Browsing by Author "Amarasingha, U.S."

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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.
Demographical characterization of dengue infected patients in Akurana medial officer of health area
(central Province of Sri Lanka, University of Sri Jayawardnapura, Sri Lanka., 2015) Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Iqbal, M.C.M.; Kusumawathie, P.H.D.; Najim, M.M.M.; Amarasingha, U.S.; Abeyewickreme, W.
Dengue has been recognized to be one of the major threats on the public health of many tropical countries including Sri Lanka. Controlling of the high rate of mortality caused by dengue, which remains without being altered regardless of the immense efforts and control strategies of the relevant authorities, has remained as a major challenge for the Sri Lankan health sector. Vulnerability assessment of communities to dengue infection is of higher importance in drafting and implementation of management plans to ensure effective management and controlling of dengue epidemics at the regional scale. Therefore, a statistic based analysis of the dengue patient characteristics was carried out to determine the susceptibility of population to dengue infection in Akurana Medical Officer of Health (MOH) area. Monthly records of reported dengue cases from 2010 to 2014 of the Akurana MOH division were collected. Normal Chi square test coupled with Paired-Chi square test was devised to investigate the impact of sex and age on the infection. MINITAB (version 14.12.0) software package was used for statistical analysis. In accordance with the results of the normal Chi square test, the Percentage Infected Male: Female Ratio (PIMFR) remains significantly altered throughout the period of study (p=0.001 61 (1.84%). However, according to the Paired-Chi square test, the vulnerability of age groups tend to shift significantly throughout the study period [>Χ2 (7, 0.95) = 14.067]. In conclusion males tend to indicate relatively high susceptibility to dengue. Age groups of 6 - 10, 11 - 20 and 21 - 30 could be recognized as highly vulnerable age groups in the community for dengue, while age group of >61 emerge as the least vulnerable age group for the infection of dengue in the Akurana MOH.
A fishery associated with floating objects in the Indian Ocean off Southern Sri Lanka
(Asian Fisheries Science, 2012) Ariyaratne, M.M.; Amarasingha, U.S.
The present study was carried out from August 2007 to January 2008 in southern Sri Lanka to investigate the catch composition of offshore fisheries from multi-day boats. Some boats were engaged in flotsam associated surrounding net fisheries. The fish landings from 77 boats were classified into three categories: (i) only from surrounding nets (S), (ii) from surrounding nets plus drift gillnetting/longlining (SGL), and (iii) only from drift gillnetting/longlining (GL). The catch estimate in each boat trip was categorised into one of the three groups for every fish species caught. The Indian scad, Decapterus russelli (Rüppell, 1830), rainbow runner, Elagatis bipinnulata (Quoy and Gaimard, 1825), common dolphinfish, Coryphaena hippurus Linnaeus, 1758 and starry triggerfish, Abalistes stellatus (Anonymous, 1798) contributed significantly to catches in S and SGL boats but were insignificant in the catches of GL boats. In flotsam-associated surrounding nets, juvenile tunas, skipjack, Katsuwonus pelamis (Linnaeus, 1758) and yellowfin, Thunnus albacores (Bonnaterre, 1788) (15-60 cm total length) were also caught. Multivariate statistical analyses revealed that fish catch composition from GL boats differed from that of S and SGL boats. The biological consequences of behavioural changes and vulnerability of fish stocks to overfishing due to aggregation around flotsam require further investigation.
Morphological correlates with diet of fish assemblages in brush park fisheries of tropical estuaries
(Springer Netherlands., 2017) Gammanpila, M.; Amarasingha, U.S.; Wijeyaratne, M.J.S.
Brush park fishery in Negombo estuary, Sri Lanka is a traditional fishing practice which relies on fishes attracted to artificial woody fish aggregation devices. This study investigates whether constituent species in these brush parks exhibit morphological variations in relation to their dietary habits. Fishes caught in brush parks were sampled from April 2014 to April 2016 covering rainy, intermediate and dry seasons. There were 817 specimens of 46 species belonging to 24 families. From each specimen, 17 morphological attributes were determined and diet composition of each species was analyzed in terms of relative biovolume. Trophic index of each species estimated from the proportions of dietary items and their possible trophic level in the community was significantly related to two body proportions (Maximum body height/Maximum body width and Total length/ Maximum body height) which described shape of fish. Principal component analysis of morphometric attributes and dietary habits indicated that the species in the higher trophic levels are characterized by slender, long-body shapes and those occupy lower trophic levels are predominantly laterally compressed with deep body shapes. As such, structure of coexisting species in brush parks of Negombo estuary is predominantly along the trophic dimension and is related to morphological traits of constituent species. The predictive power of ecomorphological correlates with diets of fish species other than mugilids which are attracted to brush parks, can therefore be considered as a useful tool for conducting rapid ecological assessment.
Patterns of species composition of beach seine fisheries off North-Western coast of Sri Lanka, fishers’ perceptions and implications for co-management,
(Pergamon, 2016) Gunawardena, N.D.P.; Jutagate, T.; Amarasingha, U.S.
As in many developing countries, small-scale fisheries including beach seining contribute significantly livelihoods and food security of coastal communities. Beach seining in Sri Lanka is seasonal mainly during calm season deprived of strong monsoonal winds, and essentially a multi-species fishery. Knowledge about the seasonal occurrence of pelagic species is important to be known for proper planning of the fishing activity, especially due to the reason that beach seine fishers in many parts of Sri Lanka make decisions to attach the cod-end of correct type depending on the target species. The possibility of identifying pattern of seasonal occurrence of target fish species in beach seine fishing sites off the southern region of north-western coast of Sri Lanka was therefore investigated using Self Organizing Maps (SOM). The analysis indicated that beach seine fishers’ local knowledge to predict the occurrence of certain species in the fishing sites to adjust their fishing strategies to target desirable species was consistent with the findings of SOM approach. Consequently, it was concluded that as beach seine fishers use indirect indicators such as colour of sea water and behaviour sea birds predict the species occurrence fairly accurately, their local knowledge can be incorporated in the management planning of beach seine fisheries in the North Western coastal area of Sri Lanka.
Population dynamics of commercially important fish species in two reservoirs of the Walawe river basin, Sri Lanka
(Asian Fisheries Society, 2010) Athukorala, D.A.; Amarasingha, U.S.
Population dynamics of dominant fish species in two lowland reservoirs of Sri Lanka were studied based on length-based stock assessment methodologies, as implemented in FiSAT II software. The estimated growth parameters of Oreochromis mossambicus in Udawalawe and Chandrikawewa reservoirs and those of O. niloticus and Labeo dussumieri in Udawalawe reservoir fall within the growth space of auximetric plots of cichlids and cyprinids indicating reliability of estimates. In the Chandrikawewa reservoir where O. mossambicus exhibited faster growth, increased fishing pressure might lead to push the population towards the extreme of ‘rselected’ life strategy so that continuation of the fishery at the present exploitation level is advisable. Relative yield-per-recruit (Y’/R) analyses indicate that for O. niloticus and L. dussumieri in Udawalawe reservoir, exploitation levels can be increased to optimize Y’/R. However, since these two species and O. mossambicus are caught in the same fishing gear, exploitation rate for O. niloticus and L. dussumieri has to be increased to a level that would not lead to over-exploitation of O. mossambicus stock.
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.