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.

The transformation of Lake Victoria that began in 1980 followed the population explosion of Nile perch Lates niloticus, causing the apparent extirpation of 500+ endemic haplochromine species and dramatic physico-chemical changes. Officially introduced in 1962-1963, but present earlier, the reasons for the long delay before its population exploded are discussed. The hypothesis that it occurred only after the haplochromine decline is evaluated, but haplochromines declined only after the Nile perch expansion began. The sudden eutrophication of the lake was attributed to Nile perch, but evidence of eutrophication from 1950 onwards led some researchers to conclude that it was the result of climatic changes. We conclude that the haplochromine destruction disrupted the complex food webs that existed prior to the upsurge of Nile perch. The depletion of fish biomass by Nile perch may have been the source of extra phosphorus responsible for the eutrophication of the lake. After the Nile perch explosion in 1980 the fish population came to be dominated by only three species, but fisheries productivity increased at least 10-fold. Fishing has caused demographic changes in Nile perch, which may have allowed some haplochromine species to recover. The condition of the lake appears to have stabilised since 2000, partly because the fish biomass has risen to at least 2 × 10 6 t, replacing the 'lost' biomass and restoring some ecosystem functioning.

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The distribution and densities of three pelagic fish taxa (Nile Perch, Lates niloticus, Rastrineobola argentea [Dagaa], and the haplochromine cichlids) in Lake Victoria were estimated through 17 lake-wide acoustic surveys conducted in two series (August 1999–August 2002 and August 2005–September 2011). Nile Perch densities were estimated through echo-counting, while Dagaa and haplochromines by echo-integration. Mixed generalized linear model estimates indicated up to 30% decline in Nile Perch densities in the deep and coastal areas and up to 65% reduction in the shallow inshore areas over the study period. There was a twofold increase in Dagaa densities and a 10% increase in haplochromines. The distribution and densities of these species were influenced by season, stratum and year of survey. In addition to fish exhibiting seasonal clustering in the upper layers of the water column, they also appeared to spread to shallow inshore waters. The Nyanza, Speke, and Emin Pasha Gulfs demonstrated diverse spatial stock oscillations in abundance, and distribution which call for a need to include area disaggregated considerations in stochastic models when predicting dynamics of fish stocks.

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Fishers' perceptions on the state of fisheries and the applicable fisheries management system in Lake Victoria (LV), Uganda, were assessed. Fisheries management in the lake is currently at a crossroads. The government abolished a co-management system in November 2015 and installed the military to temporary enforce management. The objective of this study was to explore how fishers envisage future management options by assessing past management regimes and analysing perceptions of alternative regimes. A total of 273 semi-structured interviews at six selected landing sites on LV in Uganda were conducted. Fishers targeted two dominant species, Nile perch, Lates niloticus (L.), mainly on motorised vessels representing the commercial fishers and dagaa, Rastrineobola argentea (Pellegrin), using both motorised and paddled vessels. The dominance of motorised fishing vessels depicted a consequence of the army operations and represents government priority to protect rather than regulate commercial fishing operations. Fishers mainly perceived regulations they knew about as effective, strongly opposed local governments as a management entity and assigned management to fisher groups as expected. The results support a management regime of key resource users organised by common interest groups to participate in decisionmaking and combined government structures to regulate and enforce sustainable fisheries measures.

Biomass of the schooling fish Rastrineobola argentea (dagaa) is presently estimated in Lake Victoria by acoustic survey following the simple “rule” that dagaa is the source of most echo energy returned from the top third of the water column. Dagaa have, however, been caught in the bottom two-thirds, and other species occur towards the surface: a more robust discrimination technique is required. We explored the utility of a school-based random forest (RF) classifier applied to 120 kHz data from a lake-wide survey. Dagaa schools were first identified manually using expert opinion informed by fishing. These schools contained a lake-wide biomass of 0.68 million tonnes (MT). Only 43.4% of identified dagaa schools occurred in the top third of the water column, and 37.3% of all schools in the bottom two-thirds were classified as dagaa. School metrics (e.g. length, echo energy) for 49 081 manually classified dagaa and non-dagaa schools were used to build an RF school classifier. The best RF model had a classification test accuracy of 85.4%, driven largely by school length, and yielded a biomass of 0.71 MT, only c. 4% different from the manual estimate. The RF classifier offers an efficient method to generate a consistent dagaa biomass time series.