Perca fluviatilis is an economically important species of freshwater fish. To understand the genetic structure of P. fluviatilis in China, 268 samples were collected from Wulungu Lake (WL), Jili Lake (JL), the Wulungu River (WR), and the Kalaeerqisi River (KR). These samples were then analyzed using microsatellite markers. A total of 98,425 microsatellite markers were developed based on the genomic data, and 29 polymorphic microsatellite markers were selected to analyze genetic diversity in this study. The number of alleles (N_a) and observed heterozygosity (H_o) per population ranged from 4.621 (KR) to 11.172 (WL) and from 0.510 (KR) to 0.716 (JL), respectively. The results of the polymorphic information content (PIC) showed that the WL, JL, and WR populations were highly polymorphic (PIC≥ 0.5) and that the KR population was moderately polymorphic (0.25 ≤ PIC < 0.5). The genetic differentiation coefficient (F_st) among the four P. fluviatilis populations was 0.074, indicating moderate genetic differentiation among the populations in Xinjiang. The reason for the significant difference between the rivers and lakes could be the presence of a dam blocking the flow of P. fluviatilis. The development of microsatellite markers provides support for population genetics in the future. The evaluation of the genetic structure of P. fluviatilis in Xinjiang provides a reference for the reproduction and conservation of P. fluviatilis.

To investigate the influence of factors such as tourism, agriculture, and population density on the presence of microplastic (MP) content in aquatic environments and their associated ecological risks, Jingpo Lake, a remote high-mountain lake situated away from urban areas, was selected as the research subject. This study examined the abundance, types, sizes, colors, and polymer compositions of MPs within the water body, fish, and sediments. By considering variables, including fishing practices, agricultural activities, population dynamics, and vegetation cover, an analysis was conducted to unravel the spatial and temporal distribution of MPs concerning human activities, ultimately leading to an assessment of the ecological risks posed by MP pollution. The findings revealed that the average abundance of MPs in the lake’s surface water was recorded as (304.8 ± 170.5) n/m³, while in the sediments, it averaged (162.0 ± 57.45) n/kg. Inside the digestive tracts of fish, the MP abundance was measured at 11.4 ± 5.4 n/ind. The contamination of MPs within the aquatic environment of Jingpo Lake was found to be relatively minimal. Variations in MP loads across time and space were observed, with MPs predominantly falling within the size range of small planktonic organisms (50–1000 μm). Additionally, the prevalent colors of MPs in the water samples were white or transparent, constituting approximately 55.65% of the entire MP composition. Subsequently, they were black, red, and blue. This colors distribution were consistent across MPs extracted from fish and sediment samples. The chemical compositions of the MPs predominantly comprised PE (31.83%) and PS (25.48%), followed by PP (17.56%), PA (11.84%), PET (6.71%), EVA (4.56%), and PC (2.03%). Regarding the seasonal aspect, MP concentrations were highest during summer (46.68%), followed by spring (36.75%) and autumn (16.56%). The spatial distribution of MPs within Jingpo Lake’s water body, fish, and sediments was notably influenced by human activities, as confirmed by Pearson correlation coefficients. A strong association was observed between MP levels and water quality indicators such as ammonium nitrogen (NH₄-N), total phosphorus (TP), and chlorophyll-a (Chla), suggesting that human-related pollution contributed significantly to MP contamination. The diversity assessment of MP pollutants exhibited the highest variability in chemical composition (1.23 to 1.79) using the Shannon–Wiener Index. Subsequently, the diversity of colors ranged from 0.59 to 1.54, shape diversity from 0.78 to 1.30, seasonal diversity from 0.83 to 1.10, and size diversity from 0.44 to 1.01. The assessment results of ecological risk highlighted that the risk categories for MPs within the surface water, fish, and sediments of Jingpo Lake were categorized as I for the PHI and PLI and as “Minor” for the PERI. These relatively low-risk values were attributed to the predominantly low toxicity of the distributed MPs within the Jingpo Lake basin. Moreover, the results of the risk assessment were found to be interconnected with the distribution of the local population and agricultural activities around the sampling sections. Usage patterns of coastal land and population density were recognized as influential factors affecting MP loads within the water body, sediments, fish, and other components of the lake ecosystem.

Big-head Schizothoracin (Aspiorhynchus laticeps) and Tarim Schizothoracin (Schizothorax biddulphi) are locally sympatric in the Tarim River Basin. Although another Schizothoracin (Schizothorax esocinus) in Tarim River basin has been speculated to be hybrid offspring of Big-head Schizothoracin and Tarim Schizothoracin, there was no genetic evidence. Previous studies on the genetics and evolution of Schizothoracins in Xinjiang Province were mostly based on mitochondrial DNA (mtDNA), whose characteristics of maternal inheritance made it hard to answer the question of whether there was hybridization and introgression between Big-head Schizothoracin and Tarim Schizothoracin. In this study, cytochrome b (cytb) gene of mtDNA and internal transcribed spacer 2 (ITS2) that is encoded by the nuclear genome were genotyped within the entire samples at the same time. Our results confirmed that Schizothorax esocinus was the hybrid offspring of Big-head Schizothoracin and Tarim Schizothoracin. The heterozygous ITS2 genotypes and/or Aspiorhynchus laticeps-like mtDNA were also detected in a subset of samples that should have been identified as pure Schizothorax biddulphi based on morphology. The ITS2 is characterized by multi-copy, concert evolution, and biparental inheritance. Thus, by comparing with mtDNA data, broad-scale bidirectional hybridization and introgression between Big-head Schizothoracin and Tarim Schizothoracin were revealed. Although interspecific hybridization may play a positive role in ecology and evolution, interspecific hybrids could threaten their parental species by the swamping of genetics and demography. As both parents of hybridization are critically endangered fishes, in this case, it is urgently necessary to strengthen the scientific assessment of the risks of the hybrids and the control of the hybridization and introgression between Aspiorhynchus laticeps and Schizothorax biddulphi in the Tarim River Basin.

Standardized fishing gear represents a common fisheries management intervention, yet its effectiveness in multi-species freshwater ecosystems remains insufficiently assessed. This study presents the first application of the Length-Based Bayesian Biomass (LBB) method to systematically evaluate the stock status of eight major commercial fish species in Xingkai Lake (located within China). Length-frequency data collected in 2019 (marking the policy initiation) and 2024 (after five years of implementation) were used to estimate key population parameters and exploitation indicators. The results revealed that the four species (Carassius gibelio, Acheilognathus macropterus, Hemiculter lucidus, and Hemiculter leucisculus) recovered to healthy status (B/B_MSY ≥ 1.0), demonstrating the policy’s effectiveness for small-bodied, fast-growing species. In contrast, three species (Chanodichthys abramoides, Chanodichthys mongolicus, and Chanodichthys erythropterus) remained grossly overfished (B/B_MSY < 0.5), while Culter alburnus experienced increased fishing pressure, indicating limited efficacy for larger, slow-growing species with collapsed initial stocks. Although the mesh size increase facilitated recovery of specific populations, fisheries resources in Xingkai Lake continue to face overfishing pressure. Management strategies lacking an ecosystem perspective may not only fail to achieve conservation objectives but could also trigger ecological risks. This study underscores that ecosystem-based management is essential for sustainable management of multi-species fisheries.

The Wutong River, located in northeastern China’s Heilongjiang Province, serves as an important habitat and spawning ground for fish and freshwater shellfish. To investigate the influence of geographic and geomorphic changes on the river basin ecology, the water environment and spatial heterogeneity of freshwater shellfish distribution were monitored in both summer and autumn of 2024. Key water quality indicators were analyzed, including basic parameters (pH and dissolved oxygen), eutrophication indices (nitrogen, phosphorus, and chlorophyll), and pollutant levels (nitrite nitrogen, petroleum, and volatile phenol). Water quality was assessed using the single-factor index method and the Nemerow pollution index method. Results indicated that in 2024, the Wutong River was weakly acidic in summer and weakly alkaline in autumn, with overall high dissolved oxygen levels. The Guanmenzuizi Dam site exhibited the best water quality. According to the single-factor evaluation, water quality in autumn was better than in summer, with iron, manganese, and volatile phenol as the primary pollutants, followed by total nitrogen and permanganate index. Based on the Nemerow index, the river generally met China’s Class III surface water standards. Water quality showed a trend of initial improvement followed by deterioration along the river course. Among 100 sampling points, Unio douglasiae had the highest occurrence rate (76%), followed by Cipangopaludina cahayensis (66%). Other species occurred in ≤50% of samples, with Polypylis hemisphaerula being the rarest (3%). The average species occurrence rate increased from upstream to downstream. This study provides a data baseline for understanding the water environment of the Wutong River and supports research on biodiversity and ecological conservation.

The present study reports the length-weight relationships (LWRs) for eight fish species sampled in Hailang River, a left-bank tributary of the Mudan River in Northeast China. The fishes were collected from April to October bimonthly 2017 by electrofishing (fishing 2 kilometers along the river and within 5 meters from the bank) and netting (drift gillnet: mesh size 2 cm x 3 cm; 200 m net length). The specimens were weighed (nearest 0.1 g) and measured (nearest 0.1 cm) in the laboratory. This study provides an update in maximum lengths for five species.