Acoustic space sharing in the hullabaloo of a coral reef in Mooreas Island, French Polynesia

The more vocal species in a community, the more complex the acoustic environment, and signals produced by marine organisms in order to communicate may interfere. Since acoustic space is a limited resource to be shared, selection may have favored a partitioning of the available acoustic windows both at the temporal and spectral levels. This has already been reported in insects, frogs, birds or mammals but rarely in fishes. Our study aimed to investigate sounds produced within an ichthyological community in the North Coast of Moorea Island (French Polynesia). By using passive acoustic monitoring technics, we identified a total of 38 different types of sounds, some dominating during day-time while others dominated during night-time. Over 24h, we also observed a succession of optimal sound production periods for each sound type which suggests a finer level of temporal partitioning of fish vocalizations. Finally, we further showed that acoustic features of co-occurring sound types significantly differed allowing partitioning at the spectral level too. These results demonstrate the existence of acoustic partitioning and interference avoidance in a coral reef fish community and highlight how acoustic communication might be optimized in such a biologically rich and dense environment as coral reefs.