Body fusiform, elongated, moderately compressed, smooth and streamlined. Body colour silvery on belly and sides grading to olive-green or blue on back. Dorsal, anal and caudal fins pale or yellowish with dark margins. Single dorsal fin with 2 spines and 13-17 soft rays. Short anal fin with 2 spines and 8-10 soft rays, close to caudal fin. Caudal fin large and deeply forked with large scale flaps at base in adults. Pectoral fins low on body with axillary (inner basal) scales. Pelvic fins abdominal with axillary scales and 11 or 12 rays. Scales cycloid, small and smooth, 75-91 on lateral line. No scutes (modified pointed scales) along belly. Transparent 'adipose' tissue covers eye. Mouth small and terminal without teeth. Lower jaw with small tubercle at tip, fitting into notch in upper jaw. No bony gular plate between arms of lower jaw. Four branchiostegal rays supporting underside of gill covers. Gill rakers fine and numerous. Attains typical length of 1 m but may reach maximum length of 1.8 m (male).
Milkfish farming in Indonesia, Taiwan Province of China and the Philippines started about 4-6 centuries ago. Culture methods in a variety of enclosures are constantly being improved upon. Since the 1970s, large investments have been made in the Philippines (as well as in Taiwan Province of China, Indonesia and Hawaii) in terms of infrastructure, research, credit and training in support to the milkfish industry. For example, the Southeast Asian Fisheries Development Center (SEAFDEC) Aquaculture Department (AQD) was established in Iloilo, Philippines in 1973 with a special remit to find solutions for milkfish aquaculture problems. Government agencies and fisheries institutions were also involved in a national effort to intensify milkfish farming from the mid 1970s until now. In this work, research and development on farming systems, breeding and fry production technologies was carried out. There was no attempt at genetic improvement but fry translocation and trade occurred between Indonesia, Taiwan Province of China and the Philippines and geographic variations and heterogeneity were documented. More recently, unconfirmed reports indicate that milkfish are now being cultured to fingerling or juvenile size in the South Pacific Islands and in Singapore as tuna bait.
Milkfish farming was previously a traditional industry, with little emphasis on producing sexually mature, reproductively active fish in captivity. The traditional milkfish industry depended totally on an annual restocking of farm ponds with fingerlings reared from wild-caught fry. As a result, the industry suffered from regional, seasonal and annual variations in fry availability. These variations are generally unpredictable, and may be quite large over short periods of time.
Thus, the central problem faced by the international milkfish industry was to find a way to produce a reliable, adequate, high quality supply of milkfish fry that was not subject to large unpredictable variations in time and space. During the past decade, much progress has been made, particularly in regard to milkfish propagation and the mass production of fry by private hatcheries, research institutions and government agencies. Instead of relying on wild-caught fry, milkfish farms in the Philippines, Taiwan Province of China and Indonesia now obtain the majority of their fry from hatcheries, mainly due to the significant shortage of wild-caught fry.
Milkfish (Chanos chanos) is the only species in the Family Chanidae. Its distribution is restricted to either low latitude tropics or the subtropical northern hemisphere along continental shelves and around islands, where temperatures are greater than 20 °C (Red Sea and South Africa to Hawaii and the Marquesas, north to Japan and south to Victoria, Australia; and in the Eastern Pacific from San Pedro, California to the Galapagos).
Adults occur in small to large schools near the coasts or around islands. They are well developed, migratory, large (up to 1.5 m and 20 kg), and mature sexually in 5 years. Milkfish only spawn in fully saline waters. The activity is most often correlated with the new or full moon phases, takes place mostly in the night and, in most regions, has one or two seasonal peaks. In the natural environment, spawning takes place near coral reefs during the warm months of the year, and populations near the equator spawn year-round. Juveniles and adults eat a wide variety of relatively soft and small food items, from microbial mats to detritus, epiphytes and zooplankton.
Milkfish is a heterosexual fish; hermaphrodism has not been reported. In natural spawning stocks the sex ratio is almost equal, with a slightly higher amount of females. The determination of sex is very difficult, because there are no easily identifiable morphological differences between males and females; however, the pheromone PGF2a (prostaglandin) has been found to be an effective way to identify mature male milkfish.
Milkfish eggs (1.1-1.2 mm in diameter) and larvae (3.5 mm at hatching) are pelagic and stay in the plankton for up to 2-3 weeks. Egg division begins an hour after and hatching occurs 35-36 hours after spawning. In the wild, eggs are probably released in deeper oceanic waters and in the outer reef region. Older larvae migrate onshore and settle in coastal wetlands (mangroves, estuaries) during the juvenile stage, or occasionally enter freshwater lakes. The larvae eat zooplankton and can thrive and grow in water as warm as 32 °C. They then migrate onshore and where they can be caught by fine-mesh nets operated along sandy beaches and mangrove areas; these 'fry' are 10-17 mm long and are used as seedstock in grow-out ponds, pens and cages. In the wild, juveniles are found in mangrove areas and coastal lagoons, and even travel upriver into lakes; they go back to sea when they get too large for the nursery habitat, or when they are about to mature sexually.
Milkfish can reach a maximum size of 180 cm SL (male/unsexed) and 124 cm SL (female). The maximum recorded weight and age is 14.0 kg and 15 years respectively. Resilience is low, with a minimum population doubling time of 4.5 - 14 years. Its fisheries importance is highly commercial, especially in aquaculture, and it is also used in game fish as bait. It is especially valued as a food fish in Southeast Asia.
Milkfish fry can either be obtained through collection from coastal areas or littoral waters or can be produced in captivity. The supply of wild fry is often unpredictable; catches in recent years have diminished and cannot satisfy the demand from ongrowing farms.
Fry from captive broodstock and spawners
To develop broodstock under captive conditions, large juvenile milkfish may be stocked, fed and maintained in floating sea cages in protected coves or in large, deep, fully saline ponds (as practiced in the Philippines), or in large deep concrete tanks on land (as practiced in Indonesia and Taiwan Province of China), until they reach sexual maturity with an average body weight of at least 1.5 kg. Land-based broodstock facilities are entirely dependent on fresh pumped seawater supplies and are often integrated with a hatchery.
Broodstocks reach maturity in five years in large floating cages, but may take 8-10 years in ponds and concrete tanks. On average, first-spawning broodstocks tend to be smaller than adults caught from the wild. As a result, first-time spawners produce fewer eggs than wild adults, but larger and older broodstocks produce as many eggs as wild adults of similar size. Broodstocks of about 8 years old and averaging 6 kg produce 3-4 million eggs.
Breeding milkfish in captive conditions and the mass production of fry, as practised in Taiwan Province of China, Indonesia and the Philippines, is mostly dependent on natural spawning, which assures high survival rates. Artificial induction is not normally used. On days when natural spawning occurs, the fish may feed less than usual but show increased swimming activity and exhibit chasing, occasional leaping, and water-slapping activities from late noon to early evening. Spawning usually takes place around midnight but daytime spawning sometimes occurs.
Wild-caught fry are collected with fine-mesh seines and bag nets of various indigenous designs in the Philippines, Taiwan Province of China and Indonesia. The most commonly used gear are push net 'sweepers' and dragged seines.
Milkfish hatcheries consist of larval rearing tanks, culture tanks for rotifers (Brachionus) and green algae (e.g. Chlorella) and hatching tanks for brine shrimp (Artemia). Larval rearing may be either operated in outdoor or indoor systems, depending on the specific conditions in the countries where fry are being produced.
Hatchery operations utilize either intensive (high stocking density, high volume tanks, daily feeding and water exchange) or semi-intensive (low stocking density, high volume tanks, minimal water exchange, feeding with mixed diet) systems, with an average survival rate of 30 percent (from stocked newly-hatched larvae). After hatching, the larvae are ideally kept at 50/litre in hatchery tanks (either concrete, fibreglass, canvas or polypropylene-covered earthen tanks) maintained with Chlorella and fed with rotifers during the early stages and later with copepods or brine shrimp for a total of 3-4 weeks. Following this, their size ranges between 2-3 cm and they are ready for transport to nurseries.
The fry may change hands two or more times before being used for grow-out; each time this happens, they are sorted and counted, transported, and stored for different periods of time. Fry are a highly perishable commodity and some of them die during gathering, storage, transport, nursery rearing and grow-out. The technologies for fry storage and transport are generally effective, although perhaps not yet optimized. Fry are stored in a cool place in plastic basins or clay pots at 100-500/litre, in water of 10-25‰, which is renewed daily. Dealers may store fry for 1-7 days, depending on the demand. Fry can be maintained on wheat flour or cooked chicken egg yolk for 1-2 weeks but soon begin to die, despite continued feeding. Recently, micro-encapsulated feeds have become commercially available for finfish but the cost compared to conventional live feeds is higher.
Nursery operations in milkfish producing countries vary according to established cultural practices.
In Taiwan Province of China, where commercial hatchery and nursery productions are integrated enterprises, milkfish fry are generally grown in either earthen ponds or elevated canvas or concrete tanks at intensive stocking densities of >2 000/litre.
In Indonesia, a well established backyard-type nursery is used. This consists of a series of elevated canvas or concrete 1-2 tonnes tanks and similar stocking densities to those used in Taiwan Province of China are employed.
In the Philippines, milkfish nurseries are integrated with grow-out facilities, where wild-caught or hatchery-reared fry are first acclimated into nursery compartments which comprise one third to one quarter of the total area of the Brackish water pond. Fry are stocked at a density of up to 1 000/litre and are fed with a naturally-grown micro-benthic food known as 'lab-lab' which grows on the fertilized pond bottom. Nursery rearing has also been carried out in hapa type suspended nylon nets installed in Brackish water ponds or lagoons and in freshwater lakes within the grow-out compartments, a traditionally practice in the Philippines. When natural food is becoming depleted, artificial feeds such as rice bran, corn bran, and stale bread or formulated feeds are provided. In about 4-6 weeks, the fry grow to 5-8 cm juveniles, which is the ideal size for releasing into grow-out ponds or pens. Depending on the desired grow-out period, juveniles or fingerling size milkfish are kept in nurseries or transition holding tanks up to the required stocking size of 30-40 g. Nursery rearing from fry to fingerling size normally achieves 70 percent survival.
Milkfish may be ongrown in ponds, pens or cages.
Culture of milkfish in ponds may be in shallow or deep water systems.
This system was introduced in the Philippines in 1979 in the Laguna Lake. At that time, the lake had a very high primary productivity, which met the nutritional needs of milkfish. Because of the low rate of input and the high rate of return, the pen culture area increased sharply from 1973 to 1983, and exceeded more than 50 percent of the total lake surface, which is 90 000 ha. As the primary production of the lake could not meet this sudden expansion of aquaculture, and feeding became necessary to meet the nutritional requirements of the cultured fish, the pen culture practices developed in lakes were later introduced into inter-tidal areas in the Philippines along coves and river estuaries as well. Pen operators stock fingerlings at 30 000-35 000/ha and provide supplemental commercial diets. However, disease spreads among culture pens and causes mass mortality. Government regulations are now being considered to maintain sustainable yields from this type of farming.
Fish cages are smaller and more restricted enclosures that can be staked in shallow waters or set-up in deep water with appropriate floats and anchors. Cage farming of milkfish is commonly carried out in marine waters along coastal bays. Stocking rates (in the Philippines) are quite high, from 5 up to 30/m³.
In the past, traditional feeding practices for milkfish grow-out production have consisted of natural food ('lab-lab') or a combination of phytoplankton and macroalgae (Enteromorpha intestinales, Cladophora spp. or Chaetomorpha linnum) encouraged by fertilization. In the 1980s however, special commercial feeds for milkfish were developed and became almost exclusively used. As cage and pen culture technology proliferated in the 1990s, both in marine and inland waters, extruded milkfish feeds were further developed into floating and semi-floating forms, while sinking forms were used for pond and tank-based grow-out. Feed supplies are now manufactured commercially in the form of starters, growers and finishers, which are administered according to the production stage of the milkfish.
Milkfish are normally harvested at sizes of 20-40 cm (about 250-500 g). There are three known methods used for harvesting milkfish:
200-400 g milkfish are harvested and marketed mostly fresh or chilled, whole or deboned, frozen, or processed (e.g. fresh frozen deboned, fresh frozen deboned descaled, and smoked fish deboned). In general, all marketed milkfish are produced in farms, only a few being caught from natural waters. In some countries (e.g. the Philippines) fishing for adult milkfish is officially banned in order to protect the natural broodstocks.
There are two known post-harvest processing techniques for milkfish, which are the traditional (i.e. drying, fermentation and smoking) or non-traditional methods (i.e. bottling, canning and freezing) and value-added products such as 'surimi' and deboned products as practiced in Taiwan Province of China and in the Philippines.
Regulations and standard protocols for manufacturing milkfish products exist for both domestic consumption and export, as follows:
Milkfish farming is a centuries-old industry in Indonesia, Taiwan Province of China and the Philippines. It has been slow to modernize and now faces challenges from competing aquaculture species and current economic realities. The domestic market is large and the export market has globally expanded. Milkfish price and personal income affect the amount of milkfish consumed in the countries of origin. Studies conducted in Taiwan Province of China and the Philippines concluded that price and income had a negative and positive elasticity coefficient, respectively.
The following are the major determining factors affecting the cost of production in milkfish:
The major disease problems affecting milkfish are included in the table below.
In some cases antibiotics and other pharmaceuticals have been used in treatment but their inclusion in this table does not imply an FAO recommendation.
Suppliers of pathology expertise
The following are examples of locations where expertise can be accessed:
Producers of milkfish do not usually sell fish directly to consumers, but supply them through cooperatives, brokers, dealers, collectors or wholesalers, and retailers. In general, the majority of fish products are sold in auction markets through dealers, brokers, wholesalers or cooperatives to smaller dealers, and then retailers.
Increasingly, more of the milkfish harvest is processed into value-added forms: smoked, dried, marinated (brined, sweetened), fermented with rice, and canned or bottled in various styles (salmon style, sardine style, Spanish style, smoked in oil, etc.). Some companies in the Philippines now produce frozen prime cuts of milkfish bellies and backs, and even of heads and tails. Milkfish is exported in different product forms: quick-frozen, dried, canned, smoked or marinated.
The Philippines recorded an export of over 17 040 kg of milkfish products to the EU in 2002, valued at USD 58 000. While Taiwan Province of China concentrates on processed and value-added products for export to the USA, Indonesia has strengthened its export of hatchery-reared seedstock to the rest of the Asia-Pacific region for tuna bait and for grow-out.
Research and development
Successful induced spawning and larval rearing of milkfish were first accomplished at SEAFDEC/AQD in 1976-1978. The first generation cycle of milkfish in captivity was completed at AQD when the offspring of a wild female induced to spawn in 1978 in turn spawned in 1983. Since then, milkfish have matured and spawned in floating cages, ponds, and concrete tanks in the Philippines, Taiwan Province of China, Hawaii, and Indonesia. Since the successful completion of larval rearing technology in 1984, fry production has increased significantly, which has not only provided milkfish farmers in Taiwan Province of China with ample supply but also opened an export market to neighbouring countries.
To date no substantial technical and scientific research has been documented from major milkfish producing countries other than the policy and management related research being conducted by the WorldFish Center, the SEAFDEC Aquaculture Department and the Bureau of Agricultural Research and BFAR of the Philippine Department of Agriculture.
Taiwan Province of China, however, has recently developed an improved strain of milkfish through selective breeding process resulting in a golden coloured F1 pioneered by a private farmer; this would accordingly command a better price than the original silvery coloured strain, once introduced in the market.
The development of more efficient culture systems has resulted in higher milkfish production, which continues to increase.
Diversification of aquaculture in Taiwan Province of China, however, has paved the way for prioritizing other high valued commercial marine species of fish, which has affected the growth of the milkfish industry.
Based on current trends, production in the Philippines (which has expanded its traditional land-based milkfish farming from Brackish water fishponds to marine cages in coastal communities through the establishments of mariculture parks) is expected to rise from 289 000 tonnes in 2005 to 369 000 tonnes in 2010. Assuming that the population of the Philippines reached 84 million by the year 2005, at per capita milkfish consumption of 2.5 kg/yr the total milkfish requirement would reach 210 000 tonnes. With the actual milkfish production recorded as of 289 000 tonnes in 2005, there would have been an estimated supply surplus of 79 000 tonnes.In Indonesia backyard hatchery production of milkfish seeds has become a rural industry at the village level. The majority of these hatcheries have further shifted to fry production of high-value species of marine finfish.
Marketing of milkfish products contribute a lot to the sustainability of the industry in the major milkfish producing countries - Indonesia with its seed production exports, Taiwan Province of China with value-added milkfish products and the Philippines with whole fresh and processed products both for domestic and export markets.
The General Agreement on Tariffs and Trade GATT/WTO impositions of trade restrictions and the EU/US bio-safety and quality control standards are considerably affecting the producing countries and are foreseen to be an added burden among production costs.
Although HACCP from farm to product processing are now strictly observed (for both domestic and export markets) in the major producing countries, farmers and processors view this as another trade barrier that has been set by the importing industrialized countries.
The following recommendations are suggested:
The main issues in milkfish farming can be summarized as follows:
Due to global market demand, major milkfish producing countries have recently been promoting management practices that address food quality and safety issues. At the farm level for example, the Philippines complies with the minimum aquaculture HACCP requirements, from hatchery production to harvest, before milkfish products are processed for export. Taiwan Province of China has introduced product eco-labelling in order to export quality branded processed milkfish products, while Indonesia ensures the quality of milkfish fry when exporting to neighbouring Asian countries and accompanies them with health certificates. Traceability in the use of antibiotics and unregulated drugs is already strictly imposed in these countries.
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