الفهرس 
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Abstract
The biological characteristics of Nile tilapia (Oreochromis niloticus) in the River Nile in three separate water bodies by artificial barriers: Lake Nasser, Aswan Reservoir, and Main River in Egypt, including food habit, length & weight relationship, age & growth, and reproduction. Samples were collected during different flood seasons by different fishing gears during 2019-2020. The mean total length of the O. niloticus was )24.72, 17.02 and 18.75 cm) while mean total weight was (322.11, 92.29 and 135.54 g) in Lake Nasser, Reservoir and River Nile, respectively. The mean values of the condition factor in Lake Nasser were (1.62, 1.51, 1.84), in Aswan Reservoir (1.33, 1.55, 1.77) and River Nile (1.51, 1.54, 159) Pre-Flood, Flood and post Flood respectively. The growth model parameters were L∞ = 41.11, 24.17 and 32.50 cm, K = 0.20, 0.27 and 0.22 year-1 and t0 = - 1.18, -2.59 and -1.50 in Lake Nasser, Aswan Reservoir, and River Nile respectively. The overall sex ratio M:F was (1:1.03) in Lake Nasser, (1:0.52) in Aswan Reservoir and (1:0.81) in River Nile. Two peaks of the gonadosomatic index were exhibited, the females have two peaks in pre-flood (July) and post-flood (January) in Lake Nasser and during the flood (October) and post-flood (January) in Aswan Reservoir and River Nile. The hepatosomatic index was recorded as the lowest value during pre-flood (July) and the highest was during post-flood (January) for both sexes for the three locations. The overall major food items of the species were plant origin and animal origin. The results highlighted basic biological features of Nile Tilapia species which can assist in fisheries management and conservation of the fish species in three separate water bodies in River Nile, Egypt.