Assessment of the Biological Water Status: Fish

Within the National Surface Water Quality Monitoring Programme (NAWA), water quality is recorded jointly by the federal and cantonal authorities at around 100 monitoring stations. The biological water status is assessed on the basis of fish investigations by the fish module in the Modular Step Procedure (www.modul-stufen-konzept.ch). Fish are present in almost all streams and rivers. Due to their complex and distinctive habitat requirements, they are good indicators of the morphological and hydrological water status. The mobility and migratory behaviour of many fish species also help to identify the passability and interconnectedness of the watercourses.