Cage Production of Red Drum Weaned from Trash Fish to Extruded Feed in Xiamen, Fujian Province

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Category: Aquaculture

Region: Northeast Asia

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Weaning of 161-g red drum (Sciaenops ocellata) from trash fish to extruded feed, followed by growout to market size on extruded feed, was demonstrated in a cage feeding trial at the He Sheng Fa Cage Fish Farm in Ma Nan Bay, Xiamen, Fujian Province, China. Red drum that had only been fed with trash fish were stocked in three, 8.0-m3 cages at a density of 100 fish per m3 and weaned from trash fish to extruded feed over a period of one week. After weaning to extruded feed, red drum were fed to satiation twice daily with a 43/12 extruded, floating marine fish feed formulated by ASA using dehulled soybean meal as partial replacement for fishmeal. Red drum grew from 161 g to 834 g in 155 days on the ASA feed, with an average FCR of 1.99:1. Average fish carrying capacity at harvest was 74.5 kg/m3 of cage. The average fish survival rate was 89.5%. Net economic return and return on investment for the trial were RMB 360/m3 and 43.3%, respectively. The trial demonstrated that sub-market size red drum could be weaned from trash fish to extruded feed without difficulty. However, chronic poor water quality conditions at the trial site resulted in feed conversion efficiency with the 43/12 extruded feed that was substantially below standard. FCR with the extruded feed was still significantly better than that obtained in the area with trash fish. Feed cost per kilogram of fish growth with the ASA extruded feed was RMB 9.55, which was substantially below the cost of producing red drum with trash fish. Red drum production performance was confounded by chronically poor water quality at the test site. Dissolved oxygen level was generally below 60% saturation throughout the production season. Results of the trial indicate that Ma Nan Bay is a high- risk culture site that will likely continue to experience chronic water quality problems and periodic catastrophic fish kills related to poor water quality. Use of highly polluting trash fish and too many fish cages are the primary problems that constrain fish production. The number of fish cages needs to be drastically reduced in Ma Nan Bay and the use of trash fish prohibited to permit recovery of the ecosystem and allow sustainable fish culture in the future.