Population dynamics and dietary habits of monkey goby (Neogobius fluviatilis) in its native range in the Dnieper River basin

Context Various aspects of the monkey goby (Neogobius fluviatilis) biology were studied but mainly in native marine and invaded freshwater bodies; however, in Ukraine, this species can be considered native in many freshwaters. Aim To investigate the population dynamics and dietary habits of N. fluviatilis in a freshwater habitat in its native range. Methods Samples were collected monthly in 2015–2016 and 2018 in a river flowing into the Kaniv reservoir (Dnieper River). Key results Goby abundance varied during a year and between years, depending on water temperature. Young of the year started appearing in June and reached the size of adult fish in October. N. fluviatilis had multiple spawnings occurring from May to August. Altogether, 70 taxa of prey organisms composed its diet, among which the most abundant prey were chironomids (57.7% in number). The diet of N. fluviatilis showed a clear ontogenetic shift from the consumption of benthic microcrustaceans to chironomids. Conclusions N. fluviatilis fed predominantly on prey inhabiting non-vegetated sand and mud substrate. The opportunistic feeding strategy, combined with time-expanded multiple spawnings, can facilitate the successive invasion and establishment of this species in new environments. Implications The obtained results can be used to predict the impact of N. fluviatilis on ecosystems in newly invaded areas.