Eels at the Edge: Science, Status, and Conservation Concerns

Decline of the American Eel in the St. Lawrence River: Effects of Local Hydroclimatic Conditions on CPUE Indices

Yves de Lafontaine, Michel Lagacé, Fernand Gingras, Denis Labonté, François Marchand, and Edith Lacroix


Abstract.—Changes in abundance, seasonal occurrence, and mean size of American eels Anguilla rostrata in the lower St. Lawrence River during the past 50 years were examined. Catch per unit effort indices were calculated from daily catch records of eels captured in an experimental trap fishery and from the personal logbooks of a knowledgeable fisher. These two indices indicated a significant declining trend in eel catch rate by more than 50% since the early 1970s. Interannual fluctuations in catch rate were not related to variability in water level or water temperature. The timing of eel occurrence varied significantly between years and was inversely correlated to water level in August and September. It is hypothesized that eel movement is strongly determined by climatic/hydrological conditions in the previous summer. The average weight of eels has increased by 30% over the past eight years. The decline in catch rate and the increase in mean size of migratory silver eels in recent years are interpreted as the most significant symptoms of low recruitment levels and the precursory signal that the eel fishery in the lower St. Lawrence River may not be sustainable in the near future.