Oyster Culture Using Raft Method

Commonly called “talaba” in tagalog or “tirem” In Ilocano, oyster can be cultured in bays, coves, tidal streams, mouth of rivers, marshland and shore areas.

Buguey, Cagayan is the traditional area for oyster farming in region 2. However, techno-demos conducted by BFAR R02 have shown that it can also be cultured at new areas like Sta. Ana, Gonzaga and C’laveria. all in Cagayan.

Oyster farming does not require skilled manpower. Anybody can prepare the spat collectors and can do the harvesting. It is a well-liked sea delicacy of high nutritive value and a good source of protein and calcium like any other edible sea shell.

Four Local Species of Oyster

  • a. Talabang Tsinelas ( Crassostrea iredalie) or the slipper-shaped oyster.
  • b. Kukong Kabayo (Saccostrea maiabonenesis) or subtrigional oblong oyster.
  • c. Pulid-Pulid (Saccostrea culcullata)
  • d. Kulot (Saccostrea palmipes)

Talabang tsinelas and Kukong kabayo are the most commonly cultivated species while puiid-pulid grows wild on rocky bottoms in many coastal areas in the country.

Feeding

Oysters are filter feeders. Through the opening and closing movement of the valves and the beating action of the gills, water entering the shells is strained and nutrients are obtained. No artificial or commercial feed input is needed as they depend mainly on natural food. Oyster feed on phytoplankton which are microscopic plants floating on water.

Site Selection

A potential oyster farm should have the following characteristics:

  1. Indigenous spawners should be present to ensure adequate seed supply.
  2. Should have clean brackish water whole year round, with green to blue-green in color which indicates presence of natural food. Salinity should be between 17-25 ppt and temperature between 27-32 °C.
  3. The area should be free from excessive flooding which result to very low salinity (0-10 ppt) and heavy siltation, which can result to mass mortality.
  4. Water depth should be 1.5-2.5 meter for traditional and 5 meters for eon-traditional culture methods.
  5. The area must be protected by a natural barrier or a breakwater to prevent damages to farm structure specially during typhoons.
  6. There should be sufficient tidal current for good water exchange and to prevent build-up of decaying matter.
  7. The bottom should be either hard and non-shifting or soft and muddy to minimize siltation. The type soil determines the method of cultivation.
  8. Occurrence of predators like crabs, borers, starfish, barnacles should be minimal to lessen predation. and competition for food and space. If endemic seeds are not present in the area but the other criteria are met, transplantation/seeding of oyster can be undertaken.

Common Methods Used In Oyster Culture

  • a. Broadcast – makes use of stone, empty oyster shells and other media collectors. These are positioned in hard bottom areas while natural population of oyster is known to occur.
  • b. Stake – bamboo poles either whole or halves are driven in the bottom where the water is not less than a meter deep during the lowest tide. These are aligned and spaced at 1 to 2 feet. Installation of additional bamboos for support against flash flood, tidal currents and other disturbances is a common practice among local farmers.
  • c. Plot hanging – is an off-bottom type suitable in relatively deeper water of at least 2.5 meters deep during the lowest tide. It uses several types and sizes of indigenous materials as collectors such as oyster shells, old rubber tires, plastic packaging straps and bamboo.

For plots that require staking of bamboos such as the tulos and bitin the substratum should be muddy or soft enough so that the post will be easily planted at a minimum depth of 0.5 meter.

Each plot consist of 5-8 meters bamboo poles set horizontally apart at 1 to 1.5 meters and supported parallel to each other by a bamboo framework whose tips extend up to high level. After completing the structure, different types of hanging collectors are used such as:

  1. Empty oyster shells – 6 or 7 shells are strung together by a 1 – 3 mm PE rope or mono-filament nylon line at 10 to 15 cm interval and hung with at least 0.5m clearance from the bottom, to avoid siltation and predation at the bottom.
  2. Old rubber tires – these are cut into halves and tied to the horizontal bamboo by nylon ropes at 25 to 30 cm spacing.
  3. Plastic packaging straps – 1.5 cm width straps are cut into 1.0m length and tied in bundles of 4-5 pieces and spaced at 20-30 cm from each other.
  4. Bamboo lattice – bamboo slats of 10 to 16 pieces spaced at 15-30cm intervals are woven into a lattice (1×1 m or 1x2m) using Gl wire or nylon. This type is likewise secured to the horizontal beam of the plot at 0.5 to 1.0 meter apart.

Advantages:

  1. Production per unit area is much higher
  2. Mortality caused by excessive siltation and crawling predators is minimized.
  3. Fast growth rate
  4. Oyster meat is of excellent quality
  5. Shallow .areas with bottom too soft for broadcast method may be utilized.
  6. Harvesting is economical and easy

Raft Method

Rafts are constructed using bamboo (5-7 inches in diameter) tied together ‘ with monofilament nylon or Gl wire and provided with plastic drams as floaters. Different types of hanging collectors are used same as the plot hanging method.

Oyster culture used to take 6-8 . months, but now harvest can be done after 4-6 months only. After seed collection,: spats grow to a marketable size of 4-9 cm in length.

Harvesting

Harvesting is. done- preferably during low tide when diving is easier. Tools used are usually eye googles, knife, wicker basket – or kaing and a dug-out banca or raft for transport.

Harvested -oyster are placed in wicker basket and soaked in seawater to remove silt. Small oyster are shucked or opened .using a small knife while bigger ones are sold unshucked. Too small oysters for market can be returned to the culture site for another 2-3 months culture.

Simple Cost and Return Analysis (2007 data)

A. Oyster Raft method (6m x 6m). Materials and structure can last for 3 years.

Development Cost

  • 22 pes bamboo @ P45.0()/pc – 990.00
  • 1.5 kg monofilament nylon [email protected]/kg – 397.00
  • 4 pes plastic dram 200 liter cap.@P1,000.00/pc – 4,000.00
  • 300 hangs empty oyster shell @ P3.00/hang – 900.00
  • Labor (30% of bamboo and nylon cost) – 1,600.00
  • Transportation – 500.00
  • Miscellaneous (5%) – 314.00

Total – 8,701.50

Income estimate

  • 1st year harvest 300 hangs @ P40.0()/hang – 12,000.00
  • Less Development cost – 8,701.00
  • Net income – 3,298.0©
  • 2nd year harvest – 12,000.00
  • 3rd year harvest – 12,000.00

Total income for 3 years – 27,298.00

B. Oyster Plot Hanging Method (40 linear meters). Materials and structure can last for 3 years.

Development Cost (in Php)

  • 55 pcs hard bamboo @ P60/pc – 3,300.00
  • 2 kg monofilament nylon # 180 @ P265/kg – 53.0.00
  • 30 cans empty oyster shell @ P45/can – 1,350.00
  • 3 rolls PE rope #4 @ P160/roll – 480.00
  • Labor (30% of bamboo & nylon cost) – 1,104
  • Transportation – 500.00
  • Miscellaneous (5%) – 283.00

Total – 7,547.00

Income estimate 1st year harvest

  • 300 hangs @ P40.00/hang – 12,000
  • Less development cost – 7,547.00
  • Net income – 4,453.00
  • 2nd year harvest – 12,000.00
  • 3rd year harvest – 12,000.00

Total income for 3 years – 28,453.00

For more information, contact:

Bureau of Fisheries and Aquatic Resources
Philippine Coconut Authority (PCA) Building,
Elliptical Road Diliman, Quezon City
Phones: (02) 929-9597/8074
Email : [email protected]

Bureau of Fisheries and Aquatic Resources
Regional Office No. 02
Carig Sur, Tuguegarao City
Phone: (078) 844-4252

source: www.bfar.da.gov.ph, photo from blogs.mysanantonio.com

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