Experimental demonstration of differences in sheltering behaviour between Icelandic populations of Atlantic salmon ( Salmo salar ) and Arctic char ( Salvelinus alpinus )

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Valdimarsson, Sveinn K, Metcalfe, Neil B, Skúlason, Skúli
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2000
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Arctic; Atlantic salmon; Salmo salar; Salvelinus alpinus
• Online Access: http://dx.doi.org/10.1139/f99-253; http://www.nrcresearchpress.com/doi/pdf/10.1139/f99-253

Most salmonids, as well as many other freshwater fish species in the Northern Hemisphere, have been reported to show some form of daytime sheltering behaviour over the winter. Previous work has shown that temperatures around 6-8°C trigger the onset of this sheltering behaviour. However, fish from colder environments would be expected to respond differently to temperature than fish from warmer environments. The incidence of sheltering at different temperatures between two Icelandic populations of both juvenile Atlantic salmon (Salmo salar) and juvenile Arctic char (Salvelinus alpinus) was examined by quantifying the use of refuges in identical controlled laboratory conditions. The results showed clear differences in the sheltering response between the different populations. Salmon from a warm, productive stream and riverine char emerged more by day from their shelter at low temperatures (5-8°C) than did either salmon from a cold, unproductive stream or char from a landlocked lake population. These population differences indicate local adaptations that must be kept in mind when managing fish populations; moreover, the differences do not appear to be predictable on the basis of ambient thermal regimes.