Publication Abstract

The migratory behaviour of juvenileAtlantic salmon

J.R. Thorpe and A. Moore

Migration is a fundamentalbiological response to adversity. Salmon (Salmo salar) move progressively from one habitatto another as a habitat ceases to satisfy their changing needs. Hatching from the egg intothe gravel redd, emerging from the redd onto the stream bed, moving away to establish afeeding territory, moving downstream to deeper water over winter, and finally emigratingfrom freshwater to sea - all these are abandonments of habitats once they can no longersatisfy the salmonsi needs. The downstream migration of smolting fish is interpretedchiefly as the eviction of an organism which is losing freshwater adaptation, involvingphysiological, behavioral and morphological components. Final passage through the estuaryis complicated by rhythmical tidal current reversal and salinity increase, and temperatureconditions modify the diel pattern of activity. Because the evolutionarily refined timingof arrival in the sea is critical for smolting salmon at any one river mouth, theconstruction of estuarine barrages poses serious problems for the maintenance of viablesalmon populations in those rivers.

Reference:

J.R. Thorpe and A. Moore, 1997. The migratory behaviour of juvenile Atlantic salmon. In:Memoirs of the Faculty of Fisheries, Hokkaido University, 44(1) Special Edition 1: 39-45.