This article was downloaded by: [National Cheng Kung University]On: 25 September 2014, At: 18:04Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

International Journal of RemoteSensingPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/tres20

Typhoon-enhanced upwelling and itsinfluence on fishing activities in thesouthern East China SeaYi Changa, Jui-Wen Chanb, Yuan-Chao Angelo Huanga, Wei-QuanLinc, Ming-An Leecd, Kuo-Tien Leea, Cheng-Hsin Liaoa, Kae-YihWange & Yi-Chun Kuoc

a Institute of Ocean Technology and Marine Affairs, NationalCheng Kung University, Tainan, Taiwan, ROCb Taiwan Ocean Research Institute, Kaohsiung City 852, Taiwan,ROCc Department of Environmental Biology and Fisheries Science,National Taiwan Ocean University, Keelung 20224, Taiwan, ROCd Centre of Excellence for OCEANS, National Taiwan OceanUniversity, Keelung 20224, Taiwan, ROCe Fisheries Research Institute, COA, Keelung 20246, Taiwan, ROCPublished online: 23 Sep 2014.

To cite this article: Yi Chang, Jui-Wen Chan, Yuan-Chao Angelo Huang, Wei-Quan Lin, Ming-An Lee,Kuo-Tien Lee, Cheng-Hsin Liao, Kae-Yih Wang & Yi-Chun Kuo (2014) Typhoon-enhanced upwellingand its influence on fishing activities in the southern East China Sea, International Journal ofRemote Sensing, 35:17, 6561-6572, DOI: 10.1080/01431161.2014.958248

To link to this article: http://dx.doi.org/10.1080/01431161.2014.958248

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis,our agents, and our licensors make no representations or warranties whatsoever as tothe accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Contentshould not be relied upon and should be independently verified with primary sourcesof information. Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or

howsoever caused arising directly or indirectly in connection with, in relation to or arisingout of the use of the Content.

This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

Typhoon-enhanced upwelling and its influence on fishing activities inthe southern East China Sea

Yi Changa, Jui-Wen Chanb, Yuan-Chao Angelo Huanga, Wei-Quan Linc, Ming-An Leec,d*,Kuo-Tien Leea, Cheng-Hsin Liaoa, Kae-Yih Wange, and Yi-Chun Kuoc

aInstitute of Ocean Technology and Marine Affairs, National Cheng Kung University, Tainan,Taiwan, ROC; bTaiwan Ocean Research Institute, Kaohsiung City 852, Taiwan, ROC; cDepartmentof Environmental Biology and Fisheries Science, National Taiwan Ocean University, Keelung20224, Taiwan, ROC; dCentre of Excellence for OCEANS, National Taiwan Ocean University,

Keelung 20224, Taiwan, ROC; eFisheries Research Institute, COA, Keelung 20246, Taiwan, ROC

(Received 20 January 2013; accepted 12 August 2014)

Ocean–atmosphere interactions before and after the passage of Typhoons Haitang,Fung-wong, and Morakot across the southern region of the East China Sea (ECS)were examined by assessing satellite measurements of sea surface temperature (SST)and chlorophyll-a (chl-a) concentration in conjunction with wind data. In terms of thesatellite-derived data, the SST declined and chl-a concentration increased after thepassage of the typhoons, and this could have resulted from the upwelling induced bytyphoons via their long-duration, strong winds. According to fisheries data collectedafter the passing of Typhoon Morakot, the major fishing grounds of the torchlightfishery were found to have shifted northwards from the northern tip of Taiwan to thesouthern ECS. Moreover, the major target fish species changed from skipjack tuna(pre-typhoon) to squid (post-typhoon), signifying that the typhoon-enhanced upwellingmight have caused the skipjack tuna, which typically prefer warm water, to havemigrated elsewhere. In contrast, the nutrient-rich, upwelled water might have directlyled to increases in chl-a concentrations and contributed the increase in local squiddensities. This study suggests that typhoons can cause marked cooling of the sea surfaceas well as enhance upwelling that previously resulted in not only chl-a increases butalso changes of local fish communities and, consequently, fishing activities.

1. Introduction

Nearly one-third of the world’s tropical cyclones form within the Western Pacific, andthese typhoons frequently pass over the tropical Western Pacific (Pun et al. 2011),frequently affecting the Philippines, Guam, Taiwan, Hong Kong, and Southern Japan.In general, the ocean provides the necessary energy for typhoon intensification throughair–sea heat fluxes. As typhoons traverse their respective courses, strong cyclonic windscan reduce the sea surface temperature (SST) directly as well as by bringing deeper, coldwater to the surface (Lin et al. 2003). Moreover, deep ocean nutrients brought to shallowerwaters by such typhoon-enhanced upwelling could lead to phytoplankton blooms andthereby increases in net primary production (Hung et al. 2010).

Typhoons with looping tracks could induce cold eddies and result in phytoplanktonbloom in the South China Sea as well, since the nutrient-rich subsurface waters aresupplied by Ekman pumping (Chen and Tang 2012). In the southern East China Sea

*Corresponding author. Email: malee@mail.ntou.edu.tw

International Journal of Remote Sensing, 2014Vol. 35, No. 17, 6561–6572, http://dx.doi.org/10.1080/01431161.2014.958248

© 2014 Taylor & Francis

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

(ECS), typhoons can trigger phytoplankton blooms and increase primary productivityalong their trajectories through the Kuroshio region (Chang et al. 2008; Siswanto,Morimoto, and Kojima 2009), and this may suggest that typhoon-enhanced phytoplanktonbiomass increases were attributed to upwelling of cold and nutrient-rich water from thedeeper layers of the Kuroshio Current to the upper layers. Figure 1 depicts a schematic ofthe bathymetry of Taiwan and further shows the change in the Kuroshio Current before(solid grey line) and after (dotted grey line) the passage of typhoons. In addition, after thepassage of typhoons, the biogenic carbon flux in the southern ECS has been found to varydue to the surface phytoplankton assemblages having changed from small dinoflagellatesto pinnate and concentric diatoms (Hung et al. 2010); Chung, Gong, and Hung (2012)also found that the species composition and density of microphytoplankton were differentin seawater sampled after recent typhoons. Therefore, the importance of air–sea interac-tions on upwelling and primary production in the Kuroshio region is well documented.

The waters off northern Taiwan are part of the southern ECS, a region where typhoonscan occur year-round. On average, three to four typhoons strike this area annually andtypically cause significant damage to terrestrial regions (Pun et al. 2011). Moreover, thisregion is also characterized as one of the most important fishing grounds in Taiwanbecause of high primary production driven by year-round upwelling of the KuroshioCurrent (Gong et al. 2003; Liao et al. 2006). Since the upwelling of the Kuroshio Current

China

Longitude (°E)

Lo

ng

itu

de

(°N

)

ECS

SCS

Figure 1. Map showing the bathymetric contours (units in m) in the southern East China Sea(ECS). The solid grey solid and dotted grey lines indicate the fluctuation of Kuroshio Current undernormal and typhoon conditions, respectively.

6562 Y. Chang et al.

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

can be altered by typhoon winds, fisheries catch can also be linked to changes in oceanicconditions. Some studies have found that typhoons not only affect both the distribution ofnitrogen and fisheries output by increasing water circulation, wind-driven ocean mixing,and upwelling in the South China Sea (Qiu, Lin, and Wang 2010), but they have also ledto significant shifts in the location of the squid fishing ground in the southern ECS(Liao et al. 2006).

In 2009, Typhoon Morakot severely damaged Taiwan due to the extreme rainfallcaused by the presence of warm ocean eddies (Lin, Chou, and Wu 2011). Hence, manystudies have focused on the ocean impacts of Typhoon Morakot, but most only focused onbiogeochemical or microbiological effects (Hung et al. 2010, 2013; Chung, Gong, andHung 2012; Chen et al. 2013). The influence of Typhoon Morakot on the marine fisheriesactivities in the waters off northern Taiwan is not well understood. Therefore, the aims ofthis study were (1) to examine the air–sea interactions (i.e. typhoon-driven upwelling) inthe southern ECS through analysis of satellite-derived SST and chlorophyll-a (chl-a)concentration data collected before and after Typhoons Haitang, Fung-wong, andMorakot in 2005, 2008, and 2009, respectively, (2) to archive daily ‘torchlight’ fishingdata around northeastern Taiwan before and after the passage of Typhoon Morakot, and(3) to investigate potential changes in fishery activities, including the locations of fishinggrounds, target species, and catch-related data, before and after this super typhoon.

2. Materials and methods

The study area (25.45° N, 122.00° E), located approximately 70 km northeast of Taiwan,was established at the continental shelf break in the southern ECS. The maximum depth atthis site is 130 m (Figure 1). From 5 to 10 August 2009, Typhoon Morakot swept throughTaiwan from east to west and was classified as a category 2 typhoon when it reached thesouthern ECS, bringing both strong winds and heavy rainfall. Owing to the fact that therewere 66 typhoons with different tracks and strengths that swept through the southern ECSbetween 2000 and 2009, the typhoon-enhanced upwelling phenomenon was investigatedin two typhoons that had similar strengths and trajectories as Morakot: Typhoon Haitangin 2005 and Fung-wong in 2008. We acquired the typhoon data from the Central WeatherBureau of Taiwan (http://www.cwb.gov.tw/eng/), including typhoon category scale, max-imum wind speed, and duration of high wind speeds (e.g. >17.2 m s−1 for 72 hours). Thedetailed information of the three typhoons and the hydrographic changes after the passageof each are summarized in Table 1.

To examine whether upwelling was induced by the typhoons, satellite-derived SSTdata were acquired from Advanced Very High-Resolution Radiometer sensors attached toNational Oceanic and Atmospheric Administration (NOAA) satellites and archived by the

Table 1. Detailed information on three major typhoons and the hydrographic changes they caused.

Typhoon Haitang Fung-wong Morakot

Year 2005 2008 2009

Category of typhoon entering Taiwan 3 2 1Maximum of wind speed (m s−1) 55 43 40ΔSST (°C) −3.17 −1.2 −1.94ΔChl-a (mg m−3) 0.70 0.16 1.57Maximum area of cold water <26°C (km2) 7819.0 1577.8 2797.5Lasting hour of wind speed >17.2 m s−1 in 72 hours 54 35 39

International Journal of Remote Sensing 6563

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

National Taiwan Ocean University. Chl-a concentration was measured by Sea-viewingWide Field-of-View sensors (SeaWiFS) and Moderate Resolution ImagingSpectroradiometers on board SeaStar/Orbview-2 and Terra/Aqua satellites with 1.1 kmspatial resolution. Weekly mean maps were composed before and after typhoon passagesbecause daily images were oftentimes too cloudy.

Daily catch data from the torchlight fishery, in which lights are hung above the boat toattract fish such as squid and herring, in the southern ECS from 9 July to 31 August2009, were obtained from logbooks of six commercial fishing boats of similar sizeand outfitting. Fishing catch data were expressed as the catch per unit effort (CPUE;kg boat–1 day–1) for all fishing boats for each day. The differences in daily CPUE andspecies composition of the catch were examined between the pre-typhoon (9 July–4August) and post-typhoon (11–31 August) periods.

3. Results

3.1. Variation in SST and chl-a concentration before and after typhoons

The weekly composite SST images before and after typhoons Haitang (2005), Fung-wong(2008), and Morakot (2009) are shown in Figure 2. Seawater was relatively warm innorthern Taiwan before these three typhoons (Figures 2(a), (c), and (e), respectively), butcold, upwelled water was brought to the surface in the southern ECS after all threetyphoons (Figures 2(d)–(f), respectively). Similarly, Figure 3 shows the weekly compositechl-a concentrations before and after the three typhoons, and it is evident that chlorophyll-rich, and presumably upwelled, seawater was characteristic of the study site after passageof the three typhoons (Figures 3(b), (d), and (f), respectively). These changes are dis-cussed in more detail in the following.

Warm water (SST > 28°C) characterized the southern ECS before Typhoon Morakot(Figure 2(a)), but cold, upwelled water appears to have been brought to the surface innorthern Taiwan after the typhoon had passed (Figure 2(b)). High chl-a concentrations(>1 mg m−3) in the shelf region were observed to the west of the cold upwelling water inFigure 3(b) (the red contour shows the 26°C isobath extracted from Figure 2(b)), but highchl-a concentrations were not observed within the cold upwelling water itself.

Typhoon Funghung resulted in cold SST of lower than 26°C (decreased 1.2°C aftertyphoon passage) and high chl-a concentration in patches of the southern ECS, andTyphoon Haitang induced the largest upwelling, with a SST drop of 3.17°C, as well asincrease in chl-a concentration (>3.0 mg m−3). Unlike Typhoon Morakot, high chl-aconcentrations were observed within the cold water contours created by both TyphoonsFung-wong and Haitang (red arrows in Figures 3(d) and (f), respectively).

To obtain more information about the air–sea interactions, particularly those resulting inupwelling, before and after the passage of typhoons, we collected hourly wind data from theCentral Weather Bureau of Taiwan to compare the duration of strong winds with SSTvariation around Peng-Chia Island (25° 37ʹ 31″ N, 22° 04ʹ 32″ E), near the typhoon-inducedupwelling region. The number of hours during which wind speeds were >17.2 m s−1

(minimum wind speed of typhoon criteria) were documented over a 3-day period. It wasutilized as a parameter for assessing typhoon influence on SST; the latter parameter wasaveraged over a 3-day period both before and after the typhoon. We compared the resultsfrom 11 typhoons with similar trajectories (east to west) but different intensities between2000 and 2009 (Figure 4). It is clear from Figure 4 that SST drops in the study area werepositively correlated with the duration of strong winds. The category 1 Typhoons Bilis

6564 Y. Chang et al.

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

Figure 2. Weekly averaged SST (°C) in the southern East China Sea (ECS) before and afterTyphoon Morakot ((a) and (b), respectively), Fung-wong ((c) and (d), respectively), and Haitang ((e)and (f), respectively). The white rectangle and black arrow represent the study area and areasexperiencing typhoon-enhanced upwelling, respectively. The red line with blue points indicatesthe typhoons’ locations in 6-hour increments. The western and eastern black contours indicate theisobaths of 100 and 200 m, respectively.

International Journal of Remote Sensing 6565

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

Figure 3. Averaged (across one week) chlorophyll-a (chl-a) concentration (mg m−3) in the southernEast China Sea (ECS) before and after Typhoon Morakot ((a) and (b), respectively), Typhoon Fung-wong ((c) and (d), respectively), and Typhoon Haitang ((e) and (f), respectively). The red arrowrepresents the typhoon-enhanced upwelling. The red line with blue points indicates the typhoontrajectories in 6-hour increments. Red contours indicate the SST isotherm of 27°C (calculated fromFigure 2).

6566 Y. Chang et al.

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

(in 2006) and Morakot (in 2009) had SST drops of 1.27°C and 1.94°C, respectively, whilethe durations of strong winds during their passage were 44 and 39 hours, respectively.However, the SST drop after the category 3 Typhoon Longwang in 2005 was only 0.16°C(Figure 4(a)). Despite this outlier, decrease in SSTwas positively correlated with duration ofwind speeds over 7.2 m s−1 (correlation coefficient (r) = 0.797; Figure 4(b)). These resultssuggest that strong winds around the upwelling region caused by the typhoon might be oneof the important factors in the enhancement of upwelling phenomenon rather than theintensity of typhoon itself. In other words, that wind stress induced by typhoons couldincrease the Kuroshio intrusion and enhance upwelling since the slower translation speedcould lead to stronger upwelling of subsurface deeper water.

3.2. Typhoon-induced changes in fishing activities

The torchlight fishing grounds before and after the passage of Typhoon Morakot areshown in Figure 5. Seven days before Typhoon Morakot (SST > 28°C), the fishing boats(CPUE > 300 kg boat−1 day−1) were predominantly located near the northern tip ofTaiwan and extended northeastwards to the shelf of the southern ECS (Figure 5(a)).However, after the typhoon, the locations of the torchlight fishing boats were clearlyshifted northwestwardly to the continental shelf (Figure 5(b)), and fishing locations above26° N outnumbered those in the more southernly waters nearby Taiwan.

y = –0.0403x –0.236r = 0.797

–3.5

–3.0

–2.5

–2.0

–1.5

–1.0

–0.5

0.00 10 20 30 40 50 60

Nuber of hours wind speed > 17.2 m s–1

0

10

20

30

40

50

60

70–3.5

–3.0

–2.5

–2.0

–1.5

–1.0

–0.5

0.0Bilis

(a)

(b)

(2000)Toraji(2001)

Haitang(2005)

Longwong(2005)

Talim(2005)

Bilis(2006)

Saomai(2006)

Kaemi(2006)

Fungwong(2008)

Sinlako(2008)

Morakot(2009) N

uber

of h

ours

win

d sp

eed

> 17

.2 m

s–1

∆SS

T (

°C)

∆SS

T (

°C)

Typhoon (Year)

∆SST

Number of hours

Figure 4. Comparison of SST differences ((a) post-typhoon minus pre-typhoon temperature (eachtemperature representing a 3-day average for the respective period, left y-axis) with duration ofstrong winds (>17.2 m s−1, right y-axis) for 11 typhoons that passed by Taiwan from 2000 to 2009.Relationship (b) between post-typhoon SST decrease (y-axis) and duration of strong winds (x-axis)caused by the same 11 typhoons.

International Journal of Remote Sensing 6567

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

Fishing locations were also superimposed on chl-a concentration images before andafter the typhoon’s passage (Figures 5(c) and (d), respectively). The major fishing grounds(CPUE > 300 kg boat−1 day−1) were located in the region where the chl-a concentrationwas about 0.5 mg m−3 before Typhoon Morakot (red arrows in Figure 5(c)). However,the CPUE decreased when the chl-a concentration was higher than 3 mg m−3 after thetyphoon (red arrow in Figure 5(d)). In contrast, most of fishing locations near the 100 misobath yielded a higher CPUE, and chl-a concentrations were relatively lower at thesesites (black arrow in Figure 5(d)). From the daily catch variation (Figure 6), it is evidentthat CPUE was higher in July than August. However, the CPUE on 8 August sharplyincreased to more than 800 kg boat–1 day–1 after Typhoon Morakot and then declined to180 kg boat–1day–1 as the monthly average for August.

The species composition of the torchlight fisheries catch is shown in Figure 7 as percentagesof the dominant species (based on mass). The three top-ranked target species caught beforeTyphoon Morakot (Figure 7(a)) were skipjack tuna (Katsuwonus pelamis, 64%), squid (Loligoedulis, 23%), and hairtail fish (Trichiurus lepturus, 5%). After the passage of TyphoonMorakot

Figure 5. Weekly composite map of SST and chl-a concentration (mg m−3) before ((a) and (c),respectively) and after ((b) and (d), respectively) the passage of Typhoon Morakot superimposed onthe fishing grounds of the torchlight fishery, with CPUE (kg boat−1 day−1) depicted by grey circles,in the southern East China Sea.

6568 Y. Chang et al.

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

(Figure 7(b)), 52% of the catch was squid, though skipjack tuna declined to 22%, suggestingthat there was a significant change in the target fish caught by the torchlight fishery.

4. Discussion

4.1. Air–sea interactions

It has been widely reported that upwelling at the shelf break is related to the movementsof the Kuroshio Current. Strong winds associated with typhoons could drive the KuroshioCurrent more inshore-ward and result in enhanced upwelling due to the intrusion of theKuroshio Current subsurface layer (Wu et al. 2008; Chang et al. 2008; Tsai, Chern, andWang 2008; Morimoto et al. 2009). In this study, satellite-derived images showedenhanced upwelling and chl-a concentrations in the southern ECS after TyphoonsHaitang, Fung-wong, and Morakot. The comparison of period of time wind speed>17.2 m s−1 during typhoons and SST change clearly indicates that the movement ofthe Kuroshio axis northeast of Taiwan is more strongly related to a typhoon’s trajectoryand translation speed than its intensity of stronger wind speed.

Date in 2009

CP

UE

(kg

bo

at–1

day

–1)

July

1 5 9 13 17 21 25 29 2 6 10 14 18 22 25 30 3 7 17 15 19 23 27

SeptemberAugust

1200

1000

800

600

400

200

Figure 6. Daily CPUE variation (kg boat−1 day−1) for the torchlight fishery in the southern ECS from 9July to 31 August 2009. The black arrow over 7–9 August represents the timing of Typhoon Morakot.

(b) After Typhoon Morakot(a) Before Typhoon Morakot

64%23%

5%

5%

1%1%

1%

22%

52%

10%

8%

7%1%

Auxis thazard thazardLoligo edulis Trichiurus lepturusotherScomber japonicusDecapterus maruadsiDecapterus macrosomaDiodon holocanthusAluterus monoceros

Figure 7. Species composition of fish caught by the torchlight fishery before (a) and after (b)Typhoon Morakot in 2009.

International Journal of Remote Sensing 6569

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

4.2. Enhanced chl-a concentrations

Typhoon-enhanced upwelling and resultant phytoplankton blooms in the southern ECSare well documented (e.g. Chang et al. 2008; Hung et al. 2010; Chung, Gong, and Hung2012), but such near-shore primary production increases in this study may also haveresulted from seaward advection of river and rainwater discharge by typhoon-inducedcurrents (sensu Davis and Yan 2004; Walker, Leben, and Balasubramanian 2005; Zhengand Tang 2007). In this study, satellite images taken after Typhoons Fung-wong andHaitang revealed increased chl-a concentrations’ patches that coincided in shape andlocation with the typhoon-induced cold-water patches. However, after TyphoonMorakot, chl-a imagery data revealed that not only the study area itself but also thewest side of the study area, which is connected oceanographically to the coastal waters ofnorthern Taiwan, were characterized by increased chl-a concentrations. Doong et al.(2011) revealed that 70% of Taiwan’s 2009 rainfall fell during Typhoon Morakot, andChung, Gong, and Hung (2012) found that the nutrient-enriched floodwater drove diatomblooms and changes in species composition of diatoms. Consequently, the high chl-aconcentration from the northern Taiwan Strait extending to the upwelling region might beattributed to the river and rainwater discharge after the heavy rainfall caused by TyphoonMorakot, rather than the upwelling event itself. In conclusion, chl-a concentrations in thesouthern ECS are not only affected by the vertical mixing from air–sea interactions, butalso via the horizontal transport of seawater from coastal and estuary ecosystems.

In addition, although SST images taken after the passage of Typhoon Morakot in 2009reveal larger cold upwelling areas than those generated by Typhoon Funghung, it isevident that the high chl-a concentrations documented did not necessarily occur in thesame location as the cold seawater. Chl-a-enriched seawater from coastal regions mayhave biased this measurement (red arrows in Figure 3(b)), as the effects of TyphoonMorakot were more pronounced near the coast than either of the other two typhoons (redarrows in Figures 3(d) and (f)).

4.3. Influence of typhoons on Taiwanese torchlight fisheries

In general, the catch of torchlight fisheries is strongly associated with lunar periodicityand moonlight; full moons are associated with lower fish catch, as the target fish andsquid are less likely to find the lights placed beneath the boats during such times (Liaoet al. 2006). Typhoon Morakot passed across northern Taiwan during the full moonperiod, and this may also have contributed to the variation in the fish catch data. Themajor target fish species changed from skipjack tuna (Katsuwonus pelamis) before thetyphoon to squid (L. edulis) after it. In northern Taiwan, swordtip squid are one of themajor target species of torchlight fisheries (Zhang et al. 2012). The lunar phases influencethe vertical migration of these squid, though this phenomenon becomes less pronouncedduring the period around the full moon (Gilly et al. 2006), and the squid typically remainin deeper waters at these times. Therefore, our data reveal that squid catch of the torch-light fishery increased markedly, despite occurring during the period around the fullmoon; this suggests that the typhoon dramatically affected not only the oceanic conditionsbut also fishing activities on a short-term timescale.

The major fishing grounds of skipjack tuna in the Northwestern Pacific Ocean areusually characterized by warm, oligotrophic (e.g. low chl-a concentrations) waters (Mugoet al. 2010). In this study, the change in catch from skipjack tuna to squid could beattributed to the change in oceanic conditions; the water may have become too cold for the

6570 Y. Chang et al.

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

former species in the days after the typhoon and more ideal for the latter. In September2001, the major fishing target of the torchlight fishery also changed to squid afterTyphoon Lekima passed, and the increasing population of squid could have been drivenby the increased primary production (Liao et al. 2006). These squid typically eat smallfish and crabs (Wang, Liao, and Lee 2008), and the abundant phytoplankton in the frontaledge or upwelling zones could have attracted such prey. Therefore, predatory fish, squid,and crabs would move to the upwelling areas caused by typhoons (Yu et al. 2013).

The present results provide a comprehensive view of the response of the upper ocean totyphoons as well as the influence of these typhoons on fisheries activities in the southernECS. High-resolution satellite images and meteorological wind data revealed that the strongwinds of long duration over the southern ECS after Typhoon Morakot were significantlycorrelated with declines in SST, the latter of which possibly signifying that upwelling wasoccurring. The significant upwelling post-typhoon is likely due to the Kuroshio Current,which can restrict the flow of warm waters from the Taiwan Strait, and the more shorewardmovements of wind-driven intrusion of Kuroshio to increase its intrusion on the shelf break.This study also concluded that typhoon-driven cold-water upwelling could lead todecreased densities of skipjack tuna due their preference for warm water; such upwellingmay have simultaneously resulted in increased squid densities due to their attraction of preysources that would have benefited from the upwelling-induced increases in chl-a concen-trations and presumably primary production. Collectively, these suggest that typhoons canaffect both the behaviour of pelagic fishes and fishing activities in the southern ECS.

AcknowledgementsThe authors would like to express their appreciation to Prof. Ching-Chang Hung of National SunYat-Sen University (Kaohsiung, Taiwan) for his helpful comments on this manuscript as well as toDr Anderson Mayfield of the Living Oceans Foundation (Landover, MD, USA) for his proofreadingof the English.

FundingThis study was supported by a research grant awarded by the Ministry of Science and Technology ofTaiwan [NSC102-2611-M-006-001].

ReferencesChang, Y., H. T. Liao, M. A. Lee, J. W. Chan, W. J. Shieh, K. T. Lee, G. H. Wang, and Y. C. Lan.

2008. “Multisatellite Observation on Upwelling after the Passage of Typhoon Hai-Tang in theSouthern East China Sea.” Geophysical Research Letters 35. doi:10.1029/2007GL032858.

Chen, K. S., C. C. Hung, G. C. Gong, W. C. Chou, C. C. Chung, Y. Y. Shih, and C. C. Wang. 2013.“Enhanced POC Export in the Oligotrophic Northwest Pacific Ocean after Extreme WeatherEvents.” Geophysical Research Letters 40: 5728–5734. doi:10.1002/2013GL058300.

Chen, Y., and D. L. Tang. 2012. “Eddy-Feature Phytoplankton Bloom Induced by a TropicalCyclone in the South China Sea.” International Journal of Remote Sensing 33 (23): 7444–7457. doi:10.1080/01431161.2012.685976.

Chung, C. C., G. C. Gong, and C. C. Hung. 2012. “Effect of Typhoon Morakot onMicrophytoplankton Population Dynamics in the Subtropical Northwest Pacific.” MarineEcology Progress Series 448: 39–49. doi:10.3354/meps09490.

Davis, A., and X. H. Yan. 2004. “Hurricane Forcing on Chlorophyll-a Concentration off the NortheastCoast of the U.S.” Geophysical Research Letters 31: L17304. doi:10.1029/2004GL020668.

Doong, D. J., H. C. Chuang, C. L. Shieh, and J. H. Hu. 2011. “Quantity, Distribution, and Impactsof Coastal Driftwood Triggered by a Typhoon.” Marine Pollution Bulletin 62: 1446–1454.doi:10.1016/j.marpolbul.2011.04.021.

International Journal of Remote Sensing 6571

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4

Gilly, W. F., U. Markaida, C. H. Baxter, B. A. Block, A. Boustany, L. Zeidberg, K. Reisenbichler, B.Robison, G. Bazzino, and C. Salinas. 2006. “Vertical andHorizontal Migrations by the Jumbo SquidDosidicus Gigas Revealed by Electronic Tagging.” Marine Ecology Progress Series 324: 1–7.

Gong, G. C., Y. H. Wen, B. W. Wang, and G. J. Liu. 2003. “Seasonal Variation of Chlorophyll-aConcentration, Primary Production and Environmental Conditions in the Subtropical East ChinaSea.” Deep Sea Research Part II: Topical Studies in Oceanography 50: 1219–1236.doi:10.1016/S0967-0645(03)00019-5.

Hung, C. C., C. C. Chung, G. C. Gong, S. Jan, Y. Tsai, K. S. Chen, W. C. Chou, M. A. Lee, Y.Chang, M. H. Chen, W. R. Yang, C. J. Tseng, and G. Gawarkiewicz. 2013. “Nutrient Supply inthe Southern East China Sea after Typhoon Morakot.” Journal of Marine Research 71 (1): 133–149. doi:10.1357/002224013807343425.

Hung, C. C., G. C. Gong, W. C. Chou, C. C. Chung, M. A. Lee, Y. Chang, H. Y. Chen, S. J. Huang,Y. Yang, W. R. Yang, W. C. Chung, S. L. Li, and E. Laws. 2010. “The Effect of Typhoon onParticulate Organic Carbon Flux in the Southern East China Sea.” Biogeosciences 7: 3007–3018. doi:10.5194/bg-7-3007-2010.

Liao, C. H., M. A. Lee, Y. C. Lan, and K. T. Lee. 2006. “The Temporal and Spatial Change inPosition of Squid Fishing Ground in Relation to Oceanic Features in the Northeastern Waters ofTaiwan.” Journal of the Fisheries Society of Taiwan 33 (2): 99–113.

Lin, I. I., M. D. Chou, and C. C. Wu. 2011. “The Impact of a Warm Ocean Eddy on TyphoonMorakot (2009): A Preliminary Study from Satellite Observations and Numerical Modelling.”Terrestrial Atmospheric and Oceanic Sciences 22 (6). doi:10.3319/TAO.2011.08.19.01(TM).

Lin, I. I., W. T. Liu, C. C. Wu, J. C. H. Chiang, and C. H. Sui. 2003. “Satellite Observations ofModulation of Surface Winds by Typhoon Induced Upper Ocean Cooling.” GeophysicalResearch Letters 30. doi:10.1029/2002GL015674.

Morimoto, A., S. Kojima, S. Jan, and D. Takahashi. 2009. “Movement of the Kuroshio Axis to theNortheast Shelf of Taiwan during Typhoon Events.” Estuarine, Coastal and Shelf Science 82:547–552. doi:10.1016/j.ecss.2009.02.022.

Mugo, R., S. I. Saitoh, A. Nihira, and T. Kuroyama. 2010. “Habitat Characteristics of Skipjack Tuna(Katsuwonus pelamis) in the Western North Pacific: A Remote Sensing Perspective.” FisheriesOceanography 19 (5): 382–396. doi:10.1111/j.1365-2419.2010.00552.x.

Pun, I. F., Y. T. Chang, I. I. Lin, T. Y. Tang, and R. C. Lien. 2011. “Typhoon-Ocean Interaction inthe Western North Pacific: Part 2.” Oceanography 24 (4): 32–41. doi:10.5670/oceanog.2011.92.

Qiu, Y. S., Z. J. Lin, and Y. H. Wang. 2010. “Responses of Fish Production to Fishing and ClimateVariability in the Northern South China Sea.” Progress in Oceanography 85 (3–4): 197–212.doi:10.1016/j.pocean.2010.02.011.

Siswanto, E., A. Morimoto, and S. Kojima. 2009. “Enhancement of Phytoplankton PrimaryProductivity in the Southern East China Sea following Episodic Typhoon Passage.”Geophysical Research Letters 36. doi:10.1029/2009GL037883.

Tsai, Y., C. S. Chern, and J. Wang. 2008. “Typhoon Induced Upper Ocean Cooling off NortheasternTaiwan.” Geophysical Research Letters 35. doi:10.1029/2008GL034368.

Walker, N. D., R. R. Leben, and S. Balasubramanian. 2005. “Hurricane-Forced Upwelling andChlorophyll a Enhancement within Cold-Core Cyclones in the Gulf of Mexico.” GeophysicalResearch Letters 32. doi:10.1029/2005GL023716.

Wang, K. Y., C. H. Liao, and K. T. Lee. 2008. “Population and Maturation Dynamics of theSwordtip Squid (Photololigo edulis) in the Southern East China Sea.” Fisheries Research 90:178–186. doi:10.1016/j.fishres.2007.10.015.

Wu, C. R., Y. L. Chang, L. Y. Oey, C. W. Chang, and Y. C. Hsin. 2008. “Air-Sea Interactionbetween Tropical Cyclone Nari and Kuroshio.” Geophysical Research Letters 35. doi:10.1029/2008GL033942.

Yu, J., D. Tang, Y. Li, Z. Huang, and G. Chen. 2013. “Increase in Fish Abundance during TwoTyphoons in the South China Sea.” Advances in Space Research 51: 1734–1749. doi:10.1016/j.asr.2012.11.019.

Zhang, Y. W., K. Y. Wang, H. J. Lu, and K. Y. Chang. 2012. “A Study on the Effect of Moon Phaseto the Hatching of Swordtip Squid (Uroteuthis edulis).” Journal of the Fisheries Society ofTaiwan 39 (4): 209–222.

Zheng, G. M., and D. L. Tang. 2007. “Offshore and Nearshore Chlorophyll Increases Induced byTyphoon Winds and Subsequent Terrestrial Rainwater Runoff.” Marine Ecology Progress Series333: 61–74.

6572 Y. Chang et al.

Dow

nloa

ded

by [N

atio

nal C

heng

Kun

g U

nive

rsity

] at 1

8:04

25

Sept

embe

r 201

4