Farming freshwater prawns

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important economic factor. As ponds mature, ponds tend to ‘seal’ themselves, through theaccumulation of detritus and algal growth, thus limiting seepage losses. Seepage losses canalso be minimized by a number of techniques, including sealing the ponds with organicmatter, puddling, compaction, laying out a ‘soil blanket’, applying bentonite, or lining themwith polyethylene, PVC, or butyl rubber sheeting. Details of these procedures are providedin another FAO publication (FAO 1996).There is no substitute for the site-specific determination of the water requirementsfor your farm but an example of water consumption needs for different sized farms, usinga number of assumptions is given in Table 6. Techniques for measuring water resources aregiven in books on hydrology and agricultural water assessment such as ILACO (1981).Methods for estimating seepage and evaporation losses and calculating water requirementsare given in FAO (1981). Large-scale farms may wish to consult specialist contractors.TABLE 6Example of water requirements for pondsbased on various assumptionsTOTAL FARMQUANTITY OF WATER REQUIRED (m 3 /MIN)WATER SURFACE FILLING REPLACING SEEPAGE AVERAGEAREA 2 (HA) PONDS 3 AND EVAPORATION LOSSES 4 CONSUMPTION 50.2 2.50 0.041 0.0480.5 2.50 0.103 0.1201.0 2.50 0.205 0.2392.0 2.50 0.410 0.4783.0 3.75 0.615 0.7185.0 6.25 1.025 1.19610.0 12.50 2.050 2.39220.0 25.00 4.100 4.78540.0 50.00 8.200 9.570A supply of drinking water and waste disposal facilities are an added advantage toa freshwater prawn farm site but are not absolutely essential. Provision can be made onsite,for example by obtaining batch supplies of drinking water, sinking a borehole, or collectingand filtering rainwater. However, if ice is going to be made, or prawns are to beprocessed and packed on site, a supply of high quality water, normally the equivalent ofdrinking (potable) water, is essential. Aqueous waste disposal from such activities can berouted to a septic tank, a waste lagoon, or a simple soak-away.2 Assumes an average water depth of 0.9 m3 For filling ponds at the beginning and on future occasions. Assumes that the unit pond size is 0.2 ha and that the pond can be filled within 12 hours.Also assumes that it will never be necessary to fill more than one pond (or 10% of the pond surface area, whichever is the greater) at the same time.Local experience will tell if this allowance is either not enough or too generous.4 Assumes average seepage losses of 10 mm/day, which is typical for a clayey loam which has not been puddled (FAO, 1981), 500 mm/yr evaporation(this is extremely site-specific) and 2% water exchange per day. This is equivalent to 100 m 3 /ha/day (approximately 0.07 m 3 /ha/min) for seepage,approximately 13.7 m 3 /ha/day (0.01 m 3 /ha/min) for evaporation, and 180 m 3 /ha/day (0.125 m 3 /ha/min) for water exchange in ponds with an averagedepth of 0.9 m. Total maintenance requirements are therefore 0.205 m 3 /ha/min.5 This combines the maintenance rate with the quantity necessary to fill all ponds twice per year, averaged out to a volume per minute consumptionbasis.CHAPTER 223
CHOOSING YOUR SITE: SOIL CHARACTERISTICSThere must be enough soil available for pond construction, whether the ponds are to beexcavated or pond banks are to be erected above ground. Unless good information aboutthe soil characteristics is already available, site assessments should include taking a suitablenumber of soil cores up to 1 m deeper than the expected pond depth. These must beanalysed for their soil classification and chemistry. If rocks, boulders and tree stumps arepresent, you must consider the cost of their removal (to make the pond bottoms flat and forconstructing impervious pond banks) while you are assessing the economic feasibility ofthe farm. Flooded and saturated areas are difficult to construct ponds in, and the expensesof doing so must be taken into consideration. Construction of concrete pond structures(e.g. pond outlets) is difficult in soils with a high salt content. Preferably, the site shouldhave a shape which allows you to construct regular-shaped ponds. Irregular-shaped pondsare difficult to manage; rectangular ponds are more efficient to operate.Although supplemental food is given to freshwater prawns reared in earthen ponds,a considerable amount of their food intake is from natural sources. It is therefore preferableto site the farm where the soil is fertile, as this will reduce the need and costs of fertilisation.Since a water pH of 7.0-8.5 is required for successful freshwater prawn culture,it is preferable not to build the farm on potentially acid sulphate soils. These soils havepH values of 4.5 or less, together with high concentrations of soluble iron, manganese andaluminium. Most people associate the occurrence of acid sulphate soils with mangroveareas but they also occur far away from such areas. Aquaculture ponds are frequently constructedon such soils, despite their poor suitability. However, their production levels areoften too low, or the costs of liming and fertilisation are too high, for them to be financiallyviable.Freshwater prawn ponds should be constructed on soil which has good water retentioncharacteristics or where suitable materials can be economically brought onto the siteto improve water retention. The water retention characteristics of soil are highly site-specificand prospective farmers must seek the professional advice of soil engineers and fisheryofficials from local government departments, such as the Ministry of Agriculture andthe Public Works Department. If there are other fish farms or irrigation reservoirs in thearea, you should ask the neighbouring farmers for advice, based on their specific local experience.Pervious soils, which are very sandy or consist of a mixture of gravel and sand, areunsuitable unless the water table is high and surrounding areas are always waterlogged.Soils which consist of silt or clay, or a mixture of these with a small proportion of sand, normallyhave good water retention characteristics. Peaty soils are not suitable. The clay contentshould not exceed 60%; higher clay content soils swell when moist and crack duringthe dry season, thus making repairs necessary. Methods for the preliminary assessment ofparticle sizes, permeability and plasticity (how well soils will compact to their optimumstrength and permeability) are given in FAO (1985).CHOOSING YOUR SITE: POWER SUPPLIESA source of electricity is desirable but not essential. A variety of power sources may be usedfor supplying the energy necessary for water movement on the farm including:water power itself (gravity and current flow);wind;electricity;petrol and diesel fuel; andwood.FRESHWATER PRAWNS24
Page 1 and 2: Farming freshwater prawnsA manual f
Page 3 and 4: The designations employed and the p
Page 5 and 6: abstractTHE ORIGINAL MANUAL on fres
Page 7 and 8: table of contentsABSTRACTPREFACEINT
Page 9 and 10: Feed type 114Measuring feed efficie
Page 11 and 12: 17. Measuring soil pH 10618. Reason
Page 13 and 14: 87. Keeping market-sized prawns ali
Page 15 and 16: major subject of cultivation becaus
Page 17 and 18: has little relevance, especially be
Page 19 and 20: (zoeae) are just under 2 mm long (f
Page 21 and 22: TABLE1Body segments (somites) in Ma
Page 23 and 24: Figure 5The major malemorphotypes o
Page 25 and 26: tions, where a breeding stock of bo
Page 27 and 28: most hatcheries operated on flow-th
Page 29 and 30: BOX 1Removal of iron and manganeseW
Page 31 and 32: TABLE 3Artificial brackishwater (12
Page 33 and 34: TABLE 4Diluting seawater and brine
Page 35 and 36: mentally cultured at up to 10 ppt;
Page 37: cal quality and its lack of predato
Page 41 and 42: such as fertilizers and equipment.
Page 43 and 44: perate (usually originating from st
Page 45 and 46: 3.2 Holding your broodstock in temp
Page 47 and 48: ing system that consists of a 300 L
Page 49 and 50: 4CHAPTERHatchery phaseALL FRESHWATE
Page 51 and 52: SOURCE: HASSANAI KONGKEOand dust. T
Page 53 and 54: FIGURE17This shows the water flow t
Page 55 and 56: Figure 21The water inthese larvalta
Page 57 and 58: FIGURE24Turn-down drains are the be
Page 59 and 60: FIGURE26Installing a ring main air
Page 61 and 62: Figure 28Power supplies arenot alwa
Page 63 and 64: Water dischargeYou should take care
Page 65 and 66: is recommended. The volume of these
Page 67 and 68: then multiply to cope with the nitr
Page 69 and 70: Regular monitoringof larval waterqu
Page 71 and 72: initial stocking rates shown inBox
Page 73 and 74: Recommendations forgood larval wate
Page 75 and 76: FIGURE35Many of the larvae that go
Page 77 and 78: TABLE 8Hatchery feeding scheduleLAR
Page 79 and 80: ing to avoid BSN leaving the tank.
Page 81 and 82: TABLE10The major diseases known to
Page 83 and 84: Notes on potential disease problems
Page 85 and 86: FIGURE36aA method of evaluating the
Page 87 and 88: occurred). You are therefore recomm
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5CHAPTERPostlarval holdingand nurse
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Figure 39Substrates can beused in n
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FIGURE41Postlarvae in plastic bags
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pH and temperature of the rearing f
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It is difficult to recommend exact
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6CHAPTERGrow-out phaseFRESHWATER PR
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FIGURE44ponds may become low enough
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FIGURE46Pond banks should have the
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FIGURE50The dissolved oxygen levels
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Figure 53Where thetopography of the
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Figure 56The outletstructure,someti
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Figure 58This freshwaterprawn pondh
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FIGURE59 cont.CROSS SECTIONSOURCE:
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Figure 64Long-shaftaeratorin action
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there is only a single stocking), t
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TABLE16Lime requirements for treati
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semi-intensive stocking rates vary
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Keeping rootedplants out ofyour pon
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advantages obtained in temperate cu
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Polyculture of freshwater prawnswit
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only increases the availability of
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Using water-stable feeds provides y
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MEASURING FEED EFFICIENCYYou should
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Example of feeding ratefor freshwat
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allowed to become too low and there
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found to be hosts for the bopyrid i
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Figure 81A large BCMacrobrachiumros
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7CHAPTERHarvesting andpost-harvest
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FIGURE83You can cull-harvest your p
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FIGURE85Larger ponds may also be cu
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Figure 91HarvestingMacrobrachiumros
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(Figure 95). To kill a batch of 50
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described earlier in this manual) a
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Once the prawns arrive at the point
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properly. They should also be displ
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ANNEX 1, Figures 1-12Macrobrachium
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4ANNEXSource, hatching andenrichmen
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The nutritional quality and physica
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decapsulation improves the energy c
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starved versus enriched BSN. Lavens
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1ANNEX 4TABLEDetermining hatching p
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4ANNEX 4TABLE Hydrating and decapsu
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7ANNEX 4TABLE1. Set up the hatching
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grades the particles and washes the
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2. Stock estimation when postlarvae
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animal, particularly within the gil
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ANNEX 7 FIGURE1The size of the mesh
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8ANNEXSize managementAS MENTIONED I
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2. BehaviourThe behavioural charact
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ANNEX 8 FIGURE3Changing the stockin
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ANNEX 8 FIGURE4Orange claw (OC) and
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9ANNEXFarm-made pond feedsTHIS ANNE
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ANNEX 9, Figure 3Farm-made feedsnee
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4ANNEX 9TABLEFarm-made grow-outfeed
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which the requirements are applied.
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Carapace:Caridean:Cephalon:Chela:Ch
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Genital pores:Gill chamber:Greenwat
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Puddling:Rostrum:Salinity:Sequester
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ConversionsTHIS SECTION OF THE ANNE
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Financial considerationsSOME COMMEN
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ReferencesAlston, D.E. & Sampaio, C
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Fujimura, T. & Okamoto, H. 1972. No
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New, M.B., Singholka, S. & Vorasaya
Page 215:
This new manual, which replaces an
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