Lake Ontario mean mirex concentration (ppb) in lake trout with 95% confidence intervals.Mirex is a synthetic insecticide regularly detected at higher concentrations in fish from Lake Ontario due to historical releases in the Niagara River and other locations within the lake's watershed. Median concentrations of Mirex in Lake Trout from Environment Canada are 0.061 µg/g ww and 0.041 µg/g ww from U.S. EPA. Declines in the concentration of Mirex in Lake Trout from Lake Ontario are still declining at historical rates of between 4% and 12% annually.