Bioaccumulation of Mercury in Various Fish Species from Orlík and Kamýk Water Reservoirs in the Czech Republic

The study evaluated contamination of fish by mercury in two important Czech water reservoirs, Orlík and Kamýk, which receive water from the whole watershed of Otava and Vltava rivers. Contamination of these reservoirs reflects the situation in southern and western Bohemia. Six environmentally representative sites were sampled in the area of interest and the evaluation was based on regression models relating Hg concentrations in fish tissues to the age of fish. A total number of 170 analyzed individuals from 3 indicative species (Rutilus rutilus, Abramis brama, and Perca fluviatilis) allowed site-specific analyses of model residuals. The results of biological monitoring corresponded to the sediment analyses and suggested that Orlík reservoir receives a substantial part of the pollution from the Vltava river. Temporary oxygen deficiency and decreased value of pH were probably the key factors responsible for the increased exposure of fish to Hg in the Kamýk reservoir. An additional comparison of 286 analyzed individuals belonging to 11 fish species provided the following decreasing order for muscle contamination: typical predators