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or collective redistirbutionor collective of this by of any article portion Th THE INDONESIAN SEAS published in been has is article Oceanography

Seasonal Variation of , Volume 4, a quarterly journal of Th 18, Number Pelagic Catch or other means reposting, photocopy machine, is only w permitted Around e Oceanography Society. Copyright e Oceanography 2005 by Th

BY NANI HENDIARTI, SUWARSO,

EDVIN ALDRIAN, ith the approval of Th KHAIRUL AMRI,

RETNO ANDIASTUTI, Permission reserved. Society. All rights is e Oceanography gran SUHENDAR I. SACHOEMAR, all correspondence to: Society. Send e Oceanography [email protected] or Th AND IKHSAN BUDI WAHYONO ted in teaching to copy thisand research. for use Repu article e Oceanography Society, PO Box 1931, Rockville, MD 20849-1931, USA. 1931, Rockville, Box PO Society, e Oceanography blication, systemmatic reproduction,

112 Oceanography Vol. 18, No. 4, Dec. 2005 WE PRESENT DATA on the seasonal variability of small and 1.26 million ton/year in the Indonesian EEZ. Pelagic fi sh pelagic fi sh catches and their relation to the coastal processes play an important role in the economics of fi sherman in Indo- responsible for them around the island of Java. This study uses nesia; approximately 75 percent of the total fi sh stock, or 4.8 long fi sh-catch records (up to twenty years) collected at vari- million ton/year, is pelagic fi sh. In particular, we investigated ous points around Java that were selected from the best-qual- the waters around Java because most people live near the ity harbor records. Seven years of color satellite data and an abundance of pelagic fi sh is caught under a variety of were also used in this study. The study selected four regions coastal oceanographic conditions. that represent the four edges of Java. Data analysis shows that Considering the intense fi shery activities adjacent to the the annual fi sh-catch pattern is determined by monsoonal heavily populated island of Java, the is presently over- activity. The monsoon greatly infl uences the appearance of exploited for pelagic species (Agency for Marine and warm and rich surface currents in the Java Sea, surface water Research [AMFR], 2001). The exploitation rate of pelagic fi sh transport and in the , upwelling in the in of South Java is still 50 percent or less (exploi- Indian Ocean, and indirect upwelling in the Strait (for tation rate is defi ned as catch divided by the natural fi sh stock details on the regional oceanography, see Gordon [this is- at a fi shing zone during the time period) (Luong, 1997; AMFR, sue]). These coastal processes, which differ for each region, 2001). Thus, a study such as this, which looks at the infl uence infl uence fi sh catch and fi sh distribution. The natural fi sh of coastal processes on pelagic fi sheries, will be important for stock of the entire Indonesian seas (including the Exclusive fi sh stock management on seasonal and annual bases. Study of Economic Zone [EEZ]) is estimated to be 6.4 million ton/ coastal processes in the Indonesian seas, particularly around year, of which 63.5 percent are caught annually (Agency of Java, can help the fi sheries community understand how coastal Marine and Fisheries Research [AMFR], 2001). That fi sh processes correlate with fi sh behavior, and their abundance and stock consists of 5.14 million ton/year in Indonesian waters seasonal distribution.

Oceanography Vol. 18, No. 4, Dec. 2005 113 DATA AND METHODS al area coverage data with 4-km spatial (for catches in the Bali We investigated the seasonal variability resolution as well as selected Local Area Strait), Pekalongan and Rembang (for of coastal processes in relation to pe- Coverage (LAC) data with 1-km resolu- catches in the Java Sea), and Cilacap (for lagic fi sh distribution around Java using tion. We produced chlorophyll images catches in the Indian Ocean) (Figure 1). Sea-viewing Wide Field-of-view Sensor using Ocean Chlorophyll 4-band (OC4) Monthly fi sh-catch data dominated by (SeaWiFS) and Moderate Resolution algorithms (O’Reilly et al., 2000). The pelagic fi sh were taken from daily catches Imaging Spectroradiometer (MODIS) chlorophyll determination coeffi cients of fi sherman in the fi shing ground near data of derived chlorophyll concentra- derived from LAC data for Indonesian the harbor. tions (1997–2004) taken from the Aqua waters are less than 0.43 for turbid wa- satellite, pelagic fi sh catch data collected ters and greater than 0.65 for ocean wa- RESULTS AND DISCUSSION from several harbors along the Java ters (Hendiarti, 2003). We used chlorophyll a data to observe coast (1976–2004), and meteorological In addition to Aqua data, we used the seasonal variation of data as given by wind patterns at 850 pelagic fi sh catch data from 1993–2003, blooms around Java. Different coastal millibars (mb). 1992–2002, and 1985–1995, provided by processes infl uence the growth and dis- Using SeaWiFS and MODIS data and the Ministry of Fisheries Affairs, were tribution of phytoplankton (Figure 2). Sea DAS computer software, all provided collected from documented fi sh land- Every year, higher concentrations of chlo- by the Goddard Space Flight Center of ings (the quantities of fi sh caught and rophyll a (> 0.3 mg/m3) were observed in the National Aeronautics and Space Ad- brought back to land by fi sherman) in the Indian Ocean near Cilacap harbor in ministration (NASA), we processed glob- Labuan (for catches in the Sunda Strait), the third quarter (July–September) and lower concentrations in the fi rst quarter (January–March) (Figure 2b). In 1998, a year after a signifi cant El Niño, the in-

Nani Hendiarti ([email protected]. 4°N go.id) is Program Coordinator, Center for

8 Technology for Natural Resources Inventory, 2°N Kalimantan Agency for the Assessment and Application of Technology, Jakarta, . Suwarso

0° is a researcher at the Agency for Marine and Fisheries Research, Jakarta Selatan, Indo- nesia. Edvin Aldrian is a researcher at the 2°S Agency for the Assessment and Application 6 of Technology, Jakarta, Indonesia. Khairul 4°S Java Sea 5 Amri is a researcher at the Agency for Ma- 34 rine and Fisheries Research, Jakarta Selatan, 2 6°S 9 1 7 Indonesia. Retno Andiastuti is a researcher at the Agency for the Assessment and Ap- Java plication of Technology, Jakarta, Indonesia. 8°S Sunda Strait

10 11 Suhendar I. Sachoemar is a researcher at the Agency for the Assessment and Ap- 10°S Bali Strait plication of Technology, Jakarta, Indonesia. Indian Ocean Ikhsan Budi Wahyono is a researcher at

12°S 104°E 106°E 108°E 110°E 112°E 114°E 116°E 118°E 120°E the Agency for the Assessment and Applica- Figure 1. Map of investigation areas, including the main fi shing grounds around Java. tion of Technology, Jakarta, Indonesia.

114 Oceanography Vol. 18, No. 4, Dec. 2005 a

b 0.7 Java Sea Sunda Strait 0.6 Indian Ocean Bali Strait

0.5 ) 3

0.4 (mg/m

a Figure 2. (a) (opposite page) Chlorophyll a image derived from MODIS data from August 0.3 24, 2004. (b) Average concentrations of chlo- rophyll in the waters around the Java from Chlorophyll 1997 to 2004. (c) Annual changes of sea surface 0.2 temperature (SST) and (d) chlorophyll concen- trations of the study area (for the years 1997– 2004). Note the cooling eff ect and an increase 0.1 of phytoplankton growth in the coastal area of the Indian Ocean near Java because of upwell- ing during the southeast monsoon (June to

0 October). A slight increase in SST in the Java J- O- J- A- J- O- J- A- J- O- J- A- J- O- J- A- J- O- J- A- J- O- J- A- J- O- J- A- J- O- Sea and Sunda Strait may have been caused by S D M J S D M J S D M J S D M J S D M J S D M J S D M J S D strong transport of freshwater and discharges 1997 1998 1999 2000 2001 2002 2003 2004 during the transition phase (March to May).

c d 2.5 32 Java Sea Java Sea Sunda Strait Sunda Strait 31 Bali Strait Bali Strait Indian Ocean (upwelling) 2 Indian Ocean (upwelling)

30 ) 3

1.5 29 (mg/m a

SST (°C) 28 1 Chlorophyll 27

0.5 26

25 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months Months

Oceanography Vol. 18, No. 4, Dec. 2005 115 tensity and extent of phytoplankton dis- seine in the offshore area and pelagic fi sh in new ships greater than 100 GT. Scads tribution in that region from July to Sep- caught by mini purse seine in the near- from the Java Sea were the principal con- tember were found to be less than that in shore area. Scattered shoaling stocks of tributor (approximately 50 percent) to other typical years (Figure 2b). small pelagic species are found also in the high total landing in 1994 from three During the southeast monsoon (June the eastern part of the sea to the Makas- regions surveyed (Figure 3b). Data indi- to October), surface-water cooling and sar Strait and around the southwestern cate that there are two peak seasons of an increase in chlorophyll a concentra- part of the South China Sea. fi sh catch in the Java Sea every year with tions in the Indian Ocean, particularly Approximately thirty pelagic species minimum catch observed from March along the southern coast of Java, are in are caught around the Java Sea; eleven of to April and maximum catch from Sep- response to Ekman-induced upwelling; those species account for 90 percent of tember to November (Figure 3c). During a slight decrease in sea-surface tempera- the landing (Nurhakim et al., 1995). The the peak season (September–November), ture (SST) in the Bali Strait is also a re- six major species are Carangids (scads, most of the catch is made in the Java sult of indirect upwelling (Figure 2c-d). D. russelli and D. macrosoma; trevallies, Sea, while from January–April most of Furthermore, the westward surface cir- S. crumenophthalmus), Clupeids (sardi- the catch is made in the culation transports nutrient-rich water nella, S. gibbosa, A. sirm), and Scrom- (Figure 3c) (Potier and Sadhotomo, from the eastern Indonesian seas into bids (, R. kanagurta,). Other 1995). From May to June, when low-sa- the Java Sea. These nutrient-rich waters species from the inshore area are often linity waters extend eastward and reach are responsible for the slight increase in caught unintentionally, including Sela- their maximum extension, the bulk of chlorophyll a concentrations in the Java roides leptolepis, Sardinella brachysoma, the catch is made in the South China Sea and the Sunda Strait from June to Rastrelliger brachysoma, and Stolephorus Sea (Figure 3c). Potier and Boely (1990) September (Figure 2c-d). spp. Potier and Sadhotomo (1995) di- noted that this seasonal pattern is related vided these small pelagic fi shes into three to oceanographic variation in the area, Influence of Ocean Circulation groups that correspond to three different corresponding to the monsoons. on the Distribution of types of populations among the pelagic Every year, maximum pelagic fi sh Catch catch: (a) oceanic population (D. macro- catch in the Java Sea occurs from Sep- In this section we present further inves- soma, A. sirm, R. kanagurta), which are tember to November (Figure 4a). Two tigations focusing on the annual trend caught when the oceanic waters from species of scads (layang, Decapterus rus- and seasonal variation of pelagic fi sh enter the Java Sea during the selli, and deles, D. macrosoma) account caught in the Java Sea and the Sunda southeast monsoon between August and for at least 50 percent of the total catch Strait in relation to phytoplankton dis- November; (b) neritic population (D. and are the bulk of the catch in each of tribution, oceanographic phenomena, russelli), which are caught throughout the fi shing grounds (Figure 4b). There and monsoons. the year by seines; and (c) coastal popu- are production peaks of Decapterus spp. lation (S. crumenophthalmus, S. gibbosa), in 1984, 1989, and 1997; however, in gen- The Java Sea which are caught throughout the year in eral, D. russelli catch decreases when the Surface waters of the Java Sea seasonally lower quantities. D. macrosoma catch increases. The same travel according to monsoonal winds. The annual catch of the small pe- annual trend occurs for another species Surface currents may lead to a migration lagic fi sh found in the Java Sea shows of scads (R. kanagurta). The abundance of small pelagic fi sh, which are mostly great variation (Figure 3). Offshore Java, of these two species fl uctuates greatly caught by purse seine (a type of fi shing the pelagic fi sh caught by purse seines (Figure 4b). The production peak for net used to surround and catch large reached about 120,000 tons in 1985 and this species is in 1984 (Figure 4b). The quantifi es of surface-schooling fi sh). Hi- 181,000 tons in 1994 (Figure 3a) (Po- landing of siro (Amblygaster sirm) repre- erarchically, small pelagic fi sh in the Java tier and Sadhotomo, 1995). They ob- sents up to 20 percent of the total seine Sea can be divided into two main catego- served that the increase in fi sh catch after catch (Figure 4b); the bulk of the catch ries: pelagic fi sh caught by large purse 1986/1987 was the result of investments is from the eastern part of the Java Sea.

116 Oceanography Vol. 18, No. 4, Dec. 2005 a b b 200,000 200,000200,000

180,000 Total JAVA 180,000180,000 SouthSouth China China Sea Sea Pekalongan JavaJava Sea Sea Juana MakasarMakasar Strait Strait 160,000 Rembang 160,000160,000 TOTALTOTAL

140,000 140,000140,000

120,000 120,000120,000

100,000 100,000100,000 Catch (tons) Catch (tons)

80,000 80,00080,000 Total Catch (tons)

60,000 60,00060,000

40,000 40,00040,000

20,000 20,00020,000

0 0 0 1975 1980 1985 1990 1995 2000 2005 19851985 1986 1986 1987 1987 1988 1988 1989 1989 1990 1990 1991 1991 1992 1992 1993 1993 1994 1994 1995 1995

c 25,000 Figure 3. (a) Th e annual catch of small pelagic fi sh caught by purse Java seines around the Java Sea from Makassar 1976 to 2004. (b) Annual catch China Sea of small pelagic fi sh from 1985 to 1995 in three diff erent regions. 20,000 (c) Seasonal trend of the catch of small pelagic fi shes in three of the main fi shing zones from 1985 to 1995. Th is seasonal variation cor- responds to the monsoons. 15,000 Catch (tons)

10,000

5,000

0 JAJOJAJOJAJOJAJOJAJOJAJO JAJOJAJOJAJOJAJO JAJO 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995

Oceanography Vol. 18, No. 4, Dec. 2005 117 Bentong, or bigeye scads ( crumen- acuta), bawal hitam (Formio niger), and tral north coast (Pekalongan), a species ophthalmus), were caught in a small small coastal (Auxis spp.). of (Sardinella spp.) contributes quantity in the Java Sea as compared to Figure 4c–d plots the annual changes about 35 percent of the catch (Figure the other species of pelagic fi sh (Figure in species composition that show up in 4c). In addition, a neritic species (spe- 4b). The remainder of the catch (6–8 mini purse seine in the inshore area of cies that swim in waters less than 200 percent) consists of japuh (Dusumeria the northern coast of Java. Along the cen- m deep) of mackerel (R. brachysoma) is

a b 12000 100% Others S.crumenophthalmus Auxis spp. S.gibbosa Selar S.gibbosa 10000 A.sirm R.kanagurta 80% A.sirm D.macrosoma S.crumenophthalmus D.russelli R.kanagurta Decapterus spp. 8000 60%

6000 Percentage

Catch (kg/day) 40%

4000

20% 2000

0 0% J F M A M J J A S O N D 1981 1984 1987 1990 1993 1996 1999 2002

c d 100% 100% Others Others Auxis spp. Auxis spp. Sardinella Sardinella S.crumenophthalmus 80% A.sirm 80% R.kanagurta Selar Decapterus spp. S.crumenophthalmus R.brachysoma Decapterus spp. 60% 60% Percentage Percentage 40% 40%

20% 20%

0% 0% 9 6 1 2 4 3 4 8 3 0 5 7 2 3 0 7 8 9 1 2 6 4 9 0 9 9 9 0 0 9 9 9 9 0 0 0 9 0 0 0 9 9 9 0 9 9 0 9 9 0 0 9 9 0 9 9 0 0 0 0 9 0 9 9 9 0 1 1 2 2 1 1 1 1 2 2 1 1 2 2 1 2 2 1 2 2 1 1

Figure 4. (a, b) Annual changes and seasonal variations of small pelagic fi shes in the Java Sea. (c) Annual changes in species com- position of the inshore fi shery in Central Java and (d) .

118 Oceanography Vol. 18, No. 4, Dec. 2005 also dominant. This fi sh is an important (Sardinella spp.) dominated the major pelagic fi sh catch always occurred dur- commodity in the northwestern coast of peak season (March–April) and a minor ing the southeast monsoon, but was not Java (Suwarso and Hariarti, 2002) and peak season (October–November). This followed by similar trend in large pelagic in the south coast of Borneo (Sudjastani, seasonal shift is also discussed in Gordon fi sh. If we compare the dominant catch 1976). During the period 1992–2004, et al. (2003). of small pelagic fi shes (selar bentong along northern coast of east Java (Rem- [Selar crumenopthalmus, or ], bang), an oceanic population of scads The Sunda Strait banyar [Rastreliger kanagurta, or striped (Decapterus spp.) contributes about 45 Water fl ows from the Java Sea to the In- mackerel], tenggiri [Scromberomenus percent of the catch (Figure 4d). dian Ocean through the Sunda Strait. comersonii, or barred Spanish mack- Figure 5 plots the seasonal fl uctuation The variability in water characteristics erel]), and large pelagic fi shes (tongkol of each species from 1981–2005. The dis- in the Sunda Strait (observed in satel- [Euthynnus spp., or coastal /frig- tribution of D. macrosoma (an oceanic lite data) may infl uence the distribution ate tuna]), we fi nd that both small and species of scads) is more concentrated of pelagic fi sh in that region (Hendiarti, larger pelagic fi shes are present and have in the eastern part of the Java Sea and 2003). During the southeast monsoon, similar seasonal patterns in the Sunda the Makassar Strait from September to surface waters are warm (> 29.5°C), have Strait. Frigate tuna, striped mackerel, February (Figure 5a). A. sirm () high chlorophyll concentrations (> 0.5 bigeye scad, kembung, tembang, and and R. kanagurta (mackerel) are oceanic mg/m3), and low salinity. During this scad catches begin in March (transition species that more concentrated in the period, small pelagic fi sh, which like the season); the catch increases as it enters central part of the Java Sea from March warm surface waters, are present in the the southeast monsoon season, the peak to June (Figure 5b). On the other hand, Sunda Strait in higher numbers than of catch season (Figure 6b). The catch S. crumenophthalmus (a coastal species larger oceanic species. then decreases when the next transition of bigeye scad) has a similar pattern to Pelagic fi sh catch data used in this season comes, and reaches its minimum D. russelli (Figure 5f–g). Sadhotomo and study were collected from Labuan harbor during the northwest monsoon. This Potier (1995) observed a size evolution from 1993 to 2003. Total fi sh catch per observed annual fl uctuation agrees with of small pelagic fi shes around Java; fi sh month was calculated from daily catches Pakpahan’s (1999) conclusions. He sug- got larger as you went east. This trend is of fi sherman, who caught mostly small gested that the small pelagic fi sh catch clearly seen for the oceanic species and pelagic species in fi shing grounds near in the Sunda Strait will start in the same might be correlated to spawning (Atm- the harbor. Pelagic species were found in month every year (April) and will end in adja et al., 1995; Widodo, 1991). How- that region from May to August (south- the same month (November). However, ever, juveniles and young fi sh had been east monsoon). Peak fi sh catch occurred the start and end of the fi sh catch could found inshore along the north coast of annually during the southeast monsoon come earlier or later and follow with for- Java and Karimunjava Island from April in June (Figure 6a). Beginning in Sep- ward or backward production outcomes. to August (Sadhotomo and Potier, 1995). tember–October (the transition season), Hendiarti (2003) suggested that the oc- fi sh catch decreased. This decrease con- Influence of Upwelling Events on currence of the juveniles was related to tinued until the northwest monsoon be- the Distribution of Pelagic Fish nutrient discharge, particularly from fi sh gan, and reached its lowest point in De- Indian Ocean farms, aquaculture, and big rivers, where cember–January (Figure 6a). The catch In upwelling regions, the intensity of high concentrations of chlorophyll a began to increase again in March–April nutrient infl ow from deeper layers in- were observed during the transition (transition season). creases phytoplankton abundance. These phase from the rainy to the dry season There were differences in monthly upwelling regions are suitable for fi sh (March and April). Scads (Decapterus fi sh catch of small (shelf originated) and because they provide good feeding con- spp.) in East Java dominated the peak big (ocean originated) pelagics during ditions for larvae, juveniles, and adult catch season (September–November). 1993, 1995, 1996, and 1997 (Figure 6b). pelagic fi sh. Larvae and juveniles feed However, in Central Java, the sardine During those years, the increase in small on . The fi sh catch in Cilacap

Oceanography Vol. 18, No. 4, Dec. 2005 119 a 1800 Sarang-Rembang

1600 Decapterus R. kanagurta S. crumenophthalmus Sardinella Auxis Others 1400 Total

1200

1000

Catch (tons) 800

600

400

200

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 0 JAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJO

b 500000 Pekalongan

Scads Big- scads Trvally Spotted sardines Goldstrip sardines 400000 Litle Tuna Others

300000 Catch (kgs)

200000

100000

0 JAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJOJ 1997 1998 1999 2000 2001 2002 2003 2004 2005 Figure 5. Fluctuation of small pelagic species in the inshore north coast of (a) East Java and (b) Central Java from 1992–2005.

120 Oceanography Vol. 18, No. 4, Dec. 2005 harbor from 1998 to 2004 was domi- tuna, but development of secondary pro- 1992–2002, the catch of lemuru fl uc- nated by the large pelagic fi sh skipjack duction provides an attractive habitat tuates greatly. It has two peak seasons (Katsuwonus pelamis), tuna (Thunnus for tuna species. Tuna aggregations are (Figure 7). The major peak is from Sep- ), layar (Istiophorus spp.), teng- often found close to the frontier zones, tember to November, while a minor peak giri (Scomberomorus spp.), cucut (Isurus which are important places for aggre- sometimes occurs from March to April. glaucus), tongkol (Euthynnus spp.), and gating plankton and micronekton (e.g., The production in 1993, 1994, 1997, and blue (Thunnus spp.). During the Lehodey et al., 1998). Therefore, high 2001 is known as the “normal” pattern, southeast monsoon, high amounts of abundance of tuna may also occur close whereas the production in 1995, 1996, chlorophyll a in the surface waters are to highly productive upwelling zones. 1998, 1999, and 2000 is known as the correlated with high catches of cakalang. “uncommon” pattern (Wudianto, 2001). However, for the tuna fi sh catch, the fer- The Bali Strait In 1995 and 1998, higher production tility of the South Java water in August Sadinella Lemuru is the dominant spe- also occurred from January to July. Wu- is not followed by an increase in tuna cies (more than 90 percent of total catch) dianto (2001) suggested that those two catch. From Banyuwangi fi sh harbor, in the Bali Strait’s pelagic fi shery, and years were the uncommon periods of we observed a high abundance of small is mainly exploited by the purse sein- catch fl uctuation. Spawning season oc- pelagic schooling fi sh like sardinella in ers. Annual fl uctuation is great in this curs in June and July every year (Merta, upwelling areas off the southern coast of fi shery, with three large peaks in produc- 1992a,b), which coincides with the pres- East Java, which is characterized by cold tion from 1974–2000: 1983, 1991, and ence of upwelling during southeast mon- water and high surface chlorophyll. Tuna 1998, reaching 48,000 tons, 61,670 tons, soon season (Burhanuddin and Praseno, (Thunnus spp.) is a pelagic predatory and 77,600 tons, respectively (Merta, 1982; Saliyo, 1973). The bulk of “se- fi sh that consumes small pelagic fi sh. 1992a,b). The lowest production was in menit” (size category of lemuru at 1–2 Primary production does not aggregate 1986, 1996, and 1999. Seasonally, during months old) is present during August

a b 800 120

Big Eye Scad 700 Total catch (1993-2002) Striped Mackerel 100 Barred 600 Frigate Tuna

80 500

400 60 Catch (tons) Catch (tons) 300 40

200

20 100

0 0 J F M A M J J A S O N D 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Months

Figure 6. (a) Average annual variability in total pelagic catch from Labuan Port, Sunda Strait from 1993–2002. (b) Annual catch fl uctuation of pelagic fi shes in the Sunda Strait from 1993–2003. Pelagic fi sh-catch data were collected from daily catches of fi sherman. Big pelagic fi sh are frigate tuna; small pelagic fi sh are bigeye scad, striped mackerel, and barred Spanish mackerel.

Oceanography Vol. 18, No. 4, Dec. 2005 121 and September, while adult fi sh (ma- sensing of ocean color provides the nesian archipelago plays a great role in ture) are usually present in May (Merta, general characteristics of various ocean determining the variability of fi sh catch 1992a,b). Seasonal fl uctuation of the phenomena around Java, including sur- around Java. The “pelagic fi sh season” catch is highly correlated with changes in face water transport, coastal discharge develops during the southeast monsoon. oceanographic condition. in the Java Sea and Sunda Strait, and Variability in the annual fi sh catch pat- coastal upwelling along the southern terns from the four regions show similar CONCLUSIONS coast of Java. Upwelling is character- maximum and minimum peaks during We have described, examined, and ana- ized by high chlorophyll concentrations the southeast and northwest monsoon, lyzed variability of fi sh catches, and their and low sea surface temperature, while respectively. However, it turns out that correlation to seasonal coastal processes, surface transport of the Java Sea water for each region, the monsoon system af- from four different harbors around Java: into the Sunda Strait is distinguished fects coastal processes differently, which the Java Sea (north), the Sunda Strait by higher chlorophyll concentrations infl uences the variability of the fi sh catch (west), the Bali Strait (east), and the In- and higher sea surface temperatures. We and fi sh distribution. dian Ocean (south). The fi ndings of identifi ed the characteristics of pelagic Interannual variability of the fi sh this study are summarized in Table 1. fi shes around Java—their dominant spe- catch is determined by many factors, Development of phytoplankton in spe- cies, the duration in specifi c waters, and including oceanographic processes and cifi c regions is related to coastal and when they appeared. human factors such as fi shing skill and ocean processes forced by wind. Remote The monsoonal system in the Indo- fi sh-catch equipment. Seasonal variabil- ity in sea-surface conditions is similar from year to year and interannual vari- ability is predictable. Due to lack of data, there is no detailed study on the interan- 9000 50 nual variability of all coastal processes except sea surface temperature and chlo- 8000 Tons rophyll a concentration. There is also no Tons/trip clear indication of the role of regional 40 7000 phenomena such as El Niño and La Niña events in infl uencing fi sh catch. 6000 Results of this study were built from

30 long fi sh-catch records around Java. 5000 They represent the best records from

Catch (tons) harbors along each of the island’s four Catch Rate (tons/trip) 4000 . Physical oceanography results 20 provide an explanation for variability in

3000 fi sh catches, which may help decision- makers, such as fi sh stock analyzers, de-

2000 termine future fi sh-catch policy around 10 Java. More detailed investigations of the

1000 interannual variability of all coastal pro- cesses and why they fail to explain the interannual variability of the fi sh catch 0 0 JAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJOJAJO 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 is needed. Future studies could also be Figure 7. Fluctuation of the catch (tons) and catch rate (ton/trip) of Lemuru (Sardinella lem- extended to include large pelagic fi sh or uru) in the Bali Strait landed at Muncar (East Java) from 1992–2001. additional species.

122 Oceanography Vol. 18, No. 4, Dec. 2005 Table 1: Characteristics of pelagic species and ocean phenomena. eries Research Institute 67:73–84. Merta, I.G.S. 1992b. The “Lemuru” fi sh stock assess- ment in the Bali Strait with the Cohort Analyses Characteristic Ocean Phe- (in Indonesian). Journal of the Marine Fisheries Regions Dominant Pelagic Species (when appear) nomena Research Institute 69:9–18. Small Pelagic: (a) oceanic: D. Warm and Nurhakim, S., J.R. Durand, M. Potier, and B. Sad- Max: Sep. – Nov. macrosoma, A. sirm, R. kana- high nutrients hotomo. 1995. The state of exploitation of small (southeast monsoon) pelagic fi shes by the large and medium purse Java Sea gurta; (b) neritic: D. russelli; surface water seine in the Java Sea. The fourth Asian Fisheries (c) coastal: S. crumenoph- Min: Mar. – Apr. - Forum, 16–20 October 1995. Beijing. thalmus, S. gibbosa O’Reilly, J.E., and others. 2000. SeaWiFS Postlaunch Small Pelagic: Sardinella Surface water Calibration and Validation Analysis, Part 3. Max: Jun. NASA Technical Memo, 2000–206892, Vol. 11, spp., Rastrelliger spp., transport and (southeast monsoon) S.B. Hooker and E.R. Finestone, Eds., NASA Selaroides leptolepis, De- upwelling Sunda Goddard Space Flight Center, 49 pp. capterus spp. Strait Pakpakan R. 1999. Study on several environmental meteorological aspects and their relations to the Big Pelagic: Auxis thazard, Min: Dec. - catch season of pelagic fi sh in the Sunda Strait. Scomberomorus spp. (in Indonesian). Bachelor thesis. Bogor Institute of Agriculture. Max: Jun. – Sep. Potier, M., and T. Boely. 1990. Infl uence des parame- Indian Upwelling Big Pelagic (southeast monsoon) tres de l’environnement sur la peche a la senne Ocean tournante et coulisante en mer de Java. Aquatic Min: Nov. – Jan. - Living Resources 3:193–205. Infl ow of Potier, M. and B. Sadhotomo. 1995. 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