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This work evaluates the growth and body development of Oreochromis niloticus in floating cages in the Toho Lake of Benin. Thus, 6000 juvenile monosex male with an average initial weight of 8.87 ± 4.89 g and average initial total length of 7.87 ± 1.43 cm were randomly distributed in two floating cages (5 x 5 x 2.5 m³) at the stocking density of 3000 fish/cage. The fish were hand-fed to apparent satiation, three times daily, using 45-32% crude protein commercial pelleted floating feed Skretting®. The physico-chemical parameters of lake water recorded every 72 hours during the experiment were within the suitable ranges for fish culture and were as follows: temperature (27.78 ± 0.41 °C), pH (7.55 ± 0.22), dissolved oxygen (4.03 ± 0.96 mg/l), ammonium (0.31 ± 0.18 mg/l), nitrite (0.29 ± 0.07 mg/l) and nitrate (0.27 ± 0.12 mg/l). The variables studied at the end of  the 215 days of rearing were as follows: final mean total length (26.61 ± 2.99 cm), final mean standard length (22.40 ± 2.74 cm), final mean predorsal length (6.93 ± 0.94 cm), final mean head length (3.45 ± 0.58 cm), final mean dorsal fin base length (13.55 ± 2.96 cm), final mean inter-orbital width (2.97 ± 0.37 cm), final mean body height (8.57 ± 1.56 cm) and final mean caudal peduncle height (3.27 ± 0.39 cm). The zootechnical growth parameters evaluated were as follows: survival rate (91.5%), final mean body weight (402.18 ± 137.05 g), average daily weight gain (1.83 ± 0.08 g), specific growth rate (0.77 ± 0.03%/day), feed conversion ratio (1.74 ± 0.09%) and protein efficiency ratio (1.62 ± 0.06). These results compared to the literature indicate interesting growth and body development and it would be important to promote in-cage farming of Oreochromis niloticus.