Fish biodiversity and community structure of the ecotonal zone of the mono river in benin and togo (west africa)

African rivers and floodplain lakes harbor a high fish biodiversity and support important multi-species fisheries that provide sustainable revenues and protein sources for grassroots. The present study assessed the fish biodiversity and community structure of the lower Mono of Benin and Togo in order to improve fish resource conservation and management. Fish samplings have been accomplished on the main channel and tributaries at four locations from May to December 2011. A total of 53 fish species belonging to 41 genera and 29 families were inventoried during the study period. Among the fish taxon, the most speciose family was Cichlidae with 9 species. Numerically, five families Cichlidae, Cyprinotontidae, Clariidae, Claroteidae, and Eleotridae dominated the fish assemblage and accounted together for 87.04%. The Shannon-Weaver index of species diversity (H’) ranged between 1.9 and 3.83 and higher values were recorded in the main channel and in the main tributary. Most dominant fish species showed an unimodal size distribution and higher condition factors were recorded for larger species such as Protopterus annectens (K=50.10), Clarias gariepinnus (K=17.31) and Clarias agboyiensis (K=2.63). Length-weight regression equations showed allometric and isometric growth patterns among dominant species. The lower Mono support an intense multi-species fisheries practiced by more than 13,000 professional fishermen capturing annually about 1,416 tons of fish. The lower Mono is under major ecological threats which greatly affect the fish biodiversity and the fisheries. An integrated community –based approach of ecosystem management is required to restore and to sustainably exploit this ecotonal habitat.