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THE QUEBEC REGION BULLETIN
AUGUST - SEPTEMBER 2010/VOLUME 13/NUMBER 4
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DECLINE IN THE EEL POPULATION
IS THE MATERNAL TRANSMISSION OF CONTAMINANTS THE CAUSE?
American eel American eel

NWRI  Chad Boiko

American eels reproduce in the Sargasso Sea, near Bermuda. The young eels then begin their transatlantic migration to reach fresh water where they mature for several decades before returning to the Sargasso Sea, where they die after spawning. In the mid 1980s, for no apparent reason, the number of American eels returning to Lake Ontario experienced a serious decline. Because of this decline, eel fishing was prohibited in Lake Ontario and the St. Lawrence River, and the eel was designated a species of Special Concern by the Committee on the Status of Endangered Wildlife in Canada.

Because of their longevity, unique spawning behaviour and diet, eels are vulnerable to the accumulation of persistent pollutants. For example, very weak concentrations of dioxins may cause cardiovascular problems and even death in fish larvae. These factors contributed to the failure of Lake Ontario lake trout to reproduce in the 1970s. Could they also be responsible for the decline of the eel population?

Do female eels transfer sufficient amounts of contaminants to their spawn to cause their premature death, before returning to the St. Lawrence? The hypothesis is being studied by a team of researchers from Queen’s University, Fisheries and Oceans Canada, Environment Canada, the University of Waterloo and the Université du Québec à Rimouski. American eels cannot be reproduced in captivity, so scientists from the Maurice Lamontagne Institute will use the embryos of a model fish species, namely, the mummichog. The contaminants will be extracted from the tissue of eels captured in various lakes and rivers in 2008, and in Lake Ontario from 1980 to 2008. The tissue will then be injected into mummichog eggs to simulate maternal transmission, allowing researchers to monitor the effects of these contaminants on the larvae’s behaviour, growth and overall survival

Injecting a contaminant into a mummichog egg
Injecting a contaminant into a mummichog egg

DFO/UQAR  C. Rigaud

This project will serve to evaluate the role of contaminants in the decline of the eel population and to determine whether certain lakes or rivers offer more favourable conditions for its re-introduction. The American eel is a precious legacy as well as an important ecological and economic resource. The quality of its habitat must be maintained to give it the best possible chances to reproduce and replenish the St. Lawrence eel population.


Catherine Couillard
Sciences