摘要：

1Shellfishofmarketablesizecanbeharvestedmuchmorequicklyandefficientlyusingmechanicalmethodssuchastractor-poweredharvestersandsuctiondredgersthanbytraditionalmethodsTheadverseeffectsofsuchmachinesonnon-targetorganismsneedtobeconsideredcarefullybeforelicensingsuchactivities2Atractor-towedcockleharvesterwasusedtoextractcocklesfromintertidalplotsofmuddysandandcleansandinordertoinvestigatetheeffectsonotherbenthicinvertebratesandtheirpredators3Harvestingresultedinthelossofasignificantproportionofthemostcommoninvertebratesfrombothareas,ranginginthemuddysandfrom31%ofScoloplosarmiger(Polychaeta)(initialdensity120m(-2))to83%ofPygospioelegans(Polychaeta)(initialdensity1850m(-2))Significanteffectscouldnotbedetectedinmostpopulationswithadensityoflessthan100m(-2)4PopulationsofPygospioelegansandHydrobiaulvae(Gastropoda)remainedsignificantlydepletedintheareaofmuddysandformorethan100daysafterharvesting,andNephtyshombergi(Polychaeta),ScoloplosarmigerandBathyporeiapilosa(Amphipoda)formorethan50days5InvertebratepopulationsincleansandwithrelativelyfewcocklesCerastodermaedule(Pelecypoda)recoveredmorequicklythanthoseinmuddysandwithamorestructuredcommunity,whichincludedseveraltube-dwellingspeciessuchasPygospioelegansandLaniceconchilega(Polychaeta)6Birdfeedingactivityincreasedatfirstontheharvestedareas,withgullsandwaderstakingadvantageofinvertebratesmadeavailablebyharvestingSubsequently,intheareaofmuddysand,thelevelofbirdactivitydeclinedcomparedwithcontrolareasItremainedsignificantlyreducedincurlewsNumeniusarquataandgullsformorethan80daysafterharvestingandinoystercatchersHaematopusostralegusformorethan50days7Itisconcludedfromthisstudythattractordredgingforcocklesinhighdensityareas

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