Study of Some Biological Aspects of the Nile Carp, Labeo niloticus (Pisces, Cyprinidae) from Khashm El-Girba Reservoir and Atbara River, Sudan: I Abundance; Sex Ratio; Gonado-somatic Index and Breeding Season

The aim of this study is to investigate some biological aspects of the Nile carp, Labeo niloticus, in Khashm El-Girba reservoir and Atbara River, Sudan. The study was conducted during December 2015 to November 2016. Samples were collected bi-monthly from three localities, namely; Um Aswad (Atbara River), El-Remila and El-Monaba (Khashm El-Girba reservoir), using beach seine nets of 1.2 cm 4.0 cm and 7.0 cm stretched mesh. A total number of 1,190 specimens of L. niloticus were collected from the three sampling sites. Two peaks of abundance were observed for L. niloticus at all sampling sites (February- March and September- October). Sex ratio was 1:1, except in downstream areas, where females were more dominant than males. Gonado-somatic index showed one peak of increase, and ranged from 1.28 - 1.79 and 0.50 – 1.701 for females and males respectively, indicating one spawning season.