Abstract
THE EXPERIMENT was performed in the central laboratory for aquaculture research, Egypt. Experimental fish about 10.2 g Nile tilapia were divided into four different treatments in different ratios, and fed on 25% protein pellets for 120 days at 3% of body weight. Some parameters like some digestive enzymes (amylase and lipase), glucose, cortisol, insulin, growth hormone, iron and total binding iron capacity were measured in blood serum; the 4th treatment showed the minimum value for theses measurements except for glucose and cortisol 153.6 +/- 9.2 mg/dl and 176.3 +/- 5.2 ng/ml, respectively. Haemoglobin showed the highest and minimum value (7.63 +/- 0.03 g/dl & 6.27 +/- 0.03 g/dl) in treatments (1 and 4) respectively. Erythrocytes count showed the highest value 2.52 +/- 0.01(X10(6)/Cmm) in the first treatment, while the lowest value 2.09 +/- 0.03 (X10(6)/Cmm) was recorded among treatment (4). Water samples for physico-chemical analysis were monitored bi-weekly during the study period then collected and tabulated in one mean. The growth performance of experimental fishes was significantly decreased with increasing fish density.