Abstract：
To monitor the changes in fish biodiversity and to elucidate the factors responsible for these changes, the landings composition (LC) over the past 30 years in the Nile-Delta lakes was quantitatively analyzed. The LC data indicates a shift in target species towards demersal opportunistic species. A significant difference (P < 0.001) between two main intervals highlighted in both PERMANOVA and PCA plot; the first interval (1991-2002) is dominated by Tilapia and rare species, while the second interval (2003-2020) is dominated by the opportunistic catfish and mullet species. Noticeable declines in species richness and landings of rare species were observed, where rare taxa either have been overexploited or they may be positively affected by increasing pollution levels than do other dominated species such as Tilapia. In contrast, opportunistic fish species such as catfish and mullet, have flourished in such polluted water due to their ability to tolerate seasonal pollution-related hypoxia.
摘要：
为了监测鱼类生物多样性的变化，并阐明造成这些变化的因素，定量分析了尼罗河三角洲湖泊过去30年的登陆成分（LC）。LC数据表明目标物种向海底机会物种转移。在PERMANOVA和PCA图中突出显示的两个主要间隔之间存在显着差异（P<0.001）；第一个间隔（1991-2002）以罗非鱼和稀有物种为主，而第二个间隔（2003-2020年）主要是机会鲶鱼和鱼。观察到物种丰富度和稀有物种登陆的显着下降，与罗非鱼等其他主要物种相比，稀有类群要么被过度开发，要么可能受到污染水平增加的积极影响。相比之下,机会鱼种，如鲶鱼和鱼，由于它们能够耐受季节性污染相关的缺氧，因此在这种污染的水中蓬勃发展。
