Diversity, and Some Population Parameters of Fishes inGilo and Duchi rivers, Baro-Akobo Basin, South West, Ethiopia

Abstract

Ethiopia has a freshwater system thatcan be divided into six major drainage basins in relation to its ichthyofaunal distribution. Inland water bodies of Ethiopia are estimated to be about 7400 km 2 of lake area and about 7000 km of river length. However, its freshwater fish diversity is poorly studied. This study was conducted in Gilo (Bako) and Duchi rivers, BaroAkobo Basin, with the objective of to identify fish diversity using some population parameters. Fish Samples were collected in dry (March-May, 2018) and wet (June-August, 2018) seasons using gill nets of 12, 16, 20 and 24 cm stretched mesh sizes, and hook. A total of 287 fish specimens that are categorized into seven species, four genera, two families and two orders were collected andidentified from these rivers during both seasons. The represented families were Mormyridae and Cyprinidae; the latter being the most diverse family with respect to number of species.Shannon–Weiner diversity index (H') of fish species in Gilo River (H' = 1.78) was greater than that of Duchi River (H' = 0.17). However, the fish diversity indexes recorded for Gilo and Duchi Rivers are relatively lower compared to the values reported for other rivers in the country. Labeobarbus intermedius, Labeobarbus nedgia and Labeobarbus degeni were the most abundant fish species both in terms of number and Index of Relative Importance (IRI), respectively. Overall, fish abundance in dry season was higher than in wet season. The length-weight relationships for these species were best fitted using power regression equation. The mean Fulton Condition Factor (FCF) for L.intermedius, L. nedgiaandL. degeniwere 1.85, 1.76 and 1.57, respectively, inGilo and Duchi Rivers. There was significant variation (t-test, P<0.05) in FCF of L. nedgia in the both seasons and rivers. As observed during this study, the factors contributed to the differences in fish diversity of the two rivers include human intervention, channel flow and the altitude and climatic differences of the rivers locations.However, variations were not significant (t-test, P > 0.05) for the L. intermedius and L. degeni.Besides, basic fishery activities and habitat characteristics of both rivers were discussed and compared with other previous studies. It is,therefore, believed that this study has generated base-line data on fish diversity and some population parameters of fishes in the study area that would help in the proper and sustainable utilization of the resources.Detailed studies and investigations are required on socio-economic aspects of the two rivers.