1 Research Institute for Fisheries, Aquaculture and
Szarvas Anna Liget 8, H-5541 Hungary
2MRC READ Project
An Thai Trung Village, Cai Be
Tien Giang Province, Vietnam
3School of Life Sciences, Napier University
10 Colinton Rd
Edinburgh EH10 5DT, Scotland, UK
Jeney, Z., N.V. Hao, Q.T. Trong, N.T. Mui, P.T.B. Hong, N.M. Thanh and I.H. MacRae. 2002. Preliminary results of the fish health survey in rural aquaculture of Tien Giang Province, Vietnam. p. 323-332. 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. 406.
A survey of fish health in rural, small-scale aquaculture in Tien Giang Province, southern Vietnam was carried out in September 1999, in co-operation with the Network of Aquaculture Centres in Asia-Pacific (NACA). There were 99 farms surveyed by questionnaire. Farms were selected from respondents to the baseline survey of the Mekong River Commission's Rural Extension Aquaculture Development Project (MRC READ Project). The socio-economic status of the farms is described in the MRC READ baseline survey report (MRC 1999). In general, farmers obtained fish seed from hatcheries or from traders. The farmers considered the quality of fish seed good, and they were able to select seed for themselves. The most important environmental problems that occurred on farms were flooding, bad water quality, acidic soil and the use of pesticides; farmers did not keep records of disease problems. Diseases occur immediately after stocking and during the cold and rainy seasons. Farmers seek advice from other farmers, as well as from government extension officers. Abnormal behaviour and appearance, as well as diseases with noticeable external clinical signs, are recognised by the farmers as criteria for sickness in fish. The most frequently observed disease was a group of ulcerative syndromes. For prevention of diseases, farmers applied a series of measures, most often as follows: careful pond preparation, provision of abundant natural food by manuring, application of appropriate stocking densities, stocking of healthy fish of a similar size, and bathing of fish in salt solution prior to stocking. When disease occurred on the farms, the following treatments were applied: use of lime and salt, feeding with antibiotics, use of local herbs for water treatment, feeding with food containing higher doses of vitamin C, use of salt solution to bath the fish, stopping water flow, applying a complete water exchange and moving the fish to another pond. The average cost of the treatments applied was 64,400 Vietnamese Dong (VND) (US$4.60), the maximum was 200,000 VND (US$14.30) and the minimum was 5,000 VND (US$0.35). Traditional methods of treatment using various medicinal herbs were frequently applied. Preliminary results show that diseases can play an important role in small-scale aquaculture, but that this role is often not recognised due to a lack of knowledge and veterinary backstopping services. Attention should be paid to the high prevalence of ulcerative diseases.
There are few data available on the status and importance of fish diseases in small-scale aquaculture of the Mekong Delta of Vietnam. Earlier findings of the West-East-South (WES) Project in two provinces of the Mekong Delta suggested that in spite of low intensity of production, diseases may play an important role in small-scale aquaculture (Jeney et al. 1998). The Mekong River Commission's Rural Extension for Aquaculture Development in the Mekong Delta Project (MRC READ Project) is being implemented in Cambodia and Vietnam. Tien Giang Province is the project site in Vietnam. Following the baseline survey of the project, it was decided to join the regional initiative of the Network of Aquaculture Centres in Asia-Pacific (NACA) by implementing the fish health management survey in the project area. Preliminary results of the survey are presented here.
The objective of the survey was to collect information on the impact of disease on production of fish in the small-scale aquaculture systems of Tien Giang Province. A questionnaire was prepared, and the survey was carried out over a period of two weeks (6-17 September 1999) in seven districts of Tien Giang Province. The original survey form provided by NACA contained two parts. The first part gathered data on the socio-economic circumstances of the farmers and the production techniques that are employed. Since the farmers were selected from 361 respondents of the MRC READ Project baseline survey of the previous year, data on their overall socio-economic status and production practices were retrieved from the baseline survey. The second part of the survey form contained 64 questions relating to health issues, management, knowledge and contact with extension services and other forms of assistance. If specific diseases were mentioned, an additional form was completed; this contained questions relating to prevalence, frequency, farmers' perceptions and knowledge of disease, treatments applied and types of assistance available. Ninety-nine forms were completed.
The overall socio-economic status of the respondents is described in the baseline survey report (MRC 1999). Of the 99 farms surveyed, 53 practised fish culture in ponds, 26 practised the "VAC-model" ("vuon-ao-chuong" or "garden-pond-pigsty," integration of aquaculture with gardening and livestock), and 20 practised integrated rice-fish culture. Tilapia (Oreochromis niloticus), Java barb (Barbodes gonionotus), giant gourami (Osphronemus gourami), common carp (Cyprinus carpio), hybrid catfish (Clarias gariepinus x C. macrocephalus), silver carp (Hypophthalmichthys molitrix) and sutchi catfish (Pangasius hypophthalmus) are the most widely cultured species in the province. The average age of the farms was 7.1 years, the oldest being 20 years and the youngest being three years.
The reasons for growing fish are presented in Table 1. The majority of farmers grow fish for income (41 responses); the other first-ranked reasons were for food (23) and hobby (29). The second-ranked response (47) most often given was for food. The third-ranked reason was hobby (27), and the fourth-ranked reason was status (34 responses).
Table 1. Reason for growing fish (total number of farmers surveyed = 99).
Farmers were asked to rank, in order of significance, the problems that they encountered (Table 2). The major problem was flooding, followed by theft. Disease was ranked fourth, and too little water was ranked sixth. Predation figured highly in the second and third ranking.
Table 2. Problems encountered by farmers (total number of farmers surveyed = 99).
Farmers' responses when asked what they thought about aquaculture are presented in Table 3. The majority of farmers considered aquaculture to be profitable and to have high status; only a few farmers acknowledged that aquaculture is a risky business. Disease was also seen as an important issue, but not in small-scale farms.
Half of the farmers said that they were able to choose fry (52), while the
other half (46) must take what is available. The same tendency was observed
in the question about the physical condition of the fry: 54 farmers said the
fry were healthy, while the remainder (45) did not know.
Table 3. Farmers' perceptions of aquaculture (number of farmers responding = 99).
Of the 99 farmers interviewed, 24 reported that they had experienced disease problems in the last year, seven had problems in the last four months and two had problems in the last month. The majority of farmers (52) had disease problems, but could not remember when. The outcome of the majority of the problems encountered was that "some" of the fish died; only three farmers reported that "all" the fish died. The significance of the disease to the household, as felt by the farmers, is indicated in Table 4.
Table 4. Economic results of fish disease problems (total number of farmers surveyed = 99).
Farmers were asked if they associated any particular pattern with the disease occurrence (see Table 5). According to the farmers, most of the diseases occurred after stocking, as well as in the cold and rainy seasons.
Table 5. Pattern associated with the disease (total number of farmers surveyed = 99).
Farmers were asked if the occurrence of disease changed their attitude towards aquaculture (Table 6). Disease problems did not change their attitude towards aquaculture, but they considered changing the species cultured.
Table 6. Did the problem result in a change in attitude towards aquaculture?
(total number of farmers surveyed = 99).
Farmers were asked if they contacted anyone when they had a problem. Fifty percent said that they did, and the greatest number (39) contacted other farmers for information. Thirty-six farmers contacted government extension officers, 31 contacted drug and chemical salespersons, 25 contacted hatchery owners, 20 contacted fry traders, and only one contacted nongovernmental organizations (NGOs). When a request for assistance was made, 41 farmers said that response was prompt, 11 said that it was slow, and none said that no response was received. Government extension officers were considered to be the most useful source of information, with hatchery owners being the second most useful. Drug and chemical salespersons and fry traders were also considered good sources of information.
Farmers were asked about their ability to recognise disease. Thirty-one farmers said that they could recognise some diseases, while 28 said that they could not recognise any disease. No farmer said that he/she could recognise all or most diseases. The ability to recognise disease was based on a number of factors; the most frequently cited were mortality, abnormal behaviour, abnormal appearance and reduced growth.
Response to Disease
Farmers were asked what they did in response to disease. Forty-eight farmers said that they sought help, 47 attempted treatment and 21 did something else (not specified). Ten farmers said that they carried out emergency harvest, while 11 farmers did nothing. If treatment was attempted, it generally involved the use of chemicals (36) or antibiotics (35); 29 farmers changed water, 16 stopped feeding and 12 stopped fertilising. Farmers said that they learned about these treatments from government extension officers (35 responses), other farmers (34), hatchery owners (34), drug salespersons (31), fry traders (31) and feed sales persons (20).
Types of Disease Problems
The most common problems reported are listed in Table 7.
Table 7. Problems reported and the age of fish affected.
Disease did not seem to cause catastrophic losses; a large number of the farmers (38) reported that only a few fish died. There were, however, 11 cases reported where most of the fish died. As the losses were measured by mortalities, it is not possible to estimate the loss of production due to reduced growth.
A diverse number of treatments were reported, many in multiple combinations. Liming was the most common treatment, in combination with antibiotics. Copper sulphate, salt and malachite green were also applied. Information on the cost of treatments is included in Table 9.
The average cost of the treatments applied was 64,400 VND (US$4.60), the maximum was 200,000 VND (US$14.30), and the minimum was 5,000 VND (US$0.35). Only six farmers said that the treatment was "always" successful; 23 farmers said that it was "sometimes" successful, 21 said that it was "usually" successful and four said that it was "never" successful.
Farmers generally used two or more chemicals at a time for any disease problem, according to the recommendation of chemical suppliers. Farmers learned about the treatment that they used from government extension services (32 responses), chemical salespersons (30), other farmers (28) fry traders (15), feed salespersons (10) and hatchery owners (8). Six farmers reported that they learned the treatments themselves.
Traditional methods of treatment are presented in Table 10.
Table 9. Treatments and costs.
Table 10. Traditional treatments (treatments are grouped according to separate disease signs as described by the farmers. If more than one treatment is applied, they were ranked by their importance).
The average cost of these treatments was US$0.96, with a minimum of US$0.35 and a maximum US$2.14. The majority of the farmers learned about these treatments from other farmers (21). Some of them (12) learned from government extension officers, fry traders (5) and chemical traders (4). Nine farmers reported that they knew about treatments from their own experience.
Farmers were asked when diseases were last seen. As can be seen from Table 11, the majority of diseases were reported to have occurred within the last year.
Table 11. When disease was last seen.
Frequency of Disease
Farmers were asked how often these diseases were seen, and their response was that most were seen every year, but not more frequently. When asked when in the growing cycle the disease occurred, the farmers reported no distinct pattern of disease occurrence. However, as can be seen from Table 12, the cold and wet seasons were cited as the most likely times for disease to occur, as well as the period after stocking fry.
Table 12. When in the growing cycle disease is likely to occur (total number of farmers surveyed = 99).
Farmers were asked if they had lost production due to disease. The frequency of occurrence of lost production and the cost of additional inputs to control the ulcerative diseases were remarkable. Farmers' estimated the value of lost production in a year at 569,588 VND (US$40.7) on average (N=44), and the cost of additional inputs to control the disease at 2,624,643 VND (US$187.5) on average (N=29).
Farmers were asked if they would eat fish from a pond with sick fish. Thirty-one replied that they would, and 14 replied that they would not.
The results of this survey show that disease can play an important role in small-scale aquaculture, but that this role often not recognised, due to lack of knowledge and veterinary backstopping services. Attention should be paid to the high frequency of certain ulcerative diseases. Further studies are needed to better understand the importance of fish diseases and to elaborate plans for development of fish health management systems in the area.
Jeney, G., D.T.H. Oanh, T.T. Dung, Z. Jeney and N.A. Tuan. 1998. A socio-economic survey: fish health management in the Mekong Delta, Aquacult. Asia, 2: 35-40.
MRC. 1999. Baseline survey report in Tien Giang Province in 1998. Mekong River
Commission (MRC) READ Proj. Tech. Pap. No. 7, 154 p. (draft)