Boundaries

Within the Lower Congo Rapids ecoregion, the Congo River drops 280 m as it travels 350 km between the end of Malebo Pool and the city of Matadi (Beadle 1981). The ecoregion covers parts of the Republic of Congo and the Democratic Republic of Congo.

Freshwater habitats

As the Congo River descends toward the Atlantic Ocean, the river alternately passes through narrow, deep gorges (about 200 m wide) and wider stretches (about 2 km wide), but runs swiftly through both (Bailey 1986). This stretch of river encompasses 32 falls and rapids within the Mount Cristal Rapids. In addition to rapids with strong currents, there are also some calm sections of river between Brazzaville and Matadi. The fish fauna shows morphological and behavioral adaptations to life in fast running waters.

Terrestrial habitats

Gallery forests line the rivers and tree-savanna vegetation covers the landscape. Over the last century the vegetation within this region has changed from lowland forest to wooded savanna (Shumway et al. 2003).

Description of endemic fishes

Of the 129 fish species that have been recorded from the rapids, 34 are endemic (Roberts & Stewart 1976).

Justification for delineation

This ecoregion is delineated based on the 350-km stretch of rapids in the Lower Congo River and is distinguished by an endemic aquatic fauna adapted to the rapids. It is hypothesized that during the late Pliocene or early Pleistocene, a coastal Lower-Guinean river captured Malebo Pool, connecting the previously interior Congo basin to the ocean. The Congolian nature of the endemic species that occur in the rapids suggests that this fauna evolved before the river capture (Roberts & Stewart 1976). The rapids constitute a barrier to the movement of marine and brackish fishes from the delta into the interior of the Congo Basin.

Level of taxonomic exploration

Poor. Relatively little is known about the freshwater biota of this ecoregion. There is one paper on fishes of the Lower Congo Rapids (Roberts & Stewart 1976). In its National Biodiversity Action Plan, the government of the DRC identifies rapids and waterfalls as among those habitats most in need of biodiversity surveys (République Démocratique du 1998).