2022, 29(1):102-117.
DOI: 10.12264/JFSC2021-0122
Abstract:
Coral reef ecosystems harbor the highest biodiversity of all marine ecosystems and are known as the “tropical rainforests in the ocean.” Fish biodiversity in coral reef ecosystems is extremely rich, as high as 1/3 of the total number of marine fishes. Importantly, reef ?shes are the major source of protein for many island nations and account for approximately 10% of the global ?sheries catch. Fish are an important part of coral reefs and an essential part of maintaining the health of coral reefs. Coral reef ecosystems provide habitat and the primary food sources for coral reef fishes. At present, the coral reef ecosystem off the coast of the South China Sea is experiencing a significant decline, fishery resources are under a serious threat, and catches have decreased significantly. To better understand and protect the coral reef ecosystem and fishes in the Qilian reef of Xisha Islands, we conducted comprehensive surveys from 2018 to 2020. Historical data showed that 315 fish species were found in Qilianyu Island, belonging to 49 families and 12 orders. Perciformes was the largest, accounting for 79.05%. A large number of fish species in Indo-Pacific coral reefs were composed of 29 families. In our survey, except for Microdesmidae, which was not found in this study, other 28 families were recorded and accounted for 89.52% of the total number of species. The results supported the classic theory of the high connectivity of coral reef fish. The cluster analysis of fishes on the reefs of the South China Sea at the family level showed that the coral reef fishes of Qilianyu were the most similar to the fishes of the three offshore reef islands in Vietnam. Overall, small fishes were the most abundant, accounting for 49.04%, followed by medium-sized fishes with 31.09%, and large-sized fishes with only 19.87%. Regarding food types, carnivorous fish were the most abundant with 163 species, followed by omnivorous fish with 91 species and herbivorous fish were the least with 61 species. A total of 37 fish species, mostly carnivorous species, were not found in recent years compared with the historical research data. Furthermore, large fishes were all carnivorous, indicating that the Qilianyu coral reef fishes are being overfished. The number of small fishes was as high as 66.57%, and most of these fish belonged to Pomacentridae, Chaetodontidae, and Labridae, which were all highly dependent on coral reefs, indicating a significant decline in the Qilianyu coral reef ecosystem. According to the number of coral species, it can be inferred that the number of fish species in the Qilianyu coral reef area would be 400 or more, indicating a rich fish diversity. However, nearly 100 species were not recorded in recent surveys, further indicating that the coral reef ecosystem has been severely disturbed by human and has declined. At present, the coral reef ecosystem of Qilianyu has been greatly affected by human activities, especially overfishing, which has led to an instability of the coral reef ecosystem. Therefore, protecting Qilianyu coral reef fish resources requires the control of fishing intensity and protection of this unique coral reef habitat.
