SEA FARMING AND SEA RANCHING SYSTEMS IN CHINAWord文件下载.docx
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SEA FARMING AND SEA RANCHING SYSTEMS IN CHINAWord文件下载.docx
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Culturedorganisms
Productionscale
Pondculture
Fish,shrimp,crab,molluscs,Gracilariaspp.
Commercial
Floatingraftculture
Seaweed,scallop,oyster,abalone
Mudflatculture
Laver,razorclam,hardshellclam,oyster
Penculture
Abalone,shrimp
Inshorecageculture
Fish
Offshorecageculture
Commercialandtrials
Tunnelculture
Abalone
Smallscale
Submergedcageculture
Abalone,fish
Smallscale(trials)
Indoortankculturewithwaterrecirculation
Flounder,turbotandotherfish,abalone
Seabottomcultureandsearanching
Abalone,Japanesescallop,giantcockle,seacucumber,seaurchin
Stockenhancement
Chineseshrimp,redseabream,flounder,largeyellowcroaker,mullet,jellyfish
Trials
1PondCulture
Ahighproportionoftheareaundercultivationisdevotedtopondcultureinmarineandbrackishwaters.Mostpondsarebuiltinmudflatareasandusedforfarmingshrimpandcrab.Asmallerareaproducesfish,molluscsandseaweed.Pondsarefedseawatereitherastidalpondsorbypumping.
Sincetheearly1980s,pondculturedevelopedrapidlythroughoutthecountrynotonlybecauseitstechnologywasrelativelysimpleanditrequiredlessinvestmentsbutalsobecauseofthetraditionalknowledgeoffishpondculturewhichexistedinChina.Anamplesupplyofpenaeidshrimppostlarvaeandprofitableeconomicreturnsfromshrimpculturefurtherstimulateddevelopment.
Butoverexploitationandpollutionofnaturalresourcesopenedthewaytovariousdiseasesandinparticulartothe1993viralepidemics.Thelatterledpolicymakers,investorsandfarmerstoreviewexistingpoliciesandculturalsystems.Nearly10yearslater,peopleagreethatitisindispensabletopaymoreattentiontobio-ecologicalprotection,tosocio-economicaspectsand,ingeneral,toallfactorswhichmightimpactonsustainabledevelopment.
2FloatingRaftCulture
Thereisalonghistoryofusingfloatingraftsforshallow-seafarming.Thissystemcanbeusedforavarietyofspeciessuchasseaweed(kelpandlaver),filteringorganisms(scallop,oyster,mussel)andabalone,combinedwithcultureinsmallsubmergedcages(lanterncages).
Thesystemiswidelyadoptedforfarmingkelp,oyster,scallop,abalone,etc.Thesespeciesbeingeitherautotrophicorfilteringorganisms,thereisnopollutionoftheenvironment,particularlywithkelpfarmingasmentionedbefore.
3MudFlatCulture
Thissystemisespeciallysuitableforfarmingbenthicspeciessuchasbloodcockle(Tegillareagranosa),hard-shelledclam(Meretrixmeretrix),manilaclam(Ruditapesphilippinarum),razorclam(Sinonovaculaconstricta)andseaweedsuchasPorphyraspp.ItisverypopularinChinabecauseitdoesnotrequirelargequantitiesoffoodanditdoesnotpollutetheenvironment.
Beforethe1980s,mudflatculturewaslimitedtoparticularareasbecauseofthedifficultytoobtainseedwhichhadtobecollectedfromwildstocks.Theseedsupplyisnowgreatlyimproved.Forbloodcockle,Cyclinasinensis,seedareproducedonacommercialscale.Forotherspeciesincludinghard-shellclamandmanilaclam,protectingwildbroodstockhasbeenaneffectivewaytoenhanceseedproduction.Forrazorclam,whichhasbeenfarmedinChinafordecades,wildseedarecollectedfollowingarathersophisticatedsysteminvolvingsiteselection,smootheningthespawningarea,forecastingseedsettling,collectingandtransportingseed.
Ingeneral,themudflatecologicalsystemisrathervulnerable,lyingattheinterfacebetweenseaandland.Forexample,insomeareas,mudflatshavebeenblindlyexploited,evenoverexploited,forshrimpfarmingwhichhasresultedindestroyingtheoriginalecologicalsystemandshrimpfarmingitself.Thishasoccurredtoofrequentlyandnowwehavetogiveprioritytotheprotectionofmudflatandmangroveforestareas.
4PenCulture
Sitesforpencultureareselectedinintertidalareaswherelowfencesandwatergatesarebuilt.Atlowtide,waterdepthdropstoaminimumof50to80cminsidethepens.Asthenexthightidalwaterstartscoming,itentersthepenswherewaterdepthincreasesprogressivelyagain.
ThisculturesystemispopularinsomeprovincesofChina,butproblemsarethesameaswithpondculture,pollutionhavingseriousimpactsontheenvironment.Thedevelopmentofthissystemshouldthereforebestrictlycontrolledandconfinedtoselectedareas.
5InshoreCageCulture
Inshorecagecultureisverypopularworld-wide,especiallyinAsia.Advantagesincludelowinvestmentandeasyroutinemanagement.Butthissystemisoneofthemainsourcesofinshorepollutionandthemaincauseforredtides.Ithasbeenreportedthat,inareaswhereinshorecagecultureiswelldeveloped,phosphoruscontentoftheseabottomis2000timeshigherthanthelegalvalueacceptedforenvironmentalprotection.Policymakershavebeguntonoticetheproblemsandtoissueregulationscontrollingthedevelopmentofthisculturalsystem,toprotectthenaturalenvironmentandtheaquacultureindustryitself.
Asmostfarmersusetrashfishtofeedculturedfishwithahighcommercialvalue,itdoesnottakelongbeforeagreatquantityoffaecesandfoodresiduesaccumulateontheseafloorandpollutetheentirearea.
Anotherproblemisthatfloatingcagescannotresiststrongwindsandwaves.Afteratyphoon,fewcagesarestillfunctionalandmanyofthefarmedanimalshaveescaped.Inthenearfuture,offshorecagecultureshouldbecomethemaincageculturesystem.
6OffshoreCageCulture
Chinaexperiencestyphoonsseasonally,especiallyinitssouthernregionsfromtheZhejiangProvincetotheHainanProvince.Eveniftyphoonsareonlyoccasionalinthenorthernregions,lossescanalsobeveryserious.
Traditionally,onlyfloatingcagesareusedininshorewaters.Duetopollutionandoverexploitationofthesewaters,fishcagefarmingshouldbemovedoffshore.AtpresenttherearetwotypesofoffshorecagesrecentlyintroducedintoChina.Onetypeisasinkablecage,theotherbeingaplasticgravitycage.
Researchersandfarmershavebeenencouragedtodesignnewmodelsofcageswhichwouldbeabletowithstandtyphoonsandstrongseacurrents.Inthenearfuture,offshorecagecultureshoulddeveloprapidly.
7ArtificialReefs
Anotherwayofsearanchingisusingartificialreefs.Thismethodwasexperimentedinthe1980sforfiveyears.Theoretically,itcontributestotheenrichmentoffisherynaturalresources.Butitssuccessdependsonmanyfactorssuchassiteselection,shapeoftheartificialreefs,desirablespeciesandotherenvironmentalconditions.Financialsupportisalsoimportantbecausereturnsoninvestmentsshouldbeconsideredonthelongtermonly.Thedevelopmentofthissystemhasbeenstopped.
8SeaRanchingandRestocking
Inthe1970s,DrC.K.Tsengpresentedaseriesoftalksandpublishedathesisentitled“Searanchingandseafarming”.Hedefined“ranching”asaculturesystemwhere“...atfirst,thecropisrearedinrestrictedareas,thenitsjuvenilesarereleasedintothenaturalenvironmentandfinallyitsadultsarefishedfromthisnaturalenvironment”.
Sincethe1970s,searanchingwastriedwithseveralspeciesinvarioussites.ShrimpofthespeciesPenaeuschinensiswererestockedonacommercialscale,especiallyinthelate1980sandearly1990s,attheannualrateofmorethanamilliardjuveniles.Duetounknownreasons,thisactivitywasstopped.Itwasobservedthatrecapturerateoftaggedshrimpdependedontheindividualsizeofstockedshrimpaswellasonthedurationandlocationoftherestockingprogramme.Tabulatedfiguresshowthatrecaptureratevariedgreatly.Thehighestratereached1.88percent,thelowestonly0.001percent.Itseemsthatsomeunknownfactorsinfluencerecapturealso.
Recapturerateforotherspecies,suchasabaloneandseacucumber,ismuchmorepredictablethanforshrimp.Accordingtodatarecordedfromcommercialcaptures,recapturerateforabalonemaybeashighas50to70percentifstockingsizeisgreaterthan30mm.Ifstockingsizeislessthan20mm,recapturerateisverylow.Forseacucumber,thisratedependsmoreonsiteselectionandimprovement,suchasincreasingshelteredareas.
Ingeneral,searanchingisagoodsystemtoenhanceortore-establishapopulationwhichhasdeclined,butnumerousfactorsinfluenceresults.Practically,atleastfourgroupsoffactorsshouldbetakenintoaccount:
-Speciesandnaturalpopulationcomposition
-Foodwebrelationshipsofstockedspecieswithnaturalpopulation
-Environmentalimprovement
-Factorsinfluencingrecapturerate,includingstockinglocation,durationofprogramme,sizeatstockingandpotentialpredators.
Resultsshowthatsearanchingisinitsinfancy.Thereisstillalongwaytogotoreachdesirablegoals.Cooperationinthisfieldshouldbestrengthenedandenlarged.
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