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4. RECOMMENDED AQUACULTURE TRIALS

Additional information is needed to verify the observations made during the aquaculture survey, July 1981, and to provide a sound basis for designing pilot or demonstration projects. The Aquaculture Trials discussed below should be a cooperative effort of the government of Indonesia and FAO as part of the current INFIDEP programme.

4.1 Oyster farming

There is no farming of oysters in the Riau on the Anambas Islands so there is no practical experience to provide a basis for selection of culture methods. The following work is needed.

4.1.1 Riau project

Establish an oyster culture project based at Tanjung Pinang with the following sub-projects:

1. Determine the time and intensity of setting (attachment of larvae to collectors) at selected locations, including Tanjung Pinang harbour, Los Island and the Kekip-Mentang Island channel. This will require placing of two collector strings (10 shells of oyster scallops or large gastropods on 10 cast concrete “plates”) at each location two times a month. After half a month, one collector string should be removed from the water and the attached oyster spats counted. The second collector string should be left in place for 3–6 months and then removed and all oysters counted, identified by species and measured.

2. Determine the growth rate and mortality of oysters using some of the seed collected in sub-project I planted at the following locations:

  1. Tanjung Pinang harbour. (Even though the oysters would be dangerous to eat because of pollution, growth and fatness should be excellent because of high level of nutrients in the water).

  2. Los Island (a potential seed area with good current).

  3. Telok Bintan (a large area with potential for oyster farms).

  4. Sungai Jang (Selat Dompak). (The site selected for the Research Institute for Marine Fisheries (BPPL) laboratory).

  5. Kekip-Mantang Island channel. (This is also a location selected for grouper culture studies and a potential site for commercial oyster farms).

This project will require hanging collectors with attached spat from simple wooden structures (or old fish traps) and measuring growth and mortality two times a month.

3. After good setting areas have been found, try various kinds of spat collectors such as:

  1. Oyster or scallop shells or cast concrete “plates”. (These are usually the best type of collectors and will serve as a “control” for comparing the success of other types of collectors).

  2. Large stones (about 15 cm in diameter) placed on bottom in the intertidal zone. (These are usually less effective than shells but may be available at low cost in some areas).

  3. Wooden poles about 2 m long such as old fish trap stakes or new poles about 4 cm in diameter coated with concrete or tar. Place vertically or horizontally, individually or in bundles.

  4. Wood strips about 1 cm × 5 cm × 1 m placed horizontally in bundles (New Zealand method). Try untreated, coated with cement, coated with asphalt tar.

4. After seed has been collected, try various systems for growing the oysters to market size including:

  1. “Stone” culture — Place 15 cm or larger stones with attached spat at various depths spaced 1 m apart in selected areas. (Primitive Philippine or Australian method).

  2. “Hanging” method — Build “racks” or frameworks of wooden posts with horizontal wooden poles at high tide level. Place collectors with attached spat (shells or concrete plates) about 10 cm apart on 5–6 mm diameter synthetic “strings” and hang from the horizontal poles. The lowest shells should be at least 25 cm above the bottom. Alternatively use 8–10 mm synthetic rope instead of horizontal poles (Philippine method).

  3. “Stick” method — Place 2 m wooden poles with attached spat horizontally on a “rack” or framework of wooden posts and horizontal poles. Try growing oysters at various levels by using a sloping rack from mid-tide level to low-tide level. This will determine the best level for growth and survival with least fouling. (New Zealand and Australia method).

  4. “Tray” method — Build 1 × 2 m trays with 2 × 8 cm sides and 2 cm (or 1") wire mesh bottom. Coat wire with tar to control rusting. Place trays on “racks” similar to those used for “stick” culture. Place seed oysters in trays and monitor growth and mortality. (Australia and New Zealand method).

4.1.2 Anambas project

At the DGF Fishing Base near Tarempa hang two spat collector strings from the pier 2 times each month to record time and intensity of oyster setting. For collectors use 10 cm diameter cast concrete plates with a hole in the center strung at 10 cm intervals on 5–6 mm diameter synthetic string. The highest plate should be at the upper edge of the band of oysters attached to the pilings. Remove one of the collector strings after one-half month and count the attached oyster spat. Leave the other collector string in place for 3–6 months and then count, identify, and measure the attached oysters. This will indicate the best time of year to place the collectors in the water and the growth and survival of the oysters. Some oysters should be of marketable size by the end of the six month period. Continue this experiment for at least one year.

4.2 Grouper farming

4.2.1 Riau project

Grouper farming has started here but the major problems are supplies of seed and feed. The following sub-projects are needed:

1. Conduct a resource survey to locate concentrations of juvenile (100–150 g) groupers. This should provide a basis for estimating the availability of seed as a guide for planning the expansion of grouper farming in the Riau Islands.

2. Develop better method for capturing juvenile groupers.

3. Search for smaller juveniles or fry and if found develop methods for capture and for growing them to juvenile size.

4. Evaluate the availability of low-priced or scrap fish that could be used to feed groupers in cages. Develop methods for capture, handling and perhaps processing into fish silage for storage.

5. Provide extension services to present grouper farmers in the Riau Islands to help them improve culture methods, and facilities and reduce the cost of production.

4.2.2 Anambas project

1. At the DGF Fishing Base near Tarempa install 3 to 6 net cages 2 m × 4 m × 3 m deep under the pier so that the depth of the water in the cages is at least 1 m deep at low tide. If necessary, cover the top of the cages with netting. Place 50 to 100 juvenile groupers in each cage and feed twice a day with available fish of various species including small tuna, anchovy-type fishes and shark meat. Record growth and mortality until the groupers reach a weight of 1 kg each. Also record the weight of each juvenile placed in a cage, the number of juveniles in each cage, the weight of each dead fish removed and the weight of food placed in each cage. From these records, determine food conversion rate (kg of food required to produce 1 kg of marketable size groupers).

2. If project is successful, build a raft with 3 to 4 net cages about 3 m × 4 m × 2 m deep and anchor in the deep hole on the west side of the cove where the fishing base is located. Conduct a growth and mortality experiment there as described for project 1. This will serve as a demonstration to local fishermen who might want to become part-time fish farmers.

3. If Riau grouper farming projects 1–4 are successful repeat in the Anambas Islands.

4.3 Rabbitfish mortality study

One grouper farmer in the Riau Islands also raises siganids, but heavy mortality of larger fish is a major problem. Another problem, perhaps related, is the availability of suitable feeds. These problems must be evaluated before large-scale efforts are made to develop siganid farming. The following sub-projects are needed, but are of lower priority than projects on farming of oysters and groupers.

1. Monitor growth and mortality of siganids in one or more commercial farms such as the farm at Sembur Island.

2. Evaluate water quality at siganid farms by periodic measurement of dissolved oxygen, ammonia, pH, temperature, salinity and other parameters.

3. Record feeds used since the fish may be susceptible to diseases and other adverse conditions because of poor nutrition. Try changes in type and quantity of feed.

4.4 Introduction of green mussel

No green mussels Perna (mytilus) viridis were found during the survey of the Riau area. Fishermen questioned during the survey, did not know what mussels were. However, excellent populations of green mussels exist at Singapore, N. Sumatra and Java. Many places in the Riau Islands appeared to be ideal for mussel culture. Therefore, it is proposed to transplant small quantities of mussels to determine the suitability of the environment for their survival, growth, reproduction and eventually their culture. The following sub-projects are needed but are of lower priority than work on oyster and grouper farming:

1. Transport seed mussels 5–40 mm in length from Jakarta or N. Sumatra to Tanjung Pinang via air in insulated boxes cooled with ice.

2. Place mussels in trays about 0.5 × 1.0 m × 10 cm deep with wooden sides and wire mesh top and bottom.

3. Suspend the trays of seed mussels from a structure such as an old fish trap, so they are covered by at least 0.5 m of water at extreme low tide. Suggested sites are Sungai Jang (Selat Dompak, Bintan Island), the channel between Kekip and Mantang Islands, and Tanjung Pinang harbour.

4. Monitor growth, survival, gonad development, spawning and setting. Monitor water quality periodically throughout the year. (Temperature, salinity, pH, dissolved oxygen, etc.).

5. If growth and survival are satisfactory, transplant more seed to those areas and to selected additional locations.

6. If setting occurs in any area, plant more seed there and put bamboo stakes and ropes in the area when the next setting is anticipated to collect seed.

4.5 Equipment and supplies needed for aquaculture trials

4.5.1 Laboratory equipment

1 - Microscope, binocular, dissecting, Olympus or equal

1 - Microscope, binocular, compound, Olympus or equal

1 - Balance, analytical

1 - Scales, capacity 5 kg. Glassware including graduated cylinders, beakers, flasks, microscope slides, etc.

4.5.2 Field equipment

Water analysis kits, Bausch and Lomb or Hach or equal:

3 - Dissolved oxygen, sample bottles with 10–60 ml.

2 - Phosphate

2 - Nitrogen (Ammonia)

2 - Nitrogen (Nitrate)

2 - Spectrophotometer with spare bulbs, Bausch and Lomb Minispec 20, or equal

2 - Refractometer graduated in salinity, American Optical Co., or equal

2 - pH meter, Yellow Springs Co., or equal

4 sets - pH indicator sticks, colorplast or equal

4 - Magnifying hand lens

4 - Dissecting kits including forceps, scalpel, needles, etc.

2 - Water sampler for dissolved oxygen samples

10 - Field thermometers, 13 cm, with case, graduated 0–100°C

10 - Vernier calipers plastic graduated in mm - for measuring oysters, etc.

Glassware including water sample bottles, 100–200 ml, specimen bottles, 200, 500, 1 000 ml etc.

4.5.3 Supplies


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