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The present study aimed to analyze the effect of stocking densities and feeding rates on growth performance and fish production of O. niloticus reared in earthen ponds. This experiment was conducted for 7 months extended from May to November, 2016 in 12 earthen ponds at Parsik Culture, Idko, Behira Governorate, Egypt. Each pond has 2 feddan with an average depth of 1.0 m. Monosex fries of Oreochromis niloticus were divided into 4 treatments {T1: stocking density of 6 fish/m 3 with a feeding rate of 2.5%; T2: 6 fish/m 3 with a feeding rate of 3.5%; T3: 8 fish/ m 3 with a feeding rate of 2.5% and T4: 8 fish/ m 3 with a feeding rate of 3.5%}, each treatment had 3 replicates. Results showed that the highest values of growth performance (growth in length, length gain, daily length gain, growth in weight, total weight gain, daily weight gain and specific growth rate) of O. niloticus were recorded in T3(high stocking density and low feeding rate). On the other hand, the lowest values of these parameters were recorded in T1 (low stocking rate with low feeding rate). The best average of food conversion ratio (1.37± 0.025) was recorded in T3 and its a bad average (1.56±0.034) was recorded in T2. Also, the highest average values of protein efficiency, feed efficiency ratio was recorded in T3, and their lowest values were recorded in T2.

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A feeding trial for 56 days was conducted to investigate the optimum dietary protein and stocking density that could give the maximum growth performance of Pangasius catfish, Pangasius hypophthalmus. Twenty-seven tanks (150 Liter) were used for random distribution of Pangasius fingerlings (5.5±0.2 g) at three stocking densities; 10, 15, and 20 fish/tank. Fish of each density fed either formulated diet of 30, 35, and 40% crude protein (CP). Pangas fingerlings were fed one of the tested diets up to apparent satiety twice a day at 09:00 and 14:00 h. The recorded fluctuation of water parameters was within the normal range such as 27-29°C water temperature, 5.6-6.8mg/l dissolved oxygen, 7.3-7.7pH, and 0.7-1.40 mg/l total ammonia. Obtained data showed that the final body weight, weight gain, weight gain %, specific growth rate (SGR) were significantly affected by protein level and conversely affected by stocking density. The best performance and survival recorded at diet containing 35and 40% protein at the lowest stocking density, while the poorest growth was retrieved with 30%protein at high density (20 fish/tank). Feed utilization parameters were in the same line with the protein level and stocking density effect. The best feed conversion ratio FCR, 1.57±0.06 and 1.53±0.03 was gained with 35% and 40%protein respectively at10 stocking density. Correspondingly, the highest values of PER and PPV were obtained at low density with 35 and 40% CP. No significant differences were recorded in lipid and ash contents in the fish body fed diets of different protein levels at varied stocking densities. Nevertheless, moisture