Restoration of streams and fish communities: Possibilities and challenges

Many Swiss rivers are highly channelized and fragmented. Below 600 m a.s.l., 50% of all streams have morphological deficits. Fish populations are heavily impacted by poor habitat quality and lacking connectivity. Due to the intensive hydropower use the lack of a dynamic  hydrological regime is the main difficulty  in many Alpine streams. Restoring the running waters is a challenging task and federal and local governments will invest substantial funds in the future.  Based on experiences during the last years the possibilities of river restorations are discussed. Habitat and structural fixes alone do not restore the fish populations and communities. The restoration of an appropriate flow regime and additional important processes are a prerequisite for the recovering of fish populations and communities. Successful restoration activities in streams and rivers will be presented and the reaction of the fish fauna is discussed. Restoration of fish communities will be highlighted for salmonid and cyprinid populations. In comparison, less successful restoration projects are analyzed.  Approaches to prioritize future restoration activities are demonstrated on the basis of projects carried out during the last years.