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Item Production trends and technical efficiencies of culture‐based fisheries in five tropical irrigation reservoirs: A case study from Sri Lanka(Fisheries Management and Ecology, 2020) Pushpalatha, K.B.C.; Kularatne, M.G.; Chandrasoma, J.; Amarasinghe, U.S.Culture‐based fisheries (CBF) are increasingly accepted as strategies for enhancing inland fisheries, especially in tropical Asia. In Sri Lanka, CBF development in irrigation reservoirs has gained momentum due to concerted efforts of government fisheries authorities for inland fisheries enhancement. In the present study, production trends of five irrigation reservoirs of Sri Lanka before and after the introduction of CBF were investigated and apparently optimal CBF yields were not realised. Hence, the stochastic frontier production function (SFPF) was employed to quantify technical efficiencies (TE) of CBF. For each reservoir, annual averages of input data from 2005 to 2018 (14 years) were used in the TE analysis. Hence, total sample size for estimation of SFPF was 70. Although CBF production gradually increased in all five reservoirs from 2005 to 2018, there were substantial variations of total fish production across the reservoirs. The SFPF indicated that CBF production could be further increased through more efficient management of inputs (i.e. number of fishers, mean number of fishing days per year and stocking density). https://onlinelibrary.wiley.com/doi/full/10.1111/fme.12460?af=RItem Multi-mesh gillnet selectivity of Oreochromis mossambicus and O. niloticus (Cichlidae) in the fishery of three large perennial reservoirs in Sri Lanka(Sri Lanka Journal of Aquatic Sciences, 2017) Jayasinghe, R.P.P.K.; Amarasinghe, U.S.; Moreau, J.As in many tropical reservoir fisheries, the major fishing gear in the reservoirs of Sri Lanka is gillnet. Gillnets of a wide range of stretched mesh sizes (6.9 - 11.4 cm) are used in individual boats in Sri Lankan reservoirs targeting mainly two exotic cichlid species, Oreochromis mossambicus and O. niloticus, which dominate the fisheries accounting for over 80% of the landings. Although the filament characteristics and dimensions of gillnets of different mesh sizes are uniform, their mesh composition varies from boat to boat making catch samples in individual boats are under the influence of different selectivity patterns. As such, an approach is presented for constructing the overall selection curves in the sampled boats during different sampling occasions for the two cichlid fish species in the three reservoirs. For this purpose, gillnet selectivity of each mesh size was determined using Baranov-Holt method. Probabilities of capture of mesh-wise gillnet selection curves were then summed up giving weight to the contribution of each mesh size to the total number of net pieces in the sampled boat, to determine the overall gillnet selection from gillnets of all mesh sizes. The importance of the findings of the present study for length-based stock assessment methods and for imposing mesh regulations to the gillnet fisheries in reservoirs of Sri Lanka is discussed.Item A comparative analysis on the effects of river discharge on trophic interactions in two tropical streams.(International Review of Hydrobiology, 2017) Weliange, W.S.; Amarasinghe, U.S.; Vijverberg, J.; Leichtfried, M.; Füreder, L .Discharge-mediated seasonal patterns of food web interactions were investigated in two streams in Sri Lanka; Eswathu Oya (a perennial wet-zone stream) and Yan Oya (a seasonal dry-zone stream). Based on volumetric proportions of diet composition, relative abundance of fish species and their daily food rations, the mean cumulative consumption of each prey taxon was estimated for each fish population. Food web diagrams were prepared using trophic index of fish, trophic class of prey and feeding interactions between fish and prey. Both streams showed seasonal patterns of discharge due to rainfall, but no significant effect was evident in the trophic index of most fish species. In both streams, cumulative consumption of prey taxa was highest during low discharge regime due to increased abundance of both prey taxa and consumers. In Eswathu Oya, diversity of prey taxa was higher during the low discharge regime, but in Yan Oya, high diversity occurred during the high discharge regime. Herbivorous and/or detritivorous fish species were rare in Eswathu Oya but dominant in Yan Oya. Complex food web structure in Yan Oya due to high fish species richness and high diversity of prey categories made it less sensitive to discharge extremes in contrast to relatively simple food web structure in Eswathu Oya. This study, therefore, highlights the importance of maintaining the quality of riparian environments for conservation of biodiversity.Item A rationale for introducing a subsidiary fishery in tropical reservoirs and lakes to augment inland fish production: case study from Sri Lanka(2016) Amarasinghe, U.S.; Kumara, P.D.A.; de Silva, S.S.An extra 30–40 million tonnes of food fish will be required by 2050 to meet the increasing need for a growing population. In the wake of plateauing of the traditional food fish supplies from marine capture fisheries, the gap in the supplies will have to be met from aquaculture and other plau- sible strategies, including increased inland fish production. The existing fisheries in tropical reservoirs and lakes tradition- ally tend to target only table-sized fish, often exotics and/or translocated species, using a single type of gear, mostly gill nets. In such fisheries, many small indigenous species (SIS) are unexploited due to the prohibition of the use of suitable fishing gear. The status of fisheries for small, indigenous species of four Sri Lankan reservoirs was investigated with a view to identifying regulatory con- straints to the establishment of SIS fisheries without adversely impacting existing commercial fisheries. It is estimated that a potential of 7.5 t per fisher per annum of SIS through the introduction of a new fishery is obtainable. This study is significant as SIS are recog- nized as important sources of essential macro- and micronutrients which can play a crucial role in combating malnutrition and micronutrient deficiencies in rural popula- tions of many South and Southeast Asian countries.Item Neither bust nor boom: Institutional robustness in the beach seine fishery of southern Sri Lanka(2016) Deepananda, K.H.M.A.; Amarasinghe, U.S.; Jayasinghe-Mudalige, U.K.Many fisheries authorities in the world have been compelled to accept community-based management as an invaluable means to formulate fisheries management due to failures of small-scale fisheries exclusively managed by centralized units. Beach seine fishing practices in Sri Lanka are known to be institutionalized by traditional community-based coastal fisheries management systems. Eight beach seine fisher communities in southern Sri Lanka were studied, using standard ethnographic methods, to ascertain and document the rules and norms that are in general not formerly codified in writing, and evaluate empirically the compliance of institutional arrangements with Ostrom's modified design principles for long enduring common pool resources (CPR) management systems. Fishing rights were vested to the villagers as a residential proximity right. Due to this tradition, ownership of a beach seine and fishing rights at fishing territory vested them as; exclusive, primary or secondary rights. The sole authority for governing CPR was vested to community organization termed “madel samithi” (beach seine society), which can be treated as the local administrative unit. Institutions governing the CPR addressed the excludability problem by defining fishing territory, eligibility rules and intercommunity access rule, while subtractability problem was addressed by gear rules, temporal allocation rules, first comer rules, fishing behaviour rules, conservation rules, and rules for distribution of benefits. The study highlighted that institutional architecture of beach seine fishery of southern Sri Lanka comprised all modified design principles and, 90.9% of those exhibited higher compliance (54.5% – high compliance and 36.4% – very high compliance) with modified design principles. Higher compliance of institutional arrangements with modified design principles indicates robust and stable self-governing institutions. Beach seine fishing in southern Sri Lanka is therefore an example for community-based coastal fisheries management system that relies on strong, locally crafted rules as well as evolved norms, where institutional and governance mechanisms have essentially averted the tragedy, providing significant contribution to coastal economy. Study provides the starkness to the notion that local actors in tropical community-based marine resource systems overcome the CPR dilemmas through robust self-governing institutions.Item Stilt fisher knowledge in southern Sri Lanka as an expert system: A strategy towards co-management(2016) Deepananda, K.H.M.; Amarasinghe, U.S.; Jayasinghe-Mudalige, U.K.; Berkes, F.Most small-scale fisheries throughout the world are based primarily on fisher knowledge, which is essentially experiential knowledge consisting of a replicable, verbally transmitted set of skills. Even though fisher knowledge is well documented for some fisheries, there are only a few studies that explain how it actually works as a management system. Stilt fishing is a unique method confined to the southern coast of Sri Lanka. We studied traditional stilt fisher knowledge as an expert system that helps make decisions for successful fishing. Study shows that traditional fisher knowledge base and the decision-making process can be explained as an expert system. Fisher knowledge on biological and physical indicators that gives cues on commencement date of fishing season, arrival of fish schools and its composition and ecology and behaviour of target fish were distilled and empirically confirmed. Traditional stilt fishers were found to hold detailed knowledge about weather, fishing season, feeding and migratory behaviour of target fishes, mainly the bluestripe herring (Herklotsichthys quadrimaculatus). Empirical studies on feeding behaviour, movement and migratory path of bluestripe herring indicate the reliability of fisher knowledge. Fishers’ expectations before starting fishing (ex-ante) on species composition arriving at fishing territory were 100% accurate at the actual harvest in conclusion of fishing (ex-post). Success in fishing depends mainly on technical skills, and there exists considerable variation in the level of expertise among fishers. Traditional fishers are more successful in fishing than non-traditional fishers. Traditional stilt fishers provide inexpensive information that can complement scientific information to produce better management outcomes. Fisher knowledge can therefore be effectively utilized in formulating policies for co-management of coastal fisheries in Sri Lanka. Opportunities exist to set up proper baseline for the management of artisanal coastal fisheries with the ultimate aim of incorporating traditional fisher knowledge into management decision making.Item “Ornithological eutrophication” as a source of allochthonous nutrient enrichment in Anavilundawa reservoir, Sri Lanka(2015) Gunaratne, A.M.; Jayakody, S.; Amarasinghe, U.S.Mass aggregation of waterfowls for breeding, results in allochthonous nutrient inputs intoaquatic systems. This study evaluated accumulation of bird droppings as allochthonusnutrient input and its fluctuations in Anavilundawa International Ramsar Sanctuary in SriLanka where Asian openbill (Anastomus oscitans) mass breeding occurs annually. Reservoirwas divided into four strata: Inlet, breeding ground, reservoir centre and outlet. The highestnutrients levels (NO3,PO43,NH4þ, alkalinity) and the lowest dissolved oxygen and pHlevels were recorded in breeding grounds for both surface and bottom water. The highestturbidity was recorded in inlet surface and centre bottom water. Canonical Variate Analysis ofwater quality parameters indicated the significantly distinct influence of ornithologicaleutrophication on surface water of four strata whilst, showing similarities in water quality ofbottom layers in inlet and outlet. In the breeding ground, surface water was covered with thickmats of aquatic flora consisting of Water hyacinth, Salvinia, duckweed and Polygonum.Therefore, it is concluded that in addition to dilution, amelioration of water quality could alsobe happening due to absorption by plants. Due to interactions between invasive plants andwaterfowls, restoration with native aquatic flora is needed to be considered to regain reservoirresilience and self-sustenance.Item Species diversity of wetland birds in dry zone seasonal reservoirs in Sri Lanka(TAPROBANICA: The Journal of Asian Biodiversity, 2015) Henkanaththegedara, S.M.; Amarasinghe, U.S.Item A comparative assessment of the fisheries in lacustrine inland waters in three Asian countries based on catch and effort data(Fisheries Research, 1991) de Silva, S.S.; Moreau, J.; Amarasinghe, U.S.; Chookajorn, T.; Guerrero, R.D.The catch and effort data of the artisanal fisheries of the natural lakes and reservoirs in the Philippines, and reservoirs in Sri Lanka and Thailand are evaluated. The yield (kg ha?1 year?1) to effort relationship of the Philippines lakes and Thai reservoirs conformed to a second-order curve, and that of Sri Lankan reservoirs was linear. Similarly, the catch per unit effort (CPUE) to effort per unit area relationships for the Philippines and Thai fisheries were similar and conformed to the Fox model. The relationship of the mean annual yield (kg ha?1) to mean effort in the Sri Lankan reservoirs when considered as a whole, on a yearly basis, conformed to the Schaefer model. On the basis of these relationships the effort which gave the maximum yield per annum was computed for each fishery. The yields were 515, 256 and 93 kg ha?1 for efforts of 20, 6.4 and 10 fishermen for the fisheries of the Philippines, Sri Lanka and Thailand, respectively. An attempt is made to explain the reasons for the apparent differences in these three artisanal fisheries, and the importance of the models in the management of the respective fisheries are discussed. 1 Present address: Deakin University, Warrnambool Faculty of Applied Science and Environmental Technology, P.O. Box 423, Warrnambool 3280, Australia.Item Minor cyprinid resources in a man-made lake in Sri Lanka: a potential supplementary source of income for fishermen(Fisheries Research, 1990) Amarasinghe, U.S.The reservoir fishery in Sri Lanka is based mainly on the exotic species Oreochromis mossambicus, and indigenous cyprinid resources are not exploited. Four species of minor cyprinids, Amblypharyngodon mellettinus, Barbus chola, B. dorsalis and B. filamentosus, are abundant in Parakrama Samudra, a man-made lake in Sri Lanka. Experimental fishing trials with gill nets of 18-, 38-, 52- and 64-mm mesh sizes indicate that the mesh sizes below 52 mm can be used for exploiting minor cyprinids without detrimental effects on the existing O. mossambicus fishery, confirming the findings of earlier studies. The annual potential yield of minor cyprinids in Parakrama Samudra (632 kg ha?1), estimated by comparing catch per unit effort values of minor cyprinids with those in southern reservoirs in the country, is appreciably higher than that of O. mossambicus. The value of minor cyprinid resources to fishermen as a supplementary source of income is highlighted.