Background Numerous thick shelled river mussel (Unio crassus) populations have become extinct in Sweden. The remaining populations of this endangered species have a fragmented (some 140 sites) and narrow south-eastern distribution in Scandinavia. The decline of the species can be linked to adverse physical changes to its habitats (including fragmentation, regulation, dredging and channelisation of watercourses) and the resulting scarcity of host fish. The decline in host fish abundance can lead to populations of mussels becoming so small that recruitment of young mussels cannot be maintained. This may lead to ageing populations that are slowly dying out. There are also problems concerning how to interpret and apply drainage in areas with protected species. Water legislation, which is often more than 100 years old but still applicable, requires landowners to dredge and clean rivers and streams. At sites with populations of Unio crassus, this means that the requirements according to one set of old laws are in conflict with current EU legislation, which is designed to protect rare species and vulnerable habitats. The loss of riparian protection zones, by cutting down shading trees and the removal of riverine structures, can lead to high water temperatures, a homogenous habitat and increased amounts of suspended material in the river, which might negatively affect the mussel and fish populations. Objectives At nine of the 12 project sites, the conservation status of the thick shelled river mussel has been classified as ‘unfavourable’ according to the Article 17 assessments of the Habitats Directive (2001-06). At the other three sites the species is extinct. This project aims to strengthen the conservation status of this endangered freshwater mussel species and improve the ecological status of the rivers where it is found in Sweden. This overall goal will be achieved by the following: Mapping of host fish to ensure successful conservation actions, beneficial for both Unio crassus and its host fish species at seven project sites; Recreating natural river dynamics by restoring structures (substrate and cover) and processes (connectivity and corridor functions) beneficial for the freshwater mussel species and related host fish species at the 12 project sites; and Re-introduction by rearing and stocking juvenile mussels and glochidia-infected host fish to build up populations at two project sites. Allocation of adult mussels to more favourable habitats will also be conducted to improve reproduction at six project sites. Alongside the concrete conservation actions objectives, the project aims to build up local awareness for future river management at the 12 project sites through the platform of local water councils. Expected results: Improvements in the conservation status of the mussel at eight of the 12 project sites by increased recruitment rates by juveniles. At three project sites where the species is currently absent, it is not possible to reach a favourable conservation status within the project time-frame; After-LIFE activities at the three project sites where the species is currently absent will ensure that a favourable conservation status is achieved after the end of the project; Improvements in the ecological status - from 'poor' to 'moderate' - of water bodies at two project sites and from 'moderate' to 'good' in the ecological status at nine project sites; and After-LIFE activities, including stakeholder engagement, will, alongside the implementation of the WFD, ensure a continuum of management of the rivers within the project sites.