Assessment of total and organic mercury levels in blue sharks (Prionace glauca) from the south and southeastern Brazilian coast

Mercury occurrence was evaluated in samples of edible muscle tissue of 27 blue sharks (Prionace glauca) caught in the Atlantic Ocean, adjacent to the south and southeastern Brazilian coast, indicating a slight increase in comparison with previous data obtained for the same studied area and being higher than those fish caught at different sites of the Atlantic Ocean. Total Hg concentrations ranged from 0.46 to 2.40 mg kg^-1 with the organic Hg fraction ranging between 0.44 and 2.37 mg kg^-1. A negative correlation between total Hg concentration in muscle tissue and blue shark size was obtained, and 40 % of samples analyzed had Hg concentrations higher than 1.0 mg kg^-1 Hg, the maximum concentration permitted in Brazilian predator fish. Data obtained showed that total Hg can be used as a reliable predictor of organic Hg in blue shark muscle because 95 to 98 % of the total Hg measured was found to be organic mercury. The wide range of Hg concentrations obtained for our set of samples can be explained by the heterogeneity of sampled population and the large size of the studied area. Given the adverse toxicological effects of Hg on animals and humans, a regular monitoring program of Hg contamination in Brazilian marine ecosystem can be recommended.