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Declining commercial fish catches in Lake Victoria's Winam Gulf: The importance of restructuring Kenya's aquaculture programme
Abstract
The total weight of commercial fish (metric tons) caught in the Winam Gulf area of Lake Victoria in Kenya declined from 3300 mt to 760 mt between 1995 and 2009. Associated with this decline, and ranked in descending order, the species richness of the commercial fish catch was limited to seven major groups (Rastrineobola argentea; Lates niloticus; Protopterus aethiopicus; Labeo victorianus; Haplochromis species; Clarias gariaepinus; Bagrus domac). Numerous hypotheses ranging from eutrophication, inadequate control of the exotic water hyacinth and overfishing were advanced to explain this decline. The Kenyan government, working in partnership with international organizations, implemented multiple restoration and management programmes in response, including aquaculture. Unfortunately, success for this implemented programme has been very limited because important socio-economic driving factors were overlooked. To provide a better understanding of the issues, 150 members of the Winam Gulf fishing community, ranging in age from 20 to 40 years, were surveyed. The results of this survey identified poverty and inadequate education as two major issues requiring substantial attention. The survey also suggested that if societal changes are to occur, it will rest upon changing the beliefs of the youth in the Winam Gulf area. Restructuring Kenya's aquaculture programme, with a focus on the youth, provides a pathway for increasing the literacy level of the community, as well as for reducing poverty.
... The Lake plays a vital role as a major nutritional food resource, a supply for domestic drinking water and agricultural irrigation for the riparian communities living around the lake shores (Campbell et al., 2003;Okungu et al., 2005;FAO, 2015). Water quality, with regard to the livelihoods of those who rely heavily upon this natural resource, can vary spatially within Winam Gulf compared to the wider Lake Victoria basin (Awange & Obiero, 2006;Omwoma et al., 2014). This is in part due to the localised water circulation patterns within Winam Gulf, its limnology (being shallow throughout its length) and the slow current velocities and a reduced water exchange owing to the narrow water channel at Rusinga that connects Winam Gulf to Lake Victoria. ...
... Due to the narrow Rusinga Channel (flow rate 10-50 cm s −1 ) and the recent re-opening of the Mbita Channel in July 2017 (the channel was previously closed by a causeway built in 1983, (Guya et al., 2017;Simiyu et al., 2022), Winam Gulf and the wider Lake Victoria basin have been defined as separate water bodies (Awange & Obiero, 2006;Omwoma et al., 2014). To account for the collection of samples over a two-year period, possible seasonal effects and for sample collection parameters such as variability within the water column (e.g. ...
... Al, could be a concern. Inputs from the rivers surrounding and flowing into the Winam Gulf catchment continue to be a probable source of particulate loading, which subsequently increases their wider impact into the Winam Gulf and main body of the Lake (Awange & Obiero, 2006;Omwoma et al., 2014). Similarly, an increase in urban settlements, combined with industrialisation and agricultural land clearance/use along the shores, could see a general rise in water contamination from PHEs. ...
The impact of population expansion through economic growth and development has been identified as one of the key drivers of both water and sediment contamination from potentially harmful elements (PHEs). This presents a major hazard not only to aquatic ecosystems but local riparian communities and beyond who rely heavily on this natural resource for drinking water and fish—a valuable source of dietary micronutrients and protein. The present study measured biogeochemical concentration of PHEs in water, sediment and fish from locations pooled into four zones within Winam Gulf and Lake Victoria area of Kenya. Captured fish were used as a sentinel receptor of lake health to evaluate potential risks to fisheries and aquaculture food security. In water, concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu) and lead (Pb) were observed above the United States Environmental Protection Agency (US EPA) maximum contamination level drinking water guidelines (MCL), with aluminium (Al) observed above the Aquatic Life Criteria in all four zones. Similarly, sediment concentrations in all four zones exceeded the US EPA Effects range low (ERL) threshold guidelines for Cu, nickel (Ni), zinc (Zn) and Pb, with Cu, Zn and Pb classed at moderate contamination levels using the contamination factor. Fish tissue concentrations from the four zones were calculated using recommended daily intakes (RDI) and for PHEs as provisional maximum tolerable intakes (PMTIs) and indicated most macro- and micronutrients were at or below 10% RDI from aquaculture and wild fish, with Se indicating a greater RDI (16–29%) in all the zones. Contributions of PHEs to PMTIs were below threshold guidelines for both aquaculture and wild fish with only Cd, Cr and Pb levels being above the PMTI thresholds. There is a need to assess the long-term effects of persistent anthropogenic PHE input into Winam Gulf and the wider Lake Victoria basin. Continued monitoring of PHEs using both historical and more recent data will enable future management policies to be implemented through improved mitigation strategies to reduce their impact on water quality, fish health and subsequent human health.
... Some 80% of the regional fisheries officers said that fish farming had increased during the last 10 years, and that it was likely to expand in the coming 10 years, and overall the attitude among regional fisheries officers and local farmers to aquaculture was positive (Tables 6 and 7, [24]). As the majority of the fish in Tanzania currently comes from Lake Victoria, with stagnating or even declining fish catches, partly due to overfishing and pollution, it can be expected that the demand for farmed fish will increase in the future [4,46], which was confirmed by many of the regional fisheries officers. Still, even with an expansion in aquaculture it would be difficult to keep the currently low, but nutritionally important, per capita fish consumption in Tanzania at the same level as today [2,4,9]. ...
... Also regions around Lake Victoria could be well suited for more business-oriented aquaculture. Fish from the lakes have created fish markets, and the declining catches of wild fish could potentially increase the demand for farmed fish [4,46]. The lakes also provide opportunities to establish fish cage farming, which now is quite common in Lake Victoria and has also been introduced since a few years back in Lake Tanganyika. ...
... Much fish feed, feces, and antibiotics are lost from fish cages, directly into the lake environment, which could contribute to an increased pollution of the aquatic environment. Lake Victoria is already suffering from many pollutants and any additional pollution load should be minimized [46]. Also escapes of fish from the cages could have negative impact on the native fish populations, which was seen as the main environmental drawback from aquaculture by the regional fisheries officers (Table 6). ...
Aquaculture production in Tanzania has increased in recent years, responding to an increased demand for fish, but the scale and productivity of smallholder aquaculture remains below the level needed to support significant sector growth in Tanzania. This study assesses, through geospatial analyses, the suitability for freshwater pond farming of Oreochromis niloticus and Clarias gariepinus in Tanzania, by assessing the geographical distribution of seven criteria (water availability, water temperature, soil texture, terrain slope, availability of farm inputs, potential farm-gate sales, and access to local markets) identified as important for fish pond farming. The criteria were developed and standardized from 15 sub-criteria, which were classified into a four-level suitability scale based on physical scores. The individual weights of the different criteria in the overall GIS suitability assessment were determined through a multi-criteria evaluation. The final results were validated and compared through field observations, interviews with 89 rural and 11 urban aquaculture farmers, and a questionnaire survey with 16 regional fisheries officers. Our results indicate that there is a good potential for aquaculture in Tanzania. Almost 60% of Tanzania is assessed as being suitable and 40% as moderately suitable for small-scale subsistence pond farming, which is the dominating fish farming practice currently. The corresponding figures for medium-scale commercial farming, which many regions expect to be the dominating farming method within ten-years, were 52% and 47% respectively. The availability of water was the most limiting factor for fish pond farming, which was confirmed by both farmers and regional fisheries officers, and assessed as being “suitable” in only 28% of the country. The availability of farm-gate sales and local markets were “moderate suitable” to “suitable” and were seen as a constraint for commercial farms in rural areas. The availability of farm inputs (agriculture waste and manure) was overall good (26% very suitable and 32% suitable), but high-quality fish feed was seen as a constraint to aquaculture development, both by farmers and regional fisheries officers. Soil, terrain, and water temperature conditions were assessed as good, especially at low altitudes and in regions close to the sea and south of Lake Victoria.
... Previously, the diverse effects and transport mechanisms associated with heavy metal ions such as Pb 2+ and Cu 2+ from point sources have been reported [3,4]. Among other diverse effects, their impact on aquatic organisms, including fish and sea foods, greatly affects trade and human health [5,6]. In all circumstances, the impacts are detected at very critical stages and they are irreversible [3,5,6]. ...
... Among other diverse effects, their impact on aquatic organisms, including fish and sea foods, greatly affects trade and human health [5,6]. In all circumstances, the impacts are detected at very critical stages and they are irreversible [3,5,6]. erefore, the need to detect point source contamination earlier enough is very important both to humans and aquatic systems. ...
... In this work, we present results for tablets made from Dy 2 (OH) 5 (C 28 H 20 O 6 S 2 ) 0.5 .nH 2 O due to their outstanding performance in detection of heavy metals. Firstly, Dy 2 (OH) 5 (H 2 O) n NO 3 .nH 2 O was synthesized before the nitrate was exchanged with stilbene. e FTIR spectra show that the free nitrate anions in Dy 2 (OH) 5 (H 2 O) n NO 3 .nH 2 O, with an asymmetric stretching mode at 1396 (D 3h ) cm −1 (Figure 1(a)), are completely replaced with stilbene anions, C 28 H 20 O 6 S 2 2− , to get the sorbent starting material, Dy-Stb ( Figure 1(b)). ...
Contamination of aquatic reservoirs with metal ions is a slow gradual process that is not easy to detect. Consequences of the metal ions, especially the ones with high atomic numbers (heavy metals) at high concentrations, are severe and irreversible in aquatic reservoirs. As such, early detection mechanisms, especially at trace concentration, are essential for mitigation measures. In this work, a new, robust, and effective tool for trace metal detection and monitoring in aqueous solutions has been developed. Tablets (1 mm thick and similar to medicinal tablets) were manufactured from a powder comprising stilbene intercalated into gallery spaces of lanthanide-containing layered double hydroxides. The tablets were placed in a water column having different concentrations of Pb2+ and Cu2+ ions, and the water was allowed to flow for 45 minutes at a flow rate of 100 ml/s. Thereafter, the tablets were dried and made to powder, and their phosphorescence was measured. The gradual stilbene phosphorescence turnoff in the tablets from various concentrations of metal ions was correlated with sorption amounts. The tablets were able to detect effectively metal ions (up to Pb2+ 1.0 mmol/L and Cu2+ 5.0 mmol/L) in the aqueous media. As such, the concentrations of Pb2+ and Cu2+ ions at trace levels were determined in the test solutions. This method provides a real-time metal ion analysis and does not involve sampling of water samples for analysis in the laboratory.
... Using the case of Lake Victoria, where harvest pressures to export Nile perch to international markets has precipitated dramatic fishery decline (Johnson, 2010;Omwoma et al., 2014), we analyze the ramifications of fish decline on a local scale, in the communities where fish are harvested. We employ a mixed methods approach that pairs a survey of 303 households with 30 in-depth interviews with men and women who participate in fish-for-sex exchanges. ...
... Recently, the Nile perch catch has declined amidst high fishing pressure and related environmental concerns (LVFO, 2012). From 1995 to 2009, Nile perch catch in the highly productive Winam Gulf of Lake Victoria declined by 23% while catch-per-unit-effort declined by 40% (Omwoma et al., 2014). In the wake of a declining Nile perch fishery, a small, sardine-like fish has risen in prominence. ...
... Major stressors of Winam Gulf include degraded water quality (Ongeri et al., 2012;Orata et al., 2011;Omwomo et al., 2015;Kundu et al., 2017;Outa et al., 2020b), frequent algal blooms (Sitoki et al., 2010;Nyamweya et al., 2020), habitat perturbations associated with invasive species (e.g. water hyacinth) (Wilson et al., 2007;Otieno et al., 2022), trophic perturbations due to non-native fish introductions and fish biodiversity loss (Kitchell et al., 1997), overfishing (Omwoma et al., 2014) and exponential expansion of aquaculture net-pen operations (Aura et al., 2018;Okechi et al., 2022;Mariott et al., 2023). These stressors have manifested themselves as declines in fish harvests from these traditionally highly productive waters, with total fish catch declining by 66 % between 1995 and 2009 (Witte et al., 2007;Kundu et al., 2017;Roegner et al., 2023;Omwomo et al., 2015). ...
... Further, in 2010, 96% of Mfangano residents faced some level of food insecurity (Fiorella et al., 2014), which has been associated with poor early childhood development outcomes (Milner, Fiorella, Mattah, Bukusi, & Fernald, 2017). Despite the vast natural resources of the Lake Victoria fisheries, fish access is mediated by income (Fiorella et al., 2014) and has declined due to overfishing, destructive practices, and environmental changes that have reduced incomes and altered fish access (Abila, 2000;Abila, 2003;Njiru, Kazungu, Ngugi, Gichuki, & Muhoozi, 2008;Omwoma et al., 2014). Further, a high prevalence of HIV/AIDS in these communities reduces the labour force and can push fishers to use illegal and unsustainable methods , which may further exhaust fish stocks and negatively affect local incomes and food access. ...
Research efforts have identified the power of social networks to influence health outcomes and their role in providing psychosocial, emotional, and material resources for maintaining good health practices. We evaluate an intervention designed to treat social networks affected by maternal and child malnutrition and engage not only mothers but also fathers, friends, and grandparents. The intervention included 6 facilitated sessions with sustained support for the subsequent year. Facilitators led groups (e.g. dramas, cooking demo, etc) in partnership with community health volunteers in topics of breastfeeding, infant and young child feeding, and dietary diversity. Our approach aims to foster social support to improve nutrition knowledge and infant and young child feeding practices.
We use a mixed methods approach: 1) controlled post‐intervention assessment of nutrition knowledge among participants (CHVs n=24; community n=43) and controls (CHVs n=62; community n=149), 2) a case‐control study of child feeding assessed with a 24 Hour Recall (participants n=48; controls n=211) and 3) focus groups (7).
Community members and CHVs who participated in and led nutrition social‐network groups had higher nutrition knowledge overall (community health volunteers: 10.6 to 9.4, p < 0.001; community member: 9.8 to 9.0, p<0.01; scale 1–12) and of breastfeeding practices (CHV: 5.4 to 4.4, p < 0.0001; community: 4.9 to 3.8, p<0.0001; scale 1–6) when compared to those who did not participate. Our focus group discussions affirm these findings and emphasize the role of caregiver confidence in feeding young children and ideas of nutritional balance when introducing complementary foods.
There was an increase in the percent of intervention children who met indicators of minimum dietary diversity (10% to 40%, p < 0.01) and minimum acceptable diet (8% to 31%, p<0.01) immediately after the intervention, but both returned to baseline six months later. Control children also had an increase in dietary diversity (20% to 33%, p<0.01), and subsequent return to baseline. Strong seasonality effects are evident at 6‐months. Focus group findings underscored the challenges of carrying out infant and young child feeding recommendations and the importance of multi‐dimensional support for caregivers and community collaboration to meet nutritional goals and exercise knowledge.
At two years, gains in nutrition knowledge, community support, and engagement endured; however, initial gains in young child feeding practices were not maintained at 6 months. While social network groups may be a useful platform for deepening knowledge and engagement, the intervention needs to be enhanced further to support nutrition outcomes. The relatively short duration of the program, challenges of engaging men, and substantial seasonality of food insecurity might particularly shape program outcomes. Seasonality of dietary diversity was evident in both control and intervention groups and this intervention might perform best in relatively food secure contexts or when seasonality is less pronounced. Engagement social network groups to improve access to diverse foods through durable changes to production or resilience to shocks/seasonality are potential avenues for intervention improvement.
Support or Funding Information
Nutrition Embedding Evaluation Program, PATH & DFID, NSF‐GEO grant CNH115057, Atkinson Center, NSF DDRI (KJF), USAID Global Innovation Fellowships (AA), UC Berkeley Center for Global Public Health (FW)
... We included both the social and ecological changes that to alter the availability of resources. For example, around Lake Victoria's fisheries, fish availability was a function of interactions between seasonal dynamics, fishing pressure, pollution, water hyacinth, and fishery management (Njiru, Mkumbo, & van der Knaap, 2010;Omwoma et al., 2014;Ongore, Aura, Ogari, Njiru, & Nyamweya, 2018). As the reviewed articles did not necessarily focus on the natural resource economy that was the subject of exchanges, our inference about the role of environmental change in these relationships is limited. ...
Environmental change is projected to decrease the availability of key natural resources. Decreasing availability of resources that support food security and livelihoods for vulnerable populations is hypothesised to increase engagement in transactional sex. Therefore, we systematically examined the peer-reviewed literature to characterise what is known about transactional sex for natural resources, document the natural resources that are exchanged for sex, and identify qualitative trends. Of the 1063 articles, 33 were retained for full abstraction. A majority of articles were published after 2005 (93%) and focused on Africa (90%). Two-thirds of articles focused on sex-for-fish exchanges. Reports of transactional sex were also found for other resources, including agricultural land (12%) as well as food, water, and fuel in emergency contexts (12%). Migration and altered resource availability were described as underlying causes of transactional sex. Some studies described an increased risk of sexually transmitted infection, including HIV, as a health consequence of transactional sex. We offer three possible explanations for why the preponderance of previous studies have focused on sex-for-fish rather than other natural resources, and suggest directions for future research.
... Further, in 2010, 96% of Mfangano residents faced some level of food insecurity (Fiorella et al., 2014), which has been associated with poor early childhood development outcomes (Milner, Fiorella, Mattah, Bukusi, & Fernald, 2017). Despite the vast natural resources of the Lake Victoria fisheries, fish access is mediated by income (Fiorella et al., 2014) and has declined due to overfishing, destructive practices, and environmental changes that have reduced incomes and altered fish access (Abila, 2000;Abila, 2003;Njiru, Kazungu, Ngugi, Gichuki, & Muhoozi, 2008;Omwoma et al., 2014). Further, a high prevalence of HIV/AIDS in these communities reduces the labour force and can push fishers to use illegal and unsustainable methods , which may further exhaust fish stocks and negatively affect local incomes and food access. ...
Food insecurity and poor infant and young child feeding (IYCF) practices contribute to undernutrition. The Kanyakla Nutrition Program was developed in rural Kenya to provide knowledge alongside social support for recommended IYCF practices. Utilizing a social network approach, the Kanyakla Nutrition Program trained Community Health Workers to engage mothers, fathers, and grandparents in nutrition education and discussions about strategies to provide instrumental, emotional, and information support within their community. The twelve‐week program included six sessions and was implemented on Mfangano Island, Kenya in 2014‐2015. We analyzed intervention effects on (1) nutrition knowledge among community members or CHWs, and (2) IYCF practices among children 1‐3 years. Nutrition knowledge was assessed using a post intervention comparison among intervention (community, n=43; CHW, n=22) and comparison groups (community, n=149; CHW, n=64). We used a quasi‐experimental design and difference‐in‐difference to assess IYCF indicators using dietary recall data from an on‐going cohort study among intervention participants (n=48) with individuals living on Mfangano Island where the intervention was not implemented (n=178) before the intervention, within one month post intervention, and six months post intervention. Findings showed no effect of the intervention on IYCF indicators (e.g., dietary diversity, meal frequency) and less than 15% of children met minimum acceptable diet criteria at any time point. However, knowledge and confidence among community members and CHWs was significantly higher two‐years post intervention. Thus, a social network approach had an enduring effect on nutrition knowledge, but no effects on improved IYCF practices.
... These waste dumping sites are great sources of aquatic contaminations including groundwater, river water through surface runoffs, springs etc. (Omwoma et al., 2015b;Xing et al., 2013). These contaminations end up affecting both humans and aquatic life (Omwoma et al., 2014). Hence such sites require great care and protection measures. ...
The development of Africa including industrialization such as chemical production, urbanization, agriculture,
waste disposal, and electric power generation has a direct and diverse effect on the environment. These activities
require effective planning, consultation, evaluation, risk assessment and monitoring techniques. Diverse environmental
impacts can arise out of planning, construction, operation, and end-life of such activities. Impacts of
global climate change, photochemical smog, and radioactive emissions have a direct link to development projects.
Nevertheless, there is intensive research and innovation geared towards integrating development activities
and the environment so as to achieve sustainable development. Herein, we review some of the technological
innovation breakthroughs in various fields that include the built environment, chemical production, toxicants,
municipal wastes, and electricity. The concept of sustainable chemistry is also discussed. It is found that Africa is
at an advantage towards achieving sustainable development as it can easily adopt refined technological tools
from developed countries. For instance, the use of comprehensive strategic environmental assessment tools for
proposed policies plans and programs and environmental impact assessment for projects can see Africa achieve
sustainable development. Mitigation measures for problems such as hazardous waste from chemical industries
can be minimized using technological tools such as incineration of solid wastes, biological treatment of wastewater,
batch and semi-batch conventional distillation, entrainer-based distillation, physical adsorption, and
extraction etc. However, it is noted that although Africa should adopt some of these technological tools to help
accelerate its sustainable development agenda, regional and cultural differences must be incorporated in the
adoption process.
... To reduce destructive practices, fishing gear and catch regulations are mandated, and the fishery is comanaged by fishers, national ministries, and a lake-wide organization. Despite these safeguards, Nile perch (Lates niloticus), the prevailing fishery, declined by 65% in inshore areas and 30% in deep zones in Lake Victoria from 2002 to 2014 (16), and catch per unit effort dropped 40% in the same time period (17). Fishers in Lake Victoria use a range of fishing techniques spanning different gear types, fish species, and the targeting of near-and off-shore habitats. ...
Significance
We accept that the environment influences human health, but we know little about how human health affects the environment. However, millions of people around the world rely on natural resources for food and livelihoods and confront a high burden of illness. Experience of illness may change people’s physical capacities, outlook, and planning horizons and shape how they engage with the environment. We analyze these impacts in fishing communities of Lake Victoria, Kenya. Although illness may cause the sickest individuals not to fish, many fishers continue fishing but shift their methods. When sick, fishers use methods that are less physically demanding but illegal and environmentally destructive. Our findings suggest that environmental sustainability may be integrally shaped by the health of resource users.
Drowning is an overlooked public health concern and drowning risk is dependent on environmental risk factors. The preponderance of drowning deaths occurs in low- and middle-income countries. Small-scale fishers face high occupational risk of drowning. Climate change increases the frequency and intensity of storms, thereby exacerbating fishers’ risks and creating a need to examine the contribution of storms to fisher drowning deaths for the development of mitigation strategies. We examined this relationship between weather and fisher drowning deaths in Lake Victoria, which is Africa’s largest lake, a site of high fishing pressure, and where climate change is predicted to increase thunderstorms. We conducted a verbal autopsy with people knowledgeable about recent fatal fisher drowning incidents to collect information about the deceased fishers and circumstances surrounding the incidents across 43 landing sites in the Kenyan shore of Lake Victoria. Semi-structured interviews with stakeholders also elucidated community perspectives on drowning risks. Fatal drownings were often attributed to bad weather (41.8%). Other risk factors, such as non-use of life jacket and navigation equipment, co-occurred with bad weather at high rates (69.5% and 67.8%, respectively) to jointly contribute to fatal drowning incidents. Such co-occurrence of risk factors indicates that actions across multiple risk factors can help mitigate the issue. Stakeholder analysis revealed a range of opportunities for improved communication of risks and action to mitigate risks across boat operators and manufacturers, as well as multiple levels of management. Across global small-scale fisheries, limited use of safety equipment and intensive fishing pressure may coincide with increases in extreme weather events, necessitating action to address current and mitigate future drowning risks to small-scale fishers.
Exposomics is assessment of organism exposure to high priority environmental pollutants in an ecosystem using OMIC technologies. A virtual organism (VO) is an artificial property-tool (OMIC) reflecting exposomic process in compartments of real organisms. The exposomics of aquatic organisms inhabiting Lake Victoria (L.V.) and Three Gorges Reservoir (TGR) were compared using VOs. The two reservoirs are heavily depended on for food and water both in Africa and China. The target priority pollutants in the reservoirs were polyclic aromatic hydrocarbons (PAHs) and persistent organic pollutants such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), medium chain chlorinated paraffins (MCCPs) and short chain chlorinated paraffins (SCCPs). The VOs showed that in a period of 28 days, aquatic organisms in TGR were exposed to total (∑) PAHs of 8.71 × 10-6 mg/L, PCBs of 2.81 × 10-6 mg/L, OCPs of 2.80 x 10-6 mg/L, MCCPs of 8.9 × 10-10 mg/L and SCCPs of 1.13 × 10-7 mg/L. While in a period of 48 days, organisms in L. V. were exposed to total (∑) PAHs of 7.45 × 10-6 mg/L, PCBs of 4.70 × 10-6 mg/L, OCPs of 3.39 × 10-8 mg/L, MCCPs of 4.6 × 10-10 mg/L and SCCPs of 3.6 × 10-9 mg/L. The exposomic levels in TGR after 28 days were higher than those in Lake Victoria after 48 days. In both reservoirs, bioaccumulation levels are above set standards for aquatic organisms. The sources of the pollutants into the reservoirs were diagnostically determined to originate from anthropogenic processes such as petrogenic, diesel emissions, biomass burning, coal combustion, electronic wastes, traffic emissions and historic uses.
The fisheries of Lake Victoria are highly dispersed and catch statistical information is insufficient for support-ing management. Catch assessment surveys for the three riparian countries were found to be weak or inadequate and a strategy for improving this source of information is proposed. Considerable illegal fishing, using banned gears and small-meshed nets was prevalent and considered to be detrimental to the sustainability of the fishery. The principal problems underlying the poor fishery assessment were inadequate resources, poorly trained and unmotivated personnel, and externalities, such as poverty and poor employment opportunities, which override the resource monitoring and assessment mechanisms.
Lake Victoria is an international waterbody that offers the riparian communities a large number of extremely important environmental services. Over the past three decades or so, the lake has come under increasing and considerable pressure from a variety of interlinked human activities such as overfishing, species introductions, industrial pollution, eutrophication, and sedimentation. In this paper we examine the root causes for overfishing and pollution in Lake Victoria and give possible policy options that can help remediate or mitigate the environmental degradation.
Lake Victoria's fish fauna included a large endemic flock of 300+ haplochromine cichlid species. About two-thirds of these species have disappeared or are threatened with extinction. The main cause of this large extinction event is predation by Nile perch, an introduced predator. We describe the decline of the haplochromine species and demonstrate that the rate and sequence of their decline was determined by their relative abundance, their adult size and their habitat overlap with Nile perch. Many non-haplochromine species declined as well, but in contrast, stocks of the native pelagic cyprinid Rastrineobola argentea and the introduced Oreochromis niloticus increased. There are also indications of an increase in phytoplankton, macrophytes, prawns and benthic organisms. Many of these rapid changes in the ecosystem were probably effects of the increase of the Nile perch and the disappearance of the haplochromines. The original fish fauna included many primary and secondary consumers. Currently secondary and tertiary consumers dominate. The food web in the sub-littoral and offshore areas of the lake changed considerably due to the stock replacements.
A preliminary risk assessment was undertaken on the Kenyan part of Lake Victoria to identify the major causes of degradation of water quality. Urban, industrial and agricultural loads were quantified and related to geographical and climatic conditions. A few analyses of persistent contaminants were carried out on fish. Monthly limnological investigations were conducted together with river water quality analyses. Phosphorus loads and consequent eutrophication were identified as the major causes of water quality degradation.
The book constitutes a pioneering and unique work on Lake Victoria. It is the world's second largest fresh-water lake and has existed for over 35,000 years, supporting the livelihood of more than 30 million people. Surprisingly, there has been no comprehensive book that addresses its problems and potentials. Ecology, environmental pollution, resource management, etc., are some of the issues that are addressed by the authors. This book presents comprehensive insights into the limitations, challenges and opportunities facing Lake Victoria. Students, researchers, and practitioners from various fields will find it useful.
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