Long-term changes in legacy trace organic contaminants and mercury in Lake Ontario salmon in relation to source controls, trophodynamics, and climatic variability
French, Todd D., Linda M. Campbell, Donald A. Jackson, John M. Casselman, Wolfgang A. Scheider, and Al Hayton
Limnol. Oceanogr., 51(6), 2006, 2794–2807

We used long-term (20+ yr) datasets to determine how the sum of 209 polychlorinated biphenyl congeners ([SPCB]), dodecachloropentacyclodecane ([mirex]), para-para dichlorodiphenyltrichloroethane ([ p,p'-DDT]), and total mercury ([Tot-Hg]) concentrations have changed in Lake Ontario chinook salmon (Oncorhynchus tshawytscha, 1983–2003) and coho salmon (Oncorhynchus kisutch, 1976–2003). Exponential decay models best describe temporal reductions of persistent organic pollutant concentrations [POPs], including [SPCB], [mirex], and [p,p'-DDT], in chinook (r² = 0.68–0.77, p < 0.001) and coho (r² = 0.68–0.87, p < 0.001) salmon over the record. In comparison, declines in [Tot-Hg] were slight, with linear models best describing trends (r² = 0.49–0.50, p = <0.001–0.001). Rapid declines of [POPs] from the mid-1970s through the early 1980s were attributed mostly to Canada–United States bans on usage and sedimentation; subsequent concentration oscillations were linked to salmonine stocking and nutrient abatement programs, climatic cycles, and alewife (Alosa pseudoharengus) population dynamics.