The role of invasive Chinese sleeper Perccottus glenii Dybowski, 1877 in the Ilgas Nature Reserve ecosystem: an example of a monospecific fish community

The Chinese sleeper, Perccottus glenii, is an invasive species that has spread into Eastern Europe from its natural geographic range in Far Eastern Asia. Here, we provide a complex hydrobiological study of a marsh waterbody in the Ilgas Nature Reserve Natura 2000 site (Latvia) where we registered a monospecific fish community comprised of Chinese sleeper. While benthic organisms were predominant in the diet of Chinese sleeper of < 70 mm, the diet of larger fish (particularly around 90 mm) included an increasing proportion of juvenile Chinese sleeper (cannibalism). In the case of the Ilgas marsh, we believe that medium natural production (mesotrophic waterbody), piscivory and high competition for food has resulted in a monospecific fish community represented by Chinese sleeper alone.