Knowledge of the relationship between auditory form and function is necessary to understand the role of hearing in fish ecology, as well as the potential impacts of anthropogenic noise and environmental change on hearing-mediated functions. We explored the functional significance of otolith (ear stone) morphology in a large predatory sciaenid, Argyrosomus japonicus (Temminck and Schlegel), by comparing ontogenetic changes in otolith structure to changes in habitat, diet and swimming activity. We examined an otolith metric that has previously been linked to habitat use and activity in fishes, the relative sensory area (sulcus to otolith area ratio, S:O), and a new metric that quantifies the protuberant structure (calcareous concrescence) found on the distal surface of sciaenid otoliths (otolith perimeter to area ratio, P:SA). Strong allometric growth of the sulcus acusticus was detected in the sagitta of A. japonicus ranging from 7 to 80 cm TL. Both S:O and P:SA changed rapidly until A. japonicus reached 50 cm TL, after which only a gradual increase in relative sensory area was detected. The aspect ratio of the caudal fin (CAR, an index of swimming activity) abruptly increased in A. japonicus at 41–50 cm TL. These changes coincide with an observed shift in diet from benthic invertebrates to pelagic fish, a shift in foraging habitat and an increase in foraging activity.
Située dans une partie proche de la queue.