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Ideal Free theory has furthered our understanding of the processes determining the distribution of mobile foragers in a spatially heterogeneous (patchy) habitat. The Input Matching rule derived from Ideal Free theory has been used to predict forager distributions, but does not account for unshared environmentally induced costs that individuals may incur. Drift—feeding stream fish typically contend with such costs in the form of (1) an energetic costs of maintaining position while foraging in moving water, and (2) a decrease in the proportion of drift food items they can capture as current speed increases. These costs often differ between patches, and the cost of position maintenance is unaffected by changes in the number of fish foraging in a patch. Here, we developed an Ideal Free Distribution (IFD) model (IFD With Costs) to describe forager distributions in a habitat composed of patches in which foragers compete for food and incur an energetic cost when foraging that is unaffected by the number of competitors in the patch. We tested the ability of two versions of the IFD With Costs as well as two alternative IFD models to predict the distribution of minnows (Rinichtys atratulus) foraging in a laboratory flow—tank with two side—by—side patches. In all trials the patches differed in their supply of drift food, and in some trials the patches had different water velocities. When the patches' water velocities differed, the fish distributions (1) changed as the total supply of food in the two patches increased while the ratio of food supply in the patches remained constant, (2) did not match relative food availabilities in the patches, and (3) favored the slow water velocity patch. One version of the IFD With Costs predicted each of these results while none of the alternative models could account for these findings. The results support the hypothesis that fish quantitatively integrate energetic gains and costs in a manner similar to that described by the IFD With Costs when making patch selections.

River ecosystems are driven by linked physical, chemical, and biological subsystems, which operate over different temporal and spatial domains. This complexity increases uncertainty in ecological forecasts, and impedes preparation for the ecological consequences of climate change. We describe a recently developed ''multi-modeling'' system for ecological forecasting in a 7600 km 2 watershed in the North American Great Lakes Basin. Using a series of linked land cover, climate, hydrologic, hydraulic, thermal, loading, and biological response models, we examined how changes in both land cover and climate may interact to shape the habitat suitability of river segments for common sport fishes and alter patterns of biological integrity. In scenariobased modeling, both climate and land use change altered multiple ecosystem properties. Because water temperature has a controlling influence on species distributions, sport fishes were overall more sensitive to climate change than to land cover change. However, community-based biological integrity metrics were more sensitive to land use change than climate change; as were nutrient export rates. We discuss the implications of this result for regional preparations for climate change adaptation, and the extent to which the result may be constrained by our modeling methodology.

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