الفهرس 
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Abstract
Bacterial diseases affecting marine fishes are numerous and they cause high economic losses in marine culture sector in Egypt, therefore; this study was conducted for two main goals; Isolation and identification of the bacterial isolates affecting cultured b in Egypt broodstock of sea bass as well as studying the relationship between the water quality, heavy metal concentrations in water and the incidence of these mycotic and bacterial diseases. Owning to increase in aquacultural industries, more environmental friendly strategies for controlling fish infections are urgently needed to make the aquaculture industry more sustainable. The present work aimed to study the clinical signs and postmortem lesion in broodstock of sea bass exposed to multifactorial causes in hatchery during spawning period. Isolation and identification of the bacterial isolates encountered in naturally infected broodstock of sea bass during spawning period by both conventional methods and VITEX system. Isolation and identification of the fungal isolates encountered in naturally infected broodstock of sea bass during spawning period. Understand the correlation ship between the bacterial and fungal infection during this survey. Assess different water quality parameters were analyzed all over the periods of study. Assess hematological parameters associated with such conditions. Assess clinico-biochemical changes associated with such conditions. Assess some immunological parameters associated with such conditions. Assess hormonal disruptions associated with such conditions. Sensitivity test to the most common antibiotics used in aquaculture feed. Histopathological changes associated with such conditions. 1) In our investigation, a total number of 100 broodstock of sea bass of average body weight (5000 ± 200 g) were collected from rearing fiberglass tanks (30 cubic meters) during spawning season were collected showing clinical signs from private hatchery at Borg El-Arab and Mariout valley region, Alexandria governorate, Egypt. On the same manner, another 20 apparently normal broodstock of sea bass were collected from the same hatchery to compare the immune and hormonal parameters of healthy and diseases one. Fish were transported a live to the laboratory of the department of poultry and fish diseases, Faculty of Veterinary Medicine, Alexandria university. The freshly dead fish specimens were subjected to full clinical, postmortem (PM) lesions, parasitic and mycological as well as bacteriological examinations.2) The incidence of bacterial and fungal isolates in the external and internal organs of all naturally examined sea bass broodstock has been studied and the results revealed that :A) Physicochemical parameters of water quality during hatchery processes: The level of dissolved oxygen (mg/L) 5.31± 0.31 during the hatching processes . While, the level of pH was 8.21± 0.56. The temperature level was 20.64 ± 1.31 oC. While, the level of unionized ammonia level reached to 0.01 ± 0.0001 of hatchery processes, while, the level of nitrite reached to 0.02 ± 0.0001 during the hatcher processes. B) Heavy metals concentration in water samples during hatchery processes : Iron and copper levels were higher in all water samples during the present study. The iron and copper μg / l-1 levels were 1813.17 ± 47.28 and 44.57 ± 1.74 respectively during the hatcher processes. C) Clinical signs of naturally examined sea bass broodstock : Naturally examined sea bass broodstock showing erythema in the mouth and severe exophthalmia; severe hemorrhagic patches at the body and severe hemorrhages at base of pectoral fins and severe hemorrhagic ulceration. While others show hemorrhages at pelvic and anal fins moreover showing petechial hemorrhages at the operculum and around the eye. D) PM lesions of naturally examined sea bass broodstock : Naturally examined sea bass broodstock was showing hemorrhages at gills and at heart ; others show serous ascetic fluid tinged with blood dropping on behind paper upon opening the fish while the others show congestion of different degrees on the liver of examined fish . E) Total prevalence of fungal isolates retrieved from the external and internal organs of naturally infected sea bass broodstock : The results revealed that the high incidence of fungal species was Aspergillus niger (1; 2; 0.0 and 0.0 isolates); A. flavus (2; 3; 1 and 0.0 isolates); A. fumigatus (4; 3; 1 and 1 isolates); Cladosporium sp. (3; 0.0; 0.0 and 0.0 isolates); Fusarium sp. (3; 0.0; 0.0 and 0.0 isolates); Penicillium spp (29; 8; 1 and 1 isolates) and Rhizopus spp (6; 0.0; 0.0 and 0.0 isolates) in gills; liver; kidney and spleen respectively. The yeasts isolates recorded in naturally examined broodstock sea bass was low incidence summarized in Candida spp (15; 3; 0.0 and 3 isolates); Geotrichum spp (3; 0.0; 0.0 and 0.0 isolates); Torulopsis spp (6; 0.0; 0.0 and 0.0 isolates) and Rhodoterulla sp. (3; 0.0; 0.0 and 0.0 isolates) in gills; liver; kidney and spleen respectively. F) Prevalence of bacterial isolates in naturally infected sea bass broodstock:- The data showed that the high incidence of bacterial serotypes was in gills (34.07); Liver (21.98); Kidneys (18.68) and Spleen (25.27) in naturally infected broodstock sea bass respectively. On the other hand the incidence of bacterial serotypes in broodstock sea bass was higher incidence in gills followed by liver and kidneys then spleen respectively. G) Results of the sensitivity of different bacterial species isolated during this study: The results revealed that the V. alginolyticus susceptible to Ciprofloxacin; V. parahaemolyticus susceptible to Enrofloxacin; P. aeruginosa susceptible to Gentamycin; E. coli and S. aureus susceptible to Amoxicillin and Erythromycin.