Comparison of bioenergetics drift-foraging model predictions to observed habitat use and growth of redband trout (Oncorhynchus mykiss) and cutthroat trout (O. clarki).

R.C. Addley.Utah State University, Utah Water Research Laboratory, Logan, Utah, 84321, USA

A bioenergetics drift-foraging model is used to quantify daily net energy intake (DNEI) over a range of fish sizes for specific drift densities, drift sizes, depths, velocities, turbidities and diel fluctuating temperatures. The results are compared to depth and velocity use data for cutthroat trout (Oncorhynchus clarki) in St. Charles Creek, Idaho, USA and compared to depth, velocity and growth data for redband trout (O. mykiss) in the Klamath River, Oregon, USA. The results accurately match the use data and show that drift-feeding fish are likely using an multi-objective optimization approach to foraging that maximizes DNEI and efficiency and minimizes foraging time. Drift density strongly affects modeled habitat suitability and growth. I show how bioenergetics foraging models and drift density can be used in environmental impact analysis and instream flow modeling.