Shrimp Farming and the Environment - Library

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FIGURE 8. CONTINUUM OF DIFFERENT SHRIMP FARM PRODUCTION SYSTEMSTRADITIONAL/EXTENSIVE SEMI-INTENSIVE INTENSIVE100kg/ha 2,000 kg/ha 6,000 kg/haAVERAGE PRODUCTION PER CROPUnfertilized pondFertilized pondFertilized and fed pondFertilized, fed pond with supplementalwater flow and aerationContinuous skilled management, uniformponds, formulated feeds, high capitalinvestmentClosed recirculation systemsLow200,000/haIn practice, different people use intensity classifications in different ways, and generalizations—such as“intensive shrimp culture is not sustainable”—are often misleading. “Intensity” relates to resourceutilization (land, water, capital, labor, seed, feed, fertilizer, and fuel), and different systems may bemore or less intensive depending upon which resource is considered. It is important to understand theuse of all of these resources if a thorough assessment of the sustainability of different kinds of shrimpculture is to be made. For example, so-called traditional or extensive systems are generally low oncapital, labor, seed, and feed intensity, but use a great deal of land and water. “Intensive” systems, onthe other hand, are generally low on land intensity, but high on labor, seed, and feed intensity.Traditional intensive systems were also high on the intensity of water use, but many producers (inThailand, for example) now use closed or low water-exchange systems. The desirability andsustainability of different systems depends to a great degree on the cost and availability of thesedifferent resources, and these vary tremendously between countries.Traditional/extensive systems“Traditional” shrimp farming is still conducted in some parts of the tropics (e.g., West Bengal andKerala in India; see Clay 1996) and in low-lying impoundments along bays and tidal rivers, often inconjunction with crab and finfish. Impoundments range in size from a few hectares to over 100hectares. When local waters are known to have high densities of young shrimp, the farmer opens thegates, impounds the wild shrimp, and then grows them to maturity or whenever they are marketable.The shrimp (along with assorted crabs and finfish) feed mainly on natural food in the pond. Stockingdensity depends on the abundance of wild seed but rarely exceeds 10,000 per hectare. Production iscommonly from continuous or semicontinuous harvesting, and ranges from about 50 to several hundredkg/ha/yr (head-on weight).Some farmers stock wild juveniles that they themselves have caught or purchased from fishermen.There may also be some limited fertilization and supplementary feeding. The tides provide waterexchange, dependent on the height of the intertidal zone and the local tidal regime. Construction andoperating costs are low. Cast-nets and bamboo traps are used to produce the harvests.Various forms of polyculture and mixed cropping are practiced. Shrimp can be grown in the same pondas other species such as milkfish. Ponds may be used for rice production during the wet season, and forshrimp production during the dry season. Examples of salt production (dry) and shrimp farming (wet)also occur. Such alternating use of the ponds has certain advantages, increasing the farmer’s selfsufficiencyand overall production. In addition, polyculture reduces the financial risk involved inshrimp farming. However, it is only feasible in very specific climatic and hydrological regimes.15
Semi-intensive systemsTypically conducted at the upper end of the tidal range, or above the high tide line, semi-intensivefarming usually involves carefully laid-out ponds (0.1 to 25 ha), feeding, and diesel- or electricalpoweredpumping. Pumps typically exchange 5 to 15% of the water each day. With stocking ratesranging from 25,000 to 200,000 juveniles per hectare, there is more competition for the natural feed inthe pond, so the farmers augment production with shrimp feed (commercial formulated compoundfeed, “trash” fish, or locally collected mollusks). Construction costs vary from $10,000 to $25,000 perhectare. Wild or hatchery-produced juveniles are sometimes stocked at high densities in nursery pondsuntil they are large enough to be stocked at lower densities in grow-out ponds. The farmer harvests bydraining the pond through a net, or by using a harvest pump. Farmers usually renovate their ponds oncea year. Yields range from around 500 to 10,000 kg (head-on) per hectare per year.Intensive systemsIntensive shrimp farming usually involves small ponds (0.1 to 5 hectares), high stocking densities(more than 200,000 juveniles per hectare), around-the-clock management, intensive feeding, wasteremoval, and mechanical aeration. Mechanical aeration—the addition of oxygen to the water—permitsmuch higher stocking densities and feeding levels. Water exchange rates for such systems used to bevery high—up to 30% a day, but in recent years (stimulated mainly by a fear of introducing diseasethrough the water supply) many farmers in Thailand have begun to use low water-exchange systems.These involve zero or minimal water exchange in the early part of the grow-out cycle, with waterexchanged only as required for water-quality management toward the end of the cycle. In some cases,water may be recycled through a storage reservoir, allowing for the development of completely closedwater systems, so that the only water required is to make up water lost to seepage and evaporation.Intensive shrimp culture is also practiced in raceways and tanks, which may be covered or indoors,although this method remains relatively unimportant commercially.Construction costs range from $10,000-$25,000 for simple pond systems in developing countries to asmuch as $250,000 per hectare for sophisticated concrete pond, tank, or raceways systems.Sophisticated harvesting techniques and easy pond cleaning after harvest permit year-round productionin tropical climates. Yields of 5,000 to 20,000 kg (head-on) per hectare per year are possible, althoughthe sustainability of higher rates is questionable. Production costs range from $4 to $8 per kg of liveshrimp. Experience from Taiwan, Republic of China; Thailand; and Vietnam has shown that intensiveshrimp farms can be converted relatively rapidly and without major additional investments to otherspecies such as grouper, seabass, and milkfish, although these are generally less profitable.Super-intensive systemsSuperintensive shrimp farming takes even greater control of the environment and can produce yields of20,000 to 100,000 kg/ha/year. A superintensive shrimp farm in the U.S. once produced at the rate of100,000 kg/ha/year, but it was wiped out by a viral disease. Thus far, superintensive shrimp farms haveachieved only marginal success. Generally, they require highly skilled managers and run the risk ofdisease, which leads to crop failures. They can also harm the quality of surrounding water by releasingpollutants in effluent, and must take steps to prevent other environmental damage. It seems that annualproduction levels above 10,000 kg per hectare are risky.Owing to the high density of stocking, superintensive operations require far less land area to producelarge amounts of shrimp. This fact may act in favor of superintensive operations in the future, if andwhen some of these other problems are solved.16
Page 7 and 8: sensitivity analysis should include
Page 9 and 10: ABBREVIATIONSMTkgmcmhaozPUDFOBCIFC&
Page 11 and 12: ORGANIZATION OF THE REPORTIn Chapte
Page 13 and 14: same time, development is necessary
Page 15 and 16: Current shrimp farming practice inc
Page 17 and 18: Current status of the industryToday
Page 19 and 20: In recent years, several major crop
Page 21: CHAPTER 2: SHRIMP FARMING SYSTEMSSh
Page 24 and 25: FeedsHatcheries use a combination o
Page 28 and 29: TABLE 3. COMPARISON OF INPUTS FOR T
Page 30 and 31: Shrimp farming systems vary greatly
Page 32 and 33: creeks, and sea-grass beds, fulfill
Page 34 and 35: arrangement in Thailand, for exampl
Page 36 and 37: capacity is not exceeded, the nutri
Page 38 and 39: shrimp or high-value finfish produc
Page 40 and 41: In more immediately practical terms
Page 42 and 43: Disease prevention and managementDi
Page 44 and 45: (Raa 1996) indicates that it is pos
Page 46 and 47: suitable for human consumption or f
Page 48 and 49: • Supply and effluent canals shou
Page 50 and 51: CHAPTER 4: SOCIAL AND ECONOMIC IMPA
Page 52 and 53: opportunities would need to be iden
Page 54 and 55: 26 workdays per hectare, and an ext
Page 56 and 57: One of the key elements for success
Page 58 and 59: Minimizing negative social repercus
Page 60 and 61: CHAPTER 5: FINANCIAL RISKS ASSOCIAT
Page 62 and 63: Credit riskAccess to credit at fair
Page 64 and 65: Natural factorsShrimp diseaseThe ou
Page 66 and 67: CHAPTER 6: PLANNING AND MANAGEMENT
Page 68 and 69: Planning and resource managementIna
Page 70 and 71: Such initiatives have been or are b
Page 72 and 73: Conclusions and recommendationsReco
Page 74 and 75: equired to promote sustainability a
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CHAPTER 7: PROJECT PLANNING AND ASS
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• Appraisal and supervision missi
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The structure of the executive summ
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CHAPTER 8: CONCLUSIONS, RECOMMENDAT
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• Requirements and guidance for f
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EmploymentAs mentioned in the repor
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ANNEX 1: A BLUEPRINT FOR FEASIBILIT
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• Sensitivity calculations and an
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Table A4: World shrimp farming prod
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ANNEX 4: CASE STUDIES UNDERTAKEN BY
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ColombiaThe Adoption of Good Manage
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LocationAppendix A--Meetings Held o
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BIBLIOGRAPHYAdger, W.N. 1998. Susta
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Claridge, G. 1996. Legal approaches
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Hambrey, J.B., M. Phillips, K. Chow
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Phillips, M.J., & D.J. Macintosh. 1
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World Commission on Environment and
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