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Abstract
We sampled fishes of the rivers Gendwuha, Guang, Shinfa, and Ayima with 6, 8, 10, 12 and 14 cm stretched mesh gillnet, monofilament of different mesh sizes, hook and line, fykenet and castnet. During October 2007 through January 2008 in both dry and wet seasons. 27 fish species were identified from the four rivers represented by the families: Centropomidae, Cichlidae, Bagridae, Schilbeidae, Clariidae, Mochokidae, Malapteruridae, Osteoglossidae, Mormyridae, Characidae, Citharinidae and Cyprinidae. Species richness was slightly highest in the rivers Shinfa and Ayima - 20 species each, whereas 16 and 18 species were identified from Gendwuha and Guang rivers, respectively. Most destructive fishing methods used in the region include plant poisons and chemicals (Malathion) which are nonselective and dangerous for all biota. Action towards awareness creation in this respect should be urgently undertaken before extinction of species.
Key words: ichthyofauna, diversity, guraba, Milletia ferruginea, relative abundance, physical water parameters.
1. Introduction
Ethiopia could be called the "water tower of Eastern Africa" on a continent where aridity is the rule. Inland water bodies of Ethiopia are estimated to be about 7400 km2 of lake area and about 7000 km of river length (Wood, Talling 1988). These water bodies support large populations of commercially important fish species.
Before beginning any fishery development or aquatic ecology project we require a measure of composition of fish assemblages (JERBE 1995). By knowing species composition, we can seek to conserve and sustainably use these species. Although Ethiopia has high productivity and fish diversity little work on these waters has been done. Ethiopia appears to be the least explored for their ichthyofauna of all the regions of Africa (Golubtsov et al. 1995).
The freshwater fish fauna of Ethiopia contains a mixture of Nilo-Sudanic, East African and endemic forms (Roberts 1975; Abebe, Stiassny 1998). The Nilo-Sudanic forms are related to West African fishes, hence supporting the hypothesis that the Nile has been historically connected to the central and West African river systems (Abebe 2002). The Nilo-Sudanic forms are the dominant forms in terms of diversity and represented by a large number of species found in the Baro-Akobo, Omo-Gibe, Tekeze and Abbay drainage basins (e.g., the genera Alestes, Bagrus, Citharinus, Hydrocynus, Hyperopisus, Labeo, Mormyrus). De Graaf (2003) has described some of the elements...