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The marine fishery resources of the north coast of west Java

Tatang Sujastani

Introduction

The Indonesian archipelago covers an area of 3.2 million km² of which 70 per cent is water. The coastline is 61,000 km, and the shelf area is 775,000 km². The north coast of West Java is a part of the Sunda shelf that stretches to the east and borders the Strait of Macassar and the Bali Sea.

The present marine fish catch exceeds 1 million tonnes, of which 157.4 thousand tonnes come from the north coast of Java and 55.3 thousand tonnes from the north coast of West Java (1977). The catches mostly come from small-scale fishing activities, which are estimated to produce 90 per cent of the nation's total catch.

The waters north of Java have been exploited traditionally for a long time. The fishing is mostly indigenous and static, which causes low efficiency. Better technology has been introduced, inclusing trawl fishing for demersal and purse seining for pelagic resources. Both of these, introduced in late 1970, can be considered as small-scale fishery modernization.

The development of trawl and purse-seine fisheries in this area was very fast. The trawlers operating in the coastal waters increased rapidly, concentrating especially on shrimp that fetch a high price for export. This caused a fully demersal resource exploitation level in the coastal zone, whereas the offshore zone is still under-exploited.

The North Coast of West Java

Area

For the purpose of this Workshop the term "north coast of West Java waters" refers to the sea area of the coastal zone down to 20 m depth (isobath 20 m) for demersal resource grounds and up to 30 miles (48 km) offshore for pelagic resource grounds. These limitations are related to the operational fishing capabilities of existing fishing units, especially those of trawlers and purse seiners.

The surface area of the north coast of Java waters is estimated to be 3,400 square miles (8,840 km² ); thus, the north coast of West Java is approximately one third of the total, or 1,100 square miles (2,860 km²). It belongs to the Provinces of West Java and the Jakarta Metropolitan Administration.

Depth and type of bottom

The area under consideration is limited by the 20 m isobath. The oceanographical conditions are those of the Java Sea as a whole, the bottom sediment consisting partly of thick grey mud, and partly of sand, with gravel, coral, and rocks in island areas (Emery et al. 1972).

Meteorological and oceanographical conditions

Coastal waters are under the direct influence of the east and west monsoons. The first lasts from June to September and the second from December to March. The east monsoon produces a current which flows westward, but during the west monsoon the current runs from the South China Sea with a speed of approximately 1.5 knots along the north coast of Java eastward, and through Sunda Strait to the southwest (Emery et al. 1972).

The results of the R. V. Mutiara-4 surveys show that the temperature of the surface layer ranged from 21 to over 30 C. There is no thermocline in shallow waters, and salinity goes down to 20‰ in the nearshore zone due to river discharge ( Emery et al. 1972) .

The Fishery Resources

Demersal

The data available on trawl catches of the R. V. Mutiara-4 show that the demersal fishes comprise a large number of species. Preliminary analyses of the catches indicate that in some communities, such as those of ponyfishes, Lelognatbus splendens occurs inshore while L. elongatus is found mainly offshore.

The demersal fishes here are defined as fish species caught by demersal gear (Table 1).

Table 1. List of Demersal Fishes

Source: Report of the Workshop on Demersal and Pelagic Fish Resources of the Java Sea. 5 - 9 December 1978, Semarang, Indonesia. South China Sea Fisheries Development and Coordinating Programme, Manila, Philippines, SCS/GEN/79/20 (Revised).

The exploitation of demersal resources has developed rapidly in the last six years through the use of trawlers, but the majority of the fishermen are still using traditional gear, such as traps, bottom gill-nets, handlines, lift nets (began), danish seines (dogol), and beach seines. Trawlers are of small size (20 GT) with an average of five days' fishing per trip, operating in waters less than 30 m deep. The total catch of demersal fishes by demersal gear in 1977 was more than 20,000 tonnes.

There has been an increase of 67 per cent in the demersal fish landings in recent years, due to the increased number of trawlers entering the fishery concentrated mainly in Cirebon.

Extensive demersal-resource surveys in the Java Sea were conducted by the Indonesian-German demersal fisheries project using the R. V. Mutiara4 in the period 1974 - 78. The vessel is a wooden stern trawler of 100 GT. Due to the vast area covered the data are still far from complete, but they provide useful information for the demersal fishery development programme and necessary management measures.

The catch rate is considered to be an index of abundance; therefore changes in the catch rate indicate changes in fish abundance. There are two sources of data available to study changes in the fish stock, the catch-rate data collected by the research vessel R. V. Mutiara-4 and data of fish caught on the north coast of Java. The results of the R. V. Mutiara-4 survey gave a catch rate in 1976 of 189 kg/hour with stock density of 2.8t/km²; in 1977 it was 133 kg/hr and 2.0 t/km², and in 1978 102 kg/hr and 1.5t/km². Estimation of abundance based on fishery data analyses recently made by Sujastani (1978) and Dwiponggo (1978) on demersal resources gave the values of maximum sustainable Yields (MSY) as 63,000 tonnes and 57,000 tonnes, respectively. It should be mentioned that these data refer only to the areas off the north coast of Java. For the area off West Java, the MSY figures could be roughly one third of these. The latest catch data will be important for evaluating the state of exploitation, since the last recorded catch (1977) is slightly under the MSY level.

Shrimp species in the catch from this area consisted of:

1. Udang jerbung (banana prawn, Penaeus merguiensis)
2. Udang dogol (endeavour shrimp, Metapenaeus ensis)
3. Udang cendana (Yellow-white shrimp, M. brevicornis)
4. Udang putih (white shrimp, P. indicus)
5. Udang windu (jumbo tiger prawn, P. monodon)
6. Udang windu (Bago) (tiger prawn, P. semisulcatus)

There were also other species of endeavour shrimp (Metapenaeus spp. and Parapenaeopsis spp.).

Table 2. Pelagic Catches off the North Coast of West Java [tonnes) 1973 - 77

Source: Report of the Workshop on Demersal and Pelagic Fish Resources of the Java Sea, Semarang, 1978.

Sujastani (1978) calculated the MSY of shrimp from the waters of the north coast of Java as 3,200 tonnes, whereas the actual catch is around 2,500 tonnes. However, in view ol the natural fluctuations of shrimp stocks, this level of exploitation could be considered high.

Pelagic

The number of species of pelagic fishes is great. However, only the so-called economically important species in the landings have been identified to the genus level. There is some information at species level on the chub mackerel or kembung (Rastrelliger brachysoma and B. kanagurta)..

Information on stocks in the area is not Yet available. The fish stocks in the Java Sea have not been well studied except for kembung, and a hypothesis concerning west and east monsoon stocks of round scad or layang (Decapterus spp.).

The pelagic species that are commercially important belong to the Clupeids, the Carangids, and the Scombrids.

Owing to present circumstances the following group of species could be considered as separate stocks:

1. Layang (round scad, Decapterus spp.)
2. Kembung (chub mackerel, Rastrelliger spp.)
3. Tenggiri (spanish mackerel, Scomberomorus spp.)
4. Tongkol (little tuna, Euthynnus spp.)
5. Selar (trevallies, Caranx spp.)
6. Tembang (sardine-like fishes, Sardinella spp.)
7. Teri (anchovies, Stolephorus spp.)
8. Japuh (sprats, Dussumiera acute)
9. Other Clupeids

The inshore fishery catches are dominated by Clupeids and sardine-like fishes such as Sardinella fimbriate and S. sirm, caught mainly by gill nets and surface danish seines (locally called payang). In light fishing with lift nets, which is being discouraged by the government, the dominant catch is anchovies and mysides (reborn). The catches offshore are round scads, chub mackerels, and little tuna with purseseine, and lampara using fish lures (rumpon) and gill nets.

The development of pelagic fishery has significantly increased in the last five years due to the use of more effective gear, mainly purse seines (introduced in 1970) and the improvement of payang performance ( payang-ampera) and lampara.

The purse-seine fishery started to develop in Central Java in 1971 and spread out into the Java Sea. The vessels in use are wooden boats of around 20 GT with 80 - 120 HP.

The pelagic fish catch of the north coast of Java in 1977 was 157,000 tonnes (from the north coast of West Java it was 55,300 tonnes) with a 7 per cent increase per year since 1975.

An analysis of the relationship between catch and effort to calculate maximum sustainable yields (MSY) is possible for the north coast of Java waters (30 miles [48 km] offshore). It shows that the level of exploitation is in a developing stage with an estimated MSY of 190,000 tonnes (Report 1979). Therefore, for the north coast of West Java proper the MSY level should be around 63,000 tonnes.

Table 3. Percentage of Total Catch by Type of Gear off the North Coast of West Java

Source: Report of the Workshop on Demersal and Pelagic Fish Resources of the Java Sea, Semarang, 1978.

The general conclusion is that the potential catch of pelagic resources is now higher than it was in 1977.

Management

Demersal fishes of the north coast of West Java are being taken by trawlers and traditional indigenous fishing gear Trawl fishery is not based only on finfish; its economic viability depends to a greater extent on shrimp.

The shrimp grounds are in the nearshore areas, where the local fishermen using traditional fishing gear have been exploiting these coastal resources for years. Conflict of interests, therefore, has emerged in some regions due to this overlapping of fishing operations. In order to avoid serious problems of social friction in the fishing community, the government is enforcing the Ministry of Agriculture Decree of 1975, which limits the operation of trawlers bigger than 25 GT to an area 7 miles (11 km) out and seaward. The effective implementation of this regulation requires time to allow the information to spread, and understanding by the fishermen involved. The fishing community need to be convinced that the measures are necessary to sustain their resources.

The management measures in the Ministry of Agriculture Decree of 1975 are generally closures of fishing grounds, such as exclusion from certain coastal strips of fishing vessels exceeding particular sizes and horsepowers. These were introduced to protect the small-scale fishermen using traditional gear and sailing boats, but it is unlikely that they will serve to protect the juveniles and small fishes in the nursery grounds since some of the traditional gear, such as scoop nets, traps, and push nets, is capable of destroying large numbers of small individuals Any increase in the number of traditional gear that takes juveniles should be discouraged and further extension of its use should be prevented (Report 1979).

A mesh-size limitation exists to regulate the fishing of some pelagic as well as demersal resources (e.g., trawl cod-end mesh-size regulation). The mash size of purse seine for chub mackerel, round scad, trevally, sardines, and other pelagic species should be not less than 55 mm for the wing side and not less than 25 mm for the bunt (Ministry of Agriculture Decree No. 607, 1976). There have been complaints by fishermen that the implementation of this regulation led to difficulty in using larger mesh size by taking off gilled specimens.

Because of the wide range of species involved, differing in size, shape, and value, difficulties arise in determining the optimum size for mesh-size limitation measures. The implementation of management measures should therefore be carefully monitored in order to adjust the existing regulations when required. Further investigation, by means of selectivity experiments, should be carried out.

References

Dwiponggo. A. 1978. Status of demersal fisheries on coastal areas of the Java Sea-potential and stage of effort. Paper presented at the Symposium on Modernization of Small Scale Fisheries. Jakarta, June 1978.

Emery, K. 0.; Uchup; J. Sunderland; H. L. Uktolseja; and E. M. Young 1972. Geological structure and some water characteristics of the Java Sea and adjacent continental shelf. United Nations ECAFE, CCOP Techn. Bull. vol. 6.

Report of the Workshop on Demersal and Pelagic Resources of the Java Sea (Semarang, Indonesia, 5 - 9 December 1978) 1979. Prepared by R. B. Buzeta, A. Dwiponggo, and T. Sujastani, SCS/GEN/79/20, South China Sea Fisheries Development and Coordinating Programme, Manila, 1979.

Sujastani, T. 1978. Calculating stock size of fishery resources of the Java Sea based on statistical data of the regional fisheries. Paper presented at the Symposium on Modernization of Small Scale Fisheries,Jakarta, June 1978.

Discussion

Soegiarto: Does the amount of MSY (55,000 tonnes) denote the catch or the quantity landed?

Sujastani: The figure was the official figure after making some corrections (by adding 10 - 15 per cent) to evaluate the catch, because the above-mentioned figure is the landing data.

Soegiatro: How about the activities in developing aquaculture such as tambak?

Sujastani: The development of aquaculture in North Java should have first priority. We are asking the Japanese to develop mariculture of oysters and cockles.

MacDonald: Your data on MSY of pelagic fishes suggest there should be anxiety about over-fishing.

Sujastani: Pelagic fishes are migrating species, and so the catch is unlikely to reach the MSY. Regarding the demersal fish, the government is going to limit the activities of fishing, with some limitation on the number of trawlers and fishing areas, and suggest that people develop aquaculture.

Siregar: What about the source of protein for West Java?

Sujastani: According to the statistics the population of West Java obtains its protein from Bagan Siapi-Api. How to overcome this problem is one of the main tasks of the government.

Ilahude: I suggest the speaker make some corrections in using the term MSY, using Optimal Sustainable Yield instead of the MSY.

Sujastani: To meet Indonesian socio-economic conditions it is better to use MSY than OSY for various reasons. If we use OSY there is a tendency that the only people who get the benefits are the owners, but this is not so for MSY.

Thayib: Aquaculture programmes (oysters for example) are welcome, but water conditions have to be checked beforehand for the purpose because of the pollution problem. Do you have any data?

Sujastani: We do not have complete data, but based on experience, the Pamanukan area is better than Banten Bay for mariculture.

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