Goldmining and mercury contamination of the piscivorous fish Hoplias aimara in French Guiana (Amazon basin)

Abstract

Mercury contamination of 35 freshwater fish species collected from the upper part of the Petit-Saut hydroelectric reservoir (French Guiana) was analyzed in relation to their food regimes. Results showed marked biomagnification: the ratio between extreme Hg concentrations in the muscle from piscivorous species (14.3 microg/g, dry weight (dw) for Acestrorhynchus guianensis) and herbivorous species (0.02 microg/g, dw for Myleus ternetzi) was 715. The piscivorous species Hoplias aimara was selected to define the relationships between biometric criteria and Hg accumulation. The probability of catching a H. aimara exceeding the WHO safety limit (2.5 microg Hg/g, dw) was computed from the kernel density estimator of mercury concentrations in the muscle: for fish weighing over 1 kg (fish usually consumed), the probability was 0.93. From these results, H. aimara could be considered an indicator of mercury biomagnification in the foodwebs and a potential risk to human populations that include this fish in their diet.