Boundaries

All the westward flowing rivers of Angola lie within this ecoregion. The coastal and escarpment rivers of western Angola contain a poorly known freshwater fauna that is suspected to be rich in species and to have a high number of endemics. 

Topography

This region covers a narrow coastal plain and a stepped escarpment rising to an altitude of over 1,000 m (Hughes & Hughes 1992). 

Freshwater habitats

The Cuanza River, over 970 km long, with its major tributaries the Lucala and the Luando, has the largest catchment (about 146,000 km²) of all the rivers in this ecoregion. As the river descends below the 1,000 m contour, it begins to develop a series of extensive swamps. Near the junction of the Luando and Cuanza Rivers is a large floodplain with tracts of permanent swamp and floodplains occur sporadically downstream from here until Dondo. Wetland vegetation includes Cyperus papyrus, Typha capensis, Phragmites mauritianus, and Echinochloa stagnina. Lakes and lagoon then occur adjacent to the river until it meets the Altantic Ocean, where there are extensive mangroves (Hughes & Hughes 1992; Dean 2001).

Terrestrial habitats

Cloud forests on the escarpment appear to be in part a southern extension of the central African rainforests as well as having distinct Afro-montane affinities. Inland, on the plateau, vegetation is predominantly miombo (Brachystegia / Julbernardia) woodland, containing an extensive network of grassy dambos. Dense gallery forests line the major watercourses. Rapids or falls occur in the mainstem of all of the large rivers throughout their descent down the western escarpment of Angola (Roberts 1975). Coastal savanna is the predominant vegetation on the coastal belt, although thicket is more common in the north (Stuart et al. 1990).

Description of endemic fishes

Possibly as many as thirty endemics (27%) are known from this ecoregion but the real status is difficult to ascertain given the lack of comparative information from neighboring tributaries of the Congo and the Angolan reaches of the Cunene and the Okavango (e.g., see Greenwood 1984)(Greenwood P. H. 1984).

Justification for delineation

The fish faunas of the rivers of this ecoregion are poorly known, however, it appears that they have greater affinity with the fauna of the Southern West Coastal Equatorial bioregion than with the Congo or Zambezi bioregions. The Cuanza ecoregion is considered its own distinct bioregion because the Zambezian fauna is absent or poorly represented and there are a number of endemic species described (Trewavas 1936, 1973; Roberts 1975). The Cichlidae and a number species from other families in the upper Cuanza River are related to species from the Zambezi and Cunene River basins (Trewavas 1973). The earlier Vernay Angola Expedition (Nichols & Boulton 1927) and Gray African Expedition (Fowler 1930) also record a number of species from the upper reaches that are distinctly Zambezian, thus, the upper Cuanza basin has been included in the Zambezian Headwaters ecoregion [555].

Level of taxonomic exploration

Poor. This is a critical ecoregion for major collection effort and study, as it is very little known scientifically. The faunas and ecological functioning of the aquatic systems in the region are in need of investigation, and a significant amount of further study is needed before the degree of biological distinctiveness can be determined in this area.