SINGAPORE COUNTRY PAPER ON THE CURRENT STATUS AND TRENDS OF SEAFARMING ACTIVITIES, RESEARCH AND DEVELOPMENT
R. Chou
1. INTRODUCTION
1.1 Coastal seafarming in Singapore started in 1970 and the production from this activity has since overtaken yields of traditional freshwater ponds and brackishwater prawn trapping impoundments.
1.2 There are presently 65 floating fish farms covering 33 out of the 100 hectares of available farming area in Singapore. The farms are located in the 4 designated areas off Pulau Ubin, Serangoon and Ponggol (East Johor Strait) and Lim Chu Kang (West Johor Strait) (Appendix 1).
1.3 The total net annual productivity of the East Johor Strait where about two-thirds of the farms are located is 17 000 mt of carbon, giving a possible sustainable yield of 680 mt of fish or 62 000 mt of green mussel (Perne viridis) yearly (Lim, 1980 unpublished, Primary Production Department). The former is accounted for by the palisade trap catches. About 900 mt of green mussels are harvested annually and this comes from the West Johor Strait (620 mt from culture rafts and the rest from the wild). Similar potential yield for mussels may be expected from the west Johore Strait. The production level of green mussels is thus well below (<1%) the total potential yield and could be further exploited.
1.4 Aquaculture production in 1986 was 1 490 mt or 6.8% of the local fish production of 21 769 mt. Of this, 1 290 mt (86.6%) was derived from seafarming and brackishwater aquaculture, and the remaining 200 mt (13.4%) from freshwater aquaculture.
2. CURRENT STATUS AND TREND OF SEAFARMING ACTIVITIES
2.1 Contribution of seafarming to fish production
2.1.1 In 1986, total fish supply in Singapore was 111 019 mt, of which 98.7% (109 529 mt) was chilled and frozen marine foodfish. The remaining 1.3% (1 490 mt) was farmed produce, mainly marine foodfish. Seafarming and brackishwater production (1 290 mt) was about 1.2% of the total fish supply in 1986.
2.1.2 In 1986, seafarming production was 1 290 mt of which 420 mt (32.6%) was finfish, mainly seabass (Lates calcarifer) (203 mt, 15.7%), groupers (Epinephelus tauvina, Plectopomus maculatus, Cromileptis altivelis) (129 mt, 10%), snappers (Lutjanus johni, L. argentimaculatus) (41 mt, 3.2%), other fish species (yellowfin jack, Caranx ignobilis, golden trevally, Gnathonodon speciocus, bream, Acanthopagrus sp., siganids, Siganus canaliculatus, S. guttatus) (48 mt, 3.7%) and 870 mt (67.4%) was shellfish, mainly green mussels (P. viridis) (612 mt, 47.4%), mangrove crab (Scylla serrata) (211 mt, 16.4%), banana prawn (Penaeus merquiensis) (35 mt, 2.7%) and spiny lobster (Panulirus polyphagus) (11 mt, 0.9%).
2.2 Trend of production
2.2.1 Seafarming production increased from negligible in 1970 to 1.03 mt in 1980 and 1.3 mt in 1986 (Appendix 2). This represented 0 (1970) to 5.72% (1980) to 6.35% (1986) of the local production and 0, 1.12, 1.16% of total fish supply respectively.
2.2.2 There is an increasing production trend from seafarming and brackishwater culture. It is envisaged that by 1995, this production will account for about 10% of total fish supply, with 10 000 to 14 000 mt produced annually.
3. CURRENT STATUS AND TREND IN SEAFARMING RESEARCH AND DEVELOPMENT
3.1 Production of market-sized fish (grow-out)
3.1.1 The trend in seafarming research and development is towards mechanisation and automation with the view of reducing time-consuming labour-intensive activities like netcage-hauling and cleaning, manual feeding, farm and float unit maintenance; local production of reliable and sanitary seed stocks; and the use of dry feeds dispensed from automated systems. Well-controlled intensive seafarming systems that take advantage of deeper waters are also favoured because of sea space limitations.
3.1.2 Marine foodfish cultured in floating farms are held in netcage units measuring 3m × 3m × 2–3m (depth) or 5m × 5m × 2–3m (depth). The popular species reared are finfish, such as groupers, seabass, snappers, siganids, and crustaceans such as mangrove crab, banana prawn and spiny lobster. A farm may raise several types of fish and crustaceans. Each farm consists of several netcage units supported by a floating wooden frame structure inter-connected by walkways. The floating raft is anchored within a water space of 5,000 m2.
3.1.3 Marine foodfish are initially stocked at 100–150/m2 in netcages when the fish are 7.5–10 cm Total Length (TL); then at 44/m2 when fish attain 12.5–15 cm TL. At harvest, market-sized fish are 600–800 g (TL 30– 50 cm) and density about 40/m2. Water exchange in the netcages is effected by tidal currents. Netcages are washed as frequently as once monthly to remove fouling organisms like bryozoans, tunicates, mussels, and barnacles, and silt. Netcages of increasing mesh-sizes are used as the fish grows larger.
3.1.4 Marine foodfish are fed trashfish at 3–10% body weight daily depending on their growth stage. Fingerlings of 50 g are fed at 10%, and 100 g, 300 g, and 500 g-fish at 8, 3–5 and 3% respectively. Feed Conversion Ratio (FCR) is around 4–5:1. The Government conducts research and development into dry formulated feeds for groupers, seabass and golden snappers. FCRs obtained with dry formulated feeds are around 1.2 under controlled conditions, and 2 in the field.
3.1.5 Main fish losses occur 2–3 weeks after stocking of imported fingerlings in the netcages of floating farms. Survival can be improved considerably through sanitisation, which is presently a series of 3 treatments done at various stages of shipment of the consignment. Prior to shipment, (preshipment), fish can be treated in an acriflavine bath of 10 ppm for half an hour; during shipment, (transhipment) chemicals such as nitrofurazone can be added to the packing water at 10 ppm; while at the time of stocking, (postshipment), fish can be further treated in formalin at 100 ppm for 1 hour, followed by nitrofurazone at 10 ppm for 4 hours. Sanitisation reduces the parasite and pathogen load associated with imported fish, promotes antiseptic sealing of open wounds and prevents attack by pathogens in the new environment. The Government undertakes sanitisation studies in collaboration with fish farmers and extends useful information to the farming community.
3.1.6 During grow-out, the most common disease problems encountered with cultured marine foodfish is infestation by protozoans, the commonest being the ciliate Cryptocaryon irritans. Treatment is a formalin bath at 200 ppm for half to one hour depending on fish condition and the infestation level. Vibriosis, caused by bacteria, especially the Vibrio species, (V. parahaemolyticus and V. alginolyticus), is a common infection ocurring mainly as a sequel to protozoan infestation or to wounds sustained after importation and handling. Treatment at the early stages of the disease is by feeding of the fish with antibiotics like namely oxytetracycline (0.5 g/kg feed for 7 days), or chloramphenicol (200g/kg feed for 5 days) or sulphonamides (0.5g active ingredient/kg feed for 7 days). Bath treatment may be attempted if fish are off-feed. In this case, nitrofurazone at 15 ppm for 4 hours, or sulphonamides at 50 ppm active ingredient for 4 hours can be used. The Government establishes case studies and records of the various prevalent diseases and undertakes treatment trials (controlled and in the field), challenge and immunology studies, and provides extension and advisory services to farmers.
3.1.7 Harvesting of fish from floating netcages is done by manually lifting the nets. The Government is looking into the possibility of mechanising netcage-hauling.
3.1.8 Presently, all floating farm structures are wooden rafts held afloat by drum float units. The Government will also undertake feasibility trials into the use of materials other than wood (eg., aluminium, high-density polyethylene) for floating farm structures, the production efficiency of various shapes of netcage units (eg: square, rectangular, hexagonal), rotational and deep cages to utilise deeper water layers and open water farming trials with cage designs that are new to the region (eg., submersible cages). Drum float units are quickly fouled and weighted down by encrustating organisms that have to be manually scraped off. Time and labour can be saved by covering the float units with plastic bags on which collect the encrustating organisms. These bags are discarded and replaced, leaving the float units clean for 4–6 month periods.
3.1.9 A constraint to seafarming is the limited availability and high cost of fingerlings of certain popular fish species like groupers, snappers and siganids. Seabass is presently the only marine foodfish which can be commercially bred in captivity, and the Government works closely with the private sector to assist farmers in establishing seabass hatcheries through breeding technology transfer. Government research also covers the breeding of groupers and snappers.
3.1.10 Other constraints are the difficulty of obtaining local farm labour and the limited demand for live fish in local restaurants. On the former, the Government has allowed some farms to engage foreign workers, and has designated certain areas on the main and outlying islands for intensive, high-technology farming, giving investors an option to establish land-based and less labour - intensive aquaculture as well. Land-based farms with higher degree of automation should attract local workers but require less staff. production cost can be lowered through better management and automation, to make farmed fish within the means of ordinary consumers. The possibility of promoting live fish for export is also being explored by some farmers.
3.2 Production of market-sized prawns (grow-out)
3.2.1 Grow-out is commonly done in earthern ponds or floating netcages. A commercial company is also attempting culturing Kuruma prawn (P. japonicus) in raised, rubber-lined ponds of 1,100m2 each. Experiments are conducted by Government researchers in the use of 40m2 raceways for intensive prawn farming.
3.2.2 Stocking density in floating netcages ranges from 300–600/m2 and in ponds, from 20–30/m2. Stocking density in raised, lined ponds is 50–60/m2, and around 600/m2for raceways.
3.2.3 Prawns are fed on formulated dry feed, either imported or produced locally. Ingredients include fishmeal and prawn by-products. In certain cases, as in floating netcages, prawns are also given trashfish. The Government undertakes joint studies with the commercial sector on the development of prawn feeds (tiger and banana prawns, P. monodon, P. merguiensis; kuruma prawn, P. japonicus) using regionally available feedstuffs.
3.2.4 At higher stocking densities, there is an expected higher incidence of disease occurrence, and prophylactic treatments are necessary. The causative organisms are bacteria and virus. These include Vibrio spp. which causes vibriosis in the haemolymph (as in nursery stage), chitinoverous bacteria suspected to cause “burn-spots disease” of the exoskeleton, and Hepatopancreas Parvo Virus (HPV) which causes lesions in the hepatopancreas of the prawn. Treatment for the first is mentioned in paragraph. There is no direct treatment for the second, but oxytetracycline bath at 10ppm for 4 hours may prevent secondary vibriosis of the haemolymph. No treatment is presently available for HPV infection. Other common diseases include muscle necrosis most likely caused by severe stress due to overcrowding and other environmental stress, white pleura disease of unknown origin, and the other diseases described for the nursery stage, namely Leucothrix and Zoothamnium infestations. Research includes vertical transmission studies, treatment trials and the establishment of appropriate protocols for disease control in intensively cultured prawns.
3.2.5 There is no serious constraint to the production of prawns in Singapore. In fact, the culture of prawns has considerable potential in the Republic as they can be farmed intensively. There is tremendous local demand for prawns.
3.3 Mollusc production
Mollusc culture in Singapore is restricted to farming of green mussels (Perna viridis).
3.3.1 Mussels are farmed on ropes suspended from wooden rafts. Specifications vary, but all are usually rectangular in shape, with the long axis parallel to the direction of the tidal current. Ropes are usually each 2–3m long in the water, with another 1.5m for tying on the raft.
3.3.2 Ropes are suspended at 4 ropes/m2, and are kept about 2m off-bottom. Water exchange is by tidal flow.
3.3.3 Mussels are filter-feeders, feeding on plankton from the sea. At Lim Chu Kang, where commercial mussel farming is practised, planktonic food is abundant from the waters that are relatively eutrophic throughout the year.
3.3.4 Seed is obtained from natural spatfalls. There is no attempt at broodstock management except through retention of a percentage of the grow-out population as broodstock.
3.3.5 Spats are usually collected on 2m-long strips of old netting or nylon ropes. A settlement of 10 million spats, (0.5 g) for each strip of rope/netting may be expected during a good spatfall.
3.3.6 No thinning is practised commercially as this has been found to be too time-consuming and labour-intensive by the farmers. The spats are instead allowed to thin out naturally. This however results in wasteful loss of the spats which drop off. An estimated 10–15% of spats attain market-size 6–8 months later. This technique is applicable to good spatfall areas. Nylon ropes and nettings are however unsuitable as spat collectors in poor spatfall areas. Coconut coirs have been found to be better as spat collectors. Government research effort has come up with the poly-coco for such situations. This type of rope combines both spat collection with grow-out. The coconut coir sections attract the spat while grow-out is on the polethylene main rope.
3.3.7 No serious disease or parasites have been observed to-date. However, water stagnation in a farming area can lead to low dissolved oxygen, and persistent rainfall, to lowered salinity. This may at times cause localised high mortalities.
3.3.8 Harvesting of mussel ropes is by manual lifting. This process can be mechanised. Government research effort has been towards on-site depuration of mussels.
3.3.9 The main constraint to production is not in the farming but in the low consumer demand for the product. Efforts are being made to promote mussels either as a food product or as high quality feedstuff for prawn feeds.
4. SUPPORTIVE RESEARCH AND DEVELOPMENT
4.1 Broodstock production
4.1.1 Finfish
4.1.1.1 There are presently 5 commercial marine/brackishwater hatcheries, with 2 specialising in the production of seabass fry/fingerlings, 2 on marine prawn fry production, and one on both. The finfish hatcheries use a combination of floating and shore-based techniques while the marine prawn fry hatcheries are planning on taking on seabass fry production. One floating fish farm operator is working in collaboration with the Government to raise seabass fry entirely on the farm premises. The Government hatchery facilities are used for development of breeding and rearing techniques for commonly farmed fish.
4.1.1.2 Brooders of marine finfish like seabass are maintained in netcages. Netcage dimensions vary, but are 4m × 4m × 3m (deep) at the Government Experimental Fish Farm. Broodstock netcages at commercial farms vary from 6m × 3m × 4m (deep) to 6m × 4m × 2m (deep).
4.1.1.3 Brooders are kept at either a 1:1 ratio or 2:1 males to female ratio at a stocking density of around 4–6 kg/m2 netcage area. Induced maturation is not practised. Water exchange is by tidal currents. Natural maturation takes place according to the lunar cycle.
4.1.1.4 Brooders are fed on trashfish (comprising small fish of low economical value) at 1–3% body weight daily during spawning season. Feed is given up to 3 times daily.
4.1.1.5 Brooders are raised from fingerling. They are handled carefully with deep scoop-nets and usually not disturbed unless for checking gonad development or netcage changing. If they are required for placement in shore-based tanks, eg., in induced breeding runs or prophylactic bath treatments, the fish are transported in live tanks on the boat.
4.1.1.6 Gonad development and sexing is monitored by cannulation, or for commercial operators, by visual assessment. Sexing is relatively simple in seabass because of size dimorphism and the degree of abdominal bulging in females, being indicative of their state of maturity. Gonad development monitoring through biopsy has also been attempted by Government researchers.
4.1.1.7 Seabass brooders show very low mortality rates. However, grouper brooders may suffer high mortalities from swollen air-bladder syndrome. The swelling of the air-bladder causes fish to swim upside down on the water surface. This leads to off-feeding and bacterial infection of the exposed ventral portion of the fish. Deflation of the air bladder by a needle puncture helps to right the fish. However the air bladder may re-inflate and cause the fish to revert to its upside-down position a few days later. There is no known treatment for the swim bladder syndrome but antibiotics like oxytetracycline and chloramphenicol (10 ppm) can be used in treatment baths to relieve secondary bacterial infection.
4.1.1.8 The main constraint to the commercial sector is that farmers are involved in both hatchery and farming operations. Brooders occupy valuable space in the farm, and considerable effort has to be made by the farmer to cover both hatchery and farming aspects simultaneously. Over time, operators may be expected to specialise in the separated activities.
4.1.2 Prawn
4.1.2.1 Commercial hatcheries obtain their spawners from the wild and do not hold any broodstocks for maturation. A maturation programme on Banana prawns has been initiated by the Government.
4.2 Seed/fry production
4.2.1 Finfish
4.2.1.1 Larvae of seabass are reared in fibreglass tanks on either the floating farms or in land-based facilities. Tanks are either circular or rectangular, and vary from 5m3 each (Government experimental hatchery) to 10m3 each in the commercial hatchery.
4.2.1.2 The rearing method for seabass fry basically follows that developed by Thailand. Stocking density varies from 30– 55/1. Water exchange starts at 20% daily for D3–5 and is 50% after the larvae reach D11.
4.2.1.3 Larvae are fed rotifers (Brachionus plicatilis), brine shrimp (Artemia salina), and moina (Moina micrura).
4.2.1.4 Disease is mainly from bacterial infection. Prophylactic treatment with oxytetracycline at 2–10 ppm once every 2–3 days from D15–25 will curtail the problem.
4.2.1.5 A constraint to large-scale fry production is the large tank facilities required for producing the rotifers and supporting green algae (Chlorella) for feeding the seabass larvae. Government research and development looks to the use of microparticulate feeds (commercially available or developed).
4.2.2 Prawn
4.2.2.1 Larvae are reared in tanks or canvas bags. In land-based hatcheries, larvae are usually maintained in circular or rectangular fibreglass tanks of 10–15m3 capacity. In floating hatcheries, canvas bags of 2m × 2m × 1m (deep) are used.
4.2.2.2 The stocking density in commercial hatcheries is 100/litre. Water change is limited to 30–50% daily.
4.2.2.3 Skeletonema (diatom) and Artemia are the 2 organisms fed to prawn larvae, the former from D2–11, and the latter from D4–14.
4.2.2.4 Bacterial infections cause reddening of the larvae, while protozoans (Zoothamnium sp.) and fungus (Lagenidium sp.) are some of the other common diseases encountered during larval culture. Preventive measures include good water and tank management, a proper feeding regime, and periodic prophylaxis with antibiotics like oxytetracycline, and copper-based chemicals like Cutrine-PlusR. Jelly fish infestation can also cause total larval mortality. Treatment with 20 ppm formalin for half hour is only partially effective. Larval cultures which are too heavily infested have to be discarded.
4.2.2.5 The main constraint to fry production is the present reliance on wild spawners. This often results in broodstock supply being restricted to spring tides. A technique of maturing the spawners under captivity is being looked into by Government researchers.
4.3 Nursery operation
4.3.1 Finfish
4.3.1.1 Frys can be raised either in tanks or in floating net-boxes. Fibreglass tanks (8m3 capacity) are used in the Government experimental hatchery while floating net-boxes are used at the commercial farm sites. These measure 1.8m × 1.2m × 0.9m (deep). In tank cultures, water exchange is 30% daily, while this is by tidal flow for floating-boxes.
4.3.1.2 Initial stocking density is 5,000/m3, with gradual thinning at different size stages of the fingerling to a final density of 2,000/m3 when fingerlings are 1.5–2.5 cm TL. The density at commercial farms is said to be higher, varying from 9,000– 14,000/m3 initially.
4.3.1.3 Minced trashfish and Acetes (euphausid shrimp) are fed to the fingerlings until satiation, 4–6 times daily. The fingerlings at this stage can also be weaned over to dry feed, being developed by Government researchers.
4.3.1.4 Fry may be affected by isopods especially if they are held out at sea. A formalin bath of 200 ppm for 1 hour is effective in removing the isopods but may be traumatic to the fish. Another form of treatment is the periodic transfer of stocks into freshwater.
4.3.1.5 The main constraints encountered in nursery operation are stress to fish caused by frequent grading which is required to minimise cannibalism, and time and manpower required to feed the fish to satiation. Government research is on-going on the use of automatic feeding systems for dry feed.
4.3.2 Prawn
4.3.2.1 Frys are raised in tanks, floating netcages or ponds. Tanks are usually of fibreglass and 10m3 capacity. Floating netcages are constructed from plankton netting material (0.5 mm mesh). Nursery ponds are earthern and about 0.5 ha each.
4.3.2.2 Stocking density varies from about 900/m2 in ponds to 6,000–8,000/m2 in floating netcages. In ponds, daily water exchange is estimated at about 5–10% according to tidal flow. In tanks, exchange is 80% daily, while in floating netcages, water exchange is continuous, by tidal currents.
4.3.2.3 Diseases commonly encountered during this nursery rearing are infestations by Leucothrix sp. (bacterial) and ciliates like Zoothamnium sp. on the gills, and vibriosis caused by Vibrio spp. in the haemolymph. Treatment for Leucothrix would be through prophylaxis with a copper compound (Cutrine-PlusR) at 2.8ppm for 3 hours; while Zoothamnium is eradicated by the use of formalin baths at 75ppm for 4 hours. Vibriosis may be treated by oxytetracycline baths at 10ppm for at least 4 hours or through oral feeding at 0.75g/kg feed for 8 days.
4.4 Nutrition and feed development
4.4.1 Finfish
4.4.1.1 At present all stages of fish under culture rely on trash fish and live food. The trend is towards lesser reliance on such feeds which requires labourto prepare/culture and dispense.
4.4.1.2 Commercial microparticulated feeds are presently not readily available and even if they are, are not tailored to meet the nutritional requirements of the species being farmed locally. Microencapsulated feeds for fish fry are not available and are likely to be expensive. Local effort is therefore necessary to provide the industry's needs. The Government's research and development will focus on such novel feeds and the appropriate automated feeding protocol.
4.4.1.3 Dry feeds for commercially farmed fish are presently not available for both nursery and grow-out stages. However, basic nutritional requirement and feed development studies are undertaken by the Government with a view to eventually establish several commercially-viable formulations for transfer to the commercial sector. At the same time, field and controlled studies are on-going to establish an automated feeding protocol.
4.4.1.4 Reliance on trashfish is to be discouraged in future to reduce possible disease outbreaks resulting from poor handling of wet feeds, decrease dependance on manual labour for feeding and, in the case of the hatcheries, to eliminate uncertainty in the culture of live food organisms affected by prevailing weather and other environmental conditions.
4.4.2 Prawn
4.4.2.1 Grow-out feeds for the commercial production of prawn in Singapore are mainly imported, although locally-produced commercial feeds are also available. However, these feeds have been designed for tiger prawn (P. monodon) and are being used in banana prawn (P. merquiensis) culture, no tiger prawns being farmed in Singapore. It has therefore been assumed that the dietary requirements of the former are similar to those of banana prawn. This may not be entirely true and could result in some feed wastage.
4.4.2.2 The Government is looking into the development of suitable grow-out feeds for tiger and banana prawns as well as the kuruma prawn (P. japonicus). Information gained will be passed on to the commercial sector.
4.4.2.3 In the hatchery and nursery situations, live food is preferred for the former, while commercial starter feeds from the same sources are used for the latter. In the hatcheries, the use of live foods increases the need for labour and also involves a higher degree of management in live food production control. The use of artificial feeds is being explored by the Government to ease the problems encountered in the hatcheries. At present, a compromise is being sought so that both live foods and dry artificial microparticulated feeds may be used together to take advantage of the efficiencies of both feed types. Like the grow-out feeds, dry nursery feeds will also be developed by the Government in collaboration with the commercial sector to provide nutritionally adequate feeds to various prawn species.
4.5 Disease control
4.5.1 Finfish
4.5.1.1 The previous paragraphs have revealed the prevalent diseases of intensively cultured finfish. It is obvious that good management can significantly assist in the prevention of disease outbreaks.
4.5.1.2 It is also important that the farmers be able to recognise early signs of fish stress that can lead to disease outbreaks. These are off-feeding, peculiar swimming behaviour in their animals, plankton blooms and other changes in the environment. This would enable them to alert relevant authorities and to take precautionary measures themselves.
4.5.1.3 The Government is encouraging farmers to undertake field prophylaxis/sanitisation of their fish from time to time, especially during periods of expected stress increase to the fish. This is presently done under Government supervision as and when required by farmers.
4.5.2 Prawns
4.5.2.1 A similar situation exists for intensively cultured prawns. Usually, the low incidence of affected prawns is tolerated. However, prophylactic feeding may become necessary if the risk becomes too great. This refers to bacterial diseases like vibriosis of the haemolymph or ectoparasites in the gills. In such cases, the Government provides diagnostic and advisory services to the farming community as and when required.
4.5.2.2 Diseases like HPV and microsporidiosis do not have specific curative measures at present but stocks are still monitored by Government to advise on the level of occurrence of the diseases.
4.5.2.3 Generally, as in the case of intensively cultured food fishes, good management will minimise disease problems.
4.5.2.4 Research and development trend is towards early recognition of disease and the establishment of appropriate control/prevention protocols for farmers. Basic research is also on-going to understand better the aetiology of diseases of finfish and prawn.
5. SUMMARY
5.1 Seafarming in Singapore is presently the intensive culture economically important marine food fish and shellfish species in wooden floating raft systems. The operation is still largely manual and trashfish is the principal feed used.
5.2 The general trend in seafarming research and development is towards the application of higher technology methods in farm management to
5.2.1 maximise productivity and yield
5.2.2 save on labour
5.2.3 ensure consistently high product quality
5.2.4 reduce dependance on trashfish whose supply and quality is uncertain and usage becomes limiting in larger-scale farming situations.
5.3 Higher technology methods involve therefore the use of dry formulated feeds during the life stages of the animal, and of labour-saving devices through mechanisation and automation.
5.4 Other approaches are
to investigate the feasibility of alternative seafarming systems such as floating rafts made from more durable materials (eg., aluminium, high density polyethylene) that would require minimal maintenance, rotatable netcages where in-situ maintenance is possible, deep netcages which could allow for larger water mass to be utilised for farming without compromising on farm area, and submersible cages which would make it possible to farm in deeper and open waters.
6. Reference
Country Paper presented at the Seminar on Aquaculture Development in Southeast Asia: Development and Status of Aquaculture in Singapore (8–13 Sep 87, Philippines).
APPENDIX 2.
SUMMARY OF FISH PRODUCTION STATISTICS FOR SINGAPORE
FOR THE PERIOD 1982–1986
| Year | Total fish supply*1 (mt) | Total local production*2 (mt) | Total brackishwater production*3 (mt) | Total seafarming production*4 (mt) |
|---|---|---|---|---|
| 1982 | 91 607 | 18 000 | No data | 1027.0 |
| 1983 | 102 573 | 19 549 | 20.9 | 1584 |
| 1984 | 117 637 | 25 467 | 43.5 | 1140.4 |
| 1985 | 112 290 | 23 031 | 13.1 | 1210.0 |
| 1986 | 111 019 | 20 297 | 71.3 | 1289.7 |
*3 Production from brackishwater ponds (banana prawn, Penaeus merquiensis)
*4 Production from floating fish farms
APPENDIX 3
SEAFARMING PRODUCTION STATISTICS FOR SINGAPORE FOR THE PERIOD 1982–1986
| Year | Finfish | Shellfish | Total seafarming production (mt) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Seabass | Groupers | Snappers | Others | Total | Mussels | Crab | Prawn | Lobster | Total | ||
| 1982 | 89.5 | 161.6 | 11.0 | 5.3 | 267.4 | 736.0 | 10.8 | 11.8 | 1.0 | 759.6 | 1027.0 |
| 1983 | 214.0 | 156.0 | 16.0 | 45.0 | 431.0 | 979.0 | 164.0 | 4.0 | 6.0 | 1153.0 | 1584 |
| 1984 | 184.3 | 113.5 | 16.7 | 17.9 | 332.4 | 525.5 | 255.1 | 14.5 | 12.8 | 807.9 | 1140.3 |
| 1985 | 168.6 | 93.9 | 30.3 | 47.6 | 340.4 | 618.4 | 213.3 | 21.8 | 16.1 | 869.6 | 1210.0 |
| 1986 | 202.6 | 129.2 | 41.0 | 46.9 | 419.7 | 613.4 | 211.0 | 34.6 | 11.1 | 870.1 | 1289.8 |
Seabass (Lates calcarifer)
Groupers spotted, red, polka-dot (Epinephelus tauvina, Plectopomus maculatus, Cromileptis altivelis)
Snappers, golden, red (Lutjanus johni, L. argentimaculatus)
Other fish species, yellowfin jack, golden trevally, bream, rabbitfish (Caranx ignobilis, Gnathonodon
speciosus, Acanthopagrus sp., Siganus canaliculatus, S. guttatus)
Green mussel (Perna viridis)
Banana prawn (Penaeus merguiensis)
Mangrove crab (Scylla serrata)
Spiny lobster (Panulirus polyphagus)
