Analysis of the C-O stable isotope composition of coral reef fish otoliths from Taiaro, a French Polynesian atoll normally isolated from the Pacific Ocean, has been performed to address two main questions. The first is to confirm previous results which suggest that a lagoonal coral reef fish population is able to achieve its ontogenetic cycle without any open ocean phase. If so, are O isotopic values of otoliths an indicator of temperature fluctuations in the tropical Pacific Ocean related to climate change and in particular temperature variations of water masses? delta18O and delta13C values on both lagoon and open ocean fish otoliths caught in 2006 indicated clearly that O- isotopes reached the isotopic equilibrium; in contrast, all the delta13C values exhibited a strong isotopic disequilibrium related to metabolic activity. Stable isotope compositions revealed a clear differentiation between fish from lagoons and those from the open ocean (with a delta18O enrichment of 1 pour mille in favour of the lagoon). This confirmed a lack of connectivity between habitats and that fish from lagoon lived their entire life cycle in the lagoon. Both delta18O and delta13C data indicated differences between nucleus and edge signatures with changes in fish behaviour from the larval life to adulthood (habitat, diet, etc.), and a clear adaptation of dietary behaviour of lagoon fish. The comparison of the 2006 data set with those of 1994 showed that environmental conditions were stable in the lagoon, leading to a very narrow range of variations in the delta18O values. delta18O of fish otoliths of the open ocean exhibited a wider variation (+0.25 pour mille) between 1994 and 2006, suggesting a decrease in temperature linked to a change of SST, which can be interpreted in terms of climate change associated with El Nino Southern Oscillation (ENSO). These differences could also be due to a switch of habitats during the life cycle of fish from the open ocean.