Farming freshwater prawns

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animals. It does not, unfortunately, give you much more than a vague idea of the survivalrate.4. Stock estimation when market-sized<strong>prawns</strong> are harvestedANNEX 6, Figure 3Measuring thelength of a prawn(Brazil)SOURCE: WICKINS (1972)From the practical rather than the scientific point of view, there are two vitally importantdata which must be recorded at harvest time. One is the total drained weight of theharvest and the other is theaverage size of the animalsharvested.From these data the numbersof animals harvestedcan be estimated. Since youalready have an estimate ofthe number of PL or juvenilesstocked, you can then calculatean estimated survivalrate. Together, you can usethese data to assess the productivityof your pond and theefficiency of the managementsystem you have used.Combined with the costs ofproduction and the marketvalue of the product, thisinformation enables you tocalculate the overall economicperformance of each pond.Although the length of theprawn [biologists usuallymeasure them from behindthe eye stalk to the tip of thetail (Annex 6, Figure 3); farmersusually measure themfrom the tip of the rostrum tothe tip of the telson] is a moreaccurate form of measurementthan weight, it is not so easyfor the you to measure, particularlyas you then have to convertthe measurement toweight using a calibrationcurve (Annex 6, Figure 4).The weight of the animal caneasily be measured on aportable scale. It will be inaccuratebecause of the amountTotal length (mm)of water adhering to theANNEX 6 FIGURE4Length-weight relationship of postlarvalMacrobrachium rosenbergiiWet weight (g)SOURCE: DEBORAH ISMAELANNEX 6171
animal, particularly within the gill chambers. However, especially when the same personalways does the weighing, it is possible to standardize the weighing technique and toachieve reasonable comparative accuracy.It is suggested that you individually weigh about 250 animals for every 500 kg harvested(this is equivalent to a 2% sample of the population if the average weight is 40 g).Take the sub-sample from the total harvest by dip-netting from the holding container orcage. Do not select individual animals because this will lead to a bias towards the largeranimals. Use a dip-net and weigh every prawn that you obtain in your sample.FRESHWATER PRAWNS172
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Farming freshwater prawnsA manual f
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The designations employed and the p
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abstractTHE ORIGINAL MANUAL on fres
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table of contentsABSTRACTPREFACEINT
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Feed type 114Measuring feed efficie
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17. Measuring soil pH 10618. Reason
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87. Keeping market-sized prawns ali
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major subject of cultivation becaus
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has little relevance, especially be
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(zoeae) are just under 2 mm long (f
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TABLE1Body segments (somites) in Ma
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Figure 5The major malemorphotypes o
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tions, where a breeding stock of bo
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most hatcheries operated on flow-th
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BOX 1Removal of iron and manganeseW
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TABLE 3Artificial brackishwater (12
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TABLE 4Diluting seawater and brine
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mentally cultured at up to 10 ppt;
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cal quality and its lack of predato
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CHOOSING YOUR SITE: SOIL CHARACTERI
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such as fertilizers and equipment.
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perate (usually originating from st
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3.2 Holding your broodstock in temp
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ing system that consists of a 300 L
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4CHAPTERHatchery phaseALL FRESHWATE
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SOURCE: HASSANAI KONGKEOand dust. T
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FIGURE17This shows the water flow t
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Figure 21The water inthese larvalta
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FIGURE24Turn-down drains are the be
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FIGURE26Installing a ring main air
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Figure 28Power supplies arenot alwa
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Water dischargeYou should take care
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is recommended. The volume of these
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then multiply to cope with the nitr
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Regular monitoringof larval waterqu
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initial stocking rates shown inBox
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Recommendations forgood larval wate
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FIGURE35Many of the larvae that go
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TABLE 8Hatchery feeding scheduleLAR
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ing to avoid BSN leaving the tank.
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TABLE10The major diseases known to
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Notes on potential disease problems
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FIGURE36aA method of evaluating the
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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
Page 127 and 128: Polyculture of freshwater prawnswit
Page 129 and 130: only increases the availability of
Page 131 and 132: Using water-stable feeds provides y
Page 133 and 134: MEASURING FEED EFFICIENCYYou should
Page 135 and 136: Example of feeding ratefor freshwat
Page 137 and 138: allowed to become too low and there
Page 139 and 140: found to be hosts for the bopyrid i
Page 141 and 142: Figure 81A large BCMacrobrachiumros
Page 143 and 144: 7CHAPTERHarvesting andpost-harvest
Page 145 and 146: FIGURE83You can cull-harvest your p
Page 147 and 148: FIGURE85Larger ponds may also be cu
Page 149 and 150: Figure 91HarvestingMacrobrachiumros
Page 151 and 152: (Figure 95). To kill a batch of 50
Page 153 and 154: described earlier in this manual) a
Page 155 and 156: Once the prawns arrive at the point
Page 157 and 158: properly. They should also be displ
Page 159 and 160: ANNEX 1, Figures 1-12Macrobrachium
Page 161 and 162: 4ANNEXSource, hatching andenrichmen
Page 163 and 164: The nutritional quality and physica
Page 165 and 166: decapsulation improves the energy c
Page 167 and 168: starved versus enriched BSN. Lavens
Page 169 and 170: 1ANNEX 4TABLEDetermining hatching p
Page 171 and 172: 4ANNEX 4TABLE Hydrating and decapsu
Page 173 and 174: 7ANNEX 4TABLE1. Set up the hatching
Page 175 and 176: grades the particles and washes the
Page 177: 2. Stock estimation when postlarvae
Page 181 and 182: ANNEX 7 FIGURE1The size of the mesh
Page 183 and 184: 8ANNEXSize managementAS MENTIONED I
Page 185 and 186: 2. BehaviourThe behavioural charact
Page 187 and 188: ANNEX 8 FIGURE3Changing the stockin
Page 189 and 190: ANNEX 8 FIGURE4Orange claw (OC) and
Page 191 and 192: 9ANNEXFarm-made pond feedsTHIS ANNE
Page 193 and 194: ANNEX 9, Figure 3Farm-made feedsnee
Page 195 and 196: 4ANNEX 9TABLEFarm-made grow-outfeed
Page 197 and 198: which the requirements are applied.
Page 199 and 200: Carapace:Caridean:Cephalon:Chela:Ch
Page 201 and 202: Genital pores:Gill chamber:Greenwat
Page 203 and 204: Puddling:Rostrum:Salinity:Sequester
Page 205 and 206: ConversionsTHIS SECTION OF THE ANNE
Page 207 and 208: Financial considerationsSOME COMMEN
Page 209 and 210: ReferencesAlston, D.E. & Sampaio, C
Page 211 and 212: Fujimura, T. & Okamoto, H. 1972. No
Page 213 and 214: New, M.B., Singholka, S. & Vorasaya
Page 215: This new manual, which replaces an
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Farming freshwater prawns

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