Fish acoustic community structure in Neptune seagrass meadows across the Mediterranean basin

Sound production represents an integral part of social communication in many teleost fish; however, few studies have investigated the structure, organization and variability of fish sounds at the community level. Fish acoustic community structure was recorded simultaneously in three sites located along the Mediterranean basin within the endemic habitat of Posidonia oceanica seagrass beds. Acoustic diversity and species-specific sound features were expected to differ between locations. We predicted that, in communities characterized by higher acoustic richness, fish species would specialize in their use of acoustic resources (i.e. realized acoustic niche compression), while the overall allocation of resources within the community signal space would expand. The fish acoustic communities inhabiting Posidonia beds were characterized by the same main contributors (the /Kwa/, Ophidion rochei and Sciaena umbra sound types). However, their relative occurrence, abundances and use of acoustic resources were site-specific. Acoustic diversity differed between geographic locations. The range of spectral and temporal resources exploited by the fish acoustic community was wider in sites where acoustic richness was at its highest score. Ophidion rochei was highly specialized in its use of temporal resources where acoustic richness was higher, whilst S. umbra appeared less efficient in specializing the use of spectral and temporal resources. By showing that the same species can exploit different acoustic resources between locations, this study supports the concept of Acoustic Niche plasticity (i.e. plasticity of acoustic resources allocation within a species). The results suggest that the degree of acoustic niche plasticity might be determined by the species-specific degree of sound-producing system plasticity. In turn, different degrees of acoustic niche plasticity might determine different species-specific levels of acoustic adaptability to changing biotic or environmental conditions.