Migration of Atlantic Salmon Postsmolts in Relation to Habitat Use in a Coastal System

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Abstract
Acoustic telemetry was used to monitor the early marine migration of Atlantic salmon Salmo salar from two rivers of Passamaquoddy Bay, a coastal system with numerous Atlantic salmon farms and weirs for Atlantic herring Clupea harengus on the border of Canada and the United States. Monitoring at fixed sites, active tracking, and systematic searches for tagged fish were combined. The migration success of hatchery-reared (N = 96) and wild (N = 38) smolts out of the estuaries was high (range, 90–97%), and the overall success of postsmolts moving out of Passamaquoddy Bay and into the several passages leading to the Bay of Fundy was reasonable (range, 71–88%). Estuary transit times were usually rapid (<36 h), and almost all smolts entered the bay during an ebb tide. Migration routes through Passamaquoddy Bay were then closely related to the counterclockwise residual surface current in this bay. Routes differed among groups monitored, and they influenced the location of exit from the bay. The majority o...