Fig. 7. Example of an auditory evoked potential (AEP) at 125 Hz recorded from a female Hawaiian sergeant fish, Abudefduf abdominalis. Averaged AEP traces (bottom trace shows the stimulus waveform recorded by the hydrophone at the position of the fish head) (A) and FFT analysis (B) (1024 points) of the averaged response at five different stimulus intensities. Note that the peaks on the averaged AEP FFT histograms at 240–250 Hz are twice the frequency of the recorded stimulus waveform (125 Hz; bottom FFT). Threshold for this fish was 122 dB_rms re: 1 µPa at this frequency.