Browsing by Author "Kumara, P.A.D.A."

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    Effect of crowding, food quality and body size on food utilization of the exotic snail, Pomacea canaliculata (Lamarck), a potential pest of rice in Sri Lanka
    (Sri Lanka Association for Fisheries and Aquatic Resources, 1999) Kumara, P.A.D.A.; Chandrasekera, L.W.H.U.; Costa, H.H.
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    Exploitation of small indigenous fish species using shore seines in three reservoirs of Sri Lanka
    (Sri Lanka Journal of Aquatic Sciences, 2008) Kumara, P.A.D.A.; Amarasinghe, U.S.
    The fish resources in reservoirs of Sri Lanka are not efficiently harvested due to various reasons such as gear and mesh restrictions and consumer preference. However, there is a potential for augmenting reservoir fisheries production by exploiting under-exploited and unexploited fish resources in reservoirs. In the present study, an attempt was made to investigate whether shore seining could be effectively used for differential exploitation of small indigenous fish species in three Sri Lankan reservoirs. It was found that shore seining was not effective for catching all species present in reservoirs. The index of relative importance determined for fish species indicated that apart from the differences between reservoirs, their relative importance in the shore seine catches was influenced by the water level of the reservoir. It is evident from the present study that in order to establish a fishery for this under-exploited species, shore seining is the appropriate fishing strategy. However, such a fishery is needed to be strictly managed for preventing indiscriminate exploitation of exotic cichlids in Sri Lankan reservoirs, which form productive fisheries.
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    Gillnet selectivity of Puntius filamentosus and Amblypharyngodon melettinus in three reservoirs of Sri Lanka
    (Sri Lanka Association for Fisheries and Aquatic Resources, 1999) Kumara, P.A.D.A.; Amarasinghe, U.S.
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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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    Population dynamics of Hyporhamphus limbatus (Beloniformes, Hemiramphidae) in two lowland reservoirs of Sri Lanka
    (Sri Lanka Journal of Aquatic Sciences, 2008) Kumara, P.A.D.A.; Amarasinghe, U.S.
    Although Hyporhamphus limbatus is found in several lowland reservoirs of Sri Lanka, due to gear restrictions imposed through fisheries regulations, this species remains unexploited or under-exploited in spite of having a good consumer preference. Population dynamics of H. limbatus in two Sri Lankan reservoirs, namely Minneriya and Udawalawe were investigated in the present study. Length frequency data of H. limbatus caught in shore seine nets of mesh sizes 1 mm, 5 mm and 7 mm were analysed using FiSAT software package and the von Bertalanffy growth parameters were estimated for non-seasonalised growth. Asymptotic total length was 155.4 mm for Minneriya and 156.4 mm for Udawalawe. Growth constants of H. limbatus for Minneriya and Udawalawe were 1.37 and 1.09 year-1 respectively. High total mortality rates (4.90 in Minneriya and 3.01 in Udawalawe), which are equivalent to production/biomass ratio indicate that both stocks can withstand heavy fishing. Relative yield-per-recruit (Y'/R) analyses indicate that at present these stocks are under-exploited and that by increasing size at first capture to about 70 mm, Y'/R can be optimized at the exploitation rate of 0.6. The shore seine nets of 5 mm mesh sizes can be used to exploit H. limbatus in both reservoirs. However, juveniles of exotic cichlids and other non-target species caught in the nets are needed to be released back to reservoirs.
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    Role of non-exploited fishery resources in Sri Lankan reservoirs as a source of food for cage aquaculture
    (Blackwell Publishing Ltd, 2002) Amarasinghe, U.S.; Kumara, P.A.D.A.; Ariyaratne, M.H.S.