Physical and Bioenergetic Approaches for Modeling Instream Habitat Quality of Drift-feeding Fish

Physical fish habitat models have been criticized for poor biological realism and a failure to relate with population metrics. I modeled channel hydraulics using a two-dimensional hydrodynamic model and varied fish size, invertebrate drift density, and temperature to compare longitudinal and seasonal trends in physical and bioenergetic fish habitat quality in two idealized stream systems differing in hydraulic geometry (gradient, depth, and velocity) and a natural fourth-order stream, respectively. In the idealized streams, physical and bioenergetic habitat quality increased asymptotically with stream size for all fish sizes, while peaking in adult trout due to the positive and negative effects of increased drift densities and temperatures, respectively. Although similarities between fish sizes were observed, significant correlations between seasonal physical and bioenergetic habitat quality for all fish sizes in the natural stream were not detected. Revisions to the bioenergetic model framework and the inclusion of temperature-dependent consumption may improve model predictions...