PART III
BACKGROUND PAPERS

EXPERIMENTS ON THE POLYCULTURE OF SEAWEED, SHRIMPS AND MILKFISH

I Nengah Sutika and Syamsu Alam Ali
University of Hasanuddin, Ujung Pandang, South Sulawesi

ABSTRACT

The polyculture of seaweed (Gracilaria) together with milkfish and shrimps (P. monodon) was tested in 0.1 ha experimental brackishwater ponds using 250 milkfish fry only, 150 milkfish fry plus 2,000 shrimp fry; and 2,000 shrimp fry only. Three different substrates for seaweed were also tested in each pond: direct planting on the pond bottom; off-bottom culture using nets; and off-bottom culture using bamboo screens. Best seaweed was obtained when cultured off-bottom using bamboo screen at 3,121.4 kg/ha/year as against 2,672.9 kg and 1,659.5 kg for net substrate and direct bottom culture respectively. Better survival were obtained for shrimps grown with seaweed only (56%) than when grown with milkfish and seaweed (51.6%) There seems to be no difference in the final size attained (29.16 g vs 30.4g). On the other hand there seems to be no difference in milkfish survival with or without shrimps (53% vs 52%) but growth appears to be affected by the presence of shrimps at 404 g average weight versus 443 g without shrimps. However all the results are indicative only and cannot be tested statistically due to lack of replication.

1. INTRODUCTION

1.1 Background

Seaweed is one of the non-oil commodities which has a big potential for the Indonesian economy because of the expanding export market. As the result of the development of industrial technology, the usage of seaweed is not limited to food, but has expanded to the manufacture of medicine, cosmetics, textile, beverage, canned food, etc.

The development of the seaweed culture industry is not limited to coastal areas. Seaweed may also be cultured in brackishwater ponds with shrimps and milkfish, since in nature some seaweed species grow in brackishwater areas.

Since the area of brackishwater ponds is fairly wide, it is hoped that this culture system can significantly increase the area available for seaweed farming and in so doing also increase the value of tambak production when done in polyculture with shrimps and milkfish.

1.2 Objective

The aim of this experiment is to investigate the growth and production of each of the organisms cultured together, i.e., seaweed, shrimps and milkfish. The result of the experiment is expected to provide information for fish farmers in order to increase their income, develop seaweed culture, increase non-oil commidity export and help in the conservation of seaweed resources.

2. METHOD

2.1 Method of Experiment

The experiment was carried out for three months (from October 1987 to January 1988) at the Talaka Village, Pangkep, South Sulawesi. The area of the experimental pond used was 0.3 ha which was divided into three compartments of 0.1 ha each in order to try 3 treatments as follows:

Three ways of planting the seaweed were compared in each pond: off-bottom using net substrate, offbottom using bamboo screen substrate and direct planting on the pond bottom.

2.2 Data Analysis

The growth rate of seaweed is calculated using the following formula:

G = growth rate
Wt = weight at every age observation
Wo = weight at the time planted
t = time

The production of the seaweed per hectare per year was calculated from the average of daily growth rate. Whereas the production of shrimps and milkfish were computed from the average of absolute growth and the survival rate.

3. RESULTS AND DISCUSSION

3.1 Seaweed

The best daily growth rate of seaweed (G) was obtained from those planted on the bamboo screen which showed an average growth rate of 3.09% for the three treatments (Table 1). This was followed by those planted on the net substrates at 2.36%. Table 1 shows the daily growth rate using different substrates and stocking system.

To estimate seaweed production on a per-hectare basis, it was assumed that in a one-hectare pond only 25 per cent of the area will be utilized for seaweeds. Using the average daily growth rate, it is estimated that it is possible to harvest about 3,000 kg seaweed per hectare using bamboo screen substrates as shown in Table 2.

It appears that the yields obtained per hectare is high enough to provide additional income to tambak farmers. The yield may be increased by increasing the percentage of area planted above the 25% used in this study, however this needs follow-up.

3.2 Shrimps and Milkfish

The harvest size, survival rate and production of both shrimps and milkfish are presented at Table 3. The highest shrimp production of 340 kg/ha/cycle was obtained in treatment C (seaweed + shrimps), while the highest production for milkfish was 572 kg/ha/cycle in treatment A (seaweed + milkfish). Overall, this experiment indicates that either shrimps or milkfish grow well when cultured together with Gracillaria. Ecologically it is known that seaweed supplies both oxygen and food, furthermore seaweed may also be important as shelter especially when the temperature is high.

3.3 Water Quality

Water quality during the experiment was within the range considered suitable for shrimps, milkfish and Gracillaria. Water temperature ranged from a minimum of 28°C to a maximum of 31°C, salinity 7 to 37%., pH 7.8–8 and dissolved oxygen 5.6–6.4 ppm. The high salinity of 37 ppt which already approaches the maximum tolarable for Gracillaria occurred only during the first week, but gradually decreased as the rainy season started. This may be the reason that the growth of seaweed was observed to be slower during the first week of the experiment.

4. CONCLUSION AND RECOMMENDATIONS

4.1 Conclusion

1. The highest growth rate of Gracillaria was obtained by using bamboo screens as substrate at an average growth rate of 3.09%.
2. Using bamboo screen substrates, the highest production of Gracillaria was obtained if cultured together with both shrimps and milkfish with production estimated at 3,296.2 kg/ha/year.
3. The highest shrimp production was obtained when stocked with Gracillaria only, with an average final weight of 30.4 gr, survival rate of 56% and projected production of 340 kg/ha/year.
4. The highest milkfish production was obtained when this was cultured together with Gracillaria only at an average final weight of 443 kg, survival rate of 52% and projected production of 572 kg/ha/year.

4.2 Recommendations

1. The seaweed, Gracillaria lichenoides, should be cultured in a tambak with salinity range between 10 to 30 ppt and water that is clear enough for sunlight to reach the seaweed.
2. It is best to culture the seaweed using bamboo screens or net substrates, especially in tambak with deep mud substrate.
3. The seaweed may be planted directly on the bottom of the tambak if the bottom is sandy-mud.
4. Seaweed seedstock should be free from other algae or washed with clean tambak water.
5. The proper surface area of the tambak to be allocated for seaweeds should be determined in order not to disturb the growth of the shrimps or milkfish stock.

5. REFERENCE

Anonymous. 1973 Food from the sea (in Indonesian). LON, LIPI, Jakarta.

Anonymous. 1978 Seaweeds, uses, potentials and culture methods (in Indonesian). LON, LIPI, Jakarta.

Atmaja, S.W.1978 Identifying seaweed species for culture (in Indonesian). Pewarta Oceana IV (3), Jakarta.

Gomez Edgardo, D.1981 Potential for polyculture of Gracillaria with milkfish or crustaceans. Report of the training course on Gracillaria algae. South China Sea Fisheries Development and Coordinating Programme. Manila, Philippines, pp. 91–93.

Trono Gavino, C. 1981 Pond culture of seaweeds. Report of the training course on Gracillaria algae. South China Sea Fisheries Development and Coordinating Programme. Manila, Philippines, pp. 47–50.

Table 1. Daily growth rate (G) of seaweed using different substrates grown in polyculture with shrimps and/or milkfish.

Note: A = Gracillaria lichenoides + milkfish
B = Gracillaria lichenoides + P. monodon + milkfish
C = Gracillaria lichenoides + P. monodon

Table 2. Projected annual per hectare production of seaweed in earthen ponds in polyculture with shrimps and/or milkfish based on experiments in 0.1 ha experimental ponds.

Table 3. Average harvest size, survival rate and projected per hectare yield of shrimp and milkfish cultured with seaweeds.

Notes: A = Gracillaria lichenoides + milkfish
B = Gracillaria lichenoides + P. monodon + milkfish
C = Gracillaria lichenoides + P. monodon

EXPERIMENT ON LOBSTER PROPAGATION

M. Natsir Nessa and Aspari Rachman
University of Hasanuddin, Ujung Pandang, South Sulawesi

ABSTRACT

Two species of lobsters were used for this experiment, Panulirus longipes and P. ornatus. Berried females caught from Makassar strait were brought to a penacid hatchery for incubation, hatching and larval rearing. The P. longipes spawner, measured 28.6–30.1 cm and weighed 0.76–0.88 kg, while the P. ornatus 38.2–46.8 cm and 2.96–3.84 kg. Fecundity ranged from 608,379 to 834,192 eggs for P. longipes and 807,286–982,872 eggs for P. ornatus. The incubation period was 16 days for the P.longipes and 20 days for P. ornatus, and hatching rate 96.49% and 98.50%. The phyllosoma I larvae developed into phyllosoma II ten days after hatching, during which a mortality rate of about 49% occured. The phyllosoma II larvae were released into the sea. Salinity, temperature and pH was 35–36 ppt, 28–29°C and 7–8 respectively during the incubation period and larval rearing period using a flow-thorugh system with vigorous aeration in cylindrical concrete tanks, 1.5 m in diameter and 1.0 in depth.

1. INTRODUCTION

1.1 Background

In Indonesia the spiny lobster is not yet very popular and has just been newly exploited in certain areas such as Aceh, Riau, East Java, Bali, South Sulawesi, Maluku and Irian Java. In these provinces lobsters are being caught by fishermen to supply restaurants as well as exporters. This commodity is not far behind tiger shrimps in importance because every year the demand keeps on increasing in importing countries such as Japan, Hongkong, United States, Singapore and some European countries. Furthermore the number of countries interested in lobster continues to increase.

Based on fisheries statistics from 1971 to 1985, the production of lobsters appears to be declining even if on the other hand its value has increased. The decline in production is probably due to the destruction of its habitat so that the animals are forced to transfer to other areas where the coral reef is still in good condition forcing the population to spread to deeper areas far from the coast so that fewer are caught. Meanwhile, this species has not yet been propagated or cultured in captivity.

In order for the decline in production level to be halted and the availability of lobster stock assured so that its export can be increased, there is a need to conduct research on lobster propagation. It is hoped that through propagation, enough seed lobsters can be made available both for restocking the sea and for grow-out operations.

This experiment is aimed at determining methods of spawning/hatching the spiny lobster in order to culture them in captivity as well as for marine conservation purposes.

2. REVIEW OF LITERATURE

In Indonesia there are 6 species of lobster, namely Panulirus homarus, P. penicellatus, P. longipes, P. polyphagus, P. versicolor and P. ornatus (Mooasa and Aswandy, 1984). These species are spread in 21 provinces.

In contrast with other shrimp species, the lobster has a fairly long life cycle. The age at first maturity is estimated at 5 to 8 years depending upon the species. Gravid spawners are easily recognizable because the eggs are carried on the abdomen among the swimming legs or pleopods. The eggs are orange in color during the initial phase and occur in clusters like grapes. The color changes to brownish black during the final phase and each egg hatches after a black spot has appeared on the surface of the egg. The eggs hatch in unison after a few hours depending upon the water temperature.

The fecundity varies depending upon the species and size. For example, P. homarus has a fecundity of about 275,000 eggs. Other species with a carapace length of 117 mm can have as much as 529,000 eggs and larger individuals can have fecundity ranging from 500,000 to a few million.

3. PROCEDURE

3.1 Site and Duration

The experiments were conducted at the PT Petro Utama Teknik shrimp hatchery located in Tanjung Bira, Bulukumba Regency, South Sulawesi, during a 4-month period from September to December 1988.

3.2 Experimental Animals

Two species of lobsters were used, P.longipes and P. ornatus. The spawners were caught from the waters of Makassar Strait. The spawners used measured 28.6–30.1 cm with a weight of 0.76–0.88 kg for P.longipes and for P.ornatus 38.2–46.8 cm and 2.96–3.84 kg. Both species were already berried when collected, with the eggs still in orange color. The fecundity ranged from 608,379 to 834,192 eggs for P.longipes and 807,286 to 982,872 for P. ornatus.

3.3 Culture Tanks

The tanks used were cylindrical in shape and made of cement with a diameter of 1.5 m and depth of 1 m.

3.4 Culture Method

The first step involved the disinfection of the spawners using malachite green (oxalate) solution at 5 ppm for 10 minutes. The disinfected spawners were then transferred to the incubation tanks which have been previously disinfected. Water depth was set at 89 cm and was made to flow-through.

During the incubation period, strong aeration was provided. The spawners were fed 4 times a day at the rate of 15–20% biomass per day. Fresh feed were used consisting of Tridacna clam meat, squid (Loligo) and fish. The eggs were regularly examined under the microscope to monitor embryological development. When the yolks were observed to be almost consumed, the spawners were carefully transferred to the hatching tanks. Strong aeration and flow-through water supply continued to be provided during the hatching phase but the spawners were no longer fed.

When the eggs were observed to have hatched, the spawners were removed and the water level increased so as to reduce the larval density. The incubation period, changes in the egg appearance, hatching rate were noted and the temperature, salinity and pH of the water regularly monitored.

4. RESULTS AND DISCUSSION

The incubation period for the two lobster species were 16 days for P.longipes and 20 days for P.ornatus. Based on gross visual inspection of the eggs, there did not appear to be any differences in development for the eggs located in the anterior, posterior or central part of the abdomen. All the eggs changed in color uniformly regardless of their location. The same is true with the yolk condition. No diseases were observed to infect the eggs during the entire period. This is probably because the water used was sterile enough.

The embryonic development was evident in the change in egg color and in the development of the black spot on each egg which is indicative of the different organs in the embryo. The change in color is due to the change in the amount of egg yolk. The change in egg color occurred together with the increase in size of the black spot. From the first to the fifth day of incubation, the eggs still appeared orange in color and the black spots were not yet clearly visible. On the 6th day, the black spot became more visible and grew in size until the 14th day. The egg color changed from orange to reddish-yellow or brownish and the amount of yolk decreased. Two to six days later, the eggs have changed to brownish-black for P.longipes but yellowish-black for P. ornatus. At this time only very little egg yolk was left and were concentrated towards the centre of the eggs. With this condition, the embryos started to move and some parts of the body such as the walking legs started to become visible and became clear and pale in color. As the egg yolk was consumed, the movement of the embryo became more active and finally the eggs hatched with the posterior part (walking legs) appearing first. The hatching rate for both species were quite high at 96.49% and 98.50%, and the eggs hatched in mass.

The newly hatched larvae were very active. The walking legs which were very much longer than the body moved like those of spiders. The larvae or phyllosoma appeared to have a slow growth rate when compared to that of the tiger shrimp larvae. Changes in the organ started only on the 5th day and up to the 10th day did not show any development.

Mortality rate was very high during the molting as the larvae metamorphosed from phyllosoma I to phyllosoma II. The mortality was as high as 44% for P. longipes during this stage. Although on a relative scale the mortality rate of the two species did not appear to vary, there was a higher density of P. ornatus larvae when compared to P.longipes. This was maintained up to the time the larvae were released to the sea.

The water quality was kept as constant as possible during the incubation period with the salinity level at 35–36 ppt, temperature at 28–29°C and pH at 7–8. This condition was maintained until the larvae attained phyllosoma II at which time these were released in the sea.

CONCLUSION AND RECOMMENDATION

5.1 Conclusion

1. The lobster, P. longipes and P. ornatus can be propagated in a penaeid shrimp hatchery.
2. The incubation period is 16 days for P. longipes and 20 days for P. ornatus.
3. The hatching rate for both species are high at 96.49% for P. longipes and 98.50% for P. ornatus.
4. The water quality for hatching requires a salinity of 35–36 ppt, temperature of 28–29°C and pH of 7–8. Water has to be clear and sterile and strong aeration has to be provided.

5.2 Recommendation

1. There is a need to continue the research to determine how to culture the lobster larvae, especially to determine the suitable feed for the larvae.
2. There is a need to establish special hatcheries for lobsters in specific locations such as within coral reef islands so as to facilitate restocking of these environments and in order to increase the production level of lobsters.

6. REFERENCES

Cobb, J.S. and B.F. Phillips. 1980 The biology and management of lobster, Volume I and II Academic Press, New York, London, Toronto, Sydney and San Franscisco, 853 pp.

Grzimek, B. 1970 Animal life encyclopedia Vol. I. Van Nostrand Reinhild Company, New York, p. 770.

Imanto, P.T. dan W. Ismail. 1988 Status of spiny lobster fishery in Indonesia (in Indonesian). Seminar paper, 10 pp.

Moosa, M.K. dan I. Aswandi. 1984 Lobsters (panulirus spp.) In Indonesia waters. (In Indonesian) Lembaga Oceanologi Nasional, LIPI, Jakarta, 40 pp.

Philips, B.F.. G.R. Morgan and C.M. Austin. 1980 Synopsis of biological data on the western rock lobster, Panulirus cygnus, George. FAO Fish. Synopsis (128), FAO, UN, Rome, p. 64.

Pirzan. 1988 Some aspects of lobster (Panulirus spp.) biology in Majene waters, South Sulawesi (in Indonesian). Thesis in Fisheries Resource Management, Fisheries Department, Faculty of Animal Husbandry, University of Hasanuddin, Ujung Pandang, 41 pp.

Rachman, A. dan Najamuddin. 1988 Biology, capture and development possibilities of lobsters (in Indonesian). Seminar Ilmiah Berkala Staf Pengajar Fakultas Peternakan, Jurusan Perikanan, Fakultas Peternakan, Universitas Hasanuddin, Ujung Pandang, 6 pp.

Soekarno, M. Hutomo, M.K. Moosa dan P. Darsono. 1983 Coral reef in Indonesia, resources, problems and management (in Indonesian). Proyek Penelitian Potensi Sumberdaya Alam Indonesia, LON, LIPI, Jakarta, 109 pp.

THE SHRIMP CULTURE SUBCENTRES AS REGIONAL CENTRES FOR BRACKISHWATER AQUACULTURE

Noor Hamid
Takalar Shrimp Subcentre, South Sulawesi

ABSTRACT

The Takalar Shrimp Culture Subcentre is an UPT of the Directorate General of Fisheries which is administratively under the Provincial Fisheries Service of South Sulawesi and technically under BBAP Jepara. The subcentre organization consists of hatchery section, culture section, environment section, technology transfer section along with an administrative section. The Subcentre has been tasked with brackishwater aquaculture technology development as well as with reaching out to the rural areas. Technology development includes development of new techniques and refinement or modification of existing technology. Aside from this the Subcentre also provides specialized services such as provision of algal starter culture, spawners, nauplii and shrimp fry; water quality monitoring; disease diagnosis/management and technical assistance.

1. INTRODUCTION

Development activities in the fisheries subsector still has to be accelerated in order to attain its objective of improving the living standards of fish farmers and fishermen. Under technology development, activities are directed towards developing an applied technology package which can reach farmers and fishermen. The production of technology packages and their dissemination is a programme of the Directorate General of Fisheries (DGF) through the Technical Management Units (UPT).

One important activity is the development of brackishwater aquaculture technology that can be immediately disseminated to, and applied by, farmers and fishermen. On the national level, the technology development programme is being executed by BBAP Jepara. The said technology development consists of technology testing, dissemination, training and field trials. In view of the fact that Indonesia is so wide, development in the various regions need to be made more specific to each site, hence the need for regional development centres.

In order to fill such need, regional development units were formed to provide technical services as well as development and technical guidance in brackishwater aquaculture. These regional units can also serve as testing centres for various technologies. One result in the implementation of the regional units is the Shrimp Culture Subcentres which were developed in stages in Aceh, East Java and South Sulawesi.

The Subcentre project in South Sulawesi was built the earliest and is already operational. The said project was built in Bontoloe Village, in the Subdistrict of Galesong Selatan, Takalar Regency.

2. ORGANIZATION AND FUNCTION

The shrimp subcentre at this time is still considered a project. Administratively it is managed by the South Sulawesi Provincial Fisheries Office and technically it is under BBAP Jepara.

The Subcentre will eventually be developed as part of the structural and functional organization in order to handle development activities and in order to be able to rapidly respond to technical problems which may arise. (Figure 1)

As a Technical Implementation Unit of the DGF, the Subcentre is to implement development activities in brackishwater aquaculture in terms of technological development as well as for reaching out to the rural areas. (Figure 2)

Regional development requires site specific adjustments in terms of the terrain, potentials, manpower and financing. Because of this, the Shrimp Culture Subcentre is to develop technologies that are suitable to the region.

Technology development also means a technology transfer programme that is to be implemented through training, publication, translation, demonstration and others. The Takalar Subcentre shall hasten the technology transfer process through methods that can easily be applied by the community based on their level of education and knowledge. The technology transfer process shall also be done through technical guidance including provision of technical service. Laboratory facilities, technicians and technical publication are used to fill the need of the tambak community. For shrimp hatchery, the Takalar Subcentre can provide specialized services in terms of providing algal starter cultures, spawners, nauplii, shrimp fry, water quality monitoring, disease diagnosis/management and technical assistance. Ultimately the Subcentre will become a kind of clinic for the shrimp hatcheries within the area.

Qualitatively, technological development means creating new technology and refining or modifying existing technology. For this technological research and experiments are required. One important activity of the Takalar Shrimp Culture Subcentre is to conduct technology trials. Materials that will be used will include research results from research institutes and universities or even from other countries. The output will be applied technology. (Figure 3)

3. ACTIVITIES AND MANPOWER

According to the master plan of the South Sulawesi Provincial Fisheries Service, the development of the Takalar Shrimp Subcentre is to be done in stages. In 1987 the basic facilities were already completed. Since 1987 the Subcentre started to operate, mainly in terms of shrimp hatchery operation. The said activity continues to be funded by the national budget under the Increased Fisheries Production Project in South Sulawesi. (Table 1)

In order to implement the subcentre activities, personnel consisting of both structural and functional staff will be required. The structural staffing needs at least 20 persons. Meanwhile, the number of personnel under the functional staffing will be based on need. Table 2 lists the required personnel for the Takalar Shrimp Culture Subcentre. Meanwhile the working groups are listed in Table 3.

Table 1. Implementation of APBN project in connection with the activities of the Takalar Subcentre according to its functions.

Table 2. Manpower complement of Takalar Subcentre according to the master plan of the South Sulawesi Provincial Fisheries Service, 1984.

Table 3. Assignment of work in Takalar Subcentre.

Figure 1. Organizational structure of Takalar Subcentre.

Figure 2. Area of responsibility of the three subcentres.

Figure 3. Flow of input to the Takalar Subcentre.

TAMBAK INTENSIFICATION FROM THE FARMER'S POINT OF VIEW

Ma'sum
Tambak Mina Jaya, Pati, Central Java

ABSTRACT

The tambak intensification programme was accepted enthusiastically by farmers. However, not all of the farmers are able to join the said programme because of their limited capital. The limited capital and the risk of failures make the farmers inclined to select a culture system with low working capital requirement but with high returns. Thus many farmers stock at a low density and rely on natural food. The experience of farmers is that lower stocking density results in bigger shrimps at harvest which command higher prices. One problem often encountered by farmers is the lack of good canal systems capable of removing waste water from the tambak. Also some canals may also be polluted with wastes from industries. These problems should be given the same importance. While the industries need to operate, the tambak requires good quality seawater.

1. INTRODUCTION

Various government programmes intended to accelerate development and are directed towards high economic growth and national stability have already been implemented and are running well. In turn the public has responded favorably. The farming community as beneficiaries of all intensification programmes have also responded very enthusiastically. With the existing condition the farmers are already thinking hard. Thinking logically based on their educational level and within the limits of what they possess, the farmers are determined to adjust themselves to the new conditions. The suggestions that have emerged during various opportunities appear to be stimulating. Formal and informal meetings and group discussions appear to have been beneficial.

This paper was written based upon discussions with farmers with the hope that this would reach the attention of various parties concerned. Due to limited knowledge and experience, this writer would like to apologize for the shortcomings of this paper. This writer, therefore welcomes all comments from the other participants. It is hoped that this Workshop shall be successful in meeting the expectations.

2. FARMERS AND THE TAMBAKS BEING OPERATED

In this paper in order to determine whether a tambak is traditional or not it is necessary to group the farmers separately from the tambak that each of them operates, as follows:

2.1 Traditional Tambak Farmers

Traditional farmers are those who operate their tambaks following old methods that have been handed down from one generation to another. Such farmers would continue to raise milkfish using klekapx, which are allowed to grow in the tambaks, as feed. Furthermore, such farmers would also allow the entry of extraneous organisms such as sergestids and fry of various fish species so that they can later become part of the harvest.

2.2 Modern Tambak Farmers

The modern tambak farmers are those who operate their tambaks using methods obtained from courses, books or by drawing on the experiences of others. Such farmers would adopt culture techniques which are more profitable and more efficient so that they eventually also would have better harvests.

2.3 Traditional Tambaks

Traditional tambaks are those with limited facilities. Such tambaks would have one gate which serves both for supply and drainage, one canal which serves as conduit for new as well as used water (Figure 1); and would have the excavation limited only to the peripheral canal areas.

2.4 Modern Tambaks

Modern tambaks are those with adequate facilities. Such tambaks would generally have two gates opening into separate canals, would have the entire pond bottom excavated and deepened to hold at least 1 m of water, Figure 2. Some modern tambaks may have no gates actually but would be equipped with supply and drainage pipes and would use a pump.

3. INTENSIFICATION

The degree of intensification varies, although basically all are aimed at producing better results. The bottom line is the rupiah value of the harvest.

For example in a tambak measuring one hectare and having a 4-month growing period, without considering the working capital, the income will be higher after intensification. Before intensification such a pond would probably gross only Rp. 500,000 using a working capital of Rp. 200,000, for a net income of Rp. 300,000. After intensification the same pond can yield Rp. 5,000,000 using a working capital of Rp. 4,000,000 for a net income of Rp. 1,000,000. The difference in the net income before and after intensification is Rp. 700,000.

However it should be considered that not all tambak farmers are able to have access to a large working capital. Due to the limited working capital as well as the higher risks involved in intensification, many tambak farmers have a tendency to adopt an attitude of “little capital, large production”. Because of this many farmers would stock at low densities and would depend only on natural food.

The following matters have not yet been resolved:

1. the optimum stocking density which can be supported by natural food organisms but which can yield the highest returns; and
2. the optimum stocking density for supplemental feeding which can yield the highest return.

The stocking densities applied at present are still in the trial and error stage.

4. EXAMPLES FROM THE FIELD

4.1 Case No.1

Bapak Waji stocked 10,000 P. monodon fry in a 2 ha tambak. The tambak had previously been prepared so that ganggang (general term for Chaetomorpha and Enteromorpha and aquatic plants growing in tambak such as Ruppia and Najas-editor). It was hoped that these algae and aquatic plants will serve as natural feed themselves or will provide a base for other natural food organisms to grow. Milkfish were also stocked together with the shrimps.

About 7,000 pcs of tiger shrimps were harvested weighing 540 kg which at a size ranging from 10 to 15 per kg, were sold at a average of Rp. 18,000/kg for gross sale of Rp. 9,720,000. The milkfish yielded 120 kg which grossed Rp. 197,000. Thus the total sales amounted to Rp. 9,917,000. With an operating cost of only Rp. 2,000,000 inclusive of tambak rental, the operation resulted in a net income of Rp. 7,917,000 during a 4month growing season. On per hectare basis, this means a net income of Rp. 3,960,000 with an operating capital of Rp. 1,000,000.

4.2 Case No.2

Bapak Dadap (not his real name) stocked 55,000 P. monodon fry in a 1.25 ha tambak. The fry cost Rp. 1,375,000; tambak rental Rp. 700,000 per year; and the rehabilitation cost Rp. 600,000. In the nursery, only 23,500 fry survived. During the growing period about 900 kg of supplemental feed and 300 kg of Acetes were used for a total feeding cost of Rp. 1,500,000. All in all the operational expenses including pumping cost amounted to Rp. 3,500,000.

At harvest the shrimps did not appear healthy with size ranging from 25 to 40 pcs/kg and were sold at an average of Rp. 9,000/kg. Of the 430 kg harvested about 60 kg were undersize. The gross sales amounted to Rp. 4,100,000. Thus the net income amounted to only Rp. 600,000.

4.3 Case No.3

Bapak Sakip (not his real name) stocked 40,000 P. monodon fry in his 1.5 ha tambak. During the growing period, he used 900 kg of supplemental feed which cost Rp. 1,500,000, pond repairs cost Rp. 500,000 and the shrimp fry Rp. 1,000,000. All in all the operating expenses amounted to Rp. 2,650,000 (the tambak did not have to be rented).

The harvest consisted of 690 kg of shrimps ranging in size from 25 to 40 pcs/kg and 35 kg undersized. The shrimps were sold at an average of Rp. 9,500/kg. Total sales amounted to Rp. 6,700,000. Assuming a tambak rental cost of Rp. 350,000 for one growing season, the net income amounted to Rp. 3,700,000 out of an operating capital of Rp. 3,000,000.

4.4 Assessment

From the above examples, the following observations are evident:

1. The lower the stocking density, the larger the shrimps harvested, and the higher the market price of the shrimps. (As of April 1989, Rp. 18,500/kg for size 15/kg vs only Rp. 6,500/kg for size 35–40).
2. At high stocking density the shrimps cannot grow to large sizes.
3. High supplemental feeding cost and low selling price means smaller profit margin.

One question which arises is why is the price of shrimps so low when the price of feed is fairly high? Another question is in intensified cultures what is the primary consideration-number stocked and volume harvested or net income in rupiah even if the number of shrimps stocked is low?

One challenge to some institutions or the government is to find ways to control the market or at least to find ways to be capable of managing the shrimp prices so it can be kept high and stable.

5. CANALS AND INDUSTRIAL WASTES

Canals for the tambak is analogous to the circulation system for human beings. Especially for P. monodon culture, the canal becomes a very important component. It is not an exaggeration to state that the canal system is the life of shrimp culture. This fact is understood very well by all farmers. Canals which are not able to channel water needed by the shrimp ponds can be destructive to the life of the shrimps.

The tiger shrimp has certain special characteristics, these are:

1. Sensitivity to its environment, i.e. pH, water temperature, salinity, dissolved oxygen and turbidity. In an environment which is not suitable, the tiger shrimps weaken easily, do not have appetite, are easily infected by diseases and if the poor condition of the water cannot be remedied immediately by changing with new water, the shrimps will get sick, weaken, and eventually die.
2. Tendency for cannibalism. If a shrimp becomes weak, it can be eaten by the healthier shrimps. Because of this, it often happens that a tambak which is well stocked will later turn out to have very few shrimps left with no other obvious way for the shrimps to disappear.
3. Investment and working capital requirement for shrimp culture are relatively high. The costs for seed, feed, operational and everything else are high. Because of this, failure does not mean merely loss of time but also means so much money wasted.

In an emergency situation, the canals should be capable of removing dirty water from the tambak and conversely conveying new water to the tambak.

5.1 Canals for Paddy Fields and Tambak

There is a clear difference between the requirements of paddy fields and tambak. Paddy fields require freshwater. If contaminated with saltwater, a paddy field is ruined and the rice plants die. Meanwhile tambak needs saltwater. Too much freshwater can result in shrimp mortality.

A row of paddy fields contiguous to a row of tambak served by only one canal can result in conflicts. Such a situation is shown in Figure 3. During rainy season, the canal is always filled with freshwater. The tambak will have difficulty in getting saltwater because the saltwater from the sea would probably not be able to flow inland due to the greater pressure of the freshwater flowing downwards to the sea. Tambak located in a higher elevation cannot obtain saltwater. Such condition is dangerous to shrimp culture.

Conversely during the dry season tidal water is able to go up the canal towards the direction of the paddy fields ruining the rice plants and making the paddy fields unusable for as long as the salt concentration remains at a certain level and is not yet washed away or greatly diluted by freshwater or rainwater.

In order to prevent the saltwater from reaching farther inland especially during the dry season, a control gate needs to be installed at a proper place along the canal. Figure 3 shows where such a control gate may be located. However during the rainy season this dam should not be fully closed in order to allow the rainwater to drain.

5.2 Industrial Waste Disposal

Industrial wastes can be toxic to shrimps. Chemical wastes can kill insects, microbial organisms, fish as well as shrimps. It is the usual practice of various industries to dispose of their wastes in the river or the sea. This is true for industries owned by individuals, companies and even by the government.

In principle, the disposal of industrial wastes which can pollute the environment should not happen. There are already rules governing such disposal which requires prior treatment. However in general these rules are not rigidly enforced. There are some factories which comply with such regulation to the letter but many comply only half-heartedly. Not a few also do not care at all about such matter. Will the government allow this to go on? Hopefully not. With all effort the laws ought to be enforced.

On the part of the offending factories, should they be closed? Certainly not. For the sake of its production target and its workers and their families, the factories should continue to operate. However a solution should be found.

Taking a sugar mill as an example, the production of sugar should proceed smoothly. However from time to time the sugar mill produces wastes. Such wastes pollute the environment, flows into the river, pollute the wells of the people, and kill river fishes. If such polluted river water is used by a tambak, the result is the mortality on the part of the shrimp stock. What can be done? For sure a solution has to be found. The farmers have to live, meanwhile the sugar mill should continue to operate so as to attain its production target. All of these are part of development. What are the alternatives?

5.3 Solving the Pollution Problem

Whatever the solution, it should be based on the principle that all sectors are equally important. The following actions are suggested:

1. Form a body or an institute to conduct research and development, to monitor, and to receive complaints regarding environmental problems.
2. Provide assistance to the factories in upgrading their waste treatment facilities.
3. Provide the means to protect or restore the environment in general and the agricultural environment in particular; set the direction towards a better farm management in the form of new canals including drainage canals for wastes as primary facilities for agricultural operation both for paddy fields and tambaks.
4. Improve the relationship and cooperation between the factories and the surrounding communities.

5.4 Some Expectations

On the part of both farmers and industries the following are expected:

1. The farmers by themselves in the spirit of gotong royong shall construct new canals or improve existing canals.
2. The polluting factories shall participate in the said canal construction/rehabilitation.
3. The factories shall equip themselves with the facilities to neutralize toxic wastes, and remove undesirable odors from their wastes.

6. KELOMPOK TANI

6.1 Dynamics of Kelompok Tani

Kelompok Tani or farmer's group is a vehicle for farmers' activities in the operation of their farms. The farmers feel bound informally in one field based on harmony and cooperation. One such group in Pati Regency is the Kelompok Tani Mina Jaya. This group was organized in 25 August 1986, has 93 members, and is within one KHUT unit covering 100 ha. Through discussions and deliberations, officials were selected to head its various sections, and its bylaws as well as house rules drafted and adopted.

On the 25th of each month the group manager and the members hold a routine meeting to plan out the work programme, deal with any problems and hold the arisan. This meeting is attended by the PPL who sets the direction. In order to support the farmers' activities each member is assessed a membership fee of Rp. 3,000, a monthly contribution of Rp. 1000 and another Rp. 50 monthly for the health fund. During harvest a member is also assessed a voluntary contribution of Rp. 1,000. The funds collected are kept by a treasurer and are used to lend out to members requiring emergency funds. The borrower has to pay back the loan in 6 months with a 5% monthly interest. As of this report, this fund has already reached Rp. 1,325,000. All members of the Mina Jaya farmers are also required to join the KUD, which in this case is the Tayu KUD I. For the purpose of acquiring services and farm inputs, a TPK has been formed.

6.2 Development of Infrastructure and Facilities

Immediately after the Mina Jaya farmers group was formed, the development of one infrastructure in the form of a 1.5 km, 4 m wide road to the coastline, was planned. The construction of the road was done by the tambak farmers themselves gotong royong style. The benefit obtained from the road was tremendous in terms of providing access to transport vehicles during stocking as well as during harvests. The same is true also of a canal for the supply and management of water according to the requirements of the tambak farmers.

In 26 December 1986, the Mina Jaya farmer's group hosted the 26th National Tree-Planting Week ceremonies for the Pati Regency. After the ceremonies, which was presided by the Pati Regent, 20,000 bakau trees were planted to reforest the coastline.

6.3 Farmers' Library

In order to improve the skills of the farmers, a library/information centre was formed. This houses reading materials on food crops, animal husbandry, horticulture, shrimp culture, fish culture and other related subjects. The reading materials were obtained from the Tayu Agricultural Extension Centre, Fisheries Service, Animal Husbandry Service and other offices. With this the farmers were given the opportunity to widen their knowledge within a short time.

6.4 Making Use of Tambak Dikes

After finding and absorbing information from the farmers' library, the tambak farmers by themselves started to apply their knowledge by planting their dikes with various horticultural crops such as red pepper, tomatoes, string beans and other vegetables, primarily during the rainy season. In a dike area of 6×50 m, a farmer can earn Rp. 150,000. This is additional income to what they can earn from raising shrimps.

6.5 Cadre Formation

In order for the activities and group development to proceed evenly and with continuity there is a need to form cadres within the group. Some 18 farmers have already joined cadre training programmes on various activities as follows:

1. Management, Ungaran - 2 persons
2. Aquaculture, UPBAP, Semarang - 6 persons
3. Cooperatives, BPP, Tayu - 2 persons
4. P4 Cadre, Tayu - 5 persons
5. Health, PUSKESMAS, Tayu - 3 persons

6.6 Group Discussions

In the course of tambak operation, farmers often encounter obstacles. For this, discussion groups consisting of 7 persons have been formed in various areas. These groups meet once a week. The discussions are presided over by a chairman, and are attended by the PPL and by any cadre available.

7. OPSUS INTAM IN CENTRAL JAVA

In order to increase production and tambak farmers' income the government has instituted the OPSUS INTAM programme. In Central Java, especially in Pati Regency, the programme has had a positive response from the farmers. Within the said location there are two farmer groups involved, these are the Kelompok Tani Muria in the Tunggul Sari Village and the Kelompok Tani Mina Jaya in Margomulyo Village, both in the Tayu Subdistrict. Together the two groups cover 110 ha and consist of 101 farmers.

In the implementation of this programme, the government provide technical guidance and capital in the form of OPSUS INTAM credit package. There are also farmers who are able to finance their own operation and are considered as self-financed members of the programme.

The OPSUS INTAM technology has been divided into two systems:

1. OPSUS INTAM A2, 7 ha with 6 farmers OPSUS INTAM Swadana A2, 9 ha with 5 farmers
2. OPSUS INTAM B2, 25 ha with 24 farmers OPSUS INTAM Swadana B2, 69 ha with 66 farmers

OPSUS INTAM A2 involves shrimp monoculture with a stocking rate of 40,000 PL-30 P. monodon fry per hectare, and a production target of 800 kg at a size of 30 pcs per kg. Meanwhile OPSUS INTAM B2 involves polyculture with a stocking rate of 20,000 PL-30 P. monodon fry and 1,500 milkfish fingerlings per ha, and a production target of 400 kg shrimps and 300 kg milkfish.

7.1 OPSUS INTAM Credit Package

To provide capital, the government has designated the BPD and the BRI as lending banks. The funds are channeled to the farmers following bank requirements in which the loan has to be paid back in 3 years (6 payments) with an annual interest of 12%. The credit amount is shown in Tables 1 and 2.

7.2 OPSUS INTAM Credit Realization

In order to avail of the credit package according to the stocking schedule each farmer's group should prepare their workplan RDK/RDKK two months before the stocking season. The RDK/RDKK is prepared through deliberations among the members of each farmer's group so that all their production requirements (inputs and other needs) can be put together in accordance with the recommended Sapta Usaha Pertambakan. In implementing the OPSUS INTAM technology package it is necessary to have a schedule of activities such as shown in Tables 3 and 4.

7.3 Production Target

With the technology package applied it is the hope of every farmer, especially those applying the OPSUS INTAM package, that the harvest will be optimal. For OPSUS INTAM A2, a production of 894 kg at a size of 30 pcs/kg in a 4 month and 10 days with a selling price of Rp. 9,000/kg has been attained. Other than what is provided for under the credit package, supplemental feed in the form of 1,000 kg sergestids or mysids at Rp. 200/kg was also added. OPSUS INTAM B2 has been evaluated as being unable to reach its production target because it does not use pumps so that it is not able to provide the proper water circulation required for P. monodon culture.

Those who joined the OPSUS INTAM B2 from the Kelompok Tani Muria, obtained 530 kg shrimps at size 28–30 pcs/kg in a 4 months 15 days. Their success was due to the use of pumps to maintain the quality of the tambak water. In addition supplemental feed in the form of 1,000 kg African snails (Achatina fulica) at Rp. 100/kg was also given. It is hoped that with these results all those who availed of either the OPSUS INTAM A2 or B2 will be provided with pumps.

7.4 Postharvest

In order to maintain the quality of the shrimps proper postharvest handling is necessary. Generally tambak farmers do not wash their shrimps clean enough and would leave them to dry before weighing. This lowers or destroys the quality of the shrimps. For this, dissemination of proper postharvest handling procedures through extension is necessary.

7.5 Marketing

At the beginning the farmers were happy with the increase in shrimp prices to as much as Rp. 20,000 per kg at size 15–25 pcs/kg making them inclined to expand their activity or their tambak. Generally the farmers sell their shrimps through a middleman and the shrimps are weighed only after the price has been agreed upon by which time the shrimp is already completely drained. This is very disadvantageous to the farmers.

When the shrimp prices started to drop the farmer became confused and started to complain. At present (September 1989) the shrimp price has dropped to as low as Rp. 6,000 at size 30 pcs/kg. For this, there is a need for farmers to have an agreement with processors and feed suppliers in order to stabilize the price at a satisfactory level. In this manner it is hoped that losses to the farmers can be minimized if not avoided.

Table 1. Activity schedule

Table 2. Color of flags used to indicate stage of activity of each tambak.

Table 3. OPSUS INTAM A₂ package.

Table 4 OPSUS INTAM B₂ package.

Figure 1. Traditional tambak.

Figure 2. Modern tambak.

Figure 3. Tambak adjoining paddy field with ideal position of control gate encircled.

Figure 4. Tambak located beside a factory.

EXPERIENCES OF TRADITIONAL TAMBAK FARMERS IN THE CULTURE OF TIGER SHRIMPS IN JAVA

Budiono Martosudarmo
Shrimp Culture Development Project, INS/85/009, Jepara, Central Java

ABSTRACT

Intensive shrimp farms in some areas are now reporting decreasing productivity due to accumulation of organic wastes, and lower quality of harvest due to the occurrence of blue coloration in the harvested shrimps. In this respect there is a need to promote traditional and semi-intensive shrimp culture techniques as practiced by traditional farmers by introducing improved techniques. Some shrimp culture techniques now practiced by tambak farmers such as modular system in Bangil, East Java, semi-intensive system in Cirebon, West Java, Brebes, Central Java and Surabaya, East Java have shown good results.

Many tambak farmers have successfully used different types of natural feed such as the pond crab wideng (Saesarma sp.), mujair (O. mossambicus), the polychaete worm elur (Eunice sp.) and the meniran which are tiny rice-grain size gastropods. Others have been found to use some type of dike vegetation, jruju (Acanthus sp.) and srunen (Wedelia sp.) as substrate for epiphytes which later serve as natural food for the shrimps. These techniques have potentials for dissemination to other developed tambak areas.

1. INTRODUCTION

The culture of tiger shrimp, P. monodon, specifically the intensive method, developed very rapidly during the last few years. The development of intensive shrimp culture is evident in the emergence of tambak areas for shrimp cultivation along the north coast of Java from Serang to Banyuwangi, which use aerators and are lighted during the night. However, despite the development of intensive shrimp culture using advance technology, many of the tambak farmers use traditional and semi-intensive farming methods which are based on their experiences.

The total area of tambaks in Indonesia is approximately 320,000 hectares (1988). It is assumed that the area for intensive shrimp culture is 20% of the total. From the above assumption, it seems that the production of the penaeid shrimps from non-intensive tambaks still plays an important role in generating income from the non-oil sector. Moreover, the quality of shrimps produced by the non-intensive tambaks is better than those produced by the intensive farms. Therefore, the price of shrimps from non-intensive tambaks is often higher than that from the intensive tambaks.

At present many problems are being reported as occuring in intensive shrimp farms. One is the decrease of the productivity of tambaks as the result of the accumulation of organic materials on the pond bottom (Martosubroto and Hardjono, 1989). This situation results in the production of blue shrimps from the intensive farms which are less desirable to the buyer (Kompiang, 1989). This being the case, more attention is needed for the development and improvement of the traditional shrimp farms to increase their productivity. The improvement can be done gradually such as by improving the cultivation techniques. There is no need to drastically change all of the cultivation methods which have been applied for a long time. Furthermore, some new techniques of cultivation have already been found and are being practiced by some farmers. These new techniques, however, need to be studied, improved and developed further.

This paper describes the shrimp culture methods practiced by shrimp farmers in the Island of Java. Most of these methods were learned by the farmers from the extension workers combined with their own experiences in the tambak.

2. TAMBAK PREPARATION

For experienced farmers, tambak preparation, such as drying, dike and gate repairs, pest control and fertilization are required before stocking.

2.1 Drying and Pest Control

Usually, the tambak is drained before actual cultivation begins. This means that if there are two crops a year, the tambak is also drained twice a year. However, in some areas, such as Sidoarjo, East Java, where the tambak compartments are relatively wide (3–5 ha/compartment), total drying is only done once a year, i.e. during the peak of the dry season, although the cultivation is done twice a year.

During the peak of the dry season, i.e. around October, salinity can reach 50 ppt, and the water is known as “bitter water”, which is not good for cultivation of both milkfish and shrimps. Therefore, during that period, tambak preparation, such as drying, dike and gate repairs and digging of trenches are carried out.

During the drying of the tambak bottom, liming is also applied by some of the traditional farmers to neutralize or promote the decomposition of organic materials in places which are still flooded. The lime application is done following that of the intensive shrimp culture, but the dosage of lime used is lower, about 25–100 kg/ha, and is restricted to undrainable spots. In a tambak where total drying cannot be done, the farmers use Thiodan (1 litre/ha) or saponin (40–80 kg/ha) in 20 cm water depth in order to eradicate extraneous fish.

2.2 Fertilization

Fertilization is done immediately after tambak drying and pesticide application. The purpose of fertilization is to promote the natural food growth, i.e. phytoplankton and zooplankton. Inorganic fertilizers (urea and TSP) are widely used by the farmers in the amount of 50–100 kg/ha. Organic fertilizers which are commonly used by milkfish farmers are rarely applied in shrimp farming because organic fertilizers tend to accumulate on the tambak bottom and might be harmful to the demersal shrimps.

3. CULTIVATION

The size of compartments for shrimp rearing is varied (0.5–3.0 ha). Most used to be milkfish ponds which were then redesigned for shrimp cultivation by increasing the tambak depth, i.e. by digging the tambak bottom or increasing the height of dikes. Pond bottom canals (around the inner part of the dikes and across the middle of the tambak) with width from 3–8 m and depth of 0.5 m are still being used in the shrimp ponds, the same as in the milkfish ponds. There is only one water gate for water supply and drainage. The water supply depends on the tidal movement. The gates are equipped with a screen made of bamboo screen which is lined by a very fine mesh net to prevent the shrimps from getting out of the tambak, and to prevent the wild fish from entering the tambak.

In general, most shrimp farmers stock twice a year during the early part of the rainy and dry seasons when the water salinity, at 15–30 ppt, is considered good for shrimp growth. Rainy season in Java occurs between November to January. At the beginning of the rainy season as the rain starts to fall, the water salinity gradually decreases. This is the time, the shrimp farmers start to stock. The peak of the rainy season takes place between February to March. At that time the salinity goes down as low as 5–10 ppt or even up to zero salinity. As the dry season (April-July) approaches rainfall decreases and the water salinity increases gradually. At that time, the tambaks are stocked again until before the height of the dry season, i.e. around October when the water salinity can be as high as 50 ppt.

3.1 Shrimp Fry and Stocking

“Hatcer” fry is the term generally used by the tambak farmers for fry produced by hatcheries. Hatchery produced fry is very popular among the farmers due to its low price and avail ability. Lately the shrimp farmers especially in East Java have started to classify hatchery fry into two categories based on the hatchery system: Taiwan and Hawaii. Taiwan fry are produced by the hatcheries run by Taiwanese where there is very little or no water change during the larval rearing period. Hawaii fry are those produced by hatcheries employing the method used by ADB- assisted BADP hatchery (which engaged the Hawaii-based Aquatic Farms Co. as consultants) where water changing is done during the larval rearing. The shrimp farmers appear to prefer the fry from the Hawaiian hatchery system because based on their experience the fry from this system are believed to be able to adapt better to the environmental changes in the tambak. The resistance of the Hawaiian hatchery system fry may be due to the fact that water changing is applied continuously in the system during larval rearing.

In general, the shrimp farmers believe that the healthy shrimp fry is characterized by such morphological factors as well-developed uropod, thin and long body structure. Behaviorally, good shrimp fry should not be clumped together in water and should swim against the current when the water is disturbed. Uniformity in size is prefered. Shrimp fry which swim in a group are considered unhealthy and weak, and may be the result of poor handling during harvest and high stocking density during transport.

Although hatchery fry is available all year round at a low price, some of shrimp farmers still seem to prefer natural fry, especially in East Java. Based on their experiences, the natural fry grow better in the tambak than the hatchery, even though its price is 2–3 times more expensive than the hatchery fry. However, since there are still so many fry traders who mix up the natural and hatchery fry, the shrimp farmers often hesitate to buy the natural fry except directly from the fry collector.

Before the shrimp fry is released into the tambak, the fry are acclimated to the salinity and temperature of the tambak to avoid stressing the fry. The acclimation is done in the following ways: the plastic bag which contains the shrimp fry is allowed to float on the tambak for some time to make sure that the temperature of the water in the plastic bag approaches that of the tambak. This is indicated by the condensation of water vapour on the side of the plastic bags which cause misting. After that, the plastic bag is opened, and the water from the tambak is introduced into the plastic bag bit by bit. This is done in order to adjust the salinity of the water in the plastic bag to the salinity of the tambak water. Finally, the fry is released into the tambak gradually. Stocking is generally done early in the morning or late in the afternoon when the water temperature is low.

3.2 Nursery

Generally the shrimp fry are stocked in a nursery for about 3–14 days depending on the shrimp fry growth before being released into the rearing compartment. The nursery consist of a small (10 to 1,000 m²) compartment within the grow-out pond. Sometimes feed is given to the fry in the nursery depending upon the avail ability of natural food in the nursery pond. In Karangrejo, Gresik, East Java, there are two stages of nursery. The first stage involves very small compartments known as lebonan measuring only 3 m square where the fry are initially stocked for 3 to 4 days. The purpose of this is to let the fry get adapted to its new environment. After that, the fry are then released to the main nursery (1,000 m²) for about 3–4 weeks before being finally released them to the grow-out pond (1 ha). The above method of shrimp cultivation is similar to the modular system where the shrimp stock are moved from one compartment to another in order to utilized the natural food available.

There is another reason for using the lebonan in Gresik. The tambaks in Gresik are located far away from the sea (13 km away) and are in fact known as fresh water tambaks or highland tambaks. The tambaks in this area have relatively low salinities, especially during the rainy season. To overcome this low salinity problem, the farmers buy sea water which is transported overland to fill up the lebonan. Therefore, the shrimp farmers there tend to make the lebonan small in size in order to reduce the expenses for sea water.

3.3 Cultivation Method

There are several methods of shrimp cultivation practiced by the shrimp farmers, i.e. monoculture in a single compartment, monoculture in more than one compartments (modular system), monoculture with stock manipulation, polyculture with milkfish and polyculture with the wild shrimp stock. These methods of cultivation are usually influenced by some factors, such as the condition of the tambak environment, the financial condition of the shrimp farmers and the previous experience of the farmers.

The tambaks which are close to the sea are usually rich in wild shrimp fry which then influence the farmers to utilize them. The wild shrimp yield from the tambaks can be harvested daily as a by-product and provides additional income to the small farmers. The ability of the farmers to buy the fry depends on their financial condition. When there is enough money, they will stock as much fry as their tambaks can carry. Conversely, the farmers will reduce the stocking density when their working capital is not enough or stock the fry gradually (stock manipulation) as money becomes available.

Monoculture of shrimp in a single tambak compartment from stocking until harvest is the conventional method, such as that in the intensive shrimp farming. This method is characterized by a relatively higher stocking density, i.e. approximately 10,000–60,000 fry/ha. The higher the stocking density, the more input is introduced, such as additional feed, and/or water pump in order to maintain good water quality. In this case, the presence of wild shrimp stock is prevented because the wild shrimp can act as a competitor for food. Therefore, a plastic screen is installed at the gate to prevent the wild shrimps from entering the tambak.

Some examples of the above methods can be found in Brebes and Cirebon, Central Java and Surabaya, East Java. A shrimp farmer in Brebes who has 2 ha of tambak consisting of two compartments stocked his tambak with 100,000 fry (50,000/ha). The tambak is provided with two gates, one for entry and another for discharge water. The average water depth maintained during cultivation is 70 cm. A water pump was installed but aeration was not provided. The shrimp fry were fed with commercial pellets 5 days after being stocked. After 130 days of cultivation, the yield was about 3,200 kg at a size of 37–38 pcs/kg.

Another example is in Cirebon. A tambak with an area of 0.8 ha and 90 cm water depth was stocked with 100,000 fry. Commercial pellet was given a week after stocking. Water pump was also used for supplying and changing water. Lime at 1 ton/ha and saponin were applied 1.5 months after stocking. After 140 days of cultivation, the shrimp yield was 1,700 kg at the size of 29 pcs/kg.

On the other hand, polyculture with the wild shrimp allows unlimited entry of wild stock into the tambak after the regular P. monodon stock has been in the tambak for about a month. This is done by removing the plastic screen at the gate leaving only the bamboo screen. After one month in the tambak the P. monodon is too big to get out of the tambak through the bamboo screen. The water coming in brings in the wild shrimp, such as white shrimps (Penaeus merguiensis) and werus shrimps (Metapenaeus ensis). This method is commonly used by the shrimp farmers whose tambaks are close to the sea. This type of tambak is generally large (more than one hectare). The stocking density of the tiger shrimp is around 3,000–5,000 pcs/ha. This low stocking density ensures that the natural food in the tambak is sufficient for the stock during cultivation.

The above method is practiced by the shrimp farmers in Demak, Central Java. A 1 ha tambak is stocked with 8,000 P. monodon fry. The water depth of the tambak is about 50 cm and there is only one gate serving both as entry and outlet. This tambak is characterized by a small gate which is constructed about 5 m away from the main water gate. The width of this small gate is about 40–50 cm. The function of this gate is for catching the wild shrimp by placing a woven bamboo trap in front of it. The wild shrimps are caught daily after a month of cultivation during water changing.

The modular system of shrimp culture, where the stock is moved from one compartment to another, is commonly done by farmers in Pati, Central Java and in Gresik and Pasuruan, East Java. In this method, the shrimp stock is moved from one compartment to a larger one as the supply of natural food becomes depleted in each pond. The stock is moved from one compartment to another by opening the dike between compartments. However in Pati, the shrimps are moved by using lift nets and the shrimps are counted before being released to another compartment, so that the shrimp population in the tambak is known.

A modular system of shrimp farming as practiced by a farmer in Bangil, East Java involved a stocking density of about 40,000 pcs/ha. First, the fry were stocked in a 10 m square nursery where natural food growth was promoted by fertilizing. The fry were reared in the nursery for about 2 weeks, and sometimes artificial food (pellet) was given as needed. After 2 weeks in the nursery, the shrimps were then transferred to a larger compartment (0.5 ha) for about a month without any additional food. And finally, the dikes between compartments were opened, so that the total area of the rearing pond became 1 ha. Commercial diet was given a month before the shrimps were harvested. The shrimp yield in this method was about 750 kg at the size of 20–25 pcs/kg after 4 months of cultivation.

In the polyculture of shrimp with milkfish the experience of farmers indicate that the production of shrimps is better if the stocking density of the milkfish is lower than that of the shrimps. In this case, the movement of the milkfish in the water can increase the dissolved oxygen concentration in the water. However, if the stocking density of the milkfish is too high, it can make the water turbid which in turn can negatively affect the growth of the shrimps.

An example of polyculture of shrimps and milkfish was encountered in Jabon, Sidoarjo, East Java. The tambak area was about 9 ha and consists of 6 compartments. The tambak was stocked with around 50,000 shrimp fry and only about 5,000 milkfish. The water depth in the tambak was about 80 cm. The pond was provided with only one pond bottom canal at the centre of the compartment. Additional food was not given and neither was fertilizer applied. The average yield after 4.5 months of the cultivation was around 760 kg of tiger shrimp at the size of 25–30 pcs/kg and 700 kg of milkfish with a size of about 2–3 pcs/kg. Besides the milkfish and tiger shrimps, after a month of the cultivation, the tambak farmer was also able to harvest wild shrimps daily which during one year of cultivation reached as much as 400 kg.

3.4 Shrimp Feed

In general, artificial feed is not given the shrimp at the stocking density of about 5,000–10,000 pcs/ha. The application of fertilizers can promote the natural food growth in the tambak. However, if natural food is not sufficient, supplemental food, such as chopped crabs (Saesarma sp.) and trash fish (e.g. Tilapia) are given. The type of supplemental food given depends upon its availability around the tambak area.

Shrimp farmers in Surabaya and Sidoarjo, East Java use some type of vegetation which grow wildly around the tambak as substrates for natural food. The wild plant used consist of jruju (Acanthus sp.) and srunen (Wedelia sp.) both of which grow very well along the bank of the tambak canal. The plants are used after 1.5 to 2 months of cultivation. The branches and leaves of these plants are put in the water along the side of the tambak. After these leaves and branches have been in the water for about 5–7 days, they are then shaken to let the microorganisms which have attached (ephiphyton) fall to the water. These ephiphytes serve as natural feed for the shrimps. The leaves and branches are used at least three times before being replaced.

A shrimp farmer in Rungkut Village, Surabaya stocked his tambak (1 ha) with 15,000 P. monodon fry. His tambak was constructed with a ditch in the middle of the pond bottom with a width of 5 m and depth of 0.7 m. The average water depth at the tambak bottom was about 75 cm. Two water gates were provided, one for supply and another for drain age. The shrimps in this tambak were “fed” only with the leaves and branches of jruju and srunen and after 5 months of the cultivation the shrimp yield was 250 kg with a size of 15–20 pcs/kg.

The other organisms which are commonly used by the shrimp farmers are elur and meniran. Elur is a polychaete worm (Eunice sp.) which can be found in the tambak rich in organic materials. The farmers believe that if there are a lot of elur in their tambaks, their shrimp yield will be good. Whereas meniran are small gastropods about the size of rice-grains and are greenishblack in colour. This organism is well known in Pati and Indramayu areas, Central Java. Meniran are present in the tambak when the salinity is low, i.e. between 5–20 ppt (during rainy season). They are found attached to algae present in the tambak or sometimes found on the surface of the water.

4. HARVESTING

Harvesting time usually depends on the shrimp market price, and/or on the urgency of the need for cash. Shrimp price depends not only on the market, but also on the quality of the shrimp, i.e. the bigger the size, the higher the price. Since the traditional shrimp farmers do not entirely depend on supplemental or artificial feed, harvesting time can be postponed even though the shrimps have been cultivated for about 4 months already. On the other hand, the shrimps can also be harvested earlier, i.e. before reaching 4 months of cultivation, when there is an urgent need for cash. In this case, the shrimp farmers usually harvest their shrimps selectively using seine, trap or by hand.

Several methods of harvesting are used by the farmers. In selective harvesting, lift nets known as branjang or anco are commonly used. sometimes the farmers may just use their bare hands to catch large shrimps. In total harvesting, the tambak is drained until the tambak bottom is exposed. After the tambak is drained, the shrimps are harvested by seine or are driven into the pond bottom canal using a bamboo screen where they are then caught by using scoop-nets. The latter method of harvesting can reduce the shrimp quality because the shrimps are mixed with mud during harvesting.

In general, the harvested shrimps pass through at least three middlemen before reaching the cold storage for final processing and export. This is where the traditional ponds differ with the intensive ponds where the shrimps are first sampled by the buyer who then fixes the price based on the size. Then upon harvesting everything required is already ready so that the shrimps are immediately iced once gathered and transported to the cold storage plants. The marketing of shrimps from the traditional ponds passes through a long chain of marketing because in general the traditional tambaks are located far away from the motorway. Intensive tambak units on the other hand are usually close to the road and are easily accessible to the buyers from the cold storage plants. The lengthy channel of marketing makes the quality of the shrimp from the traditional ponds lower when it reaches the processing plant. Consequently the price is also reduced.

5. REFERENCE

Martosubroto, P. dan Hardjono. 1989. Development of environmentally oriented shrimp culture (in Indonesian). Lokakarya Pembenihan Udang Skala Rumah Tangga dan Budidaya Intensif di Tambak Rakyat, 25 February 1989.

Kompiang, I.P. 1989 Selecting good feed. (In Indonesian) Primadona, Informasi Industri dan Usaha Udang. May 1989.