Juan Carlos Azofeifa-Solano

Acoustic communication plays an important role in fish ecology and behaviour. Understanding how acoustic signals vary across species and populations is central to questions of sexual selection, population divergence, and environmental modulation of communication. Yet many fish calls remain unattributed to species or behaviour, limiting their integration into broader ecological studies and monitoring. We deployed portable audio-video arrays at two coral reef systems to study the courtship calls of two sympatric damselfishes, Dascyllus aruanus and D. reticulatus. Arrays integrated four hydrophones with a video camera, enabling automated detection of pulse trains, 3D localisation, motion classification, and behavioural observations. We found interspecific differences and strong population-level divergence in call structure, with site effects often exceeding species effects. This suggests that local thermal conditions may influence the performance of sound production, potentially constraining communication under marine heatwaves. Our study shows that integrating small audio-video arrays with behavioural validation not only provides a tool for monitoring but also reveals how socially mediated courtship signals vary within and between species across broad spatial scales. This dual perspective strengthens the role of fish bioacoustics in ecological and conservation frameworks.

Extant sirenians are the only aquatic herbivorous mammals and comprise four recognized species: the dugong, the Amazonian manatee, the West Indian manatee, and the African manatee. They inhabit coastal shallow waters in tropical and subtropical areas. All sirenian species produce sounds, many of which are audible to humans. These sounds range from tonal and narrowband to pulsed and broadband. Some of these vocalizations can be frequency-modulated and amplitude-modulated, ranging from 0.5 to at least 22 kHz in frequency and from <0.02 to ~1 s in duration. The variation in sound characteristics has enabled call type categorization into barks, chirps, clicks, quacks, squeaks, squeals, trills, whistles, etc., with gradation between classes. These calls are produced in different contexts, such as mother-calf interactions, territorial assertion, and reproductive behaviors. Sirenian vocalizations are also influenced by the surrounding environment, and their communication can be affected by human-produced noise (e.g., motorized vessels). Understanding the function of sirenian sounds in different social and ecological contexts might enhance the application of passive acoustic monitoring to the conservation and management of these endangered animals.