Whitefish (Coregonus lavaretus) respiration rate governs intra-otolith variation of delta C-13 values in Lake Annecy

We generated 10 high-resolution profiles of stable carbon and oxygen isotope values (delta C-13(oto) and delta O-18(oto)) of sagittal otoliths of whitefish (Coregonus lavaretus) from Lake Annecy (France) to determine the factors that control intra-individual delta C-13(oto) variation. Dominant patterns of intra-otolith variation compared well with seasonal and age-specific respiration modeling. Conversely, intra-otolith variation of delta C-13 values did not compare well with measured dietary and environmental variation. We infer that the proportion of metabolically sourced carbon (M) is the dominant control on intra-otolith variation. Current models of otolith carbon incorporation provide different estimates of M. Once appropriate fractionation factors among otolith, endolymph, blood, and carbon sources are elucidated, delta C-13(oto) values will reveal energetic, environmental, and dietary information of teleost fish for past and present populations. Used in conjunction with delta O-18(oto) values, delta C-13(oto) values will be powerful proxies of fish environment, behavior, and evolution.