Shrimp and Mollusc Culture at the Bandon Bay in Thailand: A Situation Analysis

A socio-economic and ecological survey was conducted using farmer interviews and SWOT analysis, and monitoring of water quality parameters in Bandon Bay, Surat Thani, Thailand from January to December 1999. Monthly water samples from 29 sampling stations in the river mouth, mollusc culture and open bay areas were collected for 12 months and analyzed for ammonia-nitrogen (NH_3-N), nitrite-nitrogen (NO_2^- -N), nitratenitrogen (NO_3^- -N), soluble reactive phosphorus (PO_4^3-), and chlorophyll-a (Chl-a). Secondary information on phytoplankton abundance and shrimp culture area was collected from local research institutions. The results revealed that both oyster and cockle cultures provided net returns of USD 4,905 and 1,257 ha^-1 year^-1, respectively. Nutrient concentrations in the river mouth and shrimp culture areas were significantly higher (P 0.05) than the open bay area and Chl-a in mollusc culture areas was significantly lower (P 0.05) than the river mouth and shrimp culture areas. There was a significant positive relationship (P 0.05) between shrimp culture area and Chl-a concentration and a significantly positive relationship (P 0.05) between shrimp and oyster yields. Effluent discharging period of shrimp farms coincided with Chl-a peaks in the bay. Efficient integration of mollusc and shrimp cultures in a mutually beneficial way, i.e. to use shrimp farming effluents to attain a controlled eutrophication in the mollusc culture area and mollusc farming to recycle the waste nutrient discharged by shrimp farmers, is probably the best option for achieving sustainable development of aquaculture in the Bandon Bay. It is suggested that intensive shrimp culture areas be taken as a variable when developing zonal plans for Bandon Bay.