long term adaptation scenarios - biodiversity for life · 2 ltas climate change mplications or...
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LONG TERM ADAPTATION SCENARIOSTOGETHER DEVELOPING ADAPTATION RESPONSES FOR FUTURE CLIMATES
www.environment.gov.za
MARINE FISHERIES
315 Pretorius Streetcnr Pretorius & van der Walt StreetsFedsure Forum BuildingNorth Tower2nd Floor (Departmental reception) or1st Floor (Departmental information centre) or6th Floor (Climate Change Branch)Pretoria, 0001
Postal AddressPrivate Bag X447Pretoria0001
Publishing date: October 2013
environmental affairs Environmental Affairs Department:
REPUBLIC OF SOUTH AFRICA
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LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES2
When making reference to this technical report, please cite as follows: DEA (Department of Environmental Affairs). 2013. Long-Term Adaptation Scenarios Flagship Research Programme (LTAS) for South Africa. Climate Change Implications for Marine Fisheries in South Africa. Pretoria, South Africa.
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 1
When making reference to this technical report, please cite as follows: DEA (Department of Environmental Affairs). 2013. Long-Term Adaptation Scenarios Flagship Research Programme (LTAS) for South Africa. Climate Change Implications for Marine Fisheries in South Africa. Pretoria, South Africa.
environmental affairs Environmental Affairs Department:
REPUBLIC OF SOUTH AFRICA
The project is part of the International Climate Initiative (ICI), which is supported by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety.
CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES IN SOUTH AFRICALTAS Phase 1, Technical Report (no. 5 of 6)
LONG-TERM ADAPTATION SCENARIOS FLAGSHIP RESEARCH PROGRAMME (LTAS)
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES2
AbbREvIATIONS 4
ACKNOWLEDGEMENTS 5
THE LTAS PHASE 1 6
REPORT OvERvIEW 7
ExECUTIvE SUMMARy 8
1. INTRODUCTION 10
1.1 Estuarineandinshorefisheries 10
1.1.1 Cool-temperate region 12
1.1.2 Warm-temperate region 12
1.1.3 Subtropical region 12
1.1.4 Linefishery 12
1.2 Hakeandsmallpelagicfisheries(offshorefisheries) 13
1.3 Humandimensions 16
1.3.1 Anthropogenicimpactsonfisheries 17
2. CLIMATE CHANGE IMPACTS ON MARINE FISHERIES 18
2.1 Climate change-related observations 18
2.2 Projected impacts 19
2.2.1 Projectingimpacts 19
2.2.2 Fisheriesspeciescompositionandproductivity 20
2.2.3 Fishbehaviourandphysiology 21
2.2.4 Positiveimpacts 22
2.2.5 Humandimensions 22
2.3 Keyimpacts:Estuarineandinshorefisheries 22
2.3.1 Overallimpacts 22
2.3.2 Cool-temperate region 25
2.3.3 Warm-temperate region 26
2.3.4 Sub-tropical region 28
2.4 Keyimpacts:Offshorefisheries 29
2.4.1 KeyimpactsonHake 29
2.4.1 Keyimpactsonsmallpelagicfisheries 29
2.5 Oceanacidification 31
TAbLE OF CONTENTS
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 3
3. ADAPTATION RESPONSE OPTIONS 34
3.1 Fisheries 34
3.2 Humandimension 35
4. RESEARCH REqUIREMENTS 36
4.1 Fisheries 36
4.1.1 Currentcapacitytoprojectclimatechangeimpacts 36
4.1.2 Availableapproachesforprojectingdirectimpactsofclimatechangescenarios 37
4.1.3 Futureresearchneeds 38
4.2 Humandimensions 39
4.2.1 Futureresearchneeds 39
5. CONCLUSION 41
6. REFERENCES 43
LIST OF FIGURES
Figure1.BiogeographicregionsforSouthAfricanestuaries. 12
Figure2.SouthAfrica’scoastalandmarineinshoreandoffshoreecoregionsandecozones 14
Figure3.AnnualcatchesofCapeHakes1917–2011andsmallpelagicfish1949–2011. 15
Figure4.Thewestcoastnurseryarea,spawninggroundsoffthesouthwestandsouthcoastsandthejetcurrentbetweenCapeAgulhasandCapeColumbine 31
LIST OF TAbLES
Table1.Climaticdrivers,keyvariablesandintensityofresponseinthethreemarinebiogeographicprovinces 23
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES4
LIST OF AbbREvIATIONS
CPUE Catch per unit effort
DAFF Department of Agriculture, Forestry and Fisheries
DbEM Dynamic Bioclimate Envelope Model
DEA Department of Environmental Affairs
ENSO El Niño southern oscillation
MLRA Marine Living Resources Act, No, 18 1998
MPA Marine protected areas
MSy Maximum sustainable yield
NPP Net primary productivity
OMP Operational management procedure
REI River-estuary interface
SST Sea surface temperature
TAb Total allowable by-catch
TAC Total allowable catch
LTAS:CLIMATECHANGEIMPLICATIONSFORMARINEFISHERIES 5
ACKNOWLEDGEMENTS
i MrMatigaMotsepe,DAFFfocalperson•Tel:+27(0)123095828•email:[email protected] •20SteveBiko(FormerlyBeatrix)Street,Arcadia,Pretoria0002
ii MrShonisaniMunzhedzi,DepartmentofEnvironmentalAffairs,ClimateChangeBranch,ChiefDirectorateAdaptation •Tel:+27(0)123951730•Cell:+27(0)764000637•email:SMunzhedzi@environment
ThefirstphaseoftheLongTermAdaptationScenarioFlagshipResearchProgramme(LTAS)involvednumerouspeopleandorganisations,andwascharacterisedbyaspiritof collaboration and cooperation across organisational and disciplinaryboundaries.TheDepartmentofEnvironmentalAffairs(DEA)andtheSouthAfricanNationalBiodiversityInstitute (SANBI)would like to thank theDeutscheGesellschaftfürInternationaleZusammenarbeit(GIZ)fortechnicalandfinancialassistance,underthesupervisionofDrMichaelaBraunandMrZaneAbdul,whoalsoservedontheProjectManagementTeam.
DEAandSANBIwould like tothankDepartmentofAgriculture,ForestryandFisheries (DAFF) for theirpartnership in thisworkand inparticularMrMatigaMotsepe iwhoservedas the focalpoint fromDAFF.Specif ically, we would like to thank the groups,organisations and individuals who participated andprovidedtechnicalexpertiseandkeyinputstotheClimateChangeImplicationsforMarineFisheriestechnicalreport,namelyDrs JulietHermesandLaraAtkinson (SouthAfricanEnvironmentalObservationNetwork[SAEON]),DrLutzAuerswald(DAFF),DrGregDuggan(UCT)ProffLarryHutchings(DEA,Ma-RE),DrNikkiJames(SouthAfricanInstituteforAquaticBiodiversity[SAIAB]),ProffAstridJarre(UniversityofCapeTown)DrStevenLamberthandDrCarlvanderLingen(DAFF),DrLaravanNiekerk(CouncilforScientificandIndustrialResearch[CSIR]),DrKerry Sink (SANBI),DrDawidYemane(DAFF),LTASTechnicalWorkingGroupmembers,andmembersoftheClimateandImpactstaskteams.
DEAandSANBIwouldalsoliketoacknowledgeothermembers of the Project Management Team whocontributedtheirtimeandenergytothedevelopmentofthistechnicalreport,namelyMrShonisaniMunzhedziii and Mr Vhalinavho Khavhagali who provided keyguidance on behalf of theDEA, Prof. GuyMidgley(SANBI),MsSarshenScorgieandMsPetradeAbreu(ConservationSouthAfrica)whowerekeyeditorsofthetechnicalreport.MsGigiLaidlerservedastheSANBIprojectadministratorwithassistancefromMsFaslonaMartin,MrNkoniseniRamavhonawhoservedasDEAproject administrator andMsGwendolinAschmannfromGIZwhoprovidedadditionalprojectmanagementsupport.MsJaquiStephenson(EnvironmentalResourcesManagement)andMrDickCloete(MediaDirections)providedpreliminaryandfinaleditingofphase1productsrespectively,andStudio112conductedthelayout.
6 LTAS:CLIMATECHANGEIMPLICATIONSFORMARINEFISHERIES
TheLong-TermAdaptationScenarios(LTAS)FlagshipResearchProgramme(2012–2014) isamulti-sectoralresearchprogramme,mandatedbytheSouthAfricanNational Climate Change Response White Paper(NCCRP,para8.8).TheLTASaimstodevelopnationalandsub-national adaptation scenarios for South Africa under plausible future climate conditions and development pathways.DuringitsfirstPhase(completedinJune2013),fundamental climate modelling and related sector-based impactsandadaptationscopingwereconductedandsynthesised.ThisincludedananalysisofclimatechangetrendsandprojectionsforSouthAfricathatwascomparedwithmodelprojectionsforthesametimeperiod,andthedevelopmentofaconsensusviewofscenariosforthreetime periods (short-, medium- and long-term). Scoping of impacts, adaptation options and future research needs, identifiedintheWhitePaperandguidedbystakeholderengagement,wasconductedforprimarysectorsnamelywater,agricultureandforestry,humanhealth,marine fisheries,andbiodiversity.Thismodellingandscopingwillprovideabasis forcross-sectoralandeconomicassessmentworkneededtodevelopplausibleadaptationscenarios during Phase 2 (scheduled for completion in April 2014).
Six individual technicalreportshavebeendevelopedtosummarisethefindingsfromPhase1,includingonetechnical report on climatetrendsandscenariosforSouthAfricaandfivesummarisingtheclimatechangeimplicationsforprimarysectors,water,agricultureandforestry,humanhealth, marine fisheries,andbiodiversity.AdescriptionofthekeymessagesemergingfromLTASphase1hasbeen developed into a summaryforpolicymakers;aswellas into seven factsheets comprising the LTAS ClimateandImpactsFactsheetSeries.
THE LTAS PHASE 1
LTAS:CLIMATECHANGEIMPLICATIONSFORMARINEFISHERIES 7
ThistechnicalreportpresentstheLTASPhase1findings
for the marine fisheries sector in South Africa.
ItreferencesexistingSouthAfricanresearchcombined
with insights from international research and global
projectionstopresentapreliminarypictureofpotential
impactsof futureclimatechangeonmarinefisheries
inthecountry.Specifically, itsummarisestheclimate
changeimpactsaswellasadaptationresponseoptions
andfutureresearchneedsforthemarinefisheriessector.
This report is based on the results of relevant past and
currentresearchonextractiveuseanditsimplications
for detecting and projecting climate change impacts, on
historicaltrendsinfisheriesandobservedmanagement
andpolicy responses, andonadvances inprojecting
climate change impacts.
LTASPhase1adoptedasemi-quantitativeapproachto
analysingthelikelyimpactsofclimatechangeonmarine
fisheriesinSouthAfrica.Thisreportthereforeprovides
a narrative assessment of the estuarine and inshore, and
theoffshorefisheriestrends;andthecurrentpotential
for projecting climate change impacts. A brief description
ofeachchapterofthetechnicalreportisprovidedbelow.
REPORT OvERvIEW
Chapter 1(Introduction)providesanoverviewoftheSouthAfricanmarineenvironmentandfisheriesincludingestuarineandinshorefisheries,andoffshorefisheries.
Chapter 2(Climatechangeimpactsonmarinefisheries)synthesisesexistingresearchonclimatevariabilityandchangeandknownpotentialimpactsonmarinespeciescompositionandproductivity,behaviourandphysiology,and the related effects on human livelihoods of coastal and offshorefishers.ThechapteralsoprovidesanoverviewofoceanacidificationlinkedtoparticularconcernsforSouthAfricanfisheries.
Chapter 3 (Adaptation response options) provides an overviewofadaptationresponseoptionsforthemarinefisheriessectorinSouthAfrica.
Chapter 4(Researchrequirements)providesananalysisofkeyresearchgapsinunderstandingthevulnerabilityofthemarinefisheriessectortoclimatechange.
Chapter 5 (Conclusion) concludes the report highlighting thateffectivemanagement,whichaccountsforclimatechange, is critical for supporting the commercial, subsistence and recreational fishing sectors through improved environmental, resource and social resilience, maintenanceofecosystem,species,geneticandsocialdiversityunderfutureclimateconditions.
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES8
SouthAfricabenefitsfromawiderangeofmarineresourcesthat contribute to local, national and international food security.Commercialfisheriesareconcentratedonthewesternandsoutherncoasts,withlocalisedrecreationalandsubsistencefishingspreadalongmuchofthecoast.Thecommercialfishingindustrycontributesabout1%ofGDP,andprovidesanestimated27000jobs,withmorethandoublethenumberofjobsinsecondaryindustriessuchasfishprocessing,transportingfishproductsandboatbuilding.Subsistencefishingisimportantforcoastalcommunity livelihoods.Many South African fisheryresourcesareoverexploitedwithmoreaccessiblecoastalresources at greater risk.
Climatechangeislikelytoaffecttheproductivityanddiversity of SouthAfrica’s fisheries by changing thedistribution,abundanceandsizeofresources,theirhabitatextent,conditionandconnectivity,theirphysiologyandbehaviourandthecatchabilityofresourcespecies.Changesin sea surface temperature (SST), storm frequency,freshwater flow and runoff patterns, productivity,oxygenlevelsandwindwillallhaveimpactsonestuarine,inshoreandoffshoreecosystems,affectingrecruitment,fishbehaviourandphysiology,influencingfishsize,andincreasingfishmortalities.Thiscouldresultinsignificantadverseimpactsonsubsistencefishinglivelihoodsaswellas commercial and recreational industries.
Tropicalspeciesmaymovepolewards inresponsetowarmingtemperaturesresultinginanexpansionofthesubtropicalregion.Incontrast,temperateregionsmaycontract,withcoastalspeciesbeingaffectedbychangesinupwelling,relatedextremesintemperatures,reducedrunoffandhabitatloss,ultimatelyleadingtoadecreaseintemperatespeciesdiversityandabundance.Stocksunder intenseexploitationpressure are likely tobe
more vulnerable to the effects of climate change than optimallyexploitedpopulations.Overfishingmayresultinreducedgeneticvariability,whichmaynegativelyaffectthepossibilitiesofanevolutionaryresponsetoclimatechangeandtheabilityofdepletedstockstorecover.
Directionalshiftsinthespatialdistributionofseveralmarinespecies,whicharepossiblyattributabletoclimatechangetrends,havealreadybeenrecordedaroundSouthAfrica’sshoresaffectingintertidal,shallowcoastalandoffshorespecies.Twoprojectedconsequencesofclimatechangethatcouldhavesignificantimplicationsforfisheriesareacceleratedsealevelriseandincreasedfrequencyofhigh-intensitycoastalstormsandhighwaterevents.The effect of these events, such as reduced/increased freshwaterflow, isasignificantrisktoestuarineandinshorefisheries.Reduced/increasedfreshwaterflow,sealevelriseandincreasedstormactivitywillreduceestuarinenurseryhabitat,anddecreasedrainfallmaycausetemporarilyopen/closedestuariestoclosemorefrequently,andmayevenresultinclosureofpermanentlyopenestuaries.Onaregionalscale,KwaZulu-Natalandwestcoastestuariesarelikelytobethemostaffectedfrom a structural and functional perspective.
Scenariosofmoreextremerainfallanddryspells,coupledwithsealevelrise,couldcausedamagetooreventhelossofnurseryhabitatsessentialforprawnsandestuarinefish.Ontheotherhand,increasesinsummerrainfallcouldresultinsomeestuariesliketheStLuciaEstuaryopeningmorefrequently,withapositiveimpactontheabundanceofshallowwaterprawnonthetrawlgrounds,aslongasexistingwaterusesinthecatchmentsfeedingtheseestuariesarebettermanaged.Forbothestuarineand marine species, the positive impacts of increases in rainfallcouldbeoffsetbyseasonalshiftsinrainfallthat
ExECUTIvE SUMMARy
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 9
couldconfusebehaviouralcuesatcritical life-historystagessuchasspawningormigration.Increasedstormactivityunderachangingclimatewillhaveasignificantimpactonfishingactivitybyreducingthenumberofviableseafishingdays,anddamagingshore-basedoffloadingfacilitiesandfishingvessels.
Fisheries that are successfully managed to achieveresourcesustainabilitywillbebetterpositionedinthelong term to adapt to the effects of climate change. This is becausemarineresourcesarelikelytobemorerobusttothe effects of climate change if the compounding stresses from overfishing, habitat degradation, pollution and otheranthropogenicfactorsarereduced.Managementstrategieswouldbenefitthroughtheinclusionofsoundecosystem-basedmanagementpracticesthatfocusonrebuildingover-exploitedfishresourcesandimpactedecosystemsandimprovingmarinehabitatquality.Thiswillresultinpositivegainsforsocietyandthefishingindustrythroughmoreproductivefishstocks,securebiodiversityandimprovedresilienceandadaptivecapacitytoclimatechange.Maintaininggeneticvariabilitythroughsustainablefishingpracticesandappropriatelyzonedfishingareasincludingclimate-resilientmarineprotectedareas(MPAs)can secure genetic potential and enable adaptation to changingconditions.MPAsneedtobeeffectivelymanagedtomaintainormaximiseecosystemresiliencedespitetheeffectsofclimatechange.Thiscanbeachievedbyamelioratingstressorssuchasoverfishing,pollution,invasivespeciesandexcessivenutrientinputs,andbyimplementingandexpandingMPAsinawaythatpreservesthelinkagesandconnectivityamongsites.
Adaptation measures for the communities reliant on fisheriesforfoodandincomeincludemechanismsandprocesses to balance social and economic objectives.
Ensuringthatpoliciesencouragediversificationofactivitiesand income generation to enhance social resilience in thefaceofuncertaintyandvariabilityisalsoimportant,particularlyforthemostvulnerablecoastalandfishercommunities. The promotion of adaptation options such as education, entrepreneurial training, and training in coastalandmarinetourismandsustainableaquaculturewouldhelptopreventthepotentialdeteriorationofsocialconditionsinfishercommunities.
Projectingclimatechangeimpactsonmarinefisheriesisdifficultbecauseofthecomplexrelationshipsbetweenspecies distribution patterns, variations in their abundance,distributionandproductivity,andtheimpactsofoverfishingandotherstressors.Impactsonfisheriesdepend on distinct oceanographic scenarios dominated eitherbyprojectedchangesinsoutherlyandwesterlywinds,orbychanges in the strengthof theAgulhasCurrent.Effectivemodelling is limitedby incompleteinformation on the functioning of the biological resources andevenmorecriticallyonthephysicalchangesintheoceans. In particular,mostof the global biophysicalmodelscurrentlyinusedonotsimulatefullythesalientfeaturesintheoceansaroundSouthAfrica.Furthermore,theeffectsofoceanacidificationonfisheriesandmarinebiodiversityremainapoorlyquantifiedrisk.Focusedresearch is needed to contribute to the development ofplausible scenariosofphysicaloceanographic andcoastal habitat change. The impacts of unsustainable fishingandclimatechangeinteractinanumberofwaysand should not be treated as separate issues. To make progress on projecting direct impacts of climate change scenarios,additionaldatacollection,synthesisandmodeldevelopment is needed.
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES10
1.Introduction
SouthAfrica’sdiverseanddynamicmarineenvironmentisamongthemostcomplex intheworld,withthreemajoroceancurrentsystemsdominatingthisrelativelysmallregion:thecoldBenguelaCurrentonthewestcoast (AtlanticOcean), thewarmAgulhasCurrenton theeastcoast (IndianOcean),and thewestwardflowingCircumpolarCurrentcirculatingtheSouthernOcean(Sinketal.,2011).ThesethreecurrentsandtheirdynamicsarekeydriversofsouthernAfrica’sbroaderclimate (Reason & Hermes, 2011). The different climatic driversof thesesystems, togetherwithvariability inlocaloceanographicconditions,coastaltopographyandhabitattypesarelikelytoresultinhighlyvariableclimatechangeeffectsaroundthecoast(Rouaultetal.,2010,DEA2011).Furthermore,interactionsbetweenclimatechangeandanthropogeniceffects,specificallyfishing,resultinadditionalcomplexityinattributingthecauseofobservedchanges,andmakefuturepredictionsdifficult(Rijnsdorpet al., 2009; Cheung et al., 2012; Heath et al., 2012).
Thefisheriessectorisworthanestimatedsixbillionrandperannumanddirectlyemploys27000peopleinthecommercial sector. Thousands more, and their families, depend on marine resources for food and livelihoods and tomeetbasicneeds(DAFF,2012).ManyofSouthAfrica’scoastalandmarineresourcesareoverexploited(DAFF,2012;Sinketal.,2012)withthemoreaccessiblecoastaland inshore resources at greater risk. Poaching and illegal harvesting and trade in marine species pose additional
riskstoSouthAfricanfisheriesandthelivelihoodsoflegitimatefishers.SouthAfricahasanexcellenttrackrecordinmarinesciencewithsubstantialexpertiseinappliedresearch forfisheriesmanagement.Althoughmanyresourcesareoverexploited,managementactioncan lead to stock recovery. Effectivemanagement,that accounts for climate change is critical to resource recoveryandlongtermfoodandjobsecurityinSouthAfrica.Keyelementsinsecuringresourcesustainabilityin the long term include robust stock assessments, effectivedatamanagement,abilitytodetect,understandand predict change and science-based management action grounded in the realities of resource abundance.
Specificdetails related toSouthAfrica’skey inshoreand estuarine fisheries, and offshore fisheries are providedbelow.
1.1 Estuarine and inshore fisheriesSouthAfrica’scoastalecosystemssupportawiderangeoffisheries.Speciesrichnessislowalongthewestcoastandincreasesprogressivelyalongtheeastcoast.Mostcommercialfisheriesarefocusedonthewestandsouthcoasts.Althoughtheeastcoastsupportssmallerfisheries,thehighcoastalpopulationdensityhasresultedinintenseexploitationof inshore resources and consequentlymanycoastalresourcesinthisregionareoverexploited(Griffithsetal.,2010).AkeycomponentofSouthAfrica’scoastisitsestuaries(seeBox1).
1. INTRODUCTION
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 11
Box 1. The importance of estuaries
Estuaries offer refuge for marine species from adverse conditionsinthemarineenvironment(suchaslethallow-oxygenconditions).Inaddition,estuariesprovideimportantnurseryareasfornumerousspecies.TheOrange,OlifantsandBergestuaries,forexample,areimportantnurseryareasforexploitedmarineandestuarinespeciesbeforetheyrecruitintomarinefisheries(Lamberthetal.,2008).Certainspecies are classed as being “estuarine-dependent”, i.e. those withtheabilitytolocateandsecurerefugeinestuaries.
Riverflowsinfluencemarinefishandfisheriesdirectlyandindirectlythroughtheexportofnutrients,sedimentanddetritusintoestuariesandtheocean(Gillanders&Kingsford,2002;Robinsetal.,2005):
Nutrientsupplystimulatesproductionofphytoplanktonandzooplanktonand,ultimately,thelarval,juvenileandadultfishthatdependonthemasfoodsources.
Sediment replenishes nearshore habitats that are continuouslyerodedbyoceaniccurrentsandprovidesarefugeformanyfishbyincreasingturbidity.
Detritusmaybebrokendownintousefulnutrients,serveasasubstrateformicroorganismsorbeconsumeddirectlybydetritivorousfishandinvertebrates.
Recruitmentandemigrationofestuary-dependentfishto and from estuaries varies according to the magnitude,
frequencyandtimingoffreshwaterflowandthefloodingregime (Turpie et al., 2002; Taljaard et al., 2009). Reductionsinfreshwaterflowreachingtheseatranslateinto a weakening of recruitment cues and possiblerecruitmentfailureforthejuvenilesandlarvaeofestuary-dependentfish.Asaconsequence,climateprojectionsthattranslateintoriverflowsprovideanimportantbasisforprojectingclimatechangeimpactsonthesesystems.Thelife-historiesofestuarine-dependentfishareadaptedtothenaturalfloodregimeandanydeviationfromit,suchasasuccessionofatypicalfloods,mayremoveasuccessfulrecruitmentfromasystem.Fromafisheriesperspective,alteredfreshwaterflowsandconsequentvariationsinanyoftheabovevariablescancausechangesincatchcomposition, resource base (e.g. demersal vs. pelagic fishabundance),fleetstructure,thespatialandtemporaldistributionofeffortandultimatelytheeconomicvalueofthefisheryconcerned(Binetetal.,1995;Loneragan&Bunn,1999).
Estuarinefunctioningisalsostronglyinfluencedbylandmanagementpractices,particularlyhumanmanagementofwaterresourcessuchasimpoundments(i.e.affectingriverflow),andancillaryimpactsofwaterqualityeffectssuch as those resulting from agricultural management practices.Forexample,collapseofthewestcoastsoletrawlfisherycoincidedwiththeestablishmentofmostofthelargedamsontheOrange-Senqucatchmentbecomingoperational in the 1970s.
SouthAfrica’sestuarineand inshoreecosystemscanbebroadlydivided into threebiogeographic regions(VanNiekerk&Turpie,2012)separatedbyzonesofoverlap(Figure1,describedbelow):
• Cool-temperate(OrangeRivertoCapePoint);• Warm-temperate(CapePointtoMbashe
Estuary);and• Subtropical(MbasheEstuarytoKosiBay).
Thesubtropicalhumidzoneontheeastcoastisassociatedwith the highest rainfall in the interior of all threezones(withasummerpeak).Thesouthernportionofthewestcoasthasapredictablewinterrainfallregime(Mediterraneantypeclimate)butthenorthernportionisahighlyarid,cool-temperatezone,witherraticrainfall.ThesoutherncoastofSouthAfricaisawarm-temperatezone,withvaryingrainfallregimesthatincludesummer,winterorbimodalpeaksinrainfall(Heydorn&Tinley,
LTAS:CLIMATECHANGEIMPLICATIONSFORMARINEFISHERIES12
1980;Cooper,2001).Thisclimaticvariability,whichisinfluencedbytheregionaloceantemperatures,resultsina variation in rainfall, river runoff and surface temperature patterns along the coastline (Cooper, 2001; Hutchings etal.,2002;Taljaardetal.,2009),whichisimportantforestuarine functioning.
Subtropical humid region
(Mbashe Estuary to Kosi Bay)
Warm-temperate region (Cape Point to Mbashe Estuary)
Cool-temperate region (Orange River to Cape Point)
Limpopo
Mpumalanga
KwaZulu- Natal
Northern Cape
Western Cape
Eastern Cape
Free State
GautengNorth West
Figure1.BiogeographicregionsforSouthAfricanestuaries.Redshadingindicatesthepositionofthesubtropicalhumidzone,greenshadingindicateswarm-temperateandblueshadingindicatescool-temperate(Lamberth&Turpie,2003).OthercoastalandoffshoreecoregionsareshowninFigure2.
1.1.1 Cool-temperate region
Estuarineandinshorefisheriesinthecool-temperateregiontargetawidevarietyofbiotaincludingwestcoastrocklobster,abalone,linefishandmullet.Thisreportfocusesonthewestcoastrocklobsterasacasestudyfor this region.
1.1.2 Warm-temperate region
Estuarineandinshorefisheriesinthewarm-temperateregion of the Southern and Eastern Cape) target a diversityofbiota including linefish,mullet,squidandcoastal invertebrates (mussels etc.). This report focuses onthechokkasquidandthelinefisheryfisheriesascasestudiesforthisregion.Thesquidfisherytargetsashort-
livedspeciesandthe linefisherytargets longer-livedcoastalfishspeciesthatinhabitatestuarineandinshoreecosystems.
1.1.3 Subtropical region
Fisheries in the estuarine and inshore areas of thesubtropical region of KwaZulu-Natal target awiderangeofbiotaincludinglinefish,crustaceansandcoastalinvertebrates.Thisreportfocusesontheprawntrawlfishery,whichtargetsshort-livedprawnspecies,andtheKwaZulu-Natalcommerciallinefishery,whichtargetslonger-livedcoastalfishspecies,ascasestudiesforthesub-tropicalfisheries.
1.1.4 Linefishery
Recreational linefishing isthemostpopular formofmarine usage and occurs along the entire South African coastline (Pradervand&Baird,2002).Linefishing inestuaries is eitherboator shorebased,with shoreangling being more popular than boat-based angling. LinefishinginestuariesisprimarilyrecreationalalthoughthereareasmallnumberofsubsistencefisherswhofishintheareabetweenPortElizabethandKwaZulu-Natal(Lamberth&Turpie,2003).Nocommercial linefishingis permitted in estuaries or along the coast from the shore.Approximately48speciesoffisharecaughtinwarm-temperateestuariesandofthose28species(58%)areeitherpartiallyorcompletelydependentonestuariesasnurseryareas.Estuary-dependentspeciesdominatethe catches of recreational shore-anglers comprising 83%of thecatchbynumberandmass (Lamberth&Turpie,2003).
High levelsoffishmortality,particularly inestuarinenurseryhabitatshaveledtothecollapseofthedusky
1.Introduction
13
kobstock(Griffiths,1997).Cowleyetal.(2008)inanacoustictelemetrystudyfoundthat41%oftaggedduskykob (Argyrosomusjaponicas),alljuveniles,werecapturedintheestuarinefisherylessthanayearafterbeingtagged.Whitesteenbras(Lithognathuslithognathus), an important component in the catches of coastal and estuarine anglers in theCape (Day et al., 1981;Coetzee et al., 1989;Bennett1993a),showasimilardecline.Thecatchrateofrecreationalshoreanglershasdeclinedby90%sincethemid-1970s(Bennett,1993a).Bennett(1993b)foundthatthehighdegreeofestuarinedependence,confinementofjuvenilesandsub-adultstothesurfzone,largesizeat maturation, and predictable aggregation of mature individuals,makethisspeciesparticularlyvulnerabletoestuarinedegradationandoverfishing.
1.2 Hake and small pelagic fisheries (offshore fisheries)
Additionalinshoreandoffshoreecoregionsandecozones(Figure 2) have been identified to cover variabilityassociatedwithbiogeographic regions (presented inFigure1above)anddepth.SeveralfisheriesoperateinSouthAfrica’soffshoreecosystems.Thisreportconsidersthedemersalhakefisheryandthesmallpelagic(sardine,anchovyandroundherring)fisheries,becauseoftheirsocio-economic importance, as representatives of the offshorefisheries.Bothfisheriesarewellestablished(DAFF,2012).
Offshorefisheryresourcesdependonsuitablespawningconditionsonthesouthwestandsouthcoastsinspringandsummer,efficienttransportbyfrontaljetcurrentsofearly lifehistorystagestothewestcoastnurserygrounds,andsuitablenurseryhabitatcharacterisedbyhighretention,moderateproductivityandanoptimalvolumeoflow-oxygenwaterontheshelf.
LTAS:CLIMATECHANGEIMPLICATIONSFORMARINEFISHERIES
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES14
Port Nolloth
200m
500m
Port Elizabeth
East London
St Lucia
Durban
Cape Town
Saldanha
steadily increasedduring the1990sandearly2000sandpeakedat370000t in2004 followingsustainedpopulationgrowth.Alongwithgoodanchovycatchesduring the early 2000s this resulted in total annuallandingsbythesmallpelagicfisheryexceeding500000tforfiveconsecutiveyears.Sardinecatchesthendecreasedsharplyagainfollowingarapidpopulationdeclinecausedbysustainedpoorrecruitmentandbytheendofthe2000swerearound100000t,whilstanchovycatchesremained around 200 000 t.
Policies that have been introduced have affected hake andsmallpelagicstocksbothpositivelyandnegatively.CatchesofCapehakeswereinitiallyverylowinthe1930s(<1000t)buthadincreasedsteadilybythe1950s,andtheinclusionofforeignvesselsfromtheearly1960sresultedinsubstantialeffortandapeakcatchofcloseto300000t
Thesmallpelagicfisheryinitiallytargetedhorsemackerel(Trachuruscapensis) and sardine (Sardinopssagax) off South Africa’swestcoast,butwhilehorsemackerelcatchessteadilydeclinedduringthe1950s,catchesofsardineincreasedrapidlytopeakat410000tin1962(Figure3). Sardinecatches thendeclinedevenmorerapidlyfollowingapoorlycontrolledincreaseineffortandlikelyoverexploitation,asouthwardexpansionoffishing,andvariablerecruitment(Beckley&vanderLingen,1999),andweresubstantiallybelow100000tperannumfromthelate-1960stothemid-1990s(withtheexceptionof1975).Duringthisperiod,purse-seinersusedsmaller-meshednetstotargetprimarilyjuvenileanchovyinshoreoffthewestcoast,andthisspeciesbecamethemainstayofthesmallpelagicfishery.Annualanchovycatcheswerehighlyvariableandfluctuatedfromcloseto600000tin 1987 and 1988 to 40 000 t in 1996. Sardine catches
DELAGOA ECOREGIONDelagoa inshore
Delagoa shelf edgeDelagoa shelf
SOUTHERN BENGUELA ECOREGIONNamaqua inshore
Southwestern Benguela outer shelf
Southwestern Cape inshoreNamaqua inner shelf
Southwestern Benguela shelf edge
Southwestern Cape inner shelf
NATAL ECOREGIONNatal inshore
Natal shelf edgeNatal shelf
SOUTHWEST ECOREGIONSouthwest Indian upper bathyal
Southwest Indian abyssSouthwest Indian lower bathyal
SOUTHERN ATLANTIC ECOREGIONSoutheast Atlantic upper bathyal
Southeast Atlantic abyssSoutheast Atlantic lower bathyal
AGULHAS ECOREGIONAgulhas inshore
Agulhas outer shelfAgulhas inner shelf
Agulhas shelf edge
Figure2.SouthAfrica’scoastalandmarineinshoreandoffshoreecoregionsandecozones(Sinketal.,2012).
1.Introduction
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 15
inthewakeofthecollapsesoftheSouthAfricanandNamibiansardinestocksintheearlyandmid-1960sandearly1970s (Butterworth,1983).SeparateTACs forsardineandanchovywereappliedfrom1984onwards,withaconservativemanagementapproachbeingadoptedparticularlyforsardineinordertopromotepopulationrecovery.TheSeaFisheriesAct,No.12of1988establishedtheQuotaBoardwhichgrantedaccessrightsasopposedtojustTACs(Isaacs,2006),whichweredevelopedfurtherundertheMarineLivingResourcesAct,No.18of1998(MLRA)toestablishlong-termfishingrightsgrantedfora15-yearperiodfrom2006to2020forboththesmallpelagicandhakefisheries.
AnOMPforthepelagicfisherywasadoptedin1994(Beckley&vanderLingen,1999).Managementofthisfisherymustaccountforthefactthatsardineandanchovyshoaltogetheras juveniles,andbecausethemajority(typically>70%)ofanchovycaughtarejuveniles,largecatcheswillresultinahighby-catchofjuvenilesardine
Figure3.AnnualcatchesofCapehakes1917–2011(upperpanel;bothspeciescombined)andsmallpelagicfish1949–2011(lowerpanel;sardine,anchovyandroundherringareshownseparately).UpdatedfromDAFF(2012).
in1972(Figure3).Multiplemeasureswereimplementedto control foreign harvesting but these had little effect, and catch rates declined until the declaration of a 200mileexclusiveeconomiczonein1977.Aconservativemanagement approach that aimed at rebuilding the hake stocktothemaximumsustainableyield(MSY)levelwasthenimplementedandsince1990thedemersalfisheryhas been managed using an operational management procedure(OMP)(Payne&Punt,1995).Thisisanage-structured production model incorporating commercial catchperuniteffort(CPUE)data,andindicesofhakeabundancederivedfromresearchsurveysareusedintheOMPtosettotalallowablecatch(TAC)levels.Initially,andbecauseofthedifficultyindistinguishingbetweenshallowwateranddeepwaterhake,thetwospecieswereassessed and managed as a single resource, but since 2006 a species-disaggregated model has been used. Hake TACs andcatchesincreasedslowlybutsteadily fromabout115000t in1983to160000t inthelate-1990s,butshowedafairlyrapiddeclineinthe2000sattributedtoareductioninthebiomassofdeepwaterhaketowellbelowthelevelconsideredtosupportMSY.RecentOMPshavereduced the hake TAC in an attempt to rebuild the deep waterhakestock,andthemostuptodateassessmenthasindicatedamorerapidthanexpectedrecoveryindeepwaterhake(DAFF,2012).Currently,thestockstatusofshallowwaterhakeisconsideredoptimal(DAFF2012).
TheSeaFisheriesAct,No.10of1940generallyaimedatdevelopingtheoffshorefisheries.Intheinterestofresourceconservation,however,avarietyofmanagementregulationswere historically applied to the fisheryfor small pelagics, including limitations on vessel and processingcapacity,closedseasons,meshsizerestrictionsandvariousTACs.Duringthe1950s,acombinedsardineandhorsemackerelTACwasset,andfrom1971totheearly1980saglobalTACincludingsardine,anchovy,horsemackerel,chubmackerel,westcoastroundherringandlanternfishwasused.TheSeaFisheriesAct,No.58of1973setthesceneforincreasingconservationmeasures
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES16
term variability and change in the fisheries sector.Althoughfishersacknowledgetheimpactsofvariabilityonmultiannual scales (in addition to seasonal and interannual variability),theycontesttheexistenceofaunidirectionaltrend.Nevertheless,long-termecosystemscalechangeshavebeendocumentedalongwithtightlinksbetweenthenaturalandhumansocialsubsystems,highlightingtheneedto use lessons learnt from the past to think about future majorchangesbymeansofstructuredscenarioanalyses(Jarreetal.,2013acceptedforpublication).
Akeyconclusionfromhumandimensionstudiesisthatoffshoreandinshoresubsystemsshouldnotbetreatedseparately,becausemanyfishersorfishingfamiliesderivetheirlivelihoodsfrombothinshoreandoffshorefisheriesandsocial-ecologicaldynamicsarethereforenotsectorspecific.Ofparticularrelevanceistheobservationofregionaldifferencesininvolvementinfishing.Owingtothedifferentdevelopmenthistoriesofoffshorefisheriesoffthewestandsouthcoasts,entirefamiliescanbeinvolvedinfishingoffthewestcoast(sometimeswithgender-specificroles,menontheboats,womeninthefactories),whereasfamilyincomeoffthesouthcoasthasoftenbeenmorediversified,alongwithagreaterdiversificationofcapitalintovarious,typicallysmaller,economicsectors.
Major social restructuring has been observed as aramificationofreducedorcollapsedstocks,aswellasthelossofflexibilityofchangingresourceusealongwiththeimplementationofindividualrightswiththeMLRA.Thereducedavailabilityofsoleandhaketoinshoretrawlersalongwithpriceincentives,forexample,hasresultedininshoretrawlerstargetingkob,andhand-linefishers(inresponsetothereducedavailabilityofkob)targetingslow-growing,overexploitedredfishpopulations.
The f ishery rights allocation process in 2005 hasdecreasedfishers’resiliencetofluctuationsinresourcesbecauserightsholdersaretypicallyawardedrightsina single fisheryonlyandhencecanexploitonlyone
thatwillnegativelyimpactrecruitmentandsubsequentpopulationsize.Hence,catchesofthetwospeciescannotbesimultaneouslymaximisedandrecentOMPshavecalculatedatrade-offbetweenthetwothatrepresentsanoverallpelagicindustrypreference.Annualsardine-directedand“initial”anchovy-directedTACs,andan“initial”juvenilesardinetotalallowableby-catch(TAB),are set at the start of each year and are based onpopulationsizeestimatesderivedduringahydro-acousticsurveyconductedattheendoftheprecedingyear.Theseestimates,togetherwithcatchdata,arekeyinputsintothepopulationdynamicsmodelsusedforassessingtheseresources.A“final”anchovyTACandjuvenilesardineTABaresetmid-yearfollowingasecondhydro-acousticsurveyconductedtoestimatetherecruitmentstrengthofbothspecies.Dependingonrecruitmentthesemaybe,andtypicallyare,increasedfromtheinitiallevel.
Notably, theMLRA attempted to achieve a balancebetweenmarine conservation, social and economicobjectivesalongwithrectifyingthehistoricinjusticesinaccess to resources. Some progress has been achieved withrespecttotheneedsofcriticallydependentpredatorsonsmallpelagics(suchastheAfricanpenguin),whicharecurrentlybeingincorporatedintotheOMP.Ecologicalriskassessmentshavebeenconductedandreviewed,yieldinga better integration of the various issues in these offshore fisheriesandpromotingintegratedthinkinginresearchandmanagement(Neletal.,2007;Petersenetal.,2010).Nevertheless,Jarreetal.(2013acceptedforpublication)highlighthowtheprocessofconsolidationintheoffshorefishing industrythatbeguninthe1960s iscontinuingunder the current legislation, and argue that this is to the detriment of social-ecological health.
1.3 Human dimensionsResearch into the human social dimension of South Africanfisherieshasgainedmomentumandisyieldingresultswithrelevanceforpeople’sadaptationtolong-
1.Introduction
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 17
Thisresultsultimatelyinaclosecorrelationbetweenenvironmentalvariabilityandpopulationsizeandlengthfrequencies(Hsiehetal.,2006).Astheimpactsoffishingandclimatechangeinteractinanumberofwaystheycannot be treated as separate issues. Recent assessments ofthestatusoffisheryresourcesinSouthAfricafoundthatmanyofSouthAfrica’sinshoremarineresourcesareoverexploitedorcollapsed,withfewbeingoptimallyexploited (DAFF 2012). This was attributed to theaccessibilityofresourcestoawiderangeoffishersandanincreaseinillegalharvestingorpoaching(WWF,2011,DAFF2012).Fishingmayalsoresultinreducedgeneticvariability,whichwouldnegativelyaffectthepossibilitiesofanevolutionaryresponsetoclimatechangeandtheabilityof depleted stocks to recover (Anderson et al., 2008). Thisimpliesthatfishstocksunderintenseexploitationarelikelytobemorevulnerabletotheeffectsofclimatechangethanstocksthathavelittleornofishingpressure(Rijnsdorp et al., 2009).
Fishingtruncatestheagestructure(byremovinglargerindividuals) and causes loss of spatial heterogeneity(distributionmayshrink),whichmakesexploitedspeciesmorevulnerabletoenvironmentalvariabilityandtoclimateeffects.InaneightyearstudyofcoastalfishspeciesintheTsitsikammaMarineReserve,whichhasbeenprotectedforover27years, the fishassemblagewas found toberelativelystableintermsofabundance,taxonomicdistinctness,meanbodysizeandspeciescomposition(Jamesetal.,2012).Althoughabundanceofmostspecieswasvariablebetweenyears,adecreaseinrecruitmentofGaljoenforseveralyearsdidnotresultinasignificantdecrease in the abundance of this species. Populations of exploitedspeciesarelikelytobemorestableovertimeinMPAsthaninfishedareasbecausetheaccumulationoflargerage/sizeclassesintheprotectedareatendstosmoothoutfluctuationscausedbyrecruitmentvariability(Babcocketal.,2010).
resource, compared to the “basketful” of species that couldpreviouslybeharvested(Ragaller,2012).Tensionsbetweenconservationandtourismontheonehand,andfishingontheother,areaggravatedbyacommunicationbreakdownbetweenstakeholdersontheground(i.e.thefishersthemselves)andthemanagementagencies(theDepartmentofEnvironmentalAffairs(DEA)andtheDepartmentofAgriculture,ForestryandFisheries(DAFF))(Ragaller,2012).Theconflictdevelopedfollowingabreakdownincommunicationandresultedinanincreasein illegal,unregulatedorunreportedfishing(Schultz,2010).Legislativeloopholescombinedwiththelackoftransparencyinthesmallpelagicfisherieshavemadeitdifficult,ifnotimpossible,fornewentrantstothefisheryto establish businesses independent of the established industry(Haraetal.,2013,inreview).
1.3.1 Anthropogenicimpactsonfisheries
Fishing is seen as the greatest threat to future fishproductionandaffectsthesustainability,resilienceandabilityofexploitedspeciestoadapttoclimatevariabilityandchange(Brander,2007).Fishingisalsothegreatestpressureonmarinebiodiversity and a keydriverofecosystemthreatstatus(Sinketal.2012).Hsiehetal.(2006)comparedexploitedandunexploitedfishspecieslivinginthesameenvironmentandfoundthatexploitedfish populations showed higher temporal variabilityintheirpopulationsizethanunexploitedpopulations.Thedistributionoffishpopulationsunderfishingpressuremayshrink,reducingspatialheterogeneity,andthenumberofspawningindividualsmaydeclineasfishingtendstoremovelargeindividualsandthustruncatetheage-sizestructureofexploitedpopulations(Hsiehetal.,2008).Itisalsolikelythattheeffectsoffishingresultinmarineecosystemsbeingmoresensitivetoclimatevariabilityandchangethroughalteringthesizeandagestructureinfishpopulationsandhencereducing“bufferingcapacity”toclimate-relatedpooryearrecruitment (Rijnsdorpet al., 2009; Heath et al., 2012; Cheung et al., 2012).
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES18
2.ClimateChangeImpactsonMarineFisheries
2.1 Climate change-related observationsShifts in the spatial distribution of several marine species (includingintertidal,shallowcoastalandoffshorespecies)havebeenrecordedaroundSouthAfrica’sshores(Royetal.,2007;Cockcroftetal.,2008;Coetzeeetal.,2008;Griffithsetal.,2010;Mead,2011;Lloydetal.,2012).Theseshiftshavelargelybeenattributedtotheeffectsof climate change such as increasing/decreasing SST, changesinwindpatternsandupwelling,andcanhaveconcomitanteffectsonfisheriesbiodiversity rangingfrommildtosevere.Otherexamplesofchangesinthedistribution or other characteristics of marine species off South Africa arising from climate change are rare. Shannon et al. (2010)emphasisethenecessityforconsideringenvironmentaldrivers(bottom-up)aswellaspredationandfisheries(top-down)pressuresintermsoftheimpacton living marine resources. The most salient global and localobservationsofphysicalandbiologicalchangesarehighlighted in this section.
Oneofthegloballymeasuredeffectsofclimatechangeonmarineecosystemsisseasurfacetemperature(SST)overthepastcenturies.Onaglobalscale,anoverallwarmingtrend in the oceans and atmosphere has been detected. Locally,insituobservationsofwindandtemperaturesonthewestandsouthcoastsdemonstrateverylittletrendover30–60yearperiods(Hutchingsetal.,2012;Blameyet al., 2012), in contrast to satellite-derivedobservations(Rouaultetal.,2010).Inlinewiththehighlyvariable nature of the South African coastline, the change in SST is not uniform and there are several areas along thewest,southandsoutheastcoastswherenearshoreSSTsarecoolingseasonallyasaresultofanincreaseinwindsthatencourageupwellingoracombinationoftheseandanintensificationoftheAgulhasCurrent(Rouaultetal.,2009and2010).Forexample,apositivetrendinSST of up to 0.55°C per decade (from 1985 to 2009) in mostpartsoftheAgulhasCurrentsystemandanegativetrendinSSTinshoreoffthewestandsouthcoastshavebeen reported (Rouault et al., 2010; Hutchings et al.,
2009;Rouaultetal.,2009).However,Hutchingsetal.,(2012)showlittlechangeininshoretemperaturesinStHelenaBay,whileinstrumentedrecordsalongthesouthcoastalsoshowlittlelongtermtrend(DEA,unpublisheddata).Confounding the situation, in situ data (DEAunpublisheddata)hasshownthatinshorewatersarenotvaryingsignificantly,asincreasedupwellingcompensatesfor increased heating, increasing the thermal gradient betweeninshoreandoffshorewaters.
Globally,Boyceetal.,(2010)reportedasustaineddeclineinmarinephytoplanktonbiomassoverthepastcenturywhichtheylinkedtoincreasingSST,althoughthisanalysisisnotyetwidelyaccepted(e.g.seeMackas,2011).AdeclineinmarinephytoplanktonhasnotbeendocumentedforthesouthernBenguela,whereDemarcqetal.(2003)andLamont(2011)showedstronginterannualvariabilitybutnotrendinphytoplanktonabundanceoverthe10–15yearsobserved.Elsewhere,changesinfishdistributionpatterns(e.g. Perry, 2005;Ottersen et al., 2010) and in thephenology(thetimingoflifecycleeventssuchasspawningandmigration)ofavarietyormarineorganisms(Edwards&Richardson,2004;Koelleretal.,2009)linkedtoclimaticvariables have also been documented.
Mead (2011) detected changes in thedistributionofcold-andwarm-water intertidalspecieswithinrockyshorecommunitiesinFalseBaythatwerelinkedtotheobserveddecliningSSTandincreasedupwelling(Rouaultetal.,2010).WhilstFalseBaydoesnotnecessarilyhostasubstantiveintertidalharvestingcommunityorfishery,changes in the intertidal species composition could result inchangesinthenearshorefishcommunityabundanceanddiversitybeingdrivenbypreyavailability.Thiscouldhavepotentialimpactsonthenearshorerecreationalfisheriesthroughout South Africa. Should similar intertidal shifts inspeciescommunitiesbedetected,specificallyalongthenorthernKwaZulu-Natalcoast,subsistenceintertidalfisheriescouldbeimpacted.
2. CLIMATE CHANGE IMPACTS ON MARINE FISHERIES
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 19
Lloyd et al. (2012) reported an increase in speciesrichnessanddiversityofreeffishmonitoredalongtheNatalcoastfromBallitotoScottburghbetween1989and2007.TheincreaseinspeciesdiversityinthisstudywaslinkedtotheincreasingSSTdetectedalongtheKwaZulu-Natalinshoreregionandwasdeducedtobeasaresultofspeciesrangeexpansionslinkedtooceanwarming(Lloydetal.,2012).Severalstudiesinotherpartsoftheworldhavesimilarlyfoundincreasesinspeciesdiversityassociatedwithchangingclimateconditions(Hiddink&ter Hofstede, 2008; Last et al., 2011; Cheung et al., 2012).
Blameyetal.(2012)analysedshiftsinwindintensityandupwellingratesonthewestandsouthwestCapecoastover the period 1960 to 2010 and discussed these changes inrelationtochangesintherocklobsterfishery.Robustshiftsinwindsandupwellingweredetectedintheearly1980saswellasthemid-1990sandpossibly2009–2010,right at the end of the data series. These indicate changes inthehabitatforshelfzonespecies(smallpelagics,rocklobster,hakes)offboththewestandsouthcoasts,withthecoastspossiblyreactingdifferentlytoclimatedrivers.Fromabiologicalperspective,observationsofchangesinreeffishassemblagesofftheeastcoastlinkedtooceanwarminghavebeenreported.Thesehaveledtoahigherproportionoftropicalspeciesandalowerproportionoftemperatespecies(Lloydetal.,2012).Aneastwardexpansion inthedistributionofkelp inrecentyears,linked to cooling along the south coast, has also been documented(Boltonetal.,2012).
Thesouthwardexpansionofwarm-temperate/subtropicalwestcoastwateraswellasareductioninthefrequencyandmagnitudeofupwellingeventsinBenguelaElNiñoyearshasfacilitatedtheexpansionofwestcoastduskykobintoNamibian(andSouthAfrican)watersattheexpenseof silverkobandmayalsohave resulted inhybridisation(Pottsetal.,2012).Forthelast20years,hybridisationmayhaveexistedasfarsouthasStHelenaBay(Lamberthetal.,2010).Hybridisationisapotential
responsetoecologicalstressespeciallyondistributionalmarginsandmay,atleastpartly,beduetoastress-inducedbreakdowninmaterecognition.Infish,hybridisationisusuallyassociatedwithincreasedresistancetodiseaseandphysiologicaltoleranceofenvironmentalstressesandmayoftenallowspeciestoexpandtheirrangesandinvadenewniches.Conversely,thereismolecularsupportforpotentialreducedfitness inhybridisedfishunderenvironmentalstress(Davidetal.,2004).Thismaybeaplausibleexplanationfortherelativelyrareoccurrenceofinterspecieshybridisationinsympatricenvironments.However,thesympatricpopulationsofthewestcoastduskykobandthesilverkobarebothunderstressfromfishing,climatechange,distributionalshiftsandanincreaseininter-specificinteractions.Behaviouralandbiologicalresponsessuchasdistributionalshiftsandhybridisationmake it clear that some population thresholds have alreadybeenreachedandthatevenminoranthropogenicdriversmayprecipitatefurtherchange.
2.2 Projected impacts ThepotentialimpactsofclimatechangeonfisheriesandconsequentlyonnationaleconomiesgloballyhasbeenreportedinAllisonetal.(2009).Thiswasbasedonthreevariables:thepredictedwarming,therelativeimportanceoffisheriestonationaleconomyanddiet,andsocietalcapacitytoadapttopotentialimpactsandopportunities.BasedontheIPCCAR4B2emissionsscenario(whichrepresents a lower emission trajectory than thoseconsideredmostwidelyintheLTAS),thevulnerabilityofSouthAfrica’snationaleconomytoclimate-drivenchangestofisherieswasidentifiedasmoderate.Itislikely,therefore,thathigheremissionsscenarioswouldimplyahigherlevelofvulnerability.
2.2.1 Projectingimpacts
InSouthAfrica,projectingtheimpactofclimatechangeonfisheriesiscomplicatedbythenumberofecoregionsfoundalongarelativelyshortcoastline.Currently,there
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES20
are no reliable regional models of future climate scenarios forthemarineareasoffSouthAfrica,andtheIPCChascautionedagainstdownscalingfromglobalmodels.Oneofthebiggesthurdlesisthedeficienciesinrepresentingthetight SST, topographic, vegetation and soil gradients in theregion(ReasonandHermes,2011).Forexample,globalmodelsdonotincludetheinfluenceoftheAgulhasCurrenton regional heat andmoisture flux for thesouthernBenguela.Regionalmodelsarecurrentlybeingdevelopedwhichrealisticallycapturebasin-scalechangesinthewindfield(egVeitchetal.,2010;Loveday,2013).
Despitealackofprojections,substantialenvironmentalmonitoringinsupportoffisheriesresearchhasallowedthe development of several good observational data sets comparedwithmanySouthernHemispherecountries.However, subdividing the projected time scale tolookatimpactsintheshort(2020–25years),medium(2050–2070years)andlong-term(2100–)iscurrentlynot possible given the status of current climate models andtheoverwhelmingdominanceofdecadalvariabilityinobservationalrecordsofwind,temperature,salinityandoxygenintheBenguelasystem(Hutchingsetal.,2009,2012).Evenwith60ormoreyearsofobservationaldataoneisunabletoanticipatedecadalcycleswithanydegreeofconfidence.Cheungetal.,(2009),however,presentedglobal projections of changes in the distribution of more than1060exploitedmarinefishspeciesbytheyear2050.Theresultssuggestthatclimatechangemayleadtolocalextinctionsofmarinefishspeciesinthepolarregions,tropicsandsomeenclosedseasby2050.AfollowuppaperbyCheungetal.,(2010)basedonthesamenumberofspeciessuggestsaglobalredistributionofcatchwithanexpected30–70%increaseincatchinhighlatitudesandadropofupto40%inthetropicsby2050.
Twokeyprojectedconsequencesofclimatechangewithsignificantimplicationsforfisheriesareacceleratedsealevelriseandanincreaseinthefrequencyofhigh-intensitycoastalstormsandhighwaterevents,especiallythroughthe impacts on estuarine habitats (see sections 2.2.1.2 and
2.2.1.3).Severalclimatemodelsprojectanacceleratedrate of sea level rise over the coming decades (Solomon et al., 2007). An assessment of sea level rise in South Africa,usingavailabletidegaugedataforthelast50years,showsa1.87mm.y–1riseonthewestcoast,a1.48mm.y–1 riseonthesouthcoastanda2.74mm.y–1 rise on the east coast(Matheretal.,2009).Isostaticsettlingofthecrustcausedbytheadditionalweightofwateroverareaswithawidecontinentalshelf,suchastheAgulhasBank,willlocallyaccentuatesealevelrise,possiblybyasmuchas25%(Reddering&Rust,1990).
TheSouthAfricancoastlineisintermittentlyimpactedbyextremeswellsassociatedwithtropicalcyclonesandcut-offlowpressuresystems(Mather&Stretch,2012).Extremeweathereventsarepredictedtoincreaseinfrequencyandintensityinthe21stcenturyandappeartobeonthe increaseglobally(Solomonetal.,2007;Engelbrechtetal.,2009;2011).ExtremerainfalleventsareprojectedtoincreaseforSouthAfricaandMozambique(Davis,2011).Increasedstormfrequencyandintensityhasbeenhypothesisedtohavethepotentialtoindirectlychange the behaviour and activity of fished species(Rijnsdorp et al., 2009; Cheung et al., 2012) and the effectivenessoftrawlfishinggear(Stewartetal.,2010).
2.2.2 Fisheriesspeciescompositionandproductivity
ChangesinSST,windpatternsandpressuresystemsat local scales can af fect oceanographic features likeupwelling and thereby influenceoverallmarineproductivity(Rijnsdorpetal.,2009,Sinketal.,2011)(seesection2.1onClimateChangeObservations(p9)for further information). Projected impacts of climate changeonmarineecosystemsincludechangesinspeciesdistribution,composition,seasonalityandproduction(Brander,2009).Basedontheobservedglobalscale,thegeneralexpectationfortheimpactofclimatechangeon marine fauna is a decrease in species richness withincreasinglatitudeinbothhemispheres(Heath
2.ClimateChangeImpactsonMarineFisheries
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 21
etal.,2012).Theseobservationsarecorrelatedwithwarmingannualaveragetemperatures.However,thisisnotalwaysthecaseatlocalscalesasobservedintheSouth African marine environment (Rouault et al., 2010, Sinketal.,2011).Marineecosystemsarecharacterisedbylargenaturalvariability inclimateandecosystemprocessesandalsorespondinvaryingwaystoextractivepressures(Cheungetal.,2012).Thismakesitdifficulttomeasureandprojectchangesinclimatevariabilityanditseffectsonoceansystems,bothphysicalandbiological(Rijnsdorpetal.,2009;DEA,2011;Heathetal.,2012;Cheung et al., 2012).
Habitatchangesinresponsetoclimaticchangesarelikelytohaveaconsiderablecascadingeffectonfishspeciescompositionassociatedwiththathabitat(Lastetal.,2011).Changescouldresultinsomehabitattypesbecomingviableforcolonisationbyasuiteofnewspecies.Thiswould,however,bedependentonseveralfactorssuchasadultstocktoseednewareas,successfulrecruitmentandsurvival(Kennedyetal.,2002).Somespeciesmaysimplycontract their distribution range avoiding unfavourable partsoftheirformerrangethroughloweredsurvival,reproduction and recruitment as a result of their former habitatsimplynolongersupportingthatspecies(Kennedyetal.,2002;Heathetal.,2012).Suchbehaviourwillalsoresultinaltereddiversityoffishspeciesinaregion.
Differentmarineresourcesarelikelytorespondtotheeffectsofclimatechangedifferently.Rijnsdorpetal.(2009)proposethatspecies’sresponseswillbeinfluencedbytheirhabitatrequirements(pelagic,demersalordeep-water),life-historycharacteristics(shortorlong-lived,specialistorgeneralist)andtrophicpositionswithintheecosystem(apexpredatororforagefish).Generalistspeciesarelikelytoadapttotheprevailingconditionswhereasspecialistspeciesareusuallystronglydependentonspecificprey,habitat or environmental conditions. Species that have spatiallyrestrictedorveryspecifichabitatrequirementsforallorpartoftheirlifehistorywillbemorevulnerableto climate change effects. Short-lived species characterised
byhighreproductiverates(r-selected)arelikelytobeabletotrackthechangingenvironmentrelativelyrapidlywhilelong-livedspecies(K-selected)wouldbeslower,andlesslikelytobeabletoadapt(Perryetal.,2005),whilepelagicanddemersalspecieswilldifferintheirresponse,atrendalreadyobservedinSouthAfricanfisheries.
2.2.3 Fishbehaviourandphysiology
ChangesinSSTmayalsoresultinchangesinthebehaviourofresourcespecies,includingtheircatchability.Thismaybeparticularlyrelevanttospeciescapturedwithbaitedfishinggearsuchaswestcoastrocklobster.Itishypothesisedthatwithincreasingtemperatures,thereislikelytobea related increase in metabolism and consumption rate infishandinvertebrates(Kennedyetal.,2002),leadingto higher catch rates and potentially an increase indiversityofcatch(Cheungetal.,2012).Similarlyithasbeen suggested that an increase in temperature could resultinanincreaseinfishswimmingspeed(Pecketal.,2006).Alongwithbehaviouralmodifications,thismaymakefishmoreorlessvulnerabletotowedfishingdevicesliketrawlnets(Rijnsdorpetal.,2009).Suchbehaviouralmodificationsarelikelytoalterthebiodiversityoffishspeciesavailabletofisheries;however,furtherdetailedstudiesarerequiredinordertounderstandwhatsortofchangescanbeexpected.
Reducedfishsizesduetooceanwarmingandreducedoxygenlevelshavealsobeenpredicted,withreductionsinbothassemblage-averagedandindividualmaximumbodyweightprojectedfrom2000to2050underahighemissionscenario(Cheungetal.,2012).Forassemblage-averagedmaximumbodyweight,thereductioninbodysizeislikelyto be as a result of changes in distribution and abundance (invasion/increased abundance of smaller-bodied species andlocalextinction/decreasedabundanceoflarger-bodiedspecies),aswellaschangesinfishphysiology(Cheungetal2012).However,predictedchangesinmaximumbodyweightaremoreconservativethanobservedchangesforbothAtlanticcod(Sheridan&Bickford,2011)andNorthSeahaddock(Baudronetal.,2011).
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES22
2.2.4 Positiveimpacts
Climatechangemayresultinbeneficialeffectsonsomespecies. The change in SST, for example,may resultin a limitation on the possible range of some species butmayexpand theoptimal rangeavailable tootherspecies.Thiscouldresultinnewfishingopportunitiesascommerciallyvaluablespeciespotentiallyenternewareasand become available for harvest (Sink et al., 2011). Cheung etal.(2012)discussevidenceofseveralwarmerwaterspeciesmovingintoUnitedKingdomandIrishseasofferingnewfishingopportunitiesinthisregion.Achangeinfishbiodiversitymayalsooccurasaresultoftranslocationofdeep-waterspeciesintotheshallowershelfregionresultingin these species becoming available for capture (Rijnsdorp etal.,2009).However,HiddinkandterHofstede(2008)cautionthatanincreaseinspeciesdiversityasaresultofclimatechangemayalsohavenegativeecologicalandsocio-economiceffects.Iflargespeciesarereplacedbysmallspeciestheenergyflowthroughtheecosystemwillbealtered,therebychangingthedynamicsoftheecosystem.Such a shift from large species to increasing abundance of smallerspeciesislikelytodecreasethevalueoffisheries(Hiddink&terHofstede,2008).Furthermore,changesin distribution patterns could alter the combination of predators,parasitesandcompetitors inanecosystemultimatelyresultinginalteredecosystemfunctioningandfisheryproductivityinwaysthatcannotbepredictedwithcurrentknowledge(Kennedyetal.,2002).Someareasmayalsobecomemoreproductivewhichmayincreasefisheriesyieldbutincreasedproductivitymayalsoleadtoanincreaseinlowoxygeneventsthatmayimpactnegativelyonsomeresources.Fishersareconsideredopportunisticandrespondtoenvironmentalchangedbyadaptingtheirfishingareas,targetspeciesandstrategieswherethemanagementframeworksupportssuchadaptation.
2.2.5 Humandimensions
An increase in the global intensity and frequencyofextremeweathereventshasbeenlinkedtotheeffectsofclimatechangeandsucheffectsaresimilarlypredictedtoimpact the South African coastal and marine environment (Theron, 2010). Such an increase is likely to impactonfishingactivityintermsofreducingthenumberofviable sea fishingdays,possibly affectingcatch rates(Stewart etal.,2010;Cheungetal.,2012).Furthermore,increasedstormintensityislikelytoresultindamageanddestructiontoshore-basedoffloadingfacilitiesandfishingvessels,againresultinginlimitationsonthecatchyield.
2.3 Key impacts: Estuarine and inshore fisheries
2.3.1 Overallimpacts
Ona regional scale,KwaZulu-Natal andwest coastestuariesarelikelytobethemostaffectedbyclimatechange from a structural and functional perspective (Table 1). In KwaZulu-Natal, the major driver isincreased runoff into the numerous small, perched, temporarilyopen/closedestuaries,whichwillresultinmore open mouth conditions, a decrease in retention timeandassociated lossofprimaryproductivityandnurseryfunction.Incontrast,westcoastestuarieswillbenegativelyaffectedasaresultofreductionsinrunoff,relateddeclines innutrientsupplyandan increase insealevelrise.Thiswillincreasesalineintrusioninthepermanentlyopensystemsandincreasemouthclosureinthetemporarilyopenestuaries.SimilartoKwaZulu-Natal,thewestcoastestuarieswilldisplayadecreaseinprimaryproductionandalossofnurseryfunction.
AlthoughWildCoast,easternandsouthernCapeestuarieswillshowsomeshift inmouthstate,nutrientsupply,salinitydistributionandproduction,themostobviousimpactsofclimatechangealongthesecoastalregionswillbe changes in temperature (nearshore and land) driving rangeextensionsandchangesincommunitystructure.
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LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 23
DRIvERS RESPONSESUB-TROPICAL WARM TEMP COOL
TEMP
KwaZulu-Natal Wild Coast Eastern
CapeSouthern
CapeWestern
Cape
Oceancirculation
Current speed + + + +- +-
Current position ? ? ? ?
Upwelling + + + + +
Precipitation
Runoff + + + +- -
Mouthclosure - - - +- +
Salinity - - - +- +
Nutrientsfluxes + + + +- -
Floods&sediment + + + +- -
Droughts + + + + +
Flushingpollutants + + + + - -
Sea level rise
Salinity + + + + +
Increasedtidalprism + + + + +
Mouthclosure - - - - -
Rising temperatures
Species range extensions + + +- +- -
Communitycomposition - - - + +
Acidification Calcifyingorganisms - - - - -
Coastal storms
Mouthclosure + + + + +
Overwash + + + + +
Marinesediment + + + + +
Table1.Climaticdrivers,keyvariablesandintensityofresponseindifferentcoastalandishoreregionswithinthethreemajormarinebiogeographicprovincesinSouthAfrica.Intensityrangesfromhigh(darkshading)tolow(lightshading)(VanNiekerket al., 2012).
2.3.1.1 Temperature
Seasonal coolingofnearshoreSSTs, associatedwithintensifiedupwelling,mayhavesevereconsequencesforcoastalandestuarinespeciesalongthewestandsouthcoasts of South Africa. Sudden shifts in temperature canbelethaltofish,especiallyifshallowwaterpreventsthemfromfindingathermalrefuge(Roessigetal.,2004).Althoughestuariesandshallowbayscanprovidethermalrefugeforcoastalspeciesmassmortalitiesofcoastalfishhavebeenrecordedalongthesouthcoastwhenupwellingcausesasuddendropinwatertemperature(Hanekom
etal.,1989).Thesemortalitiesdonotnecessarilyresultfrom thermal shock but from fish aggregating in the shallowsandbeingtooweakandhypothermictoresistbeingstrandedintheswashzone.Intheshorttomediumterm, spatial and temporal shifts in these thermal barriers maydisruptcoastwisemovementsuchasthewinterspawningmigrationofwhitesteenbrastosubtropicalwaters.Inthelong-term,anincreaseinthefrequencyandpersistenceof thermalbarriersmayaffectbothtemperate and tropical species and even impede the range extensionsofthelatterintotemperateregions.Coastal
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rainfallpatterns)onSouthAfrica’swaterresourcesandpredictedthatfutureclimatemaybecharacterisedby“hotspots”ofhydrologicalchange,onebeingthepresentwinterrainfallregionoftheWesternCape.Anotheridentifiedhotspot is thebimodalrainfallzoneof thesouthernCapewhere the frequency andmagnitudeoflargefloodsaswellasthedurationandintensityofdroughtsareanticipatedtoincrease.Thesesystemsarecharacterisedbymediumtosmallcatchmentsinwhichbimodalrainfallamelioratesflowvariabilityandconfersadegreeofstabilityonestuarinehabitats.
Changesinprecipitation,runoffandstormfrequenciesdrivemodificationsinsalinewaterintrusioninestuaries,thefrequencyanddurationofmouthclosure,nutrientfluxes,themagnitudeandfrequencyoffloodsandrelatedsedimentdeposition/erosioncyclesandthedilutionand/orflushingofpollutants(Alber,2002).Thisalsoresultsinalossofnurseryfunction.Conversely,largestormeventscouldtriggertheprematureopeningoftemporarilyclosedestuariesbyintroducinglargevolumesofseawaterintothesystemandflatteningthesandbars.Reductionsintheamountoffreshwaterenteringestuarieswouldleadtoanincreaseinthefrequencyanddurationofestuarymouthclosureandchangesintheextentofseawaterintrusion, nutrient levels, suspended particulate matter load,temperature,conductivity,dissolvedoxygenandturbidity (Clark,2006;VanNiekerk&Turpie2012).Overall,alterationsinfreshwaterflowresultingfromclimatechangeintoestuarieswillaffectrecruitmentandemigrationofestuary-associatedfish.Estuarine-dependentspecies are sensitive to reductions in the volume of freshwaterrunoffandmaydeclineinabundance,whichwillhavefisheriesimplications.Reductionsinfreshwaterrunoffwillalsoreducetheamountofnutrientsenteringestuaries,witharesultantimpoverishmentofthebiota.
Anincrease inthemagnitudeoffloodsasaresultofclimate changewill cause deeper scouring, thereby
coolinginsomeareas,associatedwithupwelling,maylimittheabilityofthesespeciestoshifttheirdistributionpolewardoverlongdistances.Itisunlikelythatcoastalcoolingwillpromotethemovementofmoretemperatetaxabeyondtheirexistingrangetowardstheequator.
Changes in the distribution of tropical fish species have been recorded in temperate estuaries (e.g. East Kleinemonde,Mngazana andBreede) resulting in anincreaseinspeciesrichnessintheseestuaries.However,thereisalsothepossibilityofrangeshrinkageoradeclinein the number of temperate species in temperate estuaries and along the coast. Subtle changes in temperature have already seen range expansion, stock separation andthe establishment of viable populations of important exploitedlinefishspecies(Lamberthetal.,2012).Elevatedestuarytemperaturesmayallowfishtooverwinterandbecomeestablishedinthesesystems.Conversely,flowreductionfromwestcoastcatchmentsmayseepartialor complete loss of the nearshore thermal refugia used aswaypointsbynearshorefishmigratingfromNamibiantoSouthAfricanwaters,andultimatelyrangeshrinkage(Lamberthetal.,2008).Insummary,tropicalspeciesmaymovepolewardsinresponsetowarmingtemperaturesresulting in an expansion of the subtropical region.Estuariesinsubtropicalregionswillalsobeimpactedbyprobableincreasesinrainfall,ariseinsealevelandincreased frequencyofhigh intensitycoastalstorms.Incontrast,temperateregions(EasternandWesternCape)maycontract,withestuariesandestuarinespeciesbeingaffectedbyprobableupwellingrelatedextremesintemperatures,reducedrunoffandhabitatloss,ultimatelyleading toadecrease in temperate speciesdiversityand abundance.
2.3.1.2 Precipitation,extremeeventsandrunoff
Schulzeetal. (2005)assessedthe impactsofclimatechange (including climate change driven alterations in
2.ClimateChangeImpactsonMarineFisheries
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Sea levelriseandtherelated increases inthesizeoftidal prismswill be temperedby the predominantlyperched systems of KwaZulu-Natal (estuarine baysandlakesexcluded)whilstitwillbemoreevidentalongtheextendedcoastalfloodplainsofthesouthernandWesternCapecoast.Overall,whereasbioticchangemaybefirstdiscernibleandmoreeasilymeasurableinthebiogeographictransitionregions(e.g.WildCoastandsouth-westernCape),themostsignificantstructuralandfunctionalchangeswillberealisedintheestuariesofsubtropicalKwaZulu-NatalandthecooltemperateWesternCape.
2.3.2 Cool-temperate region
Onthewhole,itisanticipatedthatairtemperatures,sealevelandthefrequencyofstormswillincreaseforestuarineandinshoremarinehabitatsandfisheryareasalongtheWestCoast,whilstSST,rainfallandriverflowwilldecrease.Therewill,however,beexceptionstotherule.Itislikelythatthesechangeswillaffectfisheriesinthecool-temperatecoastalregioninthefollowingways:
• Sealevelrisemayreduceestuarinenurseryhabitat,whichisessentialformanyspeciescaughtinestuarineandcoastalfisheries.
• Decreasedrainfallmaycausetemporarilyopen/closedestuariestoclosemorefrequentlyandmayevenresultinclosureofpermanentlyopenestuariesallofwhichwillhavefisheriesimplications.
• Overall,itisexpectedthatoverexploitedspecies(suchasmanyofthetemperatelinefishspecies)maybemorevulnerabletoclimatechangeandvariabilitythanunexploitedandoptimallyexploitedspecies.ThelikelyimpactsofclimatevariabilityandchangeonthewestcoastrocklobsterareincludedinBox2.
increasing tidal amplitude and exposure of subtidalhabitatsandcommunities. In largepermanentlyopensystemsflowreductionmayinitiallyresultinareductionintheextentoftheriver-estuaryinterface(REI)zone,i.e.thatsectionofanestuarywithanintegratedverticalsalinityofapproximately10.Majorreductionsinriverflowcanresultinthecompleteeliminationofthismixedzone,sothatthesystemfunctionallybecomesanarmofthesea.Intemporaryopen/closedestuaries,mouthopeningandclosingisdirectlylinkedtofreshwaterinputandwaveaspect,withestuariesbecomingisolatedfromtheseabythe formation of a sand berm across the mouth during periodsoflowornofreshwaterinflowandhighwaveaction.Thesesystemsstaycloseduntilfreshwaterinflowcausestheirbasinstofillupandtheirbermstobreach(Whitfieldetal.,2008).Reducedfreshwaterinflowleadsto prolonged mouth closure and shorter open phases.
2.3.1.3 Sealevelrise
Sealevelrisewillalsoimpactonthemouthsofestuarieswhichwill interactwith reductions or increases infreshwaterflowasdescribedabovebuttheseeffectshavenotasyetbeenfullyexplored.Ariseinsealevelandanincreaseinthefrequencyofhigh-intensitycoastalstormsandhighrainfalleventsmayhavearangeofimplicationsforestuariesandestuary-associatedfish.Itisanticipatedthattheeffectsofsealevelrisewillbeexacerbatedbypredictedincreasesinthefrequencyofseverestormsand high tides impacting the coastal platform at a higher meansealevel(Bindschadler,2006).Theupstreamshiftofcoastalwetlandsinresponsetosealevelrisemaybelimitedbycoastaldevelopmentandhinterlandtopography.Thismayultimatelyresultinthelossofhabitatwhichwill,inturn,affecttheabundanceofestuarinefishandinvertebrates, and the resilience of estuarine and coastal fisheries.Coastalstormsandhighwatereventswillalsoalterthesalinityanddepthofestuaries.
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2.3.3 Warm-temperate region
Itisanticipatedthatforestuarineandinshoreecosystemsofthewarm-temperateregion,airtemperatures,sealevelandthefrequencyofstormswill increase,whileSSTwilldecreaseseasonallyinsomeareasasaresultofincreasedupwelling.Projectionsofchangesinrainfallandriverflowarelesscertainforthisregion.ThelikelyimpactsofclimatevariabilityandchangeonthechokkasquidfisheryareincludedinBox3below.
Box 3. The impacts of climate variability and change on the chokka squid fishery
Squid(Loligoreynaudii),knownlocallyaschokka,arefishedbyjigfishingwitheffortfocusedonadultsquidduringtheirspawningaggregationsonthewarmtemperatesouth coast.Abundanceof loliginid squidshasbeencorrelatedtotemperature,ElNiñoevents, turbidityandcurrentswithfluctuationsinabundancelinkedtoenvironmentalvariabilityandassociatedbiologicaleventssuchasspawningdistributionandsurvivalrateofjuveniles,andfishingpressure (DAFF,2012).Changes inwatertemperatureandupwellingmayaffectcatchesofchokkasquidinthewarm-temperateregionbutasthisspeciesisshort-lived,withrapidgrowthandhighmobility,theymaybe better able to adapt to changes in their environment thanmanyothertaxa(Pecl&Jackson,2008).
Squidhaveextremelyfastgrowthrates,shortlifespans(lessthantwoyears)andrapidpopulationturnover.Theirphysiologyisabletorespondtochangesintheenvironment,withtemperaturebeingakeydriver(Pecl&Jackson,2008).Oosthuizenetal.,(2002)foundthattheoptimaltemperaturerangefornormalembryonicdevelopment is between 12°C and 17°C. Bottom
Box 2. The impacts of climate variability and change on the west coast rock lobster
Overthepasttwodecades,therehavebeenmajorchangesinthewestcoastrocklobsterresourcelinkedwithclimaticvariability.Anincreaseintheabundanceofwestcoastrocklobsterwithintheeastwardextentoftheirdistributionrange (south coast region, Cockcroft et al., 2008) has beenobserved.Catchratesofwestcoastrocklobsterinthetraditionalfishinggroundsalongthewestcoastdeclineddramaticallyfrom1988to1996,coincidingwithreducedsomaticgrowthandincreasedlobsterwalkouts,suggestingthatenvironmentalchangesmayhaveplayedakeyroleindrivingdistributionalchange(Cockcroftetal.,2008).Duringasimilartimeperiod(early1990s)therewasamajorinfluxofrocklobstersintotheareaeastofCapeHangklip,anareanotpreviouslyassociatedwithhighrock lobster abundance (Cockcroft et al., 2008). This shift inresourceavailabilityofwestcoastrocklobsterhashadseriousecological,fisheriesandresourcemanagementimplications. Ecological impacts include reduced densities ofurchinsandwinkles(keypreyitemsofrocklobsters)andincreasedalgalcoverasaresultofreducedgrazers(Tarretal.,1992;Mayfield&Branch,2000).Reducedurchindensitiesresultedinlowabalonerecruitmentasjuvenileabaloneshelterunderurchins(Day&Branch,2000,2002).Bankcormorants,anendangeredspecies,feedonrocklobsterandhavealsoexperiencedreducedsuccessinbreeding,whichhasbecomeakeyconservationconcern(Crawfordetal.,2008).Socialandeconomicimpacts include reduced numbers of long term rights onthewestcoastandjoblossesatprocessingfacilities(Cockcroft 2011). This spatial shift in the resource and theconcomitantecologicalchangesarelikelytocausechallenges in the future management of both rock lobster and abalone resources (Cockcroft et al., 2008).
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Rouaultetal.,(2010)recordedcoolingofupto0.35°CperdecadeforthesouthcoastbetweenMayandAugust.However,nochangeintemperaturewasrecordedduringsummer,whichisthepeakspawningseasonforchokka(Rouaultetal.,2010).ItisthereforedifficulttopredicthowchangesinSSTswillaffectcatchesofchokkasquid.
Extremeweathereventsarepredictedtoincreaseinfrequencyandintensityinthe21stcenturywhichmayhavesevereimplicationsforthechokkasquidfishery(through increased turbidity in the shallow waterspawning grounds). Turbidity near the seabed alsoaffectsthespawningbehaviourofadultsquid,withhighturbiditycausingthemtoavoidtheshallowerinshorespawninggroundsandmoveintodeeperwaterswheretheyareunavailabletotheinshorefishery(Roberts&Sauer, 1994). Roberts & Sauer (1994) found that severe winterstormsin1992resultedinincreasedswellheight,beacherosionandhighturbidityontheinshoregroundsandsubsequentlyexceptionallypoorsquidcatchesinthatyear.SeverewinterstormsmaybelinkedtoElNiñoconditions,whichenhanceseverewesterlywindsonthesouth coast (Roberts & Sauer 1994), and have also been linked to longer-term climate change.
Theremaybeapositiverelationshipbetweensquidhabitatandfreshwaterflow.Nearshorehabitatandsedimentcompositionwhichisshapedbyterrigenousinputcanchangedrasticallyandsquidcouldmoveelsewheretotheirpreferred sedimentparticle size.Alternatively,changesinsedimentsize,textureandcolouraswellasinturbiditycanleadtosquid,eggsandyoungbecomingmoresusceptibletopredation.Thissquidresponsetofreshwaterflow,sedimentandturbidityishypotheticaland needs to be tested.
watertemperaturesrecordedontheinshorespawninggrounds, although more variable than those recorded offshore,arenormallybetween11°Cand17°Casaresultofwind-drivenupwellinginspringandsummer(Oosthuizenetal.,2002).DuringElNiñoconditions,withloweasterlywindintensitythereislesswind-drivenupwellingresultinginhigherbottomwatertemperatures.Undertheseconditions,spawningsquidmayavoidthewarmerinshorespawninggroundsandmayspawninthedeepermid-shelfregionwherebottomtemperaturesare cooler (Roberts, 2005).
Temperature(asanindexofupwelling)affectsfeedingand survival of the paralarvae of chokka. The inshore spawninggroundsaredisplacedfromanareaofmaximumcopepodabundance(whichtheparalarvaearefeedingon)associatedwithacoldridgebyapproximately200km.ThecoldridgeisacoastalupwellingfilamentfrequentlyfoundofftheKnysnacoastduringsummer(Roberts,2005).ItisbelievedthatsquidusethenetwestwardshelfcurrentsontheeasternAgulhasBankformovementofparalarvaetothecoldridgewestofthespawninggrounds (Roberts,2005). Intensesummerupwellingresultsingreatercoldridgestability(andthuscopepodabundance)withanegativelinearrelationshipbetweenmaximumsummerSST(anindexofcoldridgeactivity)andchokkasquidbiomassandcatchesthe followingautumn (Roberts, 2005).
Asspawningbehaviourandembryonicdevelopmentandsurvivalaredirectlylinkedtotemperatureandupwellingfrequencyandintensity,anychangesinwatertemperatureand upwelling associated with short-term climaticvariability(suchasENSOevents)andlonger-termclimatechangecouldaffectcatchesofchokkainthejigfishery.
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES28
ExistingwaterusesinthecatchmentsfeedingStLuciaarealreadyatlevelsthatcannotbecompensatedforbythepredictedincreasesinrainfallandflow.Largefloweventsareexpectedtoincreasebutdroughtsremainacharacteristicofthecatchmentandmaywellintensifywith increasedair temperaturesandrelatedmassiveevaporative losses fromStLucia’s largesurfacearea.Extreme drought conditions in St Lucia from 2003resultedinalossofestuarinenurseryhabitatinlargeareasofthesystemand,togetherwithmouthclosurethishadalargeimpactontheprawntrawlfishery(Turpie&Lamberth, 2010).
Box 5. The impacts of climate variability and change on the KwaZulu-Natal line fishery
Increasesinrainfallacrossthesubtropicalandtropicalregionswillnotnecessarilytranslateintoincreasedfishproduction and improved catches. Increased rainfallwilltendtowardstheeventscale(floods),withsomeshiftsoutsidethecurrentseasonalpatterns,andmaybeasynchronouswiththelife-historiesofthefishthatdependupontheseseasonalpatterns.Inaddition,long-term strategic planning envisages a number of future developments,ranginginmagnitudefromlocalwaterabstraction to large dams and inter-basin transfer schemes for most of the larger catchments in the subtropical region (DWAF,2004).Thenetresultwillbeareductionratherthanincreaseinflowreachingthesea.Toillustrate,long-term planning for the Thukela River entails a possible 40+%reductioninrunoffreachingtheseawithcatchesofslinger(Chrysoblephuspuniceus)andsquaretailkob(Argyrosomusthorpei)forecasttodeclineby36%and28%respectively.Thesetwospeciescurrentlyprovideover50%ofthelandedmassbythelinefisheryontheThukelaBanks(Lamberthetal.,2010)
Ina19yearstudyofthesub-tropicalreeffishcommunityatBallitoandScottburghbasedonrecreationalspearfish
2.3.4 Sub-tropical region
Itisanticipatedthatairandseatemperatures,sealevel,thefrequencyofstormsandrainfallwillincreaseasaresult of climate change and affect subtropical estuarine andmarineecosystemsThe likely impactsofclimatevariabilityandchangeontheprawntrawlfisheryareincludedinBox4andthelikelyimpactsontheKwaZulu-NatallinefisheryareincludedinBox5below.
Box 4. The impacts of climate variability and change on the prawn trawl fishery
Summer rainfall is predicted to increase along the east coastofSouthAfrica,whichmayresultinanincreaseinthefrequencyanddurationofmouthopeningoftheStLuciaEstuaryandintheavailabilityofestuarynurseryhabitat.Thismayhaveapositiveimpactontheabundanceofshallow-waterprawnsprovidedthatmouthopeningcoincideswiththeseasonalpatternsofjuvenileprawnrecruitmentandemigrationofadultstothesea.However,theanticipatedincreaseinrainfallislikelytobeintheformofmoreraindaysandheavy/extremeprecipitationevents.Thiscoupledwithsealevelrise,mayresultinthelossofnurseryhabitat(suchasmangroves),whichisessentialforprawnsandestuarinefishspecies.Coastalstorms,sealevelriseandhighwatereventswillalsoalterthesalinityanddepthofestuaries.Sealevelrisewillinteractwithincreasesinrainfallbuttheseeffectshavenotyetbeenfullyexplored.ChangesincatchmentflowvolumesandsedimentloadsreachingtheseamayalterprawnhabitatontheThukelaBanks.Abundanceofall threeoftheshallowwaterprawnspeciesisdependentonaparticularsedimentparticlesizeandassuchspeciescompositionandabundanceincatchesmayvaryaccordingtoflow.Inthelong-term,reducedflowsandcoastalerosionarelikelytoreducetheextentofthefluvialfansfromtheThukelaandothermajorcatchmentswithanoveralllossofhabitatacrossallsedimenttypes.
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LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 29
impactedbytheremovaloflarger,olderfishbythefishery(Punt et al., 1992). The resulting decrease in the number ofyearclassesleadstolessresiliencebythesurvivingpopulationtoenvironmentalvariabilityinthemediumandlong-term(Brander,2009).Hakedo,onoccasion,showastrongresponsetoenvironmentalvariability.Forexample,thedisplacementoffshoreofjuvenilehakeoffNamibiain1994,whichsubjectedthemtoincreasedpredationandmortality,wascausedbypersistenthypoxicconditionsinbottomwaterovermuchofthecontinentalshelf(Hamukuayaetal.,1998).
Wind speed,direction and frequency are importantdriversofcoastalupwelling,whichbringscooler,nutrientrichwatertothesurface.Toomuchupwellingresultsinseverehypoxia(reducedoxygencontent)innear-shorewaters.Atpresent,windspeedsonthewestcoastarealreadygreaterthantheoptimallevel,andanyincreaseinthesewindspeedswillaffectupwellingwhichmayhaveadverseeffectsonthefisheriesforhake.
2.4.2 Keyimpactsonsmallpelagicfisheries
Incontrasttohake,bothextractionandtheenvironmenthaveahighimpactonthepopulationsizesofsmallpelagicfish.Theresponsetoenvironmentalvariabilityarisesfromtheirshortlifespan,lowtrophiclevel,andhighrelativefecundity,whichresultinhighinter-annual,decadalandmulti-decadalvariabilityinrecruitmentandsubsequentpopulationstrengthinthesespecies(Checkleyetal.,2009).OffSouthAfrica, thedependenceofanchovyin particular on successful transport of their eggs and larvae fromspawninggroundsoff thesouthcoasttonurserygroundsoff thewestcoast is thought tobecrucial to successful recruitment (Hutchings et al., 1998). Thehighestrecruitmentofanchovyyetobserved(in2000)overthepast28yearswasattributedtoaparticularpattern intheprevailingwindfieldovertheanchovyspawningperiodthatfirstresultedingoodtransportofearlylarvaetothenurserygroundsandtheningoodfeedingconditionsthere(Royetal.,2001).Thefollowing
catches,Lloydetal.,(2012)foundageneralincreaseintheabundanceoftropicalspeciesincatchesaswellasachange in the proportion of tropical versus temperate species represented in catches. The results from this studywereconsistentwithapredictedpolewardshiftinthedistributionalrangesofmarinefishwithclimatechangeinresponsetowarmingoftheAgulhasCurrent.
2.4 Key impacts: Offshore fisheriesImpactsonoffshorefisheriesdependondistinctscenariosofchangeintheoceansthatwouldbesubjecttochangesinwindpatternsand inoffshorecurrents.Due toalimited understanding of the mechanisms involved, and anincompleteabilitytomodelthese,thereiscurrentlyuncertaintyovertheimpactsonresources.Thesecouldincludesignificantspatialshiftsinresourcesdrivenbychanging offshore habitat quality. Several offshorefisheriesoperateinSouthAfrica’soffshoreecoregionsandecozones.Thedemersalhakefisheryandthesmallpelagic(sardine,anchovyandroundherring)fisheriesaredescribedbelowascasestudiesbecauseoftheirsocio-economic importance as representatives of the offshorefisheries.
2.4.1 Keyimpactsonhake
In general, the relative impact of f ishing on hakepopulationsize isconsideredtobegreater than theroleplayedbyenvironmentalandclimaticvariability.Thisisduetotherelativelongevityofthesefishandaresultantlargenumberofageclasses,whichactsasabufferandreducestheimpactsofinterannualvariabilityinrecruitment.Additionally,thedeeperhabitatofhake(100–800m)issubjectedtolessenvironmentalvariabilitythantheupperlayers.Hakepreyonthemselves,bothcannibalisticallyandviapredationbylargeshallowwaterhakeonco-occurringsmalldeepwaterhakeandthiscanresultinstrongdensitydependenceeffects.Hence,hakepopulationdynamicsarelikelytobesignificantly
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES30
Scenario 1. Changesinwinddominateoceandynamicsandnetprimaryproductivity:
• West coast:thereislikelytobeincreasedupwellingalongthewestcoast,drivenbyincreasedsoutheasttradewindsinspringandsummer, leading to sub-optimal turbulent mixingandoffshorelossesforpelagicplankton,whileexcessprimaryproductionresultingfromincreasednitratesupplyfromupwellingleadstogreaterhypoxiaandareductioninhabitatforpelagic and benthic organisms in the inner part of the continental shelf.
• South coast: The strengthening of the Agulhas Current,drivenbyincreasedtradewindsinthesouthernIndianOcean,shouldresultinincreased temperatures offshore and increased divergence-drivenupwellingandproductivity,particularlyatPortAlfredaswellasheadlandsalong the south coast and along the shelf edge of theAgulhasBank.TherewillbestrongerthermalstratificationinsummerandlesswintermixingovertheAgulhasBank(lessfrequentwesterlies),increasingtheintensityandseasonaldurationofhighprimaryproduction.
• Transport area:therewillbeincreasedinshore–offshoretemperaturegradients,withstrongercurrentslinkingtheAgulhasBankspawningareatothewestcoastnurseryarea.
Based on the above, theAgulhas Bank/south coastwouldbecomemoreproductiveandthewestcoastlessproductiveandthetransportcurrentsbetweenthemwouldbecomestronger.Thisscenariocouldleadtoaneastwardandsouthwardshiftinfishresources.
year also sawveryhigh recruitment from themuchlarger adult population under different environmental conditions.Environmentalvariabilityalsoappears toimpactdistributionpatternsofsmallpelagicfish,withanchovyadultsshowinganabruptchangeintheirrelativedistributionthatoccurredconcurrentlywithachangeinSSTgradientsovertheAgulhasBank(Royetal.,2007).Environmentalimpactsnotwithstanding,overfishingcanobviouslyhaveseriousdetrimentaleffectsonsmallpelagicpopulations,asevidencedbythecollapseof,andlackofasubsequentrecoveryin,smallpelagicfishpopulations,inparticularsardine,offNamibia(Rouxetal.,2013).OffSouth Africa, the inshore populations of sardine and horse mackerelthatsustainedtheStHelenaBayfisheryinthe1950sandearly1960swerelikewisedepletedbyheavyfishingpressure(Butterworth,1983/FAO291),andthecurrentlackofrecoveryofsardineoffthewestcoastishypothesisedtobeduetoexcessivefishingpressurethere(Coetzeeetal.,2008/IJMS).
A number of scenarios under climate change can be consideredforthewestcoast,whichfunctionsmostlyasanurseryareabutpartlyasaspawninggroundforhakeandsardine;forthesouthcoast,whichismostlyasummerspawningareaforanchovyandsardine;andfortheareabetweenCapeAgulhasandCapeColumbine,whichisof crucial importance for the alongshore movement of juvenilestagesbetweenthespawningandnurseryareas(Figure4).The following twooceanographic impactscenarios have been selected based on robust global model projections for climate scenarios. The projections suggestthatsummersouth-easterlywindswouldtendtoincreaseinfrequencyandstrength,andwinterwesterlieswouldtendtodecreaseinfrequency(IPCC4),andthattheAgulhasCurrentwouldcontinuetoincreaseinstrength(Rouault et al., 2010).
2.ClimateChangeImpactsonMarineFisheries
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES 31
nutrientsbelowthedeepeningthermocline.ThisdeclineinproductivityresultsinlesssustainedspawningontheAgulhasBankinsummer.Increasedstorminessduetoincreasedlarge-scalethermalcontrastbetweenthetropicsandpolarregionsmixestheupperlayerevenmoreinwinter,reducingprimaryproductionandhence,itscarryingcapacityformarineliving resources.
• Transport area:transportremainshighor even increases as the thermal gradient betweeninshoreupwelledwaterandoffshorewaterincreases,maintainingthealongshoretransport function.
Moreeffectiveoceanographicmodellingincorporatinglocaloceanographicprocesses isrequiredtoresolvewhichofthesetwoscenarios,ifeither,ismorelikely.
2.5 Ocean acidificationThe oceans absorb a large amount of anthropogenic CO2 emissions from the atmosphere because of their largevolumeandtheabilityofseawatertobufferCO2 (Doneyetal.,2009).Sincethebeginningoftheindustrialera, oceans have absorbed a third of anthropogenic CO2emissions(approximately127billiontons;Feelyetal.,2008). IncreasingCO2 from fossil fuels has led toareductioninthepHlevelsoftheoceansaswellasashiftinthecarbonatechemistryofoceans.Oceanacidificationdoesnotsufferfromthesameuncertaintiesthat affect global temperature forecasts and, therefore, futurechanges inoceanchemistry canbepredicted(Doneyetal.,2009).Evenifemissionsstabilisedtoday,theatmosphericCO2 valuewill surpassdoublepre-industrial(280ppmv)levelsbytheturnofthecentury(Orretal.,2005).Surfacewatersinhighlatitudesand
Figure4.Schematicdepictingthewestcoastnurseryarea,spawninggroundsoffthesouthwestandsouthcoasts(cross-hatchedareas)andthejetcurrentbetweenCapeAgulhasandCapeColumbinethatconnectsthetwo.FromHutchings et al. (2002).
Scenario 2. Changes in the Agulhas Current dominate oceandynamicsandnetprimaryproductivity:
• West coast:decreasednutrientenrichmentoccursdespitestrongerwinds,asstratificationincreaseswithincreasedflowofAgulhasBankwatertothewestcoastshelfarea.Thisresultsinlessorganicloadingandhypoxiaandanimprovedhabitatvolumefortheinshorenurseryarea,despitemoreturbulentmixingandpotentialoffshore loss along the outer shelf.
• South coast: the Agulhas Current supplies morewarmsurfacewatertotheupperlayers,decreasingprimaryproductivityandtrapping
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toincreasetheircalcificationrates,whiletheabilitytowithstandoradapttothesechangesoverlongperiodsoftimewouldclearlybebeneficial(Fabryetal.,2008).Doneyetal.,(2009)predictthattheeffectsofoceanacidificationwillbefeltmoreseverelyincoastalwatersas the combined effects of nutrient fertilisation; pollution, overfishingandclimatechangewillmakeitevenmoredifficultfororganismstoadapttoorcounterchangesinoceanchemistry.AcidificationwilllikelyimpactvariouslifestagesdifferentlyasCO2 tolerance varies across life stages of organisms (Pörtner, 2008).
Theeffectsofanincreasinglyacidicoceanaremostlikelytohavegreatestimpactonthosespecieswithcalciumcarbonateshellsandskeletonsandspeciesthatpreyonthem(Orretal.,2005,Fabryetal.,2008).OfparticularconcernintermsofSouthAfricanfisheriesistheimpactofoceanacidificationonthewestcoastrocklobsterandabalone,speciesthatsupportanimportantfisheryandaquacultureindustry,respectively.ResearchconductedontheEuropeanlobstershowedreducedcarapacemassunderhighcarbondioxideconcentrations(Arnoldetal.,2009).StudiesarecurrentlyunderwayinSouthAfricatoassesstheeffectsofincreasingpHonthewestcoastrock lobster.
Thereiscurrentlylimitedinformationavailableontheeffectsofoceanacidificationonfinfish,withpossibleproposedeffectsbeingimpairedphysiologicalfunctions,reducedsuccessindevelopmentandsurvivaloftheirearlylife stages and decreases in invertebrate food sources for fish(Cheungetal.,2012).TheeffectsofincreasingoceanpHareconsideredmostlikelytonegativelyimpactonthedevelopmentandearlylifestagesofmanyinvertebratespeciesthatrequiredelicatebalancesofcalciumcarbonatein building their structure, such as coccolithophorids, foraminifera, echinoderms and shelled molluscs
inupwellingregions,suchastheSouthernOceanandEasternBoundaryUpwellingSystems,willabsorblargervolumesofCO2 from the atmosphere thanwarmerwatersinlowerlatitudes(Riebeselletal.,2009;Gruberetal.,2012).SouthernAfricanupwellingsystemshaveanaturallylowerpHandaconsiderablylowercarbonatesaturationstate(Gruberetal.,2012).ThepHlevelsinthesouthernBenguelacurrentlyrangefrom7.60to8.25,depending on the season, but have an annual average pH of ~8.1(Gregor,2012).ThissystemispredictedtohaveapHofapproximately7.8to7.5byyear2100andanevenlowerpHof7.3to6.7byyear2300(Caldiera&Wicket,2005).
Oceanacidificationaffectsorganismsintwoways,throughreducedpHandincreasedCO2(hypercapnia)(Woodetal.,2008).Researchonvariousorganismshasshownthatoceanacidificationcausesagreatdiversityofresponsesand it is therefore difficult to generalise predictions (Vézina&Hoegh-Guldberg,2008).Oceanacidificationinfluencesphysiologicalprocessesandbehavioursinmanyorganismsbyreducinggasexchange(Fabryetal.,2008;Pelejeroetal.,2010),loweringmetabolicratesandgrowth(Bibbyetal.,2007;Fabryetal.,2008;Guinotte&Fabry2008;Vézina&Hoegh-Guldberg2008;Doneyetal.,2009)anddisruptingdefensiveresponsesandbehaviours(Bibbyetal.,2007;delaHayeetal.,2012).Inaddition,insomecalcifiers,ratesofcalcificationarereduced(Gazeauetal.,2010;Riebeselletal.,2000;Gazeauetal.,2007)andshellsareevendissolved(Feelyetal.,2004;Arnoldetal.,2009;Bibbyetal.,2007).Calcifiersresidingincoldwaterhabitatssuchasupwellingsystemsareatahigherrisk to ocean acidification and decreased seawatercarbonatesaturation,astheirenvironmentisonlyjustsupersaturatedwithrespecttothecarbonatephasestheyexcrete(Anderssonetal.,2008).Theextentofthesepotentialimpactswilldependontheorganisms’abilitytoadjusttheiracid–basebalanceaswellastheirability
2.ClimateChangeImpactsonMarineFisheries
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(Heathetal.,2012).Decreasingproductivityofsuchspecies couldhavenegativeeffectsoncommerciallyimportantfishthatpreyonthem.
Oceanacidificationwillnotonlyhaveadirectimpact,butwillalsopossiblyindirectlyinfluencetheabilityoforganismstodealwithlocalphenomena,suchasthelobster‘walkouts’inresponsetolowoxygeneventsonthewestcoast(ElandsBay)(Cockcroft,2001).Estuary-dependentspecieswithapelagiclife-historystagewillbeparticularlyvulnerable.Slowergrowthanddelayedmetamorphosisoffishandinvertebratelarvaemayresultin recruitment failure if these animals miss the brief recruitmentwindowtypicalofmosttemporarilyopen-closedsystems.Insomefishspecies,slowdevelopmentandchangesinthephysicalandchemicalstructureofotoliths(andotherbonestructures)mayaltersensoryperceptionsandtheirabilitytocommunicate,avoiddanger
ordetectprey.Otolithmalformation led toatypicalbehaviour such as reliance on visual rather than sound stimuli,aswellastoincreasedcortisollevels,stresslevelsandsuppressedimmunesystemsinSciaenidae(Browninget al., 2012).
Oceanacidificationresearchhas todate focusedonphysiologicalandbiologicalinvestigationswithlimitedstudiesconsideringthepopulation-andecosystem-leveleffects(LeQuesne&Pinnegar,2011).IndirecteffectsofrisingpHcouldpotentiallyresultingreaterimpactsonfishandfisheriesthandirecteffects(Heathetal.,2012).Themostobviousindirecteffectslikelytooccuraretheimpactofacidificationonbiogenichabitatslikecold-watercoralreefsthatserveasimportantfishnurserygroundsforadiverserangeoffishspecies(Foleyetal.,2010,Huvenneetal.,2011)oralterationinnutrientrecyclingand bentho-pelagic coupling (Heath et al., 2012).
3.AdatationReponseOptions
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resiliencetoclimatechange,MPAsneedtobeadequatelyconnected,toencompassrepresentativehabitattypesandtobemanagedwell.Observedandpotentialfutureshiftsinspeciesdistributionsmaycompromisetheeffectivenessof some existing closed areas and spatial f isheriesmanagement areas (Cheung et al. 2012). The boundaries andmanagementofMPAsmayneedtobeadaptivetoaccount for changing favourable environmental conditions. ItislikelythatlargerormoredynamicnetworksofMPAsmaybenecessarytoensureeffectiveconservationofspatiallyshiftingand/ormorevariableresourcesduetoclimate change.
MPAsandno-takezonesinparticular,havetheaddedadvantage of acting as control sites for long-term monitoring and providing research opportunities that wouldmakeitpossibletoidentifywhetherobservedbiological responsesweredue toclimatechangeorotheranthropogenicimpacts,suchasfishing.Monitoringnetworks need to cover a range of ecosystems tounderstand and track changes across the marine environment.Otherelementsofecosystemmanagementinclude the implementation of integrated coastal managementandanecosystemapproachtofisheriesmanagement.Managersalsoneedtodevelopadaptivemanagementcapacityincludingenhancedmanagementflexibilitytorapidlyadapttothechangingenvironment(Sink et al., 2012). Ensuring that policies encourage diversificationofresourceuseandincomegenerationtoenhancesocialresilienceinthefaceofuncertaintyandvariabilityisalsoimportant,particularlyforthemostvulnerablecoastalandfishercommunities.
Whilst it is unanimously agreed that the predictiveaccuracyof theeffectsof climatechangeonmarinefisheriesispoor,andevenmoresointhelightofotheranthropogenic impacts (Rijnsdorp et al., 2009; Cheung etal.,2012;Heathetal.,2012;Sinketal.,2011;DEA,2011),
3.1 FisheriesBefore considering adaptation in terms of fisheriesmanagement,itisimportanttoassesstheadaptivecapacityoftheresourceorthebiologicalsystem.Theadaptivecapacityofvariousspeciesmaybeconstrainedforthreemainreasons:
1. Rateoffutureclimatechangeisexpectedtobefasterthannaturalclimatechangepreviouslyexperiencedbyspecies;
2. Resilience of species and other components of the ecosystemiscompromisedbyadditionalpressurefromfishing,pollution,habitatdestruction,diseases, introduced and invasive species (Sink et al. 2012); and
3. Thelossofgeneticdiversity(Brander,2007;Lehodeyetal.,2006).
Fisheryresourcesarelikelytobemorerobusttotheeffects of climate change if the compounding stresses from overfishing, habitat degradation, pollution and other anthropogenic factors are reduced or minimised (DEA,2011;Craig,2012;Cheungetal.,2012).Adaptationstrategies aimed at providing the best mitigation against theeffectsofclimatechangeforSouthAfrica’smarinebiodiversityneedtoincludesoundintegratedecosystembasedmanagementpractices(DEA,2011,Sinketal.2012).Maintaininggeneticvariabilitythroughadherencetostocklimits,sustainablefishingpracticesandspatialmanagementcan support adaptation to changing conditions (Sink et al., 2012).Fisheriesthataresuccessfullymanagedtoachieveresourcesustainabilitywillbebetterpositionedinthelong term to adapt to the effects of climate change.
Effective spatial management, including a representative MPA network, is a key component of the strategyrequiredtounderstandandcopewiththeimpactsofclimatechange(Sinketal.,2012).Tosupportecosystem
3. ADAPTATION RESPONSE OPTIONS
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SouthAfricacancopebysecuringexistingfisheriesandbiodiversityandworkingtowardsrecoveryofimpactedresourcesandecosystems.Oneofthemostappropriateadaptationmeasuresistoensurethatasufficientareaofdifferenthabitattypesandresourcesareprotectedfrom compounding anthropogenic stressors. Through management strategies focused on rebuilding over-exploitedfishresourcesandimpactedecosystems,andimproving thehabitatquality, societyand thefishingindustrywouldundoubtedlygainfrommoreproductivefishstocks,higherbiodiversityandimprovedresilienceandadaptivecapacitytoclimatechange.
3.2 Human dimensionAdaptationoptionsforthenear-shorehandlinefisheriesmay benefit from consideration ofmechanisms andprocesses to balance social and economic objectives. Severalmanagementoptionsmaybeavailabletofacilitateadaptation under climate change and prevent the potential deteriorationofsocialconditionsinfishercommunities.These could include education, entrepreneurial training, andtrainingintourismandaquaculture,butcouldalsoincludemorespecificadaptationstrategies.
Current short- to medium-term adaptation strategies employedbylocalcommunitiestocopewithcurrentvariabilityincludefishingfurtherafield(e.g.useoftowingtooffshorefishinggroundsandthenreturningtoshoreonownaccord),legalorillegalfishinginothermanagementareas,adaptingfishinggearandequipment,downsizingorretrofittingboats(includingimprovingfuelefficiency),switchingfromhand-liningtotrawlinginthesector,anddiversifyingincomestreamsintomotorservicingandboatrepairs, and even into other sectors such as agriculture. Remittancesfromfamilymembersandnetworksworkingoutsidethefishingindustryarealsoanimportantsourceof income.
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4.ResearchRequirements
Hollowedetal.,(2009)outlinedfourimportantstepsfor successful projection of the impact of climate change onfish:
1. Identifymechanismsunderlyingthegrowth,reproduction, and distribution of major fishpopulations.
2. AssessthefeasibilityofdownscalingtheimplicationofclimatescenariosderivedfromIPCCmodelsforregionalecosystemsandselectIPCCmodelsthatappear to provide valid representation of forcing forthestudyregion.
3. Incorporatetheenvironmentalvariables,extractedfrom climate models under a given scenario, into the population projection model.
4. Evaluate the mean, variance and trend in theproductionoffishandshellfishunderachangingecosystem.
Based on the outcome of the above process, thepotential socio-economic consequencesof changesintheproductionofimportantfishpopulationscouldbeprojected.Detailingtheimpactsofclimatechangeonfisheriesintheshort,mediumandlong-termisnotcommoninthebiological/ecologicalliteraturelargelydue to the issue of reliability of such projectionsasnoted inBrander (2007).Thereareanumberofconstraintsthataffectthereliabilityandthusconfidenceintheprojections,includingtheavailabilityofreliableenvironmental variables at the spatial and temporal scaleswhicharerelevantforthebiologicalprocessesbeingmodelled.Oncethesedataarereadilyavailable,projectionswould bemadewithmore confidence.However,climatechangeimpactsonfisheriesdistributionpatternsandresultantchangesinecosystemfunctioningandfisheryproductivityareverycomplextopredictindetail.Specificpredictionsandforecastsmaynotbefeasiblebasedonthecurrentlevelofknowledgeandmodelsavailable;however,itispossiblethatplausiblebroad forecasts could be developed.
A significant body of observational data exists fortrendsinbiophysicalconditionsandbiologicalresponsesforSouthAfricanmarineecosystems.However, thisbodyofinformationneedstobefurtherassessedandsynthesisedtosupportmoreholisticanalysisofpasttrendsandfutureprojections.Furthereffortisneededtoseparatehistoricalfisheriesimpactsfromclimatechangeresponses.Additionalreviewsandfocusedresearchonmethodologies for developing plausible broad forecasts shouldbeconductedtobuildthecapacityofthissectortoidentifyandassessclimatechangeadaptationoptions.Withrespecttothelinkagesbetweenthebiophysicaland biological aspects and human dimensions, such as economic impacts and effects on livelihoods, there have beensomerecentadvancesandthisarearequiresfocusedattention, given that it lags behind current predictive capacityforbiophysicalandbiologicalimpacts.Inthissection,somekeyareasarehighlightedtobegintoinformthisprocessofreviewandsynthesis.
4.1 Fisheries
4.1.1 Currentcapacitytoprojectclimatechangeimpacts
The projection of marine biological responses to climate changeisseverelylimitedbyincompleteknowledgeofa largenumberofparameters required foreffectivemodelling.Asignificantsourceofuncertaintyalsoarisesfromthefactthatmostofthebiophysicalmodelscurrentlyin use do not reproduce or simulate the salient features intheoceansaroundSouthAfrica.Additionalknowledgegapsremaininareassuchastheadaptivecapacityofthespeciesinquestion.Adaptivecapacityoffishspeciesisdeterminedbydispersalcapacitytomovetosuitableareas,short-termphysiologicalplasticityandthelong-termevolutionaryadaptationofapopulationtoachangein the environment.
Projecting the effect of long-term changes on marine organisms requires certain criteria to be fulf illed.
4. RESEARCH REqUIREMENTS
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effect of climate variables on changes in species distribution, and other vital rates that can affect theviabilityofaspecies.Threesetsofmodelscan be used to project the effect of future climate changeontheproductivityoffishpopulations(Hollowedetal.,2009):3.3.1.Projectrecruitmentbymodifyingthe
averagerecruitmentbytheenvironmentalvariables–nodensitydependenteffect.
3.3.2.Modelsthatmodifythespawner-recruitrelationshipwiththeenvironmentalvariablesandarandomvariable–Nodensitydependenteffects.
3.3.3.Modelsthatusespawner-recruitfunctionsthat incorporate processes at multiple life-historystages.Theeffectofenvironmentalvariablescanbeincorporatedanddensitydependent processes can be added.
Themostcommonlyusedapproachtomodellingchangesinthedistributionoffishpopulationsandtheapproachwiththeleastdataandcomputingpowerrequirementmakesuseofstatisticalcorrelativemodels(Option3.1above).Thereareanumberofstatisticalmodelscurrentlyin use to both model current distribution and project the distribution of populations under climate change. Theseinclude:generalisedadditivemodels,generalisedlinearmodels,classificationtreeanalysis,artificialneuralnetwork,generalisedboostedregressionmodelsandrandomforest.Detailsoftheirapplicationinspeciesdistributionmodelling in the context of projectingclimate change impact can be found inMugo et al.(2010),Heikkinenetal.(2006),Elith(2009),Oldenetal.(2002).SomeofthetoolsthatarecommonlyusedinthemodellingofspeciesdistributionincludeBIOMOD(Thuilleretal.,2012),anddismo(Hijmansetal.,2013).
Withrespecttomechanisticmodels(Option3.3above)adetermination of environmental tolerance and preference ranges fortheCapehake,assumingtheavailabilityof
4.1.2 Availableapproachesforprojectingdirectimpactsofclimatechangescenarios
Anumberofopportunitiesexisttomakerapidprogresson projecting direct impacts of climate change scenarios. Theselieintheareaofdatacollection,datasynthesisand model development using available and newlycollected data. Studies on the effect of climate change inthemarineenvironmenthavehistoricallyfocusedonthelowertrophiclevel.Currently,thisresearchisbeingextendedtotheuppertrophiclevelandgenerallytakesthreemainforms:
1. Long-termretrospectivedataanalysiswheretheresponseofpopulationsisanalysedoveralongtimeperiod.Thesedatasetsprovideasignificantsource to support the development of predictive models for climate change applications.
2. Laboratorywork,mainlyinvolvingthestudyofthephysiologicalresponseofindividualsfromselected populations to a gradient of change instressfactor(watertemperature,oceanacidification,oxygenconcentration,andothers)whichcanthenbeusedtoprojecttheimpactof future climate change. These provide an important source of information for detailed physiologicalmodels.
3. Modellingtheresponseoffishpopulationstochangesinclimatevariables,whichcanbefurtherdividedintothreemaingroups:
3.1. Speciesdistributionmodelling,usuallyintheformofcorrelativestatisticalmodels,whichstudythechanges in species distribution and changes in biodiversity.
3.2. Complexcoupledbiogeochemical–hydrodynamicmodels (sometimes also coupled to individual basedmodels),whichstudytheresponseofspeciesandecosystemstoboththedirectandindirect effect of long-term changes in climate.
3.3. Mechanisticmodels,whichareprocessbasedanduseempiricallyderivedrelationshipstomodelthe
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4.ResearchRequirements
WithrespecttoindirecteffectsofclimatechangeontheeconomicsofmarinefisheriesinSouthAfrica,thereareanumberoffisheryassessmentmodelsthatmayberelevant(e.g.Defeo&Seijo,1999;Whiteetal.,2008).Few,ifany,ofthesehavebeenappliedtoassesstheimpactofprojected climate changes, but some of the bio-economic modelsortheirmodifiedformscouldbeusedtoassessthepotentialeconomicconsequencetothefisheryoftheprojected changes in the production and distribution of importantfishpopulations.
Puntetal(2013)undertookareviewofstudiesthatusedthe mechanistic and empirical approach to evaluate the impact of environmental variation on the performance ofmanagementstrategies.Manyofthestudiesreviewedfoundthatmodifyingmanagementstrategiestoincludeenvironmentalfactorsonlyimprovestheabilitytoachievemanagementgoalsifthemannerinwhichthesefactorsdrivethesystemiswellknown.Theconclusionwasthatuntil stock projection models are improved, a more appropriatewaytoassesstherobustnessofmanagementstrategies is to consider the implications of plausible broad forecastsofhowbiologicalparametersmaychange,ratherthanattemptingspecificpredictions.
4.1.3 Futureresearchneeds
Overall,SouthAfricaneedstostrengthentheinformationandknowledgebaseforthedetectionandprojectionofclimate-induced changes and provide evidence-based advicetosupportclimatechangeadaptation.Focusedresearchisneededtofurtherdeveloppredictivecapacity,supportearlydetectionofchangeandcontributetothe development of appropriate adaptation measures (Sink et al., 2012).
Thefollowingareimportantareasofresearchtoaidinthe accurate projection of the impact of future climate changeonfishproduction,distribution,andconservationaswellastheresultantsocio-economicconsequences:
reasonablyaccuratescenariosoffutureoceanconditionsaroundSouthAfrica,andcouplingthese,wouldprovidenew insights.Updated, spatialisedecosystemmodels(Option3.2.above),forexampleOSMOSE(Traversetal.,2009,2010),wouldcomplementsuchnichemodelswiththenecessary top-downdynamics.Thehypothesisedmulti-stock nature of South African sardine (van der Lingen,2011)couldaddfurthercomplexitytopredictingclimate change impacts on this population as stocks that showconsistentdifferencesindistribution,biologyandlifehistorycharacteristicsmayresponddifferently toenvironmentalforcing.RecentworktodevelopspecificassessmentmodelsforputativewesternandsouthernstocksofSouthAfricansardinehasbeeninitiated(deMoor&Butterworth,2013),whichwouldpermitconsiderationof environmental drivers in terms of relative recruitment successofsardineoffthewestandsouthcoasts.
Whilemodelstoprojectclimate-inducedchangesinthedistributionofmarinefisheshavebeendevelopedglobally,nonehavebeenspecificallydevelopedforSouthAfrica.AnexampleofsuchamodellingapproachistheDynamicBioclimateEnvelopeModel(DBEM)(Cheungetal.,2008)whichsimulateschangesintherelativeabundanceandspatialdistributionofmarinepopulationsatglobalscalebyaccountingforanorganism’secophysiology,preferencesandtolerances to environmental conditions, adult movement andlarvaldispersal,andpopulationdynamics.Somedataontheenvironmentalpreferencesandtolerancesofanchovyand sardine off South Africa are available to parameterise thismodel(e.g.Twatwaetal.,2005providedenvironmentalcharacterisationsoftheirspawninghabitats),andtheseandtherelativelygoodunderstandingofsmallpelagicfishlifehistoriesinthisregionmaybesufficienttoenablethedevelopmentofalocalDBEMforthesespecies.Similardata,butperhapslesscomprehensive,existfortheCapehake, and determination of environmental preferences and tolerancesforthesespeciesisanimportantfirststepthathasyettobeconducted.
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sector,itisimportantthatresearchbededicatedtowardsunderstandingandestablishing the linkbetween theenvironmentanddistribution,growthandreproductiveratesandtheprocessesthroughwhichthechangesintheenvironmentaremanifestedinthebiologicalsystemacrossthehierarchyfromindividualleveltothewholeecosystem.Oncethisisestablished,thenextstepwillbeto project the response to climate change of the different componentsoftheecosystemandthesocio-economiccomponents that depend on it.
4.2 Human dimensions
4.2.1 Futureresearchneeds
Currentresearchexperiencehasshownthatprogresswithrespecttothehumandimensionsoffisheries ishindered by themistrust and poor communicationbetweensomestakeholders.Theseincluderelationshipsbetweengovernmentofficialsandnewentrantsand/orsmallquotaholdersintheoffshorefisheries,aswellasmembersoffishingcommunitiesmoregenerally,includingcrewonvesselsandfactoryworkers(vanSittert,2003;Schultz,2010;Ragaller,2012;Harainprep.).However,thereisgoodcommunicationbetweenassociationsthatrepresentthemajorityofrightholders(byTAC),butcommunicationseemstobelesswelldevelopedatthefishingcommunitylevel.
Immediateresearchneedsonthehumandimensionsinclude:
• Howtoprogresstowardsscenarioplanningwithavarietyofstakeholdersinwhichmutualtrustcan be built.
• Researchintocurrentadaptivestrategies:whatworksandwhy?
• Exploringtop-downversusbottom-upapproachestofisheriesmanagementthatsupportsocial-ecologicalresiliencetotheexpectedincreaseinvariability.
1. AssessandsynthesiseexistingobservationaldataontrendsinbiophysicalconditionsandbiologicalresponsesforSouthAfricanmarineecosystemstosupportholisticanalysisofpasttrendsandfuture projections.
2. Developmentofplausiblebroadforecastsand appropriate adaptation measures untilspecificpredictionsandforecastsaremorefeasible,facilitatedbymoreeffectiveoceanographic modelling.
3. Addressissuesofdownscalingbyimprovingoceanographic models to simulate inter-annual anddecadalvariability,andeffectsofglobalclimatechange.Thiswouldallowmorecredibleinformation to be generated for planning adaptation responses.
4. Linkdriverstoresponsesbyimprovingobservationsandmodelsofregionalnetprimaryproductivity(NPP).ThismayinvolvedevelopingnewmodelsorimprovingexistingonestopredicthowchangesinNPPwillcascadeupthemarinefoodwebtofisheries.
5. Considertheinteractionbetweenbiodiversityandimportantecosystemattributesbytakingintoaccounttheconsequenceofchangesinbiodiversityonthestability,resilience,andproductivityofmarinesystems.
6. Investigatethesocio-economicconsequencesofclimatechangeimpactsonthefisheriessectorandothersectorsoftheeconomythataredependentonfisheries.
7. Considertheinteractionbetweenaquacultureandcapturefisheriesandimproveunderstandingoftheconsequenceoffutureincreasesinaquacultureproductionontheproductionofaquaticecosystems.
With respect to the socio-economic and ecologicalconsequencesofclimatechangeimpactsinthefisheries
• Methodologiesforintegratedintersectoral
approaches to management of human activities relatedtotheocean(fisheriesinasetupofmanysectorslocally/regionally).
• Trade-offsbetweenthehakeandsmallpelagicfishingindustriesunderecosystemvariabilityand change.
• Theroleofinternationalmarkets(exportsandimports)andaquacultureinthesocial-ecologicalsystem.
• Social and economic challenges of threatened fisheriesinalocalandregionalperspective.
40 LTAS:CLIMATECHANGEIMPLICATIONSFORMARINEFISHERIES
4.ResearchRequirements
the current uncertain projections for key fisheriesresourcesunderfutureclimatechange.Inparticularafocusedeffortisrequiredtodevelopplausiblescenariosofphysicaloceanographicandcoastalhabitatchange.
AsignificantbodyofobservationaldataexistsfortrendsinbiophysicalconditionsandbiologicalresponsesforSouthAfricanmarineecosystems.Regularassessmentandsynthesisofthisgrowingbodyofinformationwouldsupportincreasinglyholisticanalysisofpasttrendsandfuture projections. There have been some advances recentlyregarding linkagesbetweenthebiophysicaland biological aspects and human dimensions, such as economicimpactsandeffectsonlivelihoods.However,impactsonfisheriesdependondistinctoceanographicscenariosthatcouldbedominatedeitherbyprojectedchangesinsoutherlyandwesterlywinds,orbychangesinthestrengthoftheAgulhascurrent.Focusedresearchis needed to contribute to the development of plausible broadforecasts,morespecific localpredictionsandappropriate adaptation measures. The impacts of
Climate change is likely to affect the productivityanddiversityof SouthAfrica’s fisheriesby changingthe distribution, abundance and size of resources,theirhabitatextent,conditionandconnectivity,theirphysiologyandbehaviourandthecatchabilityofresourcespecies. Changes in sea surface temperature (SST), stormfrequency,freshwaterflowandrunoffpatterns,productivity, oxygen levels and wind will all haveimpactsonestuarine,inshoreandoffshoreecosystems,affectingrecruitment,fishbehaviourandphysiology,influencing fish size, and increasing fishmortalities.This could result in significant adverse impacts on subsistencefishinglivelihoodsaswellascommercialandrecreational industries.
Predictingclimatechangeimpactsonmarinefisheriesis dif f icult because of the complex relationshipsbetween species distribution patterns, variationsin their abundance, distribution and productivity,andthe impactsofoverfishingandotherstressors.Keymodellingcapacity isrequiredtomovebeyond
5. CONCLUSION
41LTAS:CLIMATECHANGEIMPLICATIONSFORMARINEFISHERIES
LTAS: CLIMATE CHANGE IMPLICATIONS FOR MARINE FISHERIES42
5. Conclusion
unsustainablefishingandclimatechangeinteractinanumberofwaysandshouldnotbetreatedasseparateissues. South Africa needs to invest in the information and knowledgebaseavailableforprovidingevidence-basedguidance to support climate change adaptation.
Whileitisgenerallyagreedthatthepredictiveaccuracyof the effects of climate change on marine fisheries ispoor,especiallyinthelightofotheranthropogenicimpacts (Rijnsdorp et al. 2009, Cheung et al. 2012, Heath et al. 2012, Sink et al.2011,DEA2011),thisdoesnotprevent South Africa from building greater resilience in thissectorbysecuringexistingfisheriesandbiodiversityandworkingtowardsrecoveryofimpactedresourcesandecosystems, including through sound integratedecosystembasedmanagementpractices.Althoughmanyresourcesareoverexploited,managementactioncanleadtostockrecovery.Maintaininggeneticvariabilitythroughsustainablefishingpracticesandareasclosedtofishingcanhelpsecurestronggeneticpotentialthatwillincreaseresilienceunderchangingconditions.Fisheriesthataresuccessfullymanagedtoachieveresourcesustainabilitywillbemuchbetterpositionedinthelongtermtoadapt
to the effects of climate change. Adaptive measures couldalsousefullyincludeensuringtheprotectionofsufficientareasofdifferenthabitattypesandresourcesfrom compounding anthropogenic stressors in marine protected areas.Keyelements in securing resourcesustainabilityinthelongtermincludestatisticallyrobuststock assessments, effective data management and science-basedmanagementaction.Throughappropriatelyinformed management strategies focused on rebuilding over-exploitedfishresourcesandimpactedecosystems,andimprovingthehabitatquality,thefishingindustrywouldgain frommoreproductivefishstocks,higherbiodiversityandimprovedresiliencetoclimatechange.
Operationally, fisheries management could usefullyinclude tactics such as improving the speed of adaptive learningcycles,decentralisationanddiversification,andenhancingmanagementflexibilitytoadapttoachangingenvironment. These could support commercial, subsistence and recreational fishing sectors through improved environmental, resource and social resilience, maintenance ofecosystem,species,geneticandsocialdiversityandthedevelopmentofadaptivecapacitytoclimatechange.
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