Key-words:Esox lucius free embryos, 0+ pike, vertical distribution, attachment behaviour, eleutheroembryo mobilityThe vertical distribution, body orientation and mobility of pike free embryos were studied at 10• C in 25-cm individual water columns. Five steps were identified: (1) a resting phase, up to day (D) 4 post-hatching; (2) an ascent phase (D1-D4); (3) a plateau (D5-D8), characterized by a wall-attachment behaviour in the subsurface zone; (4) a break-off phase (D9-D13); and (5) a final localization between mid-water and surface, corresponding to the air filling of the swim bladder and to the transition to active, horizontal swimming (D14-D17). Free embryos could be: side-lying (phase 1, late phase 4 and phase 5); lying upright (phases 4 and 5); vertically suspended with adhesion to the wall (phases 2-3 and early phase 4); and in oblique or horizontal position (phase 5). The opening of mouth and anus occurred during phases 2 and 3 and swim bladder filling started on days 13-14. Free embryo mobility was low and stable during the first 5 days and increased regularly thereafter to reach maximal levels on days 14-16. This research provides evidence for a more complex and more variable temporal pattern of free embryo vertical distribution, posture and mobility than previously thought. au cours des phases 2 et 3 et le remplissage de la vessie natatoire a débuté à J13 ou J14. Le degré de mobilité de l'embryon libre, peu élevé et stable au cours des 5 premiers jours, a ensuite augmenté de façon régulière pour atteindre les valeurs les plus élevées entre J14 et J16. La présente étude met en évidence pour la répartition spatiale, la posture et la mobilité de l'embryon libre l'existence d'une séquence temporelle plus complexe et plus variable que ne le suggéraient les connaissances antérieures.