http://41.89.164.27:8080/xmlui/handle/123456789/1889 2026-06-09T05:52:24Z http://41.89.164.27:8080/xmlui/handle/123456789/2753 MACROINVERTEBRATE ASSEMBLAGES AND BODY SIZE DISTRIBUTION IN RESPONSE TO LAND-USE CHANGES IN HEADWATER STREAMS OF THE SONDU-MIRIU RIVER BASIN, KENYA KULUO, GIDEON Assemblages of aquatic macroinvertebrates have spatial and temporal variations in structure in response to environmental changes of their habitats, such as streams and rivers. Taxonomic approaches for monitoring the ecological status of aquatic ecosystems using macroinvertebrate assemblages face several limitations, creating a need for ataxonomic methods that are valid, disturbance-sensitive, and cost-effective for freshwater monitoring. This study evaluated the influence of seasonality and land-use changes on macroinvertebrate assemblage structure and water physico-chemical parameters of headwater streams of the Sondu-Miriu River basin, Kenya. Additionally, the study evaluated the utility of macroinvertebrate size-spectrum metrics and abundance-biomass comparison (ABC) curves as ataxonomic methods of evaluating land-use influence on the river’s ecological condition. Macroinvertebrate taxonomic abundance (individuals/m2), wet weight (mg), and physico-chemical variables were measured during the wet and dry seasons in March and September 2024, respectively, from 24 headwater streams distributed across four land-use types: natural forest (NF), tea and tree plantations (TTP), smallholder tea (SHT), and smallholder agriculture (SHA). Results based on water quality showed turbidity, total suspended solids (TSS), total dissolved solids (TDS), electrical conductivity (EC), particulate organic matter (POM), and nitrate (NO3 - -N) identified streams in NF as least disturbed and in SHA as most disturbed; TTP and SHT streams were intermediate in water quality. Taxon richness, diversity, and Ephemeroptera, Plecoptera, and Trichoptera (EPT) indices indicated land-use specific influences on assemblage structure. Redundancy analysis (RDA) showed thatsmall-bodied taxa (<8 mg wet weight) were associated with high disturbance indicators, while large-bodied taxa (>32 mg) were associated with low disturbance indicators and sites. Slopes (λ) of normalized abundance- and biomass-based size-spectrum (a measure of trophic transfer efficiency) deviated from theoretical steady-state conditions (λ=-2.0 and -1.0, respectively), indicating that the sites were disturbed, but the slopes did not vary significantly between land uses or seasons, suggesting size-spectrum slopes had low sensitivity to land-use-based changes in water quality. In contrast, size-spectrum midpoint heights (a measure of ecosystem production) differed significantly between sites, highest at SHT and NF and lowest at SHA and TTP streams. Spectrum midpoint heights were, therefore, more responsive to disturbance than slopes, highlighting their potential as indicators of land-use influence on the Afrotropical streams. Although the ABC curves indicated undisturbed conditions for all sites, Warwick’s (W) statistics revealed subtle differences among streams, suggesting variation in local-scale ecological conditions. This study demonstrated that catchment land use significantly influences water quality and macroinvertebrate assemblages in headwater streams of the Sondu-Miriu River basin. Traditional metrics (%EPT and diversity indices) are useful indicators of land use-based disturbance, while size-spectrum midpoint heights are potentially useful ataxonomic indicators of disturbance in the studied streams. It is recommended to integrate both community indices and functional metrics (especially midpoint height) into stream biomonitoring as complementary method for evaluating the ecological status of headwater streams. Management efforts should prioritize riparian buffers and nutrient/sediment control in SHA areas of the basin, while conserving less-impacted NF sites as reference areas. Long-term and broader spatial-scale studies are needed to validate the stability of size-spectrum metrics and ABC curves as rapid tools for monitoring the ecological status of headwater streams in response to anthropogenic influences. 2025-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2750 THE EFFECT OF EBB-AND-FLOW TECHNOLOGY, SUBSTRATE TYPES AND SALT-TOLERANT CROP (Apium graveolens L.) ON NUTRIENT REMOVAL FROM A BREWERY EFFLUENT OBADO, ELIZABETH Brewing industries face economic and environmental challenges of water use, energy consumption, and effluent disposal. The limited water availability and strict effluent discharge regulations in the South African Brewery justify wastewater treatment and recycling. Constructed wetland (CW) design and operation have been optimised for sustainable wastewater treatment. An ebb-and-flow technology is a CW design that creates aerobic and anaerobic conditions essential for wastewater treatment. South African Ibhayi Brewery effluent is treated onsite using a commercial-scale anaerobic digester (AD) and activated sludge units. However, the anaerobically digested effluent has high treatment costs and does not meet the environmental discharge standards. Therefore, the post-AD effluent is further treated using a low-cost CW technology. This study investigated the effect of ebb-and-flow CW operation, substrate types and celery plant growth on nutrient removal from a post-AD brewery effluent. Two experiments were conducted; Experiment 1 examined the effect of retention times (10, 20 and 40 minutes) and gravel sizes (7, 13, and 19 mm) on nutrient removal. The retention times (RT) and gravel sizes were allocated as treatment combinations and replicated thrice in a completely randomised design. In the second experiment, an ebb-and-flow CW was used to investigate the effect of media types planted with a celery crop on nutrient removal. 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 m 2 and a 12-minute effluent retention time were used. Results for experiment 1 indicated significant differences at p≤ 0.05 between RT and gravel size treatment combinations on nutrient removal. The 10-minute RT at 19-mm gravel achieved the highest reduction in chemical oxygen demand (COD) of 8.2 %, 7.7 % ammonia-N and 38 % total inorganic nitrogen removal. The 40-minute RT at 7-mm gravel had the highest nitrate-N removal of 18.6 %. Orthophosphate removal was below 5 % in all treatments. The peak removal for ammonia and total inorganic nitrogen was after 8 and 10 weeks, respectively, suggesting that the efficiency of the ebb-and-flow design on nutrient removal is time-dependent. The aerobic and anaerobic conditions of ebb-and-flow operation, gravel surface area and effluent retention time influence nutrient transformation and removal. Results for Experiment 2 indicated significant differences between unmixed and mixed media on nutrient removal (p ≤0.05). The unmixed media of clay pebbles had the highest mean reduction chemical oxygen demand of 7.5% and 8.1% ammonia-N removal. 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, chemical composition and celery plant growth enhanced nutrient removal through synergistic interactions. Experiment 1 recommends a short effluent retention time of 10 minutes on 19-mm gravel for improved nutrient removal in the ebb-and-flow system design. Experiment 2 recommends unmixed clay pebbles, bioballs, and 19-mm gravel forimproved ammonia-N removal and mixed media for multiple pollutant removal and celery productivity in the ebb-and-flow constructed wetland. 2025-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2741 MACROINVERTEBRATE FUNCTIONAL AND STRUCTURAL RESPONSES TO HUMAN DISTURBANCE AND FLOW CESSATION IN AFROMONTANE-SAVANNAH RIVERS OWADE, CHRISTINE Freshwater ecosystems in the Afrotropics are increasingly threatened by human activities and disturbances, including agriculture, livestock grazing, water abstraction, and sand harvesting. These activities degrade habitat quality, alter flow regimes, and influence the composition and functioning of aquatic communities. This study assessed the structural and functional responses of macroinvertebrate communities to varying levels of human disturbance, flow permanence, and seasonality in the Wundanyi-Bura catchment, a representative Afromontane-savannah River system in southeastern Kenya. Macroinvertebrates were sampled from 18 study sites categorized by varying disturbance levels (low, moderate, high), flow duration type (permanent vs seasonal), and season (dry vs wet). Physical and chemical water quality parameters, habitat characteristics, and land-use patterns were also quantified. Functional composition was evaluated using Functional Feeding Groups (FFGs) and 14 biological traits comprising 52 ecological trait attributes. Results showed significant degradation in water and habitat quality with increased disturbance, particularly in the lower river reaches. Functional trait analyses revealed that disturbed and seasonal sites were dominated by resilient taxa such as burrowers, predators, and collector-gatherers, while less disturbed, permanent sites had higher proportions of sensitive taxa like shredders and scrapers. Flow variability and seasonality strongly influenced trait distributions and ecosystem attributes, including trophic dynamics, organic matter processing, and top-down control. Multivariate analyses (ANOSIM, NMDS, SIMPER) and trait-based approaches provided robust indicators of ecological integrity and disturbance gradients. This study underscores the value of integrating functional traits and FFG ratios in biomonitoring and river health assessment. It provides crucial baseline data for the Afrotropics, where biomonitoring frameworks are still underdeveloped, and highlights the need to consider both structural and functional metrics in the conservation, restoration, and management of freshwater ecosystems under increasing anthropogenic pressures. 2025-01-01T00:00:00Z 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/123456789/2138 EVALUATION OF FARM-MADE AND COMMERCIAL FEEDS ON GROWTH AND ECONOMIC PERFORMANCE OF NILE TILAPIA (Oreochromis niloticus LINNAEUS, 1758) IN LIBERIA HINNEH, MANDELA KLON-YAN A study on the effect of farm-made and commercial feeds on nutritional quality, growth, water quality and economic performance on Nile tilapia in landlocked Counties of in Liberia was done. Interviews and focus group discussions (FGDs) were used to collect information on farm made feeds. Moisture, crude protein, crude lipids and ash content of all feed ingredients were determined using AOAC procedures. Test diets consisted of two farmer diets, two commercial diets and one research diet. To determine the effect of these diets on fish growth, 450 male O. niloticus fingerlings of average weight of 13g were stocked in hapas mounted in 3 earthen ponds, each with 5 hapas at the Central Agriculture Research Institute in Liberia. The effect of diets on temperature, pH, and Dissolved Oxygen (DO) was determined using oxyguard and pH meters. Rate of returns on investment were used to evaluate the cost-effectiveness of all the diets. Of 120 farmers interviewed, 81.6% practice semi-extensive aquaculture in paddies, barrages, and earthen ponds. Farmers’ annual yield was 165.7 kg ha-1, translating to USD 414.25. The research diet had the greatest amount of crude protein (30.7%) while farmers’ diet had the lowest crude protein (9%). The research diet had the highest growth performance in terms of weight, attaining 175.33g. There was a significant difference in growth of fish between research and farmer (F1) diets (P = 2 × 10-5).There was no significant difference on the effects of each feed on the quality of the pond water Economic analysis indicated that the commercial diet (C1) was most profitable (USD 259.5). For better fish performance and profitability, there is need for researchers and feed producers to develop quality and affordable feeds for Liberia’s aquaculture sector while building capacity for farmers to formulate quality diets. Continuous monitoring of water quality is recommended for the sector. 2014-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2094 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. 2023-03-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2079 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 m3 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/123456789/2049 INFLUENCE OF HIPPO AND CATTLE DUNG ON THE NUTRIENT LEVELS, ALGAL DIVERSITY, COMPOSITION, BIOMASS AND ECOSYSTEM METABOLISM IN AQUATIC ECOSYSTEMS: A MESOCOSM APPROACH KIPLAGAT, MARY JEMAIYO Large mammalian herbivores (LMH) are major agents of the movement of terrestrial organic matter and nutrients into aquatic ecosystems, which can alter the structure and functioning of aquatic ecosystems. Populations of native large mammalian herbivores have been lost or displaced by livestock in many regions of the world, and this may result in changes in the functioning of the aquatic ecosystem due to significant differences in the quality of their dung. A replicated mesocosm experiment was conducted for six weeks (42 days) at the bank of Amalo river to study the influence of large mammalian herbivores (hippo and cattle) dung input on nutrient concentration, algal biomass, composition and diversity, and flume-scale ecosystem metabolism. The treatments included: H100 (no cattle dung, 100% hippo dung), H80 (20% cattle dung, 80% hippo dung), H60 (40% cattle dung, 60% hippo dung), H40 (60% cattle dung, 40% hippo dung), H20 (80% cattle dung, 20% hippo dung), and H0 (100% cattle dung, no hippo dung). These treatments were conducted in triplicate. Nutrients were analyzed by standard colourimetric methods, chlorophyll-a was extracted using methanol and measured spectrophotometrically, total suspended solids (TSS) and ash-free dry mass (AFDM) were determined gravimetrically and algae were counted under a microscope using the counter rafter cell and flume-scale ecosystem metabolism was measured in-situ using miniDOT loggers; where dissolved oxygen and the water temperature was recorded every one minute for the six weeks. Study results showed that cattle and hippo dung inputs have contrasting effects on aquatic ecosystem function; treatment with 100% cattle dung (H0) released higher amounts of limiting nutrients, exhibited higher algal biomass, higher algal abundance and diversity and supported higher rates of gross primary production (GPP) relative to 100% hippo dung (H100). Hippo dung, which has slower mineralization rates and larger particle sizes, increased water clarity relative to cattle dung. Differences in stoichiometry (C: N:P ratio) of major elements and faecal particle sizes between cattle and hippo dung were the likely drivers of decomposition and releasing rates of nutrients, which in turn influenced ecosystem processes differently. The study suggests that large mammalian herbivores (LMH) play a significant role in the movement of organic matter and nutrients from terrestrial to aquatic ecosystems. The loss or displacement of native LMH populations by livestock in various regions of the world can lead to changes in the functioning of aquatic ecosystems due to differences in the quality of their dung. 2023-07-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/1772 DYNAMICS IN TROPHIC STATUS, WATER AND NUTRIENT MASS BALANCE AND COMMUNITIES OF LAKE KANYABOLI, KENYA KONDOWE, BENJAMIN NELSON Fishing pressure and nutrient enrichment from the catchment area threaten Lake Kanyaboli's water quality and communities. Understanding these impacts and their effect on the lake's water quality and communities is crucial for lake management and conservation. This study assessed the spatio-temporal variations in the physical, chemical, and biological variables, nutrient budget, plankton and fish communities of Lake Kanyaboli in western Kenya from February 2020 to February 2021. Primary and secondary data on water quality variables, including Secchi depth (SD), electrical conductivity (EC), temperature, pH, dissolved oxygen (DO) concentration, nitrates (NO3-), nitrite (NO2-), ammonium (NH4+), soluble reactive phosphorus (SRP), total phosphorus (TP) and total nitrogen (TN), and chlorophyll-a (Chl-a) were collected. Plankton and fish community data were also collected. Water quality variables and plankton communities were compared using two-way ANOVA, PCA, Pearson correlation, and descriptive statistics. The lake’s trophic status was calculated using SD, TP and Chl-a Carlson trophic status index (TSI) equations. Furthermore, PERMANOVA, Two-way nested ANOSIM, species diversity indices, CCA, NMDS, Kruskal Wallis test and SIMPER were also used to compare plankton and fish community data. Mass balance models were used to calculate water, nitrogen, and phosphorus mass balances. Two-way ANOVA on water quality variables showed no site × season interactions, while only Chl-a showed spatial variability. Significant seasonal differences were observed in SD, DO and Chl-a. Based on the Chl-a and SD TSI values, Lake Kanyaboli is eutrophic, whereas the TP value indicates hypereutrophic conditions. The nutrient mass balance showed that the lake receives more nutrient loads of N (90.78 t N year-1) and P (24.06 t N year-1) than it loses for both N (73.42 t N year-1) and P (15.76 t P year-1). Phytoplankton consisted of 30 genera dominated by Chlorophyceae (42.30%), with Bacillariophyceae, Cyanophyceae, Cryptophyceae, Euglenoidae, Trebouxiophyceae, and Zygnematophyceae also present. Fifteen zooplankton genera were also identified, including Cladocera (16.73%), Rotifera (27.86%) and Copepoda (55.41%). Although plankton abundance differed significantly between seasons, Two-way ANOVA showed no significant site × season interaction. The 2020 fish catch survey showed that Tilapia (50%), Clarias sp. (23%), Protopterus aethiopicus (20%), and haplochromines (7%) were the main fish species in the catch. But Kruskal Wallis showed no monthly variations in fish catches. The inter-annual fish catch and catch per unit effort (2003 to 2020) showed a decreasing trend. Despite infrequent historical data, physical, chemical, and biological variables captured anthropogenic effects over time, and the lake was eutrophic due to nutrient load. The phytoplankton community also showed that the lake was in a non-equilibrium state due to short water residence time and the uptake of nutrients by macrophytes bordering the lake. The major management issues identified are nutrient loading, fishing effort, and lake connectivity with the Yala River. Managing the catchment area holistically and monitoring the lake's water quality and fishing effort will help sustain goods and services, and livelihoods of Lake Kanyaboli riparian communities 2022-10-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/1759 NUTRITIONAL CONTENT OF FORMULATED FEEDS AND IN-SITU BASED FEEDS OF AQUACULTURE FISH IN THE WINAM GULF OF LAKE VICTORIA, KENYA OTIENO, MELVINE ANYANGO The uses of feeds are critical to success of aquaculture farming on Lake Victoria Basin. The composition of the feeds can either be derived from in situ plants or animals i.e. the lake shrimp or omena within the ecosystem of Lake Victoria or externally sourced from outside the Lake i.e. imported formulated fish feeds. The net effect from the input of those feeds from outside could increase eutrophication within the lake while feeds derived from fauna and flora from the lake may not impact as negatively. The nutritional values of the feeds and the potentials of the feeds derived from outside the Lake and those utilizing local flora and fauna within the ecosystem of the lake are compared. The consequences of nutritional level from the different sources on the quality of fish product were estimated. Samples from both the formulated and in-situ based fish feeds were collected from aquaculture farms or from local sources around the Lake area. The samples were then freeze-dried and ground to fine local powder and dissolved using acid digest process. The resulting sample-acid solution was then analyzed using an Agilent 7500cx inductively -coupled plasma mass spectrometer (ICP-MS). With the exception of Arsenic (As), Barium (Ba) and Tin (Sn) wild fish muscle had significantly high PTEs in Silver (Ag), Chromium (Cr), Lithium (Li), Aluminium (Al), Cadmium (Cd), Mercury (Hg) and Lead (Pb) and also high in trace element concentrations in boron (B) and selenium (Se) compared to the caged fish muscle. Cadmium (Cd) and lead (Pb) contents in caged and wild fish samples were all below the FAO/WHO recommended limits. This study also showed that the differences were not quite discernable and that the data indicated are important preliminary findings that indicate that the differences in concentrations of micronutrients were wider than the differences in the concentrations of the macronutrients of the omena and lake shrimps of both closed and open lakes. The potentials of sustainable production of aquaculture especially caged culture from Lake Victoria is presented taking into account the optimal ratios measured in both formulated and in-situ based feed and their possible impact both economically and environmentally. Our study therefore; presents an environmentally sustainable means of solving food insecurity among the rapidly growing human population that suffers malnutrition, hunger, joblessness and disease 2022-01-01T00:00:00Z