Time to recover the upright posture in juvenile abalones (Haliotis discus discus Reeve, H. gigantea Gmelin and H. madaka Habe)

The adoption of an upright posture in abalones is essential to enable them to use their foot, and hence to be able to move and seek shelter, as well as to avoid exposure of soft parts and possible predation. In mass restocking programs for abalone, juveniles are released by divers near the seabed, but without control over their posture when they reach the bottom. Thus, the time to recover the upright posture is an important consideration in abalone restocking programs as the quicker they assume this posture the higher the likelihood of survival. This study reports significant differences in the speed of recovering the upright posture between juveniles of the abalones Haliotis discus discus, H. gigantea and H. madaka and between tests conducted under stagnant and flowing water conditions. Longer times were required for recovery in all species in stagnant than flowing water. On average, juveniles of H. discus discus (17.16 and 10.43 s) and H. gigantea (22.54 and 11.89 s) recovered faster than those of H. madaka (161.13 and 49.02 s) under stagnant and flowing water conditions respectively. These results suggest that different species require different levels of care and that water flow or current at the time of release may affect post-release survival.