Weaning of sub-market size snapper (Lutjanus sp.), locally known as red-purple snapper, from trash fish to extruded feed, followed by growout to market size on extruded feed, was demonstrated in an ASA cage trial conducted in Dong Shan Bay, Long Gang, Shenzhen. Snapper that had previously been fed with trash fish were stocked in three, 4.5-m3 cages at a density of 150 fish per m3 and weaned from trash fish to extruded feed over a period of one week. After weaning to extruded feed, snapper were fed to satiation twice daily with a 43/12 extruded, floating feed. Snapper grew from 233 g to 522 g in 118 days on the ASA feed, with an average FCR of 1.96:1. Average fish carrying capacity at harvest was 55.8 kg/m3 of cage. The average snapper survival rate was 71.3%. The approximately 29% mortality rate was attributed to fish injuries sustained during a series of typhoons in June and July. Net economic return and return on investment for the trial were RMB 727/m3 and 48.5%, respectively. Results of the trial demonstrated that Lutjanus sp. snapper could be successfully weaned from trash fish to extruded feed at a large size. Cage production of snapper was demonstrated to be technically and economically feasible with the ASA extruded feed under proper environmental conditions. The ASA 43/12 marine fish feed is formulated with 35% dehulled soybean as a partial replacement for fishmeal. The dehulled soybean meal inclusion rate is 35% by
weight. Despite a significant fish mortality rate, snapper yielded a 48.5% return to investment in this trial.