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Open Lakes Trend Monitoring Program: Mercury

Contact Information

For further information on the Great Lakes Fish Monitoring and Surveillance Program, please contact:

Elizabeth Murphy (murphy.elizabeth@epa.gov)
Environmental Scientist
EPA Great Lakes National Program Office
(312) 353-4227 or 1-800-621-8431 x34227

Access the Data

Data produced by the GLFMSP can be obtained through the Great Lakes Environmental Database Query System or through the University of Illinois Extension website Exit EPA Disclaimer

You can also contact the program manager, Elizabeth Murphy, for information regarding the GLFMSP and/or supporting data.

Peer reviewed journal articles published using GLFMSP data can also be found on the Reports & Links page.

Total mercury concentrations for individual and composited whole body Lake Trout or Walleye collected from each of the Great Lakes

Total mercury concentrations (median & IQR) for individual (Environment Canada) and composited (U.S. Environmental Protection Agency) whole body Lake Trout or Walleye (Lake Erie) collected from each of the Great Lakes. Results of 2-segment linear piecewise regression (solid red line) or log-linear regression (solid blue line) models. (Source: McGoldrick, D., Clark, M., and Murphy, E. 2012. "Contaminants in Whole Fish", In: U.S. EPA and Environment Canada. 2012. State of the Great Lakes 2012.) (Click to enlarge)

Mean mercury concentration in lake trout/walleye from 1999 through 2008.

Mean mercury concentration in lake trout/walleye from 1999 through 2009. (Click to enlarge)

There have been several studies on spatial and temporal trends of mercury in fish in the Great Lakes region (Bhavsar et al 2010; Monson et al. 2011; Zananski et al. 2011). Both studies found that generally, the declines in mercury concentrations observed up until approximately 1990 have ceased and that mercury concentrations in fish have started to increase. Environment Canada and U.S. EPA data were used in the analyses of both studies and correspond with their findings. Concentrations of mercury are similar across all fish in all Great Lakes consistent with the assumption that concentrations of mercury in top predator fish are atmospherically driven and the recent increases may be a reflection, in part, of increased global mercury emissions (Pacyna et al. 2006). It is important to note that median concentrations of mercury in all top predator fish collected in Lakes Ontario, Erie, Huron and Michigan are below the 1987 GLWQA guideline of 0.5 µg/g and exceedances of the guideline only occurred in ~4% of the Lake Trout captured in Lake Superior. Mercury concentrations in top predator fish are currently equal to or approaching the concentrations measured at the inception of the monitoring program in the late 1970s. Two segment linear piecewise regression of the Environment Canada dataset show that declines in mercury ceased in the late 1980s in lakes Superior and Huron and the early 1990s in lakes Erie and Ontario. Following the change points in each lake, mercury levels have been stable in lakes Huron and Ontario and appear to be increasing in lakes Superior and Erie. Mercury levels at U.S. EPA monitoring locations since 1999 mirror the Environment Canada results with one exception, in Lake Huron there has been a significant annual increase of mercury in Lake Trout of ~7%. The observed trend reversal in mercury concentrations in fish is consistent with recent findings (Monson 2009; Bhavsar et al. 2010; Monson et al. 2011) of mercury. Unfortunately, the data gap from the mid to late 1990s does not leave a sufficient number of data points to determine the current rates increase due to low statistical power. Continued monitoring of mercury levels in fish is required to definitively determine the rate of increase in mercury in all the lakes and adequately assess the future risk to wildlife consumers of fish in the Great Lakes basin.

GLFMSP mercury publications:

Referenced Publications


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