IntroductionThe 2020 Yangtze River ten-year fishing ban represents a landmark conservation intervention, yet its ecosystem-level effects within ex situ reserves for critically endangered aquatic megafauna remain largely uncharacterized.MethodsWe compared pre-ban (2016) and post-ban (2024–2025) fish surveys in He-wang-miao Oxbow, a designated ex situ reserve for the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis) and a germplasm resources bank for Chinese sturgeon (Acipenser sinensis).ResultsWe documented rapid fish community reorganization. The surveys revealed a net loss of 4 species, with 15 historically recorded taxa undetected and 11 new taxa recorded after the ban. Total fish biomass increased 5.5-fold, alongside numerical increases in species diversity and a shift toward community stability. However, these aggregate gains coincided with a catastrophic collapse in small-bodied fish biomass from over 76.6% to 1.4% of total catch, the primary prey base of the Yangtze finless porpoise, while sturgeon-preferred demersal and benthopelagic assemblages remained stable. Community dominance shifted from small-bodied fish to large river-lake migratory species, a transition driven by barrier net retention, intensified top-down predation and interspecific resource competition.DiscussionWe conclude that physical barrier nets, rather than the fishing ban alone, restructured the aquatic trophic web and compromised the porpoise’s prey base, requiring targeted adaptive management to align ecosystem recovery with endangered species conservation goals.

Human activities are causing a severe decline in fish species diversity globally. Although biodiversity is inherently multidimensional, most previous studies have concentrated on taxonomic changes, neglecting functional and phylogenetic dimensions, therefore limiting our understanding of biodiversity changes. The Yangtze River, an ecologically and economically critical system, supports high fish biodiversity and important fisheries. Yet, the spatio temporal patterns and anthropogenic drivers of biodiversity changes over the past decades remain unclear. We compiled a comprehensive fish occurrence dataset covering 56 geographic units across the Yangtze River Basin for historical (1976–2010) and current (2011–2020) periods. We assessed taxonomic, functional, and phylogenetic richness and dissimilarity, and quantified overall changes using the Cumulative Change in Biodiversity Facets (CCBF) index. Over 80

This study aimed to determine the practical efficacy of passive eDNA samplers (PEDS) for monitoring fish diversity in riverine ecosystems. It investigated the utility of environmental DNA (eDNA) in accurately depicting fish composition and diversity within the Lancang River. Environmental DNA technology, particularly PEDS, may be used as a substitute for traditional water filtration techniques. However, its effectiveness in natural water ecosystems remains to be proven. The filter materials included mixed cellulose acetate and nitrate (MCE), nylon (NL), glass fiber (GF), and polyvinyl chloride filter membrane (PVC). This study used four different types of filters, each with identical pore sizes and dimensions but constructed from various materials, to assess eDNA capture under laboratory and field conditions in the water samples. The filter materials included mixed cellulose acetate and nitrate (MCE), nylon (NL), glass fiber (GF), and polyvinyl chloride filter membrane (PVC). Environmental DNA macrobarcoding was used to analyze fish biodiversity and to understand the environmental effects on species distribution. Our study identified 50 fish species inhabiting the Lancang River, with equal representation of exotic and native species. A comparative analysis of four filter-based environmental DNA samplers and traditional environmental DNA sampling methods demonstrated comparable species richness. Redundancy analysis indicated that environmental variables, elevation, electrical conductivity, salinity, and chlorophyll-a significantly influenced the distribution patterns of both non-native and native fish species in the river. This study highlights the significance of eDNA technology in evaluating fish diversity across diverse habitats, thereby establishing a theoretical framework for the sustained monitoring and management of fish biodiversity in protected areas.

The Yangtze River has experienced severe ecological degradation due to intensive human activities, including dam construction, land reclamation, and overfishing. These disturbances have disrupted the natural habitats of the Yangtze River, leading to a sharp decline in fish biodiversity and fishery resources. To address this ecological crisis, the Chinese government implemented a 10-year fishing ban in January 2021 to mitigate pressures on fish populations, restore aquatic habitats, and promote biodiversity recovery. The middle reaches of the Yangtze River are characterized by diverse fish species and a critical habitat for aquatic life, this study seeks to assess the effects of the fishing ban on fish diversity, body structure, population and community dynamics in this region. Fish monitoring data collected from 2017–2019 (pre-ban) and 2021–2023 (post-ban) were analyzed to evaluate changes in fish body size, species diversity, and community structure. The analysis results using the PSD method indicate that fish body size has increased following the fishing ban, suggesting the improvement of population structures, and a change in the complexity of food web structure. Species diversity indices showed partial recovery, but the recovery was uneven across different sampling sites. While fish populations showed signs of improvement, particularly in terms of body size and community stability, species diversity remained at relatively low levels in some areas, indicating that full recovery in biodiversity and resource levels may require extended conservation efforts. These findings suggest that while the fishing ban has had a positive initial impact on fish populations and ecological conditions, continued and long-term conservation measures are essential for fully recovering the river’s biodiversity and restoring its fishery resources. The study also highlights the importance of monitoring fish species diversity, body structure, and community dynamics as part of ongoing efforts to evaluate the effectiveness of the fishing ban and refine resource management strategies for the middle reaches of the Yangtze River.

Animal behavior diversity is a key element of biodiversity, and the establishment of an ethogram provides a crucial framework for exploring the relationship between behavioral patterns and environmental factors. However, the development of ethograms and the quantitative analysis of behavioral diversity in fish remain underexplored. In this study, focal animal sampling and instantaneous scan sampling methods, paired with the PAE (Posture-Act-Environment) coding system, were employed to investigate the ethogram and reproductive behavior diversity of silver carp. The findings revealed 12 postures, 20 actions, and 34 behaviors documented during the breeding period of silver carp. Analysis of reproductive behavior diversity revealed that the absolute behavioral diversity index (H), relative behavioral diversity index (r), and regulated diversity index (r-variable) all peaked during the 10-15 h interval following induced spawning. Notably, significant differences (p < 0.001) were observed in these indices across different post-induction time intervals and between sexes. Throughout the breeding cycle, females demonstrated lower diversity and intensity in reproductive behaviors compared to males, suggesting distinct reproductive strategies between the sexes. The reproductive behavior of silver carp exhibited distinct chronobiological disorganization patterns. This study provides a scientific basis for future research on the behavioral ecology of silver carp and the conservation of their wild populations.

The spleen is postulated to be a hematopoietic tissue in adult fish; however, clear evidence is still lacking to define its role in hematopoietic activity. In our previous study, a congenitally asplenic zebrafish was generated though gene editing, which provided a new perspective for studying the role of fish spleen in hematopoiesis. In this study, HSC-regulated and erythrocyte marker genes, such as gata1a, gata2, klf1, hbaa1, hbaa2, hbba1 and hbba2 were significantly reduced in congenitally asplenic zebrafish when compared with wild-type (WT). Subsequently, we conducted the transcriptome profiles of whole kidneys from WT and congenitally asplenic zebrafish to explore the possible molecular mechanisms underlying the impaired erythropoiesis caused by congenital asplenia. Our results demonstrated that congenital asplenia might impair heme-iron recycling during erythropoiesis, as evidenced by significant down-regulation of genes associated with iron acquisition (tfr1a, tfa, steap3 and slc25a37) and heme biosynthesis and transport (alas2, fech, uros, urod, copx, ppox and abcb10) in congenitally asplenic zebrafish. In addition, the down-regulation of hemopoiesis-related GO terms, including heme binding, tetrapyrrole binding, iron ion binding, heme metabolic process, heme biosynthetic process, erythrocyte differentiation, iron ion homeostasis and hemoglobin metabolic process confirmed the impaired erythropoiesis induced by congenital asplenia. Our study provides an in-depth understanding of spleen function in regulating heme-iron homeostasis during hematopoiesis, thereby providing valuable insights into pathological responses in splenectomized or congenitally asplenic patients.

This study provides a comprehensive analysis of the spatio-temporal dynamics of fish resources in the confluence waters of Poyang Lake and the Yangtze River, focusing on the initial phase of a 10-year fishing ban implemented in January 2020. Through hydroacoustic surveys conducted during both high-water (September 2020) and low-water (January 2021) periods, we identified significant variations in fish density and individual size across different sections. During the high water level period, fish concentrations were primarily observed in the confluence area between the Yangtze River and Poyang Lake, exhibiting higher densities compared to other regions. Conversely, fish congregated in the deep-water zones of the main river during the low water level period. The fish population was dominated by small to medium-sized individuals, with mean body lengths of 12.47 cm and 12.62 cm during the high and low water level periods, respectively. Notably, 42 and 33 fish species were recorded during the high-water and low-water surveys, respectively, emphasizing the region’s rich biodiversity. Importantly, the study demonstrates that the fishing ban has resulted in substantial increases in both fish density and mean body length, underscoring its effectiveness in fostering fish population recovery. These findings provide critical baseline data to inform scientific conservation and management strategies in this ecologically sensitive river–lake ecosystem.

The impacts of the construction of hydropower projects on fish are of particular concern.To understand its effects on fish diversity from the Xiangjiaba Reservoir in the lower Jinsha River,quantitative surveys were conducted for the spatial distribution of taxonomic and functional diversity of fish assemblages in Shaonvping,Suijiang and Huixi sections,located in the lower,middle and upper streams of the reservoir,respectively,during 2016-2018.Combined with the data before(2011)and at the beginning(2015)of impoundment,the change in fish diversity in different dimensions in the lower reaches of the Jinsha River due to im-poundment was discussed.Eurytopic and limnophilic fish species such as Pseudobagrus vachelli and Hemiculter leucisculus domina-ted the Xiangjiaba Reservoir.P.vachelli and H.leucisculus accounted for 30.15％±14.82％and 13.91％±11.16％in abundance,respectively.Nonmetric multidimensional scaling showed that the fish community structure was more similar between Shaonvping and Suijiang sections.In contrast,fish community differed from Shaonvping and Huixi sections.In Suijiang section,fish communi-ties in the three periods(before,during and after the impoundment)were significantly different,indicating that fish communities in Suijiang section have undergone dramatic changes after the impoundment.Higher values of Margalef index,Shannon-Wiener in-dex and Pielou index of fish in different river sections of the reservoir area were shown as follows:Huixi＞Shaonvping＞Suijiang;Taxonomic diversity index and taxonomic differencess index were shown as follows:Huixi＞Suijiang＞Shaonvping.The spatial pat-tern of functional diversity(functional richness,functional evenness and functional divergence)in different dimensions of fish feeding,movement and reproduction in the reservoir area was different.Generally,the highest functional richness and the lowest functional evenness were found in Suijiang Section.The species and taxonomic diversity in Suijiang section showed a decreased trend compared with that before impoundment.The functional richness and evenness also showed a decreased trend.Functional traits of different dimensions,such as feeding,movement and reproduction,had significant changes after impoundment.For exam-ple,the dominant fishes changed from the species with inferior position mouth and fusiform body shape to those with terminal posi-tion mouth and compressiform body shape.Different diversity indices focus on different aspects of fish diversity.The combination of multiple index analysis is conducive to a more comprehensive understanding of the response of fish communities to environmental changes and external disturbances.This study improved our understanding on the effects of hydropower projects on fish diversity in the lower Jinsha River,provided a scientific basis for fish conservation,and surveyed data for ecological effect assessment of Ten-Year fishing Ban.

The Qinghai–Tibet Plateau (QTP) is a unique ecological area that has faced issues like diminishing ecosystem stability and increasing pressures on resources and the environment. These issues have arisen as a result of the combined impact of global warming and human activities in recent times. The study of the growth and distribution patterns of schizothoracinae fishes can support guiding policy decisions about the conservation of aquatic species and ecological habitats in the QTP. The investigation on fish resources was carried out in the QTP section of the Nujiang River during the spring and autumn seasons of 2017, 2018, and 2019. A total of seven sampling sites were established based on variations in elevation. According to length–weight relationship (LWR) analysis, Schizothorax nukiangensis mainly displayed a negative allometric growth while Ptychobarbus kaznakovi and Schizopygopsis thermalis mainly showed near isometric growth or positive allometric growth in the QTP section of the Nujiang River. Due to temperature and food abundance, the three schizothoracinae fishes showed better growth performance in autumn than spring. Spatial heterogeneity exhibited a greater influence on the LWR of S. nukiangensis and P. kaznakovi than seasonal variation. In contrast, seasonal variation on S. thermalis showed greater influence than spatial heterogeneity. According to the linear mixed effect model (LMM), both spatial factors and seasons had influence on fish growth in the QTP. Schizothorax nukiangensis was identified as the predominant species from CWL to BS, spanning an altitude range of 1800 to 2700 m. Ptychobarbus kaznakovi was identified as the main species at LL, BB, and BR, occupying an altitude range of 2700 to 3800 m. Schizopygopsis thermalis is primarily distributed at altitudes beyond 4000 m and along the tributary river Yuqu. Principal coordinates analysis (PCOA) and nonmetric multidimensional scaling (NMDS) divided schizothoracinae fish populations into three clusters by spatial differences. Redundancy analysis (RDA) and Monte Carlo Permutation analysis revealed that habitat elevation and water temperature had a significant impact on schizothoracinae fish distribution. This article enhances our understanding of the distribution and environmental adaptation of indigenous fish in the Qinghai–Tibet Plateau.

Aims: Pelteobagrus vachelli is an important economic fish in the Yangtze River. Nevertheless, it shows a trend of younger age and miniaturization, and the number of reproductive population above the third age was small, which is not benefit to the long-term maintenance of its resources. Therefore, more attention and conservation measure are needed for this species. The aim of this study is to clarify genetic diversity and genetic structure of P. vachelli.Methods: We collected 136 samples of eight different river sections（Taipingxi, Banan, Hechuan, Minjiangkou, Yibin,Shaonüping, Huixi, Fengjiaping） from the Three Gorges Dam to Baihetan Dam in the upper Yangtze River.High-throughput SNP（single nucleotide polymorphism） markers through genome re-sequencing method was used to study genetic diversity and genetic differentiation of P. vachelli populations.Results: The number of SNP and nucleotide diversity of Taipingxi and Banan populations in the Three Gorges Reservoir region were significantly higher than those in the other populations, and there were three genetic branches and abundant genetic sources in the two populations. However, there was only one genetic branch and single genetic source in Minjiangkou, Yibin, Shaonüping and Fengjiaping populations. The populations could be divided into three distinct genetic groups with great genetic differentiation. All individuals in Fengjiaping and Minjiangkou belonged to group 1, all individuals in Shaonüping and Yibin belonged to group 2, Huixi and Hechuan populations had two genetic branches（group 1 and group 2）, and Banan and Taipingxi populations had three genetic branches（group 1, group 2 and group 3）. The SNP number and nucleotide diversity were significantly affected by channel slope. The genetic differentiation was not related to geographical distance and isolated time. Conclusion: The upstream populations with lower genetic diversity are more prone to genetic drift and thus need more attention in the fish protection. There are three distinct genetic structures in the upper Yangtze River, which can be regarded as three different genetic units for management of germplasm resource.

The South China tiger (Panthera tigris amoyensis, SCT) is the most critically endangered subspecies of tiger due to functional extinction in the wild. Inbreeding depression is observed among the captive population descended from six wild ancestors, resulting in high juvenile mortality and low reproduction. We assembled and characterized the first SCT genome and an improved Amur tiger (P. t. altaica, AT) genome named AmyTig1.0 and PanTig2.0. The two genomes are the most continuous and comprehensive among any tiger genomes yet reported at the chromosomal level. By using the two genomes and resequencing data of 15 SCT and 13 AT individuals, we investigated the genomic signature of inbreeding depression of the SCT. The results indicated that the effective population size of SCT experienced three phases of decline, similar to 5.0-1.0 thousand years ago, 100 years ago, and since captive breeding in 1963. We found 43 long runs of homozygosity fragments that were shared by all individuals in the SCT population and covered a total length of 20.63% in the SCT genome. We also detected a large proportion of identical-by-descent segments across the genome in the SCT population, especially on ChrB4. Deleterious nonsynonymous single nucleotide polymorphic sites and loss-of-function mutations were found across genomes with extensive potential influences, despite a proportion of these loads having been purged by inbreeding depression. Our research provides an invaluable resource for the formulation of genetic management policies for the South China tiger such as developing genome-based breeding and genetic rescue strategy.

为了解黑水河红尾副鳅(Paracobitis variegates)时空分布特征与最适生境,分别于2018年11月、2019年1月、2019年3月、2019年5月和2019年8月调查了黑水河中下游流域23个点位的红尾副鳅资源现状和相关环境因子,使用广义可加模型(GAM)筛选影响资源密度(CPUE)分布的主要环境因子并确定最适条件范围.结果显示,海拔、月份、温度和流速对红尾副鳅的CPUE均有极显著影响,溶解氧对红尾副鳅的CPUE有显著影响,且海拔的偏差解释率最高为33.7％,其次是月份(32.8％),环境因子中溶解氧的偏差解释率最高,为12.5％.黑水河红尾副鳅CPUE具有极显著的时空分布差异,从低海拔到高海拔,黑水河红尾副鳅CPUE的变化具有波动性,但总体呈上升的趋势,在3月和5月,红尾副鳅CPUE较高,在5-10月,CPUE逐渐下降.影响红尾副鳅CPUE分布的主要环境因子为温度、流速和溶解氧.GAM模型中,水温和流速与红尾副鳅CPUE具有极显著的非线性关系,溶解氧与红尾副鳅CPUE具有显著的非线性关系,在11.7～25.9 ℃,随着水温的上升,红尾副鳅CPUE呈先下降后有短暂上升后又下降的趋势,而流速和溶解氧与红尾副鳅CPUE之间均呈多波峰的非线性关系.研究表明,红尾副鳅最适流速为0.6～0.9 m/s,最适溶解氧为7.9～9.5 mg/L,最适水温为14.5～20.0 ℃.本研究初步探究了黑水河红尾副鳅温度、流速、溶解氧、透明度等环境因子的最适条件范围.

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 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.

Tris（1,3-dichloro-2-propyl） phosphate（TDCIPP）, widely used as a kind of organophosphorus flame retardant, has been detected in the Yangtze River water environments. Many toxicological assessments have shown that TDCIPP could change morphology of fish. Silver carp（Hypophthalmichthys molitrix） lives in the Yangtze River for its entire life story, however, the effects of TDCIPP on silver carp is unclear. In order to clarify the main morphological characters of growth inhibition of silver carp larvae caused by TDCIPP, the present study analyzed the morphological traits between four environmentally relevant concentrations（0.05, 0.5, 5 and 50 μg/L） and the control group by geometric morphometric analysis. After the image information of larvae simple was obtained, the body length and body weight were measured. Then, digitization of landmarks was carried out with the TPS series software. Finally, principal component analysis（PCA）, canonical variates analysis（CVA） and results visualization were carried out with Morpho J software. The body length and body weight of silver carp larvae decreased significantly under exposure to 0.5, 5 and 50 μg/L of TDCIPP compared with the control group, but no effects were observed in 0.05 μg/L. This indicated that environmentally relevant concentrations of TDCIPP induced growth inhibition in silver carp larvae. The results of PCA and CVA indicated that the first principal component（PC1） and the second principal component（PC2） together accounted for 62.15% of the overall variables（47.36% and 14.51%, respectively）. The first canonical variates（CV1） and the second canonical variates（CV2） together accounted for 79.48%（54.55% and 24.93%, respectively）, which satisfied the requirement of morphological analysis of silver carp larvae. The results of grid profile analysis indicated that the average morphology of silver carp larvae in different concentrations was significantly different with the control group（P＜0.05）, which identified by the growth retardation of the head, longitudinal axis of body and tail. As a conclusion,TDCIPP could induce the growth retardation of head, longitudinal axis of body and tail in silver carp larvae. Therefore,attentions should be paid to the environmental concentrations of TDCIPP in the Yangtze River Basin, and the ecological risk of TDCIPP to the replenishment of silver carp population resources should be assessed.

长江上游珍稀特有鱼类国家级自然保护区位于向家坝坝下江段,随着金沙江下游梯级水电站相继蓄水运行和"十年禁渔"政策的实施,保护区干流段鱼类群落可能会发生改变.为探究"十年禁渔"前保护区干流段鱼类群落结构特征,基于该江段2017-2019年渔获物监测数据,对鱼类种类组成、生态类型、群落相似度、物种优势度、生物多样性以及群落结构稳定性等特征进行分析.结果显示,本次调查共采集到鱼类134种,隶属于7目21科83属,其中长江上游特有鱼类有27种,外来物种有12种,分别占总种类数20.15％和8.96％.鱼类群落以底层、产沉性卵、杂食性鱼类为主.等级聚类分析(Cluster)和非度量多维尺度分析(NMDS)显示,在一定的相似性水平上,保护区干流段鱼类的群落类型基本可分为3组,宜宾、泸州与合江可以聚为一组,巴南、江津分别独立成组.保护区干流优势种共有14种,其中瓦氏黄颡鱼是整个研究区域的优势种,在合江站点的优势度最高,IRI 值为 27.00％.Shannon-Wiener 指数、Simpson 指数、Margalef 指数和 Pielou 指数变化范围分别为2.725～3.306、0.883～0.942、5.833～8.811和0.699～0.773,表明保护区干流鱼类物种丰富,群落分布均匀度较高.ABC曲线分析结果显示,江津站鱼类群落结构稳定性相对较高,其余站点鱼类群落结构均受到中度干扰.本研究补充了保护区干流鱼类群落研究的基础数据,以期为该江段鱼类资源管理与"十年禁渔"生态评估提供科学依据.

利用耳石微结构对2018～2020年在监利断面采集草鱼和鲢仔鱼群体进行日龄鉴定,推测其孵化时间和繁殖时间,结合长江水文特征,分析监利断面四大家鱼仔鱼来源,以及三峡水库生态调度等对四大家鱼仔鱼资源的影响.结果显示,草鱼和鲢仔鱼耳石轮纹特征相似,日龄结构也相似.监利断面2018和2019年苗汛期草鱼和鲢仔鱼苗汛期日龄分布范围为8～15日,其中主要分布在9～12日.2020年草鱼和鲢仔鱼日龄分布范围为10～22日,主要分布在12～15日.这表明,监利断面草鱼和鲢仔鱼群体日龄范围较窄,规格整齐,可能产自相同或相近的产卵场.基于日龄推测长江监利断面草鱼和鲢苗汛期仔鱼的繁殖时间与宜昌江段涨水日期基本一致,推测该江段四大家鱼鱼苗主要来自于宜昌江段.2018～2020年三峡水库开展4次生态调度,仅2018年6月中旬的生态调度在监利断面出现相应的家鱼苗汛,其它5月底开展的3次生态调度在监利江段未监测到相应的苗汛,可能是因为5月下旬长江中游温度较低、饵料生物较少,影响了鱼苗的早期生长和死亡率.基于研究结果,建议加强在6月下旬开展生态调度,对下游仔鱼资源的补充有较好的效果.

为了解莲花洲港生态涵养区的修复效果,2021年1月、4月、10月在武汉至安庆段的东流水道莲花洲港设置21个采样点,对底栖动物群落和鱼类分布状况进行调查,分析工程区不同区域及非工程区底栖动物和鱼类群落结构差异.结果显示,不同区域底栖动物的种类数不同,透水框架区获取底栖动物6种,鱼巢排区17种,工程其他区域25种,非工程区8种.单因素方差分析表明,不同区域的底栖动物密度差异显著(P<0.05),透水框架区最高,为191.1个/m2,其次为鱼巢排区60.44个/m2,其他工程区44.44个/m2,非工程区较少,仅28.39个/m2.各区域Pielou均匀度指数(J)差异性不显著(P>0.05),Margalef丰富度指数(D)和Shannon-Wiener 多样性指数(H′)差异性显著(P<0.05).CCA分析表明,影响底栖动物的环境因子为流速、水深、温度、溶解氧、硝态氮、氨氮.水声学调查显示,鱼类密度以透水框架区最高,为25581.21尾/hm2,鱼巢排区次之,为3239.00尾/hm2,工程其他区域为808.73尾/hm2,非工程区最低,仅6.82尾/hm2.研究表明,透水框架和鱼巢排营造了适宜底栖动物和鱼类栖息的水流条件,有利于底栖动物生存和鱼类聚集,且透水框架的生态涵养效果优于鱼巢排.

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 (CPUEN), weight (CPUEW), and species number (CPUES) 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 CPUEN and CPUEW while a longer soak time increased CPUES. CPUEN, CPUEW, and CPUES 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.