Chemical Contamination As a Potential Factor in Recruitment of American Eel to Lake Ontario

Pollutants are a possible cause of declines in yellow eel recruitment to L. Ontario since the 1980s.  L. Ontario eels accumulate dioxin-like compounds (DLCs) to the same extent as lake trout, which suffered embryo mortality from maternally-derived DLCs.   Sexual maturation transfers lipids and associated persistent, hydrophobic contaminants to oocytes.  Eels recruiting to L. Ontario in the 1980s-90s were spawned from parents that integrated contaminant exposures from the 1960s-70s, when contamination was highest.  Chemicals extracted from L. Ontario eels captured in 1988 and 98 caused dioxin-like toxicity when injected into eggs of mummichog. However, extracts from 2008 eels were non-toxic to embryos of mummichog and Japanese medaka, as were extracts of eels from other locations in E. Canada, in contrast to extracts of European eels from a contaminated site in Belgium.  The decrease in toxicity from 1988 to 2008 corresponds to decreasing concentrations of DLCs and total dioxin equivalents in eel tissues, and to early signs of a recovery of recruitment to L. Ontario.  While impacts of DLCs on eels might be a concern of the past, measurements of brominated and fluorinated compounds argue for on-going monitoring of trends in contamination and assessment of toxic effects.