Stable oxygen and carbon isotope values of otoliths (δ18Ooto and δ13Coto) enable a unique opportunity to gain insights in fish ecology and physiology. δ18Ooto values are near physico-chemical equilibrium with the environment and provide a direct record of temperature and δ18O values of the ambient water (δ18Ow). Although, otolith carbon is derived from dissolved inorganic carbon (DIC) and diet, the inability to constrain the contributions of each source have restricted the application of this tracer. Previous studies have separately concluded diet, DIC, metabolic rate, and activity to drive variation in delta13C values of otoliths. We investigated 1) vertical summer depth positioning and 2) sources of ontogenetic variations in δ 13Coto values for whitefish (Coregonus lavaretus) in Lake Annecy (France). Whitefish is a commercially valuable zooplanktivorous species common in many European lakes such as Lake Annecy. We used micromilling techniques to recover high-resolution carbonate and reconstructed 10 individual intra-otolith δ18Ooto and δ13Coto profiles at bi-weekly to monthly increments over the first three seasons of otolith growth. Contemporaneous water temperature, and δ18Ow, zooplankton δ13C (δ 13Czooplankton), and dissolved inorganic carbon delta13C (δ13CDIC) values were also measured. To determine vertical summer depth positioning, we first reconstructed fish individual thermal history using δ18Ooto thermometry via a freshwater fish otolith-specific temperature fractionation equation. Comparison of reconstructed and environmental temperatures indicate that adults generally inhabited areas close to the thermocline during summer, while juveniles often occupied areas offshore. We then investigated sources of intra-otolith variations in δ13Coto values. When we compared ontogenetic delta13Coto profiles with variations of δ13Czooplankton or delta13CDIC values in a common temporal frame, we failed to demonstrate any strong relationships. However, when we used a generalized Corregonus spp. bioenergetic model to estimate specific respiration rate (SRR), we found a strong and significant linear relationship (r2=0.68, F1,14=30.2) between SRR and delta13Coto value for age 1+ and 2+. We conclude that ontogenetic profiles of whitefish delta13Coto in Lake Annecy are governed by metabolic rate, which is in turn driven primarily by temperature. Finally, we estimated the contribution of metabolic carbon over the fish’s life. This study demonstrates that when environmental parameters are known the two tracers can be used for investigating behaviour of freshwater fishes, which is often difficult to determine by classical methods.