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 invasive nematode "Anguillicoloides crassus". In the Vistula Lagoon, the most abundant parasites of the round goby are nematodes "Hysterothylacium aduncum" and "Anguillicoloides crassus". 25 species of parasites are noted in the round goby in the Great Lakes. The trematode "D. spathaceum" is most abundant core species overall. Also the cestode "Proteocephalus" sp. and the trematode "Neochasmus umbellus" are rather abundant. The round goby may circumvent more of the metacercariae of "N. umbellus" from completing their life cycle. The parasite “load” on the invasive gobies in the Great Lakes appears relatively low in comparison with their native habitats, lending support to