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Item Gillnetting for small indigenous cyprinids in a Sri Lankan reservoir where culture-based fisheries are practiced(Sri Lanka Journal of Aquatic Sciences, 2020) Athukorala, D.A.; Amarasinbghe, U.S.In Sri Lankan reservoirs, small, indigenous fish species (SIS) are abundant and can be differentially exploited using small mesh (15-38 mm stretched mesh sizes) gillnets without any detrimental effects on the cichlid fisheries. However, in the recent past a paradigm shift in the reservoir fisheries of Sri Lanka is observed from total dependence on exotic cichlids to exploitation of exotic carps, stocked in reservoirs for the development of culture-based fisheries (CBF). As fingerlings of Chinese and Indian major carps and common carp are regularly stocked in reservoirs for the development of CBF, it is essential to investigate the potential impact of the use of small mesh gillnets to catch SIS on stocked fish fingerlings on CBF. In the present study, small mesh gillnets were used to exploit SIS during September 2011 to March 2013 when carp fingerlings were stocked in Chandrika wewa, Sri Lanka. The results revealed that no carp fingerlings (except 2 specimens of Indian carp species) were caught in any of the fishing trials with small mesh gillnets. As juvenile fish and stocked fish fingerlings occur in shallow littoral areas of reservoir, and as small mesh gillnets are laid at the depths ≥ 1.5 m, there is a habitat segregation of these two categories of fish. It is therefore possible to introduce a subsidiary fishery with small mesh gillnets to exploit SIS, which can co-exist with CBF in reservoirs of Sri Lanka.Item Life-History Strategies of Nile Tilapia, Oreochromis niloticus(Linnaeus, 1758) (Teleostei, Cichlidae), in Irrigation Reservoirs of Sri Lanka(Asian Fisheries Society, 2020) Bandara, K.V.S.N.; Ajith Kumara, P.A.D.; Amarasinghe, U.S.As in many tropical countries, reservoir fishery of Sri Lanka is dominated by the exotic cichlid, Oreochromis niloticus(Linnaeus, 1758). Oreochromis niloticuspopulations in irrigation reservoirs are expected to be under the influence of various disturbances such as changes in hydrological regimes, trophic conditions and fishing pressure. In the present study, an attempt was made to investigate the effect of biological productivity and fishing pressure on life history patterns of O. niloticuspopulations in 10 irrigation reservoirs of Sri Lanka. Oreochromis niloticuspopulations in environmentally stressed reservoirs, exhibited low age at maturity than those inhabiting reservoirs with relatively low biological productivity. Hydraulic retention time (HRT) in reservoirs also had negative influence on size and age at maturity of O. niloticus. As length at first capture of O. niloticusis positively related to mean length at maturity, these attributes have significant implications on the optimal fishing. Fishing intensity (FI) in O. niloticuspopulations also had negative influences on mean length and age at maturity. Hence, the present study supports the opinion that altricial or opportunistic traits having faster growth and achieving maturity early in the life dominate disturbed environments and that precocial or equilibrium traits exhibiting delayed maturity occur in more stable environments. Possible shifting of life history strategies of O. niloticusto opportunistic traits due to disturbance events could be manipulated by increasing FI for smaller individuals in the population.Item Population Dynamics of Nile Tilapia, Oreochromis niloticus(Linnaeus, 1758) (Teleostei, Cichlidae), in Some Irrigation Reservoirs of Sri Lanka(Asian Fisheries Society, 2020) Bandara, K.V.S.N.; Ajith Kumara, P.A.D.; Amarasinghe, U.S.Oreochromis niloticus(Linnaeus, 1758) exhibits differences in demographic parameters across the reservoirs, resulting in inconsistencies in optimal fishing strategies. This study aimed at investigating O. niloticuspopulations in 10 reservoirs. Length-frequency data of O. niloticusfrom fishlandings of 10 irrigation reservoirs in Sri Lanka were corrected for multi-mesh gillnet selection and were analysed by FiSAT II stock assessment software. Asymptotic total length ranged from 42.8 cm to 53.4 cm and growth constant ranged from 0.20 yr-1to 0.49 yr-1. As growth performance indices of 10 reservoir populations of O. niloticuswere within the range reported previously and as the estimated growth parameters fall within the “growth space” of the species, these estimates were consistent with those reported in the literature. Length-converted catch curves of 10 reservoir populations of O. niloticusalso gave reliable estimates of total mortality. Exploitation rates of the 10 populations ranged from very low (0.14) to very high (0.76) values. From the relative yield-per-recruit analyses, it was apparent that in some reservoirs, long-term fish yields can be optimised using gillnet mesh sizes of 7.6 cm. While optimal long-term fish yields of O. niloticusin other reservoirs could be achieved by increasing the permissible gillnet mesh size above the legal mesh size of 8.4 cm. Hence, the gillnet mesh regulations in the Sri Lankan reservoir fishery should not be uniform but reservoir-specific. Accordingly, site-specific management options, which are defined in consultation of resource users are necessary to be implemented in reservoir fisheries of the country.Item Institutional Robustness of Culture-based Fisheries in Perennial Reservoirs of Sri Lanka(Asian Fisheries Society, 2020) Pushpalatha, K.B.C.; Kularatne, M.G.; Amarasinghe, U.S.The utilisation of irrigation reservoirs for culture-based fisheries (CBF) development is a recent development in Sri Lanka. The trends in CBF development in five reservoirs were investigated, to identify the robustness of institutional arrangements in the rural fisheries organisations (RFOs) for the sustainability of CBF. Basic socio-economic characteristics of five fisher communities showed enabling features for implementing CBF through community participation. After the introduction of CBF, fish species composition in the landings changed with the occurrence of stocked species in the landings, resulting remarkablyelevated fishers’ income ranging from 194% to 2187% in Urusita and Ampara reservoirs respectively. The CBF management options of RFOs in two reservoirs, viz. Ampara and Jayanthi were at high compliance levels of Ostrom’s modified design principles, where fishers enjoyed increased mean annual income registering 2187% in Ampara and 409% in Jayanthi reservoirs after introduction of CBF. In Senanayake Samudra, where there was moderate compliance, there was 249% increase in CBF income. However, the lowest increase of income (194%) in Urusita reservoir was due to high annual fisheries income even during pre-CBF period. In Hambegamuwa reservoir, where levels of compliance of RFOs with design principles were relatively poor compared to other four fisher communities, increase of fishers’ CBF income, compared to that of pre-CBF period, was marginal (202%). Economic gains of RFOs due to increased levels of compliance with design principles through improving leadership qualities and empowering fishers for management decision-making would,therefore,ensure sustainability of CBF.Item Nutritional quality of Cavendish banana (Musa acuminata, AAA) as affected by basil oil and determination of basil oil residues by GC-MS(Journal of Science, Faculty of Science, University of Kelaniya, 2019) Siriwardana, H.; Abeywickrama, K.; Kannangara, S.; Jayawardena, B.The effectiveness of basil oil on the nutritional properties of Cavendish banana and chemical composition of basil oil and oil residue levels of treated banana fruits were evaluated in this study. Cavendish banana hands were treated with 1% alum (w/v), 1% alum (w/v) + 0.4% Ocimum basilicum (basil) oil, distilled water (control) and packaged in Low Density Polyethylene (LDPE) bags and stored at a cold room at 12-14ºC. After two weeks of cold storage banana were induced ripened and nutritional contents of treated Cavendish banana were determined. Gas Chromatography - Mass Spectrometry (GC-MS) was instrumental in identifying the chemical constituents of basil oil as well as residues in basil oil treated Cavendish banana peel after two weeks of storage at 12-14ºC.Item Postharvest Application of Defence Elicitors to Managae Anthracnose In Mango Fruit(Journal of Science, Faculty of Science, University of Kelaniya, 2019) Karunanayake, K.O.L.C.The use of defense elicitors; which are agents that stimulate or trigger disease resistance responses in plants have proved to be attractive alternatives to hazardous chemical fungicides in recent years. The present study investigated the possibility of using Salicylic acid and Bion® as postharvest elicitors on mango fruit. Three local mango cultivars were used in the study, ‘Karuthacolomban’, ‘Rata’ and ‘Willard’. Salicylic acid was applied as a postharvest spray at concentrations, 100, 500 or 1000 mg/L and Bion® (Acibenzolar-s-methyl, 500 WG, SYNGENTA) at 25, 50, 100 and 200 mg/L. Disease development following artificial inoculation (10 5 conidia / ml suspension) was assessed. Both elicitors were effective (P<0.05) in controlling postharvest anthracnose. The most effective concentration of SA was 500 mg/L for ‘Rata’, 100 mg/ L for ‘Willard’ and both 100 and 500 mg/L for ‘Karuthacolomban’. In Bion® the most effective concentration was 50 ppm for ‘Rata’ and ‘Willard’ and 25 ppm for ‘Karuthacolomban’. In SA treated fruits the percentage reduction in anthracnose ranged from 40- 77 % while values ranged from 67 – 99% for Bion® treated fruits. Results indicate that both SA and Bion® can be used to control postharvest mango fruit loss due to anthracnose.Item Geographic Records of Subfamilies, Genera and Species of Ants (Hymenoptera: Formicidae) In The Four Climatic Zones of Sri Lanka: A Review(University of Kelaniya, 2016) Dias, R.K.S.; Rajapaksa, R.P.K.C.Ants are a major biotic component in the terrestrial environment of Sri Lanka. For the first time, geographic records of worker ants from the surveys conducted in the four climatic zones of Sri Lanka from 1999 to 2016 have been summarized. Geographic records of subfamilies, genera and 95 species of ants from variety of localities in each climatic zone were pooled and tabulated for each taxon. Among the 11 subfamilies, Amblyoponinae, Dolichoderinae, Formicinae, Myrmicinae, Ponerinae and Pseudomyrmecinae were common to the lands in the four zones while each of the other subfamilies were recorded from a single zone or two or three zones only. The Sri Lankan Relict Ant in Aneuretinae has many records in the wet zone and two records in the intermediate zone. Twenty two among 64 ant genera were recorded from the four climatic zones; 42 genera were found in a single zone or two or three zones. Recorded occurrence of each of the 95 species showed that 24 including 8 invasive species, Anoplolepis gracilipes, Monomorium pharaonis, Paratrechina longicornis, Solenopsis geminata, Tapinoma melanocephalum, Technomyrmex albipes, Tetramorium bicarinatum and Trichomyrmex destructor were common to the four zones. Further surveys on ants of Sri Lanka are highly recommended for improving the current knowledge on their occurrence and to provide information on the distribution of endemic and invasive ant species in Sri Lanka.Item Five Layered FCC Ferromagnetic Films as Described by Modified Second Order Perturbed Heisenberg Hamiltonian(University of Kelaniya, 2016) Samarasekara, P.; Warnakulasooriya, B.I.For the first time, the 2nd order perturbed Heisenberg Hamiltonian with all the seven magnetic energy parameters was solved for fcc structured ferromagnetic films with five layers. Previously, the 2nd order perturbed Heisenberg Hamiltonian was solved for four layered ferromagnetic films under some special assumptions by us. However, the exact solution of 2nd order perturbed Heisenberg Hamiltonian without any special assumption is formulated in this manuscript. The magnetic easy and hard directions were determined using the angles corresponding to the energy minimum and maximum in the 3-D and 2-D plots. The shape of the 3-D plots doesn’t change with the number of layers except the position of spikes. However, the magnetic easy direction varies with the number of layers. Most of the theoretical data obtained by our model agree with the experimental data of ferromagnetic thin films.Item Species richness of arboreal ant assemblages (Hymenoptera, Formicidae) and frequency of Oecophylla smaragdina (Fabricius) occurrence in a wet zone cashew (Anacardium occidentale L.) field in Sri Lanka(University of Kelaniya, 2016) Dias, R.K.S.; Perera, A.P.S.Ant assemblages on cashew trees in the wet zone of Sri Lanka were recorded throughout three phenological phases from March to June in 2015. Baited trapping and hand collection recorded fourteen ant species in five subfamilies and species richness observed on each occasion ranged from 7 to 11. Absence of serious cashew pests was noticeable in the current phenological cycle. Oecophylla smaragdina (Fabricius) was the only species recorded on all trees. Number of O. smaragdina nests observed on the same cashew trees in the two plots was recorded from April to June in 2015 and nests of the species were observed only on large and medium-sized trees. The materials carried by O. smaragdina workers on cashew tree branches were also collected, preserved in 70% ethanol and identified as far as possible using a Low Power Stereo-microscope and various plant and animal materials carried by workers confirmed that the species is an omnivore and a generalist predator. In the current study absence of serious damages caused by the cashew insect pests even without any insecticide application might be due to the presence of ant assemblages on cashew trees.Item Optical and Structural Properties of Spin Coated Cadmium Sulfide Thin Films(University of Kelaniya, 2015) Dissanayake, D.M.C.U.; Samarasekara, P.Thin films of cadmium sulfide have been synthesized using the spin coating technique. Films were fabricated on inexpensive amorphous glass substrates at spin speeds of 1500, 2200 and 2400 rpm for 30 seconds. Films were subsequently annealed at 200, 300 and 400 0C for one hour in air in order to crystallize the phase of CdS. Films were characterized using X-ray diffraction patterns (XRD) and UV-visible spectroscopy. According to XRD patterns, the phase of CdS was crystallized without any secondary phases. The particle size, dislocation density and strain were also estimated using XRD patterns. All the films indicate a strong orientation in (002) direction. The optical band gap was determined using UV absorption spectroscopy. Tauc model was employed to determine the optical band gap. According to our data, the optical band gap decreases with the particle size.