Geophysical characteristics

• Lake Kyoga is located wholly within Uganda but is internationally connected via the Nile. It consists of two main arms, Kyoga and Kwania, and over 30 smaller lakes separated from the main lake by swamps
• The open waters of the lakes cover 2 600 km2.
• The Kyoga catchment extends over 60 000 km2 which is ~25% of Uganda's surface area of 240 000 km2.
• The Kyoga lakes have a mean depth of 2-4 m, with the deepest part of 7-9 m being along the course of the Nile.
• The lake's volume of ~8 km3
• Most of the water input (82%) is from Lake Victoria, 9% from catchment inflow, and 9% from direct rainfall. Most (83.7%) of the water from the lake is lost through outflow of the Nile and 16.3% through evaporation.
• Lake Kyoga is a river lake formed by convergence of a number of rivers including Victoria Nile, Mpologoma, Dopoth-Okot, Sezibwa, Kafu-Mayanja and the outflow is through the Victoria Nile over the Murchison Falls into Lake Albert. It has an extensive swamp around it but the swamp area has been reduced through conversion to agriculture.
• When the lake was first surveyed in 1928 by Worthington, most of it was covered by macrophytes with only a narrow portion of open water. The open water area expanded following a rise in lake level in 1961 which submerged the macrophytes.

Demographic characteristics

• The population density around the lake is 25-250 km-2.
• The population in the districts bordering Kyoga lakes is amongst the poorest in Uganda and fisheries are important in their livelihoods.

Fishes and fisheries

• At the time of the first survey by Worthington in 1928, the lake had at least 45 species including two native tilapia species Oreochromis variabilis and O. esculentus which are endemic to the Victoria/Kyoga system.
• The native tilapias contributed over 90% of the catch between 1937 and early 1950's after which their contribution dropped and their stocks collapsed due to use of under sized gillnets which caught immature fish..
• The Nile perch (Lates niloticus) and four tilapia species: Oreochromis niloticus, O. leucostictus, and Coptodon zilli were introduced into the lake in 1955 to increase fish productions and to provide information on the impacts of the proposed introduction of these fishes in Lake Victoria.
• The introduced species became well established after about ten years resulting in an increase in fish catches from 18,000 t in 1964 to a peak of 165,200 t in 1978 after which the catches declined to 55,000 t by 1989, and 38,000t by 2008, again due to use of destructive fishing gears and methods.
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The number of boats more than doubled from 3,500 in 1978 to 8400 by 2008 which contributed to the decline in fish catches.
The fishing gears allowed on the lake are gillnets of not less than 127mm and hooks of size 9 for the larger species especially Nile Tilapia and Nile perch, and seine nets of not less than 8 mm for the small cyprinid species Rastrineobola argentea (Mukene). Mukene is supposed to be fishes beyond 2 km from the shoreline to avoid catching immature individual of larger species which are predominantly found inshore.
Establishment of Nile perch was followed by a collapse in stocks of haplochromine species due to predation by Nile perch while the establishment of Nile tilapia contributed to elimination of the remnants of native tilapias whose stocks had already virtually collapsed due to overfishing.
Some of the fishes that disappeared from the main lake especially haplochromines still survive in some of the small satellite lakes of the Kyoga basin and should be protected in these lakes.
As the catches that increased following establishment of introduced fishes’ declined, the fishery became dominated by Nile tilapia - 61%, Nile perch -15% and Mukene (Rastrineobola argentea) - 17 %. There was also resurgence of a few haplochromine species dominated by detritevores.
Cage aquaculture has not grown on Lake Kyoga as in Victoria because it requires water of a minimum depth of 5m but there are demands to develop it and suitable technology should be developed to achieve this.

The lake habitat

• Lake Kyoga is polymictic.
• Physico-chemical conditions, nutrients, algal and invertebrate productivity and composition vary across the lake from the east to the west.
• Conductivity decreases from >168 µScm-1 in the east to <100 µScm-1 in the center to 99 µS cm-1 in the west along the Nile.
• Total phosphorus (TP) in the lake has fallen from 174 µgL-1 in the 1960s to 48-62 µgL-1 in 1990’s to 2000.
• Cyanobacteria are the dominant algae in the eastern, and diatom Aulachoseira spp in the western part of the lake.
• The zooplankton density decreases from 6,100,000 ind.m-2 in the east to 2,200,000 ind. m-2 in the west.
• The lake was heavily infested with water hyacinth in the 1989 which covered 60% of the shoreline and by Kariba weed in early 2000s.
• The lake has undergone major water level fluctuations associated with changes in climatic factors which have affected lake productivity processes, fisheries and livelihoods.

Basin factors

• People in the Kyoga lake basin depend on agriculture and natural resources especially fish for their livelihoods.
• Rampant cutting of trees to open up land for agriculture and for charcoal and wetland degradation has exposed much of the land to erosion causing siltation of the lake and this is a major threat to the lake due to its shallowness.
• The entire Kyoga lake system is a wetland but the macrophyte cover in the riparian area has decreased overtime due to conversion mainly to rice cultivation. For instance, it decreased by 48.5% between 1994 and 2008.
• There are four dams (Nalubaale, Kiira, Bujagali, and Isimba) that control the flow of the water along the Nile from Lake Victoria before it enters Lake Kyoga. Their operation affects the level of the Lake Kyoga because 84% of the water into the lake comes from Victoria.
• There are no major urban areas of concern along the lake shore except for small peri-urban areas consisting mainly of landing sites but there are some towns in the catchment including Mbale, Soroti, Palisa and Kamuli.
• There were previously ports at Namusagali and Masindi which provided railway connection but are no longer operational. There is a ferry service linking southern and northern shores of the lake.
• There were previously ports at Namusagali and Masindi which provided railway connection but are no longer operational. There is a ferry service linking southern and northern shores of the lake.

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