EFFECT OF POND FERTILIZATION AND RECRUITMENT OF NILE TILAPIA (OREOCHROMIS NILOTICUS) AND FEED COMPETITION

Six earthen ponds were stocked by Nile tilapia (Oreochromis niloticus) fingerlings at a rate of two fish per square meter for 229 days. The ex- periment was conducted at Fish Research Station at El-Kanater El-Khairia which belongs to Na- tional Institute of Oceanography and Fisheries. The experiment was conducted using factorial de- sign (2x3). The treatments were divided into three gorups, all male tilapia were cultured separately, males were cultured together with females removing about 80% of their fry during the growing season and males were cultured with females also, but their fry were not removed. The three treatments were performed in fertilized and unferti-lized pounds. All groups received artificial diet (30% protein) at a rate of 3% from fish live body weight. The results showed that the highest growth rates, protein utilization values, frequency occurrence (FO) and percentage composition (PC) values were achieved when all male tilapia were cultured separately in fertilized pounds. In case of male culture together with females, the highest growth rates, protein utilization values, FO and PC values were recorded when 80% of t-lapia’s fry were removed during the growing sea- son in fertilized pounds. In conclusion, culture of all male tilapia should be conducted, but the techniques of all male tilapia pond management can’t be fine tuned”. When males were cultured together with females, the chemical fertilizers with optimum doses should be used, because it is largely related to the abun- dance and type of food available to fry in order to avoid feed competition.