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Environmental Impacts of Cage Culture for Catfish in Chau Doc, Vietnam
Effluents and Pollution Research 3 (10ER3)/Study/Thailand and Vietnam
Asian Institute of Technology, Thailand
C. Kwei Lin
Can Tho University, Vietnam
Nguyen Thanh Phuong
University of Michigan
James S. Diana
1) Investigate the cage culture system and its related environmental conditions.
2) Determine the quality and quantity of pollutants produced by cages.
3) Detect the fate of pollutants in the river.
4) Recommend methods for pollution mitigation in cage culture.
Cage culture is commonly practiced worldwide in both freshwater and marine environments, including open ocean, estuaries, lakes, reservoirs, ponds and rivers (Beveridge, 1987). In Southeast Asia, cage culture plays an increasingly important role for fish production, which involves many small-scale farmers in Vietnam, Cambodia, Indonesia and Thailand (Liao and Lin, 2000). However, the environmental impact of cage culture is often ignored and rarely subjected to research or investigation.
The cage culture of Pangasius catfish originated many years ago in Cambodia and has spread widely to other Indochinese countries. The best known areas for intensive catfish production from cage culture are in An Giang and Dong Thap provinces (Andriesz, 2000), where annual production in the year 2000 was 42,000 and 20,000 tonnes by 3,000 and 2,000 cages, respectively (Anon., 2000). The total fish production has increased 5 fold between 1995 and 2000. Most catfish cages are concentrated along the banks of Mekong River near Chau Doc, which is also the major supplier of fingerlings for cage stocking. The main species being cultured are Pangasius bocourtii and P. hypothalamus along with minor species like Chana micropelpte and Puntius gonionotus.
Cage cultured fish are entirely dependent on formulated diet (Phuong, 1998), and the waste produced from this consumption is released directly to the river. This results in cage culture contributing nutrients, organic matter (BOD), and turbidity that causes deterioration of water quality and biota downstream (Pillay, 1992). The quantity of wastes discharged from a fish cage depends on the quantity and quality of feed inputs (Cowey and Cho, 1991). With relatively low protein and high carbohydrate diet, nutrient loading from culture of Pangasius waste is likely to be much lower than for salmonid culture in cages. However, waste in the form of organic matter, particulate matter and suspended solids may result in major heavy sediment accumulation and BOD near the site of cage culture systems. As a result of rapid expansion in cage culture in Chau Doc, water quality is reported to have deteriorated so much that fish disease outbreaks have occurred when the river is low and water flow sluggish during the dry season. While research has been done on seed propagation and diet formulation, little effort has been expended on mitigation of environmental impacts and improvement of water quality to ensure sustainability of cage culture in Chau Doc.
The results of this research will provide information directly to farmers for better management their cages based on water quality and hydrological features. It will also enable managers to estimate carrying capacity of the river for cage culture, which is essential to allow governmental agencies to establish policy and plans for cage culture development. The information will provide some evidence on the degree of water quality deterioration. It will benefit thousand catfish cage farmers in Chau Doc in long term.
Location of the Work
Laboratory and logistic support: Can Tho University
Field site: Chau Doc, Mekong River, Vietnam
Study Plan and Methodology: Social and economic aspects of cage farmers will be investigated with among 20% of farmers using a set of designed questionnaires. A structured checklist and open-ended type of questionnaires will be designed. The questionnaires will consist of socioeconomic characteristics of farmers, cage culture practices, investment cost and return, problems and other information.
Seasonal pattern of hydrological features will be measured monthly in the cage culture area, including flow rate and depth fluctuation in open river water and inside the cages.
Water samples will be taken monthly in 12 locations in the cage culture area along the river and in 12 cages for analyzing ammonia, suspended solids, organic matter, total nitrogen and total phosphorus following standard CRSP methods. DO, pH, and temperature will be measured during the sampling time. Cages will be selected to represent the variety of systems in the region.
The organic matter and nutrient deposition pattern in the river bed near cage culture operations will be determined by taking sediment samples at 12 locations along the river near the 12 cages sampled (Boyd, 1995).
Feed will be analyzed for its proximate composition and N and P nutrient contents as well as feed inputs. Mass balance equations of inputs and accumulations in animals will be made, and the resulting loss of materials to the water column estimated.
Relevant environmental regulations will be reviewed and governmental agencies interviewed for the information about regulations, enforcement and farmers' attitudes.
As cage culture is widely practiced in the Southeast Asian countries, this case study will provide an important methodology as protocols of environmental impact.
August 2001 to September 2002
Report submission: January 2003
Andriesz, P., 2000. Aquaculture in Vietnam. Global Aquaculture Advocate, 3:3638.
Anon., 2000. Annual report on rural development of Angiang and Dong Thap Provinces. Department of Agriculture, Angiang and Dong Thap Province, Vietnam.
Beveridge, M., 1987. Cage Aquaculture. Fishing News Books Ltd., England.
Boyd, C.E., 1995. Bottom Soils, Sediment, and Pond Aquaculture. Chapman & Hall, New York, 348 pp.
Cho, C.Y., J.D. Hynes, K.R. Wood, and H.K. Yoshida, 1991. Quantification of fish culture wastes by biological and chemical (limnological) methods. In: C.B. Cowey and C.Y. Cho (Editors), Nutritional Strategies and Aquaculture Waste. University of Guelph, Canada.
Liao. I-C. and C.K. Lin, 2000. Cage culture in Asia. Proceedings of International Symposium on cage Aquaculture in Asia. Asian Fisheries Society and World Aquaculture Society, Manila, Philippines.
Phuong, N.T., 1998. Cage culture of Pangasius catfish in the Mekong delta, Vietnam: Current situation analysis and studies for feed improvement. Unpublished Ph.D. dissertation, National Institute Polytechnique of Toulouse, France.
Pillay, T.V.R., 1992. Aquaculture and Environment. Blackwell Scientific Publications Inc., Cambridge, England.
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