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Browsing by Author "Mwangi, Benson M."

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Fish Species Composition and Diversity of Small Riverine Ecosystems in the Lake Victoria Basin, Kenya
(2012-09) Mwangi, Benson M.; Ombogo, Mornica A.; Amadi, Jacinta; Baker, Ntambi; Mugalu, Daniel
Riverine ecosystems in the Lake Victoria Basin (LVB) significantly contribute to the lake’s water budget and aquatic biodiversity. Despite their significance to the lakes fisheries, only limited biodiversity studies have been carried out, particularly in the smaller riverine ecosystems. This study investigated the fish species composition, diversity and distribution in two small riverine ecosystems (Rivers Awach Seme and Kisian) draining the Kenyan Lake Victoria Basin. Sampling was carried out monthly from August 2009 to June 2010, at three sampling sites of 100-m stretch along each river, representing the upper, middle and lower reaches. Fish were caught using an electro-fisher, identified with the help of relevant taxonomic guides and staff from the Kenya Marine and Fisheries Research Institute, measured for total lengths and weighed to the nearest 0.1 cm and 0.1 gm, respectively. The results showed that the two rivers had a diverse fish community consisting of 11 species, namely, Barbus altianalis Boulenger, Labeo victorianus Boulenger, Barbus cercops Whitehead, Clarias gariepinus Burchell, Barbus nyanzae Whitehead, Barbus kerstenii Peters, Barbus jacksonii Günther, Barbus appleurograma, Oreochromis leucostictus Trewavas, Gambusia affinis Baird & Girard, and Bagrus docmak Forsskål, out of which 9 were present in River Kisian and 7 in River Awach. The fish community at River Kisian was dominated by C. gariepinus, constituting over 42.5% while at River Awach, B. altianalis and B. nyanzae dominated with over 46.3% and 30.7% of the total catch, respectively. Fish abundance and evenness were much higher in River Awach suggesting that this river would provide better fisheries if managed appropriately. Generally, the results show that the two rivers may be an important source of fish for both the lakes ecosystem as well as local fisheries if appropriate management interventions are instituted
Fish Species Composition and Diversity of Small Riverine Ecosystems in the Lake Victoria Basin, Kenya
(International Journal of Science and Technology, 2012-09) Mwangi, Benson M.; Ombogo, Mornica A.; Amadi, Jacinta; Ntambi, Baker; Mugalu, Daniel
Riverine ecosystems in the Lake Victoria Basin (LVB) significantly contribute to the lake’s water budget and aquatic biodiversity. Despite their significance to the lakes fisheries, only limited biodiversity studies have been carried out, particularly in the smaller riverine ecosystems. This study investigated the fish species composition, diversity and distribution in two small riverine ecosystems (Rivers Awach Seme and Kisian) draining the Kenyan Lake Victoria Basin. Sampling was carried out monthly from August 2009 to June 2010, at three sampling sites of 100-m stretch along each river, representing the upper, middle and lower reaches. Fish were caught using an electro-fisher, identified with the help of relevant taxonomic guides and staff from the Kenya Marine and Fisheries Research Institute, measured for total lengths and weighed to the nearest 0.1 cm and 0.1 gm, respectively. The results showed that the two rivers had a diverse fish community consisting of 11 species, namely, Barbus altianalis Boulenger, Labeo victorianus Boulenger, Barbus cercops Whitehead, Clarias gariepinus Burchell, Barbus nyanzae Whitehead, Barbus kerstenii Peters, Barbus jacksonii Günther, Barbus appleurograma, Oreochromis leucostictus Trewavas, Gambusia affinis Baird & Girard, and Bagrus docmak Forsskål, out of which 9 were present in River Kisian and 7 in River Awach. The fish community at River Kisian was dominated by C. gariepinus, constituting over 42.5% while at River Awach, B. altianalis and B. nyanzae dominated with over 46.3% and 30.7% of the total catch, respectively. Fish abundance and evenness were much higher in River Awach suggesting that this river would provide better fisheries if managed appropriately. Generally, the results show that the two rivers may be an important source of fish for both the lakes ecosystem as well as local fisheries if appropriate management interventions are instituted.
Influence of large woody debris accumulations on macro invertebrate distribution in a low order forested tropical stream, Sagana river, Kenya
(Jomo Kenyatta University of Agriculture and Technology, 2014) Mwangi, Benson M.; Odhiambo, C.
Woody debris accumulations are important ecological components in low order forested streams. They provide forage and refuge for a macroinvertebrates, which are key trophic components for riverine fish. The occurrence of woody debris in tropical streams is however threatened by large scale destruction of catchment forests thereby threatening the riverine biodiversity. Despite their importance, the current status of woody debris accumulations in tropical forested streams is unknown. In this study we determined the densities of debris dams in a forested stream section, their effectiveness in coarse particulate organic matter (CPOM) retention and the associated macroinvertebrates along a 100m stream stretch within the mid‐reaches of Sagana River. Volume of woody debris was estimated from length, width and height. All components retained were collected, sorted and dried to a constant weight at 85oC. Prior to drying of the organic matter, macroinvertebrates in the CPOM were picked, sorted into different taxa and enumerated. The average density over the whole study period was 2 woody debris dam accumulations per 100m stream stretch. The macroinvertebrates occurring at the debris dams were dominated by Coleoptera (47.3%), followed by Diptera (22.7%) and Ephemeroptera (19.2%). The Coleoptera were dominated by Gyrinidae, Elmidae and Scirtidae. Woody debris play an important role as long‐term retention structures for organic matter and food resources. They forms an important component of riverine ecosystems with regard to CPOM retention, macroinvertebrates distribution and abundance which are indicators of habitat condition. There is therefore need for re‐introductions of such structures for effective channel restoration. We recommend maintenance of buffer strips of riparian vegetation along river banks to protect riverine communities from adverse effects of land‐use changes within Mt. Kenya catchment region.
INFLUENCE OF LARGE WOODY DEBRIS ACCUMULATIONS ON MACROINVERTEBRATE DISTRIBUTION IN A LOW ORDER FORESTED TROPICAL STREAM, SAGANA RIVER, KENYA
(Jomo Kenyatta University of Agriculture and Technology, 2014) Mwangi, Benson M.; Odhiambo, C.
Woody debris accumulations are important ecological components in low order forested streams. They provide forage and refuge for a macroinvertebrates, which are key trophic components for riverine fish. The occurrence of woody debris in tropical streams is however threatened by large scale destruction of catchment forests thereby threatening the riverine biodiversity. Despite their importance, the current status of woody debris accumulations in tropical forested streams is unknown. In this study we determined the densities of debris dams in a forested stream section, their effectiveness in coarse particulate organic matter (CPOM) retention and the associated macroinvertebrates along a 100m stream stretch within the mid‐reaches of Sagana River. Volume of woody debris was estimated from length, width and height. All components retained were collected, sorted and dried to a constant weight at 85oC. Prior to drying of the organic matter, macroinvertebrates in the CPOM were picked, sorted into different taxa and enumerated. The average density over the whole study period was 2 woody debris dam accumulations per 100m stream stretch. The macroinvertebrates occurring at the debris dams were dominated by Coleoptera (47.3%), followed by Diptera (22.7%) and Ephemeroptera (19.2%). The Coleoptera were dominated by Gyrinidae, Elmidae and Scirtidae. Woody debris play an important role as long‐term retention structures for organic matter and food resources. They forms an important component of riverine ecosystems with regard to CPOM retention, macroinvertebrates distribution and abundance which are indicators of habitat condition. There is therefore need for re‐introductions of such structures for effective channel restoration. We recommend maintenance of buffer strips of riparian vegetation along river banks to protect riverine communities from adverse effects of land‐use changes within Mt. Kenya catchment region.
Physicochemical Characteristics of undrainable Water Dams Utilized for Fish rearing In The Semi-Arid Naromoru Area, Central Kenya
(Jomo Kenyatta University of Agriculture and Technology, 2012) Mwangi, Benson M.; Kairu, E.; Ndiwa, C.T.; Kaluli, J.W.; Nyingi, D.
Naromoru is a semiarid area in Central Kenya, occurring on the leeward side of Mt. Kenya. Its water sources include a few permanent rivers such as Nairobi River, intermittent streams and a large number of undrainable water reservoirs. Most of the undrainable water resources have been stocked with fish but their utilization for fish rearing has generally remained very low. The purpose of this study was therefore to examine the water quality status of the dams to assess their suitability and potential for fish production. pH, electro-conductivity and total dissoved solutes (TDS) were measured in-situ from three reservoirs (Gathathini, Lusoi and Kianda dams) differing in their habitat characteristics. Water samples were collected for determination of the ionic concentartions of the reservoirs. Water quality status differed markedly between sites, with electric conductivity ranging from 350μScm-1 at Gathathini dam to over 1350μScm-1 at Lusoi dam. pH however showed only a slight variation from 8-9.6. Water temperature and transparency varied significantly between the sites, while cationic constituents (Ca2+, K+, Mg2+ and Na+), anions (SO4 2-, HCO3 2-, and Cl-1), heavy metals (Pb2- and Cu2+) and nutrients (NO3 - and PO4 2-) were all within the recommended WHO levels for fish production. Generally the water quality status was within the standards recommended for fisheries production
Physicochemical Characteristics of undrainable Water Dams Utilized for Fish rearing In The Semi-Arid Naromoru Area, Central Kenya
(Jomo Kenyatta University of Agriculture and Technology, 2012) Mwangi, Benson M.; Kairu, E.; Kaluli2, J. W.; Nyingi, D.; Ndiwa, C. T.
Naromoru is a semiarid area in Central Kenya, occurring on the leeward side of Mt. Kenya. Its water sources include a few permanent rivers such as Nairobi River, intermittent streams and a large number of undrainable water reservoirs. Most of the undrainable water resources have been stocked with fish but their utilization for fish rearing has generally remained very low. The purpose of this study was therefore to examine the water quality status of the dams to assess their suitability and potential for fish production. pH, electro-conductivity and total dissolved solutes (TDS) were measured in-situ from three reservoirs (Gathathini, Lusoi and Kianda dams) differing in their habitat characteristics. Water samples were collected for determination of the ionic concentartions of the reservoirs. Water quality status differed markedly between sites, with electric conductivity ranging from 350μScm-1 at Gathathini dam to over 1350μScm-1 at Lusoi dam. pH however showed only a slight variation from 8-9.6. Water temperature and transparency varied significantly between the sites, while cationic constituents (Ca2+, K+, Mg2+ and Na+), anions (SO42-, HCO32-, and Cl-1), heavy metals (Pb2- and Cu2+) and nutrients (NO3- and PO42-) were all within the recommended WHO levels for fish production. Generally the water quality status was within the standards recommended for fisheries production.
Towards a national policy to support wastewater reuse in Kenya
(2011) Mwangi, Benson M.; Kaluli, J.W.; Githuku, C.; Home, P.
Kenya is a water-scarce country with the capital city, Nairobi, receiving less than 100 l/capita/day. Potable water for irrigation and industrial use is generally unavailable, and this calls for alternative water sources. Despite use of wastewater being illegal in Kenya, it is used to irrigate over 720 ha in Nairobi. In order to justify the formulation of a national policy to support wastewater reuse, secondary data which included the authors’ previous work was reviewed. In a study done between 2006 and 2007, the levels of nitrates (100 mg/l) and TDS (630 mg/l) in the wastewater were found to be within the acceptable NEMA standards. The concentration of lead was 0.1 mg/lwhile cadmium and chromium were non-detectable. However, levels of BOD and Coliform bacteria were higher than NEMA limits. This implied that Nairobi sewage needed to be treated for the removal of BOD, turbidity and microbial contamination. In order to allow for safe use of wastewater in Kenya, there is need to formulate a national wastewater reuse policy which provides guidelines for maximum allowable levels of pesticides, herbicides, and heavy metals in wastewater reuse. Such a policy should also indicate the required water quality monitoring frequency for faecal indicators (Escherichia coli, faecal coliforms, enterococci), and suggest the maximum allowable concentration of nutrients (nitrogen and phosphorus) which may are usually abundant in wastewater.
Treatment of flower farm wastewater effluents using constructed wetlands in lake Naivasha, Kenya
(2012-01) Mwangi, Benson M.; Rosemary, Kimani W.; Gichuki, Cecilia M.
Lake Naivasha, Kenya, is a fresh water lake currently experiencing severe environmental problems as result of pollution from agricultural effluents and urban water surface runoff, uncontrolled water abstraction, improper land use practices in the catchment area and proliferation of wetlands’ invasive species. These problems are exacerbated and compounded by changes in climate and inadequate conservation interventions. To deal with the pollution problem, flower farms around the lake have adopted constructed wetland technologies to treat their wastes prior to release into the lake’s ecosystem. In this study, we examined the efficiency of one of the largest and oldest constructed wetland, the Kingfisher constructed wetland, owned by Home Grown Ltd. The study was conducted between October 2009 and March 2010. Measurements of water quality parameters were carried out at 9 sampling stations along the constructed wetland system from inlet to outlet. The results showed that water quality significantly improved from inlet to the outlet, with conductivity declining from 722 μScm-1 to 514 μScm-1 while TDS declined from 569 to 186 mgl-1. Other water quality parameters such as total suspended solids (TSS), BOD, COD, total nitrogen and total phosphorous similarly declined significantly (P 0.05) from inlet to outlet. Heavy metals generally occurred in low concentrations at the inlet, but still declined in their concentrations though not significantly. Results show that constructed wetlands are highly efficient in wastewater effluent treatment and can be used in amelioration of point sources of pollution into inland water bodies.
Treatment of flower farm wastewater effluents using constructed wetlands in lake Naivasha, Kenya
(2012-01) Mwangi, Benson M.; Gichuki, Cecilia M.; Kimani, Rosemary W.
Lake Naivasha, Kenya, is a fresh water lake currently experiencing severe environmental problems as result of pollution from agricultural effluents and urban water surface runoff, uncontrolled water abstraction, improper land use practices in the catchment area and proliferation of wetlands’ invasive species. These problems are exacerbated and compounded by changes in climate and inadequate conservation interventions. To deal with the pollution problem, flower farms around the lake have adopted constructed wetland technologies to treat their wastes prior to release into the lake’s ecosystem. In this study, we examined the efficiency of one of the largest and oldest constructed wetland, the Kingfisher constructed wetland, owned by Home Grown Ltd. The study was conducted between October 2009 and March 2010. Measurements of water quality parameters were carried out at 9 sampling stations along the constructed wetland system from inlet to outlet. The results showed that water quality significantly improved from inlet to the outlet, with conductivity declining from 722 μScm-1 to 514 μScm-1 while TDS declined from 569 to 186 mgl-1. Other water quality parameters such as total suspended solids (TSS), BOD, COD, total nitrogen and total phosphorous similarly declined significantly (P 0.05) from inlet to outlet. Heavy metals generally occurred in low concentrations at the inlet, but still declined in their concentrations though not significantly. Results show that constructed wetlands are highly efficient in wastewater effluent treatment and can be used in amelioration of point sources of pollution into inland water bodies.
WritingSkills and Presentations
(2015) Mwangi, Benson M.

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