Diversity, Relative Abundance and Biology of Fishes in Some Rivers, and Cestode Parasites of African Catfish (Clarias Gariepinus ) in Some Lakes of Ethiopia
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Date
2007-07
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Addis Ababa University
Abstract
Diversity, relative abundance and biology of fish species of Beshilo, Ardi and Dura Rivers
were studied in November 2005, March and May 2006. Conductivity and dissolved oxygen
showed significant variations among rivers (P < 0.05). The highest conductivity (415
μ.sm.cm-1) was observed in Beshilo River (BS1). The lowest conductivity (66.90 μ.sm.cm-1)
was recorded in Ardi River (A 2). The lowest (4.04 mgl-1) and the highest (7.03 mgl-1)
dissolved oxygen measurements were observed in Ardi River (A2). Fishes were sampled
using gill nets of 6,8,10, 12 and 14 cm stretched mesh sizes, hooks and lines and
monofilaments. Fish identification was done to species level by comparing the samples
meristic and morphometric characters with taxonomic keys found in the literature and
deposited specimens. Shannon diversity index and an index of relative importance (IRI) were
computed to evaluate diversity and relative abundance of fish species, respectively. A total of
1060 fish specimens belonging to three orders, five families, ten genera and seventeen species
were identified in Beshilo, Ardi and Dura Rivers. A higher number of species was recorded in
Beshilo River (13 species) than Ardi (7 species) and Dura (5 species) Rivers. The diversity
index was higher in Beshilo River (H’ = 1.65) than Ardi (H’ = 1.59) and Dura (H’ = 1.12)
Rivers. Cyprinids were the most dominant fish species in all studied Rivers. The Cyprinids
Labeobarbus intermedius, Varicorhinus beso, and Labeobarbus nedgia were the most
important fish species in the total catch. Labeobarbus intermedius, Varicorhinus beso, and
Labeobarbus nedgia of Beshilo River had isometric growth while Varicorhinus beso
exhibited positive allometric growth in Ardi and Dura Rivers. Both sexes of Varicorhinus
beso and Labeobarbus intermedius in Beshilo River were in better condition while females of
Labeobarbus intermedius were relatively in better condition than males.
Female to male sex ratio was 1:1 in combined catches with slight difference in Varicorhinus
beso. But, females out number males in dry season while males show preponderance in wet
season. Absolute fecundity increased as fish size increased. The L 50 calculated for some fish
species would help setting minimum mesh size for management in the riverine fishery
development.
Key words / phrases/: Ardi, Beshilo, Dura, Relative abundance, Rivers, Relative
Description
Keywords
Ardi, Beshilo, Dura, Relative abundance, Rivers, Relative importance (IRI), Species