or collective redistirbution of any portion article of any by of this or collective redistirbution Th THE INDONESIAN SEAS articleis has been in published Oceanography Seasonal Variation of 18, Number journal of Th 4, a quarterly , Volume Pelagic Fish Catch permitted only w is photocopy machine, reposting, means or other Around Java 2005 by Th e Oceanography Copyright Society. BY NANI HENDIARTI, SUWARSO, EDVIN ALDRIAN, of Th approval the ith KHAIRUL AMRI, RETNO ANDIASTUTI, gran e Oceanography is Society. All rights reserved. Permission SUHENDAR I. SACHOEMAR, or Th e Oceanography [email protected] Society. Send to: all correspondence AND IKHSAN BUDI WAHYONO ted to copy this article Repu for use copy this and research. to in teaching ted e Oceanography Society, PO Box 1931, Rockville, MD 20849-1931, USA. blication, systemmatic reproduction, reproduction, systemmatic blication, 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 coast ity harbor records. Seven years of ocean 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 Java Sea is presently over- activity. The monsoon greatly infl uences the appearance of exploited for pelagic species (Agency for Marine and Fisheries warm and rich surface currents in the Java Sea, surface water Research [AMFR], 2001). The exploitation rate of pelagic fi sh transport and upwelling in the Sunda Strait, upwelling in the in Indian Ocean of South Java is still 50 percent or less (exploi- Indian Ocean, and indirect upwelling in the Bali 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 Banyuwangi (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 phytoplankton 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 South China Sea 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, Indonesia. 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.