Publication Abstract

The migratory behaviour of wild Atlantic salmon (Salmo salar L) smolts in the estuary of the River Conwy, northWales

A. Moore, E.C.E. Potter, N.J. Milner and S. Bamber

Thirty-twowild Atlantic salmon (Salmo salar) smolts, tagged with miniature acoustictransmitters, were tracked in the River Conwy, North Wales, to describe the freshwater andestuarine patterns of migration. Migration in fresh water was predominantly nocturnal,although there was a seasonal change in this pattern with later run fish moving duringboth the day and night. Smolts tagged earlier in the study spent significantly longer inthe river (mean 456 ± 43 h) before migrating into coastal waters than fish tagged laterin the study (mean 201 ± 30 h). The movement of smolts through the estuary was indicativeof a nocturnal selective ebb tide transport pattern of migration. All of the smoltsmigrated seawards on an ebb tide close to the surface and within the fastest movingsection of the water column. The nocturnal pattern of migration would appear to be theresult of an endogenous rhythm of swimming activity that results in the smolts moving upinto the water column after dusk and migrating seawards. Smolt migration in the lowerportion of the estuary was indicative of active directed swimming and there was noapparent period of acclimation required when moving from fresh to salt water.

Reference:

A. Moore, E.C.E. Potter, N.J. Milner and S. Bamber, 1995. The migratory behaviour of wild Atlantic salmon (Salmo salar L) smolts in the estuary of the River Conwy, north Wales.Canadian Journal of Fisheries and Aquatic Sciences, 52(9): 1923-1935.