The understanding of the most influential factors on larval survival in the water column is crucial in order to predict local variations in fish abundances. This dissertation describes the composition and diversity of assemblages of fish larvae at the end of the pelagic stage in the bays and lagoon of New Caledonia, and examines the relationships between their spatial and temporal structures and various abiotic and biotic environmental factors. The peaks in abundances and diversity of larvae were observed during the warm season, between September and February. The number of sun hours per day and wind conditions at the scale of sites, water surface temperature and the concentration in chlorophyll at the scale of stations, were found to be the greatest contributors, in decreasing order of importance, to the variations in abundance of larvae from different families. Similar hierarchies were observed in contrasted sites, suggesting that these variables represent relevant predictive factors for future spatially-explicit models of assemblages structures. Moreover, in seagrass habitats, similitudes of structures were found between adult assemblages and assemblages of larvae sampled nearby, suggesting that adult communities also may play a part. Since feeding success is paramount for larval survival, the diets of different taxa were examined. The densities and relative proportions of larvae's favourite zooplanktonic prey categories were observed to be higher in bays than in lagoonal areas; yet no significant relationship between larvae and larval prey distributions could be detected in these bays. However, larval assemblages structures were positively related to prey density along an inshore-offshore gradient. This suggests that the detection of any relationship between larval assemblages structure and prey assemblages will depend on the spatial scale under consideration. Overall results reveal the importance of bays for the abundances, diversity and diet of larvae at the end of the pelagic stage in the lagoon of New Caledonia.
