Reef fish are characterized by a complex cycle of life, including a pelagic larval phase and a benthic phase during their juvenile and adult stages. Although the ecology of fish can be easily studied on coral reefs, their ecology during the larval migration in the pelagic environment is more challenging. In the present study, we used an isotopic approach to investigate the ecology of larvae from eight fish families (Acanthuridae, Apogonidae, Gobiidae, Haemulidae, Labridae, Lutjanidae, Scaridae, and Muraenidae), six of which were identified to species, and three to genus. Isotopic niches were described using carbon and nitrogen stable isotope ratios (¹³C/¹²C and ¹⁵N/¹⁴N) to discuss the partitioning of their ecological patterns at a larval stage. The results showed that individuals of different taxa exhibited close isotopic compositions indicating that the various fish taxa occupied similar isotopic niches during their pelagic migration, with the exception of the muraenid, which exhibited lower carbon isotopic composition. Most reef fish seemed to use the same food resources and habitat types during their larval stage, demonstrating their gregarious behavior during this pelagic phase.