Diversity, Relative Abundance and Biology of Fishes in Borkena and Mille Rivers, Awash Basin, Ethiopia

Diversity, relative abundance and biology of fishes in Borkena and Mille Rivers were studied in April and October, 2009 using gillnets of stretched mesh size from 6-14 cm, monofilaments of different mesh size hook and line and beach seines. Abiotic parameters, temperature, dissolved oxygen, transparency, conductivity and pH of the rivers were taken. A total of 2021 fish specimens were collected from both rivers. Here, 6 species, 5 genera and 2 families were recorded from both rivers. Family Cyprinidae was best represented in the two rivers. Garra dembecha, Labeobarbus intermedius and Clarias gariepinus were the most dominant fish species in both rivers. Mille River had higher fish species diversity (H' = 2.85) than Borkena River (H' = 2.53) in dry season (H' = 3.8) than in wet season (H' = 2.54). In dry season, C. gariepinus, G. dembecha and L. intermedius were the most abundant species in Borkena River with percentage Index of Relative Importance (IRI) of 40, 31.4 and 22.3, respectively. Whereas in Mille River during dry season G. dembecha, L. intermedius and V. beso were the most abundant fish species with percentage IRI of 54.5, 18.3 and 7.4, respectively. There was significant difference in Fulton s condition factor of G. dembecha and L. intermedius between Borkena and Mille Rivers. Fish diversity of Borkena and Mille Rivers is less as compared to most studied rivers in Ethiopia but the abundance was highest. The watershed of both rivers is highly degraded and that might have resulted in low diversity. Therefore, afforestation program should be practiced around these rivers to prevent further loss of the aquatic biodiversity.