Aquaculture production of molluscs is worth US$11 billion per year and represents 65% of World mo... more Aquaculture production of molluscs is worth US$11 billion per year and represents 65% of World mollusc product. A significant limitation to the industry is loss of stock through bacterial disease. Traditional methods to combat disease with antibiotics have been questioned and alternatives have been sought. The field of probiotics as well as the screening methods used to acquire probiotic strains for the alternative management of disease in aquaculture is discussed. This review provides a comprehensive summary of probiotics in aquaculture with special reference to mollusc culture.
Controlling the inorganic nitrogen by manipulating the carbon/nitrogen ratios is a potential cont... more Controlling the inorganic nitrogen by manipulating the carbon/nitrogen ratios is a potential control method for aquaculture systems. This approach seems to be a practical and inexpensive means of reducing the accumulation of inorganic nitrogen in the pond. Nitrogen control is induced by feeding bacteria with carbohydrates, and through the subsequent uptake of nitrogen from the water, by the synthesis of microbial proteins. The relationship among the addition of carbohydrates, the reduction of ammonium and the production of microbial proteins depends on the microbial conversion coefficient, the C/N ratio in the microbial biomass, and the carbon contents of the added material. The addition of carbonaceous substrate was found to reduce inorganic nitrogen in shrimp experimental tanks and in tilapia commercial-scale ponds. It was found in tilapia ponds that the produced microbial proteins are taken up by the fish. Thus, part of the feed protein is replaced and feeding costs are reduced. The addition of carbohydrates, or the equivalent reduction of proteins in the feed, can be quantitatively calculated and optimised, as shown here. Approximate parameters were used in this work. Additional research in this field should be directed at gathering the precise data needed for the exact planning of feed composition.
Nutrient removal is essential for aquaculture wastewater treatment to protect receiving waters fr... more Nutrient removal is essential for aquaculture wastewater treatment to protect receiving waters from eutrophication and for potential reuse of the treated water. A pilot-scale wastewater treatment system consisting of a free water surface (FWS) and a subsurface flow (SSF) constructed wetlands arranged in series was operated for around 8 months. The study was conducted to examine system start-up phenomena and to evaluate system performance in removing inorganic nitrogen and phosphate from aquaculture wastewater under various hydraulic loading rates (1.8 to 13.5 cm day−1). The wetlands system showed rapid start-up behaviors in which process stabilities were achieved in the following sequence: phosphate removal in the SSF without an adaptation period, nitrogen removal in the SSF after 1 month, nitrogen removal in the FWS after 2 to 3 months, phosphate removal in the FWS after 3 months, and vegetation cover in both wetlands after 7 months of operation. Nitrogen removals were excellent, with efficiencies of 86% to 98% for ammonium nitrogen (NH4–N) and 95% to 98% for total inorganic nitrogen (TIN). Removal efficiencies were affected little by the hydraulic loading trials. Phosphate removal of 32% to 71% occurred, with the efficiencies being inversely related to hydraulic loading. The FWS wetland removed most inorganic nitrogen, whereas the SSF wetland removed phosphate at a rate equal to or even greater than the FWS. Removal of ammonium and nitrite (effluent concentrations <0.3 mg NH4–N l−1 and 0.01 mg NO2–N l−1) were sufficient for recycle in the aquaculture system without danger of harming the fish.
… and pond soil analyses for aquaculture, Jan 1, 1992
Abstract Water and soil analyses commonly needed in aquacultural research or in making decisions ... more Abstract Water and soil analyses commonly needed in aquacultural research or in making decisions on water quality management in aquaculture ponds are described in this manual. Most procedures are useful in both freshwater and brackish water. In addition to providing ...
Microorganisms have major roles in pond culture, particularly with respect to productivity, nutri... more Microorganisms have major roles in pond culture, particularly with respect to productivity, nutrient cycling, the nutrition of the cultured animals, water quality, disease control and environmental impact of the effluent. Management of the activities of microorganisms in food webs and nutrient cycling in ponds is necessary for optimising production, but the objectives will differ with the type of aquaculture, the species cultivated and the economics. Unlike the pastoralists who fertilise and seed pastures with selected species, fish farmers only fertilise ponds and hope that useful species of algae, bacteria and other microorganisms will develop. Factors controlling the composition and development of blooms of both desired and undesirable species of algae and bacteria need to be investigated. Analysis of the complex food webs in ponds, combined with measurements of primary productivity, C cycling through bacteria, Zooplankton and meiofaunal biomass changes and nitrogen cycling will provide the basic data for generating a model to describe and predict fish productivity in ponds. Algae and bacteria have often been regarded as single groups of organisms by aquatic biologists, but there is a great diversity of species of each, with different roles and interactions in their ecosystems. This fact, together with the many environmental variables, makes it difficult to develop a single comprehensive, predictive model as a tool for managing food webs and water quality in ponds, but small models specific to given pond systems or stages of grow-out are likely to be successful.
The importance of arachidonic acid (20:4n−6, ARA) in fish nutrition has tended to be overlooked i... more The importance of arachidonic acid (20:4n−6, ARA) in fish nutrition has tended to be overlooked in preference to eicosapentaenoic (20:5n−3, EPA) and docosahexaenoic acids (22:6n−3, DHA), probably due to the predominance of the latter two HUFA in fish tissues. However, despite the abundance of EPA and DHA in fish tissues, the importance of ARA as the primary eicosanoid precursor has been recognised for some time. Only very recently has the relative importance of ARA been given due acknowledgement and already the potential benefits to fish physiology and biochemistry of optimising the ARA nutrition of fish are becoming clear. In the coming decade, the role of dietary ARA should be the focus of considerably more research activity than has occurred to date. The results will undoubtedly emphasise why this ubiquitous HUFA cannot be underestimated in fish nutrition.
Nitrogen N biogeochemistry of aquaculture ponds is dominated by biological transformations of N a... more Nitrogen N biogeochemistry of aquaculture ponds is dominated by biological transformations of N added to ponds in the form of inorganic or organic fertilizers and formulated feeds. Nitrogen application in excess of pond assimilatory capacity can lead to the deterioration of water quality Ž . through the accumulation of nitrogenous compounds e.g., ammonia and nitrite with toxicity to fish or shrimp. Principal sources of ammonia include fish excretion and sediment flux derived from the mineralization of organic matter and molecular diffusion from reduced sediment, although cyanobacterial nitrogen fixation and atmospheric deposition are occasionally important. Principal sinks for ammonia include phytoplankton uptake and nitrification. The magnitude of losses by ammonia volatilization and ammonium fixation to cation exchange sites is minor, but unknown. Interactions between pond sediment and water are important regulators of N biogeochemistry. Sediment represents a source of ammonia and a sink for nitrite and nitrate. The large volume of reduced sediment suggests that the potential for N removal by denitrification is high, although the magnitude of N removal by this mechanism is low because nitrification and denitrification are tightly coupled in aquatic sediments and sediment nitrification is limited by the depth of sediment oxygen penetration. Nitrogen biogeochemistry of aquaculture ponds is affected by feeds and feeding practices, water exchange and circulation, aeration, pond depth and other management procedures. Opportunities for management of N biogeochemistry are limited and goals are based largely on the intensity of fish production. q
A crisis has arisen in the prawn industry in many regions with the onset of disease, with Vibrio ... more A crisis has arisen in the prawn industry in many regions with the onset of disease, with Vibrio spp. being important major causal factors. The value of adding selected strains of Bacillus as probiotic bacteria to control the Vibrio is shown by comparing farms in Indonesia using the same water sources, which contained luminous Vibrio strains. The farms that did not use the Bacillus cultures experienced almost complete failure in all ponds, with luminescent Vibrio disease killing prawns before 80 days of culture were reached. In contrast, a farm using the probiotics was culturing prawns for over 160 days without problems, by using Bacillus at abundances of about 1×104 to 1×105/ml. The bacterial species composition was different in the pond water on the two farms and demonstrates that it is possible to change bacterial species composition and improve prawn production in large water bodies. Vibrio numbers, especially luminous Vibrio numbers were low in ponds where a large abundance of specially selected Bacillus species was maintained in the water column. Vibrio numbers were also low in sediments and no luminous Vibrio occurred in sediments where the probiotic Bacillus were used.
Aquaculture production of molluscs is worth US$11 billion per year and represents 65% of World mo... more Aquaculture production of molluscs is worth US$11 billion per year and represents 65% of World mollusc product. A significant limitation to the industry is loss of stock through bacterial disease. Traditional methods to combat disease with antibiotics have been questioned and alternatives have been sought. The field of probiotics as well as the screening methods used to acquire probiotic strains for the alternative management of disease in aquaculture is discussed. This review provides a comprehensive summary of probiotics in aquaculture with special reference to mollusc culture.
Controlling the inorganic nitrogen by manipulating the carbon/nitrogen ratios is a potential cont... more Controlling the inorganic nitrogen by manipulating the carbon/nitrogen ratios is a potential control method for aquaculture systems. This approach seems to be a practical and inexpensive means of reducing the accumulation of inorganic nitrogen in the pond. Nitrogen control is induced by feeding bacteria with carbohydrates, and through the subsequent uptake of nitrogen from the water, by the synthesis of microbial proteins. The relationship among the addition of carbohydrates, the reduction of ammonium and the production of microbial proteins depends on the microbial conversion coefficient, the C/N ratio in the microbial biomass, and the carbon contents of the added material. The addition of carbonaceous substrate was found to reduce inorganic nitrogen in shrimp experimental tanks and in tilapia commercial-scale ponds. It was found in tilapia ponds that the produced microbial proteins are taken up by the fish. Thus, part of the feed protein is replaced and feeding costs are reduced. The addition of carbohydrates, or the equivalent reduction of proteins in the feed, can be quantitatively calculated and optimised, as shown here. Approximate parameters were used in this work. Additional research in this field should be directed at gathering the precise data needed for the exact planning of feed composition.
Nutrient removal is essential for aquaculture wastewater treatment to protect receiving waters fr... more Nutrient removal is essential for aquaculture wastewater treatment to protect receiving waters from eutrophication and for potential reuse of the treated water. A pilot-scale wastewater treatment system consisting of a free water surface (FWS) and a subsurface flow (SSF) constructed wetlands arranged in series was operated for around 8 months. The study was conducted to examine system start-up phenomena and to evaluate system performance in removing inorganic nitrogen and phosphate from aquaculture wastewater under various hydraulic loading rates (1.8 to 13.5 cm day−1). The wetlands system showed rapid start-up behaviors in which process stabilities were achieved in the following sequence: phosphate removal in the SSF without an adaptation period, nitrogen removal in the SSF after 1 month, nitrogen removal in the FWS after 2 to 3 months, phosphate removal in the FWS after 3 months, and vegetation cover in both wetlands after 7 months of operation. Nitrogen removals were excellent, with efficiencies of 86% to 98% for ammonium nitrogen (NH4–N) and 95% to 98% for total inorganic nitrogen (TIN). Removal efficiencies were affected little by the hydraulic loading trials. Phosphate removal of 32% to 71% occurred, with the efficiencies being inversely related to hydraulic loading. The FWS wetland removed most inorganic nitrogen, whereas the SSF wetland removed phosphate at a rate equal to or even greater than the FWS. Removal of ammonium and nitrite (effluent concentrations <0.3 mg NH4–N l−1 and 0.01 mg NO2–N l−1) were sufficient for recycle in the aquaculture system without danger of harming the fish.
… and pond soil analyses for aquaculture, Jan 1, 1992
Abstract Water and soil analyses commonly needed in aquacultural research or in making decisions ... more Abstract Water and soil analyses commonly needed in aquacultural research or in making decisions on water quality management in aquaculture ponds are described in this manual. Most procedures are useful in both freshwater and brackish water. In addition to providing ...
Microorganisms have major roles in pond culture, particularly with respect to productivity, nutri... more Microorganisms have major roles in pond culture, particularly with respect to productivity, nutrient cycling, the nutrition of the cultured animals, water quality, disease control and environmental impact of the effluent. Management of the activities of microorganisms in food webs and nutrient cycling in ponds is necessary for optimising production, but the objectives will differ with the type of aquaculture, the species cultivated and the economics. Unlike the pastoralists who fertilise and seed pastures with selected species, fish farmers only fertilise ponds and hope that useful species of algae, bacteria and other microorganisms will develop. Factors controlling the composition and development of blooms of both desired and undesirable species of algae and bacteria need to be investigated. Analysis of the complex food webs in ponds, combined with measurements of primary productivity, C cycling through bacteria, Zooplankton and meiofaunal biomass changes and nitrogen cycling will provide the basic data for generating a model to describe and predict fish productivity in ponds. Algae and bacteria have often been regarded as single groups of organisms by aquatic biologists, but there is a great diversity of species of each, with different roles and interactions in their ecosystems. This fact, together with the many environmental variables, makes it difficult to develop a single comprehensive, predictive model as a tool for managing food webs and water quality in ponds, but small models specific to given pond systems or stages of grow-out are likely to be successful.
The importance of arachidonic acid (20:4n−6, ARA) in fish nutrition has tended to be overlooked i... more The importance of arachidonic acid (20:4n−6, ARA) in fish nutrition has tended to be overlooked in preference to eicosapentaenoic (20:5n−3, EPA) and docosahexaenoic acids (22:6n−3, DHA), probably due to the predominance of the latter two HUFA in fish tissues. However, despite the abundance of EPA and DHA in fish tissues, the importance of ARA as the primary eicosanoid precursor has been recognised for some time. Only very recently has the relative importance of ARA been given due acknowledgement and already the potential benefits to fish physiology and biochemistry of optimising the ARA nutrition of fish are becoming clear. In the coming decade, the role of dietary ARA should be the focus of considerably more research activity than has occurred to date. The results will undoubtedly emphasise why this ubiquitous HUFA cannot be underestimated in fish nutrition.
Nitrogen N biogeochemistry of aquaculture ponds is dominated by biological transformations of N a... more Nitrogen N biogeochemistry of aquaculture ponds is dominated by biological transformations of N added to ponds in the form of inorganic or organic fertilizers and formulated feeds. Nitrogen application in excess of pond assimilatory capacity can lead to the deterioration of water quality Ž . through the accumulation of nitrogenous compounds e.g., ammonia and nitrite with toxicity to fish or shrimp. Principal sources of ammonia include fish excretion and sediment flux derived from the mineralization of organic matter and molecular diffusion from reduced sediment, although cyanobacterial nitrogen fixation and atmospheric deposition are occasionally important. Principal sinks for ammonia include phytoplankton uptake and nitrification. The magnitude of losses by ammonia volatilization and ammonium fixation to cation exchange sites is minor, but unknown. Interactions between pond sediment and water are important regulators of N biogeochemistry. Sediment represents a source of ammonia and a sink for nitrite and nitrate. The large volume of reduced sediment suggests that the potential for N removal by denitrification is high, although the magnitude of N removal by this mechanism is low because nitrification and denitrification are tightly coupled in aquatic sediments and sediment nitrification is limited by the depth of sediment oxygen penetration. Nitrogen biogeochemistry of aquaculture ponds is affected by feeds and feeding practices, water exchange and circulation, aeration, pond depth and other management procedures. Opportunities for management of N biogeochemistry are limited and goals are based largely on the intensity of fish production. q
A crisis has arisen in the prawn industry in many regions with the onset of disease, with Vibrio ... more A crisis has arisen in the prawn industry in many regions with the onset of disease, with Vibrio spp. being important major causal factors. The value of adding selected strains of Bacillus as probiotic bacteria to control the Vibrio is shown by comparing farms in Indonesia using the same water sources, which contained luminous Vibrio strains. The farms that did not use the Bacillus cultures experienced almost complete failure in all ponds, with luminescent Vibrio disease killing prawns before 80 days of culture were reached. In contrast, a farm using the probiotics was culturing prawns for over 160 days without problems, by using Bacillus at abundances of about 1×104 to 1×105/ml. The bacterial species composition was different in the pond water on the two farms and demonstrates that it is possible to change bacterial species composition and improve prawn production in large water bodies. Vibrio numbers, especially luminous Vibrio numbers were low in ponds where a large abundance of specially selected Bacillus species was maintained in the water column. Vibrio numbers were also low in sediments and no luminous Vibrio occurred in sediments where the probiotic Bacillus were used.
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