Introduction: The study examined the concentration of total mercury and correlation coefficients between fish size or FCF (condition factor) and the content of Hg in muscle tissue of six freshwater fish: bream (Abramis brama L.), roach (Rutilus rutilus L.), whitefish (Coregonus lavaretus L.), vendace (Coregonus albula L.), perch (Perca fluviatilis L.), and pike (Esox lucius L.). Material and Methods: The fish were caught from the Lake Pluszne located in the Olsztyn Lake District (Poland). Mercury was analysed by atomic absorption spectrometry using Milestone DMA-80 (with dual-cell). Results: The content of the element in the muscles of the examined fish was as follows: pike (0.197 mg/kg) ≈ perch (0.173 mg/kg) > vendace (0.114 mg/kg) ≈ roach (0.095 mg/kg) and roach ≈ whitefish (0.065 mg/kg), and whitefish ≈ bream (0.042 mg/kg) (p ≤ 0.05). In all cases, the content of mercury correlated positively with the body weight and total length of the fish. Only the correlation coefficients between mercury concentration and weight or length of bream were slightly higher (0.979 and 0.977 respectively, p ≤ 0.001). The length and weight relationship of the fish was also determined. Conclusion: The results showed that the levels of mercury were lower than the maximum acceptable limit established by the Commission Regulation (EC) No 629/2008 of 2 July 2008. Thus, they are safe from consumer health point of view.

This paper reports polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and polychlorinated biphenyl (PCB) concentrations in fish collected from Polish and Vietnamese farms and the related risk for consumers. Altogether, 160 samples were analysed using an isotope dilution technique with high-resolution gas chromatography coupled with high-resolution mass spectrometry (HRGC-HRMS). To characterise the potential health risk associated with PCDD/F and dioxin-like polychlorinated biphenyl (DL-PCB) intake, doses ingested in two 100 g portions of fish by adults and children were calculated and expressed as the percentage of the tolerable weekly intake (TWI) newly established by the EFSA in November 2018 at 2 pg WHO-TEQ kg⁻¹ b.w. Generally, levels in fish muscles were low in relation to maximum limits (4), being in the range of 0.02–3.98 pg WHO-TEQ g⁻¹ wet weight (w.w.) for PCDD/F/DL-PCBs and 0.05–24.94 ng g⁻¹ w.w. for NDL-PCBs. The highest concentration was found in eel muscles. The least polluted were pangas and zanders and the levels were at the limits of quantification. Consumption of two portions of fish per week results in intakes of 9– 866% TWI by children and 4–286% TWI by adults. Frequent consumption of some species (for example eel and bream) can pose a health risk to vulnerable consumers and especially children and pregnant women.

The methods and results of determination of safety and relative biological value of carps (Cyprinus carpio) with philometroidosis and breams (Abramis brama) with ligulosis depending on infestation intensity with application of test-object Tetrahymena pyriformis realized in the conditions of the Republic of Belarus were presented. Research results showed that lowering of reproduction degree of protozoan on 20-30% could testify to the presence of light toxicity. Suppression of infusoria reproduction up to 30% with the simultaneous lowering of actions activity, disturbance of its character and availability up to 10% of inflected cells could testify on the moderate degree of toxicity. Lowering of infusoria reproduction degree on 30-50% with the simultaneous presence of 10-20% of cells with the affected character of motion, form and dead testified to evident toxicity of products. Lowering of infusoria toxicity on 50% and higher, presence of cysts, distorted cells, and ghosts testified to high product toxicity. Research results established that in case of high invasion intensity meat of carp philometroidosis had low toxicity (2 points). Meat of breams with ligulosis and moderate invasion intensity had low toxicity level (2 points), and in case high invasion intensity – moderate (3 points). The relative biological value in case of philometroidosis was on 13,29-28,41% lower in comparison with meat of healthy carps, and in case of ligulosis - on 18,66-57,29% in comparison with healthy breams meat