The invasive mollusc was found in the riverbed on the muddy bottom substrate at depths up to
1м. More than 100 living individuals were found with lengths of 3-19 mm along a transect 0.7×25m.divided into four size-age groups according to the shell length: up to 0.5mm; 6-10mm; 11-15mm; 16-20mm (Figure 3). Most numerous (90specimens) was the group with shell length 6-10 mm. The C. fluminea’ maturation period begins when shell length reaches 6-10mm (Sousa 2008),thus the most numerous group were considered sexually mature.