The auditory threshold of the bastard halibut Paralichthys olivaceus

Abstract

Using a classical respiratory conditioning technique, the hearing ability of the bastard halibut Paralichthys olivaceus was measured for 7 fish at 7 frequency points between 70 Hz and 500 Hz. The conditioning response was measured as suppression in the respiratory activity by the piezoelectric sensor fitted on a gill cover in a quiet water tank. The bastard halibut was sensitive to sounds in the frequency range from 70 Hz to 500 Hz. The auditory thresholds were observed among the 7 fish with much difference (about 17 dB) at 100 Hz and 300 Hz. But the audiogram had common characteristics that they had the lowest threshold at about 100 Hz and that the threshold increased rapidly with frequency of sound between 200 Hz and 400 Hz. An attempt was also made examine the escape response of each of the above 7 bastard halibut by the sound stimulus, but no conditioned escape response was observed after 7 times applying training stimulus.