The functional ecology of four invasive Ponto–Caspian gobies

Ponto–Caspian gobies are among Europe's most invasive freshwater fish species. These small freshwater and brackish water fish have spread rapidly since the end of the last century, invading the major European river systems, including the Rivers Danube, Rhine, Moselle, Meuse, Vistula, Elbe, Nemunas, Neva, Volga, while also establishing in streams, dam reservoirs, lakes, and artificial canals in 17 European countries. Two species have also successfully established in North America. The contribution of Ponto–Caspian gobies to local fish assemblages varies, but locally they are abundant or dominant components of fish assemblages in invaded ecosystems. We have considered their invasive distribution, range of occupied aquatic environments, abundance, and frequency of occurrence, and summarised their role and position in the trophic webs of invaded ecosystems. We focused on four goby species: western tubenose goby Proterorhinus semilunaris , bighead goby Ponticola kessleri , racer goby Babka gymnotrachelus and monkey goby Neogobius fluviatilis . Based on our own research and other published studies, we described the habitat preferences of these species and assessed their ecological impact on co-occurring species, both native and non-native, as predators, prey, competitors, and as hosts and vectors of parasites.