Mercury content and consumption risk of the invasive Arapaima gigas (paiche) in Bolivia

Mercury is a global pollutant present in the environment. The most frequent non-occupational human exposure pathway is fish consumption. Generally, fish species of large size and with carnivorous or omnivorous feeding habits have higher mercury concentrations. The invasive fish Arapaima (popularly known as paiche), an omnivorous large-sized species introduced in northern Bolivian Amazon about 50 years ago after escape from aquaculture in Peru, has successfully colonized this region and is now the main commercial fish species. Consumption of this species in Bolivia is increasing, and an evaluation of the risk of mercury exposure for human health is warranted. Muscle samples from 86 fish were taken from four different sub-basins (Orthon, Madre de Dios, Beni and Yata). 8.1% of the samples showed mercury content above the safe consumption recommendation of the World Health Organization (0.5 mg kg-1). Samples from the Madidi and Yata rivers scored the highest mean concentrations (0.367 and 0.306 mg kg-1, respectively), whereas individuals from the lower Beni subbasin showed the lowest (0.105 mg kg-1). According to our results, the maximum recommended paiche meat consumption is 316 g per week, divided into two meals, which is in agreement with international recommendations for fish consumption (227 g to 340 g per week), although this can vary according the place of origin of the meat. Following these recommendations, mercury exposure through paiche consumption should not represent a risk for human health.