Abstract:

Aims: The functional characteristics of species are the key factors linking community structure and function. Studies on functional diversity seeks to understand the important relationship between community structure and function. The Three Gorges Dam is currently the world’s largest hydropower project. The dam’s construction blocked fish migration, altered river habitats, and dramatically changed fish species and distribution. Our study contributes to understanding of the spatial pattern of fish community structure and diversity after the impoundment of the Three Gorges Reservoir and clarifies the relationship between species diversity and functional diversity.

Methods: In order to explore the spatial pattern of fish community structure and functional diversity, field investigations were conducted in the main stream and tributaries of the Three Gorges Reservoir area from 2019 to 2020. The main stream includes Zigui, Yunyang and Banan which are located in the upper, middle and lower reaches of the reservoir, respectively. The tributaries contain Xiakou (downstream of Xiangxi River), Gaoyang (downstream of Xiaojiang River) and Hechuan (downstream of Jialing River). They are located at the head, middle and end of the reservoir, respectively. We analyzed the structure and diversity of fish communities and explored the spatial patterns of functional diversity of fish by three characteristics: food acquisition, locomotion and reproduction.

Results: A total of 78 species belonging to 6 orders, 15 families and 56 genera were collected in the Three Gorges Reservoir. Eurytopic and limnophilic fish species dominated the reservoir. The limnophilic species, such as Coilia brachygnathus and Hemiculter bleekeri, had higher relative abundance in the Zigui, Xiakou and Gaoyang sections. In Yunyang, Banan and Hechuan river sections, the relative abundances of eurytopic species such as Saurogobio dabryi and Pelteobagrus nitidus were high. Non-metric multidimensional scales (NMDS) and Bray-Curtis dissimilarity index analyses indicated that differences in fish community structure were greatest between Hechuan and Zigui, and most similar between Xiakou and Gaoyang. Margalef richness index (D), Shannon diversity index (H') and Pielou evenness index (E) gradually increased from Zigui, through Yunyang to Banan in the main stream of the reservoir. In the tributaries, species diversity was highest in Xiakou, with lower diversity in Gaoyang and lowest in Hechuan. The spatial variation of functional diversity related to fish food acquisition, locomotion and reproduction were relatively consistent throughout the study area. The highest value was observed in Zigui and lowest in Hechuan. The total functional diversity had a consistent spatial variation with community species diversity in the Three Gorges Reservoir. The diversity indices gradually increased in the main stream from Zigui to Banan. In the tributaries, diversity indices were the highest in Xiakou, followed by Gaoyang and Hechuan.

Conclusion: Overall, there are evident spatial differences in fish community structure and diversity in the Three Gorges Reservoir area. Functional diversity is more sensitive than species diversity to changes in fish community.

Key words: Three Gorges Reservoir, fish, community structure, functional diversity, spatial pattern