Parasitic isopods have received considerable attention as they cause series impacts on their hosts either alone or with other environmental stresses such as water pollution. The present study investigated the infestation status with isopods among the fry collected from the natural sources .Also to demonstrate the effects of different salinity and temperature combination on the survival rates of the identified isopods under the laboratory conditions. In March 2017,a total of 16 thousand mugiliid fry were sampled from The Fry Collection center at Al Behera Governorate ,Egypt and examined for the presence of isopods .Samples were found infested with a rate of 10.6% , the result which practically documented that isopods were introduced into lake Qarun through dumping millions of infected fry from this source without biosecurity procedures. The isolated juvenile isopods were morphologically and molecularly identified as Livoneca redmanii species by using 16S rRNA gene and recorded in the GenBank with accession number: MK584629. The effects of variables of salinity/ temperature combination on the survival% of the identified juveniles showed that the best survival rate(100%) was recorded in salinity 15 -20% at temperature 25⁰C while the lethal combination was in salinity 10, 20,50 and 60% at temperature 35⁰C . Statistical analysis using A-two way ANOVA indicated a significant interaction between the effect of different degree of temperature and variance of salinity% on the survival of L. redmanii juveniles. Analysis of one way ANOVA indicated that the most effective temperature of overall mean temperature affected on survival of juvenile stage was 35 C⁰ while the most effective salinity percentage on survival of Juvenile from overall mean of salinity % was 10%. Results of this study provided applicable procedures which can be recommended as a precaution measures and for eliminating the isopod juvenile stages among the mugiliid fry.