Spatial and seasonal fish community patterns in impacted and protected semi-arid rivers of Burkina Faso

摘要

This research evaluates fish assemblages in both impacted and protected areas in tropical seasonal small rivers in Burkina Faso. The study zones were, respectively, in the much-impounded area of Koubri close to the capital city Ouagadougou and in the protected Ranch of Nazinga along Burkina's southern border with Ghana. The impacts on these assemblages were evaluated in terms of seasonal changes in fish and the disruption of dams as an opportunity for fish to migrate. Burkina Faso is a leading country in reservoir creation in Africa and this is the first time the impacts of these reservoirs as fish barriers have been evaluated. Analyses of comparative seasonality, electric and traditional fishing equipment are provided. A total of 35 fish species were recorded in the 14 reservoirs impacted by intense agriculture and commercial fishing. In contrast, the protected area of Nazinga recorded 48 species with a higher frequency of intolerant species, e.g. Sarotherodon galilaeus. Altogether 56 species within 16 families were recorded. Average fish size for most of the species was significantly smaller in Koubri than in Nazinga. Accidental dam breaks have impacted fish assemblages in a manner similar to dam removal. Habitat improvement and unobstructed migration to the main river have increased the number of species in comparison to the previous situation of impoundment by 30%. The results of this research make important contributions to the integration of information concerning fish ecology and land use in semi-arid areas of Africa.