Background and Objectives: The heavy metals pollution in aquatic ecosystems especially mercury, always makes concern about health of aquatic organisms. So, the purposes of this study were determination of total mercury in different tissues of the three species of the most important water birds at north of Iran and comparison with world health standards.
Materials and Methods: Generally, 51 birds were captured randomly. Then, samples of feather, liver, kidney and muscle were taken and the mercury concentrations were determined by Advanced Mercury Analyzer (Model; Leco, AMA 254).
Results: The most amount of accumulated mercury was in great cormorant's liver (piscivorous species). Means of mercury concentration in liver of great cormorant, mallard, and coot were 14.80, 2.05, 0.18; in kidney 12.00, 1.90, 0.17; in feather 6.57, 1.09, 0.23 and in muscle 8.67, 0.26, 0.09 mg/kg dry weight respectively. Means Comparison showed significant difference among all tissues (P < 0.05), But there were not significant difference between sexes (P > 0.05)
Conclusion: The levels of accumulated mercury in all tissues of great cormorant were more than the established limits by WHO, FAO and EPA. The other species had less use limitation, but mercury concentration in mallards was considerable. These results can be a serious warning for consumers these birds, especially vulnerable people.