Environmental capacity of receiving water as basis for regulating intensity of milkfish (Chanos chanos Forsskal) culture
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This paper presents the results of the assessment of the environmental condition of a receiving water and demonstrates how the environmental capacity of the system can be estimated based on effluent discharge from milkfish ponds and water criteria from scientific literature and other studies. An estuary (average volume, 295 333 m3; average depth, 1.9 m) in Punta Pulao, Dumangas, Iloilo, Philippines served as discharge and irrigation system for commercial milkfish ponds and experimental/verification ponds owned by the Southeast Asian Fisheries Development Center. Total ammonia nitrogen, nitrite, nitrate, phosphate, and chlorophyll a (chl a) were determined monthly (during spring tide) for 4 months. Samples were taken at low and high tides that coincided with the draining and flooding of ponds, respectively. Monthly concentrations of these water quality variables generally increased from the first to fourth month of sampling (April–July 2001) during low tide. Very slight increases were observed during high tide. The magnitude of changes in the diurnal patterns of phosphate, chl a, and dissolved oxygen appeared to be higher at spring tide than at neap tide. This indicates that the inflowing river at low tide (during spring tide) brought effluents containing high amounts of nutrients from ponds located upstream. The water, salt, dissolved inorganic nitrogen (DIN), and phosphate (DIP) budgets of the entire estuary were determined following the one-box model by LOICZ-IGBP (2000, LOICZ biochemical budgeting procedure: a tutorial pamphlet. L. T. David, M. L. San Diego-McGlone, C. J. Crossland and S. V. Smith (Eds). Publ. for LOICZ International Project Office, the Netherlands, 29 pp.). The budgets indicate that the system is net heterotrophic and nitrogen (N) fixing during the dry months, but that there could be no environmental impact during the rainy months because of short water exchange time. Results further suggest that the system is a source of N and phosphorus (P) during the dry and rainy months; the condition is largely influenced by the high amount of nutrient inputs in to the river. Linear regression analysis was performed to determine relationship between nutrient concentrations in the system and total DIN or DIP input to the system at low tide. Environmental capacity in terms of the maximum amount of DIN or DIP input to the system was predicted using regression analysis and following set criteria for nutrients, i.e. nitrite, nitrate, and phosphate. At present, the estuarine water quality has already reached its environmental capacity during the dry months. About 945 ha of commercial milkfish ponds are operating upstream, mostly as extensive systems. If these ponds are converted to semi-intensive or intensive systems, it is recommended that the pond area be reduced to 122 ha if the DIP criterion is to be followed so as not to exceed the environmental capacity. Exceeding this environmental capacity may affect production through reduction of fish growth, occurrence of diseases, and fish mortalities.
CitationSumagaysay-Chavoso, N. S., San Diego-McGlone, M. L., & David, L. T. (2004). Environmental capacity of receiving water as basis for regulating intensity of milkfish (Chanos chanos Forsskal) culture.
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Conference paperSM Aypa - In TU Bagarinao & EEC Flores (Eds.), Towards sustainable aquaculture in Southeast Asia and Japan: Proceedings of the Seminar-Workshop on Aquaculture Development in Southeast Asia, Iloilo City, Philippines, 26-28 July, 1994, 1995 - SEAFDEC Aquaculture DepartmentAquaculture is regarded as the most promising source of protein food in the years ahead. Milkfish and Nile tilapia are the major fishes now produced but groupers, sea bass, rabbitfish, red snappers, carps, and catfishes are grown by some farmers. The tiger shrimp is still the most important cultured crustacean, but white shrimps and mudcrabs also have great potential. Oysters and mussels are produced in considerable amounts. Mariculture of the seaweed Eucheuma is now a well established industry, and the pond culture of Gracilaria for agar extraction is beginning to take off.
Conference paperAS Camacho & N Macalincag-Lagua - In JV Juario & LV Benitez (Eds.), Seminar on Aquaculture Development in Southeast Asia, 8-12 September 1987, Iloilo City, Philippines, 1988 - SEAFDEC Aquaculture DepartmentThe aquaculture sector of the Philippine fishing industry registered the highest growth rate of 12.5% in 1977-1986. The contribution of aquaculture to the total fish production was equivalent to 24% in 1986 compared to only 85 in the early 1970's. In terms of quantity, the mariculture subsector registered the highest growth rate of 10.2% in 1982-1986, whereas in terms of value the brackishwater fishpond subsector showed the highest growth rate of 33%. Meanwhile, freshwater aquaculture production exhibited a negative growth rate due to reduction of activities in Laguna de Bay and the slow expansion in hectarage of the commercial freshwater fishponds. Research by several agencies concentrated heavily on the culture of milkfish (Chanos chanos), tilapia (Oreochromis niloticus), Chinese carps (Aristichthys nobilis and Hypophthalmichthys molitrix), tiger prawn (Penaeus monodon), and sea bass (Lates calcarifer). Innovations in seaweed, oyster, and mussel farming are also discussed. Research directions are presented to assure an ecologically sustainable growth in aquaculture with emphasis on countryside development.
Conference paperCR De la Cruz - In TU Bagarinao & EEC Flores (Eds.), Towards sustainable aquaculture in Southeast Asia and Japan: Proceedings of the Seminar-Workshop on Aquaculture Development in Southeast Asia, Iloilo City, Philippines, 26-28 July, 1994, 1995 - SEAFDEC Aquaculture DepartmentIntegrated aquaculture-agriculture systems are more common in fresh water than in brackish water. Nevertheless, southeast Asian countries already have considerable research and experience in brackishwater integrated farming systems. In the Philippines, the effects of animal wastes on water quality and production of fish have been studied: chicken wastes on the mixed culture of milkfish Chanos chanos, tilapia Oreochromis niloticus, and shrimp Penaeus indicus; chicken and cattle manures on P. monodon and Artemia; and swine wastes on tilapia O. mossambicus. In Indonesia, about 60 hectares of fish farms have crops (pumpkin, spinach, cassava, maize, and chili) or livestock (cattle, goat, sheep, chicken, and duck) grown on the dikes of milkfish ponds. In Vietnam, culture of the giant prawn Macrobrachium rosenbergii, Scylla serrata and marine shrimps has been integrated with coastal rice farming. Aquaculture-silviculture is a flourishing venture in Vietnam and Indonesia and gaining ground with experimental sites in Thailand and the Philippines. The seaweed Gracilaria has been cultured with fishes and shrimps in Taiwan, Vietnam, Thailand, and the Philippines. The production of Artemia cysts and biomass has been integrated with salt-making and fish or shrimp farming in the Philippines and Thailand. Production inputs and outputs from these integrated farming systems vary widely and socioeconomic information is nil. It is imperative to conduct follow-up research and evaluation of each system in terms of production and socioeconomics.