This new technology on shrimp farming in brackish water ponds incorporates pollution management which constitutes 9% of annual shrimp production cost per ha of the farmer. Pollution management is worth the cost considering that a shrimp farmer could lose it all during a disease outbreak.
Black Tiger Prawn Farming Techniques
Environment-friendly practices include:
(1) Lowered stocking density – this may decrease harvest volume by 20-30% but the harvest value could increase by 8-10% due to bigger size and improved feed conversion. Feeding and nutrient loading is reduced by 20%, and the risk of opportunistic diseases is reduced as well.
(2) Improvement of pond bottom management – this may increase plowing or tilling cost, add netcage construction to the expense but these costs could be recovered from the sale of added fish crop. Bacterial profile of sediment is improved, however, as well as water effluent quality. The pathogenic Vibrio count is reduced.
(3) Crop rotation – one shrimp crop may be lost but there is some income from fish culture. Crop rotation improves sediment bacterial profile, reduces Vibrio count, reduces incidence of white spot, and ultimately allow time for organic waste to break down.
(4) Improvement in feed quality – SEAFDEC/AQD has formulated a diet much improved in nutritional quality and lower nitrogen and phosphorus discharges. Farmers may also use probiotics.
(5) Stocking of laboratory-screened fry – there is a cost to fry analysis and screening and waiting time for the results, but the farmer is reducing the risks for white spot and pathogenic Vibrio infections.
(6) Use of greenwater technology – culture area maybe reduced by 25-50% due to the requirement for bigger reservoir but cost can be recovered from the sale of fishes raised in the reservoir. There is also added expense for modifying the water supply channel. The advantage is more stable water quality, and suppression of growth of pathogenic Vibrio.
(7) Use of probiotics in water and feed – this can add a cost of P20,000 to P40,000 per ha per crop but healthy, antibiotic-free shrimp is produced. Improved water quality and lower sludge accumulation are the benefits, in addition to reducing the risk of developing more virulent antibiotic-resistant strains of bacteria.
(8) Increase in aeration – addition of P150,000 to 200,000 per ha for aerators and 50-60% increase in power consumption but the shrimp grow faster and improve its feed conversion with increased dissolved oxygen levels and reduced noxious metabolites.
(9) Use of settling ponds – additional cost of P2,500 to 5,000 per ha per year but settling ponds lower load of suspended solids in effluent water and reduce the sediment accumulation in receiving waters.
(10) Employment of biosecurity measures – additional cost of P15,000 to 20,000 per ha per year for pond sanitation, carrier exclusion devices, filters, and worker hygiene but these measures significantly reduce the risk of introducing viral diseases to the pond facility.
(1) Re-engineer the farm layout by providing a bigger reservoir; impounding a portion of the mangrove area near the ponds to where effluents may be held; and assigning sedimentation and biological treatment ponds containing fish, bivalves and seaweeds.
(2) Prepare the ponds. Drain totally. Level the pond bottom. Dig peripheral and central canals. Crack-dry. Remove the black sludge that accumulated in previous cropping. Flush the pond with water then drain. Apply either agricultural lime at 2 tons per ha or hydrated lime at 0.5 to 1 ton per ha. Till the pond bottom. Compact. Install the central and side sludge collectors. Install catwalks and feeding trays in grow-out ponds. Let in water. Position the aerators and the pumps. Apply teaseed powder at 50 kg per ha to kill predators and competitors. Apply dried chicken or cow manure at 300 kg per ha together with urea (45-0-0) at 18 kg per ha by the “tea bag” method. Fertilize again if necessary.
(3) Stock biomanipulators. In the reservoir (25% of the grow-out farm), stock biomanipulators like all-male tilapia and milkfish at 5,000 to 10,000 fish per ha. Hold water for at least a week before using it in grow-out ponds.
(4) Acclimatization. In the grow-out ponds, acclimate then stock disease-free shrimp (at least postlarvae day 18) at 25 pieces per m2, which gives the highest net profit per ha of P1.8 million. Stocking lower at 15 pieces per m2 can get you P1.1 million; while stocking higher at 40 pieces per m2 gives only P0.6 million. Biomanipulators may be stocked inside walled net enclosures (10 x 10 x 1.5 m) that are placed in the middle of the grow-out ponds. These fishes can feed on the sludge that the paddle-wheel aerators tend to deposit at the center. The sides of the ponds may also be enclosed similarly and stocked with biomanipulators.
(5) Follow the usual pond routine. Feed according to the feed manufacturer’s instructions, sample stock regularly to adjust feeding demand, monitor water quality and bacterial populations regularly, keep complete records. If probiotics is an option, follow the application rate in the label. Operate the aerators from 6 pm to 6 am.
(6) Discharging water. In the low discharge system, a small amount of water is discharged from the grow-out pond and released to the sea after passing through the settling or mangrove impoundment. To be effective, hold pond effluents in mangroves for 6 hours or more.
(7) Water circulation. In the recirculating system, effluents from the grow-out pond are reused after passing through the treatment pond. Water is fully circulated by pumping twice, first from the head reservoir to the grow-out pond and then from the treatment pond to the grow-out pond.
(8) Filtration system. In treatment ponds, the effluent from the grow-out ponds passes through several hurdles. Note that the main drain canal can serve as one of the treatment ponds. Install baffles to serve as mechanical filtration units and to settle suspended solids. Dissolved nutrients can be taken up by biofilters like oysters, the seaweed Gracilaria, and green mussel, and these are stocked in the treatment ponds. Finally, a filter box fitted with a 2 hp submersible pump is installed at the end of the pond.
(9) Harvesting. Harvest in 4-5 months by totally draining the ponds. Chill and sort before packing shrimp. Average weight is at least 25 grams.
For more information, contact:
SEAFDEC Aquaculture Department
Tigbauan 5021, Iloilo
Trunkline connecting all offices: (033) 3362965, 5119170 to 71
Fax: (033) 3351008