Variability of quantitative features of the head seismosensory system in European perch <Emphasis Type="Italic">Perca fluviatilis</Emphasis> L. under conditions of anthropogenic mineralization of ponds and medium-size reservoirs

The peculiarities of the quantitative manifestation of four meristic features of the head seismosensory system have been studied in European perch individuals that inhabit ponds and medium-size reservoirs in the Middle and Lower Kama basin. The reduction trend in the interpopulation variability in the total average value of these features has been revealed under conditions of increasing mineralization of freshwater bodies, which is due to chemical pollution entering from transformed areas of their catchments.