Within the past 10 years, cage culture of Nile tilapia in Lake Victoria has transformed from a nascent, small-scale enterprise into an immense, commercial industry. Yet adequate information on production practices and the impact of fish kills is significantly lacking. To identify existing management practices, production constraints, and gaps in knowledge in Lake Victoria, Kenya, we conducted a cross-sectional survey using in-person questionnaires with 172 cage farm operations. Farms were selected using stratified proportional random sampling with additional snowball sampling. Descriptive statistical analysis indicated the major production constraints included: strikingly absent biosecurity practices, volatile input costs/availability, common incidence of large-scale fish kills, and harmful algal blooms. Fifty nine percent of farmers reported disposing dead fish into the lake, feeding to other animals, or consuming them. Only 23% of farmers reported disease to aquaculture institutions, only 2% disinfected tools used across cages, and none reported access to appropriate antimicrobial therapeutics. Forty percent of farmers experienced a large-scale fish kill within the last year. Algal blooms, present on 81% of surveyed farms, were reported to reduce fish growth/survival, clog cage nets, and trigger fish kills. Farmers are rapidly adopting commercial feeds, yet feed prices and availability remain volatile. The vast majority of farmers (90%) do not produce their own fingerlings, underscoring a critical dependency on private and government-run hatcheries that have not been well-characterized. In identifying gaps in management practices and production constraints, this study provides more specific targets for subsequent extension to improve biosecurity, fish health management, profitability, and environmental sustainability.
In recent decades, seaweed farmers in East Africa have faced declines in production and income, largely attributed to varying environmental conditions. Subtidal farming, promoted for its relatively more stable environmental conditions, has been proposed as a potential mitigation strategy, although empirical evidence remains limited. This pilot study assessed the technical feasibility and economic viability of cultivating three red seaweed species (Kappaphycus alvarezii, Eucheuma denticulatum, and Gracilaria salicornia) at three depths (0.5 m, 2 m, 4 m) in coastal Kenya, using different cultivation techniques: off-bottom, long-line, and bamboo raft. Seaweed was grown at three sites at the south coast of Kenya (Kibuyuni, Kijiweni, and Mwazaro) in one single cultivation cycle during the SEM season over a 45-day period, after which survival, growth and biomass were evaluated. Regardless of treatment and location, K. alvarezii exhibited the highest RGR (i.e. 2.5 +/- 1.5% day-1) and biomass production among the three species examined, followed by E. denticulatum and G. salicornia (i.e. 1.3 +/- 0.5% day-1 and 0.75 +/- 1.3% day-1, respectively). Survival decreased significantly at 4 m compared to 0.5 m for all three species. Site-specific variations were evident, with seaweed growth in Kibuyuni consistently exhibiting lower growth rates and biomass than Kijiweni and Mwazaro, indicating underlying environmental differences, despite the absence of strong differences in measured environmental parameters. Off-bottom farming at 0.5 m depth yielded the highest eucheumatoid biomass per rope (0.75 kg DW). Subsequent economic assessments revealed that, under current market conditions (USD 0.50 kg-1 DW), profitability is attained solely by off-bottom farming in its present form, with break-even occurring after 29 cultivation cycles (approximately 3.7 years). In contrast, deeper water cultivation systems require substantial optimization before they can be recommended as viable options. Together, these results provide a practical evidence base for future scientists, aquaculture practitioners and policymakers seeking to design sustainable seaweed farming strategies in East Africa.
Emerging outbreaks of the arbovirus chikungunya virus affect millions of individuals globally, causing debilitating arthralgia and fever. A study on the burden and etiologies of acute febrile illnesses (AFI) in Kenya reported an increase in CHIKV cases in Mombasa between December 2017 and December 2019. In January and February 2020, another outbreak of CHIKV occurred in Dadaab-Hagadera. Using next-generation sequencing on the Illumina MiSeq platform, we established molecular characteristics and phylogenetic differences of the CHIKVs collected from the two epidemiologically distinct settings. Sequenced viruses belonged to the Indian Ocean Lineage and clustered according to geographic region, with E1:K211E and E2:V264A mutations present in both settings. Additional mutations previously reported during Kenyan CHIKV outbreaks and suggested to influence CHIKV adaptation to Aedes albopictus, including E1:T82I and E1:V84D, were also identified. These molecular markers provide useful information on CHIKV spread and can help strengthen outbreak preparedness and response. Clinical features were described only for laboratory-confirmed CHIKV cases from the AFI surveillance cohort and compared with AFI cases testing negative for CHIKV. Sore muscles, headache, and convulsions were more frequently reported among CHIKV-positive participants, whereas diarrhea was less common. No differences were observed in the frequency of cough, skin rash, conjunctivitis, or vomiting. Given the limited number of confirmed CHIKV cases and the predominance of young children in the cohort, the reported clinical symptom associations should only be interpreted as exploratory and warrant confirmation in larger and more representative populations.
Macroplastics and litter pollution in freshwater ecosystems remain poorly quantified in tropical Africa despite growing concern over their socio-ecological and economic impact. This study quantified the composition, abundance, and spatial distribution of macroplastics and anthropogenic litter along the shoreline of Kisumu Bay, Lake Victoria, Kenya. All visible items > 5 mm were hand-collected from 1000 m2 shoreline plots subdivided into 100 m & times; 10 m transects across three land-use categories (industrial area, informal settlements, and beaches/ landing sites), sorted by material, counted, weighed, and geo-referenced. Densities, spatial heterogeneity, source proximity relationships, and cross-category comparisons were analyzed. Industrial-category sites accounted for 81.0% of the total macroplastic item count (n = 17,794 items), while informal settlements represented 13.2% and beaches 5.8%. Across all zones, plastics-particularly beverage bottles, packaging materials, and miscellaneous consumer items-dominated both numerical abundance and mass-based measurements. Weight-based analysis revealed that industrial areas contributed the highest mass across nearly all waste categories (e.g., 93% of glass items, 98% of food containers), while beaches accumulated mainly lightweight plastic bottles. Proximity analysis showed that major industrial facilities lie within < 1 km of drainage channels and shoreline nodes. Item counts revealed significant spatial heterogeneity, whereas mass-based comparisons were nonsignificant and highly variable, underscoring the limitations of weight alone as a monitoring metric. The observed gradient from industrial zones to shoreline accumulation areas illustrates an active land-to-lake leakage dynamic driven by proximity, waste-management gaps, and hydrological transport. The findings identify the urban-industrial corridor as the primary intervention hotspot and support catchment-scale, source-reduction, and waste-management strategies to safeguard ecosystem health and blue-economy benefits.
Understanding juvenile fish distribution across habitat mosaics is essential for interpreting ecosystem connectivity and function. This study assessed seasonal variations in juvenile reef fish assemblages across a mangrove-seagrass-coral reef continuum in Shimoni, southern Kenya. Using a beach seine net, sampling during the Northeast Monsoon (NEM) and Southeast Monsoon (SEM) seasons, a total of 8,575 individuals representing 228 species and 52 families were recorded. Species richness and diversity (H') were highest in the coral associated site (n = 168; H' = 3.77), followed by the seagrass associated site (n = 132; H' = 3.69) and the mangrove associated site (n = 119; H' = 3.64). Two-way ANOVA and Kruskal-Wallis tests revealed significant differences in diversity and mean species richness, respectively across habitats, with post-hoc pairwise tests identifying the most pronounced differences between coral and mangrove sites. While 69 species were common to all three habitats, multivariate analysis demonstrated distinct species-habitat associations, particularly in the mangrove associated habitat, influenced by salinity and temperature. The Kolmogorov-Smirnoff test further confirmed differences in the trophic signatures of the assemblages between mangrove-coral and seagrass-coral interfaces. These findings underscore the importance of the coastal habitat mosaic in sustaining fish recruitment and population dynamics, highlighting the need for integrated seascape management in the Western Indian Ocean.
