الفهرس 
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Abstract
Water quality and disease outbreaks are the most significant two related constraints hindering the sustainable aquaculture industry in Egypt. So, it is important to identify and determine these constraints and plan to alleviate or remove these challenges where possible. Therefore, the current study aimed to assess the correlations between poor water quality and disease eruption in aquaculture facilities. In this study, five selected heavy metals (Cu, Zn, Pb, Cd, and Hg) were bio monitored in muscles and different organs of three commonly consumed fish species; Common pandora (Pagellus erythrinus), Atlantic horse mackerel (Trachurus trachurus) and Round sardinella (Sardinella aurita). Besides, identification of Vibrio spp. incriminated in mass kills of the Litopenaeus vannamei shrimp from earthen ponds located at the vicinity of Lake Manzala in Shatta city, Damietta Egypt. Laboratory assessment has indicated that highest bioaccumulation pattern of Zinc (Zn), Copper (Cu), Cadmium (Cd), Lead (Pb) and Mercury (Hg) was recorded in Atlantic horse mackerel followed by Round Sardinella then Common panadora. In reported shrimp mass mortalities, moribund shrimps exhibited typical signs which are all consistent with vibriosis in shrimp. The bacteriological examination suggesting that V. parahaemolyticus and V. alginolyticus pathogens are blamed for the mass shrimp mortalities. A total of 53 vibrio isolates were retrieved from the investigated shrimp specimens. Identities of isolates were confirmed via API 20E and 16SrRNA sequence analysis. The pathogenic bacterial isolates were genetically identified by sequencing the 16S rRNA gene. The BLAST analysis of sequenced genes proved that the 6 bacterial isolates were deeply embedded in Vibrio spp. group. A combined therapeutic strategy was adopted to stop mortalities and enhance shrimp health within the affected shrimp ponds. Permanent baths of Hydrogen peroxide 40 % solution (in water) alternated with Yucca schidigera extract solution for 1week together with Florfenicol powder at a dosage of 25 mg / Kg shrimp biomass in diet were very effective in reducing mortalities, improving swimming behavior, normalizing feeding intake, and enhancing general health of the affected shrimps.