Influence of diet on stable carbon isotope composition in otoliths of juvenile red drum Sciaenops ocellatus

Stable carbon isotope values of otoliths can provide long-term records of the environmental conditions experienced by fish. However, because otoliths contain carbon from metabolic sources, it is necessary to determine the proportion of metabolically derived carbon to properly interpret otolith delta super(13)values. To evaluate the relative influence of dietary carbon and the dissolved inorganic carbon (DIC) of ambient seawater on the delta super(13)C isotopic composition of fish otoliths, juvenile red drum Sciaenops ocellatus were raised for 6 and 9 mo in tanks with flow-through ambient seawater and fed diets differing by 2.1ppt (p < 0.001) in carbon isotope composition ( delta super(13)C). At the end of the experiment, muscle tissue from the 2 treatments reflected the isotopic composition of the diets and differed by 2.1ppt (p