Chagos Archipelago Vava II Expedition, March 20-April 1, 2016In terms of nesting turtle numbers, the...

ScientificReport:ChagosArchipalgocVavaIIExpedition-Leg1

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ChagosArchipelagoVavaIIExpedition,

March20-April1,2016

ExpeditionReport

TBLetessier1,2,NEsteban3,PCarr1,CHead4,RSchallert5,MNicoll1

1InstituteofZoology,ZoologicalSocietyofLondon.2CentreforMarineFutures,OceansInstitute,UniversityofWesternAustralia.3DepartmentofBioscience,SwanseaUniversity.4OceanConservationandResearchGroup,UniversityofOxford5MBARI,StanfordUniversity


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AcknowledgementsThis expedition was made possible through support from the BertarelliFoundation,forwhichwearegrateful.Theresearchwasmadepossiblethankstopermitsand logisticalsupport fromtheForeignandCommonwealthOffice.WearegratefulforthethoroughlogisticalassistanceprovidedbytheBritishIndianOcean Territory Administration, the Brit Rep office, and environmental officerHelenStevens.We thank thecaptain, chiefengineer,andcrewof theVavaandVavaIIforexcellentsupportinourscientificactivities.

Howtocitethisreport:

Letessier T B, Esteban N, CarrP, SchallertR, HeadC, NicollM (2016). ChagosArchipelago Consortium Vava II Expedition – Leg 1. March 20st to 1st of AprilScientific Report to The Bertarelli Foundation and the Foreign andCommonwealthOffice.


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Executivesummary............................................................................................................................41.Mid-waterfishandsharks..........................................................................................................51.1 Introduction..........................................................................................................................51.2 Resultsanddiscussion.....................................................................................................5

2.Seaturtles..........................................................................................................................................72.1Introduction..............................................................................................................................72.2Resultsanddiscussion.........................................................................................................8

3.Seabirds..............................................................................................................................................93.1Introduction..............................................................................................................................93.2Resultsanddiscussion......................................................................................................10

4.Coralreefhealth..........................................................................................................................114.1Introduction...........................................................................................................................114.2Resultsanddiscussion......................................................................................................12

Appendix..............................................................................................................................................14


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ExecutivesummaryThisexpeditiononboardtheVavaandVavaIIfromthe20/03tothe1/042016,providedauniqueoccasiontosupportsixscientistsfocusingonflagshipspeciesand habitatswithin the British Indian Ocean Territory or Chagos Archipelago.The primary purpose was to survey the mid-water fish and reef sharks, seaturtles,seabirds,andcoralreefsaroundtheArchipelago.

1. Mid-water Baited Remote Underwater Video Systems (BRUVS) weredeployed in the nearshore (<50-200m) to survey themid-water fishesandsharks.Deploymentrevealedarichanddiversmid-watercommunityof sharks and fishes, with spatial trends that were possibly related toillegal fishing activities. First time mid-water BRUVS deployments onBenaresShoalprovidedararerecordofascallopedhammerheadshark.

2. Over half of the islands of the archipelago were surveyed for turtlenesting activities and beach habitat via aerial surveys (30 islands) andcoastal surveys (28 islands), providing themost complete nesting datarecord since surveys in 1999. The survey results demonstrated thatsignificant numbers of turtleswere nesting inMarch/April, outside thepeaknestingseason inOctober/November.Turtlesatellite trackingdatawereused tovalidateexistenceofa foraginggreen turtlepopulationonthe Great Chagos Bank, revealed an extensive seagrass meadows ofThalassodendron ciliatum. Seagrass samples were preserved inpreparation for the first peer-reviewed publication on seagrass in theChagos Archipelago and to contribute to a regional seagrass healthassessmentoftheIndo-Pacific.

3. Breeding seabird distribution and population data were collected from

acrosstheArchipelago.WedocumentedanexpandingbreedingrangeofboththeRed-footedandBrownBoobyinPerosBahnosAtoll.Inaddition,we tested thedeploymentof tail-mountedGPS loggersand leg-mountedGeolocators on both species of Booby, and conducted the first evertracking of a seabird in the Archipelago; with a breeding Red-footedboobymakingaremarkable425km,38hourforagingtrip.

4. The Archipelago’s coral reefs were surveyed at multiple locations to

establishtheirhealthandtorecordanyoccurrenceofbleachingthisyear.Sofarnobleachingisevidentthisyearalthoughreefshavevaryinglevelsof coral health following last year’s bleaching event. Even at degradedsites the number of coral juveniles is high suggesting good recovery ispossible.DeeperreefsasrevealedbyafirsteverROVdeploymentwereingoodconditions.

5. Sharkandfishtaggingactivitiesarereportedaspartofthemaintagging

reportfortheVavaIIleg2Apriltrip.


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1.Mid-waterfishandsharks1.1 IntroductionThepopulationstatusandpotentialrecoveryoflargemobileandpredatoryfishand sharks species inside the Chagos Archipelago is the subject of an ongoingpelagic research programme. Many species of tuna and oceanic sharks haveexperiencedworrisomedeclines as a result of industrial long-lining and purseseining fisheries. These fisheries operated within the BIOT EEZ up until thedesignation of the marine protected area in 2010, thereby allowing for thepotentialrecoveryofthesespeciestooccursincethen.Management issues inthecontextoftheBIOTEEZandthewiderIndianOceanarethusbeingaddressedbyansweringkeyquestionsregardingthedistributionofthesespeciesinspaceandtime.Questionsbeingaddressedinclude:

1. What is the effect of bathymetry and oceanographic variability on thelocationsof‘hotspots’throughoutthemarineprotectedarea?

2. Whatistheseasonalvariationofhabitat-usewithinthearea.3. Whatistherecoveryofspeciesovertime?

Understandingtheinfluenceofthecoralreefs,atollsandseamountsonthemid-water fishandsharkpopulations is thusofcritical importance inassessing theinfluenceandefficiencyof themarinereserve.Thistripenabledanassessmentof themid-waterhabitatsnear thecoralreefof themainatollsandnearSwartseamount.1.2 ResultsanddiscussionMid-water stereo Baited Remote Underwater Video Systems (BRUVS, n = 18)were deployed on 6 occasions, at 5 different locations throughout thearchipelago(SeeFig.1,atSalomonatoll,Egmontatoll,Swartseamount,NelsonIsland,andonBenaresshoal).OneachoccasiontheBRUVswerestreamedfromarescuecraft,along200mofrope.EachBRUVSweresituated50metresfromitsneighbourontheline,andsuspendedat10metersfromasurfacebuoy,withthevessellocatedattheendofthe200m.Thetypicaldeploymenttimewasaround90 minutes. Each rig was baited with approximately 1.5 kg of squid. Duringdeploymentthevesselmanoeuvredtomaintaintherigsasclosetostationaryaspossible.


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Fig.1.Mid-waterBRUVSsamplinglocationsintheChagosArchipelagoinvicinityofcoralreefBased upon a short review of the footage it was apparent that sharks werepresent at each location, with typically one or two sharks being observedsimultaneouslyoneachdeployment(Fig.2).NotableexceptionstothiswereatSwart Seamount, in the south-east corner of the archipelago, and on BenaresShoal,inthenorth-west,wheremorethan2individualsand2specieswerethenorm at each deployment. The videographic material collected will now beanalysed and will be combined analytically with results from previousexpeditions.Thedataprovideavaluablecontributiontotheongoingassessmentof the reserve, and provide rare records of the under-sampled intermediatehabitatbetweenthereefsandtheopenocean.

Fig.2.Recordsofmid-watersharks(Toppanes–hammerheadandsilvertips),andfishes(Bottompanes–barracudaschool,andcarangidsandforagefishschools)


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2.Seaturtles2.1IntroductionSeaturtlesareaflagshipspeciesfortheChagosArchipelagoMarineReserveandbaselinesurveyshaveindicatedsignificantnestingpopulationsofhawksbillandgreen turtles across the archipelago. To date, the majority of surveys of bothnesting and resident (foraging) populations have taken place on Diego Garcia,withinformationforouterislandsrelyingonopportunisticsurveysbyFisheriesOfficers. Satellite tagging of green turtles fromDiegoGarcia in 2012 and2015has revealed, for the first time, that a foraging green turtle population existsalongthe20-30mdepthcontourofSouth-EastGreatChagosBank,200kmfromlandthathasnotbeensurveyedpreviously.The expeditionprovided anopportunity to survey turtle nestingpopulation intheouteratollsinascientificallyrobustmanner,determinedbytrackcountsonbeaches and surveys of available nesting habitat. Temperature loggers weredeployedinsandatnestingdepthstocontributetomonitoringofhatchlingsexratio. In-water surveys (snorkel/SCUBA) around islands were conducted toassess foraging turtle numbers (male:female ratio). Finally, surveys wereconductedtovalidatehabitattypecorrespondingtodifferenthabitatuses(day-,night-time) toprovide critical informationon foraginggreen turtlehabitats, aswellascollectinformationrelevanttothisremotehabitat.


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2.2ResultsanddiscussionManymoresurveyswereachievedthananticipatedduetocollaborationwiththescienceteamandcrewaswellasexcellentprovisionofhelicopterandboatsupport(Table1).Table 1. Overview of turtle surveys completed during the Expedition.Turtlenestingandnestinghabitatsurveyswerecarriedoutonall islandssurveyed (aerial and foot). Figures in brackets indicate surveys by PeteCarr,MalcolmNicoll&CatherineHead.

Site Islandssurveyed(aerial)

Islandssurveyed(byfoot)

Seagrasssurveys(SCUBA)

In-watersurvey

Incubationtemperaturemonitoring

PerosBanhosatoll 17 15(+5) - 1 -Salomonatoll 11 2(+1) - - -Egmontatoll 2 1 - - 6GreatChagosBank - 3(+1) 3 1 -a) Turtlenestingpopulationandhabitatsurveys:28islandsweresurveyedby

foot,more than50%of all islands. This numberwill increasewith surveysplannedbythecrewinthefollowingexpedition.Thiscompleteassessmentofnesting populations will contribute to a planned publication on theimportance of nesting turtles in the ChagosArchipelago. Evidence of turtlenesting(tracksand/orbodypitsexcavatedduringnesting)wasobservedoneach atoll visited. As expected, the majority of turtles nesting during thepreviousweeksweregreens,asgreenturtlesnestyearround.Interestingly,ahawksbilltrackwasobserved,asthisisoutofnormalnestingseason.Intermsofnestingturtlenumbers,themostimportantatolls(specifyingthetop five islands in terms of body pit data) are Egmont Islands (295 nests),ChagosBank (Danger Island (169)andNelson’s Island (38)),PerosBanhos(Unnamed Island (39) and Ile Finon (12)) and Salomon Islands. RecentnestinghadoccurredinPerosBanhos(1hawksbill,15green,1unidentified),ChagosBank(7green)andEgmontIslands(2green).

b) Validation of foraging habitat: three sites were surveyed: one shoal

previously identified in a reefal expedition in 2010, two sites identified bysatellite tracking (Fig.3).Surveysrevealedextensivemonospecific seagrassmeadows populated by Thalassodendron ciliatum at depths of 12-27 m.Samples were taken for museum cataloguing, as the first collection ofseagrassintheChagosArchipelago,andforCarbon:Nitrogen:Phosphateratioanalysis(toprovidebaselinefromapristinehabitat).Sitesweresurveyedbyunderwater video (BRUV) for fish diversity as part of a wider researchprogramexploringthevalueofseagrassforfishecology.


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Fig.3.Threesitessampledforseagrassarehighlightedwithgreenstars:Site1(SDangerIsland),Site2(SEChagosBank-West)andSite3(SEChagosBank-East).Site1is120kmwest of site 3, 94 km west of site 2. Sites 2 & 3 are 30 km apart. ExtensiveThalassodendronciliatummeadowswerefound.

Incubation temperature monitoring: 6 temperature loggers (Gemini TinytagTGP-4017) were placed at a range of turtle nesting depths in shaded andunshadedpositionsonEgmontAtoll.Thiswillcompleteincubationtemperaturemonitoringoneachatoll.Foraging turtlepopulations:13 turtleswereobservedat6 locations. Increasedsurvey effort would be more useful during peak nesting season (potentiallyOctober-November). An injured immature hawksbill (CCL 33.1 cm) wasobservedclosetoIleFouquet.3.Seabirds3.1IntroductionThe importanceof seabirdsas crucial indicatorsofmarineecosystemhealth isbecoming increasingly recognised. In the western Indian Ocean (WIO) thebreedingseabirdpopulationisestimatedat~19millionindividuals(30species),consumes 150,000-500,000 tonnes of biomass each breeding season, which isequivalent to theannual tunaandbillfish landings in the region.However,ourunderstanding of seabirds’ status, distribution and ecology in the ChagosArchipelago is limited, which undermines any assessment of how the marineprotectedareasupportsseabirdpopulations in theWIO.Weproposeresolvingthis situation through generating novel information associated with threeobjectives:


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1. To establish the status, distribution and trends of breeding seabirds inChagos;

2. To identify and understand environmental drivers of critical foraginggroundsforbreedingseabirdswithinandoutsidetheMPA;

3. Toestablishhownon-breedingseabirds,fromwithinandoutsideChagos,utilisetheMPAinrelationtotheirat-seadistributionintheWIO.

OntheVavaIItripweplannedtocollectadditionaldatatosupplementexistinglong-term monitoring data, to enable us to achieve objective (i) and identifysuitableseabird‘study’coloniesandtaggingmethodologiestoachieveobjective(ii). Data are already available, through established regional collaborations, toanswerobjective(iii).3.2ResultsanddiscussionWhile in the Chagos Archipelagowe surveyed 24 islands for breeding seabirdpopulations. We found breeding populations of 10 species of seabird (seeAppendixTableA1)on24islands.Ofparticularnotewere:the large(>10,000)Sooty Tern colonies on Ile Longue (Peros Bahnos) and South Brother on theGreat Chagos Bank; and the first ever record of breeding BrownBooby on IleParasolandRed-footedBoobyonGrandSoeur(PerosBahnos).In order to be confident that wewill represent how seabirds, throughout theArchipelago,utilisetheMPAweidentifiedthefollowingsetsof ‘study’breedingcolonies across the Archipelago for Red-footed, Brown and Masked Booby:Parasol,Longue,GrandBoisMangueandPetitBoisMangueintheNorth;NorthBrother,MiddleBrother,ResurgentandSouthBrotherinthecentralwest.InthesouththeplanistouseDiegoGarcia.Inadditiontothisweidentifiedtwoback-upoptionsinDangerandNelson’sislands.Our plan is to use two types of tracking devices; tail-mountedGPS loggers forshort-termbreedingseasonmovementsand leg-mountedGeolocators for long-termnon-breeding seasonmovements. As none of our study species hadbeentrackedintheChagosArchipelagobeforeweneededtoexplorethefeasibilityofdeploying these two typesof tags.We testedourbirdcaptureanddeploymentmethods on both Red-footed and Brown Booby, which will be the mostfrequently,taggedspeciesandfoundthatourmethodsweresuitable.AsafinaltestwedeployedasingleGPSloggeronthetailofabreedingRed-footedBoobyon Ile Parasol, which we recovered four days later. The resulting locationinformationshowedthatthebirdmadea425kmtripover38hourstothewestof Peros Bahnos (see Fig. 4). This is the first time a seabird in the ChagosArchipelago has ever been tracked and demonstrates that our proposedapproachisvalid.


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Fig.4.Red-FootedboobytrackfromIleParasol,PerosBahnos.Thenorthernpartofthetrackistheoutwardpathandthesouthernpartofthetrackthereturn.4.Coralreefhealth4.1IntroductionCoralreefsintheChagosArchipelagoareknowntobesomeofthemosthealthyandresilientintheworld.Thisislargelyattributedtothelackofdirecthumanimpacts on the reef e.g. fishing and pollution, resulting in reefs being able to‘bounceback’quickly fromglobal climate change impacts, suchas increases insea surface temperature. Coral bleaching is the corals’ stress response toincreases inseasurface temperature,and is thevisiblesign that thecoralcellshave expelled their single-celled symbionts called zooxanthellae. Thezooxanthellaeprovide the coralwithenergy throughphotosynthesis, thereforewhen they are expelled the coral losses a major food source, and hence thisbleachingcanresultinmortalityifthecoraldoesnotrecovertheirzooxanthellaefrom thewater column. The ChagosArchipelago has in the past suffered fromcoralbleachingonmass,mostseverely in1998and2005,andhasmadequickandfullrecovery.Bleachingwasalsoreportedinthearchipelagolastyearbutwehad not had the opportunity to return and assess the damage. This year highlevelsof coralbleachingarepredictedat the timeof theexpeditionbecauseofthesteady increases inseasurfacetemperaturescausedbytheElNinoclimatepatternandexacerbatedbyglobalclimatechange.Theaimsofthistripare:

1. Toassessthehealthofthereefbuildingcorals,whicharethearchitectsofthereef,postlastyear’scoralbleaching.

2. Torecordtheoccurrenceofcoralbleachingonbothshallow(<30m)andmesophoticreefs(>30m)usingaremotelyoperatedvehicle(ROV).


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Todo thisweuse video transects on shallow reefs,which canbe analysed forcoral health metrics, and at deeper depths (>30m) we trialled the remotelyoperatedvehicle(ROV)torecordtheoccurrenceofreefspeciesanditshealth.4.2ResultsanddiscussionIn total we completed 27 reef surveys across 9 sites at Peros Banhos atoll,Salomonatoll,ThreeBrothersIslands,VictoryBank,andNelsonIsland.WealsosuccessfullytestedtheROVatIledePasseinSalomonandIleFouquetinPerosBanhos, foruseonApril’s scienceexpedition.Thispresents the first recordsofreefsbelow30metersfromtheArchipelago.Videofootagewillnowbeanalysedto establishmetrics such aspercentageof live coral cover, percentageof coralwith disease and with bleaching, which are standard ways of assessing reefhealth. Thiswillallowustoestablishthehealthof thereefpre-andpost- thisyear’spredictedbleachingeventandthereef’spotentialrateofrecovery.Initial impressions from these surveys are that northern Peros Banhos, ThreeBrothers,andNelson’sreefshavedegradedsinceourlastsurveys(April2015),mainlyduetomortalityoftablecorals(Acroporaspecies)whichdominatethesesites. In addition there has also been significantmortality of branching corals,whichareoftenthemostsusceptibletocoralbleaching,indicatingthatlastyear’sbleachingmaybethemaincauseofcoraldieoffatthesesites.Onapositivenotethe number of juvenile corals at these sites is high (Fig. 5) suggesting thepotential for good recovery, as was the case following the 1998 and 2005bleachingevents.Moreover,deeperreefsappeartobeingoodconditions,baseduponapreliminaryreview(Fig.6).

Fig. 5. Example of the high number of coral juveniles at evendegradedreefssuggestinghighpotentialforrecovery.


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IncomparisonthereefsatVictoryBankandSouthernPerosBanhosarehealthyreefs with good live coral cover and abundant fish life. At these sites coralcommunities arenotdominatedby table corals, butbyboulder corals, suchasPoritesspecies,andsoftcorals.Poritesspeciesareknowntobelesssusceptibleto coralbleachingand soperhaps survivedmuchof last year’sbleaching. TheNational Oceanic and Atmospheric Administration (NOAA)http://coralreefwatch.noaa.gov/vs/gauges/chagos_archipelago.phpnowputtheChagosArchipelagoinAlertcategory2(thehighestalertcategory)forbleachingthisyear,meaningthatcoralbleachingisimminent.WewillcontinuetomonitorthisandmanyotheraspectsofcoralhealthinthenextAprilexpedition.

Fig.6.AnexampleofthefootagefromtheROVat38mdepthshowingmanyhealthyplatecorals, suggesting reefs at deeper depths might offer refuge from coral bleaching forspeciesdependentonthereefsuchasreeffish.


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AppendixTableA1.Islandsvisited;theirlegalstatusandbreedingseabirdsobserved.Atoll Island Legal

designationSeabirdSpecies Rat

presencePerosBahnos

IleParasol SNR Lesser&CommonNoddyCommonwhite(fairy)TernSootyternRed-footedBoobyBrownBooby

NO

PerosBahnos

IleLongue SNR Lesser&CommonNoddyCommonwhite(fairy)TernSootyternRed-footedBoobyBrownBooby

NO

PerosBahnos

GrandeIleBoisMangue

SNR Lesser&CommonNoddyCommonwhite(fairy)TernRed-footedBooby

NO

PerosBahnos

PetiteIleBoisMangue

SNR LesserNoddyCommonwhite(fairy)TernRed-footedBooby

NO

PerosBahnos

St.Brandon SNR Black-napedTern NO

PerosBahnos

Morsby CommonNoddyCommonwhite(fairy)TernRed-footedBoobyLesser&GreaterFregatebirds

YES

PerosBahnos

Coindumire SNR MaskedBooby NO

PerosBahnos

GrandeIleCoquillage

SNR CommonNoddyCommonwhite(fairy)TernRed-footedBoobyBrownBoobyLesser&GreaterFregateBirds

NO

PerosBahnos

PetiteIleCoquillage

SNR Lesser&CommonNoddyCommonwhite(fairy)TernRed-footedBoobySootyTern

NO

PerosBahnos

Manon None CommonNoddyCommonwhite(fairy)TernRed-footedBooby

?

PerosBahnos

Un-named(Burtle)

None CommonNoddyCommonwhite(fairy)Tern

?

PerosBahnos

Vert None CommonNoddyCommonwhite(fairy)Tern

?


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PerosBahnos

Finon None CommonNoddyCommonwhite(fairy)Tern

?

PerosBahnos

PetiteSoeur None CommonNoddyCommonwhite(fairy)Tern

YES

PerosBahnos

GrandeSoeur None CommonNoddyCommonwhite(fairy)TernRed-footedBooby

YES

Salomon Mapou None CommonNoddyCommonwhite(fairy)TernLesserNoodyRed-footedBooby

NO

Salomon IledelaPasse None CommonNoddyCommonwhite(fairy)TernLesserNoodyRed-footedBoobyBrownBooby

?

GreatChagosBank

SouthBrother SNR Lesser&CommonNoddyCommonwhite(fairy)TernSootyTernRed-footedBooby

NO

GreatChagosBank

Resurgent SNR MaskedBooby NO

GreatChagosBank

Danger SNR Lesser&CommonNoddyCommonwhite(fairy)TernSootyternRed-footedBoobyBrownBooby

NO

GreatChagosBank

Nelsons SNR Lesser&CommonNoddyCommonwhite(fairy)TernRed-footedBoobyBrownBoobyLesser&GreaterFregatebirds

NO

Egmont Sipaille None None YESEgmont IleLubine None None YESEgmont IlesdesRats None None YESNotes:SNR–StrictNatureReserve.

Chagos Archipelago Vava II Expedition, March 20-April 1, 2016In terms of nesting turtle numbers, the...

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