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Lake Victoria
Location Africa
Coordinates 1°S 33°E / 1°S 33°E / -1; 33Coordinates: 1°S 33°E / 1°S 33°E / -1; 33
Primary inflows Kagera River
Primary outflows White Nile (river) (known as "Victoria Nile" as it leaves the lake)
Catchment area 184,000 km2 (71,000 sq mi)
238,900 km2 (92,200 sq mi) basin
Basin countries Tanzania
Uganda
Kenya
Max. length 337 km (209 mi)
Max. width 250 km (160 mi)
Surface area 68,800 km2 (26,600 sq mi)
Average depth 40 m (130 ft)
Max. depth 83 m (272 ft)
Water volume 2,750 km3 (660 cu mi)
Shore length1 3,440 km (2,140 mi)
Surface elevation 1,133 m (3,717 ft)
Islands 3,000 (Ssese Islands Uganda)
Settlements Bukoba, Tanzania
Mwanza, Tanzania
Musoma, Tanzania
Kisumu, Kenya
Kendu Bay, Kenya
Homa Bay, Kenya
Kampala, Uganda
Entebbe, Uganda
Jinja, Uganda
1 Shore length is not a well-defined measure.

Lake Victoria or Victoria Nyanza (also known as Ukerewe, Nalubaale, Sango, or Lolwe) is one of the African Great Lakes. The lake was named after the United Kingdom's Queen Victoria, by John Hanning Speke, the first European to see the lake.

At 68,800 square kilometres (26,600 sq mi), Lake Victoria is Africa’s largest lake, and the largest tropical lake in the world. As Lake Michigan-Huron is connected at the same elevation pool and is thus treated as one lake by hydrologists and geographers, Lake Victoria is the world’s third-largest freshwater lake. In terms of volume, it is the world’s seventh-largest freshwater lake, containing 2,750 cubic kilometres (2.2 billion acre-feet) of water.

The lake receives most of its water from direct precipitation. Its largest influent is the Kagera River, the mouth of which lies on the lake's western shore. The only river to leave the lake, the White Nile (known as the "Victoria Nile" as it leaves the lake), leaves at Jinja, Uganda, on the lake’s north shore [1].

Lake Victoria occupies a shallow depression in the East African Plateau, and has a maximum depth of 84 metres (276 ft) and an average depth of 20 metres (66 ft). Its catchment area covers 184,000 square kilometres (71,040 sq mi). The lake has a shoreline of some 4,828 kilometres (3,000 mi), with islands constituting some 3.7% of this length,[2] and is divided between three countries: Kenya (6% or 4,100 km2/1,600 sq mi), Uganda (45% or 31,000 km2/12,000 sq mi) and Tanzania (49% or 33,700 km2/13,000 sq mi)[3].

Lake Victoria supports Africa's largest inland fishery.[4]

Contents

Geology

Lake Victoria has, during its geological history, gone through successive changes ranging from its present shallow depression, through to what may have been a series of much smaller lakes[5]. Cores taken from its bottom show that Lake Victoria has dried up completely three times since it formed.[6] These drying cycles are probably related to past ice ages, which are times when precipitation declined globally.[6] The lake last dried out 17,300 years ago, and filled again beginning 14,700 years ago. Geologically, the lake is relatively young - about 400,000 years old - and formed when westward-flowing rivers were dammed by an upthrown crustal block.[7]

Lake Victoria and the Great Rift Valley

This geological history probably contributed to the dramatic Cichlid speciation that characterises its ecology, as well as that of other African Great Lakes[8], although there are researchers who refute this, arguing that while Lake Victoria was at its lowest between 18,000 and 14,000 calendar years ago, and it dried out at least once during that time, there is no evidence of remnant ponds or marshes persisting within the desiccated basin. If such features existed, then they would have been small, shallow, turbid, and/or saline, and therefore markedly different from the lake to which today’s species are adapted[9].

The lake's shallowness, limited river inflow, and large surface area relative to its volume make it vulnerable to the effects of climate changes.

Hydrology and limnology

Lake Victoria receives almost all (80%) of its water from direct precipitation[5]. Average evaporation on the lake is between 2,000–2,200 millimetres (79–87 in) per annum, almost double the precipitation of riparian areas.[10] In the Kenya Sector, the main influent rivers are the Sio, Nzoia, Yala, Nyando, Sondu Miriu, Mogusi and the Migori. Combined, these rivers contribute far more water to the lake than does the largest single in-flowing river, the Kagera, which enters the lake from the west[11]. The only river flowing out of the lake is the White Nile.

The lake exhibits eutrophic conditions. In 1990-1991, oxygen concentrations in the mixed layer were higher than in 1960-61, with nearly continuous oxygen supersaturation in surface waters. Oxygen concentrations in hypolimnetic waters (i.e. the layer of water that lies below the thermocline, is noncirculating, and remains perpetually cold) were lower in 1990-1991 for a longer period than in 1960-1961, with values of less than 1 mg per litre (< 0.4 gr/cu ft) occurring in water as shallow as 40 metres (130 ft) compared with a shallowest occurrence of greater than 50 metres (160 ft) in 1961. The changes in oxygenation are considered consistent with measurements of higher algal biomass and productivity[12]. These changes have arisen for multiple reasons: successive burning within its basin[13], soot and ash from which has been deposited over the lake’s wide area; from increased nutrient inflows via rivers[14], and from increased pollution associated with settlement along its shores.

Other thinkers on the subject blame the lake's eutrophication on the mass extinction of the Haplochromis species 'flock'. The fertility of tropical waters depends on the rate at which nutrients can be brought into solution. The influent rivers of Lake Victoria provide few nutrients to the lake in relation to its size. Because of this, it is thought that most of Lake Victoria’s nutrients are locked up in lake-bottom deposits[15] By itself, this vegetative matter decays slowly. Animal flesh decays considerably faster, however, and therefore the fertility of the lake is dependent on the rate at which these nutrients can be eaten up by fish and other organisms[16]. There is little doubt that Haplochromis played an important role in returning detritus and plankton back into solution [17] With some 80% of Haplochromis species feeding off detritus, and equally capable of feeding off one another, they represented a tight, internal recycling system, moving nutrients and biomass both vertically and horizontally through the water column, and even out of the lake via predation by humans and terrestrial animals and humans[18]. The removal of Haplochromis, however, may have contributed to the increasing frequency of algal blooms[19], which may in turn be responsible for mass fish kills[20].

Biology and ecology

Before 1954, Lake Victoria’s ecology was characterised by enormous biodiversity. It was inhabited by over 500 species of fish, 90% of which were Cichlids belonging to the Haplochromis genus[21]. They are known for their extraordinary ability to evolve rapidly to suit extremely localised and diverse environments, a characteristic termed ‘evolutionary plasticity’ [22]. This ability has made the cichlid species of Lake Victoria an extremely successful fish. Haplochromis species accounted for some 80% of the fish biomass of the lake[23], an abundance which led Graham [24] to believe that this species flock could support a trawler fishery of up to 200 boats. It also meant that Lake Victoria at one time boasted one of the most diverse fish environments on earth [25]. With such diversity, the cichlids of Lake Victoria managed to exploit virtually every food source available, including most detritus, zoo- and phyto-plankton[26].

On the whole, however, Haplochromis species are a small and bony species, and were generally not favoured in catches. Riparian populations preferred the lake’s two endemic species of tilapia (Oreochromis esculentus and O. variabilis[27]). Hence, by the late 1940s, British colonial authorities were debating the overall ecological efficiency of the lake. For many authorities at this time, the lake needed a large and efficient predator to turn Haplochromis fish stocks into something more economically valuable. The prime candidate was the Nile perch (Lates niloticus). This argument is central to what would eventually occur on Lake Victoria, and is therefore considered in some detail. Arguments in favour of introducing a predator was as follows:

(a) Evidence from other African lakes suggested that the Nile perch could do well commercially, and if the fish were introduced into Lake Victoria, it would no doubt eat the Haplochromis, and hence improve the overall value of the fishery. In addition, it was suggested that by introducing such a fish, fishers might turn their attentions to catching it, so easing some of the pressure on tilapia stocks[28]. Because the Nile perch can weigh as much as 200 kilograms (440 lb), it was argued, fishers would be encouraged to use large mesh-sizes to capture it[29]. Furthermore, the perch was said to prefer off-shore habitats, and this would serve to relieve pressure on the in-shore tilapia fishery[30]. (b) In those lakes where the Nile perch was a native it co-existed with tilapia species, and therefore it posed no great danger to commercially important tilapia stocks in Lake Victoria[31]. (c) The potential size of the perch made it a fine sports fish, and this might attract sports fishers and tourists to the lake region[32]. (d) Finally, archaeological findings close to Lake Victoria suggested that an ancestor of the Nile perch had been native to the Miocene predecessor of Lake Victoria, Lake Karunga[33]. It was reasoned, then, that if the perch had once been native to the lake, there was little reason why it could not be a native again[34].

The arguments against its introduction were as follows:

(a) Predators can never be as abundant as non-predators because of their nutritional requirements. In other words, the amount of fish a Nile perch has to eat to produce a single kilo of flesh is far greater than the amount of vegetative matter a tilapia has to eat to produce an equal amount of flesh. In ecological terms, the Nile perch is inefficient[35]. As mentioned above, the fertility of tropical waters depends on the rate at which nutrients (mainly detritus) are brought back into solution. The Nile perch, however, does not eat this detritus, and it was argued that its introduction would do little to improve the over-all ecological efficiency of the lake. If any fish should be introduced, it should be a herbivore or a detrivore[36]. (b) It would be wishful thinking to suppose that the Nile perch would exclusively consume Haplochromines[37]. (c) Given the complexity of tropical ecosystems, it is impossible to predict what might happen should the Nile Perch be introduced[37].

While the argument continued, it was agreed that tilapia stocks needed bolstering largely as a result of increasing fishing pressure on indigenous species, associated with the expansion of the market for fresh fish in the 1940s[38]. Tilapia introductions started in the early 1950s with Oreochromis leucostictus from Entebbe, and followed by Tilapia zillii (Winam Gulf, 1953), T. rendalli (Winam Gulf 1953/54), O. niloticus (Kagera River 1954) and O. mossambicus (Entebbe 1961/62)[39]. Because tilapia are detrivores and herbivores, these introductions were regarded as less threatening than the introduction of any carnivore. Nevertheless, while the argument over the introduction of the Nile perch raged throughout the early 1960s, it seems that it had already been surreptitiously introduced in 1954 from Uganda[40]. Once it had been discovered to be in the lake, further official introductions occurred in 1962 and 1963[41].

Introduced tilapia species were unable to establish themselves in the lake between the 1950s and 1963. Following unusually heavy rainfall in the early 1960s, however (the so-called ‘Uhuru Rains’), the lake-level rose considerably, flooding large areas of shore-line, and opening up new breeding areas to fledgling tilapia stocks, so creating the opportunities for these exotic species to compete with indigenous stocks[38]. Of the six exotic species introduced, two - Oreochromis niloticus and O. zillii - were to firmly establish themselves in the lake, so that by the early 1980’s, these two species comprised the main-stay of tilapia catches. Of the indigenous species, O. esculentus was extirpated from the lake as a consequence of competition with introduced tilapiids, while O. variabilis populations declined significantly[42].

The Nile perch is a magnificent and substantial predator. One specimen, preserved at the Kisumu Museum in Kenya, weighed 184 kg when landed. Populations of the fish established themselves in a clockwise motion around the lake, starting in Uganda, followed by Kenya and ending in Tanzania[43]. Initial catches were minimal, but grew rapidly in the 1980s, heralding the start of the so-called 'Nile perch boom'. “On the face of it...the lake after the debut of Lates [Nile perch] has turned into a fish producer that can only be described in Gargantuan terms”[44].

The introduction of the Nile perch, had a decisive impact on Haplochromis stocks which it favoured as its prey, affecting both their abundance and diversity. It is believed that the contribution of this species flock to the fish biomass of the lake has decreased from 80% to less than 1% since the introduction of the Nile perch[45], and that some 65% of the Haplochromis species were driven to extinction in the process, an event which may well represent the largest extinction event amongst vertebrates in the 20th Century[46].

Freed from their evolutionary predators, populations of the diminutive endemic Silver cyprinid Rastrineobola argentea (omena in Dholuo, mukene in Luganda and dagaa in Kiswahili), flourished, developing into huge shoals. In turn, Pied kingfisher (Ceryle rudis) populations, that had hitherto fed on Haplochromines, exploded in response to this new food source[47]. Similar and other impacts have reverberated throughout this previously unique ecosystem.

Given it's famed 'evolutionary plasticity', it follows that Haplochromis should adapt rapidly to the new environmental conditions generated by the Nile perch 'boom' (see below) and eutrophic conditions. Evidence from studies on the lake does suggest that this is happening[48]. One Haplochrimine, H. (Yssichromis) pyrrhocephalus, a zooplanktivore, was almost driven to extinction by the Nile perch. A recent study[49] of this specie found that it has recovered alongside increased exploitation of the Nile perch, at a time (the 1990s) when water clarity and dissolved oxygen levels had declined as a consequence of eutrophication. Over a period of just two decades, H. pyrrhocephalus responded to raised hypoxia (oxygen deficiency) by increasing its gill surface area by 64%. Head length, eye length, and head volume decreased in size, whereas cheek depth increased. The former morphological changes may have occurred to accommodate this increased gill size. Other morphological changes suggest adaptations in response to the availability of larger and tougher prey types.

Fisheries

By the end of the 1940s, fish stocks were under severe pressure, occasioned by (a) the growth in the fish market and associated transport infrastructure that saw fish being transported down the railway line towards the East African coast and growing urban centres in between; and (b) the arrival of improved fishing technologies, which saw boats (and, indeed, whole fleets) being used to catch fish, and flaxen gill nets introduced.[50] As described above, British colonial authorities set out to remedy this through the introduction of exotic species, including new species of Tilapia and the Nile perch. These introductions had five main impacts. The first of these was the rise of the Nile perch. The fish took some time to establish itself, and only began to appear catch statistics in the mid-1970s. By the 1980s, the ‘explosion’ of this species was being referred to as the Nile perch ‘boom’. Catches climbed from about 335 mt in 1975, to a peak of 380,776 mt in 1990.[51] The second impact was the Nile perch’s devastation of the Haplochromis species flock, its main food source. Catches of this species crashed. The third impact related to the lake’s diminutive endemic Silver cyprinid, the dagaa. Freed from competition (with Haplochromis species) for food sources, this species thrived. It was not the main target of the Nile perch, and catches increased spectacularly from 13,000 mt in 1975, to an all time high 567,268 mt in 2006. The fourth main impact of the introductions related to the exotic tilapia species. One of these, the Nile tilapia (Oreochromis niloticus), was to establish itself firmly in the fishery. Tilapia catches from the lake rose from about 13,000 mt in 1975, to an all time high of around 105,000 mt in 2000. There can be little doubt that these introductions saved the fishery from collapse. With such staggering increases, so too the entire production system on the lake changed, the fifth and final key change. Prior to the arrival of the colonial administration, the fishery was dominated by fishermen (mainly, although certain fishing techniques were reserved for women) who owned their labour and their fishing gear. Contributing to the near-collapse of the fishery in the 1940s and 1950s was the reorganisation of the fishery into fleets drawing on hired labour and much improved gear .[52] The Nile perch ‘boom’ was to accelerate and massively expand this process. It coincided with an emerging European market for high-quality white fish meat, prompting the development of industrial fish processing capacity along the lake’s shores in Kisumu, Musoma, Mwanza, Entebbe and Jinja.[53] The export of Nile perch has since expanded away from the European Union (EU) to the Middle East, the United States and Australia, and now represents large foreign exchange earnings to the lake’s riparian states. In Uganda, indeed, its export is second only to coffee in the rankings of export earnings. In 2006, the total value of Nile perch exports from the lake was estimated to be US$ 250 million.[54] The main market for the perch remains the EU, and the industry is, therefore, subject to the worries of EU health and safety inspectors. The EU has frequently closed its doors to the export for reasons ranging from unsatisfactory hygiene at factories to cholera outbreaks on the lake shores.[55]

With such high demands for Nile perch, the value of the fishery has risen considerably. Labour inflows into the fishery have increased along with growing demand. In 1983, there were an estimated 12,041 boats on the lake. By 2004, there were 51,712, and 153,066 fishermen.[56] The fishery also generates indirect employment for additional multitudes of fish processors, transporters, factory employees and others. All along the lakeshore, ‘boom towns’ have developed in response to the demands of fishing crews with money to spend from a day’s fishing[57]. These towns resemble shanties, and have little in the way of services. Of the 1,433 landing sites identified in the 2004 frame survey, just 20% had communal lavatory facilities, 4% were served by electricity and 6% were served by a potable water supply.[58]

The Nile perch fishery has proved controversial, not least between conservationists keen to see the preservation of the lake's unique ecology; and others who recognise the fish's importance to regional economies and poverty alleviation. In the 1990s, one group of thinkers argued that the export of this fish represented a net loss of fish proteins to riparian fishing communities, hence explaining high incidences of malnutrition amongst them.[59] ‘Empirical evidence. . .vividly show that the growing export of the Nile perch and the commercialisation of the dagaa are undermining the survival of households’.[60] Malnutrition amongst these communities are indeed high. One study estimates that 40.2% of children in fishing communities are stunted.[61] Rates of childhood malnutrition are, however, lower around the lake than they were in the agricultural hinterland. 5.7% of mothers at fish landing sites were found to be chronically malnourished.[61] The latter study, however, argues that these malnutrition levels do not arise from the Nile perch export, but rather as a consequence of gender relations, that tilt income distributions in favour of men, while undermining women's economic status. As the children's primary care givers, this economic status translates directly into the malnutrition rates observed. This economic disparity arises for multiple reasons, including the lack of access that women have to the fishery (very few women actually fish, although some do own fishing boats and gear); children force women to be sedentary (staying close to schools, health facilities and/or social networks), and so are unable to take advantage of the opportunities that emerge through migration, and which are available to men. Women, the authors argue, are forced to exploit peripheral economies, such as the small-scale fish trade, where they must compete against (male) buyers and the fish factories. Women, the study claims, often use sex as a means of developing relationships between fishermen, and so securing a steady supply of fish.[62] While women devote all or most of their income to their children, men have different spending priorities, such as investing in their fishing capacity, drinking and prostitution.[63]

The three countries bordering Lake Victoria — Uganda, Kenya and Tanzania — have agreed in principle to the idea of a tax on Nile perch exports, proceeds to be applied to various measures to benefit local communities and sustain the fishery. However, this tax has not been put into force, enforcement of fisheries and environmental laws generally are lax, and the Nile perch fishery remains in essence a mining operation.

Water hyacinth invasion

The water hyacinth Eichhornia crassipes, a native of the tropical Americas, was introduced by Belgian colonists to Ruanda to beautify their holdings and then advanced by natural means to Lake Victoria where it was first sighted in 1988.[64] There, without any natural enemies, it became an ecological plague, suffocating the lake, diminishing the fish reservoir, and hurting the local economies. By forming thick mats of vegetation it causes difficulties to transportation, fishing, hydroelectric power generation and drinking water supply. The plant also affects water circulation in the lake making it a breeding ground for malaria-carrying mosquitoes. By 1995, 90% of the Ugandan coastline was covered by the plant. With mechanical and chemical control of the problem seeming unlikely, the mottled water hyacinth weevil Neochetina eichhorniae was bred and released with good results.

Water Hyacinth Re-Invasion

In the late 1990s, the surface area covered by the Hyacinth reduced dramatically. It is unclear why. It is probable that the introduced weevils did serve their purpose, although El Niño weather in 1997/1998 was probably also a contributory factor[65]. It is thought that an improved light climate, an ever increasing supply of nutrients and a potentially unstable weevil population will allow a resurgence of this plant.

Satellite photos from 2006, show that the water hyacinth has re-invaded the lake. The images show that the Kenyan side of the lake around the Gulf of Winam, Kisumu bay, and Nyakach bay are covered by the plant. The new proliferation is attributed to the heavy rains that the region experienced in 2006. These rains brought in nutrients that fed the water hyacinth. Ground photos by NASA confirmed the presence of water hyacinth in Kisumu bay.[66]

Pollution

Pollution of Lake Victoria is mainly due to discharge of raw sewage into the lake, dumping of domestic and industrial waste, and fertilizer and chemicals from farms.

The Lake Victoria basin is one of the most densely populated rural areas in the world. Its shores are also dotted with cities and towns the major ones being Kisumu, Kisii, and Homa Bay in Kenya; Kampala, Jinja, and Entebbe in Uganda; and Bukoba, Mwanza and Msoma in Tanzania. These cities and towns also are home to many factories that discharge their waste directly into the lake and its influent rivers. These urban areas also discharge raw sewage into the river increasing its eutrophication that in turn is helping to sustain the invasive water hyacinth.[66]

Exploration history

The first recorded information about Lake Victoria comes from Arab traders plying the inland routes in search of gold, ivory, other precious commodities and slaves. An excellent map, known as the Al Idrisi map from the calligrapher who developed it and dated from the 1160s, clearly depicts an accurate representation of Lake Victoria, and attributes it as the source of the Nile.

The lake as it is visible from the shores of the Speke Resort in Kampala, Uganda

The lake was first sighted by a European in 1858 when the British explorer John Hanning Speke reached its southern shore while on his journey with Richard Francis Burton to explore central Africa and locate the Great Lakes. Believing he had found the source of the Nile on seeing this vast expanse of open water for the first time, Speke named the lake after Queen Victoria. Burton, who had been recovering from illness at the time and resting further south on the shores of Lake Tanganyika, was outraged that Speke claimed to have proved his discovery to have been the true source of the Nile, which Burton regarded as still unsettled. A very public quarrel ensued, which not only sparked a great deal of intense debate within the scientific community of the day, but much interest by other explorers keen to either confirm or refute Speke's discovery.[citation needed]

The famous British explorer and missionary David Livingstone failed in his attempt to verify Speke's discovery, instead pushing too far west and entering the River Congo system instead.[67] It was ultimately the Welsh-American explorer Henry Morton Stanley, on an expedition funded by the New York Herald newspaper, who confirmed the truth of Speke's discovery, circumnavigating the lake and reporting the great outflow at Ripon Falls on the lake's northern shore.

Population density around Lake Victoria
Local languages around lake Victoria

Nalubaale Dam

The only outflow for Lake Victoria is at Jinja, Uganda, where it forms the White Nile. The water 12,000 years ago drained over a natural rock weir. In 1952, British colonial engineers blasted out the weir and reservoir. A standard for mimicking the old rate of outflow called the "agreed curve" was established, setting the maximum flow rate at 300 to 1,700 cubic meters per second (392 - 2,224 cu yd/sec) depending on the lake's water level.

In 2002, Uganda completed a second hydroelectric complex in the area, with World Bank assistance. By 2006 the water levels in Lake Victoria had reached an 80-year low, and Daniel Kull, an independent hydrologist living in Nairobi, Kenya, calculated that Uganda was releasing about twice as much water as is allowed under the agreement,[68] and was the primary culprit in recent drops in the lake's level.

Transportation

Baumann Gulf in the Tanzanian portion of Lake Victoria

Since the 1900s Lake Victoria ferries have been an important means of transport between Uganda, Tanzania and Kenya. The main ports on the lake are Kisumu, Mwanza, Bukoba, Entebbe, Port Bell and Jinja. The steamer MV Bukoba sank in the lake on May 21, 1996 with a loss of nearly 1,000 lives in one of Africa's worst maritime disasters.

Movie

The impact of perch fishing upon the local economy is the subject of the documentary Darwin's Nightmare.

Lake Victoria in popular culture

References

  1. ^ Vanden Bossche, J-P. and Bernacsek, G. M. 1990. Source book for inland fishery resources of Africa. CIFA Technical Paper No. 18/1. Committee for the Inland Fisheries of Africa. Rome, Food and Agricultural Organization.
  2. ^ Hickling, C. F. 1961. Tropical inland fisheries. London, Longmans.
  3. ^ Prado, J., Beare, R.J., Siwo Mbuga, J. and Oluka, L.E. 1991. A catalogue of fishing methods and gear used in Lake Victoria. UNDP/FAO Regional Project for Inland Fisheries Development (IFIP), FAO RAF/87/099-TD/19/91 (En). Rome, Food and Agricultural Organisation.
  4. ^ Geheb, K. 1997. The Regulators and the regulated: fisheries management, options and dynamics in Kenya's Lake Victoria Fishery. Unpublished D.Phil. Thesis. Falmer, Brighton, University of Sussex.
  5. ^ a b Hickling, 1961
  6. ^ a b Reader, p. 228
  7. ^ Reader, J. Africa. Washington, D.C.: National Geographic Society, 2001. p. 227
  8. ^ Sturmbauer, C., Baric, S., Salzburger, W., Rüber, L. and Verheyen, E. 2001. Lake Level Fluctuations Synchronize Genetic Divergences of Cichlid Fishes in African Lakes. Molecular Biology and Evolution 18 (2001):144-154.
  9. ^ Stager, J.C. and Johnson, T.C. 2008. The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota. Hydrobiologia 596 (1): 5-16. DOI: 10.1007/s10750-007-9158-2
  10. ^ Ominde, S.H. 1971. Rural economy in West Kenya. In Ominde, S.H. (Ed.). Studies in East African geography and development: essays presented to S. J. K. Baker, Heinemann Educational Books Ltd., London: 207-209.
  11. ^ Whitehead, P.J.P. 1959. The river fisheries of Kenya 1: Nyanza Province. East African Agricultural and Forestry Journal 24 (4): 274-278.
  12. ^ Hecky, R.E., Bugenyi, F.W.B., Ochumba, P., Talling, J.F., Mugidde, R., Gophen, M. and Kaufman, L. 1994. Deoxygenation of the Deep Water of Lake Victoria, East Africa. Limnol. Oceanogr. 39 (6): 1476-1481.
  13. ^ Hecky, R. E. 1993. The eutrophication of Lake Victoria. Verh. Internat. Verein. Limnol. 25 (1993): 39-48.
  14. ^ Ochumba, P.B.O. and Kibaara, D.I., 1989. Observations of blue-green algal blooms in the open waters of Lake Victoria, Kenya. African Journal of Ecology 27 (1989): 23-34.
  15. ^ Beauchamp, R. S. A. 1954. Fishery research in the lakes of East Africa. East African Agricultural Journal 19 (4): 203-207; Hickling, 1961.
  16. ^ Beauchamp, 1954
  17. ^ Kaufman, L. 1992. Catastrophic change in species-rich freshwater ecosystems: the lessons of Lake Victoria. BioScience 42 (11): 846-858; Kaufman, L. and Ochumba, P. 1993. Evolutionary and conservation biology of Cichlid fishes as revealed by faunal remnants in Northern Lake Victoria. Conservation Biology 7 (3) September 1993: 719-730; Goldschmidt, T., Witte, F. and Wanink, J. 1993. Cascading effects of the introduced Nile perch on the detrivorous/phytoplantivorous species in sublittoral areas of Lake Victoria. Conservation Biology 7 (3): 686-700.
  18. ^ Kaufman, 1992
  19. ^ Goldschmidt et al., 1993; Kaufman and Ochumba, 1993; Ochumba and Kibaara, 1989
  20. ^ Ochumba and Kibaara, 1989
  21. ^ Witte, F., Goldschmidt, A., Goudswaard, P.C., Ligtvoet, W., Van Oijen, M.J.P. and Wanink, J.H. 1992. Species extinction and concomitant ecological changes in Lake Victoria. Netherlands Journal of Zoology 42 (2-3), Ch. 26: 214-232.
  22. ^ Goldschmidt, T. 1996. Darwin’s dreampond: drama in Lake Victoria. Cambridge, MA, MIT Press. Translated by S. Marx-Macdonald; Fryer, G. and Iles, T.D. 1972. The Cichlid species of the Great Lakes of Africa. Edinburgh, Oliver & Boyd; Goldschmidt et al., 1993.
  23. ^ Witte et al. 1992
  24. ^ Graham, M. 1929. A report on the fishing survey of Lake Victoria 1927-1928 and Appendices. London, Crown Agents for the Colonies
  25. ^ Coulter, G.W., Allanson, B.R., Bruton, M.N., Greenwood, P.H., Hart, R.C., Jackson, P.B.N. and Ribbink, A.J. 1986. Unique qualities and special problems of the Great African Lakes. Environmental Biology of Fishes 17 (3): 161-183
  26. ^ Goldschmidt et al., 1993
  27. ^ See for example Graham, 1929; and Beverton, R. J. H. 1959 A report on the state of the Lake Victoria fisheries. Mimeo. Lowestoft, Fisheries Laboratory.
  28. ^ Andersen, 1961
  29. ^ Anderson, A. M. 1961. Further observations concerning the proposed introduction of Nile Perch into Lake Victoria. East African Agricultural and Forestry Journal 26 (4): 195-201.
  30. ^ Anderson, 1961; Achieng, A. P. 1990. The impact of the introduction of the Nile Perch, Lates niloticus (L.), on the fisheries of Lake Victoria. Journal of Fish Biology, 37, Supplement A: 17-23.
  31. ^ Anderson 1961; Achieng 1990
  32. ^ Achieng, 1990
  33. ^ Lowe-Mcconnell, R. 1994. The changing ecosystem of Lake Victoria, East Africa. Freshwater Forum 4 (2): 76-89.
  34. ^ Achieng 1990; Worthington, S. and Worthington, E. B. 1933. The inland waters of Africa: the result of two expeditions to the Great Lakes of Kenya and Uganda, with accounts of their biology, native tribes and development. London, MacMillan and Co. Ltd.
  35. ^ Fryer, G. 1960. Concerning the proposed introduction of Nile Perch into Lake Victoria. East African Agricultural Journal, 25 (4): 267-270.
  36. ^ Beauchamp, 1954; Hickling, 1961
  37. ^ a b Fryer, 1960
  38. ^ a b Geheb, 1997
  39. ^ Hickling, 1961; Coulter et al., 1986; Mann, M. J. 1969. A resumé of the evolution of the Tilapia fisheries up to the year 1960. In EAFFRO Annual Report 1969, Appendix B. Jinja, East African Freshwater Fisheries Research Organisation, Jinja; Balirwa, J.S. 1992. The evolution of the fishery of Oreochromis niloticus (Pisces: Cichlidae) in Lake Victoria. Hydrobiologia 232 (1): 85-89.
  40. ^ Goldschmidt, 1996
  41. ^ Gee, J. M. 1964. Nile perch investigations. In EAFFRO Annual Report 1962/63, Appendix A. Jinja, East African Common Services Organization; East African Freshwater Fisheries Research Organisation, Jinja: 14-24.
  42. ^ Balirwa, 1992
  43. ^ Witte et al., 1992
  44. ^ Reynolds, J.E., Greboval, D.F. and Mannini, P. 1992. Thirty years on: observations on the development of the Nile perch fishery in Lake Victoria, Paper Prepared for Presentation at the Symposium on Impact of Species Changes in African Lakes, Renewable Resources Assessment Group, Imperial College, London, 27-31 March 1992; p. 4
  45. ^ Witte et al., 1992; Barel, C.D.N., Ligtvoet, W., Goldschmidt, T., Witte, F. and Goudswaard, P.C. 1991. The haplochromine cichlids in Lake Victoria: an assessment of biological and fisheries interests. In Keenleyside, M.H.A. (Ed.) Cichlid Fishes: Behaviour, Ecology and Evolution. London, Chapman and Hall: 258-279.
  46. ^ Goldschmidt et al., 1993: 687
  47. ^ Wanink, J.H. and Goudswaard, P.C. 1994. Effects of Nile perch (Lates niloticus) introduction into Lake Victoria, East Africa, on the diet of Pied Kingfishers (Ceryle rudis) Hydrobiologia 279-280 (1): 367-376.
  48. ^ Balirwa, J.S., Chapman, C.A., Chapman, L.J., Cowx, I.G., Geheb, K., Kaufman, L., Lowe-McConnell, R.H., Seehausen, O., Wanink, J.H., Welcomme, R.I., Witte, F. 2003. Biodiversity and fisheries sustainability in the Lake Victoria basin: an unexpected marriage? Bioscience 53 (8): 703 – 716.
  49. ^ Witte, F., Welten, M., Heemskerk, M., Van Der Stap, I., Ham, L., Rutjes, H. and Wanink, J. 2008. Major morphological changes in a Lake Victoria cichlid fish within two decades. Biological Journal of the Linnean Society 94 (2008): 41–52
  50. ^ A full description of the development of fish markets surrounding the Kenyan part of the lake is provided by Geheb, 1997.
  51. ^ See Geheb, K., Kalloch, S., Medard, M., Nyapendi, A.-T., Lwenya, C. and Kyangwa, M. 2008. Nile Perch and the Hungry of Lake Victoria. Food Policy, 33 (1): 85-98. See also catch statistics provided by the Victoria Fisheries Organisation
  52. ^ Geheb, 1997; Asowe-Okwe, C. 1996. Abavubi: an examination of the living and working conditions of fish labourers of Lake Kyoga and Victoria (Uganda). In Mamdani, M. (Ed.) Uganda, Studies in Labour. Dakar, Senegal, CODESIA: 181-240.
  53. ^ Harris, C. K., Wiley, D. S. and Wilson, D. C. 1995. Socio-economic impacts of introduced species in Lake Victoria fisheries. In Pitcher, T. J. and Hart, P. J. B. (Eds.) The impact of species change in African lakes. London, Chapman and Hall: 215-242.
  54. ^ LVFO (Lake Victoria Fisheries Organisation), 2007a. State of fish stocks. www.lvfo.org/popups/contentwindow.php?id=103&print=print. Visited January, 2007.
  55. ^ Geheb et al., 2008
  56. ^ LVFO (Lake Victoria Fisheries Organisation), 2005. Regional report on Lake Victoria Frame surveys for 2000, 2002 and 2004. Jinja, Uganda, LVFO and the Lake Victoria Environmental Management Project.
  57. ^ See for an anthropological study of these towns, called village landings, Beuving, JJ. 2010. Playing pool along Lake Victoria’s shores. Fishermen, careers and capital accumulation in the Ugandan Nile perch business, Africa: Journal of the International African Institute (80) 2: 224-248
  58. ^ LVFO, 2005
  59. ^ Kirema-Mukasa, C.T., Reynolds, J.E., 1991. Marketing and consumption of fish in Uganda. FISHIN Notes and Records: Occasional Papers No. 4. FISHIN; FAO/UNDP Project UGA/87/007; Republic of Uganda; United Nations Development Programme; Food and Agricultural Organisation of the United Nations, 1991; Abila, R. O. and Jansen, E. G. 1997. From local to global markets: the fish exporting and fishmeal industries of Lake Victoria – structure, strategies and socio-economic impacts in Kenya. IUCN Eastern Africa Programme. Socio-economics of the Lake Victoria fisheries: Report No. 2, September 1997. The World Conservation Union, Nairobi; Jansen, E. G. 1997. Rich fisheries-poor fisherfolk: some preliminary observations about the effects of trade and aid in the Lake Victoria fisheries. Socio-economics of the Lake Victoria fisheries: Report No. 1, September 1997. IUCN Eastern Africa Programme. Nairobi, The World Conservation Union.
  60. ^ Mugabe, J., Jansen, E.G., Mak’Ochieng, B., no date. Foreign cash for local food insecurity? Socio-economic impacts of liberalized trade in Lake Victoria’s fisheries. Lake Victoria Policy Brief. Nairobi, African Centre for Technology Studies. Available at www.acts.or.ke/LVpercent20-percent20Policypercent20Brief.htm.
  61. ^ a b Geheb et al., 2007
  62. ^ See also Béné, C. and Merten, S. 2007. Women and Fish-for-Sex: Transactional Sex, HIV/AIDS and Gender in African Fisheries. World Development 36 (5): 875-899. doi:10.1016/j.worlddev.2007.05.010
  63. ^ See also Appleton, J., 2000. At my age I should be sitting under that tree: the impact of AIDS on Tanzanian lakeshore communities. Gender and Development 8 (2), 19–27; Geheb, 1997
  64. ^ "Kenia: Die grüne Pest - Politik - SPIEGEL ONLINE - Nachrichten" (in German). Der Spiegel. http://www.spiegel.de/politik/ausland/0,1518,534060,00.html. Retrieved 2009-04-19. 
  65. ^ Williams, A.E., Duthie, H.C. and Hecky, R.E. 2005. Water hyacinth in Lake Victoria: Why did it vanish so quickly and will it return? Aquatic Botany 21 (4): 300-314.
  66. ^ a b "Water Hyacinth Re-invades Lake Victoria", NASA
  67. ^ "Kenya, Africa - Lake Victoria in Kenya". www.jambokenya.com. http://www.jambokenya.com/jambo/location/victoria.htm. Retrieved 2008-07-14. 
  68. ^ "Uganda pulls plug on Lake Victoria - earth - 09 February 2006 - New Scientist". www.newscientist.com. http://www.newscientist.com/article.ns?id=mg18925384.100. Retrieved 2008-07-14. 

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1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

VICTORIA NYANZA, the largest lake in Africa and chief reservoir of the Nile, lying between 0° 20' N. to 3° S. and 31° 40' to 34° 52' E. Among the fresh-water lakes of the world it is exceeded in size by Lake Superior only and has an area of over 26,000 sq. m., being nearly the size of Scotland. In shape it is an irregular quadrilateral, but its shores, save on the west, are deeply indented. Its greatest length, taking into account the principal gulfs, N. to S. is 250 m., its greatest breadth 200 m. Its coast-line exceeds 2000 m. It fills a depression in the central part of the great plateau which stretches between the western (Albertine) and eastern rift-valleys (see Africa, § I), and has an elevation of about 3720 ft. above the sea. (For the altitude see Geog. Jour., March 1907 and July 1908.) Its greatest ascertained depth is some 270 ft., which compares with soundings of 2000 ft. on Tanganyika and 2500 ft. on Nyasa. Victoria Nyanza is remarkable for the severe and sudden storms which sweep across it, rendering navigation dangerous. It contains many groups of islands, the majority being near the coast-line. The lake is full of reefs, many just below the surface of the water, which is clear and very fresh. It is abundantly stocked with fish. Geological research shows that the land surrounding the lake consists of gneiss, quartz and schistose rocks, covered, in the higher regions, with marl and red clay, and in the valleys with a rich black loam.

Table of contents

Shores and Islands

The shores of the lake present varied aspects. The western coast, which contains no large indentations, is, in its southern part, backed by precipices of 300 or more ft. high, behind which rise downs to thrice the height of the cliffs. Going north, the hills give way to papyrus and ambach swamps, which mark the delta of the Kagera. Beyond the mouth of that river the hills reappear, and increase in height, till on reaching the N.W. corner of the nyanza they rise some 500 ft. above the water. This western shore is marked by a continuous fault line which runs parallel to the lake at a short distance inland. The northern coast of the lake is very deeply indented and is marked throughout its length by rocky headlands jutting into the waters. This high land is very narrow, and the streams which rise on its northern face within a mile or two of the nyanza drain north away from the lake. On a promontory about 30 m. east of the Katonga (see below) is Entebbe, the port of Uganda and seat of the British administration. The chief indentations on the north side are Murchison Bay and Napoleon Gulf, the entrance to the last named being partly filled by the triangular shaped island of Buvuma or Uvuma (area 160 sq. m.). Napoleon Gulf itself is deeply indented, one bay, that of Jinja, running N.W. and being the outlet of the Nile, the water here forcing its way through the rock-bound shore of the lake. The north-east corner of the lake is flat and bare. A narrow channel, partly masked by islands, leads into Kavirondo Gulf, which, with an average width of 6 m., extends 45 m. E. of the normal coast-line -- a fact taken advantage of in building the railway from Mombasa to the lake. A promontory, 174 ft. above lake-level, jutting into the small bay of Ugowe, at the north-east end of Kavirondo Gulf, is the point where the railway terminates. The station is known as Port Florence. On the south side of the gulf tall hills approach, and in some cases reach, the water's edge, and behind them towers the rugged range of Kasagunga with its saw-like edge. Proceeding south the shore trends generally south-west and is marked with many deep inlets, the coast presenting a succession of bold bluffs, while inland the whole district is distinctly mountainous. At the S.E. corner of the lake Speke Gulf projects eastward, and at the S.W. corner Emin Pasha Gulf pushes southward. Here the coast is barren and hilly, while long ridges of rock run into the lake.

The largest island in the lake, Ukerewe, on the S.E. coast, immediately north of Speke Gulf, is almost a peninsula, but the strip of land connecting it with the shore is pierced by two narrow channels about 3/4 of a mile long. Ukerewe is 25 m. long, and 12 broad at its greatest width. It is uninhabited, wooded and hilly, rising 650 ft. above the lake. At the N.W. corner of the nyanza is the Sesse archipelago, consisting of sixty-two islands. The largest island in this group, namely, Bugala, is narrow, resembling the letter S in shape, and is almost cut in two in the middle. Most of these islands are densely forested, and some of them attain considerable elevation. Their scenery is of striking beauty. Forty-two were inhabited. (To prevent the spread of sleeping sickness the inhabitants were removed to the mainland in 1909). Buvuma Island, at the entrance of Napoleon Gulf, has already been mentioned. Between it and as far as the mouth of Kavirondo Gulf are numerous other islands, of which the chief are Bugaia, Lolui, Rusunga and Mfwanganu. In general characteristics and the beauty of their scenery these islands resemble those of the Sesse archipelago. The islands are of ironstone formation overlying quartzite and crystalline schists.

Rivers

The Kagera, the largest and most important of the lake affluents, which has its rise in the hill country east of Lake Kivu, and enters the west side of the nyanza just north of 1° S., is described in the article Nile, of which it is the most remote head-stream. The other rivers entering Victoria Nyanza from the west are the Katonga and Ruizi, both north of the Kagera. The Katonga rises in the plateau east of the Dweru branch of Albert Edward Nyanza, and after a sluggish course of 155 m. enters Victoria Nyanza in a wide swamp at its N.W. corner. The Ruizi (180 m.) is a deep, wide and swift stream with sinuous course flowing in part through great gorges and in part through large swamps. It rises in the Ankole district and reaches the nyanza a little north of the Kagera. Between the Katonga and the Nile outlet, the rivers which rise close to the lake drain away northward, the watershed being the lake shore. On the N.E. side of the nyanza, however, several considerable streams reach the lake -- notably the Sio, Nzoia and Lukos (or Yala). The Nzoia (150 m.), the largest of the three, rises in the foothills of the Elgeyo escarpment and flows swiftly over a rocky bed in a south-westerly direction, emptying into the lake south of Berkeley Bay. On the east side the Mara Dabagh enters the lake between 1° and 2° S. It is, next to the Kagera, the largest of the lake tributaries. All the rivers mentioned are perennial, and most of them bring down a considerable volume of water, even in the dry season. On the S., S.E. and S.W. shores a number of short rivers drain into the lake. They traverse a treeless and arid region, have but an intermittent flow, and are of little importance in the hydrography of the district. The only outlet of the lake is the Nile (q.v.).

Drainage Area, Rainfall and Lake Level

The very important part played by the Victoria Nyanza in the Nile system has led to careful study of its drainage basin and rainfall and the perplexing variations in the level of the lake. The area drained by the lake covers, with the lake itself, 92,240 sq. m. In part it is densely forested, part consists of lofty mountains, and a considerable portion is somewhat arid tableland. According to the calculations of Sir William Garstin the rainfall over the whole area averages 50 in. a year. Allowing that as much as 25% of this amount enters the lake, this is equivalent to a total of 138,750,000,000 cub. metres in a year. Measurements at the Ripon Falls show that 18,000,000,000, or some 13% of this amount, is taken off by the Nile, and when allowance has been made for the annual rise and fall of the lake-level it is apparent that by far the greater part of the water which enters the nyanza is lost by evaporation; in fact, that the amount drawn off by the river plays a comparatively small part in the annual oscillation of the water surface. Rain falls more or less in every month, but is heaviest during March, April, May and again in September, October and November. The level of the lake is chiefly affected by the autumn rains and generally reaches its maximum in July. The annual rise and fall is on an average from 1 to 3 ft., but between November 1900 and June 1901 a difference of 42 in. was recorded. Considerable speculation was caused by the fact that whereas in 1878-79 the lake-level was high, from 1880 to 1890 the level was falling, and that after a few years (1892-95) of higher level there was, from 1896 to 1902, again a steady fall, amounting in seven years to 30 in. in the average levels of the lake. In 1903, however, the level rose and everywhere the land gained from the lake in the previous years was flooded. These variations are attributed by Sir William Garstin to deficiency or excess of rainfall. Any secular shrinking of the lake in common with the lakes of Central Africa generally must be so gradual as to have no practical importance. It must also be remembered that in such a vast sheet of water as is the nyanza the wind exercises an influence on the level, tending to pile up the water at different parts of the lake. The winds may also be the cause of the daily variation of level, which on Speke Gulf has been found to reach 20 in.; but this may also partake of the character of a "seiche." Currents setting towards the north or north-west have been observed in various parts of the lake.

Discovery and Exploration

The quest for the Nile sources led to the discovery of the lake by J. H. Speke in 1858, and it was by him named Victoria in honour of the queen of England. In 1862 Speke and his companion, J. A. Grant, partially explored the N.W. shore, leaving the lake at the Nile outlet. Great differences of opinion existed as to its size until its circumnavigation in 1874 by H. M. Stanley, which proved it to be of vast extent. The invitation sent by King Mtesa of Uganda through Stanley to the Christian missionaries led to the dispatch from England in 1876 of the Rev. C. T. Wilson, to whom we owe our first detailed knowledge of the nyanza. Mr Wilson and Lieut. Shergold Smith, R.N., made, in 1877, the first voyage across the nyanza. Lieut. Smith and a Mr O'Neill, both members of the Church Missionary Society, were in the same year murdered on Ukerewe Island. In 1889 Stanley further explored the lake, discovering Emin Pasha Gulf, the entrance to which is masked by several islands. In 1890 the ownership of the lake was divided by Great Britain and Germany, the first degree of south latitude being taken as the boundary line. The southern portion, which fell to Germany, was visited and described by scientists of that nation, whose objects, however, were not primarily geographic. At the instance of the British Foreign Office a survey of the northern shores of the lake was carried out in 1899-1900 by Commander B. Whitehouse, R.N. The same officer, in 1903, undertook, in agreement with the German government, a survey of the southern shores. Commander Whitehouse's work led to considerable modification of the previously accepted maps. He discovered numerous islands and bays whose existence had previously been unknown.

Previously to 1896 navigation was confined to Arab dhows, which trade between the south end of the lake and Uganda, and to canoes. In the year named a small steamer (the "Ruwenzori") was launched on the lake by a Zanzibar firm, while in 1900 a somewhat larger steamer (the "William Mackinnon"), built in Glasgow at the instance of Sir W. Mackinnon, and afterwards taken over by the British government, made her first trip on the lake. In 1903, the year in which the railway from Mombasa to the lake was completed, a steamer of 600 tons burden was launched at Port Florence. Since that date trade has considerably increased.

See NILE and UGANDA and the British Blue-book Egypt No. 2 (1904), which is a Report by Sir Wm. Garstin upon the Basin of the Upper Nile. This report, besides giving (pp. 4-24) much original information upon the Victoria Nyanza, summarizes the information of previous travellers, whose works are quoted. In 1908 the British Admiralty published a chart of the lake (scale 4 in. to the mile) from the surveys of Commander Whitehouse. Non-official books which deal with the lake include: C. T. Wilson, Uganda and the Soudan (London, 1882); (Sir) F. D. Lugard, The Rise of our East African Empire, vol. ii. (London, 1893); Franz Stuhlmann, Mit Emin Pasha, &c. (Berlin, 1894); Paul Kollmann, The Victoria Nyanza (English translation; London, 1899); E. G. Ravenstein, "The Lake-level of the Victoria Nyanza," Geographical Journal, October 1901; Sir H. H. Johnston, The Uganda Protectorate (London, 1902). In most of these publications the descriptions of the lake occupy but a small part. (W. E. G.; F. R. C.)


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