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# of Endemic Species
526: Lake Tana
Major Habitat Type:
Michele Thieme and Ashley Brown, World Wildlife Reviewers: Leo Nagelkerke, Wageningen University Wageningen, The Netherlands
Leo Nagelkerke, Wageningen University Wageningen, The Netherlands
Main rivers or other water bodies:
Lake Tana was formed by a volcanic blockage that reversed the previously north-flowing river system (Beadle 1981). The total area of the Lake Tana basin is 16,500 km2 and the lake itself covers about 3,150 km2. Numerous seasonal streams and four perennial rivers feed the lake, while only one—the Blue Nile—leaves it (Nagelkerke 1997).
The lake is situated in the highlands of Ethiopia at about 1,800 m, and experiences a tropical highland climate.
Air temperatures range widely, between 7 oC to 31oC, whereas water temperatures stay relatively mild, normally between 18oC and 26oC (Nagelkerke 1997). The dry season lasts from October/November to May/June with maximum monthly rainfall (up to 500 mm/month) in July. Annual rainfall in the vicinity of the lake averages 1315 mm/year, but evaporation is higher at about 1,800 mm/year (Burgis & Symoens 1987).
Because evaporation exceeds rainfall, the hydrology of this shallow lake depends largely on the local climate (Burgis & Symoens 1987).
The isolation of the lake from all but inflowing rivers has led to a highly endemic freshwater biota. Fish species in the lake are most closely related to those of the Nilo-Soudanian biogeographic region.
Description of endemic fishes:
About 70% of the fish species in this highland lake are endemic, including eighteen endemic cyprinids. The fifteen large barb species of the subgenus Barbus (Labeobarbus) and the 3-4 small barb species of the subgenus Barbus (Enteromius) are currently under revision (Nagelkerke, Agricultural University, Wageningen, Netherlands, pers. comm.). The tilapia (Oreochromis niloticus) of Lake Tana belongs to a widespread species but is described as an endemic subspecies, Oreochromis niloticus tana (Seyoum & Kornfield 1992). The only river loach (family Balitoridae) known from Africa, Nemacheilus abyssinicus, was described from Lake Tana in 1902 and rediscovered in 1992 in the lake and in the upper Omo River (Dgebuadze et al. 1994).
Other noteworthy fishes:
The large catfish, Clarias gariepinus, widespread throughout
Other noteworthy aquatic biotic elements:
The invertebrate fauna is relatively depauperate. Fifteen species of molluscs, dominated by the Planorbidae family, have been described, including one endemic. An endemic freshwater sponge, Makedia tanensis, has recently been discovered in the lake. The sponge is small (specimens found were up to about 2 cm), white, and of an encrusting form belonging to a monotypic genus (Manconi et al. 1999).
A high diversity of wetland birds also lives by the lake, including the piscivorous little grebe (Tachybaptus ruficollis), great white pelican (Pelecanus onocrotalus), great and African comorants (Phalacrocorax carbo and P. africanus), and darter (Anhinga rufa). Many Paleartic migrant waterbirds also depend on the lake as feeding and resting grounds.
The radiation of cyprinid species in Lake Tana is globally recognized for its evolutionary importance (Thieme et al. 2005). The only one other extended cyprinid species flock in the world is found in the
Justification for delineation:
The ecoregion is isolated from the rest of the
Level of taxonomic exploration:
Beadle, L. C. (1981). "The inland waters of tropical Africa" England: Longman Group Limited.
Burgis, M. J.,Symoens, J. J. (1987). "African wetlands and shallow water bodies" Paris, France: ORSTOM.
De Graaf, M., Dejen, E., et al. (2000). "Barbus tanapelagius, a new species from Lake Tana (Ethiopia): its morphology and ecology" Environmental Biology of Fishes 59(1) 1-9.
Dgebuadze, Y. Y., Golubstov, A. S., et al. (1994). "Four fish species new to the Omo-Turkana basin, with comments on the distribution of Nemacheilus abyssinicus in Ethiopia" Hydrobiologia 286 125-128.
Manconi, R., Cubeddu, T., et al. (1999). "African freshwater sponges: Makedia tanensis gen. et sp. Nov. From Lake Tana, Ethiopia" Memoirs of the Queensland Museum 44 361-367.
Mina, M. V., Mironovsky, A. N., et al. (1996). "Lake Tana large barbs: Phenetics, growth and diversification" Journal of Fish Biology 48(3) 383-404.
Nagelkerke, L. (1997). "The barbs of Lake Tana, Ethiopia: Morphological diversity and its implications for taxonomy, trophic resource partitioning, and fisheries" Wageningen, The Netherlands: Special edition, Agricultural University.
Nagelkerke, L. A. J.,Sibbing, F. A. (1998). "The ‘Barbus’ intermedius species flock of Lake Tana (Ethiopia): I. the ecological and evolutionary significance of morphological diversity" Italian Journal of Zoology 65 (suppl.) 3-7.
Nagelkerke, L. A. J.,Sibbing, F. A. (1997)"A revision of the large barbs (Barbus spp., Cyprinidae, Teleostei) of Lake Tana (Ethiopia), with a description of a new species, Barbus osseensis" In Nagelkerke, L.A.J. (Ed.). The barbs of Lake Tana, Ethiopia: morphological diversity and its implications for taxonomy, trophic resource partitioning, and fisheries. (pp. 179-214) Wageningen, The Netherlands: Wageningen Agricultural University.
Nagelkerke, L. A., Mina, M. V., et al. (1995). "In Lake Tana, a unique fish fauna needs protection" BioScience 45(11) 772-775.
Seyoum, S.,Kornfield, I. (1992). "Identification of the subspecies of Oreochromis niloticus (Pisces: Cichlidae) using restriction endonuclease analysis of mitochondrial DNA" Aquaculture 102(1-2) 29-42.
Sibbing, F. A., Nagelkerke, L. A. J., et al. (1998). "Speciation of endemic Lake Tana barbs (Cyprinidae, Ethiopia) driven by trophic resource partitioning; a molecular and ecomorphological approach" Aquatic Ecology 32 217-227.
Thieme, M. L., Abell, R., et al. (2005). "Freshwater Ecoregions of Africa and Madagascar: A Conservation Assessment" Washington, D.C., USA: Island Press.