Round goby includes mollusks, crustaceans, worms, fish eggs, zebra mussels, small fish, and insect larvae. Adult round gobies feed mainly on mollusks and other small invertebrates (insects and amphipods) living on the bottom of lakes and streams. At spring, the main items in its diet in the Sasyk Lagoon are "Hydrobia", "Cerastoderma", "Abra". In the same season near the Romanian coasts of the Black Sea the round goby feeds on polychaetes, crustaceans ("Idotea balthica", "Pachygrapsus marmoratus", "Xantho poressa", etc.) and juvenile gobies. Near Sevastopol the round goby feeds on molluscs ("Mytilaster lineatus", "Abra" spp.), but near Karadag except molluscs ("Cerastoderma", "Brachiodontes") were
Round goby Nord-Ostsee (Kiel) Canal. As of 2010, the westernmost site of round goby occurrence in Europe was the Lower River Scheldt, the tidal zone in the river mouth, and Albert Canal, Belgium. In 2011, the round goby began invading the fresh waters of France: the species appeared in the Rhine River (on the border between France and Germany), and in the French part of the Moselle River. In total, 52 parasite species are registered in the round goby in the native area. Most abundant parasites of the Black-Sea round goby are metacercariae of trematodes of Heterophyidae family, such as "Cryptocotyle concavum",