Hydro-Biology And Fish Production Of The Black Volta Near The Bui Dam During The Pre- And Post-Impoundment Periods

ABSTRACT

The hydro-biology of the Black Volta near the Bui dam were studied in relation to fish production as measured by catch per unit effort (CPUE) during the pre- and post-impoundment periods between February 2011 and December 2012. The primary objective was to assess the ecological impacts of the dam on the hydro-biological factors and fish production and provide data for monitoring the hydro-biology and fisheries of the Bui reservoir. Two sampling stations at Bui and Bamboi were selected to represent the upstream and downstream stations respectively. Physico-chemical parameters such as electrical conductivity, total dissolved solids, colour, dissolved oxygen and sulphates differed significantly (p < 0.05) during the pre-impoundment (March – May 2011), immediate post-impoundment (June – December 2011) and late postimpoundment (January – December 2012) periods. Hence, indicating the impact of the impoundment on these parameters. The Canonical Correspondence Analysis was used to trace temporal phytoplankton and zooplankton community changes, and to examine the relationships between species composition and physico-chemical variables. These variables were subjected to analysis, pair-wise, to identify correlations. The relative abundance of some phytoplankton species such as Anabaena sp, Planktothrix sp and Scenedesmus sp were directly correlated to nitrates. The phytoplankton groups, namely Bacillariophyceae, Chlorophyceae, Euglenophyceae and total phytoplankton differed significantly (p < 0.05) between the pre- and post-impoundment periods. The phytoplankton and zooplankton groups were also significantly (p < 0.05) higher in the upstream station than the downstream station indicating the impact of the impoundment on the downstream ecology.