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Distribution, abundance and food of commercial fish in the Black Volta and the Volta Man-made Lake in Ghana during the filling period (1964–1968). II. Characidae.

Research paper by T. Petr

Indexed on: 01 Oct '74Published on: 01 Oct '74Published in: Hydrobiologia



Abstract

The characids Alestes and Hydrocynus are common fish of the Black Volta River in Ghana. In Lake Volta, which formed in 1964 after damming the Volta River, Alestes formed a large percentage of commercial fish landings since the beginning of impoundment. However, this genus has been gradually changing its areas of distribution in the lake, and from the third year on it has been occupying mainly the upper end of the new lake. This area with large inflowing rivers has been found to favour Alestes baremose, which has been congregating there in large numbers. The strictly lacustrine environment of the south was poor in Alestes for some time. This was evidently due to overfishing, natural mortality, emigration of the fish from this area, and possibly to small recruitment because of the poorly oxygenated waters during the first two years of impoundment. With time, however, the numbers of Alestes baremose, Alestes dentex senthente, and especially Alestes macrolepidotus have increased in commercial landings in the south.The distribution of Alestes in the lake does not seem to be determined by the abundance and easy availability of food. The rich supply of the ephemeropteran Povilla and other food items has not prevented the withdrawal or rapid decrease in numbers of Alestes in some areas.The abundance of the predatory Hydrocynus in Lake Volta seems to be directly related to the distance from the inflowing rivers. More distant areas have less Hydrocynus than areas close to the rivers. The distribution of Hepsetus odoe seems to be just the opposite.