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 Atlanticsalmon, Salim solar L., was analysed by radio-tracking in relation tosea age and size in a spawning tributary of the River Selune. Fourgrilse and four multi sea-winter fish, one of which as a previousspawner, were radio-tagged and released. Their fork length ranged from602 to 882 mm. The daily movement in the first two days after releaseand the furthest upstream distance recorded from the trap during thestudy period were independent of fish length. Maximum amplitude ofmovement observed over the entire study period was inversely correlatedwith length. Daily movement decreased in all males during the spawningperiod and was negatively correlated with the size of fish. Survivingmales remained in the vicinity of the spawning grounds after spawning.It was concluded that the length of male seemed to influence itsbehaviour in the last phase of the spawning migration, enabling a muchmore successful participation of the larger males in spawning.