Are chemical contaminants contributing to the recruitment failure of American eel (Anguilla rostrata)

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The American eel (Anguilla rostrata) is on the verge of local extinction in L. Ontario, due to a precipitous decline in the arrival of juvenile eels from their spawning grounds in the Sargasso Sea. All L. Ontario eels are female, and they are the largest and most fecund females of the species. Hence, their loss will affect the status of the entire species because eels spawn as only one population. These impacts are already apparent in the closure of the L. Ontario fishery, a reduction by more than 50% of the fishery in Quebec, and declines in many eel fisheries throughout N. America. Chemicals accumulated by eels during their freshwater growth are one likely cause of premature mortality of eel embryos as they migrate from the Sargasso to fresh water. During their growth in fresh water, eels become top predators, accumulating compounds such as PCBs and polychlorinated dioxins to concentrations similar to those causing reproductive failure of lake trout in L. Ontario. Our objectives are to evaluate if eels accumulate sufficient chemical contaminants during their growth and maturation to cause embryo toxicity, and to estimate when contaminants might have affected eel recruitment. Our team of university and government scientists, including colleagues in the US and Europe, will collect fresh and archived samples of eels from reference and contaminated ecosystems. The eels will be analyzed for concentrations of chemicals known to be embryo-toxic, such as chlorinated and brominated organic compounds, selenium, and alkyl tin. The toxicity of extracted chemicals will be assessed with a battery of tests using fish embryos and fish cells in culture. The inclusion of archived samples and an extensive literature on chemical effects on other fish species will allow a retrospective assessment of the risks of chemicals to eel reproduction. Using these data, we will advise fisheries managers about the suitability of different habitats for re-stocking with juvenile eels, priorities for chemical controls, and potential hazards to human consumers. Because eels are highly valued and have a long time to maturity (7-30 years), it is essential that this research be done now, to help avoid a complete loss of eels from the Great Lakes.