Farming freshwater prawns

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ANNEX 4 FIGURE1Artemia cysts hydrate, break, have an ‘umbrella’ stage, and then hatch1dry cyst2hydrated cyst3breaking stage, showing naupliuseye4embryo in ‘umbrella’ stage5hatching instar I naupliusattached to hatchingmembraneSOURCE: EMANUELA D’ANTONIFRESHWATER PRAWNS154
The nutritional quality and physical size of the nauplii which hatch from Artemiacysts (referred to elsewhere in this manual as brine shrimp nauplii – BSN) vary enormouslyfrom source to source and even (in the case of nutritional quality) between individualbatches from a single source. Of particular importance is the level of an essentialpolyunsaturated fatty acid, eicosapentaenoic acid [EPA] (20:5n-3), which depends on thecomposition of the primary food available to the brine shrimp in the locations where theyoriginate. Further reading on this topic can be found in Merchie (1996). The nutritionalquality of Artemia nauplii (BSN) can be improved by enrichment, as described later in thisannex. For practical purposes, cysts can be categorized by the size of the first stage naupliithey produce: small (~430 µm), medium (~480 µm) and large (~520 µm) but the size is notso important for freshwater prawns as it is for some marine fish. Freshwater prawns caningest BSN of all sizes.The two other important Artemia factors which vary from batch to batch are thenumber of cysts per gram and their hatching rate. The most effective way of checking thebasic quality of the cysts you buy is to measure the hatching efficiency, because this is acheck not only on the percentage of cysts that hatch but is also a means of judging howmuch detritus (e.g. empty cyst shells, sand, salt, etc.) that the batch contains. Hatchingefficiency is defined as the number of BSN hatched per gram of cysts purchased. Premiumquality cysts from the Great Salt Lake should yield about 270 000 BSN per gram of cysts.Smaller cysts (e.g. the San Francisco Bay source) may provide up to 320 000 BSN per gramof cysts. However, some sources yield as low as 100 000 BSN per gram of cysts. Good qualitycysts should start to hatch after 12-16 hours incubation and all should have hatched by24 hours (Van Stappen, 1996). This measure of quality is known as the hatching rate (HR).Hatching rate curves for two samples of cysts are illustrated in Annex 4, Figure 2. A procedurefor determining hatching percentage, hatching efficiency and hatching rate is givenin Annex 4, Table 1; this should be used to compare different sources of cysts, so that youknow whether you are getting value for money or not.Choosing to feed prawn larvae with 24 hour old or with 48 hour old (timed from whenthe cyst incubation process starts) BSN depends partly on the rate of Artemia hatching(characteristic of the source and the environmental conditions you supply it with) and partlyon operator preference. Some hatcheries use 24-36 hour old BSN; others use 24-36 hourold BSN at first and progress to the use of larger 48 hour or 72 hour old BSN (reared on‘greenwater’ or rice bran) as the prawn larvae grow. However, the use of 24 hour old BSNenables you to use the same equipment on a daily basis. Keeping BSN longer before usingthem is more expensive as producing food to rear them needs more equipment.Artemia cysts need treatment before the hatching process commences to ensure maximumhatching occurs and to maintain healthy conditions in larval rearing tanks. Thisprocess is described below.2. Treatment of cysts before hatchingArtemia cysts are by nature contaminated with bacteria, fungal spores, and other microorganisms,and may be contaminated with organic impurities. The use of BSN which arisefrom cysts that have not been disinfected can cause health problems in larval rearingtanks; poor water quality and larval diseases (especially those caused by Vibrio spp.) canbe introduced when untreated empty shells, unhatched cysts and cyst hatching water aretransferred to the larval rearing tanks. The decapsulation process also disinfects the cystsANNEX 4155
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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
Page 111 and 112: Figure 58This freshwaterprawn pondh
Page 113 and 114: FIGURE59 cont.CROSS SECTIONSOURCE:
Page 115 and 116: Figure 64Long-shaftaeratorin action
Page 117 and 118: there is only a single stocking), t
Page 119 and 120: TABLE16Lime requirements for treati
Page 121 and 122: semi-intensive stocking rates vary
Page 123 and 124: Keeping rootedplants out ofyour pon
Page 125 and 126: 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: 4ANNEXSource, hatching andenrichmen
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 and 178: 2. Stock estimation when postlarvae
Page 179 and 180: animal, particularly within the gil
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
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New, M.B., Singholka, S. & Vorasaya
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This new manual, which replaces an
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Farming freshwater prawns

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