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1、AUDITINGTHEACCURACYOFAVOLUNTEER-BASEDSURVEILLANCEPROGRAMFORANAQUATICINVADERBYTHOTREPHESSTEPHANIEA.BOUDREAU1andNORMAND.YAN∗1,21DepartmentofBiology,YorkUniversity,Toronto,Ontario,Canada;2DorsetEnvironmentalScienceCentre,OntarioMinistryoftheEnvironment,Dorset,Ontario,Canada(∗authorforcorrespondence,e
2、-mail:nyan@yorku.ca)(Received23April2002;accepted6February2003)Abstract.Wetestedthesamplingmethodsofavolunteer-basedmonitoringprogramdesignedtodetectthenon-indigenousspinywaterflea,Bythotrepheslongimanus,andfoundthattheprogramcoulddetectthemajorityofBythotrephesinvasions.Volunteerstaketwoverticalha
3、ulswitha30cmdiameternetateachofthreepelagicstations.Todetermineifthevolunteerswereusingalargeenoughnetattheirthreestations,weperformeda17-lakecomparisonofthevolunteer’snetwitha75cmdiameter,research-gradenet.WefoundnodifferenceinthenumberofstationsatwhichBythotrepheswasdetected(pairedt-test,p=0.155
4、)withthetwonets,becauseBythotrephesdensitieswereabovethedetectionlimitsforbothnets.Todetermineifthreestationsweresufficienttodetecttheinvaderwiththevolunteer’snet,wedeployeditat30stationsintwolakeswithaverage(HarpLake,4.17Bythotrephesm−3)vs.lowBythotrephesdensities(SugarLake,0.92m−3).InHarpLake,rep
5、eatedrandomizedsamplingofthe30setsofdataindicatedthatonlythreestationswereneededfor100%capturesuccess.InSugarLake,sevenstationswereneededfor100%capturesuccess,butthreestations,thecurrentprogramdesign,failedtodetecttheinvasiononly14%ofthetime.Keywords:Bythotrephes,non-indigenousspecies,samplingaudi
6、t,volunteersamplingprogram,zooplankton1.IntroductionEcologistsagreethatoneoftheprincipalthreatstothebiodiversityofinlandwatersisthespreadofaquaticnuisancespecies(A.N.S.,Salaetal.,2000).Bythotrepheslongimanus,hereaftercalledBythotrephes,isalarge,planktonic,predatory,ony-chopodidcladoceranthatisnati
7、vetoEurasia(Yanetal.,1992,Grigorovichetal.1998).ItwasintroducedintoNorthAmericanwatersbyballastwaterexchange,beingfirstobservedin1982inLakeOntario(Johannssonetal.,1991).SincethattimeBythotrepheshasspreadtoalmost50
