RESUMO
This study was carried out in two fish farms in EL-Fayoum Governorate to investigate water quality, evaluate the effect of chemical fertilizers and artificial diet on the performance and feed efficiency of Oreochromis niloticus and Mugil cephalus, and determine pesticide residues in water and reared fish. Average values of water temperature in fish farms and water source ranged between 25.6 and 30.6°C. The highest values of dissolved oxygen were observed during April while the lowest values were found in June and July. There was a negative relationship between water temperature and dissolved oxygen, a positive relationship was found between temperature and water salinity. The highest values of weight gain [270.90, 269.20g], specific growth rate [1.15, 1.16], feed consumption [240.60, 270.48g] and feed conversion ratio [0.89, 1.01] of O. niloticus and M. cephalus, respectively were found in fish fed on artificial feed and reared in fertilized ponds when compared to fish fed on artificial diet only or reared in fertilized ponds without supplementary feed. The pesticide residues of chlorpyrifos ethyl and fenpropathrin were detected in water at mean levels ranged 0.10 - 0.25 mg/I. Both fish species contained fenitrothion residues at values [0.525 mg/ kg and 0.255 mg/kg for O. niloticus and M. cephalus, respectively] which are higher than permissible limits. Although the residues of fenitrothion and carbaryl were not detected in water, they were found in both fish species which could be attributed to the ability of these pesticides to bioacumulate in the aquatic organisms