Tracing energy flow pathways to fish using stable hydrogen and oxygen isotopes and fatty acids

Recent studies have demonstrated that use of stable carbon isotopes and fatty acid biomarkers in combination can be a powerful approach to elucidate trophic relationships in aquatic ecosystems.  Stable δ²H and δ¹⁸O isotope ratios of lipids and essential fatty acids in fishes may reflect environmental δ²H and δ¹⁸O signatures, enabling identification of the importance of floodplain lake and riverine energy sources for large river fishes.  However, relationships between water and fish lipid or fatty acid δ²H and δ¹⁸O have not been examined.  The objectives of this study were to determine whether fatty acid profiles of bluegill differed among rivers and lakes that differed in water δ²H and δ¹⁸O and to characterize relationships between water and fish lipid δ²H and δ¹⁸O.  Fatty acid profiles of bluegill were different among sites (lake and riverine sites); bluegills could be identified to their environment of capture with 91% accuracy based on their fatty acid profiles.  δ²H and δ¹⁸O of bluegill lipids were correlated with water δ²H and δ¹⁸O. Results suggest that fatty acid profiles in conjunction with lipid or fatty acid δ²H and δ¹⁸O may provide new insights into energy sources and environments (e.g., floodplain lakes vs. rivers) that ultimately support fish production.