Swimming performance during a vertical movement.

<p>Time-series showing depth, pitch, swimming speed and swaying acceleration caused by tailbeat, and wavelet spectrogram of the swaying acceleration during a 45-minute vertical movement by a 440-cm sixgill shark. Negative pitch values indicate the shark was oriented head-downward. Warmer colours in the spectrogram represent stronger signals, whereas cooler colours represent weaker signals. From 13:42 to 13:52, a lack of strong signal in the spectrogram indicates the shark was gliding uphill. The bars above the graph show descent (black), horizontal swimming (shaded), and ascent with tailbeat (gray) and gliding (white). Periodical fluctuations in acceleration were stronger during descent than during ascent (i.e. tailbeat effort was greater during descent than ascent), and gliding was seen only during ascent.