Shrimp Culture In Thailand
John Hambrey and C Kwei Lin
Asian Institute of Technology
1. Status and Development
Thailand is now the world's largest producer of farmed shrimp, with production in 1994 /5 of 240,000mt with a farm gate value in excess of US$1.6 billion. The number of farms has increased rapidly in recent years, and there are now over 20,000, employing 100,000 people (Tavarutmanakeel and Tookwinas 1995). The industry supports a major processing and input supply industry, including feed manufacture.
Extensive aquaculture has been practiced for many years in Thailand. Conditions are ideal: 2,700 km of coastline, much of it sheltered, warm, calm seas and abundant natural seed. Originally dykes were built round rice fields, sluice gates installed, and wild shrimp seed entered the fields and were retained. Production was mainly of Penaeus merguensis in the dry season and Metapenaeus spp in the wet season. In the 70s growing demand stimulated the use of supplementary feeds and a move to semi-intensive production. In the mid 80’s a combination of technical and economic factors allowed the development of increasingly intensive systems using hatchery reared seed and formula feeds. Intensive shrimp farming took off in 1988/9, and although there have been significant local problems, overall production increased from 33,000 mt in 1987 to 240,000 mt in 1994/5. The trend is illustrated in fig 1.
Productivity has also increased steadily with average national yield (extensive + intensive) rising from 0.4mt/ha in 1986 to 3.2mt/ha in 1994 (fig 2)
The geographical focus of shrimp farm development has shifted steadily since the mid 80’s. Intensive shrimp farming began mainly in the upper Gulf of Thailand, south of Bangkok, in areas previously devoted to extensive aquaculture and salt pans. In 1989 this area suffered severe losses from disease and unexplained mortality. The focus for development then shifted to the Eastern coast. This area experienced mixed success, with many producers suffering from poor water or pond soil quality. In the early 90’s the focus shifted south to the east coast of the Thai peninsula where success has been generally more consistent. In recent years most new developments have taken place on the Andaman Sea (SW) coast. It is worth briefly considering the reasons for this progression.
1) Decline in the Upper Gulf
The serious losses which occurred in the upper gulf were related to a variety of factors including:
- shallow muddy coast, long, narrow supply canals and inadequate water exchange;
- self pollution as a result of poorly designed water supply and effluent systems;
- upstream pollution from agriculture, domestic sewage, industry;
- erratic salinity - seasonal gulf currents and major rivers;
- lack of experience
In addition, the booming industry of the area pushed up land prices, and encouraged sale and move to better areas.
2) Mixed Experience on the East Coast
Although many farmers were and are highly successful in this area, conditions were often far from ideal. In particular many farmers suffered from:
- siting on shallow muddy bays and estuaries;
- variable salinity;
- mangrove and acid sulfate soils;
- low pH; high iron and aluminium;
- pesticide runoff from fruit plantations?
- limited experience.
3) Better Performance in the South
Conditions are generally more favourable in the South, on both sides of the peninsular, and success has been greatest in these areas for a variety of reasons:
- better soils - mainly rice paddy, coconut plantation and upper mangrove;
- straight coastline, open sea, deep water;
- high tidal range, especially on the Andaman Sea coast;
- stable salinity;
- little upstream pollution;
- experience gained further north
It remains to be seen whether these initial advantages can be consolidated into sustained output through better resource management.
2. Land Use, Resources, Environment
There is increasing concern in the West and to some extent in Asia, about the impact of shrimp farming on coastal resources and the environment. In particular there is widespread concern about the impact on mangrove.
Initial developments (upper Gulf) took place mainly in existing extensive ponds, salt pans, and intertidal mud flats and degraded mangrove. Developments on the East (Gulf) coast took place in mangrove, estuarine, paddy and fruit tree zones. In the SE most of the land converted was originally rice paddy, but coconut plantation and mangrove were also used. The most recent developments on the Andaman sea coast have taken place in rice paddy and mangrove. In general, extensive production has been much more highly concentrated in the intertidal mangrove areas, with newly developed intensive farms mainly taking place in the supratidal zone. Fig 3 shows the type of land which has been converted for intensive shrimp farming, and fig 4 shows conversion for extensive farming, based on a comprehensive survey conducted in 1994.
Overall, about 20% of the original mangrove areas are now used for shrimp farming, though only a part of this has been the result of direct conversion of primary mangrove (i.e. much of the mangrove area was already reclaimed for agriculture or degraded through over-exploitation for wood and wood products). Furthermore, a large part of this conversion can be attributed to extensive, rather than intensive shrimp farming. Fig 5 shows the overall trend of mangrove destruction and the total area of land used for shrimp farming. It is apparent that the major phase of mangrove destruction took place before the development of intensive shrimp farming.
3. Socio-economics and Industry Structure
Shrimp farming in Thailand is highly dispersed and decentralized. Although several large companies are involved in the industry, the 20,000 or so small farmers produce 70% of output. The average size of intensive farms is a mere 1.6ha, usually comprising 1-2 ponds. 78% of intensive farms are owner operated. There are only around 40 large farms (>30ha).
Typically farms may be categorized as follows:
- Small family run with 1-2 ponds (0.2-2ha) using family labour (dominant type);
- Medium sized family run farms (3-9 ponds) with some hired labour;
- Medium/large farms (10-30 ponds): owner or professionally managed, hired labour;
- Large farms with >30 ponds established as corporations, managed and operated by hired professionals and labour;
Most of the 2,000 or so hatcheries are also small scale, producing a few million post-larvae. In general they use very simple and adaptable technology: relatively small free-standing tanks and flexible hoses rather than complex fixed plumbing. Larger hatcheries which can afford to hold and condition broodstock supply nauplii to these smaller hatcheries. Some hatcheries may specialize in nursing post-larvae up to PL40.
Figure 6 shows the trends in the industry in terms of farm area and number of entrants. There are no obvious trends toward centralization. Indeed, the reverse may be true. Fig 7 shows the distribution of farm size for different regions of Thailand. The more recently developed areas have a higher proportion of small farms.
4. Management Practices
Pond soil management has become relatively standard with drying (typically for around 1 month), liming, application of rotenone or teaseed cake to kill predators. Substantial numbers of farms now screen intake water and store in a reservoir prior to stocking. During this time the water may be treated with chlorine (Calcium hypochlorite @ 250-300kg/ha) to kill potential pathogens and/or carriers. During the production cycle water is usually treated with lime (an average of more than 10t/ha in intensive ponds) and a variety of other products in more closed systems (see below).
There has been a significant trend in the last few years in favour of semi-closed or closed systems with very little water exchange. In the traditional open system, water turnover rate often amounted to 20-30% a day, and up to 50% in some cases in the final stages of production. Semi closed systems only exchange moderate quantities of water in the last month of production. Closed systems dispense with water exchange almost entirely, and rely on heavy aeration and careful pond water management to maintain acceptable growing conditions. In some closed systems water may be recycled through storage/settling ponds during the final phase of production, while in others there is no water exchange, the farmer relying upon a combination of natural processes (plankton and bacterial growth) and the use of a variety of chemicals to maintain water quality. Although many farms now have the capability to recycle (i.e. they have water storage ponds) relatively few actually do this as yet (7% in the NACA/ADB survey).
In the south of Thailand at the present time there are no rules regarding water exchange. If disease is widespread then water exchange is reduced to a minimum; if pond water quality becomes poor and does not respond to treatment, water is exchanged.
Water treatments include use of Calcium chlorite to kill Oscillatoria and dinoflagellates ( @ 3-6kg/ha), pumping through a rice bag or using plankton eating fish to remove Oscillatoria and concentration and pumping out of Microcyctis (Pratungtum and Tookwinas 1996). Formalin may also be used to reduce plankton and pathogens in ponds.
Related to the generally reduced water turnover rates has been an increase in the intensity of aeration. The early farms typically used around 12HP/ha; farms with restricted water exchange may now use up to 50HP/ha. The positioning of aerators has also changed in some cases. The peripheral location favouring water circulation may be inappropriate in more intensive systems where the high power causes excessive water velocity and concentration of wastes - and shrimp - in the centre.
There is currently some disagreement about the intensity of aeration with some commentators favouring reduced use in the afternoon to reduce phytoplankton bloom (Pratungtum and Tookwinas 1995) and others favouring maximum use to encourage decomposition and mineralization of wastes.
There is now a wealth of products on the market in Thailand for water treatment and conditioning, including various bioremediation products based upon bacterial inocculi. Although there is great interest in these products, most were originally developed for freshwater environments (sewage treatment etc.) and may be less effective in brackish or saline water. To date there has been no convincing demonstration of their efficacy, although there are some promising indications. The cost of these products remains a major constraint. A simpler approach adopted by many farmers in Thailand has been to add sugar to the water in very intensive systems. This provides a carbon substrate for desirable (nitrifying and denitrifying) bacteria which my help to reduce ammonia and nitrite levels and improve water quality.
A recent survey (NACA/ADB) showed that 67% of extensive, and 65% of intensive shrimp farmers had suffered from disease outbreaks, with the intensive farms suffering at least 1 outbreak per year (0.7 for extensive). The financial loss attributed to disease amounted to US$6,629/ha/yr. Most farmers are unable to identify the disease, and most treatments fail.
The most important diseases include luminescent bacteria (Vibrio harvyii), and a variety of viral diseases including yellowhead, and whitespot (SEMBV). Red body coloration is associated with several diseases including whitespot. Yellowhead disease caused severe losses in 1992/3. Recently "red body" (probably whitespot) has caused widespread problems.
It seems likely that wild planktonic shrimp are a significant source and spreading agent for several of the diseases including whitespot and yellow head (Flegel 1995, Chanratchakool et al 1995. Exclusion (through screening and/or recycling) or elimination of carriers (e.g. using chlorine, BKC or formalin) may therefore be effective preventive measures. Lesser use of fresh feed which may also spread infection may also be appropriate and has been adopted by many Thai farmers. Antibiotics are generally ineffective but are still widely used.
6. Secrets of Success
Thailand has, so far, been the most successful farmed shrimp producer in the world. This success is based upon a wide variety of factors which may include the following:
- an extensive and suitable coastal environment;
- previous experience in extensive coastal aquaculture;
- wild seed available (at first);
- a well established commercial formula feed industry (related to the chicken industry) able to provide pelleted supplementary feed in the semi-intensive phase (Csavas 1995);
- highly developed distribution and marketing systems;
- established processing capacity related to the capture fishery;
- established support industries (e.g. pumps, tanks etc.)
- availability of investment capital, especially in the late ‘80s;
- hatchery technology developed elsewhere, tested by Thai DoF, and waiting to be applied;
- demand for seed from semi-intensive producers coinciding with availability of reasonably skilled personnel and investment finance : small scale hatchery entrepreneurial boom;
- excellent communications to major established export markets (Japan, US, Europe);
- part of emerging Asian markets (HK, China, Malaysia, S.pore, Thailand)
This is a formidable cocktail and goes some way to explaining the phenomenal growth of the industry.
7. Current Problems
The question is, can this success be sustained? There are several worrying trends or developments. It looks as if production in 1995 was similar to that in 1994. Production in the last quarter of 1995 and the first quarter of this year was down, with serious outbreaks of red body disease.
There are several possible explanations for these problems. Firstly, the very high price of artemia cysts last year caused a substantial shift to formula feeds for larval rearing, and this may have affected larval quality. Related to this was a push to sell larvae at an earlier age to reduce feeding costs. As a result there was a widespread tendency to stock young and weak seed at very high densities (commonly >100PL/m2), survival was low and disease spread.
Secondly, the hatcheries continue to use large doses of antibiotics. This may reduce the resistance of the larvae to disease once they are exposed to less sterile conditions. The rampant use of chemicals on the farms may also have stressed stock and reduced resistance to disease.
Another (and related) problem concerns the continuing haphazard development and the scant attention paid to water supply and effluent systems. A recent survey (NACA/ADB 1995) suggested that the average shrimp farmer in Thailand has another 34 within 3km, and shares a water supply with 20 others. 30% of farmers surveyed discharged their effluent to a common supply/drainage canal. The implications of this for water quality and the spread of disease are obvious.
A problem of less immediacy to the average farmer, but nonetheless potentially catastrophic, is the poor image of shrimp farming in the US and Europe. It is widely seen as environmentally destructive (especially of mangroves) and not sustainable. This may have direct impacts in terms of moves to ban or limit trade in certain shrimp products, or indirect impact in terms of demand and product price.
Given the will, most of these problems can be tackled, and some may even be turned to the advantage of some.
Seed quality can and should be improved. Specific Pathogen free (or low) seed certification (screening with DNA probe) is possible. Treatment of seed with formalin (100ppm) prior to stocking can reduce disease incidence. Challenging of seed, as a test of quality can also be done. Extended nursing of Pls prior to stocking is undoubtedly beneficial in terms of subsequent survival.
The further development of semi-closed or closed systems and wastewater treatment should help isolate farms from disease while at the same time minimizing waste and pollution.
Broodstock domestication and genetic improvement is quite possible, but has so far been uneconomic. This is likely to change. The use of other species, or alternate cropping may also reduce disease problems.
But perhaps more important than any of these technical possibilities is the need for improved organization, planning and development within the industry. The major crisis facing the industry is not technical constraint but disease and water resource management. Farmers themselves need to get together to identify water supply and effluent problems and improve them where possible (there are some signs tht this is beginning to happen. Government and development banks should also take a proactive role in this, as they have always done in the case of irrigation for agriculture.
In addition there is a need to identify those areas of mangrove of particular value in coastal protection, as nurseries for commercial fish and shellfish species, and of exceptional biodiversity or conservation interest, and apply much stricter protective measures. Ideally this should be done in parallel with the above, to minimize potential conflict.
Finally, there is real potential for the launching of a quality labelling initiative, related to both on farm production management practice, and district or regional aquaculture development planning. Only if shrimp farmers can demonstrate that shrimp farming is environmentally friendly - in terms of minimal pollution and habitat destruction - will they continue to attract premium prices for their product. These initiatives should in turn reinforce the needs for improved management and technology as noted above.
Csavas I 1995. Development of Shrimp Farming with Special Reference to Southeast Asia. Paper presented at Indaqua ‘95 Exposition of Indian Aquaculture, 27-30th January 1995, Madras, India
Flegel, T W 1995. Shrimp Health Management and the Environment. Paper presented to the Workshop on Aquaculture Sustainability and the Environment, Beijing, October 1995. NACA/ADB
Phillips, M J, C Kwei Lin and MCM Beveridge,1993. Shrimp Culture and the Environment: lessons from the worlds most rapidly expanding warmwater aquaculture sector. Environment and Aquaculture in Developing Countries. ICLARM Conference Proceedings No 31, 359p,Manila, Philippines
Tavarutmaneekul and Tookwinas 1995. Aquaculture Sustainability and the Environment. Thailand Study Report. NACA/ADB
Chanratchakool, P. J F Turnbull, S Funge-Smith, and C Limsuwan 1995. Health Management in Shrimp Ponds (second Edition). Aquatic Animal Health Research Institute, Department of Fisheries, Kasetsart University, Bangkok
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