SOCIAL AND ECONOMIC IMPACTS AND MANAGEMENT OF SHRIMP
AMONG SMALL-SCALE FARMERS IN THAILAND AND VIETNAM
Pornlerd Chanratchakool1 and Michael J. Phillips2
1Aquatic Animal Health Research Institute
Department of Fisheries
Kasetsart University Campus
Jatujak, Bangkok 10900, Thailand
2Network of Aquaculture Centres in Asia-Pacific
PO Box 1040,Kasetsart Post Office
Bangkok 10903, Thailand
Chanratchakool, P., and M.J. Phillips. 2002. Social and economic impacts
and management of shrimp disease among small-scale farmers in Thailand
and Vietnam. p. 177-189. In: J.R. Arthur, M.J. Phillips, R.P. Subasinghe,
M.B. Reantaso and I.H. MacRae. (eds.) Primary Aquatic Animal Health Care
in Rural, Small-scale, Aquaculture Development. FAO Fish. Tech. Pap. No.
Shrimp farming in Thailand is dominated by small-scale farms, which make
up around 80% of the total number. Whilst shrimp aquaculture has contributed
to income generation among coastal communities, disease outbreaks have
caused significant economic losses to farmers and the country in recent
years. Outbreaks of white spot syndrome virus (WSSV) and yellowhead virus
(YHV), as well as bacterial diseases which struck later in 1997, led to
the overall shrimp production of Thailand being reduced by 30% (from 210,000
to 150,000 mt). These diseases had a serious impact on all farmers, especially
small-scale farmers whose main income was derived from shrimp farming.
Moreover, at least 60% of small-scale farmers are thought to have become
indebted to banks due to production lost as a result of shrimp disease.
This paper discusses some of the impacts of disease outbreaks on small-scale
farmers and reviews the strategies adopted by farmers to manage risks
associated with shrimp disease.
The shrimp farming situation in Vietnam is very different from that in
Thailand, as shrimp farming is mainly low input and extensive. Shrimp
farming also provides an important source of income in some coastal areas
and has potential to contribute to poverty alleviation among coastal communities.
A project supported by the Australian Centre for International Agricultural
Research (ACIAR) looked at the impacts and management of shrimp disease
problems among extensive farms in Ca Mau Province of the Mekong Delta,
as part of a project for improving the social and economic returns to
farmers from "mixed shrimp-mangrove" farming systems. The households
in the project area were primarily dependent on aquaculture and capture
fishery as the main source of family income, the majority being dependent
primarily on shrimp aquaculture. The average household income in 1996
was 12.08 million Dong/household/yr, equivalent to around US$1,000 at
1998 exchange rates), or 2.4 million Dong/person/yr (US$170/caput/yr).
Poverty thresholds as quoted by the United Nations Development Programme
(UNDP) in 1995 were around 1.1 million Dong/person/yr. An estimated 40%
of households were below this threshold, showing a significant poverty
problem in the area. Shrimp culture provides an opportunity to improve
incomes and contributes to poverty alleviation, although effective management
to reduce risks associated with disease outbreaks is required. Disease
outbreaks severely affected shrimp yields in the Mekong Delta area from
1996, leading to negative social and economic impacts on farm households,
including reduced incomes and increased debt. In 1997, mass mortalities
occurred four times (in January, June, July and October), and were associated
with high prevalence of WSSV and adverse environmental conditions associated
with poor water and soil quality. The disease problem was also compounded
by the low educational level of most farmers, farmer inexperience with
aquaculture, and lack of access to technical advice and to capital to
invest in farm improvements and risk-reduction measures. The implementation
of technical recommendations for reducing disease risk is closely interlinked
with educational, institutional, social and economic conditions. In particular,
better educational opportunities, more flexible and accessible credit
arrangements, and greater access to regular technical support are key
factors in determining the willingness and capacity of farmers to implement
farm-level risk management strategies. In view of the lack of technical
support in the area, much closer co-operation among farmers, building
on existing farm groups, is also important to promote effective self-help
and extension of support.
This paper gives information on the social and economic impacts of disease
on small-scale shrimp farms in two contrasting environments; the first
in Thailand, which is the world's major shrimp-producing country; and
the second in Vietnam, where shrimp farming is mainly low input and extensive.
The case in Vietnam is particularly relevant to the topic of this consultation,
as it deals with the social and economic impacts of disease on a poverty-focussed
project in the Mekong Delta and the development of management strategies
which are appropriate to the farmers' social circumstances and farming
SOCIAL AND ECONOMIC IMPACTS OF SHRIMP DISEASE IN THAILAND
Thailand, as the world largest shrimp producer since 1992, has faced
many disease problems, as well as other management-related problems. Shrimp
diseases are most serious, since they can cause losses from low (chronic)
levels up to acute (100%) mortalities. The production of Thai shrimp,
which was increasing every year, reached its highest level in 1994, when
250,000 mt were produced. Due to disease and management problems, production
started to decline, first to 225,000 mt in 1995 and then to 205,000 mt
in 1996. The major pathogens affecting the Thai shrimp industry are white
spot syndrome virus (WSSV), yellowhead virus (YHV) and bacterial diseases
(vibriosis). In 1997, another 30% decline in production occurred, only
150,000 mt of shrimp being produced in that year.
WSSV is the major cause of mortality in Thai shrimp farming. Many attempts
have been made to understand this problem and many recommendations aimed
at preventing disease outbreaks have been made. This concerted effort
by farmers and supporting institutions has resulted in an increased production
to 230,000 mt in 1998. Farm management strategies have been developed
depending largely on farming conditions, as indicated below.
Economic Impacts of Disease
White spot disease, caused by WSSV, has now been reported from most Asian
countries. It has also been reported as "red body," systemic
ectodermal and mesodermal baculovirus (SEMBV) and PJ-RV. The infection
will be referred to here as "white spot disease," since the
presence of white spots on the carapace is the most noticeable of the
When outbreaks first appeared, they were all associated with extremely
severe production and economic losses, and the virus appeared to be highly
pathogenic. If shrimp were exposed to enough of the virus, they would
die, regardless of the environmental conditions. Losses due to WSSV alone
were estimated at US$600 million in Thailand in 1997, and at over US$2
billion throughout Asia in the same year (Flegel 1998). Now, however,
infections appear to cause severe losses only if the shrimp are also suffering
from poor environmental conditions in the ponds. It is still not clear
if this change has been due to an alteration in the virus, the host or
to other factors, including the implementation of better management practices
by the farmers. The direct economic impact of the virus appears to have
Other estimates of economic losses due to shrimp disease in Thailand
include an estimated US$30.6 million from yellowhead disease in 1992 (Nash
et al. 1995), and US$650 million from all shrimp disease outbreaks in
1994 (Flegel et al. 1995). Flegel (1998) pointed out that YHV and WSSV
are currently the most serious diseases threatening the shrimp farming
industry in Thailand. Together, these two pathogens may be responsible
for the drop in shrimp production in Thailand from 250,000 mt in 1994
to 220,000 mt in 1995. At approximately US$8/kg, this represented a shortfall
of $240 million. However, this small difference in production is not a
true reflection of the full impact of these diseases. At that time, Thai
production was rising at approximately 20,000 to 30,000 mt per year, and
production for 1996 had been expected to rise correspondingly. The diseases
were thus estimated to have caused the loss of 70,000 mt of shrimp (around
40% of total production) in 1996 (Alday-Sanz and Flegel 1997). At a rough
estimate of $US3-5 per kg profit, this represents between $US210 and $US350
million in lost revenues. Also, these figures do not include losses in
related businesses such as feed production, processing plants and feed
raw material producers, and the income lost by labourers.
Socio-economics and Impacts on Small-scale Farmers
The socio-economics of small-scale farmers have been studied, although
the impacts of disease at the household level in Thailand are surprisingly
less well understood. Some information on the cost-profit of Thai shrimp
farming along the Gulf of Thailand was determined from a survey of 104
farms in Nakhon Sri Thammarat and Songkhla provinces (Nipanpong and Sidthimunk
1998). The survey split the farms into six groups depending on their area.
The first three groups were small farms (less than 1.6 ha) and represented
almost 90% of the total number of farms surveyed. There are a number of
important features that have implications for disease control and management
of shrimp aquaculture:
- These farms were arranged into three groups: (1) farms smaller than
0.5 ha (32%), (2) farms between 0.5-0.8 ha (35%) and (3) farms between
0.8-1.6 ha (33%).
- The cost-profit analysis for each group revealed that the least profit
(0.6 US$/kg) (38.5 Baht = 1 US$) was obtained by the smallest farms
(equivalent to US$725/farm/crop at this time).
- Sixty percent of the farmers in the group with the smallest-sized
farms had one to five years experience, whereas over 50% of the farmers
from the group with the largest-sized farms had more than five years
experience. This indicates that farmers with smaller farms were just
moving into this business and had limited experience with shrimp culture.
- More than 50% of the total number of farmers sampled learned from,
and followed the technology used by, their neighbours. Most farm owners
were between 41-50 years old and had a low level of education.
- The major source of income for 65% of the farmers came from shrimp
- The average mortality of shrimp reported in this survey was between
46-54%, and was mainly due to disease and management problems.
- During the survey period, farmers still achieved profits, since serious
outbreaks of disease started in 1996 and 1997.
The reduction of total production by 30% that occurred in 1997 was
estimated to have a value equivalent to US$600 million, a figure which
excludes losses in related businesses such as feed production, processing
plants, and feed raw material production, and in labour. When the
same losses were applied to the smallest farm group, a 30% production
loss was equivalent to a loss of around US$1,000/pond/crop. As 65%
of the farmers were reliant on shrimp as their main source of income,
it is not surprising that disease was reported to have serious impacts
on households involved in shrimp culture. This aspect needs to be
better understood, and some further information is given in the paper
by Adis Israngkura contained in this volume.
Management of White Spot Disease
One of the many problems associated with the management of viral
diseases is that there is increasing evidence that clinical signs
similar to those seen in white spot disease may occur in shrimp that
are not infected with WSSV. It would appear that if the virus is present
in a population, a rapid rise in mortalities is associated with environmental
deterioration. Most dead shrimp will either have no clinical signs
or will have the clinical signs typically associated with the viral
infection i.e., white spots. If the environment does not deteriorate,
it is unlikely that mass mortalities will occur. In some cases, chronic
low-level mortalities are seen with the shrimp showing signs of external
fouling, vibriosis or other conditions. Some of these animals may
also show white spots, but if the mortalities are low, the virus may
not be present. These findings emphasise the difficulty of correctly
diagnosing viral diseases based solely on gross clinical signs, and
the importance of environmental management as a means of controlling
economic losses due to disease.
Although a great deal of information is still lacking regarding these
very serious viral conditions, some general recommendations for their
control have been developed. Prevention has to be based on not only
maintaining a healthy environment, but also on keeping the virus out
of the system. For white spot disease, the most common route of infection
is through entrance with infected postlarvae (PL). However, in some
cases the virus enters the population with the incoming water or via
wild crustaceans. Outbreaks due to WSSV can be prevented by eliminating
potential vectors and screening intake water. However, serious outbreaks
can still occur in ponds stocked with infected PL. Using the polymerase
chain reaction (PCR) to screen for infected PL is one way to reduce
this risk (Flegel et al. 1997, Kasornchandra et al. 1997). The technique
is now used in many countries with varying results. PCR is very sensitive
and can, therefore, detect small numbers of the virus in individual
animals. However, the technique is not as effective where populations
are large and only a small number of individuals are infected. This
might explain why outbreaks still occur in ponds with PL certified
Since outbreaks of white spot disease often stem from infected PL,
elimination of such animals from the population before stocking can
reduce the likelihood of disease. Formalin, at a concentration of
150 ppm, can be used to treat PL for 30 minutes. After treatment,
weak and unhealthy individuals should be separated from actively swimming
shrimp and discarded. This technique successfully reduces the number
of infected PL stocked into ponds (Limsuwan 1997). However, if the
prevalence of infection is high, this technique may not be practical,
especially when climatic conditions fluctuate.
It is important to keep predators and competitors out of the pond.
Initially, the pond should be filled and the water treated with calcium
hypochlorite at 15 to 20 ppm active chlorine. After the pond is filled,
water exchange should be reduced to a minimum for at least the first
month after stocking. Water should only be exchanged when it is necessary,
not as a routine procedure. It is also important to ensure that the
incoming water is free from animals and has not been contaminated
by wastes from other farms. A reservoir is essential for treatment
of incoming water.
The main aim of low water exchange is to minimise contact with poor
quality or contaminated water from outside the farm. Partial recirculation
is the system of low water exchange most commonly used in Asia. When
water cannot be pumped into the farm, effluent from the production
ponds is first allowed to settle and may be treated before being mixed
with the water reserve. The reserve water is pumped from the external
water supply when conditions are suitable, or from an inlet reservoir.
In most partial recirculation systems, harvest effluents are not introduced
to the mixing reservoir, but are normally passed through a settlement
system before discharge (Chanratchakool et al. 1998).
Although, infections can spread between ponds on a single farm, when
more than one pond is affected with white spot disease it is usually
due to a common source of infected PL. None-the-less, unless it is
absolutely unavoidable, equipment should not be used in more than
one pond. If equipment is to be moved between ponds, it must be first
thoroughly cleaned and disinfected.
If an infection does get into the population and an emergency harvest
is not appropriate, it has been suggested that removing the affected
shrimp may limit the spread of the infection within the pond. The
affected shrimp will usually be seen at the surface of the pond, especially
in the morning and evening.
Moving shrimp between countries, or between distinct areas within
a country, should be avoided, wherever possible. Moving stocks of
shrimp not only carries the risk of introducing disease to farms,
but may also have adverse effects on local populations of wild shrimp.
If a new infection occurs, it is important that it not be allowed
to spread to neighbouring farms. Dead shrimp should be removed from
the pond and disposed of in a manner that does not contaminate the
water supply. They can either be buried with quick lime, or they can
be burned. The water from the affected pond should not be discharged
from the farm. Once the infection is detected in the shrimp, it may
be possible to conduct an emergency harvest. The water from an emergency
harvest should be retained in a settling pond and treated with calcium
hypochlorite (at least 20 ppm active chlorine). In some cases, it
may not be worth conducting an emergency harvest, for example, if
the shrimp are too small or if most have already died. In such cases,
the water should be treated in the pond prior to discharge. Every
effort should be made to avoid the water from the affected pond coming
into contact with the inlet water of the affected farm or of any neighbouring
Early detection of the problem is extremely important. The shrimp
should be examined regularly for signs of disease, especially if there
is an increased risk of infection.
Management Recommendations for Small-scale Farms
Small, newly developed shrimp farms are owned by rice or fish farmers
who follow management techniques learned from neighbouring farmers.
Their farms consist of one to three ponds, and more than 80% of them
take their water directly from the source, without using a storage
reservoir. Poor-quality water supply is one of the major problems
leading to management difficulties and diseases causing severe losses.
Some farmers have returned to rice or fish farming. However, as the
income generated from rice or fish is relatively low and is inconsistent,
large families still need to generate incomes from other agriculture-based
activities. Integrated farming has shown a good potential for farmers
living in coastal areas. Dividing the land into three or four parts
consisting of a shrimp pond, a fish pond (which serves as a source
of water for the shrimp pond), a rice paddy or a cash crop (such as
vegetables), and an area for raising poultry is recommended. One or
two shrimp-production cycles per year generate the major income for
the family, whereas fish, rice, poultry and cash-crop production provide
extra income and food for direct consumption.
Since income generation from shrimp production has become a focus
for poverty alleviation for poor farmers in coastal areas, information
and technology transfer are required in order to ensure success. Extension
material and technical support in various forms are being developed
and transferred though both the government and private sectors.
Disease control and management in Thailand is not the responsibility
of a single governmental body. Many institutes have been involved
in the successful development of the shrimp-farming industry during
the past 12 years. Governmental agencies, such as the Department of
Fisheries, the universities, various research institutes and the private
sector have jointly set up a good network to study the causes, preventive
methods and treatments for diseases, as well the development of good
management practices for shrimp farming. This information and recommendations
are being transferred to the end-users by various means, such as seminars,
workshops and training courses that are jointly organised by the government
and private sectors, and via scientific publications and articles
produced by various institutions and widely circulated among the interested
parties. There are also government and private laboratories that provide
services for disease diagnosis in difference areas, which all farmers
can easily access.
When management recommendation are made, they can easily reach the
end-users through the many institutions set up in Thailand. However,
their successful application depends largely on the farmer's decision.
In order to assist the farmers, more well-trained and experienced
local staff are still greatly needed, since the shrimp culturing area
in Thailand is quite large. Establishing a disease reporting system
is one effective strategy to obtain information from the field, and
can be used to pass recommendations back to the farmer quite effectively.
SHRIMP DISEASE AND A POVERTY-FOCUSSED SHRIMP AQUACULTURE DEVELOPMENT
PROJECT IN THE MEKONG DELTA, VIETNAM
The Mekong Delta is Vietnam's most important shrimp-producing area,
with nearly 200,000 ha of ponds. In the southern tip of the delta,
the Government of Vietnam is undertaking a mangrove reforestation
programme, and mixed brackishwater farming systems - mangrove and
aquaculture - are practised. The propose of the mixed farming system
is to provide wood through mangrove reforestation and food and income
to people involved in mangrove planting through brackishwater aquaculture.
Until recently, this brackishwater aquaculture was solely shrimp aquaculture,
but the systems have recently become more diversified. The people
living in the area are poor, and an estimated 40% are living below
the "official" government and United Nations Development
Programme (UNDP) poverty thresholds. The reforestation and aquaculture-development
activities in the southern part of the delta, therefore, have a strong
poverty alleviation focus.
As part of a project to improve the economic returns and management
of these mixed-farming systems, the Australian Centre for Agricultural
Research (ACIAR) has supported a research project in Ca Mau Province.
Two enterprises, Tam Giang III and SFFE 184, in the Ngoc Hien District
of what is now Ca Mau Province were selected as the main foci for
research activities, in consultation with national, provincial and
enterprise officials. The enterprises are designated by provincial
authorities as State Fisheries-Forestry Enterprises (SFFEs).
Description of the Mixed Farming Systems
Two main fisheries-forestry farming systems presently operate in
Ngoc Hien District are:
- Traditional capture fisheries-mangrove forestry farming system.
In this system, being carried out in Kien Vang Enterprise, mangrove
forest occupies more than 80% of the enterprise area. Here, forest management
aims to produce a final yield of 200 m3 wood/ha when harvested at year
20. Fisheries products come from capture fisheries only; pond culture
is not practised.
- Fisheries-forestry farming system. In this system,
practised in the Tam Giang III and SFFE 184 Enterprises, farm households
are officially assigned 5-10 ha of land on which they must carry out
both shrimp culture and forestry. Two different farming models are practised
in Tam Giang III, (i) separate pond (20-30% of farm) and forest (70-80%
of farm) areas; and (ii) combined shrimp farming-mangrove forestry on
the same area of land. Shrimp culture is carried out in canals or channels
dug in the forest. The area for shrimp farming (canals, channels and
levees) is restricted to 20-30% of the total farm area. Both the separate
and combined models are used in Tam Giang III, but most farms in SFFE
184 use the combined model.
Description of Farm Households
Household surveys carried out in 1996 revealed information on household
incomes, and demonstrated the overwhelming importance of aquaculture
and aquatic products to people living in the enterprises. The average
reported household income was 12.08 million Dong/household/yr (equivalent
to around US$870 at 1999 exchange rates), or 2.4 million Dong/person/yr
(US$172/yr). Poverty thresholds are around 1.1 million Dong/person/yr.
It was estimated that 80 (39.4%) of the surveyed households were below
this threshold, indicating a significant poverty problem in the enterprises.
Traditional farmers or those making limited investment in their ponds
reported lower incomes than did extensive farmers, although the survey
suggested that farm households that had made investment had significantly
more debt, as a result of borrowing funds to purchase seed and undertaking
some pond improvements. Table 1 shows the relative contribution of
the different activities to family income (data from both enterprises
Table 1. Sources of household income in two forestry-fishery
The survey noted differences in income patterns between the different
farming systems. Farmers reported that they can obtain higher production
from models with stocking, but will suffer a greater loss if they
lose the crop. In other words, households can generate greater income
by undertaking shrimp stocking and pond improvements, but they are
also exposed to a higher risk of crop losses because of shrimp disease
Aquaculture Problems and Constraints
Farmers reported several aquaculture problems, which were explored
by questionnaire and during the local participatory workshops. Information
on the technical and nontechnical problems faced by farmers is shown
in Table 2.
Environmentally related problems, including water and soil-related
problems, were faced by a significant proportion of farmers. These
included problems that were perceived as being due to water pollution,
turbidity and water acidity. The water quality problems were similar
between farm types. The major problems included shallow ponds, acidic
soils, and poor productivity caused by high turbidity. Other aquaculture-related
problems reported by farmers included lack of credit, lack of experience
and a perceived lack of technology.
Table 2. Percentage (%) of farmers reporting various aquaculture
Shrimp Health Problems
Disease was clearly a major problem, with nearly all farmers (95%
of separate farms and 98% of mixed farms) reporting outbreaks causing
financial losses. Farmers found it difficult to assess the causes,
and none reported any success in solving the problem during 1996.
During participatory workshops, farmers clearly recognised shrimp
monoculture as being more risky than polyculture. They considered
diversification of aquaculture through stocking fish and crabs to
be less risky. Farmers also reported that all farms stocked with hatchery-raised
postlarvae were affected by disease. However, farmers were unable
to identify for certain whether mortality was caused by disease or
by other factors, as they had little experience in distinguishing
between different diseases. No aquaculture extension was available
at the time to provide advice on shrimp disease control.
Shrimp farms based on natural recruitment apparently did not experience
such severe problems, but yields were reported to be low. This suggests
that recruitment was poor at the time of the disease and raises a
number of questions regarding the impact of disease on wild stocks
that need to be addressed by research.
Economic Impact of Shrimp Disease
Shrimp disease has become a serious problem in the Mekong Delta of
Vietnam, and these very extensive farms were no exception. Whilst
it is difficult to estimate the overall economic losses, the figures
from the survey reported here extrapolate to an estimate that US$27
to 28 million was lost throughout the delta in 1994. World Bank (WB)
estimates are on the order of US$50 million for the same period.
Financial losses from the survey were reported as $732 per affected
separate farm and $1,249 per affected mixed farm, figures that indicate
the financially serious nature of the problem. These figures, whilst
difficult to verify, are close to the annual income of many households.
The disease clearly had a major affect on farm profitability, with
many farms falling into debt at this time.
The social impacts of shrimp disease were severe in the enterprises,
and included problems with increased debt. This situation was made
worse by a lack of alternative income. However, food was available
from the brackishwater areas. These problems affected the potential
of shrimp culture to contribute to poverty alleviation.
Shrimp Disease Investigations
The shrimp disease problems were subsequently diagnosed as being
due to viral disease and water quality problems associated with the
onset of the rainy season. Disease surveys conducted in 1997 and 1998
revealed that WSSV was simultaneously present in wild shrimp seed
and Acetes spp. during January, April and May. Monodon baculovirus
(MBV) was present in wild seed all year round, and was detected more
often in the separate farming system than in the mixed farming system.
WSSV was present in most samples of harvested shrimp, particularly
those collected in the rainy season and in the middle of the dry season.
MBV was present in harvested shrimp all year round, with greater prevalence
in the rainy season. Mass mortalities occurred four times during the
one-year sampling period, in January, June, July and October. These
were associated with the presence of WSSV at high prevalence and intensity,
and also with poor environmental conditions associated with the onset
of the rainy season.
The most important conclusion to be drawn from the results of the
disease survey was that risk was significantly higher around the peak
of the wet season in July and August, and again in the months October,
November and December, the middle of the dry season. These peaks in
disease occurrence correspond to the two extremes in the water quality
regime. In the peak months of the wet season, low pH and rapid changes
in salinity are likely to stress shrimp and predispose them to disease,
while in the middle of the dry season, above average water temperatures
may predispose the animals to disease. These extremes of water quality
partly result from the poor design of ponds, most of which are too
shallow and do not have adequate water volume to minimise fluctuations
in water quality.
Farmer Responses to Shrimp Disease Problems
Generally, the technical support for farmers is very poor. Farmers
received some technical training in mangrove forestry, but there was
very limited technical support for aquaculture. In dealing with the
various problems faced by farmers, extension support is important.
The survey questionnaire explored the extent to which farmers had
received technical assistance and their sources of technical information.
Only 7% of farmers had received a visit from an extension officer
with experience in aquaculture, in contrast to mangrove extension,
which was available through each of the Enterprises. The most important
source of information on aquaculture was other farmers. Farmers are
grouped together in local area groups under the management structure
of the Enterprise, which could provide an efficient means of information
exchange. Although these groups are currently more involved in forest
protection, the opportunity for using them as a means of extending
aquaculture advice needs to be examined.
Farmers reported that they had limited opportunities to receive aquaculture
advice. The Enterprise has no resident aquaculture extension officer,
and funds for extension by provincial fisheries/aquaculture staff
appear to be very limited. Advanced farmers were reported to have
good co-operation with other farmers and often exchange experience,
even though there is no official association. Advanced farmers also
can provide advice to poorer farmers. Exchange of ideas among farmers
was an important source of advice.
When disease occurred, the farmers could only attempt limited actions,
mainly emergency harvest. For many, the only option was to take no
Development of Management Interventions
Based on the results of the shrimp health survey and associated work
on environmental conditions in the mixed farming systems, a series
of management strategies were tried and their effectiveness evaluated.
As mortalities were related to water quality, improvement in pond
design, considered in more detail elsewhere, is a key first step to
minimising the risk of mortality from disease. The following recommendations
Improving pond design, particularly to improve water depth and settlement
of water. As this approach requires investment, it has to be incremental.
Nursing of postlarvae. As the return from the stocked shrimp was
very low, nursing was recommended to improve survival and allow farmers
to check the quality of seed before stocking.
Postlarval quality checks. Long-term improvements in seed quality
Stocking/harvesting at lower risk periods. For example, stocking
during the dry period and avoiding the higher risk, cooler winter period
and rainy season.
Diversifying away from shrimp into other income-generating practices
to reduce the risk associated with shrimp culture due to poor and unreliable
seed recruitment. Viable options to be explored include agricultural
cash crops and alternative aquaculture species. Mud crab culture and
fish culture are being tried.
It is also necessary to consider the institutional support needed
to implement the technical recommendations. The following issues are
Improved technical co-operation and support for self-help among farmers,
and co-operation among farmer groups, including development and testing
of extension materials.
Credit access and particularly, accessing arrangements for the poorer
Development of a surveillance/response system to respond more quickly
Other institutional arrangements, such as insurance for crop failures,
also need to be addressed.
Other policy and institutional issues which have an important bearing
on the provision of improved health management in these mixed farming
Improving the security of land tenure for farmers. This is necessary
to permit longer land leases or provide options for farmers to acquire
ownership of land and make longer-term investments in land development.
Providing on-going and effective training to upgrade the skills of
Devising institutional arrangements to manage risk associated with
poor people who have limited assets; joint credit schemes, joint insurance
policies etc need to be considered.
The current ACIAR project is assessing current management intervention
strategies and their success in minimising aquatic animal health problems.
It will help identify potential future intervention strategies.
Lessons Learned from the Vietnam Project
In the southern tip of the Mekong Delta, there are many poor people
involved in aquaculture and mangrove forestry. Shrimp disease has
become a constraint, even in extensive shrimp culture. Experience
has shown, however, that the management of risk is important, and
that several options exist to reduce risk to farmers and their households.
This approach relies very much on understanding and management of
the whole system. Health problems cannot be seen separately, but should
be seen as part of the system. This requires a whole-system approach
to health management, integrating health management concerns within
the whole approach to aquaculture development, including consideration
of institutional issues. There is a need to understand the farmers'
situation and institutional support structure, as well as the technical
issues faced in managing health risks in small-scale shrimp aquaculture.
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