Following the opening of the Rhine-Main-Danube waterway in 1992 the invasive gobiid Proterorhinus marmoratus started colonizing the River Main and the River Rhine. In 2005, point abundance sampling revealed the presence of the species in two impoundments of the River Moselle next to the confluence with the River Rhine. This distribution pattern suggests that tubenose goby actively immigrated into the River Moselle by using locks and fishways. Highest population densities were recorded in lentic to slightly lotic habitats in headwater reaches of weirs as well as in oxbow lakes and groyne fields. Due to regulation by weir and lock systems, the River Moselle and its largest tributary the River Saar offer numerous suitable habitats facilitating the rapid further expansion upstream to river reaches in Luxembourg and France.