Non-native Gobiid species in the lower River Rhine (Germany): recent range extensions and densities

The tubenose goby (Proterorhinus semilunaris, Heckel, 1937; all names of gobiid fishes in accordance with Neilson and Stepien, 2009) was first registered in the Lower Rhine in 1999. Initially, the North Rhine-Westphalia fishing authorities were concerned as this invasive species was thought to feed on fish eggs and fry and, thus, could potentially affect local fish communities (Jude et al., 1992). Although the tubenose goby is now widespread throughout the floodplain waters of the Lower Rhine (Scharbert, 2009), it has never reached high abundance and is found primarily in lentic backwaters. Consequently, this invasive species is no longer considered an important threat to native fish communities. The bighead goby (Ponticola kessleri, Guenther, 1861) was first recorded in the German Lower Rhine near the city of Koenigswinter (Rhine-km 644) in 2006 (Stefan Staas, unpubl. data).