Stable isotopes reveal spatial variation in trophic resource use by Pecos River fish assemblages

Authors: Jessica East, Allison Pease

Year: 2013 (xlv)

Abstract

Understanding and predicting the structure of local fish assemblages across riverscapes is a key challenge for lotic ecologists due to the complex relationships between processes at multiple scales. The Pecos River is impacted by a variety of anthropogenic influences that affect water availability, salinity, and riparian and instream habitat structure. We used stable isotope analysis to characterize changes in trophic positions and resources used by fish assemblages at twelve sites along the main stem of the Pecos River in New Mexico and Texas. Our analysis revealed variation in nitrogen signatures and sources of carbon among some of the most common species such as Menidia beryllina, Cyprinella lutrensis, and Lucania parva. Stable isotope ratios suggested a greater breadth of production sources and trophic resources used in less degraded study sites. Understanding how food-web structure changes in relation to environmental gradients altered by anthropogenic effects is important for habitat assessment, stream restoration, and management and conservation strategies.