Food and Space Revisited: Drift-Foraging Ecology and Habitat Selection

Both food and space have been identified as regulators of stream salmonid populations. In the early 1980’s research on these two factors took distinctly separate paths, developing into physical habitat modeling (e.g. Bovee 1982, FWS/OBS-82/26) and the origins of drift foraging-based models (Fausch 1984, CJZ). More recently these paths have rejoined in the development of bioenergetics-based habitat selection and growth models that include both detailed physical habitat assessment and drift foraging success. The energetic component of these models are based largely on Hughes and Dill’s (1990, CJFAS) landmark drift-foraging model, and the latest versions being implemented as both research and environmental assessment tools (Hayes et al. 2007, Ecol. Model.; Railsback et al. 2009, PSW-GTR-218). We now foresee rapid expansion in the application of energetics-based habitat models management tools for stream salmonids. It is unclear, however, just how much ecologists really understand drift foraging. For example, in a recent test of the most advanced drift foraging model, Hughes et al. (2003, CJFAS) found that it over-estimated gross energy gain by a factor of two. This has rather serious implications for accurate predictions for fish growth and habitat selection. The objective of this session is to call together research leaders in this field, to assess our present state of knowledge on drift-foraging theory and modeling, and to identify future research needs. What will the next generation of energetics-based habitat selection models look like, and how can we as ecologists improve their predictive abilities whilst being mindful of cost benefit tension with increasing model complexity? The focus will be on improving both ecological theory, and the interface with stream fish management.