The Effect of Flow on Northern Pike Habitat Selection in a Hydropeaking River and an Unregulated River

Recent efforts in developing pike habitat selection models in rivers have so far overlooked one important component of the habitat selection: flow. The present study aims at assessing the importance of river hydrodynamic to model the habitat selection by the northern pike. To achieve our objective, we designed an analytical framework that consists in three steps and applied it to two rivers having different flow regimes. Firstly, we partitioned the ecosystem (a stretch of river) into patches of different habitat type on the basis of flow conditions. Secondly, we estimated the sojourn time of pike within the patches and movements among patches using a multi-state model. Thirdly, we modelled the habitat selection by pike using the sojourn time as a response variable. Data to implement that model were collected in the field and consists in following 40 northern pikes using radio telemetry in two streams situated in Ontario: a hydropeaking river (Mississagi River) and an unregulated river (Aubinadong River). We estimated two-dimensional hydrodynamic data from maps of depths and substrates obtained by field hydro-acoustic survey. Our approach provides essential information on fish habitat use as a function of flow and is a valuable tool to implement northern pike conservation strategies.