69 resultados para Conservation of resources theory


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There is a pressing need to enhance fish production in Africa through improved farm management and the use of improved fish breeds and/or alien species in aquaculture while at the same time conserve the aquatic genetic diversity. This paper presents the outcome of the Expert Consultation on Biosafety and Environmental Impact of Genetic Enhancement and Introduction of Improved Tilapia Strains/Alien Species in Africa held in Nairobi, Kenya on 20-23 February 2002. The main topics discussed were status of aquaculture in Africa and the role of genetic enhancement; potential benefits and risks involved in introduction of genetically improved strains and/or alien species with specific reference to tilapias; existing policies and legislation for the conservation of biodiversity, their strengths and weaknesses; capacity for undertaking genetic enhancement research and implementation of policies for the conservation of aquatic biodiversity.

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This paper summarizes some of the major issues relating to ex-situ conservation of the germplasm of aquatic organisms and gives examples of some current activities and future possibilities.

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Small indigenous fish species (SIS) are an important source of essential macro- and micronutrients that can play an important role in the elimination of malnutrition and micronutrient deficiencies in the populations of many South and Southeast Asian countries. Of the 260 freshwater fish species in Bangladesh, more than 140 are classified as SIS and are an integral part of the rural Bangladeshi diet. As many SIS are eaten whole, with organs and bones, they contain high amounts of vitamins and minerals, including calcium, and iron and zinc. Some SIS, such as mola, are also rich in vitamin A. SIS are often cooked with vegetables and a little oil, so they contribute to the food diversity of the rural poor.SIS are recognized as a major animal-source food group, contributing to improved food and nutrition security and livelihoods of the people of South and Southeast Asia. The purpose of this workshop is to bring together policy makers, extension agents, researchers, non-governmental and development organizations to share knowledge about small fish, their contribution to better nutrition, production technologies, and strategies for wider dissemination of pond culture and wetland based-production and conservation technologies. The workshop is expected to generate ideas for further research and development of sustainable technologies for production, management and conservation of SIS for the benefit of the people of Bangladesh as well as the South and Southeast Asian region.

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Mahseers (Tor khudree), at one time considered to be of single species, are now represented by 6 valid species distributed all over India. Studies on their food habits, ecology of spawning grounds, eggs, larval development and especially methods of artificial propagation have advanced in recent years. Transport of eggs of Tor khudree by air in moist cotton has been possible for easy distribution. Breeding of T. khudree not only by hypophysation, but even without it in small ponds by manipulation of flow of water, exercise and feed has also been possible. Fry and fingerlings of T. khudree are being distributed to many of the states in the country to help conserve the species.

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Prior to introduction of non-native fish species into Lakes Victor i a, Kyoga and Nabugabo, the three lakes suppor ted diverse fish fauna representing 13 families consisting of six cichlid genera and fifteen non-cichlid genera. There were about 50 non-cichlid species and over 300 cichlids consisting of mainly haplochromines (Graham 1929, worthington 1929, Greenwood 1960). Many of the species were commercially and scientifically important and provided a rich variety of protein source to choose from. Following introduction of the Nile perch and several tilapiines species, most of the native species were drastically reduced and some have apparently disappeared. The few remaining species appear to be restricted in distribution due to the presence of the Nile perch. They are mainly confined to refugia such as marginal macrophytes, rocky outcrops and small satellite lakes which are separated from the areas of introduction by swamps

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Haplochrmine cichlids were the most abundant taxa in Lakes Victoria, Kyoga and Nabugabo prior to introduction of the Nile perch. As stocks of the introduced predator increased, these taxa were depleted to such an extent that they are now virtually absent from the lake. The haplochromine cichlids played an important role in the ecology of Lakes Victoria, Kyoga and Nabugabo. They occupied virtually all trophic levels in the lake and facilitated an efficient flow of energy through the ecosystem. Their depletion seem to have left much organic matter whose decomposition has contributed to accumulation of dead organic matter which may be contributing to prolonged anoxia in Lake Victoria. The haplochromines formed an important small-scale fishery. Fishermen formerly subsisting on this fishery have been driven out of business because they cannot afford the expensive nets required for Nile perch fishery. In addition to providing a cheap source of fish protein to humans, the species were an important source of Scientific material for students of genetics antd adaptive radiation.