Composition of commercially important fish species and some perspectives into the biology of the African Catfish Clarias gariepinus (Burchell), Lake Ziway, Ethiopia

Composition of commercially important fish species as well as some aspects of the biology; sex ratio and length weight relationship of Clarias gariepinus in Lake Ziway was studied. Lake Ziway is located in the Great East African Rift Valley of Ethiopia. Samples of Oreochromis niloticus, Clarias gariepinus, Carassius carassius, Cyprinus carpio and Labeobarbus intermedius were collected monthly between January and April, 2013 using longline and gillnets of various mesh sizes. Clarias gariepinus was the second most dominant species which comprises 24 % of the catch next to Oreochromis niloticus (31 %) while Labeobarbus intermedius constituted only 4% of the catch. In all cases, except for Labeobarbus intermedius, there was a preponderance of females over males. However, sex ratio was not significantly different from 1:1. Estimated fecundity of Clarias gariepinus, which was linearly related with fish and gonad sizes ranged from 443 to 1301 eggs per gram with a mean of 972. Absolute fecundity was estimated within a range of 10,000 to 560,000 eggs with a mean of 151,741. The relationship between total length of (23 to 80 cm) and total weight (165 to 6500 g) of Clarias gariepinus was curvilinear and represented as TW = 0.065 TL2.83, R2 = 0.91, P < 0.05.