生态学课件T

T1收获理论,要点,收获目标,为了使种群开发获得最大回报，管理应以使对象种群可长期持续获得最大产量为目标。,Tomaximizethereturnsgainedbyexploitingapopulation,managementshouldaimtoharvestthemaximumyieldthatthemaximumyieldthatthepopulationcanproducesustainablyoverthelongterm.,KeyNotes,Thegoalsofharvesting,T1HARVESTINGTHEORY,最大持续产量,长期收获最大产量的一种方法是最大持续产量即MSY法。随着种群密度在很低的基础上开始增加，出生率超过死亡率，种群的净补充量增加。当种群密度达到最大环境容纳量时，死亡率上升，出生率下降。因此最大净补充量发生在中等密度、种群中存在许多繁殖个体、而种内竞争又相对较弱的情况下。这一最大净补充量即为人们可长期从种群中收获的最大量MSY。,Oneapproachtodeducethemaximumlong-termyieldisknownasthemaximumsustainableyield,orMSYapproach.Asapopulationincreasesindensityfromverylownumbers,thebirthrateoutstripsthedeathrate,sothenetrecruitment(births-deaths)intothepopulationrises.Asthepopulationdensityapproachesthemaximumtheenvironmentcansupport,thedeathrateincreasesandthebirthratefalls.Themaximumnetrecruitmentthereforeoccursatanintermediatedensity,whenintraspecificcompetitionisrelativelylowyettherearemanyreproductiveindividualsinthepopulation.ThismaximumnetrecruitmentisthemaximumnumberthatcanbeharvestedfromthepopulationsustainablytheMSY.,Maximumsustainableyield,配额限制,在一定时期，可通过控制配额（收获对象生物量或个体数量），限制收获。配额控制允许收获者在每一季节或每年收走一定数量的猎物。配额限制通常应用于海洋渔业来获得MSY，但成功例不多。这表明配额限制实际上很冒险，有可能导致过捕，甚至种群灭绝。,6500万年前，行星撞击地球造成恐龙灭绝想象图。,Harvestingmaybelimitedbycontrollingthequota(thebiomassornumberofindividualsculled)inagivenperiod.Quotacontrolsthusallowtheharvesterstoremoveafixednumberofthepreyspecieseveryseasonoryear.Quotalimi-tataioniscommonlyappliedinmarinefisheriestoachieveaMSYwithlimitedsuccess.Thetheorydemonstratesthatquota-limitationisintrinsicallyriskyandmaycauseoverexploitationandevenextinctionoftheharvestedpopulations.,Quotalimitation,努力限制,配额限制潜在的危险或通过导入努力限制来缓和。努力限制具有明显的优点。因为当猎物种群数量减少时，人们往往会通过更加努力来获限正在减少中的数量。,环境波动,利用种群增长模型预测被收获种群可获潜能的效果会受到环境波动的严重影响。因为环境波动会影响种群的出生率或死亡率。,Theabilityofmodelsofpopulationgrowthtopredicttheharvestingpotentialofapopulationisesverelycompromisedbyenvironmentalvariationwhichmayaffectrecruitmentormortality.,Environmentalfluctuation,Theriskinherentinquota-limitationcanbealleviatedbyadoptinganapproachoflimitingeffort.Thishasaclearadvantage-asapreyspeciesbecomesrarer,moreeffortwillberequiredtoseekoutandcatchthediminishingnumbers.,Effortlimitation,相关主题,种群和种群结构（H1）密度和密度制约（H3）出生率、死亡率和种群增长（H2）种群动态波动、周期和混沌（H4）,动态库模型,简单的模型不考虑种群的年龄结构，这使其预测能力有限，因为死亡率与繁殖力都是与年龄相关的。收获个体通常都是种群中体大、年高的个休，具有最高的繁殖潜能。精确地考虑到不同年龄群出生率、生长和死亡率的动态库模型对对象种群的预测效果更好。举例来说，考虑到不同年龄群的动态库模型意味着可理论上检测海洋渔业中使用不同大小网具的影响效果。,远洋捕捞船队正整装待发,载重500吨渔业辅助船,Simplemodelsdonotconsidertheagestructureofpopulations,whichlimitstheirpredictivepower,asthemortalityratesandreproductiveoutputofindividualsisage-specific.Usually,theindividualsharvestedarethelargerandoldermembersofthepopulation,whichhavethehighestreproductivepotential.Dynamicpoolmodelsexplicitlyconsidertherecruitment,growthandmortalityofdifferentageclasses,allowingabettermodelofthepopulationtobederived.Thisapproachmeansthat,forexample,theimpactofvaryingmeshsizeinamarinefisherycanbetestedtheoretically.,Dynamicpoolmodels,Relatedtopics,PopulationsandpopulationDensityanddensitystructure(H1)dependence(H3)Natality,mortalityandPopulationdynamicsfluctuations,growth(H2)cyclesandchaos(H4),T2渔业和捕鲸业,要点,渔业,海洋一直为我们人类提供丰富的食物资源。现在全球渔获量约1亿吨，其中一小部分并不直接被人类消费，而是用做动物饲料。,大洋生产力,与陆地系统相比，大洋是生产力很低的生境。大陆架生产力较高，但全球单位公顷渔获量很低，部分是因为大洋区极低的生产力，部分是由于渔获物处于食物链高营养级，其生产效率很低。,舟山渔场是中国最大的渔场，也是世界著名的渔场之一,Theseashavehistoricallyprovidedavaluablefoodsourcetohumanpopulations.Thecurrentglobalfishcatchisabout100milliontons,althoughasubstantialminorityofthisisnotusedfordirecthumanconsumption,butasananimalfeedsource.,KeyNotes,Fisheries,T2FISHINGANDWHALING,Theopenoceansareveryunproductivehabitatscomparedtoterrestrialsystems.Productivityishigheronthecontinentalshelves,buttheoverallglobalfishcatchrepresentsaverylowyieldperhectare.Thisispartlybecauseoftheverylowproductivityofmostoftheoceanarea,andpartlybecausetheharvestconsistsonanimalshighupthefoodchain,whichhavelowproductionefficiencies.,Oceanproductivity,公共灾难,公共灾难假说指的是公共享有的资源（如没有任何政府管辖的公海）容易由于个体私利而导致利用过度。这种行为不可能进行最大长期持续产量的管理，并使种群遭到破坏和毁灭。,过捕,由于过捕，渔业资源正处于全球性下降，几乎所有地区年渔获量都在减少。过去两个世纪人们一直在大量捕鲸，现已导致过捕，鲸数量大幅度下降。,Thehypothesisofthecommonssuggeststhatacommonlysharedresource(suchasopenoceansoutsidethecontrolofnationalgovernments)willtendgobeoverexploitedbyselfishindividuals.Suchbehaviormakesimpossibleanymanagementtomaximizelongtermyields,andwillleadtopopulationcrashesandextinctions.,Thetragedyofthecommons,Globally,fishstocksareindeclineduetooverexploitation,withtheannualcatchdeclininginalmostallregions.Whaleshavebeenfishedintensivelyforthepasttwocenturies,whichhasresultedinoverexploitationandadramaticdeclineinnumbers.,Over-exploitation,附带收获问题,多数渔业技术导致非对象种或个体的偶然性收获附带收获问题。附带收获的非对象种或个体被扔回大海，死亡。由于该问题造成种群的非控制性破坏，因此是主要环境问题之一。附带收获个体包括对象种中太小的个体、海豚、鲨鱼、鸟类（如褐眉信天翁）和海龟。,海豚,Mostfishingtechniquesresultintheincidentalcapture,by-catch,ofnontargetspeciesorindividuals,whicharethrownback,dead,intothesea.Thisisamajorenvironmentalproblemasitrepresentstheuncontrolleddestructionofpopulations.By-catchcanconsistofindividualsofthetargetspecieswhicharetoosmall,dolphins,sharks,birds(suchasthebrown-browedalbatross)andturtles.,Theby-catchproblem,相关主题,捕食的性质（J1）,污染,来自人类活动的污染的污染影响到水体食物链，有一些影响到渔捞对象种。主要污染物是石油、有毒化合物和有机废物。油泄漏使地区海洋生物遭到破坏，通常表现为渔获量长期减少。有毒化合物通常通过食物链危害人类消费者，如60年代发生在日本水俣（min-imata）的氯化甲基汞毒害事件。含有氮磷的污水和农肥会导致水华和富营养化。富养化环境会引起当地水域鱼类和无脊椎动物死亡以及珊瑚的毁灭。,Pollutantsfromhumanactivitiesaffecttheaquaticfoodchain,andsomeofthesehaveimpactsonharvestedspecies.Majorpollutantsareoil,toxicchemicalsandorganicwaste.Oilspillscauselocaldevastationtomarinelife,butgenerallyappeartoresultinlimitedlong-termeffectsontheharvestedstocksoffish.Toxicchemicalscanbepasseddownthefoodchain