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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

545: Upper Lualaba

Major Habitat Type:

tropical and subtropical floodplain rivers and wetland complexes

Author:

Ashley Brown and Robin Abell, Conservation Science Program, WWF-US, Washington, DC

Reviewers:

Luc DeVos, Ichthyology Department, National Museum of Kenya, Nairobi, Kenya

Countries:

Democratic Republic of Congo; Zambia

Boundaries:

The Upper Lualaba ecoregion is defined by the Kamolondo Depression, and additionally by the wetlands, swamps, and lakes along the Lualaba River below the depression and along the adjacent Lululwe, Kilubi, and Lovoi Rivers to the west. The ecoregion lies within the Democratic Republic of Congo in the southeastern portion of its Shaba Province. 

Main rivers or other water bodies:

From south to north, the lakes are Kabwe, Kabale, Mulenda, Upemba, Lukanga, Kisale, Kalombwe, Zimbambo, and Kabamba. Kabwe and Kisale are expansions of the main river channel, with the Lualaba flowing directly through them. All of the lakes range in depth from 1 to 7 m (Bailey 1986). By some estimates there are about 8,000 km2 of lakes and wetlands in the depression and an additional 800 km2 of wetlands adjacent to the Lululwe, Kilubi, and Lovoi Rivers to the west. During the flood season, wetlands in the depression expand to cover about 11,840 km2 (Welcomme 1979; Hughes & Hughes 1992).

Topography:

The Kamolondo Depression covers an area 100 km wide and 400 km long between the Hakansson Mountains to the west (up to 1,200 m asl) and the Manika Plateau and Mulumbe Mountains to the east (up to 1,889 m asl) (Bailey 1986). The depression itself is at an elevation of about 1,000 m asl at its southwestern end, declining steeply to about 600 m asl and flattening out to form a series of lakes (Hughes & Hughes 1992). The well-mixed lakes and marshes of Upper Lualaba begin in this flatter portion of the depression, where elevations stay at about 500 to 600 m asl and extend for a total of 225 km.

Geologically, the Kamolondo Depression is a graben, a valley formed by an extension of the earth’s crust, probably during the Miocene-Pliocene (Poll & Renson 1948; Hughes & Hughes 1992). It is likely that an ancient lake once covered the depression (Bailey 1986). Sedimentation from the Lualaba, Luvua, Lufira, and Luvoi Rivers would have infilled the lake to form the swampy region present today (Denny 1985).     

Climate:

The climate of the ecoregion is tropical and relatively moist with a mean annual temperature of about 24o C. About 1,000 mm of rain falls each year, with rainfall increasing toward the equator (Hughes & Hughes 1992). The wet season lasts for approximately half the year, and December is the wettest month.

Freshwater habitats:

The waters of the upper Lualaba River, teeming with life, flow through the swampy valley of the Kamolondo Depression. Within this depression, a continuous swamp belt fringes the river and a series of lakes are connected to the river through narrow channels.  

Lake Upemba, with an area ranging between 500-800 km2 and a 70 km-long basin, is the largest of the lakes (Bailey 1986). Like the other lakes, it is shallow; with maximum depth reported to be only 3.2 m (Hughes & Hughes 1992). The lake is regularly stirred by winds and becomes supersaturated with oxygen at its bottom during the day. It is highly eutrophic and the site of intense algal production (Beadle 1981). The northern half of the lake is covered almost entirely with plants like Typha domingensis (Hughes & Hughes 1992).

The Lualaba River winds through the lake region and is joined below Lake Upemba by its largest tributary, the Lufira River. The Lufira derives much of its flow from calcareous subterranean streams and affluents that themselves receive input from warm saline springs. As the Lualaba leaves the depression, it is about 100 m wide (Bailey 1986). It then travels through a swampy belt that extends for 80 km and contains a cluster of small lakes, including Lakes Kittongola and Towe (Hughes & Hughes 1992).

 

The Lualaba and Lufira flood seasonally in response to the rains. Water level in the Lualaba is highest from February to April and lowest from August to October, with a total fluctuation of 2.8 m in the southern section of the ecoregion. Lake water levels also fluctuate; Lake Upemba is high from March to June and low from October to January (Hughes & Hughes 1992). 

Tall herbaceous vegetation dominates the swamps along the rivers and the lakes, with Cyperus papyrus and Typha domingensis prevalent. The papyrus swamps of this ecoregion are extensive. During the dry season the Lualaba flows through a navigable (usually dredged) channel, but in the wet season the areas surrounding the river become inundated and floating mats of papyrus can obstruct the channel (Bailey 1986). Common floating aquatic vegetation includes Nile lettuce (Pistia stratiotes), water chestnut (Trapa natans), Nymphaea caerulea, N. lotus, and Nymphoides indica (Marlier 1973). Pycreus mundtii and Paspalidium geminatum commonly grow on the swamp edges (Hughes & Hughes 1992). Swamp woodland patches occur on elevated sandy sites and are dominated by ambatch (Aeschynomene elaphroxylon) and Hibiscus diversifolius (Hughes & Hughes 1992). These sites are often inundated from 40 to 60 cm. 

Terrestrial Habitats:

In the south of the ecoregion the vegetation cover is primarily savanna, and changes to taller and denser forest to the north (Hughes & Hughes 1992). Grasslands dominate the plateau and Uapaca, Brachystegia, and Isoberlinia woodlands occur on lands adjacent to the wetlands (Demey & Louette 2001).

Fish Fauna:

The fish fauna is incompletely known, though it is relatively well sampled compared with other Congo Basin ecoregions (Poll 1976; Banister & Bailey 1979; Banister 1986). Poll (1976)) reports 182 fish species from the Upper Lualaba/Upemba system and its affluent river, the Lufira. Dominant fish families include Cyprinidae (over 30 species in the Lualaba/Upemba), Mormyridae (nearly 20 species), and Alestidae, Mochokidae and Cichlidae (each with 10 species or more). Fish biomass is high and many species are swamp and open water-adapted. Fish of the productive inundated zones include Hydrocynus, Clarias, Synodontis, and Schilbe species (Lowe-McConnell 1987). The main Lualaba channel supports the small plankton-feeding Microthrissa and small Barbus,as well as piscivores such as Hydrocynus vittatus (Lowe-McConnell 1987). Many of the tributary streams of Upemba primarily contain small Barbus species, though it is assumed that they also contain larger, seasonally spawning Barbus and Varicorhinus species (Banister 1986).

Description of endemic fishes:

The Lualaba/Upemba and the Lufira systems have distinct fish communities, each with at least 14 endemic fish taxa. Rapids tend to contain specialized species, and the rapids of the Lufira River are known to host several endemic fishes including cichlids (e.g. Lamprologus symoensi), kneriids (e.g. Kneria katangae), and mochokids (e.g. Chiloglanis lufirae).

Other noteworthy fishes:

Cichlids are numerous in the lakes and rivers of the Upemba area, and Oreochromis upembae, which is found in only three ecoregions, is an abundant species (Banister 1986).

Other noteworthy aquatic biotic elements:

The swamps, shallow lakes, and river channels of this ecoregion host a relatively rich aquatic fauna and suspected high endemism of Odonata (Kamdem-Toham et al. 2003). The crustacean, Thermobathynella adami, lives in a hot spring within Upemba National Park, and is probably endemic (Schminke 1987). The ecoregion has 12 species of molluscs, none of which is endemic, though there are reports of endemic molluscs at Kalengwe Rapids (Kamdem-Toham et al. 2003). Burrowing bivalves are abundant (Bailey 1986).

This ecoregion hosts a relatively rich aquatic herpetofauna. Of 47 known species of frogs, 6 are endemic. The slender-snouted crocodile (Crocodylus cataphractus) and the Nile crocodile (Crocodylus niloticus) are also present in the ecoregion. The aquatic mammalian fauna, comprised of hippopotomus (Hippopotamus amphibius), swamp otter (Aonyx congicus), giant otter shrew (Potamogale velox), and marsh mongoose (Atilax paludinosus), resembles that of other Congolian ecoregions. Several wetland birds of global conservation concern occur within this ecoregion, including the data deficient Estrilda nigriloris, the vulnerable Grus carunculatus, and the near-threatened Balaeniceps rex (Hughes & Hughes 1992; Demey & Louette 2001).

Justification for delineation:

It is likely that an ancient lake once covered the depression (Bailey 1986). Sedimentation from the Lualaba, Luvua, Lufira, and Luvoi Rivers would have infilled the lake to form the swampy region present today (Denny 1985) that is characterized by freshwater species adapted to swamps and open water.     

Level of taxonomic exploration:

Poor. Recent surveys have not been conducted in this ecoregion and little historic data on fish and aquatic invertebrates exist.

References/sources:

Bailey, R. G. (1986)"The Zaire River system" In Davies, B.R.;Walker, K.F. (Ed.). The ecology of river systems. (pp. 201-214) Dordrecht, The Netherlands: Dr W. Junk Publishers.

Banister, K. E. (1986)"Fish of the Zaire system" In Davies, B.R.;Walker, K.F. (Ed.). Ecology of river systems. (pp. 215-224) Dordrecht, The Netherlands: Dr W. Junk Publishers.

Banister, K. E.,Bailey, R. G. (1979). "Fishes collected by the Zaïre River Expedition 1974-75" Zoological Journal of the Linnean Society 66 205-249.

Beadle, L. C. (1981). "The inland waters of tropical Africa" England: Longman Group Limited.

Demey, R.,Louette, M. (2001)"Democratic Republic of Congo" In Fishpool, L.D.C.;Evans, M.I. (Ed.). Important bird areas in Africa and associated islands: Priority sites for conservation. (pp. 199-218) Newbury and Cambridge, UK: Pisces Publications and BirdLife International (Birdlife Conservation Series No. 11).

Denny, P. (1985). "The ecology and management of African wetland vegetation" Dordrecht, The Netherlands: Dr W. Junk.

Hughes, R. H.,Hughes, J. S. (1992). "A directory of African wetlands" Gland, Switzerland, Nairobi, Kenya, and Cambridge, UK: IUCN, UNEP, and WCMC.

Kamdem-Toham, A., D'Amico, J., et al. (2003) "Biological priorities for conservation in the Guinean-Congolian forest and freshwater region: Report of the Guinean-Congolian forest and freshwater region workshop, Libreville, Gabon, March 30-April 2, 2000". Libreville, Gabon. WWF.

Lowe-McConnell, R. H. (1987) Ecological studies in tropical fish communities. Cambridge, UK: Cambridge University Press.

Marlier, G. (1973)"Limnology of the Congo and Amazon rivers" In Meggers, B.J.;Ayensu, E.S.;Duckworth, W.D. (Ed.). Tropical forest ecosystems in Africa and South America: A comparative review. (pp. 223-238) Washington, DC, USA: Smithsonian Institution Press.

Poll, M. (1976). "Poissons.Exploration du Parc National de l’Upemba" Fondation pour favoriser les Recherches Scientifiques en Afrique 73 1-127.

Poll, M.,Renson, R. H. (1948). "Les poissons, leur milieu et leur peche au bief superieur du Lualaba" Bulletin Agricole du Congo Belge XXXIX 427-446.

Schminke, H. K. (1987). "The genus Thermobathynella (Capart, 1951) (Bathynellacea, Malacostraca) and its phylogenetic relationships" Revue D'hydrobiologie Tropicale 20(2) 107-112.

Welcomme, R. L. (1999). "A review of a model for qualitative evaluation of exploitation leveles in multi-species fisheries" Fisheries management and ecology 6 1-19.

Welcomme, Robin L. (1979)"Fisheries ecology of floodplain rivers" In London, U. K. and New York, NY: Longman.

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