Spatiotemporal Variation of Juvenile Common Carp Foraging Patterns as Inferred from Stable Isotope Analysis

Abstract

AbstractOntogenetic diet shifts from zooplankton to macroinvertebrates represent an important transition for many fishes during early life stages. However, some fishes have plastic feeding habits that allow them to take advantage of abundant prey resources or display diet specialization instead of undergoing distinct diet shifts. In this study, we evaluated ontogenetic changes in energy sources (based on the carbon isotope signature, δ13C) and trophic position (based on the nitrogen isotope signature, δ15N) for age‐0 Common Carp Cyprinus carpio from eight natural lakes in eastern South Dakota. In general, Common Carp trophic position decreased and energy sources shifted from pelagic to littoral prey resources from July to August. As anticipated, substantial inter‐ and intrapopulation variation existed in Common Carp isotope signatures. Common Carp trophic position increased with increasing fish TL in three lakes but decreased with fish TL in two systems. Intrapopulation variation in trophic position was related to Common Carp relative abundance during July, indicating that individuals may have specialized on different energy resources as a result of intraspecific interactions. The δ13C values decreased with increasing fish size in two populations during July, suggesting a shift toward pelagic resources; δ13C increased with fish size in six populations during August, suggesting a shift toward littoral resources. Our results indicate a high degree of trophic variation in juvenile Common Carp populations, indicative of a foraging generalist. Year‐class strength may increase trophic specialization of individuals but without negative effects on fish growth, suggesting that diet plasticity is an important factor contributing to the success of this invasive species.