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Annex XII

Renato Agbayani

SEAFDEC Aquaculture Department

Flor F. Abella

Bureau of Fisheries Aquatic Resources


The mollusc industry of the Philippines has contributed to the economic development of the country in terms of food production and dollar earning. The industry has continuously provided cheap but nutritious shellfishes. Production was 22, 528 MT in 1981 which increased to 41,700 MT in 1985. Shellfish and shellcraft products exported in 1987 earned an estimated US$ 26.55 million.

Producing of mollusc for food has not been a fully exploited activity area. Areas suitable for oyster and mussel farming have been underutilized. One reason for the underutilization of potential farming areas is the lack of efficient marketing and processing facilities and appropriate strategies that will encourage more consumption of shellfish. Specifically, the quality of shellfish must be improved through better harvesting, post-harvest/processing techniques and an efficient distribution system.


The annual production of molluscs from 1981 to 1987 is shown in Table 1. The figures include the yield from both capture and culture fisheries. Aquaculture production of oysters and mussels is from 69–99% of total production. From 1981 to 1985 production increased yearly by 14% but decreased in the succeeding years at an annual rate of 25% (Figure 1). In 1985 the Philippines produced 1.4% of total world production of oysters and 3.7% of mussels. In the same year, the country ranked 8th in total world production of both species (Chew 1989).

Table 2 shows the estimated area in the country with potentials for mussel farming. In 1981, 427 ha out of a potential area of 11,600 ha was used for oyster farming. Mussel was cultured in 217 ha of the potential 6,878 ha. The average size of a mollusc farm is 250 sq. m. operated on a part-time basis by fishermen who have other sources of income.

Figure 1.

Figure 1. Production of oysters and mussels in the Philippines.

Table 1. Production of bivalves in the Philippines from 1981–1986 in MT. (Source: Fishery Statistics of the Philippines 1986–87, Bureau of Fisheries and Aquatic Resources).

TOTAL22528261203105837444 3705734018


The culture system used in mollusc farming varies depending on site suitability, availability and cost of materials needed. The most popular technique is the stake method (PCARRD 1974). Bamboo is the common material used for its availability in most of the farming areas and its relatively lower cost. The bamboos, sharpened at the base, are staked 0.5 to 1.0 meter apart. This practice however has caused siltation in the sites resulting in decreasing productivity. The farmers regularly inspect the farms to monitor the growth of the stock and control unwanted organisms that compete for space.

A relatively new method introduced in Capiz Province is the rope web method. One unit of rope web consists of two 5-meter ropes, placed 2 meters apart and connected by a long rope in a zigzag fashion at an interval of 40 cm. Bamboo pegs are inserted into the zigzag rope to prevent the crop from slipping due to its weight. Each unit is strung across a pair of bamboo stakes parallel to the water current.

Table 2. Estimated potential area for mussel farming in the Philippines. (Source: Glude et al., 1981).

LOCATIONNumber of farmsArea used (ha)Potential area (ha)
Zambales  23
Bulacan  10
Mindoro Oriental  10
Palawan  25
Quezon  1200
Iloilo  10
Aklan  100
Negros Occidental62100
Cebu  50
Bohol  50
Leyte  100

Another culture technique in the Philippines is the hanging method. Holes are bored on the center of empty oyster and coconut shells and strung on 1- to 2-meter long ropes at an interval of 24 cm. The ropes are tied at one end to a series of horizontal braces of bamboo poles or rafts. Spats cling to the hanging end of the ropes.

The raft method is used in deeper waters (Sitoy et al 1983). It consists of a rigid framework or lattice structure from which the ropes are hung. Buoys are used to keep the framework, which is usually made of bamboo, afloat. Styrofoam blocks for buoys have been found to be efficient and longer-lasting if properly maintained. The initial cost however is higher than other materials.

The tray method uses bamboo trays (1.5 m × 1 m with 15 cm sides). This has been found to be practical in still waters with firm bottoms where silt is minimal. The oyster seedlings are placed in the trays to grow to marketable size.

The oldest culture practice is the broadcast method. Empty oyster shells, stones, tin cans or any hard objct are thrown into areas where spatfall occur. This is the cheapest method since no materials are needed and labor is used only during harvest. The yield per unit area, however, is low due to limited space for spat attachment.


A. Nature of the Product

Filipinos highly prefer fresh foods especially fish products including shellfish. For shellfish, which are highly perishable, the time gap between harvest and consumption directly affects the quality. Improved harvesting and post-harvesting methods are, therefore, needed to ensure that the shellfish reach the market in fresh condition.

The biggest market for shellfish is the Metro manila area. The nearest source is Cavite which is about one hour drive away. The produce of other farms located in the Visayas reach Metro Manila in 24 to 48 hours by boat. Airshipping is not advisable because of high cost. Aside from freshness, the other factor that affects the price of shellfish is the size of the meat. Harvesting must be timed before spawning, when the mantle of the shellfish is thick and fleshy.

B. Distribution Channels

The distribution channels of shellfish in the Philipines are similar to those of other fish products. The diagram below shows the flow of goods from the farm to the consumer.

The factors affecting the selection of intermediaries are the following:

  1. Prices and terms of payment
  2. Volume and quality of products
  3. Physical distance from market to farm
  4. Control of farmer over the intermediary

Bidding is practised when the harvest is brought to the fish market. There are instances of negotiated sale especially when the seller is a reliable and established supplier.

C. Pricing Schemes

Wholesale price of shellfish is determined primarily by market forces i.e. supply and demand on any trading day. The price increase during the past few years has been primarily due to inflation (8% in 1988). The cost of production in the shellfish farm does not in any way affect prices in the market. The prevailing market prices of oysters and mussels in Metro Manila as of July, 1989 were as follows:

Oysterper gallon, liveP20 – 30
Oystershucked in gallon with ice water35 – 40
Musselper gallon, live15 – 25

D. Promotions

Three years ago, the government launched a nutrition campaign using the mass media to encourage people to eat cheap but nutritious food such as molluscs. The campaign was not sustained for some reason, probably budget constraint. At present, the Department of Health is undertaking reach-out nutrition programs in the countryside.

The private sector has not undertaken any promotional campaign since most of the shellfish growers are sustenance fishermen.


One of the problems identified in the mollusc industry is the poor state of post-harvest and processing techniques. There have been headways made in the development of processing techniques by reesearch institutions such the SEAFDEC Aquaculture Department, Bureau of Fisheries and Aquatic Resources, Seafarming Research and Development Center of the Philippine Human Resource Development Center (PHRDC), and the University of the Philippines in the Visayas.

A. Post-harvest Techniques

Studies have been undertaken to keep harvested shellfish alive for a number of days by keeping them cool with ice, banana leaves and wet burlap and dipping in seawater (Guevarra 1987). The mussels were able to stay alive out of water for more than four days at a temperature of 12 to 14° C with the use of ice. Storing in styrofoam boxes with ice resulted in high survival at a 1:4 ice to mussel ratio. Frezing at -10° C with 3% brine solution showed that the freshly shucked mussels were still acceptable on the 22nd day.

The use of polyethylene bags as packing materials gave higher survival than the use of plastic sacks at a temperature of 14–16° C.

B. Processing Techniques

1. Depuration

In 1982, the Bureau of Fisheries and Aquatic Resources made a study on home depuration of green mussel, Perna viridis. The mussel was placed in clean sea water with 3% iodized salt solution for 18 to 24 hours. The bacterial load of the mussel was effectively reduced (Guevarra et al 1982). This home depuration technique can be easily and practically adopted by housewives to ensure safer oysters and mussels for home consumption.

The SEAFDEC Aquaculture Department undertook experiments on depuration (Gacutan et al 1987) using 6 rectangular (96 × 196 × 42 cm) fiberglass-coated tanks. The capacity ranges from 230 to 310 kg of oysters in 2 days. Initial findings showed that a moderate flow (7 to 10 liters/min) of water depurated grossly contaminated oysters within 48 hrs or less.

On a bigger scale, the Seafarming Research and Development Center has been continuously undertaking research on oyster depuration (Torilla et al 1987). Coliform level in oysters has been found to diminish steadily by drawing water three times from the tanks. The fiberglass tank -- 190 × 90 × 70 cm -- could contain 200 to 500 pcs of oyster in a single layer filled with 580 liters of water. The flow rate was 7 liters/min and water was changed every 1.5 hrs.

The study on water purification was done using sand-filtered and ultraviolet-radiated seawater. Acceptable coliform levels were observed from the 36th hour onward.

The BFAR also conducted a similar study using the PHDRDC facilities. Two methods were used, namely, the filtered seawater and filtered seawater treated with ultraviolet light. The microbial load samples were reduced within 48 hrs using filtration alone compared to the use of filtered seawater treated with UV rays after 12 hours.

The University of the Philippies in the Visayas College of Fisheries in collaboration with the German Agency for Technical Cooperation conducted depuration studies on mussels and oysters. The depuration tanks were designed with a weir-type overflow and baffle inlet. The tanks, measuring 240 × 76 × 14 cm, were made of marine plywood or fiberglass. Five tanks were stacked on metal frame over a sump and UV-sterilized seawater recirculated through the system for 36–48 hours to allow the molluscs to purify naturally. Microbial tests indicated the effectiveness of depuration system in reducing the coliform count to acceptable levels.

2. Social and economic study on depuration

A social and economic survey (Choudhury 1987) on the impact of depuration to potential users and the community was conducted in the province of Cavite. The survey results indicated that the mollusc farmers were not willing to accept the responsibility of depurating their produce. The reasons included the following: (1) it entailed additional process, (2) cost of investment was high and (3) there is a lower market for more expensive depurated oysters. In gneral the people of Bacoor, Cavite were wary of undertaking new projects with high investment and no assurance of profit or identified market outlets.

3. Drying and dehydration

Drying has been found to be a cheap and eficient way of preserving molluscs. Mussels can be preserved for 2–3 months and squid up to 6 months at ambient temperatures. The types od drying currently in use are through the use of solar and agro-waste dryers and ordinary sun drying. Moisture contents range from 11.69% to 12.47% depending on the type of dryer.

4. Other Methods

The other methods of processing shellfishes in the Philippines are smoking, salting, bottling/canning and pasteurizing. The last three methods have not gone beyond laboratory experiment stage.


The mollusc industry can provide the people with cheap and nutritious food and can earn dollars for the cash-strapped economy. Table 3 show the Philippine bivalve export by country of destination. The following recommendations are forwarded for consideration of appropriate government agencies.

  1. Undertake continuous research on and devlopment of culture, harvest, post-harvest and processing techniques.

  2. Establish and maintain pilot-scale processing stations in molllusc producing provinces to serve as models to farmers.

  3. Establish fishermen associations to serve as conduits for technology transfer, marketing and processing facilities and structures, and credit facilities.

  4. Educate the consumers on the nutritional value of shellfish.

Table 3. Philippines export of bivalves by country of destination (1986-1987).

ItemsCountry1986 1987 Quantity (kg)Value (Peso)
Quantity (kg)Value (Peso)Country
A. Clams, prepared or preserved in airtight containersUSA823,655USA30813,924
Pacific Is.16773Pacific Is.16711
   United Kingdom492,132
Total 380,42013,883,838 1,456,78597,260,501
B. Oysters      
1. Fresh,chilled and frozenUSA2543,582West Germany5,700110,194
2. Prepared or preserved in airtight containerCanada734,201Canada21111,576
Saudi Arabia2,734121,905Saudi Arabia96046,879
Arabian Estates1829,017Arabian Estates43318,678
Pacific Is.241,404Pacific Is.241,279
   West Germany40822,769
   New Guinea654,515
   New Zealand733,489
Total 9,206441,620 13,309494,854
C. Mussels, prepared or preserved in airtight containerUSA99146,611USA1,16556,735
Saudi Arabia1,99480,351Saudi Arabia1,22445,016
Arabian Estates45721,547Arabian Estates55522,074
   New Zealand1064,005
Total 5,384224,471 3,382141,652
D. Shells and By-productsSixty two countries7,663,314327,923,242Seventy seven countries9,679,803433,062,462

Source: Fishery Statistics of the Philippines 1986 – 1987 Bureau of Fisheries and Aquatic Resources


Anon. 1977. The Philippines recommends for mussels and oysters. PCARRD, Los Banos, Laguna, Phil. 42 pp.

Anon. 1987–1988. Fishery statistics of the Philippines, BFAR, Quezon City, Phil., 540 and 508 pp.

Anon. 1986. Status of mollusc resources and prospects for development. Proc. Seminar Workshop, Cebu City, Phil., 2–3 May 1986, 135 pp.

Caoile, S.J. 1988. Depuration - SRDC experiences. Proc. ASEAN consultative workshop on mollusc depuration, ASEAN-Australia Economic Cooperation Programme, 4–7 Oct., 1988, Penang, Mal.

Davy, F.B. and M. Graham. 1982. Bivalve culture in Asia and the Pacific. Proc. workshop in Singapore, 16–19 Feb 1982. 90 pp.

Gacutan, R.Q., M.L. Bulalacao and H.K.L. Baranda, Jr. 1986. Bacterial depuration of grossly contaminated oyster (C. iredalei). Proc. First Asian Fisheries Forum, McLean et al, eds. pp 429–31.

Genato, R.T., R.P. Ronquillo, J.B. Vista and A. Lustre. 1979. Survey of the microbial load of freshly harvested oyster in the Binakayan, Cavite area. National Institute of Science and Technology leaflet.

Guevarra, G., F.F. Abella, S.C. Villafranca and H.C. Ballo. 1978. Studies on handling and depuration of green bay mussel (Perna viridis). Phil. Journ Fish. v 16 no. 2, July-Dec 1978 pp 105–115.

Juntarashote, K., S. Bahromtanarat and H. Grizel. 1987. Shellfish culture in Southeast Asia. SEAFDEC, Bangkok. 72 pp.

Chew, K. 1989. Recent trends in bivalve culture in the Orient. Aquaculture Magazine v 15 no. 3 May-June 1989, pp41–54.

Legaspi, A.S. 1988. Shellfish depuration -- challenges and opportunities to the industries. Proc. ASEAN consulative workshop on mollusc depuration, ASEAN-Australia Economic Cooperation Programme, 4–7 Oct 1988, Penang, Mal.

Matienzo, L.H. Jr. 1983. A report on depuration: A cleansing plant for oysters. Greenfields 13 (9) : pp 42–43.

Palpal-latoc, E. 1986. The sanitary quality of four Philippine oyster-growing areas. The First Asian Fisheries Forum, McLean et al, eds. pp. 447–450.

Rosario, W., N. Poquis and M. Rice. 1982. Oyster depuration: one answer to the problem of shellfish culture in polluted estuaries. Fishery leaflet, BFAR Regon I, Dagupan City, Phil.

Sitoy, H.S., A.L. Young and M.Y. Tabnbu. 1983. Raft culture of mussels. Extn manual No. 8, SEAFDEC AQD, Iloilo, Phil. 12 p.

Torilla, H.T., C.A. Ordanza, and P.A. de Vera. 1987. Annual report of the Seafarming Research and Development Center, Phil. Human Resources Dev. Center, Dagupan City, Phil. 151 pp.

Young A. and E. Serna. 1982. Country report of the Phil. Proc. Workshop on bivalve culture in Asia and the Pacific. 16–19 Feb 1982, Singapore. pp. 55–68.

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