Journal Articles

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

Wed, 01 Jan 2025 00:00:00 GMT

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.

Macroinvertebrate functional responses to human disturbance and flow cessation in Afromontane-savannah rivers

Sat, 01 Mar 2025 00:00:00 GMT

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.

Influence of net cages on water quality and trophic status of Lake Victoria, Kenya: The case of Kadimu Bay

Sun, 01 Jan 2023 00:00:00 GMT

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.

Morphomeristic Characterization of Enteromius Species in Small Water-bodies of the North Rift, Kenya

Mon, 01 Jan 2024 00:00:00 GMT

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

Emerging frontiers for blue growth in African Great Lakes: The potential for recreational fishing industry in Lake Victoria, Kenya

Sat, 01 Jan 2022 00:00:00 GMT

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.

Profiling and Prioritizing Climate-Smart Aquaculture Technologies, Innovations, and Management Practices in Kenya

Tue, 01 Oct 2024 00:00:00 GMT

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.

Community Diversity and Dynamics of Fish Assemblages in Lake Kanyaboli, Western Kenya

Tue, 01 Oct 2024 00:00:00 GMT

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.

Role of multilateral development organizations, public and private investments in aquaculture subsector in Kenya

Tue, 01 Aug 2023 00:00:00 GMT

Role of multilateral development organizations, public and private investments in aquaculture subsector in Kenya Munguti, Jonathan M.; et al. Rapid population and economic growth, increased health benefits of aquatic food, and changes in lifestyles and preferences as a result of rapid urbanization and globalization are all contributing to the rapid growth of aquaculture production in Kenya. Despite significant investment efforts from the national and devolved governments as well as donors and international organizations, smallholder aquaculture production is yet to result in a significant increase in incomes and improved food and nutrition security. We conducted a scoping review to investigate the roles of multilateral development organizations, international financial institutions, and public and private investments in Kenya’s aquaculture subsector. We draw on lessons learned from previous projects implemented at the national, county, and farm levels to make recommendations for sustainable aquaculture intensification in Kenya. To unlock Kenya’s aquaculture potential and improve its food and nutrition status, deliberate efforts must be made to create a conducive environment for public and private investment in the industry. First, there is a need to coordinate and clearly articulate the roles and responsibilities among devolved and national governments, donors, and financial institutions through public-private partnerships to ensure optimal allocation of financial, human, and infrastructure resources. Second, more collaborative research should be devoted to the design and construction of climate smart culture systems, developing new species to guarantee supply of high-quality products; developing and scaling low-cost and highly nutritious fish feeds based on novel ingredients; and enhancing resilient livelihoods through innovative aquaculture practices and market linkages to create employment opportunities for youth and women. Finally, the national and devolved governments should create an enabling policy environment through tax incentives and regulatory reforms to combat climate change, protect nature and biodiversity, sustain livelihoods, and mainstream food and nutrition initiatives into the design and implementation of future aquaculture projects.

Effect of Different Fish Feed Sources on Growth and Economic Performance of Nile Tilapia (Oreochromis niloticus) Within Subsistence Setup in Liberia

Mon, 01 May 2023 00:00:00 GMT

Effect of Different Fish Feed Sources on Growth and Economic Performance of Nile Tilapia (Oreochromis niloticus) Within Subsistence Setup in Liberia Hinneh, Mandela Klon-Yan; et al. The wide adoption of O. niloticus for farming, particularly among smallholder farmers, can be attributed to its feeding versatility. However, its production in Liberia remains low, despite possessing desirable culture characteristics. This limited yield hampers the potential for commercialization and delays the overarching goal of utilizing fish farming to alleviate poverty and hunger. One of the primary challenges faced by fish farmers is the utilization of subpar feeds. To address this issue, we conducted a study to evaluate the effects of various feed recipes available to Liberian farmers, including two feeds formulated by farmers themselves (FF1 and FF2) and two commercially manufactured feeds (CF1 and CF2). These feeds were compared with a research-formulated feed designated as PF. The growth and economic performance of O. niloticus were assessed over a six-month period using fifteen Hapa nets. The findings of our study revealed that the feeds formulated by farmers and commercial feed CF2 exhibited inferior performance in terms of Specific Growth Rate (SGR), Feed Conversion Ratio (FCR), and Weight Gain (WG). In contrast, PF and CF1 demonstrated significantly higher values (P<0.05) with FCR scores of 7.87 and 8.27, and SGR values of 1.08 and 1.05, respectively. The present study also introduced a production cost index (PCI) that can be used as an indicator of fish feed performance in fish farming, while holding the other costs constant. PF and CF1 feeds displayed the lowest PCI of 0.92 and 1.57, surpassing the other tested feeds. The lower PCI values were associated with higher economic returns compared to alternative feeds. This study concludes that feed quality is a major factor sustaining poor O. niloticus production, however with right formulation of the locally available materials farmers can achieve optimal yields for commercial aquaculture.

Characterization of Nile tilapia (Oreochromis niloticus) Farm-2 ing Intensities in Liberia

Fri, 01 Jul 2022 00:00:00 GMT

Characterization of Nile tilapia (Oreochromis niloticus) Farm-2 ing Intensities in Liberia Hinneh, Mandela Klon-Yan; Liti, Mbeva D.; Matolla, Geraldine Fish farming is a rapidly growing food sector in developing nations. Liberia is an example 10 of least developed country with a large population facing high poverty levels. This has led to adop-11 tion of aquaculture as one of the most important strategies for solving malnutrition and food secu-12 rity problems. However, since the introduction of fish farming, fish yields have been persistently 13 low. To address the shortcomings in fish yields in Liberia, a study was conducted to provide infor-14 mation on fish farming intensities, types, and quality of feeds used by farmers in the culture of O. 15 niloticus in Bong, Lofa, Nimba, and Grande Gedeh counties. Using stratified purposive sampling, 16 120 farmers were interviewed, and their fish feeds were sampled for proximate nutrient analyses. 17 The results demonstrated that fish farming of O. niloticus in Liberia is mostly semi-extensive (81.6%), 18 mainly practiced in paddy, barrage, and earthen ponds. On average, farmers produce 165.7 kgha-19 1of O.niloticus annually, translating to USD 414.25. Farmers use mixed feeding regimes, comprising 20 farmer-made, kitchen waste, and blended commercial feeds. Farmers, on average, spend 43% of 21 their operation cost on feeds, which makes it unsustainable to maintain semi-intensive systems. The 22 main feed ingredients used by Liberian fish farmers are rice bran, wheat bran, corn, palm kernel, 23 and fishmeal. Crude protein levels in feed ingredients are as follows: rice bran (3.7±1.3%), wheat 24 bran (16.4±1.5%), corn (6.3±1.1%), palm kernel cake (14.8±1.4%) and fish meal (63.8±1.3%). Crude 25 proteins were low in formulated feeds, ranging from 8%-15% CP. From this study, poor yields and 26 the slow growth of the O.niloticus can be attributed to low protein diets, rendering farming ventures 27 unprofitable and unsustainable for poor resource farmers in Liberia.