current status of freshwater prawn culture in vietnam and the development and transfer of seed...

FISHERIES SCIENCE 2006 72 1ndash12

Blackwell Science LtdOxford UKFISFisheries Science0919 92682006 Blackwell Science Asia Pty LtdFebruary 2006721112Review ArticleFreshwater prawn culture in VietnamNT Phuong et al

Corresponding author Tel 81-298-38-6630 Fax 81-298-38-6316 Email marwiljircasaffrcgojp

aPresent address Graduate School of Kuroshio Science KochiUniversity Kochi 783-0093 Japan

bPresent address National Research Institute of FisheriesScience Yokohama Kanagawa 236-8648 Japan

Received 8 April 2005 Accepted 26 August 2005

Review Article

Current status of freshwater prawn culture in Vietnam and the development and transfer of seed

production technologyNguyen Thanh PHUONG1 Tran Ngoc HAI1 Tran Thi Thanh HIEN1 Tran Van BUI1 Do Thi Thanh HUONG1 Vu Nam SON1 Yoshinori MOROOKA2a Yutaka FUKUDA2b AND Marcy N WILDER2

1College of Aquaculture and Fisheries Cantho University Can Tho City Vietnam and 2Japan International Research Center for Agricultural Sciences Tsukuba Ibaraki 305-8686 Japan

ABSTRACT In Vietnam the giant freshwater prawn Macrobrachium rosenbergii is becoming anincreasingly important targeted species as its culture especially in rice fields is considered to havethe potential to raise income among impoverished farmers The production of M rosenbergii based onaquaculture reached over 10 000 tons per year in 2002 having increased from about 2500 tons sincethe 1990s Until recently lack of a stable supply of seed had been an important obstacle to the furtherexpansion and development of M rosenbergii culture but cumulative research on larval rearing espe-cially in the 1990s has led to the development of new seed production technology based on the lsquomod-ified stagnant green water systemrsquo Following its dissemination by the efforts of provincial authoritieshatchery operators and farmers the freshwater prawn seed production industry developed rapidly inthe Mekong Delta with over 90 hatcheries producing 765 million postlarvae in 2003 This is consid-ered to have affected the expansion of ricendashprawn farming in the Mekong Delta leading to increasedaquacultural production in the region This paper reviews the current status of freshwater prawn cul-ture in Vietnam and background history and presents a socioeconomic evaluation of seed productiontechnology implementation

KEY WORDS freshwater prawns green water Mekong Delta ricendashprawn farming seedproduction

AQUACULTURE INDUSTRY IN VIETNAM AND GENERAL STATUS OF FRESHWATER PRAWN CULTURE

Vietnam has a high potential for aquaculturedevelopment due to the countryrsquos favorable condi-tions in terms of natural habitats such as pondsrice fields rivers lakes estuaries and coastalareas The total area of water bodies that may be

targeted for aquaculture is estimated to be 16m haby the Vietnamese government1 Since the begin-ning of the 1990s the aquaculture sector inVietnam has been expanding in terms of culturearea production targeted species and degree ofmanagement intensity Production based onaquaculture has been increasing rapidly in com-parison with that from capture fisheries particu-larly recently (Fig 1) However in 2003 the totalarea of water including freshwater brackish waterand saline areas used in aquaculture was onlyabout 1m ha or under 60 of the total potentialarea

Recently some species and certain culture sys-tem types have contributed significantly to thegrowth of the aquaculture sector in terms of pro-duction and export values The black tiger prawn

2 FISHERIES SCIENCE NT Phuong et al

Peneaus monodon cultured in saltwaterndashbrackish-water areas and Pangasius catfishes Pangasiushypophthalmus and P bocourti cultured in fresh-water areas are most important showing the high-est production levels and constant growth of theindustry (Figs 23)2ndash4 Other important aquaculturetargets include the giant freshwater prawn Macro-brachium rosenbergii tilapia Oreochromis niloti-cus mollusks Anadara granosa and Meretrixmeretrix and indigenous fishes such as the climb-

ing perch Anabas testudineus and snakehead fishChana striata and C micropeltes There are manytypes of production systems observed in Vietnam-ese aquaculture not only are intensive and semi-intensive forms of aquaculture practiced but alsoextensive systems where rice cultivation is inte-grated with fish or prawn culture Much of theblack tiger prawn and Pangasius catfish culture ishighly intensive while other species are culturedunder semi-intensive or extensive systems

Total aquaculture production in 2004 slightlyexceeded 1 150 000 tons of which brackishwateraquaculture constituted 510 400 tons (mainlysaltwater-brackishwater shrimp at 290 000 tons)while freshwater aquaculture constituted 639 700tons (mainly catfish at 315 000 tons) The export val-ues of saltwater-brackishwater shrimp (sim$US12bn)and catfish ($US300m) comprised the largest pro-portion of the total value of the fisheries sector25 Nofigures corresponding to the export of freshwaterprawn has been reported as this product isdestined mostly to local markets (only a very smallquantity is exported)

Currently although the freshwater prawn cultureindustry is not equal to the scale of the saltwater-brackishwater prawn culture industry (Fig 2) thegiant freshwater prawn Macrobrachium rosen-bergii which is indigenous to the Mekong Delta isbecoming an increasingly important target spe-cies The culture of this species especially in ricefields has been a traditional activity which wasbased mainly on wild seed collected from riversand other freshwater bodies However lack of a sta-ble seed supply was a significant obstacle to thefurther expansion and development of ricendashprawnfarming systems Because the giant freshwaterprawn is a high-value species its culture by impov-erished farmers is considered to have the potentialto raise income and contribute to enhanced ruraldevelopment Therefore Vietnamrsquos Ministry ofFisheries has put forth that the annual productionof M rosenbergii must reach 60 000 tons using32 000 ha by 20106 The Vietnamese Governmenthas also implemented a policy called lsquorestructuringof agricultural production and its products con-sumptionrsquo7 In order to address the needs of thisburgeoning industry basic and applied researchhas been conducted in order to develop appropri-ate seed production technology and verify the useof artificial seed in ricendashprawn farming in theMekong Delta

Initial research on the larval rearing ofM rosenbergii commenced in the early 1980s andwas undertaken by Vietnamrsquos Cantho Universityand the Research Institute of Aquaculture no 2although the first hatchery was established outsideHo Chi Minh City in Vung Tau in 19758 Basic

Fig 1 Changes in capture fisheries and aquacultureproduction and area under culture in Vietnam from1991-20031

0

500

1000

1500

2000

2500

91 92 93 94 95 96 97 98 99 2000 2001 2002 2003 2004

Time (year)

)tm 000

1 x( noitcudorP

0

200

400

600

800

1000

1200

)ah 0001 x ( aer

A

Production (capture)

Production (aquaculture)Culture area

Fig 2 Production levels of major farmed commoditiesin Vietnam in 200323

0 100 200 300 400 500 600 700

Marine shrimp

Freshwater prawn

Mollusks

Catfishes

Tilapia

Other commodities

Production (x 1 000 mt)

Fig 3 Production and growth of the saltwaterndashbrack-ishwater shrimp and catfish industries from 1991ndash200324

0

50 000

100 000

150 000

200 000

250 000

300 000

350 000

1994 1997 1999 2000 2001 2002 2003 2004

Time (year)

Pro

duct

ion

(mt

)

Shrimp

Catfishes

Freshwater prawn culture in Vietnam FISHERIES SCIENCE 3

research using rearing systems such as the openclearwater system the closed clearwater systemand the green water system was conducted How-ever at that time it appeared that better resultscould be achieved with the open clearwater systemin comparison to other systems and it was there-fore decided to use this system in commercial pro-duction Several hatcheries were then establishednear Ho Chi Minh City and in the Mekong DeltaHowever these hatcheries faced technical andmanagement-related difficulties that inhibitedthem from maintaining operations leaving onlyone state-owned hatchery located in Can ThoProvince in the 1990s Most notably the openclearwater system hatcheries were built at verylarge scale (greater than 100 m3 capacity) makingit difficult for farmers to adopt and requiring largeamounts of sea water for the daily exchange ofwater For such reasons at least until 1998 fresh-water prawn hatcheries in the Mekong Deltaceased to function and further development of thericendashprawn farming industry was held back by ashortage of seed9

However after a period of active research a newrearing system referred to as lsquothe modified stag-nant green water systemrsquo has been in place since1998 This method of rearing is especially suitablefor the household scale and Cantho University hasconducted a series of training courses targetingprovincial authorities and private individualsallowing this technology to be transferred widelythrough the Mekong Delta and to other parts ofVietnam The concept of this system arises fromwork10 in which water quality is maintained by nat-ural microalgae (particularly Chlorella spp) in therearing water This seed production technologymakes use of this concept and has been adaptedfor use according to the environmental and socialneeds of the Mekong Delta

This review focuses on the status of freshwaterprawn farming in the Mekong Delta especially inthe context of ricendashprawn farming and also tracesthe development of the seed production industrywith an overall discussion of the socioeconomiceffect of technology development

GENERAL MODES OF FRESHWATER PRAWN CULTURE IN VIETNAM

The history and global status of M rosenbergiifarming is reviewed by New and Valenti11 In theearly 1980s global production was recorded as justabove 5000 tons but reached more than 17 000tons by the end of the decade plateauing to about20 000 tons in the early 1990s In the late 1990sChina began to contribute greatly to M rosenbergii

farming production along with Bangladesh andIndia culminating in a global production volumeof nearly 130 000 tons in 1998 In the FAOrsquos 2002statistics world production of M rosenbergii farm-ing is given as nearly 200 000 tons with a marketvalue of over $US600m12 In Vietnam production ofM rosenbergii based on aquaculture was estimatedto be less than 3000 tons per year throughout the1990s with an additional 3000 tons of productionbeing contributed by conventional fishing activity9

The production of M rosenbergii based on aquac-ulture alone exceeded 10 000 tons in 20021 In thisway the freshwater prawn culture industry is smallcompared to Vietnamrsquos saltwater-brackishwaterprawn industry and the freshwater prawn cultureindustry in other countries but is showing contin-uous progress in its development and has alreadybecome a means of allowing impoverished farmersto raise their income

In Vietnam M rosenbergii is cultured in manyways but ricendashprawn farming and fence cultureare the most important production models Thetotal area of ricendashprawn culture was estimated tobe around 750 ha in 200313 and fence culture con-sisted of 1516 units in 2002 (pers comm Depart-ment of Agriculture of Dong Thap Province 2002)Other culture modes are practiced in limited areas

The culture of prawns in rice paddy fields is atraditional practice that farmers have developedusing their own resources and has received atten-tion from the Vietnamese government as a meansof helping to raise the standard of living of impov-erished farmers Original methods are based on therecruitment of seed into farms by sluice gates withthe changing of tides seed would then be trappedand allowed to grow to full size Since early 1980ssome farmers began to stock prawn seed collectedfrom wild sources in their rice paddies and atpresent the culture of freshwater prawns in ricefields is common Of note areas where ricendashprawnfarming have taken root are located inland wherewater is completely fresh however since theMekong Delta is about 1 m above sea level inlandwater levels are greatly affected by the change oftides

With the recent success of artificial seed produc-tion technology in hatcheries ricendashprawn farminghas intensified and management practices havebecome very diverse More in-depth studies arerequired to fully categorize the ways in which thisform of aquaculture is carried out in the MekongDelta but there are two general types of cultureThe first type is an integrated culture where prawnfarming and rice cultivation are carried out simul-taneously as a form of mixed farming and the sec-ond type is an alternate culture where prawnculture and rice cultivation are carried out on an


alternate basis as a form of lsquorelay croppingrsquo Alter-nate culture consists of two types (i) type 1 whereone prawn crop and one rice crop are carried out ina year and (ii) type 2 where one prawn crop andtwo rice crops are carried out per year The type ofculture that is practiced generally depends on

region of the Mekong Delta and farmersrsquo prefer-ences A general description of each type of cultureis described below and a diagram is shown inFigure 4 A map of the Mekong Delta indicateslocations of hatcheries targeted in the socioeco-nomic survey described later (Fig 5)

Integrated ricendashprawn culture model

The cropping pattern of this model consists of tworice crops as summerndashautumn rice from March toMayJune and winterndashspring rice from Decemberto March One prawn crop is carried out betweenApril and December This farming model is prac-ticed in the Vinh Long and Tra Vinh Provinces of theMekong Delta where farmers still produce two ricecrops per year and where there are low levels offlooding (Fig 5) Farms are designed with a sur-rounding trench comprising 20ndash25 of total ricepaddy area Mostly trenches are either fenced withfine nylon netting or are built with simple earthendikes for nursing prawns during the first period ofstocking After 3ndash4 weeks prawns reach 2ndash3 cm in

Fig 4 Diagram of the major types of ricendashprawn farm-ing Periods of prawn culture are indicated by solidarrows periods of rice cultivation are indicated bydotted arrows The short heavy dotted arrow ( ) indi-cates the period of nursing culture in integrated culture

Month 3 4 5 6 7 8 9 10 11 12 1 2 Summer-autumn rice Winter-spring rice

Integratedculture

AlternateCultureType1

AlternateCultureType 2

Fig 5 Mekong Delta hatcheries(a) map showing important areasof the three main forms of ricendashprawn farming and locations ofhatcheries targeted in the socio-economic survey detailed inlsquoSocioeconomic evaluation ofhatchery technologyrsquo and (b)hatcheries selected from districtsin each province where the high-est numbers of hatcheries werelocated Ring-shaped symbols onthe map show locations of sampleclusters

ProvincesMajor areas of prawn-

(a)

(b)

rice farming Vinh Long Tra Vinh Can Tho An Giang Dong Thap Integrated culture Alternate culture Type 1

Alternate culture Type 2

ProvincesHatchery survey Can Tho An Giang Dong Thap

Total no hatcheries 41 10 9 Targeted no hatcheries 10 3 4


body length and are ready to be released to thefarm At this point rice has already been sownor transplanted The production cycle of prawnis about 6ndash8 months but prawns are culturedtogether with summerndashautumn rice crop for onlyabout 2ndash25 months Stocking density ranges from15 to 5 individualsm2 depending on seed sizeWater is exchanged every 2 weeks in order to main-tain water quality levels suitable for aquacultureTypically a metal pipe connecting the rice fieldwith a nearby canal is filled with mud because ofthe topography of the Mekong Delta even inlandareas are affected by changing tides and water caneither be let into or discharged from the field athigh and low tides respectively This method isused in alternate culture models as well The pro-ductivity of this model varies widely according tostocking density and stocking size of seed andfarm management regimes (eg use of commercialfeeds vs fresh feeds such as snail and trash fish)Productivity is low ranging from about 40 kgha toover 500 kgha because of the small size range ofprawns at harvest and low survival rates

Alternate ricendashprawn culture models

As discussed there are two types of alternate cul-ture In type 1 prawns are stocked in April and har-vested in December before the winterndashspring ricecrop (DecemberndashMarch) In type 2 prawn cultureoccurs from July to December between two ricecrops (summerndashautumn MarchndashMayJune andwinterndashspring DecemberndashMarch) Type 1 has beendeveloping rapidly in flooded areas especially AnGiang and Can Tho Provinces (Fig 5) where morethan 350 ha operated in 2002 Hatchery-rearedpostlarvae are stocked directly into the rice fieldsor in small nursing ponds for 1 month Stockingdensities vary from 3 to 12 postlarvaem2 Prawnsare fed commercial pellets and fresh feeds Freshfeeds such as golden snail trash fish and crab arecheap and abundant during the flooding periodDuring this time (JulyndashOctober) water usuallyflows over the surrounding dykes and farms areconsidered to be in a state of overflow After 6ndash8 months of stocking prawns reach 50ndash110 g bodyweight and are ready to be harvested Prawn pro-ductivity is about 900 kgha In type 2 prawns arestocked into rice paddy fields when the summerndashautumn rice is harvested This model is suitable forareas of high flooding such as in An Giang DongThap and Can Tho Provinces (Fig 5) becausethere are very favorable natural conditions duringthe culture period such as high water level abun-dance of natural feeds and ready availability offresh feed components (eg snails trash fish and

small freshwater crabs) This model operated forabout 5ndash6 months therefore stocking of large-sized seeds (average 15 gindividual) is required inorder to ensure that the harvested prawns reach amarketable size The productivity of prawns in type2 (about 360 kgha) is much lower than in type 1(about 900 kgha) Table 1 shows a simple cost-benefit analysis for type 2 Net income levels basedon both rice and prawn production reached nearly$US2000 showing that prawn culture in rice fieldscan greatly supplement income obtained from ricecultivation only Data has been obtained for type 1alternate ricendashprawn farming and integrated farm-ing however in these two models large variationsin costs and income were observed indicatingsome instability in these types of farming systems

Therefore the proper selection of culture modelthat considers the natural circumstances of eacharea is crucial for successful aquaculture Howeverfor all models of aquaculture it is essential to pro-vide a stable supply of larvae to aquaculturistsThrough the 1990s only five hatcheries existed inthe Mekong Delta region and the Ho Chi Minh Cityvicinity (with only one of these fully operating)their production levels were not sufficient to meetthe needs of the industry and there was thus adependence on the use of seed obtained from nat-ural sources9 This was an obstacle to the furtherdevelopment of the industry until new seed pro-duction technology could be developed and dis-seminated Recirculating systems are commonlyused in large-scale hatcheries in most countrieswith M rosenbergii culture industries14 Howeverthe need to develop small-scale hatcheries that canbe implemented on a backyard basis was recog-nized and during the late 1990s and early 2000sthe modified stagnant green water system wasrefined and adapted to the needs of Vietnamrsquosindustry as detailed below

Table 1 Simple cost-benefit analysis for type 2 alter-nate ricendashprawn farming (12 prawnndashrice crops)

Item Mean plusmn SD

PrawnTotal cost ($USha) 907 plusmn 507Gross return ($USha) 2093 plusmn 1187Income ($USha) 1187 plusmn 840

RiceTotal cost ($USha) 379 plusmn 191Gross return ($USha) 1187 plusmn 840Income ($USha) 733 plusmn 273

Grand total income (rice and prawn) 1920 plusmn 940

$US1 = Vietnamese Dong (VND) 15 000 SD standarddeviation


STUDIES ON THE DEVELOPMENT OF TECHNOLOGY FOR PRAWN SEED PRODUCTION BASED ON THE lsquoMODIFIED STAGNANT GREEN WATER SYSTEMrsquo

Experiments on larval rearing were conductedduring 1998ndash2002 at Cantho Universityrsquos mini-hatchery15 These experiments included the effectsof type of rearing system rearing density feed con-tent and feeding regime algal densities source ofsaline water use of probiotics and size of rearingtanks on the development and survival of fresh-water prawn larvae At the outset in order toevaluate the feasibility of different larval rearingsystems as well as appropriate rearing densities foreach system a small-scale experiment was con-ducted comparing two water maintenance sys-tems the recirculating clear-water system and themodified stagnant green water system underdifferent stocking densities of 30 60 90 and120 larvaeL for each system Fiberglass tanks of100 L were placed under an opaque roof For therecirculating system water was recycled at rate of100ndash200 tank volume daily through a biofilterFor the modified stagnant green water systemgreen water from tilapia tank culture was added tothe prawn larval rearing tanks at a density of05 times 106 cells of algaemL before stocking of prawnlarvae No water was added or exchanged duringthe larval rearing cycle Larvae in both systemswere fed with Artemia nauplii (twiceday2 ArtemiamL) alone for the first four stages Fromstage four larvae were fed with custard (4 timesday) in the daytime and Artemia nauplii (onceday2 ArtemiamL) in the evening No siphoning wasconducted during larval rearing in either system

Table 2 shows the results length of rearing cycleand survival rate results The modified stagnantgreen water system yielded significantly better sur-vival rates (323ndash923) compared to the recirculat-

ing systems (274ndash525) The presence of algae inthe rearing water may help to stabilize water qual-ity and enhance the nutritional effects from thefeeding of Artemia hence shortening the timerequired to complete the rearing cycle This in turnmay lead to decreased cannibalism of larvae andpostlarvae thereby promoting higher survivalrates Based on the survival rates given in Table 2although lower stocking densities yield higher sur-vival rates it can be calculated that mid-level den-sities provide greater numbers of postlarvae uponcompletion of the rearing cycle Higher stockinglevels lead to decreased survival rates and thusdecreased efficiency For these reasons and dueto its simple management needs and promisingresults the modified stagnant green water systemwas then selected for further development usingsuggested stocking densities of 60ndash90 larvaeL1516

In order to develop appropriate larval feeds foruse in the green water system a series of ex-periments was conducted comparing feedingtreatments including regimens of Artemia incombination with commercial feeds and hand-made custards containing chicken egg powderedmilk and fish oil only or these three componentswith other ingredients such as shrimp flesh porkliver or cockle meat Custard in combination withArtemia yielded high survival rates but the use ofArtemia alone or in combination with commercialfeed yielded very poor results The simple custardcontaining egg powdered milk and fish oil wasthen selected for application to subsequent exper-iments In follow-up studies by Hien et al17 thelipid component of the custard was modified andthe effects of differing sources of lipids in combi-nation with lecithin on larval growth and survivalwere examined As a result it was found that a ba-sic recipe containing Anlene Gold powdered milk(New Zealand Milk Wellington New Zealand538 ww) chicken egg yolk (417 ww) 3squid oil and 15 lecithin yielded satisfactory sur-vival rates and body length of postlarvae Repre-sentative data from this study are shown in Table 3Increasing dietary lecithin from 15 to 30 didnot increase larval growth rates for this reasonsupplementation at 15 was considered mosteffective in terms of cost

It was also found that a feeding regime using 1ndash2 Artemia naupliimLday with custard feeding (adlibitum) four times daily was most suitable Higherdensities of Artemia nauplii or increased frequencyof daily feeding times did not improve the survivalof postlarvae In production terms this resultmeans that 21ndash24 kg of Artemia cysts and 20ndash24 kg of custard are needed to produce 1 times 106

postlarvae The optimal density of algae was deter-mined as 1 times 106 cells of algaemL in terms of sur-

Table 2 Larval development under the recirculatingand modified stagnant green water systems1516

Treatment Rearing cycle (days) Survival rate ()

Recirculating system30 larvaeL 34 52560 larvaeL 34 28890 larvaeL 34 317120 larvaeL 34 274

Modified stagnant green water system30 larvaeL 30 92360 larvaeL 30 46390 larvaeL 30 464120 larvaeL 30 323


vival rates of postlarvae (Table 4) In order toproduce green water large tilapia (50 g) cultured in1 m3 tanks at density of 10 fishm3 were fed withpelleted feed at a rate of 5 body weight per daykeeping water salinity at 12 ppt After 1 week ofrearing the culture was filtered through a 5 microm-mesh filter bag in order to selectively obtainmicroalgae consisting mainly of chlorella

Finally in order to apply the modified stagnantgreen water system to commercial production itwas necessary to evaluate the effects of differentsizes of rearing tanks on the development and sur-vival rates of postlarvae An experiment was con-ducted using differing tank volumes of 05 10 20and 40 m3tank with three replications for eachtreatment Stocking density was 60 larvaeL Greenwater was also added to the tanks at a density of1 times 106 cellmL before stocking larva Artemia(2 naupliimL) and custard were also fed to larvaeIt was found that the smaller tanks gave bettersurvival rate and productivity therefore rearingperiods of larvae and the tanks of 05ndash1 m3 wereselected for use in commercial hatcheries Brinefrom saltpans in Bac Lieu Province was found to besuitable for larval rearing As salinity ranges 60ndash140 ppt only a small amount of seawater is neces-sary to be used in seed production operation

These studies have provided concrete data forthe establishment of a complete technical package

for larval rearing for use in Vietnam especially inthe Mekong Delta18 The modified stagnant greenwater system performs as well or better than pre-viously existing larval rearing systems that includerecirculating or open water models The survivalrate of larvae until reaching the postlarvae-15 stage(15 days after metamorphosis) in the green watersystem averages about 40 (ranging 30ndash75) com-pared to 35ndash50 for open systems or 152ndash662for recirculating systems19

There have been other studies on larval rearingof giant freshwater prawn aiming to develop vari-ous technical packages by Vietnamese scientistsMost of this research focused on the improvementof larvae survival rate using differing rearing meth-ods feeds stocking density and origin of prawnThang19 focused his studies on the applicationof exchange and recirculating water methodsand found that the survival of larvae until thepostlarvae-15 stage could attain 35ndash50 for opensystems or 152ndash662 for recirculating systemsTinh20 studied the effects of stocking density on thesurvival rates of larvae until the postlarvae-15 stageusing water exchange methods finding that undera stocking density of 80ndash100 larvaeL a survival rategreater than 40 could be attained HoweverHung and Phuc21 reported that rearing larvae usingwater exchange methods showed a variation ofsurvival rates of larvae until postlarvae-15 from240 to 532 Yen22 conducted a study on theeffects of broodstock origin on the survival ratesof larvae applying water exchange methods Hefound that the survival rate of larvae until thepostlarvae-15 stage was 519 and 165 forbroodstock of Thai and Vietnamese origin respec-tively Phuc et al23 reported that on the experi-mental scale of 100-L tanks using water exchangemethods survival rate of larvae until the postlarvalstages varied depending on stocking densityyielding survival rates of 120 130 and 446 forstocking densities of 80 100 and 200 larvaeL

Table 3 Production of M rosenbergii postlarvae reared with six experimental diets containing differing lipid sourcesand levels

DietSurvival rate

()PL body length

(mm)Rearing cycle

(days)

Soybean oil 45 220 plusmn 82a 629 plusmn 004a 33Soybean oil 30 lecithin 15 320 plusmn 119a 645 plusmn 039ab 34Soybean oil 15 lecithin 30 487 plusmn 19b 675 plusmn 013b 34Squid oil 45 511 plusmn 72b 714 plusmn 005c 31Squid oil 30 lecithin 15 650 plusmn 54c 726 plusmn 017c 30Squid oil 15 lecithin 30 681 plusmn 81c 743 plusmn 011c 30

Differing letters indicate significant differences at P lt 005Data presented as mean plusmn standard deviation Survival rate of larvae () body length of postlarvae (PL) and length of rearing cycle

are shown17

Table 4 Effects of differing algal density on larvalrearing

TreatmentRearing cycle

(days)Survivalrate ()

No algae 38 117a

025times106 cellsmL 36 222b

1times106 cellsmL 35 414c


Differing letters indicate significant differences at P lt 005


respectively However these systems were notaccepted because each of the authors referred toabove conducted only one or a few researchprojects without implementing follow-up studiesto confirm the results In our collaborative studies(Japan International Research Center for Agricul-tural Sciences and Cantho University) a series ofresearch projects were undertaken until reproduc-ible results were obtained that could be easilytransferred to end-users Moreover our model isbased on simple techniques and has been scaled-up to meet the needs of commercial productionThe active transfer of this technology to end-usershas further led to its well-grounded establishmentin the Mekong Delta

TRANSFER OF FRESHWATER PRAWN SEED PRODUCTION TECHNOLOGY USING THE lsquoMODIFIED STAGNANT GREEN WATER SYSTEMrsquo

Based on the results of the green water technologydevelopment detailed above Cantho Universitybid for funding from the relevant organizationsand authorities in 2000 in order to transfer thistechnology throughout the Mekong Delta Provin-cial extension workers and technicians and pri-vate persons were mainly targeted Traineesvisited Cantho University to learn the techniquesin a hands-on format As part of the trainingcourse each person was responsible for his or herown hatchery-scale culture tank Cantho Univer-sity staff instructed the trainees in the full use ofthe technology including larval collection waterquality maintenance and feeding techniques By2003 six new provincial hatcheries were estab-lished in the Mekong Delta and 150 trainees rep-resenting the Mekong Delta provinces and otherprovinces throughout Vietnam including Ho ChiMinh City Dong Nai Binh Thuan Ninh ThuanBac Ninh Provinces received training fromCantho University24 A technical package detailingseed production methods is detailed in a manualwith accompanying audio-visual media that hasbeen distributed widely to users in Vietnam18 Thistechnology covers all aspects of the seed produc-tion process including hatchery constructionwater quality control feed development andend-marketing

SOCIOECONOMIC EVALUATION OF HATCHERY TECHNOLOGY

Following the rapid dissemination of freshwaterprawn hatchery technology throughout theMekong Delta in the early 2000s a survey of the

status of new hatchery construction was con-ducted in each province in mid-2003 It wasrevealed that there were 91 hatcheries in theregion belonging to both provincial authoritiesand private individuals (Fig 6) Nearly 80 of thesehatcheries were located in Can Tho (45) Ben Tre(13) An Giang (11) and Dong Thap Provinces(10) (Fig 7) Whereas in 1999 there was only onehatchery in the Mekong Delta these data under-line the rapid increase in hatchery establishmentduring the past 3ndash4 years This increase in hatcheryfacilities has been accompanied by a proportionalincrease in the frequency of green water technol-ogy implementation (Fig 8) revealing the effec-tiveness of technology transfer and confidence ofend-users towards the implementation of this

Fig 6 Development of freshwater prawn hatcheriesand annual production levels of postlarvae (PL) in theMekong Delta

010

2030

405060

7080

90100

1999 2000 2001 2002 2003

Year

seirehcta

h

oN

0

10

20

30

40

50

60

70

80

90

) sn

o ill im(

LP

fo

noitc

ud

orP

Number of hatcheries

Production of PL

Fig 7 Distribution of freshwater prawn hatcheries inthe Mekong Delta in 2003

Can Tho45

Ben Tre13

An Giang11

Dong Thap10

Tien Giang8

Long An5

Tra Vinh5

Vinh Long2

Ca Mau1


technology As a result during the past severalyears there has been an increase in yearly produc-tion from 1times106 to 775times106 postlarvaeyear (Fig 6)

The general status of the hatcheries in Can ThoAn Giang and Dong Thap Provinces was surveyedto obtain a representative sampling of MekongDelta hatcheries (Fig 5) Hatcheries in Ben TreProvince were not targeted due to its geographicproximity to Can Tho Province In these three prov-inces 60 hatcheries have been established andricendashprawn farming activities are strong In orderto achieve a survey rate of 30 17 hatcheries wereselected at random from the districts of each prov-ince with the largest number of hatcheries Hatch-ery operators were interviewed using a 10-pagesurvey containing questions on general back-ground information capacity of hatchery stockingdensity broodstock treatment type of rearing sys-tem used feeding practices investment costs andrunning costs and were asked to report actualincome levels Survey rates differ according toprovince this is due to factors such as the absenceof the hatchery operator at the time of the visit orthe inability of the operator to provide a full set ofdata necessitating particular hatcheries to beexcluded from the analysis

Based on this survey it has been revealed thatthe status of technology implementation is as fol-lows With the exception of some hatcheries apply-ing the recirculating system almost all of thehatcheries (882 of the surveyed hatcheries) havebeen applying the modified stagnant green watersystem (Fig 8) The hatcheries were normallysmall-scale with total volume of rearing tanks of10ndash40 m3 normally of 20ndash30 m3 (Table 5) Rearingtanks mostly consisted of composite with a volumeof 05ndash1 m3tank Regarding management prac-tices most of the hatcheries based their operationson technology transferred from Cantho UniversitySome hatcheries used wild broodstock (52 of allhatcheries) or farmed broodstock (48) Prawnbroodstock showed a weight range of 20ndash160 gaveraging 50 g The number of larvae that could beobtained from 1 kg of broodstock ranged from150 000 to 500 000 larvae averaging 322 850 larvaeLarvae were stocked at a density of 40ndash60 larvaeLGreen water from tilapia culture media was used toinoculate to rearing water and Artemia nauplii andcustard were the main feed used for larvae duringrearing The rearing cycle normally lasted for 25ndash45 days depending on season Most hatcheriesachieved very good results with survival rates of20ndash90 to postlarvae-15 averaging 453 in CanTho 362 in Dong Thap and 467 in An GiangProvinces (Table 5)

In analysis of the green water technology ofparticular interest is the initial investmentrequired to set up a hatchery Costs cover a verylarge range according to the scale of each facility(eg total capacity and number of aquaria) Aver-age capital investment was $US2500 and did notshow a large deviation from the average but oper-ational costs showed a very large range of varia-tion (Table 6) In this way a hatcheryrsquos ability toproduce postlarvae depends greatly on rearingmethods and number of cycles There is not oneway to characterize the economic character of thehatcheries but an examination of the data of the17 hatcheries showed an average net income of$US7709 was achieved As revealed from the rangeof variation it can be considered that even if facil-ities sufficient to meet high production levels areconstructed it is necessary to make full use of the

Fig 8 Hatcheries using the modified stagnant greenwater system and open and recirculating systems in theMekong Delta

0

10

20

30

40

50

60

70

80

90

100

1998 1999 2000 2001 2002 2003

seirehctahfoo

N

Green water system Open and recirculating systems

Table 5 Characteristics of prawn hatcheries in surveyed provinces of the Mekong Delta

ProvincesTotal volume of

rearing tankshatchery (m3)Stocking density

(larvaeL)Rearing cycle

(days)Survival rate

()

Can Tho 288 plusmn 147 60 plusmn 124 25ndash45 453 plusmn 198Dong Thap 388 plusmn 315 55 plusmn 129 30ndash45 362 plusmn 94An Giang 167 plusmn 577 533 plusmn 577 30ndash45 467 plusmn 231


facilities by maximizing the number of productioncycles implemented as well as promoting othermeasures that lead to a stabilization of produc-tion In particular data presented on operatingcosts (average $US1457) and net income($US7709) suggest that there still exist risks associ-ated with running a hatchery as a business enter-prise (Table 6) The cost of larval feed includingArtemia and custard comprised 42 of total costsbeing the highest portion of total operating costsfollowed by the costs of brine water and labor(Fig 9)

In order to present a detailed case study forhatchery operations an additional hatchery in CanTho Province was selected and the hatchery ownerwas given a record book to record all costs associ-ated with three production cycles As shown by theresults in Table 7 in a typical year in which threeproduction cycles with a capacity of 10 m3 wereperformed the cost of broodstock larval feedsincluding custard and Artemia rearing water elec-tricity gasoline labor and other operational costsare calculated total operational costs were$US1777 After subtracting total costs from grossincome an average net income of more than$US5000 can be expected25 However these data

are from only one case study in this way the scaleof the facility number of production cycles andother operational factors greatly influence overallprofits More detailed analysis is required in subse-quent surveys

Table 6 Economic parameters of prawn hatcheries in the Mekong Delta

Productivity(thousand PLhatcheryyear)

Capital investment($UShatchery)

Operation costs($UShatcheryyear)

Net income ($UShatcheryyear)

1134 (180ndash5000) 2500 (2000ndash2667) 1457 (353ndash4733) 7709 (1200ndash33 333)

Table 7 Cost-benefit analysis for a standard prawn hatchery of 10 m3 capacity with three operating cycles per year25

Itemized operational costs

Productionoperation cycles per

year Unit

Unitcost

($US)

Quantity1production

cycle

Total (for 3operation

cycles)($US)

Broodstock 3 kg 667 2 40Artemia 3 kg 100 15 450Custard 3 kg 467 7 98Freshwater 3 m3 013 20 8Brine 3 m3 20 2 120Labor 3 Man-months 333 4 400Electricity 3 KW 01 624 187Gasoline 3 L 038 7 8Other costs per cycle 3 Cycle 443 133Depreciation for fixed costs (10 years) 3 Cycle 111 333Total operating costs 1777

Harvest (number of postlarvae at PL 15 stage per year = 1 034 700)Gross income per year (assumption of

$US1 for 150 PL)6898

Net income per year ($US) 5121

Fixed costs in $US Total investment for hatchery housing materials ($US1000) assorted equipment ($US667) tanks ($US1333)materials ($US333) = $US3333 Depreciation for fixed costs (10 years) is calculated as (fixed costs times 110) = $US333

Fig 9 Operating costs in prawn hatcheries

Feed

42

Broodstock

8

Labor

13

Brinewater

13

Other

24


GENERAL DISCUSSION AND FUTURE PROSPECTS

Both experimental and practical seed productionof Macrobrachium rosenbergii have been con-ducted in Vietnam generally in the Mekong Deltafor several decades However these activities havereached a very dynamic state only recently This isbecause the techniques required to implement themodified stagnant green water system are verysimple and can be practiced by nearly any personwith a minimum of training Investment and pro-duction costs are also low These conditions makethe system appropriate for use in household-scaleproduction Further the need for only limited useof brackish water (obtained from saltpans) due tothe fact that rearing water does not need to beexchanged means that it is possible for hatcheriesto be established in freshwater areas located farfrom coastal areas With the increasing demand onprawn postlarvae for grow-out seed production offreshwater prawn harbors great advantages fordevelopment Support from central and local gov-ernments in relation to agricultural restructuringpolicies and support from research institutes anduniversities have also played an important role inthe development of prawn seed production in theMekong Delta and Vietnam

However the modified stagnant green water sys-tems may incur problems especially during therainy season Large-scale hatcheries or large rear-ing tanks are sometimes difficult to manage forlarval availability feeding and water quality control(especially water temperature due to prolongeddecrease in atmospheric temperature) There isadvantage in using brine for larval rearing espe-cially when it is highly concentrated as less volumewould be required However servicing where anintermediary is employed to obtain seawater fromsaltpan areas and provide it to the hatchery opera-tor and water quality need to be controlled Inaddition often there is a very high demand forprawn seeds but during a short period of severalmonths before and after the rainy season whichhas started to put pressure on seed productionactivities At present broodstock used in seed pro-duction is mainly collected from natural waters soit is becoming increasingly urgent to develop a pro-gram of broodstock domestication These meritsand risks relating to seed production in theMekong Delta have been frequently observed byhatchery managers and technicians

Prawn farming in the Mekong Delta hadremained at low levels until hatchery-reared seedbecame widely available in the early 2000s Inte-grated and alternate ricendashprawn cultures charac-terize the main ricendashprawn farming practices in the

Mekong Delta The integrated ricendashprawn culturemodel harbors large areas that have potential to bedeveloped It is considered to be a subsistenceactivity which brings income that supplementsthat obtained from rice production This type ofculture is more suitable for non-flooding areas orin areas where two crops of rice per year are stillcarried out However this model achieves low pro-ductivity small prawn size at harvest and low sur-vival rates which leads to low economic returncompared to other models

The two alternate types are more commercialand have become a central activity of rice farmersThese types are suited for flooded areas or in loca-tions where summerndashautumn rice cultivation issubjected to high flooding risk Many provincialgovernments in the Mekong River Delta plan toexpand alternate ricendashprawn culture in the futureThe advantages of these models include high eco-nomic return and suitability to rice paddy ecologyHowever these models require high investmentand a high level of technology which may not besuitable for poor and low-skilled farmers Theeconomic return from these models is attractiveand is creating momentum toward further futuredevelopment

However while alternate culture in which onlyprawns are cultured during a specific period offershigher economic returns there is the dangerthat with increased production unit price willdecrease In addition although environmentalimpact has not been a concern until now it is pos-sible that the high profits that are being attainedwill entice farmers to engage in more intensifiedforms of culture which may have detrimentaleffects on the local environment In this regardfurther on-site studies should be conducted toexamine the relationship between prawn cultureand water quality in both rivers and sources des-tined for human use

ACKNOWLEDGMENTS

Seed production technology development andsocioeconomic evaluation of hatchery technologywas conducted within an international collabora-tive program (lsquoDevelopment of new technologiesand their practice for sustainable farming systemsin the Mekong Deltarsquo FY 1999ndash2003) between theJapan International Research Center for Agricul-tural Sciences (JIRCAS) and Cantho UniversityVietnam MN Wilder was supported by theResearch and Development Program for New Bio-industry Initiatives of the Bio-oriented TechnologyResearch Advancement Institution (BRAIN) ofJapan


REFERENCES

1 Ministry of Fisheries Aquaculture Achievements in 2002and Implementation Plan for 2003 Government of VietnamMinistry of Fisheries Hanoi 2003 (in Vietnamese)


3 Tiep NN Quality and solutions for sustainable develop-ment of catfish production National Conference on Qualityand Trade Name for Catfishes of Vietnam Angiang ProvinceDecember 14ndash15 2004 Government of Vietnam Ministry ofFisheries Long Xuyen 2004 (in Vietnamese)

4 Mieng TT Issues on planning and management for catfishproduction to the year 2010 National Conference on Qualityand Trade Name for Catfishes of Vietnam Angiang ProvinceDecember 14ndash15 2004 Government of Vietnam Ministry ofFisheries Long Xuyen 2004 (in Vietnamese)

5 Hanh DD Continuous growth of the Vietnamese fisheriessector in 2004 Fish Mag 2005 1 3ndash5 (in Vietnamese)

6 Government of Vietnam Approval of Aquaculture Develop-ment Plan Period from 1999ndash2010 Decree no 2241999QD-TTg Government of Vietnam Hanoi 1999 (in Vietnamese)

7 Government of Vietnam Restructuring of AgriculturalProduction and Its Products Consumption Decree no092000NQ-CP Government of Vietnam Hanoi 2000 (inVietnamese)

8 Thang NV Giant Freshwater Prawn Farming AgriculturalPublishing House Ho Chi Minh City 1995 (in Vietnamese)

9 Hien TTT Minh TH Phuong NT Wilder MN Current statusof freshwater prawn culture in the Mekong River Delta ofVietnam JIRCAS J 1998 6 89ndash100

10 Ang KJ Cheah SH Juvenile production of the Malaysiangiant freshwater prawn (Macrobrachium rosenbergii deMan) using modified stagnant lsquogreen waterrsquo system InChan HH (ed) Development and Management of TropicalLiving Aquatic Resources Universiti Pertanian MalaysiaMalaysia 1987 141ndash144

11 New MB Valenti WC Freshwater Prawn Farming TheFarming of Macrobrachium rosenbergii Blackwell ScienceOxford 2000

12 FAO World production of fish crustaceans and mollusksetc by principal species FAO Fisheries Department Statis-tical Databases and Software Yearbook of Fisheries StatisticsSummary Tables 2002 Available from URL httpwwwfaoorg

13 Phuong NT Duc PM Son VN Bui TV Nguyet ATA Applica-tion of high technologies for quality improvement of catfishtilapia and giant freshwater prawn products and reductionof their production costs Report submitted to An GiangDepartment of Science and Technology Long Xuyen 2004(in Vietnamese)

14 New MB Farming Freshwater Prawns A Manual for theCulture of Giant Freshwater Prawn (Macrobrachium rosen-bergii) Food and Agriculture Organization of the UnitedNations Rome 2002

15 Phuong NT Tuan NA Hien TTT Hai TN Wilder MN OgataHY Sano M Maeno Y Development of freshwater prawn(Macrobrachium rosenbergii) seed production and culturetechnology in the Mekong Delta of Vietnam a review of theJIRCAS project at Cantho University JIRCAS Working Report2003 26 39ndash47

16 Wilder MN Fukuda Y Development of freshwater prawnseed production technology in the Mekong Delta region ofVietnam Yoshoku (Aquaculture Monthly) 2002 39 98ndash101(in Japanese)

17 Hien TTT Hai TN Phuong NT Ogata HY Wilder MN Theeffects of dietary lipid sources and lecithin on the produc-tion of giant freshwater prawn (Macrobrachium rosenbergii)larvae in the Mekong Delta region of Vietnam Fish Sci2005 71 279ndash286

18 Phuong NT Hai TN Hien TTT Wilder MN Giant Fresh-water Prawn (Macrobrachium rosenbergii) Seed ProductionPrinciples and Practices Agricultural Publishing HouseHanoi 2003 (in Vietnamese)

19 Thang NV Studies on biological characteristics and seedproduction of giant freshwater prawn (Macrobrachiumrosenbergii) in the southern part of Vietnam PhD ThesisFisheries University Nha Trang 1993 (in Vietnamese)

20 Tinh NV Status of prawn seed production of the Vung TauPrawn Research Center during the past few years Confer-ence on Development of Giant Freshwater Prawn Productionin the Southern Part of Vietnam An Giang Province May 29Long Xuyen 1999 (in Vietnamese)

21 Hung NQ Phuc TT Report of the giant freshwater prawn(Macrobrachium rosenbergii) technology transfer projectfor some provinces of the southern part of Vietnam Confer-ence on Development of Giant Freshwater Prawn Productionin the Southern Part of Vietnam An Giang Province May 29Long Xuyen 1999 (in Vietnamese)

22 Yen PT Macrobrachium Rosenbergii seed production inVietnam an examination of the performance of broodstockand larvae from sources in Thailand and Vietnam Msc The-sis Asian Institute of Technology Bangkok 1999

23 Phuc TT Hung NQ Thanh V Van NTK Quyen L Nhut NLich HT Thao NTT Technical improvement and productioncost reduction for giant freshwater prawn (Macrobrachiumrosenbergii) seed production in the Mekong River DeltaReport submitted to Ministry of Fisheries Vietnam Hanoi2001 (in Vietnamese)

24 Phuong NT Hai TN Hien TTT Oanh DTH Yen NLH VietTV Transfer of giant freshwater prawn (Macrobrachiumrosenbergii) seed production technology Report submittedto the National Fisheries Extension Center Hanoi 2003 (inVietnamese)

25 Phuong NT Hien TTT Hai TN Liem PT Yen NLH Viet HVBui TV Hang BTB Studies to complete the technical packageof giant freshwater prawn (Macrobrachium rosenbergii) seedproduction using the modified stagnant green water systemReport submitted to the SUFA project Hanoi 2002 (inVietnamese)


Peneaus monodon cultured in saltwaterndashbrackish-water areas and Pangasius catfishes Pangasiushypophthalmus and P bocourti cultured in fresh-water areas are most important showing the high-est production levels and constant growth of theindustry (Figs 23)2ndash4 Other important aquaculturetargets include the giant freshwater prawn Macro-brachium rosenbergii tilapia Oreochromis niloti-cus mollusks Anadara granosa and Meretrixmeretrix and indigenous fishes such as the climb-

ing perch Anabas testudineus and snakehead fishChana striata and C micropeltes There are manytypes of production systems observed in Vietnam-ese aquaculture not only are intensive and semi-intensive forms of aquaculture practiced but alsoextensive systems where rice cultivation is inte-grated with fish or prawn culture Much of theblack tiger prawn and Pangasius catfish culture ishighly intensive while other species are culturedunder semi-intensive or extensive systems

Total aquaculture production in 2004 slightlyexceeded 1 150 000 tons of which brackishwateraquaculture constituted 510 400 tons (mainlysaltwater-brackishwater shrimp at 290 000 tons)while freshwater aquaculture constituted 639 700tons (mainly catfish at 315 000 tons) The export val-ues of saltwater-brackishwater shrimp (sim$US12bn)and catfish ($US300m) comprised the largest pro-portion of the total value of the fisheries sector25 Nofigures corresponding to the export of freshwaterprawn has been reported as this product isdestined mostly to local markets (only a very smallquantity is exported)

Currently although the freshwater prawn cultureindustry is not equal to the scale of the saltwater-brackishwater prawn culture industry (Fig 2) thegiant freshwater prawn Macrobrachium rosen-bergii which is indigenous to the Mekong Delta isbecoming an increasingly important target spe-cies The culture of this species especially in ricefields has been a traditional activity which wasbased mainly on wild seed collected from riversand other freshwater bodies However lack of a sta-ble seed supply was a significant obstacle to thefurther expansion and development of ricendashprawnfarming systems Because the giant freshwaterprawn is a high-value species its culture by impov-erished farmers is considered to have the potentialto raise income and contribute to enhanced ruraldevelopment Therefore Vietnamrsquos Ministry ofFisheries has put forth that the annual productionof M rosenbergii must reach 60 000 tons using32 000 ha by 20106 The Vietnamese Governmenthas also implemented a policy called lsquorestructuringof agricultural production and its products con-sumptionrsquo7 In order to address the needs of thisburgeoning industry basic and applied researchhas been conducted in order to develop appropri-ate seed production technology and verify the useof artificial seed in ricendashprawn farming in theMekong Delta

Initial research on the larval rearing ofM rosenbergii commenced in the early 1980s andwas undertaken by Vietnamrsquos Cantho Universityand the Research Institute of Aquaculture no 2although the first hatchery was established outsideHo Chi Minh City in Vung Tau in 19758 Basic

Fig 1 Changes in capture fisheries and aquacultureproduction and area under culture in Vietnam from1991-20031

0

500

1000

1500

2000

2500

91 92 93 94 95 96 97 98 99 2000 2001 2002 2003 2004

Time (year)

)tm 000

1 x( noitcudorP

0

200

400

600

800

1000

1200

)ah 0001 x ( aer

A

Production (capture)

Production (aquaculture)Culture area

Fig 2 Production levels of major farmed commoditiesin Vietnam in 200323

0 100 200 300 400 500 600 700

Marine shrimp

Freshwater prawn

Mollusks

Catfishes

Tilapia

Other commodities

Production (x 1 000 mt)

Fig 3 Production and growth of the saltwaterndashbrack-ishwater shrimp and catfish industries from 1991ndash200324

0

50 000

100 000

150 000

200 000

250 000

300 000

350 000

1994 1997 1999 2000 2001 2002 2003 2004

Time (year)

Pro

duct

ion

(mt

)

Shrimp

Catfishes



















Integratedculture





(a)

(b)












Item Mean plusmn SD
























DietSurvival rate

()PL body length

(mm)Rearing cycle

(days)



are shown17




No algae 38 117a













010

2030

405060

7080

90100

1999 2000 2001 2002 2003

Year

seirehcta

h

oN

0

10

20

30

40

50

60

70

80

90

) sn

o ill im(

LP

fo

noitc

ud

orP


Production of PL


Can Tho45

Ben Tre13

An Giang11

Dong Thap10

Tien Giang8

Long An5

Tra Vinh5

Vinh Long2

Ca Mau1







0

10

20

30

40

50

60

70

80

90

100

1998 1999 2000 2001 2002 2003

seirehctahfoo

N






(days)Survival rate

()















year Unit

Unitcost

($US)

Quantity1production

cycle


cycles)($US)



$US1 for 150 PL)6898




Feed

42

Broodstock

8

Labor

13

Brinewater

13

Other

24









ACKNOWLEDGMENTS



REFERENCES












































Integratedculture





(a)

(b)












Item Mean plusmn SD
























DietSurvival rate

()PL body length

(mm)Rearing cycle

(days)



are shown17




No algae 38 117a













010

2030

405060

7080

90100

1999 2000 2001 2002 2003

Year

seirehcta

h

oN

0

10

20

30

40

50

60

70

80

90

) sn

o ill im(

LP

fo

noitc

ud

orP


Production of PL


Can Tho45

Ben Tre13

An Giang11

Dong Thap10

Tien Giang8

Long An5

Tra Vinh5

Vinh Long2

Ca Mau1







0

10

20

30

40

50

60

70

80

90

100

1998 1999 2000 2001 2002 2003

seirehctahfoo

N






(days)Survival rate

()















year Unit

Unitcost

($US)

Quantity1production

cycle


cycles)($US)



$US1 for 150 PL)6898




Feed

42

Broodstock

8

Labor

13

Brinewater

13

Other

24









ACKNOWLEDGMENTS



REFERENCES

































Item Mean plusmn SD
























DietSurvival rate

()PL body length

(mm)Rearing cycle

(days)



are shown17




No algae 38 117a













010

2030

405060

7080

90100

1999 2000 2001 2002 2003

Year

seirehcta

h

oN

0

10

20

30

40

50

60

70

80

90

) sn

o ill im(

LP

fo

noitc

ud

orP


Production of PL


Can Tho45

Ben Tre13

An Giang11

Dong Thap10

Tien Giang8

Long An5

Tra Vinh5

Vinh Long2

Ca Mau1







0

10

20

30

40

50

60

70

80

90

100

1998 1999 2000 2001 2002 2003

seirehctahfoo

N






(days)Survival rate

()















year Unit

Unitcost

($US)

Quantity1production

cycle


cycles)($US)



$US1 for 150 PL)6898




Feed

42

Broodstock

8

Labor

13

Brinewater

13

Other

24









ACKNOWLEDGMENTS



REFERENCES













































DietSurvival rate

()PL body length

(mm)Rearing cycle

(days)



are shown17




No algae 38 117a













010

2030

405060

7080

90100

1999 2000 2001 2002 2003

Year

seirehcta

h

oN

0

10

20

30

40

50

60

70

80

90

) sn

o ill im(

LP

fo

noitc

ud

orP


Production of PL


Can Tho45

Ben Tre13

An Giang11

Dong Thap10

Tien Giang8

Long An5

Tra Vinh5

Vinh Long2

Ca Mau1







0

10

20

30

40

50

60

70

80

90

100

1998 1999 2000 2001 2002 2003

seirehctahfoo

N






(days)Survival rate

()















year Unit

Unitcost

($US)

Quantity1production

cycle


cycles)($US)



$US1 for 150 PL)6898




Feed

42

Broodstock

8

Labor

13

Brinewater

13

Other

24









ACKNOWLEDGMENTS



REFERENCES


































010

2030

405060

7080

90100

1999 2000 2001 2002 2003

Year

seirehcta

h

oN

0

10

20

30

40

50

60

70

80

90

) sn

o ill im(

LP

fo

noitc

ud

orP


Production of PL


Can Tho45

Ben Tre13

An Giang11

Dong Thap10

Tien Giang8

Long An5

Tra Vinh5

Vinh Long2

Ca Mau1







0

10

20

30

40

50

60

70

80

90

100

1998 1999 2000 2001 2002 2003

seirehctahfoo

N






(days)Survival rate

()















year Unit

Unitcost

($US)

Quantity1production

cycle


cycles)($US)



$US1 for 150 PL)6898




Feed

42

Broodstock

8

Labor

13

Brinewater

13

Other

24









ACKNOWLEDGMENTS



REFERENCES
































0

10

20

30

40

50

60

70

80

90

100

1998 1999 2000 2001 2002 2003

seirehctahfoo

N






(days)Survival rate

()















year Unit

Unitcost

($US)

Quantity1production

cycle


cycles)($US)



$US1 for 150 PL)6898




Feed

42

Broodstock

8

Labor

13

Brinewater

13

Other

24









ACKNOWLEDGMENTS



REFERENCES







































year Unit

Unitcost

($US)

Quantity1production

cycle


cycles)($US)



$US1 for 150 PL)6898




Feed

42

Broodstock

8

Labor

13

Brinewater

13

Other

24









ACKNOWLEDGMENTS



REFERENCES


































ACKNOWLEDGMENTS



REFERENCES



























REFERENCES


























current status of freshwater prawn culture in vietnam and the development and transfer of seed...

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