Hearing Sensitivity of the Walleye Pollock

Abstract

AbstractThe hearing abilities of three age‐groups (which correspond to size‐classes) of walleye pollock Theragra chalcogramma were determined from auditory evoked potentials. Walleye pollock had the best hearing sensitivity from 100 to 200 Hz, with thresholds around 75 dB re: 1 μPa. Hearing sensitivity decreased with increasing frequency up to 450 Hz. There was no significant difference in hearing sensitivity between the age‐groups, although there was a significant interaction between frequency and age as well as a trend in which the older fish had slightly lower mean thresholds. At the same time, there was a substantial increase in the size of the saccular otolith and associated sensory epithelia of the inner ear, suggesting that a large increase in ear size does not lead to a large change in hearing sensitivity. In addition, there was an effect of water temperature on the hearing thresholds at 350 Hz, whereby each degree of temperature (°C) increase resulted in an 8.3‐dB decrease in hearing threshold. The results suggest that the hearing thresholds of walleye pollock are generally similar to those of other gadid fishes. This knowledge can be used to evaluate the potential impact, in terms of behavioral responses or physiological effects, that various human‐generated sounds (e.g., seismic survey and underwater radiated vessel noise) may have on this species.