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BackgroundTo rehabilitate the depleted fish resources of the Yangtze River Basin, China, a 10-year fishing ban has been implemented. This national initiative has attracted worldwide attention. The present study aimed to explore the ecological process and recovery effectiveness of this complete fishing ban in the Chishui River, the first river where the fishing ban was enacted in the Yangtze River Basin. Changes in fish resources were analyzed based on investigations conducted 5 years before (2012–2016) and 5 years after (2017–2021) the implementation of the fishing ban in four reaches along the longitudinal gradient.ResultsA total of 140 fish species, including 127 native and 13 exotic species, were collected during the study period. The number of fish species as well as the diversity indices showed no significant temporal changes. However, 11 native species that had disappeared for many years appeared again after the fishing ban. The occurrence rates of some key protected species, Procypris rabaudi, Acipenser dabryanus, Euchiloglanis davidi and Myxocyprinus asiaticus, increased after the fishing ban, while Coreius guichenoti, Percocypris pingi, Onychostoma angustistomata and Leptobotia rubrilabris showed no obvious recovery. The fish assemblage structure in nearly all reaches (except the headwater) showed significant temporal changes with an increase in the relative abundance of larger body-sized species. The population structure of most dominant species improved greatly with the mean standard length and the mean body weight as well as the proportion of larger-sized individuals clearly increasing. In addition, the density of fishes changed dramatically with the catch per unit effort (CPUE) increasing by 140–210% for different study reaches.ConclusionsThe present study confirmed that the complete fishing closure is an effective measure to facilitate fish resources recovery. These results provide valuable references for evaluating the effectiveness of the 10-year fishing ban policy in the entire Yangtze River.

Coreius guichenoti , mainly distributed in upstream regions of the Yangtze River China, is currently on the brink of extinction and listed as national secondary protected animal. In this study, we aimed to obtain the chromosome-level genome of C. guichenoti using PacBio and Hi-C techniques. According to the PacBio sequencing, C. guichenoti genome was successfully assembled to 1100.1 Mb size, with a Contig N50 size of 25.0 Mb, and containing 731.0 Mb of repeats. Hi-C sequencing data was utilized for chromosome assembly and 25 chromosome sequences were ultimately yielded, with a total length of 1076.8 Mb. Moreover, a total of 22,506 protein-coding genes were predicted with average intron length of 2293 bp. Evolutionary analysis and divergence time prediction revealed that C. guichenoti was closely related to C. heterodon and they phylogenetically diverged from common ancestor ~20.7 million years ago (Mya), following the separation of Cyprinidae at 28.3 Mya. In the future, the utilization of comparative genomics research is important in elucidating the molecular mechanisms of Ichthyophthirius disease and ensuring the conservation of biological resources.

© 2016 The Author(s). Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Understanding the early life history of the endangered largemouth bronze gudgeon ( ) is crucial for optimizing artificial rearing and conservation strategies. To provide a unified scientific basis for these efforts, this study characterized the ontogeny of larvae from hatching to 30 days post-hatch (dph) by integrating analyses of allometric growth, digestive histology, and enzyme activities. Morphometric analysis revealed that total length increased exponentially with age. Positive allometric growth was observed in swimming organs (pectoral, dorsal, and caudal fins) and eye diameter, indicating a priority in developing locomotion and sensory capabilities for survival in lotic environments. Histological examination showed that the digestive tract became patent by 4 dph, and functional structures were established by 5 dph, coinciding with yolk sac absorption and the initiation of exogenous feeding. The digestive system reached near-adult maturity by 20 dph. Enzyme activity profiles showed that trypsin activity increased continuously, peaking at 30 dph, while amylase and alkaline phosphatase peaked at 20 dph. Lipase activity remained low until a slight increase at 30 dph. These results indicate that larvae adopt a \"locomotion-first\" strategy, with the digestive system becoming functional at 5 dph and maturing by 20 dph. These findings collectively define the critical windows for artificial propagation, specifically guiding the timing of initial feeding and feed formulation.

Coreius guichenoti, an endemic fish of the upper Yangtze River, has experienced severe population decline due to overfishing and habitat fragmentation. To inform its conservation, this study compared life-history traits between artificially bred and historical wild populations, revealing pronounced plasticity in response to environmental conditions. The cultured population, dominated by age 0–4 individuals but retaining a notable proportion of age 5–6 fish, exhibited faster growth and higher fecundity (mean absolute fecundity 32,724 ± 24,132 eggs; relative fecundity 37.5 ± 18.5 eggs/g) than the wild population. In contrast, the wild group consisted of >90% age 0–4 individuals, showed virtually no fish aged 5–7, reproduced seasonally with high total egg output, and tended toward a periodic life-history strategy, whereas the cultured group tended toward an opportunistic strategy that still retained some periodic traits. These results demonstrate that C. guichenoti can adjust its life history on a within-generation scale. Accordingly, we recommend pre-release conditioning with moderate flow and temperature variations to enhance field adaptability. This study provides evidence-based guidance for broodstock selection and preconditioning in restocking programs, aimed at improving post-release survival and reproductive success in the wild.

Field investigation indicated that the reduction in fish spawning was associated with the alteration in water temperatures, even a 2–3 °C monthly difference due to reservoir operations. However, the physiological mechanism that influences the development of fish ovary (DFO) remains unclear. Thus, experiments of Coreius guichenoti were conducted at three different temperatures, optimal temperature (~20 °C, N) for fish spawning, lower (~17 °C, L), and higher (~23 °C, H), to reveal the effects of altered water temperature on the DFO. Comparisons were made between the L and N (LvsN) conditions and H and N (HvsN) conditions. Transcriptomic analysis differentially expressed transcripts (DETs) related to heat stress were observed only in LvsN conditions, indicating that the DFO showed a stronger response to changes in LvsN than in HvsN conditions. Upregulation of DETs of vitellogenin receptors in N temperature showed that normal temperature was conducive to vitellogenin entry into the oocytes. Other temperature-sensitive DETs, including microtubule, kinesin, dynein, and actin, were closely associated with cell division and material transport. LvsN significantly impacted cell division and nutrient accumulation in the yolk, whereas HvsN only influenced cell division. Our results highlight the impact of altered water temperature on the DFO, thereby providing insights for future reservoir operations regarding river damming and climate change and establishing fish conservation measures.

Coreius guichenoti, once widely distributed in the upper reaches of the Jinsha River, has become a nationally protected species in China due to the profound impacts of cascade reservoirs. To assess the influence of substrate on the suitability of spawning habitat for C. guichenoti, this study develops a substrate-inclusive habitat model using fuzzy logic based on expert knowledge. Taking the Pingdi Town section of the lower Jinsha River—a historical spawning site for C. guichenoti—as a case study from March to July 2020, we simulated changes in the spawning habitat suitability index (HSI) and compared the results with those from traditional models that exclude substrate factors. The results showed that in the first and second halves of May, Weighted Usable Area (WUA) and Overall Suitability Index (OSI) increased by 42.31% and 38.73%, respectively, while MSP exhibited dramatic increases of 236.04% and 614.56%. These improvements were primarily observed along the riverbanks, where HSI increased by approximately 0.25. From a management perspective, the HSI results provide a scientific basis for optimizing ecological flow regulation. Incorporating substrate factors into spawning habitat models offers a more objective and comprehensive assessment of habitat quality. Habitat restoration measures, such as targeted substrate improvement in key riverbank areas, may further increase habitat suitability, providing additional opportunities for conservation planning in regulated rivers.

The experiment was conducted to investigate the effects of feeding rates on growth performance, liver glycolysis, gluconeogenesis, glycogen synthesis, and glycogen decomposition in juvenile largemouth bronze gudgeon (Coreius guichenoti). A total number of 600 fish were randomly distributed into 12 cylindrical plastic tanks with 50 fish per tank and triplicate tanks per treatment. Fish were fed with 2%, 3%, 4%, and 5% feeding rates (body weight per day) three times day−1 for 8 w. The results indicated that the feeding rates significantly increased the body weight, weight gain rate, and specific growth rate (p < 0.05), while showing no significant effects on the condition factor and survival rate (p > 0.05). The feed conversion ratio was significantly enhanced by the feeding rate (p < 0.05), although no significant differences were observed when the feeding rate exceeded 3% (p > 0.05). The plasma glucose levels in the 4% and 5% groups were significantly higher than those in the 2% and 3% groups. Compared with other groups, the 5% group significantly increased the crucial rate-limiting enzyme activities and mRNA levels of glycolysis (PFKL and PK) (p < 0.05), while showing no significant differences on enzyme activities (PC, PEPCK, and G6P) and mRNA (pepck and g6p) levels of gluconeogenesis (p > 0.05). In addition, the mRNA levels of hepatic glut2 and glut4 in the 5% group reached the highest levels (p < 0.05). When the feeding rate exceeded 3%, hepatic glycogen and lipid accumulation were significantly increased, leading to a fatty liver phenotype. Meanwhile, the mRNA level of liver glycogen synthetase (gysl) was significantly increased (p < 0.05), while no significant difference was observed in glycogen phosphorylase (pygl) (p > 0.05). In summary, under the conditions of this study, a feeding rate exceeding 3% significantly accelerated hepatic glycogen and lipid accumulation, which ultimately induced fatty liver formation.

The loss of freshwater fish habitats, exacerbated by climate change and dam constructions, poses a critical environmental concern. The upper Yangtze River basin, noted for its abundant fish fauna and concentrated dam development, serves as a crucial locale for investigating the impacts of climate shifts and dam construction. This study aims to disentangle the impacts of hydroelectric dams and climate change on fish habitat distribution by analyzing species presence data across different periods. Species distribution models were constructed using Maxent for Coreius guichenoti (a warm‐water endangered fish) and Schizopygopsis malacanthus (a cold‐water endangered fish). The model accuracy was assessed using the area under the curve of the receiver operating characteristic. Habitat distribution modeling and prediction for the pre‐dam period (1970–2000) and post‐dam period (2001–2020), as well as future climate change under two shared socioeconomic pathways scenarios, were conducted. The impacts of climate change and dam construction on the habitat suitability of two fish species were quantified. The results revealed dam construction predominantly diminished habitat suitability and range, with high‐suitability habitats in the post‐dam period decreasing by 56.3% (720.18 km) and 67.0% (1665.52 km) for the two fishes, respectively. Climate change would enhance the habitat suitability of Coreius guichenoti, while it would decrease the habitat suitability of Schizopygopsis malacanthus. The impact of dam construction is greater that of climate change for them. This study underscores the profound impacts of dam construction on fish habitats, particularly for cold‐water species, and highlights the critical need for habitat restoration in sustainable hydropower development. Our method of disentangling these factors also provides a new approach to evaluating environmental impacts in large river basins. Understanding how cold‐water and warm‐water fish cope with various stressors such as climate change and dam construction is crucial for the conservation of freshwater fish ecosystems. This study proposes to incorporate the information on dam impact implicitly existing in the species presence data in different periods to disentangle the impacts of hydroelectric dams and climate change on cold‐water and warm‐water fish habitat distribution in the upper Yangtze River basin.

Hydropower operations significantly alter the natural hydrological conditions of rivers, exerting adverse effects on riverine ecosystems. Accurate identification of fish habitats under hydropower operation and maintaining suitable ecological flow are crucial for riverine ecological conservation and water resource management. Coreius guichenoti was selected as the target species and the Yibin reach of the downstream Jinsha River was selected as the studied river reach. Subsequently, Weighted Usable Area (WUA) and Habitat Connectivity Index (HCI) were employed to comparatively analyze the habitat quantity and quality before and after the construction and operation of the Xiangjiaba hydropower station, namely the natural period (1991–2005), construction period (2006–2014), and operation period (2015–2020). Finally, correlations between WUA, HCI, and flow were established to determine the optimal ecological flow corresponding to optimal fish habitats. The results indicate that the average WUA and HCI during the construction period are similar to the natural period. In comparison to the natural period, the average WUA decreases by 9.2%, and the average HCI decreases by 0.05 during the operation period. It is determined that the habitat conditions are optimal when the flow is between 3000 and 5000 m3/s. After further refining the flow scenarios, the suitable ecological flow is determined to be 3500 m3/s. This study can provide a scientific basis for the water resources management in the Jinsha River and contribute to the field of riverine ecological conservation and restoration.