Rearing conditions influence refuge use among over-wintering Atlantic salmon juveniles

At low population densities, both hatchery- and wild-reared Atlantic salmon Salmo salar, which were progeny of a common genetic stock, occupied sub-gravel shelters alone. However, at high population densities, hatchery-reared fish occurred within shelters in significantly higher numbers than wild-reared fish. There was a significant effect of time after introduction to the experimental arenas on the proportion of hatchery-reared fish sheltering. These results show that rearing environment influences the behaviour of Atlantic salmon parr during winter and may also affect the carrying capacity of their environment. Copyright 2002 The Fisheries Society of the British Isles