Parasite fauna of native and non‐native populations of Neogobius melanostomus (Pallas, 1814) (Gobiidae) in the longitudinal profile of the Danube River

Parasite fauna of round goby Neogobius melanostomus (Pallas, 1814) in the Danube River was investigated in both its native range (two sites in the Bulgarian stretch of the Danube) and non‐native range of distribution (Croatian, Slovak and Austrian stretches) during 2005 and 2006. The aim was to identify possible changes in parasite communities associated with the introduction of a host into the new environment. A total of 29 metazoan parasite species were found to parasitize round goby in the Danube River; twelve of these parasite species were found in both the native and non‐native range of distribution. Introduction of a novel parasite species to the non‐native range via the round goby was not found. Eight parasite species occurred only in the native range and nine species only in the non‐native range of the round goby distribution. Losses of native parasite species in non‐native round goby populations and/or acquiring of novel parasite species in a new environment were not significant. Thirteen parasite taxa were recorded for the first time in round gobies. Three parasite taxa (Diplostomum spp., Pomphorhynchus laevis and Raphidascaris acus) were found in high prevalence and abundance at each sampling site in both the native and non‐native range. Parasite species diversity was assessed for each sampling site and season using three diversity indices (the Shannon, Simpson and Equitability indices), with the highest same‐season values found in a non‐native site in Slovakia (1.38, 0.69 and 0.60, respectively) and the lowest in a native site in Bulgaria (0.28, 0.12 and 0.14, respectively). Species diversity was higher in both non‐native round goby populations (Slovak and Austrian) compared to native Bulgarian populations. However, diversity indices values varied among almost all sampling sites.