In this study, the environmental water parameters have been analyzed to investigate their role in the initiation of microbial diseases among fishes under different salinities.The incidence of microbial diseases among Solea vulgaris, Mugil cephalus, Tilapia spp. Carp spp., Latus niloticus, Bagrus bayiad, Labeo nilotica and catfish in River Nile, Rayian Lakes, Qarun lake, Manzalah lake, and fish farms appeared to be yersiniosis, motile aeromonas septicemia, streptococosis, vibriosis and pseadomonad septicaemia. The common clinical signs reported were petechial hemorrhages on the body surface and base of fins and sometimes ulcer formations, erosion of fins, red lips, ascites and exophthalmia with or without eye cataract. Yersinia spp. and Aeromonas spp. were isolated from most fishes but Yersinia spp were more virulent between all pathogenic organisms and caused severe infection in fish fingerlings. The in vitro antimicrobial sensitivity showed that the oxytetracycline, cefotaxime and norfloxacian seemed to be the highly suitable antibiotics for the control and therapy of the isolated bacterial pathogens.
Key words: Environmental stress, microbial isolates, Yersinia spp., Aeromonas spp., and Fish treatment. Solea vulgaris, Mugil cephalus, Tilapia spp. Carp spp., Latus niloticus, Bagrus bayiad, Labeo nilotica and catfish. oxytetracycline, cefotaxime and norfloxacian
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