Upstream migratory movements of American eel (Anguilla rostrata) between the Beauhornois and Moses-Saunders power dams on the St. Lawrence River
Biology, Management, and Protection of Catadromous eels
The Beauharnois Generating Station, west of Montreal, is the first barrier encountered by the American eel during their upstream migration in the St. Lawrence River. The next power dam, Moses-Saunders, near Cornwall (Ontario)/Massena (New York), is located 80 km upstream. To study eel movements, 3,980 eels were marked with PIT tags in 1998 and released upstream (1,546) and downstream (2,434) of the Beauharnois Dam. In 1998 and 1999, 353 and 146 tagged eels, respectively, were recaptured at Beauharnois. In 1998, the movement of eels released downstream from the generating station was rather limited, since a great proportion (329/353 or 93%) of eels recaptured in the tailrace had been released at this site. However, results from 1999 indicate extensive interannual movements of a limited number of eels. At Moses-Saunders, in 1998 and 1999, 23 and 71 tagged eels, respectively, from Beauharnois were detected; most of these were released in the Beauharnois Canal. The time between release and recapture in 1998 indicates that the average migration speed during summer was approximately 1 km per day, although some eels can travel at a speed of 2.3 km per day. It is believed that most migrating juvenile eels would not have enough time to cross both dams in less than three seasons. A comparison of approximately 20 years of count data from the eel ladder at the Moses-Saunders Power Dam and lock usage in the St. Lawrence Seaway suggests that decreasing lockages are associated with the decreased number of eels at the ladder. Lastly, a change in eel commercial harvest between the two dams might have had an impact on yellow eel movements between the two sites.