http://41.89.164.27:8080/xmlui/handle/123456789/1820 2026-04-18T22:28:58Z http://41.89.164.27:8080/xmlui/handle/123456789/2582 Economic Viability of Agricultural Carbon Sources on Asian Rice (Oryza sativa Lejeunia 1753.) and Nile Tilapia (Oreochromis niloticus) Production in a Flocponic System Rono, Kenneth; Matolla, Geraldine; Manyala, Otieno Julius; Masese, Onderi Frank A flocponic system is a fish and plant-based system that uses carbon sources. However, the economic viability of using carbon sources for production remains unknown. Hence, the study assessed the economic viability of utilizing agricultural carbon sourc es in a flocponic system. A complete randomized design was employed in five treatments (wheat-bran, rhodes-hay, maize-cob, maize-stables, lucerne-hay, agricultural carbon sources, and a control (no carbon), each in triplicate. Each treatment and control had Nile tilapia and rice densities of 98 m-3 fry and 250 m-2 rice, respectively. The fish yield differed among the treatments and control, with lucernehay showing the highest output (2.53±0.02 kgm-3 ) and control having the lowest. The rice yield component also showed variability. Lucerne-hay had the highest grain yield of 5.70±0.25 kgm-3 , followed by wheat-bran, rhodes-hay, maize-cob, and maizestables treatments. The control yielded the lowest weight of grains and rice straws. The flocponic system's profitability varied between the treatment and control groups. Lucerne-hay, wheat-bran, and rhodes-hay generated positive net income, amounting to 1338.39, 474.69, and 266.1, respectively. The benefit-cost ratios for the lucerne-hay, wheat-bran, and Rhodes-hay treatments were greater than one, with lucerne-hay having the highest value (1.72). There was a slight variation in the expense structure ratio; wheat-bran had the lowest value of 0.88. The gross revenue ratio varied between the treatments and the control group; the control had the highest ratio of 145.39, and lucerne-hay had the lowest. The lucerne-hay, wheat-bran, rhodes-hay, and maize-cob treatments yielded a positive return on investment, while the maize-stable treatment and control had a negative return on investment. The proximate composition and cost of the carbon source may have impacted the profitability of the flocponic production. Wheat-bran, lucerne-hay, and rhodes-hay are suitable for flocponic output because of their high productivity and profitability, resulting in a favorable return on investment. These options are economically viable. 2024-07-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2580 Effects of Agricultural Carbon Sources On Water Quality and Phytoplankton Community Composition in Flocponic System Rono, Kenneth; Matolla, Geraldine; Manyala, Julius Otieno; Masese, Frank Onderi Carbon products promote aggregate floc-rich plankton, with diverse roles in flocponic production. Availability, low-cost, and chemical composition of agricultural by-products make them ideal substrates for phytoplankton production. Phytoplankton maintains water quality by reducing toxic substances, but it is problematic under some conditions. Therefore, the study evaluates how agricultural carbon sources affect flocponic phytoplankton community composition and water quality. Five treatments (wheat-bran, Rhodes-hay, maize-cob, maize-stables, and lucerne-hay) and a control (no byproduct) were employed in a complete randomized design, each in triplicate for nine weeks. Each treatment and control had Nile tilapia (0.155 ± 0.01 g) and rice (seeds) densities of 98 m-3 and 250 m-2 , respectively. Temperature, pH, dissolved oxygen, and salinity levels did not differ significantly between treatments and control. However, TDS, soluble reactive phosphorus (SRP), ammonia, nitrite, and nitrate showed significant differences (p<0.05) between treatments and control. Lucerne-hay exhibited the highest nitrate levels (0.9 ± 0.06 mg L-1 ), SRP (0.6 ± 0.05 mg L-1 ), and the lowest ammonia and nitrite levels compared to other treatments and control. Lucerne-hay had the highest phytoplankton diversity (2.48), while the control (1.37) had the least. Further, there were significant differences in phytoplankton abundance, with lucernehay having the highest Charophyta (1.45 ± 0.02 indsL-1 ), Chlorophyta (1.60 ± 0.02 indsL-1 ), and Ochrophyta (1.64 ± 0.03 indsL-1 ) abundance, while the control had the least. The result of the study revealed that carbon sources influence flocponic water quality and phytoplankton. The composition and solubility of lucerne-hay and wheat-bran may have improved water quality and phytoplankton. The study suggests that lucerne-hay and wheat-bran are the best flocponic carbon sources for phytoplankton and water quality. 2025-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2565 Effect of the ebb-and-flow constructed wetland operation, media type and celery (Apium graveolens L.) growth on nutrient removal from a pre-treated brewery effluent Obado, Elizabeth; Kaise, Horst; Taylo, Richard; Mabasa, Nyiko; Agembe, Simon; Liti, David; Manyala, Julius Breweries face a high cost of wastewater treatment to meet environmental discharge standards. Constructed wetland (CW) design and operation have been optimised for sustainable wastewater treatment. An ebb-and-flow CW was used to investigate the effect of media on nutrient removal from a brewery effluent. Eight media (clay pebbles, clay bricks, sand, bioballs, recycled plastic and gravel sizes), either alone or mixed, were tested. A 2:1:1 ratio of each media, pine bark and granular activated carbon, respectively, was used for mixed treatments. A uniform celery planting density of eight seedlings per m2 and 12-min effluent retention time was used. There were significant differences between unmixed and mixed media on nutrient removal (p , 0.05). The unmixed media of clay pebbles had the highest mean COD reduction of 7.5% and ammonia 8.1%. Mixing resulted in better overall mean removal efficiency of nitrite-N (7.6%), nitrate-N (15.3%), total inorganic nitrogen (29.9%), orthophosphate (12.7%) and plant biomass (11158.5 gm 2 ) than unmixed media. Media porosity, surface area and chemical composition and celery plant enhance nutrient removal through synergistic interactions. The study recommends unmixed clay pebbles, bioballs and 19-mm gravel for improved ammonia-N removal and mixed media for multiple pollutant removal and celery productivity. 2025-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2557 Macroinvertebrate functional responses to human disturbance and flow cessation in Afromontane-savannah rivers Owade, Christine A.A.; Kaiser, Horst; Simiyu, Gelas M.; Owuor, Godfrey; Sicharani, Evans; Gettel, Gretchen M.; Masese, Frank O. Wildlife, people, and livestock rely on riverine ecosystems in arid and semi-arid areas as primary water sources. Studies on the influence of human activities and livestock on the ecological health of these seasonal systems are thus necessary. This is more relevant given the increasing demand for water as human populations grow, which leads to over-abstractions and, sometimes, cessation of flows in streams and rivers during the dry periods. Although the structural composition of macroinvertebrate communities has been utilized to indicate the ecological integrity of streams and rivers, macroinvertebrate functional feeding groups (FFGs) are less studied, especially in intermittent Afrotropical streams. We used macroinvertebrate FFGs as indicators of water quality and ecological integrity of streams influenced by different levels of human disturbance and flow variability in the Afromontane-savanna Bura and Wundanyi rivers in Taita Taveta County, Kenya. A total of 18 sampling sites were identified for sampling and grouped into three (3) disturbance categories (low– n = 7, moderate - n = 4, and disturbed - n = 7) and two categories of flow permanence (permanent – n = 9, and seasonal – n = 9). At each site, sampling of physicochemical water quality parameters and macroinvertebrates was done twice during the wet and dry seasons. Ratios of five FFGs (collector-gatherers, collector-filterers, scrapers/grazers, predators, and shredders) were used to derive five metrics that are surrogates of ecosystem attributes in the rivers. There was a significant difference (p < 0.05) in the concentrations of dissolved organic carbon, total phosphorus, pH, and electrical conductivity between the three site categories. Seasonal sites recorded higher electrical conductivity and total dissolved solids compared to permanent streams. Total suspended solids and particulate organic matter were higher during the dry season. FFGs responded to the disturbance gradient, seasonality, and flow variability in the study area with high numbers of predators and scrapers during dry season, suggesting that the human disturbance influenced the functional composition of macroinvertebrates in the rivers. The findings also show that flow variability (seasonal vs flow permanence) played a important role in structuring communities and determining ecosystem functioning. Therefore, in addition to general human disturbance, there is also a need to study the impact of excessive water withdrawals or changes in natural flow regimes of streams and rivers on aquatic communities and the development of indices to assess their effects. 2025-03-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2397 ECOLOGICAL CARRYING CAPACITY AND GROWTH PERFORMANCE OF NILE TILAPIA (Oreochromis niloticus) IN CAGE AQUACULTURE WITHIN KADIMO BAY, LAKE VICTORIA, KENYA MAWUNDU, SELLU Fish production in the wild is decreasing globally due to a number of factors including overfishing, pollution, invasive species, and climate change effects. In Kenya, fisheries contribute less than 1% to the national GDP with an annual production of about 400, 000 mt against a demand of about 600,000 mt. Aquaculture production through innovative approaches such fish cage farming, has the potential to bridge the demand deficit. Despite the high potential for cage fish farming in Kenyan water bodies, there have been few studies focused on the effects of fish cages on water quality and trophic status, the nutrient carrying capacity of cage sites, and the appropriate stocking densities for cages in the water bodies. This study therefore was aimed to bridge these data gaps in order to facilitate sustainable management of the increasing fish cage farming of the Nile tilapia (Oreochromis niloticus) in Lake Victoria. Sampling for physico-chemical and biological variables, including nutrient load, was conducted from January to October 2021, at five fish cage sites and a control site within the Kadimo Bay,Lake Victoria, Kenya. The Carlson's Trophic State Index (CTSI) was used to classify the trophic state of the cage sites in the bay, and TN: TP ratio used to determine nutrient limitation in the bay. Fish cage optimum stocking density studies were carried in the bay from February to September 2022. Oreochromis niloticus fingerlings with initial mean (±SD) weight of 5.5 ± 1.72 g, were stocked at densities of 50, 75, 100, 125 and 150 fish m3 in replicate cages and growth and water quality changes monitored. The TP assimilation capacity and fish production potentials for the five cage sites within the bay were determined using a mass-balanced model. Results showed higher electrical conductivity (112.84 ± 1.94 μS cm-1 ) at cage sites compared to a Control site (97.53 ± 4.17 μS cm-1 ), similar variations were observed for nitrates and chlorophyll-a. However, 15 physico-chemical variables (DO, Temp., pH, TDS, Turb., TSS,POM, SRP, NO2 - , NO3 - , TN, TP, NH3, NH4 + , SiO4 4- ) did not vary significantly between the cage and control sites. The bay was evaluated as being in a light eutrophic state. Nitrogen as opposed to Phosphorus, was indicated to be the limiting nutrient for primary production in the bay. Growth performance results showed that fish stocked at lower densities (D50 & D75) had the highest growth performance in terms of mean weight gain (545.0 ± 15.81 and 527.4 ± 13.80 g, respectively). The Control treatment (D100), which is the normal stocking density used by cage fish farmers, showed intermediate mean weight gain (348.2 ± 11.48 g) which was significantly lower (p < 0.05) than for the D50 and D75 treatments. The feed conversion ratio (FCR) was lowest at D50 (1.2 ± 0.02) and highest at D150 (2.9 ± 2.01). Carrying capacity results, showed for all the five cage sites within the bay, the TP assimilation capacity was exceeded by the TP released by the fish cages. Additionally, the maximum estimated fish production capacities were much less than the current fish production levels for all the sites. Overall, although the results of this study showed cage aquaculture is not a current challenge to the water quality of the bay, regular monitoring is recommended to inform sustainable aquaculture development in the bay and the lake. It is recommended for fish farmers to stock fish at lower densities of 50 fish m 3 in order to maximize sustainable economic and environmental benefits of the cage culture system. Policies governing aquaculture production in the lake should be reviewed or enacted in order to include evidence-based information on environmental quality, sustainable production levels, and nutrient carrying capacity of the lake. 2024-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2388 Influence of net cages on water quality and trophic status of Lake Victoria, Kenya: The case of Kadimu Bay Mawundu, Sellu; et. al... Water quality is a critical component regulating ecosystem functioning in aquatic habitats, requiring regular monitoring for sustainable ecosystem services. Cage fish farming has the potential to affect water quality because of its rapid increase in many African waterbodies in response to dwindling wild fish stocks. Thus, there is a need for more studies to guide sustainable cage aquaculture in African lakes and reservoirs. This study evaluated the possible effects of cage farming of Nile tilapia (Oreochromis niloticus) on water quality parameters and the trophic state of Kadimu Bay, Lake Victoria, Kenya. Sampling for physicochemical and biological variables, including nutrient load, was conducted from January to October 2021, at five fish cage sites and a control site within the bay. In situ measurements of physical variables were undertaken in the field, while analysis of water samples for nutrient loads, biological and chemical variables was undertaken in the laboratory, following the methods described in APHA (American public health association standard methods for the examination of water and waste water. APHA-AWWA-WEF, 2005). The Carlson's Trophic State Index (CTSI) was used to classify the trophic state of the cage sites, while the total nitrogen:total phosphorus (TN:TP) ratio was used to determine the primary productivity limiting nutrient in the bay. The study results indicated electrical conductivity was significantly lower at the control (97.53 ± 4.17 μS/cm), compared to cage sites (105.42 ± 5.32 μS/cm at the Utonga cage site to 112.84 ± 1.94 μS/cm at the Oele cage site), indicating water of relatively lower quality at the cage sites. Similarly, the nitrite concentrations were higher at cage sites (6.35 ± .96 μg/L at the Uwaria cage site to 3.16 ± 2.25 μg/L at the Utonga cage site), and lower at the control site (2.68 ± 1.39 μg/L). In all, 14 physicochemical variables did not vary significantly between the cage and control sites, with nine variables (temperature, turbidity, electrical conductivity, total suspended solids, particulate organic matter, chlorophyll-a, TP, nitrate and TN) being within the recommended thresholds for aquatic life processes. The bay was evaluated as being in a light eutrophic state, indicating moderate influence of the fish cages on the trophic state of the sites. There was a moderate relationship between chlorophyll-a and TP concentration at the sampling sites (R2= .50), compared to a stronger relationship with NO− 3 (R2= .78). The TN:TP ratios were <10 at the sampling sites, indicating nitrogen was the limiting factor for primary production in the bay. The calculated CTSI suggests that the bay exhibited a light eutrophic state. Overall, although the results of this study showed cage aquaculture is not a current challenge to the water quality of the bay, regular monitoring is nevertheless recommended to inform sustainable aquaculture development in the bay and lake. 2023-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2365 Morphomeristic Characterization of Enteromius Species in Small Water-bodies of the North Rift, Kenya Jepleting, Hildah; et. al... Enteromius, a diverse genus of cyprinid fish native to tropical Africa, comprises around 350 species. These species inhabit various aquatic habitats, notably in Kenya’s North Rift region. Rivers and reservoirs in this area provide essential habitats but face threats from agricultural activities and habitat fragmentation. Morphometric and meristic traits help manage fisheries by offering insights into population dynamics and species identification, although misidentifications pose challenges. Conservation of Enteromius is crucial as these fish support local biodiversity and food security, yet they are increasingly threatened by environmental changes and human activities. The study, conducted in Kenya's North Rift sampled small water bodies, involved sampling 25 rivers and reservoirs impacted by agriculture. Fish were collected from February to July 2018 using electrofishing and seine nets. A total of 972 Enteromius specimens were identified, measured, and analyzed for morphometric and meristic traits. Measurements were taken with Vernier calipers, and 11 meristic counts were recorded. Unidentified samples were preserved for further identification at the National Museums of Kenya. The analysis was performed at UoE Labs following established methodologies. The results indicated that E. paludinosus from Kapsaina Reservoir had the highest standard length (SL) of 8.1±0.8 cm, while E. neumayeri from Ellegrin Reservoir reached 9.4±1.3 cm. Notable differences in operculum length, prepectoral length, prepelvic length, preanal length, and body depth were recorded across different reservoirs and rivers. For instance, Karara Reservoir populations showed the highest operculum length in E. paludinosus (28.2±4.9) and E. neumayeri (25.5±3.2). Meristic traits, such as lateral scales above and dorsal fin rays, also varied significantly, with Kapsaina Reservoir exhibiting the highest range for E. paludinosus. In conclusion, significant trait variations among E. paludinosus, E. apleurogramma, E. neumayeri, and E. cercops across habitats indicate complex genetic and environmental influences emphasizing the need for further research to understand these adaptations and their evolutionary implications 2024-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2326 Emerging frontiers for blue growth in African Great Lakes: The potential for recreational fishing industry in Lake Victoria, Kenya Nyaboke, Hilda; et. al... Sport fishing for Nile Perch and Tilapia are key attractions to recreational anglers on Lake Victoria. Existing hospitality establishments promote sport fishing with angling as the main form of recreational fishing. Development of this industry is expected to generate accrued benefits of eco-tourism and community empowerment by providing alternative sources of income from the already strangled commercial and subsistence fisheries calling for diversification within the fishing industry. Key informant questionnaires were administered to County tourism and fisheries representatives, hotel directors or managers, and officials of Beach Management Units while questionnaire-led-interviews were conducted at the beaches or community recreation sites. Seven tourist resorts, one yacht club, and seven beaches/fish landing sites were assessed. The study aimed to assess the current status of recreational fishing and identify growth opportunities within the industry. Recreational fishing was concentrated around Mfangano Island targeting Nile Perch using artificial baitfish as a tackle. On average, boat hire charges including fishing tackle were USD 30 per trip (< 3 hours) and USD 100 per day per fishing trip. “Blue tourism” rating was low across the respondents with the 2007 political unrest said to have heavily impacted the number of tourists to the region. Water Hyacinth and poor water quality remain a key challenge within Winam gulf while overfishing posed a major concern in the open lake with the number of longline fishers reported to be on the rise. Resource spatial planning should be instituted to cater for the different players in the Blue Economy. The strict enforcement of the Nile Perch slot size is recommended and cooperation among industry players on access and use of the products from recreational fishing. A national census survey on recreational catches should be conducted if its full potential is to be realized in promoting blue growth. 2022-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2206 Profiling and Prioritizing Climate-Smart Aquaculture Technologies, Innovations, and Management Practices in Kenya Obiero, Kevin; et. al... Climate-smart agriculture (CSA) has been promoted in Kenya as a panacea for climate change impacts on agricultural productivity. Consequently, various climate-smart aquaculture technologies, innovations, and management practices (CSA-TIMPs) have been developed, validated, and adopted through the Kenya Climate-Smart Agriculture Project (KCSAP). Nevertheless, there has been no evaluation of the climate-smartness of the CSA-TIMPs for priority setting. In this study, we evaluated and ranked the CSA-TIMPs using a modified Climate-smart Agriculture Prioritization Framework (CSA-PF). The prioritization process included multistakeholder validation workshops involving researchers, fisheries officers, farmers, traders, and policy makers. The climatesmartness scores of the CSA-TIMPs were given based on the CSA pillars (i.e., adaptation, mitigation, and productivity) under various climate-smartness indicators, with a score ranging from −10 (for a negative impact) to +10 (for a positive impact). This resulted in the identification and documentation of forty (40) CSA-TIMPs. Climate-smartness scores varied from 3.8 to 6.1, with higher values indicating strong synergies between the CSA pillars, with productivity having the highest average score of 6.4. The top 5 list of CSA-TIMPs with the best synergies among the CSA pillars was then developed for prioritization. Adoption of these CSA-TIMPs would be instrumental in achieving the CSA triple wins, especially in improving aquaculture productivity. Therefore, sustained efforts in stakeholder engagement, capacity building, and policy support are essential to ensure the successful adoption of CSA-TIMPs in Kenya. A dynamic approach that includes continuous validation, comprehensive monitoring and evaluation, and an enabling environment for adoption will be key to achieving sustainable and scalable impacts. 2024-10-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2201 Community Diversity and Dynamics of Fish Assemblages in Lake Kanyaboli, Western Kenya Kondowe, Benjamin N.; et. al... Although Lake Kanyaboli provides a sanctuary for fish species that are considered extinct (e.g., Oreochromis esculentus, Oreochromis variabilis and Haplochromis spp.) in Lake Victoria, comprehensive data on species diversity and abundance are lacking. This study, conducted over a year (February 2020 to February 2021), addressed this gap by assessing the temporal variation in fish diversity, abundance and catch (biomass) in Lake Kanyaboli. The primary fish data collected in the lake were supplemented with secondary data, and physico-chemical variables were used to correlate with fish assemblages. Fish catches decreased over time from 1981 to 2020, with the highest catch observed in 1981 (250 mt). Fish species composition data showed heterogeneity over the years, ranging from 9 to 15 species. O. esculentus, haplochromines, Oreochromis niloticus, Protopterus aethiopicus and Clariassp. were present in all the reviewed years (from 1981 to 2020), whereas Coptodon zillii was non-existent post-1981 results. The February 2020 to February 2021 survey recorded 14 species dominated by Cichlidae (10 species), whereas Protopteridae and Anabantidae recorded one taxon each. Interestingly, Bagrus sp. was recorded in the current study, suggesting fish movement from the Yala River to the lake. The annual fish catch in the lake comprised tilapias (50%, O. esculentus, O. variabilis, O. niloticus and Oreochromis leucostictus), Clariassp. (23%), P. aethiopicus (20%), haplochromines (7%), Cyprinids (0.03%) and Anabantidae (0.01%). There were no significant monthly differences in fish abundance and fish catches. The decline in fish catch in Lake Kanyaboli over the years is consistent with most tropical lakes and reservoirs in developing countries due to overexploitation. This study highlights the need for biomonitoring in Lake Kanyaboli to protect its fish population, including the endangered O. esculentus and O. variabilis, and ensure the long-term sustainability of the ecosystem. 2024-10-01T00:00:00Z