There is a favorable environment in south-western part of Bangladesh for shrimp culture from early age. There was a drastic change in shrimp farming during 1980 due to its market demand and economic return. But shrimp farming is a crucial sector to the fisheries department of Bangladesh now-a-days, because of risk of mortality in different stages. At present Bangladesh produces 2.3% of the total global shrimp production and earns about 300 million US$ annually from shrimp farms (Karim, 1986a and Avault J. W, 1986.). In our country disease is one of the major factors that affect shrimp production. Disease is a major concern for the shrimp industry in Bangladesh. It was reported that Bangladesh lost 44.3% of production in 1996, leading to a reduction in foreign income of 42.3% from shrimp exports from 13% of extensive and 74% of semi-intensive shrimp farms (Mahmood, 1986 and BBS, 1996). It is estimated that the average financial loss per affected farm is as high as US$ 832/year for extensive and US$ 3,928/year for semi-intensive farms respectively (Chowdhury, 1997 and Nguyen V. S. et.al. 1993.).
In Bangladesh, shrimp mainly takes place in the district of greater Chittagong, Noakhali, Barisal, Bagerhat, Bhola, Pirojpur, Patuakali, Khulna and Satkhira districts (Karim,1986b). Satkhira Bagerhat and Khulna districts are the most productive zones for Penaeus monodon culture. This shrimp industry in Bangladesh currently covers 190,000 hectares in southwestern coastal regions. There are around 145,000 farmers in Bangladesh annually producing 30,000 metric tons of shrimps under traditional methods (Gosh, 1985 and Roy B. et.al. 1991). But Penaeus monodon, the highly productive resource is not in proper use due to lack of knowledge in adopting modern technologies and applying scientific procedures in production system. The producers of Penaeus monodon in Bangladesh are poor and they are attentive to produce maximum outputs from minimum inputs. Farmers are not interested to use improved technology by investing a large amount of money. Moreover, there are also lacks of other facilities. Therefore, an initiative has been undertaken to find out how the farmers change their farming practices, their production and perception about diseases due to introduction of the viral disease.
MATERIALS AND METHODS
The village Vathshala under Debhata Upazila of Satkhira District in Bangladesh has been selected for examining the changes of shrimp farming practices. The shrimp culture is a main farming practice and it has been practicing more than ten years in the study. At first, a reconnaissance survey was conducted in the study area. Present and past disease conditions were considered in the study. Sample size was determined based on precision rate and confidence level (Kothari, 1985 and Roy B. et.al. 1991). In the study, household was taken as the sampling unit. Stratified random sampling was applied for the sampling procedure. Data were collected randomly from 65 selected farmers from 216 households. The households were categorized into three groups based on their gher size. The three groups are small gher (0.05 to 1.00 ha), medium gher (more than 1 but less than 3.0 ha) and large gher (3.0 ha and above) Data were collected from these three types of farmers in equal proportion. After performing reconnaissance survey in the study area, clear and structured questionnaire was developed. The draft questionnaire was pre-tested and performance of that questionnaire was reviewed. After that final questionnaire was developed with the help of the experience of the pre tested questionnaire. Data were collected through personal interview. Data were collected for the period of 1997-98 as before disease, 2000-01 as after diseases and 2003-04 as present situation.
RESULTS AND DISCUSSION
Traditional Farming Practices
The Changes of shrimp practices in the study area were examined in terms of introduction of new techniques such as input changes, changes in fry collection and changes of cultivation practices etc. In the study area cultivation practices have changed due to disease. The disease reduced the percentages of farmer who cultivated only shrimp and increased the mixed culture (bagda, golda and fin fish) practices. In recent years, the mortality rate of fin fish is also high and the percentage of mixed culture is reducing (Table 1). In the study area, most of the shrimp farming was practiced in traditional way. However the changes of shrimp farming practices were found after disease. In field preparation, use of plough was rare before disease but after disease (2000 - 01), 36% of the respondents and recently (2003 - 04), 90% of the respondents were found using plough for field preparation (Table 1). Table 1. Differences of shrimp practices in different years in the study area.
Use of lime and cow dung in the field preparation has also been increased at the similar rate after disease because they thought that these increase the soil fertility. Before virus disease, the farmers practice no food input because production was very good. But in last 6 - 7 years they are using different kind of foods as input. Most of the farmers are now using the urea, phosphate and TSP fertilizers, lime and fish meals in their shrimp culture pond (Table 1). Because the farmers think that food input may save their shrimp from disease. The sources of fry collection were river before disease (100%) but after disease (2000 - 01), it dropped down to 12% only due to low price of fry from hatchery. But in 2003 - 04 this percentage increased (32%), because the people think that the hatchery fry is disseminating the disease. Recently the government of Bangladesh banned to collect fry from the river and this was another cause of reducing the use of river fry. However in reality multiple use is found in fry collection practices, such as some people use both river and hatchery fry. The Hatchery fry sources are Cox’s Bazar, Chittagong and Thailand. After disease (2000 - 01), temperature and salinity acclimatization was found (65%) before release of the fry in the gher and presently (2003 - 04) all the farmers are using this technique. But this technique was not used. Nursing of fry in a small area in the farmers’ gher by providing net also recent technique after disease out break. Due to disease, farmers are taking extra to their shrimp fry. After disease, exchange of water from river in dry season was most frequent because farmers want to ensure to quality of water.
Table 2: Differences in average production (Kg/ha/yr) in different years in the study area.
Differences in shrimp production were calculated for three time periods – before disease (1997 - 98), after disease (2000 - 01) and present situation (2003 - 04). Comparative changes in production of these three periods will give an idea about the effects of disease on shrimp production. Production of shrimp was high before disease but it falls rapidly after disease and recent in years, some improvement has found. In 1997 - 98, the production was 337.47 - 381.53 kg/ha, this amount reduced to 189.68 – 220.32 kg/ha in 2000 - 01 and increased into 244.26 – 279.74 kg/ha (Table 2) in 2003 - 04. In 2003, shrimp production of Khulna district was 233.5 kg/ ha (DOF, 2004 and Ahyaundin B. Ali & M Ahmad 1886.) which were similar the production found in year 2003 - 04 in the study area. The cost of production Includes various cost items, such as field cost (land rent), farm construction, fry collection, food inputs and labor cost (Fig. 1). In the economic calculation, imputed value of own and family labor inputs was considered. When the cost of all inputs were calculated including both cash and non-cash expenses, the average cost of shrimp production were 81.1 - 99.32, 58.86 – 72.50 and 59,26 – 72.78 thousand Tk/ha for the year 1997 - 98, 2000 - 01 and 2003 - 04 respectively (Table 3).
Table 3: Differences in production cost and net income in thousand Tk/ha of farmers in the study area.
Out of the total Cost, in 1997 - 98 major portion of the cost was incurred in fry collection (69.70%) followed by labor cost (12.17%). Cost of field (11.30%), Farm construction (6.80%) and food input (0.00%). In 2000-01, major portion of the cost was incurred in fry collection (46.67%) followed by cost of field (18.28%), labor cost (17.64%), farm construction (10.90%) and food input (6.48%). In 2003-04, major portion of the cost was incurred in fry collection (42.40%) followed by cost of field (22.80%), labor cost (16.33%), farm construction (10.36%) and food input (8.08%). In this comparison of study, it is reveals that fry collection cost was decreasing in the study area. Increase in cost of field and food input was found no major changes in farm construction and labor cost (Fig. 1). However, the overall income from shrimp farm was high before start of disease (1997 - 98) as well as benefits was high. After disease (2000 - 01) income and benefit reduced. Although income and benefit at present is increasing but not as high as was before disease. The net benefit in year 1997 - 98, 2000-01 and 2003 - 04 was 91.11 – 111.37, 16.35 – 19.93 and 22.48 – 27.5 thousand Tk/ha respectively (Table 3).
Figure 1. Changes in production economics in different years (Field survey).
In the disease outbreak area of shrimp, the people perceived it differently. Around 62% of the respondent assumed that the virus disease is due to disease vector bearing fry collector from Chittagong, Cox’s Bazar and Thailand (Fig. 2). In areas where river water is not used for shrimp cultivation, disease also found due to use of fry from Chittagong, Cox’s Bazar and Thailand. Therefore the examination result can say that shrimp fry from the hatchery may be one of the major causes of the disease. Around 20% of the respondent reveals that loss of soil fertility and heavy rainfall after a dry period are some of the another reasons of disease. However, around 11% of the respondents had no comment.
Figure 2. Causes of diseases according to respondent (Field survey).
There is a clear scientific evident that heavy rainfall decreases the salinity very frequently after dry period and affects virus disease suddenly at high rate. Therefore there may be relation between salinity and disease.
In the south-west coastal part of Bangladesh shrimp is the major source of economy. The study was carried out to investigate how the shrimp farmer changes their farming practices due to disease. Some changes in farming practices were identified by the study. But those changes are not adequate to improve the situation because shrimp farming in this part of Bangladesh is still unplanned. It assumes that the farmers have lack of appropriate scientific knowledge of shrimp farming. Therefore, it is recommended that sustainable ecological knowledge with implementation practices is essential for sustainable shrimp culture in coastal Bangladesh. So, the Department of Fisheries (DOF) should take necessary steps for improving this situation.
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