APPENDIX A
LIST OF DELEGATES AND OBSERVERS

Delegates

Kenya

Odero, N.
Director of Fisheries, P.O. Box 58187, Nairobi

Ogari, J.J.
Senior Research Officer KMFRI, Box 1881, Kisumu

Yongo, O.E.
Research Officer KMFRI, Box 1881, Kisumu

Ochumba, P.B.O.
Senior Research Officer, KMFRI, Box 1881, Kisumu

Oduor, B.W.
Assistant Director of Fisheries, Western Kenya, Box 1084, Kisumu

Arap-Sige, A.K.
Under Secretary Min of Regional Development, Box 62820, Nairobi

Tanzania

Sichone, W.A.M.
Director of Fisheries, Box 2462, Dar-es-Salaam

Uganda

Kanyike, E.S.
Commissioner for Fisheries, Box 4, Entebbe

Kudhongania, A.W.
Director of Research, UFFRO, Box 343, Jinja

Orach-Meza, F.L.
Deputy Commissioner for Fisheries, Box 4, Entebbe

Ocenodongo, D.L.
Deputy Director of Research, UFFRO, Box 343, Jinja

Kateme-Kassaja, E.
Agricultural Economist, Min. of Planning and Economic Development,
P.O. Box 7086, Kampala
Kirema-Mukasa, C.T
Fisheries Officer, Box 4, Entebbe

Bugenyi, F.W.B.
Asst. Director of Research, UFFRO, Box 343, Jinja

Twongo, T.
Asst. Director of Research, UFFRO, Box 343, Jinja

Okaronon, J.O.
Asst. Director of Research, UFFRO, Box 343, Jinja

Balirwa, J.S.
Senior Principal Research Officer, Box 343, Jinja

Wanda Masifwa, F.
Research Officer, UFFRO, Box 343, Jinja

Mwaka, C.A.
Principal Asst. Secretary, Box 102, Entebbe

Wandera, S.B.
Research Officer, UFFRO, Box 343, Jinja

Mbahinzireki, F.
Senior Principal Research Officer, Box 343, Jinja

Ondongkara, O.K.
Economist, UFFRO, Box 343, Jinja

Ogutu-Ohwayo, R.
Senior Principal Research Officer, Box 343, Jinja

Olowo, J.P.
Research Officer, UFFRO, Box 343, Jinja

Kawesi, J.
Economist, Planning Unit, Box 102, Entebbe

Echaat, J.
Environment Officer, Dept. of Environment, Kampala

Muganda-Guma, P.
Foreign Affairs, P.O. Box 7048, Kampala

Mwebaza-Ndawula, L.
Senior Principal Research Officer, Box 343, Jinja

Observers

The Netherlands

Roest, F.C.
International Agriculture Centre, Box 88, 6700 AB Wageningen

Burundi

Kiyuku, A.
Director of Fisheries, B.P. 631, Bujumbura

UFFRO, Jinja

Basasibwaki, P.
Asst. Director of Research

Namulemo, G.
Research Officer

Twinomujuni, E.
Research Officer

Amiina, B.
Laboratory Technician

Mugume, F.
Laboratory Technician

Nyonyintono, P.
Laboratory Technician

Serikanda, B.S.
Research Officer

Mwanja, W.
Research Officer

Kamanyi, J.
Senior Principal Research Officer

Kibwika, D.
Fisheries Officer

Malyonga G.
Laboratory Assistant

Akumu Kabali, J.
Research Officer

Kigundu, V.
Laboratory Technician

Twongo, E.
Laboratory Technician

Magumba, K.M.
Principal Lab. Technician

Were, J.
Senior Laboratory Technician

United Kingdom

Pitcher Tony
Renewable Resources Asessment Group (RRAG), Imperial College, London

Bundy, A.
Renewable Resources Assessment Group (RRAG), Imperial College, London

U.S.A.

Baskin, Y.
Science Writer Biomass, California, USA.

Uganda Fisheries Department

Etot, J.P.
Senior Fisheries Officer, Box 972, Jinja

IFIP Project

Gréboval, D.
Co-ordinator FAO/IFIP Project, B.P. 1250, Bujumbura

Ssentongo, G.W.
Fisheries Biologist, FAO/IFIP Project, B.P. 1250, Bujumbura

Dunn, I.
FAO/IFIP Project Consultant, c/o B.P. 1250, Bujumbura

FAO Secretariat

West, W.Q.B.
Senior Regional Fisheries Officer, RAFR, Box 1628,
Accra, Ghana

Kapetsky, J.
Technical Secretary (acting for R. Welcomme)
Senior Fishery Resources Officer,
FAO/FIRI, Rome

Host Government

Dhatemwa, C.M.
Chairman Liaison Committee

Mwene-Beyanga, P.
Deputy Chairman Liaison Committee

Balirwa, F.K.
Personal Secretary

Lugolobi F.
Secretary

Isabirye, B.
Logistics Assistant

APPENDIX B
AGENDA AND TIME TABLE

Agenda item

1. Opening of the Session

2. Adoption of the Agenda

3. Election of the Chairman, Vice-Chairman and Rapporteur

4. Status of Fisheries on Lake Victoria

5. Status of the Environment

6. Aquaculture in the Lake Basin

7. Marketing of Fish from the Lake

8. Priorities for Action

   1. Research

   2. Management

9. Any other matters

10. Date and place of next meeting

11. Adoption of the report

TIME TABLE:

MONDAY 10TH FEBRUARY 1992:

Opening of the Session.

Adoption of the Agenda.

Election of the Chairman, Vice-Chairman and Rapporteur.

STATUS OF FISHERIES ON LAKE VICTORIA

Status of fisheries of Lake Victoria, Kenya sector.
By A. Asila and J. Ogari. (Kenya).

Present status of the Ugandan sector of Lake Victoria fisheries.
By F.L. Orach-Meza.

The changing fisheries of Lake Victoria, Uganda.
By J.O. Okaronon, (Uganda).

The food of surviving predators in Lakes Victoria, Kyoga and Nabugabo. J. Olowo. (Uganda).

Importance of stability in prey supply to the stocks of the Nile perch in Lakes Victoria, Kyoga and Nabugabo. R. Ogutu-Ohwayo (Uganda).

The effects of Nile perch predation and human exploitation on the population structure of Rastrineobola argentea in Lakes Victoria, Kyoga and Nabugabo. By S.B. Wandera (Uganda).

Gear and mesh size selection in the Nile perch (Lates niloticus L.) fishery from the Winan Gulf of Lake Victoria. By J.O. Manyala and C.O. Rabuor. (Kenya).

The population structure of the Nile tilapia (Oreochromis niloticus L.) in Lakes Victoria, Kyoga and Nabugabo. By J.S. Balirwa. (Uganda).

The impact of fishing gears and methods on the fisheries of Lakes Victoria, Kyoga and Nabugabo with specific recommendations on management of the fisheries. By R. Ogutu-Ohwayo, T. Twongo, S.B. Wandera & J.S. Balirwa. (Uganda).

Discussion & Close

TUESDAY 11TH FEBRUARY 1992

STATUS OF THE ENVIRONMENT

The effects of limnological factors and the changing environment on the fisheries of northern Lake Victoria. By F.W. Bugenyi. (Uganda).

The status of Lake Victoria environment. By P.B.O. Ochumba. (Kenya).

Discussions

The potential for further proliferation of water hyacinth in Lakes Victoria and Kyoga and some urgent aspects for research. By T. Twongo Bugenyi (Uganda).

Discussions

Observations on the zooplankton community of the Northern part of Lake Victoria. By L. Mwebaza-Ndawula. (Uganda).

Distribution and abundance of two dipteran aquatic larvae in Northern Lake Victoria. By G.B. Mbahinzireki. (Uganda).

Discussions

AQUACULTURE IN THE LAKE BASIN

Aquaculture in Lake Victoria Basin - The Uganda Sector. By E.S. Kanyike. (Uganda).

Aquaculture in Kenya and the Lake Basin. By B.W. Oduor (Kenya).

MARKETING OF FISH FROM THE LAKE VICTORIA

Marketing options for Lake Victoria fishermen. By E. Yongo. (Kenya).

Present aspects of marketing fish from Lake Victoria, Uganda. By C.T. Kirema-Mukasa & C.M. Dhatema. (Uganda).

The implications of the changing fishing pattern on Lake Victoria, Uganda, for fish marketing development. By O.K. Odongkara. (Uganda).

Discussions

WEDNESDAY 12TH FEBRUARY 1992

Priorities for action.

Activities undertaken by the FAO/UNDP IFIP project (D. Greboval).

Management measures (G. Ssentongo).

Establishment of a Lake Victoria Fisheries Commission (W. Sichone, in the capacity of an FAO/IFIP consultant).

Discussion

Venue and date of the next meeting.

Research Priorities and Management. By A.W. Kudhongania. (Uganda).

Tour of UFFRO and fish processing plants.

THURSDAY 13TH FEBRUARY 1992

ADOPTION OF THE REPORT

CLOSING CEREMONY

Reception

APPENDIX C
MAIN PAPERS AND ABSTRACTS OF OTHER PAPERS PRESENTED¹

STATUS OF FISHERIES OF LAKE VICTORIA
KENYA SECTOR

James Ogari and Andrew Asila
K.M.F.R.I.,
P.O. Box 1881,
Kisumu (Kenya)

¹ Authors of papers were invited to provide an abstract of their paper for inclusion in this report, however, replies were not received from all of them.

INTRODUCTION

Fish stocks of Lake Victoria have had a spectra of changes within the last 40 years initiated by a variety of factors.

Distributions which have been more conspicuous in the Lake Victoria ecosystem are:

• intensive non-selective fishing methods
• modification of the vegetation
• progressive formation of physico-chemical changes in the lake

• Nile perch invasion and introduction of other species.

Despite these disruptions the volume of catch has continued to rise in the last decade making Lake Victoria the most important aquatic protein source in East Africa. Incorporated with the rise in catch are a chain of management problems some of which need streamlining for rational harvest to take place. Okemwa (1991) proposed that the management issues in Lake Victoria are:

1. reduction of conflicts;
2. minimising over-capacity and economic waste;

3. reducing threats of over-fishing.

Ogutu-Ohwayo (1990) contends that the main changes in the fishery have been stimulated by six factors: improved communication links, increased demand for fish, influx of migrant fishermen, introduction of seine nets along the lake margins which have destroyed breeding nests and disrupted courtship of cichlids, introduction of gillnets at the mouths of rivers, and uncontrolled fishing, integrated with ill-conceived fishing practices.

Ochumba et al., (in press) observed that the decline of haplochromine and tilapiine fishes resulted in not only a reduction in their contribution in commercial catches, but also a disruption of trophic dynamics in the lake ecosystem (since these fishes were consumers of the dominant bloom forming algae and detritus) and their high feeding capacity prevented water quality deterioration, detritus accumulation in deep layers and consequently followed by enhancement of anoxia. The authors summarize the changes which are evidence towards eutrophic status of the lake as:

1. importation of contaminants by inflowing waters which accumulate in the ecosystem by increasing concentrations in the lake waters, in sediments in the biota;
2. substantial increases in chlorophyll, primary productivity and decreases in silica concentrations;
3. sulphate concentrations are lowest in the lake;
4. a shift in phytoplankton community towards nitrogen fixing;

5. zooplankton community is presently dominated by small bodied species of copepods and cladocerans with low densities.

Bugenyi and Magumba (1990) indicated that silica has reduced by a factor of ten in the lake; they further propose that a remineralisation from dissolved organic compounds may be an important source of nutrients to support algal productivity.

Balirwa (1990) observed that the Nile tilapia in Lake Victoria has an omnivorous diet and wider ecological tolerance. The author further remarked that the trophic characteristics of Oreochromis niloticus at present may be a reflection of ecological changes that have occurred in the lake. The abundance of O. niloticus is attributed to the decline in the trophic groups of haplochromines. The decline in catch of the indigenous species, mainly the potamodromous species, might be a combination of fishing practices, environmental and ecological changes which have taken place in Lake Victoria.

This paper reports on the recent state, and the likely reason for the changes of stocks in Lake Victoria fishery with regard to dietary, reproduction and distribution patterns. The paper concludes by proposing a couple of management guidelines.

Changes in diet

Anon, (1988) reported the major effect of Nile perch in Lake Victoria were the predation on other cherished fish species, competition for food with the other species and disruption on the food chain through predation of phytoplanktivores and detritus feeders leading to non-utilization of that particular food chain. It was further noted that Nile perch has been shifting from one food item to another (Anon, 1988; Asila and Ogari, 1988) due to its rational energy budget, Lates has been feeding on Rastrineobola argentea in shallower waters and Caridina nilotica in deeper waters around the entry to the Gulf and a mixture of Rastrineobola, haplochromines and Caridina in the mid gulf. Cannibalism has been one of the major factors in shallower depths.

Changing diet by depth in Lates niloticus might be a direct result of decreasing food (prey) variety in shallower depths and the advancement of the anoxic waters into the gulf which restricts Nile perch through stress to a limited hunting field.

Rastrineobola has been reported to feed on zooplanktons and insects in their pelagic habitat. Increasing yield of Rastrineobola in commercial catches might be interrelated with the decreasing biomass of haplochromine zooplanktivores due to the abundance of zooplankton previously exploited by zooplanktivores. One other reason for the increase in Rastrineobola yield could be increase in the effort (number of nets) in its fishery in order to tap more revenue being undertaken by the fishermen. The same view is held for O. niloticus. The latter was reported to be predominantly herbivorous (Trewavas, 1983).

Gophen et al., (in press) noted decrease in the mean sizes of zooplanktons in Lake Victoria and a reduction in the availability of preferred food has led to a reduction in the availability of preferred food has led to a reduction in the condition factor of the predator (Nile perch) and an increase in cannibalism. Recent results from Kenya waters suggest there has been significant changes in the condition factor for various size groups of Lates in the Kenya sector of Lake Victoria (Table I).

Recent observations suggest that O. niloticus is omnivorous (Getabu, 1988, Balirwa, 1990). Abundance of O. niloticus in the lake is attributed to its body shape, wider ecological tolerance, omnivorous diet and decline in the trophic groups of haplochromines. Opinions advanced for its abundance over the endemic tilapiines suggest that adaptability could be a result of hybridization with the endemic species, competition for same food resources, large size, faster growth rate, high fecundity, longer life span, a wider food spectrum and less habitat restricted (Ogutu-Ohwayo, 1990), Ogari and Omondi (1990) studied the food of Potamodromous species (esp. Schilbe) in River Nyando and generally observed that the diet of most of the species has not changed significantly. The species are insectivore (facultative feeder) as reported by Lowe-McConnell (1977) whose work was concentrated in the lake. The major genus was choronomid larvae.

Changes in reproduction

Reproductive capacity of Lates niloticus has been reported by Asila and Ogari (1988). Mature fish have been noted to be available throughout the year and the smallest mature Nile perch has been observed at much lower sizes than previously reported (Asila, 1991). Ligtvoet (1989) reported a fecundity length ratio of Nile perch at F = 19.23L 2.733L total length (in cm). Fifty percent maturity seems to have decreased recently to 55 cm TL for males and 70 cm TL for females (Asila, 1991) respectively, (Asila and Ogari, 1988) while Ligtvoet (1989) reported 60cm TL and 96cm TL for males and females, respectively, for southern waters of Lake Victoria.

Recent observations give the length at first maturity for Oreochromis niloticus at 22.3 TL for males and 23.7 cm TL for females while 50% maturity for males at 27.5 cm and 31.5 cm TL for females. No study has been undertaken on the reproductive biology of Rastrineobola argentea in Kenya waters.

Changes in the distribution patterns and fisheries

Biomass has been decreasing (Table III) from 54.67 kg ha^-1 to 32.30 kg ha^-1 1982/83 with the important fishery also shifting from Haplochromis to Lates. Because of the predatory role of Lates, the biomass of the other species has been suppressed greatly with the other species accounting for 2.92 kg ha^-1 compared to 32.70 kg ha^-1 for Lates. O. niloticus, also an introduced species, accounted for a biomass of 1.7 kg ha^-1 in 1990/91.

Available species from the most recent trawl survey data are Lates niloticus, Rastrineobola argentea, Oreochromis niloticus, Haplochromis sp., Schilbe mystus, Barbus sp., and Clarias gariepinus. Lates forms 90% by weight from bottom trawl catches followed by Oreochromis niloticus. Lates is present in most stations sampled as opposed to O. niloticus which was available at shallower depths only (up to 10 m). Species diversity has been decreasing in the bottom trawl survey hauls and there has been a decrease on the ichthyomass within the Nyanza Gulf.

Northern beaches have constantly provided 80% of the sampled weights. Landings have been increasing in magnitude, though the overall percentage contribution by each sector has been constant (Table II); Lates accounted for 57.6% of the yield and tilapiines accounting for 2.3% while the other species account for 1.1% of the yield from sampled beaches for 1991.

There has been an increase in the volume of catch from 1988 although a constant percentage from different sectors between 1989 and 1991. Surveys of Dunga beach in Kisumu reveal a shift from 8 in (203 mm) to 6 in (152 mm) in the gillnet fishery and a shift from hook sizes 6–7 into 8–9 in the longline fishery suggesting that the fishermen have further reduced the mesh and hook sizes in order to obtain their desired catch. Oreochromis niloticus was noted to be more frequent in the smaller meshes.

Casual interviews with a handful of fishermen reveal that a good number of them are now moving out of open waters (outside the gulf) into the Nyanza Gulf because of low catches realized in those areas.

Consequences on the fishery

The effect of Lates niloticus on the other species has been striking. Species diversity is already tending towards scarcity through predation and competition over the same food resources (haplochromines, Bagrus, Clarias, Schilbe). Massive algal blooms reported by Kibaara and Ochumba (1985) can be largely attributed to Nile perch besides agricultural contributions.

While attempting to catch for the small bodied riverine species fishermen have been using small meshed nets which have been destructive to the juvelines of Lates niloticus and Oreochromis as well as gravid riverine species partly accounting for their decline.

Catches of Lates and Rastrineobola are on the upsurge while Lates is shifting to Rastrineobola as the main prey in shallow water posing a question on the future of Rastrineobola fishery in Lake Victoria. Caridina nilotica which is important as Nile perch prey is being harvested for commercial purposes by fishermen. There is doubt whether the Caridina nilotica will sustain the twin stress both from predation and fishing. Advancement of the anoxic waters might eliminate bottom trawling and further affect the distribution of plankton from the benthos. Explosion of Rastrineobola might further inhibit the revival of the haplochromine fishery through competition over common food resources in the shallow waters.

Decrease in overall biomass of fish after the Nile perch introduction suggests an unstable fishery despite high annual yields. Decrease in species diversity is also a further confirmation of the instability of the fishery.

Decrease of hook sizes and mesh sizes of gillnets used in the fishery does not augur well for proper management of the fishery since it implies increased effort on the Nile perch.

Discussion of management strategies

It is abundantly evident that fisheries' patterns of Lake Victoria are closely following those of Lake Kyoga (Ogutu-Ohwayo, 1990; Twongo, 1991). It is therefore important that every strategy is directed at regulation of fishery effort which has been uncontrolled for a long time. Proposals have been made for minimum mesh to be set at 5 in (127 mm) which is still too low for the Nile perch fishery where a majority of the females mature at a much larger size than the optimum length cropped by 5 in gillnets. A mechanism should be devised to license the number of nets progressively. Minimum allotment should be made for 5 in meshes and maximum for 8 in meshes; alternatively, close the lake for meshes below 6 in for a period of six to twelve months to allow the fish to grow. Lowering of mesh sizes and hook sizes in the Nile perch fishery might soon lead to a collapse of the fishery.

The recent increase of Nile perch in the Nyanza Gulf has induced fishermen to move back into the Gulf. Increase of Nile perch has been due to low fishing activities at the time when most of the boats moved outside the Nyanza Gulf, and also due to pursuing of their prey. There has also been an increase in the yield of haplochromines in the sampled beaches, resulting from the success of some haplochromines in seeking safe refuge from Nile perch and hence thriving in the sheltered bays. In order to conserve the fish stocks and maintain species diversity, some areas of Lake Victoria should be protected.

Education programmes should be started to make the fishermen appreciate their role in the management of the lake resources. This will give the fishermen and the managers a better tool for reinforcement of regulations since they will be equally aware of the problems and repercussions of overfishing as well as regulations. Through education programmes extension officers will become better communicators.

Table I. Comparisons between condition factor of Lates niloticus of 1979–1981 and 1990–1991 by the length group

Table II. Total landings from sample beaches (in kg)

Table III. Comparison between stock densities from different trawl surveys (kg ha^-1)

LITERATURE CITED

Asila, A., 1991. Fishery resource base for the Kenyan sector of Lake Victoria presented in the National Seminar on the Management of the fisheries of Kenyan sector of Lake Victoria.

Asila, A. and J. Ogari, 1988. Growth parameters and mortality rates of Nile perch (Lates niloticus) estimated from length frequency data in the Nyanza Gulf (Lake Victoria). FAO Fish. Rep., 389: 272–287.

Anon., 1988. The state of Lake Victoria fisheries, Kenya. FAO Fish. Rep., 388: 22–28.

Balirwa, J.S., 1990. The effect of ecological changes in Lake Victoria on the present trophic characteristics of Oreochromis niloticus in relation to the species role as a stabilizing factor of biomanipulation. International Agriculture Centre, Wageningen. Occasional Paper No. 3: 58–66.

Bugenyi, F.B. and K.M. Magumba, 1990. The physico-chemistry of the Northern Waters of Lake Victoria In Prevailing activities on the Lake Victoria Basin with particular reference to the fisheries of the lake.

Getabu, A., 1988. Aspects of the Lake Victoria Fisheries with emphasis on Oreochromis niloticus and Alestes sadteru for the Nyanza Gulf. FAO Fish.Rep., 389: 416–431.

Gophen, M., U. Pollongher and P.B.O. Ochumba (in press). Limnology and plankton and fish feeding.

Lowe-Mc Connell, R.H. 1977. Ecology of fishes in tropical waters. Studies in Biology, No. 76. Edward Arnold Publications.

Ochumba, P.B.O., M. Gophen and U. Pollinger (in press). Ecological changes in Lake Victoria after the invasion of Nile perch (Lates niloticus): The catchment, water quality and fisheries management.

Ogari, J. and R. Omondi (in press). Preliminary study on the food and feeding habits of Schilbe mystus in a riverine (Nyando) environment.

Ogutu-Ohwayo. 1990. The decline of native fishes of Lake Victoria and Kyoga (East Africa) and the impact of introduced species especially Nile perch, Lates niloticus and Nile tilapia Oreochromis niloticus. Environmental biology of fishes, 27: 81–96.

Okemwa, E. 1991, Management and directions for future research in Lake Victoria multispecies fisheries.

Trewavas, E. 1983. Tilapiine fishes. British Museum (Natural History) 1983, 583 p.

Twongo, T. (in press). Some biological and ecological considerations for research in the Management of the fisheries of Lakes Victoria and Kyoga

PRESENT STATUS OF THE UGANDAN SECTOR OF LAKE VICTORIA FISHERIES

By

F.L. Orach-Meza, Ph.D.
Deputy Commissioner for Fisheries
Ministry of Agriculture, Animal Industry and Fisheries
P.O. Box 4, Entebbe, Uganda.

S U M M A R Y

The fisheries on the Ugandan Sector of Lake Victoria are characterised by still being primarily artisanal in nature featuring legions of small-scale operators working mainly with gill-nets. Most of the 8,674 fishing crafts are frame-planked canoes of which 14.4% are fitted with outboard engines. Other characteristics of the fisheries include limited fishing range and the suspicion and fear of government authorities as these are often identified with law enforcement and tax collection.

The concept of commercial yields being sustained through natural fish production and growth on the one hand and fishing effort as well as causes of natural mortalities on the other is upheld. It is on the basis of this knowledge that the fisheries development and management policies of sustainable production are formulated and implemented in Uganda.

With a total commercial production of 129,850 tonnes in the 1991 statistical year, the fisheries resources of the lake are attracting greater attention now than ever before. Both local and international business interests are now looking at the fisheries as one with a promise.

Considering the shared nature of the fisheries resources, it is noteworthy that the riparian states have recognised the importance of establishing a regional mechanism for co-ordinated development and management of the fisheries of Lake Victoria. Advantage should, therefore, be taken of the technical and financial assistance being provided by the international organizations to facilitate this exercise.

INTRODUCTION

The multispecies fisheries of Lake Victoria for the periods before the 1970's gradually declined reaching the lowest level in the 1980's (Orach-Meza, et.al., 1989). It is possible that overfishing, predation by the introduced Nile Perch and environmental changes in the lake basin are responsible for the reduction in the diversity of the fish species in the lake. The stock assessment survey conducted between 1969 and 1971 (Kudhongania and Cordone, 1974) is still scientifically valuable but its results on species abundance and distribution are now of marginal value. It is, therefore, necessary that what was known about the fisheries of Lake Victoria has to be re-assessed. Before another thorough stock assessment survey can be carried out, the only useful guide available for assessment of the fisheries is the trend of commercial catch statistics (Fig. 1).

It is along these lines that this paper presents an assessment of the present status of the fisheries resources, the fishing factors employed, the actual commercial fish production, the potential for increased fish production from the lake, and the need for closer regional collaboration in the development and management of the fisheries of Lake Victoria.

THE FISH RESOURCES

The commercial fish stocks on the Ugandan Sector of Lake Victoria consist mainly of Nile Perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) both of which are introduced fish, plus one indigenous pelagic fish, Rastrineobola argentea. Bagrus, Clarias, Protopterus, Barbus, Mormyrus, Haplochromis, and the indigenous tilapiine species are very rare in commercial catches (Table 1). So far, the Nile Perch, the Nile tilapia and the small-sized MUKENE fisheries have widespread commercial viability in the Ugandan Waters (Reynolds and Greboval, 1988). The introduced species, in particular, have already produced the highest catches ever known for Lake Victoria, although they are still undergoing a process of adjustment in an environment which itself is undergoing profound structural and functional changes (Kudhongania and Coenen, 1991). Available knowledge on the biology and ecology of these commercial species is insufficient. There is need to know about their abundance and distribution over time and space, their size structure, stock sizes and the dynamics of their populations and feeding habits before it is possible to draw any long term management plans. Since Nile Perch preys on Nile tilapia and on Rastrineobola argentea as well as on its own progeny, it is also essential to know about predation pressure and its impact on the fish stocks while assessing the long term viability of the fisheries. The work started by Ogutu-Ohwayo (1984) on the impact of predation in view of the current intensive commercial exploitation should be continued.

Recent catch statistics suggest that stocks of R. argentea have increased over their previous levels (Reynolds and Orach-Meza, 1989) as has the abundance of Caridina niloticus (Wannink et. al. 1988). Sustained increase in abundance of these species could have a positive bearing on the long-term prospects for the Nile Perch fishery. But with the statistical and ecological uncertainties that exist, any attempt to determine the sustainable exploitation level on Lake Victoria at the moment would amount to little more than guesswork.

THE FISHING FACTORS

Fishing at the moment is carried out almost exclusively in the inshore waters by fishermen using artisanal techniques. The types of boats that are currently being used fall into two categories: dug-out canoes and frame-plank canoes. Planked canoes can be constructed to larger size than that of dug-out ones; and are more durable and stable. With the introduction of outboard engines since 1953 (Mann, 1970), the fishermen can now venture further into the deeper waters. The mechanised canoes also enable quicker deliveries of the catches to the markets.

As shown on Table 2, the recent detailed on-water frame survey in the Ugandan part of Lake Victoria (Tumwebaze and Coenen, 1991) identified a total of 715 fish landing places and a total of 8,674 active canoes (8,000 fishing and 674 transport canoes). Compared to earlier inventory survey results, fishing effort on the lake, measured in number of active canoes and fish landing centres, have more than doubled during the last two decades (Table 3). It was also found that this evolution was accompanied by an increased scattering of the fishing operations into more dispersed and smaller fish landing sites. This dispersal has made it more difficult to collect fisheries statistics more fully. However, the results allowed the elaboration of a new catch assessment survey design for Lake Victoria consisting of five major and 52 minor strata. These are being sampled at random according to predetermined sampling schemes routinely worked out at the Fisheries Department Statistical and Information Systems Unit at Entebbe.

The most commonly used fishing gears are gill-nets, hooks (on long lines) and traps. It is estimated that each fishing boat carries 16 gill nets on the average. A total of 58,000 hooks and 4500, traps are known to be in use. There were about 201 seine nets in use before beach seining was banned in 1991. Some are however still being employed illegally.

Developments in the fishing gears and crafts on Lake Victoria were encouraged by increasing demand for fish which was stimulated by the growth of the urban centres along the lake shores. A pilot pair trawling experimental fishing commenced in 1989 with some controversial results so far.

COMMERCIAL FISH PRODUCTION

At the moment, the once multispecies fisheries of Lake Victoria are dominated by only three species as mentioned earlier - Lates niloticus, Oreochromis niloticus and Rastrineobola argentea. It is significant to note that although the variety of fish species landed has greatly declined, the total annual yield has increased significantly, mainly due to increased landings of Nile Perch and Nile tilapia. The annual average catch appears to be stabilising around a total figure of 120,000 tonnes (Table 4). The estimated catch for 1991 was recorded as 129,850 tonnes, once again dominated by Nile Perch (Table 1). R. argentea is shown to be picking up. This is the result of increased fishing for it at night using mosquito-net type of lift or seine nets in the open waters.

A striking result is the fact that almost 62% of the catch was recorded from landing centres in the islands. The three dominant species constituted 97.1% of the total catch from the lake. The other main genera in the catch were Clarias, Protopterus, Bagrus and Mormyrus. Less important ones were Barbus, Labeo, Schilbe, Haplochromis and Alestes which together constituted only 0.1%.

The average landing price per kg. of fish was shown by Kirema-Mukasa and Reynolds (1991) to have increased from UShs.153/= in March, 1991 to UShs.213/= in May, 1991. The cheapest fish was R. argentea sold at UShs.131/= in May, 1991, and the most expensive one was Bagrus which was sold at UShs.310/=.

POTENTIAL FOR INCREASED FISH PRODUCTION

Overall potential annual yield from Lake Victoria as a whole has not yet been precisely determined, but some educated prediction can be advanced on the basis of the reported catch statistics by the three riparian states. An optimum sustainable catch is likely to level within the range of 400,000 and 500,000 tonnes per year. On this basis, it therefore seems likely that substantial increase in production could still be achieved without risk to the continued viability of the fisheries.

To ascertain this, a major effort is currently being directed at assessing the exact state of the fish stocks, the actual harvest potentials the resources can sustain in the long run, and at the proper management of both the fish stocks and the fisheries. This is important because additional potential remains to be tapped through the rehabilitation and further development of lake-based aquaculture, enhanced natural production systems of the lake, and utilisation of currently unexploited aquatic organisms.

Although the statistics in Table 4 support the belief among fisheries scientists that the existing stocks are dominated by species in a clear predator/prey relationship where Nile Perch stocks are greatly supported by R. argentea (Twongo et. al., 1991), there are several examples of the existence of commercially sustainable fisheries based on predator/prey systems such as in Lake Tanganyika (Roest, 1988), Lakes Albert and Turkana and elsewhere. It is therefore possible that the current fish stocks in Lake Victoria could also co-exist, perhaps, at lower equilibrium levels than at present.

In addition, the present management and development policy in Uganda recognises the concept of “obtaining optimum sustainable economic yield of fish from the available water bodies.” This takes into account two characteristics of the fisheries resources: the uncertain and limited yields, and the free and open access mode of exploitation (MAAIF, 1984 and 1989). The fisheries of the lake are as a result provided for under the Laws of Uganda through the Fish and Crocodiles Act, Revised Edition, 1964. These laws are re-inforced or amended from time to time.

Lake Victoria fisheries are, however, still largely uncontrolled with respect to access to the fishery, and places for landing and disposal of fish. Laws protecting immature fish, prohibiting the use of destructive fishing gears and methods, and providing for licences do exist in the Statutes. They only need to be enforced more effectively.

REGIONAL COLLABORATION

The fisheries resources of Lake Victoria are currently administered separately by Tanzania (51%), Uganda (43%) and Kenya (6%). Because of the shared nature of the resources of the lake, regional collaboration through the harmonisation of efforts for fisheries development and management is obviously desirable.

Following the break-up of the East African Community in 1976, the meetings of the Sub-Committee of the Committee for the Inland Fisheries Africa have served well as avenues for deliberations and the creation of some consensus on matters of mutual interest by the scientists of the riparian states. In addition, practical steps are already being taken through EEC-funded Lake Victoria Fisheries Project towards lakewide coordination of research work. The riparian states, with the assistance from UNDP/FAO Regional Project based in Bujumbura, Burundi, are also currently involved in the formulation of a protocol covering all the problems related to the development and management of the lake basin and its fisheries to be agreed upon and adopted and to conclude a convention for establishing a Joint Fisheries Commission for Lake Victoria (Reynolds and Orach-Meza, 1989).

REFERENCES

Kirema-Mukasa, C.T. & J.E. Reynolds, 1991. Marketing and Consumption of fish in Uganda. Occasional Paper No. 4, FISHIN Notes and Records. Fisheries Statistics and Information Systems, FAO/UNDP Project UGA/87/007.

Kudhongania, A.W. & A.J. Cordone, 1974. Batho-spatial distribution patterns and biomass estimates of the major demersal fishes in Lake Victoria. Afr. J. Trop. Hydrobiol. Fish : 167–181.

Laws of Uganda, 1964. Fish and Crocodiles Act, Chap. 228, with subsequent amendments.

Mann, M., 1970. A Resume of the Evolution of the Tilapia Fisheries of Lake Victoria up to the year 1960. In: EAFFRO, Annual Report, 1969, Jinja, Uganda, App. B: 21–27.

MAAIF, 1984. (Ministry of Animal Industry and Fisheries). Blueprint for Fisheries Development in Uganda, Kampala: 26p.

MAAIF, 1991. Brief to the Minister of Agriculture, Animal Industry and Fisheries on the Livestock and Fisheries Sector. MAAIF, Planning Unit, July, 1991, 10p.

Ogutu-Ohwayo, R., 1984. The effect of predation by Nile perch, Lates niloticus (Linne) introduced into Lake Kyoga (Uganda) in relation to the fisheries of Lake Kyoga and Lake Victoria. FAO Fish. Report No. 335: 18–41.

Orach-Meza, F.L., E.J. Coenen, and J.E. Reynolds, 1989. Past and recent trends in the exploitation of the Great Lakes fisheries of Uganda. In Fisheries of the African Great Lakes, Occasional Paper No. 3. Fisheries and Aquaculture Unit, International Agricultural Centre, Wageningen, The Netherlands.

Reynolds, J.E. & D.F. Greboval, 1988. Socio-economic effects of the evolution of Nile perch fisheries in Lake Victoria: a review. CIFA Tech. Pap., (17): 148p.

Reynolds, J.E. & F.L. Orach-Meza, 1989. Development and management of Lake Victoria Fisheries: deliberations of the CIFA Meeting, Mwanza, Tanzania, Sept., 1989. SEC Field Report No.9, FISHIN Notes and Records. Fish. Stat. and Inf. Systems. FAO/UNDP Project UGA/87/007.

Roest, F.C., 1988. Predator-prey relations in Lake Tanganyika and fluctuation in the pelagic fish stocks. CIFA Occ. Pap. No. 15: 104–129.

Tumwebaze, R. & E.J. Coenen, eds. 1991. Report on the frame survey conducted in the Ugandan part of Lake Victoria (3rd Sept. to 20th Dec., 1990). BIOSTAT Field Report No.22. FISHIN Notes and Records. Fish. Stat. and Inf. Systems. FAO/UNDP Project UGA/87/007.

Twongo, T., J.E. Reynolds & P. Mwene-Beyanga, 1991. Management issues, options, and strategies for Lake Victoria fisheries. Paper presented at the National Seminar on the Management of the Fisheries of Lake Victoria, Jinja, Uganda: 6–8 August, 1991. 38p.

Wannink, J.H., W. Ligtvoet, & F. Witte, 1988. HEST/TAFIRI research in Lake Victoria: some preliminary results and their relevance for fishery management. Report presented at the National Seminar on Fisheries Policy and Planning, Dares-Salaam, 224 May, 1988. (mimeo).

Figure 1. Trends in annual catches, 1965–1991

Table 1. : Percentage Weight Distribution (Lake Victoria).

Source: UFD Records

TABLE 2. CHANGES IN THE FISHING FACTORS

Source: Tumwebaze, R., & E.J. Coenen (Eds.), 1991.

TABLE 3 : TOTALS OF SELECTED VARIABLES FOR THE FIVE REGIONS AND THE WHOLE UGANDAN PART OF LAKE VICTORIA.

Source: Tumwebaze R., & E. J. Coenen (Eds.), 1991.

Table 4. : Evolution of the catch (in tonnes) for Lake Victoria (Uganda), 1965–91.

* Figure for 1991 are provisional estimates

Source: UFD Records

THE CHANGING FISHERIES OF LAKE VICTORIA, UGANDA

John Obbo Okaronon
Uganda Freshwater Fisheries Research Organization
Jinja, Uganda

ABSTRACT

Lake Victoria had a complex multi-species fishery dominated until the late 1970s by the tilapiine and haplochromine cichlids but with important subsidiary fisheries of more than 20 genera of non-cichlid fishes. Since the 1980s, however, the fishery has been dominated by the Nile perch (Lates niloticus), Nile tilapia (Oreochromis niloticus eduardianus) - both introduced into the lake during the late 1950s and early 1960s - and Rastrineobola argentea, a pelagic cyprinid. Although the actual landed commercial catch figures from the Uganda sector of the lake point to the increased landings since 1984, the catch rates in the experimental trawl fishery and mean weight of fish in both experimental trawl and commercial fishery have been on the decline.

THE FOOD OF THE SURVIVING PREDATORS IN LAKES VICTORIA, KYOGA AND NABUGABO

John Paul Olowo
Uganda Freshwater Fisheries Research Organization,
P.O. Box 343
Jinja, Uganda.

ABSTRACT

Predators formed about 30–40% of the fish in lakes Victoria, Kyoga and Nabugabo. Since the introduction of the predatory Nile perch in lakes Victoria, Kyoga and Nabugabo, many of the native fish species have been depleted and some completely disappeared. This study is intended to examine the biology and ecology of the surviving endemic predators in these lakes and to find out their ecological relationship with the Nile perch. This paper specifically examines the food of five endemic surviving predators.

IMPORTANCE OF STABILITY IN PREY SUPPLY TO THE STOCKS OF THE NILE PERCH IN LAKES VICTORIA, KYOGA AND NABUGABO

Richard Ogutu-Ohwayo
Uganda Freshwater Fisheries Research Organization
P.O. Box 343
Jinja, Uganda

ABSTRACT

The food of the Nile perch has changed since its introduction into lakes Victoria, Kyoga and Nabugabo and stabilized on Cardina nilotica, Anisopteran nymphs, Rastrineobola argentea, Nile perch juveniles, and tilapiines. For the Nile perch to sustain production in these lakes, it is important that these prey species are properly managed.

THE EFFECTS OF NILE PERCH PREDATION AND HUMAN EXPLOITATION ON THE POPULATION STRUCTURE OF RASTRINEOBOLA ARGENTEA IN LAKES VICTORIA KYOGA AND NABUGABO

Wandera S.B.
Uganda Freshwater Fisheries Research Organization
P.O. Box 343
Jinja, Uganda

ABSTRACT

Rastrineobola argentea is endemic in Lakes Victoria, Kyoga and Nabugabo into which the Nile perch, Lates niloticus was introduced and is well established. It is a major source of food to the Nile perch in the three lakes and is also an important commercial fish species especially on Lake Victoria. Predation and fishing has led to changes in the population structure of R. argentea in the three lakes. The mean size of R. argentea caught has decreased and the size at maturity has also greatly reduced especially in Lake Kyoga where Nile perch established itself much earlier. In areas of Lake Victoria where intensive fishing pressure exists, the trend towards the Lake Kyoga situation is more apparent. Combined effects of fishing and predation in shallow waters such as Lakes Kyoga, Nabugabo and inshore areas of Lake Victoria could lead to over-exploitation and thus the collapse of the Rastrineobola fishery in a short time.

GEAR AND MESH SIZE SELECTION IN THE NILE PERCH (Lates niloticus L.) FISHERY FROM THE NYANZA GULF OF LAKE VICTORIA

C.O. Rabuor and J.O. Manyala
Kenya Marine and Fisheries Research Institute
Kisumu Laboratory
P.O. Box 1881
Kisumu, Kenya

ABSTRACT

The total mortality coefficient (Z) of the Nile perch (Lates niloticus) determined from a variety of fishing gears indicated a large variation in these values. Hook number 7 exhibited the highest Z value of 3.803 yr-1 while all hooks combined had a Z Value of 0.769 yr-1. The Z values derived from gillnets were relatively high (2.155 yr-1) but the value of Z from all the gears were not significantly different from previous values in the Winam Gulf of Lake Victoria (P > 0.10). Corresponding Lc50% and Lc75% for all the gears indicated observed selection lengths of 58.0–70.0 cm TL except for the beach seine (18.9 and 26.8 cm TL). Estimated theoretical Lc50% and Lc75% shows that most gears harvest undersized specimens except the hooks in the long line fishery. The effect of gillnet mesh size on the mean length of harvested specimens shows a linear relationship. The implication of gear and mesh size selection on this fishery is discussed.

THE POPULATION STRUCTURE OF THE NILE TILAPIA (Oreochromis niloticus L.) IN LAKES VICTORIA, KYOGA AND NABUGABO

John S. Balirwa
Uganda Freshwater Fisheries Research Organization
P.O. Box 343
Jinja, Uganda

ABSTRACT

The commercial fisheries of Lake Victoria are presently based on Lates niloticus (Nile perch), Oreochromis niloticus (Nile tilapia) and the cyprinid, Rastrineobola argentea. The present character of the fisheries offers management possibilities of effective enforcement which were in the past difficult to carry out due to the complexity of the multispecies fisheries. Research findings can also be more easily implemented if they relate to the status of the stocks.

The seasonal gonad status, length-frequency distributions, size at first maturity and length-weight factors in Oreochromis niloticus were analyzed for the period 1988 to 1990. Comparison of these aspects in fisheries from Lakes Victoria, Kyoga and Nabugabo are presented. Length frequency distributions seem to indicate higher exploitation of smaller fish in Lake Victoria than L. Kyoga. The fish appear to mature at a smaller size in Lake Victoria than in Lake Kyoga.

THE IMPACT OF FISHING GEARS AND METHODS ON THE FISHERIES OF LAKES VICTORIA, KYOGA AND NABUGABO WITH SPECIFIC RECOMMENDATIONS ON MANAGEMENT OF THE FISHERIES

Ogutu-Ohwayo. R., T. Twongo, S.B. Wandera & J.S. Balirwa
Uganda Freshwater Fisheries Research Organization
P.O. Box 343
Jinja, Uganda

ABSTRACT

There has been an obvious increase in fishing pressure on many lakes. Gill nets, beach seines and mosquito seines are the dominant fishing gears used on Lakes Victoria and Kyoga. Trawling is practised to a limited extent in some regions of Lake Victoria but its use might expand in the future depending on short-term economic considerations. In view of these factors, the impact of the above gears and methods on the fish stocks have been analyzed in relation to biological parameters of the Nile perch, Nile tilapia and Mukene. The analysis shows that the Fish and Crocodiles (Immature Fish) Instrument of 1981 (for Uganda) is inadequate to protect the fish stocks from over-exploitation. The need for management to take effective control of the fisheries is emphasized. Mechanisms to achieve this are proposed in form of specific recommendations.

THE EFFECT OF LIMNOLOGICAL FACTORS AND THE CHANGING ENVIRONMENT ON THE FISHERIES OF NORTHERN LAKE VICTORIA

F.W. Bugenyi
Uganda Freshwater Fisheries Research Organization
P.O. Box 343
Jinja, Uganda

ABSTRACT

The once, multi-fish species fishery of Lake Victoria is no more. The whole freshwater ecosystem is changing. The changes are mainly the result of various human induced activities on the water itself and within the watershed. The increasing population within the region lays a stress on the increasingly unavailable water and on its quality. Precipitation, mainly, the rivers and streams, and rainfall-runoff have increased the nutrient input. This is responsible for the noted increase in eutrophic conditions of the water. This, together with absence of most of the herbivorous fish species will ensure prolific production of algal biomass which in the end will result in anoxic conditions in the hypolimnion. The lake has also been sensitive to past changes in climate and would be expected to respond to global warning which is being forecast.

This calls for concerted efforts in research in trying to understand the hydrological, physico-chemical and biological dynamics of the lake and then solutions can be attempted.

THE POTENTIAL FOR FURTHER PROLIFERATION OF WATER HYACINTH IN LAKES VICTORIA AND KYOGA AND SOME URGENT ASPECTS FOR RESEARCH

T. Twongo, F.W.B. Bugenyi and F. Wanda
Uganda Freshwater Fisheries Research Organization
Box 343
Jinja, Uganda

ABSTRACT

The water hyacinth invaded Uganda hardly ten years back and has accumulated in many areas of the Lake Victoria - Uganda and Lake Kyoga. This trend is extremely worrying in view of the detrimental effects of the water hyacinth to most uses of the aquatic environment such as fisheries production, transportation, hydro-electric power generation, irrigation and the maintenance of aquatic biodiversity.

The purpose of this paper therefore is first to try and illustrate the above danger by discussing the enormous magnitude of the water hyacinth. The paper also outlines some urgent aspects for research to improve knowledge on the biology and ecology of the water hyacinth.

OBSERVATIONS OF THE ZOOPLANKTON COMMUNITY OF THE NORTHERN PART OF LAKE VICTORIA

Lucas Mwebaza-Ndawula
Senior Principal Research Officer
Box 343
Jinja, Uganda

ABSTRACT

The zooplankton community is dominated by Crustaceans, constituting over 90% in terms of the numbers while meroplanktonic insect larvae and pupae contribute only small proportions. Cyclopoid copepods, their nauplius larvae and copepodites form the most important taxon both in terms of distribution and abundance while the Calanoid (Diaptomid) copepods are generally poorly represented. Equally poorly represented are various species of cladocerans. The benthic decapod prawn, Caridina nilotica Roux is frequent in the zooplankton of the pelagic zone, albeit in low proportions. Larvae and pupae of Chaoborids and Chironomids are occasionally caught in the samples. There is evidence that the zooplankton community has undergone remarkable structural changes probably as a result of corresponding changes in the water environment, algal community and food-web structure following the establishment of the Nile perch, Lates niloticus in the lake.

DISTRIBUTION AND ABUNDANCE OF TWO DIPTERAN AQUATIC LARVAE IN NORTHERN LAKE VICTORIA

Godfrey B. Mbahinzireki
Senior Principal Research Officer
Box 343
Jinja, Uganda

ABSTRACT

Initial findings on the distribution and abundance of two dipteran larvae in an ecologically and environmentally changed northern Lake Victoria are presented. Results suggest that density of Chironomid larvae have gone up about four-fold since the preperch era and that of chaoborid larvae maintained at more or less the same level. Possible reasons for this increase are proposed. Inshore stations held higher densities of larvae when compared with the offshore station of Bugaia. Type of the sediment and physico-chemical factors seem to influence the production and distribution of the insect larvae in the lake. Body length did not suggest anything conclusive yet as the identity of the individual larval groups is still unclear. More work remains to be done.

PRESENT ASPECTS OF MARKETING FISH FROM LAKE VICTORIA, UGANDA

C.T. Kirema-Mukasa and C.M. Dhatemwa
Fisheries Officer
Box 4
Entebbe, Uganda

ABSTRACT

Over the recent years, there has been steady growth in the fish catches of Lake Victoria due to increased investment into the production sector. In terms of fish distribution, marketing, and utilisation there has been only a slight change mainly towards the export market, with no parallel development for the domestic market.

This paper, which briefly describes the present marketing system, discusses the problems of marketing Lake Victoria fish, highlights the impact of industrialisation on the domestic market, and focus particularly on the problems besetting the islands which are the major sources of Lake Victoria fish.

THE IMPLICATIONS OF THE CHANGING FISHING PATTERN ON LAKE VICTORIA, UGANDA, FOR FISH MARKETING DEVELOPMENT

O.K. Odongkara, Economist
Uganda Freshwater Fisheries Research Organization
Box 343
Jinja, Uganda

ABSTRACT

The fish marketing system on Lake Victoria had over the years become well established. Recently, however, there has been a shift of fishing activities from the mainland to bases on the several islands that lie off the shores of Lake Victoria. This change in the fishing operations has presented additional demand for new facilities and services for the marketing of the catch. More significantly, it has led to the intensification of common market activities in fish over the lake with the neighbouring Kenya. These issues are examined in the paper for their implications for marketing and general fisheries development and co-ordination on Lake Victoria.

APPENDIX D
PRIORITIES FOR ACTION: RESEARCH AND MANAGEMENT

A. INTRODUCTION

Fish stocks are inherently renewable so that it is theoretically possible to exploit the resources indefinitely. However, exploited fish stocks are highly amenable to irreparable damage if harvested indiscriminately. Discreet exploitation is needed for perpetuating the viability of the fisheries. Fisheries management is the established tool for appropriate fisheries exploitation while fisheries research is the basic tool for sound fisheries management. Thus, for sustainable fishery systems, research, management and exploitation are interrelated and must go hand in hand. This particularly so in the context of the current Lake Victoria fisheries.

B. RESEARCH

Considering its size and high biological productivity potential, Lake Victoria is an important fishery resource. But there have been far-reaching changes, both to the fishery and environment of the lake, which have been occurring in recent years.

While the total commercial fish yield from the lake has been increasing, it is not yet clear whether the optimum potential fish production has been realised neither is it clear if the current high catch levels would be sustained. The uncertainty is a result of the lack of adequate lake-wide scientific knowledge on the present fish stocks under the changing environmental conditions.

The Lake Victoria ecosystem has been changing with respect to mixing, stratification, oxygen levels and nutrient supply. There are also significant changes in the composition of phytoplankton (green and blue-green algae), zooplankton and other organisms. In addition, the lake has been invaded by the water hyacinth (Eichornia crassipes) which is rapidly spreading along the lake shore.

Lake Victoria was originally a multispecies fishery. Current fish stocks in many parts of the lake are dominated by two introduced species (Lates niloticus and Oreochromis niloticus) and one indigenous cyprinid (Rastrineobola argentea). Most of the traditional fish species, including the once ubiquitous and preponderant haplochromines, have either declined to insignificant levels or almost disappeared from the lake. A very disturbing point is that since the changes started taking place there has been no scientific information on the status of the fish stocks and limnology in the offshore deep waters of the lake. Consequently, it has often been assumed that there may be large stocks of fish there. In order to sustain the biological viability of the Lake Victoria fishery resources, the current situation offers two possible options:

1. To aim at reviving the once multi-species itchthyofauna through restocking, closed areas, closed seasons, catch quarters, etc.

2. To nurse the current three-species fishery.

In choosing between the two options one has to consider which system is likely to be successful and more beneficial to society. Catch data from the Kenya, Tanzania and Uganda sectors of Lake Victoria reveal the intriguing situation that fish yields under the three-species dominance in recent years have been much higher than when the exploitable species were still numerous. On the other hand, while the option for higher catches dominated by three species may be economically very attractive, the aesthetic value for the consumer to have a variety to choose from is among the criteria for good fishery management practices in some countries.

However, in dealing with exploited fish stocks as living dynamic systems particularly in the case of Lake Victoria where the water environment is dramatically changing, the desirable fishery objectives may be set by biological feasibility. Is it biologically feasible to sustain the current higher catches and at the same time satisfy aesthetic considerations? To address the biological feasibility of the resources requires extensive research to cover the major relevant parameters governing ecosystem dynamics.

On that understanding, a research programme competent enough to achieve the desired objectives should aim at evaluating the status of the fishery (which is not currently clear) and its long-term potential production. The research strategy should embody the major components of the ecosystem and energy flow. Social and economic studies need to be included for evaluating the benefits of specific regimes of the fishery.

PROPOSED RESEARCH PROGRAMME

The following research programme for Lake Victoria was endorsed by the Research and Management Committees of the EEC Lake Victoria Fisheries Research Project. The Committees consist of the three Directors of Research (Kenya, Tanzania, Uganda), the three Directors/Commissioner for Fisheries (Kenya, Tanzania, Uganda) and the three Heads of research work on Lake Victoria (Kenya, Tanzania and Uganda).

1. Stock Assessment

1. Stock size, relative abundance, size structures.
2. Temporal and spatial distribution patterns.

3. Fish movements, growth, etc. through a co-ordinated tagging programme (UFFRO, TAFIRI, KMFRI).

2. Biology, ecology and population dynamics for Lates:

1. Breeding - potential, periodicity, sites, size.
2. Trophic relationships - prey resources, predation pressure.
3. Cannibalism - onset, impact to fishery potential.

4. Optimum level of exploitation.

3. Biology, ecology and population dynamics of O. niloticus and other tilapiines.

1. Breeding - potential, periodicity, sites, size.
2. Trophic relationships - food resources, predation pressure.
3. Hybridization - evidence, extent.
4. Competition and resilience to predation.
5. Optimum level of exploitation.

6. Distribution pattern of the commercial fishery and its impact on fish yield.

4. Biology, ecology, population dynamics and fishery of R. argentea:

1. Breeding - potential, periodicity, sites, size.
2. Trophic relationships - food resources, predation pressure.
3. Methods and optimum level of exploitation.

4. Distribution patterns of the commercial fishery.

5. Limnology and water quality:

1. Physico-chemical characteristics
2. Water quality characteristics and criteria.
3. Nutrient dynamics and primary/secondary production.
4. Human activities and impact.

5. Fish kills - cause, periodicity, control.

6. Invertebrate Investigations:

1. Planktonic and benthic organisms.
2. Taxonomy, abundance, production, distribution.

3. Trophic relationships - food resources, predation pressure.

7. Studies on anadromous and other fishes.

1. Barbus, Labeo, Schilbe.
2. Bagrus, Clarias, Protopterus, mormyrids, Synodontis.
3. Genetic preservation and stock revival - enhancement.
4. Micropterus salmoides - Development of stocks, how to contain.

5. Haplochromine - stock monitoring.

8. Wetland ecotone interactions:

1. Ecological structure and function.
2. Mitigating effects.
3. Management options.

4. Water hyacinth: biology, ecology surveillance.

9. Socio-economic Aspects:

1. Socio-economic aspects of fish production, fishing, profitability, fishery technology, investment levels, employment, fish marketing, distribution and trade, and fish utilization.
2. Bio-economic production models and input-output variability.

3. Economics of different management systems.

The success of research in the various aspects would enable the formulation of suitable management strategies among the desirable options.

C. Management

Lake Victoria is traditionally a great source of employment, cheap animal protein and income (including foreign exchange earnings in recent years). The lake is trinational, was once a multi-species fishery, has multi-purpose uses and is now in a transient state - both ecologically and economically. As such, in order to realise the full social, nutritional and economic potential benefits from the lake it is essential to harmonize prudently exploitation and management practices so that the viability of the available resources would be sustained. The strategy certainly calls for shared responsibility among the riparian states.

Re-stocking, closed area, closed seasons, catch quotas, gear restrictions, water quality criteria, etc. are among the established options for fisheries management.

Re-stocking a lake of the size of Lake Victoria has its practical limitations. While catch quotas may be applicable to industrial operators, their application to the artisanal sector of the fishing industry may be restrained. However, the current open access to the Lake Victoria fishery need to be controlled in terms of the number of boats, nets and fishermen. On the other hand closed areas and seasons could be integrated and successfully implemented with sound scientific reasons as well as cooperation (through education) with the fishing communities.

Gear restrictions in the Lake Victoria os today, when the fishery is dominated by three species (Nile perch, Nile tilapia, Mukene), can be readily justified:

1. L. niloticus and O. niloticus, the mature ones of which are caught in large gill-net mesh sizes (i.e. 5 inches and above), contribute over 90% of the commercial fishery while other fish species caught in gill-nets with smaller mesh sizes contribute less than 1% of the commercial catches. Gill-net mesh size restriction measures geared towards the sustainability of L. niloticus and O. niloticus in Lake Victoria should be well justified.

2. The use of long lines could be encouraged as a useful management strategy since they catch mostly large mature fish (Nile perch) with no apparent detrimental effects on the fishery.

3. Beach seines catch immature fish and interfere with breeding strategies of the fish stocks. Use of beach seines have to be prohibited except for research purposes by Government research institutions and universities.

4. Cast nets, lift nets, trawl nets and gill-nets fished actively have detrimental effects on the stocks so that they have to be banned.

5. The third commercially important fish species in Lake Victoria is Rastrineobola which is a pelagic fish. Research investigations have already shown that the most appropriate gear to exploit Rastrineobola is the 10mm mesh Lampare type of seine net operated only offshore.

Water Quality

The quality of the water environment determines the potential productivity of a given water system. In Lake Victoria the water quality is being influenced by:

• Exogenic materials from the surrounding land

• Industrial and urban effluents

• Heavily loaded rain

• Eutrophication

• Inversion by the water hyacinth (Eichornia crassipes).

Management measures should be put in place in order to minimize the negative effects from the various factors.

1. Establishment of a minimum boundary where the land must not be cleared should be set up along the lake shores and banks of the affluent rivers.

2. The requirement for construction of effective effluent treatment plants for all industrial complexes.

3. Set up standards for acceptable levels of the effluents be discharged into the water systems, and allow free access to the various factories for the research scientists.

4. Minimize pollution of the atmosphere (by industries and bush fires).

5. The riparian states and the KBO should actively cooperate in the fight against the water hyacinth. In this exercise precautions must be taken in considering the use of chemical, biological and mechanical methods of controlling the water weed.

Co-ordination of management measures

Management measures to be effective and successful have to be carefully coordinated by the riparian states. In addition there should be improved interactions and understanding between the researchers, fisheries administrators and fishermen.

Co-ordination should involve:

• Harmonization of research activities

• Standardization of statistical methods

• Implementation of uniform management measures

In the context of the nutritional value of the artisanal fishery as the main source of animal protein to local population, management practices should not overlook to limit the development of fish processing plants until the magnitude of the available fish stocks has been adequately defined.

For effective co-ordination of management measures the establishment of a Lake Victoria Fisheries Commission would be necessary. The commission may consist of the Directors/Commissioner for Fishery and the Directors of Research from the three riparian states plus any appropriate officers nominated by their respective governments.

APPENDIX E: MANAGEMENT MEASURES FOR LAKE VICTORIA DERIVED FROM THE THREE NATIONAL SEMINARS ORGANIZED BY THE FAO/IFIP PROJECT IN 1991