Grow-out culture of mangrove red snapper (Lutjanus argentimaculatus Forsskal, 1775) in ponds
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The mangrove red snapper is among the high-value marine fishes with great potential for export. Snapper is important to coastal fishery and ideal for aquaculture particularly in Southeast Asia. Grow-out culture of snapper are described - pond culture and culture in cages inside the ponds. In the pond culture, the whole area can be maximized and the available natural food can be utilized by snapper. In rearing snapper in cages inside the pond, fish sampling and harvesting are easily done and also in preventing of disease infection and securing of fish stocks during flooding. In both culture methods a good site would have a mangrove buffer space about 20-100 m that lies between the ponds and the source of water like river or sea. Pond soil with a good water retention property is desirable for dike construction. Water supply should be adequate year-round, free from pollutants and run-off flooding. Pond supplies, labor and technology should be available on the selected site which is also accessible to markets with peaceful locale. The pond for growing snapper should be prepared well in order to promote good growth of fish, to minimize pollution, and prevents the proliferation of pathogens. Stocking of healthy and larger uniform size juveniles will mean higher survival, faster growth and shorter culture period. Proper handling of juveniles during harvest, size-grading, counting, packing, transport, acclimation and stocking should be observed and should be done during the cooler part of the day. Recommended juveniles for grow-out is about 20-100 g average body weight (ABW) and stocking densities of 5,000/ha in ponds, and at 5 pcs/m3 or 5,000 pcs/ha when stocked in cages inside the pond. During culture, good water quality is maintained and when necessary the cleaning of net cages, repair of dike leaks and seepages, and aeration are to be considered. Snapper dietary protein is about 48-50%. The following are the factors to consider in the feeding management of snapper: total stock (pcs), survival (%), ABW (g), feed rate (% biomass), feed type, feed size, feeding frequency and time. Economic analysis based on 0.422 ha pond shows that feeds accounted for 60-67% and juveniles contribute 23-25% of the variable cost. The feed conversion ratios, return on investments, payback period and discounted benefit-cost ratios are 2.5 and 2.6; 203 and 43%; 0.46 and 1.76 yr; 1.4 and 1.2 for culture of snapper in pond and culture in cages inside the pond, respectively, are likewise acceptable.