Seasonal change of sediment condition in aquaculture area and fishery resource management in Sam-An Truyen Lagoon, central Vietnam
2009
Okamoto, Y.(Kyoto Univ. (Japan)) | Tanaka, U. | Mizuno, K. | Nguyen P.N.
The Survey conducted with the following aims; 1) grasp the transition of the fishery utilization and the condition of the fishery management, and 2) understand the environmental condition of the coastal fishery area. Questionnaire, legwork, and checking the Acid-volatile-sulfide (AVS) of the sediment in the fishery area are conducted to understand the seasonal and spatial differences in the fishery environment and fishery management. Present aquaculture field are used be paddy field and fish corral ground. Paddy fields which located on the land or shoreline of the lagoon were altered into earth-pond aquaculture area, and fish corrals were changed into net-enclosure aquaculture fields. Acquirement processes of the right to use an aquaculture field were various (provided from commune authority, accession from family and relatives, purchase from other user and owner, and borrow from others). Amounts of the AVS in the sediment around the aquaculture area were increased with the start of culture season. Spatial difference about AVS amounts were also found, and some aquaculture area surrounded by many aquaculture ponds and net-enclosures were concerned the lack of oxygen. The place where was good for the tidal condition, AVS amounts especially super layer of the sediment was lower than other places. Lastly, the frequency of occurrence about the disease outbreak among the cultured fish and crustacean is getting higher than last 10 year from the recognition of the fishermen observation.
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