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Sustainability of World Shrimp Farming

CJEORGEW. CHAMBERLAIN

/>»/raeni, and hard currency. Annual world productionof farm-raisedshrimp grew rapidly and steadily I'rom a negligiblelevel in 1980to 799,00 inc>ac! tons mt;live weight! in 19n»puttered between 789 000 and 89 l.00 ! mt, a» increasesin someregion» were otfset by declinesin other».Alt!a>ugh oflicial Food and Agnculture Organizationof the L!nited Nations data ai« iu>t yet available for 19'!»and 1996, Projections indicate that produc- tion declinedbecause of a wor»eningdi»ease epidemic in Asia. Although production hurdlesexist, di»ea»«» havebeen the direct causeof recentproduct>on decline». Despite»enous elf<>rt» to control them.di»ea»e» con- tinue to plaguethe industry.The first »ignof larg«-scaleproblems occurred in I qgg,when Taiwan's pron dramaticallydropped. The causeof'the w«lc»pre;idmortality waspoorly under»tood.Another crippling decline occurredin 19' in China. Much of Asia i» now struggling with rapidly spreadingviral epidemic'. In»onie cases,exten»ive complexes of shrimp pond»hav«been abandoned owing to insurmountabledisease problein». Nearlv 20 shrimp viru»e»have beenidentified thu» far. but the mo»tthreatening during the mid-199 >»have beenwhite-spot virus in Asia andTaura Syndrome virus in the Americas. An increasingnumber of environmentaland social i»sue»have been documented as the shrimpaquaculture industryhas grown and intensified. Regulati<>ns iiretightening to addressi»sue» such as mangrove urce» suchas healthy wild shrimp,clean estuarine water, and a larg»adjoining ecosystem to assimilatewaste». I'arm- ersare being encouraged to rely lesson uncontrollableresources and more on thefundamental discipline» ol' sanitation,animal health.genetic». nutrition, and soundrnanageni»ingnew techniquesare be>ngdeveloped to rec>enc!. and predictthe carryingcapacity of ecosysteni».These tools will pavethe way towardgreater production efficiency and a newphase of environmentally»ust

During the 1980»,world landingsof shrimpI'rom cap- intensive farms produced 115,000 mt ol' Pe»<» irx ture fisheries reached a plateau ol' approximately m<»><>dkrnin 1987. I-lowever, devastating shrimp mi>rtiil- 1,900,000 metric tons mt! per year while shri mp aquac- ity in 1988dropped Taiwan's producti an to only 44.000 ulture begana periodof rapid growth. World production mt NMFS 1992!. Thc causes of mortality v ere attrib- of farm-raisedshrimp grew dramaticallyfroiu lessthan uted to industrial pollution, bacterialand viral di»eases, 84,000 mt in 1982 to 891,000 tttt in 1994 National Ma- and recirculation of pond effluents among I'arm» F!»- rine Service NMFS] 1992; Food and Agricul- peatedefforts to revive the industry in Taiwan re»ulicd ture Organizationof the United Nations FAO] 1996!. in collapsesin 1992and 1993despite;,tten>pts t<>»iviich However,widespread crop failures and environmental from P. m<>n<>rr»i<»» concerns have raised questions about the su»tainability and P. Pe»i- of shrimp .Sustainability wa» defined by duction in Taiwan was estimated to bc 2S,OOO iiit Hulse993! as"satisfying present needs without preju- Rosenberry 1994!. and most Taiwanese shrimp f;irrncr» dice to the needs of the future." The follov;ing issues had switched to marine fish culture. illustratethe major concerns challenging the shrimp farm- ing industry. China

The 1988 crop failure in Taiwan had little impact <>n Disease Outbreaks the world supply of shrimp because the shortfall w - In 1993,China's production plummeted to 88,000mt, ductionin coastalpond». However, beginning;mingtide, muchof this sedimenr lien cc- [mr]! «f farm-raisedpenaeid shrimp. 1982 94 i I'AO I'!96!. phaloth

'I'At!t.ri 1. Statistic»for size, number und priidu«tiviiy ot' to pump effluent trom the ponds to the offshore»ii« Thai shrimp farms by managementtype, 1991 '. P. Group Despiteall the»emeasures, shrimp productionin Th;ii 1991!. land is cstimatcd n> have dropped by 25&0/c duriiig Numberof t'ron 1996, and the long-term impact of white-spot viru» i» Managementtype farm» Area ha! imi! still unclear. If the white-spot epidemiic expands t<>tl!e h xle li »' i vi' 2,»87 22.00 ! 7,sss Western Hemisphere, it could cause s veri niortalit! iii Semi-in

Ecuador causedup to 100% mortality in 3 S d in si!- effort was instituted by the Thai Department of Fisheries. dition» favored bacterial growth, especially pathogenic Farmers were instructed not to feed trash fishe». which Vibrio spp. Bactcri;il infection may have been facilitated often include palaeomonid shrimp. Filter sock» were in- by grcgarine parasites, which break th epithelial lining stalled on inlet water systems to prevent entry

The TS virus initially wasconsidered to be causedby ing seriouslosses that ultimately resultedin farm clo- water-bornefungicides from the bananaindustry. How- sure Mangiboyat 19g7!. ever, it later was diagnosedas a viral disease Brock et The speciesP. iv»rn IHHR al. 1995!.Retrospective histological studies showed that virus than P. »tvlirostris. Nevertheless, IHHN virus in- the TS virus waspresent in Ecuadoras early a»Septem- fccts P. ici»numei and causes "Runt Deformity Syn- ber 1991 D. Lightner,Dep. VeterinaryScience, Univer- drome" RDSI in which a portionof the at'fectedpopu1;i- sityof Arizona,Tucson, USA, pers. comm.!. In mid-1993. tion display»reduced girowth, highly variablesize clas»i », the TS virus wa» found in wild postlarvae collected near and s<>metimcsreduced survival. Severe ca»es of RDS the mouthof theGulf of Guayaquil,Ecuador, anti in wild canreduce the productivity and profitability <>I'farms by adults collected off the Pacific coast of Honduras, El 30 50% Kalagayan ct al. 1991!. Salvador,and Chiapasin southernMexico I.ightner et The U.S. MarineShrimp Farming Program began is >. al. in press!.During 1994to 1996,the TS virus quickly lating populations ot specific-pathogen-free SPF! /'. spreadto all shrimp-producingcountries in the Western ivuinumei in early 19! I as a seedsource f<>r the 1.'.S Hemisphere,except Venezuela, where few farmsimport shrimpfarming industry. The offspring from thesepopu- or larvae. Transmission of the disease is not lations,referred to as 'High-Health" shrimp, pe>4'orrnecl completelyunderstood. but both a wingedaquatic insect well in commercial I'iirms in the LJSA during 1991 i<110 andsea gull» havebeen documented to carry viable viral 1992.During 1993,High Healthstocks werc suppliedtci particlesin their gut Lightner et al. in press!. 400 ha of commercialponds in Fcuador, hiit surviv;rl Despitethe continuingpresence of the TS virus, high averagedle»s than I S'inowing to an outbreiikot' the TS market prices during 1995drove Fcuador'sshrimp in- virus IPruder et al. 1995!. During 199S and 1996, most dustry to recordproduction of 115,000mt Ro»enberry »hrimpfarms in the LJSAalso were hit by an outbreakot 1996!.By mid-1996,many growersreported griidually theTS virusdespite their useof High-HealthP. i a>znu»iez. improving survival rates.Some speculate that Fcuador- Survival ratesranged from IS 30%. Thus, the SPFap- ian shrimppopulations may be developingresistance to proachdocs not »cernpractical when tlie I;irni»u»ing theTS virus.This patterni» not yet evidentin othercoun- those stock»;ire unable to control entr! <>t'pathogen» tries affected by thi» virus. Lightner 1996!.

Philippines Risk of Disease Transmission As of mid-1996,white-spot virus had not been reported Diseasesare a primarylimiting factorfor shrimpfar>ni- in the Philippines. However, production ot' shrimp is nggtoday, and the risk of diseaselosses is I rkel!to woi>sen plaguedby luminescentVibrio spp., which are present a»the industrycontinues to grow. Near ! 20»hrimp vi almostall year.Farmers are treating it with an antibiotic, ruse» have been identified thus far Lightncr ct al. in 1'urizolidone,in the feed.Typical productionresults are press!.Many of thesebegan as localized patliogens hi» not asgood as earlier years: feed conversion ratio FCR! quickly spreadto nev regions Lightner and Redinaii of 1.9 2.2, survivalof 40'Io,postlarval PL! costol $25- 1991!. Once a nev disease becomes established in vvil»tris,P. setifi'rus, P. uzte<'u»,all»tris iluz>ruru»z! and to cause serious disease I.ightner in in their super-intensivegreenhouse-covered ». press!.White-spot virus also causesmcrtality in non- After a devastatingoutbreak of infectious hypodeanal penaeid,freshwater and marine crustacean».including andhematopoietic necrosis IHHN! virusin their research Mncrobrnspp., Procambarus nanus. White-spot virus infi.ct» hut rigoroussanitation and quarantine procedures. However, does not causesignificant diseasein a variety of «rab a secondoutbreak of IHHN virus occurred in 19!, caus- and spiny lobster Chang ct al. in press;Wang et ai. in SUSTAINABILITY OF SHRIMP FARIVIIRO pre»s!.In LatinAmerica, the most seriou» viral disca»e demic Asian viru»cs to the Western Hermsphere and vie< is theTS virus.The susceptibilityof Asian speciesto the versa.Tighter regulationsare neededto;is»ure pn>pei TS virus is unknown. It is, nonetheless, critical to pre- di»po»afof wa»t»sfrom frozen imported shrimp. vent the establishment of Asian viruses in the Western Hemisphere and vice versa. Other Risk Factors The mostcommon means of shrimpdiscase transmis- Wiley 993!categorized andprioritizccl the risk»I;ic sion has been direct transfer of infected animal», Uncon- ing shrimpaquaculture from the viewp<>int nf' an in»ur. trolled shipmentsof broodstockor postlarvae1'rom in- ancecompany. Scdgwick, James, Ltd. Th< most imp<» fectedfarms or wild populationshave quickly expanded tant factor influcn<.ing the successof a farm, in Wile! ' the rangeof severalviral di»eases Lightner andRedman view, wasthe competency of personneland mii manhealth, are processed and marketedthrough normal levels above II mt>'hato be very risky and Wiley inrain 1=x for worldwide transmissionof shrimpviruses i» through changeinitiated this program in July 1991,but the n bait for recreationalfishing Lightner 1996!. tinual input of cleanwater and discharge of wastewrit»r In November 1995,white-spot virus and a possible Waterexchange is thoughtto improv» water qualit> bv co-infection of yellow-head virus were detectedin a flushingout wasteproducts, avoiding excessive eutn>phi- populationof P.setiferus at a southTexas shrimp farm cation, and maintaining a healthy plankton bloom. In Lightneret al. in press!.The diseases had not reappeared extensivesystems, it also may havevalue in adding;id- as of January 1997 P. Frelier, Dep. Veterinary ditional forage prey.As a function of stocking density, Pathobiology,Texas A&M University,College Station, averagedaily waterexchange rates typically vary I'rom Texas,pers. comm.!. A secondcase of white-spotvirus, I 5% in extensivesystems to 25 30% in intensive»ys- whichagain appeared with a possibleco-infection with tems Clifford 1985!. yellow-headvirus, was detected at the Waddell Maricul- Nutrient budgets for intensive and»cmi-inten»iv» tureCenter Bluffton, SouthCarolina, USA! duringJanu- shrimp pondsindicate that only 6 24% of the nitrogen ary 1997.The origin andextent of the latterinfection and4 13%rporatedint<> were unknown at the time of this writing D.V. Lightner. harvested shrimp Briggs and Funge-Smith 1994: Dep.Veterinary Science, University of Arizona,Tucson, Robertsonand Phillips 1995!.The remainderi» retain»cambarusspp. and O<>ronectespu>tcri»>u.t, being change,harvesting, and sediment disposal. However. thc held at the U.S. National Zoo Lightner ct al. in press!. receivingwater body can assimilate only a limitedquent»,known asthe critical load,before w;iter 200 CHAMBERI AIN qualityand ecosystem diversity begin to change.Robertson oper and the concernedregulatory body in which the and Phillips 99.>! estimatedthe amountof mangrove developercompensate» for loss»f mangrove1iabitat by area needed to assimilate the total nitrogen and phospho- creating a similar habitat nearby. rous load generatedby shrimpponds as a resultof water Large-scalede»truction of mangroveareas can have exchange,drainage during harvesting,and sedimentdi»- seriousecological and»ocial consequence~. Man rove» posalwas 2 3 hafor eachha of semi-intensivepond area arecritically importantas highly productiveniirsery ar- and 7 22 ha for each ha of intensive pond area. easfor estuarinespecies, habitat for birds andniammal», In some cases,shrimp farming development»have buffer zones against »torm events, stabiliziiig forces clusteredin certainregions, resulting in nutrientdischarge again»tsoil erosion, and sourcesof revenue for poor well beyondthe critical load of the receiving body.The coastalcommunitie» Bailey 1988!.Neverthel< ss, in the scenarioof overdevelopmentoften beginswith success- earlyrush to capitalizeon thc profitability ol'shrimpfarm- ful resultsfrom a singlepioneer farm in a givenregion. ing, local policy often overlookedor even encollr'age This lead~to rapid,unplanned development of additional conversionot mangroveareas to ponds3ailcy 1988!. farms.As neighboringfarms pump and dischargewater For example,in the Philippines,the Bureauof Fi»heries to a comlllon estuary,water quality begiils to deterio- andAquatic Resources listed mangrove are;is a» "swamp- rate,shrimp become stressed, and disease organism» are landsavailable 1'or development" until 1984 Primaver:i transmittedamong farms. This type of developmentis 199S!. vulnerableto massmortality of shrimp,and hence i» not Shrimpt'arming is rarely the main causeol'iiiangrove sustainable. destruction. It i» e»tirnated to have destroyed le»s than Oneapproach used to avoid suchproblems i» to regu- 5% of the global mangroveresource by 1988, hut lo- late the quantity and quality of effluents from existing cally theimpact may be more severe Phillips et ul. 1993!. farms.However, experience has shownthat a proactive Aquacultureprmd construction i» estimatedto havede- approachcan be more effective by avoiding problems stroyed 20% of the mangroveforest in some piirts of beforethey arise.This involves integratingaquaculture Ecuador Snedaker et al. 1986!. In Thailand, 34% ol' the resource allocation within a broader system of resource cleared mangrovearea is used for aquacultureponds planningthat considers the needsof a varietyof re»ources Network of AquacultureCentres in Asia andthe Pacific andresource users. For example,Canada has developed [NACA] 1994!. In Vietnam, 240,000 ha of coa»tal ponds an applicationsystem for leasingcoastal areas to alreadyhave been developed, largely in m;rngrirveareas growers that involves evaluating the capability of the C. P.Group 1994!.In Indonesia,most of the 30,000 hii proposedsite to assimilatethe organicload of thc farm. of habitat being usedto culture shrimp wa» mangrove In addition,a minimumspacing of 3-km i» requiredbe- forest Macintosh 1996!. tween salmon farms located within a single enclosed Most shrimp-producingcountries now reco nizc th» water body Black andTruscott 1994!. value of mangroveareas and have regulaiion»in place to protectthem. However,they often lack the icsource» Mangrove Destruction to monitor and enforce those regulations Bailey 1988; Macintosh 1996!. A goocl example is the "informal" The rapid growth of shrimp I'armingworldwide has shrimp farms in Fcuador Fay 199S!.The»e are usually resulted in the construction of new pond» in many coastal small,poorly fundedoperations established without per- areas.Thc preferredenvironment for pond construction missionin intertidal mangroveareas because !rond» can is salt flats, which are relatively unproductive and easy bc constructed there without heavy equipment;ind oper- to develop.In the early days of shrimp farming, man- atedwith minimalfunrls and technology. In contrast,"for- grove areasalso wereconsidered suitable sites for pond mal' shrimpfarms are largerand bettercapitalized units constructionon the presumptionthat thi» was the envi- thatare licensed by thegovernment and req uireil to avoiil ronment where shrimp occurred in nature Fegan 1996!. mangrove area». However, experiencehas shown that mangroveareas Several U.S. environmental groups have threateneil makepoor sitesfor shrimpponds because their acid sul- to boycottimported farm-raised shrimp if mangrovedc- fate soils become extremely acidic pH 3 4! when dried. »tructionby the internationalshrimp farming industryi» Most farms now prefer to use land abovethe intertidal not stopped Woodhou»e1996!. The issueot mangrove zone because it is more accessible to heavy equipment, destructionis complex and is the topic of considerable more manageable,and moreproductive. Farm develop- debate.It is complicatedby the many differeni typesot ers disturb the mangrovearea only to constructan inlet mangroves,which vary in their commercial,physical, canal for access to estuarine water. In some countries, and ecological value. Those mangrove area»;ilong thc evenminor conversionof mangroveareas require» miti- coastal fringe are valued the most becau»ethey are gation. Mitigation is an agreementbetween the devel- thoughtto function as key nurseryareas for the offshore SL/STAINABIL.ITY OF SHRIMP FARMING 201 fisheryand as buffer zones against storm» and erosion. valuabletools in a healthmanagement program, they are Thebulk of mangroves,which are located inland, are sometimesused inappropriately or in exce»».This re- oftenassigned a lower ecological value Hambrey 1996 1. sults in ineffective treatment,financial R>ss,imd poten- Social issuesare also contentious.In mostcountrie», tial contamination<>f natural waters and shrimli with re»i- legalownership ofmangrove areas i»claimed by the state. dues.Clearly, improved method» are needed u> diagno»«, eventhough local communities often depend heavily on prevent,and treat shrimp diseases. exploitationof thoseresources. The transformation ol' sucha multiple-userresource into a privateaquaculture Other propertycan create social conflicts Bailev 1988; Otherenvironmental issues, which arenot addres»etl Sebastiani et al. 1994!. In order to protect and managemangrove re»ources in thispaper, include dependence onwild post larvae and morecarefully, Hambrey 996! recommendedthat reproductiveadu!t», excessive pumping of ~r<>undw;- land.The analysis excluded those mangrove area» within gramsare ba»ed upon appropriate prophyla< tie anddi- Thailand'sconservation zone, which i» kept a»a natural agnosticmeasures rather than therapy to forest.Pongthanapanich 996! concludedthat 61% of disea»esymptoms. Diagnostic technology ha» advancei.l the area outside the conservation zone should be con- rapidlyin recentyears with the application i!f inethod» servedin its naturalcondition, 17%should be de»ignated suchas DNA probe»,enzyme linked immunosorbent a» for wood concessions,10% for reforestation,12% for says,mono- and polyclonal antibodies, and polymer waterseepage into the watertable or throughsaliniza- brood»tockby hemolymphsampling or reinovalof;i tion of freshwater used for irrigation. Salinizution of singlepleopod. They also can be used to screenpo»tlar- groundwatercan affect scarce drinking water»upplies val populations,In Thailand,many farin» and govern- in coastalvillages. Salinization of shrimpponds becomes ment laboratoriesare now performing routine analy»ii anissue if pondsfail andrequire conversion hack to ag- of 5- to g-day-old,hatchery-reared postlarva« for white- ricultural production. spotvirus by usingPCR followed by a dotblot test T. Flegal, Dcp. Biotechnology,Mahidol llniver»ity, Bangkok,Thailand. pers. comm.!. IncreasedUse of Therapeutants In addition,sophisticated diagnostic tool»;ue becom- The increasedincidence of diseasehas led to increased ing availableat thefarm level through i.h«use of coiri- useof varioustherapeutants, including antibiotics, anti- merciallyavailable DNA probesand diagno»tie kits ti>i coccidials,copper compounds, quarternary ammonium viral DiagXotics",Inc., Wilton, Connecticut, ICOSA!;iseaseSection. andmalachite green. Although such treatments can be Freshwater FisheriesResearch Centre, Melaka, Malaysia i 202 'HAM B ERLAIN

Thus, a test for IHHN virus, which previously required a immunity.Hemolymph lectins of shrimpare alsorecog- 6-week bioassay followed by histology in a well- nized for their role in causingagglutination of foreigii equippedlab, cannow be accomplishedin a simplelabo- proteins Fragkiadakisand Stratakis 1995!. Recentre- ratory in a matterof hours.Even faster testsare on the searchabout inducibleantibacterial peptides and primi- horizon. Human health researchers at the University of tive cytokinesmay leadto importantdisease-resistanc» California Berkeley,California, USA! recently devel- treatments in the future Beck and Habict 1996!. opedpolydiacetylene films that can detecttarget patho- In pigs,probiotics have enhanced growth through colo- gensor their toxins instantly.The films, which arecom- nizationof thecolon by microflorathat block pathogenic posedof highly ordered crystalline arrays coupled to microorganisms Russell et al. 1996!.A similar concept antibodies,undergo mechanical disruption upon contact has beenapplied in shrimp larval culture tank»to con- with the target antigen,which causesan instant color trol pathogenicbacteria. The probiotic conceptinvolves change Coghlan 1996!. intentionallyseeding sterilized seawater tank» with ben- Therapeutants. Necrotizing hepatopancreatitis eficial bacteriato reducethe opportunity for coloniza- NHP! was diagnosedas the causeof high shrimp mor- tion of pathogenicbacteria Garriquesancl Are valo 1996!, talityrates in Texasponds, which began in 1988 Frelier This is an exciting alternativeto using antibiotics for et al. 1993!. Since then, NHP has been diagnosed in Peru, control of pathogensin larval culture systems. Venezuela, Ecuador, and Panama Lightner et al. 1992; Stress. During viral epidemics,often certain farina Lightner and Redman1994; P. Frelier, Dep. Veterinary seemto operatewith minimal diseaselosses. Much ol Pathobiology,Texas A&M University,College Station, this advantageis attributedto low stres:. For example, Texas, pers. comm.!. The diseasecan be controlled in a trial conducted in Thailand, shrimp v ere injecte 30%. In a Polysaccharidesare being used to enhancethe shrimp study designedto evaluatethe relative contribution ot immune system.Sung et al. 994! showedthat beta geneticsversus nutrition to the improvementin broiler glucansimproved disease resistance and growth of P. growth in the last 40 years,genetics was found to ac- monodonchallenged by Vibrio vulnificus. Further re- count for approximately 85 90% of the contribution searchshowed that betaglucans stimulated P. monodon while the remainder was attributed to nutrition hemocytesto increaseproduction of reactive oxygen Haverstein et al. 1994!. Genetic background has als» specieswhichare important in microbiocidalactivity beenshown to influencedisease resistance piitential and Song and Hsieh 1994!. immunocompetencein chickens Ruff andBacon 1984; Other potential immune enhancersinclude elevated Puzzi et al. 1990!. vitamins, selenium, and astaxanthin Tacon and Kurmaly Atlantic salmon Salmosalar! and carp Cyprinus spp.! 1996!. There is still much to learn about invertebrate have demonstrated considerable improvement in disease SUSTAII>IAIIILITY OF SHRIMP FARMING 2

resistancethrough genetic selection Gjedrurn«nd than 7 years and is resistant to IHHN vit tts Fimland1995!. In vertebrates also have genetic potential Wi lkenfeld 1996!. toincrease disease resistance. Gaffney and Bushek 996! ~ Aquamarina de la Costa Caracas, Venezuela! re- studiedthe resistance of oyster Crassosrrehe to twoparasites, Perkinxus nu1rinus and MS X. Theydem- causedby IHHN virus in captivepopulations <>I P onstratedthat oysters originating from areas chronically vanna>neihave decreased from initial levels of 3S- infestedby P. marinuswere more resistantto infections 4S% to current levels of 3 10% due t< ri<>orouss<- with that parasitethan oysters originating from non- lection over severalyears Rosenberry199S!. affectedareas. Furthermore, selective brectding studies ~ Laboratorychallenge tests at University of Ariz< tlii increased resistance to either MSX or P. mari aux. How- haveconfirmed field resultsindicating improved r<- ever, oysters selected for resistance to MS X had reduced sistance to the TS virus of P. vann

of disease introduction. It also has environmental and fi- infectedsystems, water exchangeis reducedto a mini- nancial implications. Shrimp pond effluent represents a mum becauserepliicement water needed durin the evcle significant source of eutrophication for receiving water~. must be disinfected in a separate pond before introdu«. Briggs and Funge-Smith 994! estimated that 22riiie do~L' routine water exchange. In addition, water exchange can tor disintection depends upon the chlorire dern >nd;md causemortality of impinged and entrained organisms dur- pH of the water. ing pumping. I'inancially, water exchange i» costly in Harvest drainage. Brigg» and I'unge-Smith 994> terms of pumping, maintaining predator screens. and re- estimated that I 3c/eof the total input nitrogen;m c>t moving sediments from supply canals and ponds < Boyd the total input phosphorus of an intensiv »hi in>p pond 1992; Peterson and Daniel» 1992!. are released during harvest drainage. Schwarz and Boyd Until recently, little systematic research had been con- 994! found that 509 of the nitrogen, pho»pl>orus,;»>d ducted to evaluate the need for water exchange in aer- BOD discharged during drainage of channel catfi»h ated systems. Browdy et al. 993! demonstrated that I< isw;iste impact on growth or survival of P, ionnnniei in fiber- can be greatly reduced by using sedimentati<>i>ponds ii> glass tank» as long as acceptable DO level» were main- receive the final portion of harvest water Chanratchakool tained. Allan and Maguire 993! found that water ex- et il. 995!. change rates of 0 40% did not »ignificantl! affect Pond sediments. Shrimp pond» can accumuliite con- performance of P, monodon stocked in plastic-lined pools »iderahle quantities of' sediment from suspended soil at 20-40/m-. particles in inlet water supplies and from eix>sionof tlie Hopkins et al. 993! found that daily water exchange pond wall» and bottom. Two intensive shriml> ponds in could be reduced froiri 2 >e/<>to 2. >'/r in ponds stocked at Thailand accumulated an average depth of 7.s «m ol' 44/m' with no reduction in shrimp growth or produc- loosely consolidated sediment in a single 4-nionth pro- tion. In the absence of water exchange, biological oxy- duction cycle Boyd 1992!. Such high rates of seended use of sedimentation ponds At a density of 22/m-, shrimp performance was not hin- to rcmove sediments trom incoming water hef'ore it is dered by lack of water exchange, but at den»itic» of 44 used in shrimp pond». Erosion of ponds is caused mainly and 66/m-, water exchange was required to;ivoid mor- by aerators positioned around the periphery o>'thc p<>nd tality. Hopkins et al. 993! cautioned that the as»imila- and by wind-driven waves. Smith 996! estiinaied thiit tive capacity of ponds with zero water exchange and 20 erosion in aerated pond» for P. rnonodon ace<>untedlo> hp/ha of aeration i» approximately 70 140 k > <>fleed 19!t k ha d ol'sediment from pond wall».md 90 hg ha ' d '. Hopkins et al. 995! demonstratedthat lixed ha ' d from thc pond bottom Smith 1996!. daily rations of 68 136 kg/ha could produce 5.8 g.2 mt/ The quantity of org;mic material that accuniulates oii ha of P. i aimamei with zero water exchange and 20 40 the pond bottom t'rom uneaten 1'eed,organic t'ertilizer, hp/ha of aeration. shrimp excrement. and dead plankton increases in direct Little systematic research on water exchange ha» been proportion to stocking density Boyd 1992 Clifforrl conducted in non-aerated pond», where water exchange 1994!. Thi» or >anic inaterial enriches the sed>mentanil is used to control plankton density and thereby regulate generally results in;i much faster accumuliiti<>n rate. DO levels. Nevertheless, with the onset of the TS virus Brigg» and Funge-Smith 994! estimated thiit 31'/e <>1 in Ecuador, many farms reduced daily exchange rates the nitrogen and f"/> of the phosphorus inpui in an iii- from typical levels of 5 20'/r to I 4'/< with no negative tcnsivc shrimp pond was transferred to the»ediments. effects L. Anderson, Morrison International, O>uayaquif, To avoid inhibitin ~ effects of accumulated»eenton Ecuador, pers. comm.!. shrimp performance, many farmers wash the»edimen>s Disinfection of inlet water. Chlorine disinfection of' out of the pond follov ing harvest Clifford 1'!94!. This pond water is being used by more farms in Asia as mcans practice can deteriorate the quality of the receiving w;i of operating in areas affected by virulent pathogens and ter body. Sediments»houfd either be dried ai>d spread their carriers. The process involves treating pond water evenly over thc pond bottom between cycles Bi>yd 1992! with approximately 30 ppm of hypochlorite solution or removed from the pond when wet and dried in a sedi 0% concentration!, allowing a reaction time of 2--3 d. >1>entationpond. Chanratchakool et al. 99s! recoil>- dissipating chlorine residue with aeration, and then us- mended that the black anaerobic layer be flu»hed out i>r ing the pond 1'orculture C. P. Group 1994!. In such dis- the pond with a prcssure washer and pump d into a»edi. Sl>S'I'AI NAB1l.ll'Y OF SHRIMP FARMING ' !s

mentation pond. Sandifer and Hopkins 996! recom- tio could he balanced by providing a carbohydrate»upplc- mended that sludge be pumped 1'rom the ponds weekly ment to the pond<>r by including a carhohydratedilu<.nt during the productioncycle, settled,dried, and u»edto in the feed. The lack of water exchange is important i« improve agricultural land. give bacteriaimd other microorgani»ln!iden de- potentialopportunity in termsof polycultur« Shpigclct tritu»and zooplankton as a secondaryfoo hieh al. 1993; Chanratchakool et al. 199S; Sandifer and improves feed et'I'iciency. Moss et al. I'>92! found that Hopkins1996!. Promising polyculturc species are bivalve effluent I'rom a shrimp pond enhance'ar>l>an>ei89 zi more than inlet watei to the pond. feedingfish suchas tilapia and mullet. Seaweedsuch as Bombeo-Tuburan ct al. 993! found thai organic detri- Graeilaria sp. can also be reared in effluent» to strip ni- tu» was the most important food source in pcnaeid»i<>ni- trogen and phosphorus from the water column. ich». Some re»earchersattribute the nutr>tional v;>Iiita- bution of important nutrients Moss et .iI. 1992:H;irri» Continual advancements in shrimp nutrition are re- 1993!.Shpigcl et al. 993! found that niitritional v;iliie ducing the cost and improving the efliciency of shrimp of particulate matter also was enhanced hy att;><:hed feeds. This is partly related to a bette» understanding of benthic diatoins. nutrient requirements, ingredient digestibility, attract- Both Hopkins et al. 99S! and Avnimelech et,.il. ants, pigments, health additive», and feed processing 992! reporteda 50% reduction in fee<1c<>»t by u»ing methods D'Ahramo et al. 1997!. However, it i» also due minimal water nelech e< al. methods, particularly the u»e of feeding tray» to estiinate 992! used aeration rates of 200 hp/ha,;ind Hopkins el the daily consumptionrate of shrimp Chanratchakool al. 995! used rates of 20 40 hp/ha. Apparcntlv,;ier:i- ct al. 1995!. tion is es»entiiil to prevent sedimentation and relea.e <>I Low protein fccds. One of' the most proini»ingnew growth-retardinganaerobic metabolite»»uch a» hy- developmentsin shrimp nutrition is the usc of lov pro- gen sulfide. nitrite, and methane.Aerobic decoinp«»i- tein feed» in conjunction with zero water exchange. Re- tion lead» to the clean end-products of < arhon din»isle searchby Hopkins ct al. 995! indicated that P. >an»arnei and water. The potential of achieving high produ<.n reared in intensive ponds with zero water exchange per- rates and low FCRs using low protein feed and little <>r formed;is well with 20% protein feed a» with 40% pro- no water exchange looks very promising. I'uture rese;irch tein. Analogous results were also reported by Israeli re- should focus on optimizing pond design io reduce;i< r;i- searchersworking with tilapia Avnimelechct al. 1992!. tion requi>ement». This approach uses the ecology of the pond environment to maximize thc efficiency ol' feed Kochha et al. 1994!. Site Selection and Predictive Models In conventional shrimp ponds, only 6-24<%of the nitro- gen and 4 13% of the phosphorousinput are incorpo- Ecological inodels are being developtingthe tlusli- Phillips 1995!.In pondswith zerowater exchange, there ing time ot'coa»talinlehs based on meandepth, net evalx>- is an opportunity to usc the microbial coinmunity to re- ration rate, salinity of the open ocean, and salinity <>I'ihe cycle a portionof thesewastes for later con»umptionin inlet. The state of South Carolina, USA. asc» a dilution thc form of enriched detritus or plankton. model to deter>nine whether the effluent iii The threshold carbon to nitrogen C:N! ratio of food a proposedshrimp farm would causea significantchaiige for zooplankton and bacteria is approximately 10:I in the water quality of' the receiving stream Hopi in» <>t Anderson 1992!. Above thi» threshold, nitrogen i» lim- al. 1993!. Ward in press! developed a model of thc a»- iting and below it carboni» limiting. Typical leeds f<>r similative capacity of a Honduran estuary with re»pedy 206 "HAMBERLAIN as a function of farm area. Such models, coupled with headviral intection of Americanpenaeids hase,ilready routine monitoring,could allow plannersto regulateex- beendocumented. Tighter regulationsare needed to pre- isting shrimpfarming areasand avoid overdevelopment vent introduction of exotic diseases in frozen shrimp. of new areas. Major environmentaland social issues associated with shrimp farming include eutrophicationof estuaries,de- Legislation struction of mangrovcs,salt-water intrusion, discharge of chemicals and therapeutants. collectinii of wild A majoreffort hasbeen undertaken in Thailandto pre- postlarvacand reproductive adults, introduction of exotic vent a recurrence of the failures in Taiwan, China, and diseases, and social conflicts concerning land and water the upperGulf of Thailand.The following is a summary use.Proper resource planning, allocation, moniti>ring, and of recentshrimp farming legislation NACA 1994!: enforcementcan prevent many of theseproblems. ~ All shrimpfarms must register with theDepartment Newpond management technology is beingading ~ Farmslarger than 8 hamust submit the farm's con- ot'receiving waters,and reduce the cost ol'feed. Shrimp ceptualizeddesign and layout to the Departmentof aquacultureis in a stat«of transitionto a morecontrolled, Fisheriesfor approvalbefore construction. The de- efficient, and environmentally sustainabl« form, which sign mustinclude a wastewater oxidationpond no will positionit for substantialgrowth in the next century. smaller than 10% of the total pond surface area. The BOD of effluent should not exceed 10 ppm. Pond References effluent from the final portion of a pond haivest must be passedthrough the sedimentationpond before Allan, J. L.. and G. B. Maguire. 1993.The effects ol water dischargein order to reducethe load on public wa- exchangeon productionof Metat>enaeusmhieieuvi and wa ter quality in experimental pools. Journal of thc World ters. AquacultureSociety 24:321-328. ~ Farmersare no longer allowed to wash their sedi- Anderson,T. R. 1992.Modeling the influenceof fo >dC:N r;i ments into public waters following each harvest. tio, and respiration on growth and nitrogen excretion in They must dry the sedimentsand disposeof them marine zooplanktonand bacteria.Journal of PlanktonRe- in another manner. search14:1645-1671 ~ Biological treatment.such as cultivation of oysters, Avnimelech,Y., S. Diab. and M. Kocha. 1992.Conti ol anduti lizationof inorganicnitrogen in intensivefiss cultureponds. mussels, and seaweed in the sedimentation pond, is Aquacultureand Fist>eriesManagement 23 421-430. recommended. Bailey, C. 1988.The social consequencesof tropical shrimp mariculturedevelopment. Ocean hl'z Shoreline Management Conclusions 11:31-44. Beck, G., and G. S. Habicht. 1996.Immunity and the inverte- Shrimpfarming has been a multibillion-dollarincome brates.Scientific American275:60-66. earnerfor thetop-producing countries; however, the dis- Black, E. A., and J. Truscott. 1994.Strategies for reguhitionof tressingpattern of rapidexpansion followed by dramatic aquaculturesite selectionin coastalareas. Journal of AP- decline has raisedquestions about the sustainabilityof Plied Ichthyology 10:294-306. Bombeo-Tuburan,I., N. G. Guanzon,Jr., and G. I.. Schroeder current shrimp farming practices.Worsening viral epi- 1993.Production of Penaeusmonadan Fabr>eius,'i using four demicsare the primary factor limiting shrimp produc- natural food types in an extensive system. Aquaculture tion worldwide.By 1996,white-spot and Taura Syndrome 112:57-65. viruses were documented in virtually every shrimp- Boonyaratpalin, S., K. Supamataya,J. Kasornchandra,S. producing country in Asia and the Americas, respec- Direkusarakom, U. Ekpanithanpong,and C. Chantana- tively. This is a multifacetedproblem that must be ad- chookhin. 1993.Non-occluded baculo-like virus the caus ative agentof yellow-headdisease in the black tiger shrimp dressedby a multifacetedapproach. Penaeu.imh>nh>dhrn. Gyobo Kenkyu Fish Pathology!28:103. Clearly,improved systems for diseasemanagement are 109. neededif shrimpfarming is to recover.Fisheries authori- Boyd, C. E. 1992.Shrimp pond bottom soil andsediment man- ties andaquaculturists should work togetherto limit ex- agement.Pages 166-181 in J. Wyban,editor. Proceedings posure to new diseasesby restricting imports of live of the specialsession on shrimpfarming, Orlando, I'lorida, shrimp.Selective breeding for diseaseresistance shows 22-25 May ] 992,USA. World AquacultureSociety, Baton Rouge,Louisiana. promiseas a meansof adaptingto virusesalready estab- Boyd, C. E. 1996.Chlorination and water quality in aquacul lished in the local environment. ture ponds.World Aquaculture27:41-45. White-spotand yellow-headviruses are known to be Briggs, M. R. P.,and S. J. Funge-Smith.1994. A nutrientbud- enteringthe Western Hemisphere through imports of fro- get of some intensive marine shrimp ponds in Thailand zenshrimp, and the first casesof white-spotand yellow- Aquacultureand FisheriesManagement 25:789-811. SUSTAINABILITY OF SHRIMP FARMING 2

Brock, J. A., R. Gose,D. V. Lightner,and K. W. Hasson.1995. D' Abramo. L. R, D. E. Conklin. and D. M. Akiyama, I997. An overview on Taurasyndrome. an important diseaseof Crustaceannutrition. Advancesin World Aquaculture.Vol- farmedPenaeus vann«mei. Pages 84-94in C.L. Browdyand ume 6. World AquacultureSociety, Baton Rouge,I.ouisi- J.S. Hopkins, editors. Swimming thrns i. Aquaculture'95. WorldAquaculture Society, Baton Rouge, 1996.Time serieson aquaculture quantities and values. Louisiana. FAO FisheryInformation, Data, and Statisiics Unit F IDI i, Browdy, C. L., J. D. Hollow«y, C. O. King, A. D. Stokes,J. S. Aquacult-PC,Release 8494/96, April 1996. Hopkins, and P.A. Sandifer.1993. IHHN virus and inten- Fay, R. R. I995. Environmentalstudy of the < '.ayapas-Maiaje sive culture of Pe»ac»sv<>nnamei: Effects of stockingden- areafor the purposeof recommendingmanagement strate- sityand water exchange rates. Journal of CrustaceanBiol- gies,province ot Esrneraldas,Ecuador. Report prepared for ogy 13!:87-94. CamaraNacional de Acuacultura de Ecuadd kk Stratakis. 1995. Characterization of he i io-i Carr, W. H., J. N. Sweeney,L. Nunan, D. V. Lightner, H. H. lymph lectins in the prawn Parapenaeusi<>ngimxiri>..liiur- Hirsch,and J. J. Reddington.1996. The useof an infectious nal of InvertebratePathology 65:111-117. hypodermaland hematopoieticnecrosis virus geneprobe Frelier, P. F., J. K. Loy, and B. Kruppenbach,I 993.Transniii- serodiagnosticfield kit for the screeningof candidatespe- sionof necrotizing hepatopancreatitis in Pei«>e«sv«nn«»«i. cific pathogen-freePenaeux vannamei broodstock. Aquac- Journalof InverlebratcPathology 61:44-4K u tureI 147:1-8. Frelier,P. F.. J. K, Loy, A. L. Lawrence,W. A. Bray,and G. W. Chamberlain,G. W. 1991. Shrimp farming in Indonesia. I: Brumhaugh.1994. Status ot'necrotizing hepatopancreaiiris growout techniques.World Aquaculture22:12-27. in Texasfarmed shrimp, Pe»acus van»<. Pages 55-5>< i n Chamberlain,G. W. 1994.Taura Syndrome and China collapse USMSFP 10th AnniversaryReview, Gulf Coast Research causedby new shrimp viruses.World Aquaculture25:22- LaboratorySpecial Publication No. I, OceanSprings, Mii- 25. sissippl Chang,P. S., C. F. Lo, Y. C. Wang, and G. H. Kou. In press. Gaffney,P. M., andD. Bushek.1996. Genetic aspects of dis- Detectionof white spotsyndrome associated virus WSSV! easeresistance in oysters.Journal of Shellfish Research in experimentallyinfected wild shrimp,crabs and lobsters 15:135-140. by in situ hybridization.Aquaculture. Garriques,D., and L Arevalo. 1995.An evalu.itionof the pri>- Chanratchakool,P., J. F. Turnbull, S. Funge-Smith,and C. duction and useof a live bacterialisolate tn 15 IV-42 in G. W. Chamberlain,M. G. Haby, and R. J. on shrimpfarming, Aquaculture '95, World AquacultureSo- Miget,editors. Texas shrimp farming manual. Publication ciety, Baton Rouge,Louisiana. of TexasAgricultural ExtensionService, College Station, Harris, J. M. 1993.The presence,nature and rn;ilMann» Itami, T.. Y. Takahashi,and Y. Nakamura.1989. Elficacy of FisheriesService, Silv

harvestof channelcatfish from watershedponds. Progres- 'lacon, A. G. J., and K. Kurmaly. 1996.Nutriti.P. Alvizu, M. A. 1996Annual Meetingof theWorld AquacultureSoci«ly, ."> Oliveira, J. Perez,A. Quilici, M. Rada,M. '. Yaber,and M. January-21ebruary 1997, Bangkok, Thail pleas of land-useconflicts. EnvironmentalManagement I:647- White spotsyndrome associated viru< WSSV! infection in 661. culturedand wilIII, M. S. Brown, and E. J. Honduras, 26 29 April, 1995. Asocia«ii>nNaci<>n;il ACOP I <><. Office of the ScienceAdvisor, U.S. Agency for International Demonstaciondc altascualidades de la cep i deP»-232 in Song,Y.-L., andY.-T. Hsieh, 1994.Innnunostimulation of tiger MemoriasCongreso Ecuatoriano de Acuicu ltura. CISN k IM. shrimp Penaeu»monodon! hemocytes for generationof Guayaquil,Idcuador. microbiocidalsubstances: analysis of reactiveoxygen spe- Wiley, K. 1993.I'.nvironmental risk assessmentin shrimpaqu;i«- cies.Developinental and Comparative Immunology I I :201- ulture. Infofish Magazine February!:49-55. 209. Wilkenfeld, J. 199 '>.Aspectos operativos cn laboratorii>.ea giga» 'I'hunberg. Aquac- Organizedby Bancode Mexico, Mazatlan,Mexico. ulture and FisheriesManageinent 24:52urairatana,J. E. Vickers A Strutton,P. Ci., J, A. T. Bye, andJ. G. Mitchell. 1996.Determin- Akraja>norn,V. Boonsaeng,S. Pany m, A. Tassanak.i!on. ing coastalinlet flushing tiines: a practicalexpression for B. Withyachumnarnkul,and T. W. Flegel.1'>95. Yellow-head usein aquacultureand pollution management.Aquaculture virus of Penaeu1 Research27:497-504. Aquatic Organisms22:45-50. Sung,H. H., G. H. Kou, and Y. L. Song. 1994.Vi!>rio»is resis- Woodhouse.C. 19'. Farms avoid nev, U h. turtle curb < n tanceinduced by g lucantreatment in tiger shnmp Penaeu» shrimpimports. Fish Farminglnternatiorial 23!:2 . monodon!.Fish Pathology29:11-17.