Migratory strategies of Atlantic salmon ( Salmo salar) postsmolts and implications for marine survival of endangered populations

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Author: Lacroix, Gilles L.
• Other Authors: Jonsson, Bror
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2013
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/cjfas-2012-0270; http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjfas-2012-0270; http://www.nrcresearchpress.com/doi/pdf/10.1139/cjfas-2012-0270

The migration of wild and hatchery Atlantic salmon (Salmo salar) postsmolts of different origins was monitored using ultrasonic tags and arrays of acoustic receivers across the Bay of Fundy (BoF), Canada. Postsmolts from outer BoF populations migrated rapidly into the Gulf of Maine (GoM) and did not return, and most were classified as distant migrants (77%–100%). In contrast, postsmolts from inner BoF populations were usually classified as coastal migrants that returned to the BoF for the summer (30%–90%). They used well-defined migration corridors, close to shore, associated with prevailing surface currents. An Akaike information criterion (AIC) evaluation of migration models identified region and watershed, date of river exit, and migration speed as important predictive variables for coastal residency. A late or slow migration increased residency, as did delaying hatchery releases. The BoF provided returning postsmolts with a summer thermal refuge (8–14 °C) encircled by warm water (>20 °C), but extended residency in this coastal habitat increased exposure to sources of mortality absent further at sea. This reduced marine survival of inner BoF salmon to almost nothing. It is likely that the different migratory strategies of inner and outer BoF salmon populations influenced their relative marine survival and endangered status.