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.

Mercury in muscle and liver of ten ray species from Northwest Mexico.

We determined total mercury (Hg) distribution in muscle and liver of ten ray species and assessed health risk considering Hg levels in muscle and average consumption of rays in Mexico. Rays were collected from five sites in NW Mexico between March and November 2012. Hg concentrations ranged from 4.465 µg g(-1) in muscle of the longtail stingray Dasyatis longa to 0.036 µg g(-1) in liver of the diamond stingray Dasyatis dipterura. Considering all the individuals, Hg in muscle (1.612±1.322 µg g(-1)) was significantly (p<0.05) higher than in liver (0.745±0.616 µg g(-1)). Regarding local health risk assessment, none of the ray species may cause adverse effects on consumers.