Farming freshwater prawns

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power supplies, or individualtank aerators being blocked orleft turned off. Losses also occurbecause late-stage larvae (close tometamorphosis) jump quite a lotand some get stranded above thewater line. Some hatcheries cutout a strip of mosquito screen andPREVENT the introduction of disease organisms or chemical contaminantsby workers and visitors entering the hatchery by using chemical with epoxy-resin in the region ofstick it to the inside of the tankfootbaths, and washing hands prior to and when returning to work. the water surface level. Since thewater level varies it is suggestedKEEP all equipment, supplies, and food clean at all times. Special carethat the strip of mosquito nettingshould be taken before a new larval cycle is begun.should be about 12 cm wide. ThisAVOID disease transfer by using equipment for only one recirculation helps to prevent larvae becomingsystem. Keep another set for each system.stranded.It cannot be over-stressedthat while this manual attemptsto lay down guidelines for a particular method of freshwater prawn culture, successfulhatchery operation is a blend between factory discipline and husbandry. The most importantthing to remember is that if you do not pay close attention to your animals, yourhatchery will fail. You and your staff must always closely observe the behaviour of yourlarvae and the condition of your tanks.Additionalrecommendations forrecirculation system hygiene⌖⌖⌖BOX 12Problems of disease and predationSeveral diseases affect freshwater prawn larvae. These are summarized within Table 10.Some preventative measures are listed in Table 11. More information is provided inJohnson and Bueno (2000). If you see problems which may be caused by disease you shouldseek the advice of local aquatic animal health specialists (where available) and microbiologistsfor identification and treatment purposes. Some brief notes are provided in Box 13.Some hatcheries use formalin (200-250 ppm daily dip for 30 min) as an effective remedy forprotozoal and hydrozoan infections and fungal diseases. Where the treatment period is shortit is best to apply it when the tank water level is very low (10-15 cm) so that it can be rapidlyflushed with ‘new’ 12 ppt water after treatment. The flushing process should continue forone hour. Aeration must continue during treatment as normal. Formalin can also be used ata lower level of 25-30 ppm for a longer period, followed by a water change after 24 hours.Mortalities from hydroid infestation can also be reduced by transferring healthy larvae tonewly disinfected tanks every 5-10 days. Malachite green (0.2 ppm daily dip for 30 min) hasalso been used for treatment. However, you are recommended not to use this substancebecause it may be toxic to hatchery workers; its use is banned in some countries. Similarly,the use of copper sulphate (previously suggested as a 0.4 ppm dip for 6 hours) is not now recommended.Antibiotics are sometimes used to control filamentous bacteria (Leucothrix spp.).Some hatcheries use lime (CaO) as a prophylactic between larval cycles. Othersapply antibiotics and/or sulpha drugs as prophylactics but this practice is definitely notrecommended in this manual, partly because their use in aquaculture may become bannedin future and partly because of the danger of inducing the development of resistant diseasestrains. The use of these and other treatments for disease problems is described in Johnsonand Bueno (2000).FRESHWATER PRAWNS66
TABLE10The major diseases known to affect freshwater prawns,and their exterior symptomsVIRUS DISEASESBACTERIAL AND RICKETTSIAL DISEASESFUNGAL DISEASESMacrobrachium hepatopancreaticparvo-like virus (MHPV): none; notassociated with significant morbidityor mortality.Black spot (sometimes called brownspot or shell disease): one or manymelanized lesions on the cuticle; oftencaused by opportunistic bacteriawhich enter following physicaldamage; problem may disappear atthe following moult but sometimesdevelops into deep spreading lesions;reduces marketable value of harvestedprawns.Lagenidium infection: affects larvae:an extensive mycelial network can beseen through the exoskeleton; candecimate hatchery populations within24 hours.Macrobrachium muscle virus(MMV): muscle tissues becomeopaque, followed by necrosis; occurswithin 10 days of stocking PL and maycause up to 50% mortality.Appendage necrosis: larvalappendages become necrotic andmelanized; affected larvae do not eatand may become bluish in colour; maybe associated with a heavy surfaceburden of the filamentous bacteriumLeucothrix.Infections by Fusarium andSaprolegnia: cause necrosis andmelanization; follow physical damage.White spot syndrome baculovirus(WSBV): targets the cuticular epidermis,stomach, gills and hepatopancreas;important disease in marineshrimp; Macrobrachium is known tobe a carrier but it is not yet certainwhether WSBV causes mortalities infreshwater prawns.Internal infections: caused by a varietyof Gram negative bacteria such asVibrio spp. and Aeromonas spp.;feeding discontinues; discolouration ofthe body (usually pale and white)occurs; animals listless; infections byluminous vibrios are usually serious.Yeast infections: muscles appear yellowish,bluish or grey; causes heavymortalities in grow-out ponds; particularlyprevalent when temperatures arelower than optimal and organic matteris allowed to accumulate and eutrophicationoccurs.Nodavirus (MRNV): opaque whitishappearance of the abdomen, followedby severe mortalities.Bacterial infection caused byEnterococcus: necrosis in musclesand hepatopancreas; begins in thehead portion and proceeds to the tail;animal appears opaque; exacerbatedin high temperature (33-34°C) andhigh pH (8.8-9.5) conditions.Rickettsial disease: larvae becomewhite throughout their bodies andgenerally inactive before death; infectedpopulations experience significantmortalities.NOTE: THIS TABLE DESCRIBES THE EXTERIOR SYMPTOMS AND THOSE THAT CAN BE SEEN BY SIMPLE MICROSCOPIC EXAMINATION. DISEASES DETECTABLE BYOTHER TYPES OF INVESTIGATIONS ARE MENTIONED IN THE ORIGINAL REVIEW (JOHNSON AND BUENO, 2000)As noted earlier in this section, severe disease problems very frequently begin becauseof basic management failure. Such failures will be minimized if you follow the recommendationsin this manual. However, diseases will still sometimes occur. You are recommended tototally discard any seriously infected batch, to drain the tanks, and to disinfect all the hatcheryequipment. Do not waste time on treating a serious infection. Cut your losses, try to findout the basic cause of the problem, eliminate it, and start a new larval batch.CHAPTER 467
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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
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 and 38: cal quality and its lack of predato
Page 39 and 40: CHOOSING YOUR SITE: SOIL CHARACTERI
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: ing to avoid BSN leaving the tank.
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
Page 89 and 90: 5CHAPTERPostlarval holdingand nurse
Page 91 and 92: Figure 39Substrates can beused in n
Page 93 and 94: FIGURE41Postlarvae in plastic bags
Page 95 and 96: pH and temperature of the rearing f
Page 97 and 98: It is difficult to recommend exact
Page 99 and 100: 6CHAPTERGrow-out phaseFRESHWATER PR
Page 101 and 102: FIGURE44ponds may become low enough
Page 103 and 104: FIGURE46Pond banks should have the
Page 105 and 106: FIGURE50The dissolved oxygen levels
Page 107 and 108: Figure 53Where thetopography of the
Page 109 and 110: 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
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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
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This new manual, which replaces an
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Farming freshwater prawns

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