Cheng-Sheng Lee and Jessie E. Banno
Honolulu, Hawaii, U.S.A.
World Finfish Aquaculture
In 1985, the world total finfish production from aquaculture was 4,717,500 mt, with Asia leading the other seven continents with 80.4% or 3.8 million mt (FAO, 1987). The majority of aquaculture activities and production occurred in East and Southeast Asian countries (Table 1). The most important finfish cultured were carp, milkfish, tilapia, catfish, Japanese amberjack, salmon and trout (Table 2). In 1985, 329,000 mt of milkfish was produced.
Table 1. Leading producers of finfish, crustaceans, molluscs, and seaweeds, 1985 (in mt).
|Republic of Korea||790,200|
|Democratic People's Republic of Korea (EA)||190,000|
* EA = East Asia
** SEA = Southeast Asia
Source: FAO, 1987
Table 2. Production of important species in 1985 (in mt)
|Giant river prawn||6,000|
|European flat oyster||2,800|
|Pacific cupped oyster||684,100|
|American cupped oyster||124,500|
|“Other” cupped oyster||444,300|
Source: FAO, 1987
Milkfish, Chanos chanos, is one of the two most important species being cultured in Asia, the other being carp. It is distributed throughout the entire tropical Indo-Pacific Ocean, from 40° E to about 100° W and 30 to 40° N to 30 to 40° S (Schuster, 1960). It can tolerate wide ranges of salinity and temperature fluctuations (see review by Gordon and Hong, 1986). Schuster (1960) reported that milkfish has been recorded in the Red Sea, the Aden Gulf, the California Gulf, and off the coast of East Africa, including Zanzibar and Madagascar, South and West India, Sri Lanka, Malaysia, Thailand, Vietnam, and Mexico.
Milkfish farming has been concentrated in Southeast Asian countries of Malaysia, the Philippines and Indonesia. Other Southeast countries, including Burma, Thailand, Laos, Cambodia, Vietnam, and Singapore, have not reported milkfish farming activity. In Malaysia, milkfish are cultured only in coastal brackish water ponds in the state of Sabah. No detailed information was available at this time, so Malaysia will not be included in this paper. Indonesia and the Philippines are the two countries with a multi-million dollar milkfish industry.
Although Taiwan is part of East Asia, it has a major milkfish industry.
Milkfish culture can be traced back about 700 years in Indonesia (Ronquillo, 1975), and at least 400 years in Taiwan and the Phillippines (Ling, 1977). In 1983, these countries utilized more than half a million hectares of brackish water and freshwater areas to produce more than 365,800 mt of milkfish estimated by Smith and Chong (1984) to be worth over US $200million. Culture methods have been improved according to the environmental conditions of individual countries. Culture knowledge has been interchanged through the sponsorship of international organizations, such as the United Nations Food and Agriculture Organization and donor countries, such as USA and Canada. Recent information regarding milkfish culture can be found in the proceedings of meetings held in 1983 (Juario et al., 1984) and 1985 (Lee and Liao, 1985) and in the review book (Lee et al., 1986). The economic aspects can also be found in the above references, and in reports by Chong et al., (1982) and Lee (1983).
This paper provides an overview of the fry industry, and current milkfish culture, production, marketing, distribution and problems in Southeast Asian countries, followed by prospects of milkfish farming in the future.
- Source of Fry
Milkfish fry supplies come from annual ocean recruitment and from hatcheries. Wild fry was the major source for milkfish culture until recent success in natural spawning and mass larval rearing in several of Taiwan's milkfish farms.
- Fry from the Wild
The fry collection season varies by location and runs from a few months to throughout the year (Table 3). Kumagai (1984) concluded that the fry season is longest near the equator and becomes progressively shorter at the higher latitudes of the northern hemisphere. Most of the fry were collected during the new and/or full moon period because intense spawning occurs during the quarter moon period (Kumagai, 1981). The total fry catch showed annual fluctuations due to such factors as climate and fishing efforts.
Taiwan's highest yield of 234.87 million fry occurred in 1970 and gradually decreased to 104 million in 1983 (Liao and Chen, 1986). The most recent government statistics (1987) report 184 million, including hatchery production. Major fry collection areas were along the south and east coasts of the island. In the Philippines, milkfish fry occur practically throughout the year (Villaluz, 1986). Table 4 shows the location, occurrence and major peak season of milkfish fry.
There are two milkfish fry seasons in Indonesia: April-June and September-December. Milkfish fry harvest have been estimated to be 700–800 million per year (Chong et al,. 1984). The fry grounds are located off the Bali, South Sulawesi, Halmahera, Sumatra, and Madura coasts. In 1986, 737.7 million young fish of less than 5 cm in length were stocked in brackish water ponds in addition to 594.7 million of 5 cm or more for a grand total of 1.3 billion fry and fingerlings. The fish smaller than 5 cm came mostly from Java (489.1 million), Sulawesi (205.5 million), Bali-Nusatenggara-Timor areas (23.2 million), Sumatra (15.8 million), Kalimantan (3.8 million) and Maluku-Irian Jaya (0.281 million). Those of lengths of 5 cm or more came from Bali-Nusatenggara-Timor (510.2 million), Sulawesi (45.3 million), Sumatra (17.3 million), Java (13.1 million), Kalimantan (8.6 million) and Maluku-Irian Jaya (0.310 million). Total seedstock increased by 260 million from the 1.04 billion of 1985.
Table 3. Peak season and estimated annual catch of milkfish fry in Southeast Asia countries.
|Philippines||Jan-Dec||1.15–1.35 billion||Smith, 1981; Villaluz et al., 1983|
|Indonesia||Jan-Dec||0.74–1.30 billion||Noor-Hamid et al., 1977; Chong et al., 1984 Fisheries Statistics of Indonesia, 1988|
|Taiwan||Apr-Sep||May||Aug||34–235 million||Lin, 1969; Lee, 1984; Taiwan Fish. Bureau.,1988|
|Vietnam||Apr-Oct||Kuronuma and Yamashita, 1962|
- Fry from Hatchery
The instability of wild-fry supplies is an obvious problem for the culture of any aquatic species and milkfish is no exception. Since Vanstone et al. (1977) produced the first hatchery larvae, much progress has been made in artificial propagation (see review by Kelley and Lee, 1986). One milkfish farmer in Taiwan has produced millions of hatchery fry for culture every year since 1982 (Lin, 1984). Three more milkfish farmers started to produce fry from hatcheries in 1988. A project in Hawaii, funded by the United States Agency for International Development (USAID), is working together with the research groups in Taiwan, the Philippines and Indonesia to establish artificial propagation techniques. The significant progress made so far indicates that the technology will be developed completely within the next few years.
- Method of Fry Collection
Fry collection methods of Southeast Asia were reviewed by Villaluz (1986). A detailed description of current fishing gear was provided, such as fry barriers or fences in Indonesia and the Philippines, filter bag nets in most of the fry-producing countries, seine nets in Sri Lanka and the Philippines. The selection of fishing gear is based on the topography of fishing ground and ocean currents. It is important to realize that driving the fry into the net, rather than filtering them through it, results in higher survival.
Table 4. Milkfish fry grounds, occurrence and peak season in the Philippines.
|Northern Philippines: Caguyan, Pangasinan Manila Bay, Batangas, Albay, Bicol and Mindoro Coasts||Mar-Aug||May-Jul||--|
|Central Philippines: Around Panay Island Negros and Cebu||Mar-Jan||Apr-Jun||Oct-Nov|
|Southern Philippines: Zamboanga, Cotabato, Davas Coasts||Jan-Dec||Mar-May||--|
No food is offered during first night after fry are caught. It is also common practice to lower water salinity in the storage tank. In the Philippines, three parts seawater and one part freshwater were used (Villaluz, 1986). In Taiwan, water with 10 to 15 ppt salinity was used (Liao and Chen, 1986). In either case, the purpose was to reduce stress from osmotic pressure differences. The temporary storage methods for collected fry as summarized by Villaluz (1986) is shown in Table 5.
Following fry collection, they are transported to fry middlemen or dealers. The mode of fry transport is very critical to their survival in the pond. Table 6 summarizes the various methods practiced, the most popular of which is using plastic bags containing oxygenated water. The number of fish per bag depends on the size of the bag, water volume, oxygen content, water temperature, size of the fish, and distance to transport. Upon arrival at the destination, acclimation to the pond condition is required to ensure better fry survival. More detailed information can be found in the paper by Villaluz (1986).
- Fry distribution
The distribution of milkfish fry is illustrated in Figure 1. The milkfish fry distribution routes seem longer in Indonesia than in Taiwan and the Philippines. After collection, the fish will change hands 3 to 5 times from dealer to dealer before reaching the fish culturists. Fry will be grown to the required size for either marketing as food fish or as baitfish for tuna fishing. Demand and profitability will decide the fry's final destination.
Table 5. Milkfish fry storage in the Philippines, Indonesia and Taiwan (after Villaluz, 1986).
|Conditions||Fry Storage Practice|
|Container||a. plastic basin||a. earthen jars||a. plastic basin|
|b. earthen jars||b. bamboo basket||b. bamboo basket|
|Water Volume (liters)||a. 15 – 23||a. 10||no report|
|b. 10 – 20||b. 30|
|Salinity (ppt)||10 – 15||10 – 25||< 20|
|Feeds and feeding||egg yolk or wheat flour every day or every other day||rice, flour, dried wheat or egg yolk||no report|
|Water management||complete change or 1/2 of total volume every day or every other day||complete change||no report|
|Stocking rate (fry/container)||a. 3,000–8,000||a. 1,000||no report|
|b. 2,000–3,000||b. 15,000|
|Stocking density (fry/liter)||a. 150–500||a. 100||no report|
|b. 100–300||b. 500|
|Days of storage||1 – 7||10 – 20||no report|
|Mortality (%)||2 – 10||5 – 10||< 2|
Source: Villaluz et al., 1983 Noor-Hamid et al., 1977 Lin, 1969
Culture Methods in Taiwan
According to the Water Depth of Pond
There are two methods used to culture milkfish in pond systems: i.e. shallow-water culture and deep-water culture.
1. Shallow-water culture
Shallow-water culture is the traditional culture system. The management of the system involves several standard steps as described by Liao and Chen (1986); these are pond preparation, stocking fry or fingerling, pond management, selective harvesting and overwintering.
Table 6. Methods of milkfish fry transport in the Philippines, Indonesia, and Taiwan.
|Conditions||Fry Transport Practice|
|Container||a. plastic bag||a. plastic bag||a. plastic bag|
|b. earthen jar||b. bamboo basket|
|Mode of transport||a. surface (land)||a. air||a. surface (land)|
|b. air||b. surface (sea)|
|c. surface (sea)|
|Transport time (h)||a. 12 – 14||a. 12||a. 2 – 3 days|
|b. 3 – 6||b. 4 – 7 days|
|Water volume (liters)||a. 8 – 10||a. 10||a. 10|
|b. 3 – 5||b. 20|
|Salinity (ppt)||12 – 22||10 – 15||7.5 – 10|
|Stocking rate||a. 4,000–6,000||a. 10,000–20,000||a. 4,000–5,000 (fry)|
|(fry/container)||b. 4,000–8,000||b. 1,000||b. 1,000–2,000 (3.5 cm)|
|c. 15,000–40,000||c. 600–1,000 (5–10 cm)|
|d. 100–200 (10–15 cm)|
|Stocking density||a. 400–750||a. 1,000–2,000||a. 400–500|
|(fry/liter)||b. 800–2,000||b. 500||b. 100–200|
|c. 500–1,300||c. 60–100|
|Mortality (%)||2 – 6||a. 5, b & c 20||< 2|
|Source:||Villaluz et al., 1983||Schuster, 1960; Noor-Hamid et al., 1977; Noor- Hamid and Mardjono, 1976||Liao and Chen, 1986|
- Pond preparation
Following the final harvest each year, the pond is prepared for the next growing season. This involves the following procedures:
Fig. 1. Milkfish fry marketing distribution route.
- Stock manipulation
Different sizes of over-wintered milkfish fingerlings and new fry are stocked at various times during the growing season. As described by Lin (1968), in April, 4,000 to 5,000 over-wintered fingerlings ranging in size from 5 to 150 g are first used to stock the ponds, then 5,000 to 8,000 new fry are added from May to September at about 1,500 new fry per ha per stocking.
- Pond management
The management strategy for shallow-water milkfish ponds is to maintain continued growth of benthic algae to provide a food source. Inorganic and organic fertilizers are used to promote the growth of benthic algae. The amount of fertilizer applied depends on the condition of the pond. It is important to keep the water clear to allow light to penetrate to the pond bottom for growth of benthic algae.
At the end of May, milkfish weighing 500 g or more are thinned out selectively by using gill nets to allow the smaller fish to grow more rapidly. Fish are harvested two to three more times in June and July since fish biomass is quite high. Additional harvests occur about once a month, and the final harvest is done in mid-November.
Fish farmers expect an 85 to 95% survival rate for the over-wintered fingerlings and 80% for the new fry. An expected average annual pond yield of 1,300 kg per ha weighing 300 to 600 g per fish for the fingerlings and 800 kg per ha weighing 200 g per fish for the new fry, make a total of 2,100 kg per ha production. The fish that do not reach table size (less than 200 g) are transferred to the “over-wintering pond” which protects the fish from the dry winter cold of November-March. Some of the fish weighing 80 to 120 g are sold as bait for the tuna longliners.
Over-wintering is a special feature and necessary procedure for shallow-water pond culture operation in Taiwan but not in the Philippines and Indonesia. The pond water temperature in southern Taiwan drops to 10°C (Liao and Chen, 1986) and sometimes to as low as 5 to 6°C, deadly to the milkfish which can tolerate temperatures as low as 12°C (Chen, 1976).
The over-wintering pond, less than 1% of the total pond area, is rectangular in shape with dimensions of 5 m by 100 m to 2,000 m and 1.5 to 2 m in depth. It is aligned perpendicular to the direction of the wind and is always protected with windbreaks of grass straw, canvas, or polyethylene plastic. The location should also have access to water and a connection to the grow-out pond. Stocking density is less than 1.3 kg per m2 and rice bran is provided as food. Other detailed management procedures have been reported by several researchers (Ting, 1978; Lin et al., 1981; Lin, 1982; Ting et al., 1984).
2. Deep-water culture
The deep-water method was developed in the mid 1970s when fish farmers experienced declining profits from milkfish farming (Chong et al., 1982; Smith and Chong, 1984), limited land, and increasing value of land and manpower resources (Liao and Chen, 1986). Furthermore, the observation that a more or less stable environment could be maintained in the over-wintering pond expanded its use as a production pond. This development has also created a field of fish farmers who specialize in producing only overwintered fingerlings to be sold to grow-out producers. This has led to more efficient use of land resources. Large tracts of shallow-water ponds (20 ha or more) have been converted into 1 ha lots with depths of 2 to 3 m. The stocking density was increased from 10,000 to 15,000 fish per ha to more than 25,000 fish per ha which increased pond yield by more than fourfold.
The procedures of the deep-water method are very similar to the shallow-water method: pond preparation, fry stocking, harvesting and over-wintering. The first stocking of 12,000 per ha over-wintered fingerlings (1.5 cm in total length) is done at the end of April. The second stocking of 13,000 per ha is done after the first harvest of milkfish in August.
Benthic algae are present during the initial period of culture but the pelletized feed with 23 to 27% crude protein content are the main nutrient source for fish growth. Automatic feeding dispensers with pipes extending toward the pond are installed on the dikes to meet the frequent feeding schedules. Because of high stocking density and intensive feeding, mechanical aerators such as 1 HP paddle wheel at two units/ha were installed to maintain the necessary oxygen level. This measure is particularly necessary from 2300 to 0800 hours when dissolved oxygen is usually low.
As with shallow-water systems, milkfish weighing 500 g or more are thinned out selectively with gill nets. Harvesting begins in August and thereafter as demanded by growth of the fish. Final harvest takes place in November before the arrival of winter. The deep-water method of milkfish culture yields from 8,000 kg per ha to as high as 120,000 kg per ha per year. A comparison of both systems is summarized in Tables 7 and 8.
Table 7. Summary of the difference between shallow- and deep-water methods of milkfish culture.
|Features||Shallow-Water Method (Traditional)||Deep-Water Method (New)|
|Pond Area (ha)||1 – 10||1 – 6|
|Water Depth (m)||0.35–0.45||2 – 3|
|Fertilization||Organic;during pond preparation and culture||Pond preparation stage only|
|Feeds/Feeding||Benthic algae plus feed supplements||Artificial feeds; some algae|
|Stocking Rate (fish/ha/season)|
|a. overwintered fish||3,500 – 5,000||-----|
|b. fry||6,000 – 10,000||25,000|
|Pond Yield (kg/ha/yr)||1,800 – 2,500||8,000 – 12,000|
According to the Composition of Cultured Species.
We can also classify milkfish culture into monoculture and polyculture systems according to the number of species stocked in the same pond.
1. Monoculture system
In this system, milkfish is the only species in the pond. It is found in both shallow-water and deep-water systems.
2. Polyculture system
The polyculture system is found mostly in shallow-water systems. Polyculture of milkfish with other aquatic species is found in freshwater and brackish water ponds in Taiwan. In freshwater ponds, milkfish have been cultured together with mullet, tilapia and carp for many years and yields were as high as 7,500 kg per ha (Bardach et al., 1972).
Brackish water polyculture can be more profitable. Shrimp (P. monodon, Metapenaeus ensis), mudcrab or Samoan crab (Scylla serrata), sea bass (Lates calcarifer) and seaweed (Gracillaria sp.) were the most common species found in brackish milkfish ponds.
The rates of stocking of the different species are subject to such factors as their biological requirements, farmers' preferences and the market demand for the cultured species. Liao and Chen (1986) indicated that milkfish grew better in ponds containing 25 shrimp for every milkfish.
According to Taiwan Fisheries Bureau's 1987 Yearbook, 17.2% of milkfish ponds were operating with polyculture systems, most of which were freshwater. Polyculture systems represented 43.6% of total operating area.
Table 8. Comparison of the advantages and disadvantages of shallow-water and deep-water methods of milkfish culture.
|Shallow-Water Method||Deep-Water Method|
Culture Methods in the Philippines
According to Culture Sites
In the Philippines, milkfish are cultured in freshwater and brackish water areas by methods known as pen culture and pond culture, respectively.
1. Pen Culture
Pen culture was introduced in the Philippines by the Laguna Lake Development Authority in 1970. Because of the low rate of input and high rate of return, the pen hectarage increased sharply from 4,800 ha in 1973 to 45,311 ha in 1983 (Chong et al, 1982; Samson, 1984).
Fish pens located in Laguna Lake are enclosed by posts cut from bamboo, coconut, palm or other trees, netting materials (nylon and kuralon type) and bamboo mattings. The netting and bamboo matting materials are used to prevent the fish from escaping.
Detailed information on fish pen design and construction were reported by Alferez (1977), Marichamy (1979) and Felix (1980). As reported by Pamplona and Mateo (1985), milkfish were stocked at densities 10 to 12 times higher than in brackish water ponds but they grew to marketable size within 5 to 6 months with very limited commercial feed. The lake had very high primary productivity and could meet most of the nutritional needs of milkfish. Yields were reported to be as high as 10,000 kg per ha but generally ranged from 2,000 to 4,000 kg per ha. Unfortunately, many problems emerged from the overcrowded operation. The primary production of the lake could not meet the sudden expansion of culture. In 1983, the culture areas covered 45,000 ha, over 50% of the total lake surface. Feeding became necessary to meet the nutritional requirements of milkfish. Furthermore, disease spread among culture pens and eventually caused periodic mass die-off. It was no longer a desirable or affordable location for the small fish farmers.
2. Brackish Water Pond Culture
The culture systems developed in the Philippines have been based on traditional techniques and imported ones from Taiwan. Basically, they can be divided according to the food source into “lablab” method, “lumut” method and plankton method. “Lab-lab” is equivalent to the benthic algae in Taiwan.
i. “Lablab” method
The culture of benthic algae called “lablab” for rearing milkfish was introduced into the Philippines under an FAO project in 1968. This technique was adopted by the fish farmers from Bulacan and Iloilo provinces who could afford to buy the necessary inputs to immediately implement the technique. As a result, these provinces have the highest current pond yields of 1,000 to 2,000 kg per ha per year compared to the national average production of 600 to 800 kg per ha per year.
Pond preparation is the same as the Taiwanese method of fish culture with slight modifications to suit local conditions. Agricultural lime is commonly used to neutralize or reduce pond soil acidity. A recent innovation to reduce acidity is the repeated drying, tilling and flushing with sea water (Poernomo, 1984). It is recommended that this be done at the start of the first culture period so that the growing period for lablab culture will be shorter during the next pond preparation stage. The initial stocking density in grow-out ponds is 3,000 fingerlings (2 to 5 g) per ha. During the late rainy season, lablab disintegrates and “lumut” and/or plankton become part of the main natural food base. Lumut is the term used to denote the filamentous green algae mainly the Enteromorpha sp. and Chaetomorpha sp.
A more advanced management practice is called the “modular pond method”. The modular pond consists of nursery, transition and grow-out ponds of first, second and third modules at pond sizes at a 1:2:4 ratio, respectively. The stocking density is 3,000 fingerlings per ha, based on the size of the last module. This system is operated by stocking milkfish fingerlings and transferring stocks every month from one module to the next. After each transfer, the vacated pond is prepared for the next batch of fish. If operated efficiently, fish can be harvested three months after the first stocking and every other month thereafter. A minimum of four harvests is easily attainable. The annual production ranges from 2,000 to 4,000 kg per ha.
ii. “Lumut” method
In a few northern and southern Philippine provinces such as Pangasinan, Agusan and Zamboanga where a low salinity of 10 to 20 ppt is found, lumut was used as a main food item for milkfish. The pond was fertilized with inorganic fertilizers to promote the growth of filamentous algae. The stocking density was usually at 1,500 fingerlings per ha per year. The culture period was from 4 to 6 months and the fish grew up to about 250 to 300 g.
The main disadvantages of this method are: a) the algae occupies a lot of space which restricts movement of the fish and results in the fish becoming stunted, b) the algae generally has a low crude protein content and high fiber which makes the food less palatable, c) it is difficult to eliminate predators and d) the growing season is long, hence, only 1 or 2 croppings can be performed with low yields of 300 to 400 kg per ha per year. This method has long been practiced but has become less popular with the introduction of the lablab method.
iii. Plankton method
Plankton are free floating micro-organisms of plants and animals that drift in the water. This method is based on the assumption that milkfish is a plankton feeder and was made popular by the University of the Philippines Systems Brackish Water Aquaculture Center. (Villaluz et al., 1976; Banno, 1980).
Wild plankton is cultivated by using the “platform” or broadcast method whereby the required amount of inorganic fertilizers are placed on a wooden platform submerged in water about 15 to 30 cm below the pond water surface.
Water management is critical because sudden plankton blooms can occur and cause mass mortality of milkfish. Plankton blooms usually occur when Secchi disk reading is less than 15 cm. When this happens, the pond water has to be changed. Growth of plankton is optimal when Secchi disk reading is between 30 and 70 cm. The pond is infertile when water transparency is more than 70 cm.
The plankton method has been found to have many advantages similar to the deep-water method of Taiwan. These are: a) more stable environmental changes such as salinity and temperature because of the water depth of 0.7 to 1.2m, b) lesser problem of dissolved oxygen depletion compared to the traditional method and c) relatively high stocking density of about 6,000 fingerlings per crop.
This technique has not yet been perfected because of the wide fluctuations of pond yield (Fortes, 1984) from below the national average production to over 1,000 kg per ha per year.
According to the Composition of Culture Species
As in Taiwan, milkfish are cultured alone (monoculture) or together with other species (polyculture). The declining profitability of milkfish and the additional income from culturing other species in the same pond have prompted more and more fish farmers to shift to polyculture systems of high value species like the shrimp (Penaeus monodon, P. monodon, P. indicus, Metapenaeus ensis), crab (Baliao et al, personal communication), tilapia, and sea bass (Banno et al. 1984, Unpbl.).
Lumut method yields are below 400 kg per ha, while lablab method yields average 1,000 to 2,000 kg per ha. Harvesting methods for all types of pond operations consist of either a single method or a combination of the following methods: a) by partial draining, seining the milkfish and eventual complete emptying of the pond water, b) by using a catching or harvesting pond adjacent to the main gate per exit, c) by using a barricaded portion of the main canal near the gate as a form of harvesting area and collecting the fish by seine or big scoops nets, d) by selective harvesting using gill nets.
Culture Methods in Indonesia
Basically, the milkfish culture in Indonesia is very similar to the shallow-water method in Taiwan or lablab method in the Philippines. However, the standard operating procedures were not previously carried out. Monoculture and polyculture are both practiced.
Monoculture system predominate in Indonesia. However, it is not uncommon for extraneous species to enter the ponds because of lack of care during the pond preparation stage. Some of the common extraneous species found in the grow-out ponds are Oreochromis mossambicus, Megalops cyprynoides, Elops hawaiiensis, Mugil sp., Lates calcarifer, and Therapon sp. The main polyculture species, however, are milkfish and penaeid shrimps in the brackish water ponds. The stocking density is 750 fingerlings of milkfish and 10,000 Penaeus mondon fry per ha.
Harvesting of milkfish is done usually when the fish have reached an average of 300 to 800 g body weight. Pond yields have reportedly ranged from 50 to 500 kg per ha per year (Bardach et al., 1972). Normally, however, milkfish monoculture averages 300 to 1,000 kg per ha per year (Fuad et al., 1980) while in the government demonstration farms, with proper care, it averages 2,168 kg per ha per year (Chong et al., 1984). In the polyculture system, pond yields average 600 kg per ha of milkfish and 100 to 300 kg per ha of jumbo tiger prawn, P. monodon.
The culture methods and milkfish production in the above three countries are summarized in Table 9. In general, the production methods can be classified as the shallow-water and deep-water methods and the brackish water and freshwater systems. The shallow-water system in brackish water is most commonly practiced in these countries. However, the deep-water system in freshwater became very attractive because of its high yields. Its shortcoming is the high capital input required. If milkfish should be the “people's fish,” it should be produced by the shallow-water systems to lower production costs. This is the only way to make milkfish affordable for the general public.
Production in Taiwan
From 1960 to 1983, the area used for milkfish production was around 15,000 ha. In 1983, the role of deep-water culture became increasingly important. According to the statistics report of the Taiwan Fisheries Bureau, the total production of milkfish in 1976 was 26,800 mt, of which 26,600 mt were from shallow-water systems and only 200 mt from deep-water systems. However, the production from deep-water systems increased to 9,000 mt in 1983, representing 24.3% of total production. There was no growth in production from shallow-water systems. The most recent report of Taiwan Fisheries Bureau (1988), indicated that the culture area in deep-water systems increased to 1,351 ha or 16.3% of total milkfish culture area. According to the average annual production of deep water culture systems, it should represent almost 50% of total production, 28,852 mt valued at about U.S.$56 million (Table 10).
Table 9. Different culture methods and systems practiced in the three milkfish-producing countries of Asia.
|Country||Culture Methods||Stocking Size|
|Culture Period per crop|
|Average size at harvest|
|1. Accdg. To Pond Depth|
|1.1 Shallow-water Method||>500||1,900–2,500|
|1.1.1 Fingerlings||5–150||0.4–0.5||2 – 3|
|1.1.2 Fry||0.1||0.5–0.8||3 – 4|
|1.2 Deep-water Method||>500||8,000–12,000|
|1.2.1 First Stock||0.1||1.2||4|
|1.2.2 Second Stock||0.1||1.3||N.A.|
|2. Accdg. To Composition of Cultured Species|
|2.1 Monoculture System||0.1–150.0||>1.0–2.5||2 – 4||>500||1,900–1,200|
|2.2 Polyculture System||N.A.*||N.A.||N.A.|
|3. Accdg. To Culture Sites|
|3.1 Freshwater Area|
|3.1.1 Pen Culture||12.5 cm||3.0–4.0||5 – 6||200–300||2,000–10,000|
|3.2 Brackish water Area|
|3.2.1 “Lumut” Method||N.A.||0.15||4 – 6||250||500–600|
|3.2.2 “Lablab” Method|
|18.104.22.168 Multi-size||2–5||0.15–0.6||3 – 4||225||1,600–3,000|
|3.2.3 Plankton Method||N.A.||0.6||4||225||<3,600|
|4. Accdg. To Composition of Cultured Species|
|4.1 Monoculture System||2–5||0.15–0.60||3 – 4||200–350||800–4,000|
|4.2 Polyculture System|
|4.2.2 Milkfish-||2–5||0.15||3 – 5||300||810|
|Shrimp||Post larvae||1.0||3 – 5||25||250|
|4.2.3 Milkfish-||2–5||0.3||3 – 5||300||675|
|Tilapia-||25–50||0.4||3 – 5||150||600|
|Sea bass||15–30||0.5||3 – 4||350||1,750|
|5. Brackish water Culture|
|5.1 Monoculture||<5.0 cm||0.6||3 – 4||300–800||300–1,000|
|system||>5.0 cm||N.A.||2 – 3||300–800||300–1,000|
|5.2 Polyculture System|
|5.2.1 Milkfish-||<>5.0 cm||0.075||3 – 4||300–800||600|
|Shrimp||Wild Post larvae||1.000||3 – 4||N.A.||100–300|
* N.A. Data not available.
Table 10. Milkfish annual production in Taiwan, The Philippines, and Indonesia, 1950–1987.
|TAIWAN (1986 Population = 19,700,000)|
|Brackish water area (ha)||13,084||13,869||16,713||15,616||16,738||18,115||15,095||14,412||14,563||14,740||14,072||12,839||10,223||6,959|
|Milkfish Production (tons)||15,360||22,407||26,157||27,562||27,857||33,490||27,964|
|Freshwater area (ha)||35||498||651||725||747||777||701||1,351|
|Milkfish Production (tons)||9,021|
|Total milkfish production (tons)||15,360||22,407||26,157||27,562||27,857||33,490||19,324||23,912||29,524||36,985||30,603||31,689||27,615||28,852|
|PHILIPPINES (1987 Population = 55,000,000)|
|Brackish water area (ha)||168,113||176,032||176,199||176,230||195,832||196,269||206,525|
|Milkfish Production (tons)||96,500||106,500||135,849||153,388||162,432||165,396||198,729|
|Freshwater area (ha)||25,000||45,311|
|Milkfish Production (tons)||56,922||84,647||91,530||81,913||43,680|
|Total milkfish production (tons)||96,500||106,500||192,148||238,035||253,962||247,309||242,409||209,240||194,172|
|INDONESIA (1987 Population = 165,000,000)|
|Brackish water area (ha)||179,911||182,701||188,601||198,210||208,695||242,308|
|Milkfish Production (tons)||35,800||44,692||58,922||61,041||73,330||81,506||84,365||93,508||103,588|
|Freshwater area (ha)|
|Milkfish Production (tons)|
|Total milkfish production (tons)||35,800||44,692||58,922||61,041||73,330||81,506||84,365||93,509||103,588|
|World milkfish production (tons)||265,366||347,421||357,166||366,147||357,664||336,518||328,370|
Production in the Philippines
Milkfish production comes mainly from brackish water ponds and from the fish pens in Laguna de Bay, the biggest lake in the Philippines. Since 1950, production of milkfish steadily increased from 36,734 mt to its peak of 253,962 mt in 1982 with an estimated contribution from the freshwater areas, mainly Laguna lake, of over 90,000 mt (Table 10). Production, however, declined after 1982. Milkfish profitability had decreased over the past decade, (Smith and Chong, 1984), prompting 50–60% of pen operators to shift to the pen/cage culture of Nile tilapia (locally called “pla-pla”) because of its low input, high output, and growth performance. The production dropped to 194,172 mt in 1986. From 1980 to 1986, milkfish production contributed 12.2% (ranging from 10.1 to 14.2%) of the total nominal fish production. In 1981, total milkfish production was valued at 1.9 billion pesos (Samson, 1984) or about US$95 to 135 million.
Production in Indonesia
Common carp is traditionally favoured by Indonesians, but milkfish production has increased tremendously in recent years. Between 1970 and 1986, milkfish production grew from 35,000 mt to 103,240 mt, while carp production fluctuated from 40,000 to 53,047 mt from 1971 to 1983. Milkfish is now the single most cultured species in Indonesia in terms of tonnage. In 1986, milkfish comprised 4.1% of the total fishery production of 2,529,899 mt and 17.1% of the total aquaculture production of 607,118 mt. 1986 milkfish production was valued at US$61.0 million (these and other values are based on the 1987 exchange rate of US$1 = 1650 Rupees). In terms of value, milkfish ranked third to the giant tiger prawn, P. monodon, (with a total production of 15,424 mt valued at US$86.9 million) and carp (68,130 tons worth US$71.8 million). The milkfish and the common carp are the two most cultured species in the country.
The average milkfish farm in Indonesia is 2.1 ha in size, and is usually owned privately. Most milkfish farms (118,063 ha) are located on the island of Java where 60 to 70% (Chong et al., 1984) of the Indonesian population lives. The other culture centres are located in South Sulawesi (46,851 ha) and West Sumatra (4,222 ha) as reported by Fuad et al. (1980).
In Taiwan, aside from being a food fish, milkfish has been used as baitfish for the tuna longline fisheries. Most of the fish are marketed fresh in local markets. However, attempts to process milkfish in other forms such as canning and drying are being developed to open more markets.
The bait size of milkfish required for tuna fishing is 80 to 120 g per fish. This is reached after two to three months of culture from the stocking size of 5 cm in total length (Liao and Chen, 1986).
The Philippines have two major fish commodities: fresh and cured (FAO Yearbook of Fishery Statistics, Fishery Commodities, 1960, 1967, 1971, 1976, 1981 and 1987). This leaves the other processes as canning and reduction open for expansion.
In Indonesia, milkfish is an important food in Java. Fish are marketed fresh, iced, cured in brine, boiled, or reduced to a paste called “petis” which is used as a food flavouring. Smoked milkfish, considered a luxury, is enjoyed by well-to-do Indonesians. Large milkfish, ready a meter in length and weighing over 7 kg are sold for up to US$1,500 a fish for such special occasions as religious offerings during certain annual festivals.
Recently, the Indonesian government also considered promoting the use of milkfish as baitfish for the tuna fishery.
Problems and Future Prospects
Although it has been practiced for several centuries, milkfish farming is becoming more challenging and presents now problems.
Milkfish is a traditional food fish in these three milkfish producing countries, but is not popular in many other countries because it is a bony fish. In order to open new markets, promotion of milkfish is required. Additional milkfish commodities such as the famous “boneless bangus” in the Philippines and smoked fish in Indonesia can be developed to make the fish more attractive for exports to non-traditional consumers of milkfish.
Limited capacity of existing market
Milkfish have been mostly marketed as fresh fish. Therefore, market demands at certain times created price fluctuations. The peak prices can double or triple non-peak prices, depending on market supply and demand. In Indonesia, it is not unusual for the transportation cost for fresh fish to be higher than the cost of fish itself. Transportation between the production area and the market is often not readily available and costs are high. Techniques for processing milkfish in other forms, such as canning and drying, have been developed in Taiwan. These techniques are not well applied and current production levels cannot economically support such a plant. However, we can not overlook its possible future importance.
The declining profitability of milkfish (Smith and Chong, 1984) is related to the increasing cost of land and labour as well as the two factors mentioned above. This problem can be overcome with an increase in market demand and establishment of new markets. Another solution is to diversify markets. One area that can be expanded is providing baitfish for the tuna industry. Milkfish is a very good bait for the longline tuna fishery because of its hardiness during transport, attractive silver color and schooling behavior under the boat. The catch ratio is 1 to 15–25. The use of cultured milkfish as bait also saves tuna fleets time and energy spent looking for bait at sea.
Competition of land usage
Some of the brackish water ponds for milkfish culture are very suitable for tiger shrimp farming. Owing to the high price of shrimp, many fish farmers completely or partially shift to shrimp farming or other high value aquatic products. For example, milkfish pond hectarage fell by more than half between 1983 and 1988 according to Taiwan Fisheries Bureau. The improvement of culture techniques to increase the unit yield is the only way to increase income.
Instability of Fry Supply
Availability of milkfish fry is unstable. The cost of fry represented 40%, 15% and 19% of the total production cost in Taiwan, the Philippines and Indonesia, respectively (Shang, 1986). A stable and adequate supply of milkfish fry at a reasonable price is expected by the future milkfish industry. Mass production of fry from hatcheries should become available in the very near future in view of recent technological developments. Currently, there are four milkfish farmers in Taiwan producing milkfish fry for culture purposes. Through funding from USAID, the Oceanic Institute is developing a technology for mass production of milkfish fry. Those efforts will ensure the stable supply of milkfish fry in the next few years.
In spite of the problems that the milkfish industry is encountering, milkfish will continue to be one of the favored aquatic products in major milkfish producing countries. The total milkfish culture area may decline because the shift of land use to other aquatic animals, but total milkfish production will remain able to meet the market demand through the improvement in production technology. This has been demonstrated in Taiwan. The traditional shallow-water culture system will continue to play its role in providing affordable animal protein source to the general public. At the same time, more and more milkfish farmers will change to the more intensive deep-water culture method. The milkfish industry can also be expanded through development of marketing strategies to open new markets and by providing bait for the tuna industry.
This report was written with the support of a project funded by the United States Agency for International Development (DAN-4161-A-00-4055-00). We are especially grateful to Dr. C.S. Tamaru for his technical assistance and C.Bingham for editing help.
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