Authors: Adeosun F.I., I. T. Omoniyi, Y. Akegbejo-Samsons and O.O. Olujimi
Asiatic Journal of Biotechnology Resources; 2011; 2(04)374-383
Abstract
Ikere Gorge is one of the recently constructed man-made lake in Oyo State, Nigeria. The need to assess the fish resources of this new water body was necessary hence there is no information on detailed physico-chemical parameters and fish fauna of the gorge, this study is representing the first comprehensive post-impoundment investigation of this gorge. Data on fish species was collected on monthly basis using
multi-fleet gillnet sampling techniques for two years. Four sampling stations were randomly selected for the investigation of the fish composition and abundance. A variety of sampling methods were used at each site in order to reach every fish species. At the river channel and the floodplain sites, traps, cast nets (2.55 cm mesh), monofilament nylon gillnets (15.55 cm mesh) and hook and line were employed. Efforts were made in order to catch fish species in large abundance. Some sampled fish (dead) were collected and placed in cool boxes and examined within 18h of capture, others were preserved in 15% formalin and stored for later examination. Samples of catches from the stations was the Cichlids, with Sarotherodon galilaeus, contributing 30.6% by number and 36.0% by weight, T. melanopleura, 43.0% by number and 56.2% by weight, T. melanotheron, 28.8% by number and 7.5% by weight while Tilapia zillii contributing 2.66% and 3.01% by number and weight respectively. Chrysicthys nigrodigitatus, was well represented in all the four stations, contributed 96.7% by number and 13.4% by weight while Clarias gariepinus represented 2.8% by number and 23.7% by weight. Parachanna obscura contributed only 2.1 by number and 15.4% by weight. Based on the total number of fish species encountered in all the harvests analyzed, fish diversity was highest in station III (29) i.e the river channel, which consisted of the flooded bush patches; followed by station IV (27) i.e the deepest central axis of the gorge. Station I, the shallow bays of the gorge, which consisted of the intake tower of the gorge, had (26). The lowest fish diversity (24) was obtained in station II i.e open water that covers the in-shore and off-shore area occupied by the central or middle portion of the gorge. The need to monitor human activities and fishing intensity on the gorge, in order not to destroy the fish diversity was recommended. Copyright © 2011 Pacific Publishers International.