Contaminants and Ecotoxicology

The lake charr Salvelinus namaycush is a sentinel of chemical pollution in North America due to its broad distribution and trophic position as an apex predator. We reviewed the extensive literature on contaminants in lake charr, as well as the more limited information on their biological effects. Strong evidence for PCBs and chlorinated dioxins/furans causing reduced hatchability of Great Lakes lake charr embryos emerged in the 1980s. Other stressors, such as thiamine deficiency and parasitism by sea lamprey Petromyzon marinus are now thought to be important factors. Measurements of persistent organic pollutants (POPs) and mercury (Hg) in lake charr began in the 1970s. Long-term trends showed major declines in concentrations of PCBs and dioxins/furans in lake charr in the Great Lakes. New contaminants, such as perfluoroalkyl substances and polybrominated diphenyl ethers increased until the early 2000s but are now declining. Similar trends occurred for many of the same POPs in northern large lakes in Canada. Extensive monitoring of Hg in lake charr showed small annual increases from the mid-2000s to 2015 in the Great Lakes and many inland lakes. Understanding future contaminant trends in lake charr will require strong ancillary data and information on lake thermal regimes and other climate indicators.