Hydrodynamic characteristics of spawning grounds are important factors affecting the spawning of four major Chinese carps (Mylopharyngodon piceus, Ctenopharyngodon idella, Hypophthalmichthys molitrix, and Aristichthys nobilis). To investigate the relationship between the preferred hydrodynamic characteristics of spawning sites and the response of fish spawning behavior, we monitored the flow field of spawning sites during ecological operation of the Three Gorges Dam (i.e., man-made flood regulation) in 2014 and 2015. We used the data to explore the correlation between vorticity changes in spawning grounds and the spawning amount. Pearson correlation coefficients of the average vorticity in all cross-sections of the Yidu spawning ground and spawning amount in 2014 and 2015 were 0.730 and 0.822, respectively, indicating a significant positive correlation between vorticity and spawning activity. In some specific regions, this correlation was even stronger (Pearson correlations of the regional vorticity and egg production were >0.95). To further corroborate and analyze the relationship between these specific regions and the distribution of broodstock during the breeding season, an ultrasonic telemetry test of broodstock was conducted in the Yidu spawning ground in 2016. The results showed that the broodstocks were concentrated in the reach near the Quantong Pier (~76 km from the Three Gorges Dam). These regions were consistent with areas of river characterized by highly correlated vorticity and egg production levels, suggesting that these regions are areas preferred by four major Chinese carps for spawning.

The patterns of carbon flow in large rivers influenced by dams are still not well known. We hypothesized that spatial variation in fish assimilation of basal production sources would be affected by heterogeneity of landscape-scale hydrology within a watershed due to the impoundment. We used stable isotope analysis and Bayesian mixing models to estimate relative contributions of basal production sources to fish consumers in a tributary of the Three Gorges Reservoir (TGR) with remarkably heterogeneous habitats between the upper and lower reaches. Model estimates indicated that riparian C₃ plants were the main basal food source irrespective of reaches or feeding groups. Autochthonous algae carbon also appeared to be important as secondary carbon sources. However, the major contributive aquatic algae in the upstream were benthic algae while planktonic algae were important in the downstream, and this difference was related to their distinct hydrological characteristics. The contribution from C₄ plants was comparatively less important to all fish consumers. Our results highlighted the significance of the riparian C₃ carbon source to fish consumers in the TGR tributary and that the difference in landscape-scale characteristics was not enough to influence the pattern, which may be attributed to abundant standing stock of the riparian plants as well as hydrologic regimes in this river.

A multi-mesh trammel net has been developed and used for sampling freshwater fishes. However, little is known about the catch efficiency of the net. This research investigated the catch efficiency of a multi-mesh trammel net (nominal mesh size; 10.0, 30.0, 50.0, and 70.0 mm) for fish sampling in the Yangtze River of China. Catch composition and factors affecting catch per unit effort based on fish number (CPUE_N), weight (CPUE_W), and species number (CPUE_S) were analyzed. The results showed that the net was capable of capturing a wide range of fish sizes (total length, 5.5 to 121.0 cm) and species (n = 50). Increasing soak time from 9.4 to 24.0 h resulted in a decrease in CPUE_N and CPUE_W while a longer soak time increased CPUE_S. CPUE_N, CPUE_W, and CPUE_S varied significantly with fishing locations. The net provides a potential complement to the current fish sampling techniques used in freshwater ecosystems (e.g., large rivers, lakes, and reservoirs). The findings of this research help to improve our understanding of the catch efficiency of the multi-mesh trammel net and provides insight into better designs for gears and methods for sampling diverse fish sizes and species.

In order to investigate the influence of the high-altitude aquatic environment on indigenous fish metabolites, metabolomics studies were applied in this study. Widespread throughout the main stem of the Nujiang River of Schizothorax nukiangensis, we established sampling sites at high (3890 m) and low (2100 m) altitudes and selected six S. nukiangensis at each location, each weighing approximately 150 g and looking healthy. Then, metabolomics analysis was performed to compare the various metabolites of the two groups. Low concentrations of amino acids, dipeptides, eicosapentaenoic acid, docosahexaenoic acid, pentadecanoic acid, Thioetheramide-PC, 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine, 1-Stearoyl-sn-glycerol-3-phosphocholine, 1-Myristoyl-sn-glycero-3-phosphocholine and 1-Palmitoyl-sn-glycero-3-phosphocholine, high concentrations in S-Methyl-5’-thioadenosine, creatine, D-mannose-6-phosphate, D-mannose-1-phosphate, oleic acid and myristoleic acid were found in high-altitude fish liver. These differentially accumulated metabolites were involved in oxidative stress, energy metabolism, carbohydrate metabolism and lipid metabolism. mTOR signaling pathway, apoptosis and lysosome were the KEGG pathways that were enriched between different groups to ensure energy supply and limit tissue damage of fish at high altitudes. All these results contributed to the understanding of the high-altitude adaptation of S. nukiangensis in the Nujiang River. Nicotine and methoprene, two organic pollutants, performed differently in fish at different altitudes. Overall, our findings advanced the fundamental understanding of fish responses to high-altitude environments, adaptive mechanisms and organic contaminants pollution in the Nujiang River.

The length–weight (LWR) and length–length (LLR) relations of 23 species of native freshwater fishes of six families and three orders collected from the Yuanjiang River in the upper reaches of the Red River were analyzed. From June 2023 to October 2024, specimens representing 23 freshwater fish were obtained: Cyprinus rubrofuscus Lacepède, 1803; Placocheilus caudofasciatus (Pellegrin et Chevey, 1936); Poropuntius krempfi (Pellegrin et Chevey, 1934); Microphysogobio yunnanensis (Yao et Yang, 1977); Abbottina rivularis (Basilewsky, 1855); Opsariichthys bidens Günther, 1873; Hemibarbus medius Yue, 1995; Onychostoma gerlachi (Peters, 1881); Rasbora atridorsalis Kottelat et Chu, 1988; Schistura macrotaenia (Yang, 1990); Schistura fasciolata (Nichols et Pope, 1927); Vanmanenia tetraloba (Mai, 1978); Beaufortia leveretti (Nichols et Pope, 1927); Sinogastromyzon tonkinensis Pellegrin et Chevey, 1935; Bagarius rutilus Ng et Kottelat, 2000; Glyptothorax quadriocellatus (Mai, 1978); Glyptothorax honghensis Li, 1984; Glyptothorax interspinalum (Mai, 1978); Hemibagrus pluriradiatus (Vaillant, 1892); Pseudobagrus kyphus Mai, 1978;Tachysurus fulvidraco (Richardson, 1846); Tachysurus virgatus (Oshima, 1926); and Channa gachua (Hamilton, 1822). The total length (TL), standard length (SL), and body weight (BW) were determined for each fish individual to the nearest 0.1 cm and 0.1 g, respectively. All LLR and LWR parameters of 23 fish species were statistically significant (P < 0.001). The length–weight relations of 17 species have not previously been available in FishBase. Moreover, we provided a new distribution record of fish (Rasbora atridorsalis). Our study provided LWR values for the first time, which will help validate the accuracy and predictability of Bayesian models in estimating species-specific growth parameters for data-poor species. The majority of the LWR relations obtained in this study are new to this region. The availability of species- and region-specific data on length–weight relations could help inform future research and management of these species.