El niņo southern oscillation (enso) impact on sea surface temperature (sst) derived from satellite imagery and its relationship on tuna fishing ground
In the south java seawaters
3. Result and Discussion
3.1. SST in the South Java Seawaters
Monthly mean SST for each station of twelve selected stations during non-ENSO and ENSO years are presented at Table 1. The average of SST from all selected twelve stations range from 26.0°C to 28.5°C for non-ENSO years and from 25.9 °C to 27.1°C during the ENSO year.
Table 1. SST Mean Data During the Non-ENSO Years Versus ENSO Year in the South Java Seawaters.
| Stations |
Non-ENSO year (1996) |
ENSO year (1998) |
| 1 |
26.0 |
25.9 |
| 2 |
27.5 |
25.8 |
| 3 |
28.5 |
27.1 |
| 4 |
28.0 |
26.3 |
| 5 |
28.0 |
25.9 |
| 6 |
28.0 |
26.7 |
| 7 |
27.5 |
26.2 |
| 8 |
28.0 |
26.4 |
| 9 |
29.0 |
26.4 |
| 10 |
28.0 |
25.9 |
| 11 |
28.0 |
26.1 |
| 12 |
28.5 |
25.6 |
The monthly mean SST plots for each station during non-ENSO and ENSO years are presented in Figure 3. In general, monthly mean SST value in the south Java seawaters for the Non-ENSO year is higher than that of the ENSO year with the average different of 1.7°C. The lower monthly mean SST during ENSO year could be connected to the cold front shifted to the north in South Pacific, east of Australia. That cold front affecting the south Java seawaters by passing Arafuru Sea.
Fig. 3. SST Average Non-ENSO (1996) versus ENSO Year (1998).
The minimum value of monthly mean SST of twelve stations in the south Java seawaters occur in July for non-ENSO and ENSO years. This result is coherent with the study conducted by Pariwono (1995) that found SST minima in Java Sea occur in July to September.
In July to September, SST near Bali Island is lower than that it's surrounding. This phenomenon known as indicator of upwelling process.
3.2 Tuna Catch in South Java Seawaters
Based on the "PT Perikanan Samudra Besar" tuna fishing vessels catches, big eye tuna is the dominant catches beside yellow fin tuna in south Java seawater in 1996 and 1998. Total big eye tuna catch for each month is shown in Table 2. Total tuna catches in 1996 and 1998 are 30,401 fishes and 42,209 fishes respectively. On the other word, the big eye tuna catch in ENSO year is higher than that non-ENSO year.
Table 2. Total Big Eye Tuna Catches in 1996 (Non-ENSO year) and 1998 (ENSO year) for Every Months
| Month |
ENSO, 1998(fishes) |
Non-ENSO,1996(fishes) |
| February |
1564 |
2627 |
| March |
1617 |
2316 |
| April |
1821 |
2332 |
| May |
27577 |
2746 |
| June |
2814 |
2234 |
| July |
2572 |
1875 |
| August |
1565 |
1739 |
| September |
1117 |
1247 |
| October |
863 |
1403 |
| November |
699 |
11882 |
| Total |
42,209 |
30,401 |
The highest big eye tuna catch in south Java seawaters in 1998 is related to the lower SST in ENSO year. Temperature changing in ENSO year can directly affect the abundance of big eye. In ENSO year is predicted that big eye tuna move up to sea surface because temperature in deeper water is too cold.
In 1996, the higher tuna catches occur for period of May, June and July, with maximum catches (2814 fishes) in June. In 1998, the higher catches occur for period February, April, May and June, with maximum catches in May (2746 fishes) (Fig 2).
Fig. 2. Big eye monthly catches in the south Java seawaters in 1996 and 1998 respectively.
The monthly migratory pattern of big eye in Indian Ocean was deduced by use of 1967-1985 catch data of Japanese tuna long line fishery (Mohri et al., 1997). During the southern hemisphere winter season, from April to September, the big eye tuna are generally distributed in the high latitude area of Indian Ocean. However, some big eye tuna also occur in the waters north the Madagascar in June, and off Java in July.
The catches pattern of big eye in 1996 and 1998 (Fig. 3) in south Java seawaters is coincided with the study conducted by Mohri et. al, 1997, who found that the higher big eye catches occur for period of February, May, June and July.
Fig. 3. The pattern tuna catch in the south Java seawater in 1996 and 1998.
4. Conclusion
Defining ENSO years as the years that fall in standard deviation of Southern Oscillation Index <= -1.5, the SST monthly mean in the south Java seawaters range from 25.9 to 27.1°C for non-ENSO year and 26.0°C to 28.5°C during the ENSO year.
Monthly mean SST value in the south Java seawaters ENSO years are lower than that of the non-ENSO year with the average different of 1.7°C.
Total tuna catch in 1996 and 1998 are 42,209 fishes 30,401 fishes respectively. Therefore, big eye tuna catch in ENSO year is higher than that non-ENSO year.
References
-
Bigg, G. R. The Oceans and Climate. Cambridge University Press. Cambridge. 1996. 266p.
-
Mizuno, K., 1995. Variabilities of Thermal and Velocity Field in the Vinicy of North of Australia Basin with Regard to the Indonesia Trough flow. In: Proceeding of International Workshop the Trough flow Studies in Around Indonesian Waters. BPPT. Indonesia.
-
Mohri, M., E. Hanamoto, M. Nemoto, and S. Takeuchi, 1997. Fishing Season, Fishing Ground and Migratory Pattern of Big Eye Tuna in the Indian Ocean as Seen from Tuna Long Line Catches. In Japan Fisheries Bulletin, pp 1-5.
-
Pariwono, J.I : Effect of El-Nino Southern Oscillation (ENSO) on Fish Catch in Indonesian. Bogor Agricultural University, pp. 20-25.
-
Philander, S. G., 1990. El NIŅO, La Nina, and the Southern Oscillation. Academic Press, Inc. San Diego, pp. 12-25.
-
Polis, G. A., S. D. Hurd, C. T. Jackson, and F. S. Pinero, 1997. El NIŅO Effects on the Dynamics and Controls of an Island Ecosystem in the Gulf of California. Ecology. Vol. 78. No.6. pp. 1884-1897.
-
Quinn, W. H., V. T. Neal, and S. E. Antunez de Maloyo, 1987. El NIŅO Occurrences over the Past Four and Half Centuries. J. of. Geophys. Res. Vol. 92, pp. 14449-14461
-
Trenberth, K. E., 1991. General Characteristics of El Nino-Southern Oscillation. In: Glantz, M. H., Katz, R. W., and Nicholls, N. (eds). Teleconnections Linking Worldwide Climate Anomalies. Cambridge University Press. Cambridge, pp.13-42.
