Food Webs in Riverscapes: Toward a Spatial Ecology of Food Webs That Sustain Riverine Fishes

A spatial ecology of food webs is needed to improve understanding and management of fishes in riverine landscapes.  However, few foodweb investigations have made spatial heterogeneity a focus, and attempts to scale to river networks have been rare.  Here we describe the results of a combination of empirical investigations focused on the spatial heterogeneity of food webs and productivity in the Methow River, WA, USA, along with attempts to link these efforts to models to predict spatial patterns of productivity and responses to adaptive management scenarios in this river network.  We quantified annualized, production-based food webs for the main channel and an array of floodplain habitat types, describing a mosaic of webs that fuel the fish assemblage, including endangered anadromous salmonids.  In addition, a thought experiment involving assembly of meta-food webs of sequentially more heterogenous riverscapes demonstrated how increasing spatial complexity decreased the strengths of interactions between fish and their prey, which may be an important stabilizing mechanism for fish populations and the maintenance of diverse communities.  Finally, food web data are being linked to reach-scale measurements of ecosystem metabolism, and coupled with mechanistic modeling and spatial extrapolation to extend food web perspectives from site-based investigations to the river network.