关键词: α多样性, 河口, 外来物种, 城市鱼类, 红树林

Abstract

Aims: The tropical coastal regions have very unique fish diversity, and these coastal regions are also becoming the hotspots of the significant urbanization. Sanya City, located in the south of Hainan Island, is a typical tropical coastal city with the Sanyahe River as its main river system. This study aims to provide an overview of the current fish diversity in Sanya City.
Methods: Two field collection journeys were conducted throughout Sanyahe River system in May (dry season) and July (rainy season) of 2022. Additionally, long-term monitoring was carried out at nine monitoring stations across different sections of the river from March to July in the same year. Relevant historical literature and the voucher records from ichthyologic collections of the Institute of Zoology, Chinese Academy of Sciences, were also integrated. Three α diversity indices (Margalef richness index, Shannon-Wiener diversity index, and Pielou evenness index) were used to assess the diversity across different habitat, river sections, and seasons.
Results: There were 133 fish species distributed in Sanya City, 120 of which were native. The brackish zone had the most abundant fish species. Among the four main tributaries of the Sanyahe River, the Tangtashui River and the Liuluoshui River had a higher fish diversity. The mangrove brackish habitat, the four reservoirs, and their downsteam areas, which were closely located with the dense urban residence, had a higher proportion on individual number of exotic species. Estuary and upper stream habitats had a lower proportion of exotic species, both in terms of individual numbers and species.
Conclusions: Exotic species are currently the main threat to fish diversity in Sanya City. Based on the results of this study, the conservation of native fish diversity in Sanya City should primarily focus on preventing and controlling exotic and invasive fish species. This should be followed by the restoration of various types of wetlands, controlling non-point and point source pollution, and coordinating the ecological flow of the local reservoirs.

Key words: α diversity, estuary, exotic species, fishes in urban, mangrove