Fig. 3. Stroke volume data from an individual northern elephant seal during the pre-dive, dive and post-dive (PD) periods. Blood flow (ml) over a cardiac cycle during the dive exhibited a distinct peak in the first quarter of the cardiac cycle, then decreased momentarily before leveling off. In the second half of the cardiac cycle (frames 17-32), flow did not fall to zero at any point [mean flow (± S.E.M.) per frame = 2.23±0.08 ml].