Abstract
In this study, species compositions, distributions, and diversity patterns of fish assemblages were investigated at 50 sampling sites in the Weihe River and its two largest tributaries, the Jinghe River and the Beiluo River, under high- and low-flow conditions in 2017. For every condition tested and in the all rivers tested, Cyprinidae was the richest family, containing 17 of the 39 identified fish species. Carassius auratus was the most common species, accounting for 11.3% of the total individuals. Nonmetric multidimensional scaling (NMDS), analysis of similarities (ANOSIM), and similarity percentage analysis (SIMPER) revealed that fish species composition differed significantly among rivers (p < 0.05), with dissimilar species assemblages found in the different rivers. Variation was influenced by a combined effect of habitat conditions, environmental factors, and human impact. Canonical correspondence analysis (CCA) identified variables explaining the variation in fish species (p < 0.05), and elevation contributed the most under both flow conditions. Alpha diversity decreased with increasing elevation within rivers as a result of changing environmental conditions, especially for wetted width. Alpha and beta diversities of rivers increased with increasing drainage area, which is related to habitat heterogeneity. The decrease in alpha diversity and the increase in beta diversity with increasing elevation can be explained by variations in habitat and geographic features.
Highlights
With population growth, rapid socio-economic development, and unreasonable development and utilization of biological resources, natural aquatic ecosystems, such as rivers and lakes, have experienced challenges, including declining biodiversity and degradation of ecological service functions [1]
Elucidation of spatial composition, distribution, and diversity patterns of species along elevational gradients at different spatial scales is essential in biogeography and ecology [5,6]
The numbers of fish species found in the four elevation classes were 27, 29, 24, and 16
Summary
Rapid socio-economic development, and unreasonable development and utilization of biological resources, natural aquatic ecosystems, such as rivers and lakes, have experienced challenges, including declining biodiversity and degradation of ecological service functions [1]. Understanding the diversity of fish species and the drivers of diversity change can help scientifically manage and protect river ecosystems [4]. Elucidation of spatial composition, distribution, and diversity patterns of species along elevational gradients at different spatial scales is essential in biogeography and ecology [5,6]. Analysis of fish species distributions and diversity patterns in freshwater ecosystems plays a crucial role in understanding how local organisms respond to biotic and abiotic changes along ecological gradients [9,10]. Elevation is one of the most prominent ecological gradients impacting biodiversity and is considered a major factor constraining the dispersal of fish species in river systems [11,12,13]
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