Food chains, also called food webs, food networks and/or trophic networks, describe the feeding relationships between species to another within an ecosystem. Organisms are connected to the organisms they consume by arrows representing the direction of biomass transfer. Typically a food chain or food web refers to a graph where only connections are recorded, and a food network or ecosystem network refers to a network where the connections are given weights representing the quantity of nutrients or energy being transferred.

"The loss or decline of this fish species could extend throughout the stream network and food web, affecting populations algae, bacteria, insects and other fish species,"

Food webs trace the flow of energy through an ecosystem. Parasites are small and invisible, hidden inside their hosts. However, parasites strongly affect food web structure and parasite links are necessary for measuring ecosystem stability.

Scientists have discovered that parasites are surprisingly important in food webs. "Parasites have been missing from this framework and, as a result, we know relatively little about the role of parasites in ecosystems. It's like driving with a highway map, but with no knowledge of the smaller road network," said USGS scientist Kevin Lafferty.