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Item Ancient Reservoirs of Sri Lanka: A Modern Biological Resource for Assuring Food Security in Rural Communities(University of Kelaniya, 2005) Kularatne, M.G.; Amarasingha, U.S.Reservoir construction in Sri Lanka dates back to times even before the period of written history. In Sri Lanka (64,652 km2), there are over 200 large (750 – 7,793 ha) and medium-sized (250 – 750 ha) reservoirs with a cumulative extent of over 130,000 ha, which support capture fisheries. In addition, there are over 15,000 small (<50 ha) village reservoirs with a total extent of about 39,000 ha. The reservoir density in Sri Lanka (about 2.6 ha for every km2 of island) is one of the highest, if not the highest in the world. Almost entire reservoir resource in Sri Lanka, with the exception of recently constructed hydroelectric reservoirs, supports agricultural food production in the country. As the extent of perennial reservoirs in each district is directly related to per capita freshwater fish consumption, in addition to agricultural production, major perennial reservoirs of Sri Lanka support animal protein production in the form of fish production. This is of particular importance because marine fish consumption is much low in inland districts possibly due to the availability of good quality freshwater fish locally. Also, there is a significant potential for the development of culture-based fisheries in small, village reservoirs of the country. An average fish yield of about 450 kg ha-1 can be achieved during a single culture cycle within a year from the culture-based fisheries in these village reservoirs. However, in order to achieve success of this strategy, a strong extension mechanism is needed to obtain active community participation. As inland fishery is a source of relatively cheap animal protein for rural communities, future prospects of this sector for food security need to be properly understood to give a high priority for inland fisheries research and development in national development plans.Item Species composition and abundance of littoral oligochaete fauna in Lunuwila reservoir, Sri Lanka(International Review of Hydrobiology, 2000) Weerasundara, A.; Pathiratne, A.; Costa, H.H.Item Morphological and histological changes in the gonads of the estuarine cichlid fish Etroplussuratensis (Bloch) during gonadal development(Bulletin of the National Institute of Oceanography, 1984) Pathiratne, A.; Costa, H.H.Item The Effects of leaving central bare areas in traditional circular brush-parks on the yield of fish in the brush-park fishery in Negombo estuary, Sri Lanka.(Japan International Marine Science and Technology Federation, 1995) Costa, H.H.; Wijeyaratne, M.J.S.Item Limnology and culture-based fisheries in non-perennial reservoirs in Sri Lanka(Lakes & Reservoirs: Research & Management, 2005) Jayasinghe, U.A.D.; Amarasinghe, U.S.; de Silva, S.S.This study was carried out to investigate the possibility of using the limnological characteristics of non-perennial reservoirs in Sri Lanka for the future management of culture-based fisheries. Forty-five reservoirs were randomly selected to study their limnology, out of which 32 were stocked with fish fingerlings of Chinese and Indian carps, tilapia and freshwater prawn at stocking densities ranging from 218?4372 fingerlings ha?1. Of these, 23 reservoirs were harvested at the end of the culture period (6?10 months). Thirteen limnological parameters were measured during the water retention period of each of the 45 reservoirs between November 2001 and January 2004. The mean values of the limnological parameters were used to ordinate the reservoirs through principal component analysis. Ordination showed a productivity gradient among reservoirs where Secchi disc depth, total phosphorus, chlorophyll-a, inorganic turbidity and organic turbidity were identified as key factors. The total fish yield of culture-based fisheries was positively correlated to the scores of the first principal component axis. This study reveals that it is possible to classify non-perennial reservoirs in Sri Lanka based on the above limnological parameters in order to develop culture-based fisheries and that they could be applicable in comparable water bodies elsewhere in the tropics.Item Some aspects of photosynthetic characteristics in a set of perennial irrigation reservoirs located in five river basins in Sri Lanka(Hydrobiologia, 2002) Silva, E.I.L.; Amarasinghe, U.S.; de Silva, S.S.; Nissanka, C.; Schiemer, F.Phytoplankton primary productivity of eleven irrigation reservoirs located in five river basins in Sri Lanka was determined on a single occasion together with light climate and nutrient concentrations. Although area-based gross primary productivity (1.43?11.65 g O2 m?2 d?1) falls within the range already established for tropical water bodies, net daily rate was negative in three water bodies. Light-saturated optimum rates were found in water bodies, with relatively high algal biomass, but photosynthetic efficiency or specific rates were higher in water bodies with low algal biomass, indicating nutrient limitation or physiological adaptation of phytoplankton. Concentrations of micronutrients and algal biomass in the reservoirs are largely altered by high flushing rate resulting from irrigation release. Underwater light climate and nutrient availability control the rate of photosynthesis and subsequent area-based primary production to a great extent. However, morpho-edephic index or euphotic algal biomass in the most productive stratum of the water column is not a good predictor of photosynthetic capacity or daily rate of primary production of these shallow tropical irrigation reservoirs.Item Impact of Oreochromis mossambicus ? O. niloticus (Pisces: Cichlidae) hybridization on population reproductive potential and long-term influence on a reservoir fishery(Fisheries Management and Ecology, 1996) Amarasinghe, U.S.; de Silva, S.S.Exotic cichlids, introduced to Asia during the second half of the twentieth century, contribute significantly to the reservoir fisheries in the region. The two major cichlid species, Oreochromis mossambicus (Peters) and O. niloticus (L.), tend to interbreed easily. In Sri Lankan reservoirs, introgressive hybridization of these two cichlids takes place. The reproductive biology of O. mossambicus, O. niloticus and their hybrids in three reservoirs in Sri Lanka was evaluated. An imbalance in sex ratio with male dominance was evident. The estimated fecundity for 20-cm fish, using fecundity-total length relationships for various populations, indicated that there was a decline in fecundity in hybrid forms. It is hypothesized that the long-term effect of crosshybridization between the two cichlids might lead to a decline in fish yields in perennial reservoirs of Sri Lanka. The importance of the findings of the present study for the management of the reservoir fisheries in Asia is highlighted.Item A Study of Temperature and Salinity Variations with Depth in Salt Pans at Palavi in North-West Region of Sri Lanka(Annual Research Symposium, Faculty of Graduate Studies, University of Kelaniya, 2000) Hewageegana, P.S.; Amarasekara, C.D.; Jayakody, J.R.P.; Punyasena, M.A.Item Land preparation water management by canal simulation in a paddy estate(Proceedings of the Tenth Asian Congress of Fluid Mechanics (ACFMX), 2004) Najim, M.M.M.; Lee, T.S.; Haque, M.A.; Mowjood, M.I.M.