الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
A total number of (400) marine fishes (200 Seabass (Dicentrarchuslabrax L.) and 200 Gilthead Seabream (Sparus aurata L.) were collected from private marine fish farms at Damietta governorate and subjected to clinical, bacteriological and histopathological examination. Seabream was the most infected fish species (62%) while seabass was the lowest infected species by a percent (46.5%). Vibrio spp. was implicated in the most bacterial infections during this studyby a prevalence of (56.15%) involving V. vulnificus (25.04%) followed by V. parahaemolyticus (17.45%) and V. alginolyticus (13.66%). However, the lowest prevalence was recorded for Cryseobacterium indologenes with a percentage of (0.46%). The prevalence of bacterial isolates in different organs as (liver. Kidney, gills, spleen and heart) of naturally infected marine fish showed that the highest prevalence of isolates in naturally infected marine fish were recorded in liver (34.14%) followed by kidney (29.74%), gills (14.26%) and spleen (13.66%) while, the lowest incidence was obtained by heart (8.19%). Seasonal prevalence of identified bacterial strains during the whole period of examination of naturally infected seabass revealed the highest incidence in Spring season (32.95%) followed by summer (28.03%) then Autumn (20.45%) and the lowest prevalence was recorded in winter (18.56%). Norfloxacine (NOR 10 µg) and Florphenicol (FFC 30 µg) were the most effective antibiotics against all isolated bacterial strains meanwhile, tested isolated strains showed resistance to Ampicillin (Aml 10 µg).