الفهرس 
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Abstract
The study have been applied on 320 marine fishes of four equal different species which are represented as Sparus auratus, Mugil cephalus, Mugil seheli and Tilapia zillii and (each 80) .They were collected seasonally and rendomly from la;e Temsah Ismailia governorate from September 2015 to August 2016 . the signs and the were revealed on the clinical picture of some fishes. Isolation and identification of yellow and green pignented colonies on TCBS and creamy coloured on TSA media with NaCI concentration (2.5%) . The causative agent was identified as vibrio sp. Concerning gene expression, most isolates were molecularly identified using the pvsA gene primers giving a product size of 338-bp siz and 348-bp for V. alginolyticus and V.parahemolyticus respectively . the highest prevalence of vibriosis was recorded in T. zillii (63.75%) , M .seheli (37.5%) then M.cephalus and Sparus auratus (28.75%) while the total prevalence was 39.69% . the highest seasonal prevalence was recorded in summer (81.25%) followed by spring (35%) then autumn (23.75%) and winter (18.75%) . The highest prevalence of organs was in liver, kidneys then spleen and gills. Antibioram sensitivity and challenge tests were also carried out . the histopathological studies of some of the examined marine fishes showed activation of melanomacrophage centers , degeneration , necrosis and congestion of blood vessels in liver ,spleen ,kidneys and gills.