【摘要】 为了解禁捕初期长江上游宜宾段鱼类群落结构特征及年际变化,本研究基于2018-2022年共5年的鱼类科研捕捞监测数据进行统计分析,结果显示5年间共监测到鱼类90种,隶属于4目14科57属,其中长江上游特有鱼类18种,占总种类数的20%。等级聚类分析(Cluster)和非度量多维尺度分析(NMDS)显示,在42.16%的相似水平上,宜宾段鱼类群落可聚分为2组,分别为2018-2019年和2020-2022年。5年间鱼类优势种组成差异较大,优势种以瓦氏黄颡鱼和吻■(Rhinogobiotypus)等中小型鱼类为主,优势种种类及规格发生明显变化,禁捕后宜宾段瓦氏黄颡鱼优势体长与优势体重年际变化均呈增长趋势,显示小型化趋势得到一定的缓解。多样性指数显示Shannon-Wiener指数和Margalef指数在2022年达到顶峰,整体波动较大,Pielou指数和Simpson指数则较为稳定,无明显波动。ABC曲线结果显示,禁捕后宜宾段鱼类群落结构总体呈稳定态势。长江十年禁渔制度的全面实施有效缓解了长江上游鱼类小型化趋势,禁捕初期宜宾段鱼类群落结构总体稳定。更多还原

【Abstract】 Due to its special geographical form and habitat type, the upper reaches of the Yangtze River have cultivated rich and diverse fish resources, showing high biodiversity.According to historical records, the upper reaches of the Yangtze River are rich in fishery resources, with 286 species of fish, and 112 species of endemic fish, accounting for the highest proportion in the domestic water system, and also an important treasure house of freshwater fish resources in China.The "National Nature Reserve of Rare and Endemic Fish in the Upper Reaches of the Yangtze River" was established in 2005,and the functional zoning and scope were adjusted in 2011.The establishment of the reserve has protected the fish resources in the upper reaches of the Yangtze River to a certain extent.As the first city in the protected area core, Yibin City is in a very special geographical position, where the Jinsha River and the Minjiang River join together to form the Yangtze River.The rare and endangered and endemic fish in the upper reaches of the Yangtze River, such as Psephurus gladius and Acipenser dabryanus,were the main protected objects in the Yibin section of the protected area, which had an important ecological barrier role.With the construction of the Three Gorges Dam, Xiangjiaba and other large-scale water conservancy and hydropower projects, the original river ecosystem in the upper reaches of the Yangtze River had been divided into discontinuous environmental units, and migratory fish had been blocked out, which had seriously affected their habitat distribution and population reproduction.Large migratory and carnivorous fish such as Psephurus gladius,Anguilla japonica,Luciobrama macrocephalus,and Ochetobius elongatus had been elusive in the wild for many years.At the same time, it also changed the hydrological environment and the structure of food biomes in the upper reaches of the Yangtze River, destroying habitats required by endemic fish in the upper reaches, and the fishery resources showed an obvious decline trend.On January 1,2018,the "ten-year fishing ban" policy of the Yangtze River was first implemented in the National Reserve of Rare and Endemic Fish in the upper reaches of the Yangtze River, which plays a key role in the restoration and conservation of fishery resources in the Yibin section of the upper reaches of the Yangtze River.At present, the most of the reports about the fish community in the Yibin River section focus on the pre-closed fishing period, but few reports about the changes in fish community structure characteristics after the closed fishing period.In order to further understand and grasp the dynamic change trend of fish community structure in Yibin section of the upper reaches of the Yangtze River in the early period of the fishing ban, and to provide a scientific basis for implementing of the "ten-year fishing ban" policy.A total of 90 fish species belonging to 4 orders, 14 families and 57 genera were detected in the Yibin section of the upper reaches of the Yangtze River during 2018-2022,of which 18 species were endemic to the upper reaches of the Yangtze River, accounting for 20% of the total species.In each year, 45,44,35,40 and 57 species were investigated respectively, including 6 national key protected wild animals such as A.dabryanus,Myxocyprinus asiaticus,Coreius guichenoti,Procypris rabaudi,Leptobotia elongata and L.rubrilabris,and the number of fish species was relatively rich.The dominant species and fish diversity index were used to determine the inter-annual changes of the dominant species and fish diversity index.The results showed that the dominant species composition varied greatly in the past five years, and the dominant species were mainly small and medium-sized fish such as Pelteobagrus vachelli and Rhinogobio typus,and the dominant species and specifications changed significantly.After the ban on fishing, the dominant body length and dominant body weight showed an increasing trend.The miniaturization trend has been alleviated to some extent.In terms of rare fish, the rare endemic fish in the Yibin section gradually changed from small and medium-sized fish such as Leptobotia elongata,Leptobotia rubrilabris to medium and large such as Acipenser dabryanus.It was speculated that this phenomenon might be due to the fact that the selection of sampling sites was more inclined to the ecological environment preferred by Acipenser dabryanus during 2021-2023,which might lead to the bias of relevant data.The diversity index showed that Shannon-Wiener index and Margalef index peaked in 2022 with large overall fluctuations, while Pielou index and Simpson index were relatively stable with no significant fluctuations.Hierarchical clustering analysis and non-metric multidimensional scale were used to group the fish communities, so as to gain insight into the differences in the composition of the fish communities between the test years.The results showed that at 42.16% similarity level, the fish communities in the Yibin section could be clustered into two groups, namely 2018-2019 and 2020-2022.ANOSIM test showed that the difference of community structure between the two groups was not statistically significant.The similarity level in 2018-2019 and 2021-2022 was greater than 50%,while the similarity level between the results of fish community in 2020 and the other years was about 45%(the average value was 45.19%),indicating that 2020 was a year in which the results of fish community changed.This might be related to the fact that only one sampling was conducted in the Yibin section in 2020.SIMPER analysis identified 10 key species that led to differences in fish community grouping in the Yibin section from 2018 to 2022.In order to evaluate the stability of fish community structure, we selected the quantity-biomass comparison curve proposed by Warwick, and the ABC curve showed that the fish community structure in the Yibin section was generally stable after the fishing ban.In summary, the full implementation of the 10-year fishing ban system in the Yangtze River effectively alleviated the trend of fish miniaturization in the upper reaches of the Yangtze River, and the fish community structure in the Yibin section was generally stable in the early days of the ban.更多还原