The Yangtze River Basin, one of China’s five major watersheds and a primary source of drinking water for the country, is experiencing serious environmental pollution as heavy metals are discharged into its rivers. To evaluate the water quality of the river, determined water quality parameters were compared with the maximum permissible limit values recommended by the World Health Organization and Chinese drinking water standards. Physical and chemical analyses were conducted on water samples taken from 19 locations along the river’s path. The study quantified the contents of sodium (Na), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lithium (Li), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), scandium (Sc) and mercury (Hg). The results show that the average values of Mg, Sr, Co, Cu, Fe, Mn and Sc are higher than the historical background values. Moreover, through a correlation analysis it was concluded that these nutrients and trace metals have high values due to anthropogenic pollution in the study area. The computed WQI values range between 9.59 and 20.26, indicating excellent water quality in the river basin. Finally, hazard quotient (HQ) values show that exposure to the detected pollutants will have no adverse effects on human health and does not pose a potential non-carcinogenic risk.

The mechanism of bacterial community assembly has been the hot spot in the field of microbial ecology and it is difficult to quantitatively estimate the influences of different ecological processes. Here, a total of 23 pairs of planktonic and sedimentary samples were collected from five lakes in Wuhan, China. significant higher α-diversity (p < 0.001) and β-diversity (p < 0.001) of bacterial communities were observed in sediment than those in water. Some phylum had linear relationships with the comprehensive TSI (TSIc) by regression analysis. Non-metric multidimensional scaling (NMDS) and redundancy analysis (RDA) revealed that the depth of water, NO₃⁻-N, NH₄⁺-N, PO4³⁻, and COD_cr were the key environmental variables in planktonic bacterial communities, whereas in sediment they were the depth, NO₃⁻-N, and NH₄⁺-N. Furthermore, variation partitioning analysis (VPA) showed that spatial and environmental factors could only explain 40.2% and 27.9% of the variation in planktonic and sedimentary bacterial communities, respectively. More importantly, null model analysis suggested that different assembly mechanisms were found between in water and in sediment with the fact that planktonic bacterial community assembly was mainly driven by dispersal limitation process whereas variable selection process played a vital role in that of sediment.

Macrobrachium nipponense is a major farmed species freshwater shrimp in China and its genetic diversity is of high value in aquaculture. The construction of the Three Gorges Project has slowed down the water velocity in the Three Gorges Reservoir (TGR) and made the water more clear, which is more favourable for the survival and reproduction of M. nipponense. However, there are lack of studies on the genetic diversity of M. nipponense populations in the TGR. In this study, mitochondrial COI gene sequences were used as molecular marker to analyze the genetic diversity, genetic differentiation and historical demography of eight M. nipponense populations in the TGR. The results showed that the M. nipponense populations in TGR have high genetic diversity. There was some genetic differentiation between the four populations in lower reaches of the TGR and four populations in the upper reaches of the TGR. We also found that there was a significant correlation between genetic distance and geographical distance among the M. nipponense populations in the TGR. The M. nipponense population in the TGR has experienced population reduction in the recent year, which might be related to the ice age movement in the Little Ice Age and human activities. This study provides a theoretical basis for the rational development and protection of M. nipponense resources in the TGR.

In the present study, we obtained the first complete mitochondrial genome sequence of Leucosoma (Salanx) chinensis. It was 16,595 bp in length and consisted of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and a non-coding control region. The nucleotide composition was A (23.1%), T (25.2%), G (20.0%) and C (31.8%), and the A + T content (48.3%) was a little lower than G + C content (51.80%). Phylogenetic analysis of 10 species of Salangidae identified three major clades. These results may facilitate the future genetic research of L. chinensis and Salangidae.

Human activities have altered rivers worldwide, but how their combined effects shape fish assemblages remains unclear. We therefore surveyed fish and habitats seasonally along the middle and lower reaches of the Han River, China, during 2022, specifically in June–August (wet season) and October–November (dry season). This study analyzed the spatial distribution pattern of fish diversity, explored the effects of natural factors (e.g., hydrology, water quality) and human stressors (e.g., dam, land use) on the spatial pattern of fish diversity, and identified the key driving factors. Cluster analysis and Non-metric Multidimensional Scaling (NMDS) showed that the fish communities could be divided into three groups: the Danjiangkou reservoir area (DRA), the middle reaches (MR), and the lower reaches (LR). For α-diversity, the LR had the highest value, followed by the DRA, with the MR being the lowest. For β-diversity, the MR had the highest value, followed by the LR, with the DRA being the lowest. Random Forest model showed that fish diversity was mainly affected by natural factors; among these factors, the key drivers of α-diversity were hydrological factors such as the water level (3.56–5.97%) and river width (4.53–4.69%), while for β-diversity, the key drivers were water quality factors, including the dissolved oxygen (10.08–12.36%), total nitrogen (6.49–9.31%), and chlorophyll a (8.26–8.40%). Structural Equation Modeling further revealed that natural factors affected β-diversity mainly through direct pathways, while human stressors affected β-diversity mainly through indirect pathways. The results revealed the differential roles of natural factors and human stressors in driving the patterns of fish α-diversity and β-diversity in human-disturbed rivers, which will provide a scientific basis for the conservation of fish diversity in the Han River.

Coptodon zillii and Oreochromis niloticus are dominant invasive fish species that have successfully established and coexisted in the Jinghong Reservoir of the lower Lancang River, Southwest China. To explore the mechanisms underlying their invasion and coexistence from the perspective of reproductive traits, we conducted monthly sampling from January to December 2025 to compare key reproductive parameters, including size at first sexual maturity, sex ratio, breeding season, spawning pattern and fecundity. The results showed that the predicted sizes at first sexual maturity for females and males of C. zillii (83.4 mm and 81.7 mm, respectively) were significantly smaller than those of O. niloticus (127.7 mm and 125.8 mm, respectively). Both species exhibited early sexual maturation. The sex ratio of C. zillii was approximately 1:1, whereas that of O. niloticus was significantly female-biased. The breeding season of C. zillii lasted from April to September, peaking in May and June, while O. niloticus spawned from May to November, with a peak in August, showing a staggered temporal distribution. Both species were batch spawners; however, O. niloticus had significantly larger egg diameters than C. zillii. Absolute fecundity, length-relative fecundity and weight-relative fecundity were significantly higher in C. zillii than in O. niloticus. Moreover, the absolute fecundity of C. zillii showed stronger correlations with body length, body weight, net weight and gonadal weight. C. zillii adopted a more r-selected strategy, while O. niloticus exhibited a more K-selected strategy. The two species displayed clear divergence in their reproductive strategies, including size at maturity, breeding season, egg diameter and fecundity, which reduced interspecific competition and promoted niche separation and coexistence in the Jinghong Reservoir.