The evolution of the fishery of Oreochromis niloticus (Pisces : Cichlidae) in Lake Victoria

The Lake Victoria ecosystem has experienced changes associated fishing levels, arise in lake level of the 1960s, fish introductions and human activities in the drainage basin. Following the fish introductions of the 1950s and 1960s, niloticus has become the most abundant and commercially important species among the tilapiines. It appears to be the only species which has managed to co-exist with the Nile perch not only in Lake Victoria but also in Lake Kyoga where the two species were also introduced. There is, however, little published information on the biology and ecology of the species in the habitats. It has therefore been found necessary to initiate studies as have been developed for Lates niloticus, especially as the two species have assumed major role in the lake's fisheries.

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.

Invertebrate communities of Lake Nabisojjo

Invertebrates are organisms without a backbone on the basis of body size. Aquatic invertebrates can be divided into two broad categories: micro-and macro-invertebrates. The former commonly known as zooplankton, ranging in size from < 100um 10 ca.1500um and are mainly planktonic (i.e living suspended in the water column). The latter, also known as benthos, (bottom dwelling) are associated with bottom sediments(ie, living on sediment surface or burrowing in sediments), are much bigger organism greater than 1500um in body size.

The fishery potential of the minor lake (Nabisojjo) - Luwero District

Luwero district before the creation of Nakasongola District had a share of south-western portion of Lake Kyoga. After loosing the portion of the lake, they want to resort the minor lake (Nabisojjo) for supply of fish at least to the population around this lake. The plans were to start commercial fishing. The lake is 45 km from Luwero town adjacent 10 the road going to Ngoma town. River Nabisojjo, a tribulary of river Mayanja flows through the lake on its way to river Kafu. The main objective of the scientific field study on Lake Nabisojjo was therefore to generate information on the status of the lake fishery and recommend to the local authorities the next line of action.

The need for a trawl fishery on Lake Victoria

The idea of mechanised fishing on Lake Victoria is not new. Trawling experiments have been carried out in the past by the East African Freshwater Fisheries Research Organisation (EAFFRO), the Lake Victoria Fisheries Service and the Uganda Fisheries Department. In 1950 it was recognised by EAFFRO that commercial possibilities existed in the exploitation of Haplochromis by this gear. However, it was not until 1966 that, by a happy collaboration of the Uganda Fisheries Department and EAFFRO, the vessel 'Darter' was converted into a stern trawler and serious and successful experimentation into trawl fishing commenced. Darter has continued to undertake trawling work ever since and this work was augmented by the arrival in 1967 of the Lake Victoria Fisheries Research Project's vessel 'Ibis'.

The effects of trawling on the fish stocks of Lake Victoria

Species composition for Lake Victoria can be divided into two major groups. Haplochromis includes at least four genera, the largest consisting of 120 major species, while the remaining species together number about eighteen. The fish species of this lake have been grouped into two for obvious reasons-Haplochromis forms at least 80 per cent, by weight, of the yield of the lake. When carrying out the survey, the lake was divided into thirteen sampling areas and, although there were variations, all the species were encountered throughout most of the sampling units, except that there were definite trends as one species moved as one from shallow water towards the centre of the lake. It was noted that there was a numerical decrease of species the nearer one got to the centre of the lake, and the catch rates of the species in deeper waters also tended to decrease. The species that were found most consistently throughout the whole lake included Haplochromis complex and Bagrus, and the species found to be confined almost entirely to the shallow waters was Tilapia, in particular Tilapia nilotica.

The marketing, processing and distribution implications of trawling on Lake Victoria

Work which has been carried out by exploratory and stock assessment scientists indicates that some 200,000 metric tons of freshwater fish could be harvested annually from Lake Victoria. Haplochromis forms approximately 83 per cent of the total stocks

The present-day fishery of the Uganda waters of Lake Victoria

The Uganda waters of Lake Victoria comprise an area of 28,500 square kilometres with a shore line of 2,380 kilometres extending from the Uganda/Tanzania border in the west to the Uganda/Kenya border in the east. A large part of the Uganda waters of the lake is less than 60 metres deep, waters deeper than 60 metres being on the eastern side of the lake. Thus the Uganda part of the lake is tilted towards the east. A number of rivers drain into the lake from the north and the River Nile flows out of the lake towards the Mediterranean Sea. The Ssese, Kome, Buvuma and Busoga Islands form a very distinctive feature of the lake. These are perhaps the remaining high hills which survived the drowning of the northern valleys during the formation of the lake. In fact, in T. P. O'Brien's book 'The Prehistoric Uganda Protectorate (1939)', Solmon gives a critical summary of the work on the formation of Lake Victoria and shows that the northern part of the lake has numerous drowned valleys, a feature which provides varying habitats for particular species of fish and which may have an effect on the species composition reflected in the catches in different areas along the northern shore of the lake. It is interesting to note that although Lake Victoria as a whole has a number of rivers draining into it, Halbfass (1923) calculated and found that 76 per cent of the water entering the lake is precipitation on the lake surface.

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.

A discussion of possible management methods to revive the Labeo victorianus fishery of Lake Victoria, with special reference to the Nzoia river, Kenya

Labeo victorianus Boulenger, the "ningu", is commercially the most important migratory fish of Lake Victoria, as well as being one of the most abundant of all species landed. Annual catch records of the Fisheries Departments of Uganda, Kenya and Tanzania show that a high yielding seasonal, floating gill net fishery is based on the concentration of sexually mature fish at the river mouths at the time of migration during the bi-annual floods. Migrating fish used also to be caught in high numbers at "kek" barrier traps across the river, as at Hainga on the Nzoia river. Since the heavy exploitation at the river mouth which occurred with the introduction of nylon gill nets in 1956.

Observations on the taxonomy and biology of Lates (Cuvier 1828) in Lake Albert

Both in terms of commercial landings and biological importance, the Nile Perch is one of the most prominent fish in Lake Albert. It can bear considerable further exploitation, is the source of stockings elsewhere, and it is, therefore, important to know whether more than one species is being dealt with, and, if so, what differences there are in the ecology of the different species.

Notes on the decline of the dug-out canoe on Lake Albert

Cadwalladr and Stoneman drew attention to the fact that dug-out canoe construction had ceased around the shores of Lake Albert by 1963. Up to this year, however, dug-out canoes were probably still landing the largest proportion of the commercial fisheries catch on the lake, and its associated waterways. It is only since this time that the catch from dug-outs has declined. and currently the commercial fisheries of the lake are based predominantly on motorised planked canoes.

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.

Freshwater medusae in Lake Kyoga

Freshwater medusae have been observed in Lake Kyoga by several members of the Fisheries Department on a few isolated occasions over the past two years. Sightings have been made at Lwampanga at the western end of the lake, at Bukungu near the inlet of the River Nile into Lake Kyoga, and at Lalle, on the eastern extremity of the main lake. Most sightings have been made near the margin of the lake under very calm conditions. At Lalle and Lwampanga large numbers of medusae have been seen swimming near the surface; on these occasions, the medusae were pulsating regularly and maintained a position within a few inches of the surface. Apart from noting that sightings have occurred under calm conditions near the lake margin, no other observations to indicate when medusae are likely to be seen have been made. Most of the medusae are of similar size, the largest being 12 mm in diameter.

A baseline survey of water quality, invertebrates, fisheries and socioeconomics on Lake Edward for proposed seismic surveys in block 4B : Final report

The National Fisheries Resources Research Institute (NaFIRRI) on behalf of OPEP Consult Ltd undertook a baseline survey of the transition zone (basically along the shoreline) and near shore habitats of the Uganda apart of Lake Edward and Kazinga channel during December 2007 to January 2008. A major objective of the baseline survey was to generate baseline information on the aquatic ecosystem features related to the fisheries and socio-economics of the fish catch including issues raised by residents in the fish landing sites. Therefore, the baseline survey captured information on water quality, the aquatic invertebrate fauna, aspects of fish biology and ecology, the fish catch including facilities at fish landings, value in the catch and related fisheries socio-economic issues perceived by residents in the settled areas along the shores.