Ngày nay, những ứng dụng của vi điều khiển đã đi sâu vào đời sống sinh hoạt và sản xuất của con n... more Ngày nay, những ứng dụng của vi điều khiển đã đi sâu vào đời sống sinh hoạt và sản xuất của con người, là một phần tất yếu không thể thiếu trong đời sông hiện đại. Thế kỷ 21 được xem là thế kỷ của khoa học công nghệ, là thế kỷ mà máy móc được thiết kế và lập trình một cách tự động để thay thế các hoạt động của con người trong sản xuất, cũng như để phục vụ các công việc trong sinh hoạt. Trong một cuộc sống mang tính tự động hoá cao thì các mạch vi xử lý như là một công cụ đắc lực, quan trọng , hỗ trợ cho con người thực hiện nhu cầu ngày càng cao và càng hoàn thiện của mình.
Shrimp yields and harvest characteristics were monitored at mixed shrimp-mangrove forestry farms ... more Shrimp yields and harvest characteristics were monitored at mixed shrimp-mangrove forestry farms in two state forestry-fisheries enterprises, Tam Giang 3 and 184, in Ca Mau province, southern Vietnam. The aim was to identify key factors contributing to poor and declining shrimp production in the region over recent years. Shrimp yields were highly variable between farms but were generally low with mean annual yields of 286 " 106 kg ha y1 yr y1 and income of 388 " 146 USD ha y1 yr y1 . Secondary fisheries products, such as fish and mud crabs, increased total farm Ž ) Corresponding author Present address: D. Johnston . 0044-8486r00r$ -see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 0 4 4 -8 4 8 6 0 0 0 0 3 4 8 -3 ( ) D. Johnston et al.r Aquaculture 188 2000 263-284 264
Rates of pelagic primary production, respiration, and bacterioplankton dynamics were measured in ... more Rates of pelagic primary production, respiration, and bacterioplankton dynamics were measured in relation to water quality parameters in three extensive shrimp ponds in the Mekong delta, Vietnam. There were few consistent differences in pelagic characteristics among different locations within these ponds, among the three ponds, or between the ponds and adjacent river Ž 14 .
Water quality and plankton densities were monitored in shrimp ponds at 12 mixed shrimpmangrove fo... more Water quality and plankton densities were monitored in shrimp ponds at 12 mixed shrimpmangrove forestry farms in Ca Mau province, southern Vietnam, to detail basic water chemistry and assess whether conditions are suitable for shrimp culture. In general, water quality was not optimal for shrimp culture. In particular, ponds were shallow (mean + 1SE, 50.5 + 2.8 cm), acidic (pH , 6.5), had high suspended solids (0.3 + 0.03 g l À1 ), low chlorophyll a/phytoplankton concentrations (0.2 + 0.05 mg l À1 and 8600 + 800 cells l À1 respectively) and low dissolved oxygen (DO) levels (3.7 + 0.15 mg l À1 ). Eight out of the 12 farms sampled had potentially acid sulphate soils (pH , 4.2). Salinity, DO and pH were highly variable over short time-periods (hours); DO in particular was reduced to potentially lethal levels (1±2 mg l À1 ). Seasonal variations in water chemistry and plankton communities (i.e. salinity, DO, phosphate, temperature, phytoplankton and zooplankton densities) appear to be driven by differences in rainfall patterns. The presence or absence of mangroves on internal pond levees (`mixed' versus`separate' farms) and the source of pond water (rivers versus canals) were of lesser importance in determining water quality patterns and plankton biomass. Zooplankton and macrobenthos densities were sufficient to support the current (low) stocking densities of shrimp. However, natural food sources are not adequate to support increases in production by stocking hatchery reared post larvae. Increasing productivity by fertilization and/ or supplemental feeding has the potential for adverse water quality and would require improvements to water management practices. Some practical strategies for improving water quality and plankton densities are outlined.
Ngày nay, những ứng dụng của vi điều khiển đã đi sâu vào đời sống sinh hoạt và sản xuất của con n... more Ngày nay, những ứng dụng của vi điều khiển đã đi sâu vào đời sống sinh hoạt và sản xuất của con người, là một phần tất yếu không thể thiếu trong đời sông hiện đại. Thế kỷ 21 được xem là thế kỷ của khoa học công nghệ, là thế kỷ mà máy móc được thiết kế và lập trình một cách tự động để thay thế các hoạt động của con người trong sản xuất, cũng như để phục vụ các công việc trong sinh hoạt. Trong một cuộc sống mang tính tự động hoá cao thì các mạch vi xử lý như là một công cụ đắc lực, quan trọng , hỗ trợ cho con người thực hiện nhu cầu ngày càng cao và càng hoàn thiện của mình.
Shrimp yields and harvest characteristics were monitored at mixed shrimp-mangrove forestry farms ... more Shrimp yields and harvest characteristics were monitored at mixed shrimp-mangrove forestry farms in two state forestry-fisheries enterprises, Tam Giang 3 and 184, in Ca Mau province, southern Vietnam. The aim was to identify key factors contributing to poor and declining shrimp production in the region over recent years. Shrimp yields were highly variable between farms but were generally low with mean annual yields of 286 " 106 kg ha y1 yr y1 and income of 388 " 146 USD ha y1 yr y1 . Secondary fisheries products, such as fish and mud crabs, increased total farm Ž ) Corresponding author Present address: D. Johnston . 0044-8486r00r$ -see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 0 4 4 -8 4 8 6 0 0 0 0 3 4 8 -3 ( ) D. Johnston et al.r Aquaculture 188 2000 263-284 264
Rates of pelagic primary production, respiration, and bacterioplankton dynamics were measured in ... more Rates of pelagic primary production, respiration, and bacterioplankton dynamics were measured in relation to water quality parameters in three extensive shrimp ponds in the Mekong delta, Vietnam. There were few consistent differences in pelagic characteristics among different locations within these ponds, among the three ponds, or between the ponds and adjacent river Ž 14 .
Water quality and plankton densities were monitored in shrimp ponds at 12 mixed shrimpmangrove fo... more Water quality and plankton densities were monitored in shrimp ponds at 12 mixed shrimpmangrove forestry farms in Ca Mau province, southern Vietnam, to detail basic water chemistry and assess whether conditions are suitable for shrimp culture. In general, water quality was not optimal for shrimp culture. In particular, ponds were shallow (mean + 1SE, 50.5 + 2.8 cm), acidic (pH , 6.5), had high suspended solids (0.3 + 0.03 g l À1 ), low chlorophyll a/phytoplankton concentrations (0.2 + 0.05 mg l À1 and 8600 + 800 cells l À1 respectively) and low dissolved oxygen (DO) levels (3.7 + 0.15 mg l À1 ). Eight out of the 12 farms sampled had potentially acid sulphate soils (pH , 4.2). Salinity, DO and pH were highly variable over short time-periods (hours); DO in particular was reduced to potentially lethal levels (1±2 mg l À1 ). Seasonal variations in water chemistry and plankton communities (i.e. salinity, DO, phosphate, temperature, phytoplankton and zooplankton densities) appear to be driven by differences in rainfall patterns. The presence or absence of mangroves on internal pond levees (`mixed' versus`separate' farms) and the source of pond water (rivers versus canals) were of lesser importance in determining water quality patterns and plankton biomass. Zooplankton and macrobenthos densities were sufficient to support the current (low) stocking densities of shrimp. However, natural food sources are not adequate to support increases in production by stocking hatchery reared post larvae. Increasing productivity by fertilization and/ or supplemental feeding has the potential for adverse water quality and would require improvements to water management practices. Some practical strategies for improving water quality and plankton densities are outlined.
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