Parasitization of monkey goby, Neogobius fluviatilis (Pallas, 1814) (Actinopterygii: Gobiidae), at localities with different salinity levels

Parasitism of monkey goby, Neogobius fliviatilis, was assessed at three brackish water localities with different salinity levels (Gulf of Odessa, Khadzibey Estuary, Lake Kytay) and one freshwater site along the Lower Danube River (Vidin). A total of 25 parasite taxa were identified, with minimum parasite richness recorded in the Khadzhibey Estuary (three species) and the maximum along the Lower Danube (11 species). Parasite richness in the mesohaline Gulf of Odessa and oligohaline Lake Kytay was lower, but still relatively high compared to the Khadzibey Estuary. Our study indicates that freshwater populations of monkey goby host richer and more abundant parasite communities than those inhabiting brackish waters with (more or less) stable salinity. Unstable abiotic conditions that probably affected the parasite's intermediate hosts contributed to the reduction in parasite species in the estuarine zone of the Danube.