Private sector representative
I. Introduction
Intensive culture of finfish in floating netcages is widely practised in
Singapore mainly due to space limitations. The coastal waters around
Singapore suitable for this culture practice are in the East Johor Strait
around Pulau Ubin, Serangoon and in the West Johor Strait around Lim Chu
Kang.
At present, 70 commercial floating farms occupy 35 ha of the total 300 ha
available area.
The production output from these farms in 1987 was 1825 MT, which accounted
for 1.5 % of the overall 126,000 MT produced in Singapore in 1987. The
per capita fish consumption is over 30 kg/annum.
It is envisaged that production from coastal aquaculture will reach about
9,000 MT by 1995, 20 % of which will be from finfish production, the other
80 % from shrimp, crab and mussel culture.
II. Species
The main finfish species cultured in netcages are grouper, seabass, and
golden snapper. These fish were initially selected because they command a
high market in value and demand and can be cultured under intensive
conditions.
Seabass fingerlings are readily available from local and Thai hatcheries.
This species takes about 8 to 10 months to reach the marketable weight of
600 g or more from initial weight of 20–30 g.
The grouper popularly farmed is the Estuarine Grouper, Epinephelus tauvina.
Grouper fingerlings are limited in supply in Singapore and thus there is a
heavy dependance on their supply from neighboring countries like Thailand,
Philippines, Malaysia, India and Sri Lanka. This fish takes about 6–8
months to reach the 600 g marketable weight from an initial weight of 50–
100 g.
The golden snapper, Lutjanus johni and red snapper, Lutjanus malabaricus
are also stocked in netcages. The fry are caught locally from the wild,
and they are easy to rear as they are relatively less susceptible to
disease. The golden snapper takes about 6 to 8 months to reach market
weight of 600 g from an initial weight of 50–100 g, while the red snapper
takes over a year to reach similar size.
Other finfishes of economic value that have been introduced are the red
tilapia hybrid (Oreochromis niloticus), the rabbitfish (Siganus
canaliculatus), the red grouper (Plectopomus maculatus) and the tiger
grouper (E. microdon).
III. Farming and Management
The Farm Structure
The Government has designated coastal areas off Pulau Ubin, Loyang,
Serangoon, Ponggol in the East Johor Strait and Lim Chu Kang off the West
Johor Strait for netcage finfish culture.
A fish farm licence is issued to the farm owner at S$ 500 per annum for a
5,000 m area.
The farm consists of a simple wooden structure floated by plastic drums.
The dimensions of the frame units vary from farm to farm, popular sizes
being 2m × 2m and 3m × 3m.
Netcages
The netcages are usually of polyethylene, that is either of knotless or
knotted netting material. The nets are changed once every 2 to 4 weeks to
ensure good water circulation for the fish in the cage. Well maintained
nets tend to last longer.
They are cleaned and maintained on-farm. High pressure seawater jets,
produced by portable generators, are used to clean the nets.
Stocking and Feeding
The fish stocks obtained range in size from 2.5–5 cm, 7.5–10 cm and 12.5–15
cm.
The fish are sized and culled from time to time, especially during the
juvenile stage to reduce cannibalism.
The fish stocks are either fed on trash fish or on practical feed
consisting of a formulated dry mix and trash fish or just a formulated mix.
The use of the latter feed is more progressive and is practised by some farmers. Improper handling of trash fish could also expose the fish stocks to disease. Moreover, its supply is unreliable during the monsoon months.
Diseases
Diseases usually occur when fish are stressed by environmental changes or poor handling. Disease outbreak among fish stocks is prevented by good management practice, that is, maintaining clean netcages, watching for off-feeding and making timely decision for treatment which is either through medicated feeds or baths. Netcages are raised occasionally to check on fish condition.
Harvesting and Marketing
The fish for the market are stored for 1 to 2 days prior to harvesting. Transportation of fish is done in tanks filled with cool, aerated water, and ferried to land by boats as quickly as possible. They are then transported live to their destinations, usually restaurants, under similar conditions.
IV. Conclusion
The Government has identified aquaculture as a potential growth industry in Singapore. It is expected that in the future, netcage floating farms will operate with a higher degree of mechanization such as in netcage changing and fish feeding. Other floating systems can also be considered and also open-water farming on a larger scale.
