998 resultados para 17 m-Lake
Resumo:
Cichlids are known for their explosive radiation especially in the African Great Lakes marked with a high level of lake endemism. These fishes have been characterized mainly along trophic and habitat differences, by variation in morphological structures such as teeth and jaws and by differences in body shape and coloration. Cichlids are important as a microcosm of macroevolution. The explosive radiation, young evolutionary scale, and the isolation of groups characterized with high levels of endemism and presence of living fossils makes the group important for evolutionary and genetic studies. Lake Victoria region cichlids which are isolated and relatively more recent in evolution were the last to be appreciated in their diversity. Recently Ole Seehausen has found scores of rock fishes in Lake Victoria which were up to then thought to be absent from the Lake and only known to occur in Lakes Malawi and Tanganyika. Greenwood put together the species groups of Lake Victoria, and later in the early 1980's revised the classification of haplochromine species to reflect the phyletic origin and interrelationship of the various groups in Lake Victoria region. Melan Stiassny has been interested in early evolution of cichlids while the likes of Paul Fuerst and Lees Kaufman and Axel Meyer have been interested and are working to explain the speciation mechanisms responsible for the explosive radiation and evolution of cichlids. Locally S.B Wandera and his student Getrude Narnulemo are spearheading the biodiversity and taxonomic studies of cichlids in Lake Victoria region
Resumo:
Genetic biodiversity is the vaflatlOn among individuals within and between units of interbreeding individuals (populations) of a species. It includes inheritable and transmittable differences that occur between individuals andlor popuhitions of a given species through reproductive interaction. There exists enormous variability among individuals andlor populations of a species for most living organisms, and most of this variation is inheritable. differences among individuals arise through mutation and via recombination of genes during meiosis. These ifferences are then transmitted to successive generations through sexual reproduction and maintained in the populations through processes such as natural selection and genetic drift. Unfortunately much of this variation is normally threatened and often in danger of extinction because most focus in conservation of natural resources is put at saving species or habitats than varieties or strains of a species
Resumo:
An overview of the biology and ecology of some of the constantly less important commercial species is given below. These included Bagrus docmac, Clarias gariepinus, Protopterus aethiopicus, Labeo victorianus, Barbus spp, Mormyrids, Synodontis spp, and Schilbe intermedius. The stocks of most of these species declined due to over-exploitation and introduction of non-native fishes especially Nile perch. A few of these taxa still survive in the main lake and others in satellite lakes. The current status of these species in the Victoria lake basin is not known but the available information provided some information on some habitat and other requirements of some of these originally important species of the Victoria lake basin.
Resumo:
Many haplochromine cichlids coexisted in Lake Victoria before the upsurge of Nile perch. The introduction of the Nile perch led to depletion of many haplochromines and other fish species in Lake Victoria. The impact of Nile perch predation on haplochromines differed for different haplochromine trophic groups. Yssichromis fusiformis (G) and Yssichromis laparogramma (G) are among the species that have survived in the lake. Yssichromis spp. was studied with the aim of determining their trophic role, food and feeding habits. Samples were collected from Bugaia, Buvuma channel and Napoleon Gulf in the northern part of Lake Victoria. The food of Yssichromis spp. varied with size of fish. Both Y fusiformis and Y laparogramma fed on Copepods, Cladocerans, Chaoborus and Chironomids. Juvenile Yssichromis spp. fed exclusively on zooplankton comprising Cyclopoid copepods, Calanoid copepods and Cladocera. The relative importance of Chironomid larvae and Calanoid copepods was higher in Bugaia than in Buvuma channel while Cyclopoid copepods and Chironomid pupae were relatively less important in Bugaia. The main food items that Yssichromis spp. fed on in Buvuma channel were Chironomid larvae Cyclopoid copepods, Cladocerans and Calanoid copepods. In Napoleon Gulf, fish caught from commercial fishery of Rastrineobola argentea (P) had fed on Chaoborus and Chironomids. Overall, Yssichromis spp. fed on more zooplankton in Buvuma than in Bugaia. Yssichromis spp. and R. argentea are presently the most abundant zooplanktivores in the northern part of Lake Victoria and are playing an important trophic role as major consumers of zooplankton and insect larvae in the foodweb of the lake ecosystem. Yssichromis spp. are bridging the transfer of energy from the lower to the higher trophic levels as secondary consumers. The fishery is still not contributing to the direct conversion of the primary products, the phytoplankton and detritus that were efficiently utilised by the diverse haplochromine trophic groups that existed before the Nile perch boom.
Resumo:
The Victoria and Kyoga lake basins had a high fish species diversity with many fish species that were found only in these lakes. Two Tilapiines species Oreochromis esculentus and Oreochromis variabilis were the most important commercial species in these lakes and were found nowhere else on earth except in the Victoria and Kyoga lake basins (Graham 1929, Worthington 1929). Lakes Kyoga and Nabugabo also had endemic haplochromine species (Worthington 1929, Trewavas 1933, Greenwood 1965, 1966). As stocks of introduced species increased, stocks of most of the native species declined rapidly or disappeared altogether. The study was carried out on Lakes Victoria and Kyoga, River Nile, some selected satellite lakes from the two basins namely Lakes Mburo, Kachera, Wamala, Kayanja, Kayugi, Nabugabo, Victoria, Victoria nile and River Sio(Victoria lake basin). Lakes Kyoga (Iyingo), Nawampasa, Nakuwa, Gigati, Nyaguo, Agu, Kawi and Lemwa (Kyoga lake basin). Species composillon and relative abundance of fishes were estimated by detennining the overall average total number of each species encountered. A trophic consists of species using the same food category. Shannon-Weaver Index of diversity H (Pielou, 1969) and number of trophic groups, were used to estimate the Trophic diversity of various fish species in the lakes. Food analysis has been done on some fishes in some of the sampled lakes and is still going on, on remaining fishes and in some lakes. Generally fish ingested detritus, Spirulina, Melosira, filamentous algae, Planktolyngbya, Microcysists, Anabaena, Merismopedia, Spirogyra, higher plant material, rotifers, Ostracodes, Chironomid larvae and pupae, Choaborus larvae, Odonata, Povilla, Insect remains, Caridina, fish eggs and fish. Eight trophic groups were identified from thes food items ingestes. These included detritivores, algae eaters, higher plant eaters, zooplanktivores, insectivores, molluscivores, prawn eaters, paedophages and piscivores. Trophic diversity by number of trophic groups was highest in Lake Kyoga (6) followed by lakes Kayugi, Nabugabo, River Nile and Mburo (3) and the lowest number was recorded in kachera (2).
Resumo:
In September 2007, the National Fisheries Resources Research Institute carried out a socio-economic survey on Governance in Co- Management in the fisheries of Lake Victoria. The purpose of the study was to determine the nature and performance of governance of the fisheries resources through co-management structures and systems.
Resumo:
The overall objective of the study was to develop a better understanding of how people perceived and responded to the fisheries management measures on Lake Victoria and were affected by them.
Resumo:
The purpose of the survey was to gain a better understanding of the role of factory agents in buying fish and setting prices, and of their place and role in fisheries co-management on Lake Victoria, Uganda.
Resumo:
The purpose of the Socio-economic Baseline Survey of the Fishing Communities was to provide information on the fish landing beaches, people involved in fisheries, their livelihood activities and facilities available to them.
Resumo:
Under the implementation of the fisheries management plan (IFMP) for Lake Victoria result area 4, bottom trawl monitoring surveys are undertaken to monitor changes in the status of the fish stocks and environment of Lake Victoria. Trawl together with the lake-wide Hydroacoustic surveys give a reflection on the status of fish stocks in the lake to guide management decisions The National working group for bottom trawl surveys in Uganda undertakes these surveys within the Uganda sector of Lake Victoria. For the purpose of this survey, the Uganda sector of Lake Victoria is divided into three zones. A cruise lasting twenty days is conducted in two phases (two legs) 13 days covering Zones I and II and 7 days in Zone III.
Resumo:
Following a general outcry by the population riparian to the Ugandan portion of lake Albert about dwindling fish catches, there was concern both from the FAO Country representative in Uganda and the government of Uganda on the state of the fisheries of this lake. The FAO representative accompanied by an official from the Uganda Fisheries and Fish Conservation Association (UFFCA) visited the lake in July 1999 (Appendix I). The Ugandan minister of state in charge of the Fisheries sector also visited the lake in November 1999 (Appendix II). The two were in common agreement that the lake was in a stocks crisis and there was need for remedial measures. It was therefore deemed necessary to initiate a technical report updating the present state of the fisheries resources of this lake. An agreement was thus signed between the author and the Food and Agricultural Organization of the United Nations - Sub-Regional Office for Southern Africa in Harare, to undertake this exercise.
Resumo:
Fishing using light to attract fish (The light fishery) was introduced on Lake AIbert from Lake Victoria where it is used to catch mukene Rastrineobola argentea. The light fishery on Lake Albert targets ragoge brycinus nurse and mukene/muziri (Neobola bredoi), These species species now contribute to more than 50% of the catches from this lake. Ragoge and muziri were until the early 1990's not important in the commercial fishery but only served as food to the large predatory fish species that formed the basis of the fishery.
Resumo:
Lake Albert contributes about 10% to the national fish production. It supports a multi-species fishery based on endemic species. To local fishermen, Lake Albert is a lifeline providing food and income.
Resumo:
This CAS report provides estimates of the quantities of fish landed in the riparian districts sharing the Ugandan waters of Lake Victoria;the monetary value of the fish catches; the contribution of different fish species to the catches; and the trends in fish catch rates, and the monthly catches for the sampled month since the beginning of the current CAS activities from July 2005 to May 2011. So far there have been 14 CASs conducted in the Uganda sector of the lake. The report also compares the annual catch and gross beach value of the catch in 2005, 2006, 2007, 2010 and 2011.
Resumo:
Research was done to assess the dissemination and implementation by the Fisheries Department, Local Govemments and beach management units and the awareness, acceptance and compliance among fishers to the CoM Directives on management of Lake Victoria fisheries. Conducted by the National Fisheries Resources Research Institute (NaFIRRI), the research focused on the implementation and effectiveness of measures following the LYFO Council of Ministers (CoM) Directives for improved management of the fisheries of Lake Victoria, with particular reference to the 2009 CoM Directives as a case study, it was established that many of the Directives have not been implemented. In cases where the directives were implemented, their effectiveness remains questionable. While steps were taken to disseminate and implement the Directives, there were some challenges, including the unclear legal status of the directives, limited dissemination materials and poor methods of dissemination, language barriers and inadequate resources for enforcement.