Diel patterns of activity and substrate preference in young Arctic char from the Koroc River, northern Quebec

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Abstract
Young Arctic char (Salvelinus alpinus) were observed in a stream tank located on the bank of the Koroc river, northern Quebec. Early in the summer, char were most active from dusk to dawn, and at midday, mainly over gravel or sand. Some nocturnal feeding activity was evident. As the summer progressed, this diel periodicity in activity became less pronounced; char exhibited increasing diurnal activity, most of it over rubble substrata. Char preferred rubble for resting throughout the summer. Invertebrate drift decreased from July through August so that, although fish were active more of the time, the rate of feeding during periods of activity declined.