Total mercury contamination of some fish species in the firth of Vistula and the Lower Vistula River, Poland

The muscle tissue samples of smelt (Osmerus epelanus), herring (Clupea harengus), sabrefish (Pelecus cultratus), roach (Rutilus rutilus), bream {Abramis brama), ruff (Acerina cernua), perch (Perca fluviatilis), pikeperch (Stizostedion lucioperca), flounder (Platichthys flesus), brown trout (Salmo Irutta) and burbot (Lota lota) collected in the Firth of Vistula, the Lower Vistula River at the Btotnik site and the Gulf of Gdansk in May and June 1997 have been analyzed for total mercury content. The method of mercury measurement was flameless cold-vapour atomic absorption spectroscopy (CV-AAS) after wet digestion of the samples with concentrated nitric acid in a whole glass system. The study indicated around twice higher concentrations of Hg in fish collected from the Lower Vistula River than from the Firth of Vistula. Total mercury concentrations for a relatively large number of the specimens (between 12 and 41) of bream, perch, ruff, herring, flounder and pikeperch caught in the Firth of Vistula correlated (0.05 < p < 0.01) with total body length and body weight (age) of fish. Any of the fish species examined contained mercury at concentra­tions exceeding 300 ng/g wet weight. Nevertheless, smelt, herring, sabrefish and ruff were the only mature specimens, while other fish examined were rather of small body size. An ongoing study on mercury in the ecosystem of the Lower Vistula River will further focus on a larger number of fish species, specimens and including individuals large in body size.