Bioaccumulation of mercury in various fish species from Orlik and Kamyk water reservoirs in the Czech Republic

The study evaluated contamination of fish by mercury in two important Czech water reservoirs, Orlik and Kamyk, which receive water from the whole wate rshed of Otava and Vltava rivers. Contamination of these reservoirs reflect s the situation in southern and western Bohemia. Six environmentally repres entative sites were sampled in the area of interest and the evaluation was based on regression models relating Hg concentrations in fish tissues to th e age of fish. A total number of 170 analyzed individuals from 3 indicative species (Rutilus rutilus, Abramis brama, and Perca fluviatilis) allowed si te-specific analyses of model residuals. The results of biological monitori ng corresponded to the sediment analyses and suggested that Orlik reservoir receives a substantial part of the pollution from the VItava river. Tempor ary oxygen deficiency and decreased value of pH were probably the key facto rs responsible for the increased exposure of fish to Hg in the Kamyk reserv oir. An additional comparison of 286 analyzed individuals belonging to 11 f ish species provided the following decreasing order for muscle contaminatio n: typical predators < benthophagous species with substantial portion of fi sh in food < typical benthophagous species < planktonophagous species. Comp aring the tissues, Hg appeared to be preferentially accumulated in muscle a nd less in liver and rather negligible concentrations were found in gonads. Considering overall situation in the Czech Republic, the obtained data doc umented a relatively low exposure of fish populations to Hg in the examined reservoirs. (C) 1999 Academic Press.