Range expansion of an invasive alien species, Chinese sleeper, Perccottus glenii Dybowski, 1877 (Teleostei: Odontobutidae) in the Vistula River drainage

In October 2007 an invasive alien species, the Chinese sleeper, Perccottus glenii Dybowski, 1877 (known also as the Amur sleeper), was recorded in carp ponds in Krakow-Mydlniki (southern part of Vistula River drainage). As far as we know, this is the uppermost site in the Polish pail of the Vistula River drainage. Thirty-six individuals of P. glenii were collected during fishery works. Basic morphometric measurements were obtained, following the commonly accepted procedures, in order to describe the general body shape of P. glenii.