Culture of Milkfish Using Semi-Intensive System Part 1

Over the years, there has been a big steady demand for milkfish or bangus in the country. It has also been doing well in the international market with Philippine export of frozen or chilled bangus reaching over 526 metric tons or some P8.5 million annually.

The following gives a good overview of how to manage your own fishponds using a site already developed.

Site selection

Select existing brackishwater fish farms that are fully developed and operational. Former prawn farms can be used for milkfish farming. The site should have:

  • high tidal range and can hold water at least one meter deep;
  • good water quality and more or less have constant salinity and temperature throughout the year;
  • longer dry season, sandy clay loam, silty clay loam; and
  • access to roads and power supply.

Pond layout and design

  1. Improve or modify existing structures to suit the management requirements of the proposed production scheme.
  2. Concentrate on the repair and strengthening of dikes, cut-and-fill levelling of pond bottom, and construction of diagonal canal, drain canal and drain culvert gate to improve pond structures.
  3. Modify pond structures to improve water management and stock manipulation systems as well as to meet desired management schedules and production targets. The pond can be of any size (the bigger, the better) for optimum production using the modular method.
  4. Divide pond into four compartments: nursery pond (NP); transition pond (TP); formation pond (FP); and rearing pond (RP).
  5. Provide a separate culvert-type drain gate and canal system opposite the inlet gate and canal system for rearing ponds to effect efficient water exchange and circulation.
  6. Construct an inside-pond diagonal canal to facilitate draining and harvesting of stock.

Figure 1. Layout for a semi-intensive farm system

Pond preparation and food requirements

  1. Carry out thorough pond preparation such as crack drying, liming and tilling once a year.
  2. Prepare the ponds grown with lab-lab before fish stocking.
  3. Apply organic and inorganic fertilizer to stimulate growth of natural food organisms.
  4. Extend pond preparation and food growing in grow-out ponds to 45 days to allow more time for the abundant growth of lab-lab

Figure 2. Schedule of pond preparation and food growing

Cumulative days for completion of activities / Activities:

  • 1 Pond draining, soil sealing, leveling and repair
  • 2-7 Pond drying
  • 2 Gate screening
  • 2 Pest predator control
  • 2 Liming (optional for low pH)
  • 7 Washing
  • 8 Organic fertilization (2 tons/ha)
  • 8 First water intake, 5 cm
  • 8-17 Evaporation
  • 11 Inorganic fertilization 3 sacks/ha 21-0-0
  • 18 Second water intake, 10 cm
  • 18 Fertilizer dressing, 25 kg/ha 16-20-0 13.
  • 25 Third water intake, 15 cm
  • 25 Fertilizer dressing, 25 kg/ha 46-0-0
  • 32 Fourth water intake, 20 cm.
  • 36 Fertilizer dressing, 25 kg/ha 16-20-0
  • 39 Sixth water intake, 25 cm 18.
  • 39 Fertilizer dressing, 25 kg/ha 16-20-0
  • 45 Sixth water intake, 30 cm
  • 46 Fish stock

Production strategy

  1. Purchase the required fry once every year of operation, especially during the peak season in May.
  2. Start production in the nursery pond, then the transition pond, formation pond, and finally the rearing pond.
  3. Divide the grow-out process into two phases: formation and rearing phases.
  4. Allow the fingerlings to from a 20 g fingerling size to a 50 g post-fingerling size in the formation pond using natural food organisms as primary food for the stock.
  5. Transfer the post-fingerlings to the rearing pond. Milkfish will grow to the marketable size of 250 g in three months at an average growth rate of 2.2 g/day. Expect the milkfish to grow bigger during the dry season at an average growth rate of 3 g/day.
  6. Provide supplementary feeds to sustain fish growth particularly during the wet season when lab-lab and other natural foods in the pond are depleted. A weekly feed conditioning is necessary to determine the attractability of the feed.
  7. Efficient feeds should be used. Unattractive feeds result in poor health of the milkfish.
  8. Eradicate snail pests called suso and bangungon. These pests destroy lab-lab mat and compete with bangus for lab-lab. Use alternative molluscicide, like tobacco dust, applied at 300-400 kg/ha or collect the snails by sweeping or handpicking and burn them with rice straw.

Pond water management

  1. Increase water depth from 0.6 m to 1 m particularly during the last two months of culture operation. Note: An abrupt increase in water depth will cause lab-lab to detach and float. Install fine-meshed screens (bastidor or lumpot) at the gates to prevent the re-entry of wild species or the possible escape of stock.
  2. Monitor water quality parameters (turbidity, salinity, dissolved oxygen, temperature regularly to check for any sign of risk. Maintain the optimum water condition to support maximum growth of milkfish.
  3. Change water at least every two weeks or as frequent as possible.
  4. Install a stand-by water pump to maintain desired water depth when water management through tidal fluctuation is not possible.

Figure 3. Stocking Density [Pond – Stock]

  • NP – 40 fry/sq m
  • TP – 5 fingerlings/sq m
  • FP – 2 juveniles/sq m
  • RP – 1 grown fish/sq m

Figure 4. Milkfish Production Schemes

Pond Growing stage (wt-g) Culture period (days) Growth rate (g/day) Food type Harvest size (pc/kg)
NP 0.02-.05 30 0.016 Lab-lab 2000
TP 0.5-10 30 0.32 Lab-lab Bread crumbs 100
FP 10-40 30 1.00 Lab-lab Bread crumbs 20
RP 50-215 75 2.2 Lab-lab/Pellets 4.6
Dry 50-275 75 3.0/higher Lab-lab/Pellets 3.6

Figure 5. Feeding Requirement Scheme

Pond Growing size (g) Feed type % Feed rate (Biomass) Feeding frequency
NP 0.02-.05 Lab-lab Starter mash 8-10 5x/day
TP 0.5-10 Lab-lab Bread crumbs/rice bran 5-8 4x/day
FP 12-50 Lab-lab Bread crumbs 4-5 3x/day
RP 50-100 100-250 Lab-lab/algae Finisher Pellets 3 3-4x/day

 

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