Science

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Author: search.filters.author.Schiemer, F.Has files: No

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    Promotion of sustainable capture fisheries and aquaculture in Asian reservoirs and lakes
    (Hydrobiologia, Springer Netherlands, 2001) Amarasingha, U.S.; Dancun, A.; Moreau, J.; Schiemer, F.; Simon, D.; Vijverberg, J.
    A collaborative international project funded by the European Union’s INCO-DC programme is undertaking limnological, fish biological, environmental and socio-economic research in five tropical lakes and reservoirs in Sri Lanka, Thailand and the Philippines over the period 1998–2001. The aim is to determine their trophic structure and their capacity to sustain both their existing fisheries and present and future aquaculture. In some cases, these activities could potentially be expanded for the benefit of rural communities and of the local market within the bounds of social and environmental sustainability. This paper describes the concepts and methods involved in this innovative multidisciplinary project which aims to integrate limnological, fisheries and socio-economic issues in a comparative approach involving Asian and European research teams.
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    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.
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    Trophic relationships and possible evolution of the production under various fisheries management strategies in a Sri Lankan reservoir
    (Reservoir and Culture-based Fisheries: Biology and Management, 2001) Moreau, J.; Villanueva, M.C.; Amarasinghe, U.S.; Schiemer, F.
    The ECOPATH trophic model has been used to describe an extensive study of the trophic relationships of Parakrama Samudra reservoir, Sri Lanka, during the 1970s. It has supported preliminary assessments made regarding the importance of unexploited fish stocks and can possibly provide the link to understanding the further evolution of the lake under various fisheries management schemes.
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    Promotion of sustainable fisheries and aquaculture in Asian reservoirs and lakes
    (Hydrobiologia, 2001) Amarasinghe, U.S.; Duncan, A.; Moreau, J.; Schiemer, F.; Simon, D.; Vijverberg, J.
    A collaborative international project funded by the European Union's INCO-DC programme is undertaking limnological, fish biological, environmental and socio-economic research in five tropical lakes and reservoirs in Sri Lanka, Thailand and the Philippines over the period 1998?2001. The aim is to determine their trophic structure and their capacity to sustain both their existing fisheries and present and future aquaculture. In some cases, these activities could potentially be expanded for the benefit of rural communities and of the local market within the bounds of social and environmental sustainability. This paper describes the concepts and methods involved in this innovative multidisciplinary project which aims to integrate limnological, fisheries and socio-economic issues in a comparative approach involving Asian and European research teams.
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    Distribution and abundance of unexploited fish species in three Sri Lankan reservoirs
    (Asian Fisheries Science, 2009) Kumara, A.; Amarasinghe, U.S.; Schiemer, F.; Winkler, G.; Schabuss, M.
    In the reservoirs of Sri Lanka, two exotic cichlid species, Oreochromis mossambicus and O. niloticus are dominant. Small indigenous cyprinid species are abundant in reservoir fish communities, but they remain unexploited due to poor consumer preference. In the present paper, an attempt is made to investigate the spatial and temporal fluctuations of distribution of these unexploited small indigenous cyprinid species in three reservoirs of Sri Lanka. Experimental fishing with multi-mesh gillnets (12.5 mm to 37 mm stretched mesh) having the spread height of 1.5 m, was carried out in inshore and offshore areas of the three reservoirs during the seasons of high and low water levels. As cichlids exhibit depth preference with size, their juveniles were not caught in these gillnets which were set in offshore areas with depths greater than 1.5 m. Amblypharyngodon melettinus, Puntius chola and P. filamentosus were found to be the most abundant species in all three reservoirs. The species composition in the gillnet catches appears to be influenced by water level fluctuations in reservoirs perhaps due to inshore-offshore migration of individual fish species associated with water level fluctuations. Despite the site-specific differences in species distribution and abundance and their temporal variations, a small mesh (12.5 mm to 37 mm) gillnet fishery with the minimum panel height of 1.5 m can be introduced to exploit small indigenous cyprinids in Sri Lankan reservoirs without harming the existing fishery of exotic cichlids.
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    Gillnet selectivity of small cyprinids in three Sri Lankan reservoirs
    (Asian Fisheries Science, 2009) Kumara, P.A.D.A.; Amarasinghe, U.S.; Schiemer, F.; Winkler, G.; Schabuss, M.
    As it has been reported that there is a harvestable potential of presently unexploited small cyprinid species in Sri Lankan reservoirs, attempts were made to investigate the gillnet selectivity for small cyprinids in three reservoirs with a view to defining regulatory measures for the subsidiary gillnet fishery. As exotic cichlids support profitable fisheries in reservoirs of Sri Lanka, any strategy to exploit small cyprinids should not adversely affect the cichlid stocks. Possibly due to the depth preference, exotic cichlids are not caught in small mesh (12.5 to 37 mm) gillnets which are set in the areas with water depths of over 2 m. The effective mesh sizes (stretched) of gillnet which were set in these areas were 16 and 20 mm for Amblypharyngodon melettinus and 33 and 37 mm for Puntius chola and P. filamentosus. Although P. dorsalis is caught in significant numbers in 50 and 60 mm mesh gillnets, this species is unlikely to be exploited without harming exotic cichlids because sub-adults of exotic cichlids are also caught in these mesh sizes. The importance of gillnet selectivity studies of small indigenous cyprinids in Sri Lankan reservoirs is discussed.
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    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.