Mortality and Exploitation Rates of Challawa Gorge Dam Fishes, Kano State, Nigeria

Ahmad IM, Yola ID and Suleiman

Abstract

Analyses were done on length-frequency data to study the mortality and exploitation rates of fish species of Challawa gorge dam. The species were: Bagrus bayad macropterus, Synodontis schall, Oreochromis niloticus, Pollimyrus isidori, Marcusenius senegalensis, Schilbe uranoscopus, Clarias lazera, Lates niloticus, Brycinus nurse and Auchenoglanis occidentalis. The total mortality (Z), the fishing mortality (F), the natural mortality (M), the current exploitation rate (E), Probabilities of Capture and their Biological Reference Points were all assessed. Bagrus b. macropterus, Synodontis schall, Clarias lazera, Lates niloticus, Schilbe uranoscopus and Auchenoglanis occidentalis were over-exploited. Oreochromis niloticus was optimally harvested. While Pollimyrus isidori, Brycinus nurse and Marcusenius senegalensis were underexploited.