The technology of cage culture is relatively cheap and easy to run. The materials used in construction are indigenous and readily available like the bamboo supports. Filipinos are used to working with bamboo. In addition, grouper fry can now be produced in hatcheries or transported from areas where fry collection is an established industry, and there are a lot of places in the country where this is so.
Marine cage culture of grouper can be done in 4- to 12-compartment cage as one unit. There are nursery (small mesh is used in the cage) and grow-out phases (larger mesh). Grouper need to be sorted and size-graded every week. Other routine procedures include feeding (trash fish and/or formulated feeds), net maintenance, stock sampling, and monitoring water quality.
Groupers can reach the market-size of 400-600 g in 6-8 months when 2.5-7.5 cm fry are stocked. The live export market has the best price to offer.
|(1) Construct floating netcages, usually of size 5 x 5 x 3 m, and having 4 to 12 compartments. Attach floats (plastic drums, barrels) and sinkers or anchors (concrete blocks, etc). For the nursery cage, use a 0.5 to 1 cm mesh; for grow-out, use a 2-5 cm mesh. Place hides and shelters inside the netcage; these may be made of sawed bamboo tied in triangular bundles.
(2) Stock wild- or hatchery-reared fry (2-10 cm length) in nursery cages at 100-200 per m3. Install hover-type lamp to attract copepods and other young fishes and crustaceans; these can be eaten by the grouper. But give added feed like mysid shrimps or finely chopped trash fish at 10% of fish biomass. Feeds are divided and given 2-4 times a day. If formulated feed is also used, go with the directions in the manufacturer ’s label. Do not overfeed; pollution can bring a fish kill.
(3) Sort, size-grade, or thin out stock every week. Transfer same-sized grouper to the next vacant cage. When groupers are twice as big as initially stocked, they can be considered in the grow-out phase.
(4) Do the same procedures as in the nursery: feed (reduced to 5% because large fish are over their growth spurt), size-grade and transfer, monitor water quality, change the nets at least once a month, sample the stock, and monitor fish for diseases and parasites.
(5) Selectively harvest the 400-g or bigger groupers. Do not give feeds a day prior to harvest.
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