MANUAL ON SEAWEED CULTURE 2. POND CULTURE OF CAULERPA AND 3. POND CULTURE OF GRACILARIA
	TABLE OF CONTENTS

by

Gavino C. Trono, Jr.
Professor
Marine Science Institute, College of Science
University of the Philippines
Diliman, Quezon City
Philippines

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ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project
Manila, Philippines
1988

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TABLE OF CONTENTS

2. POND CULTURE OF CAULERPA

1. INTRODUCTION

2. TAXONOMY AND DISTRIBUTION OF CAULERPA

2.1 Objective

3. MAJOR ACTIVITIES

3.1 Site selection
3.2 Pond construction
3.3 Planting of the ponds
3.4 Water management
3.5 Harvesting and post-harvest activities

4. ESTIMATE PRODUCTION AND ECONOMICS

REFERENCES

3. POND CULTURE OF GRACILARIA

1. INTRODUCTION

2. TAXONOMY, DISTRIBUTION AND BIOLOGY

3. MAJOR ACTIVITIES

3.1 Site selection
3.2 Culture ponds
3.3 Culture method
3.4 Pond management
3.5 Harvesting and post-harvest activities
3.6 Polyculture with shrimp and/or crab
3.7 Pests and predators
3.8 Economics of Gracilaria farming

REFERENCES

MANUAL ON SEAWEED CULTURE

2. POND CULTURE OF CAULERPA

by
Gavino C. Trono, Jr.¹

1. INTRODUCTION

Several species and varieties of Caulerpa may be utilized as food in the form of fresh vegetables. These are mainly produced through gathering of natural stocks. Only C. lentillifera is commercially cultivated in ponds in the Philippines. The culture of this species started in the early 1950s in the island of Mactan, province of Cebu, Central Visayas. The accidental introduction of C. lentillifera with some other seaweed species to fishponds as fish food initiated its formal cultivation. The high demand for this alga in the local markets in metropolitan Cebu was a major factor contributing to the success of its commercial production. The species is preferred because of its delicate, light taste, soft and succulent texture. It is also a fast growing species.

The pond culture of C. lentillifera was started by a fishfarmer in 1952 utilizing his fishponds with milkfish and shrimp. At the beginning, Caulerpa was a secondary crop to fish and shrimp but later, because of the marginal production of fish and shrimp compared to the high production of Caulerpa, the farmer shifted to Caulerpa as his major crop and milkfish and shrimp became secondary crops. Interviews made among farmers revealed that some 400 hectares of ponds are presently used for the culture of Caulerpa. Although the commercial culture of Caulerpa in ponds started more than two decades ago, it has not been successfully transferred to other parts of the Philippines as yet, with the exception of the pond and open reef culture in Calatagan, Batangas, introduced by the author in early 1980s, so that the bulk of the fresh supply of Caulerpa in Metro Manila and some bigger towns in Central Luzon still comes from Mactan, Cebu. Although local consumption statistics are not available, it is probably safe to assume that several tons of Caulerpa are transported to Metro Manila from Mactan, Cebu every month. This seaweed is always available in the local markets any day of the week. The statistics of the Bureau of Fisheries and Aquatic Resources showed that in 1982 some 827 tons of Caulerpa were exported to Japan and Denmark in fresh, brine-cured and salted form.

The present cultivation utilizes the traditional brackishwater ponds. However, results of recent studies (Trono, 1987) have shown that water management is a primary factor in the productivity of Caulerpa, the culture of which would require a flowthrough system to facilitate water exchange. Thus, some modification of the traditional ponds such as the introduction of water control gates have to be made. Unlike pond culture of fish where water exchange is relatively infrequent (e.g., once a week or a fortnight) pond culture of Caulerpa requires more frequent water exchange in order to maintain the necessary level of nutrients required for growth and development. Some of the more progressive farmers in Mactan had through experiences, learned the importance of proper water management and achieved higher production through the introduction of some form of a flow-through system by providing both entry and exit gates for each pond compartment.

¹ Professor, Marine Science Institute, College of Science, University of the Philippines, Quezon City, Philippines.

2. TAXONOMY AND DISTRIBUTION OF CAULERPA

The genus Caulerpa belongs to the Family Caulerpaceae, Order Caulerpales in the Division Chlorophyta. All representatives of this genus have thalli consisting of long branching horizontal stolon which gives rise to rhizoids at its ventral side for attachment and many simple or branched erect portions which are green in color. The erect branches come in various forms depending on the species, e.g., strap-shaped or blade-like with or without teeth or spines at their margins, or, these bear short determinate laterals (ramuli) of various forms, e.g., coarse teeth, fine cylindrical branchlets (pinnules), clavate, globose or peltate branchlets.

The members of this genus are large coenocytes, i.e., the thallus is a single cell, large continuous tube without cross walls (aseptate). The algal body is strengthened by the structures known as internal trabeculae, the extensions of the inner wall. Information available on reproduction is based mainly on the results of studies of a few species. The alga is diploid (diplontic) and no alternation of generation has been recorded. Gamete (biflagellated) formation in undifferentiated gametangia is preceded by meiosis. The gametes are liberated through superficial papillate structures.

There are more than 30 species and varieties of Caulerpa reported in the Philippines. Among the more common species (Trono and Fortes, 1988) are C. racemosa (Figure 1), C. lentillifera (Figure 2), C. brachypus (Figure 3), C. sertularioides (Figure 4), C. serrulata (Figures 5a-5b); C. taxifolia (Figure 6), C. peltata, C. urvilliana and C. cupressoides. Caulerpa racemosa (Figure 7) and C. lentillifera are gathered from wild stocks and sold in markets. Only C. lentillifera is presently cultured in ponds.

The genus Caulerpa is mainly distributed in the tropics but also forms a major component of the seaweed flora in Australian temperate waters.

Figure 1. Caulerpa racemosa

Figure 2. Caulerpa lentillifera

Figure 3. Caulerpa brachyphus

Figure 4. Caulerpa sertularioides

Figure 5. Two forms of Caulerpa serrulata

Figure 6. Caulerpa taxifolia

Figure 7. Caulerpa racemosa - harvest from wild stocks

2.1 Objective

This manual is designed to give the prospective farmers important guidelines for a successful pond culture of Caulerpa.

3. MAJOR ACTIVITIES

The development of a new area into Caulerpa ponds consists of several stages, namely; site selection, pond construction, planting of the ponds, maintenance of the culture, harvest and post-harvest activities. Fishponds with marginal production are usually preferred because initial investment for their conversion to Caulerpa ponds is low and usually the location of these unproductive fishponds generally fits the ecological requirements of Caulerpa culture, that is, they are far from sources of freshwater and pollution sources.

3.1 Site selection

The success in the culture of Caulerpa depends primarily on the selection of a good site. The following ecological factors have to be considered when selecting sites for pond culture of Caulerpa.

1. The site must be far from sources of freshwater such as rivers and streams. Caulerpa is a purely marine stenohaline alga and will die even in slightly brackish seawater. The salinity should not be lower than 30 ppt.

2. The elevation of the pond bottom must be at or just a little above the zero tidal level. This is necessary in order to enhance proper water management in the ponds. Frequent water change is necessary for the growth and development of Caulerpa.

3. The site must be protected from the destructive effects of wind and waves. A buffer zone of mangroves and/or coral reef is necessary.

4. The substrate must be loamy-muddy. However, very deep, soft mud must be avoided.

5. Sites with acidic soil should be avoided. Caulerpa will not grow in areas characterized by low pH.

6. The area must be near the source of unpolluted seawater supply. Caulerpa is consumed fresh, thus it must be grown in areas free from both domestic and industrial pollution. Bacterial contamination of the crop should be avoided. Caulerpa may also absorb pollutants such as heavy metals and toxic chemicals which it can accumulate with deleterious effects to the consumers.

7. Existing saltwater ponds can be used for Caulerpa culture. Some farmers stock milkfish in Caulerpa ponds as a secondary crop.

3.2 Pond construction

The maintenance of good water quality necessary for good growth of Caulerpa through proper water management is dependent on the proper design of the ponds. The traditional layout of ponds for milkfish and shrimp production does not provide the necessary water exchange required in Caulerpa culture.

Caulerpa ponds may be divided into compartments of 0.10 to 0.25 hectare and should incorporate a flow-through design; each of the compartments should be provided with individual entrance and exit gates positioned in such a way that the water could easily be changed and circulated during the draining and flooding process. The flow-through design is important to facilitate frequent and complete water change necessary in maintaining high nutrient level in the seawater required by the seaweed for rapid growth and development. Peripheral or diversion canal may also have to be provided to divert runoff water from the ponds during rains to avoid drastic lowering of salinity in the ponds which is detrimental to the crop (Figure 8).

Figure 8. Caulerpa pond layout in Balong Bato, Calatagan Batangas*

* Source: Trono and Denila, 1987

3.3 Planting of the ponds

The ponds should be drained to a depth of 0.3 meters to facilitate planting. During the early development of the culture, broadcasting was used to “seed” the ponds with Caulerpa cuttings. However, this technique was found to be inefficient because the “seeds” were not uniformly distributed on the pond bottom and resulted in the uneven growth of the crop.

Planting is done by burying into the mud one end of a handful of Caulerpa cuttings at about one meter interval. Uniform planting is facilitated with the use of lines as guide or the planted spots are marked by pieces of bamboo. After planting, the ponds should be flooded to a depth of about 0.5 to 0.8 m. Flooding should be done slowly to prevent the newly planted cuttings from being uprooted and carried away by the current. The newly planted ponds must be inspected a day or so after planting and the unplanted areas should be planted to ensure uniform growth. The pond water should be changed only several days after planting to make sure that the cuttings are already well rooted and could not be carried away by water currents.

An initial stocking rate of 1 000 kg per hectare under favourable weather conditions can produce a good crop in about two to three months.

3.4 Water management

Proper water management is also a key factor in the successful pond culture of Caulerpa. Ideally, the pond water must be changed every three to four days at the start of the growing period in order to avoid strong water currents which may uproot the seedlings. The frequency of water changes should be increased to every other day at about the third week after planting especially when the plants start to form a thick growth on the pond bottom. Frequent water exchanges provide fresh supply of nutrients for the normal growth and development of Caulerpa, thus, it will eliminate the need for fertilizer application.

In general the water in the ponds must be maintained at a depth where the Caulerpa is visible from the surface of the water. Thus, the depth of the water in the pond would vary depending on the transparency of the pond water to provide enough light for the photosynthetic needs of the plants. However, adjustments in water depth should be made to avoid perimeter dikes from collapsing during spring tides when the tidal amplitudes are extreme. During rainy days the pond water should also be maintained at a slightly greater depth to reduce the possibility of a dilution below 30 ppt. Caulerpa will die when the salinity goes below this level and the entire crop may be lost. After heavy rains the pond water should be immediately drained and replaced by fresh seawater to ensure that the salinity is maintained at or above 30 ppt.

Fertilization may not be necessary as long as frequent water exchange can be made. However, fertilizer has to be applied especially one or two weeks before the harvest, when a large crop has already been produced and when the plants appear to be pale in color (that is light green or yellowish). The sufficient rate of fertilization is about 16 kg per hectare. Nitrogeneous fertilizers have produced very good results. The plants regain their healthy green color a few days after application. The fertilizer may be broadcasted, but past experience had shown that wrapping the fertilizer in many layers of gunny or plastic sacks and suspending these in strategic places in the pond at a level where the bags are just about half submerged in water, produces very good results. The fertilizer should be applied right after water in the pond has been changed. The pond water should not be changed for several days after the fertilizer has been applied.

Weeding is an important activity which should be done regularly to remove other seaweed species and associated organisms growing in the pond. Weeds compete with Caulerpa for space, light and nutrients. The weeds and the associated organisms should be removed before they take over as dominants. The presence of the weeds results in decreased production and low quality of the product and adds extra labor cost to sort them out before the product is sold in the market.

The dikes and gates of the ponds must be continuously maintained to effect efficient water management. This is especially critical during the monsoon season when strict and efficient water management is required to avoid extreme dilutions due to heavy rains.

3.5 Harvesting and post-harvest activities

Depending on the growth rate of the plants the crop may be harvested two months after the initial planting, when the plants had already formed a relatively uniform carpet on the pond bottom. The plants at this stage are of high market quality, light grass-green in color, soft and succulent in texture. Older plants though high in biomass are of lower quality because they are tougher in texture and their basal portions are pale or colorless. The paling of the basal portions of the fronds are caused by self-shading when the plants became older and form very thick carpet.

Figure 9. Pond-grown Caulerpa lentillifera

Figure 10. Harvesting of pond-grown Caulerpa lentillifera

Harvesting is done by uprooting the plants (Figures 9–10) from the muddy pond bottom. More crops can be produced during a growing season if partial harvesting is done leaving a sizeable amount of 20–25 percent of the crop in the pond to serve as seedstock for the next crop. Harvesting should be done in such a way that the leftover of the crop is more or less uniformly distributed in the ponds. Large vacant areas of the pond bottom should be replanted to ensure uniform crop stand. This practice has drastically reduced production costs by savings made in labor costs for replanting. The sizeable amount of seedstock left in the pond also results in a much shorter growing period and the farmers in Mactan, Cebu claim they can harvest every two weeks after the first harvest during the optimal growing season (dry season). Studies have shown that the algae could triple its initial weight after two months (Trono and Denila, 1987).

Harvested seaweeds are thoroughly washed in seawater to remove the mud and other debris. They are then sorted, unsuitable thalli and other seaweed species are removed. The clean seaweed is placed in bamboo baskets lined with banana leaves or other seaweeds such as Sargassum. The baskets are filled with clean seaweeds, then topped with leaves or Sargassum and finally covered with plastic sack which is secured by lacing its margin to the basket. The baskets (Figure 11) are placed under the shade where they are allowed to drip before transporting them to the market. The product can stay fresh for four to five days.

Figure 11. Pond-grown Caulerpa lentillifera packed in bamboo baskets and ready for transport to market

Caulerpa destined for export to other countries (such as Japan) is exported as a fresh product or in brine-cured or salted form. The seaweed is first thoroughly washed several times in seawater. Then thalli of good quality are selected. The clean seaweed is first completely drained of water, packed in styrofoam boxes provided with aeration holes on the upper side or cover of the box, taped and sent to its destination by air cargo. A large portion of Caulerpa exported to other countries is either brine-cured or salted. The latter two forms can be kept for longer periods and may be transported by surface cargo.

4. ESTIMATE PRODUCTION AND ECONOMICS

Based on experimental work on pond culture of Caulerpa conducted for a one year cycle at varying amounts of seed stock, the estimate annual production per ha of pond is optimum at an initial seeding of 100 g/m² as shown in Table 1.

Table 1. Estimate production of Caulerpa lentillifera two months after planting based on the biomass production (wet weight) studies from April 1981 to May 1982¹

¹ Source: Trono and Denila, 1987
^* The amount of initial seedstock has already been subtracted

The estimate economics of production is encouraging as shown in Table 2. An annual estimate farm income of 78 000.00 in the first year is highly profitable considering a farm gate wholesale price of 8.00/kg. This is equivalent to a ratio of net income to capital at the rate of 146 percent which is rather very optimistic. On the other hand, this is a possibility if pond management is good and the pond conditions are kept favourably well for the growth of the algae.

REFERENCES

Trono, G.C., Jr. 1987 Studies on the pond culture of Caulerpa. Phil. Jour. Sci., Monogr. 17: 83–98.

Trono, G.C., Jr. 1986 Seaweed culture in the Asia-Pacific Region. RAPA Publication 1987/8: 15–18. FAO, Bangkok.

Trono, G.C., Jr. 1988 and E.T. Ganzon-Fortes. Philippine seaweeds. 330 pp. National Bookstore Inc., Metro Manila, Philippines.

Table 2. Estimated annual cost and returns of a one-hectare Caulerpa farm based on the results of biomass production study in Balong Bato, Calatagan, Batangas¹

		First Year	Second Year
A.	Fixed costs
	1. Fishpond lease per year	850.00	850.00
	2. Farmhouse	3 000.00	-
	3. Dike construction (labor)	36 000.00	-
	4. Gates construction, materials (cement, woods, nails, etc.)	10 000.00	-
	5. Labor	1 900.00	-
	6. Dugouts (bancas)	200.00	-
	7. Tools	500.00	-
	8. Others	1 000.00	1 000.00
	Total	53 250.00	1 850.00
B.	Production costs
	1. One-ton initial seed stock
	(100 g/sq m) (8.00/kg)	8 000.00	8 000.00
	2. 500 baskets (bamboo) 10.00 each	5 000.00	5 000.00
	3. 500 plastic sacks (1.00 each), strings	600.00	600.00
	4. Caretaker (500.00/mo)	6 000.00	6 000.00
	5. Wages for laborers (4) (15/day/15/days/month)	10 800.00	10 800.00
	6. Repairs and others	5 000.00	5 000.00
	7. Transportation (8.00/basket)	4 000.00	4 000.00
	8. Depreciation	5 000.00	5 000.00
	Total	44 400.00	44 400.00
C.	Sales of 15.3 tons at 8.00/kg (wholesale)	122 400.00	122 400.00
D.	Net income	24 750.00	76 150.00

¹ Note: Values were based as of 1982. Present retail price of Caulerpa is 20.00/kg (Trono and Denila, 1987).

3. POND CULTURE OF GRACILARIA

1. INTRODUCTION

Although several species of agarophytes belonging to the genera Gelidium, Pterocladia and Gracilaria have been reported to be commercially produced through some form of farming in several countries such as Japan, China, Republic of Korea, Vietnam, India and the Philippines, it is in Taiwan where the production of Gracilaria through pond culture has achieved a high degree of success. An average of 12 000 tons of dried Gracilaria was produced in Taiwan during the past few years (Chiang, 1981). It is a very important raw material for the manufacture of agar which finds wide variety of uses in the food, pharmaceutical and several other industries.

Out of the several species presently used for culture in some countries (e.g., Gracilaria chorda, G. edulis, G. “verrucosa”, G. lichenoides, G. compressa and G. gigas). G. “verrucosa” is the most popular due to its ability to adapt to a wide range of ecological conditions, its higher production rates and better gel quality. The culture of Gracilaria started in 1962 in southwestern Taiwan. Production in ponds is primarily influenced by three ecological factors, namely; salinity, light and temperature. High production is recorded during the months characterized by higher temperatures and growth is slow during winter. High light intensity exerts adverse effects on the growth, therefore, control of light conditions is practiced by adjusting the water depth in the ponds. Salinity of 20 to 24 ppt appears to be optimal for growth. The increase in salinity during the summer months is controlled by the addition of freshwater, thus farms need to be located near freshwater sources.

2. TAXONOMY, DISTRIBUTION AND BIOLOGY

The genus Gracilaria belongs to the Family Gracilariaceae, Order Gigartinales in the Division Rhodophyta. It is a large genus represented by more than a hundred species widely distributed in the tropical and temperate waters of the world.

The thalli of Gracilaria are generally fleshy and vary widely in form from flattened to foliose forms or mainly branching forms, the branches being compressed to cylindrical in transverse section. The tissue is mainly pseudo-parenchymatous.

Figure 1. Gracilaria eucheumoides

More than 17 species have been recorded in the Philippines. However, only G. eucheumoides (Figure 1), G. arcuata (Figure 2), G. coronopifolia (Figure 3), G. salicornia (Figure 4), G. “verrucosa” (Figure 5) and G. gigas (Figure 6) are well documented. Of these species only G. “verrucosa” and Gracilaria sp. 2 (Trono, et al., 1983) are presently gathered from wild stocks and utilized in the local manufacture of agar although the other species have been reported to have good quality agar.

The genus Gracilaria is characterized by the alternation of three somatic generations, the sporophyte, the gametophyte and the carposporophyte stages. The last stage is microscopic and is parasitic on the female gametophytes, thus the gametophytic and tetrasporophytic stages are the macroscopic stages used as planting materials in the pond culture. The tetrasporangia are of the zonate type. Although the reproductive potential of Gracilaria through spores is high, vegetative propagation by cuttings is presently used in the pond culture because of the very high regenerative capacity of the plant and the simplicity of the method. However, “hatchery produced” seedlings from spores have been demonstrated to be superior in the open field culture of Gracilaria.

Figure 2. Gracilaria arcuata

This manual is designed to provide the prospective farmer guidelines for a successful pond culture of Gracilaria.

3. MAJOR ACTIVITIES

The following are the major activities required in the pond culture of Gracilaria.

3.1 Site selection

The success in pond culture of Gracilaria is highly dependent on the selection of appropriate site. The following criteria are recommended in the selection of sites.

1. The prospective farmer should choose a site located and accessible to sources of seawater and freshwater supply. Gracilaria is a euryhaline alga and would grow very well in a wide range of salinity. Brackish water with a salinity range of 20 ppt to 28 ppt favors growth although salinity of 25 ppt is optimum. Salinity rises during sunny months due to evaporation reaching values as high as 35 ppt which depresses growth or cause the death of the plants. It is, therefore, important that salinity should be lowered to its normal range of tolerance by adding freshwater into the ponds. Salinity may also drop to very low levels beyond the minimum limits for heavy rains. Very low salinity is also detrimental to the plants and may cause mass mortality. The salinity level should be raised to its optimal range by adding seawater.

   Thus, the maintenance of optimal salinity conditions in the ponds requires the readily available freshwater and seawater supply.

Figure 3. Gracilaria coronopifolia

Figure 4. Gracilaria salicornia

Figure 5. Gracilaria “verrucosa”

Figure 6. Gracilaria gigas

2. The pond site should also be protected from strong winds or waves. Strong winds produce waves which tend to transport Gracilaria towards the leeward portion of the ponds. The formation of thick heaps of Gracilaria has also adverse effects on growth due to shading. On the other hand, strong waves can wash out the dikes and cause tremendous loss and damage to the pond and crop.

3. The pond bottom should be at or just a few centimeters above the zero tide line. The maintenance of optimum salinity levels in ponds is a major factor in the production of good crops. The ease and efficiency in water management is highly influenced by the level of the pond bottom in relation to the tidal changes. Frequent water changes is very necessary to maintain the nutrient and salinity levels in ponds favourable to the growth of Gracilaria.

4. The pH of the water in ponds should be slightly alkaline from seven to nine and a pH range of 8.2–8.7 is optimum for growth. Sites with low pH (acidic) should be avoided. Frequent water change may also help in the maintenance of optimum pH levels in ponds.

5. The pond bottom should be sandy loam. Ponds with very soft muddy bottom should be avoided. Cuttings of Gracilaria will easily sink in mud and die.

6. Existing brackishwater ponds are usually used for Gracilaria farming as the seaweed could be grown with crabs and shrimps.

3.2 Culture ponds

The average size of ponds used for the culture of Gracilaria is about one hectare or smaller. Smaller ponds are easier to manage than larger ones because in large ponds Gracilaria tend to accumulate at one side due to the influence of wind-induced waves. Pond management is also easier when Gracilaria is polycultured with shrimp and/or crab. Provision of entrance and exit gates also facilitate proper water management.

The depth of the ponds vary from 50 to 80 cm. The bottom generally is of clayey loam, or sandy loam. It was observed that Gracilaria easily gets buried in the bottom of the pond due to the effect of wind. This problem, however, could be resolved by increasing the depth of the water during windy periods. In larger ponds, wind breaks consisting of bamboo slots are installed perpendicular to the direction of the wind to prevent the seaweed from being transported to one side of the pond.

3.3 Culture method

The following method is generally followed in the pond culture of Gracilaria.

The ponds should be drained and dried for several days after which water is introduced. Healthy stocks of Gracilaria are selected as planting materials. These are generally characterized by their elastic feel to touch, reddish brown color, brittle texture, stout and well-branched thalli and are free of dirt and extraneous materials. The planting materials are transported from its source to the pond site early in the morning to prevent its exposure to the sun. During long distance transport, the materials should be frequently sprinkled with seawater and perforated bamboo or plastic pipes are inserted into the bottom of the heap to provide aeration. The plants must immediately be placed in water in the pond upon arrival. The planting material should be cut into pieces and should be broadcasted uniformly on the bottom of the pond. Stocking rate is 5 000 to 6 000 kg per hectare although lesser amounts may be used. Cropping season usually starts during warm summer months of March or April.

3.4 Pond management

The water should be maintained at a depth where the surface is approximately 30 to 40 cm above the heap of the algae. However, the depth should be increased to 60 to 80 over the algae during the warm summer months to prevent a significant rise in the water temperature. Water depth should be increased during the cold months to prevent water temperature from dropping to very low levels which may be lethal to Gracilaria. Water temperature range of 20–25 (29)°C or slightly higher should be maintained in ponds for maximum growth.

Frequent change of water is necessary to maintain the optimum temperature of water in the ponds. The water is changed every two to three days. About 50 to 75 percent of the “old” pond water should be drained and replaced with fresh seawater.

Fertilization with either organic or inorganic fertilizers may be done to enhance the growth of Gracilaria. Weekly application of 3 kg of urea per hectare should be sufficient. Fermented pig manure may be applied at a rate of 160 to 180 kg per hectare two to three days after the pond water has been changed. Pond water should not be changed for several days after fertilization.

3.5 Harvest and post-harvest activities

The harvesting may be done two to three months after seeding depending on the growth of the crop. The crop may be harvested manually or by using scoop nets every 10 to 40 days. The frequency of harvests should be primarily dictated by the market price, amount of harvestable biomass and the season. In subtropical and temperate areas, the low temperature during winter is inimical to the growth of the crop.

The harvest should be thoroughly washed in pond water to remove the silt, sand, pieces of shells and other extraneous materials such as snails and other algae. The clean Gracilaria is spread uniformly on bamboo screens or plastic sheets for drying. An average wet to dry ratio of 7:1 is generally attained.

Standards set by the Bureau of Standards in Taiwan for the export of dried Gracilaria require that the product should not contain more than 1 percent of mud and sand, not more than 1 percent shells and not more than 18 percent other seaweed species. Moisture content should not exceed 20 percent (T.P. Chen, 1976).

Dried Gracilaria is packed into bales of 100 kg weight for export or sold to local processing plants. Production of 10 to 12 metric tons of dried Gracilaria is attained in a hectare of pond in Taiwan. More recently fresh Gracilaria crops are utilized as feed in the culture of abalone.

3.6 Polyculture with shrimp and/or crab

Gracilaria may be polycultured with shrimp (Penaeus monodon) and/or crab (Scylla serrata) as is being done in southwestern Taiwan. Stocking materials for a hectare of farm consist of 4 000 to 5 000 kg of Gracilaria, 5 000 to 10 000 crabs and 10 000 to 20 000 shrimp fry. Crushed trash fish and snails are generally used as feed for the crabs. Crabs are harvested after three months and the shrimps after four to seven months. Survival rates as high as 80 percent for crabs and 80 to 90 percent for shrimps have been documented making this polyculture one of the most profitable aquaculture methods in Taiwan. The net income from polyculture has been proven to be three times as much as from monoculture.

3.7 Pests and predators

The presence of other seaweed species (weeds) in the ponds mixed with Gracilaria is one of the problems in the culture of this seaweed. The weed species have to be removed or weeded out to prevent these from becoming dominant. The weeds compete with Gracilaria for nutrients and light. These also lower the quality (value) of the crop. Epiphytes, other smaller algae growing on Gracilaria, are other problems which may be solved by the introduction of grazers in the ponds. Tilapia has been found to be effective in the control of epiphytes. A low density of milkfish or tilapia may be stocked in Gracilaria ponds to control epiphytes and other green algae.

3.8 Economics of Gracilaria farming

The culture of this alga in the Philippines used to be an extensive method applied by milkfish farmers primarily for the food of the milkfish. During the period of abundance of Gracilaria in Manila Bay, fishpond operators collect them for stocking in milkfish ponds. There has been no documentation of this practice but the use of the algae as milkfish feed has been reported. Unfortunately, there was no economic evaluation of the practice. The Philippine experience on the farming of this seaweed, although not for its agar but for milkfish feed was, however, short lived due to the heavy pollution of Manila Bay. Milkfish ponds generally rely on benthic algae or “lab-lab” by organic and inorganic fertilization of ponds.

The economics of Gracilaria farming in this manual is, therefore, based on Taiwanese experience where the practice is more intensive. Table 1 summarizes the costs and earnings per hectare of Gracilaria farming.

Table 1. Costs and returns (NT$ of Gracilaria monoculture per hectare) 1975 and 1977¹

¹ Source: Smith, I., 1987
² Shang (1976)
³ Chueh and Chen (1982)
⁴ Included in tax figure above
⁵ Chueh and Chen did not report an estimate of initial investment
In both 1975 and 1977, NT$38 = US$1.00

REFERENCES

Abbott, I.A. 1985 Gracilaria from the Philippines: List and distribution of the species. In: I.A. Abbott and J.N. Norris (eds.). Taxonomy of Economic Seaweeds. With reference to some Pacific and Carribean species. pp. 89–90. California Sea Grant Publication.

Chen, T.P. 1976 Aquaculture practices in Taiwan. Fishing News Book Limited. Garden Walk, Farnham Surrey, England.

Chiang, Y.M. 1982 Cultivation of Gracilaria (Rhodophyta, Gigartinales) in Taiwan. Proc. Intl. Seaweed Symposium 10:569–574.

Shang, Y.C. 1976 Economic aspects of Gracilaria culture in Taiwan. Aquaculture 8: 1–7.

Smith, I. 1987 The economics of small-scale seaweed production in the South China Sea Region. FAO Fish. Circular No. 806.

Trono, G.C., Jr. and E.T. 1976 Ganzon-Fortes. Report on the training course on Gracilaria algae. SCS/GEN/81/29. South China Sea Fisheries Development and Coordinating Programme. Manila, Philippines.

Trono, G.C., Jr. 1986 Seaweed culture in the Asia-Pacific Region. RAPA Publication 1987/8. Regional Office for Asia and Pacific (RAPA) FAO of the U.N. Bangkok, Thailand.

Trono, G.C., Jr. and E.T. 1988 Ganzon-Fortes. Philippine seaweeds. 330 pp. National Bookstore, Inc., Metro Manila, Philippines.

PUBLICATIONS AND DOCUMENTS OF THE ASEAN/UNDP/FAO REGIONAL SMALL-SCALE COASTAL FISHERIES DEVELOPMENT PROJECT
(RAS/84/016)

Working Papers

ASEAN/SF/86/WP/1 Rabanal, H. R. Seafarming as alternative to small-scale fishing in ASEAN region. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1986. 55p.

ASEAN/SF/86/WP/2 Soeyanto, T. The status of Bali Strait fisheries with special reference to Muncar, Kedonganan and Jimbaran coastal villages. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1986. 36p.

ASEAN/SF/86/WP/3 Boongerd, S. and S. Chitrapong. Small-Scale fishing for squids and related species in Thailand. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1986. 44p.

Workshop Reports/Other General Reports

ASEAN/SF/86/GEN/1 Report of national consultative meeting on aquaculture engineering held in Tigbauan Research Station, SEAFDEC Aquaculture Department, Iloilo City, Philippines, 2–5 October 1985. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1986. 186p.

ASEAN/SF/86/GEN/2 Zabala, P.T. (Comp.) Preliminary annotated bibliography on small-scale fisheries in the ASEAN Region. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1986. 41p.

ASEAN/SF/87/GEN/3 Report on the training course on shrimp culture held in Jepara, Indonesia, 2–19 December 1987. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1987. 63p.

ASEAN/SF/88/GEN/4 Report on the training course on small-scale fisheries extension held in Semarang, Indonesia, 26 January-14 February 1988. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. (In preparation).

ASEAN/SF/88/GEN/5 Report on the training course on fisheries extension methodology held in Penang, Malaysia, 13–26 March 1988. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. 266p.

ASEAN/SF/88/GEN/6 Report on the training course on seaweed farming held in Manila, Philippines, 2–21 May 1988. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. 169p.

ASEAN/SF/88/GEN/7 Report on the training/study tour of pelagic fishing with the use of “payaw” held in Manila, Philippines, 16 May-4 June 1988. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. (In preparation).

ASEAN/SF/88/GEN/8 Report of the workshop on artificial reefs development and management held in Penang, Malaysia, 13–16 September 1988. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. (In preparation).

ASEAN Fisheries Manuals

ASEAN/SF/86/Manual No.1 Suprayitno, H. Manual of running water fish culture. Manila, ASEAN/UNDP/ FAO Regional Small-Scale Coastal Fisheries Development Project, 1986. 34p.

ASEAN/SF/88/Manual No.2 Godardo, L.J. Manual on seaweed farming: 1. Eucheuma spp. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. 25p.

ASEAN/SF/88/Manual No. 3 Trono, G.C., Jr. Manual on seaweed culture: 2. Pond culture of Caulerpa. 3. Pond culture of Gracilaria. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. 20p.

Periodic Progress Reports

ASEAN/SF/86/PR-1 Soesanto, V. Project progress report of the ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 5 October 1985–5 April 1986. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1986. 9p.

ASEAN/SF/86/PR-2 Soesanto, V. Project progress report of the ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 6 April-6 October 1986. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1986. 11p.

ASEAN/SF/88/PPER-3 Delmendo, M.N. Project performance evaluation report of the ASEAN/UNDP/ FAO Regional Small-Scale Coastal Fisheries Development Project, 31 July 1988. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. 23p.

Technical Reports Contributed to Symposia/Meetings, etc.

ASEAN/SF/85/Tech. 1 Rabanal, H. R. and V. Soesanto. The world fishery and culture of Macrobrachium and related prawn species. Contributed to the National Conference on Prawn Technology, sponsored by the Philippine Fishfarmer's Technical Assistance Foundation, Inc., Manila, Philippines, 27–28 November 1985. 16p.

ASEAN/SF/86/Tech. 2 Rabanal, H. R. and V. Soesanto. Commercial species of shrimps and prawns, their sources and export markets. Contributed to the Seminar on Quality Control in the Production, Processing and Marketing of Frozen Shrimps for Export, sponsored by Food Research Department, Food Terminal Incorporated, Taguig, Metro Manila, Philippines, 29–31 July 1986. 64p.

ASEAN/SF/86/Tech. 3 Rabanal, H. R. Status and prospects of Shrimp farming in the Philippines. Contributed to the Monthly Seminar Series on Timely and Related Fisheries Issues, sponsored by the Philippine Council for Agriculture and Resources Research and Development, (PCARRD), Los Banos, Laguna, Philippines, 5 November 1986. 24p.

ASEAN/SF/87/Tech. 4 Delmendo, M. N. Fishery administration and policy in the Philippines: Past and present. Contributed to the National Conference on Fisheries Policy and Planning, Baguio City, Philippines, 16–20 March 1987. 35p.

ASEAN/SF/86/Tech. 5 Delmendo, M. N. Milkfish culture in pens: An assessment of its contribution to overall fishery production of Laguna de Bay. Paper read in the Seminar on the occasion of the Fish Conservation Week, BFAR, October 1987. 17p.

ASEAN/SF/87/Tech. 6 Delmendo, M. N. and B. H. Delmendo. Small-scale aquaculture operations in the ASEAN countries. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1987. 49p.

ASEAN/SF/88/Tech. 7 Rabanal, H. R. History of aquaculture. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. 13p.

ASEAN/SF/88/Tech. 8 Rabanal, H. R. and M. N. Delmendo. Organization of the aquaculture industry. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. 10p.

ASEAN/SF/88/Tech. 9 Rabanal, H. R. Report on the World Aquaculture Society, 19th Annual Conference and Exposition, Honolulu, Hawaii, U.S.A., 4–10 January 1988. Manila, ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project, 1988. 99p.