Differences in movements of northern pike inhabiting rivers with contrasting flow regimes

Little is known about the effect of short-term flow changes on the movement of northern pike (Esox lucius L.). We conducted a comparative study in two rivers with different flow regimes (i.e. one regulated and one unregulated) to evaluate the extent to which adult northern pike movement is influenced by short-term river flow conditions. Data on northern pike hourly movement were collected in northeastern Ontario on 40 individuals in the Mississagi River, a river subjected to extreme daily flow variations associated with hydro-electric operations (i.e. hydropeaking), and the Aubinadong River, an unregulated river. Using manual tracking by radio-telemetry, we found that northern pike moved at a higher rate in the river subjected to short-term changes in river flow than in the unregulated river. Results also show that the relationship between movement of northern pike and flow can vary among rivers. In the Mississagi River, flow had a significant positive effect on northern pike activity, while the effect of flow in the Aubinadong River depended on water temperature. Moreover, fish in the Mississagi River utilized a restricted river section and travelled more laterally in comparison to fish inhabiting the Aubinadong River, where longer upstream-downstream movements were more common. The present study contributes to our understanding of the effects of short-term changes in flow on fish movement. This constitutes the first step towards assessing the effect of flow on fish habitat use, and eventually developing flow management strategies to mitigate impacts on fish. Copyright (C) 2016 John Wiley & Sons, Ltd.