To study the influence of different photoperiodS on growth, fed utilisation and
chemical composition of Nile tilapia, Fingerlings (4.21 0.1g) of O. niJolicus were reared
under five photo periods. OOL:240, 08L:160, 12L:120. 16L:08D and 24L:OOO. Over 56
days experimental period, fish exposed to OOl:240 cycle showed a lower specific
growth rate, a lower feed intake, a higher food conversion ratio, a I<>wer protein
efficiency ratio snd a lower protein productive value compared with those exposed to
24L:OOO cycle. Growth and feed utilisation data ranged from 2.57 to 2.11, 21.70 to
17.13,1.63 10 1.83, 1.94 to 1.72 and 31.771026.71 forspecificgrowth,feedinlake,
food conversion ralio, protein efficiency ratio and protein productive value respectively
being highest for fish reared under continuous light. In terms of carcass cornpcsitlon.
there were no differences regarding moisture, crude protein, crude lipid and ash
contents among all tested groups. Present results show that continuous light stimulates
the activity of fish, increases feed intake and then enhances the growth rate and feed
utilisation parameters of fish; whereas continuous dark inhibit the activity of fish, reduce
feed intake and deCl"ea~ed 9fCW\h rate and feed utilisation parameters.