WORLD AQUACULTURE 63 Kamrangir Char to the west, although the extent and nature of production is not known with certainty. The major constraints to the development of periurban aquaculture in Dhaka city include lack of community awareness, multiple ownership of water bodies, rapid urbanization, flood, drought, poor water quality, environmental and public health concerns. Marketing and Trade More than 100,000 t of fresh fish are sold in markets annually but per capita fish consumption within the city is below the average for Asia (Islam et al. 2004). Only a very small amount of fish fulfilling the city demand is supplied from the periphery. All the surveyed upazilas, except the Kaliakoir of Gazipur district and Bandar of Narayanganj district, produce less fish than is demanded. High-cost fish, such as carps, catfish and live fish from periurban areas are sold to affluent consumers. Mixed fish are usually sold to the vast majority of the people who are low-income. From 7,150 to 9,530 t of fish come to Dhaka from periurban areas, less than 10 percent of the total supply. The remainder comes from around Bangladesh. Distribution and marketing networks for fish within Dhaka are very complex. However, all types of fish, from high cost to low cost, are easily sold because of the presence of a heterogeneous mixture of buyers in the city. Domestic markets and distribution of fish are dominated by a large number of intermediaries. Fish can pass through many channels, depending if it is traded internally or for export. Fish distribution from periurban areas to the city usually involves four steps (Fig. 3). Fish come to the city market through intermediaries because of the better price in the urban area of Dhaka. Aquaculture, Food Security, and Climate Change Aquaculture in and around cities creates jobs and can improve the environment, reduce waste and provide quality food. Previously the risk of contamination from waste water posed dangers. But safe ways of producing fish and growing water vegetables around cities are now available. There is a concern that climate change could increase food insecurity. From this point of view, periurban aquaculture represents a new dimension in fish production in Bangladesh. Aquaculture offers opportunities to increase food production that may also help to increase income, food security, and the livelihoods of millions of poor residents. Periurban aquatic systems of Dhaka are located in wetlands on the peripheries of the city. Urbanization, with its ever increasing pressures on land and water, gradually encroached on these wetlands, leading to their disappearance. Loss of floodplain wetlands has severe consequences, particularly for poor people. Wetland loss has reduced their capacity to act as buffers or sinks by soaking up, containing, and then safely releasing floodwaters. When drained, filled and built up, city authorities end up spending increased proportions of budgets on flood protection as a consequence. Removal of existing wetlands for urbanization has accelerated the overuse of groundwater, resulting in lowered water tables. Conclusions Urban and periurban aquaculture, in various guises, is a reality throughout Bangladesh and West Bengal, India. An estimated 150 farms are in operation around Dhaka, with a growing number producing high-value fish, such as Thai catfish in response to growing demand from more affluent urban consumers. Research in Saidpur suggests that 125-135 periurban ponds are used to culture traditional carp species for local sale and consumption. Formal and informal wastewater treatment and water reuse through urban and periurban aquaculture is practiced in Bangladesh and West Bengal, India. Pen and cage culture on floodplains adjacent to Dhaka indicate the growing diversity of urban and periurban aquaculture. Without comprehensive data concerning urban and periurban aquaculture, it is difficult to assess its significance compared to rural production. Where practiced, urban and periurban aquaculture is important for income, livelihoods and food security, and can contribute to enhanced wastewater management and environmental protection. Information on the nature and extent of urban and periurban aquaculture is required to specify its value in competing for scarce development resources. Notes 1 Bangladesh Centre for Advanced Studies, Gulshan-1, Dhaka-1212, Bangladesh 2 Department of Zoology, University of Chittagong, Chittagong-4331, Bangladesh 3 Market Development in Prawn, Winrock International, Gulshan-1, Dhaka, Bangladesh * Contact address of the corresponding author: Prabal Barua. Bangladesh Centre for Advanced Studies, House-10, Road-16/A, Gulshan-1, Dhaka-1212, Bangladesh. Cell :: +8801843777965, E-mail : prabalims@gmail.com References ADB (Asian Development Bank). 2005. 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