Fish communities along environmental gradients within the Comoé River basin, Côte d'Ivoire
Eighty-four sites in the Comoé basin (Côte d'Ivoire, West Africa) were sampled to identify fish assemblages and their relationships with some environmental variables. Seventy-six freshwater fish species were collected from 22 families and 44 genera: 11 marine and/or brackish water species, one introduced species, and one hybrid form. Nine species were reported for the first time in this basin. Seventeen species collected previously were not detected. Among the fishes sampled, characids were the most abundant. Statistical analysis identified four groups of sites characterised by distinct fish assemblages within the Comoé basin. Assemblages from Comoé National Park were characterised by a higher proportion of Mormyridae. In the upper catchment, Cyprinidae were predominant. Downstream, assemblages were distinguished by the presence of marine and/or brackish-water fish species and the absence of Mochokidae. The middle catchment was characterised by the presence of more Characidae, Clariidae and Cichlidae than in the other sectors. The main environmental factors influencing fish distribution were substrate types — comprising rocks, mud and leaves or wood — pH, total dissolved solids, temperature and river width.