Preliminary Data on the Ichtyofaun of Djiri River (Affluent of right bank of Congo River)

A preliminary study of the ichtyofauna of the lower course of the Djiri River, tributary of right bank of the Congo River was undertaken during period of February 2008 to January 2009. Located at 20 kilometers in the North of Brazzaville, the Djiri River has never been the subject of an ichtyologic study. Median values of the following physicochemical parameters: temperature, pH, conductivity, dissolved oxygen, TDS, show that there is little variation during the year. Only turbidity varies considerably with minima in April (7,83 NTU) and maxima in May (33,1 NTU) and November - December (28,67 NTU). 2808 specimens of fishes, 95 species and 53 genera belonging to 23 families and 11 orders were inventoried during this study. The order of Characiformes is most representative with 30% of species, follow-on by Siluriformes (22%), Osteoglossiformes (20%), then by Perciformes and Cypriniformes (8,5% each one). The family of Mormyridae is the most diversified with 17% species, followed by Alestidae (15%) and Distichodontidae (11%). Two species dominate the collection: Synodontis nigriventris (13%) and Bryconaethiops boulengeri (11%), they are followed by Bryconaethiops microstoma (10%) and Micralestes stormsi (8%). The temporal evolution of specific diversity shows that the Shannon index is very high (superior to 2), and whatever the period of the year, that characterizes diversified populations, however a weak equitability is observed in January, March and April.