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  • 1
    Publication Date: 2021-05-19
    Description: Using our own experimental data and published data, we review information on the control process of water hyacinth and its status in Lake Victoria basin, Kenya. Experimental results show that the mean fecundity of the two weevils is 290 and 237 eggs per female laid over a period of 16 weeks, with an adult longevity of 98 and 112 days for Neochetina bruchi and N. eichhorniae respectively. There was significant difference between the egg laying capacities of the two weevil species (p=0.002). The survival rate of the two species was significantly different (p〈0.05) for all life stages except for larvae to pupa. There was no significant interaction between the species and the method of experimental egg setting (p〈0.05). The fecundity of both N. bruchi and N. eichhorniae significantly decreases with time in weeks (t = 4.09; p〈0.01 and (t = 3.40.09; p=0.004 respectively). N. bruchi method had a significantly (p〈0.05) high larvae to pupa survival percentage (33.8 ± 6.00 for Incision Egg Setting (IES) method as compared to the Free Egg Setting (FES) method (18.7 ± c 2.6). In the case of N. eichhorniae, the percentage survival for IES (25.4 ± 4.6) was also significantly higher (p〉0.05) than the FES method (19.7 ± 4.1).On the basis of these results, we review and discuss data on the damage caused by the two weevil species as a basis for large-scale biological control of water hyacinth in Lake Victoria basin.
    Description: Published
    Keywords: Biological control ; Biological development ; Life cycle ; Biological development ; Life cycle ; Plant control ; Biological control ; Aquatic insects ; Insect eggs ; Entomology ; Environment management ; Survival
    Repository Name: AquaDocs
    Type: Proceedings Paper , Non-Refereed
    Format: 121841 bytes
    Format: application/pdf
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  • 2
    Publication Date: 2021-05-19
    Description: Experiments were set to determine the effect of monthly and seasonal harvesting on temporal papyrus population density. Mean initial culm count was 21.6±2.26/m2. Initial culm counts varied across sites, but spatial differences were not significant. Mean monthly culm counts declined with successive harvests, and each sequential harvest significantly reduced culm counts. Seasonal culm counts were generally higher in unharvested than in harvested plots, and the differences were significant in Nduru (F=13.569; p〈0.05). There were no culm counts differences within and among sites between initial and seasonally harvested plots. Overall, there were more culms in seasonal (32.3±3.34/m2) than in initial counts. It was found that culm counts do not depend on site, and that harvesting reduces culm counts. It is evident that seasonal harvesting does not affect culm counts. Leaving a papyrus crop stand unharvested for more than a season increases its culm count. Given that frequent harvesting reduces culm count, and considering that initial papyrus population densities were the lowest across sites, it may be concluded that Winam Gulf papyrus is harvested faster than the wetlands can replenish. This finding highlights the need for urgent conservation measures in the area. It is suggested that papyrus conservation steps be undertaken most urgently in Winam Gulf. A minimum-harvesting regime at the start is once per patch per season. However, fewer patches were studied relative to the entire swamps. A more elaborate assessment, covering larger areas and more swamps, with greater effort, should be undertaken to determine the replenishment break-even point.
    Description: Published
    Keywords: Freshwater weeds ; Aquatic plants ; Plant control ; Cyperus papyrus ; Harvesting ; Replenishment ; Swamps ; Wetlands
    Repository Name: AquaDocs
    Type: Conference Material , Not Known
    Format: pp.307-416
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  • 3
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    Kenya Disaster Concern - VIRED - UNDP | Nairobi, Kenya
    Publication Date: 2021-05-19
    Description: The greatest challenge in the conservation and management of wetland ecosystems in Kenya is the fact that most of them are found in unprotected areas and the lack of a national wetland policy. Community based approaches therefore become the most viable option. This chapter describes experiences gained in community based management of Nyando Wetland, an intervention initiated by two local NGOs (Kenya Disaster Concern and VIRED International) and the Nyando Wetland Community and funded by UNDP-Kenya. The principle of co-management of natural resources on which the intervention was based is outlined with some examples of other initiatives carried out by other institutions in Kenya. The objectives of this project are given with an emphasis on its relevance to Kenya’s Vision 2030, the MDG goals and UNDP, the funding agency. The overall objective however was the rehabilitation, restoration and conservation of the degraded Nyando Wetland. The chapter explores in greater detail the approaches used in achieving the project objectives. Activities were strategically planned on a Quaterly and Annual basis starting with community mobilization, awareness creation, capacity building to catalyze full participation of the local communities. The use of alternative livelihood activities is highlighted as an incentive to the local communities, research was to enable the project team to make informed decisions and the formation of a coalition with multiple partners. The chapter ends with approaches to ensure sustainability of the initiated activities. As a pioneering initiative, experiences gained are invaluable.
    Description: Nyando Wetland Utility Resource Optimization Project, Ref:- AKEN/05/427
    Description: Published
    Keywords: Wetlands ; Water resources ; Environment management
    Repository Name: AquaDocs
    Type: Book Section , Not Known
    Format: pp.81-99
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  • 4
    Publication Date: 2021-05-19
    Description: The Lake Victoria Catchment (Kenya) harbours six species of tilapia. Two species Oreochromis variabilis (L) and Oreochromis esculentus (L) are endemic while four species Oreochromis niloticus, Oreochromis leucostictus, Tilapia zillii(Gervais) and Tilapia rendalli(Gervais) were variously introduced in 1950s and early 1960s. The existence of six tilapia species in the same geographical range has had significant ecological and economical implications. The study investigated the ecological impacts by determining species diversity, distribution, association (allopatric, sympatric and parapatric) and habitat preferences for the six-tilapia species. Shannon-wiener index was used to determine diversity, while species distribution was evaluated on the basis of 39 habitats (dams and satellite lakes) within the catchment. Species associations were determined using Cole’s Cab index. The Shannon Weiner function values of 2.44-2.7 indicate relatively high species diversity in 15% of 33 habitats where Tilapia were resident. Cole’s Cab indices showed significant relationships in O. esculentus X O. variabilis, O.leucostictus X O. esculentus, O. niloticus X O. variabilis and O. niloticus X O. leucostictus at P 〈 0.05. Habitat preference for the six species is provided.
    Description: Published
    Description: Geographical distribution; Interspecific relationships; Associated species; Stocks; Freshwater fish; Inland fisheries; Catchment area; Endemic species; Biodiversity; Species diversity; Habitat selection; Check lists; Ecological associations; Introduced species;Oreochromis variabilis; Oreochromis esculentus; Oreochromis niloticus, Oreochromis leucostictus, Tilapia zillii; Tilapia rendalli
    Repository Name: AquaDocs
    Type: Proceedings Paper
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  • 5
    Publication Date: 2021-05-19
    Description: Nile tilapia, Oreochromis niloticus together with other tilapiines of Oreochromis leucosticus, Tilapia zillii and Sarotherodon melanopleudra (=T. rendalii) were introduced into Lake Victoria (Kenya) between 1951 and 1962 to boost the then declining fishery. Only O. niloticus was able to establish leading further to reduction in endemic tilapiines of Oreochromis variabilis and Oreochromis esculentus. O. niloticus currently forms the third commercially important species after introduced Nile perch, Lates niloticus and a native cyprinid Rastrineobola argentea, whereas other tilapias are extinct or are occasionally caught in the lake. Information was collected from by bottom trawling and from published literature to ascertain possible factors leading to dominance of O. niloticus. Compared to other tilapiines, Nile tilapia is widely distributed, feeds on a variety of food items, grows to larger sizes, is highly fecund and can survive in a wide range of physical chemical parameters in the lake. These attributes could probably be the reason for its dominance over the tilapiine groups in the lake. Studies further show that ecology and biology of the O. niloticus has changed probably in response to changes occurring in the ecosystem. Management measures to sustain the fishery which include reduced fishing pressure, use of legal fishing methods, and control of environmental degradation have been discussed.
    Description: Published
    Description: Introduced species; Endemic species; Geographical distribution; Depleted stocks; Rare species; Species extinction; Fishery management; Resource management; Environment management; Species diversity;Oreochromis niloticus; Oreochromis leucosticus; Tilapia zillii; Sarotherodon melanopleudra; Oreochromis variabilis; Oreochromis esculentus; Lates niloticus; Rastrineobola argentea
    Repository Name: AquaDocs
    Type: Proceedings Paper
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  • 6
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    African Studies Centre | Leiden, Netherlands
    Publication Date: 2021-05-19
    Description: A total of 17 bivalve species belonging to 135 families were collected and identified in Malindi, Mombasa Marine National Parks, and Kanamai from Oct.'97 to Mar.'98. Bivalve fauna showed densities 2/m super(2), and low diversity. Modiolus auriculatus and Pinna muricata were the most represented. There was a significant difference in species diversity between Malindi and Mombasa reef flats at p〉0.10. Shallow lagoons had very low density and diversity as compared to sea grass and reef flat zones. This was attributed to the high deposits of shell, coral, and sand. Swimming, goggling/scuba diving, walking/trampling and turning of rocks were identified as the main forms human activities causing disturbance to the bivalves. Frequencies of occurrence of these activities varied in the three areas with Kanamai exhibiting the highest. Trampling had the most notable impact and was used to show the impact of human activities on the most vulnerable species. Results show that the distribution of bivalve fauna in the protected and unprotected areas is density independent and is not only influenced by human activities and management strategy but rather by other biological and environmental factors such as substrate type, tide range and wave activity. Human activities however affect those bivalves with fragile shells such as Pinna muricata, through trampling resulting in injury and/or death. Presence of man affects the routine activities of the others such as Tellina flavum, Anadara antiquata, Tridacna squamosa and Codakia punctata. Therefore spreading out of human activities within the marine parks is recommended to reduce their impacts. These activities should be spread out into the reserves and unprotected areas.
    Description: Published
    Keywords: Mollusc fisheries ; Community composition ; Protected resources ; Marine parks ; Man-induced effects ; Check lists
    Repository Name: AquaDocs
    Type: Report Section , Not Known
    Format: pp.81-95
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  • 7
    Publication Date: 2021-05-19
    Description: Tropical wetlands are known to be very productive, providing water and primary productivity upon which large numbers of plants and animal species depend for survival. In the Lake Victoria Basin (LVB), wetlands are part and parcel of many water bodies where they are hydrologically and ecologically linked through the supply of water, nutrients and organic matter. In the upper reaches of the LVB, many wetlands have been formed by spring water draining into valley bottoms where the gradient is low and hence water accumulates, hence supporting characteristic biota. Other wetlands are formed as a result of shallow water table in depressions, though most of these are seasonal and their area fluctuates depending on the prevailing weather conditions. Other wetlands in the upper reaches have been formed out of damming of streams and rivers for domestic and industrial water supply. In the middle reaches, springs fed wetlands still dominate, with a few riverine wetlands occurring along the edges of the large rivers. In the lower reaches and floodplains, we have seasonal wetlands that form during the rainy season when rivers over-top their banks. Many of the large wetlands in the LVB are found at the river mouths of the major rivers and in the inshore areas of the lake. Examples include the Nyando Wetland, Yala Swamp, Bunyala Wetland, River Mara Swamp, Mosirori Wetland, Osodo Swamp, Ngegu Wetland and Kuja Delta Wetland. Because of their high productivity, these wetlands are threatened by human activities, exacerbated by high human population growth. Changing land use and intensity in the catchments has compromised their integrity, resulting into sedimentation, poor water quality and eutrophication. There is thus a need for awareness creation, adoption of best management practices at the catchment scale and research, especially in socioeconomics, to help avert the negative influences on the wetlands in the LVB.
    Description: Nyando Wetland Utility Resource Optimization Project, Ref:- AKEN/05/427
    Description: Published
    Keywords: Wetlands ; Inland waters ; Water reservoirs ; Environment management ; Resource conservation
    Repository Name: AquaDocs
    Type: Book Section , Not Known
    Format: pp.1-14
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  • 8
    Publication Date: 2021-05-19
    Description: Nyando Wetland is endowed with rich biological diversity and supports the livelihoods of many people in the Lake Victoria Basin. It provides ecological services (climate modification, water purification, waste water treatment, flood control and water storage and distribution in space and time); direct uses such as water for domestic purposes, livestock watering, source of fish, medicinal plants and animals and various materials. Despite the intricate link between human well-being and wetland functions, the wetlands are threatened by high and increasing population density of both humans and livestock, unsustainable agricultural practices, effects of Climate Change (prolonged droughts and floods), pollution of surface water sources, unpredictable and low rainfall, deforestation, unplanned human settlement, overgrazing, limited access to clean water, poor sanitation, inappropriate and degrading fishing practices, among other factors. Since the livelihoods of the people largely depend on the utilization of wetland resource, it is important to ensure sustainable use of natural capital by striking a balance between its utilization and conservation. The underlying message of this chapter is that long-term human development cannot be achieved without prioritizing environmental conservation and management. It is therefore incumbent upon all Kenyans to value wetlands as the “kidneys of the earth” and support their sustainable use for the benefit of present and future generations. This is especially true for Nyando Wetland resources that are vital to the local and regional socioeconomic development but are easily accessible to the poor. This chapter articulates the socioeconomic, gender and cultural contexts in which the inhabitants of Nyando Wetland operate in meeting their livelihoods. It is organized to include a contextual narrative of the origin of the people of Nyando Wetland, their demographic characteristics and selected social indicators with a focus on implications to sustainable resource management. The interaction of people with resources and the influence of gender and cultural issues to natural resources use are also articulated. The chapter concludes with a discussion of the policy framework for the community based management of Nyando Wetland resources.
    Description: Published
    Keywords: Wetlands ; Socioeconomic aspects ; Resource conservation ; Resource management
    Repository Name: AquaDocs
    Type: Book Section , Not Known
    Format: 32-52
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  • 9
    Publication Date: 2021-05-19
    Description: Nyando Wetland is endowed with rich biological diversity and supports the livelihoods of many people in the Lake Victoria Basin. It provides ecological services (climate modification, water purification, waste water treatment, flood control and water storage and distribution in space and time); direct uses such as water for domestic purposes, livestock watering, source of fish, medicinal plants and animals and various materials. Despite the intricate link between human well-being and wetland functions, the wetlands are threatened by high and increasing population density of both humans and livestock, unsustainable agricultural practices, effects of Climate Change (prolonged droughts and floods), pollution of surface water sources, unpredictable and low rainfall, deforestation, unplanned human settlement, overgrazing, limited access to clean water, poor sanitation, inappropriate and degrading fishing practices, among other factors. Since the livelihoods of the people largely depend on the utilization of wetland resource, it is important to ensure sustainable use of natural capital by striking a balance between its utilization and conservation. The underlying message of this chapter is that long-term human development cannot be achieved without prioritizing environmental conservation and management. It is therefore incumbent upon all Kenyans to value wetlands as the “kidneys of the earth” and support their sustainable use for the benefit of present and future generations. This is especially true for Nyando Wetland resources that are vital to the local and regional socioeconomic development but are easily accessible to the poor. This chapter articulates the socioeconomic, gender and cultural contexts in which the inhabitants of Nyando Wetland operate in meeting their livelihoods. It is organized to include a contextual narrative of the origin of the people of Nyando Wetland, their demographic characteristics and selected social indicators with a focus on implications to sustainable resource management. The interaction of people with resources and the influence of gender and cultural issues to natural resources use are also articulated. The chapter concludes with a discussion of the policy framework for the community based management of Nyando Wetland resources.
    Description: Published
    Keywords: Wetlands ; Socioeconomic aspects ; Resource management
    Repository Name: AquaDocs
    Type: Book Section , Not Known
    Format: pp.32-52
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  • 10
    Publication Date: 2021-05-19
    Description: The impact of agro-industrial activities on the water quality within River Nyando, Lake Victoria Basin (Kenya) was studied at different hierarchical levels between August 1997 and June 1999. Triplicate water samples were collected on a monthly basis from various stations ranging from the source to the mouth of the river and analyzed for selected physical and chemical water quality parameters using standard analytical methods. Statistical analysis was performed using MINITAB and STATISTICA computer packages. Agricultural land use was found to be the major factor contributing to changes in water quality. Salinity and pH varied at river basin scale, turbidity, TDS and conductivity at catchment scale, while DO, alkalinity and pH at subcatchment and river reach scale. The nutrient loads increased downstream. Anthropogenic sources contribute to high levels of nutrients within the basin. The changes recorded in water quality along the river were comparable to the modified Index of Biotic Integrity (IBI) and Nyando Habitat Evaluation Index (NHEI) derived for the river during the same period of study. Findings of this study can be used to design measures for mitigating and monitoring environmental impacts arising from agro-industrial activities within the Lake Victoria Basin. The study recommends a comprehensive Nyando River Basin Management Programme to address the multiple issues environmental within the basin.
    Description: Published
    Keywords: Water quality ; Environmental impact ; Rivers ; Statistical analysis ; Land use ; Environmental monitoring ; Industrial wastes ; Inland waters ; Anthropogenic factors ; Physicochemical properties ; Resource management ; Water quality ; Environmental impact ; Industrial wastes ; Inland waters ; Rivers ; Anthropogenic factors ; River basin management ; Statistical analysis ; Physicochemical properties ; Land use ; Limnological data ; Environmental monitoring ; Resource management ; Environment management ; Agricultural pollution
    Repository Name: AquaDocs
    Type: Proceedings Paper
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