FisheriesResearch79(2006)103 - PDF document

FisheriesResearch79(2006)103–111 FishinggearassociatedwithglobalmarinecatchesII.TrendsintrawlinganddredgingR.Watson,C.Revenga,Y.Kura Anewmethodforassociatingglobalmarinecatchstatisticswithshinggearshasallowedthecreationofmapswhichdetailthechanging 1.IntroductionBottomtrawlsanddredgesareamongthemostdestruc-tiveshinggearsinuse(EngelandKvitek,1998),withthecapacitytogreatlydisruptbenthicecosystemsinshallowaswellasindeepseawaters.Typicallybottomtrawlsarelargenetsthatarepulledacrosstheseabedheldopenbythedragonlargeplanningsurfacescalledboardsordoors.Theseareusuallyheavilyweightedandscourthebottom,whilethebot- R.Watsonetal./FisheriesResearch79(2006)103…111Anothermajorimpactofbottomtrawlingisthelargeinci-dentalcatchofnon-targetedspecies.Someofthisbycatchisretainedforsale,butaportionofit–oftenalargeportion–isreturnedtothesea,usuallydeadordying.Ingen-eral,shinggearsthataretowedalongthebottomseemtohavethehighestbycatchrates.AccordingtoAlversonetal.(1994),thetop20highestdiscardratios(theratiooftargetspeciestodiscards,byweight)aredominatedbybottomtrawlsherieswhereonlyone-fthorlessofthecatchisusuallyretained.ArecentreviewofthedifferentshinggearsusedintheUnitedStatesandtheirimpactonecosystemsconrmsthatbottom-trawlingrigs,bottomgill-netsanddredgeshavetheworstecologicalimpacts(MorganandChuenpagdee,2003;Chuenpagdeeetal.,2003;NRC,Giventheconcernabouttheuseoftrawlanddredgegearsthereisnecessarilymuchconcernaboutwheretheydeployed,andhowtheirusehaschangedinrecentyears.Thereispotentialtoimpactcriticalhabitatssuchascoralreefsandseagrassareas(Kaiseretal.,2002).Thereisalsoconcernabouttheiruseindeepwaterandinunregu-latedhighseasareas(Hall-Spenceretal.,2001;Cryeretal.,2002;Fossaetal.,2002).Usinganewgearassociatedglobaldatabasedescribedinacompanionpaper(Watsonetal.,thisvolume)weareabletocharacterizetheassoci-atedcatchesofthesegears,andexaminepatternsoftheiruseglobally.2.MethodsForeachorganismorgroupoforganismsreportedintheglobalcatchdatabasedevelopedbytheSeaAroundUsProject(SAUP)basedonFAOandotherdatasources(Watsonetal.,2004Watsonetal.(thisvolume)associatedgeartypeasdenedbyvonBrandt(1984).Theyfounditpossibletoassociatethemajorityofglobalcatchrecordswithuptovegeartypesinorderofimportanceandtoextrapolatetheseassociationstoallglobalcatchrecords.InthiswayitwaspossibletousethemappedresultsoftheSAUP(Watsonetal.,2005)toproducemapsofcatchesbyallgeartypesannu-allysince1950.3.Results3.1.GlobalcatchbytrawlanddredgeThereportedcompositionoftrawlanddredgecatchisquitediverse.BrokendownbymajorISSCAAPgroupings(i.e.,thebroadtaxonomicgroupsreportedbyFAO),thelargestcatcheswereofshrimpsandprawns,followedbysev-eralshgroups(Table1).Themolluscgroupssuchasclams,cockles,arkshells,scallops,pectensandoystersweretakenpredominatelybydredgegear.Othergeartypes,suchaspurseseine,tookthemajorityofthecatchreportedforsomegroups,Table1Breakdownofaverageglobalcatch(tonnes)takenbybottomtrawl,dredgeorothergearintoFAO’s‘InternationalStandardStatisticalClassicationforAquaticAnimalsandPlants’(ISSCAAP)groupsannuallyforthe1970sand1990s ISSCAAPgroup1970s1990s BottomtrawlDredgeOtherTotalBottomtrawlDredgeOtherTotal Shrimps,prawns6122435–12571562481502385189–3620722747261Marineshes(notelsewhereincluded)2888503–78130136698041203034–8199912023025Sharks,rays,chimaeras2051973–2312502283223452837–315361768198Squids,cuttleshes,octopuses473612–71063411842461528082–13515492879631Salmons,trouts,smelts29425–2917770294719532509–21072672139779Lobsters,spiny-rocklobsters26454–12595415240840964–180348221312Craylets,squatlobsters24180–853381095185478–6644171919Sea-spiders,crabs6793–340082346875205694–8786591084353Krill,planktoniccrustaceans55143461906776651221326169793176241Flounders,halibuts,soles––202757202757833190–2016861034876Cods,hakes,haddocks––903576790357672005888–845745010463338Redshes,basses,congers––272922927292292549853–38474936397346Jacks,mullets,sauries––21108892110889327645–26751503002795Herrings,sardines,anchovies––16762081167620811646588–2373820025384788Tunas,bonitos,billshes––66790866679086914–90971749098088Mackerels,snoeks,cutlassshes––341731334173131133641–78297778963418Abalones,winkles,conchs–4871855431104149–8971974097163816Oysters–3965651204397769–2435441476245020Mussels–179948304374484322–93881229813323694Scallops,pectens–344358344358–1208742–1208742Clams,cockles,arkshells–63022276865707087–9191701228701042040Sea-squirtsandothertunicates–116641905356–166348956558Horseshoecrabsandotherarachnoids–62430–276–276Seacucumbersandotherechinoderms–379373980877745–13042104452117494Total11628889163926646738968600071231335662825713636263601479564005 R.Watsonetal./FisheriesResearch79(2006)103…111 Fig.1.Mapsofcatchrate(tonneskm)associatedwithbottomtrawl(a–c)anddredgegears(d–f)fromNorthAmericaforthe1950s,1970sand1990s.largelypelagicspecies,suchasthegroup‘Tunas,Bonitosand3.1.1.NorthAmericaMappedcatchratesofallanimalscombinedtakenbybot-tomtrawlanddredgegearsrevealmanychangessincethe1950s(Fig.1).Inthe1950sthehighestcatchratesforeithertypeofgearwerealongthemidtonorthernseaboardoftheUS(Fig.1aandd).Bythe1970s,thebottomtrawlanddredgesherieshadincreasedtheirranges,particularlytonorthernAlaskaandthewestcoastofCanada.Mostnotableherewerethemajorbottomtrawlsheriesforpandalidshrimps,kingcrabs(Paralithodes)andyellownsole(MonochirusluteusAlsobythe1970s,bottomtrawlsheriesalongthenorth-eastcoastofNorthAmericaforhaddock(Melanogrammusaegle“nus)andseacatshes(Ariidae)sherieshaddeclined,followedbythedeclineofsheriesforsilverhake(ciusbilinearis)by1977.Notwithstandingindividualdeclines,bottomtrawlanddredgesheriescontinuedtoexpandeachdecadeandpeakedinthe1980swhenmajortrawlareasincludedmuchofAlaskanwaters,northernWashington,areasoftheGulfsofCaliforniaandMexico,aswellasNovaScotia.AlongtheNorthAmericannortheastcoasttherewereincreasesincatchofbottomtrawledyellowtailounder(Limandafer-),summerounder(Paralichtysdentatus),Americanplaice(Hippoglossoidesplatessoides)andpandalidshrimps.AlongthesoutheastcoastofNorthAmericaandintotheGulfofMexico,therewereincreasesinthecatchofbot-tomtrawledAtlanticseabob(Xiphopenaeuskroyeri)andseacatshes(Ariidae).AlongthewestcoastoftheU.S.therewereincreasesintrawledPacicOceanperch(),tongueshes(Cyanoglossidae)androckshes(Scor-Bythe1990s,catchesfrombottomtrawlingwereingen-eraldecline.Alongthenortheastcoast,therewerereduc-tionsinFloundercatches.AlongthesoutheastandintotheGulfofMexicothereweredeclinesincatchesofthenorth-ernpinkshrimp(Penaeusduorarum).Otherbottomtrawlsheriesthatincreasedafterthe1970sandalongthenorth- R.Watsonetal./FisheriesResearch79(2006)103…111 Fig.2.Mapsofcatchrate(tonneskm)associatedwithbottomtrawl(a–c)anddredgegears(d–f)fromEuropeforthe1950s,1970sand1990s.eastcoastincludedsheriesfornorthernprawn(Pandalusborealis),Greenlandhalibut(ReinhardtiushippoglossoidesAmericanangler(Lophiusamericanus)andpikeddogshSqualusacanthus).Furthersouth,therewasanincreaseintrawlsheriesthattookrays()andshrimp(PenaeusAlongthenorthwestcoastandintoAlaskaincreasesinbottomtrawledcatchesincludedyellowsole(M.luteusPaciccod(Gadusmacrocephalus),thelessersandeelAmmodytesmarius)androcksole(LepidopsettabilineataAlongthesouthwesttrawledcatchofcommonsquid(ThecatchofdredgesheriesinNorthAmericaincreasedafterthe1950s.TheincreasesalongtheEastcoastincludedAtlanticsurfclam(Spisulasolidissima)inthenorthandtheAmericancuppedoyster(Crassostreavirginica)tothesouth.Alongthenorthwestcoast,therewereincreasesintheweathervanescallop(Patinopectencaurinus),stripedVenus(Chameleagallina),Paciccuppedoyster(Cras-sostreagigas)andStimpson’ssurfclam(SpisulapolynymaSomedredgesheriespeakedbeforethe1990s;theseincludethoseforthecalicoscallop(Argopectengibbus)inthesouth-eastandforscallops(Pectindae)inthesouthwest.Bythe1990s,thedredgesheryfortheAmericancuppedoyster(virginica)haddeclinedandthatfortheoceanquahog(Arc-ticaislandica)hadincreasedinthenortheast.InthesouthwesttherewasadeclineindredgedcatchesofthePaciccuppedoyster(C.gigas3.1.2.EuropeTheexpansionofbottomtrawlanddredgesheriesinEuropewasasstrongasinNorthAmerica(Fig.2).ThoughhistoricallysheriesintheNorthSeapredatemanyothersintheWesternWorld,therewasneverthelessaclearincreaseinintensityfromthe1950suntilabout1980.Startingfromthe1950s,therewasanincreaseinbottomtrawlcatchofsandlances()andAtlantichorsemackerel(Trachurustrachurus).Atthistime,therewasadecreaseincatchesofoceanperch(Sebastesmarinus).FordredgesheriestherewereincreasesincatchesofthegreatAtlanticscallop(Pectenmaximus R.Watsonetal./FisheriesResearch79(2006)103…111 Fig.3.Mapsofcatchrate(tonneskm)associatedwithbottomtrawl(a–c)anddredgegears(d–f)fromSouthAmericaforthe1950s,1970sand1990s.Therewerepeaksinthecatchofsomebottomtrawlsh-eriesafterthe1970sandtheseincludedthoseforhaddock(aegle“nus),saithe(Pollachiusvirens)andsomesandlances.Thedredgesheriesforthebluemussel(Mytilusedulis)andcuppedoysters(Crassostrea)alsopeaked.MostexpansionoccurredoffshoreonthenorthernboundaryoftheNorthSea.Inthe1990stherewereincreasesincatchesofbottomtrawlednorthernprawn(P.borealis)anddredgedcommoncockle(Cerastodermaedule).Bythistime,theareaofmaxi-mumtrawlcatchrateshadcontractedtotheNorthSeaclosertoGermanyandDenmark(Fig.23.1.3.SouthAmericaAlongthecoastsofSouthAmerica(Fig.3),therehasbeenasteadyexpansionintrawlanddredge-relatedcatchuptoandincludingthe1990s,especiallyalongthecoastofArgentina.HerethebiggestbottomtrawlexpansionwasthesheryforArgentineshort-nnedsquid(Illexargentinus)inthemid R.Watsonetal./FisheriesResearch79(2006)103…1111980s.TherewasasteadyexpansioninthetrawlsheryfortheArgentinehake(Merlucciushubbsi)andsouthernbluewhiting(Micrormesistiusaustralis).AlongthewestcoastofSouthAmerica,wherepurseseinegeardominates,thebottomtrawlsheriesforsouthernhake(Merlucciusaustralis)andPeruvianhake(M.gayiperuanus)expandedafterthe1950s.Inthe1990s,paralleltothatalongtheArgentinecoast,therewasanincreaseinthecatchofthesouthernbluewhiting.ChangesalongSouthAmericasincethe1950swerelessthanthoseshowninNorthAmerica.Dredgesheriesinthispartoftheworldareminorcom-paredtothosebasedonothershinggears.AlongtheArgen-tinecoasttherewasanincreaseinthe1990sincatchofscallops(Pectinidae),andalongthecoastsofPeruandChile,thedredgecatchofTacaclam(Protothacathaca),Peruviancalicoscallop(Argopectenpurpuratus),carrotsquatlobsterCervimunidajohni)andslippercuppedoyster(Crassostreairedalei)increasedafterthe1950s.3.1.4.AfricaAlongthecoastofAfricatherehasbeenanexpansioninthecatchratesassociatedwithbottomtrawlgear.Thisexpan-sionrstoccurredalongtheWesternSahara,SenegalandtheGambia,andbythe1970sincludedthecoastofNamibiaandthesouthofAngola.IsolatedareasoftheGulfofGuineawerealsoinvolved(Fig.4).TherewassomeincreasealongMozambiqueandthenorthcoastofMadagascar.Dredgesh-erieswerenotimportantinthesetimeperiodsandthereforearenotdescribedhere.AlongNWAfrica,therewereincreasesinthetrawledcatchesofcuttleshes(Sepiidae)andthecommonsole()afterthe1950s.Bythe1970s,therewasapeakincatchesoftrawledSenegalesehake(Merlucciussene-),large-eyedentex(Dentexmacrophthalmus),por-gies(Sparidae),rays()andAtlantichorsemackerel(trachurus).SimilarlyalongtheSWcoastofAfrica,trawlingforhakes,especiallytheBenguelahake(Merlucciuspolliandfordentex(Dentexspp.)alsopeakedinthe1970s.Asthesedeclinedinthe1990s,othersincreasedincludingsh-eriesforoctopus(Octopodidae)andseacatshes(Ariidae)intheNW,andAtlantichorsemackerelintheSW.3.1.5.AsiaMapsofAsiashowasteadyexpansioninreportedcatchratesforbottomtrawlanddredgeassociatedsheries(Fig.5Throughouttheregion,therewasanincreaseinthetrawledcatchofcuttlesh(Sepiidae)afterthe1950s.InthetrawlsheriesoftheEastChinaSeaandtheSeaofJapanthereweredeclinesinthecatchofyel-lowcroaker(Larimichthyspolyactis)afterthe1950s.Therewere,however,increasesbythe1990sinthecatchesofsmallerspecieswithlowertrophiclevelsincludingJapaneseanchovy(Engraulisjaponicus),Gazamicrab(Portunustritu-berculatus),southernroughshrimp(Trachypenaeuscurvi-rostris),yellownsole(Lamadaaspera)andgoldenthreadnNemipterusvirgatus Fig.4.Mapsofcatchrate(tonneskm)associatedwithbottomtrawlfromAfricaforthe(a)1950s,(b)1970sand(c)1990s.IntheSouthChinaSea,extendingtotheArabianSeaandthewestcoastofIndia,therewereincreasesafterthe1950sinthetrawlcatchesofanchovies(spp.),gianttigerprawn(Penaeusmonodon)(thoughsomeofthelatter R.Watsonetal./FisheriesResearch79(2006)103…111 Fig.5.Mapsofcatchrate(tonneskm)associatedwithbottomtrawl(a–c)anddredgegears(d–f)fromAsiaforthe1950s,1970sand1990s.couldbemisreportedaquacultureproduction).TherewerealsoincreasedbottomtrawlcatchesalongthecoastofIndiaofseacatshes(Ariidae)andthesouthernroughshrimp,whileshrimpsfromthefamilyCrangonidaepeakedinthe1970s.Trawledcatchesofsomeunidentiedpenaeidshrimpdecreasedinthisareainthe1990s.ThoughtheexpansionappearstohavepeakedalongthewestcoastofIndiabythe1970s,thecoastofChinashowedacontinuedexpansionofreportedcatchrates,asdidthoseofThailand,MalaysiaandDredgingwaslessimportantinthisregionbutwasimpor-tantininshoreareasoftheSeaofJapanandtheEastChinaSea.ThoughcatchofdredgedJapanesecarpetshell(tapesphilippinarum)peakedinthe1970s,othersliketheJapanesescallop(Patinopectenyessoensis)andarkclamsArca)continuedtoincrease.FurthersouthintheSouthChinaSea,dredgedcatchesofbrownmussel(Pernaviridis)peakedinthe1970s,theshort-neckedclams(Paphia)peakedinthe1980s,whileAnadaraclams(Anadara)continuedtoincreaseafterthe1950s.3.2.ProportionofcatchusingtrawlordredgegearTheexpansionofbottomtrawlgearasthedominantgearassociatedwithcoastalsheriescatchinmanyareasoftheworldisevidentinFig.6.Thisgureshowstheproportionofallcatchthatistakenbybottomtrawl.Eveninthe1950s,formanyareasoftheworld,thisgearaccountedformorethan40%ofallreportedcatches.Theassociationincreaseddecadebydecadewithconcentrationsoftrawlingincreasinginmanylocations.Bythe1970s,trawlsheriesforAmericanplaiceH.platessoides)alongthewestcoastofGreenlandandtheGrandBanksofNewfoundland,marbledrockcod(niarossii)alongthecoastofAntarcticaandtheWeddellSea,Japaneseanchovy(E.japonicus)inAsia,andprawns,suchasbananaprawn(Penaeusmerguiensis),alongthenorthcoastofAustraliadominatedsheriesbyallothergears.Thisexpan-sionprocesscontinued,andbythe1990s,trawlsheriesforbluegrenadier(Macruronusnovaezelandiae)aroundNewZealandandfortheArgentineshort-nsquidalongthecoastofArgentinadominatedsheriesusingothergears. R.Watsonetal./FisheriesResearch79(2006)103…111 Fig.6.Mapoftheproportionofallreportedcatchassociatedwithbottomtrawlgear(excludesdredges)forthe(a)1950s,(b)1970sand(c)1990s.4.ConclusionsThistypeofdetailedspatialinformation(Watsonetal.,thisvolume)willbeinstrumentalininvestigatingthechangesintheimpactsofshinggearssuchasbottomtrawlanddredgingonmarinehabitatsandcommunities.Thereisconsiderablefearfordeep-watercoralsandothercommunitiesinthepathoftheexpansionoftrawling.Withthecontinuedexpansionofshinggearsintodeeperwatersandremoteareas,thistypeofanalysiswillbeextremelyvaluabletoinformpolicydevelopmentandtohelpdevelopfuturemanagementoptions.Considerabledebatecontinuesonhowbesttolimitdestruc-tiveshingactivitiesonthehighseaswherenational,andevenregionalbodieshavelittlepowertointercede.Withtheexpansionofdeep-watertrawling,andwiththeincreaseduseofoffshoreseamountsitesthereisagreaterneedtomonitorchangesinshingactivitiesandtheirimpacts.Inordertomakeinformationaboutglobalshingpatternswidelyavailable,theSAUPhascreatedawebsitethatmakesmuchofthedatareferredtohereavailable(Watsonetal.,).Itishopedthatthiswillinformthedebateontheeffectsofshingonthemarineenvironmentingeneralandontheimpactsoftrawlingspecically.AcknowledgementsThisworkwassupportedbytheSAUP,initiatedandsupportedbythePewCharitableTrustsofPhiladelphia,andbytheWorldResourcesInstitute,Washington,DC,throughfundsmadeavailablebytheSwedishInternationalDevelopmentCooperationAgency.WearegratefulfortheconsiderableeffortsofJordanBeblow,AdrianKitchingmanandErikoHoshino,andforsuggestionsandinsightsprovided R.Watsonetal./FisheriesResearch79(2006)103…111byDanielPaulyandotherSAUPcolleagues.GabrielleNowaraassistedwithediting.Anonymousrefereesandthejournaleditorsweremosthelpfulinprovidingdirectionsforrevision.ReferencesAlverson,D.L.,Freeberg,M.H.,Murawski,S.A.,Pope,J.G.,1994.Globalassessmentofsheriesbycatchanddiscard.FAOFisheriesTechnicalPaper339.Chuenpagdee,R.,Morgan,L.E.,Maxwell,S.M.,Norse,E.A.,Pauly,D.,2003.Shiftinggears:assessingcollateralimpactsofshingmethodsintheU.S.waters.FrontiersEcol.Environ.10(1),517–524.Cryer,M.,Hartill,B.,O’Shea,S.,2002.Modicationofmarinebenthosbytrawling:towardsageneralizationofthedeepocean?Ecol.Appl.12(6),1824–1839.Engel,J.,Kvitek,R.,1998.Effectsofottertrawlingonabenthiccom-munityinMontereybaynationalmarinesanctuary.Conserv.Biol.12,Fossa,J.H.,Mortensen,P.B.,Furevik,D.M.,2002.Thedeep-watercoralLopheliapertusainNorwegianwaters:distributionandsheryimpacts.Hydrobiologia471(1–3),1–12.Hall-Spencer,J.,Allain,V.,Fossa,J.H.,2001.TrawlingdamagetoNorth-eastAtlanticancientcoralreefs.Proc.:Biol.Sci.269(1490),507–511.Jennings,S.,Pinnegar,J.K.,Polunin,N.V.C.,Warr,K.J.,2001.Impactsoftrawlingdisturbancesonthetrophicstructureofbenthicinvertebratecommunities.MarineEcol.Prog.Ser.213,127–142.Kaiser,M.J.,Collie,J.S.,Hall,S.J.,Jennings,S.,Poiner,I.R.,2002.Impactsofshingonmarinebenthichabitats.In:AbstractsofPapersPresentedattheReykjavikConferenceonResponsibleFisheriesintheMarineEcosystem,Reykjavik,Iceland,1–4October2001,FAOFisheriesReportNo.658.Morgan,L.E.,Chuenpagdee,R.,2003.ShiftingGears:AddressingtheCollateralImpactsofFishingMethodsinU.S.Waters.IslandPress,Washington,DC.NRC(NationalResearchCouncil),2002.EffectsofTrawlingandDredg-ingonSeaoorHabitat.NationalAcademyPress,Washington,DC.Poiner,I.,Glaister,J.,Pitcher,R.,Burridge,C.,Wassenberg,T.,Gribble,N.,Hill,B.,Blaber,S.,Milton,D.,Brewer,D.,Ellis,N.,1998.FinalReportonEffectsofTrawlingintheFarNorthernSectionoftheGreatBarrierReef:1991–1996.CSIRODivisionofMarineResearch,Cleveland,Australia.vonBrandt,A.,1984.Classicationofcatchingmethods.In:FishCatch-ingMethodsoftheWorld,3rded.FishingNewsBooks,Surrey,Watling,L.,Norse,E.A.,1998.Disturbanceoftheseabedbymobileshinggear:acomparisontoforestclearcutting.Conserv.Biol.12(6),1180–1197.Watson,R.,Alder,J.,Kitchingman,A.,Pauly,D.,2005.Catchingsomeneededattention.MarinePolicy29(3),281–284.Watson,R.,Kitchingman,A.,Gelchu,A.,Pauly,D.,2004.Map-pingglobalsheries:sharpeningourfocus.FishFisheries5,168–Watson,R.,Revenga,C.,Kura,Y.Fishinggearassociatedwithglobalmarinecatches:Idatabasedevelopment.FisheriesRes.(thisvolume).