Radio-tracking of male adult Atlantic salmon, Salmo salar L., during the last phase of spawning migration in a spawning stream (Brittany, France)

Abstract

The final phase of spawning migration of eight adult male Atlantic salmon, Sulnio solar L., was analysed by radio-tracking in relation to sea age and size in a spawning tributary of the Kiver Sélune. Four grilse and four multi sea-winter fish, one of which as a previous spawner, were radio-tagged and released. Their fork length ranged from 602 to 882 mm. The daily movement in the first two days alier release and the furthest upstream distance recorded from the trap during the study period were independent of fish length. Maximum amplitude of movement observed over the entire study period was inversely correlated with length. Daily movement decreased in all males during the spawning period and was negatively correlated with the size of fish. Surviving males remained in the vicinity of the spawning grounds after spawning. It was concluded that the length of male seemed to influence its behaviour in the last phase of the spawning migration, enabling a much more successful participation of the larger males in spawning.