Offshore distribution of invasive gobies (Pisces: Gobiidae) along the longitudinal profile of the Danube River

Abstract

The invasion of fish and invertebrate species of Ponto-Caspian origin is in the forefront of freshwater research due to the extremely fast range expansion of many species and their radical effects on the structure and functioning of ecosystems in their non-native habitat. This study provides the first assessment of the offshore distribution of invasive Ponto-Caspian gobies along the longitudinal profile of the Danube River using the data of the Joint Danube Survey 3 research expedition. Six goby species were collected, the round goby Neogobius melanostomus, the monkey goby N. fluviatilis, the Kessler goby Ponticola kessleri, the racer goby Babka gymnotrachelus, the stellate tadpole-goby Benthophilus stellatus, and the tubenose goby Proterorhinus semilunaris, which showed large differences in their offshore distribution along the river. N. fluviatilis was found for the first time as a new species in Austria, which shows the slow spread of this species upstream in the Danube River or alternatively, its introduction by ships. Offshore trawling confirmed the use of deep channel habitats by gobies, and is suggested as a useful tool for monitoring spatial and temporal trends in the dynamics of invasive benthic species for riverine fish biological research.