Publication Abstract

The migratory behaviour of wildAtlantic salmon smolts in the River Test and Southampton Water, southern England

A. Moore, S. Ives, T.A. Mead and L. Talks

Thirty wild Atlantic salmon Salmo salar (L.) smolts, tagged withminiature acoustic transmitters, were tracked in the River Test and Southampton Water, todescribe the freshwater and estuarine patterns of migration. Migration in freshwater waspredominantly nocturnal (mean time 23:42) and smolts tagged earlier in the study spentsignificantly longer in the river before migrating into the estuary than fish tagged laterin the study. Movement in the upper estuary section of the River Test was indicative of anocturnal ebb tide transport pattern of migration. The majority of smolts migratedseawards at night and during an ebb tide (mean time after High Water +1 h 54 min), closeto the surface and within the fastest moving section of the water column. Smolts continuedto emigrate seawards through the lower estuary and Southampton Water during the ebb tide(mean distance 4908 ± 609 m; mean ground speeds of 35 cm s^-1), although thediurnal pattern of movement was not evident. There was also a significant seawardmigration of smolts during the latter part of the flood tide (mean distance 3469 ± 522 m;mean ground speeds of 14 cm s^-1), suggesting active directed swimming. Smoltsemigrated rapidly through Southampton Water, and there was no apparent period ofacclimation required when moving from fresh to saltwater. The results are discussed inrelation to the environmental cues controlling smolt migration.

Reference:

A. Moore, S. Ives, T.A. Mead and L. Talks, 1998. The migratory behaviour of wild Atlanticsalmon smolts in the River Test and Southampton Water, southern England. Hydrobiologia,371/372: 295-304.