Factors Influencing Mercury Concentrations in Walleyes in Northern Wisconsin Lakes

Abstract

Abstract We examined relations between mercury concentrations in walleyes Stizostedion vitreum and the characteristics ofclear-water Wisconsin lakes, which spanned a broad range of pH values (5.0–8.1) and acid-neutralizing capacities (–9 to 1,017 μeq/L). Total concentrations of mercury in axial muscle tissue of walleyes (total length, 25–56 cm) varied from 0.12 to 1.74 μg/g wet weight. Concentrations were greatest in fish from the eight lakes with pH less than 7.0; concentrations in these fish equaled or exceeded 0.5 μg/g in 88% of the samples analyzed and 1.0 μg/g in 44%. In the five lakes with pH of 7.0 and above, concentrations exceeded 0.5 μg/g in only 1 of 21 walleyes. Multiple regression revealed that lake pH and total length offish accounted for 69% of the variation in mercury concentration in walleyes. Regression models with total length and either waterborne calcium or acid-neutralizing capacity as independent variables accounted for 67% of the variation in concentration. The observed differences...