Food Webs: Key Components of Ecosystem Resilience and Productivity

The food web concept remains one of the most useful – and challenging – ideas in ecology. Our presentation provides an overview of food webs and their application to the restoration of riverine resilience and productivity. Food webs, pathways by which energy, nutrients and other materials move to species of interest, are often considered as reflections of habitat. Nevertheless, many factors shape food web organization, productivity and resilience: species diversity, native and non-native species, chemical contaminants, habitat carrying capacity, nutrient delivery and cycling, competition, predation, disease and associated system-scale processes. Complex food webs have been successfully manipulated to improve water conditions and recreational fisheries while ill-advised manipulations have resulted in serious environmental issues (mysid introductions). We illustrate the usefulness of the food web concept using examples from the Columbia River Basin that reveal insights into basic properties underpinning productivity and resilience that cannot be obtained from an exclusive focus on hydrosystem, habitat, hatcheries and harvest. We examine the Basin’s capacity to produce fish, the mechanisms leading to widespread occurrence of salmonid density dependence despite apparently low abundances, and how knowledge of capacity and density dependence can be applied to restore the degraded ecosystem to benefit salmonids and other native species.