Farming freshwater prawns

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differences between these morphotypes are so dramatic. An OC metamorphoses into a BCafter it becomes larger than the largest BC in its vicinity (Annex 8, Figure 4). As a new BCmale it then delays the transition of the next OC to the BC morphotype, causing it in turnto attain a larger size following its metamorphosis. The newly transformed BC is larger(sometimes much larger) than the largest BC previously present. This is known as the‘leapfrog’ growth pattern, because the weight of one type of animal leaps over another.BC males dominate OC males, regardless of their size, probably because of theirlarger claws. A prawn that has metamorphosed into a BC male and is larger than any otherBC in its vicinity (following the ‘leapfrog’ growth pattern) becomes the most dominantprawn in the vicinity until it is overtaken by another prawn metamorphosing from OC toBC. The ‘leapfrog’ growth pattern results in the gradual descent in the social rank of existingBC males. When a new and larger BC appears on the scene, the ‘social ranking’ of allBC males present before that event fall.Growth suppression of small malesThe growth of runts (SM) is stunted by the presence of BC males. Food conversion efficiencyseems to be the major mechanism controlling this growth suppression in runts.Runts have poorer (higher FCR) feed efficiency when BC males are present. This seems tobe governed by physical proximity; the phenomenon has not been demonstrated whenthese two types of prawns are separated, even when they are in the same water system andcan see each other (i.e. chemoreception and sight are not factors).As noted earlier in this annex, SM are sexually active. While they stay small theyattract less aggression from dominant BC males (which are busier interacting with OCmales) and are probably less vulnerable to cannibalism since they can shelter in smallcrevices. Being small and highly mobile, runts can find food on the bottom before beingchased away by larger prawns, whether they be males or females. If BC males are removedfrom the population, some runts will increase their growth rate, and transform into OCmales and, finally into BC males, following the normal ‘leapfrog’ growth pattern. This highlightsthe importance of regular cull-harvesting.4. Managing grow-out in the light ofheterogeneous individual growth (HIG)Several important characteristics of freshwater prawns that affect the potential harvestfrom grow-out have been described above. These create various management options; acheck-list of those procedures is provided below. The first three techniques have beendescribed in the main text of this manual. The final technique (monosex culture) is a possiblefuture development and is not part of the current manual. In grow-out management:there is an opportunity to improve the final harvest, both in terms of average marketsize and total production, by grading, because the prawns that are going to growfastest become identifiable within 2-5 weeks after the PL metamorphose from larvae.there is an opportunity to increase the final harvest, both in terms of average marketsize and total production, by cull-harvesting. This removes the BC males,many of the OC males, and the larger females, thus encouraging small males to growfaster in the absence of dominant males (sometimes known as compensatorygrowth).there are opportunities for increasing productivity through the use of substrates.These provide refuges for newly moulted prawns (which increases survival) andFRESHWATER PRAWNS182
ANNEX 8 FIGURE4Orange claw (OC) and blue claw (BC) male Macrobrachium rosenbergiigrow with a leapfrog patternSOURCE: REPRODUCED WITH PERMISSION FROM BLACKWELL SCIENCE FROM KARPLUS, SAGI AND MALECHA (2000), WHERE THE ORIGINAL SOURCES OF THETHREE ILLUSTRATIONS ARE CITEDANNEX 8183
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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
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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
Page 137 and 138: allowed to become too low and there
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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 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: ANNEX 8 FIGURE3Changing the stockin
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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