Spatial Variability in the Rate of Mercury Accumulation in Muscle Tissue of Perch of Different Sizes from the Rybinsk Reservoir

The relationship between mercury (Hg) content in the muscle tissue of perch Perca fluviatilis L., 1758 (Perciformes, Percidae), and fish length was studied in fish from different reaches of the Rybinsk Reservoir and from the tailwater of the Uglich Hydroelectric Power Plant; these areas differ in physicochemical characteristics. Hg in the samples was measured by atomic absorption spectrometry using an RA-915+ mercury analyzer with a PYRO attachment (Lumex), without preliminary sample preparation; the detection limits for Hg in biological samples were 0.0005–2.0000 mg/kg. Mean metal concentrations ranged from 0.004 to 0.87 mg/kg wet weight in fish 2.2–45.0 cm long and differed among reaches. For each group, the relationship between fish length and metal content in muscle tissue was characterized by the regression-line slope, used as an indicator of the Hg accumulation rate, and by the y-intercept, used as an indicator of baseline Hg content in organisms at the base of the food web. The Hg accumulation rate characteristic of perch up to 10 cm long decreased significantly in larger fish and varied among sampling sites within the Rybinsk Reservoir.