Impact of Climate Change on Some Seasonal Bacterial Eruptions among Cultured Marine Fishes from Egyptian Coastal Provinces

Climate change is now considered one of the greatest challenges and is expected to have a drastic impact on mariculture. The present study aimed to evaluate the impact of climatic changes on the emergence of bacterial pathogens among cultured marine fish in northern Egyptian provinces. 135 samples of three marine fish species, represented as 45 of Dicentrarchus labrax (700 ±25 g), 45 of Sparus aurata (350 ±25 g), and 45 Argyrosomus regius (1 kg ±50 g) were collected from private marine fish farms located in Deeba Triangle, Shataa Damietta(Damietta governorate) and Ismailia province, Egypt. Moribund fishes exhibited erratic swimming behaviour, haemorrhage, erosion and ulcers on the skin. Necropsy findings of infected fish revealed congested liver or pale with engorged gall bladder, congested kidney and spleen. With the presence of serous to hemorrhagic ascetic fluid. Vibrio alginolyticus, Vibrio parahaemolyticus, and Photobacterium damselae subspecies piscicida were the most retrievable bacterial strains from moribund fish. V. alginolyticus was the most prevalent isolated bacterial strain and represented 50%, 50% and 40% of the total isolates recovered from Sparus aurata, Dicentrarchus labrax and Argyrosomus regius, respectively. Retrieved isolates were morphologically and biochemically identified using the API 20E system, followed by further confirmation by sequencing of 16S rRNA genes. The histopathological examination revealed severe inflammatory reactions together with melanomacrophage center alterations within the examined splenic, hepatic, and renal tissues. Data analysis has shown that poor water quality and severe climatic change, especially during the summer, were implicated in the emergence of bacterial infections among cultured marine fish.