Mercury concentrations in three species of freshwater fishes from the Lower Gallego and Cinca Rivers, Spain

Mercury pollution in aquatic ecosystems has received great attention since the discovery of mercury as the cause of Minamata disease in Japan in the 1950s. Large quantities of mercury are released to the environment and are washed into aquatic systems, where it is biologically converted into methylmercury and taken up by aquatic organisms. Fishes accumulate mercury directly from food and the surrounding water (Rainbow 1985) and they can concentrate large amounts of this metal. They are, for instance, the single largest source of mercury to man, often from natural sources (Chovjka and Williams 1980). Investigations of mercury in aquatic ecosystems have been documented in North America and many countries of Europe, but few studies have been concerned with levels of contamination that occur in natural fish populations in Spain. There is, therefore, increasing need for current information on mercury contamination in these aquatic ecosystems. The objectives of the present study were: (1) to determine mercury concentrations in fishes of the lower Gallego and Cinca Rivers; (2) to determine the distribution of this pollutant within the fish community; and (3) to compare the concentrations of mercury in these fishes with action levels established by the European Union (EU) in order to protect the public health.