This study examined the efficacy of community‐level fishery co‐management organizations called Beach Management Units (BMUs) along the Kenyan shores of Lake Victoria. BMUs were established to enhance sustainable Lake Victoria fishery management through increasing the level of community participation to assist in the administration of fisheries rules and regulations by, and for, the fishers. Inefficiencies have emerged, however, inhibiting the effective execution of sustainable fisheries management by the BMUs. Data were collected from 36 BMUs along the Kenyan shores of Lake Victoria. Descriptive and inferential analyses were performed using SPSS Version 20.0. The results indicated that BMUs are successful at educating fishers and that they are aware of fishing rules and regulations. Nevertheless, high violation rates were also observed, suggesting BMUs have limited impact on fisher decisions to comply with regulations. Data suggest that the failure to comply may be due to lack of adequate financial and equipment resources for monitoring, control and surveillance (MCS) operations, making them unable to control illegal fishing in their areas of jurisdiction. Furthermore, financial mechanisms, which would allow BMUs to sustainably fund their administrative and MCS operations, are weak, thereby reducing the BMUs ability to effectively function. The data from this study highlight two activities illustrating significant indices of good performance, namely resolving disputes and receiving visitors. The data also suggest the creation of BMUs has not ensured successful implementation of co‐management of Lake Victoria fisheries. BMUs are successful at activities of a social nature, but have poorly undertaken their core functions related to enforcement and compliance with fishing rules.

The Lake Victoria Basin (LVB) is a global hotspot of aquatic biodiversity, but aquatic ecosystems are under threat from multiple stressors. Most studies on fish have focused on Lake Victoria, while patterns of fish diversity, distribution, and assemblage structure in influent rivers remain poorly understood. To assess threats and conservation status of riverine fishes, we used sampling surveys and searches of published and gray literature to compile data on diversity, distribution, and abundance. In total, 72 fish species were found to inhabit Kenyan rivers and associated wetlands and lakes (excluding Lake Victoria). Low‐order streams (first to third order) in headwaters of rivers are species‐poor and dominated by small‐bodied cyprinids (Enteromius spp.) and clariids (Clarias spp.). A small number of fishes are endemic to rivers, and species turnover across river basins is low. Species dominance is high, with 10 species accounting for >90% of all individuals and weights. Two cyprinid species (Labeobarbus altianalis and Labeo victorianus) account for >65% of all individuals and weights (biomass) per unit effort. Most species occur in small numbers and low biomass is insufficient to sustain a commercial riverine fishery. A review of the literature continues to indicate a reduction in migratory runs of potamodromous fishes from Lake Victoria into influent rivers, although some species, such as L. victorianus and L. altianalis, also maintain stenotopic populations in rivers. Most of the exotic fishes introduced in Lake Victoria, such as Oreochromis nilotics, Oreochromis, Coptodon zillii, Coptodon rendalli, and Gambusia affinis, have invaded and established themselves in rivers, thereby posing a threat to riverine populations. Although this study focuses on Kenyan rivers, the distribution patterns of fishes reflect other rivers of the LVB and have broad implications on threats to riverine biodiversity in other regions undergoing development around the world.

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Comparative growth performance of male monosex and mixed sex Nile tilapia (Oreochromis niloticus) was conducted in six earthen ponds each measuring 150 m 2 at the Kenya Marine & Fisheries Research Institute (KM-FRI), Kegati Aquaculture Research Station. Male monosex and mixed sex of O. niloticus juveniles at an average weight of 12.2 ± 0.02 g and average length of 7.6 ± 0.02 cm were collected from nursery production ponds. The male monosex juveniles were obtained by feeding newly hatched juveniles with feed dosed with 17--methyltestosterone hormone for a period of one month. Stocking was at 3 juvenile m -2 and feeding was carried out using 28% crude protein diet twice daily for six months at 4% body weight. Selected water quality parameters (dissolved oxygen, temperature, pH, electrical conductivity and total ammonia nitrogen) were measured weekly in situ, while sampling for weight and length measurements was conducted on a monthly basis for a period of six months. Specific Growth Rate (SGR), Feed Conversion Ratio (FCR), Condition Factor (CF) and survival rate (%) were measured at the end of six months. Data were subjected to one-way analysis of variance (ANOVA). At the end of six months, the average weight of male monosex and mixed sex fishes was 200.8 ± 0.81 g (mean ± SE) and 123.4 ± 0.76 g, respectively, while the average length of male monosex and mixed sex was 22.4 ± 0.21 cm and 18.6 ± 0.23 cm, respectively. The male monosex O. niloticus achieved significantly increased final weight and length, SGR, FCR and CF than the mixed sex O. niloticus (p < 0.05). However, both male monosex and mixed sex fish recorded similar survival rates (p > 0.05). There were no significant differences in mean water quality parameters in male monosex and mixed sex ponds (p > 0.05). The male monosex fish performed better because most energy was spent on muscle and tissue development while the mixed sex fish spent most energy on reproduction activities at the expense of muscle and tissue development. Further studies should be done in other culture systems such as liner ponds, tanks, cages and raceways. How to Cite

Streams and rivers are globally threatened ecosystems because of increasing levels of exploitation, habitat degradation and other anthropogenic pressures. In the Lake Victoria Basin (LVB) in East Africa, these threats are mostly caused by unsustainable land use; however, the monitoring of ecological integrity of river systems has been hampered by a lack of locally developed indices. This study assessed the health of four rivers (Nzoia, Nyando, Sondu–Miriu and Mara) on the Kenyan side of the LVB using physicochemical water quality parameters and a fish-based index of biotic integrity (IBI). Fish tolerance ranking was derived from principal component analysis of water quality parameters, and the concept of niche breadth (NB). The relationship between fish species and water quality parameters was examined with canonical correspondence analysis, whereas community metrics and stressors were evaluated through Pearson network correlation analysis. Fish species richness, trophic structures, taxonomic composition and species tolerance were used to generate the metrics for fish-based IBI. NB showed that most of the fish species were moderately tolerant to poor water. Moderately tolerant and intolerant fish species were negatively correlated with a high level of organic loading in the Mara River. Fish-based IBI scores for the rivers ranged from 26 to 34, with Sondu–Miriu scoring the lowest. Our results show that the cumulative effect of stressors can adequately rank fish species tolerance according to the disturbance gradients and further develop regional metrics to assess river health. Despite the fact that fish communities are declining, continual management and enforcement of environmental regulations are important, with conservation and management of headwaters and low-order streams being essential while they are still species rich.

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