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Shrimp Farming and Water Quality Conditions in Phuket, Thailand
Thesis Abstract:
The study characterized the shrimp farming industry in Muang and Ta-lhang Districts and conducted a preliminary assessment of the potential impacts on water quality in the coastal zone of Ban-Chi-Lao, Phuket, Thailand from February to June 2003. A total of 29 randomly selected shrimp farmers were interviewed. Water samples were collected from four shrimp ponds and the adjoining coastal area and chemically analyzed based on salinity, pH, temperature, transparency, TSS, Chl-a, DO, BOD, NH3-N, NO2-N, NO3-N, TN, ortho-P, and TP. Descriptive statistics and correlation analysis were done using SPSS.
The shrimp farmers from Phuket were primarily male and with a college degree. Most of the large-scale farmers owned the land and had longer experience than the small-scale farmers. Sex, educational attainment, experience of respondents, and farm scale had no relationship with farm productivity and profitability. However, experience had a positive relationship with farm scale. Large-scale farms had the highest productivity and incurred the highest production cost. Medium and smallscale farms had higher profitability than the large-scale farms.
The general stocking rate in the study area exceeded the recommended stocking densities for shrimp farming. As a result there is tendency toward overfeeding, which could lead to water quality degradation, reduced survival rates, and increased possibility of shrimp disease outbreaks, hence, low production. This chain of events might explain the diminishing shrimp production currently experienced in Phuket. The use of some dangerous chemicals and prohibited antibiotics by farmers might have a potential health risk for humans.
The intake and coastal waters satisfied the coastal water quality standards for temperature, pH, DO, and NH3-N. The pond water pH and DO were within the acceptable ranges for shrimp production. Pond water temperature, TSS, secchi transparency, and salinity did not meet the optimum ranges for shrimp growth. The discharge water was of acceptable quality based on the pH, BOD, NH3-N, TN, and TP standards for effluent water from aquaculture, except TSS. Overall, the study showed that shrimp farming did not seem to degrade the quality of the water used in shrimp ponds and that of the coastal area when the pond water is released. Since this study was done during the transition period from dry to wet season, it is essential that the same assessment be carried out at other times of the year in order to get the annual trend.
To achieve sustainable shrimp farming development, it is recommended that the stock density be reduced and better quality of brood stock be used.