Water quality and partial mass budget in extensive shrimp ponds in Bangladesh
2003
Wahab, M.A. | Bergheim, A. | Braaten, B.
In a Bangladeshi-Norwegian project, water quality analyses have been conducted in some brackish water shrimp ponds stocked with Penaeus monodon in Bangladesh. The water-sampling program included five extensively improved farms in the Khulna region and four improved extensive farms in the Cox's Bazar region, annually producing 100-500 kg ha(-1). In addition to water sampling, data of input of manure, fertiliser and feed; shrimp stocking density, mortality and production; and water exchange rate data were collected. Measured pH, salinity and concentrations of dissolved oxygen and gaseous ammonia were usually within acceptable ranges for shrimp farming. However, sub-lethal levels of ammonia can be present and create stressing conditions. Low salinity could also create unfavourable environmental conditions. In one Gher, frequent sampling of inlet-outlet water was carried out during one production cycle. On average, the concentrations of total phosphorus and total nitrogen were reduced by 70% and 40% through the pond (inlet-outlet), respectively. Apparently, 80-90% of the supplied nutrients in fertiliser and inlet water was trapped in the pond. Consequently, the extensive shrimp culture in Bangladesh seems to act as a sink for solids and nutrients in the water that led to the system.
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