| Summary: | As part of the preparation for the mass cultivation of the brown seaweed, Sargassum aquifolium, the following were investigated in a replicated experiment: patterns on the early post-settlement stage of the germlings on three types of artificial substrates (i.e., clay, limestone, and nylon string), and growth and development of the hatchery-derived S. aquifolium juveniles out-planted in the sea. Our investigation during the early post-settlement stage demonstrated: 1) recruit density to be highest on nylon string followed by clay, then limestone throughout a one-week observation period, 2) survival rate of germlings to be highest on limestone, followed by clay, then nylon string at day 9, and 3) higher daily growth rate (DGR) of germlings on clay at day 14, 21, 35, and 49. Recruits on clay substrates were the first to reach young juvenile stage and were used in out-planting. Young juveniles demonstrated continuous increase in length until 42 days post out-planting with some fluctuations thereafter. Lateral branches started to decrease 7 days post out-planting and throughout the sampling days. Overall, clay substrate was found to be suitable for the attachment and cultivation of S. aquifolium. However, an optimal density and optimal site selection seemed to be required during hatchery cultivation and out-planting, respectively. This would also prevent infestation of epiphytic organisms and grazers, and accumulation of sediment which could hamper the growth and development of S. aquifolium. Keywords: Early algal settlement, Growth rate, Sargassum aquifolium, Seaweed cultivation, Tropical seaweed
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