Several studies on abiotic and biotic factors that may influence metamorphosis induction and early postlarval survival and growth of the abalone Haliotis rufescens (Mollusca: Gastropoda) in culture systems were conducted. The availability of appropriate cues for metamorphosis induction is crucial. The conventional cue provided in abalone culture (diatom films) is inadequate for this species. This study shows, for the first time, that the gamma-aminobutyric acid (GABA) can be used successfully in massive-scale conditions. Metamorphosis induction by this amino acid was 75-76% (after 24 h) while only 8-12% larvae responded to diatom films. Bacterial interference can be minimized by exposing larvae to GABA in clean tanks and adding diatoms (and associated bacteria), as a postlarval food, after metamorphosis is induced. Alternatively, the conventional GABA concentration (1 micromolar) may be increased within safe limits (up to 2-3 micromolar) to cope with potential degradation of the amino acid by bacteria. Another important factor is the timing of settlement, since a suboptimal induction occurred in precompetent larvae or after a prolonged delayed metamorphosis. However, a maximum response to GABA and increased early postlarval development were observed for larvae settling 1-3 days after the onset of competence. Although GABA is now routinely used to improve settlement in many H. rufescens hatcheries, high mortality or slow postlarval growth are still common. Ecological conditions in the benthic boundary layers above diatom-films of culture systems may play an important role on postlarval fitness. Oxygen microgradients within 1 mm above biofilm surfaces were observed in laboratory studies, with bottom levels higher than 180% or lower than 50% saturation in light and dark conditions, respectively. Reduced postlarval survival and growth can also result from the depletion of biofilms after excessive grazing. Thus, information on grazing rates and the factors controlling them is crucial for the optimal management of culture systems. This contribution provides the first estimates of grazing rates of H. rufescens postlarvae, based on the digital analysis of video-recorded images, ranging from 20 to 724 diatom cells/individual/hour during the first month after settlement.