Establishment of Water Quality Model of Farming Ponds in the Pearl River Delta and its Application
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The intensive hike-ponds in the Pearl River Delta are taken to establish a water quality model for pond farming.The results of model verification indicate that the simulation of the model fits the real situation well and it can be used as a research tool for pond aquaculture ecosystem or as a decision support tool for the management of pond farming.The model established is used to research main factors affecting the water quality and the carrying capacity of farming ponds.Results show that DO is generated mainly from phytoplankton photosynthesis and artificial oxygen enhancement,and consumed mainly by fish respiration.DO contents are influenced by various factors.TAN and SRP are generated mainly from fish metabolization and consumed mainly by absorption of phytoplanktons.They change much slowly compared with DO.The farming capacity of the farming ponds is influenced by many factors,including internal factors such as feed digestion and utilization and external factors such as the DO level and the TAN accumulation.The farming capacity of the mainly farmed fish increases with the increase of feed digestion rate and is restricted by the lack of DO and the high TAN concentration.The farming capacity of secondarily farmed fish increases with increasing availability of the heterotrophic feed caused by the decrease of digestion of feed for mainly farmed fish,and is restricted by the lack of DO.Mixed,rotational fishing model makes full exploitation of farming space,which can further extend the farming capacity in fish ponds.Keywords:
Carrying Capacity
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Abstract Increase of production of fish by traditional methods, based primarily on the extensive use of natural resources, has certain natural limitations.The limiting factors are land, water and the environment. Considering this fact, the perspective expansion of industrial farms, provided with superintensive technologies, is actual. The role of abiotic environmental factors in the life of fish is enormous. For example, the water temperature determines the intensity of metabolism and is a natural stimulus determining the begining of spawning migration of fish. Water temperature has a very important influence on the life of the organism, particularly on the metabolic processes, the behavior and dispersion of organisms. Water quality is one of the most important factors stimulating the development of water biotechnology. In this regard, we explored the physical and-chemical features of the Volga water from the viewpoint of the trout-breeding. The analysis revealed that the water does not fully meet the required water quality for trout ponds. Characteristics as pH, absence of hydrogen sulfide meet the requirements; such indicators as permanganate and bichromate oxidation, BPK5, ammonium ion, nitrates and nitrites, oxygen content are noted exceeding the standard values for trout farms. Power engineering and fish farming are connected closely – power plants contribute to the creation of favorable conditions for the cultivation of commercial fish, including valuable and fish-breeding complexes based on water coolers help to improve their environmental condition. At the same time in Russia in recent years, this industry is beginning to receive attention it deserves. The experience of Western countries shows a new direction of the industry development: in the previous period the favorable conditions for growing and breeding fish were created on the basis of the warm water for increasing production capacity of energy enterprises due to energy production and fish production, nowadays the power plants are built at fish-breeding enterprises in order to optimize costs and increase profitability of fish production.
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Salt-affected soils occur naturally, extending along the coastal area and the northeastern part of Thailand. Besides that the activities such as brackish water shrimp farming have caused soil salinization due to the addition of concentrated brine and salt granules into the ponds to create suitable salinity for the growth of shrimp. Shrimp farming area has rapidly increased just over a decade ago. It is estimated that the total area of shrimp farming is approximately 72,000 ha in the coastal area, while 22,400 ha are located in 23 Central Plain provinces. This activity has caused severe anthropogenic soil salinization. Discharge of sludge, excess feeds and saline water into nearby irrigation canals, including seepage of saline water to adjacent cultivated areas and under the ground has led to a significant built-up of toxicity and salinity. It is estimated that the total area of salt-affected arable land caused by shrimp farming extended to an area of 90,650 ha. The government had been concerned about these problems, so it decided to ban shrimp farming in freshwater areas in July 1998. At the same time it introduced the plan to reclaim the Soil and land problems have occurred from various reasons, resulting in the degradation of land resources, eventually causing the decline in crop yields. Soil salinity is one of the oldest problems for mankind that has affected agricultural production since ancient time. It is a major factor that has turned high quality lands to be low quality ones. Salt-affected soils in Thailand are found along coastal area and in the northeastern part of the country. Beside that, some other activities such as brackish water shrimp farming have also caused soil salinization due to the addition of concentrated brine and salt granules into the ponds to create suitable salinity level for the growth of shrimp. Brackish water shrimp farming in Thailand has been operated along the coastal zone and estuaries for the last 70 years. As a lucrative business, the number of farms has been rapidly increased in recent years. However, because of improper farming practices, soil and water pollution and shrimp disease outbreak occurred in many areas. The shrimp farming was then introduced to freshwater areas of arable land in the Central Plain, which is considered the rice bowl of the country. It is estimated that the total area of shrimp farms is approximately 72,000 ha in the coastal area, while 22,400 ha are located in 23 provinces of the Central Plain. Thailand is an agrarian country; its economy depends very much on agriculture. The land resource is an important factor and is the foundation for agricultural production. Agriculture sector has contributed significantly to economic growth especially to the Gross Domestic Product (GDP). Therefore, the aims of land use at present are considered on the sustainable use of land. The diverse use of land for many purposes without care resulted in the adverse effect to the land for future generations. The activity on shrimp farming is a good example to show that soil and water resources could become degraded as a result of anthropogenic soil salinization. This is a major cause for production constraint that would eventually affect the National Action Plan for Food Security.
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Arable land
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Commercial fish feed
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As potential areas for fish culture are being rapidly used up for various other purposes, high production targets are being fixed for the available water bodies for providing required amount of fish protein to the escalating population. Such high production targets can only be achieved by enhancing the productivity levels of available resources. This can be done by adoption of judicious management practices of various factors which govern productivity of the culture system. One of the most important factors to be taken into account in this respect is the availability of nutrients in the fish pond soil and waters. It is, therefore necessary to maintain the nutrient status of the pond to optimum ranges for obtaining maximum production of fishes from aquatic ecosystem. To reduce the possibility of indiscriminate application of nitrogenous fertilizers in any fish pond, an idea about the status of this nutrient element in the pond soils appears to be necessary. In the present study, therefore, occurrences of different forms of nitrogen in three different kinds of pond soils commonly observed in India viz. alluvial, red and lateritic and hilly, were studied with respect to their relationships with various other soil properties and, especially, the production of primary fish food organisms in water.
West bengal
Fish pond
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Dike
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Shrimp farming
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In the beginning, fish farming was considered to be harmless to marine environment. Nowadays we know that fish farming can cause changes in ecosystem and is considered to be a potential polluter. The intensity and the range of pollution caused by fish farming depends on the stability of every single ecosystem (geomorphology, currents, and depth… ) and on the technology of fish farming as well as on the number and species of farmed organisms. The time and space dimension of eutrophication (excessive blooming of algae) depends on dynamics of the water body and can range from several days to a few years. Some side effects of fish farming can be solved by technical and technological improvements (off - shore farming) and by the complete integration of fish farming into ecological, social and economical structure of shore region. It is necessary to establish total control over the negative influences of fish farming on the marine environment and to notice potential changes in ecosystem on time.
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Pen crab farming has become a main part of inland water fishery in China in the past ten years. However, its influences on lake environment is unclear till now. In 1997, a research was carried out to show to what degree and how the pen crab farming of different pattern may impact on the water quality, hydrobiological communities and sediment environment by comparing these factors inside and outside pens in East Taihu Lake. The results showed that the impacts of the crab farming both with bait casting and without on factors of water quality, planktonic community and the water vegetation were not obvious, because of the dilution of huge amount of water. But it was apparent on the sediment quality that was characterized by a sharp increase of total nitrogen, phosphorus and organic carbon inside the pen as much bait not utilized effectively had deposited. The number and biomass of benthonic molluscs decreased rapidly by prey of crabs. It has been also known that the crab farming without bait casting had a net output of nutrient from lake and that the crab farming with bait casting had a big net input of nutrient to lake as the utilization rate of bait was very low. It was obvious that pen crab farming of low density without bait casting was the best pattern in obtaining modest fishery production while keeping a good environment. However, it was still needed to control and plan the farming scientifically as it may result in such influences as the physical clog against current and accumulation of pollution.
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Abstract The major limitations to the development of aquaculture in many regions are availability of water resources and environmental impact. Water is critical to aquatic animals, for it both serves as the medium that supplies the required oxygen and creates the physical environment that allows for movement of the animals. As world population has grown and industries have increased their production to meet the demands of the growing population, water has become a scarce resource that has had many conflicting demands placed upon it. Consequently, the major strategy for increasing aquaculture production with this limited water resource is production intensification. As fish biomass density increases, however, the amount of oxygen dissolved naturally in water becomes limited, thus necessitating supplemental aeration and oxygenation. In addition, the increased use of artificial feed as a means to developing a high density culture system leads to water pollution that stems from the facts that aquatic animals cannot completely utilize the feed and that the animals will excrete other metabolic products such as ammonia that are toxic to the aquatic animals at elevated levels. Internally, the waste produced deteriorates the water quality and makes the water unsuitable for fish to live in, while externally, discharge of the polluted water, if not properly managed, may lead to adverse effects on the environment.
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