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The Rhine-Neckar region is one of the most urbanised areas along the Rhine River and the world's largest industrial site, BASF SE, is located here at Ludwigshafen am Rhein. When the water quality dropped to its lowest values in the 1970s, BASF SE implemented a sewage treatment plant at its production site. In addition, electrofishing at this site has been carried out at regular intervals since 1976 in order to monitor changes in the fish population, whereby clear trends in both fish diversity as well as abundance have been noted.Especially rheophilic fish species such as asp Aspius aspius(L.), barbel Barbus barbus(L.) and nase Chondrostoma nasus(L.) which were rarely found during the first catching period (1976 – 1980) were then caught in increasing numbers and abundance. Starting with 6 to 8 fish species per catch in the 1970s, the number has raised to 25 fish species (including 4 neozoans) in recent catches. Overall 31 species have been monitored in the last 34 years.This indicates good river water quality and an increase in fish biodiversity along the BASF site at Ludwigshafen over the last three decades. However, focussing on the past decade, new invasive fish species such as the sunfish Lepomis gibbosus(L.) and three gobies have been found in high densities along the river banks which might have an impact on the fish population in this area in the future.