School of Natural Resources and Environmental Studies
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Item Influences of land use/cover on water quality in the upper and middle reaches of River Njoro, Kenya(Blackwell Publishing Asia Pty Ltd, 2007) Muchiri, Mucai; Shivoga, William A.; Kibichi, Samuel; Odanga, Jethro; Miller, Scott N.; Baldyga, Tracy J.; Enanga, Eric M.; Gichaba, Maina C.Item Macroinvertebrate assemblages along a land-use gradient in the upper River Njoro watershed of Lake Nakuru drainage basin, Kenya(Blackwell Publishing Asia Pty Ltd, 2007) Muchiri, Mucai; Miller, Scott N.; Shivoga, William A.; Kibichii, SamuelItem Remote Sensing Applications for Sustainable Aquaculture in Africa(IEEE, 2007) Quansah, Joseph, E.; Rochon, Gilbert, L.; Quagrainie, Kwamena, K.; Amisah, Steve; Muchiri, Mucai; Ngugi, CharlesThe authors review the current state of the science with respect to remote sensing applications for aquaculture, including site location, aquaculture facility mapping, market proximity analysis and associated roadway infrastructure, epizootic mitigation, meteorological event and flood early warning, environmental pollution monitoring, and aquatic ecosystem impact, primarily for catfish (Clarias spp.) and tilapia (Tilapia spp.; Oreochromis spp.), inter alia. The potential of technology transfer from the controlled environment aquaculture research facilities at Purdue University, West Lafayette, Indiana, USA to partnering institutions in Ghana and Kenya are explored. The potential for multi-sensor remote sensing deployment to support sustainable fish production in these environments and subsequently in other African countries is evaluated.Item Influences of land use/cover on water quality in the upper and middle reaches of River Njoro, Kenya(Lakes & Reservoirs: Research and management, 2007-06) Shivoga, William, A.; Muchiri, Mucai; Kibichi, Samuel; Odanga, Jethro; Miller, Scott, N.; Baldyga, Tracy, J.; Enanga, Eric, M.; Gichaba, Maina, C.Data from 10 sampling sites along the River Njoro are used to examine the contribution of nutrients from upstream land uses draining each of the sampling sites. The data also are used to assess whether both the proportion of land uses and the size of the subwatersheds account for the variability in water quality in the River Njoro watershed. Geographical Information System analysis was used to determine the spatial distribution of land-cover types and subwatersheds contributing run-off to the sampling sites in the River Njoro. Standard Digital Elevation Model-based routines were used to establish the watershed area contributing run-off to each sampling site. Water and sediment samples were collected for chemical analysis, and the nutrient levels were related to the upstream land-use types and the size of the subwatersheds. The mid-stream portion of the River Njoro (near Egerton University) accounts for the highest nutrient contributions. The percentage contribution is magnified by additions from industrial, human settlements and agricultural land uses around the University. There is a significant decrease in nutrient levels downstream, however, indicating natural purification as the river flows through an area of large-scale farming with intense, well-preserved riparian and in-stream vegetation. Steep slopes of the land upstream of Egerton University enhance erosion and nutrient losses from those subwatersheds. Mixed small-scale agricultural and bare lands contribute over 55% of the phosphorus load to the upper and mid-reaches of the River Njoro. The size of the subwatershed accounts for about 53% of the variability in the soluble phosphorus in the river. The land-use subwatershed proportions are important for characterizing and modelling water quality in the River Njoro watershed. Upland land uses are as important as near-stream land uses. We suggest that conservation of intact riparian corridor along the river and its tributaries contributes significantly to natural purification processes and recovery of the ecological integrity of the River Njoro ecosystem.Item Ecology and Management of Lake Naivasha, Kenya, in Relation to Climatic Change, Alien Species' Introductions, and Agricultural Development(Environmental Conservation; Cambridge Journals, 1990) Harper, David, M.; Muchiri, Mucai; Mavuti, Kenneth, M.Lake Naivasha is an important freshwater resource for Kenya's foreign-currency-earning agriculture and tourism, and for water-supply. It has always experienced extensive water-level fluctuations as a consequence of irregular rainfall patterns that are affected by continental-scale climatic events, and its communities — particularly of aquatic plants — were adapted to these changes.Item The status and future of the Lake Naivasha fishery, Kenya(Kluwer Academic Publishers, 2002) Muchiri, Mucai; Kundu, Rodrick; Taylor, Andy; North, Rick; Harper, David M.; Bailey, Roland; Hickley, PhilLake Naivasha is a freshwater lake situated in the eastern rift valley of Kenya. Only five species of fish are present, all of which have been introduced. They are Oreochromis leucostictus, Tilapia zillii, Micropterus salmoides (largemouth bass), Barbus amphigramma and Poecilia reticulata (guppy). The first three of these form the basis of an important gill net fishery and bass are also taken by rod and line for sport. Barbus are occasionally caught by dip net. Actual and potential yields for the Lake Naivasha fishery are discussed and the fishery is shown to be under-performing. The feeding regimes of the commercially exploited fish were examined in the context of available food supply, in particular the benthic fauna. Small bass depend heavily on Micronecta and large bass mostly take crayfish. Detritus predominates in the diet of Oreochromis leucostictus and Tilapia zillii but the former also eats algae and the latter, Micronecta and macrophyte. Various food resources, especially the benthos, appear to be under-utilized and so it is possible that further species could be introduced to enhance the commercial fishery.Item Economic Gain versus Ecological Damage from the Introduction of Non-native Freshwater Fish: Case Studies from Kenya(2008) Muchiri, Mucai; Hickley, Phil; Britton, Robert; Boar, RosalindNon-native freshwater fish species that have been introduced to the inland waters of Kenya are listed and the consequences of stocking such fish are reviewed. Original species composition and lake ecosystem function can be detrimentally affected but, also, the introduction of non-native species can result in significant economic benefit. In the context of impact on recipient fish communities and the performance of exploited fisheries, the merits or otherwise of alien fish species introductions are discussed with the aid of two case histories; lungfish (Protopterus aethiopicus) in Lake Baringo and a number of species, particularly carp (Cyprinus carpio), in Lake Naivasha.Item Habitat degradation and subsequent fishery collapse in Lakes Naivasha and Baringo, Kenya(2004) Muchiri, Mucai; Hickley, Phil; Boar, Rosalind; Britton, Robert; Adams, Chris; Gichuru, Nicholas; Harper, DavidLakes Naivasha and Baringo in the eastern Rift Valley of Kenya are shallow, freshwater lakes that are subject to major fluctuations in water level and suffer from habitat degradation as a consequence of riparian activity. Lake Naivasha is approximately 160 km2, is bordered by Cyperus papyrus and its aquatic macrophytes are in a state of flux. The most significant riparian activity is the large scale production of flowers for the European market. Lake Baringo is approximately 140 km2 and lies in a semi-arid region. Its most noticeable feature is its extreme turbidity which is mainly due to excessive soil erosion resulting from deforestation and overgrazing. This turbidity has led to near extinction of submerged macrophytes and a lake bed virtually devoid of benthic fauna. Fishing pressure has added to the environmental stresses being endured by the fish populations and commercial catches have been detrimentally affected. Accordingly, periods of fishery closure are now imposed upon both lakes. Limited remedial action is feasible and some local stakeholders are attempting to introduce mitigation measures. For Lake Naivasha there is an agreed riparian owners' management plan which tackles issues such as water usage and protection of the C. papyrus margin. For Lake Baringo there is a Rehabilitation of Arid Environments initiative which promotes such activities as restoration of riparian vegetation and appropriate stock management.