永乐环礁是南海西沙群岛最大的环礁,它是一个具有重要生态和经济价值的珊瑚礁生态系统。为了更好地保护和管理永乐环礁珊瑚礁鱼类资源,我们分析了手工渔业的实地调查数据,渔获物,和2020年至2022年的水下视频,并结合历史研究,探讨永乐环礁近50年鱼类物种组成和群落结构的变化。结果表明,在永乐环礁上共发现了336种鱼类,属于17个订单和60个家庭。其中,Perciformes的鱼类种类最多,有259种,占物种总数的77.08%。永乐环礁珊瑚礁的鱼种数量与其相应的最大长度呈指数相关,并随着其增加而显著减少。永乐环礁的鱼类群落结构发生了变化,大型食肉鱼类的比例显著下降,而中小型鱼类的比例增加。同时,永乐环礁有18种鱼类被列入IUCN红色名录,其中15条是大鱼。平均分类学差异(Delta+,Δ+)和变异分类差异(Lambda+,Λ+)2020-2022年低于历史数据,和鱼单的数量,家庭,永乐环礁属明显减少,这表明永乐环礁目前的珊瑚礁鱼类种类近亲和鱼类种类均匀性较高。此外,永乐环礁鱼类的相似性在不同时期相对较低,进一步证明鱼类群落结构发生了显著的变异。总的来说,由于多重影响,比如过度捕捞,捕鱼方法,环境变化,和栖息地退化,永乐环礁的鱼类组成可能基本上已经从食肉进化到食草,从大鱼到小鱼,从复杂到简单,使永乐环礁处于不稳定状态。因此,我们需要加强对永乐环礁珊瑚礁生态系统的持续监测,实现对其生态环境和渔业资源的保护和恢复,以及可持续利用和管理。
Yongle Atoll was the largest atoll in the Xisha Islands of the South China Sea, and it was a coral reef ecosystem with important ecological and economic values. In order to better protect and manage the coral reef fish resources in Yongle Atoll, we analyzed field survey data from artisanal fishery, catches, and underwater video from 2020 to 2022 and combined historical research to explore the changes in fish species composition and community structure in Yongle Atoll over the past 50 years. The results showed that a total of 336 species of fish were found on Yongle Atoll, belonging to 17 orders and 60 families. Among them, Perciformes had the most fish species with 259 species accounting for 77.08% of the total number of species. The number of fish species in the coral reef of Yongle Atoll was exponentially correlated with its corresponding maximum length and significantly decreases with its increase. The fish community structure of Yongle Atoll changed, and the proportion of large carnivorous fish decreased significantly, while the proportion of small-sized and medium-sized fish increased. At the same time, Yongle Atoll has 18 species of fish listed on the IUCN Red List, 15 of which are large fish. The average taxonomic distinctness (Delta+, Δ+) and the variation taxonomic distinctness (Lambda+, Λ+) in 2020-2022 were lower than the historical data, and the number of fish orders, families, and genera in Yongle Atoll has decreased significantly, which indicates that the current coral reef fish species in Yongle Atoll have closer relatives and higher fish species uniformity. In addition, the similarity of fish species in Yongle Atoll was relatively low at various time periods, further proving that the fish community structure has undergone significant variation. In general, due to multiple impacts, such as
overfishing, fishing methods, environmental changes, and habitat degradation, the fish species composition of Yongle Atoll may have basically evolved from carnivorous to herbivorous, from large fish to small fish, and from complexity to simplicity, leaving Yongle Atoll in an unstable state. Therefore, we need to strengthen the continuous monitoring of the coral reef ecosystem in Yongle Atoll to achieve the protection and restoration of its ecological environment and fishery resources, as well as sustainable utilization and management.