The migration of stocked, trapped and transported, and wild female American silver eels through the Gulf of St. Lawrence

The stocking of juvenile eels and trap and transport programs of large yellow eels were initiated in Ontario to mitigate mortalities observed at hydroelectric dams and to increase escapement from the upper St. Lawrence River and Lake Ontario (Canada). A total of 380 migrating female silver eels (« Stocked », « Trapped and Transported », and « Wild ») were tagged with acoustic transmitters between 2011 and 2014. Their migration and escapement at the exit of the Gulf of St. Lawrence, the Cabot Strait, were recorded using acoustic receivers. Escapement rates varied between 8.9 and 20.0% annually (mean= 11.4%). A high proportion of stocked eels were detected (N=27 of 43 detected at Cabot) demonstrating their ability to escape the Gulf. No differences in migration speed, and crossing locations at Cabot Strait, were found among the 3 categories. Eels crossing Cabot Strait did not display diel and tidal patterns but their estimated swimming depth indicated diel vertical migrations. The low escapement rates obser...