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Within the fish inner ear, three otolithic end organs (utricle, saccule and lagena) serve both auditory and vestibular roles. The Oyster toadfish (Opsanus tau) is a vocal fish species that has been extensively studied to understand both the vestibular and auditory functions of the fish inner ear. Previous studies, however, have primarily been conducted on restrained or stationary fishes so it remains unclear how self-generated movement impacts the otolithic end organs. Additionally, the effects of self-generated and anthropogenic sound on fish hearing remains to be known. To address these questions, microwire electrodes were inserted into utricle of free-swimming toadfish using an implantable micromanipulator. Experiments measured the neural response of the utricle to playbacks of conspecific vocalizations at variable speeds while swimming. During movement, fish remained sensitive to conspecific playbacks, indicating that the inner ear can detect auditory stimuli during movement. Additionally, acoustic evoked potential recordings were conducted to measure the auditory sensitivity of toadfish pre- and post-exposure to conspecific vocalizations and anthropogenic sound. Toadfish exhibited auditory sensitivity between 100 and 500 Hz, which overlaps the frequency range of conspecific vocalizations and anthropogenic sound, such as those generated by ship traffic. Exposure to conspecific vocalizations had no significant effect on toadfish auditory sensitivity; however, exposure to anthropogenic sound caused significant auditory impairment that was sustained for at least 3 days. For vocal fishes, the ability to detect and localize conspecific vocalizations is critical for their reproductive success. In the following chapters, I show that toadfish are capable of sound detection while swimming and after exposure to conspecific vocalizations, but their hearing is impaired by anthropogenic sound.

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

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

A long standing question in the field of neuroethology is how do fish localize sound? Fish are capable of detecting acoustic information through both an auditory system, the otolithic inner ear, and a mechanosensory system, the lateral line. Both systems are sensory hair cell based and exhibit directional sensitivity responses. Although the fundamental “auditory” anatomy is well characterized in fish, the physiological mechanism of how each system specifically aids in sound source detection is unknown. Using interaural time delays (ITDs) between sensory organs is the well characterized mechanism for terrestrial species sound localization; however, due to the rapid speed of sound underwater and the close proximity of otolithic organs in fish, using ITDs to localize sound is problematic. Alternatively, the conserved lateral line system in fish contains sensory organs located around the entire body, posing a potential sensory system capable of ITDs sufficient for sound localization. The inner ear also plays a dual role functioning in both the auditory and vestibular system, which further questions its potential for acute sound localization during self-induced movements, such as swimming and ventilation. Therefore, the lateral line system may provide additional information about the direction and distance of a sound source that the inner ear in fish cannot.