Post-invasion spread of Chinese sleeper (Perccottus glenii) in the Lower Danube drainage (Budjak region of Ukraine)

The Chinese sleeper Perccottus glenii (Actinopterygii: Odontobutidae), is an invasive alien species (IAS) of fish that has been included into the European IAS list of Union Concern. The present study aims to describe the current distribution of Chinese sleeper in the Ukrainian Lower Danube drainage. Fish assemblage monitoring took place at 70 localities inside the Budjak historical region in south-western Ukraine over a twenty-year period (2001???2021), with Chinese sleeper occurrence confirmed at 24 localities. Our data not only confirm the spread of invasive Chinese sleeper within the Budjak region, but also outside the Danube basin, including the Sasyk Lagoon (2 ind.) and several overgrown banks along sea foreshore. Considering that Chinese sleeper are presently found in waterbodies intensively used as fisheries, in river forefront marshes and at one site outside the Danube basin, it is highly plausible that further expansion of this fish species will be observed in the near future.