Positive Catch & Economic Benefits of Periodic Octopus Fishery Closures

24 Pages·2015·2.24 MB·English

RESEARCHARTICLE
Positive Catch & Economic Benefits of
Periodic Octopus Fishery Closures: Do
Effective, Narrowly Targeted Actions
‘ ’
Catalyze Broader Management?
ThomasA.Oliver1,2‡*,KirstenL.L.Oleson1,3‡,HajanainaRatsimbazafy1,
DanielRaberinary1,SophieBenbow1,AlasdairHarris1,4
1 BlueVenturesConservation,39–41NorthRoad,London,N79DP,UnitedKingdom,2 Departmentof
Biology,UniversityofHawaiʻiMānoa,2853McCarthyMall,EdmondsonHall309,Honolulu,Hawaii,96822,
UnitedStatesofAmerica,3 DepartmentofNaturalResourcesandEnvironmentalManagement,University
ofHawaiʻiMānoa,1910EastWestRoad,Sherman101,Honolulu,Hawaii,96822,UnitedStatesofAmerica,
4 EnvironmentalChangeInstitute,UniversityofOxford,SouthParksRoad,Oxford,OX13QY,United
Kingdom
‡Theseauthorsareco-primaryauthorsonthiswork.
* [email protected]
OPENACCESS
Citation:OliverTA,OlesonKLL,RatsimbazafyH,
RaberinaryD,BenbowS,HarrisA(2015)Positive Abstract
Catch&EconomicBenefitsofPeriodicOctopus
FisheryClosures:DoEffective,NarrowlyTargeted
Actions‘Catalyze’BroaderManagement?PLoSONE
10(6):e0129075.doi:10.1371/journal.pone.0129075 Overview
AcademicEditor:DennisM.Higgs,Universityof EightyearsofoctopusfisheryrecordsfromsouthwestMadagascarrevealsignificantposi-
Windsor,CANADA
tiveimpactsfrom36periodicclosureson:(a)fisherycatchesand(b)villagefisheryincome,
Received:February14,2014 suchthat(c)economicbenefitsfromincreasedlandingsoutweighcostsofforegonecatch.
Accepted:May4,2015 Closurescovered~20%ofavillage’sfishedareaandlasted2-7months.
Published:June17,2015
FisheryCatchesfromEachClosedSite
Copyright:©2015Oliveretal.Thisisanopen
accessarticledistributedunderthetermsofthe Octopuslandingsandcatchperuniteffort(CPUE)significantlyincreasedinthe30daysfol-
CreativeCommonsAttributionLicense,whichpermits lowingaclosure’sreopening,relativetothe30daysbeforeaclosure(landings:+718%,
unrestricteduse,distribution,andreproductioninany
p<0.0001;CPUE:+87%,p<0.0001;n=36).Open-accesscontrolsitesshowednobefore/
medium,providedtheoriginalauthorandsourceare
credited. afterchangewhentheyoccurredindependentlyofothermanagement(“noban”,n=17/36).
Ontheotherhand,open-accesscontrolsitesshowedmodestcatchincreaseswhenthey
Funding:Fundingforthisstudywasprovidedbythe
WaterlooFoundation,theJohnD.andCatherineT. extendeda6-weekseasonalfisheryshutdown(“ban”,n=19/36).Theseasonalfishery
MacArthurFoundation,theUSNSFOISE0853086, shutdownaffectstheentireregion,soconfoundallpotentialcontrolsites.
andtheNetworkforSocialChange.Thefundershad
noroleinstudydesign,datacollectionandanalysis,
FisheryIncomeinImplementingVillages
decisiontopublish,orpreparationofthemanuscript.
CompetingInterests:Theauthorshavereadthe Invillagesimplementingaclosure,octopusfisheryincomedoubledinthe30daysaftera
journal'spolicyandhavethefollowingpotential closure,relativeto30daysbefore(+132%,p<0.001,n=28).Controlvillagesnotimple-
conflicts:Theauthorsareeitheradvisorsto(Oliver, mentingaclosureshowednoincreaseinincomeafter“noban”closuresandmodestin-
Oleson)oremployeesofBlueVentures
creasesafter“ban”closures.Villagesdidnotshowasignificantdeclineinincomeduring
Conservation,theNGOthatco-managesthe
VelondriakeLocallyManagedMarineArea(LMMA). closureevents.
PLOSONE|DOI:10.1371/journal.pone.0129075 June17,2015 1/24
Catch&EconomicBenefitsofPeriodicOctopusFisheryClosures
Thepresentedworkanalyzesfisherymanagement NetEconomicBenefitsfromEachClosedSite
techniquesperformedintheVelondriakeLMMA,by
Landingsinclosuresitesgeneratedmorerevenuethansimulatedlandingsassumingcon-
theco-managingpartners:(1)theVelondriake
Committee,amanagementbodyrepresentingthe25 tinuedopen-accessfishingatthatsite(27/36showpositivenetearnings;mean+$305/clo-
villagesoftheLMMAand(2)BlueVentures sure;mean+57.7%monthly).Benefitsaccruedfasterthanlocalfishers’timepreferences
Conservationstaff.Thesefactsdonotalterthe
during17-27ofthe36closures.Highreportedratesofillegalfishingduringclosurescorre-
authors'adherencetoPLoSONEpoliciesonsharing
dataandmaterials. latedwithpooreconomicperformance.
BroaderCo-Management
Wediscusstheimplicationsofourfindingsforbroaderco-managementarrangements,par-
ticularlyforcatalyzingmorecomprehensivemanagement.
Introduction
Asover-exploitationandglobalchangethreatenreefsworldwide,sustainablymanagingcoral
reefsiscrucialtoprotectingbothreefbiodiversityandthefoodsecurityofhundredsofmillions
ofcoastalpeople[1–4].Becausetwo-thirdsofallreefslieindevelopingcountries[5],thegoal
ofconservingreefsgloballyrequiresmanagementstrategiesthatcaneffectivelybalanceboth
conservationanddevelopmentgoals.Thisdevelopingworldsettingfrequentlyincludeshigh
populationgrowthrates,lowincomes,andweaknational-scalegovernance[6–8].Inthiscon-
text,localcommunities’supportformanagementactionsiscrucialtoeffectivelyprotectbiodi-
versityandhumanlivelihoods[9–13].
Thereisagrowingbodyofresearchreportingoncoastalmanagementeffortsdesigned,en-
forced,andmaintainedbycommunitiesorcommunitieswithanexternalpartner(co-manage-
ment)[9,14–16].Employingabroadarrayofmeasures,communityandco-management
arrangementsaroundtheworldhaveproducedpositiveoutcomesforbothconservationand
developmentgoals[9,13,16].Wheneffective,sucharrangementscanhelpcommunitiesbetter
managetheirresourcesoverthelongterm,helpingthembreakfromthetragedyofthecom-
mons,whereopenaccessleadstooverexploitation,andfromresource-dependentpoverty
traps,wherenaturalresourcedepletionanddependencereinforceeachother[17–19].Howev-
er,whilecommunityandco-managementmodelsarebecomingmorecommon,quantitative
impactassessmentsremainuncommonandmanymanagementfailuresareunder-reported.
Theseresearchgapshinderrobustgeneralizationsabouttheeffectivenessofcommunityand
co-managementapproaches[9,11].
Theperiodicfisheryclosure,inwhichfisherstemporarilyrefrainfromharvestinginspecific
areas[20,21]isanincreasinglypopularcommunity-basedtoolwithagrowingbaseofempirical
support[22–24].Periodicclosureshavelongbeenapartoftraditionalfishingculturesacross
theIndo-Pacific[20,25–27],andstillplayanactiveroleincommunitymanagementofmarine
resourcesintheregion[22–24,28].Periodicharvest,orpulsefishing,alsohasbeenacommonly
discussedstrategyinthewesternfisheriesliterature[29],andhasbeensuggestedasaviableal-
ternativetoconstant,orstationary,fishingyieldssinceatleastthe1970s[30,31].
Manyperiodicharvestregimeshavebeendesignedwithasingle-speciesinmind[32].Prac-
ticalexamplesfrombothmodelsandfielddatagenerallytargetsedentarymarineinvertebrates,
andhighlightthaturchins[33],seascallops[34,35],andabalone[36]makegoodcandidates
foraperiodicregime.PeriodicclosureregimesinthetropicalIndo-Pacifichaveshownpositive
effectsonabundanceingiantclams(Tridacnaspp.)[22]andvariedresultsfortrochus(aka
topshell,Tectusniloticus)[22–24,37,38].
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Catch&EconomicBenefitsofPeriodicOctopusFisheryClosures
Periodicharveststrategiesinartisanalcontextsfrequentlyapplynottosingletargetspecies
butinsteadtomulti-speciesassemblages,includingrelativelylong-livedreeffishes[22–
24,28,39,40].Thefewstudiesthathaveshownpositiveeffectsofperiodicclosuresonmixed
reeffishfisheriesnotedincreasesinfishbiomassinperiodicallyclosedareasrelativetoopenac-
cesssites[22,23].Allthreefocalareasinthesestudies,however,werecharacterizedbysmall
humanpopulationsexertinglowfishingpressureonresourcestowhichtheyhaveexclusive
tenure[22,23];theresultsdonotholdinareassubjecttohigherfishingpressures[28,39–41],
perhapsbecauseclosureperiodsweretooshort,openperiodstoolong,orfishingintensitydur-
ingopenperiodswastoointensetosupportrobustrecoveryfromfishingmortality[28,39–41].
Anotherreasonmaybethatinareaswithhigherpressureandcompetition,fisherpopulations
preferimmediaterewardfromlandingasmallercatchtodayoveralargerandmoreuncertain
futurecatch[42].
Whileresultsfromthefieldhavebeenvariable,modelsoffisherieseconomicssuggestthat
incertaincasesaperiodicharvestcanprovideabettereconomicyieldthanstationaryharvest
[30,31],specificallywhenthefisheryhaslowselectivity[31,43].Afishery’soptimalopening/
closingcycle(i.e.,thepulse-length)isafunctionofboththetargetspecies’biology(i.e.,specifi-
callythetargetspecies’growthrateandlife-span)andthefishery’seconomics(i.e.,landing
pricesandthelocalfisher’sdiscountrate,theirtimepreferenceforimmediateversusdelayed
reward)[43].Thetimebetweenopeningsvariesdramaticallydependingonthetargetspecies’
biology[32],andhigherdiscountratesleadtoeithershorteningtheoptimalclosuredurations
orshiftingtheeconomicoptimumtostationary,ratherthanperiodicharvest[31,44].
Modelsandexperiencesuggestthatthesuccessorfailureofaperiodicclosureregimede-
pendsonthegovernancesystem’sabilitytomatchfishingpatternstoafishery’s“optimal”peri-
odicharvestschedule[23,24,29].Factorsshowntoimprovetheoddsofmatchingactualand
optimalharvestinthecontextofperiodicclosuresinclude:exclusivetenuretotheresourcein
question,respectedandlegitimateleadership,highsocialcapital,lowfishingpressure,loweffi-
ciencygears,androbustecologicalknowledge[22–24,45].Notsurprisingly,thesegovernance
factorsmirrorthosethatmoregenerallycorrelatewithsuccessfulcommunity/co-management
[13,16,46].
Experiencewithsuccessful,targetedmanagementmightalsoserveasacatalystforbroader
communitymanagement[24,45,47].InVanuatu,government-sponsoredmanagementefforts
employingarangeofinterventions,includingperiodicclosures,ledtocommunityengagement
withmanagersandco-managementofmanyotherspeciesoffishandinvertebrates[47].InIn-
donesia,villageswithactiveorlapsedperiodicclosuretraditionsshowedbroader,moreactive
marinemanagementthanvillageswithnosuchtradition[45].Commonstheorysuggeststhat
communitiesaremorelikelytoengageinmanagementwhenexpectedbenefitsoutweighthe
perceivedcostsofmanagement[17].Inthesecases,successfuldemonstrationsofdesirableben-
efit:costratioslikelyinformedexpectations,whileofferinganopportunitytobuildgovernance
capacityandsocialcapitalneededtobroadenmanagementefforts[17].
Herewepresentananalysisofthefisheryandeconomiceffectsofperiodicoctopusfishery
closuresintheVelondriakeLocallyManagedMarineArea(LMMA)insouthwestMadagascar
(Fig1).Thisworkservestofillresearchgapsbyprovidingempiricalimpactassessmentsofco-
managementoutcomesforaspecificperiodicfisheryclosureregime.Establishingthebaseline
efficacyoftheseinterventionsisparticularlytimely,astheuseofperiodicclosuresasafisheries
managementtoolisproliferatingacrossthewesternIndianOcean[48].
Todoso,first,wequantifyeffectsonsite-specificlandingsandcatchperuniteffort(CPUE)
frommultipleperiodicclosureeventscomparedtopairedcontrols.Second,weexamineocto-
pusfishery-generatedincomeaccruedatthevillagelevel.Third,weassesswhetherindividual
closedsitesgenerateneteconomicbenefits,andcomparetheratesatwhichthesebenefitsare
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Catch&EconomicBenefitsofPeriodicOctopusFisheryClosures
Fig1.MapsofStudyArea.(A)Large-scalemapofMadagascarandtheAfricancontinent,(B)Insetofthe
25villagesoftheVelondriakeLocallyManagedMarineAreainsouthwesternMadagascar.Vertical
boxextentis~75km.(C)Representativeexampleofaperiodicoctopusfisheryclosure.Indicatedinthemap
aretwovillages,AndavadoakaandAmpasilava,withtheirrespectiveoctopusfishingsitesmappedinorange
andyellow.Ingreen,youcanseethesitesAmagnahitseandNosinkara,inwhichthesetwovillageshave
repeatedlyco-implementedaperiodicoctopusfisheryclosure.
doi:10.1371/journal.pone.0129075.g001
generatedtolocalfishers’timepreferences(Fig2).Finally,asbroaderco-managementefforts
intheLMMAfollowedthewidespreadadoptionoftheoctopusclosureregime,wediscussa
fertileareaforfutureresearchtestingthehypothesisthateffectiveperiodicclosurescanserve
asacatalystforbroadercommunitymanagement.
Methods
2.1.MarineResourceManagementintheVelondriakeLMMA
Startingin2003,thenon-governmentalorganizationBlueVentures,withlocalandinterna-
tionalpartners(InstitutHalieutiqueetdesScièncesMarines,WildlifeConservationSociety,
COPEFRITO)beganaseriesofmeetingswiththecommunityofAndavadoakainsouthwest
Madagascartodiscussapproachestomanaginglocalmarineresources.Ininitialconversations,
thecommunitydemurredfromengaginginpermanentno-takeareas,butwaswillingtoat-
tempta7-monthclosureofoctopusfishingonashallowoffshorereefbeginningNovember1,
2004[49].
Afterafavorableinitialreception,thisclosureregimespread.Locally,the25villagesthat
nowcomposethe~1,000km2VelondriakeLMMAoversaw69differentoctopusclosuresbe-
tween2004and2011[48,50].AnAfricanDevelopmentBankprojectsupported50additional
closuresaroundsouthwestMadagascarbetween2009and2013[49].Further,beginningin
2005thenationalgovernmentformalizedthecommunityinitiativebyshuttingdowntheentire
southwestregionoctopusfisheryforsixweeksbetweenmid-DecemberandlateJanuary[49].
Themodelalsospreadinternationally,withtheneighboringislandstateofMauritiusenacting
similarlegislationin2012[51].Followingthespreadoftheoctopusclosureregime,theVelon-
driakeregionalmanagementcommitteetookbroadermanagementstepswithintheLMMA,
institutingperiodicmangroveclosurestargetedatalocalcrabfishery,banningdestructivefish-
ingpractices,engaginginecologicalmonitoring,and,fiveyearsafterrefusingtheidea,institut-
ingthefirstofnowsixpermanent,community-enforcedno-takeareas[48,49].
TheoctopusfisheryinVelondriaketargetsagroupoffourshallow-waterspecies:Octopus
cyanea(95%oflocalcatches),Callistoctopusmacropus(~4%),Amphioctopusaegina(~1%),
Callistoctopusornatus(rare)(D.Raberinarypers.comm,[52]).Thesefouroctopusspecies
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Catch&EconomicBenefitsofPeriodicOctopusFisheryClosures
Fig2.Experimentaldesignandsamplessizesusedtoinvestigateeffectsofperiodicfisheryclosures.(A)Sitefisherycatches,(B)Villagefishery
income,and(C)Siteneteconomicbenefts.Colorshighlightthedistinctionsamong“no-ban”and“ban”closures,andbetweenclosuresites/villagesand
eitheropen-accesscontrols(A&B)orsimulatedlandings(C).
doi:10.1371/journal.pone.0129075.g002
eachhavealifecycleofaboutoneyear,dispersingasparalarvaefor2–3months,thengrowing
over6–9monthsfrom<1gatsettlementtocommonlyabove3kg[53–55].Theyappeartobe
year-roundspawners,althoughrecentstudiessuggestthatrecruitmentfluctuatesthroughout
theyear[52].
Thebulkofoctopusiscaughtduringspringlowtidesbygleaners,predominatelywomen.
Theygenerallysellanyoctopusoverthenationallyregulatedminimumsizeof350gtooutside
buyers[56,57].Thoughonly180kmnorthofToliara,thisregionlackstransportinfrastructure,
renderingtheisolatedvillagesdependentonprivateexportingcompaniesformarketaccess.
Uponinstitutinganoctopusclosure,villagerstypicallycloseaboutonefifthoftheirvillage’s
octopusharvestarea(~124ha+/-45CI95),foraperiodbetween2–7months,sometimesre-
peatedly(Fig1C;KeyInformantInterviews,ShawnPeabody,co-manager).TheVelondriake
Committee,anelectedmanagementbody,selectsclosuresites,choosesclosuredurations,and
coordinatesmanagement.Communitiesself-enforcetheclosures,sanctionsareprescribedby
locallaw(dina),andenforcedbyconsensusatcommunitymeetings[58].BlueVenturesCon-
servation,theco-managingnon-governmentalorganization,providestechnicalandfunding
supportformanagementeffortsincooperationwiththepartnersmentionedabove[49].
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Catch&EconomicBenefitsofPeriodicOctopusFisheryClosures
2.2.Socioeconomicbackgroundandsurveys
Mostoftheapproximately7,500peoplelivinginVelondriake(S1andS2Tables,S1File)are
Vezo,asubgroupoftheSakalavaethnicgroupwhoseculturalidentityistiedtoafishingand
gleaninglifestyle[59].Consistentwiththeirlivinginaverypoornation,Vezopopulationsare
frequentlycharacterizedbylowincomes,highresourcedependence,andrapidpopulation
growth(~3%annually)[60].
Toexpandthelocalinformationavailable,asocio-economichouseholdsurveywascon-
ductedbetweenAugustandSeptember2010across16villagesand301households(alsosee
[61]).The35-questionhouseholdsurveycollecteddataonhouseholddemographics,income
sources,fishingpractices,wealth,andresourceextractionhabits.Thesurveydesignwasbased
onregionalsocio-economicmonitoringguidelines[62]andvalidityrecommendations[63].To
ensurevalidity,atrained,localVezosurveyteamundertookthesurveyinVezo;abi-lingual
fieldmanagersupervisedtheteams.Pilotsurveysinthreevillageshelpedinformthefinalsur-
vey.AllsurveydataweredoubleenteredinExcelandqualitycontrolled.
Villageswerestratifiedaccordingtogeographicregion(north,central,south)toaccountfor
proximitytomarket,andsurroundinghabitat(island,coast,mangrove,inland)toaccountfor
differencesinfishinghabits.Inlandvillageswereeliminatedfromthestudyduetotheirgreater
dependenceonfarmingratherthanfishingandnosouth-islandvillagesexist.Theeightre-
mainingstrata(north-island,north-coastal,north-mangrove,central-island,central-coast,
central-mangrove,south-coast,south-mangrove)allowforextrapolationtonon-sampledvil-
lages.Whenpossible,fortyrandomhouseholdsweresampledineachstratum,andfemaleand
maleheadsofhouseholdwerealternatelyinterviewed(S1Table).Uponenteringavillage,each
memberofthesurveyteampickedarandomnumberbetween1and12representingthedirec-
tionheorshehadtowalk(e.g.,3meant3o’clock).Walkinguptoeachhouseholdalongthat
trajectory,surveyorsconsultedalistofpreviouslygeneratedrandomnumbersbetween1and
100;ifthenumberwasbelow“X”thenthehouseholdwassampled.“X”wasdifferentforeach
village,andisthe(#ofsampledhouseholdsdesired)/(thetotal#ofhouseholdsinthatvillage).
FocusgroupswithfishersandgleanersinthemainvillageofAndavadoakaprovideddata
onmarketpricespaidforcatch,quantityandcostofgearused,andseasons(totalof12focus
groups).Interviewswithfishers,commercialbuyers,localmiddlemen(“souscollectors”),fish
mongers,managers,andvillagersacrossVelondriake(totalof26interviews)providedinforma-
tionon:marketprices,patternsofcommunitydecisionmaking,localengagementwithman-
agement,etc.Focusgroupparticipantsandkeyinformantswereopportunisticallysampled,
andsnowballsamplingidentifiedadditionalparticipants/informants.Marketsurveysanddi-
rectobservationscorroboratedinformationsuchasmarketpricesoffishandgear.
2.3.LandingsData,SalePrice,ParticipatoryMapping
Since2004,traineddatacollectorsrecordedoctopuslandingsacrossVelondriakeatthepoint
ofsale.Eachday,collectorswaitedatthepointofsaleineachparticipatingvillage,whichal-
lowedeasycollectionofalargeproportion(ifnotcompletecoverage)oftheday’scatch.Collec-
torsrecordedeachfishingtripincludingthenumberoffishersinthegroup,numberof
octopuscaught,weightofeachindividualoctopus,fishingsite,date,villagename,geartype,
fishernames,fisherages,andfishergenders.Datacollectedafter2008includesoctopussexas
well.Thedataset’s258,108individualweighedoctopusesfrom67,990tripsweredouble-en-
tered,cross-checked,andqualitycontrolledin2010–2011.
Thepriceperkilogramoctopuswasassessedthroughdirectobservationsatpointsofsalein
June-August2009,andtrendsinthe“beachprice”overtimewereconfirmedthroughfocus
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Catch&EconomicBenefitsofPeriodicOctopusFisheryClosures
groupsandkeyinformantinterviews(S2Table).Priceswereadjustedforinflationandpur-
chasingpower[8].
In2009–10,weconductedparticipatorymappingexerciseswithfishersinallVelondriake’s
villagestodefineboundariesofeachfishingsite.Thisexerciseimprovedthemanagers’andre-
searchers’abilitytotranslatebetweenlocalsitenamesandspecificfishingareas.Afocusgroup
ofeachvillage’soctopusfisherswasaskedtodelineatetheirvillage’snamedsitesonlarge,lami-
natedpostersshowingthesatelliteimagery(GoogleEarth)ofthevillage’scoast.Thesemaps
werethendigitizedandtransferredintoGISshapefiles.Eachsitewasgivenauniqueidentifier,
cross-referencedtothelocalsitenames,andconfirmedwithvillagers[64].
2.4.IllegalCatchRate
Asameasureofcompliancewithclosures,weassessedtheseverityofreportedillegalfishingin
theclosedsitesas“low,”“moderate,”or“high.”Toassignthesecategories,weassessedlevelsof
illegalfishingreportedinthelandingsdataduringaclosurerelativetobaselinecatches,defined
astotallandingsfromtheclosuresiteinthe30daysbeforeaclosure.Here,“low”indicatesthat
octopuscatchesrecordedduringtheclosureequaled0–5%ofbaseline“before”catches;“mod-
erate”,5–50%ofbaseline;and“high”atleast50%.Fishersreadilyreportedthisactivity,but
neverthelessweconsiderthesereportsasaminimumestimateofillegalactivity.
2.5.Fisheryeffectsanalysis:Landings,effort&catchperuniteffort
WeusedaBefore,After,Control,Impact(BACI)statisticaldesignandmixedmodelANOVA
totesttheeffectsofoctopusclosuresintheVelondriakeLMMAon(a)octopusfisherylandings
(kgoctopus/30days),(b)octopusfishereffort(totalfisher-days/30days),and(c)catchper
uniteffort(kgoctopus/fisher-day).Asubsetof36closureeventshadadequatebaselinedata,
definedasatleast5fishersand10octopusesrecordedineachofthe30-dayperiodsbeforeand
aftertheclosure(Fig2A).
Seventeen(17)ofthese36closuresoccurredindependentlyofothermanagementmeasures,
whiletheother19extendedthesix-weekgovernmentally-imposedregionaloctopusfishery
shutdownthatwasineffectinaustralsummereachyearbeginningin2005.Wereferthrough-
outthepapertothe17independentlyoccurringclosuresas“no-ban”closures,andthe19clo-
suresthatextendedtheshutdownas“ban”closures(Fig2).
ControlSiteSelection. Wematchedeachofthe36focalclosuresiteswithasimilarcon-
trolsitethat(a)neverhadalocalclosure,(b)showedtrendsinbaselinedatasimilartothoseof
theclosedsite(i.e.,thesite’smonthlyoctopuslandings;seebaselinelandingscorrelation(r)
below),and(c)hadadequatedataavailableduringthefocalperiods(seerelativedataavailabil-
ityindexbelow).Wetookfivestepstoestablishasetofimpact-controlpairings.(1)Wepre-
paredabaselinedatasetfreeof‘closureeffects’byremovingdatafromeachknownclosuresite
fortheperiodfromclosureto60daysafterreopening.(2)Generatebaselinelandingscorrela-
tion:Tohighlightsitepairsthatpresentedcorrelatedbaselinetrends,weaggregatedthetotal
baselinelandingsofoctopusbymonthforeachfishingsite,andthencomparedthefullrecords
ofthe36focalclosedsitesto318potentialcontrolsitesusingPearson’scorrelationofmonthly
catchtotals(i.e.,r).(3)Generaterelativedataavailabilityindex:Toassessrelativeavailability
ofdataatpotentialcontrolsites,wecountedtheminimumnumberoffisher-daysavailablein
eitherthe30daysbeforeoraftertheclosure,dividedbythevaluefromthecontrol-closure
pairingwiththehighestrecordedfisher-days.Minimumavailablefisher-daysduringfocalperi-
odsinselectedcontrolsitesrangedfrom6to120,withameanof27.6fisher-days.(4)Wethen
rankedeachofthe11,448potentialcontrolsite-closuresitepairingsbasedonasuitabilityscore
thatwascomposedoftheaverageofthepair’sbaselinelandingscorrelationandrelativedata
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Catch&EconomicBenefitsofPeriodicOctopusFisheryClosures
availabilityindexduringfocalperiods.(5)Finally,giventhesuitabilityscorerankings,werana
“draft-pick”algorithm,allowingeachclosuretoselect(andexclude)itstop-rankedcontrol;
thenrandomizedtheselectionorderofthe“draft-pick”setof36control-closurepairsover
10,000times,takingthebestglobalcontrol-closuresolution.
Normalityandhomoscedasticityofresponsevariableswereassayedusingq-qplotsand
Levene’stest.Uponfailureofeitherconditionwelog-transformedthevariableinquestion,
whichmettheseassumptionsineachcase.Eachanalysiswasperformedusingthelme4pack-
ageinR[65],usingPeriod(i.e.,BeforeorAfterclosure),Control/Impact,andco-occurrenceof
theregionalfisheryshutdown(“ban”/”noban”)asfixedeffects,and,becausemultipleclosure
eventscouldhappenwiththesameclosuresite(atdifferenttimes),weincludedClosureSiteas
arandomeffect.Allreportedsignificanceprobabilitiesderivefromindependentcontrasts
withinthismixed-modelframework[65–66].
2.6.VillageIncome
Forallvillagesthatimplementedaclosureevent,weusedamixedmodeldesignsimilartothat
describedabovetotestfordifferencesinthreevariables:(a)totalvillageoctopusincome(alloc-
(cid:1)
topuslandedinavillage(kg) beachprice($/kg);$),(b)totalfishingeffort(fisher-days),and
(c)incomeperuniteffort(2011$PPP/fisher-day)acrossthreeperiods:(i)30dayspre-closure
(before);(ii)closureperiod(during;normalizedto30-daymeasure);(iii)30dayspost-reopen-
ing(after).Weanalyzedincomeandeffortfromvillagesimplementing28closureevents,
whichrepresentthesubsetofthe36closuresanalyzedaboveforwhichwehaddatacoverageto
pairvillagesimplementingaclosurewithcontrolvillagesthathadnoclosureatthesametime.
Ofthese28,14were“no-ban”closures,and14were“ban”closures(Fig2B).
2.7.Stochasticmodelingofsite-specificclosureneteconomicbenefits
Toassessthesite-specificneteconomicbenefitsofeachclosuresite,wecomparedlandings
fromclosuresitestostochasticallymodeledlandingsassumingcontinuedopen-accessfishing
atthesamesite.Todoso,wemodeledboththeforegoneearningsforperiodsduringand60
daysafter36closuresandthencomparedthesemodeledearningstotheactualcatchdatafrom
36closureevents(Fig2C).
Ourdataprovideuswithtwoobserveddistributionsrequiredforoursimulations:(1)V,the
numberoffishersvisitingthefocalsiteonagivenday,and(2)C,thebeachvalueofoctopus
caughtbyonefisherononeday.Eachofthesedistributionsaredrawndirectlyfromthefishery
data,andstochasticallysampledtogenerateoursimulateddatacomparison(S7Fig).Tobuild
thevisitationdistribution,V,wefirstrecordedthenumberoffishersthatwenttothefocalsite
eachdayitwasvisitedduringtheentirestudyperiodexcludingclosureperiodsandsix-weeks
afteraclosurereopened.Ondaysthatasitereceivednorecordedlandings,therearethreepos-
sibilities:(1)therewasnofishingactivity,(2)therewasactivitybutnoonevisitedthesite,or
(3)atleastonefishervisitedthesite,buttheycaughtnooctopus.Toaccuratelyestimatecase2
(actualzero-visitdays)wefirstexcludedcase1(nofishingdays)byonlycountingzerodayson
which(a)therewasfishingrecordedinavillagethathadeverfishedthefocalsite,and(b)no
landingswererecordedfromthesiteinquestion.Tofurthercorrecttheestimatedzero-visit
daysforcase(3)wefittheparameterZ,whereasite’smodeled#ofzero-visitdays=(Z(cid:1)zero
dayswithactivefishing).Weran100iterationsofourlandingssimulationmodelondatafrom
36open-accesscontrolsitesforeachpotentialestimateofZ(from0to2,by0.025)andthen
calculatedthedifferencebetweenourmodeledfisherylandingsandtheactuallandingsin
those36sites.Byfindingtheminimummediandivergencebetweenactualandmodeledvalues,
PLOSONE|DOI:10.1371/journal.pone.0129075 June17,2015 8/24
Catch&EconomicBenefitsofPeriodicOctopusFisheryClosures
wedeterminedthattheminimalmodelbiaswasgeneratedwithavalueofZ=0.525.Allsimu-
lationsthereafterusedthatparametervalue.
Thiszero-binmultipliertuningmadeourneteconomicbenefitcriterionmoresevere.That
is,byroughlyhalvingtheprobabilityof“novisit”,thisprovidedahigherestimateofcounter-
factualcatches(or“cost”),andthereforemadeour“profitability”criterionmoreconservative.
Thevalueperuniteffortdistribution,C,derivesfromCPUEat150controlsitesduringthepe-
riodinquestion(duringorafter),usingbeachpricesonthedayandvillageofsale.
Tosimulatethe“noclosure”catchvalue,foreachdayinwhichfishingisreportedinarele-
vantvillage(i.e.,onethathasfishedinthefocalsiteinthepast),wesampledfromthefocal
site’sV,returninganumberoffishersthatvisitedthatsitethatday:V .ThenwesampledV
d d
timesfromCtogenerateadistributionofsinglefisher’sdailycatchvalues(C).Thedailysum
f
ofC overallfishersonagivendaygeneratedatime-seriesoftotaldailycatchvalues,L .The
f d
sumofdailyvalueeachday(L )overalldayssampled(N ),generatedatotallandingsL.
d FD
X
L ¼ Vd C
d f¼1 f
X X X
L¼ NFDL ¼ NFD Vd C
d¼1 d d¼1 f¼1 f
BytreatingL,thesimulatedcatchvalue(i.e.,whatpeoplewouldhaveearnedhadtheynot
institutedaclosure)asthecost,andA,thetotalactualrecordedlandingsvaluefromtheclosure
siteoverthesametimeperiodasthebenefits,weestimatedthenetearnings(NE)oftheclosure
relativetoitscounter-factualcontrol(NE=A-L).Foreachofthe36modeledclosures,weran
ourstochasticmodel1000timesresultinginadistributionofnetearningsvaluesforeach
closure.
2.8.Internalrateofreturn
Theinternalrateofreturnofaparticularclosureisthediscountrateatwhichthenetpresent
valueofthenetearningsisequaltozero:
X 1
NPV ¼0¼ T NE
NE t¼0 tð1þ@Þt
whereNPV isthenetpresentvalueofthenetearnings,tisthedayssinceclosure,NE isthe
NE t
dailynetearnings,[email protected]’spercentagere-
turnoninvestment(ROI)bydividingthenetbenefitsbythecosts.
2.9.SeasonalityofsettlementandCPUE
Weassessedseasonalpatternsofsettlementandcatchperuniteffortfrom2004–2011(S9Fig).
First,toassesspatternsunaffectedbyclosureeffects,weremovedallclosuresitesfromthefish-
erydataset.Thenusinganoctopus’massatcaptureandagrowthcurveforO.cyanea[67]we
back-calculatedanestimateofthatoctopus’settlementdate.Fromthiscollectionofdates,we
reporttherelativefrequencyofestimatedsettlementeventsoccurringonagivenJulianday
(S9Fig).ThenweassesstheCPUEacrosstheentiredatasetoneachdayfrom2004–2011,and
presentaLOESSfitofthesedata(with95%confidenceintervals).Wethencalculatethelagged
cross-correlationbetweensettlementfrequencyandsubsequentseasonalCPUEshift.
PLOSONE|DOI:10.1371/journal.pone.0129075 June17,2015 9/24
Catch&EconomicBenefitsofPeriodicOctopusFisheryClosures
Results
3.1.Socioeconomics
TheVezowithintheVelondriakeLMMAhaveameanincomeof$1.72perpersonperday,
belowthe$2perdaypovertystandard,andtheyrelyheavilyonseafoodproteinfortheirfood
security(all$figurespresentedarein2011internationaldollars,whichadjustsforpurchasing
powerparity(PPP);S1File,S3andS4Tables).Gleaningcontributedatleasthalfofhousehold
incomefor62%ofhouseholds[S1File],thoughindividualfishersearnmorefromseacucum-
bersandfinfish[61].
3.2.FisherylandingsandCPUE–BACIAnalysis
The36closuresitesforwhichwehadadequatebaselinedatashowedsignificantincreasesafter
re-openinginbothoctopuslandingsandCPUEofoctopus,regardlessoftheirtimingwiththe
annualregionaloctopusfisheryshutdown(Figs3,S1andS2).Acrossthe36closures,median
octopuslandingsincreasedfrom49.5(±22.8CI95)kginthe30daysbeforeclosureto404.8
(±119.9)kginthe30daysafterreopening,a717.8%increase(p<0.0001,S2Fig).Thissignifi-
cantincreaseisrobusttothetimingoftheregionalshutdown,appearingbothinthe17“no
ban”closures,thatoccurredindependentlyoftheregionalshutdown(+550%,p<0.0001),and
the19“ban”closures,thatextendedtheshutdown(+821%,p<0.0001;Figs2andS1).
Controlsiteshadmedianlandingsof44.5(±35.5)kginthe30daysbefore,and74.6(±46.6)
kgafterre-opening(+67%;S2Fig).Thoughthisincreaseincontrolsitesisstatisticallysignifi-
cant(p<0.01),itisten-foldsmallerthaninclosedsites(S2andS3Figs).Moreover,theeffectin
controlsisdrivenbythe19“ban”closuresthatextendedtheshutdown(+97%,p<0.05)andab-
sentinthecontrolsforthe17“noban”closures(+67.7%,p=0.36;S1Fig).
Aclosure’sreopeningattractedmanyfishers.Againcomparing30-dayperiodsimmediately
beforeeachclosureandafterre-opening,the36closedsiteshadamedian477.8%increasein
effort(fisher-days;p<0.0001,S1andS2Figs).Thereisalsoaweaklysignificantefforteffectin
thecontrols(median+74%,p=0.05;S2Fig),however,oncesplitbytimingrelativetothere-
gionalshutdown,neithercontrolsforthe17“noban”closuresnorthoseforthe19“ban”clo-
suresshowedsignificanteffortincreases(median+88%,p=0.37;+117%,p=0.28;Figs2,3
andS1).
Catchperuniteffort(kg/fisher-day,CPUE)showedlargeandsignificantincreasesatclo-
suresiteswhilecontrolsitesshowedonlyaminorboost,whichwasagainrestrictedtothose
“ban”closuresco-occurringwiththeregionalshutdown(Figs2andS2).Inclosuresitesfishers
caughtamedianof2.37(±0.33)kgofoctopusperfisher-daybeforeclosure,butaftertheclo-
surere-opened,fisherscaught4.42(±0.51)kg/fisher-day,aCPUEincreaseof86.6%
(p<<0.0001;S2Fig).ThesesignificantCPUEincreaseswerepresentbothin“ban”and“no
ban”closures(Figs2and3).Incontrolsitesforthe17“noban”closures,medianCPUE
showednosignificantchange(p=0.93;Fig3),whilecontrolsforthe19“ban”closuresshowed
amoderateboost(+49%,p<0.01;Fig3).
BoththelandingsandCPUEboostsweregreatestimmediatelyaftertheclosure’sreopening,
anddiminishedwithindaystoweeksaftertheopening(S3andS4Figs).Landingstendedtore-
turntobaselinelevelsafterthefirstorsecondtidalseries,generallywithinabout7–10days
afterreopening(S3Fig).CPUEeffectswerealsostrongestinthefirstsetofspringlowtides
aftertheopening,butcontinuedintothesecondorthirdsetofspringlowtides(i.e.,14–25
days;S4Fig).Asthisfisheryisdepthlimited,mostactivefishingoccursduringthelowesttides
(i.e.spring)tides.
PLOSONE|DOI:10.1371/journal.pone.0129075 June17,2015 10/24