Abstract:The Yangtze River is the mother river of China. To promote the aquatic ecosystem protection of the great river, the Project of Yangtze Fisheries Resources and Environment Investigation (2017-2021) supported by the Ministry of Agriculture and Rural Affairs, carried out by 24 universities and institutes mainly located in the Yangtze River basin surveys the statued of (1) fish species composition and spatial distribution, (2) current fish abundance, (3) endangered fishes, (4) Yangtze finless porpoise, (5) aquatic eco-environments, (6) water-level fluctuation areas, (7) capture fisheries and recreational fisheries of the Yangtze River mainstream and 10 of its main tributaries, including Yalong River, Heng River, Min River (including Dadu River), Chishui River, Tuo River, Jialing River, Wu River, Han River, Dongting Lake and Poyang Lake. The results showed that there were 443 fish species (belonging to 163 genera, 37 families, and 18 orders) before 2017, but only 323 fish species (including 15 newly recorded exotic species) were recorded in the project of 2017-2021. Among them, Cyprinus carpio, Carassius auratus, Hypophthalmichthys molitrix, Pelteobagrus fulvidraco, Coilia brachygnathus, Silurus asotus, Saurogobio dabryi, Ctenopharyngodon idellus, Pelteobagrus nitidus, Hemiculter leucisculus, Siniperca chuatsi, Coreius heterodon, Culter alburnus, Parabramis pekinensis, and Aristichthys nobilis were the dominant species in the whole Yangtze River system. It was estimated that there were 886 million individuals weighing 124.8 million kg, merely equivalent to 27.3% of the resources in 1950s, 30.9% of the resources in 1960s, or 58.7% of the resources in 1980s. In the new list of protected fishes that recorded in the Yangtze River system, only 15 of 29 were collected in this project of 2017-2021. Psephurus gladius has been affirmed to be Extinct by International Union for Conservation of Nature (IUCN). The wild individuals of Tenualosa reevesii and Luciobrama macrocephalus have disappeared for many years and maybe have been extinct already. Acipenser dabryanus has been affirmed to be Extinct in the Wild by IUCN. The natural propagations of Acipenser sinensis, Myxocyprinus asiaticus and Trachidermus fasciatus have been interrupted for many years. The populations of Yangtze finless porpoise in the Yangtze River mainstream, Dongting Lake and Poyang Lake had steadily rising sizes and expanding distributions in 2017-2021. Parts of them migrated from one region to another with the seasons, which would result in the fluctuation of Yangtze finless porpoise population within some regions. The conventional indicators of water quality in the Yangtze River system were good and conformed to the water quality criteria of fishery in 2017-2021. In the last 40 years, the maximum water surface area in the Yangtze River basin extended to approximately 63 360 km², the minimum water surface area covered approximately 26 396 km², and the seasonal water-level fluctuation areas occupied approximately 36 964 km². Compared with 1984-2000 period, the 2001-2020 period witnessed an overall decreasing trend in the frequency of water surface occurrence within about 25 869 km² of aquatic areas. From 1984-2000 period to 2001-2020 period, permanent water surface has decreased by nearly 8 750 km². From 2019 to 2020, the maximum and minimum water surface areas in the key waters of the Yangtze River basin were 19 663 km² and 14 281 km² respectively, with a combined total of 6 337 km² of water-level fluctuation areas, of which 633 km² were reversed-rhythm water-level fluctuation areas. In 2017, the fishermen were mainly 40-60 years old and their educational levels were mainly lower than junior high school. In 2017, most anglers were older than 40 and used hand rod and/or sea rod. Their average catch of each time was mainly less than 1 kg. Results suggested that the fishing ban in key waters of the Yangtze River basin is not only an ecological project of aquatic ecosystem conservation, but also a livelihood project for the fisherman to embrace industrial transformation and improve their living conditions. After the implementation of the fishing ban, the fisheries resources would gradually recover, and the Yangtze finless porpoise population size would also see a steady increase. However, the endangered species would remain threatened for a long time. The degraded water bodies and water-level fluctuation areas would be the key restrictive factors for future aquatic ecosystem recovery in the Yangtze River basin. Since this survey was carried out before the fishing ban, the current results could provide a baseline for future evaluation of the effect of the Yangtze River fishing ban.

Abstract:The water fluctuation zones are widely distributed in the Yangtze River Basin, with diverse types, different kinds of formation, various functions and complex habitats. The intensive analysis of the historical changes, current situation and component types of the water fluctuation zones is of great significance for maintaining the aquatic biodiversity and ecosystem balance along the banks of rivers and lakes, and protecting the ecological and environmental security of the Yangtze River system. In this paper, the medium-large scale remote sensing monitoring method is used to investigate and analyze the water area and the fluctuation area of the Yangtze River Basin, focusing on the change trend from the natural water body to the artificial water surface, and its potential impact on the decline of the natural fishery resources in the Yangtze River Basin. The results show that, in the past 40 years, the historical maximum water surface of the whole Yangtze River Basin is about 63,360 km², the minimum water surface is about 26,396 km², and the historical maximum ebb and flow area is about 36,964 km². From 2019 to 2020, the "One River, Two Lakes and Seven Rivers" region had a maximum water surface of 19,663 km², a minimum water surface of 14,281 km², and a fluctuation area of 6,337 km², including an anti-seasonal fluctuation area of 633 km². Compared to period of 2001-2020 and period 1984-2000, more than 80% of the reduction of surface water was due to the loss of the area of seasonal natural water fluctuation, while the increase that resulted from reservoir filling was up to 5500 km². As a result, the structure of water ecosystem in the Yangtze River basin changed dramatically. The proportion of natural water body and fish resources was less than half of that in the 1980s. Furthermore, this study clarified the concept of anti-seasonal artificial water fluctuation area for the first time, and investigated the relationship between the anti-seasonal artificial water fluctuation zone formed by the filling of cascade reservoirs in the Yangtze River Basin and the loss of fish critical habitat.

Abstract:The Yangtze River Basin is a priority biodiversity conservation area of global significance. To understand the diversity, threatened situation, and conservation status of the aquatic amphibians and reptiles in the Yangtze River basin, the basin was divided into 11 geographical units mainly based on the natural drainage. The cataloging method was conducted to reveal the species composition of aquatic amphibian reptile in the area. The G-F index method was used to measure regional species diversity. The weight assignment method was used to assess the species' threat status and conservation priority in the region. The result showed that 281 species were recorded in the area, including 225 amphibians and 56 reptiles. The amphibians contained 2 orders, 9 families and 37 genera, and reptiles contained 3 orders, 9 families and 22 genera. There were 119 endemic species to the Yangtze River Basin, accounting for 42.35%; 60 species are under state key protection, accounting for 22.06%; 102 species were threatened, accounting for 36.30%. The species diversity of the two taxa showed a similar distribution pattern of "Upstream high, downstream low and right bank high, left bank low". For aquatic amphibians, the Jinshajiang-Yalong sub-basin (JSYL), Minjiang-Tuojiang sub-basin (MJTJ) and Wujiang-Chishuihe-Qingjiang sub-basin (WCQ) have higher conservation priority; For aquatic reptiles, the Headwater of Yangtze River basin (JY), the Taihu sub-basin (TH) and the Middle-Lower mainstream sub-basin (ZXG) have higher conservation priority. The results indicated that the irreplaceability of aquatic amphibians and reptiles was strong in the Yangtze River Basin, the protecting attention and the protection urgency were also high. So, we suggest further strengthening the investigation of the background resources in the basin, establishing a scientific and efficient integrated protection management system for joint prevention and control, establishing and improveing monitoring and evaluation mechanism for regional species diversity, and paying attention to increasing scientific research investment and enhancing public conservation awareness. This study provides an important reference for the conservation of species diversity in the Yangtze River basin.

Abstract:This paper summarized the changes in the natural resources of three sturgeon species (Psephurus gladius, Acipenser sinensis, and Acipenser dabryanus) over the past 40 years, quantified the artificial stocking populations of A. dabryanus and A. sinensis, and then assessed the effectiveness of restocking. The influence factors that cause the ineffective releases widely depend on species characteristics and distribution. Overfishing of ten resulted in the fact that the artificial released A. dabryanus individuals were inevitably captured within 6 months as bycatch after they were released. The insufficient number of released A. sinensis combined with overfishing in the Yangtze River and offshore caused the inefficient contribution to the wild population of A. sinensis. We believe that the past releasing input intensity of both A. dabryanus and A. sinensis cannot reach the sufficient replenishment level of the natural breeding population. We discussed the misconceptions and shortcomings in the action, management, and policy-making of P. gladius, A. sinensis, and A. dabryanus conservation over the past 40 years. In the current ecological protection era , We should promote the implementation of 3 key protection measures urgently: 1) to prepare and implement the priority project of A. dabryanus rescue action plan; 2) to propose more operational priority projects for in situ conservation, ex situ conservation and genetic diversity conservation based on A. sinensis rescue action plan; 3) to establish a species rescue action plan project of A. sinensis and A. dabryanus, and to optimize and integrate the existing ecological compensation programs involving their habitats or protected areas. We believe that we can restore the natural populations of A. dabryanus and A. sinensis, by restoring their natural reproduction. Then we can realize the harmonious coexistence between human and nature, and promote the sustainable development of social economy in the Yangtze River basin.

Abstract:In the new situation of ten-year ban on fishing in the Yangtze River, recreational fishing will become an important direction for the development of the Yangtze River fishery. In order to understand the current status of sport angling in the main stream of the Yangtze River, 872 anglers were interviewed from 2017 to 2018. The results showed that anglers of the Yangtze River mainstream were mainly middle-aged and elderly people. The main types of fishing tackle were hand rod and sea rod, accounting for more than 80% of the total fishing tackle. The anglers of the upper Yangtze river and the Three Gorges reservoir area, accounting for more than 50%, invested in fishing gear less than 500 yuan per annum. However, the anglers of more than 50%, in middle and lower Yangtze River, invested in fishing gear more than 1000 yuan per annum. The number of anglers in the upper Yangtze River, the Three Gorges Reservoir area, the middle Yangtze River and the lower Yangtze River were estimated to be 2 344, 4 764, 4 600 and 6 649, respectively. In addition, the annual fishing volume was respectively estimated to be 45.0 tons, 294.7 tons, 171.1 tons and 478.7 tons. The proportion of annual fishing amount in the current stock of fish resources was 8.6%, 2.0%, 1.8% and 3.6%, respectively. This indicates that fishing has a relatively large impact on fishery resources in the Upper Yangtze River, which need urgent attention attention. In order to guide the healthy and sustainable development of the fishing industry, it is suggested to delimit the no-fishing area and no-fishing period, establish a white-list system of fishing tackle and fishing method in natural waters, establish a scientific management system, further explore the traditional fishery cultural resources, and establish the fishing fishery brand.

Abstract:The National Nature Reserve of Rare and Endemic Fish in the upper reaches of the Yangtze River is located in the lower reaches of Xiangjiaba Dam. With the impoundment of cascade hydropower stations in the lower reaches of Jinsha River and the implementation of the "ten-year fishing ban" policy, the fish community in the main stream of the reserve may change. In order to explore the characteristics of fish community structure in the main stream of the Reserve before the "ten-year fishing ban", based on the catch monitoring data from five sampling sites of this section from 2017 to 2019, the characteristics of fish species composition, ecological types, community similarity, species dominance, biodiversity and community structure stability were analyzed. The results showed that 134 fish species were collected in this investigation, belonging to 7 orders, 21 families and 83 genera, among which 27 species were endemic to the upper reaches of the Yangtze River and 12 species were exotic, accounting for 20.15% and 8.96% of the total species respectively. The fish community was dominated by demersal fish, sunken eggs and omnivorous fish. Cluster analysis and Nonmetric Multidimensional Scaling (NMDS) analysis showed that the fish community types of five sections in the main stream could be basically divided into three groups at a certain level of similarity, as Yibin, Luzhou and Hejiang sections formed one group, Jiangjin section and Banan section formed separate groups independently. There were 14 dominant species, among which Pelteobagrus vachelli was the dominant species in the whole area, with the highest dominance in Hejiang section where the IRI value was 27.00%. Shannon-Wiener index, Simpson index, Margalef index and Pielou index ranged from 2.725 to 3.306, 0.883 to 0.942, 5.833 to 8.811, 0.699 to 0.773, respectively. As a result, fish species diversity and the community distribution uniformity was high in the main stream of the reserve. The results of ABC curve analysis showed that the fish community structure in Jiangjin section was relatively stable, but moderately disturbed in the other section. This study could supplement the basic data of fish community information in the main stream of the nature reserve, and also provide theoretically scientific support for fish resource management and ecological evaluation of "ten-year fishing ban" in this section of the river.

Abstract:The upper reaches of the Yangtze River, with its special geology, geomorphology, climate and natural ecological environment, has bred a rich diversity of fish. However, in recent years, the fishery resources have been declining significantly due to the development of water conservancy projects and the increase of human fishing intensity. As a buffer zone of the “National Nature Reserve for the rare and endemic fishes in the upper reaches of the Yangtze River”, the Jiangan section in the upper reaches of the Yangtze River is rich in fish resources. Surveys were carried out in the Jiangan section from April to May in 2022 to study the fish resources of early life. The eggs were identified by molecular biology methods. At least 20 species of fish breed in the Jiangan section, including 13 species of drifting eggs and 3 species of endemic fish in the upper reaches of the Yangtze River. During the monitoring period, there were 4 spawning peaks at S1 and S2 sites, and 5 spawning peaks at S3 site. It is estimated the total fish eggs passing through the Jiangan section is 3.94 × 10⁸ ind. The Shannon-Wiener diversity index, Margalef richness index, Pielou evenness index and Simpson index of the Jiangan section ranged 0.306-0.496, 1.636-2.087, 0.108-0.169, and 0.816-0.885, respectively. Environmental factors such as water temperature, pH, dissolved oxygen, transparency, water level and water discharge were found to have different degrees of influence on egg density through redundancy analysis. The research results showed that the Jiang’an section was spawning ground for a variety of fish, and the early resources were large in scale but poor in diversity. The natural reproduction of Acipenser dabryanus, Myxocyprinus asiaticus and Procypris rabaudi was not monitored. The increase and decrease in water discharge had a stimulating effect on fish reproduction. Therefore, it is suggested to continue to carry out breeding and releasing scientifically and appropriately and carry out ecological dispatching research to meet the breeding demand of fish in the upper reaches of the Yangtze River.

Abstract:In order to explore the characteristics of fish community structure in the Middle Reaches of Tuojiang River before the "ten-year fishing ban", based on the catch monitoring data from ten sampling sites of this section from 2017 to 2020, the characteristics of fish species composition, ecological types, community similarity, biodiversity and community structure stability were analyzed. The results showed that 87 fish species were collected, belonging to 5 orders, 14 families and 52 genera. Among which 18 species were endemic to the upper reaches of the Yangtze River and 6 species were exotic, accounting for 20.69% and 6.90% of the total species respectively. The fish community was dominated by demersal fish, sunken eggs and omnivorous fish. According to index of relative importance (IRI), the dominant fish species were small fishes, such as Saurogobio dabryi and Cyprinus carpio. Shannon-Wiener index, Simpson index, Margalef index and Pielou index ranged from2.700 to 3.742, 0.873 to 0.968, 5.374 to 11.323, 0.737 to 0.887, respectively. As a result, the community distribution uniformity was high in the Middle Reaches of Tuojiang River. The results of cluster analysis and non-metric multidimensional scale ranking (NMDS) analysis showed that the fish community types of ten sections in the Middle Reaches could be basically divided into three groups at a certain level of similarity, as Lianhuashan,Maliuba industrial park and Tielugou sections formed one group, Wangumiao , Wulidian hydroelectric station, Zizhou Bridge, Yinshan, Second Water Plant and Xilin Ferry section formed one group; Tuo Bridge section formed one group independently. The abundance/biomass comparison curve showed that the fish community structure in Xilin Ferry and Tuo Bridge section was relatively stable, but moderately disturbed in the other sections. The results showed that compared with the historical data, the fish community structure in the Middle Reaches of Tuojiang River has changed significantly, the proportion of economic fish has decreased, and the fish individuals have become smaller and younger. This study could supplement the basic data of fish community informationin the Middle Reaches of Tuojiang River, and also provide theoretically scientific support for fish resource management and ecological evaluation of "ten-year fishing ban" in this section of the river.

Abstract:Understanding the patterns and ecological determinants of β diversity is critical for community ecology and conservation biology. However, only few studies have investigated fish β diversity in large rivers, and even fewer have included multiple facets of biotic and abiotic diversity indices simultaneously. Based on sampling data from the Chishui River basin in 2019 and 2020, we calculated fish species, functional, taxonomic, and environmental β diversity, as well as the relative contribution of individual sampling site to each facet of β diversity (also known as site uniqueness). Further, we assessed the degree of complementarity and redundancy between the calculated indices of site uniqueness. By doing these, we tried to provide a scientific basis for the conservation and management of fish resources in the Chishui River basin, which is a pioneer area for the protection of the upper Yangtze River. The results showed that a total of 125 fish (sub) species belonging to 7 orders, 20 families and 80 genera were collected from the Chishui River basin, including 112 native fish (sub) species and 13 exotic (sub) species. Species β diversity of fish assemblages were 0.719, and species uniqueness of sampling sites S1, S2, S22 and S27 was significantly different from other sites. Functional β diversity of fish assemblages were 0.009, with sampling sites S10, S20, S21, S28 and S36 having significantly different functional uniqueness values compared with other sites. Taxonomic β diversity of fish assemblages were 0.004, with sample sites S20, S21, S28 and S32 having significantly higher taxonomic uniqueness in comparison with other sites. Environmental uniqueness of sampling sites ranged from 0.010 to 0.058, and the four highest sites were S22, S29, S33 and S34. Fish species uniqueness of sampling sites showed a significant U-shaped relationship with fish richness, that is, species uniqueness of sampling sites firstly decreased and then increased with fish richness. There was a high degree of complementarity between different facets of diversity indices, and functional and taxonomic uniqueness of sampling sites explained more diversity variation than species uniqueness of sampling sites. This study suggests that fish diversity assessments need to integrate different facets of biotic and abiotic diversity indices, as they can be useful in revealing spatial and temporal variation of freshwater fish community structure and the underlying mechanisms.

Abstract:Wujiang River is the longest river in Guizhou province and one important tributary of Yangtze River. To explore the original data about species composition and diversity of fishes in Wujiang river, we conducted 12 field surveys at 135 sites in Guizhou province from 2017 to 2021. A total of 5 065 fish specimens (weight about 204 kg) were collected, and 107 species belonging to 6 orders, 22 families, 73 genera were identified. Cyprinidae had the largest number with 53 species, accounting for 49.53%. Species diversity G-F index of different areas of Wujiang River were 0.40, 0.47 and 0.45 from upper to lower reaches, showing that upper stream has lower species diversity within family and genus than middle or lower streams. In middle Wujiang River, the Shannon-Wiener diversity index (H') was 3.54, Margalef richness index (D) was 9.63, Pielou evenness index (J') was 0.81. Results showed that the first ten species with weight and number included：Spinibarbus sinensis, Oreochromis niloticus, Saurogobio dabry, Carassius auratus and Hemiculter leucisculus. According to Index of Relative Importance, the dominant species (IRI>500) in middle reaches of Wujiang river were C. auratus, H. leucisculus, S. sinensis and Opsariichthys bidens. This study showed that construction of dams would be the main factor to impact species composition of Wujiang River. This study could provide important data for species composition and diversities of Wujiang River, and it would be valuable to evaluate the effect of ten-year fishing ban policy of Yangtze River.

Abstract:To understand the relationship between fish community structure and diversity and environmental factors in the middle reaches of the Yangtze River, fish and environmental surveys were conducted in five sections of the middle reaches of the Yangtze River (Yichang, Shishou, Jiayu, Wuhan and Hukou) in June and November 2021. Using these data, fish community structural characteristics, the spatial and temporal distribution pattern and its relationship with environmental factors were analyzed. A total of 16 335 individuals belonging to 76 species, 50 genera, 13 families, and 6 orders were collected, among which, Cyprinidae was the most abundant with 52 species, accounting for 70%. Among the three living habits, the number of resident fish species was the largest (80%). Among the three feeding types, the number of carnivorous fish species was the largest (46%). Among the three spawning types, sticky-egg fish had the largest number of species (50%). According to index of relative importance (IRI), the dominant fish species were small fishes, such as Pelteobagrus vachelli, Xenocypris argentea, Megalobrama terminalis, Coreius heterodon. The average Margalef richness index was 5.11, the average Pielou evenness index was 0.63, the average Shannon-Wiener diversity index was 3.23, and the average Simpson dominance index was 0.26. The abundance/biomass comparison curve showed that the fish communities in Yichang and Hukou were seriously disturbed, and those in Shishou, Jiayu, and Wuhan were relatively stable. The results of Cluster analysis and non-metric multidimensional scale ranking (NMDS) analysis showed that the fish communities in the middle reaches of the Yangtze River could be divided into three groups, and Yichang belonged to one group. Shishou, Jiayu and Wuhan belonged to one group, and Hukou belonged to one group. Redundancy analysis (RDA) was used to analyze the relationship between fish community and environmental factors. It was found that ammonia nitrogen (NH₄⁺-N) and bottom type were the main factors affecting the differences in fish community structure in the middle reaches of the Yangtze River. The results showed that compared with the historical data, the fish community structure in the middle reaches of the Yangtze River has changed significantly, the proportion of economic fish has decreased, and the fish individuals have become smaller and younger. These changes were caused by the joint effect of long-term human activities and natural environmental changes.

Abstract:The Yangtze Estuary is the largest estuary in the Northwest Pacific Ocean. From January to May every year, a large number of Japanese eel (Anguilla japonica) elvers arrive at the area under the influence of the Kuroshio and Taiwan Warm Current. The Yangtze Estuary is an important upstream migration channel for Japanese eel elvers, and the most important producing area of eel elvers in China. The protection and utilization of elvers resources here will not only help to maintain the healthy and sustainable development of elvers related industries in China, but also help to maintain biodiversity and ecological security in the Yangtze River Basin. This study carried out investigation of Japanese eel elvers for four years in the Yangtze Estuary from 2017 to 2020. Seven stations were set up to basically cover the main migration distribution area of elvers , which could better reflect the distribution and migration in the Yangtze Estuary. By analyzing the fishing capacity and resource status of Japanese eel elvers in the Yangtze Estuary in the past four years, it was found that the the main bloom period of glass eel in the Yangtze Estuary was from February to April, and the main fishing areas were distributed in Dongwangsha, Sheshan and near Nanhuizui water area. In recent years, with the strengthening of the fishing management and the implementation of the ban on fishing in the Yangtze Estuary, the fishing capacity of elvers in the Yangtze Estuary has gradually decreased, and the effective net area has decreased by 36%, from 78.72×10⁴ m² in 2017 to 50.40×10⁴ m² in 2020. The main fishing waters of elvers have also shifted from the inside of estuarial mouth (Dongwangsha and Jiuduansha) to outside the mouth (Nanhuizui and near Luchaogang). The CPUE results of catching elvers in bloom season showed that the average catch in 2017 was (4 474±256) ind./100 m²; in 2018 and 2019, it gradually decreased to (1 917±335) and (1 365±257) ind./100 m² respectively; the maximum CPUE value in 2020 was (5 220±1 063) ind./100 m². The total yield of elvers is relatively high in 2017 (33.34 million ind.) and 2020 (20.74 million ind.), and low in 2018 (13.37 million ind.) and 2019 (9.86 million ind.), showing a cyclical fluctuation trend of about 2-3 years. It is suggested to strengthen the monitoring of Japanese eel elvers resources, scientifically evaluate and analyze the changes of elvers resources, and analyze the ecological impact of elvers fishing, so as to provide technical guarantee for the research and formulation of scientific management policies and measures, and provide scientific basis for the evaluation of the effect of the Yangtze River fishing ban.

Abstract:Zooplankton is an important part of the river food web and plays an important role in the energy flow and nutrient cycling of the river ecosystem. However, there is a lack of systematic survey of zooplankton in the main stream of the Yangtze River. During 2018–2019, fifty-one survey stations were set up in about 5000 km of the main stream of the Yangtze River. And the surveys were carried out during the fish reproductive (March to June), feeding (August to October) and wintering (November to January) seasons every year. And the zooplankton community structure and distribution in the main stream of the Yangtze River were systematically studied. The results showed: ① There were 187 species of zooplankton in the main stream of the Yangtze River, including 56 species of protozoa, 59 species of rotifers, 34 species of cladocerans and 38 species of copepods. The species of zooplankton was most abundant in the Three Gorges Reservoir. And the species of zooplankton in each river reach were as follows: 59 species in Jinsha River, 68 species in the upper reaches of the Yangtze River, 87 species in the Three Gorges Reservoir, 54 species in the middle reaches of the Yangtze River, and 56 species in the lower reaches of the Yangtze River. The species of zooplankton was the most abundant in the fish reproductive season. And the zooplankton species in the breeding season of each river reach were as follows: 45 species in Jinsha River, 56 species in the upper reaches of the Yangtze River, 47 species in the Three Gorges Reservoir, 41 species in the middle reaches of the Yangtze River, and 32 species in the lower reaches of the Yangtze River. ② The density of zooplankton in the main stream of the Yangtze River ranged from 1.12 to 644.40 ind. /L. In the middle and lower reaches of the main stream of the Yangtze River, the zooplankton densities were significantly higher than that in the upper reaches. The high value of zooplankton density generally occurred during the fish reproductive season, and the low value generally occurred during the fish feeding season. ③ The zooplankton biomass: in the main stream of the Yangtze River, the zooplankton biomass ranged from 231.78 to 45638.57×10^?5 mg/L. And the zooplankton biomass in Jinsha River, the middle and lower reaches of the Yangtze River were significantly higher than that in the upper reaches and the Three Gorges Reservoir. ④ The dominant species of zooplankton in the main stream of the Yangtze River mainly included Tintinnidium entzii, Leprotintinnus fluviatile, Arcella vulgaris, Brachionus calyciflorus, Polyarthra trigla, Mesocyclops leuckarti, Neutrodiaptomus incongruens and Nauplius. The community structure and distribution of zooplankton in the main stream of the Yangtze River showed typical lotic freshwater zooplankton characteristics. The species and numbers were poor in the river. Small animals such as rotifers and protozoa played an important role in the community. The abundance of zooplankton varied from upstream to downstream and changed with season. The research results can provide important basic data for the aquatic ecology management of the Yangtze River.

Abstract:As an important component of aquatic biodiversity, fish are the most sensitive and reliable indicator of ecosystem function in aquatic areas. Its growth and development are closely related to the environmental factors of the inhabiting waters, and have an important indicator of environmental changes. In order to grasp the characteristics of the fish community in Poyang Lake, we conducted fish resource surveys in ten regions of Poyang Lake involving five habitats and collected water environment samples simultaneously in spring (May), summer (August), autumn (November) of 2020 and winter (January) of 2021 before the comprehensive fishing ban. We identified a total of 67 fish species, belonging to 8 orders 14 families 47 genera, of which Cyprinidae had the the maximum no. of species, accounting for 61.19%. According to different groups, the dominant ecological types of fish were mainly lake sedentary (61.19%), omnivore (44.78%), and lower fish (35.82%). Small fish was the dominant group in this community, accounting for 68.70%, and the index of relative importance (IRI) showed that there were six dominant species, the first one was Pseudobrama simoni. Significant seasonal differences were observed in fish community structure (P<0.05), and the fish species diversity index in spring was higher than that in winter (P<0.05), because the diversity and richness of species were affected by seasonal factors. Changes in water temperature and water level may be the main reasons for affecting the spatial and temporal pattern of fish community diversity in Poyang Lake. Non-metric multidimensional scaling analysis (NMDS) showed that fish could be spatially divided into two taxa, namely the estuary taxon and the grassy-lake branch-lake center-coastal zone taxon. In redundancy analysis (RDA), we observed that total phosphorus, chlorophyll a and transparency were key environmental factors affecting the spatial and temporal distribution of fish species. With the change of hydrological rhythm in the lake area, with the increase of water level, nutrients flow into the lake area, providing a rich food source for fish, and fish feeding activities are enhanced. When the total phosphorus is too high, it will lead to eutrophication of the water body, and the nutrient load and suspended solids will limit the habitat and even survival of sensitive species. Chlorophyll a is an important indicator reflecting the change of phytoplankton content, and in spring, with the increase of temperature, the surface water temperature rises rapidly, and phytoplankton in the water body begins to multiply in large quantities, which is reflected in the increase of surface chlorophyll a content. Abundance-biomass comparison curve (ABC curve) analysis showed that the fish community was severely disturbed (W=−0.091). This study can provide a scientific basis for the evaluation of the effect of fishing ban and the conservation of fish diversity in Poyang Lake.

Abstract:Water course in the lower reaches of the Yangtze River is bent, and flow pattern is tangled, which leads to diverse habitat, and makes it a good breeding, feeding place and important migration channel for fish. In order to study the fish community structure during initial period of 10-year fishing ban, fish was collected seasonally from April to December 2021, in the lower reaches of the Yangtze River. A total of 84 fish species from 63 genera，18 families and 10 orders were collected during the investigation, with dominance by Cyprinids (47.62% of total species). Results of the species numbers and diversity indices showed that fish diversity was high in the lower reaches of the Yangtze River, while species are less than historical records. One-way ANOVA indicated that significant spatial differences were found for fish species, number and biomass，while no obvious differences were observed among seasons. Pelteobaggrus nitidus, Parabramis pekinensis, Hypophthalmichthys molitrix, Coilia brachygnathus, Hemiculter bleekeri and other 4 species were the dominant species. Piscivorous (47.62%) and omnivorous (40.47%) fishes prevailed in species number among the 4 feeding functional groups, sedentary fishes (76.19%) predominated among the 3 ecological groups, and demersal fishes (46.43%) predominated among the 3 habitat types. The number of large commercial fishes account for a small part of the fish community, but the index of relative importance is high due to the comparatively large individuals. The Shannon-Weiner index in the lower reaches of the Yangtze River is 3.28, which indicate the fish is relatively diversified. In the present study, the richness index was also high, while community evenness was stable. Overall, the fish continue to become smaller and younger, the fishery resources declined clearly, fish species, diversity index and catch per unit effort increased during initial period of 10-year fishing ban, and effect of the prohibition gradually appeared. In order to consolidate the effect of 10-year fishing ban, promote fish resources recovery, and optimize fish community structure, further scientific monitoring and higher strength patrol were recommended in the Yangtze River. Our study can obtain the basic characteristics of fish communities during initial period of 10-year fishing ban, and can also provide reference for fishing ban effect evaluation and aquatic organisms integrity index assessment.

Abstract:The fishing-ban effects in Yangtze River are mainly indicated by the community recovery of aquatic organisms. To identify the effects, the aquatic organism community monitoring is critically needed. However, monitoring duration, monitoring tools and monitoring sites may severely impact its result. The current study aims to identify the impacts of monitoring duration, monitoring tools and monitoring sites on the results of fish communities monitoring and then provide suggestions for the technical details of monitoring fish community. Here, we used gillnets and cages to monitor the fish communities for 15 consecutive days in 10 sites in the middle reaches of Yangtze River form May to July, 2021. Then, we analyzed the catch per day, the recorded species per day and the fish community structure per day to research the impacts of monitoring duration, monitoring tools and monitoring sites on the monitoring results. The results showed that the catch of each day varied day by day and the average catch per day of accumulated 11 days monitoring results reached a relative stable status. The fish community structure result of each day varied day by day and the fish community structure showed by the accumulated 15 days monitoring results reached a relative stable status. Nearly 70% detectable fish species (estimated by species accumulation curve analysis) could be monitored by accumulated 15 days monitoring. The types and sizes of fishing tools obviously impacted the monitoring results of fish species and community structures. The fishing durations obviously impacted the monitoring results of catch per day. There were obviously spatial variations among the fish community structures in different reaches of Yangtze River. It suggested that in the middle reaches of Yangtze River, (1) the monitoring duration of 15 consecutive days was suitable for the fish stocks and community structure, (2) an adaptive tool assemblage is essential, (3) the fish community structure assessment of a definite reach should be based on the monitoring results of the definite reach, rather than a neighbor reach, (4) checking the sufficiency and efficiency of raw monitoring data was essential for assessing the fish stocks and community structures. Overall, the current study could provide scientific supports for the monitoring and evaluation of aquatic organism resources in key waters of the Yangtze River Basin after the fishing-ban.

Abstract:The Yangtze River is the longest river in China, with the richest fish resources in inland China. With the rapid economic development of the Yangtze River basin in recent decades, the intensity of human activities has been increasing, and the fish resources in the Yangtze River basin have declined sharply. To protect the ecological environment in the Yangtze River Basin, the Ministry of Agriculture and Rural Affairs has decided to ban fishing in key waters for 10 years. In order to scientifically evaluate the preliminary implementation effect of the ten year fishing ban policy in the reservoir at the lower reaches of the Jinsha River, the catch and hydroacoustic survey were carried out in Xiangjiaba Reservoir at the lower reaches of the Jinsha River in November 2020 and May 2022, and the changes of fish resources were analyzed. The results of catch survey showed that 9 species of fish belonging to 2 families were collected in November 2020, among which Hemiculter leucisculus and Pelteobagrus vachelli were dominant; In May 2022, 14 species of fish were found in 5 families, with Saurogobio dabryi and Pelteobagrus vachelli predominating. The results of hydroacoustic survey showed that there were significant differences in the distribution of fish target strength among different years, different regions and different water layers. The fish density in May 2022 (0.60 ind./1 000 m³) was higher than that in November 2020 (0.46 ind./1 000 m³). The spatial and temporal distribution of fish resources was not uniform. There were some differences in the densely populated areas of fish in different survey periods. In November 2020, there was no significant difference among most areas, while in May 2022, there was a significant difference. The density of upper layer fish in May 2022 (0.44±0.83 ind./1 000 m³) was significantly higher than that in November 2020 (0.06±0.15 ind./1 000 m³). The distribution of fish in different water layers was significantly different, and the lower layer density was higher than the middle and upper layers. The estimated fish resources in Xiangjiaba Reservoir were 3.22×10⁶ ind. (2020) and 3.53×10⁶ ind. (2022), respectively. The method of hydroacoustic survey is suitable for the monitoring of fish resources after the total fishing ban. In general, the method of hydroacoustic survey is suitable for the monitoring of fish resources in the reservoirs at the lower reaches of Jinsha River, and fish resources in Xiangjiaba Reservoir area have been recovered to some extent after the implementation of the ten-year fishing ban.

Abstract:The Yangtze River is the longest river in China, stretching 6300 km and playing an irreplaceable role in the country's ecosystem. It is also home to one of the world's richest aquatic biodiversity, with 443 freshwater fish species and 156 of them being endemic to the river. As a major source of freshwater fishery production in China, the capture fishery yield accounts for 60% of the total Chinese inland fisheries output. However, human activities such as hydro project construction, enclosing-lake cultivation, overfishing, water pollution, shipping development, and exotic fish species invasion have caused a declined aquatic ecosystem service of the Yangtze River ecosystem. This decline is reflected in the decrease in fish species, increase in endangered species, miniaturization of fish individuals, and increase of exotic species. To resolve this issue, the Chinese government has implemented a ten-year fishing ban in the Yangtze River, starting on January 1, 2021, with the aim of restoring the aquatic environment and conserving the aquatic biodiversity. To ensure the sustainable development of fishery resources in the Yangtze River, it is suggested to coordinate the relationship between ecological protection and fishery development, innovate the management system and mechanism, and adjust service objectives according to changes in the Yangtze River aquatic ecosystem. These studies aim to provide a scientific policy suggestion for the protection of the Yangtze River aquatic ecosystem and the sustainable development of its fishery resources.

Abstract:The conservation of biodiversity in the Yangtze River basin is at the centre of gravity in the strategic layout of China's ecological civilisation. However, a number of factors, in particular the long-standing absence of legal protection, have caused serious damage to the biodiversity of the Yangtze River basin. The Yangtze River Protection Law, as the first special river basin law in China, provides legislative safeguards to achieve a high level of ecological protection and high-quality economic and social development in the Yangtze River basin. The Yangtze River Protection Law is goal-oriented in terms of biodiversity conservation in the river basin, and provides clear provisions and systematic arrangements for the establishment of a basin-wide coordination mechanism, the establishment of an aquatic life integrity index evaluation system, the construction of an ecological restoration and ecological protection compensation system, the conduct of biodiversity surveys and biological resources monitoring, and the in-depth promotion of fishing bans, providing a solid legal basis for biodiversity conservation in the Yangtze River basin. However, it should be noted that the construction of a biodiversity protection system in the Yangtze River basin is still in the exploratory stage, and there are practical problems in the protection of biodiversity in the basin, such as a delayed supporting system that affects the effectiveness, the lack of prominent protection functions in relocated areas, confusion in the enforcement status due to multiple enforcement bodies, and blind spots in the prevention of invasive alien species. Focusing on the above problems, this paper put forward targeted suggestions so as to speed up the reform process of the supporting system and management system, emphasise the dual role of relocation and in situ protection, improve the comprehensive law enforcement system in the Yangtze River basin, and fill the loopholes and gaps in the prevention and control of invasive alien species, with a view to providing some reference for the conservation and management of biodiversity in the Yangtze River basin.