The relationship between biotic factors and the content of chosen heavy metals (Zn, Fe, Cu and Mn) in six wild freshwater fish species collected from two lakes (Łańskie and Pluszne) located in northeastern Poland

The effect of biotic factors such as species, condition factor, body weight and total length of fish on concentrations of iron (Fe), zinc (Zn), copper (Cu) and manganese (Mn) in organs of Rutilus rutilus (L.), Abramis brama (L.), Coregonus lavaretus (L.), Esox lucius (L.), Perca fluviatilis (L.) and Tinca tinca (L.) from reservoirs of Warmia and Mazury region (northeastern Poland) were determined. Differences in the content of metals were observed between species (p≤0.05). Some metals demonstrated specific affinity for particular tissues. Lower concentrations of metals were found in muscles and ranged as follows: Zn 3.427-9.950, Fe 1.297-2.550, Cu 0.133-0.279 and Mn 0.050-0.162 (expressed mg kg-1 wet weight). The highest levels of Fe (33.49-123.6) and Cu (3.994-27.14) (except for copper in perch) found in the liver (p≤0.05) was related to detoxification, whereas high concentrations of Mn (1.366-5.113) and Zn (15.91-135.0) (except for Zn in tench) in gills may be associated with excretion processes or uptake (p≤0.05). The two organs (gills and liver) may be used as bioindicators of metal contamination of aquatic environments. Studies on the size and condition factor dependency of heavy metal concentrations have showed that, although the relationship exists, in most cases it was not statistically significant for organs. Metal Pollution Index (MPI) in organs of fish examined was 1.503