The article gives the result of the research of such fishes of the Gobiidae bloodline as Neogobius fluviatialis Pallas, 1814, Neogobius melanostomum Pallas, 1814, and Mesogobius batrachocephalus Pallas, 1814, in the waters of the Dnipro-Buh estuary and the Black Sea near Mykolayiv and Odessa regions. It established the possible associations of cryptocotylosis with other types of parasitic invasions of Gobiidae fishes. It has been set up that the researched fishes have been the most invaded by such agents of parasitic diseases as trematodes and nematodes – 52.2% and 37.3% respectively. The smallest parasitic group affecting commercial fishes is cestodiasis – 0.37%. Neogobius fluviatialis Pallas, 1814, has been noticed as invaded by Asymphylodora pontica Chernyshenko, 1949. The prevelence (P) counted 2.58%, and the invasion intensiveness (II) counted 4–12 samples. Cryptocotyle concavum Creplin, 1825 (P – 30.4%, ІІ – 9–124 samples); Cryptocotyle jejuna Nicoll, 19 07 (P – 15.9%, ІІ – 12–103 metacecaria); Ligula pavlovski Dubinina, 1959 (P – 0.21%, ІІ – 1sample); Cucullanellus minutus Rudolphi, 1819 (P – 9.05%, ІІ – 1–3 nematodes); Eustrongylides excisus, Jägerskiöld, 1909 (P – 23.06%, ІІ – 1 – 4 larvae); Raphidascaris sp. (P – 2.8%, ІІ – 1 nematode); Telosentis exiguus (Linstow, 1901) (P – 1.07%, ІІ – 1–2 samples.); Ergasilus nanus (Beneden, 1870) (ІE – 8.18%, ІІ – 1–31 maxillopods).The parasitic fauna of Neogobius melanostomum Pallas, 1814 was characterized by such agents as Asymphylodora pontica Chernyshenko,1949 (P – 10.2%, ІІ – 5–36 samples); Cryptocotyle concavum Creplin, 1825 (P – 59.2%, ІІ – 94–211 samples); Cryptocotyle jejuna Nicoll, 1907 (P – 44.8%, ІІ – 4–87 metacercaria); Stephanostomum bicoronatum (Stossich, 1883) Fuhrmann, 1928 (P – 26.5%, ІІ – 6 – 69 larvae); Ligula pavlovski Dubinina,1959 (P – 2.04%, ІІ – 1sample); Cucullanellus minutus Rudolphi, 1819 (P – 16.3%, ІІ – 1–6 nematodes); Eustrongylides excisus, Jägerskiöld, 1909 (P – 22.4%, ІІ – 1–4 larvae); Raphidascaris sp. (P – 4.08%, ІІ – 1–2 nematodes); Telosentis exiguus (Linstow, 1901) (P – 8.16%, ІІ – 1–2 samples); Ergasilus nanus Beneden, 1870 (P – 14.2%, ІІ – 2–8 maxillopods). Parasitic invasions of Mesogobius batrachocephalus Pallas, 1814, also took place. For example, there were registered the cases of invasion with such agents as Cryptocotyle concavum Creplin, 1825 (P – 17%, ІІ – 18–89 samples); Cryptocotyle jejuna Nicoll, 1907 (P – 13.5%, ІІ – 7–21 metacecaria); Stephanostomum bicoronatum (Stossich, 1883) Fuhrmann, 1928 (P – 6.77%, ІІ – 5–11 larvae); Cucullanellus minutus Rudolphi, 1819 (P – 35.6%, ІІ – 1–3 nematodes); Eustrongylides excisus, Jägerskiöld, 1909 (P – 32.2%, ІІ – 1–3 larvae); Сontracaecum sp. (P – 5.08%, ІІ – 1 nematode); Ergasilus nanus Beneden, 1870 (P – 8.74%, ІІ – 1–15 parasites).
Експериментальне зараження каченят метацеркаріями трематод Cryptocotyle Lühe, 1899 (Trematoda: Heterophyidae)