Abstract
AbstractFood-chain length (FCL) is a key factor underlying patterns of energy flow and trophic structure in food webs. Natural gradients in resource availability, ecosystem size, and disturbance are thought to govern FCL in rivers. However, anthropogenic influences on FCL, including landscape modification (e.g., land-cover change) and river regulation (e.g., dams), remain unresolved. From 2010 to 2013 we characterized fish food webs at 12 river reaches along an ∼185-km section of the 6th-order Scioto River system (Ohio, USA) to assess the effects of natural and anthropogenic factors and the potential influence of shifts in foodweb structure (e.g., diversity, top-predator body size, intermediate predator richness) on fish FCL. Stable isotope-derived estimates of FCL ranged from 3.66 to 4.35, which are comparable to global values of FCL in rivers. A model-selection approach returned a set of linear regression models that explained 38 to 74% of the variation in FCL. Local ecosystem size (i.e., channel width)...
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