Fish species diversity in the Victoria and Kyoga lake basins: their conservation and sustainable use

Introduction of exotic fish species especially the Nile perch Lates niloticus, is believed to be responsible for the decline of fish species diversity in lakes Victoria, Kyoga and Nabugabo.About 60% of the haplochromine cichlids are thought to have become extinct from L. Victoria due to predation by the Nile perch. However there are many lakes satelite to the lakes Victoria and Kyoga basins which still have fish fauna similar to that of the main lakes. many of the satellite lakes are separated from the main lakes in, which Nile perch was introduced by extensive swamps that provide a barrier to Nile perch .A survey was carried out in a number of these satelite lakes and an inventory made of existing fish species. Their distribution and relative abundances were also determined. The lakes studied included Nawampasa, Nakuwa,Kawi Lamwa Gigate, Nyaguo, Agu, Nabugabo. Kayanja, Kaytigi, Mburo, Kachera and Wamala.Some habitats within the main lakes Victoria and Kyoga, especially those with rocky outcrops· and macrophyte cover that provide refugia for endangered species from Nile perch,were also surveyed) Various stations along the River Nile were also sampled to quantify the fish species that are still resent. Kyoga minor lakes were found to have the highest number of fish species especially of haplochromine cichlids. Many haplochromine trophic groups that were thought to be extinct from 1. Victoria still occur in these lakes.!Some of the satellite lakes, especially lakes Kayugi, Mburo and Kachera still contain .healili populations of oreochromis. I esculentus that could be used as brood stock in fish farming. Many of these lakes should .I ( I therefore be protected for conservation offish species diversity

The diversity of amphibians, reptiles and mammals and their importance in the Victoria and Kyoga lake basins

The shore margins of Lakes in the Victoria basin are highly dented and mostly swampy, fringed by Papyrus and other wetland vegetation types important habitats for herpetofauna and wetland adapted mammals. Of recent, the extent of the 'wetland' has been extended in several places by the Water Hyacinth (Eichornia cryaseps). Ecologically, amphibians are important in many ways; they are mostly predators, acting as primary and secondary carnivores. Their prey consists mostly of insects, some of which are pests to crops or disease vectors. They are also inter-inked in food chains, often acting as food for other vertebrates, such as pigs, birds, snakes and sometimes man. Because of their ectothermic physiology, the life history and ecology of amphibians often differ markedly from that of birds or mammals (McCollough el ai, (992).Amphibians are known to be an easily recognisable taxon in given habitats; and populations are sometimes specialised within a narrow habitat. This makes it easy and practical to monitor changes in composition over time, given different onditions (Heyer el al 1994, Phillips 1990). Impacts on their habitat are reflected in changes in numbers and species diversity in a short time. These are some of the factors that have made amphibians to be recognised, nowadays, as good indicators of habitat change

Genetic status of selected fish taxa in relation to conservation of genetic and species diversity in the Victoria and Kyoga Lake basins

Cichlids are known for their explosive radiation especially in the African Great Lakes marked with a high level of lake endemism. These fishes have been characterized mainly along trophic and habitat differences, by variation in morphological structures such as teeth and jaws and by differences in body shape and coloration. Cichlids are important as a microcosm of macroevolution. The explosive radiation, young evolutionary scale, and the isolation of groups characterized with high levels of endemism and presence of living fossils makes the group important for evolutionary and genetic studies. Lake Victoria region cichlids which are isolated and relatively more recent in evolution were the last to be appreciated in their diversity. Recently Ole Seehausen has found scores of rock fishes in Lake Victoria which were up to then thought to be absent from the Lake and only known to occur in Lakes Malawi and Tanganyika. Greenwood put together the species groups of Lake Victoria, and later in the early 1980's revised the classification of haplochromine species to reflect the phyletic origin and interrelationship of the various groups in Lake Victoria region. Melan Stiassny has been interested in early evolution of cichlids while the likes of Paul Fuerst and Lees Kaufman and Axel Meyer have been interested and are working to explain the speciation mechanisms responsible for the explosive radiation and evolution of cichlids. Locally S.B Wandera and his student Getrude Narnulemo are spearheading the biodiversity and taxonomic studies of cichlids in Lake Victoria region

The biology and ecology of native non-cichlids in the Victoria and Kyoga lake basins

An overview of the biology and ecology of some of the constantly less important commercial species is given below. These included Bagrus docmac, Clarias gariepinus, Protopterus aethiopicus, Labeo victorianus, Barbus spp, Mormyrids, Synodontis spp, and Schilbe intermedius. The stocks of most of these species declined due to over-exploitation and introduction of non-native fishes especially Nile perch. A few of these taxa still survive in the main lake and others in satellite lakes. The current status of these species in the Victoria lake basin is not known but the available information provided some information on some habitat and other requirements of some of these originally important species of the Victoria lake basin.

Trophic interrelationships and food-webs among the fishes in ecosystems of the Victoria and Kyoga lake basin

The Victoria and Kyoga lake basins had a high fish species diversity with many fish species that were found only in these lakes. Two Tilapiines species Oreochromis esculentus and Oreochromis variabilis were the most important commercial species in these lakes and were found nowhere else on earth except in the Victoria and Kyoga lake basins (Graham 1929, Worthington 1929). Lakes Kyoga and Nabugabo also had endemic haplochromine species (Worthington 1929, Trewavas 1933, Greenwood 1965, 1966). As stocks of introduced species increased, stocks of most of the native species declined rapidly or disappeared altogether. The study was carried out on Lakes Victoria and Kyoga, River Nile, some selected satellite lakes from the two basins namely Lakes Mburo, Kachera, Wamala, Kayanja, Kayugi, Nabugabo, Victoria, Victoria nile and River Sio(Victoria lake basin). Lakes Kyoga (Iyingo), Nawampasa, Nakuwa, Gigati, Nyaguo, Agu, Kawi and Lemwa (Kyoga lake basin). Species composillon and relative abundance of fishes were estimated by detennining the overall average total number of each species encountered. A trophic consists of species using the same food category. Shannon-Weaver Index of diversity H (Pielou, 1969) and number of trophic groups, were used to estimate the Trophic diversity of various fish species in the lakes. Food analysis has been done on some fishes in some of the sampled lakes and is still going on, on remaining fishes and in some lakes. Generally fish ingested detritus, Spirulina, Melosira, filamentous algae, Planktolyngbya, Microcysists, Anabaena, Merismopedia, Spirogyra, higher plant material, rotifers, Ostracodes, Chironomid larvae and pupae, Choaborus larvae, Odonata, Povilla, Insect remains, Caridina, fish eggs and fish. Eight trophic groups were identified from thes food items ingestes. These included detritivores, algae eaters, higher plant eaters, zooplanktivores, insectivores, molluscivores, prawn eaters, paedophages and piscivores. Trophic diversity by number of trophic groups was highest in Lake Kyoga (6) followed by lakes Kayugi, Nabugabo, River Nile and Mburo (3) and the lowest number was recorded in kachera (2).

The biology, ecology, population parameters and the fishery of the Nile tilapia, Oreochromis niloticus (L)

Oreochromis niloticus (the Nile tilapia) and three other ti1apine species: Oreochromis leucostictus, Tilapia zi11ii and T. rendallii were introduced into Lakes Victoria, Kyoga and Nabugabo in 1950s and 1960s. The source and foci of the stockings are given by Welcomme (1966) but the origin of the stocked species was Lake Albert. The Nile tilapia was introduced as a management measure to relieve fishing pressure on the endemic tiapiines and, since it grows to a bigger size, to encourage a return to the use of larger mesh gill nets. Ti1apia zillii was introduced to fill a vacant ,niche of macrophytes which could not be utilised' by the other tilapiines. Tilapia rendallii, and possibly T. leucosticutus could been introduced into these lakes accidently as a consquence of one of the species being tried out for aquaculture. The Nile perch and Nile tilapia have since fully established themselves and presently dominate the commercial fisheries of Lakes Victoria and Kyoga. The original fisheries based on the endemic tilapiines O. escu1entus and o. variabilis have collapsed. It is hypothesized that the ecological and limnological changes that are observed in Lakes Victoria and Kyoga are due to a truncation of the original food webs of the two lakes. Under the changed conditions, O. niloticus to be either playing a stabilizing role or fuelling nutrient turnover in the lakes. Other testable hypotheses point to the possible role of predation by the Nile perch, change in regional climate and hydrology in the lake basins.

Changes in fish fauna and the impact of the introductions on fish yield

There have been considerable changes in fish species composition in Lakes victoria, Kyoga and Nabugabo since the Nile perch were introduced. Populations of most of the native species have declined and many species may have become extinct. The original decline in the fish stocks was due to overfishing but the recent and more drastic decline has been attributed to predation by the Nile perch. Nile perch feeds on invertebrates changing to a piscivorous diet with size. Haplochromine cichlids, which were the most abundant fish in Lakes Victoria just before the Nile perch populations started increasing rapidly have been depleted. As more suitable types of prey were depleted in the new habi tats, Nile perch switched to other prey types to the extent of feeding even on its own young. There are, fears that the Nile perch will overshoot its food supply, resulting in a reduction of its own population and subsequently a collapse in the fishery (FAD 1985).

Fishes and fisheries of Uganda: their biology, ecology, expoiltation and management

This chapter brings together some information on the fishes and fisheries of Uganda. It starts with an overview of the biology and ecology of the fishes highlighting those aspects that are important in providing an understanding that can be used to manage the fishes. This is followed by a discussion of the fisheries of the major lakes including the management challenges that have and are facing these lakes.

The water hyacinth problem and the biological control option in the highland lake region of the upper Nile basin: Uganda's experience

The rapid proliferation and extensive spread of water hyacinth Eichhornia crassipes (Mart) Solms in the highland lakes of the Nile Basin within less than 15 years of introduction into the basin in the 1980s pauses potential environmental and social economic menace if the noxious weed is not controlled soon. The water weed has spread all round Lake Victoria and, in Uganda where infes tation is mos t severe, water hyacinth estimated at 1,330,000 ton smothers over 2,000 ha of the lakeshore (August,1994). Lake Kyoga which already constantly supplies River Nile with the weed is infested with over 570 ha, while over 80% of the river course in Uganda is fringed on either side with an average width of about 5m of water hyacinth. As the impact of infestation with water hyacinth on water quality and availability, transportation by water, fishing activities, fisheries ecology, hydro-power generation etc becomes clear in Uganda, serious discussion is under way on how to control and manage the noxious weed. This paper pauses some of the questions being asked regarding the possible application of mechanical and chemical means to control the water weed.Uganda has already initiated the use of biological control of water hyacinth on Lake Kyoga with a strategy to use two weevils namely Neochetinabruchi and Neochetina eichhorniae. The strategy to build capacity and infrastructure for mass multiplication and deployment of biological control of the weevils in the field developed in Uganda by the Fisheries Research Insti tu te (FIRI) and the Namulonge Agricultural and Animal production Research Insti tute (NAARI) is proposed in outline for evaluation. Plans to deploy this strategy on lake Kyoga are under way

Farming a new economically viable fish species: Kisinja (Barbus altianalis)

Kisinja (Barbus altianalis)is an indigenous omnivorous fish, of high economic value in Uganda. It was widely distributed in most lakes and rivers in the country but its stocks were depleted due to overfishing and degradation of its natural habitat. 1t can grow up to a maximum length of 120m and a weight of 15kg in the wild and grows faster, attains larger size than commonly farmed fishes in Uganda, including the Nile tilapia, the African catfish, and mirror carp. Kisinja is a highly valuable table fish with good taste and aroma especially when smoked. Increased production of Kisinja is therefore necessary to meet economic and nutritional benefits of the communities and conservation of the spedes.

A study of Rastrineobola argentea (Pellegrin), (Pisces : Cyprinidae) and its importance in the fisheries of Lake Kyoga and the northern waters of Lake Victoria

Rastrineobola argentea is the only native fish species which is still abundant in Lakes Victoria and Kyoga, the others being two introduced species; Lates niloticus and Oreochromis niloticus. It forms an important commercial fishery in Lake Victoria and is very important as food of Lates niloticus in both lakes. The depletion of the originally abundant insectivorous and zooplanktivorous hap lochromines due to predation by Lates niloticus appears to have favoured it by reducing potential competitors for food. It now consumes a wide range of invertebrate organisms that originally used to be eaten by different specialised species of haplochromines which include: larvae and pupae of chironomids and chaoborids, copepods and ostracods. Its size in Lake Kyoga (where the Nile perch was introduced earlier) has, however, decreased and is smaller than that in Lake Victoria probably due to high predation pressure. The twin effect of predation and fishing are likely to exert heavy pressure on the species. Research is therefore required to provide information for its management.

Fishery resources: their exploitation, management and conservation in Africa

The beginning of the 20th century saw the discovery of Africa's vast natural resources. Not only did explorers "discover" lakes, rivers, forests and mountains but scientists and naturalists also "discovered what at that time were called new species of plants, fish and other animals. Thus scientific names were tagged to various species using the famed binomial nomenclature and immortalising the names of some of the people who first described those species. Africa of course abounds with thousands of different floral and faunal varieties and the early colonial scientists found the African environment lucrative fron the point of discovery of new species. This paper therefore attempts to descrihe the role science could only in the development and exploitation of one of Africa's renewable resources namely fisheries. This paper has attempted to expose the value of fish in human nutrition, provision of employment and uplifting of social and economic standards. The fishery resources of Africa are extensive and in the main not fully exploited. These resources like other natural resources are exhaustible although renewable. Efforts to exploit these resources must be encouraged but scientific planning and management of the resource is called for.

Trolling for Nile perch (Lates niloticus) in Lake Kyoga

Nile perch were introduced into Lake Kyoga in the mid·1950s from Lake Albert. Murchison Falls on the River Nile, between the two lakes, prevented Nile Perch and other elements of the typical nilotic fish population from naturally reaching Lake Kyoga. The introduction has been successful and considerable stocks of Nile Perch now exist in Lake Kyoga. In 1967, 13,000 tons of Nile Perch were estimated to have been landed by the commercial fishermen, fish of 200 lb. being now caught and specimens of 100 lb. being fairly common. Large Nile perch are caught commercially on long lines baited with live Protopterus' spp. or Clarias spp. Large mesh gillnets uccasionally take Nile Perch of up to 30 lb., but the high cost of the nets does not, at the moment, appear to justify this method of fishing; a 10 in. net, stretched 100 yards long (unmounted). 15 meshes deep and 60-ply nylon. costs approximately U. Shs. 300. The long·lines used are extremely simple and cheap to make, but considerable labour is needed to catch bait. Small Protopterus are normally caught by turning over floating rafts of grasses and papyrus, and extracting the fish from the root mass; this is hard and dirty work. Other small fish, more readily available, do not, according to fishermen, work as well, possibly because they are not as durable as the Protopterus or Clarias. Dead bait is never used.

Increase in fish production achieved by stocking exotic species (Lake Kyoga, Uganda)

The Lake Kyoga complex lies towards the north of Uganda, at 311 altitude of 3,400 feet, between 10 and 2° north of the Equator. The lake is extremely elongate and digitate, shallow (1 metre-7 metres), and almost all the coast-line is swampy, with many papyrus beds. Floating islands of sud are a feature. At its eastern extremity, it breaks up into many swampy, isolated lakes. The Nile from its source at Jinja enters Lake Kyoga on its southern side, and leaves the lake at its western extremity, and winds on through to Lake Albert and the Sudan. The Kyoga/Salisbury /Kwania complex covers 2,354 sq. km. of water. Geologically, the lake is a series of flooded river valleys, probably resulting from the uplifting of the western edge of the basin in the Pliocene and the Pleistocene ages aud the endemic fish fauna is very similar to that of Lake Victoria, although Kyoga has not developed the species flocks of haplochromis which characterise the larger lake. The Victoria fauna extends down-stream of Lake Kyoga to the Murchison Falls on the Nile, which forms an almost complete barrier between Kyoga and the typical nilotic fauna of the Nile below Murchison and Lake Albert.