General characteristics of ichthyological fauna

Résumé 0

Currently, among nearly 11,000 fresh and brackish water fish species described in the world (Nelson, 1994; Froese & Pauly, 2016), 3,360 species have been described from Africa, belonging to 95 families (Lévêque et al., 2008). Initially, these species were listed in the Check-List of the Freshwater Fishes of Africa or CLOFFA (Daget et al., 1984, 1986a and b, 1991), but since its publication numerous species have been described or placed in synonymy following taxonomic revisions. These revisions also concerned the higher entities (genera, families). Thus, many families have been broken up into several others. For example the old family Bagridae has been divided into three families: Bagridae, Claroteidae and Austroglanididae (Mo, 1991). Conversely, some families who still retained an uncertain status could now be grouped. Thus, genetic studies have confirmed the monophyly of the Cromeriidae and Grasseichthyidae with the Kneriidae within the Gonorynchiformes (Lavoué et al., 2005).The discovery and description of new species of fish still constitute an important scientific activity in Africa. Rich faunas of cichlids endemic to the Great Lakes of East Africa have not yet delivered all their secrets. Similarly, still poorly-explored areas, such as Angola and some areas including parts of the Congo basin, should still reveal many other species.In countries where the fish fauna is considered to be relatively well-known, the introduction of new fishing techniques (electro-fishing for example) can lead to the identification of species that had not been captured using traditional techniques alone. Similarly, using new taxonomic tools (i. e., molecular techniques, specific parasitic markers, electrical signals, behaviour, etc.) has facilitated the revision of some taxonomic groups previously based solely on morphology.For example, we can mention the striking species flock of Brienomyrus (Mormyridae) in Ogowe basin in Gabon (Sullivan et al., 2002; Sullivan et al., 2004). At least 41 different forms could be identified, while only five species are described (figure 4.1). However, the specific status of some of these forms remains uncertain. Thus, it is not possible to distinguish the two groups that have different electric waves using only morphological or genetic characters (Arnegard et al., 2005) (figure 4.2).