Marine fish larvae consistently use external cues for orientation

Abstract The larval stage is the main dispersive mechanism of most marine teleost fish species. The degree to which larval behavior controls dispersal outcome has been a subject of debate in the past decades. Multiple studies demonstrated orientation mechanisms in several species separately, however a cross-species analysis examining fundamental orientation traits has not been carried out. Here, we apply a cross-species meta-analysis, focusing on the fundamental question of whether larval fish use external cues for directional movement. We compare the observed directional patterns to those expected under a strict use of internal cues. We find that the bulk of fish larvae use external cues for directional swimming, highlighting the contribution of larval orientation behavior to larval dispersal outcome. This finding is an essential step towards a proper implementation of larval behavior in biophysical dispersal models, improving our understanding of population connectivity, and facilitating sustainable management and conservation of marine resources.