LAUSR

Detecting acoustic pressure can improve a fish’s survival and fitness through increased sensitivity to environmental sounds. Pressure detection results from the interactions between the swim bladder and otoliths. In larval fishes, those interactions change rapidly as growth and development alter bladder dimensions and otolith-bladder distances. We used computed tomography imagery of lab-reared larval red drum (Sciaenops ocellatus) in a finite-element model to assess ontogenetic change in acoustic pressure sensitivity in response to a plane wave at frequencies within the range of detection by fishes. We compared the acceleration at points on the sagitta, asteriscus, and lapillus when the bladder was air-filled to results from models using a water-filled bladder. For larvae of 8.5–18 mm, the air-filled bladder amplified otolith motion by a factor of 54–3485 times that of a water-filled bladder at 100 Hz. Otolith-bladder distances increased with standard length, which decreased amplification. The concomitant rapid increase in bladder volume partially compensated for the effect of increasing otolith-bladder distances. Using idealized geometry, we found that the backbone and ribs have a negligible influence on bladder motion. Our results help clarify the auditory consequences of ontogenetic changes in swim bladder morphology and otolith-bladder relationships during larval stages.Detecting acoustic pressure can improve a fish’s survival and fitness through increased sensitivity to environmental sounds. Pressure detection results from the interactions between the swim bladder and otoliths. In larval fishes, those interactions change rapidly as growth and development alter bladder dimensions and otolith-bladder distances. We used computed tomography imagery of lab-reared larval red drum (Sciaenops ocellatus) in a finite-element model to assess ontogenetic change in acoustic pressure sensitivity in response to a plane wave at frequencies within the range of detection by fishes. We compared the acceleration at points on the sagitta, asteriscus, and lapillus when the bladder was air-filled to results from models using a water-filled bladder. For larvae of 8.5–18 mm, the air-filled bladder amplified otolith motion by a factor of 54–3485 times that of a water-filled bladder at 100 Hz. Otolith-bladder distances increased with standard length, which decreased amplification. The concomitant...