Environmental conditions and paternal care determine hatching synchronicity of coral reef fish larvae

For all fishes, hatching is a short but crucial event, and the conditions under which it occurs considerably influence the success of the larvae. For coral reef fish, hatching is even more important because it marks the beginning of the dispersal phase. The timing of hatching dictates the conditions that the larvae will encounter, potentially influencing their survival and dispersal. Despite this importance, very few studies have looked at hatching of marine fishes in the natural environment because of important technical constrains. In this study, we directly examined the temporal pattern of hatching during the night. Using remote night vision cameras and infrared lights to avoid disturbances, we successfully documented in situ hatching events of three coral reef fish species, all benthic brooders (Abudefduf saxatilis, Stegastes partitus, and Elacatinus lori). Hatching timing, rate, and duration were computed from the observations, and highlight different hatching strategies used by the fish species. The analysis of the fish behaviors shows that the males display parental care beyond the incubation period of the eggs and increase activity during the hatching events. With this study, we can relate the hatching events to the environmental context, giving us a better understanding of the factors influencing the beginning of the larval phase. These observations highlight the benefit of in situ studies to better understand the characteristics and potential consequences of hatching.