Auditory threshold and critical ratio of black rockfish Sebastes schlegeli

The auditory threshold of the black rockfish Sebastes schlegeli was determined by heartbeat conditioning using six pure tone stimuli from 100Hz to 1000Hz, which was coupled with an electric shock. In order to measure the critical ratio, noise was projected to stable spectrum levels at all test frequencies of background noise. Black rockfish could hear a sound in the frequency range from 100Hz to 1000Hz, with greatest sensitivity of 90.7dB at 200Hz. The threshold at 500Hz was higher than others. Until 500Hz the critical ratio increased from 29.7dB to 59.8dB. These results show that the auditory sensitivity of the black rockfish at 500Hz is poor.