Mercury and selenium concentrations in fish samples from Cachoeira do PiriáMunicipality, ParáState, Brazil.

Mercury is a major public health concern because of its widespread occurrence in the environment and its toxic effects on humans, mainly through fish ingestion. On the other hand, selenium is known by its antioxidant effect. For this reason, the knowledge of the correlation between mercury and selenium concentrations in fish samples can bring important information allowing a better understanding of mercury equilibrium in the inhabitants of the Amazon region. In this paper, total mercury and selenium levels were measured in carnivorous (47), omnivorous (44), and herbivorous (4) fish species caught in rivers and in an artificial lake in Cachoeira do PiriáMunicipality, situated in ParáState, Amazon region. The mercury concentration ranged from 1.15 to 13.44 nmol g(-1) and selenium from 2.44 to 14.56 nmol g(-1) for carnivorous species. For noncarnivorous species, mercury concentration ranged from 0.08 to 2.03 nmol g(-1) and selenium from 1.27 to 15.32 nmol g(-1). The molar ratios between mercury and selenium contents obtained for carnivorous and noncarnivorous species were 0.65 and 0.14, respectively. Mercury and selenium levels were positively correlated with fish body mass (weight) only for Hoplias malabaricus (n=35, R2=0.565, P<0.005 and R2=0.608, P<0.005, respectively). Selenium and mercury concentrations were statistically positively correlated only for H. malabaricus (n=35, R2=0.787, P=0.005) and Leporinus sp. (n=38, R2=0.485, P<0.005) known locally as Traíra (carnivorous) and Aracu (omnivorous), respectively.