Auditory masking was determined for the black rockfish by using white noise as masking stimuli with spectrum levels of around 70, 80 and 90dB re 1 μPa/Hz1/2. The auditory thresholds at four frequencies from 100 to 500Hz varied with background noise, and increased from 10 to 24dB at the highest noise level as compared with thresholds in a quiet condition for each frequency. Values for the critical ratio, calculated in terms of the masked thresholds in relation to masking noise spectrum level, ranged from 27dB at 100Hz to 40dB at 500Hz. The noise spectrum levels that start masking are estimated to be 66-77dB at the test frequencies suggesting that background noise larger than those values affects hearing in the black rockfish. The thresholds are 27-40dB higher than the spectrum level of the noise.
