Population Aspects of Fishes in Geba and Sor Rivers, White Nile System in Ethiopia, East Africa

Simagegnew Melaku,Mulugeta Wakjira,Abebe Getahun

doi:10.1155/2017/1252604

Abstract

This study was carried out to assess the diversity, condition factor, length-weight relationship, and sex ratio of fishes in Geba and Sor Rivers located in Baro-Akobo Basin, White Nile system within Ethiopia. Fish samples were collected in one wet and one dry season. The length-weight relationships were fitted using power equation for the most abundant species. A total of 348 fish specimens were collected using gillnets and hooks. These were identified into eight species and one Garra sp. representing seven genera and four families. Family Cyprinidae was the most dominant with six species (66.7%). Labeobarbus intermedius, Labeobarbus nedgia, and Labeo cylindricus were the most abundant fish species, respectively, with 60.72%, 16.83%, and 14.66% index of relative importance (IRI). The diversity index was higher for Geba River (H′ = 1.50) than for Sor River (H′ = 1.10). All the three most abundant species had negative allometric growth. Seasonal variations in the mean Fulton condition factor (FCF) were statistically significant for L. cylindricus (p<0.05). There was variation in the sex ratio with the females dominating in all the three most abundant species. Further investigation into the fish diversity, food, feeding, and reproductive behaviors of fish species especially in the tributaries of these rivers and their socioeconomic aspects is recommended.

Highlights

Ethiopia could be called the “water tower of northeastern Africa” on a continent where aridity is the rule
The present study was undertaken to address this gap, and as such it represents a baseline study on the diversity, relative abundance, and some biological characteristics of fishes in the rivers addressed in the present study, in an effort to contribute to any conservation attempts of their fish fauna
Labeobarbus intermedius, Labeobarbus nedgia, and Labeo cylindricus were recorded from both rivers

Summary

Introduction

Ethiopia could be called the “water tower of northeastern Africa” on a continent where aridity is the rule. A review by Tedla [3] listed 93 fish species for the entire Ethiopian freshwater system. Reviews by Getahun [5, 6] listed up to 153 valid indigenous fish species and subspecies in 25 families for the Ethiopian freshwater systems. A more recent survey by Golubstov and Darkov [7] provided a basin-wide summary of the nation’s ichthyofaunal diversity. A study on the diversity of the Ethiopian fish fauna still remains far from complete largely owing to the large expanse of its geography (i.e., 1.1 million km total area) and limited surveys. Geba and Sor Rivers are among such rivers that lack exhaustive studies on the diversity and associated biological characters of their fish fauna.

Materials and Methods

Results and Discussion

Conclusion