Diversity and status of the ichthyofauna of small rivers on the Southern slope of the Shu-Ile Mountains (Shu River Basin, Kazakhstan)

The article presents an analysis of the ichthyofauna of 23 small rivers located on the southern slope of the Shu-Ile Mountains, based on data collected in 2024. Among the 23 rivers studied, fish were recorded in 16 rivers, where a total of 16 species were identified, belonging to 15 genera, 9 families, and 4 orders, with a predominance of Cypriniformes. The ratio of native to alien species was approximately 1:1; however, native species prevailed in terms of abundance. Species richness of the rivers ranged from 1 to 6 species. Native species such as Gobio lepidolaemus and Rutilus lacustris demonstrated high ecological plasticity, whereas alien species Pseudorasbora parva and Micropercops cinctus often formed the core of simplified communities. The highest diversity of species was observed in the Karakonyz, Karasu, and Turan rivers, whereas in several rivers only one or two species were recorded. Analysis of community structure revealed substantial spatial variation, driven by hydrological regime, orographic isolation, and the impact of irrigation. Simpson and Shannon diversity indices, Sorensen similarity coefficients, cluster analysis, and principal component analysis (PCA) indicated differences among communities, ranging from simplified systems dominated by a single species to relatively balanced ecosystems. The data obtained highlights the importance of comprehensive monitoring of small rivers for assessing the stability of native species, controlling introduced species, and conserving the biodiversity of riverine ecosystems in the region.