Mercury in the blue tilapia Oreochromis aureus from a dam located in a mining region of NW Mexico: seasonal variation and percentage weekly intake (PWI).

Uptake of mercury (Hg) through fish consumption is one of the key aspects of the Hg cycle in the aquatic ecosystems. In tropical latitudes, biomonitoring of Hg in freshwater reservoirs is scarce. The objectives of the study were to determine Hg distribution in muscle, liver, and kidney of blue tilapia Oreochromis aureus from a dam located in a mining region of northwest Mexico, to define temporal variations of Hg concentrations in fish collected during the dry and rainy seasons, and to estimate the percentage weekly intake (PWI) of Hg through fish consumption considering the individual weekly intake of fish in Mexico and the provisional tolerable weekly intake of Hg (5 μg kg(-1) body weight). The sequence of Hg concentrations was liver > kidney > muscle during the rainy season and kidney > liver > muscle during the dry season. Levels of Hg were significantly higher (p < 0.001) in muscle (0.36 μg g(-1)) and kidney (0.65 μg g(-1)) of specimens collected during the dry season in comparison to individuals collected during the rainy season; accordingly, average PWI in the dry season (5.41) was higher than in the rainy season (1.80). Though collected fish were adults, Hg levels in the edible portion are not harmful to consumers, even during the dry season that Hg levels were higher.