Fig. 1. Schematic illustration of the experimental setup. The video camera is positioned above the displaying fish. Output from the camera is viewed with a TV monitor and fed into the video channel (V) of the VCR. EMG activity is amplified, monitored via an oscilloscope, and fed into the audio channel (A) of the VCR.Video output — kinematics data — is analyzed and plotted by a computer equipped with a frame-grabber and the ‘ColorImage’ analysis program. Audio output — EMG data — is digitized in a waveform analyzer and displayed on a computer.