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The current fishing pressure in Lake Victoria, Tanzania indicates that the Nile perch (Lates niloticus) is overfished and no regulations are enforced to maintain a sustainable fishery despite its significant contribution to the economy. This study examines the determinants of Nile perch overfishing and its intensity in Lake Victoria, Tanzania, using a double-hurdle model that is based on baseline survey data collected from 268 Nile perch fishers. The model analysed the data in two sequential hurdles, the first hurdle being whether or not a Nile perch fisher overfished (probability of overfishing), and the second hurdle being the difference between the actual average catch size and the minimum slot size of 50 cm total length (TL) (intensity of overfishing). The study revealed that different socio-economic, institutional and fishing effort influence Nile perch overfishing and its intensity in Lake Victoria, Tanzania. This, therefore, suggests that, to attain a balance between sustainable fishery management and the livelihood for Nile perch fishers in Lake Victoria, there is a need for the government to design policies that will consider the dynamics of the institutional setup and fishing effort in this lake. [ABSTRACT FROM AUTHOR]

Abstract: The past subsistence of the Lake Victoria fishery was dominated by rich, diverse haplochromine cichlids. This multispecies fishery has undergone a decline over the past four decades, evolving into a commercial fishery consisting mainly of Nile perch (Lates niloticus), Nile tilapia (Oreochromis niloticus) and cyprinid (Rastrineobola argentea species). To better understand Lake Victoria fisheries, studies dating as far back as the 1920s have been carried out to assess the status of the fish stocks. These past studies indicated the lake fisheries were declining because of numerous major challenges, including intense fishing, invasive species, loss of biodiversity, ecological alterations, climate change, inadequate information to inform management and unharmonized policies. Numerous policies and regulations have been developed and implemented over the years to address these issues and manage the fisheries sustainably. Most of the interventions have been sectorial, disjointed and unharmonized and have not reduced the declining fish catch rates. With reestablishment of the East Africa Community (EAC) with several institutions in 1994, the Lake Victoria riparian states initiated an ecosystem approach to manage the Lake Victoria fishery resources in a sustainable manner. This study reviews the development of the Lake Victoria fisheries, outlines major past and present management challenges and provides a set of new strategies to manage the lake's fisheries resources, with emphasis on an ecosystem approach. [ABSTRACT FROM AUTHOR]

Beach seine gear is one of the prominent fishing gears in Nile Perch fishery. Before Nile Perch was introduced to the lake, beach seines the species targeted with beach seine were Tilapia, Bagrus, Haplochromis, Protopterus and Labeo. In 1994, beach seines were banned in Tanzania and by 2004, this particular regulation and others, were harmonized and applied to the entire Lake as a result of implementation of Regional Plan of Action to Prevent, Deter and Eliminate Illegal, Unreported and Unregulated Fishing on Lake Victoria. The paper describes research findings on how the Nile Perch (NP) beach seine fishery is organized in Lake Victoria, Tanzania. The paper is guided by the following research questions: How is the Fisheries Department in Tanzania trying to govern the fisheries of Lake Victoria? How the beach seine fishery is governed in reality? What are the drivers for its continuity despite the ban? What are the counter-tendencies at local level and how and why do they emerge? We argues that it is the markets and associated graft - that drives coordination between the beach seine fishery; and the networks that depend on individuals' network motivations - to get money, that together shape the fishery's management and governance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Lake Victoria, East Africa, supports a fishery that yields about one million tonnes per annum consisting predominantly of three species, Nile Perch(Lates niloticus), Nile Tilapia(Oreochromis niloticus)and a native sardine-like cyprinid called Dagaa(Rastrineobola argentea). The non-native Nile Perch is the most valuable of these species and supports an important commercial export industry; there are fears that overfishing, due to the growth of fishing capacity, is threatening the Nile Perch fishery. Based on its economic importance and the notion that overfishing is threatening the resource, the current fishery management system was developed to control fishing capacity and effort. This system, using the concepts of co-management, where fishing communities and stakeholders participate through community organizations called Beach Management Units (BMUs) to actively manage the fishery in partnership with the central government, has been criticized that it is “fishery-based,” focusing on a single species and taking no account of ecological conditions in the lake, nor other species. A more “holistic” approach, which places a greater emphasis on changing nutrient concentrations and primary productivity as drivers of fish populations, has been proposed. Though fishery biologists and managers on Lake Victoria recognize that ecological conditions affect fishery populations, there appears to be two major challenges hindering the implementation of such approaches: first, the lack of a coherent objective of the Lake Victoria fishery, and second, the challenges associated with incorporating and implementing concepts of nutrient information and multiple species into a practical fishery management program. This article describes the current fishery co-management program to determine the feasibility of implementing a holistic approach on Lake Victoria. It is concluded that whether a management system should be “holistic” or “fishery-based” is of little importance; what is needed on Lake Victoria are clear objectives and a management plan that will enable those objectives to be achieved, utilizing both ecological and fisheries data where appropriate. [ABSTRACT FROM AUTHOR]

Aquatic hypoxia can affect predator-prey interactions by altering the success rate of the predator and/or the vulnerability of prey. For example, in the Lake Victoria basin of East Africa, native prey exploit hypoxic wetlands as refugia from predation by introduced Nile perch ( Lates niloticus). Here, it is predicted that species exploitation of wetlands depends on their hypoxia tolerance relative to the heterogeneity of wetland hypoxia. In this study, we compared the hypoxia tolerance of four fish taxa that differ in their use of hypoxic wetlands in Lake Nabugabo, Uganda: the cichlid Pseudocrenilabrus multicolor victoriae that inhabits the dense swamp interior; and three taxa that inhabit wetland ecotones including Nile tilapia ( Oreochromis niloticus), L. niloticus and juvenile endemic haplochromine cichlids. We characterised hypoxia tolerance by exposing fish to progressive hypoxia and quantifying variation in aquatic surface respiration (ASR). The effect of body size on tolerance was explored in L. niloticus by quantifying ASR behaviour across a range of size classes. ASR behaviour was also compared between O. niloticus groups from wetland versus open-water habitats to detect habitat-associated intraspecific variation. The most tolerant taxon was the swamp specialist P. multicolor, indicated by its low ASR thresholds and small percentage of fish using ASR during the final sample interval. The other three taxa did not differ in ASR behaviour, and no differences were detected between O. niloticus groups. Body size effects were present for L. niloticus suggesting a lower tolerance to hypoxia in larger-bodied individuals, thus limiting their ability to penetrate wetlands. [ABSTRACT FROM AUTHOR]

Abstract: Results of estimation of target strength (TS) of physoclistous Nile perch using in situ TS measurements and deformed cylinder model (DCM) at 70 and 120kHz are presented. The results of the two methods are compared with those from cage experiments conducted between 1999 and 2000. Cage experiments that assumed the 20Log(L) relationship (TS=20Log(TL)−66.55) provided a good fit only over the length range of 18–38cm total length, but overestimated the length of large fish (>60cm TL). The DCM which lead towards a 30Log(L) provides more accurate conversion over the full length range of single targets. An in situ study that made no assumptions about the shape, structure or orientation of the fish provided a close fit of acoustically estimated length frequency distributions to net hauls with the equations: It is suggested that using this approach can provide valid TS to length relationships for acoustic surveys on species for which little information exists and there is little opportunity for direct observation of behavioural aspects that are known to affect TS such as tilt angle and vertical migration. [Copyright &y& Elsevier]

Nile Perch fishing in Lake Victoria is done using gillnets and long lines. These gears have been deployed in the lake indiscriminately to the extent that in early 2000s the species showed signs of over-fishing. To address this situation, a slot size of 50-85 cm total length (TL) was instituted by the partner states to protect immature fish, and large adults to replenish the stocks while at the same time harvesting mature individuals. Catch Assessment Surveys, have been conducted regularly by the partner states between July 2005 and December 2008 to generate data for setting policies, development planning, and management intervention. A study involving two-stage stratified sampling on the Tanzanian side of the lake showed that Nile Perch caught in the minimum legal 5' gillnets were immature by more than 80%. In contrast Nile Perch of ≥85 cm total length, targeted by long-lines, were seldom encountered to validate the upper limit of the slot size. We advise to abolish the upper slot size limit and introduce a lower legal limit of 7' for gillnets. [ABSTRACT FROM AUTHOR]

A fundamental feature of the Anthropocene is the inexorable erosion of the self-repairing capacity or adaptive renewal of natural systems because of natural perturbation, exploitation, or management failure. The concept of resilience offers a systematic framework for understanding the dynamics and variables that govern response dynamics of ecosystems. Resilience of haplochromine cichlids is assessed using limnological and biodiversity changes in Lake Victoria, the world's second largest freshwater lake, over the last five decades. The review explores the resurgence of the haplochromine cichlids using Holling's adaptive renewal cycle and attempts to illustrate how resilience-based management approaches might learn from an inadvertent management experiment. The introduction in the 1980s of the Nile perch (Lates niloticus), a fecund and voracious predator of the endemic phytoplankton feeding haplochromine cichlids, anthropogenic eutrophication, and deep water hypoxia have combined in a synergistic way to increase the vulnerability of the lake ecosystem to perturbations that were hitherto absorbed. However, the upsurge in commercial Nile perch fishing appears to be enabling the resurgence of the haplochromine cichlids. The resurgence of haplochromine cichlids is characterized by phenotypic plasticity, ecological and life history traits and demonstrates the critical role of response diversity in the maintenance of systems resilience. Resilience of the haplochromine cichlids resides in the requisite functional response diversity and habitat diversity that provide the resources for renewal and regeneration. This paper concludes that management of Nile perch fisheries and control of nutrient loading into Lake Victoria could halt or reverse eutrophication, hence offer the best promise for a diverse, productive, and resilient social-ecological system. [ABSTRACT FROM AUTHOR]

The determination of the history and causes of recent eutrophication and intensified thermal stratification in Lake Victoria is still hampered by the sparsity of paleolimnologic coverage of the enormous lake. Five new diatom records from Ugandan waters now show that a transition from Aulacoseira-dominated planktonic assemblages to those dominated by long Nitzschia spp., occurred in northern coastal sites from the mid-1970s to mid-1980s. Similar transitions developed from the late 1960s to early 1970s offshore and from the 1940s to early 1950s along the Kenyan coast, suggesting a time-transgressive process. These changes are not readily attributable to the trophic effects of Nile perch population growth during the early 1980s, but more likely reflect responses to long-term nutrient enrichment and climatic instability in the region. The diversity of planktonic diatom communities has declined dramatically, and a namesake variety of Aulacoseira nyassensis may now be nearly extirpated. Although local phytoplankton communities varied considerably in the past, the current domination of diatom assemblages by Nitzschia is apparently unprecedented in the 15,000-year history of Lake Victoria. [ABSTRACT FROM AUTHOR]

Nile tilapia, Oreochromis niloticus and Nile perch, Lates niloticus were introduced into Lake Victoria in the 1950s and 1960s. The former was to boost the then declining tilapiine fishery, while the latter was to convert the abundant bony haplochromines to fish flesh. Fish samples were collected by bottom trawling from 1998 to 2000 and in 2004 to 2005 from the Kenya waters of Lake Victoria. The goal was to evaluate the current population characteristics and ecology of the species. Length frequency distribution and size at maturity of Nile tilapia depicted a stable population with high proportions (30%) of mature fish, unlike Nile perch where more than 98% of the individuals were immature. Nile tilapia previously distributed in < 10 m, were caught in areas up to 20 m depth. Catches of Nile tilapia have increased from < 1% in 1970-80s to > 25% in 2005; while Nile perch declined from 95% in 1990s to 58% in 2005. The increase in Nile tilapia catches and its spread into deeper waters is attributed to declining stocks of the predatory Nile perch, availability of suitable food and the species occupying vacant niches left by declining stocks of indigenous species, especially the haplochromines. Increase of anoxic conditions in the lake is also precluding Nile perch thereby affording tilapia refuge. The previously herbivorous tilapia has diversified its diet to include insects and fish. All these factors could be contributing to an increase in Nile tilapia biomass in the lake. If management measures to reduce Nile perch exploitation and its rapid decline are not instituted, the next important demersal commercial fishery in Lake Victoria will probably be Nile tilapia. The establishment of Nile tilapia will be replacing a multimillion-dollar export industry of Nile perch, which will have several economic consequences. However, biodiversity in the lake is expected to increase and thus so will the availability of protein to local communities. [ABSTRACT FROM AUTHOR]

Inland fishery ecosystems in Africa are characterized by patterns of overexploitation, environmental degradation and exotic species introductions. Ecological complexity and diversity of aquatic habitats dictate that fishes in general are not evenly distributed in a water body. However, fisheries management regimes tend to ignore this basic principle, assume generalized conditions in a water body, and focus more on ‘desired’ objectives such as maximizing catch. The result is to disregard fish habitat boundaries and anthropogenic influences from the catchment that influence fish production. Overexploitation and environmental degradation disrupt sustainable socioeconomic benefits from the fisheries, create uncertainty among investors, but leave some managers calling for more information with the expectation that the fisheries will recover with time. Open access to the fisheries and full control of fishing effort remain challenges for managers. Exotic species introductions and fish farming can increase production, but such interventions require firm commitment to sound ecological principles and strict enforcement of recommended conservation and co-management measures in capture fisheries. The general tendency to downplay fishing effort issues, other ecosystem values and functions or rely on temperate fisheries models until a new cycle of overexploitation emerges, characterizes many management patterns in inland fisheries. Aquaculture is not an option to challenges in capture fisheries management. Aquaculture should be developed to increase fish production but even this practice may have negative environmental impacts depending on practice and scale. Decades of information on Lake Victoria fisheries trends and aquaculture development did not stop the collapse of native fisheries. The successfully introduced Nile perch ( Lates niloticus) has shown signs of overexploitation and aquaculture has again been considered as the option. By reviewing significant trends associated with Nile perch and its feasibility in aquaculture this paper uses Lake Victoria to illustrate ‘special interest management’ targeting selected species of fish rather than the fisheries. [ABSTRACT FROM AUTHOR]

The article discusses the environmental state and the management of the Nile Perch Fishery on lake Victoria. Lake Victoria, shared by Kenya, Uganda and Tanzania, is the world's second largest freshwater lake. The Nile Perch was introduced into the lake in the 1950s and its population exploded in the late l970s. Predation by this expanding population was the main cause of the extinction or near extinction of an estimated 300 fish species. The Nile Perch is a large, white, meaty fish which finds a ready international market. The Tanzanian State faces a complex policy environment as it seeks ways to manage the new fishery. Agencies responsible for economic growth and structural adjustment encourage the fish export industry. The agencies responsible for fisheries research and management, however, are more immediately affected by a second kind of globalization: an intense interest in the lake from international scientific, environmental and development groups. Fisheries management on Lake Victoria is an interesting case study of the environmental state. Resource management and conservation in Africa is central to the problem of structural adjustment because pressures to increase exports fall most heavily on agriculture and natural resources. The Lake Victoria case addresses several questions in the debate between conceptualizing the environmental state as the coordinator of the treadmill of production and the more recent idea of an ecological modernization that seeks to bring "human interaction with the subsistence base under rational ecological control."