NETCAGE CULTURE OF FINFISHES IN THE PHILIPPINES

Marita R. Ocampo ¹
Emmanuel Delamide ²
Teodulo Toledo ³

I. Introduction

Fishing is a major industry in the Philippines, an archipelago of 7,100 islands, with a coastline 17,460 kilometers long. Its water surface area of 1.7 million km consisting of archipelagic and treaty-negotiated territorial sea, is bigger than its land area of 300,000 km though its productive shelf area within the 200 m isobath is about 225,000 km only.
Fish, together with rice, is a main staple in the Filipino diet, and is the main source of protein. The per capita consumption of fish is 35.7 kg. The demand for fish as food, which is greater than what can be presently supplied, provides the impetus to further production.
The fishing industry contributes 5 % of the country's GNP. It employs over one million people, which constitutes 3.1 % of the total national labour force. In 1987, the industry produced 2,140.00 MT of fish, worth approximately US$ 2 billion, or 42 billion pesos.
The future of the Philippine fishing industry lies not only in sustaining the productive capacity of its marine fishing grounds but also in tapping the potentials of aquaculture, where new areas like swampland, tidal flats, and coves can be made available to reproductive fish farming systems. The industry is however facing a crisis in capture fisheries, its leading sector. The fish stocks in seashore fisheries are being depleted due to overfishing, illegal fishing and environmental changes.

II. Seafarming as an Alternative to Small-scale Capture Fisheries

The catch of 675,677 fishermen in coastal fishing grounds provides the main bulk of the country's total fish production. In 1987, municipal culture fishermen landed 1,056,970 MT of fish, or 49 % of the total. On the surface, this catch statistics seems impressive, but on closer look at the trend, it becomes less so. From 1978 to the present, the production growth rate in this sector has been decreasing. Actual decrease in production was experienced in 1979, 1981, 1984, 1985 and 1987.
The decline in municipal fisheries can be traced to the depletion of fish stocks in overexploited traditional fishing grounds. Other factors such as pollution, illegal fishing methods which destroy natural habitats like coral reefs and mangrove forests, and too many fishermen, also contribute to this declining trend.

¹ Senior Fishery Biologist, Department of Agriculture, Region III, San Fernando, Pampanga.

^2,3 Fish farmers engaged on Marine Cage Culture of Cebu City and Occidental Mindoro respectively.

Programmes have been designed to increase productivity per fishing effort - such as the introduction of multi-fishing gears, the modernization of fishing gears, and the motorization of boats (bancas) have not improved the situation. Instead, they resulted in competition among many fishermen over the already diminishing resources.
The decline in production is reflected in the economic status of the sustenance fishermen. A socio-economic survey conducted in 1986 showed that 372,927 of the sustenance fishermen, or 55 % of them lived below the poverty line. The officially cited poverty line is 2,500/month or 30,000/year.
The Philippines has initiated fishery programmes to improve the economic and social status of the small-scale fishermen. A countryside development program is now being implemented to improve their income and profitability through the establishment of viable fishery-based livelihood projects. The identification of mariculture as one of these projects has encouraged the development of netcage culture of high value finfishes.

III. Mariculture and the Netcage Culture of Finfishes - the State of the Art

Mariculture, a sub-sector of aquaculture, is the culture of fishery resources from the shoreline to open sea. It involves the open water culture of mollusk and seaweeds and the netcage culture of high value finfishes.
In the Philippines, the major mollusc and seaweed species being cultured are green mussel (Mytilus viridis), oyster (Ostrea iredalei), red alga (Eucheuma sp.), and the green alga (Caulerpa). For these resources, there are already established industries since the early 1960's. For finfishes, there are at present several hundred units of netcages scattered throughout the country where siganids (Siganus gutatus), groupers (Epinephelus tauvina), seabass (Lates calcarifer), and red snappers (Lutianus johni) are cultured. However, the netcage culture of finfishes is not as established nor as developed as the culture of molluscs and seaweeds. In 1987, the estimated production of mollusc and seaweeds was 319,506 MT, while the rough estimate for cage culture of marine finfishes was less than 150 MT.
This status of finfish farming in cages is not at all surprising. While interest on it as an alternative culture system began in the late 70's, actual technology refinement, transfer and practice took place in the late 80's. This can be accounted by the priority given to pond culture; country's pond culture resources are extensive and it was more easy and economically viable to culture other species. The government's campaign to promote seafarming as an alternative livelihood activity for sustenance fishermen and the high price of these species in the export and local luxury markets gave the impetus for fishfarmers to go into netcage culture. At present, there are netcages for finfishes in Leyte, Capiz, Bohol, Cebu, and Negros in Southern Philippines and in Mindoro, Pangasinan, and Zambales in Luzon. Most of these are protected coves and estuarine areas, away from polluted waters, strong waves and currents, and strong typhoons, yet accessible to water and land transportation.
The culture of finfishes in the Philippines has taken two directions. On one hand, fishfarmers put up nursery netcages to rear fry from the wild, or buy them from gatherers, stocking them in the nursery cages where the fry are reared into fingerlings. The fingerlings are then sold to fishpond operators for earthen pond culture. On the other hand, some fishfarmers stock their grow-out cages with fingerlings, rearing them to marketable size for the local luxury and export market.
Most fishfarmers prefer to culture groupers and siganids, the live groupers for the export market and the siganids for local restaurants and hotels. Groupers and siganids are the most widely cultured species, and the two are often cultured together. Because of the demand for them in local Chinese restaurants, the culture of red snapper is becoming popular, too. The culture of sea bass, which is dependent on the supply of excess trash fish, is seasonal and sporadic.

IV. Culture practices in the Philippines

The early netcage culture practice for groupers and siganids was described as “put and take” method, where fish are held in cages for fattening. However, improved techniques learned from neighboring Asian countries, verified and refined from demonstration farms, and modified by the fishfarmers themselves, are now being used. The culture practices herein cited are an observer's account as seen in Binmaley and Sual towns in Pangasinan and in Zambales, and a personal account of a fish farmer who operates a netcage farm in Capiz.

Case I - Cage Culture Practices in Pangasinan and Zambales

The netcage farms are located in areas suitable for survival and maximum growth. Hydrobiological parameters have been considered. The areas are free from pollutants. They are also near sources of fry.
The netcage farms are located in estuarine areas in protected coves. They are protected from strong winds by aquatic vegetation. Currents during low and high tides do not exceed 60 cm/sec. Waves one meter high occur during the monsoon season but normally the waves are less than 1/2 meter during the rest of the year.
The netcages are set 5 to 15 meters away from the shoreline and at an average depth of 6 meters. The netcage bottoms are 2–3 meters off the sea floor to allow sufficient water exchange at the bottom area. The salinity averages 33 ppt during summer when there is less stratification in the surrounding water column. However, surface and bottom salinities differ during the rainy season. During the rainy months, surface salinity ranges from 18–20 ppt, bottom salinity from 25–30 ppt.
Dissolved oxygen levels stay at stable and acceptable levels from 7–8 ppm. Variation in temperature occurs during the rainy and summer months. Temperature during summer is about 30 °C, and during the rainy season, it is normally 25 °C.

Netcage Construction

The floating netcage farm consists of interlocking cages suspended in a bamboo and/or wooden frame. The farm is floated by either bamboo raft or styrofoam floats, and is held in place by heavy anchors.
The netcages are of different sizes, with nettings of different mesh sizes. The mesh sizes of the netcages depend upon the kinds of netcage. The following are the kinds of netcage with the corresponding mesh size of their nettings:

1. Hapa cage - This is made of very fine-meshed net. It is used for rearing fry to fingerlings. Fry measuring 1–6 cm are initially stocked in this cage.

2. Nursery cage - The netting specification of this cage is nylon V-net No. 60 K. This cage is stocked with 10 cm fingerlings till they reach a size ranging between 15–20 cm.

3. Grow-out cage - The netting specification is PE net No. 400 2 ply 7 K. Fingerlings are reared in this cage till they attain marketable size.

The rope which is used for the main and hanging lines of the hapa and nursery cages is PE Rope No. 6, PE Rope No. 10 is used for the main lines of the grow-out cages.
The frame which is used to hold the interlocked cages together in place also serves as a catwalk and working platform. A frame made of bamboo is preferred over a wooden one mainly due to economic reasons. Besides, the bamboo frame also acts as a flotation device.

Stocking and Stock Manipulation

Fry measuring 1.5–6 cm are sorted out and stocked in 1.5 × 1.5 × 1.5m hapa cages at a stocking density of 100 pcs/m³. When the fry grow to 10–15 cm, they are sorted out again and transferred to 1.5 × 1.5 × 1.5m nursery netcages till they attain a size ranging between 20–50 cm. The stocking density in netcages is 50 pcs/m³. They are then finally transferred to 2 × 2 × 2m grow-out cages at a stocking density of 40 pcs/m³, till they attain marketable size. In thinning out the stock, the expected natural mortality is 10–15 %.
Small fishes like anchovy (dilis) and caesio (tirong) are fed to the carnivorous species. Siganids are fed with algae (lumut). The food for the fry are finely minced and bigger pieces are fed to the bigger fish. Feeding is done once daily, usually at 9.00 a.m. . The fish are fed to satiation which is more or less 15 minutes of continuous hand feeding. The fry are given food daily at 15 % of body weight. The fingerlings receive food equal to 6 % of their biomass. The computed FCR is 1:5.

Maintenance

Regular inspection and repair, at least once every 15 days, is carried out to ensure the safety of the stock. The submerged netting of the hapa and nursery cages are cleared of debris and algae regularly. The entry of siganids in grow-out cages is encouraged for the siganids to clean the nettings from algae.

Prevention of Disease

So far there is no known occurrence of any fish disease in the cages. The good water quality around the site and the favorable environmental conditions ensure the vitality of the stock. Yet, the operators practice regular sanitation measures, like thorough cleaning of the cages.

Harvesting and Marketing

When a greater percentage of the stock weights from 500–800 g., which is usually attained after 6–8 months of culture, the cages are harvested. The farms are situated 160 km from Manila and the buyers come to get their orders. The live fish are loaded in aerated hauling boxes and trucked to Manila. Siganids are usually sold in the local market, while the live groupers and snappers are exported.

Case II - Cage Culture Practice in Basiao, Ivisan, Capiz

This is a personal account of the operation of a finfish farm in netcages in Capiz. The farm which started as a pilot project was established near the fishing villages at Basiao, Ivisan, Capiz.
It started in the middle of 1982, and was jointly founded by Edward Wong, a Hongkong based investor and Rafael C. Dinglasan of the Philippines. The main species under culture conditions is the estuary grouper, Epinephelus tauvina. However, sea bass and panther are also experimentally cultured.

Site Selection Criteria

Although the use of floating netcages has greatly minimized the danger of predation, the problems of environmental stress remains, until a proper site is chosen in respect to pollution, tidal range and, water current; and accessibility by land, air and water transportation in respect to seed collection and marketing. The preliminary observation confirms that the survival of fish is good. The Basiao cove site is not affected by industrial pollutants because it is far from the city. The site is strategic from seed collection point of view and approximately 30 mins from the airport. The tidal range at the culture site is 1.5 m and the water current flow is strong enough to provide sufficient exchange of oxygenated water and mild enough to avoid unnecessary loss of energy as a result of active swimming by the cultured fish species. Some of the important physical and chemical water parameters at the Basiao cove site are, as follows:

Culture Method (Rearing of the Fish)

1. Seed collection and supply

Grouper seed supply depends on collection from natural water, although induced spawning of this species has recently been reported. The seed of estuary grouper and other marine fishes cultured in Basiao are collected along the shoreline and in the mouth of the rivers. The main grouper fry catching season occurs between September to January. Young fish are transported in aerated styrofoam boxes filled with water, with the same salinity as where the fish were caught. In case the collecting site is far from the culture site, the fry are transported in oxygenated bags in which the seawater temperature has been lowered by means of ice bags.

2. Stocking and rearing of young fish

The newly arrived fish are first graded according to their sizes which range from 3 to 7 cm. Damaged fish are sorted out and dipped in weak sodium sulfamethazine or in methylene blue for 20 minutes to prevent bacterial infection. The fish are then transferred to the floating netcages of 3 × 3m with a stocking density of 60 fish per cubic meter.
In the first 2 weeks after stocking fingerling, we experienced a 5– 10 % mortality or less than 5 % when the seed is in good condition. The recommended feeding frequency for young groupers is 2 times daily. Fresh trash fish or green mussel finely chopped is fed. The food conversion ratio with chopped trash fish and green mussel is about 5–6 kilogram per one kilogram of grouper. Fish of size 150 g were stocked at a density of 45 per cubic meter. They grow to a marketable weight of about half a kilo in 6–7 months. To reduce the size hierarchy within the cages and ensure uniform growth constant grading of the fish is necessary. This is especially true for the young grouper.

Disease control

In our case, we did not encounter any kind of disease during the past two years of culture in this pilot project experiment. The water is good for grouper culture with average salinity of 33 ppt. Preventive measures are always taken, like proper and frequent changing of the netcages. This ensures better growth, due to efficient flow of water in and out of the cage and providing adequate supply of oxygen. Moreover, sharp edges of barnacles and oyster shells injure the fish through abrasion during feeding. We know that in cages heavily fouled with barnacles, oysters and green algae, the incidence rate of bacterial diseases in an unchanged cage is about 2–3 times higher than in netcages frequently changed.
Netcages of smaller mesh are changed once a week, while medium mesh once every 2 weeks. Netcages of bigger mesh are changed once a month. The cleaning operations mainly involve the drying of the net in the sun for 2–3 days. Dead barnacles and other fouling organisms are crushed and knocked off the net with a wooden club. With regular cleaning and proper maintenance, the nets can last 3 – 4 years.
Neglect in checking damaged meshes on the net cages would result in the loss of fish during culture. It is especially true for nets with bigger mesh. Netcages should therefore be carefully checked and damaged mesh mended before being used again.

Harvesting, handling and marketing strategies

Harvesting is done after confirmation from a buyer on the quantity he requires. Staggered harvest is scheduled if the order of the buyer is more than the load allowable by the chartered aircraft. When the product is harvested the netcages are raised by pulling up the four corners of the netcage. One operator catches the fish by means of a scoop net. Two others pack the fish in an oxygenated plastic bag. These are placed in styrofoam boxes and a little amount of ice is placed under the plastic bag. Ice is also placed in a little plastic bag tied with a rubber band. So far grouper in the Philippines has a good price. At present groupers are sold at 190.00 - 200.00 per kilogram, with weight ranging from 500–1,000 g. The market demand is high and the only major problem is the supply of seed.

Annual Production

Annual production depends upon the supply of seed and their survival. We produced 9.5 MT of live groupers in the first year of operation in fifteen 3 × 3 × 3m cages. Currently we produce 25 MT annually. Usually the price of groupers during December is much higher compared to other months due to the many festivities during this month.

V. Applied research activities

Research activities are concentrated on problem areas identified by the public and private sectors. These are on broodstock development, seed production and culture techniques. The finfishes studied are groupers, sea bass, siganids and milkfish. Significant accomplishments include seed production of sea bass and siganids in hatcheries. These activities were conducted at the Leganes station and the Igang substation of SEAFDEC.

VI. Constraints

The main problem is the availability of quality fry and fingerlings. The supply coming from natural fry grounds is not sufficient to meet the needs of culturists. Netcage operators compete with the needs of fishpond operators. While this can be solved by the establishment of fry hatcheries, there is a need to develop broodstock of good quality and to refine and standardize techniques for the mass production of fish seeds. There is also need to improve existing culture techniques consistent with local conditions and to develop practical and economical feeds for fry and juveniles.
The operators should be taught to meet the requirements and specifications of foreign buyers. Efficient and economical ways of handling and transporting live fish for the foreign market should be instituted to avoid mortality and waste and to meet the requirements of quality control. Sufficient credit for marginal fishermen should be provided to encourage them to engage in this alternative fishing activity. Stringent credit requirements should be relaxed for fishermen interested to go into netcage culture.

VII. Rules and regulations

The utilization and development of available areas for finfish net-cage culture is governed by the fishery ordinance P.D. No. 704 and by Fisheries Administrative Order (FAO) No. 160, S 1986. Coastal areas are a public domain and their use is regulated to protect the public interest. A license issued by the Director of Fisheries is needed for the construction and the operation of the netcages. A license is issued only to Filipino citizens and to corporations and partnerships whose capital stocks belong to Filipinos by at least 60 percent. The license to construct and operate is valid for five years.

Appendix A - Philippine Fish Production Activities (Valves in Tonnes)

Source: 1987 Philippine Fisheries Profile - BFAR