Abstract
This study was directed towards providing a comprehensive overview on the describing the clinico-pathological picture of the bacterial isolates affecting cultured seabass during episodes of mass mortalities in the private marine farm at Borg-El Arab, Alexandria province, Egypt and to make a full bacteriological investigation of the isolated Vibrio sp. Was done by morphological, colonial, biochemical characters, and VITEK 2 compact system.
A total number of 100 apparently healthy European seabass were used in the experimental challenge with an approximate bodyweight of 30.0 ± 5.0 g, and an approximate average body length of 13.0 ± 2.0 cm was provided from the marine fish hatchery at Kilo 21 region - Agami, Alexandria province, Egypt. Fish were maintained in 1 m3 reinforced polyethylene ponds for acclimation to the new culture conditions for two weeks before the experiment. Random samples were collected for bacteriological examination to ensure that fish were not previously infected.
This study concluded that, there is a close correlation exists between poor deteriorated water quality parameters and the incidence of Vibriosis in cage-farmed European seabass (Dicentrarchus labrax). In this case, several environmental parameters, such as the increased water temperature, un-ionized ammonia, and nitrite levels, in addition to decreased dissolved oxygen levels, triggered a devastating outbreak of Vibriosis in 40 cages of cultured European seabass. This finding confirms the nature of fish diseases as a “stress-related origin”.
To sum up, from the findings mentioned above, we suggest further in vivo experiments for testing these antibiotics for treating Vibriosis in diseased European seabass additionally, developing more environment-friendly approaches and competent biosecurity strategies should also be evaluated for controlling and preventing such infections in mariculture.

Key words: : Vibrio parahaemolyticus - (Sparus auratus) - (Dicentrarchus labrax)