NRU :: Browsing by Author "Natugonza, Vianny"

Browsing by Author "Natugonza, Vianny"

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Assessment of exploited fish species in the Lake Edward System, East Africa
(Journal of Applied Ichthyology, 2021) Musinguzi, Laban; Bassa, Samuel; Natugonza, Vianny; Van Steenberge, Maarten; Okello, William; Snoeks, Jos; Froese, Rainer
The unknown status of inland fish stocks hinders their sustainable management. Therefore, increasing stock status information is important for sustainable inland fisheries. Fisheries reference points were estimated for five exploited fish species (11 stocks) in the Lake Edward system, East Africa, which is one of the most productive inland water systems. The aim was to ascertain the status of the fisheries and establish reference points for effective management. The reference points were based on four linked stock assessment approaches for data-limited fisheries. Estimates showed poor stock status with the stocks defined as either collapsed, recruitment impaired or overfished. However, higher catches could be obtained under sustainable management. Estimates of maximum sustainable yield (MSY) and supporting biomass (Bmsy) are provided for 10 of the stocks as targets for rebuilding plans. The immediate target of management should be rebuilding biomass to Bmsy. Applicable measures include shifting length at first capture to the length that maximizes catch without endangering size structure and biomass, and livelihood diversification out of fisheries.
Building Capacity for Climate Change Mitigation and Adaptation Through Mainstreaming Climate Change in Curricula of Tertiary Training Institutions in Africa
(Springer, Cham, 2017) Efitre, Jackson; Natugonza, Vianny; Musinguzi, Laban; Olokotum, Mark; Naigaga, Shamim; Ogutu-Ohwayo, Richard
Climate variability and change, which intensified since 1970s, are threatening natural resources and livelihoods in Sub-Saharan Africa where people depend on climate sensitive natural resources, such as agriculture and fisheries, but have limited capacity to adapt. Increasing human and institutional capacity to address threats posed by climate change to natural resources and livelihoods requires building capacity to generate and disseminate information and knowledge on climate change, its impacts, adaptation and mitigation through research, education and raising awareness by tertiary training institutions. Most tertiary training institutions in Africa have curricula covering basic and applied natural resources management but most of them do not include climate change. This paper presents a training curriculum and manual that was developed to fill this gap. The purpose of the paper is to provide in-depth information on how Climate Change can be integrated into the fisheries and aquaculture curricula of tertiary training institutions. It also provides students, scientists, practitioners, and policy makers with an understanding of key concepts and approaches to climate change mitigation measures, adaptation strategies, and policies. The aim is to mainstream climate change in fisheries training. The specific objectives are to facilitate introduction of climate change in fisheries training in Uganda that can be developed further and adopted by other countries in Africa and elsewhere; Equip students with scientific and technical capacity to anticipate and evaluate changes in climate and its influence, communicate information to stakeholders, design, and test adaptation strategies and mitigation measures; and Increase human resource capacity to address climate change issues through reviewing and strengthening of the national education system. The curriculum consists of seven modules covering: Major threats to natural resources; Introduction to climate change; Implications of climate change on aquatic productivity processes and fisheries; Implications of climate change on aquaculture; Livelihoods, impacts, adaptation and mitigation; Aquatic ecosystem modeling in relation to climate change; Principles, policies, regulations and institutions required to address impacts of climate change. The modules will be delivered through lectures, discussions, case studies and field visits. It is recommended that the curriculum and manual be incorporated into training programs of tertiary training institutions to build the capacity required to address climate change challenges particularly for fisheries in Africa.
Ecosystem modelling of data-limited fisheries: How reliable are Ecopath with Ecosim models without historical time series fitting?
(Journal of Great Lakes Research, 2020) Natugonza, Vianny; Ainsworth, Cameron; Sturludóttir, Erla; Musinguzi, Laban; Ogutu-Ohwayo, Richard; Tomasson, Tumi; Nyamweya, Chrisphine; Stefansson, Gunnar
Long-term time series data are not available for many of the African Great Lakes. This precludes fitting ecosystem model parameters to time series data, and we do not know how reliable non-fitted models are compared to fitted ones in terms of predicting consequences of alternative management strategies. To investigate this, we generate a historical Ecopath with Ecosim (EwE) model for Lake Victoria (East Africa), fitted to time series data (1980–2015), and a present-day EwE model (representing average conditions for the period 2010–2015). We do scenario simulations using the present-day model and the comparable 2015 end-state of the historical model, and test if incorporating information on short-term biomass trends by adjusting biomass accumulation (BA) parameter in the present-day model increases its reliability. We find that there are differences in model predictions, but those differences can be lessened by adjusting BA terms in the present-day model to reflect biomass trends from short-term empirical data. We also compare the models with and without fitted vulnerability parameters. The models generally give comparable results for the dominant commercial fisheries at low fishing pressure; when fishing mortality is increased, the models give variable predictions. This study adds to the current understanding of the limitations of EwE models that are not challenged to reproduce long-term historical fishery responses to perturbations. We conclude that for the less productive groups, as well as groups that suffer heavy mortality (either due to predation or fisheries), it may be appropriate to use negative BA as first draft assumption in present-day models.
Ecosystem models of Lake Victoria (East Africa): Can Ecopath with Ecosim and Atlantis predict similar policy outcomes?
(Journal of Great Lakes Research, 2019) Natugonza, Vianny; Ainsworth, Cameron; Sturludóttir, Erla; Musinguzi, Laban; Ogutu-Ohwayo, Richard; Tomasson, Tumi; Nyamweya, Chrisphine; Stefansson, Gunnar
Ecosystem simulation models are valuable quantitative decision tools for supporting ecosystem-based fisheries management. However, the application of ecosystem models in fisheries management is still undermined by the lack of simple procedures to test the effect of model uncertainty on policy outcomes. The use of multiple ecosystem models is viewed as ‘‘insurance” against the effects of uncertainty emanating from modelling complex systems, which calls for investigations to ascertain whether models with different structure and assumptions can give consistent policy evaluations. We compared two structurallydistinct ecosystem models, Ecopath with Ecosim (EwE) and Atlantis, for Lake Victoria by varying fishing mortality of the key functional groups: Nile perch (the top predator) and haplochromines (key prey species). We compared model behaviour at the ecosystem level and at the level of functional groups, by evaluating changes in biomass of targeted groups and the consequent effects of changes in target groups on non-target groups. Results showed qualitative similarities (direction of change) for the major harvested groups; however, the cascading effects on non-target species varied across models, depending on the species interaction feedbacks. We conclude that: EwE and Atlantis, despite the huge differences in ecological processes between the models, can give consistent qualitative advice, which is needed for strategic management decisions; consistency in the representation of trophic interactions may help to minimize variations in simulated fishery responses due to model structure. This study helps to highlight scenarios that are robust to model choice, and for which simpler models (such as EwE) could also provide reliable advice.
Exploring the structural and functional properties of the Lake Victoriafood web, and the role of fisheries, using a mass balance model
(Ecological modelling, 2016) Natugonza, Vianny; Ogutu-Ohwayoa, Richard; Musinguzia, Laban; Kashindye, Benedicto; Jónsson, Steingrímur; Thor Valtysson, Hreidar
tHuman and environmental factors have greatly challenged Lake Victoria ecosystem, especially in the lastfour decades. However, the lake continues to support the World’s largest freshwater fishery, currentlyproducing ca. one million tons of fish per year and directly supporting livelihoods of ca. four millionpeople in three riparian countries. We used the Ecopath component of Ecopath with Ecosim modellingsoftware to re-parameterise two existing mass balance models to reflect ecosystem state of Winam Gulfin 1971–1972 and 1985–1986, and construct a new model for the whole lake to reflect ecosystem statein 2014. The aim was to understand the structural and functional properties of Lake Victoria food weband the role of fisheries on the ecosystem. We found a decrease over time in productivity in relationwith biomass and respiration, and food web connectivity, and an increase in biomass cycling. The totalsystem throughput, decreased fivefold between 1971 and 1972 and 1985–1986, but was slightly higherin 2014 with a moderate shift from herbivory to detritivory. The implication of these changes on systemmaturity and resilience are discussed. The trophic level of catches increased between 1971 and 1972and 1985–1986 due addition of high trophic level catches from the introduced piscivorous Nile perch(Lates niloticus) i.e. “fishing up”. However, the decline in trophic level of catches between 1985 and 1986and 2014 seems to have been due to sequential addition of low trophic level catches, especially fromthe native Silver cyprinid (Rastrineobola argentea), a phenomenon termed “fishing through”, as opposedto a decline of high trophic level catches (or “fishing down”). Currently, exploitation is unbalanced andskewed to the least productive species at higher trophic level, with significantly less fishing occurring atthe most productive species at lower trophic level, and the causes are discussed.
The extent of cage aquaculture, adherence to best practices and reflections for sustainable aquaculture on African inland waters
(Journal of Great Lakes Research, 2019) Musinguzi, Laban; Lugya, Jessy; Rwezawula, Philip; Kamya, Ashraf; Nuwahereza, Colleb; Halafo, Jose; Kamondo, Stephanie; Njaya, Friday; Aura, Christopher; Shoko, Amon P.; Osinde, Robert; Natugonza, Vianny; Ogutu-Ohwayo, Richard
Cage aquaculture is expanding on African inland waters and has potential to close the fish supply deficit in the region and provide other social benefits such as employment and income. However, if not appropriately guided and regulated, cage aquaculture could become unsustainable, causing conflicts with other water uses, environmental degradation and economic losses to aquaculture enterprises. To enhance sustainability of cage aquaculture on the African inland waters, we developed an inventory of cage aquaculture installations and used it to investigate the distribution and magnitude of cage aquaculture and adherence to best practices for sustainable aquaculture. Our results show evidence of spatial expansion of cage aquaculture on the African inland waters, of varying magnitude across and within water bodies and partial adherence to best practices. Cage aquaculture was confirmed on 18 water bodies which together share 263 installations with more than 20,000 cages. Lakes Victoria, Kariba, Volta and River Volta host 82.9% of cage aquaculture installations on the African inland waters and are major areas for cage aquaculture. Contrary to best practices, evidence shows cage aquaculture installations entirely or in close proximity to protected areas, in eutrophic and hypertrophic waters, shallow water bodies and sites ( 5 m average depth) and close to the shoreline. Cage aquaculture is qualified as an additional stressor to the African inland waters and because it is expected to continue expanding, adherence to best practices should be promoted for sustainability.
Fishers’ perceptions of climate change, impacts on their livelihoods and adaptation strategies in environmental change hotspots: a case of Lake Wamala, Uganda
(Environment, Development and Sustainability, 2016) Musinguzi, Laban; Efitre, Jackson; Odongkara, Konstantine; Ogutu-Ohwayo, Richard; Muyodi, Fredrick; Natugonza, Vianny; Olokotum, Mark; Namboowa, Sharon; Naigaga, Shamim
Fisheries resources support livelihoods of fishing communities but are threatened by over-exploitation, habitat degradation, pollution, invasive species and climate change. Unlike the other threats, climate change has received limited consideration and reducing its risks requires appropriate adaptation strategies. This study used quantitative and qualitative methods to generate knowledge on fishers’ perceptions of climate change, changes in climate variables and their impacts on livelihoods, adaptation strategies, constraints to adaptation and required interventions to promote adaptation strategies that would enable fishers to build resilience to sustain their livelihoods. We found that fishers were aware of changes in climate conditions manifested by unpredictable seasons, floods and droughts. Fishing remained the main livelihood activity. However, the dominance of fishes had changed from Nile tilapia (Oreochromis niloticus L.) to the African catfish (Clarias gariepinus Burchell). Floods and droughts were associated with damage to gears, boats, landing sites and changes in fish catches and sizes, income from fishing and fish consumption. The fishers adapted by increasing time on fishing grounds and changing target species and fishing gear among other things. Some innovative fishers diversified to high-value crops and livestock. This increased their income beyond what was solely earned from fishing which provided an incentive for some of them to quit fishing. Livelihood diversification was enhanced by use of communications technology, membership of social groups, increasing fishing days and fishing experience.
Implications of climate variability and change for African lake ecosystems, fisheries productivity, and livelihoods
(Journal of Great Lakes Research, 2016) Natugonza, Vianny; Musinguzi, Laban; Olokotum, Mark; Naigaga, Shamim; Ogutu-Ohwayo, Richard
Inland fisheries are important for nutrition, employment, and income, but climate variability and change are adding to other stressors, such as overexploitation, pollution, habitat degradation, and invasive species, to threaten their productivity as well as livelihoods of fisheries-dependent communities. Understanding the whole socio-ecological system to enable communities to adapt and build resilience is therefore vital. Here, we present results froma review of the responses of African lakes, fisheries productivity, and livelihoods to climate variability and change, and provide suggestions on required policy interventions to promote adaptation and build resilience. Changes in climate variables, especially temperature, wind speed, and rainfall have contributed to changes in lake water levels, loading, and recycling of nutrients. In somelakes, such disruptions in physical and chemical conditions have triggered changes in water quality, algae and invertebrate productivity, life history of fish, and contributed to shifts in fish community composition, proliferation of invasive aquatic weeds, and changes in parasite–vector–host interactions. Fish yield has either increased or decreased depending on climatic events,with the latter negatively affecting livelihoods, and forcing affected communities to adapt. Because adaptation strategies are location specific, and influenced by local conditions, many adaptation strategies have been unguided and have negatively affected fisheries. The responses of fisheries to climate change vary among lakes of different morphometric characteristics. There is need for consistent data to examine the direction and consequences of climate variability and change on fisheries and livelihoods of specific aquatic systems, and promote location specific adaptation and mitigation measures.
Increasing Capacity For Conservation Of Threatened Fish Species Through Data Mobilization And Training (BID-AF 2017-0206-SMA)
(Biodiversity Informatics, 2017) Natugonza, Vianny; Musinguzi, Laban
Despite presence of huge biodiversity data on primary species occurrence records available through the Global Biodiversity Information Facility (GBIF), more data remains inaccessible while policy formulation in some countries still does not directly benefit from mobilized data. This is because many institutions have not published their data and, in most cases, data are mobilized without a prior understanding of the needs of the users, respectively. With support from the European Union, GBIF, and the National Fisheries Resources Research Institute (NaFIRRI), NaFIRRI intends to mobilize at least 10,000 fish records and create a first—ever—comprehensive dataset of fish species occurrence in Uganda with most up—to—date information. To ensure that mobilized data directly benefits policy makers, data needs and mapping surveys were undertaken to assess the user specific needs for fish biodiversity data as well as identify data holding institutions. Data on species occurrences, especially in highly vulnerable ecosystems that are faced with multiple stressors, as well as data limited ecosystems got high ranking. Policy makers also need data presented in easily comprehensible formats, such distribution maps, checklists, graphs, and factsheets or policy briefs. Five data holding institutions and some individuals willing to share fish biodiversity data with NaFIRRI were identified. The identified data needs will guide development of user—driven data format for mobilizing and presenting fish biodiversity data in Uganda, while the data holding institutions will be engaged to ensure that their data is published.
The non-Haplochromis fish fauna in Uganda: an update on the distribution and a review of data gaps
(Research Square, 2022) Akoth, Dorothy; Natugonza, Vianny; Efitre, Jackson; Muyodi, Fredrick Jones; Musinguzi, Laban
Freshwater fishes are the second most threatened group of vertebrates after amphibians. In most developing countries, the conservation of freshwater fishes is largely hampered by limited information and data. The Red List assessments by the International Union for Conservation of Nature (IUCN) provide a benchmark for conservation and planning, but these assessments require, inter alia, quantitative information on the species range in the wild. This information is largely missing for many species that face extinction threats. In this paper, we combined species occurrence data, expert knowledge, and literature to review and update the distribution of non-Haplochromis fish species native to Uganda and determine their geographical extent relative to the global range. Results showed that (i) at least 110 non-Haplochromis species occur in Uganda, (ii) the current status in the entire native range for more than 60% of these species is unknown; (iii) five species previously known to occur in Uganda: Amphilius kivuensis, Bagrus degeni, Marcusenius macrolepidotus, Petrocephalus catostoma, and Lacustricola pumilus lack a native locus and hence not Ugandan fishes, (iv) 17 species occur in areas beyond their previously known range, and therefore, their presence needs further investigations, preferably by examining specimen collections, and (v) majority of the non-Haplochromis species native to Uganda have a wide distribution outside the national boundaries. We anticipate this information to be relevant both for the national and global IUCN Red List assessments for the non-Haplochromis fishes in Uganda. Furthermore, the identified data gaps will be relevant in prioritizing limited resources during surveys and collections.
Paradigm shifts required to promote ecosystem modeling for ecosystem-based fishery management for African inland lakes
(Journal of Great Lakes Research, 2017) Musinguzi, Laban; Natugonza, Vianny; Ogutu-Ohwayo, Richard
Ecosystem-based fishery management (EBFM) is the best option where other fishery management objectives have failed. This makes EBFM important for the African inland lakes and fisheries resources that are among the most threatened in the world despite existing management interventions. Ecosystem modeling provides information that guides EBFM, and, to promote EBFMfor the African inland lakes and fisheries, we present strategies required to promote ecosystemmodeling. The strategies are based on an examination, presented herein, of (i) publication trends in literature applying two leading aquatic ecosystem modeling platforms, Ecopath with Ecosim (EwE) and Atlantis, on the African Great Lakes as representatives of African inland lakes and (ii) deficiencies in data eminent in ecosystem models existing on these lakes. The examination indicated that ecosystem modeling is inactive on the African Great Lakes, and there is limited local and regional capacity for ecosystem modeling with existing models predominantly led by foreign researchers and marred by data deficiencies. The implications of these observations for ecosystem modeling and EBFM for the African Great Lakes are discussed. The strategies required to promote ecosystem modeling include supporting short-term training workshops to equip local scientistswith basic skills for ecosystemmodeling,mainstreaming ecosystemmodeling in fisheries training curriculum of local universities, and conducting data collection surveys to fill data deficiencies. These are envisaged to increase capacity and activate ecosystem modeling, and consequently promote EBFM.
The role of gender in improving adaptation to climate change among small-scale fishers
(Climate and Development, 2017) Musinguzi, Laban; Natugonza, Vianny; Efitre, Jackson; Ogutu- Ohwayo, Richard
Climate change disproportionately affects marginalized groups, especially women. To guide the integration of gender roles in interventions to improve adaptation, we examined gender roles among fishers on Lake Wamala, Uganda, which has been increasingly affected by climate change. We found lower participation of women than men in preharvest and postharvest fishing activities, with 99% of fishers and 92.9% of fish processors and traders combined being men. The men had more fishing experience, started fishing at a younger age and exited at a later age, targeted more species, used more fishing gears and bought more fish for processing and trading. Although we observed diversification to non-fishery livelihoods, such as crop and livestock production to increase food security and income among others, income from these activities was not controlled or shared equally between men and women. Compared to men, women worked longer hours, engaging in more simultaneous activities both in and out of the home and reported less time resting. The income controlled by women was used directly to meet household needs. The implications of these differences for adaptation, what men and women can do best to enhance adaptation and how some adaptation practices and interventions can be implemented to benefit both men and women are discussed.
Simulating trade-offs between socio-economic and conservation objectives for Lake Victoria (East Africa) using multispecies, multifleet ecosystem models
(Fisheries Research, 2020) Natugonza, Vianny; Ainsworth, Cameron; Sturludóttir, Erla; Musinguzi, Laban
Most small scale inland fisheries worldwide are open access, and fishing provides the only source of employment and livelihood for the riparian communities. Management of these fisheries requires information on trade-offs between fish production, profits from fishing, employment, and conservation objectives. We use the non-linear optimization procedure in Ecopath with Ecosim (EwE) modelling package to determine long-term, gear-specific fishing effort that can maximize economic, social, and conservation objectives for Lake Victoria (East Africa). Then, the resulting “optimal fishing effort” levels are applied in both EwE and Atlantis models to simulate longterm changes in the ecosystem. Results show profit maximization to be more compatible with conservation objectives than is the maximization of catch (or employment). However, maximizing economic value, while maintaining ecosystem structure, would require a reduction in fishing effort of almost every fishing gear. This trade-off can be severe (high social cost) for fishing communities with limited alternative livelihoods. This study provides an understanding of relative risks and benefits of various management objectives, which will enable stakeholders and the public to conduct informed discussions on future management policies.
Using sediment fingerprinting to identify erosion hotspots in a sub-catchment of Lake Kivu, Rwanda
(Environmental Monitoring and Assessment, 2020) Akayezu, Providence; Musinguzi, Laban; Natugonza, Vianny; Ogutu-Ohwayo, Richard; Mwathe, Ken; Dutton, Christopher; Manyifika, Marc
Sedimentation of water bodies affects water quality and biotic communities of aquatic ecosystems. Understanding the causes and origin of sediments is crucial for planning watershed management activities and safeguarding aquatic biodiversity and critical ecosystem services. Rwanda, as a hilly country, experiences increased sedimentation due to unsustainable land use practices in upstream catchment areas which negatively affects irrigation, fishing and hydropower generation. We used a sediment fingerprinting technique to determine sources of sedimentation and identifying hotspots of soil erosion in Sebeya River Catchment (area of 357 km2), a subcatchment of Lake Kivu located in Northwest Rwanda. Five soil samples were collected from each of the six geological classes, and 34 suspended sediment samples were taken within key locations of the hydrological network in the catchment. X-Ray Spectrometry was used to determine the geochemical composition of suspended sediments and soil. A multi-step statistical procedure with a Bayesian mixing model was used to determine the contribution of each geologic group and sub-catchment to the suspended sediments in the river. Erosion hotspots were classified based on the underlying land use and their contribution to the suspended sediments. The resulting erosion hotspot map shows that about 70.9% of the Sebeya Catchment area contributes at least 50% of sediment load in the river and currently experiences unsustainable land use and land cover. The erosion hotspots identified and culpable factors should be used to guide best land use practices, prioritizing the areas with high contribution to the river sedimentation in Sebeya Catchment.

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