The article presents the results of the study on nuclear damages or injuries of red blood cells (RBCs) and asymmetry of meristic characters of the European perch (Perca fluviatilis Linnaeus 1758) that lives in small and medium rivers of Rivne Region. The research has found that the species representatives living in the small rivers demonstrated worse cytogenetic homeostasis indicators compared to the fish from the medium rivers: the lowest frequency of P. fluviatilis’ nuclear damages appeared to be 4.25 times higher for the individuals living in the small rivers given the noticeable excess of spontaneous mutations by average damage frequency. Fish morphological homeostasis demonstrates a tendency to injuries in small rivers as well. The functional relationships between the studied parameters which have been established by the author were “close” for the fish from the small rivers and primary “moderate” for the fish from the medium rivers. It is concluded that the enhanced activity of the stressors existing in the water environment affects the physiological state of the P. fluviatilis species.
For the first time, an analysis of structural damage of the peripheral blood erythrocyte nucleus in Rutilus rutilus (Linnaeus, 1758) was carried out for the rivers of the north-western region of Ukraine. The effect of the hydrochemical regime on the formation of cytogenetic disturbances of the representatives of this species was also clarified. It was observed that during 2013–2017, the content of phosphates, suspended solids, fluorides, iron, copper, zinc, manganese, nitrite nitrogen and nitrate nitrogen in the surface waters of rivers most significantly exceeded the current quality standards. The average frequency of nuclear disorders of peripheral blood erythrocytes R. rutilus from the studied hydrosystems is 5.25 ± 0.29 ‰ (p < 0.01), with a noticeable excess of the level of spontaneous mutations in the older age groups of fish. In all analyzed samples of R. rutilus, among the total number of identified structural disorders of the nucleus, the largest share is made up of red blood cells from the micronucleus (from 40.0 to 62.0 %), which is evidence of cytogenetic disturbances in the body of fish. At the same time, disturbances of erythrocyte blood of roach from small rivers are on average 1.3 times (or 21.9 %) higher compared with individuals from medium-sized rivers. The formation of cytogenetic disturbances in R. rutilus under the conditions of the hydrochemical regime of rivers is described by a close (r = 0.99 at p < 0.003) multifactorial regression dependence. More important regressive coefficients of the dependency are acquired by such biogenes (NH4+, NO3−, PO4−) and toxicants (Cu2+, Zu2+, Mn2+, F2) in the background of oxygen regime peculiarities (COD, BOD5, O2).