Fish populations in two West-African coastal rivers facing different agricultural and hydroelectric schemes
Da Costa, K.S.; Gourene, G.; De Morais, L.T.; Van den Audenaerde, D.F.E.T. (2000). Fish populations in two West-African coastal rivers facing different agricultural and hydroelectric schemes. Vie Milieu (1980) 50(2): 65-77
In: Vie et Milieu. Observatoire Oceanographique Banyuls: Banyuls-sur-Mer. ISSN 0240-8759, meer
The relationship between fish species richness and water quality related variables are studied in the Agnebi and Bia rivers. Both are coastal rivers in eastern Cote d'Ivoire submitted to the impacts of small (Agnebi) and large (Bia) reservoirs. Up-stream fish species composition is similar in both rivers whereas it differs in the median and lower course, mainly due to the presence of the large dams of Ayame I and II. The presence of the dams on the river Bia explains the longitudinal gradient of species richness observed. Such gradient is much less effective in the Agnebi river where the small reservoirs are located to the upper-most part of the affluents of the river. Water quality is similar in both rivers. Yet the ordination of the water related variables by principal component analysis indicates a difference between the upper zone in the Agnebi and the median zone in the Bia river. Main discriminant factors are conductivity, total dissolved solids and hardness of water to a less extent. There was a reduced seasonal rhythmic variability in some water quality related variables, mainly nitrogen compounds and water temperature. A co-inertia analysis was performed to relate fish abundance and water quality variables. Fishes are distributed into five groups according to their affinities to specific water conditions.
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