Content of heavy metals in the muscle tissue of fish from two rivers in the Morava river basin (Czech Republic)

Heavy metals are notorious environmental pollutants with serious health implications for both aquatic ecosystems and human consumers. In 2022, we assessed the cadmium, chromium, mercury, nickel, and lead contents in fish (in wet weight muscle tissue) from two rivers in the Czech Republic subject to pollution incidents, the rivers Bečva and Svratka, to identify potential risks for human consumption. Three fish species were examined: chub ( Squalius cephalus ) from the Bečva (four sites), and chub, perch ( Perca fluviatilis ) and roach ( Rutilus rutilus ) from the Svratka (one site). While concentrations of nickel, chromium, and lead were generally higher in water from the Bečva than the Svratka, all heavy metals (aside from cadmium) were higher in sediment from the Svratka. In chub, nickel concentrations varied greatly between individuals, with the highest concentration reaching 5029.9 µg/kg. In comparison, nickel concentrations in roach and perch were generally low and often below the detection limit (14.8 µg/kg). Mercury concentrations varied between 14.3 and 249.4 µg/kg, with the highest mean concentration found in perch. Cadmium concentrations were highest in the Svratka, though the difference was non-significant, with concentrations in the Bečva mostly under the detection limit (1.49 µg/kg). Lead and chromium concentrations only occasionally exceeded the detection limit, except for one chub in which chromium concentrations exceeded 159.94 µg/kg. In general, aside from nickel, heavy metal concentrations in fish muscle tissue were low and appear not to represent any threat to human health. However, the samples with the highest nickel content could represent a potential risk for nickel-sensitive individuals.