MERCURY LEVELS IN NORTHERN PIKE,ESOX LUCIUS, RELATIVE TO WATER CHEMISTRY IN NORTHERN MINNEOSTA LAKES

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Abstract
Previous studies on lakes in northern Minnesota revealed elevated fish mercury concentrations. These results prompted fish consumption advisories on several lakes. As a followup to that work, fish fillet samples were collected for mercury analysis from 98 lakes in northern Minnesota from 1981 through 1983. Northern pike (Esox lucius) was picked as an indicator species because of its distribution throughout the region. Mercury concentrations ranged from 0.10 μg/g to 2.72 μg/g. This paper will focus on the relationship between the water chemistry of these lakes and the mercury concentration in a single size class of northern pike (50–63 cm). Correlation analysis (Spearman) revealed significant positive correlations between fish mercury and water measurements of aluminum and color and significant negative correlations between fish mercury and pH, alkalinity, and calcium. A multiregression procedure (SAS RSQUARE) revealed that the best multivariate model for predicting fish mercury concentrations, for this data set, included water aluminum, pH, and trophic status (expressed in terms of Carlson's TSI). This model will be used to identify lakes in Minnesota where future fish mercury studies should be focused.