Abstract: hybrid tilapia were distributed into twelve tanks, each stocked in six fish(A,B,C,D,E,F) with different body size. The initial body weight was 62.69?1.46 g for fish A, 56.48?1.30 g for B, 50.75?1.19 g for C, 35.56?1.18 g for D, 31.05?0.88 g for E, and 27.35?0.95 g for F (mean盨E). The fish were reared under four ration levels (deprived of feed, fed at 1.5% body weight per day (BW穌^-1), fed at 3.0% BW穌^-1, or fed excess) throughout four weeks, respectively.The specific growth rate (SGR) and feed efficiency (FE) of the fish increased with increasing ration level up to 3.0% BW穌^-1, and then, SGRmaintained at a constant level while FEdropped with continuing increase of ration.The variance coefficient of SGRand final body weight was relatively high in the fish that fed at 1.5 % BW穌^-1 .For fish A, SGR was not significantly different, between 1.5 %BW穌^-1,3.0% BW穌^-1 and fed excess, while in fish F,relatively high variations were found among different ration treatments. This experiment revealed that the growth and size hierarchy of hybrid tilapia were related to their ration level and initial body size. Under ration levels more than 3.0% BW穌^-1, SGRwas usually high, and size hierarchy was relatively weak.

Key words: Hybrid tilapia, Growth, Ration level, Body weight, additive system, seemingly unrelated regression., stand-level biomass, error structure