The fisheries of Lake Victoria have undergone very substantial changes in recent decades, owing to a number of factors. These include environmental variations, increased fishing intensity, and stresses arising from the implantation of exotic species (Ssentongo and Welcomme 1985). In relation to the latter, rapid proliferation of the introduced predatory fish Lates niloticus, the Nile perch, has had most dramatic consequences and has occasioned much concern and comment.
Lake Victoria (map, Fig. 1.1, Appendix A) historically has hosted a lively multiple species fishery exploited mainly by artisanal, small-scale fishermen using an assortment of techniques, but depending heavily on canoes and gillnets. Past surveys showed huge concentrations of Haplochromis species stocks. In the 1960s and 1970s, they constituted an estimated 80% of the Lake's fish biomass (FAO 1973). But these small cichlids remained relatively underfished by lakeshore communities (CIFA, 1982). The tilapiine cichlids, on the other hand, have always been highly relished, and have therefore been principal targets for subsistence and commercial exploitation. The enduring popularity of the “tilapias” over the years is reflected in their consistent high market value and the consequent overfishing pressure to which they have been regularly subjected (CIFA, 1982; Mann 1970; Ogutu-Ohwayo 1988). Along with the endemic tilapiine stocks of Oreochromis variabilis (=Tilapia variabilis) and the much favoured and exploited O. esculentus, the Lake since the 1950s contains exotic O. niloticus - a species that has apparently thrived well - and, of less common occurrence in the catches, O. leucostictus, Tilapia zillii, and T. rendalli.
Other species groups which have supported fisheries of regular or intermittent significance in the past include Bagrus, Clarias, Rastrineobola (=Engraulicypris), Protopterus, Mormyrus, Synodontis, and the anadromous Labeo, Schilbe, Alestes, and Barbus (see list of common and local names in Table 1.1, Appendix A).
The relative importance of most of these species groups in the total Lake Victoria catch tonnages as of 1975 is shown in Tables 1.2 and 1.3. It can be seen that the tilapiine and haplochromine cichlids figure prominently in the catches (46.5% total: “tilapias” 17.3%, haplochromines 29.2%).
The tables also provide indications of how drastically the picture has changed in recent years, with the rapid upsurge in catches of Nile perch. From a trace occurrence in the catches of 1975 (0.4%), Lates comprised 4% of all catches by 1979 (the last year for which figures are available for Uganda), and almost half of the total tonnage reported (Kenya and Tanzania only) for 1985.
Over the same ten year period, moderate to severe proportional declines are registered for nearly all other species groups, though actual tonnages have in some cases remained high or increased. A notable development is the R. argentea or dagaa fishery, which has shown remarkable growth.
Haplochromis stocks appear to have been particularly depleted. While no comprehensive stock assessments have been carried out in the Lake since the early 1970s (Kudhongania and Cordone 1974, 1974a), recent surveys across more limited areas confirm the general picture conveyed by the production statistics -- that is, of serious declines in the haplochromine population especially, and in several other species groups as well (Ogutu-Ohwayo 1985, 1988; Okaronon, Acere, and Ocenodongo 1985; Goudswaard 1987).
Controversy over the role of Lates in Lake Victoria has intensified with its proliferation across ever wider areas from the first points of introduction in Uganda waters during the late 1950s and early 1960s. Lines of argument are not always clearly demarcated, but generally observer opinion can be divided into two camps. On the one hand are those who censure the presence of the exotic predator in the Lake, and on the other are those who regard Nile perch as a positive development, or at least not as a wholesale disaster.
Points of debate in the ongoing controversy are more fully reviewed in Appendix B. References to the considerable body of literature and press accounts that has been generated over the past few decades are cited in Appendix C and Appendix D. In summary, the controversy bears on the following issues:
ecological disruption caused by the depredations of Nile perch on endemic fish species flocks;
the loss of crucial subsistence and commercial resources for lakeshore communities;
resentment towards Nile perch by local people;
adverse social and environmental impacts due to local processing methods used on Nile perch; and
the general economic displacement of artisanal fishermen and petty traders occasioned by the Nile perch presence.
These issues will be addressed in greater detail in the conclusion, after mission findings are presented in the three country review sections.
During the Fourth Session of the CIFA Sub-Committee for the Development and Management of the Fisheries of Lake Victoria (Kisumu, Kenya, 6–10 April 1987), much attention was given to various aspects of what can be called “The Nile Perch Question.” This is reflected in the Fourth Session Report (CIFA 1988), relevant sections of which read as follows:
23. While considerable attention has focused on biological and technical issues related to the rapid spread of Lates in Lake Victoria, socio-economic aspects of the situation have been relatively neglected. Past observation of human welfare impacts and potentialities largely have been based on indirect and informal evidence rather than thorough study and documentation. It is recognised therefore that a pressing need exists for information on the Nile perch fishery with reference to its current and possible future effects upon local and regional communities. Such information would provide a sound foundation for practical development initiatives.
24. The Sub-Committee noted the lack of knowledge of socio-economic implications of recent changes in the lake fisheries and recommended that a project be prepared to carry out studies to resolve this.
48. The Sub-Committee expressed its concern as to the often alarmist and ill-informed articles that have appeared in the popular and scientific press as to the effects of Nile perch on the fish and fisheries of the lake. At present it is far too early to express a definite opinion as the eventual balance which will emerge between the advantages and disadvantages of this introduction. However, from the evidence presented at this meeting there are now indications that adjustments are being made both by the fish community and the fishermen.
This report is the result of a first urgent assessment of the situation, organised by the Fishery Policy and Planning Service (FIPP) of the Fisheries Department of FAO under its Regular Programme activities, prior to developing and negotiating more detailed proposals for follow-up project activities. The conclusions and recommendations of this assessment are submitted for immediate consideration by the Governments managing the rapidly evolving fisheries of Lake Victoria.
Given the limited duration of the field visits (see below), it was not possible to cover a wide range of fishing communities or markets around the Lake within each of the three states. Nor was there opportunity to organise systematic sample surveys of the various categories of people involved in the fisheries. Instead, information was collected through direct observation of activities at landing sites and markets, and through discussion with fishing operators, boat and gear owners, boatbuilders, traders, government fish scouts and beach enumerators, market masters, and various local residents.
In addition, contacts were made with Kenya, Tanzania, and Uganda Government officials, including staff of the Fisheries Departments and representatives of research and training institutes concerned with Lake Victoria fisheries in each country. Statistical records and other documentary material were also reviewed wherever they could be obtained.
There was considerable variation between the countries in terms of quantity and quality of background material available. Thus, various aspects of the Lake fisheries cannot be examined at the same levels of detail for all three countries. Information on Uganda was particularly weak in many respects due to the unsettled circumstances that have existed there in recent years.
Assessment of the Tanzania part of the Lake was conducted over a two-week period in August 1987 (Reynolds and Greboval), and of the Kenya part over a similar period in August-September 1987 (Reynolds). The report on Uganda is based on a series of three brief visits during February, July and October-November 1987 (Greboval). In addition to the formal visits, the authors have drawn on their wider experiences derived from work and residence in the three countries.