Using Large-Scale Application of a Foraging Model in the Interior Columbia River Basin to Help Understand Patterns of Habitat Use in Salmonids

Foraging models integrate local flow patterns, food availability estimates, and temperature effects to predict energetic profitability of habitat. In doing so, they have potential to provide valuable insights into fish habitat use. Unfortunately, data availability and computational costs are often hurdles to successful foraging model application, especially at large spatial scales. We adapted an existing foraging model to evaluate the net rate of energy intake (NREI) for Chinook and steelhead at sites monitored by the Columbia Habitat Monitoring Program (CHaMP) in the interior Columbia River Basin. This process included automating hydraulic model solutions at ongoing monitoring sites and developing a raster-based methodology for describing flow patterns near modeled focal points. We used foraging model outputs and territory size requirements from the literature to estimate carrying capacity for juvenile fishes at a site. We simulated NREI and carrying capacity at hundreds of sites and compared predictions to observed fish abundance and growth. In addition to providing insight into habitat quality and use, this research also provided useful information when considering alternative habitat scenarios. We believe these models are a useful tool for recovery planning for these endangered species.