Fish species occurrence, estimates and human activities on the islands of the Congo River, Central Africa

Human induced habitat destruction and modifications cause losses of aquatic and terrestrial biodiversity. The Congo and its islands constitute special ecosystems and have been used by humans for many purposes over centuries. However, little is known about the effects of these human activities on the fish species richness and distribution. This study is a preliminary assessment of island habitat types, fish species richness and effects of human activities on fish distribution. Islands were randomly selected to describe island habitats, to collect fish specimens using nets and to record human activities, including agriculture. Terra firma island habitats were mostly mixed mature forest with clay and muddy substrates. We captured 29 fish morphotypes (13 families). Clariidae and Cyprinidae were widely distributed whereas Alestidae, Chanidae, Malapteridae and Polypteridae were restricted in their distribution. Humans permanently settled 76 % of the islands and 70 % were cultivated. Permanent human settlements and agriculture were related to erosion on similar to 50 % of islands. For reasons that are difficult to explain at this stage, fish morphotype richness decreased with increasing field sizes, warranting further investigations.