THA: 75/008/80/WP11 THE STATUS OF MACROBRACHIUM FARMING IN THAILAND

by

Somsuk Singholka, Michael B. New and Paiboon Vorasayan
National Freshwater Prawn Research and Training Centre
Inland Fisheries Division, Department of Fisheries
Ministry of Agriculture and Cooperatives

(FAO/UNDP/THA/75/008)

Bangpakong, Chachoengsao
Thailand, 1980

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THE STATUS OF MACROBRACHIUM FARMING IN THAILAND^a

Somsuk Singholka^b, Michael B. New^c and Paiboon Vorasayan^b

ABSTRACT

The farming of Macrobrachium rosenbergii is widespread in Thailand. Currently over 200 farms are being supplied with juveniles from the main government hatchery. Many small ‘backyard’ hatcheries exist and the number of large commercial hatcheries and production farms is increasing. Over half the Thai provinces now have Macrobrachium farms but the species is still being imported to satisfy local demand. Production of farmed freshwater prawns is estimated at 245 tons per year in 1979. Retail market values of US$10.00– $12.50/kg, whole, shell-on, give the industry a scale of nearly 2.8 million annually. Unsatisfied local demand, together with optimal rearing conditions and export potential, promises to stimulate further significant development in this industry in Thailand.

1. INTRODUCTION

Early work with Macrobrachium rosenbergii in Thailand has not received international recognition because it was mainly published in the Thai language, with few English summaries. The work of the Songkhla Fisheries Station in larval, pond and net culture has been documented by Tongsangna and Potaros (1964, 1965), Brohmanonda and Sahavacharin (1966–67, 1968, 1970a, 1970b), Brohmanonda and Pongsuwanna (1966–67), Sahavacharin and Brohmanonda (1970, 1973-4a, 1973-4b), Sahavacharin and Pongsuwanna (1973–74), Brohmanonda (1973–74), Sungkasem and Boontae (1978) Tattanon and Ruangpanit (1978), Tattanon et al., (1978) and Wongsonnuk and Parnichsuka (1978), while early pond culture work at the Chainat and Bangkhen Fisheries Stations has been recorded by Sidthimunka and Choapaknam (1966) and Ayaru (1970, 1971). Experiments on the larval culture of Macrobrachium rosenbergii began at the Bangkhen Fisheries Station^a in 1966 (Pinyoying and Tongutai 1966) and continued intermittently (Gatesanchai and Suksucheep, 1970, 1971) until work with this species within the Inland Fisheries Division of the Department of Fisheries was transferred to the new fisheries station at Chacheongsao in 1976. Information on freshwater prawn farming in Thailand which has been published internationally has so far been restricted to FAO publications (Sidthimunka and Choapaknam, 1966; Kloke and Potaros, 1975). Our paper describes the present status of Macrobrachium farming in Thailand, the scale of which is largely the result of the work of the Chacheongsao Fisheries Station since 1976, which was built on the firm foundations of earlier work elsewhere in Thailand. Macrobrachium farming in Thailand now is already on a larger scale than in any other country except perhaps Hawaii.

^a Paper presented at the 11th Annual Meeting of the World Mariculture Society, New Orleans, Louisiana, U.S.A., March 5–9, 1980.

^b Department of Fisheries, Ministry of Agriculture and Cooperatives, Rajdamnern Avenue, Bangkok 2, Thailand.

^c FAO Project THA/75/008, c/o UNDP, P.O. Box 618, Bangkok 2, Thailand.

About 20 years ago, Koong Yai^b (Macrobrachium rosenbergii) supplies, caught in the central plain region of Thailand, were sufficient to supply local demand (Singholka, 1978). Indeed Rabanal (1975) states that Thailand exported freshwater prawns to Malaysia, Hong Kong, Singapore, Japan, USA, Italy and France. A fishery for this prawn existed in all the major rivers of the country and in the Songkhla Lake. Although Rabanal (1975) says that the catch per unit effort bycast net fisherman in Songkhla Lake had declined significantly from 500g/hour to 150g/hour, it is difficult to substantiate the commonly heard remark that the natural fishery for Macrobrachium rosenbergii has been and is declining rapidly, due to over-fishing, the construction of dams preventing migration and the pollution of estuarine areas. Total catch of Macrobrachium in Songkhla Lake did not decline between 1968 and 1978 but varied between a low of 56 tons in 1969 and a high of 131 tons in 1971, 101 tons being caught in 1978. Fishery statistics which show that the annual catch of freshwater prawns in Thailand peaked in 1974, but has declined since then (Table 1) include all species of Macrobrachium (Table 2). Since the greater portion of this catch is represented by Macrobrachium lanchesteri rather than Macrobrachium rosenbergii it is not possible to quantify the decline in the fishery of the latter. Koon Yai now has to be imported, mainly from Burma (Anonymous, 1979d), even to partially satisfy local demand, while a demand for exports from Thailand by foreign countries remains unsatisfied (Anonymous 1979c). These have been the stimuli to the rapid growth of freshwater prawn farming in Thailand.

The early laboratory experiments of Ariya Sidthimunka in 1950's in Bangkok on the rearing of larval Macrobrachium rosenbergii^a, were taken up by Shao-Wen Ling in Malaysia who finally succeeded in metamorphosing the first hatchery reared freshwater prawn in June 1962 (Ling, 1977). Sufficient juvenile prawns for stocking ponds were not produced by Ling until 1963. This achievement was paralleled in Thailand in 1966 at the Songkhla Fisheries Station (Brohmanonda and Pongsuwan, 1966-7) at about the same time as work on this topic began in Hawaii (Fujimura, 1966). The work at Songkhla and the success in larval rearing at the Bangkhen Fisheries Station (Gatesanchai, 1970) formed the basis for establishing a hatchery specifically for producing juvenile freshwater prawns for government distribution to farmers at the Chacheongsao Fisheries Station, which became fully operational in 1977. Small commercial hatcheries began to appear in 1973 and there were at least seven of these two years later (Rabanal, 1975). Juveniles produced by these hatcheries were used for stocking ponds, a practice that had probably existed since time immemorial through the use of wild caught juveniles (Sidthimunka and Choapaknam, 1966).

^a Now the site of the National Inland Fisheries Institute, Bangkhen

^b Koong = prawn; Yai = Giant

2. HATCHERY PRODUCTION

Currently there are two government funded freshwater prawn hatcheries in Thailand. Post-larvae are still produced in the far south at the Songkhla Fisheries Station on an intermittent basis, mainly for stocking in ponds in the 616 750 rai (98 680 ha) brackishwater lake there but also in ponds in the surrounding area. A little over 1.1 million post-larval Macrobrachium rosenbergii have been produced at this station since 1970. However, the major thrust in stimulating the expansion of freshwater prawn farming in Thailand centres on the Chacheongsao Fisheries Station, situated some 70km east of Bangkok. This station is unique in Thailand in being solely devoted to the production and distribution of post-larvae of one species (Macrobrachium rosenbergii) throughout the country and with training and extension work in larval and post-larval rearing. The high level of interest in the work at this fisheries station can be gauged by the fact that the number of visitors it receives in organised parties alone currently exceeds 10 000 per year. In addition to government hatcheries, the number of small or ‘backyard’ hatcheries has grown to over 30 and there are currently 3 large commercial hatcheries. The estimated current and potential output of these hatcheries is summarised in Table 3. Current output exceeds 32 million post-larvae per year from existing hatcheries while potential output nears 100 million, without taking into account other private hatcheries which are in the planning stage.

All the hatcheries, except that at Songkhla and the new one planned for the same region under an ADB financed aquaculture loan, are within 150 km of Bangkok, mostly to its east and south-east. Most of the ‘backyard’ hatcheries are on inland rather than coastal sites. Post-larvae from private and government sources are transported by road, rail and air throughout Thailand. Normally, long road journies will be made overnight, sometimes for distances as far as 800 km. Inflated plastic bags containing water are invariably used; the Chacheongsao Fisheries Station has developed a system used on long journies which stacks plastic bags containing post-larvae on shelves in a closed truck, temperatures being kept low by blowing air over ice cubes by means of a battery operated fan. This station has, since its first full year of operation (1977) distributed over 6 million juveniles to farmers by October, 1979 and had placed over one million in natural waters. Production from this station is expected to be 20 million per year within 2 years.

^a Personal communication, 1979. Boon Indrambarya, National Research Council, Bangkok.

The existence of at least 37 Macrobrachium hatcheries in Thailand means, almost by definition, that at least 37 different larval rearing techniques are used; however, some generalisations are possible. The ‘clear-water’ technique is invariably employed although some hatcheries previously used ‘greenwater’. A salinity of 12ppt, sometimes reduced gradually before and after metamorphosis, is used with water changes after the first ten larval rearing days varying from 10% – 50% daily, depending on the availability of seawater. A wide range of larval feeds are used, including Artemia nauplii and prepared feeds consisting of mussel flesh, fish flesh, whole egg custard, egg yolk custard and soybean curd (Tufu), alone or in combination. One ‘backyard’ hatchery maintains its larvae entirely on a diet of a cladoceran (Moina spp.). The high cost of importing brine shrimp cysts is likely to be reduced in future in Thailand, now that local inoculations of Artemia are successfully producing ‘Thai’ cysts (Tunsutapanich, 1979). The number of days to metamorphosis in Thai freshwater prawn hatcheries varies widely but each batch of larvae is normally completed within one month. Some berried female prawns are obtained from natural waters but most of the larger hatcheries either maintain their own broodstock or draw from the ponds of farmers which they have previously stocked with juveniles. The easy availability of berried females has enabled hatcheries to concentrate more on maximising output of post-larvae per tank than on maximising survival rate per se. It is estimated that average survival rates of 10% – 50% are achieved in the private hatcheries and 30% – 50% at the Chacheongsao Fisheries Station. The containers used for larval culture are varied. Most custom-made tanks are constructed in concrete, which is cheaper in Thailand than plastic. Many other containers are used however, including modified concrete drainage pipes, earthenware jars used for domestic water storage, known colloquially as ‘Klong pots’^a. Water depths of 75cm are normally used but some hatcheries economise on water consumption and labour by using a water depth of only 25cm.

The ‘backyard’ hatcheries are mostly run as a part-time occupation and, in any case, normally employ family labour only. The highest operational cost of the inland ‘backyard’ hatchery is seawater, which is sometimes fetched by the operator but frequently bought from a supplier at a 1979 cost of US$10/m³. Most ‘backyard’ hatcheries use tap water as their source of freshwater although some use klong^a water. The larger hatcheries mostly use well water. Singholka (1978), giving further details of the methods used in ‘backyard’ hatcheries, estimates that the cost of seawater represents 80% of operational costs, with 20% being accounted for by feed and power. The cost of constructing a family-run hatchery for Macrobrachium rosenbergii obviously depends on its size but many start up with capital expenditure as low as US$2000. At the other end of the scale, the largest commercial freshwater prawn hatchery existing in Thailand in 1979, which complies with the highest international standards of hatchery construction and has a potential output of 30 million post-larvae per year, required a total capital input of US$500 000. This hatchery employs a manager, three biologists and seven workers, with a total labour cost estimated to be about B540 000 (US$27 000) annually.

^a Klong = canal

Post-larvae from government hatcheries were originally distributed free within 1–3 weeks of metamorphosis and it has been this policy which has encouraged the rapid growth of Macrobrachium farming in Thailand. A price of 25 satangs each (US$12 50/1 000 juveniles) is now being applied selectively to those farmers deemed to be able to pay. The freshwater prawn juveniles sold by private hatcheries very from 35–75 stangs each (US$17 50/1 000 juveniles) depending on profit margins and on the age of the juveniles sold, many small hatcheries retaining them in nursery tanks for up to one month after metamorphosis. The saleable value of freshwater prawn post-larvae in Thailand is therefore currently comparable to international prices (Table 4), while capital and operating costs are lower.

As in freshwater prawn hatcheries in other countries, the problems encountered in larval rearing center round site selection, water supply and management. Predation has been observed and mortalities (more accurately referred to as losses) occur without the specific cause being detected. The principle cause of such losses is often human mistake. According to site, the reliability and quality of both freshwater and seawater may be questionable. Although the large government and private hatcheries treat incoming water by sedimentation, filtration and/or chemical treatment, the smaller units generally use raw, simply screened, water. Improvements in water quality using simple and cheap techniques have recently been made at the Chacheongsao Fisheries Station and methods of surveying new sites to detect the availability of natural filter media have been demonstrated (Cansdale, 1979).

3. GROW-OUT

Current statistics show that there are at least 228 farms in Thailand where Macrobrachium rosenbergii is grown in ponds (Table 5). Of these, six have a water surface area of 40rai (6.4ha) or more. One farm may challenge Hawaii's claim to have ‘the largest (freshwater) prawn farm in the world’ (Anonymous, 1979a), by having a water surface area of 250 rai (40ha). The total area of ponds committed to freshwater prawn rearing in Thailand is over 1 540 rai (246ha). This contrasts with the 47ha under Macrobrachium under culture in Hawaii in 1977 (malecha, 1979) and the estimate of 246ha there in 1980 (Anonymous, 1979f). Although annual production rates of 350–400kg/rai/year (2 188-2 500kg/ha/year) are achieved in some farms, the average production rate is 200kg/rai/year (1 250kg/ha/year). Two of the larger farms are not in full production yet and the estimated annual production of Macrobrachium rosenbergii from ponds in the country in 1979 was 246 tons (Table 6) with a retail value of approximately ฿55 million (2.76 million). The output of freshwater prawns in 1978 in Taiwan, by comparison, was 34 tons (Anonymous, 1979g). Hawaiian Macrobrachium farms produced 51 tons in 1978 and were projected to produce 405 tons in 1980 (Anonymous, 1979k).

Macrobrachium farms exist in at least 40 of the 72 provinces in Thailand (Figure 1), with the largest numbers being in the Central Plain area particularly in Chacheongsao, Bangkok and Rachaburi provinces and the greatest area being in Chacheongsao, Pathumthani, Samut Prakarn and Chonburi provinces. Invariably the ponds are constructed by pushing excavated material to the sides to form bunds. In general, ponds in the smaller farms are of simple construction with screened pipe inlets and outlets; very few of the farms have concrete sluice gates or monks. Inlets are often below pond water level and in many farms ponds are supplied sequentially with water. The water supply is not normally filtered other than by screen and is taken from wells, rivers, and lakes, but mostly from irrigation klongs^a. Water is obtained by gravity or through the use of fossil fuel energy. Some farms however use the traditional means of water movement in Thailand, utilising water or wind power. Normally only evaporative losses are replaced with an occasional (e.g. bi-monthly) flushing of the ponds. Regular flow-through is not normally practised. Severe bund erosion, especially in some areas, is commonly seen.

Pond construction costs vary from ฿10 000/rai ($3 125/ha) for simple ponds to ฿25 000/rai ($7 813/ha). One of the largest freshwater prawn farms in Thailand has invested a total of ฿40 million ($2 million) in its venture. This figure includes land and construction costs for 40ha of rearing ponds, a modern hatchery with a potential output of 30 million post-larvae per year, a feed mill, cold storage facilities and refrigeration trucks (Anonymous, 1979c) together with some working capital. Of the $2 million total investment, $550 000 was provided through a loan from the Industrial Finance Corporation of Thailand. Land costs vary between ฿10 000 and ฿15 000 per rai ($3 125-4 688/ ha).

The small farms usually employ family labour for operation. Some of the larger ones are owned by farmers growing other crops, such as pineapple and rice or by rice mill owners who supply most of the labour for Macrobrachium farming through part-time usage of existing staff. It is therefore difficult to assess labour costs generally. One large farm which is not run by family or existing staff employs 2 managers and 6 labourers who care for a water surface area of 250 rai (40ha) plus an associated feed mill. A typical salary for a fish farm manager in Thailand is about ฿8 000/month ($4 800 per year) in 1979, while labour costs about ฿1 500/month ($900 per year).

Ponds are stocked at 5/m² – 20/m², the lower stocking density achieving a greater proportion of market sized animals under the management systems in use now. Post-larvae are usually stocked within two weeks of metamorphosis but some of those obtained from small private hatcheries are four or more weeks old at stocking. Management systems vary but typically, after six months at optimal rearing temperatures (Table 7), ponds are seined to remove market sized animals (10 – 15/kg, head on, shell on), using a 3.81 – 5.08 cm mesh (stretched) monofilament net. Prawns below market size are either left in the same pond or placed in a new one. A further intermediary culling may take place before the pond is totally harvested by seine or draining after eight months. Ponds are then dried, treated with lime at 1 ton/ha and with rotenone or similar chemicals before re-stocking.

Broiler chicken starter pellets are commonly used as feed for freshwater prawns in Thailand but the FCE achieved through their use in ponds is not available. A wide variety of other feeds is also used, including chopped fish and broken rice - rice bran - fish meal mixtures with or without vitamin premixes. Whole chicken originating as mortalities in associated poultry enterprises and calf bones having adhering flesh remaining are also in some cases placed in ponds as an additional source of feed. The broken rice - rice bran - fish meal mixtures are cooked, to gelatinise the starch and improve water stability, often at the pond bank, on a daily basis. Food is normally presented twice per day at rates depending on demand. Broiler starter pellets cost ฿8/kg ($400/ton) in 1979. Freshwater prawn rearing ponds are not normally fertilised. The scale of freshwater and marine shrimp farming in Thailand is generating interest in feed production by feedstuff mills who may be expected to build on research experience in this topic (New, 1976).

^a Klong = canal

The operators of Macrobrachium farms vary in origin. Many farms are part of or substitute for what was originally a fish farm. Some are owned by rice mill owners, some by local government officers, yet others are being developed by individual and corporate entrepreneurs. Many owners have no previous experience in aquaculture although most have devoted considerable time and energy to desk study and practical observation in Thailand and elsewhere.

Although most Macrobrachium ponds are protected by low fences of nylon netting around their perimeters and by coarse screening of water intakes, all the types of predation normal to tropical inland aquaculture, particularly that from carnivorous fish, occur. Of the predators, man is by far the most important. Problems associated with the quantity and quality of water available are also common since most farms are supplied with surface water in areas where intensive agriculture is practised and where competitive demands exist.

4. THE MARKET

Harvested freshwater prawns grown in Thailand are marketed whole (shell on), uncooked, in selected market places in the towns, particularly in Bangkok, and through direct and indirect sale to restaurants and hotels, where most of the Macrobrachium rosenbergii is now consumed in Thailand. Freshwater prawns are normally transported and displayed for sale on ice. Some are transported to the point of sale by the farmer or sold at the farm gate. Prawns are not normally sold live. There is at least one combined hatchery, farm and restaurant. In other cases, wholesalers collect from a number of farmers. In 1979, farm gate prices for Macrobrachium rosenbergii were ฿150–200/kg ($7.50–10.00/kg) for whole, shell on, while retail prices were ฿200–250/kg ($10.00–12.50/kg).

Frequent comments, which are based on the observations of fishermen, farmers and fishery officers, are heard about the declining availability of Macrobrachium from natural waters in Thailand. However it does not seem possible to quantify this in terms of Macrobrachium rosenbergii alone. Fisheries statistics show that the catch of freshwater shrimp has fluctuated between 2 900 tons and 5 700 tons a year between the years of 1971 and 1977 (Table 1) but indicate a general decline recently. However this category in the statistics embraces many species of freshwater shrimps, including eleven species of Macrobrachium (Table 2). Of these, M. lanchesteri is the species most commonly found. This shrimp is sold in quantity at a small size (3–5cm) in all the local markets in Thailand at about ฿20/kg ($1.00/kg), whereas those markets which stock Macrobrachium rosenbergii are limited by availability and product cost. It is therefore reasonable to suppose that most of the freshwater prawns caught in natural waters are not Macrobrachium rosenbergii but other Macrobrachium spp. In this case the estimate we give in Table 6 of a current annual production of only 300 tons of M. rosenbergii from natural waters in Thailand may be as accurate as possible.

Similarly it is not possible to quote figures for the import or export of Macrobrachium rosenbergii since import/export data given in the Fisheries Record of Thailand does not differentiate between lobsters, marine shrimp and freshwater prawns. It is commonly stated however that freshwater prawns are imported from Burma and, to a lesser extent, from Bangladesh, to satisfy local demand. One source quoted an annual import from Burma of 300 tons/year (Anonymous, 1979c).

5. THE FUTURE

Technical improvement and business growth of Macrobrachium farming in Thailand is proceeding a pace. A comprehensive extension programme for farmers and fisheries officers is being run by the Chacheongsao Fisheries Station to improve hatchery and pond rearing techniques. This Royal Thai Government program is being assisted by UNDP/FAO. Research on Artemia cyst production, freshwater prawn nutrition and recirculation systems to reduce water consumption in hatcheries is being carried out at this station and similar work is being conducted by university researchers and private farms^a. Facilities at the Chacheongsao Fisheries Station are being improved so that the potential production rate of 20 million post-larvae per year can be achieved; in addition a site for a new government hatchery east of Bangkok is being sought. At present there is a waiting list of about 300 farmers registered at this station with a demand for 6 million post-larvae, a figure which would take a year to satisfy at current monthly output rates.

^a Personal communication, 1979. Piamsak Menasveta, Chulalongkorn University, Bangkok.

In addition to the expansion of government aid to pond farmers of Macrobrachium rosenbergii based on the Chacheongsao Fisheries Station, a new 20 million post-larvae per year hatchery is planned north of Songkhla Lake as part of a $14 million loan project for aquaculture development in Thailand financed by the Asian Development Bank. This hatchery will principally serve the development of pen culture for Macrobrachium in Songkhla Lake and supply ponds in the surrounding provinces.

According to sources in the Department of Fisheries of the Royal Thai Government (Anonymous, 1979b), up to 20 000 families of freshwater fish raisers may be interested in converting to freshwater prawn production. The government seeks to stimulate an increase in the total production of post-larvae of Macrobrachium rosenbergii in Thailand to 250 million/year within 5 years. This output, at present stocking levels and production rates, would be sufficient to raise production of farmed freshwater prawns in Thailand to over 4 000 tons/year. Improvements in pond management could push the potential production from this number of post-larvae to 10 000 tons per year.

There are also several plans for new commercial freshwater prawn farms and hatcheries. To date, all investment in this type of aquaculture has been of Thai origin but there may now be interest in investment from abroad, notably from Japan and the US. Extensive promotional privileges are extended by the Board of Investment of the Royal Thai Government to new commercial enterprises. Little governmental control is exercised over the establishment of new Macrobrachium farms and hatcheries. While this may be welcomed by some entrepreneurs, it spells out a possible danger signal for the future when competition for the available sources of suitable land and water may become acute and when water quality or disease problems experienced by one farm may affect its neighbours. Careful site selection is therefore, as always, of paramount importance (New et al., 1978). Aquaculture generally is an established form of business in Thailand; finance for freshwater prawn farming is available for existing businesses of other types. The smaller farmer, however, has difficulty in raising enough loan capital for substantial expansion because freshwater prawn farming is still a young industry. It is hoped that the increased international knowledge about the achievements of Thai Macrobrachium farming, and its potential for development, generated by this paper and by the forthcoming international conference on freshwater prawn farming in Bangkok (Anonymous 1979e), may encourage foreign as well as local investment in a promising industry.

6. ACKNOWLEDGEMENTS

The authors wish to acknowledge the assistance given to them in the preparation of this paper. In particular, our thanks to Boon Indrambarya, Ariya Sidthimunka, Umpol Pongsuwanna, Pairoj Brohmanonda, Cherdchan Amatyakul, Suman Swegwan, Mali Boonyaratpalin, Peng Tham Trachai and the staff of the library of the National Inland Fisheries Institute, Bangkhen, Thailand. Thanks are also due to Teera Jang Ploy who prepared the figure used in this paper.

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Tunsutapanich, A., 1979. Cyst production of Artemia Salina in salt ponds in Thailand. FAO Working Paper, Ref: THA/75/008/79/WP/9.

Varikul, V., 1971. List of shrimps in Thailand. In: Annual Report Unit of Taxonomy, Inland Fisheries Division, Department of Fisheries, Bangkok, Thailand: pp. 163–166.

Wongsonnuk, S. and Parnichsuka, P., 1978. Experiments on culture of giant freshwater prawn (Macrobrachium rosenbergii) in nylon net enclosure. Annual Report of the Songkhla Fisheries Station, Thailand: 140–144.

Table 1. Annual catch of all species of freshwater prawns in Thailand (1971–77)^a.

^a Source: Fisheries Record of Thailand, Department of Fisheries, Ministry of Agriculture and Cooperatives, Royal Thai Government.

^b $1.00 = ฿20.00

Table 2. List of Macrobrachium spp. found in natural waters in Thailand.

^a Varikul, 1971

Table 3. Estimated output of post-larval Macrobrachium rosenbergii from hatcheries in Thailand, 1979.

^a Not yet built.

Table 4. Value of post-larval freshwater prawns produced in hatcheries in Thailand and other countries, 1979.

^a “Technical operating cost” (Aquacop 1979)

^b “Overall cost” (Malecha, 1979)

^c “Price” (Anonymous, 1979g)

^d “Price” for minimum quantities of 1 million (Anonymous, 1979h)

^e “Rate” for post larvae (Anonymous, 1979i)

^f “Rate” for juveniles, depending on quantity supplied (Anonymous, 1979i)

^g ‘Price’ (Anonymous, 1979j)

^h Chacheongsao Fisheries Station

ⁱ Private hatcheries

^a Farms supplied with juveniles by or known to the Chacheongsao and Songkhla Fisheries Stations only; actual number and area of farms is undoubtedly greater than the above.

^b 1 rai = 1 600m²; 1 hectare = 6.25 rai.

^c of the total of 1 542 rai, 1 332 rai is in full production; the other 210 rai represents farm not fully stocked yet because of shortage of juveniles.

Table 6. Estimated consumption of Macrobrachium rosenbergii in Thailand, 1979.

^a Anonymous, 1979c

Table 7. Example of water temperatures in Thailand^a

^a °C

^b Bangkhen Fisheries Station (now National Inland Fisheries Institute) is in the Centrel Plan area, near Bangkok

^c Ubolratana reservoir is in the North Eastern area of Thailand