Migration of hatchery reared juvenile Atlantic salmon, Salmo salar L., smolts down a release ladder. 3. Reactions on exiting the ladder

Twenty‐eight hatchery‐reared Atlantic salmon ( Salmo salar L.) smolts were tracked as they left a release ladder and moved through the estuary of the Lussa River and out to sea. Smolt passage through the estuary was fastest at high water and slowest at low water; the reverse of the situation observed for passive objects floating in the surface water layer. At low tide the water channel was effectively a freshwater stream and the smolts behaved in it accordingly, attempting to maintain station. At high water smolts moved downstream with the current close to the water surface. The degree of variation in individual speed through the estuary was the main difference observed between immature S2, stripped mature male S2, unstripped mature male S2 and S1 smolts. Smolts moved directly out of the estuary with no apparent check in their progress. Sea contact times in the vicinity of the river mouth, for both passive objects and smolts, were longest around high water and shortest around low tide. In the sea no differences were observed in the behaviour of the four different smolt types. While passive objects showed no tendency to move off in a particular direction, smolts showed a significant inclination to head off on a southerly bearing.