The present study was carried out in a private fish farm located in the area of Tolompat 7, Riyad, Kafr El- Sheikh Governrate, Nile Delta district, Egypt. The study aimed to evaluate the effect of stocking density of different fish species on growth performance, feed, conversion, chemical body composition and economic efficiency. Three stocking densities in replicates each of one Feddan area were arranged in the present study. The first stocking density was the traditional stocking density in the study area (16000 fish/Feddan) (T1) (12000 Nile Tilapia Oreochromis niloticus + 3000 Tobara Liza ramada + 1000 Bouri Mugel cephalus). The second treatment included the stocking density 19200 fish/Feddan (T2 14400 Ttilapia + 3600 Tobara + 1200 Bouri) and the third (T3) treatment was stocked with 22400fish /feddan (16800 Tilapia + 4200 Tobara + 1400 Bouri). Each treatment was carried out in replicates each of one Feddan (4200m2) area and study lasted 24 weeks from the start. The initial weights of the experimental fish were 25g, 10g. and 15g. for Tilapia; Tobara and Bouri, respectively. The experimental fish were fed on a diet containing 25% protein at a rate of 3% & the fish biomass daily. The diet was offered in two portions at 10.00am.and 2.00 pm daily then fish samples were taken from each pond every 15 days to calculate the feeding rate for the next period. Water quality parameters were determined every two weeks. Water dissolved oxygen and pH were determined twice weekly. Results obtained are summarized in the following:
1- Averages of final weights of Tilapia decreased significantly with each increase in the stocking density and the same trend was observed with total weight gain and relative growth.
2- Final body weight, total weight and gain and relative growth rate of Bouri and Tobara rate decreased significantly with each increase in the stocking density.
3- Stocking density released significant differences in dry matter, protein NFE and gross energy contents of tilapia whole bodies. On the other hand, stocking density released significantly differences in whole body composition parameters of Bouri and Tobara.
4- Feed conversion ratio (kg. of feed required for each kg. /gain in weight) increased with each increase in the stocking density.
5- Water quality parameters including water temperature, dissolved oxygen, pH value, total ammonia, nitrate, nitrite and salinity, were within the permissible levels required for the tested species.
6- Total fish yield kg. /feddan increased significantly with each increase in the stocking density.
7- Percentages of net returns over costs for T1, T2 andT3 were 50.59, 44,97, and 12.92%,respectively indicating the most profiTable stocking density of tilapia and Bouri and Tobara lie between 16000 and 19200 fish /feddan. Based on the obtained results, a stocking density of 16000 fish /feddan (1200 tilapia + 300 Tobara + 1000 Bouri) is recommended in the study area for higher profit. Increasing thestocking density may require frequent pond water exchange and intensive water aeration and higher feeding rates.