Giving Fish More Energy without Giving Them More Food: Can Streambed Topography Influence a Fish's Net Rate of Energy Intake?

A number of researchers have attempted to predict profitable foraging positions for drift-feeding fishes by combining process-based foraging models with spatially explicit hydraulic models.  The foraging model component allows for estimates of energy intake while energy expenditure is estimated using the depth and velocity information provided by the hydraulic model.  Subtracting energy expenditure from energy intake for a number of locations within the area of interest yields spatially explicit net rates of energy intake (NREIs). 

            We use a model developed by Hayes et al. (2007) to predict NREI in a headwater stream in Southeastern Washington.  Next, we manipulate the three-dimensional (x,y,z) points of the streambed topography survey to be consistent with future planned restoration actions including addition of large woody debris and a corresponding increase in the number of pools.  After the manipulation, we again model NREI and note differences between the two scenarios.  Results suggest channel structure can influence potential NREI for fish even when food and temperature are held constant.  We suggest example analyses based on differencing predicted NREI surfaces as a means to assess how physical changes to channel structure directly pertain to fish.