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CI A ION

Villanoy, C.L., O.C. Cabrera, A. Yiguez, M. Camoying, A. de Guzman, L. . David, and P. Flament.

2011. Monsoon-driven coastal upwelling off Zamboanga Peninsula, Philippines. Oceanography

24(1):156165, doi:10.5670/oceanog.2011.12.

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2/11Oceanography | Vol.24, No.1156

P H I L I P P I N E S T R A I T S D Y N A M I C S E X P E R I M E N T

Monsoon-Driven

Coastal UpwellingOff Zamboanga Peninsula, Philippines

ABSTRACT. Cooler temperatures and elevated chlorophyll a , indicative ofupwelling, are observed off the coast of Zamboanga Peninsula, Philippines. Tisupwelling is driven primarily by offshore Ekman transport as the northeast monsoonwinds blow parallel along the coast of Zamboanga, with enhancement of positivewind stress curl due to the lands frictional retarding force. Analysis of sea surfacetemperature time series reveals interannual variations in upwelling, with weakeningduring the 2007/2008 La Nia and strengthening during the 2006/2007 El Nio.Upwelling areas are known as productive and biologically rich, and the Zamboangaupwelling supports a thriving sardine shery in the southern Philippines. Sardinelanding data correlate remarkably well with monthly chlorophyll values during20092010. Despite the prevailing notion that La Nia causes strengthening of themonsoon-driven upwelling, long-term sheries production data for Zamboangademonstrate a decrease in sh catch due to weaker upwelling during the 1999/2000and 2007/2008 La Nias. Interannual variations in upwelling, phytoplanktonproductivity, and sardine catch suggest that interannual El Nio-Southern Oscillation variations can affect the small Zamboanga Peninsula pelagic shery.

B Y C E S A R L . V I L L A N O Y, O L I V I A C . C A B R E

A L E T TA Y I G U E Z , M A R I A N N E C A M O Y I N G , A S U N C I O N D E G U Z M

L A U R A T. D AV I D , A N D P I E R R E F L A M E

Oceanography | Vol.24, No.1156

INTRODUCTIONTe Philippine Archipelago consistsof more than 7000 islands in a varietyof shapes and sizes. Between-islandbathymetry is complicated, consisting ofnarrow shelves, steep slopes, and deepbasins connected by shallow sills. Oceancirculation here is a result of complexinteraction between the bathymetry, theseasonally reversing monsoons, and thetidal and nontidal circulation betweenthe South China Sea and the westernPacic (Wang et al., 2008; Han et al.,2009; Gordon et al., 2011).

Te dominant wind system overthe Philippines is the Asian monsoon

Photo courtesy of Leilani Solera


3/11Oceanography | March 2011 157

account or 6080% o total annualupwelling transport (Rykaczewski andCheckley, 2008).

Te objective o this paper is todescribe upwelling off Zamboanga

Peninsula and to make use o satellite seasur ace temperature (SS ) and chloro-phyll a distributions as proxies to deter-mine interannual upwelling variability.We also briey discuss the relationship oupwelling and recent local sardine sherytrends, as well as upwelling variability.

UPWELLING MECHANI SMAND VARIABILI Y

Dipolog Strait is 42-km wide andis located between Mindanao andNegros islands. Te sill lies at ~ 470 m(Gordon et al., 2011) and serves asthe boundary between the Sulu andBohol seas (Figure 1). Te northerncoast o Zamboanga Peninsula is westo this strait. Te coastline is oriented

northeast/southwest, with sharp coast-line bends at about 122E and 123E. Teshel is generally narrow, with the 200-misobath located about 410 km romthe coast. Te shel s widest part is to

the west o a small cape at 12240'E thaprotrudes about 2 km offshore.

During the northeast monsoon, thewind vector is directed toward the south-west, approximately parallel to the shel(Figure 2), promoting offshore Ekmantransport (Pond and Pickard, 1983) andcoastal upwelling to replace the displacesur ace water. Coastal upwelling isevident rom the SS eld along the

Zamboanga coast during the upwelling-avorable NEM season (Figure 2). Teseasonal SS variation is large (45C)compared to the cross-shel temperaturegradient (nearshore SS is about 1Ccooler than offshore SS ). Tis cross-shel gradient is consistent throughoutthe NEM months, indicating that the

that blows rom the northeast betweenDecember and March and rom thesouthwest between June and October(Wang et al., 2001). Monsoonal winds

orced through the complicated topog-

raphy can give rise to lee eddies andwind stress curl zones, particularlyduring monsoon surges (Pullen et al.,2008, 2011). Winds blowing throughgaps between islands can induceupwelling and downwelling along theleeward sides o the islands (Chavanneet al., 2002). Interestingly, most o these

eatures in the Philippines occur onlyduring the northeast monsoon (NEM;

Wang et al., 2006; Pullen et al, 2008),probably because warmer sur acetemperatures during the southwestmonsoon increase near-sur ace strati-cation. Te stronger winds and coolertemperatures during NEM can enhanceconvective mixing, resulting in elevatedchlorophyll signals in many areasaround the country, as seen rom satel-lite ocean color data (Wang, et al., 2006;Peaor et al., 2007).

Zamboanga Peninsula ormsthe northwest coast o the island oMindanao (Figure 1). Te coast isoriented northeast-southwest, similarto the axis o the monsoon winds. Tus,when the northeast monsoon blows,conditions become avorable or Ekmantransport directed away rom the shore-line. In addition, upwelling along thisshel can be enhanced by wind stresscurl induced by the rictional retarding

orce o the land. Both types o processescontribute to upwelling in most shelsystems, even along a relatively straightcoast such as Cali ornia (Pickett andPaduan, 2003; Capet et al., 2004). In act,off the central and southern Cali orniacoast, wind stress curl is believed to

Figure 1. Map of the Zamboanga Peninsula shelf area showing bathymetry. Data fromSmith and Sandwell (1997)



lower nearshore SS is not due toseasonal variation in sur ace heat uxalone. Te negative temperature anoma-lies adjacent to the coast extend about30 km rom the coast.

Wind stress curl is anothermechanism that can drive upwelling.Un ortunately, because no weatherstation data are available or this area,the only sources o wind data are

satellite measurements (e.g., the NationalAeronautics and Space AdministrationsQuick Scatterometer [QuikSCA ] andthe Advanced Scatterometer [ASCA ]instrument), which are too coarse toprovide wind stress curl in ormationwithin 50 km o the coast. Alternatively,we may use model winds rom regionalatmosphere models such as theCoupled Ocean/Atmosphere Mesoscale

Prediction System (COAMPS)1. Modelwinds o the Philippine Archipelagousing COAMPS show the same general

eatures as QuikSCA wind elds(Pullen et al., 2008).

With COAMPS, it is possible tocompute both alongshore wind stressand wind stress curl close to the coast.Figure 3 shows a map o the February2008 mean wind stress and wind stresscurl elds. Note that all along thenorthern coast o Zamboanga Peninsula,the wind stress curl is positive, mostlikely due to rictional retardation byland. Te maximum positive curl values

are ound off coastline bends (near122N and 123N) and may contributeto upwelling transport in these areas. Inthe Cali ornia and Benguela upwellingsystems, bands o positive wind stressare believed to be important in shapingthe upwelling systems (Fennel, 1999;Capet et al., 2004). Te curl band also

orces a downwind sur ace ow underthe maximum wind axis and an inshoreupwind countercurrent (Fennel, 1999).Similar offshore downwind and near-shore upwind ows were observedusing underway acoustic Dopplercurrent proler (ADCP) data during theDecember 2007 Joint US/PhilippinesCruise and the March 2009 IntensiveObservational Period cruise (IOP-09),but these ows were absent duringIOP-08 in January.

Upwelling interannual variability wasexamined by using empirical orthogonal

unction (EOF) analysis o monthly4-km resolution Pathnder SS data

Cesar L. Villanoy ([email protected]) is Professor, Marine Science Institute, University

of the Philippines Diliman, Quezon City, Philippines.Olivia C. Cabrera is a PhD candidateat the Marine Science Institute, University of the Philippines Diliman, Quezon City,

Philippines.Aletta Yiguez is Assistant Professor, Marine Science Institute, Universityof the Philippines Diliman, Quezon City, Philippines.Marianne Camoying is a Research

Assistant at the Marine Science Institute, and a Master of Science candidate at the Instituteof Environmental Sciences and Meteorology, University of the Philippines Diliman, Quezon

City, Philippines.Asuncion de Guzman is Professor, Mindanao State University, Naawan,Misamis Oriental, Philippines.Laura T. David is Professor, Marine Science Institute,

University of the Philippines Diliman, Quezon City, Philippines.Pierre Flament is Professor,Department of Oceanography, University of Hawaii, Honolulu, HI, USA.

1 COAMPS or Coupled Ocean/AtmosphereMesoscale Prediction System (COAMPS) is a regionalweather prediction model used operationally by theUS Navy and developed by the Marine MeteorologyDivision of the Naval Research Laboratory,Monterey, CA.

Figure 2. QuikSCA monthly mean wind stress (in N m -2) and mean sea surface temperature (SS ;in C) for February/northeast monsoon (left) and July/southwest monsoon (right). Monthly SSwas calculated from Pathnder SS for the period 19852009.



(http://data.nodc.noaa.gov/opendap/pathnder). Te seasonal SS rangeis about 45C, while the sur ace SSsignal associated with upwelling is onlyabout 1C cooler than offshore ambient

temperatures. In order to highlight hori-zontal temperature gradients and at thesame time remove the seasonal signal,the spatially averaged temperature wassubtracted rom the monthly SS databe ore EOF analysis. Figure 4 showsthe result o the analysis. Only the rstmode is described as it contributes 23%o the variance, while the contributionso the succeeding modes are too small to

be signicant. Te spatial pattern o therst mode is associated with the cross-shel temperature gradient off the coasto Zamboanga Peninsula (Figure 4, toppanel). Te temporal variation o thismode shows that upwelling conditions(negative values) prevail mostly duringthe NEM months and vary at interan-nual time scales (Figure 4, middle panel).Te bottom panel in Figure 4 shows thetime series o the Multivariate El Nio-Southern Oscillation (ENSO) Index(MEI; Wolter and imlin, 1993, 1998)

or the same time period. Negative MEI values represent the cold (La Nia) phaseo ENSO, while positive values representthe warm phase (El Nio). Te occur-rences o negative values o the Mode 1temporal variation, associated withstronger cross-shel SS gradients andupwelling, coincide with El Nio events(e.g., the 1987/1988 El Nio, the series oweak El Nio events in the early 1990s,1997/1998, 20022005, and 2007/2008).Comparison o the MEI time series withthe temporal variation o the rst EOFmode shows an inverse relationship(r = -0.43) signicant at p < 0.05.

Te EOF analysis suggests that the

general response to ENSO is lower SS(stronger upwelling) during El Nioand higher SS (weaker upwelling)during La Nia. Tis result appears tobe counterintuitive because La Nia(El Nio) is ofen associated withstronger (weaker) winter monsoonwinds (Webster et al., 1998; Wu andChan, 2005). In the adjacent Bohol Sea,a similar pattern observed between the variability o chlorophylla and ENSO isattributed by Cabrera et al. (2011) to the

ormation o a barrier layer due to thelow-salinity sur ace layer produced byincreased precipitation during La Nia.Te same mechanism appears to modu-late Zamboanga Peninsula upwelling.Rain all anomalies derived rom precipi-tation estimates using ropical Rain allMeasuring Mission ( RMM) data romthe area bounded by 8830'N and12215'123E are more positive duringLa Nia and more negative during

El Nio (Figure 5). Te rain all anoma-lies were negatively correlated to MEI(r = -0.73 and statistically signicant atp < 0.05). Field observations rom theIOP-08 and IOP-09 cruises were consis-tent with these ndings. Conductivity-temperature-depth (C D) data off theZamboanga coast show lower sur acesalinities, and consequently density,during January 2008 compared to March2009 (Figure 6, top panel).

Te upwelling was also evident romunderway data or March 2009. Teshel area was cooler and had higherchlorophyll a concentration compared tooffshore values (Figure 6, bottom panel)Because o higher salinity shoreward,the higher chlorophyll concentration isunlikely to be ed by nutrients coming

rom river runoff, but rather romupwelling o more nutrient-rich water

rom below the sur ace.Te weaker upwelling during the

Figure 3. Mean wind stress (in N m -2) and wind stress curl (in N m -3) during February 2008from the COAMPS model of the Philippine seas (Pullen et al., 2008).



2007/2008 La Nia may also be relatedto the weakening o the prevailing windsduring the 2007/2008 NEM season.However, unlike rain all, the seasonalQuikSCA wind anomalies rom January

2000 to October 2009 or the area off theZamboanga shel did not show a clearrelationship with ENSO events.

CONSEQUENCESOF UPWELLINGBecause algal blooms and an increasein primary production are some o theconsequences o upwelling, chlorophylla pigment concentrations measured rom

satellites are good tracers or upwelling,particularly in the tropics where thetemperature differences between

upwelled and ambient sur ace watersare small. Chlorophyll concentrations vary seasonally, with the highest sur aceconcentrations occurring during theNEM months. EOF analysis o monthly

chlorophyll images (20032009) withthe spatially averaged concentrationremoved show the highest concentra-tion at the shel and a decrease offshoreup to more than 50 km rom the coast(Mode 1 accounting or 65% o the vari-ability). Te temporal pattern o the rstEOF peaks during the rst quarter o theyear is consistent with upwelling inducedby NEM winds. It is interesting to note

that the results o the EOF analysis ochlorophyll yielded a more signicantdominant mode than the EOF analysis

Figure 4. Distribution of the rst empirical orthogonalfunction mode calculated from Pathnder monthlySS data (top) and its temporal variation (middle).Negative values (blue bars) of the SS temporal distri-bution represent a positive cross-shelf SS gradient(e.g., upwelling condition). Te bottom graph showsthe Multivariate El Nio-Southern Oscillation (ENSO)Index (MEI). Positive (negative) MEI values indicateEl Nio (La Nia) conditions. Correlation betweenSS temporal distribution and MEI (r = -0.43) issignicant at p < 0.05.

o SS (65% variance explained orchlorophyll a and only 23% or SS ).Tis is an indication that the upwellingsignal is much more evident in remotelysensed chlorophyll than in remotely

sensed SS . Udarbe and Villanoy (2001)earlier reported the lack o mani estationo upwelling in the SS signal.

Te most dramatic change in chloro-phyll concentration since 2002 occurredduring the NEM seasons o 2006/2007and 2007/2008. Te ormer was anEl Nio year and sur ace chlorophyllconcentrations were among the highestsince 2002, while the latter was a La Nia

year and chlorophyll concentrations offZamboanga Peninsula were among thelowest (Figure 7).



Figure 5. Monthly rainfall anomaly from the area bounded by 8830N, 12215123E(top) overlain with the ve-month running mean (red solid line). Rainfall data are from

the ropical Rainfall Measuring Mission (http://trmm.gsfc.nasa.gov/data_dir/data.html).Te bottom bar graph is the MEI.

IMPAC S ON HESARDINE FISHERYDespite their small size relative to theopen ocean, coastal upwelling areasare the most biologically rich (Ryther,

1969; Bots ord et al., 2006). In produc-tive upwelling systems, the intermediatetrophic level is ofen dominated by smallpelagic plankton- eeding species thatplay a critical role in upwelling trophicdynamics (Cury et al., 2000; Santoset al., 2001). Common upwelling speciesinclude sardines and anchovies. In theZamboanga upwelling, the dominantsmall pelagic species is the Indian oil

sardine (Sardinella longiceps).Monthly chlorophyll a time series orve zones rom July 2002 to May 2010

Figure 6. (top panels) Salinity and densityproles from conductivity-temperature-depth stations off the Zamboanga coastfrom the Intensive Observational Periodcruises of 2008 (blue) and 2009 (IOP-09; red).(bottom panels) Surface temperature, salinity,and chlorophyll a concentration from theship underway system along the cruise trackoff Zamboanga Peninsula during IOP-09.



(Figure 8, upper panel) rom SindanganBay (o Zamboanga Peninsula) andacross the Bohol Sea to Butuan Baywere investigated to examine spatialand temporal changes in relation to thesardine sheries. Te data set used wasderived rom Level 3 MODIS Aqua.R1.1

chlorophyll a data through the GoddardEarth Sciences Data and In ormationServices Center (GES DISC) InteractiveOnline Visualization And aNalysisIn rastructure, (GIOVANNI; http://disc.sci.gs c.nasa.gov/giovanni) or the periodJuly 2002May 2010. Acker et al. (2009)

used GIOVANNI or trend detectionin river-inuenced coastal regions andTompson et al. (2009) used it or deter-mining long-term changes in temperateAustralian coastal waters. Monthly aver-

aged chlorophyll a values were generated(Figure 8) or the ve zones identi-ed in Figure 7.

Zone 1 (Sindangan Bay along thenorthern coast o Zamboanga Peninsula)exhibited the highest chlorophyll a concentration (Figure 8, upper panel)

ollowed by Zone 2 (west o DipologStrait). Chlorophyll a concentrations inthe Bohol Sea (Zones 35) were much

lower. Zone 5 (Butuan Bay) exhibitedthe highest concentrations in the BoholSea, most likely due to the large riverine

reshwater discharge it receives rom theAgusan River, the second largest river inthe Philippines (Alejandrino et al., 1976).Te highest concentration occurredduring the NEM season o 2006/2007and more recently in 2009/2010. Botho these periods are El Nios. On theother hand, chlorophyll concentrationswere lowest both off the ZamboangaPeninsula (Zone 1 and 2) and in theBohol Sea during the 2007/2008 La Nia.

Butuan Bay, in the Bohol Sea, is alsoa sardine shing area and is comparedhere to the Zamboanga upwellingto show the relationship o sardinesto primary productivity. Both theZamboanga upwelling and Butuan Bayare high-productivity areas, but theButuan Bay primary production is prob-ably ueled mainly by nutrients coming

rom the large Agusan River and possibleentrainment o subsur ace watersthrough the double estuarine circula-tion mentioned in Gordon et al. (2011)and Cabrera et al. (2011).

Sardine catch data in Sindangan Bay

Figure 7. Spatial distribution of chlorophyll in mg m -3 off Zamboanga Peninsula and inthe Bohol Sea during (A) January 2005, (B) January 2007, and (C) January 2008.



(Zone 1, Zamboanga Peninsula shel )rom daily sh landing monitoring

show a strong seasonality and are highlycorrelated to chlorophyll a (Figure 8,lower panel). Chlorophyll a values were

highest during the NEM and upwellingperiod o December 2009 until February2010. Sardine production in SindanganBay was also correspondingly stronglyseasonal, with a pronounced peak romJanuary to February (Figure 8).

High annual production rom sardinesheries motivated the rapid growtho the sardine postharvest industryin Sindangan Bay in the early 1980s.

Te collective memory o shers andpostharvest investors pointed to thegreatest abundance o sardine in 2007,which coincided with the phenomenalspike in chlorophyll a concentrationin the upwelling area (Figure 8). In2008, shers observed a remarkabledecline in the abundance o Indian oilsardines (S. longiceps) in the Zamboangaupwelling. Many sardine postharvestoperators noted that the decline in avail-able resh sardines started in 2008/2009.Tese anecdotal accounts seem tocoincide with the decline in sea sur acechlorophyll a concentration recordedaround the upwelling zone rom April2007 to November 2009 (Figure 8). Tecauses or the decline are still not wellunderstood but may be related eitherto shifs in the exploitation level and/or modulation o upwelling by eithermonsoon or rain all variability associ-ated with ENSO. In contrast, a relativeincrease in sardine catch has been notedin Butuan Bay, coinciding with a modestincrease in chlorophyll concentration(Figure 8, bottom panel).

Te variability in the upwelling-drivenproductivity o Zone 1 and Zone 2,

relative to Butuan Bay, can exert a largeinuence on sardine shery productionand spatial distribution in these areas.Sindangan Bay in particular can bemore vulnerable to interannual uctua-

tions in both primary production andavailability o small pelagics than thoseseen in other coastal upwelling systems(e.g., Rykaczewski and Checkley, 2008;Prez et al., 2010). During the 2007/2008

NEM season, the signicant decreasein sardine catch in Sindangan Bay coin-cided with a decline in chlorophylla.Fishers shifed operations to the BoholSea (in particular, Butuan Bay) and

during the 2009/2010 season, the sardinelanded catch in Butuan increased to apeak o about 250 tons in December2009 (Figure 8, lower panel). Chlorophyconcentrations in Butuan Bay also

Figure 8. Chlorophyll time series for ve zones from July 2002 to January 2010. Panel A (top)represents Zone 1 (Sindangan Bay) and Zone 5 (Butuan Bay); Panel B (middle) consists ofZones 2, 3, and 4. Te bottom panel shows chlorophyll values (in mg m -3) and landed sardinecatch (in metric tons) in Sindangan Bay and Butuan Bay from May 2009 to May 2010.



Figure 9. Historical data on the marine municipal sheries productionfor Zamboanga del Norte province ports during the northeast monsoon(NEM). Data are from the Philippine Bureau of Agricultural Statistics(http://www.bas.gov.ph, shery production database accessed in August2010). Te assumption that sardines comprise the majority of sh catchduring NEM is based on sh catch monitoring data along the northerncoast of Zamboanga Peninsula. Bar colors represent ENSO phases duringthe NEM season.

peaked during the same month. In themeantime, the Zamboanga sardine catchin Sindangan Bay during the 2009/2010season also increased to more than ourtimes the landed catch in Butuan and

peaked at the same time the chloro-phyll a concentrations were highest.

Except or tuna, long-term sherydata in the Philippines or specic shgroups are not available. o determineinterannual variations, especially inrelation to the upwelling off the coast oZamboanga, we make use o rst quarter(JFM) municipal sheries production

or Zamboanga del Norte province rom

19982009 (http://www.bas.gov.ph).Te assumption here is that the majorityo the sh catch landed in Zamboangadel Norte ports rom January to Marchis sardines, and is based on one-yearsh catch landing monitoring data

(recent work o author de Guzman).By denition, the municipal sheryinvolves the use o small shing vessels(< 3 gross tons) within 15 km o thecoast. Limiting the data presented

here to the rst quarter municipal shproduction (accounting or 75% o thetotal Zamboanga del Norte shery)will most likely reect the variation inlanded sardine catch rom the upwellingarea (Figure 9). Although the smallnumber o data points in the timeseries does not make the relationshipbetween ENSO and catch data statisti-cally signicant, it is interesting to note

that the sardine shing seasons with thetwo highest landed sh catches occurredduring El Nio years (2004/2005 and2006/2007) while the two lowest shcatches occurred during La Nia years(1999/2000 and 2007/2008). Tus, there

appears to be a connection between shcatch and ENSO wherein landed shcatch is low during La Nia years andhigh during El Nio years. A much morerobust data set is needed to show this

relationship with condence. Other datasets, such as sardine production data

rom sardine bottling actories in thearea, will be obtained and analyzed.

SUMMARY AND CONCLUSIONSA major upwelling regime exists off thenorthern coast o Zamboanga Peninsulain the Philippine Archipelago. Upwellingis driven by NEM winds, which are

directed toward the southwest romDecember to March. Te NEM windsblow alongshore roughly parallel to thenorthern coast o Zamboanga; thus, theupwelling is driven mainly by offshoreEkman transport and possibly enhancedEkman pumping rom topographicpositive wind stress curl, particularlywhere the coasts have sharp bends.Upwelling intensity seems to be modu-lated by ENSO, as shown by the negativecorrelation between SS and MEI, andis likely inuenced by rain all anoma-lies. Excessive rain all during La Nia

reshens the sur ace layer and increasesnear-sur ace stratication, hamperingupwelling. Satellite measurements ochlorophyll a and SS reveal upwellingweakening during the 2007/2008 La Niaand strengthening during the 2006/2007El Nio, and more recently in 20092010,despite the notion o strong (weak)monsoons driving a stronger (weaker)upwelling during La Nia (El Nio).

An important consequence o theupwelling along Zamboanga Peninsulais the relatively large sardine shery.Monitored sardine landing data

rom 20092010 show a remarkable


11/11O h| March 2011 165

correlation with average monthly chlo-rophyll. A reported drop in sardine catchin early 2008 was consistent with SS ,chlorophyll a, and rain all data, whilerecent data or 20092010 show signs o

increasing catch levels. Improved under-standing o the relationship betweensardine catch and ENSO variability willhelp develop a sustainable managementplan or this important resource.

ACKNOWLEDGEMEN STe authors would like to thank JuliePullen and James Doyle o the MesoscaleModeling Section, Marine Meteorology

Division, Naval Research Laboratory,Monterey, CA, or sharing with us modelwinds rom their Philippine ArchipelagoCOAMPS model, and the officers andcrew o R/V Melville. We also thankthe PhilEx collaborators, and CesariaJimenez, Juliet Madula, Angelo Macario,and Ryan Neri or sardine catch moni-toring. Tis work was unded by theOffice o Naval Research, under awardand subaward N00014-06-1-0686 to theUniversity o Hawaii and the Universityo the Philippines. Te Office o NavalResearch unded the PhilEx programand the cruises aboard R/V Melville. Tesardine shery monitoring is part o thePhilippine Department o Science and

echnology ICECREAM Program. Wealso appreciate the help ul comments othe reviewers, which greatly improvedthe paper. Tis work is Marine ScienceInstitute contribution number 397 andSOES contribution number 8017.

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