Farmed marine fish constitute 20% of the total farmed fish production in Egypt, and the Deeba Triangle produces a relatively large portion of this percentage. Last year, several private fish farms in the Deeba Triangle have suffered severe economic losses due to acute fish mass kills. This study aimed to investigate the hidden aetiologies behind these colossal mass fish kills and to propose an emergency control strategy. Several tons of dead farmed fish were remarkably scattered throughout affected ponds and at the vicinity of impacted fish farms. Moribund farmed European seabass (Dicentrarchus labrax), thin-lipped grey mullet (Liza ramada) and gilthead seabream (Sparus aurata) have exhibited skin darkness, emaciation, congested gills and fins, ascites, skin erosions and ulcerations. Internally, moribund fish emitted unpleasant odour upon opening the abdomen together with severe congestion and haemorrhages in kidneys and brain. Mottled atrophied spleens were the most prominent findings, while the gastrointestinal tracts were filled with whitish caseous material. The liver was pale with multiple whitish nodules. Photobacterium damselae was the most retrievable bacterial pathogen from most infected fish and trash fish. Photobacterium damselae subspecies piscicida and Photobacterium damselae subspecies damselae were definitively identified from examined moribund fish using both conventional morpho-chemical and molecular assays. Data analysis has revealed that the poor water quality was profoundly incriminated in triggering the bacterial infections with a fate of mass mortalities. Conclusively, adopting various strict biosecurity strategies will be the key factors in prevention of future episodes of mass kills.

中文翻译：

---

埃及迪巴三角洲养殖的海鱼受光杆菌引起的灾难性大规模死亡

养殖海水鱼占埃及养殖鱼类总产量的 20%，而迪巴三角生产的这一百分比相对较大。去年，迪巴三角洲的几家私人养鱼场因大规模鱼类死亡而遭受严重的经济损失。本研究旨在调查这些大规模鱼类死亡背后的隐藏病因，并提出紧急控制策略。在受影响的池塘和受影响的养鱼场附近，显着地散布了数吨死鱼。垂死的养殖欧洲鲈鱼 ( Dicentrarchus labrax )、薄唇鲻鱼 ( Liza ramada ) 和金头鲷 ( Sparus aurata )) 表现出皮肤变黑、消瘦、鳃和鳍充血、腹水、皮肤糜烂和溃疡。在内部，垂死的鱼在打开腹部时会散发出令人不快的气味，并且肾脏和大脑严重充血和出血。斑驳的萎缩脾脏是最突出的发现，而胃肠道充满白色干酪物质。肝脏苍白，有多个白色结节。少女光杆菌是从大多数受感染的鱼和杂鱼中最容易恢复的细菌病原体。少女光杆菌亚种piscicida和少女光杆菌亚种damselae使用传统的形态化学和分子分析从检查的垂死的鱼中明确地鉴定出。数据分析表明，糟糕的水质与引发细菌感染以及导致大量死亡的命运密切相关。最后，采取各种严格的生物安全策略将是预防未来大规模杀戮事件的关键因素。