Zoology
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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 Application of a Multiple-criteria decision making approach for selecting non-perennial reservoirs for culture-based fishery development: Case study from Sri Lanka(Elsevier, 2016) Wijenayake, W.M.H.K.; Amarasinghe, U.S.; de Silva, S.S.In Sri Lanka, small non-perennial reservoirs (mostly < 50 ha) are numerous in the dry zone receiving less than 185 cm annual precipitation. These are irrigational and are not traditionally used for inland fisheries, due to inadequate natural recruitment, but have the potential for utilization for the development of culture-based fisheries (CBFs), a form of extensive aquaculture. However, the suitability of water bodies for CBF is wide ranging because of the seasonal water retention period and fingerling availability for stocking, variable biological productivity, and community willingness to adopt CBF. In such circumstances multi-criteria decision making (MCDM) approaches are useful for selection of water bodies for CBF. Analytic hierarchy process (AHP), a MCDM approach was employed in this study where, three main criteria (reservoir productivity, catchment characteristics and socio-economic factors) that influence CBF yield were considered. There were two, five and three sub-criteria under each, respectively. As most of the sub-criteria in the analysis are essentially spatial data, it was possible to quantify the influence of each of these on CBF yield using geographical information systems (GIS) and remote sensing (RS) techniques, which were subsequently weighted. Based on the total scores from the weighted linear combinations of the AHP for various sub-categories, the reservoirs were categorized for their suitability for CBF in to four levels as excellent, good, fair and poor. As there was a positive significant relationship between the total AHP score and CBF yield, it was concluded that use of AHP based weighted linear combination would be a feasible approach for selection for CBF development, and that this methodology would be applicable to comparable situations in the tropical region.Item Fishes and fisheries of Asian inland lacustrine waters(John Wiley & Sons, Ltd, Chichester, UK., 2015) Amarasinghe, U.S.; de Silva, S.S.In tropical Asia, there is a general paucity of natural lakes that are mainly located in the island states of the Philippines and Indonesia. Reservoir construction is extensive in the region primarily for irrigation, flood control and hydroelectricity generation, and fish production is essentially a secondary use of these reservoirs. Although the degree of endemism can in no way be equated to those in the great lakes of rift valley region of East Africa, familial diversity of fishes in Asia, but not species diversity, is considerably higher than in African lakes. Asia has a significant contribution to the world inland capture fisheries production of 11.5 × 106 t that is c. 69%. In most countries in Asia, the bulk of inland fisheries for food fish production occur in lacustrine waters, albeit productive riverine fisheries occur in the Lower Mekong Basin. Nevertheless, fisheries in multipurpose reservoirs are not fully appreciated compared to their other economic uses. Fisheries enhancement in lacustrine waterbodies in Asia through culture-based fisheries (CBF) is considered environmentally friendly due to low external inputs such as provision of supplementary feeds. There is a great potential for food fish production through CBF development in many parts of Asia. Hitherto, deterioration of water quality due to anthropogenic activities is less frequent in Asia than in other regions as local authorities are active in maintaining water quality in reservoirs used for multiple purposes. As reservoir water levels range from highly stable systems to highly fluctuating systems, a combination of flood pulses and mean depth can be used as a fish yield predictor in lakes and reservoirs. Approaches directed towards addressing both human and ecological well-being, in the lake and reservoir fisheries development strategies, are useful to combine the important aspects that are of ecological and societal interest. There is a paucity of studies on climate change impacts on inland fisheries, although some isolated studies are reported on specific aspects. Hence, there is a need to step up research on climate change impacts on inland fisheries for enabling adoption of mitigation and adaptive measuresItem Effect of a commercial bacterial production water quality and shrimp production in low water exchange shrimp culture ponds in Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2005) Epa, U.P.K.; de Silva, S.S.; Widanapathirana, G.S.Item An approach to classify seasonal reservoirs of Sri Lanka using Carlson’s Trophic State Index(Sri Lanka Association for Fisheries and Aquatic Resources, 2003) Jayasinghe, U.A.D.; Amarasinghe, U.S.; de Silva, S.S.Item Influence of socioeconomic heterogeneity on culture-based fisheries in non-perennial reservoirs of Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2008) Kularatne, M.G.; Amarasinghe, U.S.; de Silva, S.S.For culture-based fisheries (CBF) development in non-perennial reservoirs of Sri Lanka, importance of integration of economic, socio-cultural, political/institutional and ecological domains needs to be recognized. Farmer communities of 47 randomly selected non-perennial reservoirs in five districts were chosen for the present study. Reservoirs were stratified into three groups on the basis of the interest expressed by communities (i.e., disagree, somewhat agree and fully agree to get involved in CBF) during a preliminary questionnaire-survey. Attempts were then made to examine the significance of socioeconomic heterogeneity for decision-making in CBF activity with particular emphasis on the group characteristics and attitudes of communities towards state-sponsored services for the development of CBF. The community groups, which are in full agreement to take part in CBF are small in size (23) compared to those which disagreed (42). Level of education in office bearers also influences the decision-making process for involvement in CBF. Leadership qualities of members of communities positively influenced decision-making. The functional groups in CBF in various reservoirs are either all members of the farmer organization (FO), a sub-group of FO, community based organizations (CBO) or participation on individual basis. In reservoirs where FO or a sub-group of FO is involved in culture-based fisheries, socioeconomic heterogeneity influences the decision-making. Mean equality percentage of the active members of the fully agreed group is the highest (80%) when compared with the other two groups (< 73%). Homogeneity of the age, caste, kinship, political ideology also positively influenced decision making in these communities. Communities with high proportions of younger (<40 years of age) members have a positive attitude towards development of CBF. Farming communities with several sources of income in a household are highest in the group of full agreement, which perhaps indicates an attitude of each community to maximize household income. Level of satisfaction about the government services varied among the communities. The group of communities, which disagreed with CBF development, is more satisfied with the existing government services than the other two groups indicating their poor attitude towards social uplifting. The present analysis shows that homogeneity of the group characteristics facilitates the collective decision-making. As such, socioeconomic heterogeneity in communities has an important impact on collective decision-making as regards to this development activity.Item Importance of limnological characteristics for the development of culture-based fisheries in non-perennial reservoirs of Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2004) Jayasinghe, U.A.D.; Amarasinghe, U.S.; de Silva, S.S.Culture-based fisheries development in non-perennial reservoirs of Sri Lanka is an important strategy for the enhancement of inland fish production. However, little emphasis has been laid on the limnological aspects for planning this extensive aquaculture procedure. The present study was carried out to investigate the possibility of using limnological characteristics of non-perennial reservoirs for future management of their culture-based fisheries. Forty-five reservoirs were randomly selected to study their limnology, of which 32 were stocked with fish fingerlings of Chinese and Indian carps, GIFT variety of Oreochromis niloticus and freshwater prawn at stocking densities ranging from 218 to 3900 fingerlings (or post-larvae) ha-1. Of these, 23 reservoirs were harvested at the end of the culture period (6 – 10 months). Thirteen limnological parameters were measured during the water retention period of each of the 45 reservoirs, between November 2001 and January 2004. Mean values of limnological parameters were used to ordinate reservoirs through principal component analysis. Ordination showed productivity gradient among reservoirs where Secchi disc depth, total phosphorous, chlorophyll-a, inorganic turbidity and organic turbidity were identified as key factors. Total fish yield of culture-based fishery was positively correlated to scores of the first principal component axis. This study reveals that there is a possibility to classify non-perennial reservoirs of Sri Lanka based on limnological parameters such as Secchi disc depth, total phosphorous, chlorophyll-a, inorganic turbidity and organic turbidity in order to develop culture-based fisheries.Item Feasibility of rearing Labeo rohita (Hamilton) fry in cages with community participation: A case study in Sri Lanka(National Aquatic Resources Research and Development Agency, 2007) Ariyaratne, M.H.S.; Wijeyaratne, M.J.S.; de Silva, S.S.Item Use of geographical information system and remote sensing techniques for planning culture‐based fisheries in non‐perennial reservoirs of Sri Lanka(Journal of Lakes & Reservoirs: Research & Management, 2014) Wijenayake, W.M.; Gunaratne, A.B.; de Silva, S.S.; Amarasinghe, U.S.The presence of a wide areal extent of small-sized village reservoirs offers a considerable potential for the development of culture-based fisheries (CBFs) in Sri Lanka. To this end, this study uses geographical information systems (GISs) and remote sensing (RS) techniques to determine the morphometric and biological characteristics most useful for classifying non-perennial reservoirs for CBF development and for assessing the influence of catchment land-use patterns on potential CBF yields. The reservoir shorelines at full water supply level were mapped with a Global Positioning System to determine shoreline length and reservoir areal extent. The ratio of shoreline length to reservoir extent, which was reported to be a powerful predictor variable of CBF yields, could be reliably quantified using RS techniques. The areal extent of reservoirs, quantified with RS techniques (RS extent), was used to estimate the ratio of forest cover plus scrubland cover to RS extent and was found to be significantly related to the CBF yield (R2 = 0.400; P < 0.05). The results of this study indicated that morphometric characteristics and catchment land-use patterns, which might be viewed as indices of biological productivity, can be quantified using RS and GIS techniques.Item Land-Water Linkages in Rural Watersheds Electronic Workshop(2002) de Silva, S.S.; Amarasinghe, U.S.; Nissanka, C.