الفهرس 
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Abstract
Overpopulation is considered to he the major constraint facing tilapia farming. In order to avoid unwanted spawning aquaculturist have been concerned on production of monosex tilapia. As the male tilapia grow bigger and faster than female, all male tilapia populations are preferred. The goal of this study is to through some lights on I) the effect of steroidal compounds (17 a MT) on sex ratio, growth rates and survival rates of 0. niloticus, treated fiy, 2) effect of non steroidal compounds(letiozol and tarnoxifen) on sex tatto, giowth rates and smvival iates of o mioticus, Heated fry, 3) effect of steroidal and non steioi&l compound, on the body features of the treated fl-v. 4) effect of steroidal and non steroidal compounds on gonadal histology, and 5) determination of 17 a MT residual values in the treated fish.A total of 3300 fry were obtained from Abbassa Arab fisheries bompany Sharkia at April 2003. The fry were experimentally used for the production of all male mono sex tilapia. The experiment was designed into two sets based on the exposure time (15 and 30 days). Each set was divided into three categories according to the type of treatment (17 cx MT,letrozol and tamoxifen) every one was subdivided into three groups(according to dose) each of two replicates except qontrol (one replicate).On day 90 post hatching, survival and growth rates weredetermined as well as sex ratios were estimated using Macro-and microscopic examination (acetocarmine squash technique) of the gonads.In addition histological studies on gonads was done to confirm the results of squash technique. The percentage of deformed fish was estimated and vertebral column deformity was radiographed using X-ray. Hormonal residue was determined using radio immunoassay kits.High male percentage (98.93%) were obtained in groups treated with l7~ MT at 60 mg for 30 days followed by 40 mg MT treated groups for 30 days (97.85%). The lowest male percentage were observed in groups treated with 40 mg MT for 15 days (85.15%). A percentage of intersex individuals were found in 40 and 60 mg MT treated groups for 15 day (2.08 and 6.67% respectively). While 30 days treated groups revealed 0.54% intersex individuals in 40 mg MT treated groups. No intersex individuals were observed in 60 mg MT treated groups for 30 days and the control groups.The survival rates of fry in MT treated groups showed no significant difference comparing with the control groups. While the growth within treated groups revealed significant increase. The average body weight of 60 rng MT treated groups for 30 days were the highest between other treated groups (7.35 g) vs (5.11 g) in the control group.Letrozol treated groups produced 96.63% male percentage in 100 rng treatea groups for 30 days, while 50 mg treated groups for 30 and 15 days produced 88.59% and 82.07% respectively. The highest intersex percent were observed in groups treated with 50 mg letrozol for 15 days(5.59%). While tamoxifen treatme induced less percentage of males(94.83%) with the highest dose (100 mg) and longer duration (30 days).The lowest treatment concentration (50 mg) for 1 5 days induced sex reversal in 72. 16% of the individuals into males. The percentage of intersex individuals reached 11.86% in 50 mg Tamoxifen treated groups for 15 days followed by 6.3 2% in 30 days treated groups.The average growth and survival rates of non steroidal compounds(letrazol and tamoxifen) were significantly differed from the control one.The survival rates showed its lowest levels in groups treated with 100 mg letrozol for 30 days (74%) while it reached 89.5% in 50 mg letrozol treated groups for 30 days.Tarnoxifen treatment had much little effect on the survival rates than letrozol. The survival rate reached 89% in 100 mg treated groups for 50 days. Both letrozol and tamoxifen showed an increase in average body weight of the treated fry than the control.In methyltestosterone, letrozol and tamoxifen treated groups, anumber of deformed fish were observed, these deformities included:Short operculum, malformed mouth vertebral deformity and deformed pectoral fin. The highest deformity percent were found in letrozol treated groups (18.5%) in 100 mg treated groups for 30 days, most of those deformed fish was with short operculum and died.Gonadal differentiation was confirmed by acetocarmine squash technique, then the gonads were subjected to histological examination to identi’ the testis and the ovary with their structures. Mixed structure were observed in the sections where it testicular and ovarian tissues and termed intersex gonads. The residual values of the 1 7 ct MT hormones were measured Vkusing radioimmunoassay.•( The residual values of the hormone in the control group were 5.847 ng/g muscle and 6.6 10 ng/g muscle at 120 and 180 days samples. These values didnt differ significantly from those obtained by other Mt treated groups as it reached 6.946 and 6.865 ng/g muscle in 60 mg MT treatment for 30 days at 180 and 120 day sample respectively.