Abstract
Most demersal marine organisms have a bipartite life history and larvae are pelagic before recruiting in the adult population. This pelagic episode is often the sole opportunity for dispersal in the life of these organisms. Therefore, it structures the connections between populations, which, in turn, determine demographic dynamics and genetic composition of benthic metapopulations. Nevertheless, these “larvae” are not just drafts of the adults, dispersed by oceanic currents before their metamorphosis. They are very specialised organisms, often tightly adapted to their environment. In this doctoral research, we strove to evaluate the impact of larval behaviour during the pelagic interval. We focused on fish larvae (particularly coral-reef fishes) which sensory and swimming capabilities are particularly high. Experimental approaches were developed to quantify larval orientation and swimming in situ. During an oceanographic campaign, synchronous observations of physical properties of sea water and of the distribution of larvae enabled to characterise their distribution in three dimensions within the pelagic environment and to understand physical-biological interactions determining recruitment. Finally, a novel modelling framework, drawing from cost minimisation and benefit maximisation techniques traditionally used in economics or optimal foraging models, allowed to integrate larval behaviour in Lagrangian models of larval dispersal.