FAO/GCP/MAL/009/CAN
November 1985
| CANADA FUNDS-IN-TRUST FAO/GCP/MAL/009/CAN November 1985 |
A report prepared for the
Besut Integrated Fisheries Development Project
based on the work of
Prasit Aguru
Aquaculturist
This report was prepared during the course of the project identified on the title page. The conclusions and recommendations given in the report are those considered appropriate at the time of its preparation. They may be modified in the light of further knowledge gained at subsequent stages of the project.
The designations employed and the presentation of the material in this document do not imply the expression of any opinion whatsoever on the part of the United Nations or the Food and Agriculture Organization of the United Nations concerning the legal or constitutional status of any country, territory or sea area, or concerning the delimitation of frontiers.
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome, 1985
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2.1.1 Demonstration of Freshwater Prawn Fry Propagation
2.1.2 Demonstration on Live Food Culture
2.1.3 Demonstration on Tiger Prawn (Penaeus monodon) Fry Propagation
2.1.4 Demonstration on Nursing of Seabass (Lates calcarifer) Fry
2.2 Development of Aquaculture
2.2.1 Seabass Fry Nursing in Nylon Net Cages
2.2.2 Fish Culture in Ponds at Kampung Fikri
2.2.3 Fish Culture in Floating Net Cages
2.2.4 Tiger Prawn Culture in Plastic Net Cages
3. DISCUSSION AND RECOMMENDATIONS
3.2 The Fisheries Development Area
3.2.1 Seabass Culture in Ponds at Fikri
3.2.2 Fish Culture in Floating Net Cages
4. POTENTIAL FOR AQUACULTURE DEVELOPMENT
4.2 Fish Culture in Floating Net Cages
LIST OF TABLES
1. SIZES OF TIGER PRAWN FINGERLINGS WHEN STOCKED AND CONTROLLED AND MORTALITY DURING 18 DAYS REARING
The Malaysian Government has received technical assistance through the Besut Integrated Fisheries Development Project. The project had several components. The Tanjung Demong Hatchery and the development of aquaculture in the Besut Fisheries Development Area (FDA) were part of the project. The Tanjung Demong Hatchery conducted demonstration of freshwater prawn, Macrobrachium rosenbergii, fry propagation, the technique of tiger prawn, Penaeus monodon breeding, and the demonstration on nursing seabass, Lates calcarifer from one day old fry to 1.5–2 cm fingerlings. The development of aquaculture included the demonstration on the technique of seabass culture in ponds at Fikri, from 8 to 10 cm fingerlingers to marketable fish of 600–700 g, which takes about six months. Demonstration on techniques of seabass and greasy grouper Epinephelus tauvina culture in floating net cages at Setiu Lagoon and Kuala Bharu were also conducted. The fingerlings from 8 to 10 cm took about 7–8 months to raise to marketable size.
This year stocking of fingerlings started in February at Setiu Lagoon, in March at Kuala Bharu and in April at the Fikri ponds. This fish both in cages and ponds should reach marketable size in September. On 15 June the seabass ranged from 40 to 160 g and greasy grouper from 60 to 105 g.
Trials on tiger prawn fry culture in plastic net cages were also conducted. Average stocking size was 0.463 g in weight and 3.53 cm in length. Within 18 days the average weight was 1.356 g with an average length of 4.76 cm; the average weight gain was 0.893 g. It means that the weight gain was more than double from the date of stocking. Mortality was only 1.2%.
The Malaysian Government, with technical assistance from the Food and and Agriculture Organization of the United Nations and financial aid from the Canadian International Development Agency (CIDA), has been engaged in the Besut Integrated Fisheries Development project (GCP/MAL/009/CAN) whose main objective has been to assist in the improvement of the socio-economic status of those engaged in small-scale fisheries.
Project activities include the production of fry of both marine and freshwater prawns and fish at the Tanjung Demong Hatchery, and the development of aquaculture in Besut. The main species produced in the Hatchery were giant freshwater prawn (Udang Galah) Macrobrachium rosenbergii, tiger prawn Penaeus monodon and seabass, Lates calcarifer. The aquaculture programme included fishculture in ponds and in nylon net floating cages, the main species being seabass and greasy grouper, Epinephelus tauvina.
As part of the project operations, FAO assigned Mr P. Aguru as hatchery management expert from 1 January to 30 November 1984;
to train and demonstrate the techniques of breeding fish/prawn to local counterparts as well as to manage and operate the hatchery at the initial stage until it is operating smoothly;
and as aquaculture field adviser from 1 December 1984 to 30 June 1985;
to demonstrate to national staff and fish farmers, the nursing techniques of seabass grouper fry to 10 cm fingerlings both in ponds and cages;
to conduct trials on various feed formulations and their applications, in order for trash fish feeding to have a positive alternative;
to assist national staff and fish farmers in the implementation of other approved aquaculture field activities consistent with the project;
to keep a “watching brief” on the Tanjong Demong Hatchery during the intervening period without a hatchery adviser.
Early project work was carried out at Tanjung Demong Hatchery, which was under the responsibility of the Department of Fisheries. The hatchery started functioning in January 1984. Facilities were installed such as, nursing tanks, pipes for freshwater and sea water, aeration, cement tanks, etc. Before commencing hatchery operations, the staffing structure was planned and individual duties specified. As the equipment was unfamiliar to the staff, instructions were given regarding its use.
About 60 giant freshwater prawn breeders were collected from the Sabak Hatchery in January 1984. Male and female breeders were stocked together in breeding tanks containing rainwater from 100-t outdoor circular tanks. They were fed with squid flesh three times daily. About 50% of the water volume was changed every day. During the process of water exchange, the uneaten feed left in the bottom of the tanks was siphoned out with a plastic hose in order to prevent water contamination from fermented feed, causing oxygen deficiency in the tanks. Eggs were checked periodically on the underside of the female abdomen. Berried females with yellow eggs were transferred from breeding tanks to hatching tanks with a salinity of 5 ppt. The yellow eggs then became grey in colour. The grey eggs hatch within 3 to 4 days, after which it is advisable to separate the grey egg females together in one tank.
After the eggs hatched, the spent females were moved from the tank to the breeding tanks again. The salinity of water in the larval tank was adjusted from 5 ppt to 12 ppt.
With respect to the larval nursing, the prawn larva was stocked in appropriate numbers in nursing tanks containing water salinity of 12 ppt. The stocking density is about 15–20 pieces per litre. The larva was fed with brine shrimp nauplii on the third day evening after hatching. The amount of brine shrimp is about 2–5 pc/ml depending on the size of the larva. The early stage brine shrimp was fed twice a day, morning and afternoon. The prepared food was given when the larvae were 7–10 days old, depending on the size. The prepared food is composed of egg, fish flesh, cockle and shrimp shell. The composition is mixed with an electric blender, then steamed in a rice cooker. The mixture was sifted with a sieve to reduce the pieces to about 0.3 mm in size. In addition to giving prepared feed, artemia was fed once a day, at 16.00 h. The prepared feed should be given 5 times a day at about 2-hourly intervals. However, no feed should be given at night, this would cause overfeeding which in turn causes water pollution. The prepared feed should be observed in the morning, and if large quantities of prepared feed are left, this indicates overfeeding and the amount of prepared feed should be reduced.
The volume of water in the nursing tanks was changed every day until completion of nursing. The procedure of water exchange is by siphoning with a plastic hose. Aeration is stopped to allow the settlement of small particles in the water and then the food and other particles in the bottom of the tanks are siphoned off. This siphoning of the water (about 50–80%) was done quickly so that the aeration restarts as soon as possible to avoid oxygen deficiency causing mortality of larvae.
Larvae usually develop into post-larvae about 23–30 days after hatching, at which point feeding with artemia stops completely, and prepared feed only is given when about 90% larvae become post-larvae. The water in the tank is changed from brackishwater to freshwater but the reduction of salinity should be gradual, about 2–3 ppt a day. During January-February 1984, during production of freshwater prawn fry at Tanjung Demong Hatchery, about 100 000 fry was produced.
Presently, there are many brackishwater hatcheries in Malaysia. The main species to produce fry for culture are marine prawns, seabass and freshwater prawn, which are all of economic importance to the country. For mass production of fry, the main problem had previously been suitable food to feed the fry in the initial stages. Many kinds of dead feed had been tried, but the results were not satisfactory because this facilitated water pollution. Finally, live feed was given, as rotifers, diatoms, etc., were readily available in the brackishwater.
Tanjung Demong Hatchery started functioning in January 1984, and facilities are very limited. In 1984, when production of fry began, only thirteen 600-litre circular cement tanks were used for culturing live food organisms. In order to expand production, starters were brought from the National Institute of Coastal Aquaculture (NICA), Songkhla, Thailand (the nearest and most convenient place). These included rotifers, Chlorella and Chaetoceras. About one litre is taken of each organism. They were packed in plastic bags, inflated with oxygen, and transported to Tanjung Demong Hatchery by car. The procedure usually began in the laboratory with a temperature control at about 25°C and exposed to fluorescent light for 24 h/day.
The water used for culturing the live food organisms was boiled seawater, salinity 25 ppt. The water was added to the fertilizer composed of KNO3 50 g/t, Na2HPO4 20g/t, Na2SiO3 10 g/t, NaHCO3 16.8 g/t and FeCl3 5 g/t.
Diatom Culture: Diatoms were generally used for feeding marine prawns. Chaetoceras and Skeletonema are usually used for feeding prawn at the Zoea stage, but at Tanjung Demong, only Chaetoceras has been used. Culture began under laboratory conditions. The starter from the plastic bag was divided into 1–1 flasks, and the culture water added with aeration supplied 24 h/day. Chaetoceras in flasks will bloom within 3 days, and is reproduced in bigger flasks and aquaria in the same way. For mass production in outdoor cement tanks, tanks are exposed to sunlight, and the fertilizer used is similar to the Chlorella culture, but adding the Chaetoceras culture at 10 g/t Na2SiO3.
Thirtyone tiger prawn breeders were obtained from fishermen collected from the sea near Besut, and 40 other breeders were collected from the Kampong Merchang ponds. They were stocked in 2.2 m rectangular tanks containing seawater, salinity 30 ppt. The stocking rate of tiger prawn in each tank was 12–16 pieces. The ratio of male to female was about 1:1. Eyestalk ablation was carried out on every female. The tanks were shielded from light with black plastic sheeting in order to prevent the prawns from becoming overexcited and to encourage them to eat better. The water was continually running through 24 hours from the inlet pipe into the breeding tanks and the overflow from the draining pipe to furrow. The same quantity of water flowed through the inlet pipet and draining pipe into each tank. Every day, the leftover feed was siphoned out of the tanks. Breeders were fed with squid 4 times daily. The tank water was continually aerated.
Breeders were periodically checked for egg formation. Breeders with eggs at stage IV were separated and put into 1 m conical tanks to allow spawning, normally once every 2–3 days. Breeders which were collected from fishermen from the sea were undoubtedly healthy and formed eggs easily. Generally prawns spawn at night, and the next morning eggs were checked to determine the percentage of fertilization, and then washed in clean seawater to eliminate the mucus from the tanks. In the meantime, the water in the spawning tank was also changed by siphoning. The eggs hatch in the afternoon. It took about 12–18 hours after fertilization depending on the temperature of water. The newly hatched fry or nauplii was separately stocked in appropriate numbers in tanks for nursing. Normally the stocking number of nauplii is about 20–30 pieces per litre. Before stocking, the tanks were well prepared by cleaning and filling with 30 ppt seawater. About two days after hatching, the nauplii metamorphose to Zoea I. From this day, the larva started feeding (the time for metamorphosis of each stage of prawn larva was recorded as follows: nauplii = about 2 days, Zoea I = 2 days, Zoea II = 2 days, Zoea III = 2 days, Mysis I = 2 days, Mysis II = 2 days, Mysis II = 2 days, then they become post-larvae). The programme of feeding was as follows:
| Feed Given | Age (Approx. Days) | Stage |
| Mixed Diatom | 2–15 | N2-M3 |
| Baker's Yeast | 3–9 | Z1-Z3 |
| Egg Yolk | 5–15 | Z2-M3 |
| Artemia | 10–23 | M1-P18 |
| Prepared Food | 21–30 | P16-P115 |
N = Nauplii, Z = Zoea, M = Mysis, P1 = Post-larva
The water in the nursing tanks was changed every day, the quantity depending upon the variety of feed given. About 20=40% of the tank water was changed before the fry was given artemia and about 50–80% after having the prepared feed.
For the production of prawn fry, most of the females spawned were collected from the sea, and the yield of nauplii was about 2.6 million, estimated by random sampling. The actual number of P1-7 was 506 233 pieces. The survival rate should be higher, but the facilities available at Tanjung Demong Hatchery were insufficient with the result that fry was stocked in nursing tanks at too high densities. Later, they were sent for nursing at Sabak Hatchery, another Department of Fisheries Hatchery, where there were mor nursing tanks available.
As already mentioned, the Tanjung Demong Hatchery is new. Last year, it was not ready to breed seabass; the main problem was the limited seawater intake system which restricted the collection of large quantities. Now the problem has been solved because installation of the system has been completed. However, demonstration of nursing seabass fry was carried out on two lots of seabass fry received from the Fisheries Research Institute (FRI) in Penang. The number of fry obtained totalled about 340 000 pieces, of about 3–6 days old. The newly hatched larvae was transported by airplane from Penang to Tanjung Demong Hatchery in plastic bags inflated with oxygen. The fry arrived without mortality during transportation. Before releasing the fry into nursing tanks, plastic bags containing fry were put in the water for about 20 min in order to adjust the water temperature in the plastic bags. The fry was stocked in 1 m conical tanks, 2.2 m rectangular tanks and 5 m circular tanks. Tanks for nursing fry were prepared well by cleaning and filling with 28 ppt clean seawater. Stocking density was about 20 pieces per litre. Upon arrival at the hatchery, feeding with rotifer commenced immediately to those fry sufficiently developed. Normally feeding started on the third day after hatching. The density of rotifer given was about 10–20 pieces/cm3. Partial artemia feeding began when fry was 8 days old. The rotifer ratio was reduced and partial artemia was added. Rotifer feeding completely stopped when the fry was 15 days old; and artemia alone was given up to 23 days old. Then the fry was trained to eat some chopped fish flesh in this period, and the artemia was also reduced and chopped fish flesh added. It took about 4–5 days for the fry in this age to become used to eating the chopped fish flesh. Then chopped fish flesh only was given to the fry.
About 20–30% of the water in the tanks was changed every day during rotifer feeding; 30–50% during artemia feeding; and about 50–80% during chopped-fish-flesh feeding. Water salinity had been reduced from 28 to 25 ppt when fry was 15 days old and further reduced by 3 ppt per day until it reached 18 ppt, at which point it was stabilized. This was done in order to eliminate fry growth.
Grading of the fry is necessary because seabass is cannibalistic. Grading started when the fry was 14 days old, and carried out at least once a week. Without grading the larger fry would have devoured the smaller fry. The equipment required is different sized plastic basins punched through the bottom, with different sized holes depending on the size of fry to grade, from 2.0 to 7.0 mm.
After 30 days, fry was about 1 cm long. At this period the survival rate was about 120 000 fry. Due to the limitation of the tanks at the hatchery, it was impossible to stock fry in the proper density. Consequently fry was sent to Sabak Hatchery for nursing purposes.
Aquaculture within the project area has remained underdeveloped and static for several years, the main constraints to development having been the lack of technical skills and a shortage of fish fry. To aid aquaculture development, to overcome the constraints, and to encourage fish culture, the author was requested to assist the Fisheries Development Authority (LKIM) in aquaculture development in Besut. Activities have been as follows:
There are two types of fishculture in the project area: in ponds at Kampong Fikri, and in cages at Setiu Lagoon and Kuala Bharu. All the work was carried on by local fishermen, with materials and seed subsidized by LKIM. Species preferred are seabass (Lates calcarifer) and greasy grouper (Epinephelus tauvina). The length of fingerlings required is about 9–10 cm. The problem is the shortage of 9–10 cm seabass fry. Previously, fry of this size had been purchased from Thailand, but this proved difficult because of high mortality and high transportation costs. Thus, to solve the problem, the project planned to nurse fry from 2 to 9–10 cm since 2 cm fry can be easily obtained from Tanjung Demong Hatchery.
The nursing of seabass fry was attempted at the Fikri pond project. In November 1984, the project received 4 000 fry from the Sungai Merbok Hatchery. They were stocked in nylon net cages, mesh size of 2 mm. The size of the cages is 175 × 75 × 75 cm deep. Cages were set in Pond A. The stocking rate was 500 fry per cage and there were 8 cages. Cages were suspended inside a 3 × 3 m wooden frame, kept afloat with styrofoam blocks. Planks are laid over the blocks to make walkways.
Fry obtained differed in size ranging from 0.3 to 1.2 cm. Thus, the fry was initially graded by the author and Mr Harun bin Man, one of the staff assigned to fishculture in ponds. Fry was divided into three sizes: group A 0.1–0.5 cm, group B 0.6–1.0 cm and group C >1.1 cm. Before grading, fry was taken from cages and results were as follows:
The total fry caught was 188 pieces; 110 pieces of group A, 58 pieces of group B and 20 pieces of group C, i.e.,
58.51% ranged from 0.1 to 0.5 cm
30.85% ranged from 0.6 to 1.0 cm
10.64% was 1.1 cm and more
Fry was fed with Moina only during nursing in Sungai Merbok Hatchery; this is the feeding procedure for 15–20 day-old fry. The Moina culture was brought with the fry from Sungai Merbok Hatchery to the project site.
The first day after arrival, fry was fed with Moina only; the second day with Moina mixed with ground trashfish as there was not sufficient Moina. From the third day, fry had to be fed with ground trashfish alone because the project had no facilities to culture Moina and Artemia. Thus, certain fry feeding procedures had to be eliminated. The fry did not know how to eat the trashfish which is dead and not moving, as they had not been trained to do so. They were used to feeding on Moina which is living and moving.
As a result, the fry starved due to lack of suitable food. When there is no suitable food for many days, they become stunted and the body turns black in colour. If seabass become stunted at an early age, they rarely grow and gradually deteriorate.
Suitable feed for seabass fry depending on age is as follows:
3–14 days old larvae: rotifer
7–25 days old larvae: Artemia
15–35 days old larvae: Moina
25–35 days old larvae: trashfish and Acete
Fry usually has to be trained to eat trashfish before distribution the the fish-farmer or government farm fro rearing in cages or ponds, and no distribution should be done until they are fully trained to eat trashfish. It is difficult for the fishfarmers to prepare live food such as rotifer, Artemia and Moina and there are no facilities available to culture live food in the fishfarms because funds are needed for construction, but trashfish should be available everywhere.
Normally, fry to be distributed to the farm should be about 30–40 days old, about 1.5–2.0 cm in length, and can be fed with trashfish only.
At Fikri care has been taken to train the national staff and fishfarmers in nursing seabass fry. Before feeding, trashfish was cleaned and diluted in the water and sprayed in the cages. Feed was given to fry 3 times daily, at 08.30, 12.30 and 15.30 h. Cages were cleaned once every three days to sweep out leftover food and fouling materials, to avoid blocking the mesh and reducing the water exchange rate. Consequently, the level of oxygen in cages was reduced or deficient. When the cages were cleaned, fry was graded in size in order to prevent cannibalism.
It was unpredictable that on 8, 14, 15, 21 and 22 December 1984, and 8 and 11 January 1985, the cages were found damaged by crabs, and there were many holes in the bottom of the cages. The crabs had damaged the cages during low tide when the water level was about 50 cm and the cages lay on the bottom of the pond. Crabs entered the cages not only to eat the fry but also the feed. About 50% of the fry escaped. In this situation there are no ways of preventing the crabs from entering. Later, holes in the cages were checked everyday and repaired if found. Fry was also lost during 22–31 December 1984, when there was a heavy flood around the site. The water of low pH from the jungle entered into the pond over a period of many days. The pH of the soil around this area was lower than its required 2.5–3.5. The soil is also acidic. On 5 January 1985, the pond water was checked by the author and the staff, the pH of water was found to be less than 4 (solvent of pH solution for water of which pH less than 4 was not available at the site). In this situation, the mortality of the fry was about 40%.
On 14 January 1985, the fry was checked and counted. There were only 151 pieces remaining of size 1.5–7 cm.
To date 28 ponds have been constructed by the Department of Irrigation and Drainage (JPT) on behalf of the Fisheries Department. Seven fishermen's families have been given four ponds each for the purpose of rearing fish and fishermen have been instructed in regard to fish culture by the Fisheries Development Area (FDA). JPT has also constructed two canals along both sides of the pond site and a main gate was built in the canal to control the water level. Each pond can be filled with brackishwater by installing 6 inch diameter ceramic pipes. The Fikri ponds have been stocked with seabass fingerling since 1983, but there have been many problems. To continue rearing fish in these ponds, in 1984 corrections have been carried out to improve the pond environment as follows:
Changing the pond inlets: The previous inlets were too small and inlet pipes were clogged by deposits left by seawater. The 6 inch diameter original inlet pipes were changed to 12 inch diameter pipes in February 1984. More good quality seawater could enter the ponds during high tide and the large quality of acid in the soil was dissolved in the water. At low tide, therefore, the acid water runs off into the sea. Gradually reducing the acidity of the soil.
Liming the ponds: The ponds with soil pH less than 6, were adjusted by using 100–150 kg CaOH plus 50 kg CaO per pond (pond area about 0.25 ha each). Before liming, the mouths of the inlet pipes were closed with styrofoam covers to prevent the water in the pond from draining out to sea. Once the acid in the soil was neutralized by the lime, the inlet pipes were reopened to allow seawater to enter the ponds at high tide and drain out of the pond at low tide, thus removing the acid from the pond.
One month after changing the pond inlets and liming the ponds, the pH level of all ponds was checked. The pH level appeared to have increased to between 6.0 and 7.1 whereas before liming, the pH level ranged from pH 3 to pH 7. Thus the water quality in the ponds has greatly improved and the ponds are now suitable for rearing fish. All ponds were stocked with seabass fingerlings about 9–10 cm, average weight 10g. The stocking was completed on 31 May 1984. The fish was fed with chopped trashfish regularly, about 4–5 times a week, depending on the availability of trashfish, which the supplier was unable to deliver every day. Seawater was allowed to enter and drain freely in the ponds, thus renewing continually. To prevent the wild fish entering the ponds, the mouths of the inlet and outlet pipes were screened by nylon net and in this way the fish grew very fast. It took about 6–7 months (from May to November/ December 1984) to rear seabass to be harvested for sale, when the average weight was about 600 g (ranging from 400 to 1 000 g). There was about 60% survival and estimated production was about 1 080 kg/pond or 4 320 kg/ha.
In 1985, preparation of ponds started in January. The bunds of ponds were repaired, as otherwise not all the water could be kept in ponds, as the bunds had been seriously damaged by heavy floods in December 1984. In the middle of February 1985, Tea sea cake was applied to eliminate fish predators such as wild fish, i.e., catfish, and some seabass remaining from the previous crop. In April 1985, ponds were stocked with the first seabass fingerlings, about 5–10 cm in length and average weight 8.33 g. The stocking density was 1 750 pieces per pond. Fish were fed with chopped trashfish once a day. At the time of writing this report - June 1985, the fish were growing well, length is 12–18 cm and weight 45–90 g.
At the moment, 17 fishermen have a business in fishculture in cages in the Besut Fisheries Development Area. Two sites are used for the cages for fish culture: Setiu Lagoon and Kuala Bharu. The investment for construction of cages, costs of seed, feed and other materials is subsidized by the government. Each owner has cages of three units and four cages per unit. Thus one owner has 12 cages. Therefore, there are altogether 51 units with 204 cages.
Cages are made of nylon net, mesh size 2.5–5.0 cm. The size of cages is 3 × 3 × 3 m. Cages are suspended inside a 3 × 3 m wooden frame. At Setiu Lagoon, cages are kept afloat with styrofoam blocks, but at Kuala Bharu, bamboo rafts are used. Planks are placed over the wooden frames to make walkways.
Seabass and greasy grouper are preferable species for rearing in cages and normally, fingerlings of 9–10 cm are selected. Stocking density is 300 pieces per cage at Setiu Lagoon and 500 pieces per cage at Kuala Bharu. Feed given to fingerlings is chopped trashfish, the size of feed depending on the size of the fish. Feeding is once a day, the amount of feed given is not limited and is given until the fingerlings stop eating. Size grading is done periodically in order to separate the bigger from the smaller because seabass and greasy grouper are cannibalistic.
At both Setiu Lagoon and Kuala Bharu, the net walls of cages become clogged by fouling organisms very soon, causing a reduced water exchange rate and also a reduction or a deficiency in the level of oxygen. Thus, the cages are examined and cleaned periodically. If the fouling organisms are causing too much clogging the cages have to be replaced. Fouling organisms are killed by drying under sunlight and are then cracked by a hammer and easily removed. Thus, the cages have to be examined and cleaned regularly.
Stocking with seabass and greasy grouper in Setiu Lagoon this year began in February and was completed in April. The size fingerlings stocked was about 8–10 cm; the average weight for seabass was 8.33 g, and for grouper 13.33 g.
At Kuala Bharu, cages were stocked with seabass fingerlings only. They could not be stocked with greasy grouper because the salinity of water is not stable. Stocking started in March and was completed in April. The length of fish was 8–10 cm, the average weight was 8.33 g, (as at Setiu). By mid June 1985, the weight of the seabass in cages at Setiu Lagoon ranged from 45 to 200 g and for grouper in cages from 60 to 105 g. Seabass in cages at Kuala Bharu ranged from 40 to 160 g. The fish reach marketable size (about 600–700 g) in about 7–8 months. The growth of the fish also depends on the amount of trashfish given, i.e., the more trashfish is fed, the faster the growth of the fish.
Trials started end-May 1985, in the Setiu Lagoon, where the salinity of water was more stable than at other sites. The objective is to study the feasibility of culturing the tiger prawn, Penaeus monodon in plastic net cages. Two types of cage are used, one outside the other. The advantage of having two nets in one set is that it ensures protection from predatory wild fish. Cages are suspended inside a 3 × 3 m wooden frame, which is kept afloat with bamboo rafts.
The larger outside net cage is 3 × 3 × 3 m, with 2.5 cm mesh. The smaller net cage inside the larger net cage is a 175 × 75 × 75 cm, with a 2 mm mesh. There are seven cages.
The length of tiger prawn fingerlings stocked ranges from 2.4 to 4.6 cm with an average 3.53 cm and an average weight of 0.463 g. Each cage is stocked with 300 pieces, except for cage 7 which was stocked with 346 pieces. The total is thus 2 146 pieces.
Trashfish is the appropriate feed for the tiger prawn fingerlings. It should be spread throughout the cages and the amount given should be more than enough. It was started on 28 May 1985. And the first check of the growth was on 15 June 1985, i.e., 18 days after stocking. The results are shown below:
SIZES OF TIGER PRAWN FINGERLINGS WHEN STOCKED AND
CONTROLLED AND MORTALITY DURING 18 DAYS REARING
| Cage No. | 28 May 1985 | 15 June 1985 | Mortality (pieces) | Remarks | ||
| No. | Wt (g) | No. | Wt (g) | |||
| 1 | 188 | 85 | 33 | 45 | 3 | Within 18 days Mort. = 1.2% Lot gain = 0.893 g |
| 2 | 168 | 65 | 51 | 60 | 2 | |
| 3 | 185 | 95 | 48 | 55 | 3 | |
| 4 | 200 | 95 | 53 | 55 | 5 | |
| 5 | 137 | 50 | 52 | 55 | 4 | |
| 6 | 152 | 75 | 42 | 45 | 3 | |
| 7 | 146 | 80 | 38 | 45 | 6 | |
| Total | 1 176 | 545 | 317 | 360 | 26 | |
| Average | 0.463 | 1.356 | ||||
After 18 days from stocking the average length of 3.53 cm reaches 4.76 cm, ranging from 4.20 to 6.50 cm; and the average weight grows from 0.463 to 1.356 g. Thus the average weight gain is 0.893 g, more than double the initial weight. The mortality is 26 pieces or 1.2%. However as the author's brief assignment limited his participation in the trials to only 18 days, these trials should be continued by the project until prawn reach marketable size.
Because the depth of the 2.2 m rectangular tanks used in the hatchery is only 60 cm, the water content in the tanks becomes cold in the morning (especially after night rain, the water temperature drops to 22–25°C), which causes the death of fry. Thus, this type of tank should not be used for nursing fry until the walls of the hatchery are constructed; for future construction of nursing tanks, the depth should be at least 90 cm, to ensure a constant water temperature.
Sea and freshwater pumped into the storage tanks should generally be screened with a cloth filter before being allowed to pass into the production tanks, as this water contains many living organisms and sand. Some of this material is rotten and sinks to the bottom of the tanks, where it causes pollution and contaminates the live food. For instance, in a case of fry being reared on rotifer culture, it was found that the rotifer was being eaten by copepods carried into the tanks in unfiltered seawater. For Chlorella culture, the water has to be screened through fine mesh (60 micron) cloth filters, otherwise rotifers in the seawater will enter the Chlorella tanks and contaminate the Chlorella.
After use, the filter cloths should be washed well and dried in the sunlight before the next use in order to prevent the formation of holes. If this occurs, organisms such as rotifers or copepods, are able to pass through the holes into the tanks causing water contamination.
Water flowing into the breeding tanks was sometimes dirty. This should be checked before use, as water containing rotten materials causes water pollution. It is harmful to fry, as eventually they cannot eat the food and die.
Tiger prawn breeders collected from the ponds are not so healthy and strong as those from the sea, even though during breeding, the spawners produce a lot of eggs and also hatch out nauplii, but most fry die at nauplii and Zoea stage. Thus research on food and proper stocking rate should continue in order to ensure the fitness of spawners the whole year round.
Hopefully, electricity from the National Electric Board will soon be available at the hatchery. However, the author has observed that the electricity supply in this area is often problematic. Sometimes there is no electricity for many hours and this would result in the death of fry during nursing. Therefore, a 25–50 kVA power generator should be installed for emergencies.
The old and new wells of freshwater at present are brown in colour and very turbid, and not suitable for nursing fry and breeders. Thus the seashore well available should be reconsidered for use because of its better water quality.
Seabass breeders in cages at Setiu Lagoon should be fed every day, and the suitable food is sardine. The feed should be given gradually to the breeders at the same time every day, usually at 13.00–14.00 h.
Seabass reared in ponds should be fed every day, otherwise their growth will be retarded.
Since the Fisheries Development Area has many sites for rearing fish, there is a considerable amount of trashfish available for feeding the fish in ponds and cages. Sometimes the shortage of trashfish has occurred. Moreover, the delivery of trashfish is expensive due to the high cost of transportation and the long distance. It is proposed that the government construct a cold store in the main office of the project at Rhu Sepuluh for the store of trashfish. This would greatly reduce the cost of production. A cold store would also enable the building-up of a stock of trash-fish during the fishing season when it is cheap and easily obtained.
There is a lot of grass in some of the ponds which should be be removed. Otherwise it will cause problems, e.g., it will prevent the use of a drag-net to catch the fish in the pond, it will provide shelter for predators such as snakes, birds, etc., and as it decays in the pond, it will increase the acidity level of the water and cause oxygen deficiency.
The water in some ponds is quite shallow and heats up during the hot season. A part of every pond should be shaded with coconut leaves which are abundant around Kampung Fikri.
Monitoring of the ponds shows that there is accumulation of trashfish at the bottom as a result of overfeeding. It must be stressed that excess trashfish must not be thrown into the ponds, otherwise pollution and eventually oxygen deficiency will occur.
Dead fish should be removed from the ponds as soon as possible, otherwise they ferment and cause a rise in the NH4 and CO2 content of water. This also kills the remaining fish.
If fish in the pond do not come to the surface to feed, then feeding should be stopped for that day. It indicates that fish are not well. If feeding continues in such conditions the excess feed will sink and ferment, eventually giving rise to a further loss of oxygen and subsequently fish mortality.
Feed should be spread over a wide area of the pond to ensure that the smaller fish manage to eat.
With regard to stocking fish in ponds or cages there may be wounded or diseased fish. To cure the wound and prevent disease, the fish should be treated in potassium permanganate 500 ppm for 30 sec to 1 min before stocking into the water.
Before moving the brackishwater fish elsewhere, the salinity of the water where the fish were kept should be adjusted to the same level as the new site. The level of salinity adjustment should not be more than 5 ppt a day.
Fish reared in cages should be given feed gradually and it should be spread thoroughly throughout the cage in order that every fish can feed. Feeding should be stopped when the fish slows down its eating in order to avoid overfeeding. Otherwise feed left over could ferment and cause oxygen deficiency.
The salinity of water in Setiu Lagoon and Kuala Bharu frequently fluctuated. The cage should be deep enough (at least 2 m) to give the fish a chance to escape into deeper parts where the water has a higher salinity. Especially during heavy rain a large amount of water comes from the jungle resulting in freshwater at the surface but higher salinity in the deeper areas.
In Setiu Lagoon and Kuala Bharu, the mesh of the cages was frequently fouled by organisms or small particles. Consequently the water exchange rate is reduced, and the level of oxygen inside the cages is also reduced. Therefore the cages should be frequently checked for cleaning or replacing a new net.
Cages should be placed in rows, with a 1–2 m gap between rows. This way, every cage is connected to the open water so that each one can obtain good quality water.
The quality of the soil at Besut is the same as at Fikri's pond area which is estimated at about 100 mi2. To date, local people have done nothing on this land. Formerly rice was grown, but production was low. This is because the quality of the soil is acidic, pH being about 3.
The government has tried to utilize the land for agriculture, but no crops grow well. Later, the canal was constructed by the Drainage and Irrigation Department to drain the water from this area because it was thought that too much water was available for rice planting. After that, the land dried and consequently it was no longer suitable for rice growing.
However, an attempt had been made to utilize the land, thus 28 ponds at Fikri were constructed by the Department of Fisheries along the canal in order to try rearing fish. After completion, the ponds were given to seven fishermen. At the beginning, seabass fingerlings 8–10 cm in length were stocked. Seawater was allowed to enter and drain out of the ponds freely through 6 inch pipes. The mouth of the pipes was screened with nylon net in order to prevent wild fish entering the pond and the fish in the pond from escaping. The ponds has no gate and the soil was too sandy to retain the water, resulting in low production. This was due to a low pH in the soil; also many fish escaped because of the flood and the bunds of ponds were swept out by the current of water coming from the nearby jungle.
In February 1984, the inlet pipes were changed from 6 to 12 inches and CaOH plus CaO was used for liming. The quality of the soil improved to a pH of 7.2, the water became suitable for rearing fish and the production of seabass reared is high. Within 6 months, fish grew to a marketable size of about 600 g.
It was thus shown that this land could be utilized for rearing fish. However, fish culture can only be operated from April to October, during which period the rain is not heavy and consequently the fluctuation of salinity of water was not great. From November to March, there are heavy floods and the water is poor quality. It is black-brown in colour, its salinity is zero, and the pH is below 4. This is because the acid in the soil in the jungle is swept out by rainwater and drained into the lower part of the canal and and finally it reaches the ponds. So the construction of the pond gates was necessary to control the water, i.e., the gates will be closed to block bad quality water, and will be opened to allow the seawater to enter the pond during high tide.
Setiu Lagoon is productive, and mangroves grow on its banks. The leaves of the plants drop onto the ground and after fermentation this acts as a natural fertilizer which is washed by the tide into the lagoon.
The lagoon is connected to many rivers and streams. The fertilizer from the jungle was cleaned by rain water and swept into the rivers and streams. Finally, it goes along the water current into the lower part of the lagoon. This means that the lagoon obtaines natural fertilizers from many different sources. It will certainly be always fertile and a suitable habitat for living things. However, occasionally there are also environmental problems as follows:
Water exchange: At the moment the level of water at the mouth of the lagoon is shallow and sandy (as reported by fishermen). The seawater coming into the lagoon at high tide and draining out at low tide undergoes no improvement. Thus, the sand should be removed from the mouth of the lagoon to make the water level deeper and thus improve the water exchange.
The quality of water: There is a lot of rain in this area during November to March (from observations in 1984 and 1985). During heavy rain, the water in the lagoon was poor quality, black-brown in colour and containing a large amount of small particles (quickly blocking the meshes of the cages). The pH of the water was only about 4 or sometimes less, there was too much fluctuation in salinity, which often dropped to zero ppt. This condition is due to heavy rain, the rain water cleaning the acid soil, and a lot of small particles coming into the lagoon. There are no dams to control the amount of water at the upper part of the lagoon. The water from the jungle comes to the lagoon, causing sudden changes in salinity, maybe from 10 or more to zero. The fish in cages greatly suffered from these salinity changes. The fish had no chance to adapt, did not come to the water surface, and refused food for many days, and then escaped to depths where the salinity was higher. This condition causes a lot of fish mortality. Thus, it is strongly recommended that there is no stocking of fish during November to March.
