SS3.17 Global Mercury Cycling: From Natural to Anthropogenic Sources
Date: Tuesday, June 11, 2002
Time: 4:15:00 PM
Location: Carson C
 
SuretteC, Université du Québec à Montréal, Montréal, Canada, celinesurette@hotmail.com
Lucotte, M, , Université du Québec à Montréal, Montréal, Canada, lucotte.marc_michel@uqam.ca
Tremblay, A, , Hydro-Québec, Montréal, Canada, tremblay.alain@hydro.qc.ca
 
EFFECTS OF INTENSIVE FISHING ON THE DISTRIBUTION OF TOTAL MERCURY AND METHYLMERCURY IN THREE NATURAL LAKES AS DETERMINED BY A MASS BALANCE APPROACH.
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It has been demonstrated that intensive fishing, i.e. removing over 25% of the fish biomass, can reduce mercury levels in predator fish in a lake. We test here the hypothesis that by removing an important part of the fish biomass from a lake, a significant amount of methylmercury can be eliminated, therefore reducing the mercury available to the remaining biota. A mass balance approach is used to evaluate the distribution of total mercury and methylmercury in three lakes of northern Quebec before and 3 years after the intensive fishing experiment. Preliminary results show that although Hg levels in fish seem to have significantly diminished after the intensive fishing experiment, the contribution of fish to the mercury burden in lake shows no significant difference with the contribution before the intensive fishing. Therefore, the removal hypothesis doesn’t explain the observed reduction of mercury in fish. Two other hypotheses are being studied: 1) A biodilution of the mercury in remaining fish took place because of higher growth rates; 2) A shift in diet towards a lower intake of mercury by fish has happened.