Predicting the influence of source and receiver variation in the use of acoustic cues by larval fishes

Soniferous reef animals produce sound through intentional behaviors like communication and as byproducts of activities like feeding and defending. Sounds from individuals collectively create habitat-specific and temporally variable biological soundscapes. As sounds propagate away from their sources, they may influence larval fishes that use acoustic cues during settlement. Therefore, animal behavior creates spatiotemporally-variable soundscapes, which in turn influence the behavior of fishes during a critical life history transition. These different scales of marine bioacoustics were investigated. The soundscapes across a range of reef quality were recorded for six weeks in an anthropogenically-degraded region of Caribbean Panama. The same contributors to the soundscapes were observed across sites, with taxa-specific variation in spatiotemporal patterns of acoustic behavior. The observed rate of these potential cues was predicted by an individual-based model to improve larval settlement, suggesting resiliency of some components of these acoustic cuescapes. The toadfish Ampicthyses cryptocentrus was a dominant contributor to the soundscapes and showed site-specific temporal variation. Analyses of recordings of ten focal males and males in neighboring burrows demonstrated that males were responsive to multiple neighbors, not just the perceived loudest competitor, and a null model supported that grunts overlapping neighbors’ calls were used as acoustic competition. These results suggest the contribution of toadfish to the soundscape is dependent on both abundance and spatial distribution. Calibrated propagation modelling was used to predict the acoustic fields created by reef-based sounds. It was found that spatial heterogeneity in cue strength increases with frequency and changes with source location, with implications for cue detection. Detection of reef-based cues is enhanced when the otoliths receive energy from the bladder’s response to pressure fluctuations. Changes in bladder size and otolith-bladder distances are likely to create ontogenetic changes in pressure sensitivity, which was tested with a combination of micro-computed tomography and finite-element modelling using larval Sciaenops ocellatus. Otolith-bladder distances increased with fish size, reducing predicted pressure sensitivity. Bladder volume also increased with growth, compensating for increasing distances by partially recovering predicted pressure sensitivity. Combined, these results highlight the system’s complexity: social behavior, spatiotemporal variation, and ontogenetic patterns dynamically influence how soundscapes influence larval behavior