The Ningxia section of the Yellow River represents a critical habitat for freshwater fish biodiversity, yet its ecological integrity faces increasing threats from anthropogenic activities. To comprehensively assess the fish community structure, diversity, and its relationship with environmental factors in the Ningxia section of the Yellow River, we conducted seasonal surveys of fish resources and environmental conditions at 15 selected sites from July 2022 to September 2023. Our study employed quantitative analyses to evaluate fish community characteristics, spatiotemporal distribution patterns, and their interactions with environmental variables. A total of 42 fish species, belonging to 34 genera, 11 families, and six orders, were identified, with Cyprinidae being the dominant family (57.14%). Carnivorous species were the most abundant (22 species), followed by omnivorous (16 species) and herbivorous (four species) fish. The Relative Importance Index ( IRI ) identified Gobio huanghensis and Carassius auratus as the dominant species in this region. Biodiversity indices revealed a mean Margalef richness index of 3.066, Pielou evenness index of 0.5911, Shannon-Wiener diversity index of 1.791, and Simpson dominance index of 0.7083. The Abundance-Biomass Comparison (ABC) curve indicated moderate disturbances to fish communities in spring and autumn, while communities remained stable in summer and winter. Spatially, six sites (Nanchangtan, Shapotou, Jinshawan, Meijiawan, Linhe, and Taole) exhibited significant disturbances, while others showed moderate or stable conditions. The results of cluster analysis and non-metric multidimensional scaling (NMDs) indicated no significant differences in fish community structure among the sampling sections in the Ningxia reach of the Yellow River. Redundancy analysis (RDA) identified water temperature and ammonia nitrogen as the primary environmental factors influencing fish community structure. Our findings highlight the combined impacts of human activities and environmental changes on fish communities in the Ningxia section of the Yellow River. These results provide a scientific basis for the conservation and sustainable management of fishery resources in this ecologically sensitive region.

Against the backdrop of hydropower development in the upper Yellow River, comprehending the spatiotemporal variation and ecological evaluation of macroinvertebrate functional feeding groups (FFGs) is paramount for the conservation and restoration of aquatic biological resources in watersheds. Detailed surveys of macroinvertebrates were conducted in the gorge and plain areas of the upper Yellow River in July 2022 and March, May, and October 2023, culminating in the identification of 65 taxonomic units (genus or species) spanning 4 phyla, 14 orders, and 35 families. Of these, 41 taxonomic units were discovered in the gorge areas and 57 in the plain areas. Among the FFGs of macroinvertebrates in the upper Yellow River, collector-gatherers were overwhelmingly dominant, followed by scrapers, collector-filterers, predators, and shredders. Concerning river section types, dominant species in the gorge areas included Gammarus sp., Limnodrilus hoffmeisteri, and Polypedilum sp. among collector-gatherers, while in the plain areas, dominant species included Ecdyonurus sp. among scrapers, Hydropsyche sp. among collector-filterers, and Gammarus sp., Limnodrilus hoffmeisteri, and Chironomus sp. among collector-gatherers. A Mantel test revealed that dissolved oxygen, conductivity, and orthophosphate were the primary environmental factors affecting the FFGs of macroinvertebrates in the upper Yellow River, with variations observed in their effects across different months. The evaluation results of the Hilsenhoff Biological Index and Shannon–Wiener Index indicate that the water quality of the upper Yellow River is at a moderate level. An assessment of the upper Yellow River ecosystem using FFG parameters demonstrated that macroinvertebrate biomass progressively increased from upstream (gorge areas) to downstream (plain areas) spatially, accompanied by increasing habitat stability, with cascade hydropower development identified as a key factor impacting habitat stability. These findings provide pertinent data and a theoretical foundation for the protection of aquatic biological resources and watershed management in the upper Yellow River.

To investigate the age structure, growth pattern, mortality and exploitation rates of Leuciscus chuanchicus in the upstream Ningxia section of the Yellow River, four sampling surveys were conducted between 2022 and 2023. A total of 472 individuals were measured for their total length (TL) and body weight (W). Age determination was performed using otoliths. The collected samples had a range of total lengths from 4.52 to 37.45 cm, body weights ranging from 0.68 to 552.43 g, and ages ranging from 1 to 7 years old. The relationship between total length and body weight was expressed as W = 0.0052 L^3.19 for all samples, which indicates that the growth of L. chuanchicus adheres to allometry. The Von Bertalanffy growth equation revealed that the fish had an asymptotic total length (L_∞) of approximately 37.9 cm with a growth coefficient (K) value of approximately 0.461 yr⁻¹. Using the age-based catch curve method, the calculated total instantaneous mortality rate (Z) for all samples was determined as being equal to approximately 1.1302 yr⁻¹. Additionally, three methods were used to estimate the average instantaneous rate of natural mortality (M), resulting in an approximate value of 0.7167 yr⁻¹ for all samples. Furthermore, the instantaneous rate of fishing mortality (F) for all samples was calculated as 0.4134 yr⁻¹, leading us to determine that the exploitation rate (E) is 0.3658. It was concluded that the growth rate of L. chuanchicus in the upstream of the Yellow River is relatively fast, and L. chuanchicus has not been subjected to excessive exploitation, yet its relatively high natural mortality rate underscores the need for targeted management measures aimed at preserving its habitat.

Silurus lanzhouensis is a large-sized commercial fish species endemic to the mid-upper reaches of the Yellow River, serving as a “Card of Aquatic Biological Species in the Yellow River”. However, due to factors such as overfishing and habitat changes, it has been listed as an endangered species. In order to protect and restore its wild resources, we conducted a detailed study for the first time from 2022 to 2024 on the age composition, growth characteristics, mortality rate, and current status of resource exploitation of the S. lanzhouensis population in the upper Yellow River. A total of 489 individuals underwent measurements for their total length (L) and body weight (W), with age determination conducted using lapillus otoliths. The collected samples exhibited a spectrum of total lengths spanning from 2.5 to 63.7 cm, body weights ranging from 0.11 to 1974.15 g, and ages ranging from 1 to 6 years. Further analysis of the length–weight relationships unveiled an allometric growth index (b) of 2.9562 for the overall samples, indicating an isometric growth pattern. Additionally, insights into the growth characteristics of S. lanzhouensis were provided by the von Bertalanffy growth function, revealing an asymptotic total length (L_∞) of 119.30 cm and a growth coefficient (K) of 0.1278 yr⁻¹. The growth characteristic index (φ) totaled 3.2598, suggesting a moderate growth rate in comparison to other Silurus species. The total mortality rate (Z) recorded for the population of S. lanzhouensis was found to be 0.5296 yr⁻¹. Through the application of three distinct methodologies on exhaustive samples, the average natural mortality rate (M) was calculated to be 0.3105 yr⁻¹. Consequently, the fishing mortality rate (F) for the entire sample set was determined to be 0.2191 yr⁻¹, leading to an exploitation rate (E) of 0.4137. Based on the survey findings, it is evident that the population of S. lanzhouensis has not been subjected to over-exploitation, attributable to ongoing stock enhancement. These results also provide foundational data for the protection and restoration of S. lanzhouensis in the upper Yellow River.