Diversity Relative Abundance And Biology Of Fishes In Some Rivers And Cestode Parasites Of African Catfish (clarias Gariepinus ) In Some Lakes Of Ethiopia

Diversity, relative abundance and biology of fish species of Beshilo, Ardi and Dura Riversrnwere studied in November 2005, March and May 2006. Conductivity and dissolved oxygenrnshowed significant variations among rivers (P < 0.05). The highest conductivity (415rnμ.sm.cm-1) was observed in Beshilo River (BS1). The lowest conductivity (66.90 μ.sm.cm-1)rnwas recorded in Ardi River (A 2). The lowest (4.04 mgl-1) and the highest (7.03 mgl-1)rndissolved oxygen measurements were observed in Ardi River (A2). Fishes were sampledrnusing gill nets of 6,8,10, 12 and 14 cm stretched mesh sizes, hooks and lines andrnmonofilaments. Fish identification was done to species level by comparing the samplesrnmeristic and morphometric characters with taxonomic keys found in the literature andrndeposited specimens. Shannon diversity index and an index of relative importance (IRI) wererncomputed to evaluate diversity and relative abundance of fish species, respectively. A total ofrn1060 fish specimens belonging to three orders, five families, ten genera and seventeen speciesrnwere identified in Beshilo, Ardi and Dura Rivers. A higher number of species was recorded inrnBeshilo River (13 species) than Ardi (7 species) and Dura (5 species) Rivers. The diversityrnindex was higher in Beshilo River (H’ = 1.65) than Ardi (H’ = 1.59) and Dura (H’ = 1.12)rnRivers. Cyprinids were the most dominant fish species in all studied Rivers. The CyprinidsrnLabeobarbus intermedius, Varicorhinus beso, and Labeobarbus nedgia were the mostrnimportant fish species in the total catch. Labeobarbus intermedius, Varicorhinus beso, andrnLabeobarbus nedgia of Beshilo River had isometric growth while Varicorhinus besornexhibited positive allometric growth in Ardi and Dura Rivers. Both sexes of Varicorhinusrnbeso and Labeobarbus intermedius in Beshilo River were in better condition while females ofrnLabeobarbus intermedius were relatively in better condition than males.rnFemale to male sex ratio was 1:1 in combined catches with slight difference in Varicorhinusrnbeso. But, females out number males in dry season while males show preponderance in wetrnseason. Absolute fecundity increased as fish size increased. The L 50 calculated for some fishrnspecies would help setting minimum mesh size for management in the riverine fisheryrndevelopment.rnKey words / phrases/: Ardi, Beshilo, Dura, Relative abundance, Rivers, Relative

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