الفهرس 
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Abstract
Bacterial diseases affecting marine fishes are numerous and cause high economic losses in marine culture sector in Egypt. Therefore; this study was conducted to put spot light on, Detection of the most important bacterial disease affecting different life stages of cage cultured seabream (Sparus aurata L.), and seabass fish (Dicentrarchus labrax L.) in Wadi Mariut (Borgh-El-Arab city), Alexandria governorate. Monitoring the relationship between heavy metal concentrations found in fish tissues and water and other water parameters and the occurrence of such diseases. In this study, a total number of 360 cage-cultured marine fishes of different body weight range (0.5 g to 3 Kg according to the stage of growth from fry up to adult stage) of two different species were collected; 180 Seabass fishes (Dicentrarchus labrax L.), 180 of Seabream fishes (Sparus aurata L.), fishes were collected showing clinical signs from private fish farm at Borg-El-Arab city, Alexandria governorate, Egypt. The sources of water in these farms are numerous; underground water, drainage of canal originated from El-Banger area as well as from rainfall water downstream from Borg-El-Arab city. Fishes were transferred as soon as possible to the laboratory located in the same farm where sampling and measurement of metals occured. The freshly dead fish specimens were subjected to full clinical, postmortem (PM) lesions, and bacteriological examinations in the Lab. of Animal Health Research Institute, Tanta branchThe collected samples were under go : Gross clinical examination Clinical examination of naturally infected fishes was performed to investigate any clinical abnormalities according to the method described by Amlacher (1970).
Postmortem (PM) examination Necropsy was performed on variable number of freshly dead and moribund fishes for detection of PM lesions according to Conroy and Herman (1981Bacteriological examination and Biochemical characterization, serotyping of bacterial isolates, PCR for detection of virulent strain of Y. ruckeri The results revealed that The best media used for isolation of bacteria from the seabream and seabass were arranged in TSA medium + 1.5% NaCl. Followed by, TSA medium + 3% NaCl and the least bacterial isolates observed in TSA medium + 7% NaCl.The bacterial incidence in the different organs observed in seabream fish followed the rank: in lower intestine> heart> Kidney> Spleen and liver, respectively, while in seabass fish followed the rank: in lower intestine> Kidney> liver>heart> spleen, respectively. Heavy metals concentration in water cages of Seabream and seabass, includes Cadmium, that ranged from (0.0001 to 0.0091 and its permissible level (0.004 mg/L), Lead level ranged from 0.0249 to 0.0679 and it’s the permissible level (0.05 mg/LThe Copper level ranged from 0.1380 to 0.9960 and its permissible level (0.20 mg/L). The results of Zinc level ranged from 0.0110 to 0.0260 mg/L and its permissible level was (2.0 mg/L). The iron level ranged from 0.9090 to 1.1723 and its permissible level 1.00 mg/L. The Nickel level ranged 0.0583 to 0.1760 mg/L and the permissible level of was 0.001 mg/L. The results of Mercury level ranged from 0.0034 to 0.0042 mg/L and the permissible level of it was (0.001 mg/L). The Phosphate level ranged from 0.01 to 0.03 ppm and its permissible level was ranged from (0.03 – 0.05), the phosphorus level ranged from 0.30 to 0.5 ppm and its permissible level was ranged from (0.21 – 0.25). The Total chlorine level ranged from 0.053 to 0.16 ppm. The Ammonia level was 1.129 ppm in fry seabream water cages only and its permissible level in the other cages were (0.125>The results of Nitrite level ranged from (0.02 - 0.05 mg/L) and its permissible level was ranged from (0.1 – 0.2). The results of Salinity level ranged from 17 to 31 pptThe results of water Temperature ranged from 22 - 30 oC, the pH level ranged from 6.5 – 8 and its permissible level is 7. The level of dissolved oxygen (DO) ranged from 2 to 3 ppm. And the results cleared that, the DO level lower than the permissible limit of DO which reached to 4 ppmThe results of the relationships between the incidence of bacterial infection heavy metals contamination, in seabream fish, the Vibrio, Yersinia, Aeromonas and Pseudomonas infection increased with the increasing contamination of water with cadmium, lead, copper, iron and Nickel and the infection decreased in case of increasing the zinc value.