Background The freshwater pearl mussel (Margaritifera margaritifera) is generally restricted to nutrient-poor freshwater streams. It has a widespread but fragmented and declining distribution across Europe. In Sweden, the mussel has disappeared from around 40% of the rivers and streams in which it was found 100 years ago. Reproduction levels are low or failing in most of the remaining ones. The threats to the species are complex and either affect the mussels directly, or else its hosts, brown trout and salmon, which carry the mussel larvae. However, the principal threats can be identified as changes to water quality - including acidification and pollution - inadequate regulation of water-flow, and habitat degradation - such as by silting. Reflecting the precarious situation for the species in various countries, the pearl mussel has been the target of several LIFE Nature projects, in Finland, Germany, Spain and Belgium as well as this project in Sweden. Objectives The main objective of this project was to develop and test methods to achieve a favourable conservation status for the freshwater pearl mussel in Sweden. The project was planned to operate across 21 rivers and streams in southern Sweden. The sites were selected with reference to viability and size of the populations, geographical location and options for success. Together they contain 5% of the Swedish population and are to serve as “demonstration rivers”. The restoration activities planned by the LIFE project included the elimination of migration obstacles to host fish along ten watercourses, improvements to the river bed in eight watercourses and the management of the banks along two small rivers. Re-introduction of young mussels was to be tested in one stream. Since the conservation status of fresh pearl mussels is largely dependent on external factors related to land use outside and upstream of the mussel site, the project was to place a lot of emphasis on stakeholder consultation and dialogue. Both the regional nature conservation authorities and forestry authorities - partners in the project - would be actively involved in negotiating water rights with land owners across five counties. Results The project successfully developed and tested methods to achieve a favourable conservation status for the freshwater pearl mussel in Sweden. However, given its complex life cycle, it will take 5-10 years before it is possible to assess the real conservation impact of these actions. The project contributed to the implementation of the national action plan for the species. It undertook a series of non-recurring management activities in the project sites aimed at improving habitats for mussels and their crucial host species: removal of obstacles to the migration of host fish - such as brown trout and salmon - from ten streams removal of spruce and other vegetation which impact on streams, in favour of deciduous trees along two shoreline sites restoration of around 1 300 m2 of stream grounds across eight sites through the deposit of gravel and small stones in fast-flowing river sections - this was less than anticipated due to research which revealed lower need - but involved the innovative use of helicopters blocking of 17 ditches with wood and ground materials to reduce negative impact from siltation repairing of a dam to assure a minimum water flow during dry seasons - one planned dam repair was not conducted because further investigation indicated a lack of predicted nature conservation benefits The project re-introduced 1 000 mussels into nine locations at one project site at Silverån. The mussels were taken from a healthy and relatively abundant population in the River Sällevadsån. Monitoring found that the mussels were surviving, but could not yet find glochides on the gills of host fish, which would demonstrate reproduction. Encouragingly, however, young trout were found in restored areas. Actions were carried out in dialogue with local landowners. Further information was provided through a series of printed media, a film and events. The project conducted trips abroad to visit LIFE and other mussel projects. Around 80 participants from 14 European countries participated in a very successful final conference. Looking to the future, the project produced a manual - in English and Swedish - on the "Restoration of Freshwater Pearl Mussel Streams." This summarises the experiences of this - as well as other projects - and provides detailed and specific guidance for the conservation of Natura 2000 sites with fresh pearl mussels. Furthermore, project sites have been used to demonstrate good management of aquatic nature conservation more generally. Project data on good water quality for the fresh pearl mussel has led to changes in the SEPA Handbook for managing acidity levels in lakes and streams. Further information on the project can be found in the project's layman report (see "Read more" section).