The experimental was carried out in the second lake of Wadi EI- Rayian Lake
at Fayoum Governorate. Twelve floating cages were used as experimental units, each
cage measures 7x 7x x2 m with submerged depth 1 m (net volume=49 m\
Fingerlings of Nile tilapia with an initial average weight of 22g ±O.7g were randomly
distributed into cages at 30 fish/m³ with total biomass of 1470 fish in each cage. Four
treatments were conducted to study the effect of feeding levels on performance of
tilapia. In the T1, fish were fed on the available natural food, whereas in T2 and T3,
the fish fed daily at 3 and 5% from their body weight, respectively. However in the
fourth treatment (T4), fish were fed to apparent satiation. The commercial pelleted diet
(25% C.P.) was offered two timesl day. The Performance of tilapia showed Significant
differences among treatments (p < 0.05). The best performance records for gain, GR,
SGR. and PER were obtained with the fish fed to apparent satiation (T 4), followed in a
decreasing order by fish fed daily at 3% from their body weight. On the other hand,
fish depended only on the natural food and which received 5% of B.W., showed
inferior performance parameters compared with the other treatments. The carcass
composition of tilapia was not affected by feeding levels, except that of fish fed 5%
B.W. which gave less increase in their body fat content. In the same trend, the blood
characteristics of tilapla (hematocrite. hemoglobin and plasma protein content) were
not affected by feeding levels. The total fish production and net returns showed an
increase in yields for the .cages fed to apparent satiation. It could be concluded that
fish fed to apparent satiation (feed amount equivalent 2.7% of body weight/day)
enhance the growth performance, blood characteristics and yields of tilapia
Oreochromis niloticus .