PLA SALID (TRICHOGASTER PECTORALIS REGAN)
A LIFE HISTORY AND MANUAL FOR CULTURE

by

Jiamjit Boonsom*

1. Trichogaster pectoralis or Pla Salid in Thai is a true native fish of Thailand. It is a traditional food fish and the people prefer it salted and sun-dried before serving with rice as deep fry fish.

About 40 years ago the most tested dry Pla Salid came from a specific area called Don Kam Yan, Suphanburi Province (Smith, 1945; Indraramphan, 1981). But since 1943 Pla Salid had vanished from that area and the fame had transferred to the area of Samutpraktan Province, Bang Pli and Bang Bo, about 30 km. southeast of Bangkok. This area formerly is estuarine swamp. The Thai Government has reclaimed for rice cultivation in 1931 by building the earthen dike along the sea shore. The dike had been developed to be the Sukumvit road today.

In 1957, the Department of Fisheries started a rice cum fish project in several well irrigated area in central plain and this area is one of the project site. Pla Salid, along with the other fish species in the Project is found to be the most suitable for this Samutprakran area and yield a higher income than rice production. Paddy farming was no longer interesting. The farmer converted the rice field to culture Pla Salid and called it fish field since the year 1962.

Pla Salid fish field culture has increased markedly over the last 20 years. The annual production has reached over 20,000 tons which is about 40 – 50 percent of the total freshwater fish farming production. Until recently, due to the encroachment of industrial and other economic activities including the housing area, the production has declined from the previous mark to about 13,000 tons and cover only 20 percent of the total freshwater fish farming production (Dept. of Fisheries, 1985). Even this number is still being one of the highest yield among the other pond fish production, something has to be done. In an intensive study and experiments, measures of improving culture methods has been established and this paper is the result of those experiments and the author's own experience plus the studies and records of other biologists and experts before times.

The paper prepared as a documented paper and instruction manual at the same time.

* Fisheries Biologist
National Inland Fisheries Institute
Bangkok, Thailand. 10900

2. Life History

2.1 Distribution

T. pectoralis is widely distributed and common in swamps, canals, lakes and rice fields or in any shallow water and sluggish current of the central plain of Thailand. It is indigenous species and distribution extend to Cambodia and Vietnam. The fish is naturally absent from southern peninsula, Northern or Western Thailand (Smith, 1945).

There is no record of this fish in “The Fishes of India” (Day, 1876 – 1878) neither in the book of “Catalogue of the fishes in the British Museum” (Gther, 1859 – 1870) nor in the book “The freshwater fishes of North Borneo” (Ingen and Kong, 1962). But this was reported that the fish was transplanted to lakes in Celebes in 1937 (Hickling, 1961).

There was evidence that the fish had been introduced to Singapore in late nineteen century and to Krien District, Perak (Malaysia) in the early twentieth century (1913), where the fish is called Sepat Siam, now. The fish is well established in Krien District (Tweedie, 1952). Dr. H. M. Smith recorded about this fish in his book that the fish introduced to Malay from Thailand is now widely distributed, abundant and an important food commodity (Smith, 1945).

Henry W. Fowler also stated in his book of “A list of fishes known from Malaya” that this fish was introduced (Fowler, 1938). In Laos the fish is called Pla Salit (Taki, 1974) and in Vietnam the local name of this fish is cä säc ran (Chevy, 1932; Kawamoto, 1972).

Therefore from the above documents, the author quite agree with H.M. Smith that T. pectoralis is indigenous species to the central plain of Thailand, extending from Chao Phaya Basin to Cambodia and Vietnam, Laos. The fish which is now found in other part of Thailand, India, Bangladesh, Ceylon, Indonesia and Philippines had artificially been introduced recently. In Thailand, the Dept. of Fisheries had tried to promote Pla Salid culture since 1939 (Kasikorn, 1939) and after that time the seeds and brooders were sent all over Thailand.

2.2 General Morphology

Pla Salid is the biggest size fish among the local Trichogaster group. The recorded size is 24 cm in total length and 200 gm in weight. The general average adult size age 6–8 months old is 16–21 cm in length and 95–120 gm in weight.

It is a tuft fish. Since it belongs to the suborder Anabantoidei which this group of fish contain suprabrachial organ that help the fish to breathe directly from air; the fish can stand the condition that dissolved oxygen is zero. Even this, the young fry can also stand the low pH level, up to 4.5, better than other fish fry (Sitasit, 1969).

Description

Body compressed, oblong. Depth of body is 2½ - 3 in standard length (Regan, 1910); 2.4 –2.5 (Taki, 1976) or up to 3.1 (Kawamoto, 1972); mouth small, terminal and directed obliquely upward, lip thick, continuous. Dorsal fin, in male the tip is pointed and extended beyond the caudal base; while in female the tip is rounded and not reaching the caudal base. Pectoral fin large, longer than head, first soft ventral fin ray prolonged into a long filament reaching to the posterior end of anal fin. Caudal fin slightly emarginated. Scale in lateral line 42-27 (Regan, 1910) or 52 in specimen from Laos (Kawamoto, 1972).

2.3 Reproduction

Pla Salid is a heterosexual fish. The differentiation between the sex is explicit. (See “Description” above). This was pointed out by Boon Indrambsya in 1930 (Smith, 1945) which is the most important point of practical value in fish culture.

The fish is nearly a whole year round breeder. The spawning season starts from February to November which peak between May to August. In average, the fish will spawn twice a year and the total eggs laid out is 13,000 to 62,000 annually (Tongsanga, 1965). In the study of embryology it was found that the fish laid 30,000 eggs and the larvae start to feed within 6–7 days after they hatched out (Potongkaun, 1968). From the author's own experience, counting 20 females, fish size 17–21 cm in total length, the average fish contains about 40,000 eggs. Hora and Pillay (1962) reported that the breeder contain 7,000 to 8,000 eggs but a nest seldom yield more than 4,000 larvae. The author found that at the latter part of the breeding season, the small size nest diameter about 14 cm contain only 1,700 larvae.

Male fish will prepare the bubbles nest between the grass blade. Nest size is different according to the size of the fish and the thickness of the grass. The rang is from 10 cm to 20 cm in diameter. Potongkam (1968) reported that the nest diameter is about 10–15 cm and exposed above the water level at about 2 cm. Some reported that the nest diameter is about 5 cm (Hora and Pillay, 1962).

The male collects the fertilized eggs and deposit the eggs attached to the bubble nest. Eggs hatch within 24 hours and started to feed within 6 days (Potongkam, 1968). he early food of the fry is zooplankton especially Rotifera and after it reach about 1.3 cm the fish turn to feed on epiphyte (Boonsom, 1982).

Some reports state that the embryo hatch out in 36–48 hrs after fertilization. The author's own in situ experiment, showed that larvae can be found under the nest in 24 hrs after the eggs were first seen in morula stage and started to feed on the 5th day after hatching.

Egg size is about 1.2 mm in diameter, yellowish in color and contain oil globules.

2.4 Feeding Habit

When yolk sac had been absorved, the fish fed on zooplankton especially Brachionus sp, while Cladocera, nauplii and Protozoa play a secondary role and when they reach 1.5 cm in length the fish turn to feed on detritus and algae (Boonsom, 1983). Most of the reports on feeding habit of this fish is saying that the adult fish is feeding on epiphyte (Hora and Pillay, 1962; Hickling, 1961) and the larvae feed on phytoplankton and zooplankton such as bacillariophyceae, cyanophyceae, and flagellate, ciliate, Rotifer, Cladocerans, copepods and detritus (Chinabut, 1973).

2.5 Taxonomy

Tate C, Regan who described this fish in 1910 had placed this fish under the Family Anabantidae and the systematic arrangement are as follows:

Regan got the type specimen from Thailand and Singapore and was first named Trichopodus pectoralis taking that the pectoral fin of the adult fish is longer than its head.

The common name of this fish in Thailand and Laos is Pla Salid in Malaysia, Singapore, Indonesia is Sepat Siam; in Vietnam, it is called Ca sot ran and the English name is gourami or snake skin gourami.

Nelson (1967) has placed the species under Family Beloniidae (Polyacanthidae) subfamily Trichogasterinae.

2.6 Embryology

The study of the embryology of Pla Salid had been recorded and illustrated on the work of Fisheries Biologist Mr. Kamtham Pothongkam (Pothongkam, 1968) and also on a Bachelor thesis at the Kasetsart University (Srirungroj, 1968) both of the works are in Thai. The author would like to summarize those works and tabulated as follows:

2.7 Parasites and Predators

2.7.1 The Parasite

Until recently, the fish has no serious record of disease. The ulcerative disease outbreak throughout the country in 1983 has also attacked Trichogaster pectoralis. The disease, which until now is not fully understood, was reported that Aeromonas hydrphylla were found in tremendous number in the wounded area.

Observations done during this study showed that there are some living worms found in the body cavity of the fish. Closer investigation revealed that the worm is the metacercaria of the trematode Clinostomum pisidum and the statistic show that there is some effect to growth of fish aging over 7 months (Charoenpornsook, 1985).

2.7.2 The Predators

The main predators of the fish are wild carnivorous fishes listed in Table 1. The smaller size fish attack Pla Salid from egg stage to fry stage. The larger fish size such as Ophiocephalus striatus attack even the adult size fish. Preliminary experiments in aquaria showed that young O. striatus of 10 cm size need at least 6 of 2–3 cm Pla Salid fry to feed on per day.

Insects are also important enemy especially during breeding season. The flies capture young Pla Salid fry for sap sucking.

Birds are the other predator group. Especially during cold season when the temperate region birds migrate down to the warmer areas. Fish-eating birds found in Pla Salid ponds are well recognized and are listed in Table 1.

Table 1. List of Parasite and Predators

3. Culture System

3.1 Old Traditional System

The Department of Fisheries had introduced the rice cum fish culture to the farmers in many well irrigated area since 1962 in order to use fish excreta as fertilizer for the paddy to increase rice production and at the same time gain some fish as by-products. The instruction to farmers is to build a peripheral ditch with a high bund surrounding their field. Rice were planted on the center platform area while fish can wander throughout the field and in the ditches. The result was not all satisfactory. Some areas have problems with insecticides and herbecides which kill all the fish. Some areas have problems with the soil, such as Samutprakran Province, which is an irrigated area and a reclaimed land. The area have problems with salty soil and low pH. The rice production is very low while the fish production such as Trichogaster pectoralis, Ophiocephalus striatus are very high inspite of the less labour inputs. Therefore, the farmers around this areas deserted rice plantation and cultured fish in their fields. The center platform area is left for the native weed to grow. Thus, the beginnings of fish field culture had been established particularly in the Samutprakran Province and some parts of the adjacent Province of Chachengsao. It is the only place in Thailand that have developed and succeeded in fish field culture.

The size of these fish fields ranges from 3–20 ha (Boonsom, et. al., 1980). The farmers stock their field with the spawner that were retained from their previous harvest. They do not select the sex nor the physical health of the fish but rather, they stock by weight. The rate of stocking varies from 40–220 kg/ha (Boonsom, et. al., 1982; Sawaegwan, 1971; Varikul, 1969).

Before stocking, the fish had to be kept very crowded in a small pond without any additional food nor fertilizer. This practice is to get lean fish which they believe are very good brood fish.

The culture season starts in early February. The brood fish, is released in the peripheral ditch for a while before raising water level to flood the center platform area about 35–50 cm high. A few days later the fish spawn and nurse their fry, and the fry grow out to adult size in the field.

If the farmer finds out that the water condition in the field is not good due to the low pH level which can be distinguished by the color of the water, they drain out all the water and flush the field with fresh water. For some years the farmer had to wash the soil two times before he is satisfied with the results.

The fertilizer, the only fertilizer used in this fish field culture are the green manure. The farmer cut the weeds biweekly and pile or scatter on the field to ferment. During the rearing period, the farmer have only to keep the water level well above the platform area and maintain the good condition of water. If the water turn black or has a strong smell due to grass fermentation, the water must be drained out and fresh water is pumped in. Harvesting is done during the dry season which starts from November to January. Therefore, the rearing period is 8–10 months and may even be longer depending on the size and the prevailing market price of the fish. The optimum marketable size of the fish is 100 gm in weight. The yield of this type of culture range from 450–1700 kg/ha which vary from farmer to farmer and year after year (Boonsom, etal., 1982; Sawaegwan, 1971; Varikul, et.al., 1969).

3.2 Developed System

The simple traditional system and the uncertain yield show that the farmers knowledge of modern fisheries is poor. Most of them believe in superstitious practices. Variable yields are explained by way of the unseen power such that good or bad behaviour of farmers may influence their farm yields.

Farmers always overstock their field to guarantee the production. They are not aware of the carrying capacity of the field, as a result of overstocking, small fish predominate and command a low market price per kilogram. Inspite of the heavy stocking, fry production by farmers is only 6–23 fry per pair of brood fish (Boonsom, 1984). This is quite low compared to the fecundity of this fish (see 2.3 Reproduction). The high mortality of the fry is due to many factors such as low water quality, inadequate food at the early stages of life and predation.

The poor water quality is mainly due to pH level and salinity at the early culture season. The long exposure of the field to the sun during the dry season create the pH problem. Bigger size farms which need more water to fill field create water shortage in the area hence salinity and pH problems follow.

The technique of washing and cleaning land with water to improve pH level of the water, consumed a tremendous amount of water. A 20 ha field will need about sixty thousand cubic meter of water to cover 30 cm above the platform which means that it need the whole column of 5 m wide, lm deep and 12,000 m long of supply canal. It is impossible to supply such amount of water to the fsrmer with 16,000 ha fish field during the dry season. Thus, size of the farm is causing problems and needs to be changed especially during the dry season when breeding and nursing periods take place.

Food of the fry is also very important. The fry need more food than adults per unit body weight. As mentioned above, the only source of fertilizer is the fermented grass. This green manure need 7–10 days before it can release suffecient nutrient to be an effective fertilizer. This is insufficient for the amount of larvae produced by 125–250 kg/ha of brood fish. Animal manure is more effective fertilizer than the green manure. In Rotifera culture, using dry chicken manure at 0.7 gm/1, the number of Rotifers increased to 1,515 × 10³ ind/l on the 5th day and to 3,795 × 10³ ind./l on the 7th day (Montien-art, 1985). A study of the stomach contenthad revealed that Pla Salid fry take Rotifera as their main food items during the early stages (Boonsom, 1985). The experiment also showed that the fry fed on Moina macrocopa grew faster than fry fed with rice bran (Bumnengsuk, 1970). A report on fish nutrition (common carp) stated that the most suitable food for fish fry is Rotifera (Horvath, 1978). Therefore, fertilizer should be applied to increase survival rate of the fry per pair of brood fish.

Predation from the wild carnivorous fish is the most serious problem. A preliminary experiment showed that a 6–10 cm size of snake head fingerling consumes about 6 individuals of Pla Salid fingerling size 3–5 cm per day. It is impossible to eradicate these predaceous fish from the big area field especially during the high water level season because the process incurs high cost and heavy labour inputs. However, if the area of the field is decreased, closer attention given to the breeding period and more care for the young helpless fry under 2 months, then culture will be more beneficial.

Therefore, from the above discussions, a number of solutions had been presented in order to improve fish production and expectedly will result to a more consistent yield. In summary, the measures are presented below:

1. Brood fish have to be properly selected and fed with appropriate feed for a certain period of time. Good brood fish will bear a great number of healthy eggs and fry.

2. Breeding pond should be separate from the grow out field and should be well protected from predators.

3. Fertilizers, other than green manure should be added to help increase the natural food production for the fry. Animal dung is preferred.

4. The fry should be kept in the breeding pond for about 2 months before releasing to the grow out field to improve the survival rate by minimizing if not totally eliminating predation.

3.2.1 Culture Pond

The culture pond should resemble the traditional grow out field with peripheral ditch about 3–4 meters wide and 0.75 m deep. The ditch should be wider and deeper at the harvesting site. The central platform area should be planted with weed which can be used as the indigenous green fertilizer, also for protection of the fingerlings and as base for periphyton which serve as the main food of Pla Salid. (Fig 1)

3.2.2 Breeding, Pond

Breeding pond should have an area size of about 1 to 10 ratio to the grow out field. The area should not be too large for easy management and should not incur high expenditures in setting up the protection fence. The biggest size of breeding pond recommended is not larger than 0.8 ha, while the grow out field should be about 8.0 ha. It is preferred that the breeding pond should be connected with the grow out field.

The shape of the pond should resemble the grow out field, i.e. rectangular or square with peripheral ditch and earthen dike around the pond. Native grass should be grown in the center platform or planted if necessary. On the dike, set up the net fence about 50 cm high or even higher if the breeding pond is in the lowland area or adjacent to the outer water bodies. The inlet should be protected with a fine mesh size net to prevent entrance of eggs and fry of predator fish. It is preferred that the outlet of the breeding pond should go into the grow out pond.

3.2.3 Farm Equipments

The most important one is the motor pump. The power of the pump should be appropriate to the size of the fish field. At least the biggest pump should be able to fill the fish field within 3-4 days. The popular pump in Thailand is the dragon bone pump (water wheel run with motor).

The other important tool is the grass cutting blade or the grass cutting machine. Formerly, most of the farmers were using grass cutting blade but recently the grass cutting machine had been developed and can work out very well hence is in popular use today. The only constraint is that the machine can not be used during the breeding and nursing periods.

4. Farm Operations

4.1 Brood Fish

The brood fish that was retained from the previous harvest should be sexed and health determined and kept in a brood fish pond, at the rate of not more than 1 individual per square meter. If such a pond is not available, the brood fish can be kept in the ditch of the breeding pond.

4.2 Feed and Feeding

Feed the brood fish every day for at least 3–4 weeks with a high protein food. The feed NIF no. 12 is preferable. The feed formula is as follows:

* if dry flour is using the feed will come out as powder feed

Feed the above food to fish at the rate of not more than 2. % of the fish total weight.

4.3 Breeding

During the reconditioning period of brood fish, the farmer has to check the abundance of grass on the platform. If the weed grows sparsely, the farmer has to plant until the central platform is full of weeds. If the farmers are satisfied with the amount of weeds, they should raise up the water level to about 30 cm well above the platform. When the fish begin to build the nest they will spawn on the next morning. On the same day, while raising the water level, chicken manure is applied to the breeding pond at the rate of 220 kg per ha. The manure should be applied at the same rate every 7 days for 8 weeks. At the end of the 8th week the Pla Salid fry will reach about 3–5 cm in length and ready to be released for stocking in the grow out field.

4.4 Calculation for Brooders and Area of Breeding Pond

The number of brood fish to be used is calculated depending on the area of the grow out field. If the grow out field is 3 ha in area and the expected minimum production is 2,000 kg per ha then the total yield is 6,000 kg. The average adult size fish is 100 gm. A 6,000 kg harvest can contain 60,000 individuals.

The experiment on separate breeding showed that each female brooder can produce about 500 fingerlings. If we set the figure at the low margin of only 250 fingerling produced and the expected mortality in the grow out field is 25 percent. Therefore, if 60,000 individuals is needed at harvest time, the field should be stocked with 80,000 fingerlings.

250 fingerlings produced from 1 pair of brooder

320 pairs of brooders need about 3,200 m² of breeding area

Therefore in 3 ha area of fish field, the breeding field should have about .32 ha in area and stocked with 320 pairs of brooders.

5. Environmental Factors

5.1 Water Quality

The water quality creates less problem to Pla Salid fish field culture than the quantity of water. Pla Salid which has an accessory breathing organ can stand the water with zero amount of dissolved oxygen. The author prefers to keep the transparency secchi disc reading between 30–70 cm especially in the breeding field. The water color should be a clear light brown. The alkalinity should be maintained around 200– 400 ppm.

5.2 Weeds

Weeds in the Pla Salid field are very important in its culture. Not only as an indigenous fertilizer but also as protection to the egg nests against strong winds, hard rain and intense sunlight; a shelter for the fry and fingerlings; a substrate for aufuch or periphyton which are the main food items of Pla Salid (See Section 2.4) when harvesting time comes, the bunch of grass stems are used as a tool to help in dragging the fish and muddy water to the harvesting site. Therefore, weeds in Pla Salid field are very important in its culture from the beginning to end.

5.2.1 Species Composition

There are 31 species of weeds found in the field. Among these, 22 species originate from the platform area and classified as emergent type, 2 species of subemergent type and 7 species are floated type (Table2).

The most important groups of weeds are the emergent type, constituting about eighty percent of the total area of the field. The prominent species are Eleocharis equisitoides, Paspalum conjugatum, and Llymenachne myurus. The chemical analyses of these 3 species are shown in Table 3.

5.2.2 Timing for Cutting

Most of the farmers do not set themselves a fix schedule for cutting grass for fertilizer purposes. Most of them use their own judgement which depends on the color of the pond water and the degree of crowdness of the fish in their ponds. But usually the grass are cut every 2–3 weeks time. Cutting is in a scattered pattern if hand blade is used and in even rows if machine blade is used.

6. Harvesting

At harvesting time, the farmer calls a “broker” and fix the date of harvest. On the harvesting day, the water is drained or pumped out. The fish are collected in the peripheral ditch. A tractor is used to drag all the fish and the mud along the ditch to the harvesting site and the fish is carried up from the ditch by means of dragon bone pump. The broker takes a look at the size of Pla Salid and set the price. They have to bargain until they agree. Usually the price per kilogram is between 10–16 Baht, depending on the season and the size of the fish.

7. Processing

As it is well known, the good tasting salty Pla Salid come from Bangpli and Bang Bo area. The following informations for processing the fish are supplied by the farmers in these areas:

Harvesting is done in the morning and at around noon time the fish will reach the processor. For the whole afternoon, the farmer is busy with cleaning, scaling, beheading and taking out all the visceral organs. After that the fish is mixed with salt at the ratio of 3:1 approximately. Some farmers are adding a certain amount of ground rice to prevent weight loss. After that, the fish is put into a container either in porcelain container or wooden container for overnight. Early in the morning, the fish will be washed with clean water and then put in the wooden screen to dry under the sun. The farmer collects the fish at about 3 o'clock in the afternoon and sell it to the merchant who comes by at their doors at about 40 Baht per kilogram. Some farmers dry the fish for 2 whole days and the fish are nearly completely dried. This farmer can sell the goods at 80–90 per kilogram.

8. Conclusion and Recommendations

The improved method of separating the breeding field from the grow out field help to ascertain the farmers' production; selection of brood fish; decreasing area of breeding field helps to minimize the cost of brood fish, fuel and the amount of water to be used in the fish field. Also with the help of trifling farm management, farmers can arrange to have 2 crops a year, and gain more income. The following is an example of a farm schedule:

9. References

Boonsom, J., et al. Fertilization in Pla Salid (Trichogaster pectoralis) culture. Thai Fish. Gaz. Vol. 35 (5): 533–539 (in Thai; abstract in English).

Boonsom, J., 1984. Zoolplankton feeding in the fish Trichogaster pectoralis Regan. Hydrobiogia. 113, 217–221

Bumrungsuk, S. 1970. Moina macrocopa for feeding Pla Salid fry Ann. Rept. Fish Culture Section, Freshwater. Fish. Div. Dept. of Fish. 87–94 pp.

Charoenpomsook, K. 1985. Clinostomum pisidum South well and Prashad 1918. A digenetic trematode in the body cavity of Pla Salid Trichogaster pectoralis Regan 1910. MSc. Thesis Mahidol University. 55pp.

Days, Francis. 1876–1878. The fishes of India; being a natural history of the fishes known to inhabit the seas and freshwaters of India, Burmam, and Ceylon. Vol. I text 778 p., Vol. II 195 plates. London Dawson

Dept. of Fisheries 2477 Handbook of Fishes in Siam p. 58.

Dept. of Fisheries. 1982. Freshwater fish farm production 1980, Fisheries Economics and Planning Sub-Division, Dept. of Fisheries No. 11/1982.

Dept. of Fisheries. 1985. Freshwater fish farm production 1983, Fisheries Economics and Planning Sub-Division, Dept. of Fisheries No. 8/1985.

Fowler, H.W. 1934a. Zoological results of the Third de Schauensee Siamese expedition. Part 1 Fishes Proc. Acad. Nat. ci. Philadelphia, vol. 86. p149.

Fowler, H.W. 1938. A List of Fishes Known from Malaya. Fisheries Bulletin no. 1 Singapore p.123.

Günther, A. 1868. Catalogue of the fishes in the British Museum. vol. 1–8. Proc. Zool. Soc. London.

Hickling, C.H. 1962. Tropical Inland Fisheries. John Wiley & Sons Inc. New York N.Y. pp. 239–241.

Hora, S.T., and T.V.R. Pillay. 1962. Handbook of Fish Culture in the Indo-Pacific Region. FAO Fisheries Biology Technical Paper No. 14 p.10.

Horvath, L. 1978. The Rearing of Warmwater Fish Larvae. Proc. World Symposium on Finfish Nutrition and Fish Feed Technology. Hamburg 20–23 June 1978. Vol. I Berlin 1979.

Indrabraya, B. 1981. Pla Salid (Trichogaster pectoralis) Thai Fish. Gazett. Vol 34 (2) :1945–1960 (in Thai, Summary in English).

Monthien-art, B. 1985. Preliminary Study of Freshwater Rotifer Culture. Using Dry Chicken Manure. MSc. Thesis. Kasetsart University, Bangkok. 62 pp.

Pothongkam, K. 1968. Embryological and morphological development of Sepat Siam, Trichogaster pectoralis (Regan) Ann. Rept. Fish Culture Section, Freshwater Fish. Division Dept. of Fish. 36–75 pp. (in Thai).

Regan, C.T. 1910. The Asiatic Fishes of the Family Anabantidae Proceedings of the Zoological Society of London p. 784.

Sitasit, P. 1969. Tolerance of fish fry in different pH water. Annual Rept. Fish Culture Sect., Freshwater Fish Div. Dept. of Fish. 153–164 pp. (in Thai).

Smith, H.M. 1945. The Freshwater Fishes of Siam or Thailand Reported 1965. Smithsonian Institution United States National Museum. Bulletin 188. p464–465.

Srisuwanatach, V. et. al. 1982. Impact of manure on the ecology of fish pond. Thai Fish Gazet. Vol. 35(1): 101–108. (In Thai; abstract in English)

Taki, Y. 1974. Fishes of the Lao Mekong Basin. USAID Mission to Laos. 1974 p.184.

Thanchalanukit. W. 1966. The growth of Pla Salid fry. In Supranee Chinbutra 1074. Biology of pla Salid. Annual Rept. Fish. Culture Section, Freshwater Fish. Div. Dept. of Fish. 48–72 pp (in Thai)

Tonguthai, K. 1969. Species and Control of Predatory Insects on Sepat Siam Trichogaster pectoralis Regan. Ann. Rept. Fish Culture Section Freshwater Div. Dept. of Fish. 165–177 pp. (in Thai)

Tonguthai, K. 1985. A preliminary account of ulcerative fish diseases in the Indo-Pacific Region. (a comprehensive study based on Thai experience) FAO TCP/RAS/ 4508 1985 39pp.

Table II. List of weeds found in Pla Salid field.

Table III. Chemical analysis of some important weeds in Pla Salid Field

* Analysis done by Ms. Nantiya Unprasert National Inland.

Fig 1 Top view and cross-section of Trichogaster field

ACKNOWLEDGMENT

The author is grateful to the following persons for their assistance without which, the paper would not have been finished on time: Jocelyn L. Antiporda, Ms. Phuochorn Bumrungkul and Ms. Kulvimol Wasuntiwongse and also to the Ecology Staff of NIFI for their assistance in collecting the data in the field.