers where up to 98% of the world’s giant pearl mussel population can be found. The project aims to use artificial breeding and restocking of rivers as the basis for the species’ long-term conservation in Western Europe. It will thus help implement French and Spanish National Action Plans for this species. Project actions also form part of the EU biodiversity strategy for 2020. Expected results: Extension of the survival time of captivity-bred giant pearl mussels from 2-3 months to one year and beyond, by improvements in artificial rearing techniques; Development of an innovative breeding technique using new feeding methods, a nursery for juveniles and the identification of alternative host fishes to European sturgeon for captive breeding; Reproduction and optimisation of rearing conditions in a controlled laboratory environment; Release of up to 2 000 viable individuals every year during the project’s duration; and; Conservation of the Charente River's giant mussel population, in order to provide a temporal window of survival for the species until an appropriate dam sediment management plan is implemented.