Tracking Atlantic salmon smolts, Salmo salar L., through Loch Voil, Scotland

Twenty‐two salmon smolts, Salmo salar L., carrying miniature sonic tags were tracked individually for periods of up to 175 h in Loch Voil, Scotland, during May 1979 and 1980. Activity was predominantly nocturnal, 80% occurring between 21.00 and 06.00 hours, and was apparently undirected. Average velocities during this active interval were 0.6 body lengths per second (bl s−1), with 98 and 93% of the time spent moving at less than 2 and less than 1 bl s−1, respectively. The rates of downstream displacement were 0.04 bl s−1 in 1979 and 0.01 bl s−1 in 1980. The direction of displacement of smolts and of movement of water at a depth of 1 m was positively correlated (P