Zoology
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Item Studies on the fish ponds at Pitipana, Negombo 1. Seasonal and diurnal variation of some hydrobiological factors(The Fisheries Research Station, 1979) de Silva, S.S.; Silva, E.I.L.Item Fish Fauna of a coastal lagoon in Sri Lanka: Distribution and seasonal variation(The Fisheries Research Station, 1979) de Silva, S.S.; Silva, E.I.L.Item Size dependent photosynthetic characteristic of phytoplankton in the Victoria reservoir(Sri Lanka Association for Fisheries and Aquatic Resources, 2003) Amarasinghe, U.S.; Silva, E.I.L.; Weerasinghe, W.M.D.Item Ecosystem Structure and Dynamics?A Management Basis for Asian Reservoirs and Lakes(Reservoir and Culture-based Fisheries: Biology and Management, 2001) Schiemer, F.; Amarasinghe, U.S.; Frouzova, J.; Sricharoendham, B.; Silva, E.I.L.INCO-DC FISHSTRAT Project, funded by the European Commission, is an ongoing multidisciplinary research program undertaken over the period 1998?2001. Three reservoirs in Sri Lanka (Victoria, Minneriya and Udawalawe) of different morphology, age and geographic location, Ubolratana reservoir, in Thailand, and Lake Taal, in the Philippines, are the object of this study. The scope of the project encompasses a comparison of the limnology, fisheries and socioeconomic aspects of local communities in order to determine whether the trophic characteristics and key ecosystem processes sustain the available fisheries, and to examine the ecological potential for increased fish production by intensive cage culture. The paper first presents integrated results on trophic state, trophic structure and food web relationships of different water bodies. The results demonstrate the importance of ecosystem-orientated analysis in order to optimise management strategies. The broad spectrum of Asian water bodies studied allows testing of a set of hypotheses on: 1) the control of the trophic state of lakes and reservoirs by geographic, climatic and morphometric conditions; 2) the significance of the structure of the fish assemblages (biogeography, exotic species) on ecosystem processes; 3) bottom up versus top down control under Asian reservoir and lake conditions (in comparison to established concepts for water bodies in the temperate zone); and 4) the human impact and resilience of ecosystem processes and trophic conditions towards human impact.Item The occurrence of Cyanobacteria in the reservoirs of the Mahaweli River basin in Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 1999) Silva, E.I.L.; Wijeyaratne, M.J.S.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.