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close this bookLivelihood Options for Coastal Communities (IIRR, 1995, 77 p.)
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Eucheuma farming

Eucheuma is a red seaweed that is endemic in Philippine waters. When dried, a substance called carageenan may be extracted from the seaweed. Carageenan has a wide variety of uses for products (food preparations, pharmaceutical industries and pet foods) that need gelling, suspending, binding, thickening, emulsifying and water-holding properties.

Commercial seaweed farming first began in the Philippines in 1972 in Sulu, Tawi-Tawi and Zamboanga. The rapid development of the Eucheuma industry has made it the country's third ranking fishery export. In 1986, about 50,000 mt, with an estimated worth of P840 million, were exported to Europe, the USA and Japan (Aquabusiness Weekly, June 2-9, 1989).


Eucheuma

Conditions for seaweed farming

Favorable


Where other organisms grow


Moderate water current


Where Eucheuma will not be exposed to air during the lowest low tide

· Over firm substrates
· Salinity ranges from 25 to 35 parts per thousand.
· Temperature of about 25°C

Unfavorable


Where area is relatively devoid of other organisms


Still water or rough water


Eucheuma is exposed to air.

· Soft bottom
· Beyond the range
· Extreme temperatures

At present, there are about 60,000 families engaged in seaweed farming. The two most commonly grown are the Eucheuma cotonii and E. spinosum. They are locally known as tambalang or gozo.

Eucheuma favors moderate water current. It is, therefore, best cultured in protected coves, bays or coral flats. The seawater should also have a salinity range of 25-35 ppt and a temperature of about 25°C. The best time for planting is just after the rainy season.

Among current methods of farming Eucheuma, the bottom monoline method is the best, due to lower material and labor costs and it is easy to maintain. For the bottom monoline method, depth is quite important. During low tides, depth should be about 0.5-1.0 m; while during high tides, the water should not be more than 2.0-3.0 m deep.

It is also important to note whether the site has had a history of the ice-ice disease. If so, it may not be wise to farm in the area for the probability of an outbreak is greater.

Culture

1. Clear the area of other seaweeds, seagrasses, stones, starfish and sea urchins.

2. Construct the farm support system.

Make holes on the substrate by driving down an iron bar with a sledge hammer. Place a 1.50 m wooden stake in each hole and drive it down with the sledge hammer. Arrange the wooden stakes in rows at 1.0 m intervals and make the distance between two posts in one row at 10.0 m. Tie the 11.0 m long monofilament line securely to the stakes at each end of the row. Distance of the monoline from the ground is 0.30-0.50 m.


Lay-out for bottom monoline method

Adapted from: Trono, G.C., Jr. and E.T.Ganzon-Fortes. 1989. Ang Paglinang ng Eucheuma (Eucheuma farming). Seaweed Information Center (SICEN), Marine Science Institute, University of the Philippines, Diliman, Quezon City, Philippines. Through a grant from the International Development Research Centre (IDRC) of Canada.

If currents are strong, put up an additional row of stakes, placed in the middle of the original rows. This provides greater support to the line. The distance of the additional stakes along the row depends on the strength of the local current. The shorter the distance between rows, the stronger the support system.


Floating bamboo seedbed

3. Procure the appropriate seedplants or propagules from the nearest source. Get seedplants which are mature and free from diseases. Transport the propagules with the use of a wooden boat filled with water, so that the seedplants are submerged continuosly during transport. Excessive exposure to sunlight and air will weaken or frill seedplants that are not submerged in water. Transporting can also be done with floating bamboo with coralon net sidings.

4. Cut the seed pieces in the 1 let position (not slant) at an estimated 100 gm per propagule. Use only one branch. Do not cut the tips of the seaweed branches because new growths will occur in that area.

5. Tie the seedplants at a center balance with the use of strong plastic straw twine. Do not lie them too loose nor too tight. The tie should have at least a 25.4 cm allowance for tying at the monoline filament to hold the propagules.

6. Tie the planting materials at the monoline bottoms so as to hold the seedlings tightly in place while providing enough slack to move smoothly with the water. The distance between seedplants is 40.0-50.0 cm.

7. Farm maintenance. Visit the planted area every three days. Remove infected plants immediately to minimize spread. The disease may be detected by the presence of ice-like white dots.

Keep the seaweeds clean. Remove adhering materials and other plants which compete for nutrients and sunlight.

Remove grazers, such as sea urchins and starfishes. In farm sites characterized by strong water currents, place a coarse nylon net at the leeward side of the farm to catch broken plants carried by the water.

8. Harvesting and drying. Eucheuma has an average growth rate of 3.5 to 5 percent of their weight. It is best harvested between 5060 days after planting. A 100-g plant usually weighs 700-1,000 g after two months or more.

Harvesting can be done by either removing the seaweeds individually or by untying both ends of the monoline from the post and loading them in bunches in a wooden boat or in bamboo crates. The mature seaweed plants can be detached from the monoline in the drying pads or platforms later.

Drying is done on any clean pavement by covering with coralon net or canvass, sawali, bamboo slat platforms or coconut fronds. Drying usually takes tour to six days. Eight kilograms of fresh seaweed will yield about one kilogram of dry seaweed.


Drying on sawali (woven bamboo)


Drying on cement

Economics of production - Seaweed farming


Value (in pesos)

Total Value (in pesos)

Annual Revenue


At 5% average daily growth rate of




40,000 seedlings, of 300 g




each within 2 months = 48,000 kg



Less:


Original weight of seedlings (12,000 kg)




20% mortality (9,600 kg)




Net production-wet weight = 26,400 kg




Net production-dried; 8:1 wet to dry ratio = 3,300 kg




Sale of 3,300 kg/harvest × P7.00/kg × 5 harvest/year


115,500

Annual Production Cost


1,200 pcs mangrove × P0.80/pc

960



250 kg of nylon monofilament × P95/kg

2,375



15 rolls of Finolas twin-plastic straw or tie-tie × P45/roll

675



4,800 kg seedlings × P4/kg

19,200



25 cm Coralon net for 5 × 5 m seedbin × P 15/m

375



100 m monofilament nylon net × P15/m

1,500



(3) laborers × P850/month

30,600



Fuel expenses at P500/month × 12 months

6,000



Transport cost at P0.40/kg × 16,500 kg

6,600



Depreciation

3,530



----------




71,815

Fixed Investment


(1) Non-motorized banca

1,500



(1) motorized pumpboat

22,000



Farm house

8,000



Drying platform

3,800



-----------




35,300

Net Return


Annual revenue

115,500



Less: Annual production cost

71,185



------------




43,685

Return on Investment



1.24

Source: Trono and Fortes, 1989

Mud crab fattening

Mangrove or mud crab (Scylla serrata) fattening is similar to the principle of fattening or growing chicken (broilers) swine or cattle. The goal is to add weight and size so that they can sold at higher price.


Scylla serrata

The Philippine mud crab is a much sought-after gourmet seafood especially on important occasions. The gravid or pregnant females with red-orange aligue or egg berries in their bodies are being exported with unlimited demand to Japan China Hong Kong and Taiwan. The Chinese believe that gravid female mud crabs have medicinal properties for the aged and convalescent.

Persistent and extensive catching of the mud crab has led to low catch; it is becoming a rare and expensive food delicacy. Efforts to breed and culture the mud crab in captivity 'have not been successful because of its unique egg-laying and hatching requirements. The female mud crab with eggs on its outer stomach goes to deep waters up to 200 m to lay and hatch its eggs. It is in this area where salinity temperature and available larval food are favorable to the growth of young crabs. The crablets or juveniles return later to brackishwater or mangrove areas to mature. Mud crabs as the name implies dwell in brackishwater habitats such as mangrove swamps where the bottom or substrate is muddy.

Studies gathered through interviews in Himamaylan, Negros Occidental and Pontevedra Capiz in Region Vl have shown that 100 to 175 gram thin crabs can be fattened to 250 to 350 grams in 15 to 20 days. Because of the availability of trash fish and brown mussels in the place the thin crabs are provided food five percent of their body weight. Mud crabs are voracious eaters that can be fattened in a short period.

Methods

There are two methods that are commonly used in fattening crabs. One method is the use of bamboo cages 1.83 m long 92 cm wide and 23 cm high. The top cover is provided with holes used in feeding trash fish or mussels. One unit is composed of 18 cubicles or compartments that can hold one thin mature crab each. The cages are anchored to the muddy bottom by a post (813 cm in diameter and 1.221.83 m long) at 1 to 2 m below the tide level.


The cubicle or compartment-type method.

The other method is the fishpond method. The pond may be constructed in varying sizes ranging from 10 to 20 m wide, 20 to 40 m long and 1 to 2 m deep dikes. It is placed in brackishwater areas. The fishpond dikes are provided with bamboo slat fences of 2.54 cm wide and 0.91-1.52 m long. The bamboo slat fence is anchored to a 8-13 cm post at a 45-degree angle towards the inside pond. This is done because gravid crabs have the tendency to escape during their spawning period to go to deeper seas. During heavy rains that cause stratification or reduction of oxygen level in the water, the crabs are forced to come out to breath. Also, mud crabs have the instinct to go out at night from their burrows to look for food. At a 45-degree slant of the bamboo slat fence the crabs cannot escape clue to their weight. The bamboo slat is also hard and slippery to cling on. They will only fall back into the fishpond. Fattening ponds can accommodate four to six nieces per square meter.


Mud crab-fattening pond method

The mud crabs are fed with fresh trash fish, roughly five percent of the crabs' body weight, in the early morning and late afternoon. Mud crabs increase their weight at an average of 10 grams per day. Feeding three to five kg of fresh trash fish (brown mussels, fishes, shells, etc.) can give one kg added weight to the mud crabs.

Economics of production—1-ha mud crab farm (2 croppings/year)


Value(in pesos)

Total Value(in pesos)

Annual Revenue


Sale of 2,038.08 kg × P80/kg


163,046

Annual Production Cost


2,000 kg chicken manure × P0.66/kg

1,320



10,000 pcs crab juveniles × P0.55/pc.

5,500



3,505 kg trash fish × P5.50/kg

19,280



Labor - 2,000 personhours × P5.50/personhour

11,000



Marketing expenses

3,260



Repair and maintenance

3,200



Interest

4,938



Depreciation

16,618



(1) Caretaker × P400 × 12 months

4,800



Tax

31,545

101,461

Fixed investment


88,201

Net return


Annual revenue

163,046



Less: Annual production cost

101,46




61,585

Return on investment



Net return

61 585


Fixed investment

88,201

0 70

Source: SEAFDEC Asian Aquaculture, Vol. XIV, no. 4, December 1992.

Mollusc culture: Abalone

Abalone is a nutritious shellfish, with its meat containing 20 percent protein; it is a highly priced delicacy. Locally, the fresh and dried meats are sold at P70.00 and P300.00/kg, respectively.

The Philippines exports abalone in dried, frozen (steamed, boiled or fresh), canned or bottled forms.


Philippine abalone

Abalones are canned as boiled, preserved in brine solution, smoked in oil, seasoned or roasted. In 1989, the Philippines exported 70,703 kg of abalones worth P446,583 to Japan, Hong Kong and Australian.

The blue-gray mother-of-pearl shell of abalone is widely used in the manufacture of buttons, buckles, inlays, ornamentals and jewelry. It is also used for medicinal purposes. Its viscera yield good quality glue (PCAMRD, August 1991).

Despite the above, however, no serious attempts have been made to undertake research and development of the abalone culture, such as spawning, hatching, larval rearing, juvenile growing, eating habits at various stages and nutrition. Japan, U.S.A. and Australia have undertaken research with their local abalone species, but their cultural technology needs further improvement. It is also expensive and too technical. However, the success in rearing juvenile abalone (more than one year and about 3-7 cm) can supply the needs of grow-out artificial marine ponds and for re-seeding or re-stocking of the natural habitats of abalone. Yet, due to the site specificity of abalone and the different species that exist in different countries, adaptation of the cultural techniques is difficult to evolve.

The existence of favorable environmental factors in the Philippines put the country in a considerable advantage in the development of abalone culture, especially in grow-out technology. Many areas in Southern Philippines have wide and extensive natural grounds and habitats for Philippine abalone. They are the protected bays of coral and rocky bottoms of 5-10 m deep that are free from pollution and abundant in natural food, like diatoms and algae.


Bays and coral reef areas are natural habitats of abalone.

Preliminary findings in the culture of Philippine abalone juveniles at the Mindanao State University in Tawi-Tawi and the Sea Gardens of the Department of Agriculture in Sulu showed promising results in the growth pattern of abalone juveniles. Consistent results were obtained by the two agencies that a captured juvenile abalone of 2.54-5.8 cm long can grow up to 8-15 cm in about 3-5 months in their natural habitat. This breakthrough can now place abalone culture in the Philippines into a very profitable venture by producing export quality abalones with sizes 100-150 percent higher in farmgate price than those collected from the wild which is less than eight cm.

Hundreds of tons of dried abalone whose sizes are less than the export size of 13 cm (mostly 2 54-8 cm) arc being gathered in these areas as observed. This means that production requires 3-5 times in quantity per kg weight and less income due to undersizing. But, if this same quantity is cultured, produce is at least five to eight times the weight with more than double profit.

Due to the local practice, in addition to the tradition of common rights to exploit bottom-dwelling marine resources, by necessity, there must be some form of government involvement in a regulatory capacity. The government should oversee the re-seeding process by prohibiting gravid (spawning) abalone to be caught and restocking process by banning capture of juveniles (2.54-5.08 cm) to replenish the declining stock. To promote the culture of growing abalone, juveniles are only allowed to be captured for growing culture purposes.

It was observed that the occurrence of Philippine abalone in its natural habitat has a seasonal pattern. It is directly related to wind/current movements. In areas where there is a group of adjacent islands with extensive coral reef areas, they are usually found at the east side of the islands during south-westerly winds (habagat) and at the western side during north easterly winds (amihan). They are mostly found in areas with calm waters. The peak period of gathering occurs in two to three months during summer (March to June) when amihan and habagat are absent.

Abalones are active at night (nocturnal) when they come out and stay in shaded or dark areas on the sea bottom during the day. The abundance of seaweeds in the south as natural food for growing juvenile abalones may have contributed to the abundance of abalone.

The simple method of artificial culture in growing young abalones (over one year or 2.54-6.35 cm) is to enclose a natural habitat area of at least 200 sq m with bamboo slats or coralon nets. Pile boulders and other materials, such as dead coral stones (if available), gathered from natural habitat, inside the fenced area. While transferring these materials, ensure that they are continually submerged in sea water Exposing them to sunlight too long may kill the microorganisms growing in these stones. They may even be affected by toxic substances that may hamper the growth and survival of young abalones.

The piled coral rocks serve as attachment, sanctuary and shade for the growing abalones. Twenty to thirty abalone juveniles can be stocked per square meter of abalone pen. They can grow in their natural state without feeding.


Layout of fixed pen showing (A) perspective with guard house and sampling raft,


(B) Detail section of fishpen (C) Partial detail elevation

Source: SEAFDEC Manual Series No. 9. 1985

Mollusc culture: Green mussel

The green bay mussel or tahong (Perna viridis) is a popular and delicious food item. It is rich in vitamins, minerals, protein and carbohydrates.

Green mussels were originally regarded as pests before World War II because they competed with food and space in oyster farms. In 1950, it was recognized as a primary bivalve food. The first mussel commercial farm started in Bacoor, Cavite, in 1955.


Male


Female

Site selection

Mussels are known to exist in bays, coves and inlets. They are found in Manila bay, east coast of Panay, Negros Occidental southwest coast and in Maqueda Bay and Jiabong, Samar.

Green mussels may be transplanted in new areas with seeds (juveniles) or breeders for growing and multiplication.

Mussels grow best in brackish to salty waters, with salinity ranging from 20-35 ppt. Good culture sites are indicated by the presence of indigenous existing mussels in the area to have sufficient breeding stock and spatfall. The water must be greenish in color which is an indication of abundant natural food of mussels.

The site must be free from pollution, with enough tidal exchange and moderate currents for the transport of food. It must be protected from strong winds and waves and must be relatively deep from two to four meters. Muddy to sandy bottoms that is semihard and sticky usually produce high yields.

Species, reproduction, food and growth

There are two species used as food in the Philippines, namely: the green mussel and the brown mussel (Modiolus philippinarum). The green mussel commonly referred as tahong is the commercial species.

The male mussels's mantle or meat is milky white to creamy and the female is orange to red orange. Since they have stationary forms of life, either one can change sex for the purpose of reproduction.

Spawners release eggs and sperms into the water where fertilization takes place in a few seconds. Eggs hatch into free swimming larvae within 24 hours and remain at this stage for 15-20 days. After the larvae are ready to settle, they secrete hair-like threads called byssal filaments to attach themselves. This ability to secrete new byssal when cut will allow thinning and transplanting operations. The settlement of larvae is called spatfall and the young mussels are called spats. Spawning normally occurs every two months, but the peak spatfall season in Manila Bay (Bacoor) occurs from April to May and October to November; February to March and September in Eastern Panay; and January to March and July to September in Western Negros Occidental. The spat is about the size of a grain of beach sand.

Mussels eat waterborne phytoplankton and minute organic materials by sucking and filtering water through its four rows of gills that is directed to the mouth. The gills serve both as a respiratory or breathing organ and as a filter-feeding organ.

Spats or larvae are attracted by filamentous objects and later move on to solid substrates or objects. Coconut coir and abaca coir are the best materials that can lure the spats.

Mature mussels can reach the size of 15 cm. in length, but they can be harvested in four to six months' time. Frequent visit, at least every three days, is recommended to check the growth of filamentous algae and the presence of starfish and crabs that prey on the spats. It is best to place bottom nets for crabs or crab traps as an added income to mussel farming. Usually, there are plenty of blue crabs in oyster and mussel culture areas.

Methods of culture

There are five common methods of culture, like: stake (tulos), wigwam, raft or hanging, tray and rope web. The best and most popular ones, however, are the stake and rope-web methods.

Logs, hard bamboo (Bambusa sp.) and light bamboo or bagakay (Schizostachyum lumampao) can be used. However, hard bamboo is more popular because they are readily available and cheaper than logs.

Sharpen the bottom tips of the bamboo and drive it (pile) at the bottom by about one-half meter. Place a hole at the upper section of the bamboo segment to reduce buoyancy. The distance of the bamboos as post is 1-1½ m. Tic or nail the 2-3 m row of horizontal braces (bila). Connect every two rows of poles with short horizontal supports (baral) forming a square with the long bila.


Light bamboos can be used for the supports and braces. The series of squares forms the plot. Leave 1½-2 m in between 2 rows or plots for the wooden boat (banca) to pass through. Tie spat collectors to the poles. Preferably use abaca rope with coconut or abaca coir in the rope lay at 7.62-12.7 cm distance.

The best time to construct plots is the month before the occurrence of peak spatfall in the area to insure higher production. Mussels settle in the plot materials. The depth of the plots should be 1-2 m below zero tide level at the upper portion and about 0.50 m from the bottom. An average of 1,000-2,000 seeds or pieces of mussels per meter can be attained at these levels.

The rope web method is recommended in areas where there is heavy occurrence of spatfall. A sharpened hard bamboo pole is driven by piling at the bottom by at least ½ m. The upper portion of each segment of the bamboo must have at least 2.54 cm hole to prevent too much pressure from floating. The bamboo poles are 4.0-5.0 m apart. Abaca or polypropylene (nylon) ropes of 12mm-15mm are tied horizontally at the upper portion of at least ½-1 m from zero tide level. Another rope is tied horizontally at the lower portion with at least ½ m from the bottom. The upper and lower rope tied between the 5.0 m distance pole will form a parallel. The distance between the parallel ropes can be 1.5-2 m.

Abaca or nylon ropes of 10.0-12.0 mm diameter are made into webs that are tied vertically in zigzag fashion to the parallel ropes between the bamboo poles. The interval of the zigzag ropes or webs must be at least 30-40 cm. Web-rope lines can be spaced at 1.0-1.50 m rows for space to work on and for wooden boat to pass through.


The stake method


Rope-web method

Bamboo pegs of 20 cm length and 2.0-3.0 cm width are inserted into the zigzag rope lay at spacing of 30-40 cm to serve as spat collectors. Abaca or coconut coir can also be used because mussel spats prefer filamentous or hairy objects as cultches. The two rows of rope webs will form the plots.

Juvenile mussels can be placed in wet gunny sacks in clusters and transported to new areas to be transplanted. Transplanting is done by tying the young or small mussel clusters into the culture medium, like rope web or stakes.

Harvesting

Market preparation and knowledge of peak demands and high prices season are important in the timing of harvesting. Selective harvesting can also be done by harvesting the bigger ones first and leaving the smaller ones to grow further.

Divers are hired to do harvesting in the stake method. This is done by scraping the mussel clusters from the stakes and supports with the use of sharp knife or bolo. Care is taken not to pull the mussel shells because the byssus or beard when detached, can kill the mussels. The byssals are parts of the muscle structure of the green mussel. The mussels are placed in bamboo or rattan baskets and cleaned by continuously dipping them in the sea water. The mussels are separated or detached with the use of scissors.

Marketing of green mussels has never been a problem because of its demand as a source of low-cost protein. Also, it has generated employment in the coastal-producing areas. Green mussels can live three to four days after harvesting by continuously wetting them with sea water. It his a high nutritional and medicinal value.

Mussels are versatile aquatic products. Bivalves culture has a relatively simple technology and the labor is not intensive. The cost of investment is minimal but high profits can be expected.

Economics of production of mussel farm


Value (in pesos)

Total Value (in pesos)

Annual Revenue


15,154

Annual Production Cost


Materials

6,406



Hired labor

2,334



Miscellanous

448



Unpaid owner labor

514



Unpaid family labor

428



Depreciation

813

10,943

Fixed Investment




(non-motorized boat, nipa hut, tools, wooden oar)


2,904

Net Return


Annual revenue

15,154



Less: Annual production cost

10,943

4,211

Return on Investment

Net return

4,221


Fixed investment

2,904

1.45

Source: Samonte, Giselle PB., Oyster and Mussel in Western Visayas, Greenfields, April 1993.

Mollusc culture: Oyster

Oyster culture in the Philippines began at Hinigaran, Negros Occidental, in 1921. Oyster or talaba is a popular bivalve delicacy because of its excellent flavor and taste. It is mostly marketed in the shell as freshly-shucked meat. Some salted oyster or bagoong are made during peak harvest season. It is rich in vitamins, minerals, proteins and carbohydrates. The shells are mostly used as raw materials for the manufacture of lime and poultry grit. The shells also serve as spat collectors for culturing.

Mariculture of oysters have been expanding to other areas in the past years. There are about 5 sq km used for oyster culture ranging from 1,500 m-5,000 sq m in about 1,300 farms. Oyster farms are located in 17 provinces comprising Regions I, IV and VI. Major producers are Negros Occidental, Pangasinan and Cavite (Oyster, Commodities Series, No. 64, TLRC 1988). There are little or no available records of oyster preparation exports and data on consumption. Oysters are mostly consumed near production areas.


Oyster or talaba.

Site selection

Oysters thrive best in brackish to marine waters with salinity ranging from 15-26 ppt at 20-30ºC water temperature. Viable oyster farming grounds have indigenous species of spawners that are present. The water should be free from pollution with green to blue-green color. The area should be free from flooding that may result to 0-10 ppt salinity; this causes heavy mortality and heavy siltation. Water depth should be at least 1.5-4.0 m at the lowest tide.

The bottom is either hard non-shifting or soft and muddy. Areas for culture must be naturally protected against strong wind and wave action along landlocked bays or estuaries. Materials for structures should be readily available and cheap. Preferably, sites should be near markets or centers of population within 100 km. The presence of endemic seeds or spats in the area is preferred, but seeding or transplanting of oysters may be undertaken.


Oyster farms are found in 17 provinces located in Regions 1, IV and Vl.

Culture aspects

There are four popular species of oyster for culture:

· Crasostrea iredalei (Talabang tsinelas or slipper-shaped)
· Saccostrea malabonensis (Kukung kabayo or oblong)
· palmipes (Pulid-pulid or palm-rooted)
· cucullata (Kulot or wild oyster)

The first two species arc recommended for growing.

Peak natural spatting season or spawning usually occurs in January to February and May to September. Fertilization of spawned oyster eggs takes place in the water. After hatching, a planktonic larva emerges and remains in the waters for two to three weeks before settling down. Spats or seeds about the size of sand grain attach to suitable substrates (like logs, stones, shells, bottoms, etc.). The most suitable and commonly used spat collectors are empty oyster shells.

After a growth period of one month, the juvenile oysters (young) measure about 1.27 cm long. Oyster food consists of microorganisms, phytoplankton and organic matter which they strain or filter out from the water with their gills. This explains why oysters thrive well in fertile waters. It normally matures after 6-10 months from seeding.

Culture period should be started before spatting season or spatfall. Juvenile oysters can be transplanted to other areas with no available spats.

Methods of culture

There are several methods of culture: stake (tulos), hanging (pabitin), long line (sampayan) or stone (paringit). However, the hanging method is recommended.

The hanging method is constructed by piling a 3.04.0 m bamboo post or 7.6212.70 cm diameter wooden post at 4.0 meter distance in between rows and 1.0-1.5 m between rows. The rows should be 8 m long (the normal length of hard bamboo) and the number of rows should be ten per lot. In-between rows are lanes of at least 2-3 m for the caretaker's dugout wooden boat to pass. Bamboo pole platforms are tied to the post at about 0.50 m below zero tide level. Threaded empty oyster shells ranging from 12-16 pieces at a distance of 7.62-10.16 cm in-between shells or clutches serve as the spat collectors. Use No. 3 or 4 polyethelene ropes or plastic twines. The threaded cultches arc then hung al the bamboo pole platforms. Maintan, 20.0-25.0 cm distance between substrates or cultches.


Hanging method


Stake-and-tray method

Maintenance

1. Check the structure for damage and promptly replace damaged parts, where appropriate.

2. Set the hanging oysters just below the normal low tide level.

3. Remove sponges growing on the surface of the oysters. They impede the flow of water and food as well as compete for oxygen and food.

4. It is desirable to construct a caretaker's hut in the farm to deter potential poachers and to facilitate management of the farm.

Harvesting

Not much care is needed in oyster farming, except by guarding it from poachers through frequent visits or by staying at the site two to three months before harvest. Harvesting is done by pulling the hanging cultch lines. Separate the bigger oysters for market and leave the small ones at the bottom bamboo tray to grow further. Submerge and clean harvested oyster shells. Pack them in gunny sacks or bamboo baskets or kaing. The bamboo basket contains about 40 kg freshshell oysters. The marketable size is 6.0-12.50 cm long. Oysters are best harvested before the spatting season of March to May because they are fat and delicious during summer (dry months).

Production can reach 8-12 metric tons per hectare. A family-sized growing area of 2,500 sq m is an ideal, livelihood project for beginners.

In areas where there is an occurrence of red tide that cause poisoning to humans, harvesting should be suspended or stopped until the area is cleared or free from red tide organisms.


Harvesting of oysters

Economics of production - ½ ha oyster farm (139 plots) using plot hanging method with empty oyster shell collectors

Assumptions

1.

139 plots (18 m × 1 m) for one-half ha

2.

1 sack of empty oyster shells (800 pcs) makes about 114 collector strings at 7 cultches or shell per string

3.

350 collector strings per plot × 139 plots = 48,650 strings

4.

6-8 month culture period


Value (in pesos)

Total Value (in pesos)

Annual Revenue


Sale of 2,862 kaings × 160/kaing

457,920

457,920

Annual Production Cost


427 sacks empty oyster shell × 20/sack

8,5402



50 rolls polypropylene film × 10/roll

2,500



48,650 preparation collectors × 0.50/collector

24,325



(4) hanging collectors × 60/day × 7 days

1,680



Harvesting cost - 2,862 kaings × 10/kaing

28,620



(1) Caretaker × 1,000/month × 12 months

12,000



Depreciation

109,725



Miscellaneous

21,645

209,035

Fixed Investment


Cost of materials and labor for plot construction



24 pcs bamboo post (7 cm.) 3/pc × 139 plots

116,760




6 pcs bamboo horizontal pole (10-15 cm) × 45/pc × 139 plots

37,530




2 kg monofilament nylon line × 120/kg × 139 plots

33,360



Contract labor for construction



- 200/plot × 139 plots

27,800




Dug-out banca, 5 m long

5,000




Tools and diving paraphernalia

1,000




Shed

2,000

223,450

Net return

Annual revenue

457,920


Less: Annual production cost

209,035

248,885

Return on Investment



Net return

248,885


Fixed investment

223,450

1.11

Source: The Science and Business of Growing Oysters, PHRDC, 1991.

Natural oyster populations, farming areas and potential sites in the Philippines

1 Buguey, Cagayan (NG,FA)
2 Ilocos Norte (NG, FA)
3 Ilocos Sur (NG, FA)
4 Aringay & Sto. Tomas, La Union (NG, FA)
5 Lingayen Gulf & Tambac Bay (NG, FA)
6 Agno River, Manat, Binmaley, Pangasinan & Davel, Dagupan City (NG, FA)
7 Binuangan & Malolos, Bulacan (NG, FA)
8 Abucay & Mariveles, Bataan (NG, FA, PS)
9 Cavite—Bacoor & Ternate Bays (NG, FA)
10 Balayan Bay, Batangas (NG, FA)
11 Batangas Bay (NC, FA)
12 Tayabas Bay (PS)
13 Makato, Aklan (PS)
14 Sapi-an Bay, Iloilo (NG, FA)
15 Banate Bay, Iloilo (NG, FA)
16 Bacolod (Port of Banago) (NG, FA)
17 Binalbagan and Hinigaran, Negros Occidental (NG, FA)
18 Himamaylan, Negros Occidental (NG, PS)
19 Panguil Bay, Misamis Occ. (PS)
20 Luuk, Bongao Cove, Sacol [s], Zamboanga del Norte (PS)
21 Scall Lagoon, Sta. Cruz, Zamboanga del Norte (PS)
22 Malalag Bay, Davao City (NG, FA)
23 Del Caman Dapa, Surigao del Norte (PS)
24 Calape, Bohol (NG, FA)
25 Cebu (NG, FA, PS)
26 Leyte (PS)
27 Maqueda Bay & Jiabong, Samar (PS, NG)
28 Catbalogan, Samar (PS)
29 Sorsogon (NG, FA)
30 Pagbilao Bay, Quezon (PS)
31 Alabat Island, Quezon (PS)
32 Polilio Island, Quezon (PS)

Legend

NG - Natural grounds
FA - Farming areas
PS - Potential sites


Farming areas and potential sites in the Philippines

Source: The Feasibility of Oyster and Mussel Farming by Municipal Fishermen in the Philippines, South China Sea Fisheries Development and Coordinating Programs, January 1982.

Fish culture in cages

Both fish pens and fish cages are confinement structures used for rearing fish. The pen, however, is larger; it ranges from 10,000 sq m to more than a square kilometer in contrast to the cage which ranges in size from one square meter to several hundreds of square meter. Also, cage culture is done in at least one-meter water depth or in deeper waters. Thus, this type can either be stationary or a floating cage which can then be established in the sea, lake, cove or river where biophysical factors are favorable.

Species of fish that are grown in fish cages are usually expensive and sold live for a certain group of consumers. Demand for live fish exports to Taiwan, Hongkong and China is fast-increasing. Seafoods that are popularly exported alive and grown in cages are grouper, humphead wrasse, lobster and seabass. These species, when cooked alive, command more than triple in prices. Wrasse and groupers are first-class fish species that are believed to also have medicinal properties for sick and recuperating people.

Site selection

Fish cages should be installed in suitable areas that are protected from strong waves and currents, free from pollution and accessible to the farmers and market. A minimum depth of one meter is required.

Fish cages

There are two common types of floating fish cages: the bamboo frame cage and the nylon net cages with frames. They are both provided with anchors and floats. Fish cage rearing can be done in freshwater and brackishwater areas.

Bamboo frame fish cages

They are made of hard bamboo slats tied or nailed to wooden frames. The usual measurements are: 2 m long, 2 m wide and 2 m deep, 3 × 3 × 2 m and 4 × 2 × 1.75 m. They are provided with whole bamboo floats or empty drums at the top side. Net or bamboo top cover with door and lock is provided.

Advantages

· Cages are easy and cheap to construct.
· Cages can be operated cooperatively.
· Cages are easy to stock and feed
· Fish grow fast in cages.
· Cages are easy to harvest.

Net fish cages

They are made of fine-meshed (0.32-1.27 cm) nylon nets connected to a float frame of whole bamboo with empty drums of plastic or styrofoam to enhance buoyancy. The empty drum is optional for a small-sized net cage. The usual size is 8-10 sq m with 2 m-2.5 m depth. The net cages are provided with concrete weights that also serve as anchors. The cage is also provided with a mooring line to keep it in place, as well as reinforcement bamboo frames to spread the nets.


Floating bamboo fish cage

Management

Fish cages can be used for fish fattening or growing. For growing purposes, use fingerlings. Before stocking, weigh and count the fish.

As a nursery for fingerlings, the cage should be made of fine mesh net. The size is appropriate for easy handling. There are two cages —the first is a brooder's cage with a 1.255.0 cm mesh size This is placed inside a bigger cage which functions as the confinement cage or as a conditioning cage for fishes, subject to transport. This is commonly used for rearing fingerlings to marketable-sized fish. The net's mesh size depends on the size of fish or fingerling that would be stocked initially. The cage area usually ranges from 1 sq m to 100 sq m or more and the depth ranges from 1.0-2.0 m or more. Cages are subject to fouling organisms. Clean heavily fouled nets as often as necessary to ensure efficient water change.


Floating fish net cages

Check the net daily for possible damages to prevent escape of the stocks. Check also the structure (e.g., bamboo structures, ropes, sinkers, floats, etc.). Guarding the fish cages should be done at all times to prevent losses from poaching. Construct a caretaker's hut at the culture site to discourage poachers.

Rearing of the stock

Fish sampling is done at least every month to determine the growth rate and the proper quantity of feed to be given. Expose the fish to outside parameters that may affect their feeding performance which eventually affects their growth rate. During the wet season, water temperature usually drops; thus, decelerating growth rate. In summer, the growth rate is faster. Hence, feeding should be regulated. Practice an addition feeding to determine the actual food needs of the fish, especially before the sampling schedule. Do not feed fish subject for sampling.

On the average, depending on the fish species and the kind of feeds, the feeding rate is three to five percent of the body weight. Give commercial feeds at three percent and trash fish at five percent. In the absence of commercial type, an alternative feed may be made at home, suited to fish requirement, e.g., a 70-percent rice bran, mixed with 30-percent fish meal or fine trash fish for Tilapia mosambica (hybrid). Feeding should be done early in the morning and late in the afternoon by equally dividing the feed needed. It is important that feeds are available at all times when using fish cages. Feeding trays may be used to mimize wastage of feeds.

Culture period ranges from three to five months. The stocking rate can be 5-20 pieces per square meter.

Harvesting and marketing

Here is one way of harvesting fish: For the net cage, untie the bindings at the corners and sides of the net from the float frame. Insert a bamboo pole at the upper edge of the net cage and push the net along in order to corner the fish at one end. Scoop the fish with hand nets.

The fish, if sold live, fetches a higher price. It is, therefore, advisable to place the fish in double plastic bags containing well-oxygenated water. The bags are then placed in styrofoam or burl bag containers. Dead fishes to be sold should be packed in crushed ice at the rate of 1:4 by weight (1 kg ice to 4 kg fish) for nearer markets and 1:1 ratio for more distant markets at a temperature of 0° C which is good only for 24 hours or less.


Pull out the net for cleaning and repair after harvest.

Fish culture in pens

The implementation of the Agrarian Reform Law covered fishponds which resulted the imposition of a ban on the issuance of new fishpond lease agreements and their renewal. The law prompted many businessmen to grow fishes in pens instead, because this is exempted.

Fish-pen culture also became popular because of the fast-increasing demand for live fish both for export and domestic consumption. The price of exotic live fish is about triple to quadruple compared to the traditional chilled fish, such as groupers, seabass, lobsters, etc. Many Chinese and Japanese businessmen believed that eating live fish gives good fortune and luck. Studies also show that the prices of developing fishponds are quite prohibitive compared to establishing fishpens.

The availability of fingerlings for growing in fishpens also promoted the rapid expansion of fish culture using pens. Southeast Asian Fisheries Development Center (SEAFDEC) and the private sector have made breakthroughs in breeding milkfish, seabass and grouper in captivity. Prawns, tilapia and shrimp (Macrobrachium spp.) were successfully produced earlier in hatcheries.

Also, although the fish pen is similar to fishponds, free-flowing water in the pen provides adequate supply of dissolved oxygen critical to fish culture. The use of aerators in fishponds is becoming expensive and risky because of erratic electricity. Fish pens will likewise put underutilized freshwater and brackishwater aquatic resources into productive use.

Fish pens can be set up in brackish and freshwaters, depending on the type of culture and kind of fish to be grown. Bays and coves, places with laminar and steady flow of water, optimum oxygen content and food are desirable places for establishing a fish pen. For small lakes and rivers, fish-pen management is relatively easier due to its proximity. However, seasonal patterns (e.g., seasonal overturn or oxygen cycle) should first be determined to ensure viability of this activity.

In freshwater bodies, polyculture may be done to maximize its use and efficiency, provided the species to be grown are compatible. An example of polyculture is a combination of carp, tilapia, shrimp and clams in the fish pen. Tilapia is a surface feeder while carp is a bottom eater, like the clam and shrimp. Tilapia mosambica can also exist in brackishwater and can be combined with seabass or grouper.


How to construct the fence

Polyculture can be practiced in both saline and freshwaters. For instance, Tilapia mosambica can co-exist with seabass or grouper. Tilapia fingerlings can, thus, serve as natural food since the grouper and seabass are carnivorous while the tilapia is planktonic. Milkfish can also be combined with mud crab and tiger prawn.

Freshwater fish pens should be shallow, ranging from 50.0 to 80.0 cm to allow rapid multiplication of food materials, such as phytoplankton, algae (lumot) and other plants. On the other hand, brackishwater fish pens should be 1.0 m to 1.5 m below zero tide level to allow effective photosynthesis. Ideal salinity conditions are usually from 10 to 25 ppt.

Methods of fish-pen construction

The type of construction depends on the configuration of water bodies and the desired species. Two common fish pen structures are the barricade and full-fence type. Both types can use either the slat or flattened bamboo fence or the combination of nylon nets and bamboo frames. Hang the net one meter from the water surface to prevent fish from escaping while the bamboo posts should be higher than the highest high tide level by at least 30 cm to ensure confinement of the stocks inside even during the flooding period.

Barricade Type

This type of fish pen is applicable in narrow shallow inlets, small coves or submerged protected bays or lakes. Barricade fish pen is more economical because you have to fence only one, two or three sides.


Barricade fish pen

Conventional fish pen

This type is more common in big bodies of water, like bays and lakes where tidal fluctuation occurs and where waters rise and recede frequently. It is fully enclosed with a fence, using either flattened bamboo or bamboo slats and polyethylene or coralon nets framed with bamboo or wood.


Typical conventional fish pen

Management of fish pens

Check the net enclosure daily for damages to prevent the escape of fish. A practical method of monitoring is by setting up a gill net in the four corners of the pen. A fish caught in any of these corners would indicate net damage in the enclosure net. Another is simply by finding out if those fishing (with gill net) near the pen have caught any of the species grown in the pen. This may, however, become a difficult way of monitoring net damages.

Supplemental or full feeding depends on the species of fish grown. Freshwater fish, like milkfish, tilapia or carp, need full feeding for the intensive method (20,000 to 30,000 fingerlings per 10,000 sq m) and supplemental feeding for semi-extensive (10,000 to 15,000 per 10,000 sq m). Selective feeding is done under extensive method of culture (3,000 to 7,000 per 10,000 sq m).

The amount of commercial feed given is normally computed at three percent of the body weight.

Monoculture of brackishwater fish species, like seabass and grouper, needs full feeding of trash fish, mussels or snails. Fresh trash fish is computed at five percent of the body weight of the fish population. Sampling of weight should be done at least every five days. Siganid or rabbitfish also needs supplemental feeding together with prawns.

Polyculture of tilapia with grouper or seabass needs supplemental and selective feeding. Stock the tilapia breeders at least one to 1½ months earlier to allow lead time for the production of fingerlings as feed.

Feeding should be done at least twice a day-one in the early morning and one in the late afternoon, equally dividing the amount of feeds required.

Monoculture stocking in fish pens can be done at two to five fingerlings per square meter.

Harvesting

Selective harvesting can be done using pole and hook, cast net or gill net. Full harvesting is usually done with the use of seine nets during low tide. Tilapia cannot be fully harvested because about 20 - 30 percent burrow in the bottom during harvesting. At any rate, any volume can be harvested everyday, depending on the market (i.e., demand, price). The culture or growing period of different species ranges from three to five months.

Since live fish fetch higher price, transport harvested fish in double plastic bags with oxygenated water. Use styrofoam or burl bag containers.

Profitability of fishpen culture

There is less initial capital needed in fish pen culture because, unlike with fishponds, purchase of land is not necessary. The economics of production varies, depending on the site, type of pen, kind of fish cultured and method of culture. Profits for brackishwater fish are usually higher than those from freshwater. It is more advantageous and profitable to grow expensive fish species in fish pens that are popularly sold alive. Growing in fishpens can be done two to three times a year.

Fish corrals


Fish corral

Establishing fish corrals (baklad) is one popular method of catching fish along tidal flats, in coral reefs and mangrove areas. They are located in bays or near estuaries with moderate currents (not strong waves), affected by tidal fluctuations. This fishing gear is stationary and is constructed in areas known to be rich fishing grounds.

Most fish species that travel with tide currents are trapped by the fish corrals. They can trap different species, like crustaceans (crabs and shrimps), demersal fish (groupers, snappers, etc.), mollusks (squid, cuttlefish, etc.), etc.

A fish corral needs high capital but requires only minimal and periodic light labor. It can also be highly profitable.

Method of construction

The fish corral consists of a guiding barrier or leader made of bamboo slats with nylon nets connected to a 3.0 cm wooden post. The size of the corral varies from 30.0-100.0 m wide. It is shaped like an arrow tip, pointed towards the sea from shoreline. At the back of the leader is the playground, a semiround shape made of the same materials as the leader. Connected to the playground is the terminal pound or bunt where the fish are trapped. The bunt is usually heart-shaped with a small opening. The nylon net of the leader and playground is finemeshed with sizes of 1.27-1.9 cm opening. The terminal pound is similarly built as the playground, but with finer mesh nylon nets of 1.27-1.90 cm. This is to prevent small impounded fish to escape.

Normally, the movements of fish are guided by tidal currents. At high tide, they travel towards the shore to forage and look for food. During low tide, they follow the current drifting towards the sea. If they happen to enter the fish corral contraption, they are finally trapped.

Harvesting

Collecting the captured fish can be done daily or every two to three days. It is usually done early in the morning or sometimes during low tides. Collect the trapped fish by scooping them with hand nets. Small fish net seines are sometimes used to fully empty the pound.

Economics of fish corral

Information on fish catch from fish corrals may be difficult to extract from fishermen. However, records from the Negros Occidental School of Fisheries at Binalbagan in 1987 showed a return on investment (ROI) of about 200 percent. Very informal discussions with fishermen reveal rough estimates of about 300-800 percent ROI per year.

Other considerations

Owners of fish corrals should be organized and vigilant in protecting their municipal waters from illegal commercial fishing, such as blast and poison fishing to ensure sustainability. Efforts should also be made to undertake mangrove protection and development, where appropriate, to ensure the health and productivity of the surrounding area which, in turn, will redound to the productivity within the fish corral.

Fish trap: Amatong

Traps, like the amatong, were commonly used before and during World War II. The adoption of this fishing method was facilitated because of the abundance of fish and because it was safer for fishermen to fish near the coast to avoid being sighted by Japanese ships. The depletion of fish and reduced catch in the last two decades, due to massive destruction of fish habitats and use of destructive fishing gear saw the disappearance of the amatong. However, coupled with care and consideration of other factors, such as number of amatong users and the like, it can be utilized in addition to other traditional fishing gears.


Fish trap: Amatong

Site selection

The amatong should be located in areas that are not exposed to strong winds and water currents. Preferably, it should be in sandy to muddy-sandy bottoms with wide tracts of low-tide areas within the vicinity of mangroves, seagrasses and coral reefs. Brackishwater areas are preferred because of the presence of several species of seafoods, like demersal fishes (grouper, seabass, rabbitfish, snapper, etc.), crustaceans (shrimps, crabs, etc.) and some seashells. Protected bays, coves, mangroves, seagrass beds, tidal flats and atolls are ideal sites; while areas along reservoirs, lakes, rivers, swamps, estuaries, idle fishponds and water impoundments are alternative sites. If possible, the amatong should be located near residences for better security.

Construction of amatong

The best time to establish fish shelter traps along the coast is during the lowest low tide.

The recommended dimension is 6 m-3 m and 0.50-1 m deep. Excavate the seafloor or bottom and place the excavated materials around the trench. Excavation is done to reduce the sudden change of temperature during the tidal fluctuations. Excavation may not be necessary in submerged areas two to three m deep.

Coral rocks are piled first at the bottom for at least three tiers. Filling of rocks can be in heaps or continuous. Pile small bundled tree twigs and branches on top of the coral rocks all around the trench. Bundling will facilitate easier removal during harvest. Pile a few bigger branches on top of the twigs to keep them in place or as weight. Use ropes to tie the top of the piles to prevent loosening of the tree branches pile and washing away during strong currents.

A few days after the amatong is established, moss, algae, plankton, etc., grow at the surface of the piled materials of rocks and tree branches. The accumulation of food materials in this substrate attracts various species of fish which feed on them. During high tides, some fish leave the contraption to forage for other foods. During low tide, most of the fish return to them. Soon, the amatong becomes a permanent shelter. Normally, several units of amatong are established near each other in groups of at least five or more units. They should be closely guarded from poachers who sneak inside using poisons, nets, or dynamites. Staying and sleeping in the amatong area with dogs few days before harvest will deter poaching. Cooperative vigilance should be practiced by amatong fishermen in each village.

Harvesting

Depending on the abundance of fish and the prevalence of amatong in the area, harvesting is usually done one month after the initial establishment and every two to three weeks thereafter. In Bohol, where many fishermen use amatong, they harvest at 11.5 months interval.

Harvesting is done as soon as colonies of fish are observed inside the contraption. Enclose the whole trench with bamboo strips or any fish net similar to fish corrals during low tide. Remove the piled materials inside and carefully place them around the amatong. Piled materials are continuously submerged in water or not overexposed to sunlight so as not to kill the microorganisms and plants attached to the substrates as future food materials in the next amatong.

The excavation is filled with coral rocks or dead corals, stumps and small branches of trees.

Use hand nets or just simply comb it with nets (ring net) to catch the fish inside after the enclosure is cleaned with amatong materials. See to it that small fishes (fry or juveniles) and gravid (pregnant) fishes are set free as a conservation measure. They will continue to grow or multiply in the amatong areas.

If sedimentation occurs in the trench, the depth is maintained by further digging. The contraption may be lined with coral rocks at the top edge of the trench.

In areas with limited mangrove stands, cooperative effort should be exerted by amatong users to establish additional mangrove areas.

Economics of production

Preliminary trials conducted in Batangas in 1987 showed that establishing amatong will cost about P300.00 per unit. For economies of scale and as an income-generating project, at least five units should be taken cared of by one fisherman or family. Batangas data average 3-5 kg assorted fish caught every three weeks. In Bohol, the reported average catch per unit is 5-7 kg every month.

At an assumed catch of five kg per unit per month, five units may have a total catch of 25 kg per month. At an assumed average price of P30.00 per kilo, a fisherman's expected income is about P750 per month or P9,000 per year. With an initial investment of P1,500 for five units, an amatong fisherman may attain a 500-600 percent of ROI (return-on-investment) per year. This is a favourable investment for employed people, granting that the sharing is 60 percent for fisherman and 40 percent for the financier.

This is an all-year-round fishing method and ecologyoriented livelihood project that is highly profitable.

Fish traps: Modified multipurpose fish trap


Bubo, a fish trap used throughout the Philippines for catching coral reef species.

Fish trap (bubo) is the most common and widely used fishing paraphernalia in the Philippines. However, for the past decades, not much has been done to improve or modify this fishing gear to increase its efficiency to catch and lengthen its use at a lower cost than the traditional types. It takes a longer time to finish one unit and one must have the skill of weaving.

The most common material is bamboo or rattan, which usually lasts four to six months of continuous use because it is easily broken and damaged during the catching process. It is made in different sizes of 0.61-3.05 m long and at various forms of opening or mouth, ranging from 0.61-1.5 m wide. Also, the cost is quite expensive, ranging from P150-P600 per piece. To some extent, it has limited use and efficiency. It is for this reason that modification was undertaken. Various improved models were tried in the Batangas-Mindoro area in 1986 and 1987.

The traditional fish trap is weaved at hexagonal-shaped hole with or without corner frames. Usually, it is oval-shaped from top view, semihalf round at front and back view and semioval at side view.

Many fishermen who use plastic net, mononylon net, wire net and other stronger materials for their fish trap say that it catches lesser fish compared to the common fish trap. They believe that these materials contain certain chemicals that, when emitted, make fish shy away from the traps. Also, there is a theory that bamboo, rattan and wood can produce plankton and other microorganisms that attach themselves to the common fish trap, which attracts fish better because they serve as their food. It is from this theory that the modified fish trap has to retain the wood and bamboo as its material components and the coralon net as its cover because they can produce indigenous food materials of fish and do not emit chemical substances that distract fish.

The proposed modified fish trap uses coralon net with sizes from 1.27-2.54 cm opening as its top, side and bottom covers. This is the net usually used as fence in fish corrals or fish pens. The use of coralon net is to keep the fish trap light for easy handling and can last three to five years. The entry or front opening is made of thin bamboo skin, nailed to a lumber strip of 2.543.81 by 5.08-6.35 cm The back or opposite opening for fish caught is also made of the same materials. The frames are usually made of hard lumbers, like guijo or other tree species, that are used for wooden boat building. These lumber species are more durable in water-submerged conditions. Copper nails are used to resist rusting. The bamboo strips should be nailed at horizontal position. They are rectangular in shape and varying in sizes from 0.61-3.05 m long, 0.61-1.5 m wide and 0.35-0.76 m height. The size preference is normally dictated by the frequency of harvesting the trapped fish. The longer the interval of the harvest, the bigger is the size.


Cover with coralon or nylon net

The fish trap can be used with or without fish baits inside. Placing fish baits inside the laid fish traps increases the chance of trapping carnivorous fish species, like groupers.

Weights or stone boulders are attached at the corners to serve as anchors.

The principle behind fish traps is the tendency and instinct of many fish species to look for shelters. The mouth or opening of the fish traps serves like the mouth of coral, sand and mud holes as shelters, sanctuary or hiding place.

Fish pots can be used in different water conditions, such as freshwater, brackishwater and salty water areas. The various places for fish traps are rivers, lakes, reservoirs, estuaries, mangroves, bays, intertidal flats, coral reefs and semideep sea.

The fish naps are laid at the bottom by dropping them in the waters. They are provided with sinkers (stone, metal, concrete, etc.) to keep them in place. A buoy is connected to the fish trap with ropes to serve as a marker and for pulling out during harvest.

Economics of fish trap

Field data from coral reef areas in Albay gulf showed an average catch of 1-2 kg per day; Negros Occidental with an average of 0.50-1 kg; Mindoro-Batangas area at 0.25-1 kg; and SUBASTA (Sulu/Basilan/Tawi Tawi), at an average of 2-4 kg per day.

The modified fish trap recommended will cost about P150-P200 per unit, which can last for at least two years. With an estimated average of 0.50 kg catch per unit per day, a one-year catch can reach about 150 kg of various species of fish. An expected income of P4,000.00 per unit is possible.

Fish trap operators should be encouraged to engage in mangrove reforestation and protection to attain sustainability of the project. At the same time, they should be vigilant in protecting their municipal waters from illegal fishing, like trawls, blast, cyanide and electric fishing. It was observed in Sulu that the introduction of fish traps in coastal areas has practically eliminated illegal fishing.

Milkfish-fry gathering

Normally, milkfish fry (Chanos chanos) are collected along brackish coastal waters near the mouth of rivers and streams where stands of mangroves are present. The fry appears in different places and various seasonal peaks. Fry season usually starts in March until July, with May and June as the peak months. The bangus fry is very much in demand to stock freshwater and brackishwater milkfish fishponds. However, the supply of bangus fry is highly erratic and unstable because it is highly dependent on wild fry catch. Breeding and raising milkfish fry in captivity is already being tried at Southeast Asian Fisheries Development Center, Iloilo.

Bangus growers usually stock their fishponds at 1020,000 fry or fingerlings per 10,000 sq m. The length of culture varies from 4-8 months or twice a year.

Rearing period coincides with the abundance of natural fish food. Usually, the culture period starts from March to April until July and August and the other is July-August to February-March of the next year. Seeding or growing is also timed with the fry season.


Bangus fry grounds in the Philippines

Adapted from: Philippines Recommends for Milkfish, PCARRD 1983.

Fry grounds and season

Areas like Leyte del Sur, Western Samar, Bohol, Negros Oriental and Occidental, Antique and Iloilo have two peak seasons that occur in March to July and October to November. Regions like Cotabato and Zamboanga del Sur have a year-round fry occurrence.

Peak gathering days occur during high tides after two or three days following a new moon or a full moon.

The gonadosomatic index (GSI) or peak-spawning season of milkfish begins in March to June and drops in August to September. During the breeding season, the rising GSI value coincides with rising seawater temperature. Spawning regularly occurs among five to seven-year old milkfish or sabalo in the wild with body weight of three to five kg. Fertility is about 300,000 to 1 million eggs per kilogram weight of sabalo. Sabalo is the female milkfish or breeder. (Greenfields, December 1989).

Collecting or gathering gear

Some commonly used bangus fry catching methods are: (Philippines Recommends for Milkfish, PCARRD, 1983)

Tidal set net (Saplad or Tangab)

This is a stationary V-shaped barricade with bagnet placed hammock-like behind the narrow end. The walls or wings are made of split bamboo slats 3-15 m long or fine-meshed nylon netting with ends tied to poles (post) set firmly at the bottom ground. Tangab is set in shallow portions along river banks, estuaries and tidal creeks near the opening of the sea. The parts are detachable during impending floods. The fry are guided by the wings into the bagnet where they are scooped out. The Tangab can collect 3,000-20,000 fry in a day's operation.


Tidal set net or tangab

Skimming net (Hudbud)

It is made of double sheet nylon netting (mosquito net), mounted on a triangular frame 1-2 m long and 1/2-1 m wide opening. It is pushed or towed in wading depths to deeper waters mounted in a banca. This gear is useful in mangrove areas that inhibit the use of the other types of active gears.


Skimming net or hudbud in operation. (Source: Villaluz et al, 1982)

Fry sweeper (Bakabaka)

This is a fan-like gear framed by whole hard bamboos and a detachable fine meshed nylon netting. The frame measures 2-4 m at the sides and 2-3 m at the opening. A bagnet is strung within the narrow end of the frame. Sinamay is usually sewn over the nylon net at the end portion of bagnet to prevent sticking of bangus fry in the nylon netting. The wings of the bottom net are provided with stone or lead metal sinkers. The sweeper is pushed along waistdeep to chest-deep waters for 28 hours depending on fry availability. Daily catch can reach from 200-2,000 fry.


Fry sweeper or bakabaka.

Double stick net (sarap or sagyap)

This is a rectangular seine held between two light bamboo poles. The net is made of fine meshed nylon (mosquito net) or sinamay cloth 1-1.50 m wide and 6-8 m long. It is operated in wading depths with two persons at each end dragging the net seine along the seashore. The catch can range from 200-1 500 fry in two to six-hour operation.


Double stick net or "sagyap"

Bulldozer

This is similar to the fry sweeper but is provided with bamboo platform (raft) along the sides of the bagnet and at the back . It is generally operated at night with a strong kerosene lamp (Coleman or Petromax) mounted in front of the bagnet. The bulldozer gear is propelled by bamboo poles by pushing. Sometimes, outboard motor is used. The catch ranges from 1,000-10,000 fry in three to sixhour operation.

Bangus fry are attracted to strong steady lights, hence the bulldozer method is recommended. Other collecting gears can also use strong lamps during night catching to increase efficiency of catching.


Bulldozer milkfish try catcher

Handling and marketing

The collected bangus fry are placed in well-ventilated containers, preferably wooden vats or big earthen jars filled with clean brackishwater. Keep them in cool areas. Overexposure to sunlight should be avoided. The fry are brought to the concessionaires' buying stations (or fry buyers/assemblers in the village if there is no concessionaire) without delay.

Economics of production-27,100 sq m milkfish pond


Total value (in pesos)

Annual Revenue


Sale of 5851 kg × P21/kg × 7 runs/year


122,871


Annual production cost (lime, fertilizer chicken manure, fingerlings, labor)


24,206

Fixed investment


27,100

Net return


Annual revenue

122,871



Less: Annual production cost

24,206

98,665

Return on investment

Net return

98,665


Fixed investment

27,100

3.64

Source: Alvarez, Ramiro C., The New Modular System of Raising Milkfish, Greenfields, February 1991.

Prawn-fry gathering

Most black tiger prawn or sugpo (Penaeus monodon) growers in the Philippines are concerned with the efficient production of marketable and good quality prawns from post-larvae (juvenile to sub-adult) in brackishwater fishponds.


Penaeus monodon

Majority of the prawn growers believe that efficient production with high survival, good growth and relatively disease-free prawn fry will come from the wild (not hatchery-bred). It is also preferred by most prawn growers and commands a higher price than the nursery-bred fry.

Natural seasonal occurrence of prawn fry is normally observed in areas with mangrove stands along brackishwater (15-27 ppt salinity) areas. Fry catching has generated seasonal income among the coastal people, especially children, unemployed youth and mothers who cannot brave the high seas for fishing.

Spawning and fry stage (post-larvae)

The life cycle of the crustacean prawn starts when the female attains sexual maturity at the age of 10-12 months when mating occurs during the molting of the female. The gravid (pregnant) prawns go to offshore areas of 20-70 m deep to lay their eggs. Two or three consecutive spawning can release half to one million eggs that can take place in one season.

The eggs hatch 12-15 hours after spawning. After 10-12 days and two more larval stages, they metamorphose into post-larvae which are similar to the adults. The post-larval stage occurs in brackishwater areas.

The adults remain in the sea (offshore) up to the old age of three to five years. However, some prawn species undergo spawning and stay in brackishwater without going to the open sea. Normally, the fry catching peak season is from September to February and May to June.

Methods of prawn-fry gathering

Most prawn-fry gathering municipalities still use the traditional method of fry catching—the hand net, push net (sagyap), fry sweeper and the fish corral type (tangab). Improved fry-catching technology not only increases catch that would otherwise be eaten by other fish species or lost, but also bigger income for fry gatherers.

An improved method of prawn-fry gathering is by placing several (5-20) bamboo torches (sulo) along seashores or near river mouths at night. Prawn fry is attracted by low-intensity moving lights. Fry catching can now be done during the night by using the fry sweeper.

Another improved method of catching prawn fry is with the installation of a series of bundled (tied) coastal grasses (dried or fresh) tied on long lines or rows of strings (plastic twine or No. 4 nylon rope). Place several sulo along the beaches or near river mouth and install several lines with bundled grasses tied to the lines at 40-50 cm distance of at least 20-30 m long. The rows or lines should be facing the sea. At night, the prawn fry are attracted by the sulo and, at the same time, cling to the substrates. Clinging to the materials (or bundled grasses of 5.08-7.62 cm diameter and 30.48 cm long) is an instinct of prawn fry for them to seek food source and as their shelter and sanctuary. Gathering of the fry is best done by using rectangular hand nets. Place the hand nets below the grass bundles, lift the grass line and shake the substrates so that the clinging fry will drop at the hand net. Fry gathering under this method can be done at dawn or daytime.


Prawn fry catching using the sulo and grass.

Prawn fry that are caught are placed in well-ventilated containers like pails, drums or wooden vats and kept in cool areas. Earthern jars or pots are used in bringing them to buying or concessionaire centers. Counting can be done by scooping the fry in the water.

Studies conducted in Western Batangas and Lubang Island (Occidental Mindoro) showed that higher catch by two to eight times is attained by using the improved method, using sulo and substrates versus the traditional ones.

Economics of production (prawn)

Assumptions


Stocking density

less than 50,000/10,000 sq m


Water management

tidal or pump


Aeration

no aeration


Fry source

wild


Feed use

natural supplementary


Dike construction

earthen


Crops/year

1-2


Harvest method

total harvest


Survival rate

60% or less


Production/cycle (kg.)

500 or less

Economics of production


Capital investment (per ha)




a. Pond development cost

P 30,000-50,000



b. Working capital

P 10,000-48,000


Total production cost per cycle

P 64,254.64



a. Direct cost

P 50,987.50



b. Indirect costs

P 13,167.14


Cost/kg output

1a 47.60


Net return per year

P 195,490.71


Return-on investment

1.09

An extensive system (stocks subsist on natural food grown with or without fertilization and pond water is changed through tidal exchange) of prawn culture requires a stocking density of less than 50,000/10,000 sq m and an investment requirement of P40,000-P98,000/10,000 sq m. With a survival rate of 60 percent, maximum annual production is approximately 1,000 kg. Annual production cost is P126,509.28 while net return is P195,490.71. Return on investment is 1.09 (Greenfields, Vol. 7, No. 1, January 1987).