Coral reefs are known as “tropical rain forests” in the ocean. Fish diversity is extremely high, accounting for one-third of marine fishes. To better protect and manage coral reef fishes, this study systematically compiled documents and databases published in China. We counted 2855 species of coral reef fishes in China, which belong to 3 classes, 41 orders, 252 families, and 1017 genera. Among these, Perciformes was the dominant order, accounting for 57.31% of the total species. Gobiidae (7.43%), Labridae (5.36%), Pomacentridae (4.52%), and Serranidae (4.38%) were the main families, while other families accounted for less than 4%. Furthermore, 5.56% of coral reef fish species have entered the IUCN Red List. The present study found that coral reef fishes can be divided into nearshore and offshore. This was mainly because the nearshore coral reef fishes were more affected by human disturbance and runoff from the mainland, whereas offshore coral reef fishes were in areas with high salinity and temperature far from the mainland, where human disturbance was less. Coral reef fish species’ diversity had a significant positive correlation with coral species diversity (p < 0.05), mainly because corals provide habitat and shelter. This study is the first systematic compilation and analysis of coral reef fishes in China and provides a basic reference for global protection management and biological geographical analysis.

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.

Coastal lagoons are crucial transitional zones connecting land and sea, and their ecological connectivity with adjacent open waters directly sustains regional biodiversity and ecosystem functions. However, how lagoon fish communities connect on a diurnal timescale remains poorly understood. In this study, we selected Xincun Lagoon on the southeastern coast of Hainan Island, China, as the study area. We established six sampling stations along an environmental gradient from the lagoon interior, through the tidal inlet, to the open sea, and conducted repeated diurnal sampling at six time points on 24 January 2024. Using eDNA metabarcoding, we analyzed the spatiotemporal dynamics of fish communities to examine spatial functional differentiation within the lagoon ecosystem and the potential corridor role of the tidal inlet. Our results showed clear spatial functional differentiation of fish communities along the environmental gradient. The lagoon inlet (XC4) exhibited the highest rate of community temporal change and the greatest amplitude of diversity fluctuation, with a peak change rate of 0.854 during the evening period (18:00–21:00). Its coefficient of variation for Shannon diversity was 6.2 times that of the mangrove creek (XC3). The mangrove creek area (XC3) had the highest Shannon diversity and the smallest fluctuations, functioning as a biodiversity hotspot and a region of relatively stable community structure. Within the lagoon interior, the temporal dynamics at the marginal zone (XC1) were substantially stronger than those in the central zone (XC2). Offshore stations indicated that the ecological influence of the lagoon extended to the 5 m isobath but weakened at the 10 m isobath. Furthermore, Clupeidae eDNA signals were strongest inside the lagoon during the day, at the tidal inlet in the evening, and in offshore waters at night. This study demonstrates the utility of eDNA metabarcoding for capturing fine-scale diel variation in fish community composition and distribution across the lagoon–inlet–offshore gradient, providing information that is difficult to obtain through conventional surveys. These patterns suggest, rather than confirm, that the tidal inlet may play an important role as a corridor linking lagoon and offshore habitats, and provide a reference case for using eDNA technology to study fine-scale connectivity in similar systems.