Atlantic salmon post-smolt migration routes in the Gulf of St. Lawrence

The migration of Atlantic salmon (Salmo salar) post-smolts from the Rivie` re Saint-Jean on the north shore of the Gulf of St. Lawrence (Canada) was studied during 2009 and 2010. Salmon from rivers in this region spend >= 2 years at sea before returning to spawn, and are believed to migrate to ocean feeding areas off Greenland. To determine residency time in the nearshore environment, and to define the migration routes of post-smolts, tagged post-smolts were tracked passively in Jacques Cartier Strait and at the two exits of the Gulf of St. Lawrence to the Atlantic Ocean (Cabot Strait and the Strait of Belle Isle). Post-smolts moved rapidly south in the nearshore area; two of them were detected 45 km south of the estuary exit, suggesting that they were moving towards the centre of the Gulf of St. Lawrence. One tagged post-smolt was detected exiting the Gulf of St. Lawrence via the Strait of Belle Isle after 44 d and exhibited a minimum swimming speed of 14.4 km d(-1). There was no apparent linkage between the detection patterns of post-smolts and surface water temperatures or surface water currents close to shore. Post-smolts, however, appeared to orient to higher salinity.