959 resultados para Marginal lakes


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The Globalisation and fish utilisation and marketing study is a collaboration between the Fisheries Resources Research Institute (FIRRI) and the Mike Dillon Associates Limited , with funding from the Department for International Development (DFID) of the Government of the United Kingdom. The study is designed to examine the impact of the development of the export fishery on the fish producers, processors, traders and consumers in the artisanal fishery in Uganda. FIRRI 's role is to collect field data relating to the livelihoods of artisanal fish producers, processors, traders and consumers. in particular data relating to income and revenue flow. The initial focus is on the eccnomic structure of fish landing sites. The purpose of this paper is to review the progress in implementation of the project and present the interim findings for discussion. During the first quarter, namely April to June, 2002, work was carried out on Lakes Kyoga and Albert and a report produced. During the second quarter, July to September, 2002, Lake Victoria was covered. In both phases, the focus has been on the economic structure of fish landings.

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A reduction in native fish stocks and the need to increase fish production for food, recreation, ornamental purposes and to control disease vectors and weeds have often justified and led to introduction of non-native fishes. Some of these introductions have been followed by benefitial and others by undesirable consequences. For instance introduction of the Nile perch Lates niloticus L. and several tilapiine species into lakes Victoria and Kyoga, and the clupeid Limnothrissa miodon into lakes Kariba and Kivu have resulted in increases in the quantity of fish available to the people around them. Predation by Nile perch and competition with introduced tilapiine species in lakes victoria and Kyoga have caused a severe decline and in some cases total disappearance of many of the native fish species.therefore the concern about fish introductions arises

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The study was conducted between 1998 and 1999. Physical, chemical and biological factors of the water quality characteristics were collected and analysed

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Kisoro is a small district (734 km2 ) located in the highland areas of south western Uganda; bordering with Rwanda in the south, Democratic Republic of Congo in the west and Kabale District in the north and the east. The district contains four medium- to- small lakes namely: Mutanda (26.4 km2 ), Mulehe (4.1 km\ Kayumbu (2.2 km2) and Chahafi 1.0 km2). These lakes support small subsistence fisheries for a largely agricultural local population. They are, therefore, locally important as a source of animal (fish) protein, income and employment to the riparian human communities. The fish species include tilapiine fishes: Oreochromis niloticus, 0. leucostictus, Tilapia zillii; Clarias carsoni (Nsonzi), Barbus spp, Cyprinus carpio (Common carp) and the red shrimps

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Increased stocks of mukene Rastrineobola argentea and the subsequent interest in its fishery on Lake Victoria has been attributed to the poor performance of the endemic fishery as a result of introductions into this lake of foreign fish species Lates niloticus and Oreochromis niloticus. R. argentea now remains the only endemic fish species of economic importance ranking second to the Nile perch in this lake. Despite this importance, biological information on the species and knowledge of its fishery is scanty. Preliminary observations on the species in the Ugandan waters indicate that R. argentea feeds mainly on zooplankton (copepods) during daylight hours. Small quantities of aquatic insect larvae/pupae (chironomids and chaoborids) are also eaten mainly at night. These fishes breed just after the rainy seasons and the young eventually mature at between 43-44 mm standard length. Growth and population parameters show a rate of growth (K) of 0.92 with L of 64.5 mm S.L. Natural mortality (M) is given at 2.371 and total mortality (2) of 3.594. Two mesh size nets 10 and 5 mm are in use in the lake. The smaller mesh size which is more preferred by the artisanal fishermen however tends to capture many immature fishes. There is therefore need for a unified lakewide data collection on the species and its fishery in order to obtain more reliable biological information necessary proper management of this fast developing fishery.

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The fisheries of Lakes Victoria and Kyoga have changed from the native tilapiine species and are now dominated by two introduced species; Nile perch and Nile tilapia, and one native species; Rastrineobola argentea (mukene). Because of the differences in the size of the species, it may be necessary to change the type and sizes of nets used.

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Increased management attention to the fisheries tn Uganda is fuelled by five major factors:socio-economic demands, human population increase,stock depletion, biodiversity loss and,environmental degradation.Fish exports from Uganda to overseas and regional markets have rapidly increased since the mid 1990s and it is estimated that total exports are worth at least US$ 200m three quarters of the value due mostly to Nile perch exports to overseas markets.Exports to regional markets are dominated by variously processed tilapia "mukene" (Rastrineobo/a argentea),Nile perch "angara"(A/estes baremose) and cat fishes.Virtually all major water bodies contribute to this trade. A combinatilm of exports and an increased human population has seen the per capita fish consumption in Uganda drop from 15kg in the early 1990s to almost 10kg by 2005.this figure is below the WHO recommended fish protein intake of 17kg. the apparent fish gap in a liberalised economic framework has stimulated interest in commercial fish farming

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Combined effects of lack of firm and effective management measures for years, over exploitation with destructive fishing gears and interspecific competition, particularly among tilapiines and profound effects on the fish stocks of Lake Victoria and Kyoga. It has been proposed that these have been more important in the decline of the indigenous fisheries than predation or competition by Nile perch.

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A comprehensive Frame survey was carried out on lakes Kwania, Bisina, Nakuwa, Kyoga and other minor lakes in the Lake Kyoga Basin in June 2008 (Figure 1). The Frame survey was coordinated by the Department of Fisheries Resources (DFR) in collaboration with the National Fisheries Resources Research Institute (NaFIRRI) in terms of technical support. The riparian districts through the sub-county fisheries offices and the BMUs provided the enumerators and supervisors. The frame survey captured all the important characteristics of the fisheries and facilities supporting the fisheries and thus provides a strong baseline for future reference of management interventions in the basin.

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Invertebrates are some of the key food items for fish diets. They thus form an important fish food environment upon which the fisheries thrives in terms of production through dietary support. Invertebrates communities of Lakes Albert and Kyoga have been evaluated and considered the implications for diets and production of commercial fishes.

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Thirty-three groups of geochemically related natural lake and river waters collected from 368 sites scattered over East and West Africa, were investigated to determine correlations between their various ions and the patterns of change in their ionic composition across the African continent. The following nine significant correlations were found to exist in the entire area or in a major part of it: sodium and potassium; sodium and chloride; sodium and sulphate; potassium and ammonium; potassium and chloride; ammonium and nitrate; calcium and magnesium; magnesium and chloride; sulphate and chloride. When compared with the world average composition. The concentration of potassium in these waters was found to be high, that of calcium and nitrate was low. With respect to the area of East Africa only, trends in the pattern of change involving the ionic composition of the lake and river water and the longitude at which the sites were present, were found to exist for the ratio of sodium: conductivity (which showed an increase in the direction of West to East), magnesium: conductivity, and for the sum of calcium and magnesium: phosphate was generally found to increase in East Africa in the direction of west to East.

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This report presents the information obtained during catch assessment surveys made by the ADP Fishery Survey of Lake Kyoga and Lake Kwania between August 1990 and July 1991. It supersedes previous interim reports on these surveys. The Kyoga lakes had not been surveyed in a long time. Information on the state of the stocks was largely confined conclusions drawn from data collected along the southern shore of L.Kyoga proper. The effect of harmful/illegal gear types on the stocks was not documented. Part I provides a description of the survey. Part II comprises a review of the fishing strategies. Parts III and IV present the principal results obtained on L.Kyoga and L.Kwania. Part V presents a discussion of the main conclusions.

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The vertical temperature profile is a poor indicator of sratification in most tropical lake. Data from Lake Bunyonyi, Uganda, showed, however, that the density profile highlighted discontinuity layers whieh were not obvious from the temperature profile, It is suggested that the vertical density profile and the region of maximum discontinuity, the pycnocline, could be adopted as a useful index of stratification especially in tropical lakes.

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The paper reviews the distribution of organic compounds in freshwater lakes and rivers. The study of dissolved organic matter in natural lakes and rivers is of importance for a variety of reasons. The organic matter may serve in part or whole as an energy source for organisms living in the aquatic environment, or it may supply them with materials essential for their nutrition.

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The relationships between water level and catch per effort in two Zambian lakes are compared. In the relatively stable Lake Mweru, a positive correlation exists which can be used, with certain reservations, to predict the state of the fishery two years in advance. The cause of the relationship is probably the effect of water level on the marshy and swampy breeding areas, where at least the most common species in the commercial catch (Tilapia macruchir) has definite limits for the depth of water in which it will breed. For Mweru wa Ntipa, a consistant definite relationship does not exist, probably because the water level and extent of the lake fluctuate widely.