Trend analysis reveals a recent reduction in mirex concentrations in coho (Oncorhynchus kisutch) and chinook (O. tshawytscha) salmon from Lake Ontario.

Lake Ontario, bordering both Canada and the United States, is the only Great Lake with persistent, significant levels of mirex in its biota. Some models suggested that it would take hundreds of years before mirex disappeared from the ecosystem. From 1977 to 1996 the mirex concentrations in coho and chinook salmon greater than 2 kg in weight exceeded the 0.